SCR Battery Charger

The silicon controlled rectifier (SCR) or thyristor is a commonly used device for handling large amounts of power. The device is rugged and can control high voltages and currents. The one important feature of the thyristor is that once it is turned on it will not turn off again, even if the gate signal is removed, unless the current through the device falls to zero. As this happens at every cycle of AC power, the controlling of the device becomes fairly simple, and is known as phase-angle firing or control.

Thyristor based battery charger uses thyristor switching principle for achieving the desired DC output. It consists of a transformer, a semi-conductor bridge rectifier, a filter circuit and a control circuit.

The AC mains voltage is transformed to a suitable level and fed to the rectifier bridge. After being smoothened by the filter circuit, it rectifies the AC input and feeds controlled DC output to the battery and load. The power output requirement is adjusted by using phase control technique which is provided by the controller. The feedback signals from the output to the controller are used for maintaining voltage regulation and current limit.