Thread Starter


Joined Jun 11, 2008
I am working on a motor control project and need to convert a DC control signal into a PWM signal to drive a MOSFET. The DC signal is coming out of an analog PI controller.

Is there a simple way to do this? I have looked at some 555 timer circuits, but haven't found good design equations. I need an almost 0 - 100% duty cycle on the PWM. What voltage range corresponds to those duty ratios on a typical 555 (pin 5 I believe)?

Are there chips I can buy to just make the conversion? Am I better off building my own triangle wave oscillator and comparator PWM circuit?

Any help is much appreciated. Thanks.


Joined Apr 19, 2007
Hi there.

Easiest way to do this, is to use microcontroler. One of the 8 pin devices from microchip will do it. Just read the A to D, convert it to PWM with a few code lines. 0 to 5 volts will give you 0 to 100% duty cycle.