Brian: I have a customer who is asking "why would I select a galvanically isoalted gate driver over an optocoupler driving a high-voltage gate driver?" Can you help me answer this question?
Rachel: A concern with using an optocoupler driving a high-voltage gate driver is that the gate driver relies on junction isolation to separate voltages in power supply application, and parasitic inductance in the circuit can cause the output voltage to go below ground during a switching event. I have attached a schematic diagram on High Voltage Half Bridge Gate Drivers from an article I wrote on Half-Bridge gate drivers, which shows where the the Vs voltage is which can go negative during the switching event. When this happens with a device using junction isolation, if the circuit inductance causes the Vs voltage to go sufficiently negative, the high-voltage driver can latch-up and become permanently damaged. Using a galvanically isolated gate driver, like the ADuM3223, the Vs voltage can go negative and this gate driver will not latch-up and continue operation as long as absolute maximum voltages are not exceeded.
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