Fan PWM to DC voltage converter

[Topher]

Wondering if anyone had a solution to driving cheapy 2 wire dc fans with PWM. We go through a lot of fans here because the PWM seems to destroy them. I was looking at making a converter to convert my 24v pwm signal to a DC voltage that varies by PWM duty. Ive tried making some inductors with a flyback diode and it works pretty well but because I need roughly 1k turns of wire, the coil just becomes a big resistor at full power not allowing the fan to spin to its full RPM when needed. With duet, the fan PWM is limited to 65khz which is pretty low for the inductor route so I started hunting for an electronic solution. I found this little circuit which is a good starting place.

I need to make 60pcs, one for each of our duet printers so it will be worth putting in the effort to layout something and have JLC PCB run some boards.

[alankilian]

@leckietech Maybe this thread will help:

https://forum.duet3d.com/topic/21680/designing-a-pwm-to-analog-mini-board-for-fans/8?_=1628813976498

[Topher]

@alankilian oh wow, long thread. Can't believe I missed it. Thanks!