Half bridge circuit with bootstrap capacitor charging circuit

A method of using a half bridge circuit, the half bridge circuit comprising:

• a low side GaN-based transistor having a low side transistor gate,
• a high side GaN-based transistor having a high side transistor gate, and
• a GaN-based semiconductor circuit configured to allow current to flow from a ground referenced power supply node to a first floating power supply terminal, wherein the semiconductor circuit comprises:
• a first transistor, comprising:
• a first transistor gate,
• a first transistor source connected to the ground referenced power supply node, and
• a first transistor drain connected to the first floating power supply terminal,
• the method comprising:
• controlling a low side transistor gate voltage at the low side transistor gate with a low side gate signal;
• controlling a high side transistor gate voltage at the high side transistor gate with a high side gate signal;
• and
• controlling a first transistor gate voltage at the first transistor gate with a gate drive circuit control signal,
• wherein the gate drive circuit control signal is configured to:
• A) cause the first transistor to become conductive while the low side gate signal causes the low side GaN-based transistor to be conductive,
• B) cause the first transistor to be conductive while the low side gate signal causes the low side GaN-based transistor to be conductive,
• C) cause the first transistor to become non-conductive while the low side gate signal causes the low side GaN-based transistor to be conductive, and
• D) cause the first transistor to be non-conductive while the low side gate signal causes the low side GaN-based transistor to be non-conductive.