On Fri, Feb 7, 2025 at 02:02 PM, Roy J. Tellason, Sr. wrote:
The overvoltage circuit at are all effective but the one with the PNP transistor and SCR are the most stable as far as trigger point.
If I where going to use a TRIAC, I'd use it in SCR mode with the PNP transistor.
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You can vary the value of the capacitor C1 to achieve different firing delays. There are systems that can tolerate a few milliseconds of overvoltage.
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Reduce the value to speed up the delay, remove it for super fast but be aware the circuit might be prone to tripping on exterior events like nearby lightning.
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I use 50nF and I'm not bothered by falses but it still trips if I emulate a regulator failure.
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Call me paranoid but when I built a linear power supply for a Perseus SDR (~1K in 2000) I used two OVP crowbars in series with two SCRs at the output of the filter capacitor and two SCRs, one each, at the output of the OVP.
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