Re: Over-voltage protection circuit does not work as expected
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Dave, thanks for the advice. The ramp down is not needed indeed. Anyway, the original model of TLV1805 is a nice find. ? Jurek ? From: <[email protected]> on behalf of "Bell, Dave via groups.io" <Dave.Bell@...>
Reply to: <[email protected]>
Date: Wednesday, 5 February 2025 at 22:09
To: "[email protected]" <[email protected]>
Subject: Re: [LTspice] Over-voltage protection circuit does not work as expected
Resent from: <Dave.Bell@...>
Resent date: Wed, 05 Feb 2025 13:09:29 -0800 You¡¯re right - it does work! I found the output voltage curve a little confusing by itself, with the ramp Up and ramp Down. But reducing the output cap to 10u or increasing the load to 100 ohms, it became clear; it was just the slooow decay that looked weird. ? Dave ?
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From: [email protected] <[email protected]> On Behalf Of jerzy przezdziecki via groups.io
Sent: Wednesday, February 05, 2025 12:51 PM
To: [email protected]
Subject: EXTERNAL: Re: [LTspice] Over-voltage protection circuit does not work as expected? Yes, it¡¯s uploaded in TEMP as ¡°TLV1805_overvoltage_protection_circuit_works¡± ? Jurek ? Is there a circuit for this thread? Ild like to look at it myself when i get home. ? On Wed, Feb 5, 2025 at 3:41 PM, jerzy przezdziecki via groups.io I can imagine that crowbar is much better, but I would not be afraid about transients. This chip is extremally fast, a few ns. So ¨C as you said ¨C the TLV1805 is made for this purpose. Jurek ? I understand that overvoltage protection (OVP) must be a very simple and reliable circuit.
I've had a lot of problems with this circuit because sudden load variations can cause transients in the output voltage and reach high values triggering the triac! That's terrible.
Extreme situations can generate noise and lead to malfunctioning protection circuits.
My overvoltage detection, for this reason, is done by simple zener diodes and only components like the TLV1805 are suitable, as they have been designed for this purpose.
Because of these problems, in one specific case I used a microcontroller to trigger the crowbar. The microcontroller was able to distinguish between an overvoltage and a transient.
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