140313smartctrl 2.1 help - psim electronic simulation … · 16.4 simulation issues with digital...

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SmartCtrl

User’s Guide

Powersim Inc.

SmartCtrl User’s Guide

Version 2.1

Release 1.0

March 2014

Copyright © 2009–2014Carlos III University of Madrid, GSEP Power Electronics Systems Group, Spain.All rights reserved. No part of this manual may be photocopied or reproduced in any form or by anymeans without the written permission of Powersim and the Carlos III University of Madrid.

Disclaimer Powersim Inc. (“Powersim”) and the Carlos III University of Madrid make no representation or warranty with respect to the adequacy or accuracy of this documentation or the software which it describes. In no event will Powersim and the Carlos III University of Madrid or its direct or indirect suppliers be liable for any damages whatsoever including, but not limited to, direct, indirect, incidental, or consequential damages of any character including, without limitation, loss of business profits, data, business information, or any and all other commercial damages or losses, or for any damages in excess of the list price for the license to the software and documentation.

Powersim Inc.

email: [email protected]

http://www.powersimtech.com

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Table of Contents

CHAPTER1: INTRODUCTION 1

1.1 Why SmartCtrl? 1

1.2 Program Layout 3

CHAPTER2: MAINMENUSANDTOOLBARS 5

2.1 File Menu 5

2.2 Design Menu 6

2.3 View Menu 6

2.4 Window Menu 8

2.5 Main Toolbar 8

2.6 View Toolbar 9

2.6.1 SmartCtrl additional transfer functions 11

CHAPTER3: DESIGNAPREDEFINEDTOPOLOGY 13

3.1 DC‐DC Converter ‐ Single loop 13

3.1.1 Single Loop 13

3.2 DC‐DC Converter ‐ Peak Current Mode Control 15

3.3 DC‐DC converter ‐ Average Current Mode Control 19

3.4 Power Factor Corrector 23

3.4.1 Power Stage 31

3.4.2 Graphic panels 33

3.4.2.1 Oscillator ramp and internal compensator 33

3.4.2.2 Line Current 33

3.4.2.3 Rectified voltage and external compensator output 34

3.4.3 Multipliers 35

3.4.3.1 Multiplier 35

3.4.3.2 UC3854 Amplifiers 36

ii

CHAPTER4: DESIGNAGENERICTOPOLOGY 37

4.1 s‐domain model editor 37

4.1.1 s‐domain model (equation editor) 38

4.1.2 s‐domain model (polynomial coefficients) 41

4.1.2.1 Plant Wizard 43

4.2 Import frequency response data from .txt file 46

CHAPTER5: DESIGNAGENERICCONTROLSYSTEM 51

CHAPTER6: DC‐DCPLANTS 55

6.1 Buck 56

6.2 Boost 59

6.3 Buck‐Boost 62

6.4 Flyback 65

6.5 Forward 67

CHAPTER7: SENSORS. 70

7.1 Voltage Divider 70

7.2 Embedded voltage divider 70

7.3 Isolated Voltage Sensor 71

7.4 Resistive Sensor (Power Factor Corrector) 71

7.5 Resistive Sensor (Peak Current Mode Control) 72

7.6 Hall effect sensor 72

7.7 Current Sensor 72

CHAPTER8: MODULATOR 73

8.1 Modulator (Peak Current Mode Control) 73

8.2 Modulator (PWM) 73

iii

CHAPTER9: COMPENSATORS 75

9.1 Single loop or inner loop 75

9.1.1 Type 3 compensator 75

9.1.2 Type 3 compensator unattenuated 76



9.1.5 PI compensator 79

9.1.6 PI compensator unattenuated 80

9.2 Outer loop and peak current mode control 81

9.2.1 Single pole compensator 81

9.2.2 Single pole compensator unattenuated 82

9.2.3 Type 3 regulator 83




9.2.7 PI compensator 87

9.2.8 PI compensator unattenuated 88

CHAPTER10: GRAPHICANDTEXTPANELS 89

10.1 Bode plots 89

10.2 Nyquist diagram 91

10.3 Transient response plot 94

10.4 Steady‐state waveform 97

10.5 Text panels 98

CHAPTER11: SOLUTIONSMAPS 105

CHAPTER12: EDITORBOX 107

CHAPTER13: IMPORTANDEXPORTTRANSFERFUNCTION 109

13.1 Export 109

13.1.1 Export transfer function 109

13.1.2 Export to PSIM 110

13.1.3 Export transient responses 114

13.1.4 Export Global. 116

iv

13.2 Import (Merge) 117

13.2.1 Add Function 119

13.2.2 Modify Function 120

CHAPTER14: DESIGNMETHODS 123

14.1 K‐factor Method 124

14.2 Kplus Method 125

14.3 Manual 126

14.4 PI tuning 127

14.5 Single Pole tuning 128

CHAPTER15: PARAMETRICSWEEP 129

15.1 Input Parameters Parametric 129

15.2 Compensator Components Parametric Sweep 133

CHAPTER16: DIGITALCONTROL 135

16.1 Introduction to Digital Control 135

16.2 Digital Settings 135

16.3 Parametric sweep in digital control 137

16.4 Simulation issues with digital control 138

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Introduction

SmartCtrl 1

Chapter1: Introduction

1.1 WhySmartCtrl?

SmartCtrl is the control designing tool for power electronics. It provides an easy to use interface for designing the control loop of almost any plant.

It includes the predefined transfer functions of some of the most commonly used power electronics plants, such as different DC-DC topologies, AC-DC converters, Inverters and motor drives.

However, it also allows the users to import their own plant transfer function by means of a text file. Therefore, this feature provides flexibility to design an optimized control loop for almost any system.

In order to make easier the first attempt when designing a control loop, an estimation of the stable solutions space is given by the program under the name of "solutions map". Based on the selected plant, sensor and type of regulator, the solutions map provides a map of the different combinations of fc and phase margin that lead to stable systems.

Thus, the designer is able to select one of the points of the stable solutions space and to change the compensator parameters dynamically in order to adjust the system response to the user requirements in terms of stability, transient response, ... Since the program provides, at a glance, the frequency response of the system as well as the transient response and the compensator component values for the open loop given features. All of them are real time updated when any parameter of the system is varied by the designer.

Key Features

Pre-defined transfer functions of commonly used DC-DC converters, Power Factor Correction converters, sensors and regulators.

Different control techniques for DC-DC converters are supported:

o Single control loop structures: voltage mode control and current mode control.

o Peak current mode control.

o Double control loop structure: two nested control loops that implements an average current mode control.

Capability of designing the controller of any converter by means of:

o Importing its frequency response data from a .txt file.

o Defining its transfer function through the equation editor.

Capability of designing a generic control system.

Digital control is also available.

Estimation of the stable solutions space ("Solutions Map").

Sensitivity analysis of the system parameters.

Introduction

2 SmartCtrl

Real time updated results of the frequency response (bode plots), transient response and the steady state waveforms.

Possibility of importing and exporting any transfer function by means of .txt files.

Introduction

SmartCtrl 3

1.2 ProgramLayout

When SmartCtrl is started, all the available options are shown, and the user can select which of them is going to use. The aforementioned window is shown below. It is divided into four sections:

1. Design a predefined topology

This option provides an easy and straightforward way of designing the control circuit of the most widely used power converters. Through a guided process, the user will be able to select amongst different control strategies:

DC-DC Converter- Single loop

Two different control strategies are available in this case: voltage mode control and current mode control.

DC-DC Converter - Peak Current mode control

DC-DC Converter - Average current mode control

Two nested loops are needed to implement the average current mode control. The outer loop is a voltage mode control loop, and the inner one is a current mode control.

PFC Boost converter

2. Design a generic topology.

This option allows to design a converter by two different ways:

s-domain model editor.

