Hello,

I need 12V 8A power supply with ability to control output voltage through PWM.
First i thought of driving MOSFET with PWM at the output, but it seems, that this would interfere with frequency, at which SMPS is working.
My second theory is to modify existing SMPS to add PWM output voltage regulation.
Example SMPS would be cheap Chinese board with CR6842 IC for switching.
My question would be: is it possible to modify existing circuit to add PWM output voltage regulation,
or is it generaly better idea to drive the PWM regulation with MOSFET at the output?

To explain my goal: I would use driver from Ikea Zigbee Bulb to drive several meters of 12V LED strip.

 

I see the 12V power supply.
You have a 12V LED strip. There are many different types of LED strips. Please give us more information on the strip. Some are 5 volt and some are 12 volt. Some have a ability to get dimmer.
Please send information on the Ikea Bulb driver.

 

Ah yes. Power supply mentioned is SMPS board delivering DC 12V 8A (from 230V AC).
Led strip works on 12V 6A.
Ikea driver is best described in this article. Basically works on 3V3 and delivers PWM output on certain PIN.