Under utilize an LED driver? Electronics experts?

[SC Reefaholic]

Looking at changing up my LED build and want to know what effect under utilizing an LED driver will have. HLG240H-48B is rated at 48v and 5A. But I want to run 5 strings of 10 XPE RBs on it at 1000mA MAX. Forward voltage is only rated at around 38V. What effect will that have on the life of the driver and on its output in amps?

I ask because the HLG240H-42B is rated at 42V and 5.72A so that would be too much current for 5 strings at 1000mA but if I only put 38v on the 240-48 will it cause the output to go up above 5A any?

In other words, with this driver, is output in A affected at all by use in Volts?

 

[jedimasterben]

I would instead purchase the HLG-240H-48 (or -48A) and use five LDD-1000H in between. I would not run parallel strings off of such a high-amperage power source, if one LED in one string fails, the rest of the current will now be divided among four strings, increasing their temperatures and likelihood of failure, which will again lead to increased current in the other strings.

In addition, if they are not all on the same heatsink, then if one string's LEDs get hotter than the others, they will reduce the amount of voltage they need and their current will increase, and the other strings will decrease, reducing their temperature and increasing their forward voltage, while the hotter string will get even hotter from more current, which further reduces the voltage, leading to getting hotter, and so on. It's called thermal runaway.

tl:dr, buy drivers and use the HLG only as a power supply.

 

[SC Reefaholic]

Strings are balanced, they are all on the same heatsink and have fastblow fuses protecting each string. Have been running 4 strings off a hlg185h-36b controlled by an Apex for 2 years with no problems. Increasing the size of my build and want to use the 36b for another setup so need a new driver for the new 5 string setup. Just need to know what effect it will have on the new driver and its output with the lower voltage demand.

 

[oreo57]

. Just need to know what effect it will have on the new driver and its output with the lower voltage demand.

nothing...it is a constant current driver.. It will "ramp up" the voltage till it outputs 5A..

If your worried about the voltage.. get the "c" version....

 

[jedimasterben]

nothing...it is a constant current driver.. It will "ramp up" the voltage till it outputs 5A..

If your worried about the voltage.. get the "c" version....

No, the voltage will not increase as long as the load of the LEDs does not increase. The current is what changes via dimming on the HLG when run in constant current (direct drive) mode. When run in constant voltage mode (when it has separate DC-DC drivers connected, no LEDs) then the voltage runs constant 42v (or whatever model it is) and the current changes depending on the load.

e.g., running 4x strings of 10 LEDs with 3.6v each, the HLG-240H-42 will output 36v and 5.72A split across the four strings, which in a perfect world would be 1.43A each. Take that to 5x strings of 10 and it will still output 36v but with 1.15A each string. The voltage will not increase.

 

[SC Reefaholic]

Thanks Jedi. I asked because I know that with the ELN series there is a correlation. The ELN60-48D is supposed to be rated max 48v and max 1.3 amps. But if you only utilize 38 to 40 volts on an ELN60-48D then it will actually drive at near 2 amps. Its been documented.

So, if I only have 38v on an HLG240-48b I just wanted to make sure the same issue didn't cause it to exceed the 5 amp max rating like the ELNs do.

 

[jedimasterben]

Thanks Jedi. I asked because I know that with the ELN series there is a correlation. The ELN60-48D is supposed to be rated max 48v and max 1.3 amps. But if you only utilize 38 to 40 volts on an ELN60-48D then it will actually drive at near 2 amps. Its been documented.

So, if I only have 38v on an HLG240-48b I just wanted to make sure the same issue didn't cause it to exceed the 5 amp max rating like the ELNs do.

Those were defective ELN. Constant current drivers don't act like that when they're working properly

I've tested and used many ELN drivers and never had one that would output more than the current set as maximum via SVR2, but there are always bad apples (and probably in that case a bad production run). 2A would have destroyed their LEDs very, very quickly.

 

[oreo57]

No, the voltage will not increase as long as the load of the LEDs does not increase. The current is what changes via dimming on the HLG when run in constant current (direct drive) mode. When run in constant voltage mode (when it has separate DC-DC drivers connected, no LEDs) then the voltage runs constant 42v (or whatever model it is) and the current changes depending on the load.

e.g., running 4x strings of 10 LEDs with 3.6v each, the HLG-240H-42 will output 36v and 5.72A split across the four strings, which in a perfect world would be 1.43A each. Take that to 5x strings of 10 and it will still output 36v but with 1.15A each string. The voltage will not increase.

The 48B has max amp at 5 you will never get 5.72A (in theory)
PWM "flickers" the current.. it does not change.. only the full on off period changes.. Analog dimming will change current ...
And..as I understand it..

What any current regulator does is this: measure the current through the device, then vary the voltage supplied to the LED accordingly in order to maintain a particular constant current. If an LED has a lower Vf, the driver will supply a lower voltage in order to still see 80mA. If an LED heats up and CHANGES Vf, current will start to increase, the driver will sense this, then back off the voltage slightly until the current settles back down to 80mA again.

