Increasing Electrical Damping in Energy Harnessing Transducers
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2. Limitation of the present system
3. Suggestion that is offered
5. Ambient energy
6. Electrical damping
7. Electrostastic transducers
8. Electromagnetic transducers
9. Piezoelectric transducers
Focuses on the need for energy investment.
Boosting of output power by increasing damping
Transducers included : electrostatic, electromagnetic,
Limitations of the present system
Wireless micro sensors use small batteries to meet the power
Miniaturized batteries unfortunately exhaust easily.
This limits the deployment of the micro sensor devices
to few niche markets.
Increase in the budget.
Suggestion that is offered
Harnessing ambient energy .
Increasing the electrical damping force against which
the transducers work.
Investing energy to increase the damping.
Converts one form of energy to another.
Can be any conversion.
Used for measuring purposes.
Also known as Energy Scavenging or Power Harvesting.
Process of obtaining energy from environment.
Classified as Energy reservoir , Power distribution or Power
Enable battery independent wireless or portable systems .
Investing voltage in capacitor or current in inductor
raises damping force.
Rise in voltage or current → rise in battery investment →
square of voltage or current.
EF - EINV rises with VINV and I INV.
Removed capacitors and replaced
Synchronous on chip MOSFETs.
SEPD and SEND close during positive half cycle.
Energizes LS through Lp.
SEPD and SPD close and SEND opens : negative half
Depletion of Ls energy to VBAT.
Current reverses ; invests into LS.
SEND closes and SPD opens.
Current increases below IINV by ΔiL.
Invested into VBAT
Cycle concludes .
Final energy = 0.5LS(IINV +ΔiL)2
ΔiL ≈ 2VEMF.S(PK)/ωoLs
At 0.06, Po increases iff IINV<400µA.
AT 0.03, Po peaks at 750µA.
Kc << 1,conduction losses increases.
Investment below threshold holds
CVAR precharged by energy investment.
Used to establish electrostatic attraction
and opposes physical movement.
Vibrations produces energy ; FDE is
FDE increases as square of vc ;also EC.
Implies higher voltage induces more
More damping ⇒ more output power.
vc close to VMAX ⇒ more energy
TYPES OF CONNECTIONS
PERMANENT CONNECTION :
Constraining CVAR voltage with Li battery :
no additional capacitor needed.
disadvantage : VBAT not the max voltage sustained.
CCLAMP used to overcome the above difficulty.
Tx invest energy EINV from VBAT : precharging both capacitors.
Discharges after harvesting cycle.
CCLAMP >> CVAR, more conduction losses.
ASYNCHRONOUS CONNECTION :
TX charges CVAR near VMAX before the other..
Higher than CCLAMP high voltage.
Interface circuit transfers energy from CCLAMP to VBAT.
Less energy transfer.
Diode dissipates power.
TX charges CVAR to CCLAMP initial
S3 closed ; energy extracted into
TX discharges CVAR to VBAT
De energizing less often
S3 dissipates less power.
Cvar remains near to VMAX.
PIEZO ELECTRIC TRANSDUCERS
Charge generated in response to mechanical
OC current energizes and de energizes CP.
CP charged to VBAT + 2VD.
Excess flows through rectifier.
Unloaded : CP charged to 2VOC CP .
Loaded : excess charge to VBAT .
BATTERY COUPLED DAMPING
EH =2(QOC – 2VBAT CP )VBAT
LRE and SRE included.
CP ‘s energy recycled in the opposite
Positive half cycle : CP charged to
Negative half cycle: SRE closes ; LRE
de energizes CP .
Collects all of QOC .
SRE dissipates energy.
EH = 2QOC VBAT =4CP VOC VBAT
BATTERY DECOUPLED DAMPING
Decouple VBAT : increased damping
Vibrations charge CP to max value.
Discharges through LH and DN in
LH and DI negative cycle.
De energizes to VBAT .
Cp energizes with 2VOC in half cycle.
Twice as EH
’ and 4 times EH
Energy gained reinvested to other half.
Precharged CP to –2VOC .
Voltage increased to 4VOC .
Energy increases with square of voltage.
’’’ = 0.5CP (-4VOC)2
Increasing investment diminishes PO.
More energy transfer through
Conduction losses increases.
Enlarged FET’s balances losses ; raises
72000µm raised 56% PO .
Shows that investing energy increases output power.
Coupling factor of transducers low ⇒low power.
Invest energy to raise electrical damping.
Transducers draw more energy.
Limitation in increasing output power.
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