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An Efficient Ac-Dc Step up Converter for Low voltage

Energy Harvesting

Under the guidance ofU.Krishna Prasad(Assistant Professor)

Batch No- EE8Miss.Zeba Anjum(11B71A0202)

ABSTRACT

An efficient A.C to D.C power converter that avoids the bridge rectification and directly converts the low input voltage to the required high D.C input voltage at higher efficiency.

The proposed converter consists of a boost converter in parallel with a buck boost converter.

The electromagnetic micro generators typically consists of a moving permanent magnet, linkage flux with a stationary coil.

The variation of the flux linkage induces A.C voltage in the coil.

The output voltage of an electromagnetic micro generator is sinusoidal .

Fig:- Schematic diagram of a resonance inertial micro generator.

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Fig:- Conventional two stage power conversion consisting diode bridge rectifier.

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Fig:- Direct A.C to D.C conversion.

The proposed converter consists of boost converter (inductor L1,switch S1 & Diode D1) in parallel with buck-boost converter (inductor L2,switch S2 & diode D2).

In this converter, the negative output to input voltage gain of buck boost converter is utilized to step-up the negative half input voltage of the micro generator to a positive high D.C output voltage.

Fig:- 2-switch H-bridge boost converter.

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Modes of operationMode 1 Mode 1 starts when

the gate drive voltage, Vg1 is high and the boost-switch, S1 is turned on.

The current in the boost-inductor, L1 starts to build from zero.

During this mode, gate drive voltage, Vg2 is low.

So, S2 is in ‘off’ condition and the diodes, D1 and D2 are also ‘off’.

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Mode 2

Mode 2 starts at the end of Mode 1 when Vg1 becomes low and S1 turns off.

During this mode, L1 forward biases D1 and its stored energy charges the output capacitor, C.

S2 and D2 remains ‘off’ in this mode.

It is to be noted that during Mode1 and Mode2, the input, applies reverse voltage across S2 but the higher forward voltage of the MOSFET body diode holds back any current conduction through it.

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Mode 3 In mode 3, the gate

drive voltage, Vg2 becomes high and S2 turns on.

The current in the inductor L2 builds in the negative direction.

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Mode 4 The MOSFET S2 is turned off in mode 4 and the inductor L2 forward biases the diode D2.

The energy stored in L2 charges the output capacitor, C.

The output capacitor C is charged in the same direction in each half-cycle.

So, the output voltage is DC because of the boost and buck-boost converter.

The boosted DC voltage is obtained in the output.

Waveform

Input voltage and the gate drive pulsed tothe lower switches (S1 and S2 ).

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ANY QUERIES

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