Importing the frequency response data from .txt file

Introduction

4 SmartCtrl

3. Design a generic control system - Equation editor.

SmartCtrl also provides the option of defining the whole system though its equation editor. And so, help the user though the designing process of any control problem regardless its nature, for example temperature control, motor drives, etc

4. Open...

Default file. It opens a pre-designed example.

Recently saved file. It opens the last file the user worked with.

Previously saved file. It opens the folder where user used to save its designs

Sample design. It opens the folder where SmartCtrl examples have been previously recorded.

Regardless of the selected option, once the converter is completely defined, the main window of the program is displayed. Different areas are considered within the main window and all of them are briefly described below:

1. There are six drop-down menus, this is:

File It includes all the functions needed in order to manage files, import and export files, establish the printer setup and the print options.

Design SmartCtrl libraries, modification of input data, access to the digital control settings (only available in SmartCtrl 2.0 Pro) and parametric sweep.

View Allows the user to select which elements are displayed and which are not.

Window Functions to create, arrange and split windows.

Help SmartCtrl Help.

2. The Main Toolbar provides quick access to the most commonly used program functions through left click on the respective icon.

3. The View Toolbar icons allows the user a quick selection of the elements displayed.

4. The Status Bar summarizes the most important parameters of the open loop control design (cross frequency, phase margin and attenuation at the switching frequency).

5. The compensator Design Method Box includes the three calculation methods of the compensator as well as the Solution Map.

6. Graphic and text panels include the most relevant information of the system: frequency response, polar plot, transient response, input data and the designed regulator components. To access the help topic regarding each panel just right

Main Menus and Toolbars

SmartCtrl 5

Chapter2: MainMenusandToolbars

2.1 FileMenu

New Create a new project (Ctrl+N)

New and initial dialog Create a new project and displays the initial dialog box

Open Open an existing project (Ctrl+O)

Open sample designs Open a sample design from the examples folder

Close Close the current project window

Save Save the current project (Ctrl+S)

Save as... Save the current project to a different file

Open txt files Open any .txt file in Notepad

Import (Merge) Merge data of another file with the data of the existing file for display. The curves of these two files will be combined. (Ctrl+M)

Export The program provide different exporting options. It allows exporting the following.

Export to PSIM the schematic and the parameters file, or update parameters file

Export transfer functions to a file. The available transfer functions are: plant, sensor, control to output, compensator, etc.

Export transient responses to a file. The available transient responses are: voltage reference step, output current step and input voltage step

Export temporal signals to a file. The available steady state waveforms are: inductance voltage and current, diode voltage and current, carrier, modulating signal and PWM.

Generate report Generate a report to either a .txt file or notepad. It contains information regarding both the input data (steady-state dc operating point, plant input data, ...) and output data (compensator components, cross frequency, phase margin, ...)

Print preview Preview the printout of any of the graphic and text panels ( Transfer function magnitudes (dB), Transfer function phase (º), Nyquist diagram, Transients, Data input, Results)


6 SmartCtrl

Print Print any of the panels of the main window (bode plots, Nyquist diagram, transient, input data or results)

Printer setup Setup the printer

Exit Exit SmartCtrl program

2.2 DesignMenu

The SmartCtrl Design Menu contains the elements that can be used in the SmartCtrl schematic. The library is divided into the following sections:

Predefined topologies Contains the most commonly used DC-DC plants both in single and double loop configurations, as well as AC-DC plants.

Generic Topology Allows the user to define a of a generic plant transfer function either in s-domain or importing a .dat, .txt, or .fra file. And use the predefined sensors and compensators provided by SmartCtrl to desing the closed-loop control system.

Generic Control System Allows the user to define the plant and the sensor transfer functions through the built-in equations editor. And design the compensator for this user defined system.

Modify Data Open the schematic window of the current project to modify the parameters.

Digital control Access to the digital control settings (only available in SmartCtrl 2.1 Pro)

Parametric Sweeps Allows performing the sensibility analysis of the system parameters. It is divided into three different parametric sweeps: Input Parameters, Compensator Components and digital factors.

Reset all Clear the active window

2.3 ViewMenu

Comments Open the comments window. It allows the user to add comments to the design. These comments will be saved together with the designed converter.

Loop Select the loop to be displayed in the active window (inner or outer loop)


SmartCtrl 7

Transfer Functions Select the transfer function to be displayed

Plant transfer function, G(s)

Sensor transfer function, K(s)

Compensator transfer function, R(s)

Sensor-Compensator transfer function, K(s)·R(s)

Control to output without regulator transfer function, A(s)

Control to output transfer function, T(s)

Reference to output transfer function, CL(s)

Digital compensator transfer function

Digital control to output transfer function

Digital reference to output transfer function

Additional transfer functions Select the additional transfer functions to be displayed, like the audiosusceptibility Gvv, the output impedance Gvi, etc. For more information regarding these transfer function, see section 2.6.1.

Additional t.f. toolbar Show a toolbar with all the additional transfer functions. For more information regarding this toolbar, see section 2.6.1.

Transients Select the transient response to be displayed.

The available transient responses are:

Input voltage step transient

Output current step transient

Reference step transient.

Organize panels Resize all panels and restore the default appearance of the graphic and results panels window.

Enhance Select the panel to be displayed in full screen size

Bode (magnitudes) panel (Ctrl+Shift+U)

Bode (phase) panel (Ctrl+Shift+J)

Nyquist diagram panel (Ctrl+Shift+I)

Transient responses panel (Ctrl+Shift+K)

Input data panel (Ctrl+Shift+O)

Output (results) panel (Ctrl+Shift+L)

Input data View design input data

Output data View design output data


8 SmartCtrl

2.4 WindowMenu

New Window Create a new window

Maximize active window Maximize the current window

Cascade Arrange the windows in cascade form

Tile horizontal Tile the currently open windows horizontally

Tile vertical Tile the currently open windows vertically

Split Click on the intersection of the lines that delimit the different window panels and drag. This will change the size of the panels

Organize all It restores the default size of the graphic and text panels.

2.5 MainToolbar

Create a new project

Create a new project and open initial dialogue box

Open an existing project

Open sample design

Close the current project window

Generate report

View document comments

DC-DC converter - Single loop

DC-DC converter - Peak Current Mode Control

DC/DC - Average Current Mode Control

PFC Boost converter

Design a generic topology using a s-domain model editor

Design a generic topology from a .txt file

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10 SmartCtrl

Display the frequency response (Bode plot) of the compensator transfer function

Display the frequency response (Bode plot) of the discrete compensator transfer function

Display the frequency response (Bode plot) of the control to output transfer function

Display the frequency response (Bode plot) of the control to output transfer function with digital control

Display the frequency response (Bode plot) of the reference to output transfer function

Display the frequency response (Bode plot) of the reference to output transfer function with digital control

View additional transfer functions toolbar

Display transient response due to a reference voltage step

Display the transient response due to an output current step

Display the transient response due to an input voltage step

Display inner loop results

Display outer loop results

Enables or disables the display of the compensator calculation method toolbox

Input Parameters Parametric sweep

Compensator Parameters Parametric sweep

Digital Factors sweep

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12 SmartCtrl

Closed loop transfer functions.

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Gtivi Closed loop Input voltage to inductor current or diode current transfer function

Gtiio Closed loop Output current to inductor current or diode current transfer function

The nomenclature will be clarified through two examples.

Example 1: Open loop transfer function.

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Example 2: Closed loop transfer function.

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14 SmartCtrl

The predefined DC-DC plants are the following:

Buck

Buck-Boost

Boost

Flyback

Forward

Once the plant has been selected, regardless the magnitude to be controlled is voltage or current, the program will display the appropriate type of sensor.

The different sensors available are the following:

Voltage Divider.

