LTC3780 voltage falling after a couple of seconds under load

Thread Starter

Moshtaraq

Joined Aug 12, 2021
2
Hi,

I just made a variable voltage power supply like GreatScott on youtube has made. I tried the supply with a 48W 12V LED work light I want to fit on my car. When I plug it in the 12V, the current reads 1.8A for about five seconds and then it goes to 0.8A and 10.8V. Even when I increase the voltage with the potentiometer on the LTC3780, voltage and current stay the same.

Any advice on how to go about debugging this?
My only idea is that the LED light is somehow regulating something, so I've ordered a power resistor just in case.

Thanks in advance,
Jens
 

LowQCab

Joined Nov 6, 2012
1,189
It's probably over-heating,
possibly from an undetected oscillation.
What Frequency are You Trying to operate this device at ?
How did You determine the Choke and Capacitor Values in the Output-Stages ?
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Juhahoo

Joined Jun 3, 2019
226
I tried the supply with a 48W 12V LED work light I want to fit on my car. When I plug it in the 12V, the current reads 1.8A for about five seconds and then it goes to 0.8A and 10.8V. Even when I increase the voltage with the potentiometer on the LTC3780, voltage and current stay the same.
So the LTC board gets power from the 12V battery and LTC feeds 12V LED light? Which amperage you measured, output from LTC or the Battery output?
Does it work with lower loads?
Did it work before you made the mods ?
What mods you made to it?
 
Last edited:

LowQCab

Joined Nov 6, 2012
1,189
When You said "I made", I assumed that You built the Regulator yourself.
Now You say it's from China, that explains a lot.
You really never know what you're going to get from China,
You might be able to just buy another one, and it may work acceptably.
Quality Control is very questionable from China,
and Power-Electronics is especially bad in this respect.
I'll bet it was advertised as being "500-WATTS" too.

It's also very likely that the LTC3780 is a cheap copy, (more like 100% guaranteed),
and who knows what type of "cheap-knock-off" FETs they gave You.
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