Electronics > Projects, Designs, and Technical Stuff
Run into a wall (3180 fet drive circuit)
T3sl4co1l:
In cases where the output isn't pulled down, and where (Vin - Vout) < rising UVLO threshold, you need either a charge pump to deliver a little high side power (maybe a '555 wired to a half-wave voltage doubler on the driver), or something to yank the switch node momentarily low (a synchronous switch would do, but it doesn't need to be operated synchronously, it can just be pulsed a few times).
Note that the bootstrap probably shouldn't be supplied from the full 18V. Not with a mere 20V rating on the driver. A 10-15V regulator could be inserted, if you don't have such a supply handy (to draw bootstrap power from) already.
Tim
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