Embedded Voltage Divider.

Isolated Voltage Sensor.

Current Sensor.

Hall Effect Sensor.

Finally, the compensator is selected. The ones provided by SmartCtrl are:

Compensator types:

Type 3

Type 3 Unattenuated

Type 2

Type 2 unattenuated

PI

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Single Pole

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Buck

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Once the plant has been selected, the value of the resistor that implements the current sensor

must be set.

Current sensor available:

Resistance

Next, the modulator must be configured (see section 8.1)


SmartCtrl 17

Modulators available:

Modulator (Peak Current Mode Control).

Voltage sensor available:

Voltage devider.

Embedded Voltage Divider

The last element that must be set is the compensator.


18 SmartCtrl

Regulator types:

Type 3

Type 3 Unattenuated

Type 2

Type 2 unattenuated

PI

PI unattenuated

Finally the user must select the control loop initial characteristics (cross frequency and phase

margin), aided by the Solutions Map. After that, click OK and the program will automatically

show the graphics panels.


SmartCtrl 19

3.3 DC‐DCconverter‐AverageCurrentModeControl

The average current control is formed by an inner current loop and an outer voltage mode loop. As well as the single loop, the double loop setup must be built sequentially. The program will guide you to built it, enabling the following step and keeping everything else disabled.

In all the available plants, the outer loop is a voltage mode control (VMC), while the inner loop is a current controlled one. Depending on the selected plant, the current is sensed either on the inductance (LCS) or on the diode (DCS). The DC/DC plant must be selected among the following list.


Buck (LCD-VMC)

Buck-Boost (LCS-VMC)

Boost (LCS-VMC)

Boost (DCS-VMC)

Flyback (DCS-VMC)

Forward(LCS-VMC)

Next, the inner control loop will be configured. This is, the current sensor and the regulator type must be selected.

The available current sensors are the following:

Current Sensor

Hall Effect Sensor

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24 SmartCtrl

Depending on the first choice, there are two different options to generate the power factor corrector.

If the selection is a Generic Multiplier, the current is sensed by the Hall Effect sensor H(s).

Otherwise, if the selection is UC3854A multiplier, the current sensor is a resistor Rs.


SmartCtrl 25

It is followed by the choice of the plant. The predefined plants are the following:

Boost PFC (Resistive load)

Boost PFC (Constant power load)

Next, the inner control loop will be configured: since the current sensor has been already configured, it is necessary to select the inner loop compensator.

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28 SmartCtrl

Next, the outer loop compensator must be selected.

Compensator types:

For multiplier option: For UC3854 multiplier option:

Type 3

Type 2

PI

Single Pole

For Voltage Divider:

Type 2

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Single Pole

For Embedded Voltage Divider:

Type 2 Unattenuated

PI unattenuated


As well as in the case of the inner loop, the crossover frequency and the phase margin must be selected. Also in this case, the solution map is available to help the selection of a stable solution.

Press the "Solution map (outer loop)" button and the solution map will be displayed. Then select a point just by clicking within the white area.

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SmartCtrl 31

output voltage can be different from the specified output voltage. As mentioned above, if the estimated Vo (shown in the method panel) differs from the specified one in more than 10%, there is a warning.

Finally, the flowchart to generate the types of the power factor is the following:

3.4.1 PowerStage

The Boost PFC is based on a double loop control scheme, and therefore the output voltage and a current through the inductor are sensed simultaneously. There are four options for the plant, depending on the load and the multiplier:

Generic multiplier + Boost PFC (Resistive load)

Generic multiplier + Boost PFC

POWER FACTOR CORRECTOR

MULTIPLIER & VrmsFEED‐

FORWARD

INNER LOOP SENSOR

PLANTINNER LOOP

REGULATOR

OUTER LOOP SENSOR

OUTER LOOP

REGULATOR

Boost PFC (Constant power load)Boost PFC (Resistive load)

Type 2Type 3PI

Multiplier Hall effect sensor Isolate V sensor

Type 2Type 3PISingle Pole

Boost PFC (Constant power load)Boost PFC (Resistive load)

Type 2PI

UC3854AMultiplier

Resistive sensor

Voltage dividerType 2PISingle Pole

RegulatorEmbeddedVoltage Divider

Type 2_unattPI_unattSingle Pole_unatt

H(s)

Rs


32 SmartCtrl

UC3854A multiplier + Boost PFC (Resistive load)

UC3854A multiplier + Boost PFC (Constant power load)

The current loop is designed considering a piecewise linear model of the plant: using quasi-static assumption, the small signal model for each operating point is calculated as in a DC-DC boost converter.

The input data variables are listed and defined below:

Input data

Vin(rms) Input Voltage (V)

RL Equivalent Series Resistor of the Inductance (Ohms)

L Inductance (H)

Rc Equivalent Series Resistor of the output capacitor (Ohms)

C Equivalent Series Resistor of the output capacitor (Ohms)

Vo Output Voltage (W)

R Load Resistor (Ohms)

Po Output Power (W)

wta Line angle(º). The current loop is designed considering the plant calculated for this operating point. This line angle is indicated as a red dot in the output panel that represents the Rectified voltage and external compensator output(See Graphic and text panels window for detailed information)

FSW Switching frequency (Hz)

Line frequency Line frequency (Hz)


SmartCtrl 33

3.4.2 Graphicpanels

The window is divided in six different panels:

The graphic panels are:

Bode plot Magnitude (dB)

Bode plot Phase (º)

Polar plot

Line current

Oscillator ramp and internal compensator

Rectified voltage and external compensator output

3.4.2.1 Oscillatorrampandinternalcompensator

This graphic panel provides information about the output of the inner control compensator (blue line) compared to the oscillator ramp (red line). The output of the internal compensator is represented for the line angle corresponding to the maximum current ripple through the inductor. This line angle is identified by means of a blue dot in the Rectified voltage and external compensator output graphical panel.

This comparison can be useful to determine whether there could be oscillations. If the slopes of both functions are too similar, there could be more than one intersection per period.

3.4.2.2 LineCurrent

This graphic panel provides information about the line current and its harmonic distortion. The line current waveform is calculated assuming that the current loop follows perfectly the reference generated by the outer loop. However, in some occasions there is a zero-cross distortion and the actual line current would differ from the one represented. In these cases, a warning message would appear in the solution map window.


34 SmartCtrl

3.4.2.3 Rectifiedvoltageandexternalcompensatoroutput

This graphic panel provides information about the external compensator output voltage. Its phase shift compared to the rectified voltage can be assessed. If the compensator output voltage has not an appropriate phase shift compared to the rectified voltage (reference), the line current distortion will increase.

The current loop is designed considering a piecewise linear model of the plant. The current plant represented in the Bode plot panels (see Graphic panels window) corresponds to the operating point marked with a red dot in the rectified voltage. The small signal model for the plant is calculated as in a DC-DC boost converter for this operating point. This dot can be moved by clicking and dragging with the mouse, resulting in a variation of the operating point. As the dot changes its position, the Bode plot corresponding to the inner loop varies, as well as the attenuation information in the K-factor panel refreshes according to the indicated operating point.

The blue dot in the rectified voltage represents the operating point that corresponds to the maximum current ripple through the inductor. The graphics in the Oscillator ramp and internal compensator panel have been represented for this operating point.

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4.1.1 s‐domainmodel(equationeditor)

When the power converter is defined through its s-domain transfer function, the design procedure is as follow:

First, the user must define the s-domain transfer function of the plant, To do that are two different options:

Import a previous design (click on open)

Define a new transfer function (click on editor). To check the syntax rules of the equation editor, please refer to Chapter 12: Editor Box

Once the equation has been introduced:

Click on "Save" to save the mathematical equations in a text file with extension .tromod

Click on "compile" to continue.

