The above circuit can be useful to detect if the load of any battery charger or plug-in adaptor supply is not properly connected. The load can be a set of batteries to be charged or any other type of battery or low dc voltage operated device.
The circuit can safely operate over a 3 to 15V range and 1A max. current, provided the supply voltage is about one volt higher than the voltage required by the load.
The circuit is inserted between the supply and the load, therefore