Re: Mosfet and HV coil burning µC
Posted: Fri Jun 07, 2019 3:46 pm
It is hard to know what is the best method or device to use. It would be very helpful to be able to see what kind of pulses are riding on the battery voltage when the bike is in operation.
I would put a 1mH inductor in series with the input. That will give some separation, a reduction, of the energy the clamping device needs to handle. The value can be evaluated when running the board. This may not necessarily be the best approach, just one that I have used in the past.
I changed the schematic to what I would do. I would not try and clamp the power for the ignition coils. I would add a series inductor, then clamp the voltage for the regulator input as well as the driver chip.
Crude edit, but it is the best I can do.
A few years ago I designed the electronics for an electric motor driven sand and salt spreader. For sanding streets and parking lots in the winter. There was a conveyor motor and a spinner motor. The conveyor was a 3/4 hp motor. The rated running current was 55 amps at 12 volts. The electronics and firmware limited the starting current to about 120 Amps. The spinner motor was 1/3 hp. I the running current was about 30 Amps. The operator was able to set the speed of the spinner and conveyor with a Bluetooth app.
There was three mosfets for the spinner motor. Four (and another four for the reverse direction) on the conveyor. I used gate drivers like in the above design. I used 12 Ohm resistors in series with the gate of each mosfet.
The motors used created high power transients. I had three stages of filtering/clamping to deal with the transients. High power transorbs, resistor with series capacitor as a snubber circuit, and back emf diodes (big) across the motors. It was an interesting project.
I would put a 1mH inductor in series with the input. That will give some separation, a reduction, of the energy the clamping device needs to handle. The value can be evaluated when running the board. This may not necessarily be the best approach, just one that I have used in the past.
I changed the schematic to what I would do. I would not try and clamp the power for the ignition coils. I would add a series inductor, then clamp the voltage for the regulator input as well as the driver chip.
Crude edit, but it is the best I can do.
A few years ago I designed the electronics for an electric motor driven sand and salt spreader. For sanding streets and parking lots in the winter. There was a conveyor motor and a spinner motor. The conveyor was a 3/4 hp motor. The rated running current was 55 amps at 12 volts. The electronics and firmware limited the starting current to about 120 Amps. The spinner motor was 1/3 hp. I the running current was about 30 Amps. The operator was able to set the speed of the spinner and conveyor with a Bluetooth app.
There was three mosfets for the spinner motor. Four (and another four for the reverse direction) on the conveyor. I used gate drivers like in the above design. I used 12 Ohm resistors in series with the gate of each mosfet.
The motors used created high power transients. I had three stages of filtering/clamping to deal with the transients. High power transorbs, resistor with series capacitor as a snubber circuit, and back emf diodes (big) across the motors. It was an interesting project.