Constant Current Driver

[john2k]

I have a slight problem, when testing the Driver and LED with a spare car battery it all works fine but when actually connecting to the side light powe source of the car, the driver blows a fuse and if i change the fuse to higher amps, the driver just shuts off. any ideas why this could be happening? i tried with another driver that is very similar and the other driver works fine but the diffrence is that the other driver has a 12V regulator soldered on to the input wire.

The supplier of the driver recommends I use a 5W 12V or 13V Zener Diode to keep the voltage at 12V. He thinks that the high voltage is causing the driver to draw too much current. I just dont understand how a 280mA constant current output driver is blowing a 2A fuse, because i measured the current draw from the driver to the LED and it's 280mA exactly. And even when i increase the fuse size, it doesnt blow the higher rated fuse but instead the driver shuts down.

any help would be very much appreciated.

thanks

 

[wquiles]

I have a slight problem, when testing the Driver and LED with a spare car battery it all works fine but when actually connecting to the side light powe source of the car, the driver blows a fuse and if i change the fuse to higher amps, the driver just shuts off. any ideas why this could be happening? i tried with another driver that is very similar and the other driver works fine but the diffrence is that the other driver has a 12V regulator soldered on to the input wire.

The supplier of the driver recommends I use a 5W 12V or 13V Zener Diode to keep the voltage at 12V. He thinks that the high voltage is causing the driver to draw too much current. I just dont understand how a 280mA constant current output driver is blowing a 2A fuse, because i measured the current draw from the driver to the LED and it's 280mA exactly. And even when i increase the fuse size, it doesnt blow the higher rated fuse but instead the driver shuts down.

any help would be very much appreciated.

thanks

Per the specs you provided earlier, it looks like it is shutting down due to a short circuit condition, OR the driver simply can't handle the voltage spikes of the auto circuitry - that would explain the recommended Zener Diode to clamp the input voltage and bleed off the extra energy during a spike. I would try to double check that you have not shorted something by accident while mounting/bolting things down, and then try the Zener.

Will

 

[john2k]

Thanks for your reply Will,

At first that is what i thought that it was a short circuit. I tested the driver indoors, and the short circuit protection is on the output wires. I tried to short the output wire on purpose and it just does not short, the driver protects it. but the input line does short. so i thought its the input line that is shorting, but i tried with new wires and everything and it still does it. The supplier themselves are not too sure why but they think its the voltage fluctuation that is the cause. I'm wondering if i should use a zener 5W 12V or use a 12V regulator on the input wire? what do you think? i will try with a zener to see if that resolves the problem.

 

[wquiles]

A voltage regulator will be more work to wire (minimum 3 terminals) vs. the Zener (2 terminals, right across the existing/front of your driver), plus the voltage regulator will have some voltage drop (depending on design/style) so your driver will see less than 12V, so it is easier to try the Zener.

Will

 

[john2k]

Thanks Will, very much appreciate your help. I will try out a zener 12v 5w later today. two of my drivers combined add up to just under 600mA total current draw. If a zener sorts the problem, will a single 5W, 12V zener do the trick for both?

oh, do i wire a zener inline with the positive input like a signal diode? or does a zener go across from positive to negative like a capacitor?

Thanks once again.

 

[wquiles]

Connect the diode across the + and - input of the LED driver, like if it were a filtering capacitor. Look in there at the section "Zener Diode Rating":
http://electrical-info.com/zener-diode/

I don't know how your driver will work with parallel drivers so I don't know. Start with the single driver, verify it works, and go from there.

Will

 

[john2k]

I don't know how your driver will work with parallel drivers so I don't know. Start with the single driver, verify it works, and go from there.

Ahhh, just realised something, could that be the problem? i've wired 2 drivers in parallel because i got one input wire coming in. but if that is the problem should it also not cause the same problem during the testing on a spare car battery indoors? i will try to seperate the two later today and see maybe that is the problem.

regarding the zener, why is the driver supplier insisting that the Zener needs to be attached inline on only the positive line and not the negative line?

 

[wquiles]

Ahhh, just realised something, could that be the problem? i've wired 2 drivers in parallel because i got one input wire coming in. but if that is the problem should it also not cause the same problem during the testing on a spare car battery indoors? i will try to seperate the two later today and see maybe that is the problem.

John,

We can't help you (I certainly can't) if you don't share with us "everything" you are doing. What you state here is NOT what you said you did above. Even if a hand-drawn shetch, please share with us "exactly" what you are wiring, how you are wiring it, etc..

Will

 

[john2k]

Sorry Will :mecry: i will draw up a quick sketch of how exactly i've wired it and post it in a few minutes.

 

[john2k]

here is a quick sketch i've drawn up. only thing i missed telling you is that when finalizing the setup i joined the 2 drivers in parallel. didnt realise that can cause a problem. specially since it worked fine indoors with a car battery

 

[wquiles]

What size fuses have blown up, and where they the slow type or fast type?

Do the fuses blow when the car is off, or while the car is running?

I would imagine the fuses blow when you turn ON the lights, right? What is the measured voltage at the terminals right before the fuses blow?

