I have built a small LED panel from straw hat LEDs (blue), 4 in series each, and 12 in parallel. I have figured out forward voltage is about 3 volts.
Brightness distribution is 100% even.
I am using a MC34063 buck regulator. It even has a 1m piece of wire as a current sense resistor. Maybe it is too high a resistance (thin wire wrap wire).
Because the chip turns too hot even at only 280mA output current. It turns so hot the current is decreasing down to 230mA.
Maybe the inductor is not right? I use a 220uH toroid with 1 Amps spec.
Input voltage is 19.5 VDC from a laptop adapter. Output voltage is about 12V.
The diode is a good fast recovery diode, as well 2x 100uF caps.
I tried 1nF and 470pF but both frequencies result in too much heat dev.
Should I add an external IRF MOSFET? As they have a larger metal tab, and can easily be cooled. The type I want to use is a PNP MOSFET. I also have various BJTs around here. If I have PNP is it better to use than NPN for a buck regulator? But why not use a MOSFET.
True I have never done that with MC34063.
The light output I get from the 48 LEDs panel is very satisfying. But getting so much heat from one small panel already! There must be something wrong in my circuit, or is it really the MC 34063 is only good for a few 100mA?
Also I have a few different coils here to change if need be. I am not too bright to know the values for a buck so maybe if the value is not right, explain.
Brightness distribution is 100% even.
I am using a MC34063 buck regulator. It even has a 1m piece of wire as a current sense resistor. Maybe it is too high a resistance (thin wire wrap wire).
Because the chip turns too hot even at only 280mA output current. It turns so hot the current is decreasing down to 230mA.
Maybe the inductor is not right? I use a 220uH toroid with 1 Amps spec.
Input voltage is 19.5 VDC from a laptop adapter. Output voltage is about 12V.
The diode is a good fast recovery diode, as well 2x 100uF caps.
I tried 1nF and 470pF but both frequencies result in too much heat dev.
Should I add an external IRF MOSFET? As they have a larger metal tab, and can easily be cooled. The type I want to use is a PNP MOSFET. I also have various BJTs around here. If I have PNP is it better to use than NPN for a buck regulator? But why not use a MOSFET.
True I have never done that with MC34063.
The light output I get from the 48 LEDs panel is very satisfying. But getting so much heat from one small panel already! There must be something wrong in my circuit, or is it really the MC 34063 is only good for a few 100mA?
Also I have a few different coils here to change if need be. I am not too bright to know the values for a buck so maybe if the value is not right, explain.
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