@crutschow, I have learned a lot from your comments on other Zener snubber posts and I kindly request your input regarding the selection of suitable diodes in the application below.
I thought I had finally found a good Zener and diode that could withstand the high current of this inductor kickback, but I soldered these SMD components onto a protoboard and the solenoid fired nicely 5-6 times and then I fried the MOSFET (magic smoke). Modeling in LTspice, I think maybe the voltage on the drain spiked high enough to fail the MOSFET. The voltage on the MOSFET drain is exceeding 80V and the Zener is only conducting 90mA of current. Is this because the kickback is fast and the Zener can't break down fast enough? I thought the voltage would clamp at 30V (Zener breakdown voltage for SZ1SMB5936BT3G) + 19V (Vcc) or approximately 50V. The MOSFET is rated 70V. Here is blue trace current through the coil, green trace voltage at the mosfet drain, and red trace current through zener.
Theoretically, I would want to see this (modeled with default components):
Could a TVS diode replace the Zener in this application and begin dissipating the kickback faster than the Zener as the voltage spikes up? Or do you think the Zener I picked breaks down fast enough and the MOSFET failed for other reasons like bad heat dissipation?
The inductor is solenoid B11HD-255-B-3. It is rated 19V, 90W, 4.75mH, 4.3 Ohms, 10% duty cycle
Are these calculations correct?:
Inductor energy storage E = 1/2 * L * I² is approx. 0.048 J. I would like to turn off the solenoid in 0.5 ms. 0.048J/0.0005s = 96W. So, I want to dissipate 96W over 0.5ms.
I thought I had finally found a good Zener and diode that could withstand the high current of this inductor kickback, but I soldered these SMD components onto a protoboard and the solenoid fired nicely 5-6 times and then I fried the MOSFET (magic smoke). Modeling in LTspice, I think maybe the voltage on the drain spiked high enough to fail the MOSFET. The voltage on the MOSFET drain is exceeding 80V and the Zener is only conducting 90mA of current. Is this because the kickback is fast and the Zener can't break down fast enough? I thought the voltage would clamp at 30V (Zener breakdown voltage for SZ1SMB5936BT3G) + 19V (Vcc) or approximately 50V. The MOSFET is rated 70V. Here is blue trace current through the coil, green trace voltage at the mosfet drain, and red trace current through zener.
Theoretically, I would want to see this (modeled with default components):
Could a TVS diode replace the Zener in this application and begin dissipating the kickback faster than the Zener as the voltage spikes up? Or do you think the Zener I picked breaks down fast enough and the MOSFET failed for other reasons like bad heat dissipation?
The inductor is solenoid B11HD-255-B-3. It is rated 19V, 90W, 4.75mH, 4.3 Ohms, 10% duty cycle
Are these calculations correct?:
Inductor energy storage E = 1/2 * L * I² is approx. 0.048 J. I would like to turn off the solenoid in 0.5 ms. 0.048J/0.0005s = 96W. So, I want to dissipate 96W over 0.5ms.