This is a power supply circuit that produce voltage 12 to 24 V. It is very simple, doesn’t need regulator just bridge rectifier, filter capacitor and transformer. A bridge rectifier makes use of four diodes in a bridge arrangement to achieve full-wave rectification. This circuit will give you 15 VDC at up to 3A.
To prevent damage to circuit or blowing that during testing, you should use a 10 ohm 25W resistor to limit the current.
Here is the schematic diagram of the circuit: