I was browsing through eBay LEDs a couple weeks ago and came across something pretty interesting… a new COB that runs directly from AC. In other words, driverless! You may have seen them either on eBay or Aliexpress, but if not, they look like this:
(sorry for the rough picture – it’s the result of adding a poor camera to my already-poor photography skills)
Being the first “AC” COB I’ve seen on eBay, I was pretty intrigued. Sure, I made a custom directly-rectified-from-AC LED bar (link to write-up) about a year ago, but this was the first low-cost ($15 CAD or about $11-12 USD) and fully integrated design I’ve seen. It was worth checking out!
I couldn’t find much in the way of details on the web when I ordered it, so I figured I’d do a short write-up with some details (power draw, observations, etc). If you’re interested in this thing, maybe something here will help you.
First a few physical notes:
- This is the 110v model. They’re less common than the 220v versions.
- The aluminum substrate is about 1mm thick.
- There are 6 rows of 48 LED chips -> 288 chips in total!
- It’s big – dimensions are about 190mm x 53mm (not exact, but within +/- 1mm).
- It has L and N pads for soldering the load and neutral to.
- Model number on the PCB is AC110V-53190-F17020 A0
- There are 6 smaller holes (about 3mm diameter), likely intended for screw mounting. I suspect the 2 larger holes (just under 4mm diameter) are meant for running wires through (trace clearance on the L end is only 2mm from outside edge of hole so mounting larger screws there probably isn’t a great idea).
A closer look at a couple chips
I wasn’t keen on cutting away the silicon from each and every chip. However, for those interested, here’s what I did find:
The chip shown is (3 lines) BP5132H / 16D57K / G29B – I didn’t peel the silicon from *all* of them but based on the size/layout there appear to be 15 of them. It’s a linear constant-current LED driver from BPSEMI (product sheet here).
The 2 largest chips (in the 1st picture of the write-up, bottom-rightish) look to be bridge rectifiers – I only peeled 1 but it had the +/-/~/~ labels you’d expect.
Many of the smaller covered chips I would guess are resistors or capacitors and are all of similar physical size – I didn’t dig here.
2 chips that are different in size from everything else but which I didn’t dig at are the ones located between the 2 bridge rectifiers – no idea what they are but maybe in the future someone a little more accurate than me with an exacto-knife will reveal the details.
I don’t have fancy light-testing equipment, but did check the wattage and temperature.
To temporarily mount it, I used a finned aluminum heatsink that came with a Mars Hydro light (184x117x8mm). Soldered some lamp cord leads, added a little thermal paste, some electrical tape to hold it in place, and plugged it in.
When plugged in, wattage at the wall ran from 180-185 watts. Yep, that’s not a typo. This is the first LED-anything I’ve bought from eBay/China that actually delivered more watts than advertised! Note that I only tested 1 of the units so far. Also note that reading through some Aliexpress reviews of 220v variants (which seemed somewhat similar to my 110v unit physically) people seemed to be hitting slightly just under the advertised wattage (~14_ for a 150w, 9_ for a 100w, etc). So this higher-than-expected-wattage could be a 110v thing, could be related to our home power actually being closer to 120v, or could be a one-off. Update: When our voltage dropped from ~120 AC to ~116v AC, I ran other test and it pulled 167-168 watts. So there definitely appears to be a correlation between the line voltage and the power drawn/output. After looking through the datasheet for the “Smart” integrated controller this would seem to make sense. I’d imagine that if your line voltage was exactly 110 volts you’d probably get pretty close to the advertised 150 watts.
Either way, I was pretty impressed that it was actually delivering some real wattage.
I checked the power factor. PF was 0.92.
When it comes to temperature though, things became a little more concerning: Within 30 seconds the heatsink had gone above 80˚C (above 176˚F) – my electrical tape wasn’t exactly clamping down hard either so you can bet the chips and components themselves were well over 100˚C. Now to be fair, this heatsink is meant to handle something like 140w as part of a forced-airflow system. Having it upside-down taking 180+ watts with no forced airflow isn’t terribly fair.
But suffice it to say, this LED really pumps out the heat and you’re probably going to need a custom heatsink with forced air cooling to deal with it. And unless you’ve build something massive that can handle passive cooling, if your fan dies, your LED probably will die very shortly thereafter… assuming it doesn’t do something exciting first like melt out some wire insulation (or melt off the solder and drop a live wire).
I’m betting longevity will be an issue unless I put together a system that does some heavy cooling. There are just so many components that could fail (at least 36 I could visually see + each of the 288 LED chips themselves), and there’s a lot of heat to deal with.
A few really cool things:
- Driverless (price) – consider that even a “cheap” 150w driver is currently around $70 CAD (~$50 USD). The benefit of skipping the driver is huge price-wise. This might be the first time you can get 150W worth of LED lighting for under $20 (plus heatsink and wiring costs).
- Driverless (space) – I personally hate having to make room in custom enclosures for a driver. Being driverless means more space for heatsinks and/or fans (which you’ll likely need).
- Simplicity – Just hook the thing up to AC. No fussing with driver specs, a zoo of wires, troubleshooting failure, etc. If it dies, you desolder the leads and solder a new one in.
A couple down-sides:
Can’t be underdriven – want higher a higher lumens/watt ratio, the ability to control light intensity, or the ability to lower power to keep temps down for longevity/cooling reasons? Too bad.Update: Did a few tests (which can be seen in the comments). Short version is that dimmer switches can work, and applying resistors to the AC end works to dim also (down to below 1 watt total consumption). I’d prefer it if a component-swap on the board itself could be used to set a certain current level instead, but until someone really maps the thing out, using an external dimmer or resistors may be the route to go for now.
- AC-safety – you’ve got mains voltage at the leads with no isolation. Thus you’re probably going to need to mount it in an enclosure with a panel/lens so that it can’t accidentally be touched or shoot flaming debris at something if it self-combusts. You’ll have to be dead-serious about grounding and probably want to use a GFCI for extra measure.
It would definitely be interesting to see a circuit diagram for the “Smart IC” chips utilized, and see if it’s the BP5132H chips or others that actually offer the “Smart IC” behavior. Update: Located the datasheet at
http://www.bpsemi.com/en/Data/BP5132H_EN_DS_Rev_0.9.pdf http://www.bpsemi.com/uploads/file/20161215114728_476.pdf for those interested! In looking through some of the 220V COBs that used SMD’s it appeared they were using a CYT3000B (datasheet for it can be found here and product sheet for CYT3000C can be found here for those curious). Perhaps if someone really in-the-know dissects one of these and gets a little more information it’ll be possible to modify resistors to tweak the power being used.
In any case, for the time being, I’m still pretty pleased with these. No doubt if they start taking off, we’ll start to see more of them – as it is there are 150/100/70/50/30w variants (plus 50/30/20w variants in the more common square package), but if they gain enough popularity I wouldn’t be surprised if we started seeing adjustable ones way down the line or something else moderately cool.