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I am trying to make a simple circuit to control two MOSFETs with only one PWM generator.

I would like to send the red waveform to the PWM generator and I would like that after a simple circuit the MOSFET A and the MOSFET B receive respectively the green and blue waveform.

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Do you have a simple tip or do you know an IC which do this ? I would like to modify the frequency of the input PWM waveform without changing the circuit.

I was thinking about something which could keep the PWM high until the next rising edge, but I am not able to find this, and an AND gate. Like this :

enter image description here

Is there a better way?

JRE
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Jess
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  • Which PWM generator? Sounds like you just need a MCU with enough timers and PWM channels per timer to generate any waveform you want and you don't even need the existing PWM generator. – Justme Jun 12 '22 at 11:17

1 Answers1

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Maybe try simulating this circuit first to try out various scenarios. I've just tested a couple: -

enter image description here

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The microcap simulation uses D type flip-flops to divide-by-two. Inverter U8 ensures that the two flip-flops work on alternate clock edges from X1. Then I've ANDed each flip-flop output with the original clock input. The above is a 100 kHz clock with a duty of 10%. Here's a 1 MHz clock: -

enter image description here

Remember, this is just a simulation and, in the extreme situation of really fast clocks, there will be duty cycle errors and processing delays.

Update - simplification suggestion from jp314: -

enter image description here

Andy aka
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    Be careful with that circuit - the upper DFF can generate a glitch on the output. If Q=1 and clock rises, then the AND will see a 11 until the DFF toggles. Depending on components, this may propagate to the output. Instead just use the lower DFF (clocked on FALLING edge); one output signal is clock AND Q, the other is clock AND Qb. – jp314 Jun 12 '22 at 16:12
  • @jp314 I might just add that modification later! – Andy aka Jun 13 '22 at 15:01