LibreSolar / mppt-2420-rc

Solar/Wind MPPT charge controller for DIN rail mounting
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Q8 gate drive via half bridge driver via not sufficient #14

Open martinjaeger opened 4 years ago

martinjaeger commented 4 years ago

Already in previous MPPT designs, the reverse blocking MOSFET (here: Q8) was supplied via the low-side gate driver of the half bridge, switching it on automatically when the power stage is on.

In this design the reverse blocking MOSFET can be used also as a dump load switch for wind turbine applications (with the generator negative connected via separate terminal W-), so it should be possible to switch it on even if the power stage is off. R12 allows to supply power directly from the 12V rail.

Unfortunately, the 10k pull-up resistor R45 necessary for this use case prevents the MOSFET Q8 to stay on if powered by the low-side driver, especially at low duty cycles.

Preliminary solution: