The circuit operation commences once the power supply is available. AC power of 230V RMS is stepped down to a voltage of 15V RMS by the step down transformer. This low voltage AC voltage is then rectified by the bridge rectifier to produce an unregulated DC voltage with AC ripples. The filter capacitor allows the AC ripples to pass through it, thus producing an unregulated and filtered DC voltage across it. Here two operations take place: – 1. This unregulated DC voltage is fed directly to the DC load (The battery in this case) through a relay. 2. This unregulated DC voltage is also fed to the voltage regulator to produce a regulated 12V DC supply.