Abstract: A low cost switching mode power supply particularly adapted for use in an electric vehicle is characterized by an extreme input voltage range, immunity to high input voltage transients, and stable operation. A negative voltage feedback arrangement applied to a controllable voltage clamp serves to continuously vary oscillation pulse width and frequency. The power supply includes an output filter capacitor, and, to compensate for phase lag introduced by the output filter capacitor, the negative feedback arrangement includes elements for introducing phase lead compensation. Preferably, the oscillation period is less than the duration of expected input voltage transients, and the power supply regulates right through such transients.