Class D Amp Bus Pumping repair

[kiermee]

Good night,

I am working on a Class D amp half bridge using IRS20124s Driver and 4227 mosfets.

The B+ and B- are at 80v. The unit works but the main filter caps were blown due to bus pumping.

Could anyone advise/help to solve this issue?

Thanks

 

[bucks bunny]

This is a well documented issues with half-bridge topology. You could add another half-bridge amp, drive this with a phase-reversed input signal and apply this to 2 subs that are wired anti-phase as well. At the end this is the same as driving a full bridge with two 8Ohm speaker in series.

Or you build one full bridge with half the supply voltage.

 

[kiermee]

Thanks for the reply. I have read up on this issue. But this is an amplifier by Yorkville that I am repairing. It stated presenting this issue. Looking for assistance with troubleshooting the current issue. Would is be an issue on the output stage? It drives 4 6” speakers at a 2 ohm load.

 

[bucks bunny]

You could fix that by wiring the 4 speakers in 8 Ohms configuration instead of 2 Ohms.

 

[ionutzxpo]

Or add more than 10.000uF/100V capacity on the supply rails ...my recomandations is at least 22.000uF/100V 🙂

 

[bucks bunny]

2 Ohms with +-80V supplies is in the ballpark of 1600Wrms or 28Arms. No wonder the electrolytics explode.

And, btw, I do not know any 6" drivers capable for 400Wrms.
All in all this looks insane to me.

 

[wg_ski]

If it’s a switching power supply it might not be happy with that much capacitance added. The 20,000 uF per side is recommended for linear supplies to keep the impedance low at 20 Hz. Not necessary or even recommended on a switcher with the charging pulses very close together.

The supply is likely unregulated or there would be correction or at least attempted correction for the bus pumping. Might be +/-80 V dropping to +/-40 (or even current limiting) under heavy load, and periodically going as high as 120V on a side due to reactive loading, which blows the caps eventually.

 

[RedWhite]

Check during no signal if supply voltage pos and neg already not balanced there is error or damage component.

If supply healthy check input, must be balanced well before comparator stage. Some HB class D amp will be trouble if receiving unbalanced signal. If signal before comparator is in good balanced, then amplification at pos vs neg side is not balance. That can be bootstrap problem, like cap empty, leak current and so on.

 

[AllenB]

Check during no signal....

You were asked previously why you have gone on to create a second account after originally asking for your then existing account to be closed.

Why have you created a new account, after specifically saying you wished to leave, and after asking to have your previous account disabled, which we did for you?

We are therefore closing this latest 'puppet account' as you failed to respond to our request.