TDA8920 stability problems w. boost circuit

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Cyberzim

Member
Joined 2009
Hello there.
I have bought this amplifier from ebay: TDA8920 Class D Amplifier board/ audio Power AMP 2X100W - eBay (item 120592625186 end time Oct-04-10 06:18:32 PDT)
It runs just fine on AC, but when I try to use DC from a LM2577 boost circuit I have made it just starts chopping (if you know what I mean). It runs 55VDC with the AC connected, and about 52-53VDC with the booster circuit.
I have some thoughts of, that it is because of high frequency noise from the output from the LM2577 that cause instability.
If so can I remove that noise somehow?
I would really like it to work with battery supply.

Thanks in advance,

Simon H.A.
 
Frank Berry

Frank Berry

Member
Joined 2003
Perhaps the battery supply can't produce enough current to power the amplifier.
Have you measured the voltage from the booster circuit while the amplifier is delivering power to the speakers? If the voltage is sagging, you probably need a battery supply which can deliver more current.
 
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Cyberzim

Member
Joined 2009
The voltage on the output is swinging with about +/- 0.2 volt (40VDC). But I guess I need to charge my battery since it got low voltage. It swings from 11.1V to 11.5V. It is a 12 volt drill battery. Should be able to take the amps.
I will come with results after it has been charged.
I will also change the wires from the battery to the boost circuit, since it's just some thin alligator clip wires right now ;).

Regards,

Simon H.A.
 
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Cyberzim

Member
Joined 2009
Hmmm... no results from charging the battery.
I think I will make a DC to AC converter instead. Does anyone have a simple solution to this? Well I mean a ciruit that is not too advanced to build.
I will also be graceful for any suggestion to this problem. I have an oscilloscope so it is possible to make some measurements if needed.
But here is how it works when I power on:
  • A lot of noise from the LM2577 (I have a pretty large capacitor on the board, so I guess its normal?)
  • The amplifier starts playing just fine for 3-5 seconds
  • The amplifier starts clicking
The voltage output from the regulator doesn't swing so much. About +/- 1 volt max.

Regards,

Simon H.A.
 
C

Cyberzim

Member
Joined 2009
My booster has an internal frequency of 52 KHz, so I will have to set the frequency of the amplifier to 416 KHz.
My problem now is, that I can't seem to find any formulars on how to calculate the frequency for the amp. They only say you will get 345KHz when using a 30 KOhm resistor.

Regards,

Simon H.A.
 
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