 

[john2k]

2A regular blade fuses blow. The fuses blow as soon as the side lights are turned on not with ignition. I replaced with a higher 5a one and instead of blowing the fuse, the driver lit the leds and then after a few seconds shutdown. I'm going to go to the car shortly and I'll measure the voltage just before the fuse and get back with the results, I couldn't find any Zeners at my local electronics store so I'll test with a regulator for now

 

[john2k]

after testing on my car i have realised that after the fuse blew the first time, the driver itself actually blew and thats why when i put a new higher rated fuse nothing happens. i tried with a new set of drivers wired in parallel with a fuse and it did the exact same thing the fuse blew because something happens to the driver and it blows and during this time it also blows the fuse and after that point the driver no longer works and then just does not draw any more current. I thought i had a spare 12v regulator but couldn't find it to test with a regulator. The voltage just before the fuse reads 13.8V and it didn't really fluctuate much. The indoor car battery i have reads about 13.5v and when i wire the drivers to that it does not blow. I'll try and get a regulator tomorrow and test with that.

 

[wquiles]

after testing on my car i have realised that after the fuse blew the first time, the driver itself actually blew and thats why when i put a new higher rated fuse nothing happens. i tried with a new set of drivers wired in parallel with a fuse and it did the exact same thing the fuse blew because something happens to the driver and it blows and during this time it also blows the fuse and after that point the driver no longer works and then just does not draw any more current. I thought i had a spare 12v regulator but couldn't find it to test with a regulator. The voltage just before the fuse reads 13.8V and it didn't really fluctuate much. The indoor car battery i have reads about 13.5v and when i wire the drivers to that it does not blow. I'll try and get a regulator tomorrow and test with that.

If the car was OFF when the fuses are blown, there should be no spikes in the system (alternator is not running), so you are just slowly draining a very large capacitor battery. The 13.8 volts sounds a little high for a car that is not running- same with the inside battery - they both seem high. What are you using exactly to measure the voltage?

At any rate, the specs you quoted earlier state a max. of 24 volts, so either way your regulator is not living up to its specifications as 14volts is well bellow the max. rating. Something is still not right .....

 

[john2k]

I opened up one of the blown drivers and there is no regulator component on the circuit board itself, i'll take a picture later and post it. The driver doesnt have any regulator yet has a variety of input range (confused how that works). I thought maybe it is the fluctuating voltage issue so i used a indoor A/C - D/C adjustable voltage PSU but that only outputs 300mA so when i adjust the voltage output of that to the MAX of 18V nothing happens to the driver (but i am guessing that could be because of the low current of the PSU)

Also, just reading the specs i posted above, the Input voltage says 12V AC / DC and the maximum ratings says Supply Voltage (Vin): 24VDC / 15VAC. So based on this i thought it can take 14V easily. Well at least indoors it was taking it.

 

[john2k]

Will,

I think i've got to the bottom of the problem. I built a 12V 1.5A low dropout regulator with a few capacitors and then connected that just after the fuse before the input of the 2 drivers and then from the regulator the 2 drivers are wired in parallel powering the two led units and it all works fine. Only concern is that i put the regulator on a matrix board with a heatsink and heatsink compound and after 10 minutes of running the plastic box was rather hot. Not hot to melt anything but hot as if its been in the sun. Shouldn't the regulator only be drawing under 600mA as each driver is 280mA? is 600mA of current supposed to get very hot that the enclosure will feel it?

 

[wquiles]

Will,

I think i've got to the bottom of the problem. I built a 12V 1.5A low dropout regulator with a few capacitors and then connected that just after the fuse before the input of the 2 drivers and then from the regulator the 2 drivers are wired in parallel powering the two led units and it all works fine. Only concern is that i put the regulator on a matrix board with a heatsink and heatsink compound and after 10 minutes of running the plastic box was rather hot. Not hot to melt anything but hot as if its been in the sun. Shouldn't the regulator only be drawing under 600mA as each driver is 280mA? is 600mA of current supposed to get very hot that the enclosure will feel it?

John,

Power lost in the regulator as heat is calculated by the voltage drop across the regulator * times the current going through the regulator (input and output current are equal in this type of regulator).

So while the unit is working, measure:

1) Input voltage to the regulator in volts
2) Output voltage to the regulator in volts
3) Input or output current (same value) in amps (around 0.6A in your case)

Power lost (in watts) = (Input voltage - output voltate) * current

My guess is that you have quite a bit of voltage drop across the voltage regulator, hence why it is getting so hot. You might need to put a heatsink on that regulator (make sure it is expose to air). It would be even better to bolt the external regulator/heatsink to a metal part of your car (but be careful that your particular regulator has the heatsink tab tied to GND, NOT TO THE OUTPUT - or else you will short the output when you touch the metal in your car).

Will

 

[john2k]

Thanks for your reply Will. I have put quite a big heatsink on it and thats why i think the plastic enclosure is getting hot. Its not getting that hot. Just hot as if it was sitting in the sun for a while. Input voltage to the regulator is 13.8V output is 12V and current is 0.56A. So based on the formula the power lost in watts is just around 1W. I guess i'll see how it goes. Was just concerned that the heat made the plastic enclosure hot. I am guessing because its enclosed thats probably why. Maybe I should vent it out somehow.

 

[wquiles]

A heasink enclosed in plastic case is "almost" as good as having no heatsink at all. What you have now is basically a miniature oven, slowly cooking its contents to death.

You "need" to make sure the heatsink's fins/surface is exposed to moving air. Or as I mentioned above, bolted to a metal part of your car to transfer heat by conduction.

Will

 

[john2k]

Thanks Will,

I have another question. I've been using another branded driver for my brothers car for a few months which is very similar in specs. it's been working perfectly. One driver for each LED unit. But each LED driver has a 12v regulator circuit with some capactiors wired to the input. But recently one outputs dimmer than the other. And after about 40minutes or so the dim one shuts down. I am assuming it might be the regulator or even the driver that is going wrong. Just wondering if this is normal behavour of a failing driver?