Symmetric two-channel power supply 2x30V 5A Lm317 lm337

[Vermes]

Assumptions of the project were: the power supply should be small and have big current efficiency, display the voltage, current, power and temperature, have voltage adjustable by a switch.
Transformers used have 24V and about 5A. Schema was taken from **broken link removed**, relays were added, there is no protection I the form of thyristor. Kit **broken link removed** was modified and it was used as display module instead of DS18B20, a thermistor was inserted (temperature is displayed using bar graph in the upper right corner), operational inverting amplifier was added. The plate had to be designed in a different way, it was about the analogue and digital mass, a couple of capacitors was also added. Too small heat sink was replaced with a larger one. After replacing at current of 5A, the power supply runs for 20 minutes, then the thermal protection turns on. In addition to thermal protection, it has a current protection (adjustable) and voltage protection (enabling when the voltage exceeds 31V). Atmega8, which controls the relays and ventilator, is also responsible for all the protections. The power supply allows turning on the service menu, in which values of the ADC relay are displayed. The program was written in BASCOM.
The power supply has adjustable voltage 1,25-30V and does not change after the transistors are turned on. The voltage is stable, there are no derives.





Link to original thread – **broken link removed**

 

[RetroTechie]

Hehe, 'small' is relative. ;-)

For 5A and wide range of 1.25-30V I would have used switching regulators, linear regulators waste a lot of power (in the form of heat, as you found out) especially with a large input -> output difference (low output voltage where DC input voltage remains roughly constant).

That said, linear regulators usually have low ripple voltage at their output, which doesn't hurt for a lab power supply. As long as it works for you: cool (and mechanical construction looks like a good job). :grin: