[SOLVED] Power Supply Design ideas Please for Mains LED Strip

[Deltatango]

It seems I have some LED light strips to fix, these are run by an obsolete IC TP8533FD with a few capacitors, resistors, coil and rectifier for dc creation and pulse up it diodes.

Most of these units have simply blown capacitors 15uf 400v, 2.2uf 400v and small 50v DC supply (too much pulse power to deal with), these create a supply to run a pcb strip of led's with no resistors (unless built in) I can see. I have replaced capacitors with better quality parts also fitted a filter cap and fuseable resistor (as none fitted) to reduce surge plus balance some heat around.

The spec on this IC is 120v @ 200mA output drive and feeds two of these strips in series so make a 40-50W 4ft cheap light batten, power is not isolated from mains!

Out of the many I have fixed four have problems beyond capacitors, pulsating, no output and dim or low output. I started on one after I got some other alternate versions of its IC this gave the same fault so suspect some leaking led issue.

Has anyone got an idea for a simple safe power supply to run these strips to check them, which I think should be about 60v or so, I have bought a led driver with 48v which I hope might be adjusted to suit plus be isolated from mains.

Thanks for any help

 

[KlausST]

Hi,

My recommendation: buy an isolated LED supply.
They should be rather cheap and safe.

It´s not worth to repair a broken non isolated one ... regarding safety, effort, cost..

Klaus

 

[BradtheRad]

Consider installing an ordinary lamp bulb in series. This reduces house voltage going to your testing setup. Try different watt ratings, 40, 60, 100, 150. Put two 100W in parallel to make 200W. A higher watt rating lets through greater current and greater voltage to your project.

This is resistive drop method. However light bulbs are a reasonable choice for this.

Convert AC to DC with a full diode bridge (assuming your led strips require DC).
The output is unfiltered DC. Add a smoothing capacitor if you wish

 

[FvM]

I would measure LED strip current and voltage of a known good exemplar and compare with the values observed at the non-working. You'll easily see if it's problem of the strip or the switcher.

 

[cupoftea]

Please be careful with this unisolated one...but its a very simple way for you to check leds............here in jpeg and the free LTspice so you can run it there first...

The fet dissipates circa 6W in the attached..so needs a heatsink...but if you want you can increase the sense resistor and make the fet dissipate less.

The source on the left is the mains by the way.

 

[Deltatango]

Thank you guys give me some good ideas to work with, I will be trying to cross check power supplies and light strips on my next batch, just seemed at first it was the power supplies as the sick ones had blown their mains bridge diodes so thought that flash might have damaged the chips internals. Now getting a variant of those IC's in a SOP7 form plus conversion board to DIP7 beginning to think they are quite tough.

As I said in my original text I am buying a LED driver supply that has a 42v listed output which I hope is both isolated and modifiable to a variable output, on another worry found a long cardboard box to put the LED strip on (a long bendy pcb) as I was not inclined to use their aluminium back frame, had enough of that years ago working on "live" chassis valve tv's plus bumping in a couple of houses with reversed mains supply!!

Will get my digital meter out and try to spot a weak LED and get a supply of them, I think I have seen which sort listed, some rectangular types with high current forward ability.

Thanks again from David