Anyone know of a good variable driver?

[FPS]

Maybe it just is too hard to do but does a good flyback driver that has variable frequency and duty exist? from what I've seen they all break down at higher frequencies going from a nice square wave to an awful slope l\l\l\l\l\l\ at the trailing edge.

I've tested dimmers, and the expensive variable frequency "0.01-1.5MHz" PWM from RMCybernetics but it craps itself and cannot maintain anything that looks like a square wave beyond 1kHz.  Its writeup is good https://www.rmcybernetics.com/shop/cyber-circuits/pulse-generators/pulse-modulator-ocxi but really doesn't deliver, its decent for ignition coils though.

This is the only other one I've found with both variable freq. and duty. https://www.elecbee.com/en-31968-YF-22-PWM-Dimming-Speed-Controller-Module-Frequency-Duty-Ratio-Pulse-Adjustable-Square-Wave-Rectangu?search=frequency I've ordered but isn't here yet.

I've tried this one, ZK-PP2K PWM https://www.ebay.com.au/itm/403032556643 it's an extremely weak driver.

I've also tried switching a mosfet with a signal generator, it works but is weak.

Any schematics or modules with variable freq.?

[Mads Barnkob]

"Good" depends on your use-case. I designed and a flyback driver with a 38 kHz to 150 kHz range, based on TL494: https://kaizerpowerelectronics.dk/high-voltage/tl494-flyback-driver/

[FPS]

Thankyou Mads, it seems to perform well. So its a 12v driver that switches rectified mains like the RMcybernetics one above but looks to actually give a square wave.

What limited its lowest frequency to 38kHz? Is it a huge leap to get that down to 10kHz or so?

[Mads Barnkob]

I seem to recall that it was a trade-off between bandwidth and duty-cycle, but I honestly don't remember.

I did also make a TL494 calculator that would fit perfect for your design questions https://kaizerpowerelectronics.dk/calculators/tl494-calculator/

[FPS]

For arguments sake, if you could have a "universal driver" would you prefer a variable square wave +10/0, an alternating square +10/-10, or a sinusoidal wave? or other?

I've noticed some square waves perform very well like dimmers, and some not at all or extremely weakly like motor speed controllers. I've tried numerous types and I'm not sure why.

[NyaaX_X]

It may not good enough -- A comparator schmitt oscillator with triangle wave - voltage level dutycycle controller like this --


That is from Electroboom's article https://www.electroboom.com/?p=575.
And you can try other faster comparator, and simulate them on the SPICE software first to check the waveform.

[FPS]

This is the only other one I've found with both variable freq. and duty. https://www.elecbee.com/en-31968-YF-22-PWM-Dimming-Speed-Controller-Module-Frequency-Duty-Ratio-Pulse-Adjustable-Square-Wave-Rectangu?search=frequency I've ordered but isn't here yet.

The above didn't work, set to 16kHz 50% it was a weak driver that quickly went up in a puff of smoke.

[FPS]

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This is a mosfet driven from a signal generator which seems to work quite well, at least for ignition coils.

I have an older version schematic as attached, but am wondering what the improvements in the video one are? I see a capacitor has been added but where and for what purpose?.