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

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

Energy Applications Energy Source Energy Management Energy Application 3

Energy Applications Sensor Node Power Requirements: Supply Voltage: Vs Continuous Current: Ic Additional Pulsed Current: Ip Pulse Duration: tp System On Time: ton Number of Sequences: N Sequence Duty Cycle: DC Total Energy Bill: Courtesy Linear Technologies Corporation 4

Energy Applications Where is the sweet spot for maximum power transfer between Source and Load? What is the transferred power at that point? Courtesy Linear Technologies Corporation 5

Energy Applications Over time  decouple output and input: e.g. Caps/battery to buffer energy Storage Cap collects charge during Sensor Idle State. Acts as low impedance source when Power is needed. 1 2 Aux Cap collects charge before enabling VOUT control Over source parameter  control harvester input power e.g. Maximum power point control Adjust current to keep the input at the desired voltage. Effectively raises the input resistance of the Harvester when the load is overdriving the source. Known as MPPC for Solar Cells. 3 Courtesy Linear Technologies Corporation 6

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

Energy Applications Circuit Collections Advanced Linear Devices ALD110902 Source: Advanced Linear Devices Note: Circuits shown are for example purposes only. You must carefully verify circuitry used in your application. 8

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

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

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

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

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-up Transformer 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

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

Energy Applications Circuit Collections LTC3588 Piezoelectric Energy 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

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

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

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

Energy Harvesting Additional 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 Harvesting Alper Erturk / Daniel Inman (Wiley 2011) Materials, Preparation, and Characterization in Thermoelectrics, D.M. Rowe (CRC 2012) 19