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Report On

PWM Square Wave Inverter Using IRF830B MOSFET (Course: Power Electronics)

Submitted by Submitted to

Sheshadri Shekhar Rauth Shri. Suriya Prakash J

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Contents

SL. N. Contents Page No. 1 Introduction 3

2 Basic Fundamentals 4

3 PWM technologies 7

4 MOSFET Switch 8

5 Components Need for Hardware Implementation 9

6 ARDUINO Program 10

7 Proposed Circuit Diagram and description 11

8 Simulated Circuit & Scope Output 12

9 Analysis & Result 13

10 References 14

SQUARE WAVE INVERTER

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CHAPTER 1

INTRODUCTION

A power inverter, or inverter, is an electronic device or circuitry that changes direct

current (DC) to alternating current (AC).

The input voltage, output voltage, frequency, and overall power handling capacity are

depends on the design of the specific device or

circuitry. The inverter does not produce any power

as the converted power is provided by the DC

source.

A power inverter can be entirely electronic or may

be a combination of mechanical effects (such as a

rotary apparatus) and electronic circuitry. Static

inverters do not use moving parts in the conversion

process.

There are 3 major types of inverters - sine wave

(sometimes referred to as a "true" or "pure" sine wave), modified sine wave (actually a

modified square wave), and square wave.

Inverters can also be used with transformers to

change a certain DC input voltage into a

completely different AC output voltage (either

higher or lower) but the output power must

always be less than the input power: it follows

from the conservation of energy that an inverter and transformer can't give out more

power.

AIM: TO CONVERT DC TO AC

Figure I: An 140W Inverter Image

Figure II: Electrical Sign of an Inverter

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CHAPTER 2

BASIC FUNDAMENTALS

Input voltage

A typical power inverter device or circuit requires a relatively stable DC power source capable

of supplying enough current for the intended power demands of the system. The input voltage

depends on the design and purpose of the inverter. Examples include:

12 VDC, for smaller consumer and commercial inverters that typically run from a

rechargeable 12 V lead acid battery.

24 and 48 VDC, which are common standards for home energy systems.

200 to 400 VDC, when power is from photovoltaic solar panels.

300 to 450 VDC, when power is from electric vehicle battery packs in vehicle-to-grid

systems.

Hundreds of thousands of volts, where the inverter is part of a high voltage direct

current power transmission system.

Output waveform

An inverter can produce a square wave, modified sine wave, pulsed sine wave, pulse width

modulated wave (PWM) or sine wave depending on circuit design. The two dominant

commercialized waveform types of inverters as of 2007 are modified sine wave and sine wave.

There are two basic designs for producing household plug-in voltage from a lower-voltage DC

source, the first of which uses a switching boost converter to produce a higher-voltage DC and

then converts to AC. The second method converts DC to AC at battery level and uses a line-

frequency transformer to create the output voltage.

Square wave

This is one of the simplest waveforms an inverter design can produce and

is best suited to low-sensitivity applications such as lighting and heating.

Square wave output can produce "humming" when connected to audio

equipment and is generally unsuitable for sensitive electronics.

Sine wave

A power inverter device which produces a multiple step sinusoidal AC

waveform is referred to as a sine wave inverter. To more clearly distinguish

the inverters with outputs of much less distortion than the "modified sine

wave" (three step) inverter designs, the manufacturers often use the

Figure III: Square Wave

Figure IV: Sine Wave

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phrase pure sine wave inverter. Almost all consumer grade inverters that are sold as a "pure sine

wave inverter" do not produce a smooth sine wave output at all, just a less choppy output than

the square wave (one step) and modified sine wave (three step) inverters. In this sense, the

phrases "Pure sine wave" or "sine wave inverter" are misleading to the consumer. However, this

is not critical for most electronics as they deal with the output quite well.

Where in power inverter devices for standard line power, a sine wave output is desirable

because many electrical products are engineered to work best with a sine wave AC power

source. The standard electric utility power attempts to provide a power source that is a good

approximation of a sine wave.

Sine wave inverters with more than three steps in the wave output are more complex and have

significantly higher cost than a modified sine wave, with only three steps, or square wave (one

step) types of the same power handling. Switch-mode power supply (SMPS) devices, such as

personal computers or DVD players, function on quality modified sine wave power. AC motors

directly operated on non-sinusoidal power may produce extra heat, may have different speed-

torque characteristics, or may produce more audible noise than when running on sinusoidal

power.

