Class D - about current consumption from the supply - a question folks

destroyer X · 27th July 2008, 01:46 PM

When operating, class D switches the supply voltage and the heat is small...because on and off and using fets...but about the curent flowing from the supply without speaker connected?

Is the current consumption, from the supply, drained in a constant way WITH and WITHOUT load (speaker) connected?

I have suspections that not.... but i have doubts, and some folks asked me that and i do not know what to answer.

In my imagination you need to insert the speaker to have big current consumption...but i may be wrong...very confused i am in this moment about this subject.

Can you help me folks, to help brazilian folks about that?

regards,

Carlos

Steerpike · 27th July 2008, 03:08 PM

Power supply current will be very low with no speaker load.

Workhorse · 27th July 2008, 05:15 PM

Hello Carlos

The current consumption in class-d amps is not more than 100mA in typical setups.

analogspiceman · 27th July 2008, 06:33 PM

Hi,

It's been a while since I last posted, but I couldn't resist this thread.

Theoretically speaking, an ideal switched mode amplifier would consume no power internally - its average input power draw would be exactly equal that provided to the load (so no load - no power draw).

In actuality, there will always be some small amount of housekeeping power (typically a few watts) and some output f C V squared losses and possibly some shoot through losses if near zero dead time timing is used in an effort to minimize distortion. - a.s.

.

Ouroboros · 28th July 2008, 07:26 AM

I've found that on self-oscillating amps designed for PA applications (using fairly long dead times - distortion only has to stay below 1%), then the dominant cause of the idle current in the output stage is the ferrite losses in the output filter. Even with no load, you're still magnetising the output filter chokes in one direction, then the other direction at perhaps 300kHz. Moving to the Ferroxcube 'Polo Mint' gapped ferrite toroids, I see a useful reduction in idle current.
Certainly in 'ucd' style amps, the quiescent current tends to drop when a load is connected to the amp. (With no input signal obviously).

Pano · 28th July 2008, 07:48 PM

I agree, there seems to be very little difference in idle current with andwithout loads in the amps I've measured.

But I've measured low power amps, so YMMV.

destroyer X · 18th August 2008, 01:57 PM

Now my doubts do not exist anymore...thank you all.

Sorry by the enormous delay to answer you all....thanks.

regards,

Carlos

27th July 2008, 05:15 PM	#3
Workhorse diyAudio Member Join Date: Dec 2004	Hello Carlos The current consumption in class-d amps is not more than 100mA in typical setups. __________________ It's a fruitless endeavor to try and educate a fool that rejoices in ignorance

28th July 2008, 07:48 PM	#6
Pano diyAudio Moderator Join Date: Oct 2004 Location: North Carolina Blog Entries: 4	I agree, there seems to be very little difference in idle current with andwithout loads in the amps I've measured. But I've measured low power amps, so YMMV. __________________ Take the Speaker Voltage Test!

18th August 2008, 01:57 PM	#7
destroyer X diyAudio Member Join Date: Feb 2004 Location: Recife - Brasil Northeast	Thank you folks... and hello my dear Workhorse Now my doubts do not exist anymore...thank you all. Sorry by the enormous delay to answer you all....thanks. regards, Carlos __________________ Audiophoolery; http://www.youtube.com/watch?v=m7ERMu825m4; Dx Super Etching; http://www.youtube.com/watch?v=WED3Bvmxepk

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27th July 2008, 03:08 PM	#2
Steerpike diyAudio Member Join Date: Jan 2006 Location: Johannesburg, South Africa	Power supply current will be very low with no speaker load.

28th July 2008, 07:26 AM	#5
Ouroboros diyAudio Member Join Date: Dec 2003 Location: Nottingham UK	I've found that on self-oscillating amps designed for PA applications (using fairly long dead times - distortion only has to stay below 1%), then the dominant cause of the idle current in the output stage is the ferrite losses in the output filter. Even with no load, you're still magnetising the output filter chokes in one direction, then the other direction at perhaps 300kHz. Moving to the Ferroxcube 'Polo Mint' gapped ferrite toroids, I see a useful reduction in idle current. Certainly in 'ucd' style amps, the quiescent current tends to drop when a load is connected to the amp. (With no input signal obviously).

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