Analysis of a charge pump power supply with a floating voltage reference

Charge pump circuits can be used to generate floating power supplies for th e high side circuitry of half-bridge inverters. Because of its small input to output voltage drop, the charge pump circuit supports a nide range of su pply voltages and is ideal for powering high side circuitry with low voltag e requirements. A model for the operation of the charge pump is derived, wh ich offers an improvement over previous models by accounting for the effect of a load current and which includes a variable pump oscillator duty term and current dependent diode models to allow for a more accurate prediction of the charge pump behavior More importantly, the model also predicts the c ritical effects of switching transients at the output of the half-bridge on the charge pump. The model has been verified against experiments and shows a good agreement, Using the model, a charge pump circuit mas designed for use as the high side power supply for a typical half-bridge inverter.