Joe Voytovich
Newbie level 6
I've got a project where we're redesigning a pump controller board and have reached a serious road block. The triac reaches a certain temperature (it seems) and locks on. I can hit it with some freeze spray for a second or 2 and it will shut off.
I've tried all types of circuit changes - added gate pulldowns (240 ohms), different gate bias resistors (220, 1k, 5k), changed the snubber circuit. Adding a larger heat sink helped for a while, but we need a longer run period also, and the board design is locked for now.
The pump draws about 10A, and after 30 seconds switching the gate off with a manual switch doesn't turn off the triac. I removed the MOC3022 opto driver because I wanted to test with it out of the circuit, and it also made no difference.
The triac currently reaches about 60C on the case (it's a D2PAK package) in 30 seconds. I can't see that this would be enough for thermal breakdown, but apparently I'm missing something here somewhere.
Any help or ideas on this would be appreciated, since I've just about used mine all up.
Thanks.
I've tried all types of circuit changes - added gate pulldowns (240 ohms), different gate bias resistors (220, 1k, 5k), changed the snubber circuit. Adding a larger heat sink helped for a while, but we need a longer run period also, and the board design is locked for now.
The pump draws about 10A, and after 30 seconds switching the gate off with a manual switch doesn't turn off the triac. I removed the MOC3022 opto driver because I wanted to test with it out of the circuit, and it also made no difference.
The triac currently reaches about 60C on the case (it's a D2PAK package) in 30 seconds. I can't see that this would be enough for thermal breakdown, but apparently I'm missing something here somewhere.
Any help or ideas on this would be appreciated, since I've just about used mine all up.
Thanks.