That is how the driver works.. After that the PWM will flicker the duty cycle..AFAICT.. I'm sure there are variations..

This is very different from "PWM Drivers" used in some flashlights which run the LED at a fixed current only during the "on" portion of the cycle, and modulate the light output duty cycle to dim the light. In a regulted switching mode regulator, the output current to the LED is held constant, and the input current from the battery is modulated. In some cases, both the power from the battery, and the power TO the LED are filtered so that the whole PWM and transforming action only really happens "inside" the driver.

HLG240H-42B is rated at 42V and 5.72A.

That will output 5.72A unless adjusted internally.. W a PWM dimmer you can "pulse" the full current and keep the LED's from overheating and/or burning out by dimming.. giving the LED a "rest" period..so to speak.. Not recommended though.

you can test this "theory" easily.. Why do you think you can run any single Vf LED w/ a 1000mA constant current driver (if the LED can take 1000mA).. It adjusts the V out..

.

Thus, the total resistance around the outside loop of the circuit remains constant. Since the circuit is a current regulator, you know that output voltages will vary as the regulator maintains a constant current output.

http://www.tpub.com/neets/book7/27l.htm

 

[SC Reefaholic]

The 5.72A he was referring to was from the 42B I mentioned in my first post.

 

[SC Reefaholic]

I think my final configuration is going to be:

HLG185H-48B with 4 strings (48 total) of B/RB at 975mA per string max
HLG120H-42B with 2 strings (24 total) of CW/NW at 1450mA per string max
ELN60-48D with 1 string (12 total) of Lime/Green at 1000mA per string max
ELN60-48D with 1 string (12 total) of Violet/Red at 700mA per string max

Each driver independently controlled by a separate channel on my Apex. All strings are balanced and have fast blow fuses inline. I've been running a similar setup on a smaller scale for a couple years now and it has worked really well. Now as long as the advertised max amps are accurate for these drivers, I shouldn't risk over driving any LEDs here. But the fuses are there just in case.

 

[oreo57]

Seems you got things in hand.. How are you sizing your fuses??
If you run 5A through 5 strings and lose one you have 1.2A through each of the 4 remaining.. If you lose 2..1.66A each... So what size fuse?...

Addendum for understanding..
http://grietinfo.in/projects/MAIN/EEE/A.2-CONSTANT CURRENT AND CONSTANT VOLTAGE REGULATOR.pdf

CONSTANT CURRENT:

Constant current
is a term most often used in
electronics to describe a system that can vary the
voltage across an electronic circuit to maintain a
constant electric current.

An important usage of constant current power supplies
are
LEDs, Fluorescent lamps that have very dynamic
electrical resistance and optimally must be operated
within a short range of currents.

 

[SC Reefaholic]

Actually only sending 90% to the strings to begin with. The Apex has an issue with its 0-10v control. Sometimes it has been known to send as much as 15 volts! So I built a zener diode regulator with a max capacity of 9.1 volts. Therefore, no matter what the Apex sends, the drivers will never receive more than 9.1 volts. Using a 1 amp fuse on the 1000mA strings and a 1.5 amp fuse on the 1500mA strings. That way if one string blows, the other 4 fuses will blow before I burn up any LEDs. I have a couple ELN60-48Ds in a box as backup if I need them. If I cant fix the main issue, I can simply plug the remaining strings into an ELN60 for a short time until I figure out the problem. Plug n Play.

This is my current setup.

 

[oreo57]

Actually only sending 90% to the strings to begin with. The Apex has an issue with its 0-10v control. Sometimes it has been known to send as much as 15 volts! So I built a zener diode regulator with a max capacity of 9.1 volts. Therefore, no matter what the Apex sends, the drivers will never receive more than 9.1 volts. Using a 1 amp fuse on the 1000mA strings and a 1.5 amp fuse on the 1500mA strings.

Oh if I remember correctly that can be compensated for in the driver.. but your fuses would probably blow. One of the reasons to change the amps on the driver so it outputs 1000mA @9V... I believe the driver can exceed its spec by a bit.

also supposedly the P drivers work in dual mode (10v or PWM) but the D don't... so you may be able to hedge your bets here.. I'll see if I can find the info.. though many here are way more familir w/ this driver than I.

I've already gone though this nightmare and have shifted to the LDD series and "pure" PWM... W o2 surpluses "converter" there is no need really for "analog" dimming.. Just an FYI I believe there is a "commercial clone" for sale out in the wild..

PS: your image links appear bad...

Here is this:

You only have to make a minor adjustment to the SRV2 screw inside the Meanwell to "trick" it into giving you a full 1,000mA using 9v, but it works like a charm and couldn't be easier, so long as you know how to use the DMM to measure current while you are adjusting that SRV2 screw.

http://www.reefcentral.com/forums/showthread.php?t=1793374&highlight=meanwell&page=7