microelectronic circuits for energy harvesting · switch control (peak detector, zero crossing...

Microelectronic Circuits forEnergy Harvesting

Microelectronic Circuitsfor

Energy Harvesting

C. Moranz1, Y. Manoli1,2

1Fritz Huettinger Chair of MicroelectronicsDepartment of Microsystems Engineering - IMTEK

University of Freiburg, Germany

2HSG-IMIT, Villingen-Schwenningen, Germany

Introduction on Micro Energy Harvesting

Interfaces for Vibration Energy Harvesting

Energy Storage

Conclusion and Outlook

Outline

- 3 -

Energy Supply by Energy Harvesting

Vision

Total autonomy

“Unlimited” lifetime

Less maintenance

Easy installation

Operation at not easily accessibleplaces

- 4 -26.04.2012 Christian Moranz

0 100 15050t / [s]

Vge

n/ [

V]

0

1

2

3

excitation time [sec]excitation time (sec)0 50 100 150

1

2

3

|Vg,

oc| (

V)

0

Kinetic Micro Energy Harvesting (µEH)

Vibrational Energy Harvesting

Random generator excitation

High vibration Vg,oc

Low vibration Vg,oc

Low power in average (µW…mW)

Large supply voltage swings

Discontinuous supply voltage


Vbuf

Interface 1:Synchronous Charge Extraction

[ESSCIRC 2011]

Interface forpiezoelectric harvesters

Concept Pulsed power transfer

Blocks Negative voltage converter („Rectifier“) Switch Control (Peak detector, zero

crossing detector, active diode)

Features 0.35 µm CMOS, 18 V input transistors ASIC powered excl. by buffer capacitor Low power loss (~ 12 µW @ Vbuf = 3 V,

f = 175 Hz, L = 10 mH) Startup from uncharged buffer capacitor Timing independent from Vbuf and

adaptive on varying excitation conditions



- 7 -








26.04.2012 Christian Moranz


- 8 -









Requirement 1:Efficient transfer of harvested energy into buffer

Requirement 2:Independence ofbuffer voltage charge state transfer state

Interface 2: Resistor-Emulating Charge Pump


Interface forelectromagnetic Transducer

Concept Power-optimal point of charging Direct voltage conversion (charge pump)

Blocks Two capacitor arrays Charge and ratio control Async. comparator triggered

Features Harvesting independent of Vbuf

Generator: 100-800µW, < 400Hz Supply: Vbuf 0.8V – 3.3V, 20-40 µW

Interface 2: Resistor-Emulating Charge Pump

[ESSCIRC 2009]


- 11 -

Ideal Impedance Matching

For piezoelectric generatorswithout resonant excitation: SECE method (state of the art)

is very frequency sensitive Broadband excitation

Ideal impedance matchingin frequency domain: Power optimization

for each frequency

Outlook: Switched voltage converter with controlledinput current

generators adaptiveinterface


- 12 -

Ideal Impedance Matching

For piezoelectric generatorswithout resonant excitation: SECE method (state of the art)

is very frequency sensitive Broadband excitation

Ideal impedance matchingin frequency domain: Power optimization

for each frequency

Outlook: Switched voltage converter with controlledinput current

generators adaptiveinterface


- 13 -

Energy Storage: CMOS Integrated Fuel Cell Systems

Fully autonomous microsystem On-chip energy storage Voltage stabilization and

system control

Integrated components Oscillator & Timer Voltage reference Variable LDO CMOS integrated fuel cells Fuel cell switching array

Features 42 + 6 self breathing CMOS integrated

fuel cells Power saving by periodic system activation


[PowerMEMS 2011 / SSI Conference 2012]

+ +1...6

1...6+++

+++

1...6+++

+++

++

Timer

Vcore

Vout

selection en

Bias / Vref

3

5

Vout

Vref

Energy Storage:Measurement Results – Load Regulation

- 14 -

1µ 10µ 100µ 1m0

2

4

load current (A)vo

ltage

(V)

3.3V2.6V6x7 FCs

2.2V1.8V7x6 FCs

1µ 10µ 100µ 1m0

2

4

load current (A)

volta

ge (V

)

1µ 10µ 100µ 1m0

2

4

load current (A)

volta

ge (V

)

1.3V1.1V14x3 FCs

2.2V1.8V7x6 FCs6x7 FCs

1µ 10µ 100µ 1m0

2

4

load current (A)

volta

ge (V

)

1µ 10µ 100µ 1m0

2

4

load current (A)

volta

ge (V

)

1.3V1.1V14x3 FCs6x7 FCs

Imax,LDO Imax,FC

Decreased voltagelosses (up to -76%)

Improved LDOefficiency

Increased fuel celland system life-time

Increased fuel celland system life-time


Conclusion and Outlook

26.04.2012 Christian Moranz- 15 -

Conclusion

Interface circuits

Fuel cell based energy storage

Outlook

Multiple-input-multiple-outputpower management Increased reliability and

flexibility

Low-voltage signal processing 400 mV ≤ VDD ≤ 3 V Omit voltage regulator Decrease system complexity Decreased power consumption

Thank you for your attention.

Christian Moranz

Email: [email protected]

Fritz Huettinger Chair of Microelectronics - Prof. Dr.-Ing. Yiannos Manoli -

Department of Microsystems Engineering - IMTEKUniversity of Freiburg, Germany

microelectronic circuits for energy harvesting · switch control (peak detector, zero crossing...

Documents