Muting Relay ..... buzzing

[Baldin]

Ok, after some trial and error, I have ended up with this.
It wasn't that easy to get it to turn off fast enough.

For a class-AB amp this would be no problem, as it would take some time for the PSU to loose enough voltage for it to make a plob in the speaker.
The way my class-d amp it makes a noise just after the switch is turned off.

For fastest turn off the trick is:
- Choose C2 as small as possible. The turn on delay is determined by R2-C2.
- Choose R1 as small as possible. At turn off, both C1 and C2 is discharged through this resistor.
- Lower the voltage over C1 as much as possible. I have put in a zenner on 6,3 V for this purpose. The less voltage the less time it takes for C1 to discharge. C2 which determines the turnoff time, will not start discharging before V_C1 is lower than V_C2 minus Vdiode .....

Anyway with the components shown, it works quite well

[AndrewT]

this is a delayed turn on.
There is no instant off circuit.
It waits for the charge to slowly diminish and eventually switches off.

[unclejed613]

the circuit i posted had the discharge path through a negative rail, not ground......

[Baldin]

the circuit i posted had the discharge path through a negative rail, not ground......

I know, and it would of course work a lot faster, but I don't have a negative rail in the circuit (the amp is a full bridge)

Anyway it works good enoughfor my purpose.

See picture of both + 16 VDC PSU for the gate driver and the realy circuit.