This Power Supply was designed as an easy Project to get used to soldering - and at the end - have something useful. The fact that factories stop producing linear Power Supplies makes it even more interesting.

This device is based on the "good old" LM723, UA723 e.a. It uses 4 diodes which form a bridge rectifier, followed by three large capacitors. As the LM723 by itself can only deliver 150 mA, we added two transistors (BD243C) and a driver (TIP117) to deliver "some more" current. The two currents are added up with R5,R6 (each 0.22 Ω) to compensate for Ube differences.

The current is then sensed via R10 (0.33 Ω, fine adjusted with R11) and the voltage is used to drive a transistor inside the LM723 - so the max. current is approx. 0.6 V / (R3//R11).

For the case that this device is in a surrounding with very few convection, the temperature is also monitored with an NTC (10kΩ, from Epcos, B57703-M103-G40 or whatever is in your treasure box :-). A comparator triggers, if the resistance of the NTC drops below 1.8 kΩ - this is somewhere near 70 °C.

The webmaster does not read these comments regularely. Urgent questions should be send via email. Ads or links to completely uncorrelated things will be removed.