If desired, the frequency response of the transfer function can be exported as a .txt file by clicking on "Export transfer function".

If default option "Bode plot" is selected, the frequency response of the previously defined transfer function is shown on the right hand side panels.

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SmartCtrl 41

And finally select the cross frequency and the phase margin on the Solutions Map.

4.1.2 s‐domainmodel(polynomialcoefficients)

SmartCtrl offers the possibility of describing the data of the plant introducing the coefficients of its transfer function. This feature is only available for single loop designs, and two options are available:

Voltage mode controlled (Shift+L)

Current mode controlled (Shift+U)


42 SmartCtrl

The coefficients of the s-domain transfer function have to be introduced. The maximum order of the transfer function is 10. The coefficients in the numerator are n0 to n10 and the coefficients in the denominator are d0 to d10.

It is also possible to introduce the transfer function data by using the option Plant wizard.

Some additional data must be specified:

The frequency range (minimum frequency and maximum frequency) to consider in Hertz.

The switching frequency (Fsw) in Hertz.

The desired output voltage (Vo) in Volts. (Only if the plant is voltage mode controlled).


SmartCtrl 43

By clicking “View bodes” it is possible to visualize the frequency response (magnitude and phase) that corresponds to the introduced transfer function in the selected frequency range.

4.1.2.1 PlantWizard

The plant wizard is an assistant that allows to introduce a every coefficient of the transfer function (n0,n1,…,n10, d0, d1,…,d10) as a symbolic expression.

Global block

The “Global block” corresponds to the definition ofthe variables and expressions that are common for most coefficients of the transfer function.By clicking on the button Edit, a new edition box is opened (Edit box), which helps the user to introduce the data and the equations with the appropriate format.


44 SmartCtrl

Coefficients block

The “Coefficients block” corresponds to the expressions to calculate the coefficient selected in the combo box. These equations can use the global variables defined in the “Global block” or new ones can be defined that will be available only locally for the selected coefficient.

By clicking on the button Edit, a new edition box is opened (Edit box), which helps the user to introduce the data and the equations with the appropriate format.

Once the equations have been introduced, it is recommended to click the button “Compile”. This way, the numerical value of the coefficient is calculated by means of the mathematical expression in the return assignment, considering all the variables previously assigned both in the “Global block” and the “Coefficients block”.

If the compilation is successful, the numerical value of the selected coefficient will be displayed in the “Value” box. Otherwise an error message will appear.

Syntax of the “Global block” and the “Coefficients block”:

1. There are two types of instructions: assignment and return.

2. Only one instruction per line is permitted (whether it is assignment or return).

3. Blank lines are allowed.

4. The syntax of the assignment statements is: Var = Expr, where 'Var' is the name of a variable and 'Expr' represents a mathematical expression.

5. Regarding the variable names in the assignments:

a. They must begin with an alphabetic character.

b. They can consist of alphabetic or numeric characters, or underscore.

c. The names sqrt, pow, return and PI are reserved names that cannot be used as variable names.

6. Regarding the mathematical expressions:

a. Algebraic expressions are expressions where valid operators are +, -, *, /.


SmartCtrl 45

b. Expressions can use the function sqrt(a), which calculates the square root of a, and the function pow(a, b), which calculates 'a' raised to 'b'.

c. Expressions can use grouping parentheses.

7. The syntax of the return statements is: return Expr, where 'Expr' represents a mathematical expression.

8. The overall block can only contain assignment statements.

9. In the “Coefficients block”, each coefficient can have assignment statements, but it is mandatory to have at least one return statement, which will always be the last instruction in the block. This return statement defines the mathematical value of that particular coefficient.

10. Comments can be included as annotations made by the designer in order to make the text readable. Comments start with the delimiter doble slash ‘//’ and continue until the end of the line. These annotations are ignored by the compiler.

All coefficients block

In the block “All coefficients”, some commands can be executed that affect all coefficients:

Compile: the numerical values of all the coefficients are calculated. If an error

occurs, a message will be displayed.

Save as: the contents of the “Global block” and the “Coefficients block” are stored in a file with extension .trowfun.

Load: the data stored in the files with extension .trowfun is loaded. Therefore, the “Global block” and the “Coefficients block” will be updated with the loaded information.

View: the content of the “Global block” and the “Coefficients block”, as well as the numerical value of the coefficients, is displayed in a new window.

Results box and OK button

All the warning messages are displayed in the “Results” edit box.

Once the “OK” button in pressed, all the coefficients are automatically recalculated. If an error occurs, a warning message will be displayed. If the calculation is successful,


46 SmartCtrl

the coefficient values are displayed in the Plant from s-domain transfer function window.

4.2 Importfrequencyresponsedatafrom.txtfile

The single loop is formed by three different transfer functions: plant, sensor and regulator, which must be selected sequentially. Whether the imported plant is voltage mode controlled or current mode controlled, the single loop design process is the same in any case. The only differences are the sensors available in each case.

To perform the single loop design from an imported plant transfer function, just enter the data menu and select imported transfer function. It is also available at.

SmartCtrl allows the designer to import his own transfer plant function and design an appropriate control loop. This feature is only available for single loop designs. To define the imported transfer function the user must specify the intended control type:

Take into account that, wether the imported plant is current mode controlled or voltage mode controlled, the single loop design process will be the same. The only difference is related to the available sensors, which are different for each case.

Once the control type has been selected, the file that contains the plant frequency response must be selected. SmarCtrl is able to load the following file formats: *.dat, *.txt, *.fra


SmartCtrl 47

Once the file has been selected, the data is loaded to SmartCtrl and the magnitude and phase are displayed as depicted in the next figure.

And some additional data such as the output voltage (only in voltage mode control) and the switching frequency must be specified.

Click OK to continue.

Depending upon it is a current mode controlled or voltage mode controlled, the available sensors are the following:


48 SmartCtrl

Voltage mode controlled

Voltage divider

Embedded Voltage Divider

Isolated V. sensor

Current mode controlled

Current sensor

Hall effect sensor

Finally, it is necessary to select the compensator.

Compensator types:

Type 3 Unattenuated

Type 2

Type 2 unattenuated

PI

PI unattenuated

Single Pole


Once the system has been defined, SmartCtrl calculates the solutions map in which all the possible combinations of crossover frequency and phase margin that lead to stable solutions are shown graphically.

To continue, click on set and the solutions map will be displayed. After that, select a point within the stable solutions area (white area) and then click OK.

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Once the equation has been introduced:

Click on "Save" to save the mathematical equations in a text file with extension .tromod

Click on "compile" to continue and the Bode plot will appear on the right side of the window.

If desired, the frequency response of the transfer function can be exported as a .txt file by clicking on "Export transfer function".

If default option "Bode plot" is selected, the frequency response of the previously defined transfer function is shown on the right hand side panels.

To check the gain, phase and rectangular components of the frequency response at a particular frequency, the option "One frequency" is frequency is provided. As depicted in the following figure: first "one frequency" must be selected, secondly the frequency should be specified and finally, click on compile and the gain, phase and rectangular components at the specified frequency are shown below.

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54 SmartCtrl

And finally, the compensator must be selected to complete the definition of the system components.

Once the compensator type is set, the Solutions Map will help the user to select the phase margin and the crossover frequency.

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6.1 Buck

When a single loop control scheme is used, the magnitude to be controlled in a buck converter can be either the output voltage or the inductance current. Both possibilities have been included in SmartCrl. If the control technique is peak current mode control, the current is sensed in the inductor, as shown in the table. The schematics are shown below.

VoltageModeControlledBuck L‐CurrentSensedBuck

Peak Current Mode Control

In the case of an average current control scheme, two magnitudes must be sensed simultaneously, a current and the output voltage. The resultant buck scheme is the following:

Buck (LCS‐VMC)

The input data window allows the user to select the desired input parameters and provides useful information such as the steady state dc operating point. This information is placed right below the converter image.

