Hello all. The issue of PWM has been discussed many times in the context of driving motors but still havent been able to understand how one calculates the PWM cycle time.

For 70% duty cycle -

PWM cycle = 1second. PWM ON = 700ms and PWM OFF = 300ms
PWM cycle = 100ms. PWM ON = 70ms and PWM OFF = 30ms
PWM cycle = 10ms. PWM ON = 7ms and PWM OFF = 3ms

in all the above cases V[avg] = 0.7 x V .

So would be very grateful if someone could explain how one arrives at the optimum value of PWM cycle