It costs about 4$, and every other specification is already in the product name.
Now I wanted to use one of these modules to directly drive a high power LED with any 12V battery (I'm using a lead-acid battery).
Modifying this module is not very complicated, anyway I will show you some details of this module, gathered whilst analyzing this part.
Currently, this setup is working, but its not tested well:
* The current can be regulated to: ~0.9-1.4A
* Only one LED setup tested (2x 10W LEDs, 1050mA)
* Only one input voltage tested: 12V/1.5A
* Further testing: input voltage range
* Further testing: output current/voltage range and ripple
* Test different combinations of Shunts
It's very easy to modify this converter to be constant-current controlled:
You need following parts:
3W shunt (the value depends, first setup: 0.86Ohm)
2pin Screw terminal
A little bit of 1.5mm² wire
As you can see in the schematic image, not very much to do.
If you need further help, please write :-)
I tested this setup already with following currents and LED power:
Vin: 12V Iout 1050mA, 2x10W LED
Vin: 12V Iout 1750mA, 1x50W LED
You can adjust the current with the poti, if it has the lowest resistor, the current is also the lowest possible one. Due to the FP1539 feedback circuit, the controller regulates until there are 0.5V at the feedback pin.
If you have a 0R poti, this eqals to:
I = U / R = 0.5V / <R-shunt> = 0.5V / 0.68Ohm = 0.735A
Of course, a lower shunt value increases the minimum current, but it also decreases the power losses on the resistor:
Pshunt = I out ² * Rshunt = 1.75A² * 0.68Ohm = 2.1W -> nice, within the specs :-)
If you want to increase the efficiency, decrease the Rshunt value.
For example: If I know, that I only use about 1.5A (or 1.75A+/- a little bit adjustment), let's try different values:
I = U/R = 0.5V / 0.47Ohm = 1.06A min -> Pshunt = 1.75² * 0.47 = 1.43W (only 70% of the previous value)
I = U/R = 0.5V/0.33Ohm = 1.51Amin -> Pshunt = 1.75² * 0.33 = 1.01W (even more efficient)
Ok, for my setup, I will modify my CC controller to support only 1.5A+, but it reduces the wasted heat by 1W (2% :-)).
Next time, I will write about the whole feedback circuit in detail!