Two examples of the input data window are shown below, in each of them, the white shadowed boxes correspond to the input data boxes while the grey shadowed ones correspond to the additional information provided by the program.

Please, note that the input data is different in case of a voltage controlled plant (output voltage is an input) or a current controlled plant (in this case the current to be controlled is the input data). An example of the input data windows is provided below:

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DC-DC Plants

58 SmartCtrl

Other parameters of the converter

Vin Input Voltage (V)


L Inductance (H)


C Output Capacitor (F)


Po Output Power (W)


DC-DC Plants

SmartCtrl 59

6.2 Boost

There are three possible magnitudes to be controlled in the boost converter when a single loop control scheme is selected. This is the output voltage, the inductor current and the diode current. The corresponding schematics are the following:

Voltage Mode Controlled Boost Converter

L‐current sensed Boost Converter

Diode Current Sensed Boost Converter

In the case of a peak current mode control (PCMC), the output voltage and a current must be sensed simultaneously.

Boost (PCMC)

In the case of an average current control scheme, the output voltage and a current must be sensed simultaneously. The available plants for an average current mode control are included below:

Boost (LCS‐VMC)

Boost (DCS‐VMC)

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DC-DC Plants

SmartCtrl 61

Duty Cycle ton/T of the active switch

IL avg Inductance average current (A)

IL max Maximum value of the inductance switching ripple (A)

IL min Minimum value of the inductance switching ripple (A)

Io avg Output average current (A)

Vo Output voltage (V)




L Inductance (H)




Po Output Power (W)


DC-DC Plants

62 SmartCtrl

6.3 Buck‐�oost

In a single loop control scheme there are three possible magnitudes to be controlled in the buck-boost converter. This is the output voltage, the inductor current and the diode current. The corresponding schematics are the following:

Voltage Mode Controlled Buck‐Boost Converter

L‐current sensed Buck‐Boost Converter

Diode Current Sensed Buck‐Boost Converter

In the case of an average current mode control scheme or a peak current mode control (PCMC), the magnitudes sensed are the output voltage and the L current.

Buck‐Boost (LCS‐VMC)

Buck‐Boost (PCMC)




DC-DC Plants

SmartCtrl 63

Input Data Window of a Voltage Mode Controlled Buck‐Boost

and for a Buck‐Boost with a Peak Current Mode Control

Input Data Window of a Current Mode Controlled Buck‐Boost

The parameters shown in the input data windows are defined below:

Steady-state dc operating point

Conduction Mode It can be Continuous or Discontinuous





DC-DC Plants

64 SmartCtrl






L Inductance (H)




Po Output Power (W)


DC-DC Plants

SmartCtrl 65

6.4 Flyback

In a single loop control scheme, the magnitude to be controlled in a Flyback converter can be either the output voltage or the diode current. Both possibilities have been included in SmartCtrl. The schematics are shown below:

Voltage Mode Controlled Flyback Diode Current Sensed Flyback

In the case of a peak current mode control scheme(PCMC), the magnitudes sensed are the output voltage and the MOSFET current.

Flyback (PCMC)

In the case of an average current mode control scheme, the magnitudes sensed are the output voltage and the diode current.

Flyback (DCS‐VMC)




DC-DC Plants

66 SmartCtrl

Input Data Window of a Voltage Mode Controlled Flyback

and also for a Peak Current Mode Control Technique.

Input Data Window of a Current Mode Controlled Flyback











DC-DC Plants

SmartCtrl 67



L Inductance (H)




Po Output Power (W)


(*)N2 is the transformer secondary side number of turns

N1 is the transformer primary side number of turns

6.5 Forward

The magnitude to be controlled in a Forward converter can be either the output voltage or the inductance current. Both possibilities have been included in SmartCrl. The schematics are shown below:

Voltage Mode Controlled Forward L‐Current Sensed Forward

In the case of a peak current mode control(PCMC) scheme, the magnitudes sensed are the output voltage and the L current (sensed in the MOSFET).

Forward (LCS‐VMC)

In the case of an average current mode control scheme, the magnitudes sensed are the output voltage and the L current.

DC-DC Plants

68 SmartCtrl

Forward (LCS‐VMC)




Input Data Window of a Voltage Mode Controlled Forward

and for Peak Current Mode Control.

DC-DC Plants

SmartCtrl 69

Input Data Window of a Current Mode Controlled Forward













L Inductance (H)




Po Output Power (W)


(*)N2 is the transformer secondary side number of turns. N1 is the transformer primary side number of turns

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72 SmartCtrl

7.5 ResistiveSensor(PeakCurrentModeControl)

The resistator measures the inductor current and transforms the current into an equivalent voltage.

The sensor gain corresponds to its characteristic resistance value (Rs).

G=Rs

7.6 Halleffectsensor

The Hall effect is a current sensor represented through a generic transfer function box. Internally, its transfer function corresponds to the following equation:

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fpK is the pole frequency in Hertz

7.7 CurrentSensor

The current sensor is represented by a generic transfer function box. Internally, the transfer function corresponds to a constant gain in V/A.

( )K s Gain

For example, if the current is sensed using a resistor Rs, the current sensor gain will be the value of this resistor:

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SmartCtrl 75

Chapter9: Compensators

9.1 Singlelooporinnerloop

9.1.1 Type3compensator

Input Data

R11(ohms) Its default value is 10 k

Vp(V) Peak value of the ramp voltage (carrier signal of the PWM modulator)

Vv(V) Valley value of the ramp voltage

Tr(s) Rise time of the ramp voltage

Tsw(s) Switching period

Output Data

The compensator components values (C1, C2, C3, R1, R2) are calculated by the program and displayed in the corresponding text panel


76 SmartCtrl

9.1.2 Type3compensatorunattenuated

The voltage divider needed in order to adapt the sensed output voltage to the reference voltage is embedded within the compensator. It corresponds to R11 and Rar. This compensator configuration eliminates the attenuation due to the external voltage divider.

Input Data


Vref(V) Reference voltage





Output Data

The compensator components values (C1, C2, C3, R1, R2) and the resistor Rar are calculated by the program and displayed in the corresponding text panel


SmartCtrl 77


Input Data






Output Data

The compensator components values (C2, C3, R2) and the resistor Rar are calculated by the program and displayed in the corresponding text panel.


78 SmartCtrl



Input Data







Output Data

The compensator components values (C1, C2, C3, R1, R2) and the resistor Rar are calculated by the program and displayed in the corresponding text panel


SmartCtrl 79

9.1.5 PIcompensator

Input Data






Output Data

The compensator components values (C2, R2) are calculated by the program and displayed in the corresponding text panel.


80 SmartCtrl

9.1.6 PIcompensatorunattenuated


Input Data





Tr(V) Rise time of the ramp voltage


Output Data

The compensator components values (C2, R2) and the resistor Rar are calculated by the program and displayed in the corresponding text panel.


SmartCtrl 81

9.2 Outerloopandpeakcurrentmodecontrol

9.2.1 Singlepolecompensator

Input Data

R11 Its default value is 10 k

Vsat Saturation voltage of the op-amp. In the case of the power factor corrector using a UC3854A multiplier, this value is equal to 6.0 V

Output Data



82 SmartCtrl

9.2.2 Singlepolecompensatorunattenuated


Input Data


Vref Reference voltage. In the case of the power factor corrector using a UC3854A multiplier, this value is equal to 7.5 V

Vsat Saturation voltage of the op-amp. In the case of the power factor corrector using a UC3854A multiplier, this value is equal to 6.0 V

Output Data

The compensator components values (C3, R2) and the resistor Rar are calculated by the program and displayed in the corresponding text panel.


