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voltage across the inductor in this circuit??

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sandeep_sggs

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Dear All,
i am trying to simulate following circuit. When i switch on the MOSFET momentarily at zero crossing of the Iin, and measure voltage across the capacitor(C1), am i not supposed to get response resembling a square wave?

I think momentarily switching the inductor at zero crossing of Iin, should flip the voltage across C1 and i should get a square wave across C1...
But i am not getting a square wave across C1...

Any suggestion how to get it?
 

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The goal is unclear. This looks as though it might resemble a current limiting circuit, to smooth current going to the diode bridge. However the inductor needs to be placed between the power source and the diode bridge.

Or is the purpose to boost voltage of the sinewave from the power source?

Additionally, it is hard to predict how much the N-mosfet turns on, with the inductor placed in its source leg. Since the bias of an N-device is referenced to the source/emitter leg, then biasing is more reliable and predictable if it has a direct path to ground.
 
How about making one step back and explaining the intended circuit function. Whatever it is, I'm quite sure that it can't be achieved by the given circuit.
 

Actually, i have fig.1, where shaded portion(of Ip) is lost and is not available to flow through the output capacitor. To improve this fig2 has a switch across the piezo-harvester equivalent circuit, which turns on at zero crossing of input current Ip and hence the shown waveform in fig.2 and hence the amount of charge not available for output capacitor is reduced (shaded portion in waveform).
Similar is the working of fig3. and fig3 is intended to reduce the shaded portion by flipping the voltage across the inductor instantaneously. I do get similar simulated response for fig1 & 2 but not for fig3.

any help?
 

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I understand that the switched inductor circuit can fast discharge Cp and precharge it to opposite polarity. But as already guessed, the post #1 circuit doesn't work as intended, for two reasons.

- the MOSFET shorts negative voltages by it's substrate diode
- wrong connection of gate pulse source

You can use a pair of "antiserial" MOSFETs (source-source and gate-gate parallel) and a floating voltage source between source and gate node.
 
If you're not clear about MOSFET behavior, simply watch Id and Vds in your simulation.

Possible bidirectional switch configuration

antiserial.png
 
Yes, the M1 switch in the diagrams needs to be a proper AC switch, i.e. 2 mosfets connected source to source...
 

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