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eem2am 25th June 2011 02:00 PM

Regulations for Audio Amp SMPS?

We are designing SMPS's for Class D audio amplifiers.
These power supplies will be housed inside the Class D amplifier case.

These are for 85-265VAC connection.

Powers are from 50W to 300W

Regarding regulatory body approvals:-

1. Will we need to conform to the new standby power regulations (ie consume less than 500mW in standby)?
2. Do we need power factor correction for a 100W power supply.......after all, most of the time the amp will draw much less than 75W.
3. Will the SMPS have to be run at its peak power level during the EMC test.....after all, most of the time , it will operate far under its peak power level.

luka 25th June 2011 05:08 PM

1: don't know
2: probably not, too low power
3: don't know

nigelwright7557 25th June 2011 08:59 PM

You will need to look it up in the EMC regs or get in a consultant at great cost to advise.

The testing should be done under full load conditions as this will probably be worst case emissions.

It is probably worth getting the equipment tested anyway to find out what is wrong but only after making sure you are following full regs. Redesign can become very expensive.

eem2am 26th June 2011 07:17 PM


The problem is that the EN regulations cost money....and i'm not sure which one of the many thousands has the information that i seek.

The EN governing body do not respond to requests as to which is the correct document to buy.

Another thing, i am wondering, is is there a minimum acceptable efficiency for guitar amp Switch Mode Power Supplies?

(ie SMPS's that supply Class D audio amp)

marce 27th June 2011 11:43 AM

Look around here for EMC questions:
EMC Information Centre - The EMC Journal (Free in the UK)
generaly for Europe and a CE mark, it is self certification, you do the tests and sign the declaration.
If you specify a product to work up to a certain power level you test it at that level, that is a fundemental part of good product design practice, and should be standard practice, otherwise you have not tested the design to its rated capacity.
You also need to brush up on SELV regulations as your PCB will have to have creepage and clearance gaps because of the input voltages.

hesener 28th June 2011 08:44 PM


on your questions:

1. No, audio gear is to my knowledge excluded at this point from the new EuP regulations. However, it can be a major selling point, and there is no problem in reaching these levels with modern PWM controllers for the power range you mention.
2. No, PFC is not required at this point for audio gear, according to EN61000. It may be a good idea though, because the noise from the input rectifiers can be significant, and - depending on which topology is used - the main converter may operate much better with a smaller input voltage variation.
3. The power supply will have to meet EN550xx regulations at all power levels, and on both lines (L and N), whatever the worst case may be.

By the way, and since this came up in another post, the "CE" marking is a different story - it implies compliance with safety rules, recycling and hazardous materials and has nothing to do with EMC or power factor. Yes, it can be self-testing for compliance but most (industrial) companies chose outside labs for the certificate because thats the safer way.

just my two cents....

VivaVee 28th June 2011 08:52 PM


Originally Posted by hesener (
By the way, and since this came up in another post, the "CE" marking is a different story - it implies compliance with safety rules, recycling and hazardous materials and has nothing to do with EMC or power factor.

This is completely wrong. The CE marking means that the product is compliant with ALL relevant EC Directives. That includes the EMC Directive if that is relevant which is the case here.

DF96 28th June 2011 08:52 PM

I thought EMC is included in CE. CE is not just about safety, but other Directives too.

kevinkr 28th June 2011 09:03 PM

As far as I know both VivaVee and DF96 are correct, this is my understanding too.

hesener 28th June 2011 09:16 PM

just ate my tung.... you are correct guys, CE includes EMC as well....

sorry about that

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