4 Design Recommendation

To achieve this design properly, V₂ must be larger than V₁.

When V₂ is larger than V₁, bootstrap diode can keep reverse bias all the time which means V₁ can only provide power to internal circuits of gate driver and low side FET. Energy to drive high side FET can come from V₂.

Based on the previous analysis, we can also improve the current ability of gate driver to avoid the risk. The suggestion is to add external bootstrap diode such as Schottky or fast recovery diode.

Or we can just use half-bridge gate driver without built-in bootstrap diode. Because in this design, bootstrap diode can always work in reverse bias, so we can just simply remove this diode and the requirement of power supply’s amplitude can not exist. For example, we can use UCC27888 to simplify the design process.