I ran into a very interesting scenario today. After doing some tests with a DC-DC converter using a constant current DC electronic load, my efficiency was able to hit 99%. When I connected the converter to a series of high power LEDs using the same current, my efficiency dropped to 80%. The input voltage remained constant for the entire operation.

Any ideas why this would have happened? I'm a bit baffled.

 

Show us a rough draft of your layouts. Right now all we can do is guess.

 

Essentially, my DC-DC convert is one I build from scratch and pretty much looks like the one here:

It's okay, I don't want to trouble anyone by going into too much. It's nothing critical or very important, however I was just kind of curious if there was an immediate reason or consequence of powering LEDs.

 

Please post the circuit that limits the current for the LEDs.

Maybe the Mosfet has poor conductance.
Maybe the inductor's core saturates when the curcuit is overloaded by the LEDs.

 

Here is my schematic, and below is a photo of the actual circuit. I am controlling the MOSFET via PWM from an FPGA.

Schematic:

I am using the following components:

MOSFET: IPP50CN10NG
470uH Inductors: 542-2320-V-RC
Schottky Diode: STPS40M100CT
Ceramic caps: CKG57NX5R1H226M

Thanks