We've installed hundreds of these without a single failure. Then last week we had one go. What surprised me was that rather than no voltage on the output, after the failure the voltage on the output pins was the input voltage! Not good, No voltage I can live with but putting the input voltage on all of the downstream components made it a nightmare. I've been through the spec sheets and I see no options to control this. Can you suggest how we protect against this kind of event?
Tim
Timothy:
The buck regulators have no internal protection for a short between input voltage and output voltage.
1. One method to minimize OVP occurrence it to add a fuse on the input bus. Then add a high power Zener diode on the Vout Bus to ground . The selected high power zener diode when the maximum voltage is detected will short out the secondary bus to ground. Then the input fuse will open when the current is exceeded by 2x the normal input current rating .
2. Another method would be to use the TPS2400 with N ch power FET. Zener diode clamp and input fuse. See SLVA163 and TPS2400 for additional details . One diagram from the TPS2400 OVP detect.
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Tom
