A current averaging circuit for averaging a piecewise linear switching current waveform of a PWM power converter including first, second and third sample and hold circuits and a sample averaging circuit. The first sample and hold circuit samples a short duration of the current waveform for each PWM cycle and provides corresponding short samples. The second sample and hold circuit samples a long duration of each PWM cycle and provides corresponding long samples. The sample averaging circuit is coupled to the first and second sample and hold circuits, averages corresponding ones of the short and long samples and provides corresponding average values. The third sample and hold circuit samples each average value and provides a current average signal. The waveform may include ramp-on-a-step voltage pulses representing switching current. The current average signal is updated after each current pulse.