Fuel Injector Firing circuit/Clamping circuit?

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oscaryu1

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Hi there,

I was looking for some input as to what the two diodes in this circuit does:



I believe they're for clamping, but I'm not sure. The input is just a thermistor.

The following is a fuel injector driver (low side driver):



Is the reason there isn't a freewheeling diode because the injector needs a quick turnoff? If this is true, would you forego the diode for a FET of adequate Vds rating?

Thank you!

Best,
Oscar
 


Yes the diodes in the first picture are standard clamps which keep the signal at a voltage between those two rails.


I don't know enough about the load (I.E whether it may have some protection itself) in the second picture but note that that's a "protected mosfet". It has active clamping at 40V.
 

A half bridge driver ensures low impedance rise/fall times and bipolar rail diode clamps clip the back EMF voltage outside the rails to 1 diode drop. Off driver state is used between pulses.
 

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