TDA8920 stability problems w. boost circuit

Cyberzim

Member
2009-04-29 2:04 pm
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.
 

Cyberzim

Member
2009-04-29 2:04 pm
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.
 

Cyberzim

Member
2009-04-29 2:04 pm
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.
 

Cyberzim

Member
2009-04-29 2:04 pm
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.