Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.
As you can see, in PWM the frequency is fixed while the duty cycle is proportional to the control voltage. In PPM the frequency is inversely proportional to the control voltage and the duty cycle is proportional to it while the time off is fixed.