Half Bridge Driver

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sciencedude1990sciencedude1990 04/25/2024 at 03:220 Comments

Built a half-bridge driver based on the MPS MP18021.  I like the MP18021 because the SW pin is tough.  It can go to -5 V, in case there is something pulling down the switch voltage.  Also, it has the diode built in for the VDD to BST path, so that saves a part.

I drove the INH and INL from a raspberry pi pico (PIO programmed), and tested it with 2 Ohms of resistance.  The 8x8 powerpak transistors have quite a lot of gate capacitance, so you can drive a few hundred kHz, but beyond that the MP18021 starts getting kind of warm.  A few MHz and it will go into thermal shutdown.

I am debating a full bridge versus a flyback design for the DC/DC converter, and I think I'll probably go with the flyback, but building the half bridge is kind of fun since you can re-purpose them for other projects like motor drivers.  At the bottom was a TC620CVOA for checking the board temperature, and that worked as expected.  It is a super simple chip - if the temperature passes a setpoint, it outputs a voltage.  That is the third wire going to the raspberry pi pico for monitoring (the TC620VCOA is powered from 12 V, so there is a voltage divider at the output to match with the 3.3V of the pico).