Comparison of charge pump circuits for half-bridge inverters

Charge pumps can be used to generate floating voltage supplies owing to their low input to output voltage drop and circuit simplicity. When used to power the high-side circuitry of half-bridges, the charge pump circuit can be simplified significantly by replacing the function of the dedicated pump oscillator with the switching action of the half-bridge output voltage. Three classes of the auto charge pump are identified, and a model is derived for each of the circuits. Using the model, auto charge pump circuits are designed for use in a half-bridge inverter and tested. The tests show a good match between the models and the experimental results. Finally, a comparison of the the various auto charge pump circuits is made.