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Mosfet SSR triac output shunt circuit design

Salvador12

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Hey.

So my idea sis this. I will build/change my speaker protection output from mechanical relay to mosfet relay. But because mosfets can switch current at a fast rate, during a DC fault at the output the mosfet will switch off and the current within wires/coils will produce an inductive spike. In order to mitigate this spike I want to add a triac in series with a low ohm resistor to dissipate such spikes. The idea is that each time the mosfets switch OFF the triac comes ON.
The problem is I can't come up with a circuit that would accomplish this.

It would need to function like this. When the opamp switches the 2N5401 transistor off, current stop flowing through the Si8752 chip and the output mosfets switch OFF. at the same time when current is switched off through the Si 8752 a voltage would need to be applied to a triac to short the output.
I would think I could somehow use the circuit switching the Si8752 primary side to accomplish this but how?

Please see the schematic.
 

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  • APEX Protect Stereo schematic with MOSFET output.jpg
    APEX Protect Stereo schematic with MOSFET output.jpg
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danadakk

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Salvador12

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TVS Diodes ?




Regards, Dana.
But TVS diodes as well as MOV's are designed for limited amount of use , + I have to chose them with a high voltage rating - higher than the amplifier output voltage otherwise they will conduct under high output power.
Meanwhile a thyristor aka triac would only switch on when the mosfets switch off and can be a long term solution
 

danadakk

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But TVS diodes as well as MOV's are designed for limited amount of use , + I have to chose them with a high voltage rating - higher than the amplifier output voltage otherwise they will conduct under high output power.
Meanwhile a thyristor aka triac would only switch on when the mosfets switch off and can be a long term solution

The Zener based TVS diodes have reliability specs. In fact a zener is "normally" operated in its
avalanche region. Albeit at controlled currents.


MOVs are more limited -



Regards, Dana.
 

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