LED Shop light - EMI problem - Chip info needed

[mu2]

Hi,

I have a bunch of 4ft. led shop lights purchased from a farm store that have severe radio interference. Seems like any weaker station gets wiped out if the lights are turned on. Very bad on 103.1 but also any weaker fm station. Didn't realize the problem until well after the purchase and also I really like the brightness of the lights and don't want to return them.
There are two banks of leds (110 in each row) - the 110 leds are grouped in 5 parallel banks of 22 leds in series. So there are actually 10 parallel banks of 22 leds in series.
There is a boost type power supply (see photo)which has a chip marked TP5060 and LHR4734. Looks like the ac is rectified and the filter cap is 68mf 200 volts. Dc output is 65 volts and that filter cap is 47mf 160 volts. I haven't been able to find any information on the chip. I'd like to see what the suggested circuit looks like and see if there is any reference to eliminating rfi or emi in the data sheet. I think it's safe to assume that the chip and entire circuit are Chinese.
I've tried wrapping the power cord (6 turns) through a mix 31 ferrite ring. Made no difference.
Anyone have any info on the chip or suggestions of circuit mods to eliminate the problem?
Couldn't focus well enough on the board to show the chip number.

Thanks,
Mike

[stj]

Re: LED Shop light - EMI problem - Chip info needed

probably made by Nanjing Top Power
watch your fingers, it's a non-isolated linear regulator by the look of it.
i cant see where the noise would come from though.

[CapLeaker]

Re: LED Shop light - EMI problem - Chip info needed

"I've tried wrapping the power cord (6 turns) through a mix 31 ferrite ring. Made no difference."

yeah... i believe that. The are only 2 ways to keep that PSU silent.
A: unplug it
B: and smash it afterwards.

Seriously there is no AC input filtering etc. Pick up a new real LED driver PSU from Digikey or where ever you want and be done with it.

[petehall347]

Re: LED Shop light - EMI problem - Chip info needed

have you tried shielding it ? maybe sticky aluminium tape inside the housing might help .

[stj]

Re: LED Shop light - EMI problem - Chip info needed

is it direct-drive or in series with an old ballast?
because it does not look like a high frequency design to me.
there is no sign of a diode/choke combo in the usual sense.

[eccerr0r]

Re: LED Shop light - EMI problem - Chip info needed

It has that L and N on the left hinting at an off-line design. Looks like a direct buck supply perhaps? Not sure that IC can handle wattage if it were a series dissipative either.

Tried putting chokes on the output too?

[kc8adu]

Re: LED Shop light - EMI problem - Chip info needed

that would be my first move.
its a buck alright.

Tried putting chokes on the output too?

[mu2]

Re: LED Shop light - EMI problem - Chip info needed

The power supply is not connected to a ballast. Line voltage comes into the board on the left side and 65 volts dc is on the right side connected to the led strings.
Originally, the board had thick heat shrink around it and a piece of double sided tape that held it against the light housing. I tried sliding a piece of metal conduit over the board - also no difference in the noise.
Should I try the ferrite rings on the output side to the leds?
Pin 1 of the ic has a 4.7mf 50 volt electrolytic connected and it's marked C3 - directly beside it is an outline for a smd cap. There is no smd cap soldered at that position and it is also marked C3. Perhaps I should try a ceramic cap in parallel with the electrolytic - like .1 mf? Also pin 5 of the ic is not connected to anything but it seems like it is a ground pin that is connected to the ground tab of the chip which is soldered to ground.
Spraying the chip area with freeze spray seems to change the interference slightly.

Mike

[stj]

Re: LED Shop light - EMI problem - Chip info needed

c3 sounds like the startup cap, leave that as is.

[eccerr0r]

Re: LED Shop light - EMI problem - Chip info needed

What's on the back of the board?

[mu2]

Re: LED Shop light - EMI problem - Chip info needed

Nothing on the back of the board - no components.

I don't think the chip is made by http://tpw-asic.com, it does not have their logo.

Mike

[redwire]

Re: LED Shop light - EMI problem - Chip info needed

There's really no parts to deal with EMI on this board.
It can give off EMI at either end, mains or LED output.

You can try add a small 2,200pF X cap disk cap across the LED output, or as Y-cap there, or try move the common-mode ferrite there.

[kaboom]

Re: LED Shop light - EMI problem - Chip info needed

Needs common mode chokes (and film caps), on both line input and LED output.

Look at the input section of any legit SMPS for examples.


Without the filters, one should expect severe RFI...

[petehall347]

Re: LED Shop light - EMI problem - Chip info needed

in the old days i would have used a portable fm radio to home into the noise source . or even am if it was there . might even be coming from the lamps . wrap things in aluminium foil and see what stops the noise . or try and shield the radio from the noise just for fun .

[mu2]

Re: LED Shop light - EMI problem - Chip info needed

Thanks for all the suggestions. Now I just need some time to try things like common mode chokes.
We finally have a day without rain in this part of the country and I have to catch up on my grass cutting.
I'll report back with my progress soon.
Mike