Electronics > Beginners
Powering a regulated 12V Fan with a 24V PWM power supply, help please :-)
Efe_114:
I would limit the max duty cycle to 50% and use a chunky cap to smooth it to 12 volts but it wouldnt be so proffesional
Zero999:
--- Quote from: Efe_114 on November 28, 2018, 05:53:33 pm ---I would limit the max duty cycle to 50% and use a chunky cap to smooth it to 12 volts but it wouldnt be so proffesional
--- End quote ---
An inductor would be required to smooth a 24V 50% duty cycle waveform to 12VDC, just adding a huge capacitor results in massive current surges, every time it's charged and very little smoothing.
David Hess:
Two fans in series will likely work fine. If necessary, a 15 to 18 volt zener diode or TVS can be placed across each one to limit peak voltage but if you do this, use a higher power zener or TVS.
Is the 24 volt output actually chopped? If so, usually a simple LC filter will be on the output to produce rough DC because otherwise the PWM output end up driving any capacitance in the DC brushless fan which is a problem.
spec:
--- Quote from: David Hess on December 02, 2018, 12:24:56 am ---Two fans in series will likely work fine. If necessary, a 15 to 18 volt zener diode or TVS can be placed across each one to limit peak voltage but if you do this, use a higher power zener or TVS.
Is the 24 volt output actually chopped? If so, usually a simple LC filter will be on the output to produce rough DC because otherwise the PWM output end up driving any capacitance in the DC brushless fan which is a problem.
--- End quote ---
Well said :-+
Prokktor:
Solution 3 (MosFet + 12V Power Supply) works absolutely perfect, so I did not even try the other.
Thanks a lot for your help.
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