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A LED lighting fixture in my apartment (in Israel/Palestine) started flickering for a while before coming on, then went bust. I suspect it's the driver/power supply rather than the LEDs themselves, since it was all very uniform.

the LED area cover has a sticker saying "9V DC 40W 196 LEDs".

Question: What can I replace this driver with?

That is, what tolerance ranges do I have for the different driver parameters, to fit my LEDs?

The supposed manufacturer's website (www.xz-power.com) gives me an HTTP 403 page, "Your request was rejected", so no help there. There's this webpage with a list of what are supposedly the manufacturer's products, but - I'm not sure I know what to look for; plus, I'm not sure these things are available in single units for retail where I live (in fact I doubt it).

Notes:

  • I'm not sure the driver was the right one to begin with, seeing how it failed. I didn't buy this fixture myself.
  • I'm not asking for specific product recommendations.
  • I don't care about how much such a driver would cost - for the purposes of this question.

This is the sticker on the driver:

enter image description here

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  • It may be just as expensive to replace the driver as it is to get a new fixture. "can it be that the driver was inappropriate to begin with?" How are we supposed to know that?
    – Alaska Man
    Apr 3, 2021 at 16:43
  • @AlaskaMan: 1. See edit about my Internet search. 2. Maybe you can tell based on the other sticker text which I quoted, or just speculate based on the fixture failing and your experience. Also, that's not my actual question.
    – einpoklum
    Apr 3, 2021 at 16:49
  • It reads as a shopping question which off topic here. Without doing the shopping for you, The answer is to tell you to search for drivers with the same specs.
    – Alaska Man
    Apr 3, 2021 at 16:53
  • Answering why the driver failed or if it was inappropriate to begin with is outside the scope of your main question (picking a replacement), would require a lot more information about the fixture and LEDs themselves, and would probably belong on electronics.stackexchange.com instead of here
    – CJC
    Apr 3, 2021 at 17:06
  • @CJC: See edit.
    – einpoklum
    Apr 3, 2021 at 17:08

2 Answers 2

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That's crazy, there's another thread using the word "driver" to talk about a constant-voltage LED power supply, and now this thread using the word "power supply" to talk about a constant-current driver. Marketing is funny lol.

The sticker on the LED cover is mistaken. The driver labeling contradicts it, and the driver is far more likely to be correct, since the lamp did work.

The ruling figure on this driver is SEC: Constant current: DC540ma. This is a 540 milliamp driver designed to output exactly that current (at whichever voltage that happens at). This voltage is decided by the LED characteristics.

However, the driver is not magical; and is only electrically tuned for an output in a certain voltage range. That is specified next: 30-56 volts, with 60V an absolute max. Further, it has a maximum power output of 31 watts, which jibes with the 56 volts.

LEDs work at best performance when driven at constant-current. They are not ohmic, and cannot "work as their own resistors" the way an incandescent bulb can. (that was the hardest part about designing incandescent bulbs; Edison had no access to constant-current power supplies (though Tesla did, because of AC).

So, the replacement driver you need has

  • An input voltage within 220-240V (whatever your AC mains power is in your country)
  • An output current of 540ma on the button. (or slightly less, but that will mean proportionately less light)
  • An acceptable output voltage range of - well, whatever your lamp actually needs, but clearly that is between 30V and 56V.

Noting that your driver module has a "TUV" logo, that means whoever built this lamp actually complied with quality standards and used a driver approved by an NRTL (Nationally Recognized Testing Lab) - a list maintained by USA's OSHA, but that is considered the gold standard worldwide for reliable suppliers. The "CE" logo is not enough.

I would shop for drivers at mouser.com, Digi-Key, etc. Avoid at all costs the cheap Cheese junkstream coming out of Shenzhen.

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  • "but clearly that is between 30V and 56V." <- That means I need something with a range covering that entire range :-(
    – einpoklum
    Apr 3, 2021 at 18:03
  • @einpoklum no, only the range the LED array actually needs. That will only be a narrow range such as 44-52V which will vary by temperature, age, etc. The hard part is knowing that, when it's already failed :) I suppose you could stick it on a bench power supply and set the PS for 540ma and see what voltage that happens at... then add some margin for thermal and aging.
    – Harper - Reinstate Ukraine
    Apr 3, 2021 at 18:10
  • The best I got is a multimeter... well, I guess the advice will help other readers at least.
    – einpoklum
    Apr 3, 2021 at 18:12
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Based on the input voltage in the picture being 200-240V, I'm guessing you're not in the US, but I could be wrong. Be aware of different rules that may apply based on where in the world you are.

When looking for a replacement LED driver, what is important?

A replacement driver should have a similar voltage input and output range, but what is more critical to match is the current supplied to the LEDs, as over current and over temperature tend to be what kills LEDs. If a direct replacement is not available, look for a driver with an adjustable current limit that you can change to match to the old value, by using a multimeter with a current measurement.

Where can I find a suitable driver to purchase, and how can I make sure it's safe?

Constant-current LED drivers are available from many electronics suppliers like DigiKey or Mouser (US examples, no affiliation). Be sure to select a reputable supplier that sells drivers with the relevant certifications (UL, CE, ETL, etc) and be wary of online marketplaces that may not have the same safety guarantees for what they sell.

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  • Sorry, I should have said explicitly where in the world I live. Yes, the mains here is 220V. Also, is there no significance to the one sticker saying "maximum 31W" and the other saying "40W"? Or the one saying "9V" while the other says "30-56V"?
    – einpoklum
    Apr 3, 2021 at 16:59
  • Also, how about undercurrent? And how close does the current have to cut it? e.g. what about 500mA? 550 mA?
    – einpoklum
    Apr 3, 2021 at 17:03
  • Interesting. I got pulled off onto something else while writing my answer, and was unaware of your answer until I hit "post". I duplicated some of your answer by accident. Interesting we came up with the exact same suppliers lol, and similar comments on quality.
    – Harper - Reinstate Ukraine
    Apr 3, 2021 at 17:55
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    @einpoklum Your entire life in electronics, you've been taught that voltage is king and devices simply draw the current they need. Forget all that. It's exactly the reverse with LED drivers: current is king and voltage is 'whatever'. 550ma will overload the LED (albeit very slightly). Realistically when you start searching for drivers, you will find a bunch of peculiar values, not nice round ones.
    – Harper - Reinstate Ukraine
    Apr 3, 2021 at 17:59

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