TPA3116 turn on/off pop - Page 1
Forum section: electronics / projects

author: Michaelaudio
author_rank: Regular Contributor
timestamp: September 12, 2020, 04:53:07 pm
content: I have this circuit for anti turn off/on pop for the tpa3116, its wired exactly as the typical application. The anti turn off pop works just fine (10uf on the mute pin) But my comparator solution doesnt work as good as I want. There is still a pop when I disconnect VCC, not as bad as without the comparator but I want to have absolutley no turn of Pop, how can I do it?

author: Michaelaudio
author_rank: Regular Contributor
timestamp: September 14, 2020, 03:41:02 pm
content: So I found out that when I turn it off while music is playing, the pop isnt as loud as when no music was played for several minutes. I guess that are the input caps which are loaded?

author: Michaelaudio
author_rank: Regular Contributor
timestamp: September 16, 2020, 09:53:30 am
content: No ideas?

author: Michaelaudio
author_rank: Regular Contributor
timestamp: September 16, 2020, 10:29:42 am
content: Everything is powered from a 24V supply. When I turn the switch off the Voltage is cut and cousing a pop. What would be another way?

author: Renate
author_rank: Super Contributor
timestamp: September 16, 2020, 11:18:34 am
content: You're only using MUTE, not SDZ (shutdown).As I've said before, you're jumping through a lot of hoops to avoid doing things normally.The TPA3116 take 50 µA, that'smicroAmperes nominally when in shutdown modeYou don't need to cut the power with a MOSFET.The power losses in the MOSFET and the associated circuits is greater than the quiescent power of the TPA3116.

author: Michaelaudio
author_rank: Regular Contributor
timestamp: September 16, 2020, 12:16:25 pm
content: The board is already done, ofc I would do things different in the next project. Mosfet isnt the problem I just want no pop when psu is disconected

author: Renate
author_rank: Super Contributor
timestamp: September 16, 2020, 12:54:55 pm
content: Quote from: Renate on September 16, 2020, 11:18:34 am

author: Michaelaudio
author_rank: Regular Contributor
timestamp: September 16, 2020, 12:58:36 pm
content: U mean if id use the comparator on sdz instead mute it would be solved?

author: Renate
author_rank: Super Contributor
timestamp: September 16, 2020, 01:13:53 pm
content: Using shutdown should work better.Of course the best would be to mute, wait a tiny bit, then shutdown.I think that I wait 50 mS, it works fine, I've never bothered to search for any other way.(I'm using a TDA7296, but it's the same type of Class D.)

author: Michaelaudio
author_rank: Regular Contributor
timestamp: September 16, 2020, 01:40:16 pm
content: Okay, ill try that as soon as my other problem is fixed

author: Michaelaudio
author_rank: Regular Contributor
timestamp: September 27, 2020, 01:30:32 pm
content: So I tried to pull SDZ low after psu is removed but it doesnt work with this circuit (opamp goes high to slow and quick)What would be a better solution?

author: Renate
author_rank: Super Contributor
timestamp: September 27, 2020, 09:18:13 pm
content: That's heading in the right direction, but by the time the circuit senses the voltage drop it has already affected all those rail splitters.Theoretically, the opamps don't need a regulated supply but it would simplify things to have the opamps and the rail splitters on the same regulated supply.Even with a high dropout regulator the opamps would not be affected untitl the main voltage dropped below 18 V or so.This is really the kind of problem that a digital scope or storage scope or logging app would really be useful.You need to be able to see how things crash when the power gets removed.Still, a regular scope set on "Normal" sync mode should be able to show you what you need to see.

author: Michaelaudio
author_rank: Regular Contributor
timestamp: September 28, 2020, 06:02:34 am
content: Well I can see that the Supply Voltage of the board drops pretty quick. If I dont connect the OP anywhere I can see that the output shortly gets high after removing psu, but its only a vew Volts. It seems I need something faster bc the op doesnt turn on the transistor quick enough (otherwise I wouldnt have a turn of pop)Idk if a LM393 would be better

author: Renate
author_rank: Super Contributor
timestamp: September 28, 2020, 02:25:39 pm
content: Well, you need some advance knowledge that things are crashing.Not proposing this, but some have used contacts on the power switch or sense of the AC line.In a transformer, full-wave-bridge, capacitor supply you normally get a long decay, especially with low load.Some switching supplies have a "power good" output. I'm not sure how the timing on that goes.Obviously some of the schemes might not work so well if the amp was blasting when the power died.OTOH, you wouldn't hear anything noticeable.

