A very simple high current power supply circuit can be designed using this circuit diagram that allows a maximum output current of 1A. This high current power supply circuit is designed using conventional electronic components and output voltage adjustment can be switched between some preset values, between 3.5 and 9 volts.
When there is current through the load, the voltage on D1 and D2 is sufficient for the T2 to lead and activate relay . Following open relay T1 and power.
When is no load current, T2 locks. Base current through T1's it will charge C2, such that after a few seconds, the relay will be deactivated. Supply will be connected again by reconnecting load and pressing S1.
For each increase of 100 ohms of resistance connected between points A and B output voltage will increase by about 1 V.