Modified sine wave

A "modified sine wave" inverter has a non-square waveform that is a useful rough

approximation of a sine wave for power translation purposes.

Most inexpensive consumer power inverters produce a modified sine wave rather than a pure

sine wave.

The waveform in commercially available modified-sine-wave inverters is a square wave with a

pause before the polarity reversal, which only needs to cycle back and forth through a three-

position switch that outputs forward, off, and reverse output at the pre-determined frequency.

Switching states are developed for positive, negative and zero voltages.. The peak voltage

to RMS voltage ratio does not maintain the same relationship as for a sine wave. The DC bus

voltage may be actively regulated, or the "on" and "off" times can be modified to maintain the

same RMS value output up to the DC bus voltage to compensate for DC bus voltage variations.

Output frequency

The AC output frequency of a power inverter device is usually the same as standard power line

frequency, 50 or 60 hertz

If the output of the device or circuit is to be further conditioned (for example stepped up) then

the frequency may be much higher for good transformer efficiency.

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Output voltage

The AC output voltage of a power inverter is often regulated to be the same as the grid line

voltage, typically 120 or 240 VAC, even when there are changes in the load that the inverter is

driving. This allows the inverter to power numerous devices designed for standard line power.

Some inverters also allow selectable or continuously variable output voltages.

Output power

A power inverter will often have an overall power rating expressed in watts or kilowatts. This

describes the power that will be available to the device the inverter is driving and, indirectly,

the power that will be needed from the DC source. Smaller popular consumer and commercial

devices designed to mimic line power typically range from 150 to 3000 watts.

Not all inverter applications are solely or primarily concerned with power delivery; in some

cases the frequency and or waveform properties are used by the follow-on circuit or device.

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CHAPTER 3

PULSE WIDTH MODULATION

Pulse-width modulation (PWM), or pulse-

duration modulation (PDM), is

a modulation technique used to encode

a message into a pulsing signal. Although this

modulation technique can be used to encode

information for transmission, its main use is to

allow the control of the power supplied to

electrical devices, especially to inertial loads

such as motors. In addition, PWM is one of the

two principal algorithms used

in photovoltaic solar battery chargers, the other

being maximum power point tracking.

The average value of voltage (and current) fed

to the load is controlled by turning the switch

between supply and load on and off at a fast rate.

The longer the switch is on compared to the off periods, the higher the total power supplied to

the load.The PWM switching frequency has to be much higher than what would affect the load

(the device that uses the power), which is to say that the resultant waveform perceived by the

load must be as smooth as possible. Typically switching has to be done several times a minute

in an electric stove, 120 Hz in a lamp dimmer, from few kilohertz (kHz) to tens of kHz for a

motor drive and well into the tens or hundreds of kHz in audio amplifiers and computer power

supplies.

The term duty cycle describes the proportion of 'on' time to the regular interval or 'period' of

time; a low duty cycle corresponds to low power, because the power is off for most of the time.

Duty cycle is expressed in percent, 100% being fully on.

The main advantage of PWM is that power loss in the switching devices is very low. When a

switch is off there is practically no current, and when it is on and power is being transferred to

the load, there is almost no voltage drop across the switch. Power loss, being the product of

voltage and current, is thus in both cases close to zero. PWM also works well with digital

controls, which, because of their on/off nature, can easily set the needed duty cycle.

PWM has also been used in certain communication systems where its duty cycle has been used

to convey information over a communications channel.

Figure V: PWM pulse example

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CHAPTER 4

MOSFET AS A SWITCH

1. Cut-off Region

Here the operating conditions of the transistor are zero input gate voltage ( VIN ), zero

drain current ID and output voltage VDS = VDD. Therefore for an enhancement type

MOSFET the conductive channel is closed and the device is switched “OFF”.

Then we can define the cut-off region or “OFF mode” when using an e-MOSFET as a

switch as being, gate voltage, VGS < VTH and ID = 0. For a P-channel enhancement

MOSFET, the Gate potential must be more positive with respect to the Source.

2. Saturation Region

In the saturation or linear region, the transistor will be biased so that the maximum amount of

gate voltage is applied to the device which results in the channel resistance RDS(on being as small

as possible with maximum drain current flowing through the MOSFET switch. Therefore for the

enhancement type MOSFET the conductive channel is open and the device is switched “ON”.

Figure VI: MOSFET as OFF switch

Figure VII: MOSFET as ON switch

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CHAPTER 5

COMPONENTS NEEDED FOR HARDWARE IMPLEMENTATION

Table I. Components Needed

SL.N. NAME SPECIFICATIONS PICS.

1 ARDUINO UNO R3 with ATmega328 1

2 PC TO PROGRAM ONCE Any programmable PC 1

3 IRF830 VDS = 500V, ID = 5.3A 4

4 TC4427 0.4V to 18V, 1.5A 1

5 RESDISTOR 10K 2

6 CAPACITOR 0.1F 1

7 TRANSFORMER 12V/230V 1

8 BATTERY 12V, 7.5Ah 1

9 DC BULB AS LOAD 9W, 240V, AC 1

10 MULTYMETER --- 2

11 COMMON PCB BOARD 6cm*4cm 1

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CHAPTER 6

USED ARDUINO PROGRAM

The ARDUINO UNO is a microcontroller board based on the ATmega328 (datasheet).

It has 14 digital input/output pins (of which 6 can be used as PWM outputs), 6 analog

inputs, a 16 MHz ceramic resonator, a USB connection, a power jack, an ICSP header,

and a reset button.

The program used here to generate PWM signals (complement to each other):

Frequency = 50Hz, Duty Cycle = 50%, Time Period = 0.02 Second, Pulse Width = 0.01

Second

Code:

void setup() {

pinMode(9, OUTPUT);

pinMode(10, OUTPUT);

}

void loop() {

digitalWrite(9, HIGH);

delay(10);

digitalWrite(9, LOW);

delay(0);

digitalWrite(10, HIGH);

delay(10);

digitalWrite(10, LOW);

delay(0);

}

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CHAPTER 7

PROPOSED CIRCUIT DIAGRAM

Description:

The circuit contains ARDUINO, IRF830 MOSFETs, TC4427, Transformer, Load for

testing, Battery, Resistors, Capacitor, PC for programming, Multi-meter etc. With

ARDUINO software installed PC I have programmed our ARDUINO microcontroller.

Now it can generate two PWM pulses. One is complementary to another. To amplify

these PWM pulses I have used TC4427 as shown above. Those two pulses I have used to

ON & OFF the MOSFET switches simultaneously. The main intention of that MOSFET

maid H-Bridge circuit is to apply positive and negative voltage across the load

periodically, hence producing a pulsating current through it. And the DC source I have

taken from a battery. Now to increase the voltage across the load I have used a

transformer. After completing the total configuration I can check it.

Figure VIII: Basic Square Wave Inverter Circuit

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CHAPTER 8

MATLAB SIMULADET CIRCUIT & THE SCOPE OUTPUT

Figure IX: Basic Square Wave Inverter Simulated Circuit

Figure X: Scope Displayed Wave Forms

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CHAPTER 9

RESULT & ANALYSIS

Result and Analysis:

From that above simulation (Figure IX) I got that above scope output display (Figure X).

From that I have realized the result as bellow.

The input is a 12V, 7.5 Ah Lead Acid battery (DC source)

Output is a 9W 240V AC bulb (AC load)

After running the simulation file on MATLAB I got

Load current Irms =0.04A

Load Voltage Vrms=240V

Output frequency = 50Hz

Power consumed by the load=Vrms*Irms*COS (Ø) = 240*0.04*0.95=9.12W (Taking load

efficiency = 95%)

Current drawn from the battery IB-PEAK=0.8A

Battery voltage=12V

Input Power (DC) = V*I=12*0.8=9.6W

Output power (AC) = 9.12W

System efficiency = (PAC/PDC) = (9.12/9.6)*100 % =95 %

Conclusion:

By simulating this inverter I have got 95% efficiency considering the load power factor =

0.95. If the load had the power factor value 1, than theoretically the simulated inverter

efficiency would be 100%. Though here I have simulated a simple square wave inverter,

the good voltage profile point of view, the output wave form should be as closer as

possible to the sin wave. And that can be done by controlling the switching frequency

and pulse width by a well programmed pulse generator.

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References:

[I] https://en.wikipedia.org/wiki/Power_inverter

[II] https://www.arduino.cc/en/Tutorial/PWM

[III] http://www.electronics-tutorials.ws/transistor/tran_7.html