need help with dead time in PWM

[dm927]

Does anyone know how to add deadtime in the attached PWM code?

 

[pike]

A dead time is a small period in the oscillation that totally cuts power to an output pin. I don't think this is needed, cuz i can't think of any reason you would want to do this.

A dead time is usually incorporated into Switch-mode power supplies, this stops both mosfets on the primary winding from firing on the same time.

If you did include the "dead time" the lo time would be extended, so if you had a 50/50 PWM this "dead time" period would alter the low time and aswell as the frequency.

Why do you need this dead time???

 

[dm927]

Some dead-time is needed for switching a full-bridge inverter. Probably about 1us.

 

[pike]

In that case, you can't do it. PIC's dont support a dead time in a PWM. The best way to do it is to do it manually.

I think there are 2 pins which you are using to switch simultanously on the PIC. You gonna have to incorporate a 1us when both pins are off.

to do this just incorporate a "nop" in between the transistions. Your gonna have to do the switching manually without using using the PWM module.

@ 4mhz, a "nop" will take exactly 1us
@8mhz, a nop will take exactly 500ns
....and so on