SmartCtrl 83

9.2.3 Type3regulator

Input Data


Output Data

The regulator components values (C1, C2, C3, R1, R2) and the resistor Rar are calculated by the program and displayed in the correspondingtext panel.


84 SmartCtrl


Input Data


Vref Reference Voltage

Output Data

The compensator components values (C1, C2, C3, R1, R2) and the resistor Rar are calculated by the program and displayed in the correspondingtext panel.


SmartCtrl 85


Input Data


Output Data

The compensator components values ( C2, C3, R2) and the resistor Rar are calculated by the program and displayed in the corresponding text panel.


86 SmartCtrl



Input Data



Output Data

The compensator components values (C2, C3, R2) and the resistor Rar are calculated by the program and displayed in the corresponding text panel.


SmartCtrl 87

9.2.7 PIcompensator

Input Data


Output Data



88 SmartCtrl

9.2.8 PIcompensatorunattenuated

The voltage divider needed in order to adapt the sensed output voltage to the reference voltage is embedded within the regulator. It corresponds to R11 and Rar. This regulator configuration eliminates the attenuation due to the external voltage divider.

Input Data



Output Data

The compensator components values (C2, R2) and the resistor Rar are calculated by the program and displayed in the correspondingtext panel.

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SmartCtrl 99

The following example shows the text panels contents for a Forward converter with double loop control. Therefore, input and output information regarding the inner and outer loop is provided

Input data panel. Output data panel.

The following example shows the text panels contents for a Forward converter with double loop control. Therefore, input and output information regarding the inner and outer loop is provided

INPUT DATA PANEL

Text shown in the panel Description

INPUT DATA

DC-DC double loop (outer loop)

--------------------------------------

Frequency range (Hz) : (1, 999 k)

Cross frequency (Hz) = 10 k

Phase margin (°) = 65

Plant

--------------------------------------

(inner loop)

Frequency range

Minimum and maximum frequency to be plotted in the graphic panels.

Cross frequency

Selected crossover frequency for the open loop gain of the outer loop (0 dB crossing frequency).

Phase margin

Selected phase margin for the open loop gain.

Plant

The type of converter is shown. In the case of double loop control, the outer loop plant is the inner loop closed loop transfer function.


100 SmartCtrl

INPUT DATA PANEL (Cont I)


Sensor

--------------------------------------

Isolated voltage sensor

Vref/Vo = 0.0892857

HFPole(Hz)= 500 G

Sensor:

--------------------------------------

Ra (Ohms) = 30.3413

Rb (Ohms) = 94.8168

Pa (Watts) = 21.0933 m

Pb (Watts) = 65.9166 m

Compensator

--------------------------------------

Type 3

R11(Ohms) = 10000

Vref(V) = 2.5

Vsat_minimum(V) = 13


--------------------------------------

IC_C3(V) = -7.5

IC_C2(V) = -7.5

IC_C1(V) = 0

Sensor

The type of outer loop voltage sensor is shown. In the case isolated voltage sensor, the sensor gain and the cut-off frequency are provided.

When a voltage divider is used as voltage sensor, the resistor values (Ra, Rb) and its power dissipation are given:

Compensator

The type of outer loop compensator is shown. User´s input values are shown: Input impedance resistor, R11, the reference voltage, Vref and the error amplifier saturation voltage are provided.


The initial conditions for the regulator capacitors are provided.

INPUT DATA PANEL (Cont II)


INPUT DATA

DC-DC double loop (inner loop)

--------------------------------------

Frequency range (Hz) : (1, 999 k)

Cross frequency (Hz) = 20 k

Phase margin (°) = 60

Frequency range

Minimum and maximum frequency to be plotted in the graphic panels.

VO

Ra

Rb

VFB

Pa

Pb


SmartCtrl 101

INPUT DATA PANEL (Cont III)


Plant

--------------------------------------

Forward (LCS_VMC)

R (Ohms) = 2.8

L (H) = 14 u

RL(Ohms) = 1 n

C (F) = 2.2 m

RC(Ohms) = 1 n

Vin (V) = 270

Vo (V) = 28

Fsw (Hz) = 100 k

Nt = 218 m


--------------------------------------

Mode = Continuous

Duty cycle= 0.475705

Vcomp(V) = 2.18926

IL (A) = 10

ILmax(A) = 15.2429

ILmin(A) = 4.75705

Io (A) = 10

Vo (V) = 28

Sensor

--------------------------------------

Current sensor

Gain = 1

Compensator

--------------------------------------

Type 3

Gmod = 0.4

R11i(Ohms)= 10000

Vp(V) = 3

Vv(V) = 1

tr(sec) = 8e-006


--------------------------------------

IC_C3_i(V) = 7.81074

IC_C2_i(V) = 7.81074

IC_C1_i(V) = 0

Cross frequency

Selected crossover frequency for the open loop gain of the inner loop (0 dB crossing frequency).

Phase margin

Selected phase margin for the open loop gain.

Plant

The type of converter and the type of control are shown. The abbreviation LCS-VMC is referred to “inductor current sensed – Voltage mode Control”. The values of power stage parameters are provided.


Mode indicates de conduction mode of the converter.

Vcomp is the steady state voltage at the output of the operational amplifier of the regulator.

IL is the average value of the inductor current.

ILmax is the maximum value of the inductor current.

ILmin is the minimum value of the inductor current.

Io is the output DC current of the converter.

Vo is the output DC voltage of the converter

Sensor

The type of inner loop current sensor voltage sensor is shown. In the case of “current sensor”, the sensor gain is provided.

Compensator and PWM modulator parameters

The type of outer loop compensator is shown. User´s input values are shown:

Input impedance resistor: R11i,

Ramp parameters: Peak voltage value (Vp), valley voltage value (Vv), rise time (Tr). Gmod is the small signal gain of the modulator.

Steady-state dc operating point (regulator initial conditions)

The initial conditions for the regulator capacitors are provided.


102 SmartCtrl

OUTPUT DATA PANEL – Operational amplifier based regulator


RESULTS

Regulator (Analog):

--------------------------------------

R1 (Ohms) = 6.03942 k

R2 (Ohms) = 902.951 k

C1 ( F ) = 1.61707 n

C2 ( F ) = 28.7245 p

C3 ( F ) = 17.3479 p

fz1 ( Hz ) = 6.13625 k

fz2 ( Hz ) = 6.13625 k

fp1 ( Hz ) = 16.2966 k

fp2 ( Hz ) = 16.2966 k

fi ( Hz ) = 345.445 k

b2 ( s^2) = 6.72719e-010

b1 ( s ) = 5.18736e-005

b0 = 1

a3 ( s^3) = 4.39429e-017

a2 ( s^2) = 8.99901e-012

a1 ( s ) = 4.60725e-007

a0 = 0

Loop performance parameters:

--------------------------------------

PhF ( Hz ) = 23.6721 k

GM ( dB ) = 11.506

Atte( dB ) = 6.55592

Components values

The resistor and capacitor values are provided.

Poles and zeroes frequencies

The frequencies of the regulator poles and zeroes are given accordingly to expression (1).

s s1 1

2 fz1 2 fz2R ( )3 s s s1 1

2 fi 2 fp1 2 fp2

sT

(1)

s-domain coefficients

The coefficients of an equivalent s-domain transfer function (2) are given:

22 1 1R ( )3 3 23 2 1 1

b s b ssT a s a s a s

(2)

Loop performance parameters

At PhF frequency, the phase of the open loop gain, reaches -180º.

GM. Gain margin

Atte. Attenuation of the gains product sensor x regulator at the switching frequency.


