Energy Harvesting

1. Energy Harvesting Day 5: Energy Applications - Energy Conversion and Management Silicon April 19, 2013Paul NickelsbergOrchid Technologies Engineering and Consulting, Inc.www.orchid-tech.com

2. Energy Harvesting Review • Energy harvesting is the process of capturing trace amounts of naturally occurring energy from various sources. • Accumulating the Energy • Storing the Energy • Applying the Energy for Useful Purpose

3. Energy Applications EnergySource Energy Management EnergyApplication 3

4. Energy Applications • Sensor Node Power Requirements: • SupplyVoltage: Vs • ContinuousCurrent: Ic • Additional PulsedCurrent: Ip • Pulse Duration: tp • System On Time: ton • NumberofSequences: N • SequenceDuty Cycle: DC Total Energy Bill: Courtesy Linear Technologies Corporation 4

5. Energy Applications Whereisthesweetspotformaximum power transferbetweenSource andLoad? Whatisthetransferred power atthatpoint? Courtesy Linear Technologies Corporation 5

6. Energy Applications Storage Cap collectschargeduringSensor Idle State. Actsaslowimpedancesourcewhen Power isneeded. 1 2 Aux Cap collectschargebeforeenabling VOUT control Over source parameter  control harvester input power e.g. Maximum power pointcontrol Adjustcurrenttokeeptheinputatthedesiredvoltage. EffectivelyraisestheinputresistanceoftheHarvesterwhentheloadisoverdrivingthesource. Knownas MPPC for Solar Cells. 3 Courtesy Linear Technologies Corporation Over time  decouple output and input: e.g. Caps/battery to buffer energy 6

7. Energy Applications Circuit Collections Rechargeable Lithium Thin Film Battery Source: Cymbet Note: Circuits shown are for example purposes only. You must carefully verify circuitry used in your application. 7

8. Energy Applications Circuit Collections Advanced Linear DevicesALD110902 Source: Advanced Linear Devices Note: Circuits shown are for example purposes only. You must carefully verify circuitry used in your application. 8

9. Energy Applications Circuit Collections SeikoS-882Z Source: Seiko Note: Circuits shown are for example purposes only. You must carefully verify circuitry used in your application. 9

10. Energy Applications Circuit Collections SeikoS-882Z Source: Seiko Note: Circuits shown are for example purposes only. You must carefully verify circuitry used in your application. 10

11. Energy Applications Circuit Collections Source: Mide Note: Circuits shown are for example purposes only. You must carefully verify circuitry used in your application. 11

12. Energy Applications Circuit Collections Solar Cell orTEG Source: Texas Instruments Note: Circuits shown are for example purposes only. You must carefully verify circuitry used in your application. 12

13. Energy Applications Circuit Collections LTC3108/-1: Ultra-Low Voltage (20mV) Step-Up converter and Power Manager • Operates from inputs as low as 20mV • Alternate Fixed Output Voltages • Unique Resonant Power converter / Energy Harvester • Auxiliary LDO • Manages Energy storage between Reservoir and Main Cout or Batt • Compact Step-upTransformer • 3x4mm DFN or GN16 packages Courtesy Linear Technologies Corporation Note: Circuits shown are for example purposes only. You must carefully verify circuitry used in your application. 13

14. Energy Applications Circuit Collections VOUT2: Switched VOUT Rectifier 20mV Vin Source VOUT: Main Output Digital Vout Select Compact Step-Up transformer Depletion mode MOSFET VSTORE: Energy Reservoir 3mA LDO: uController power Courtesy Linear Technologies Corporation VAUX: Intermediate Charge storage and IC bias supply Charge Control and Prioritizer Note: Circuits shown are for example purposes only. You must carefully verify circuitry used in your application. 14

15. Energy Applications Circuit Collections LTC3588 PiezoelectricEnergy Harvester • Key Features: • Integrated rectifier converts piezo AC output to DC ( extremely low leakage ) • 500nA UVLO circuit allows input cap to be charged up before DC/DC enabled – ensures reliable startup • Synchronous step-down DC/DC operates over wide VIN and load current with high efficiency • Overvoltage shunt protects input – dumps excess energy to GND at VIN > 20V • 1uA (typ) no load ICC minimizes wasted energy at low vibration levels Courtesy Linear Technologies Corporation Note: Circuits shown are for example purposes only. You must carefully verify circuitry used in your application. 15

16. Energy Applications Circuit Collections High Efficiency Solar Energy Harvester • Synchronous Boost Converter + LDO starts up at 250mV • Includes Maximum Power Point Control (MPPC), which adjusts the peak inductor current to maintain Vin at a programmed voltage • Operates from higher resistance sources than traditional boosts • Uses burst-mode architecture with variable Ipk and Ivalley Courtesy Linear Technologies Corporation Note: Circuits shown are for example purposes only. You must carefully verify circuitry used in your application. 16

17. Energy Applications Circuit Collections LTC3105: Block Diagram Courtesy Linear Technologies Corporation Note: Circuits shown are for example purposes only. You must carefully verify circuitry used in your application. 17

18. Energy Applications Circuit Collections • LTC3105 boosts the low solar panel output voltage to a higher voltage to allow charging • LTC4070 shunt battery charger limits the maximum battery voltage to 4.2V • NTC thermistor reduces the battery float voltage in 100mV steps at high temperatures • P-FET disconnects the load to prevent damaging the battery from over discharge Courtesy Linear Technologies Corporation Note: Circuits shown are for example purposes only. You must carefully verify circuitry used in your application. 18

19. Energy HarvestingAdditional Reading • Electrical Energy An Introduction 3rd Edition • Mohamed A. El-Sharkawi • The International System of Units (SI) • Catalog of Units 8th Edition, 2006 • Piezoelectric Energy HarvestingAlper Erturk / Daniel Inman (Wiley 2011) • Materials, Preparation, and Characterization inThermoelectrics, D.M. Rowe (CRC 2012) 19