Hi All,
I'm switching a large inductive load (350h) at low frequency (2-30hz) with 12vdc. The resistance across the inductor is 4ohms. The switching circuit is 5v logic (avr) and a pair of P channel mosfets in parallel. For a snubber, I have been using a byw29e (http://www.nxp.com/documents/data_sheet/BYW29E_SERIES.pdf) wired anti parallel across the inductor immediately proximal to where the inductor connects to the pcb. Looking at it on my low res scope I thought I had the transient issue under control but I'm not so sure now. I've had the voltage regulator for the logic fry twice now, this last time actually blew the side of the regulator off near the vin pin. The 5v side only demands 170ma from the Ti r104 regulator. The voltage regulator has a large copper area for heat dissipation and has internal thermal controls. I also have the same regulator with the same supporting components sans inductor in a couple of other projects and they work great so I'm lead back to the inductive spike.
The questions are: Does this BYW29e look like sufficient protection? If not, will a TVS diode be a better choice? When selecting the TVS for this circuit should I base the clamping voltage on the 5v side or the 12v through the coils?
Any help will be greatly appriciated.
Thanks.
I'm switching a large inductive load (350h) at low frequency (2-30hz) with 12vdc. The resistance across the inductor is 4ohms. The switching circuit is 5v logic (avr) and a pair of P channel mosfets in parallel. For a snubber, I have been using a byw29e (http://www.nxp.com/documents/data_sheet/BYW29E_SERIES.pdf) wired anti parallel across the inductor immediately proximal to where the inductor connects to the pcb. Looking at it on my low res scope I thought I had the transient issue under control but I'm not so sure now. I've had the voltage regulator for the logic fry twice now, this last time actually blew the side of the regulator off near the vin pin. The 5v side only demands 170ma from the Ti r104 regulator. The voltage regulator has a large copper area for heat dissipation and has internal thermal controls. I also have the same regulator with the same supporting components sans inductor in a couple of other projects and they work great so I'm lead back to the inductive spike.
The questions are: Does this BYW29e look like sufficient protection? If not, will a TVS diode be a better choice? When selecting the TVS for this circuit should I base the clamping voltage on the 5v side or the 12v through the coils?
Any help will be greatly appriciated.
Thanks.
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