US Patent 7612602 Resonant gate drive circuits

A resonate gate drive circuit for driving at least one power switching devices recovers energy loss for charging and discharging the input capacitance of the power switching devices. The gate drive circuit charging and discharging the gate capacitor with a high level current, so the switching loss of the power switching devices can also be reduced. The gate drive circuit can clamp and keep the voltage across the gate capacitor to a certain level while the power switching devices turn on, and it can also clamp and keep the voltage across the gate capacitor to almost zero while the power switching devices turn off. The gate drive circuit comprises four small semiconductor bidirectional conducting switching devices connected in full-bridge configuration. An inductor is connected to the two junctions of the full-bridge configuration to help switching the current direction. A capacitor in series with the inductor is necessary for some applications. A bootstrap circuit, which is widely used in conventional gate drive circuitry, is also necessary for this resonant gate drive circuit when it is adopted for high-side and low-side applications.