Low loss emergency power supply for vehicle door lock

摘要

The door lock mechanism of a vehicle door is normally actuated by a motor (2) supplied from the main battery (1). In case of main battery failure a capacitor (9) which has been charged to a higher voltage than the motor operating voltage provides supply to the motor (2). The motor current under emergency supply conditions is limited by chopping the voltage. This is done by opening and closing a series switch (4) at a frequency determined by a cycling ratio controller (10). When the series switch (4) is open the motor current persists due to the self inductance of the winding and the presence of a freewheeling diode (14).