Pwm of regulated output.

[sureshot]

I've never tried this, so just some advise if anyone can help. Can I pwm a smps using a pwm unit to control the smps voltage for DC motor control. All is 12 volts. Smps is a converted server psu, the pwm unit has a 2.5 - 35 volt input, load on the modual is 6.5 Amps maximum. Would the pwm unit cause issues with the smps. Thanks any help appreciated.

 

[Harald Kapp]

This cannot be generally answered. Some power supply circuits can be adjusted using pwm, others need a DC voltage. Of course you can generate a DC voltage by low-pass filtering the pwm.

A much more efficient approach, however, is to use the pwm directly to switch the fixed 12 V DC voltage to the motor and control the motor's speed by adjusting the pwm's duty cycle. This will reduce losses in the (as far as I know) best possible way.

 

[sureshot]

Thank you Harald. I was looking to control the final 12 volt out put of a converted server psu. Putting the smps regulated voltage into the unit in the picture. It would be a model railway DC controller I would build with reverse toggle switch, making use of the few converted server power supply's I already have. I wandered if the server smps might not like this type of voltage attenuation.

 

[Harald Kapp]

I think I understand your original post now better.

A computer power supply "sees" a lot of switching noise from the regulators on the mainboard, graphics card etc. So it is perfectly suited to drive a pwm controller as you show.

 

[sureshot]

Thank you Harald for your help, much appreciated.