Protecting the LTC3780 (or other DC/DC converter)

The main problem when playing with LTC3780 (or other) is it can fry easily.
Especially when you are playing with the feedback loop.

How so ?

Easy, just disconnect the feedback pin, it will crank up the output voltage to the max and burn
As a bonus, it will also fry what's connected to it if they don't like higher voltage.

So here, we'll add a very simple protection circuit :

  • An enable pin that turns the LTC off by default, i.e. if the signal is not driven
  • A shutdown circuit if the output voltage exceeds ~ 28v

The right side is glued to the DC/DC converter
The left side is on the control board.

If the Enable pin is high (or floating), the STBY pin is pulled down and the DC/DC turns off
Similarly, if Vout exceeds ~ 26 V, STBY is pulled down, and the DC/DC turns off

Very primitive, but that should help when connecting/disconnecting stuff all the time

NB: If you use another N-FET (Q4), you'll have to change R9 to something else

Test setup with a very cheap boost/buck converter that i can afford to fry :


It is far from perfect as the output will still go to 27v when the feedback is not driven, but it's better than 60 V and death



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