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I used LTspice to simulate a oscillator circuit to convert DC to AC. The oscillator is then connected to a class AB power amplifier to increase the circuit current. The load of the Class AB amplifier is two coupled inductors to simulate wireless charging pad. The other side of the coupled inductor is connected to a rectifier circuit to convert AC back to DC.

This is the LTspice circuit:

enter image description here

This is the simulated waveform:

enter image description here

V(n005) is the voltage output of oscillator circuit and input of class AB amplifier

V(n006) is the voltage output of class AB amplifier.

V(n009) is the voltage output of rectifier circuit.

Based on the simulation results, I have some questions:

Is the output of the class AB amplifier supposed to look like this?

Why is the output of the rectifier circuit so low?

For the output of the oscillator circuit, what should I do to make a DC offset so the the AC voltage can be completely positive?

Would doing this increase the output of the rectifier circuit?

Overall, how do I improve on this circuit?

JYelton
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Jeremy
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1 Answers1

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The first problem is that the DC output level feeding the primary inductor MUST BE 0 volts. However, your push-pull output is delivering (or trying to deliver) an average voltage level at around 10 volts DC. So, put a 100 nF capacitor in series with the output that feeds the primary inductor.

Then, try raising the amplitude of the oscillator's 100 kHz waveform up to the point where you see significant distortion on the voltage across the primary inductor.

Then you should parallel tune the primary inductor to make it resonant at 100 kHz and then reduce the coupling coefficient on the transformer to something like 0.1 to be more realistic.

Then, you'll probably find that you will need to parallel tune the secondary inductor with a similar capacitor to that used for tuning the primary inductor.

These are all basic things that you either MUST DO or, give significant performance benefit or, make the simulation more realistic.

Andy aka
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  • The 100nF capacitor is added to the output of the class ab amplifier? Before the coupled inductor? Raising the amplitude of the oscillator's 100khz waveform is raising the voltage amplitude? – Jeremy Jul 22 '23 at 06:56
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    *put a 100 nF capacitor in series with the output that feeds the primary inductor*. The output of the oscillator section should connect to the amplifier input via a potentiometer (or resistor divider) to ensure that optimum drive levels are used without causing too much distortion on the output @Jeremy <-- presumably you saw the two comments on other questions addressed to you? – Andy aka Jul 22 '23 at 09:17