Patent ID: 7009352

Claim:
A power-window jamming preventing apparatus, comprising; a current sensing circuit, which senses a motor current flowing through a motor for driving a window glass; a current limiting circuit, which increases and decreases the motor current based on a current limitation control signal outputted from the current sensing circuit when an amount of increase of the motor current exceeds a predetermined vale; and a jamming determining circuit, which determines a jamming of a foreign matter in the window glass based on increase of the motor current to reverse a rotation of the motor, wherein the current sensing circuit includes; a shunt resistor, on which the motor current is flown; a reference resistor, which has a resistance value that is n times the shunt resistor; and a current following circuit, which increases and decreases a following current flowing through the reference resistor so that voltages respectively applied to the shunt resistor and the reference resistor become always equal to each other; wherein the current following circuit includes: a following current control circuit, which controls the following current so as to be one n-th of the motor current, and generates a first reference voltage having a pulsating component of the motor current; and a capacitor, which generates a second reference voltage indicating an average value of the first reference voltage by charging and discharging; and wherein the current sensing circuit includes a first comparator which compares a third reference voltage higher than the first reference voltage with the second reference voltage, and outputs the current limitation control signal based on a comparison result thereof, the apparatus further comprising, a motor current sensing range expanding circuit, which expands a motor current sensing range by increasing a ratio of the current sensing circuit having the shunt resistor and the reference resistor when the first reference voltage becomes equal to or lower than a comparing voltage indicating a voltage input range of an active element of the following current control circuit and the state of the first reference voltage and the comparing voltage continues for a constant period of time.