Hi all
I was planning on using NCP3065 to drive some leds
and a design tool
I have 2 LEDs on it, hence 0,35mA / 6,6-7V
I have pretty much the same as their buck circuit Cin - 470uF Rs - 2x0.33 ohm in parallel = 0.165 ohm CT - 2.2nF Rsense 0.68 ohm L - 470 uH D - 1N4001 Cout - 22uF (the default value in the design tool is 220uF)
I have now created 2 independent circuits with this NCP3065. One is fried. My first circuit was on a test board. The other (present) is on a PCB made for this using design software.
My main problem is that the 3065 heats up and the LEDs starts flashing. My total current is just under mt Led current. My LED current is 320-360mA, my battery current it 310-360mA. Sometimes it simply starts off with a LED current of 30, 70 or 960mA. These 3 cases are somewhat stable, meaning the numbers are the same. It is sure that it does not switch as lot, it rather just burns off the heat until the temperature control shuts it off.
In the design tool I set Rsense to 0,68ohm / 0,35A, default there is 293mOhm / 0,8A My Rs is a bit higher, but that should not be that much a problem. And using 0,33ohm does not change anything.
Cout is 22uF in the datasheet, the desing tool says 220uF. I tried 100 and 470 but the result remains - except that when using 470uF it gives off a high tone. The coil(s) - is from Elfa, and can handle the current. I have a few but they all act the same. The diode is a 1N4001, not a swicth diode, I wonder if that can be it?
Still it does not explain why it sometimes find a stable current at 30, 70 or 960mA? And I bought 4 of this 3065's and 2 setups act the same? I am out of ideas -
The odd thing is that the K8071 kit from velleman seems to a better option - it actually works...