SmartCtrl 103

OUTPUT DATA PANEL – Digital control


RESULTS

Compensator (Analog):

--------------------------------------

R1 (Ohms) = 2.32153 k

R2 (Ohms) = 36.6071 k

C1 ( F ) = 2.36137 n

C2 ( F ) = 794.811 p

C3 ( F ) = 184.518 p

fz1 ( Hz ) = 5.47005 k

fz2 ( Hz ) = 5.47005 k

fp1 ( Hz ) = 29.0323 k

fp2 ( Hz ) = 29.0323 k

fi ( Hz ) = 16.2514 k

b2 ( s^2) = 8.4656e-010

b1 ( s ) = 5.81914e-005

b0 = 1

a3 ( s^3) = 2.94311e-016

a2 ( s^2) = 1.07374e-010

a1 ( s ) = 9.79329e-006

a0 = 0

Compensator (Digital):

--------------------------------------

b0 = 3.54492

b1 = -2.625

b2 = -3.48438

b3 = 2.68359

a0 = 1

a1 = -1.92383

a2 = 1.13672

a3 = -0.212891

Regulator (Digital).

Only in SmartCtrl - Pro

z-domain coefficients

The Type 3 regulator in z-domain can be expressed as the following transfer function:

3 20 1 2 3R ( )3 3 20 1 2 3

b z b z b z bzT a z a z a z a

When a0 = 1, the output y and the input u can be expressed by the following difference equation:

0 1 1 2 2 3 3

1 1 2 2 3 3

y n b u n b u n b u n b u n

a y n a y n a y n


104 SmartCtrl

OUTPUT DATA PANEL – Digital control (Cont I)


Sensor:

--------------------------------------

Ra (Ohms) = 30.3413

Rb (Ohms) = 94.8168

Pa (Watts) = 21.0933 m

Pb (Watts) = 65.9166 m

Loop performance parameters:

--------------------------------------

PhF ( Hz ) = 2.63194 k

GM ( dB ) = -36.5853

Atte( dB ) = 2.73095

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106 SmartCtrl

When the first design point has been selected within the “Solution Map”, SmartCtrl shows its main screen. In the main screen the solutions Map will be shown as a floating window. The position of this window can be changed by the user by right clicking on the Solution Map window plus mouse move. Important Warning messages will be shown in the bottom part of the Solution Map window.

Editor box

SmartCtrl 107

Chapter12: Editorbox

Following are detailed the rules of procedure of the editor.

1. There are two types of instructions: assignment and return.

2. Only one instruction per line is permitted (whether it is assignment or return).

3. Blank lines are allowed.

4. Rules for naming variables in assignment instruction:

a. The names must begin with an alphabetic character.

b. The name can be formed of alphabetic or numeric characters, or underscore.

c. The names sqrt, pow, return and PI are reserved names that cannot be used as variable names.

5. Rules related to mathematical expressions:

a. Valid operator for algebraic expressions are +, -, *, /.

b. Expressions can use grouping parentheses.

c. The available built-in functions are:

sqrt(a) calculates the square root of a

pow(a, b) calculates 'a' raised to 'b'.

d. Algebraic expressions can include the built-in functions.

Editor box

108 SmartCtrl

Import and export transfer function

SmartCtrl 109

Chapter13: Importandexporttransferfunction

13.1 Export

13.1.1 Exporttransferfunction

SmartCtrl provide three different exporting options which are available under the export item of the File Menu. The first of the exporting options is export transfer functions

which is also available through left click on the icon placed in the main toolbar.

Any of the transfer functions available can be exported to a .txt file. To do that, the designer must select the function to export within the available list and set the options of the file in the corresponding dialogue box.

The addressed file is formed by three columns containing the frequency vector, the module in dB and the phase in degrees respectively.

The file options and characteristics are contained in the "Exporting transfer function dialogue box" and they are described below:


110 SmartCtrl

File Header It contains the name of the three columns of the file.

Export function between The designer is able to set the frequency range of the exported transfer function

Number of points Number of points to be saved in the file

Points will be equi-spaced along a:

Logarithmic scale in the frequency axis

Decimal scale in the frequency axis

Data separated by:

tabs

spaces

commas

13.1.2 ExporttoPSIM

SmartCtrl provides a link with PSIM software. Once the regulator has been designed, the power stage and the compensator can be exported to PSIM, providing an automatic generation of the schematic and/or an exportation of the parameters of the design performed in SmartCtrl. This schematic can be used to validate the design using PSIM.

There are three different options for exporting to PSIM, which are briefly described below:

Export to PSIM (schematic)

The designer is able to export the parameters of the design to a PSIM schematic that is automatically generated by the program.

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114 SmartCtrl

Power stage and sensors

The schematic and parameters of the power stage and the sensors will be exported.

Initial conditions

The initial voltage across the output capacitor and the initial current through the inductor will be exported. This way the initial transient of the simulation can be reduced.

Export to PSIM (parameters file)

Only the text file with the necessary parameters will be exported to a PSIM schematic previously generated. Similarly to the previous option, SmartCtrl will ask the designer to select the path of the PSIM schematic to which the parameters file must be exported. Then the designer will have to select the exporting options (regulator exporting way, power stage and sensors and initial conditions).

Update parameters file

Once one of the previously described options has been configured, only the updating of the existing parameter file is needed. When the designer clicks, the previously inserted parameter file will be updated automatically.

Simulation issues

13.1.3 Exporttransientresponses

SmartCtrl provides three different exporting options which are available under the export item of the File Menu. The third of the exporting options is "export transient functions" which export any of the available transient responses to a file.


SmartCtrl 115

This option is also available through right click on the transient response graphic panel. The corresponding dialogue box is displayed below. It shows the transient response to be exported as well as the following parameters:

Time shift The user is able to set a customized time shift (in seconds) if necessary, and the transient response will be translated accordingly along the time axis.

N. of points to be exported SmartCtrl shows the total number of points of the graph.

Print step Its default value is 1 and it means that every data point will be exported to the file. If it is 4, only one out of 4 points will be saved. This helps to reduce the size of the resultant file. The two buttons placed at both sides of the pint step box allow to increase (x2) or decrease (/2) the print step easily.

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SmartCtrl 117

It is possible to export the following information:

Input and output data of the design.

Transients: time (s) and magnitude (V or A) of a transient step.

Transference functions: frequency (Hz), magnitude (dB) and phase (deg) of the basic transfer functions.

Additional transfer functions: frequency (Hz), magnitude and phase (deg) of additional transfer functions, like audiosusceptibility, impedances, etc.

The designer is asked to configure the file format for the transference functions, like in Export transfer functions.

Finally, the user is asked for the path to save the file/s.

13.2 Import(Merge)

Import (Merge) data of another file with the data of the existing file for display. The curves of these two files will be combined. The Merge function is available within the

File Menu and through click on . Itis oriented to the comparison of frequency response curves (Bode plots).

The file to be merged with the current one can be either a .tro file, a .txt file or a .fra file. This is, the comparison of the current file results can be compared with the results previously saved by the SmartCtrl Program, with any transfer function saved in a .txt format or with a PSIM frequency AC analysis, respectively.

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SmartCtrl 125

So, the maximum open loop phase boost is achieved at frequency f, and it is assumed that the regulator is designed so that the open loop cross-over occurs at frequency f also.

K factor for Type 2 regulator

A Type 2 regulator is formed by a single zero, a single pole and a low frequency pole. When a Type 2 regulator is selected the pole and the zero are placed as follows:

The zero is placed at f

K

The pole is placed at ·f K

Where the K factor is defined as the square root of the ratio of the pole frequency to the zero frequency andf is the geometric mean of the zero frequency and the pole frequency.

The maximum phase boost from the zero-pole pair occurs at frequency f, and it is assumed that the regulator is designed so that the open loop cross-over occurs at frequency f also.

14.2 KplusMethod

The Kplus method is based on the K‐factor and the inputs are the same:

The desired cross-over frequency (fc)

The target phase margin (PM)

However, unlike K-factor method, cross-over frequency is no longer the geometric mean of the zeroes and the poles frequencies.