author: Michaelaudio
author_rank: Regular Contributor
timestamp: September 28, 2020, 02:52:33 pm
content: Im using a smps but it shouldnt have a pop even when I pull the plug of the psu out of the board, so its just the voltage of the board itself that im looking at, for the comparator. I have a cap close to the op amp (100uf) but that doesnt change anything sadly. I thought about a boost converter for the op amp so the voltage stays long er st 24V for the op, but that would be a shitty solution

author: Renate
author_rank: Super Contributor
timestamp: September 28, 2020, 04:21:40 pm
content: You still haven't said how the 24 V crashes.If it crashes quickly there is not much that you can do.How much does that 100 µF slow things down?Have you measured the idle current of your entire circuit?

author: Michaelaudio
author_rank: Regular Contributor
timestamp: September 29, 2020, 06:16:58 am
content: If no speaker is connected it goes down to zero in ~1.5sec. With a speaker (who pops) its under a Second (but only bc of the pop ofc) so I would clculate with the ~1.5sec.The strange thing is, on my previous board I did tit with a comparator too which goes high on mute, when the Voltage is under 23V. This board had a too loud noise (coused by the zeners from the VCC/2 biasing on the op amps). When I realized it where the zeners I replaced them with resistors and suddelnly I had a turn of pop!So maybe it was something with the caps that where charged from the noise of the zeners and somehow it helped..

author: Renate
author_rank: Super Contributor
timestamp: September 29, 2020, 12:29:38 pm
content: Without the zeners there is no power supply rejection.(A 15 V regulator on the whole op amp bits would work too.)Here's how you can test/prove it to yourself.Feed the relay with a 1 Hz (square wave) signal.The voltage to the load will jump up and down 0.7 VYou will hear horrible whumps.

author: Michaelaudio
author_rank: Regular Contributor
timestamp: September 29, 2020, 02:06:57 pm
content: Yea in the next project id use a Regulator for this.There must be an easy way to get a quick high signal, when VCC is under 23 Volts and going down to zero in about 1.5sec. But whats the way? Why isnt my op amp fast enough

author: Renate
author_rank: Super Contributor
timestamp: September 29, 2020, 02:49:17 pm
content: No, the point is when it drops from 24 V to 23 V you've already made a whump.

author: Michaelaudio
author_rank: Regular Contributor
timestamp: September 29, 2020, 05:28:34 pm
content: I have an chinese tpa amp board, which is pretty good. It doesnt have a turn on/off pop at all, no matter what I do. How do they do it? They only have a few resistors for the pop circuit (tried to reverse engenier it, but its no easy)

author: Renate
author_rank: Super Contributor
timestamp: September 29, 2020, 06:06:41 pm
content: Quote from: Michaelaudio on September 29, 2020, 05:28:34 pmSimple, they don't have a lot of op amps all with their own independent unregulated rail-splitting references.To make anything pop-free you need to have power supply rejectionandthe ability to disable everything when it really crashes.If you are really interested, make the relay/diode thing (or just use a switch/diode) and try it on your board and the Chinese board.Seriously, you've had plenty of suggestions.

author: Michaelaudio
author_rank: Regular Contributor
timestamp: September 29, 2020, 07:39:43 pm
content: Yea I can imagine but I Stil havent a solution if I Check the diode thing. Obv I cant use a Regulator for the op amps itself. Its a already finished pcb but would the op amp methode Help when I have a Regulator for the Bias resistor deviders?

author: Renate
author_rank: Super Contributor
timestamp: September 29, 2020, 07:48:23 pm
content: Cut a trace, put in the 15 V to the opamps/splitters. The TPA3116 still gets the 24 V.