Therefore in this variable power supply circuit using 2N3055 transistor, the transformer being a 0 - 40 V, the output becomes variable right from 0.6 to 40 volts maximum, that's very handy indeed. For implementing the current control feature, T3 along with P1, R5 and R4 are involved. The value of R4 is specifically becomes responsible for Step 1: Gather Things You Need. Everythings you need are: - A piece of perf board (I marked the real size of perf board which needed) - 0.23$ for that full size perfboard. - A ruler. - A knife. - A MOSFET (I use IC 06N03LA which I recycle from an old computer) - 0.18$ - Soldering wire and a solder (I forgot to take a photo) Then knowing he needed 4 mA to power each LED for backlighting he used some 1978 vintage current limiting diodes designed to pass 2mA each regardless of voltage source, within limits of course. Figure 2 The PCB layout and components layout. NOTE: Because IC number is high price.You may use the LM317 and transistor, to expand the current demand. Click HERE >>> Best DC power supply 3Amp to adjust 1.2V-20V & 3V-6V-9V-12V add transistor 2N3055 parallel from 3A to 5A easily. Related: Dual 15V Power Supply Schematic With PCB, +15V -15V 1A 1-20V, 10A Adjustable DC Power Supply Why not only change the output voltage of the SMPS (that's easy) and add an external linear current limiter (also very easy, 2 pnp's transistors with heat sink, a 0R6 resistor more two other resistors). Power dissipation will be max. 15W, that's acceptable. 15W of heat extra is 15W too much. SaL7.

power supply with current limit