The Kplus method provides an additional design freedom degree with respect to the conventional Kfactor method, since the Kplus method places the double zero frequency

fz a factor “α” below fcross ( CZ

ff

) and the poles a factor “β” above fcross ( ·Z Cf f ).

Where “α” is set from fcross and phase margin. This parameter allows the designer to select the exact frequency in which the zeroes will be placed. After that, “β” is automatically calculated.

The additional degree of freedom obtained with Kplus can be used as follows:

If “α” is set to be lower than K (from the K-factor method), higher gain at low frequencies but less attenuation at switching frequency (fsw) are obtained.

On the contrary, if “α” is set higher than K (from the K-factor method), the control loop has less gain at low frequency but more attenuation at fsw. It should be remarked that the phase margin is the same in all cases.

When “α” is equal to K, both methods are equivalent.

Therefore, the Kplus method can be used to improve the overall performance of the control loop in those cases where a slightly larger high frequency ripple could be admitted at the input of the PWM modulator.

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SmartCtrl 127

14.4 PItuning

The PI tuning method input parameters are the same as in the K-factor method:

Phase margin

Cross-over frequency

From these two input parameters, SmartCtrl calculates the both the proportional (Kp) and integral (Kint) gains and shows them in the corresponding output boxes.

The same as in the other automatic calculation methods, the phase margin and cross-over frequency can be set directly by clicking in the solutions map.

Additionally, there is a Kp and Ti Solution Map that allows the tuning of the PI regulator by directly tuning its parameters Kp and Ti.

A Proportional Integral controller(PI) is defined by the following transfer function:

:is the Gain of the PI controller.

:is the time constant of the PI controller, in seconds.

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The constant time Ti is located on the x-axis of the graphic and the gain Kp is placed on the y-axis. Any change will involve an instantaneous update of the rest of the windows of the graphic panel, as well as in the solution map.

Every point in the recommended area of the Solution Mapbox has an equivalent point in the Kp and Ti Solution Map control box, which is also expected to be stable. However, several points of the Kp and Ti Solution Map control box might correspond to an unique point in the Solution Map.

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Parametric sweep

SmartCtrl 129

Chapter15: ParametricSweep

The parametric sweep can be accessed either through the Data Menu or the View

Toolbar icons. The SmartCtrl program distinguish among two different parametric

sweeps:

Input Parameters Parametric Sweep .

It allows the variation of all the input parameters of the system. These are:

General Data

Plant

Sensor

Regulator

Compensator Components Parametric Sweep .

It allows to vary the component values of the compensator. This is, the resistances and capacitances that conform the regulator.

15.1 InputParametersParametric

To access the input parameters parametric sweep the user can either click must click on

the button , placed within the View toolbaror through the Data Menu > Parametric Sweep > Input parameters.

The functions available within the input parameters parametric sweep are the following:

Loop to be modified Select which loop would you like to modify. This option is only available in the case of a double loop design, where the designer can select amongst the inner loop or the outer loop

Tick box "calculate regulator" When this box is selected, the regulator is recalculated for each new set of parameters along the parametric sweep. If it is not selected, the regulator is fixed to the last one calculated

Loop to be shown Select which loop results would you like to display. This option is only available in the case of a double loop design, where the designer can select amongst the inner loop or the outer loop.

The parameters to be varied are related to the open loop parameters. The designer is asked to provide a range of variation. The available parameters are:

Cross Frequency (Hz)

Phase Margin (º)

Parametric Sweep

130 SmartCtrl

Tag "General Data"

The parameters to be varied are related to the open loop parameters. The designer is asked to provide a range of variation. The available parameters are:

Cross Frequency (Hz)

Phase Margin (º)

Tag "Plant"

The parameters available for variation are related to the plant input parameters. The user must introduce a minimum and a maximum value for the variable selected, in order to provide its range of variation. Only one parameter can be varied at a time

Parametric sweep

SmartCtrl 131

Tag "Sensor"

Two different sensor are available for variation. The voltage divider and the Hall effect sensor. The parameter to be varied in the voltage divider is its voltage gain (Vref/Vo). In the case of the Hall effect sensor there are to available parameters: its gain at 0Hz and the pole frequency.

Parametric Sweep

132 SmartCtrl

Tag "Compensator"

The parameters available correspond to the modulator gain and the Resistor R11.

Parametric sweep

SmartCtrl 133

15.2 CompensatorComponentsParametricSweep

To access the compensator components parametric sweep the user can either click on

the button , placed within the view toolbar or through the Data Menu > Parametric Sweep >Compensator components.

The compensator components parametric sweep is oriented to the variation of the resistances and capacitances values that conform the regulator. The parametric sweep is available for Type 3 and Type2 regulators. For instance, in the figure below a parametric sweep window for a type 2 is shown.

Parametric Sweep

134 SmartCtrl

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Sampling frequency. It is the sampling frequency of the digital regulator. The sampling period Tsamp=1/fsamp is the time between two consecutive samples of the output signal of the regulator.

In many applications, the sampling frequency (fsamp) of the regulator is equal to the switching frequency (fsw) of the power converter. In SmartCtrl the user can select different values for switching and sampling frequency, but the sampling frequency must be a multiple or submultiple of the switching frequency.This parameter is used to calculate the digital regulator by means of discretization of the analog regulator.

In current loops, the controlled quantity in the converter has a significant ripple. Therefore, it is recommended to use a Hall Effect sensor that includes a first order low pass filter that can act as an antialiasing filter.

Bits number. It is the number of bits used to represent the coefficients of the digital compensator considering a fixed point representation. The obtained coefficients are rounded to the nearest number that can be represented with the specified number of bits. One bit is used to represent the sign, and the rest to represent the integer part and the decimal part.

A low number of bits can result in a digital regulator significantly different from the analog regulator. It is recommended to check the similarity between the analog and digital regulator. If analog and digital responses are too much different, especially at low and medium frequencies, it is recommended to increase the “Bits number”.

Accumulated delay(s). It represents the total time delay in the control loop (modulator delay, calculation delay, ADC delay, etc).

This delay affects the actual phase margin obtained with the designed digital regulator. The delay is a negative phase that is subtracted to the phase of the open loop transfer function in the Bode plot. As the original (analog) regulator is calculated without considering the time delay, the obtained phase margin will be lower than the obtained in the analog regulator. This phase margin loss can be compensated by selecting a higher phase margin in the specification of the analog regulator.

It is recommended to check the effect of the delay in the Bode plot of the open loop transfer function and the closed loop transfer function. The accumulated delay is not represented in the Bode plot of the discretized compensator.

When exporting a design of SmartCtrl to PSIM, a time delay block appears in the schematic, to take into account the different time delays of the control loop. This time delay block represents only the ADC delay and calculation delay, since the modulator delay is included in the behavior of the implemented PWM modulator. Therefore, the “accumulated delay” specified by the user must be equal at least to the modulator delay. Otherwise, inaccurate simulation results may be obtained. For the trailing edge modulator used in the proposed PSIM circuit, the time delay due to the modulator tpwm is:

tpwm=DutyCycle/fsw - floor(DutyCycle*fsamp/fsw)/fsamp if fsamp>=fsw

tpwm

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SmartCtrl 139

In the case of double loop control, this additional limiter can be added both in the inner control loop and/or in the outer control loop. In the case of the outer control loop de limits suggested for the limiter are:

• Upper limit: 5-Vref

• Lower limit: -Vref

In the case of inner control loop, the reference is not fixed. It is suggested to start with these limits:

• Upper limit: 0.97*Vp

• Lower limit: -5

140313smartctrl 2.1 help - psim electronic simulation … · 16.4 simulation issues with digital...

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