Driving circuit with improved startup performance, power conversion circuit comprising the same and driving method for power switching device

A power conversion circuit, comprising:

• a high-side power switching device comprising a first terminal, a second terminal and a control terminal, wherein the first terminal of the high-side power switching device is configured to receive an input voltage;
• a low-side power switching device having a first terminal, a second terminal, and a control terminal, wherein the first terminal of the low-side power switching device is coupled to the second terminal of the high-side power switching device, and the second terminal of the low-side power switching device is coupled to a reference ground;
• a high-side driving circuit for driving the high-side power switching device, coupled to the control terminal of the high-side power switching device, for controlling the turn-on and turn-off switching of the high-side power switching device, wherein the high-side driving circuit comprises:
• an input terminal, configured to receive a high-side switching control signal;
• an output terminal, coupled to a control terminal of the high-side power switching device and configured to provide a high-side driving signal to control turn-on and turn-off switching of the high-side power switching device;
• and a power supply terminal, configured to receive a bootstrap voltage;
• wherein the high-side driving circuit is configured to:
• in a startup phase or an initialization phase of the high-side driving circuit, output the high-side driving signal after a delay period has elapsed since the bootstrap voltage reaches or exceeds a first under-voltage threshold;
• and in a stable operation state of the high-side driving circuit, stop outputting the high-side driving signal in response to the bootstrap voltage becoming lower than a second under-voltage threshold, wherein the first under-voltage threshold is lower than the second under-voltage threshold;
• a low-side driving circuit, coupled to the low-side power switching device, for controlling the turn-on and turn-off switching of the low-side power switching device;
• and
• a bootstrap capacitor coupled between the power supply terminal of the high-side driving circuit and a common terminal of the high-side power switching device and the low-side power switching device and configured to provide the bootstrap voltage for the high-side driving circuit.

A method for operating a high-side driving circuit, wherein the high-side driving circuit is provided with a supply voltage by a bootstrap capacitor and is configured to output a high-side driving signal to drive a high-side power switching device, wherein the method comprises:

• detecting whether the supply voltage becomes higher than a first under-voltage threshold in a start-up phase or an initialization phase of the high-side driving circuit;
• outputting the high-side driving signal after a delay period has elapsed since the supply voltage reaches or exceeds the first under-voltage threshold;
• detecting whether the supply voltage becomes lower than a second under-voltage threshold during a stable operation state of the high-side driving circuit;
• and
• stopping outputting the high-side driving signal when the supply voltage becomes lower than the second under-voltage threshold, wherein the first under-voltage threshold is lower than the second under-voltage threshold.