Electronics > Beginners
Filtering PWM to smooth DC
wraper:
--- Quote from: Rapsey on October 01, 2018, 05:19:16 pm ---I also came across this article which offers a more complex circuit to convert PWM to linear voltage to reduce acoustic noise. I'm still trying to wrap my head around it. It's interesting that he was able to do it without resorting to large capacitors even though his PWM frequency is a measly 93.5Hz. I'm not sure why he inverted the output though (100% PWM = 0V), that's something I could do without.
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This is what I was suggesting. Convert PWM to DC for control and go linear. In your case you can do it simpler. You don't have tachometric output from the fan so you can control voltage on the GND side as well.
--- Quote ---It's interesting that he was able to do it without resorting to large capacitors even though his PWM frequency is a measly 93.5Hz
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Nothing interesting. Just normal design contrary something abnormal you tried to do.
Zero999:
--- Quote from: Rapsey on October 01, 2018, 05:19:16 pm ---I also came across this article which offers a more complex circuit to convert PWM to linear voltage to reduce acoustic noise. I'm still trying to wrap my head around it. It's interesting that he was able to do it without resorting to large capacitors even though his PWM frequency is a measly 93.5Hz. I'm not sure why he inverted the output though (100% PWM = 0V), that's something I could do without.
--- End quote ---
It also requires an extra power wire, which I thought you wanted to avoid.
Here's another possibility which will give as lower voltage loss as possible, using only jelly-bean parts. It does this by using a common emitter amplifier on the output and a differential pair input. The simulation says it can go from 0.6V to 11.58V, with a 12V input. If lower loss is required, the Schottky diode can be replaced with an ideal diode MOSFET rectifier circuit.
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