Led-tech underpowered Buck problem

[M:kko]

Hi all!

I'm having problems with Buck (non?)constant current power supplies bought from www.led-tech.de. The models are marked for 700mA and 1000mA, but the outputs are only about 580-600mA and 750-800mA for different set-ups consisting from one to four leds. Input voltage is 24V. The output current is increased slightly if the input voltage is increased (I've also tried with 12V) or the number of leds is decreased. No PWM dimming signal is connected.

Is it normal for bucks that the actual output current is so much below the spec??

-Mikko

 

[panicmechanic]

:welcome:
I found a discussion in their forum, people are having the same problems there.
If you need the correct output, and if you like to order from a german shop, I recommend those from PCB-Components.

 

[M:kko]

Thanks! I tried to look for information on their forum, but didn't find anything as I don't speak german. I contacted the seller about the issue, but haven't received any comment. Now I'll try to send the bucks back to the seller on account they don't function as advertised. Instead of buying new bucks, I guess I will give the Meanwell ELN-60-48 a shot. (I'm building led grow lights using about 50 leds, so the Meanwell driver is probably more convenient way to go anyway. I just didn't know about it's existence at the time I ordered the bucks.)

 

[Nos]

you need a multimeter with true rms function to measure the current. Since bucks are using pwm some multimeters cant show you the right current.

 

[M:kko]

The measurements have been made with Velleman DVM850BL. I couldn't find information whether it has this "true rms function" or not.

Another thing is that the measured current changed (about 40mA) depending on the number of leds connected to the output (and also on the input voltage). Even if the Velleman is not giving the correct value of the current, it should still remain constant. Right?

 

[M:kko]

Well, it seems that led-tech is ignoring my enquiries on how to return the Bucks. I know one shop I'm not doing business with ever again... :thumbsdow

 

[SemiMan]

If the output is not PWMed, then you do not need a true-RMS meter to read the current to a relatively high degree of accuracy unless the output is capacitor free which is possible. Some driver chips out there work without capacitors.

Semiman