A Study on the Negative Supplying Voltage for Floating Switches using Charge Pump Capacitor with Bootstrap Circuitry

The unipolar gate driving method provides a low cost and simple solution for inverter system design. However, the unipolar gate driving can cause issues like ‘parasitic oscillation’ during turn-on of power switches and ‘unintended parasitic turn-on’ caused by the Miller-effect of power semiconductors. Hence the maximum value of gate resistance has to be limited. The proposed bootstrap circuit can generate a negative gate voltage with minimal increase of components. For this purpose a charge-pump circuitry is merged with a standard bootstrap topology which can generate a negative as well as a positive gate voltage for floating switches without additional isolated power supply.