# Understanding this Mean Well Power Supply

I purchased, I believe, the wrong power supply for my purposes, but I'd like to understand a few aspects of its specs: https://www.meanwell.com/webapp/product/search.aspx?prod=ELG-200&mws=8519DC592A6AAA18

This unit appears to have no way to adjust the constant voltage aspect - so am I correct that this will never output above 24V, even if I were to hook up several LED strips in series (each one with an operating range of 23-24v) - so what is the purpose? I can hook up my LEDs in parallel, but then the constant current aspect seems wasted?

In the INPUT section, it says lists 142 ~ 431VDC - what does this mean? This power supply can handle both AC and DC input?

• What are your LED current specs? – Tony Stewart Sunnyskyguy EE75 Jan 21 '19 at 21:55
• @SunnyskyguyEE75 sorry, my LEDs are SI-B8U261560WW (F562B) – Doug Moscrop Jan 21 '19 at 22:20
• What is the exact part number of your PSU? The datasheet you linked is for a series of products, of varying voltage ratings. – marcelm Jan 21 '19 at 22:27
• The ELG-200-24B – Doug Moscrop Jan 21 '19 at 23:59

Since this 24Vdc max CC regulator works in both CC or CV 24V mode, it is safe to put 23~34V Strip LEDs in parallel but will not work in series. For that you would need >=48V+ regulator.

But you still have up to 200W available LED power. Since LEDstrips also have series R current limiting they can operate off 24V CV and they dim at ~3/4 of rated voltage due the series R drop voltage on the strips, which can vary.

The % PWM of max current must be compared to your load current. If your load current is greater than 8.3A then the supply starts to limit, so if your load was expected to be 10A in parallel or 240W then you must adjust PWM to <=8.3/10=83% MAX to keep operating at 200W.

If the load on 1 string was only 50% of rated current when attached, then PWM from 50% to 100% would result in 24V or no change then full range regulation works from 0 to 50%.

The pertinent tolerance is @ 1120mA P= 24.5 to 27.1 W. This means round down 200W/24.5= 8 strings or 200/27.1 = 7 strings.

So you can use 8 strings but you must monitor current to stay within 100% which might be as much as 200/27W*8= 92%max PWM and 7 strings requires no testing but full dim range might be from 0 to 24.5*7/200 = 87% PWM at full brightness and same above this at 100% current.

• Thanks, I do in fact have 7 strings but because my supply is 120ac the unit is only rated for 150w, I think your advice is similar - I can do 7 but they won't reach full brightness – Doug Moscrop Jan 22 '19 at 0:01
• So then use only 6 and set maximum PWM ~ 95% or 7 and set max to < 75% – Tony Stewart Sunnyskyguy EE75 Jan 22 '19 at 1:21

With LED's you want constant current This keeps the LED's from exceeding their current rating and let's the designer avoid using a current limiting resistor or some other circuit to keep the current through the LED constant.

This supply does both, but it depends on the load placed on it. It's a PWM driver, meaning it modulates the voltage to get the correct amount of current through the LED's. If the supply is in constant current mode (with the dimmer option with a 0-10V signal or PWM to go from 0 to 100%) then it will run from the voltage from 50% to Max. If you use 100% PWM then it will output it's full voltage.

You can string LED's in parallel and still use constant current.

• I have several (flexible on how many) Samsung F562B which are 24V LED strips. You're saying I can run them in parallel and basically they won't get more than 24V, and I can use the current limiting feature of the power supply to give them less (so dimming will still work). If one fails, the others won't get more than ~24V though (so no cascading failure) ? – Doug Moscrop Jan 21 '19 at 22:25
• But "full voltage" is 24V, right? Compared to say mouser.ca/datasheet/2/260/meanwell_HLG-320H-C-spec-1179890.pdf, I would have been running the LEDs in series and had more (N times ~24, depending on the current I choose) – Doug Moscrop Jan 21 '19 at 22:27

Some LED strips are designed to work with 12 V as they have build-in current limiting resistors for the LEDs so these can be powered directly from 12 V DC.

If you have two identical LED strips that are designed for 12 V then you can connect them in series so that each gets 12 V. You have to make sure that the LED strips are identical and designed for 12 V DC. Do note that if some LEDs break on a strip the other LEDs might get more current and break sooner. To avoid that use a 12 V supply and connect the strips in parallel (not series).

If your LEDs specify a current then use a LED driver with the rated current.

In the INPUT section, it says lists 142 ~ 431VDC - what does this mean? This power supply can handle both AC and DC input?

Yes it can. That's because these type of supplies convert the input voltage to DC in order to work. So AC will be rectified to DC. DC will just remain DC.

The rest of the circuit is designed to work on high-voltage DC. The electronics will adapt automatically to compensate for low (142 V DC) or high (431 V DC) input voltages. It does that by measuring what voltage comes out at the low voltage side (here 24 V DC). It is a common principle nearly all power supplies (most common example: a phone charger) use.