A feedback loop regulated bootstrap driver circuit with improved drive capability for high voltage buck DC-DC converter

A novel bootstrap driver circuit applied to high voltage buck DC-DC converter is proposed. The gate driver voltage of the high side switch is regulated by a feedback loop to obtain accurate and stable bootstrapped voltage. The charging current of bootstrap capacitor is provided by the input power of the DC-DC converter directly instead of internal low voltage power source, so larger driver capability of the proposed circuit can be achieved. The bootstrap driver circuit starts to charge the bootstrap capacitor before the switch node SW drop to zero voltage at high-side switch off-time. Thus inadequate bootstrap voltage is avoided. The proposed circuit has been implemented in a high voltage buck DC-DC converter with 0.6 µm 40 V CDMOS process. The experimental results show that the bootstrap driver circuit provides 5 V stable bootstrap voltage with higher drive capability to drive high side switch. The proposed circuit is suitable for high voltage, large current buck DC-DC converter.