I know why the drivers heat up

Posted on September 16, 2014

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Njay: I think I know what warms up more in the drivers. It must be the transistors that pull the N-FET up (to turn on), Q3 and Q8 in the schematics.

When it’s ON, pumping current into the capacitor that is the MOSFET gate, is dissipates a lot of heat because it is being fed from the battery voltage on one side and at most 12V on the other, capped by a zenner diode. Usually FET driving circuits are supplied with  a voltage that is matched to the gate turn-on voltage, so they don’t stress out too much, but here I had to invent this adaptation.

When time permits, we should try putting a resistor or zenner  to lower the voltage before the transistor, so that the heat is lost outside of it. We should divide (the power) and conquer (the heat).

(to be continued…)Lisbon_MMF_logos_Banner_big

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