Low EMI with TOP246Y 1

[GonzaloEE]

Hi. I'm in charge of designing a FCC/IEC compliant flyback SMPS, using the TOP246Y switcher IC. As usual, we have a tight budget and about 5 days to deliver the layout and BOM, so we have no such time for calculations.

I'd appreciate any hints on how to use this part to get a flyback with reduced EMI and conducted noise. Any tips on PCB layout guidelines, and component values calculators, or cookbooks for filter stages will be highly valued. I have digital devices background, so any help with analog design will be appreciated.

The PS reqs. are:
Input: 190~230VAC/~50Hz
Protections: short-circuit, overvoltage(<230VAC)
Output: 13.8VDC
I max.: 1.5A
Protections: short-circuit, overvoltage (<13.8VDC)

It has also an auxiliary output for battery charging, with Iout max: 300mA

Thanks in advance!

 

[treez]

either just buy ready made module ..

or maybe do one of those continuous mode flybacks that does PFC too....theres an IC that does it for you...forget the name...is it one of the fairchild or onsemi or texas or unitrode ones?....

you can get the PFC stage and the PWM converter as one stage.

hold on...its such a small power output....~20W....it doesnt come under regs does it?...since its under 50W output..

also, there must be a cheep off the shelf part for you...there are loads at the low powers like yours

 

[Madcow]

This is one of my favorites:

http://www.infineon.com/dgdl/AN-EMI...Semiconductors.DOCUMENTS.AN-EMI-01_v1-1_1.pdf

Also search the major power semiconductor sites
ie National, Fairchild, TI ect.

 

[GonzaloEE]

Thank you for your answers. I'm not sure if FCC specs. apply for our power levels, but the customer is asking for FCC/IEC compliant PS anyway.
The PDF looks very useful, including some simpler circuits for quick testing.

Thanks a lot!

 

[MacGyverS2000]

I believe FCC specs are of importance based upon what the power supply will appear in, not power output. For example, the FCC wants a guarantee the unit will not radiate heavily if it's going into a typical desktop computer, but would probably care less if it's being used as a backup in a remote jungle scenario.

Dan - Owner

http://www.Hi-TecDesigns.com

 

[GonzaloEE]

Well, that was the main subject of my morning meeting with the customer: I also thought we were talking about a jungle scenario, then the guy came up with a wireless alarm transmitter they claim it's being jammed by non-compliant SMPS.

 

[MacGyverS2000]

Well, Part 15 is your area of interest if we're talking about interference with alarm transmitters. If your SMPS can fit under those rules, you'll be fine.

Dan - Owner

http://www.Hi-TecDesigns.com

 

[BobM3]

Have you looked at Power Integration's application notes and sample circuits? Many of the application notes included sections on measured RF noise.

 

[GonzaloEE]

Thanks Dan for the lead. I'll look into it.
Thanks Bob. I'm reading it all, specially AN-15 -focused on EMI issues, and some documented designs.

I've found they have a s/w and a pre-filled spreadsheet available in their website, for automated parameter calculation.

Cheers!