Abstract: An LED drive circuit for driving an LED includes a reactor L1, a switch element, a current detection resistor R1 to detect a current of the switch element, a constant current circuit 2 that generates a first control signal to control a current of the switch element to be constant, a disconnection detection circuit 4a that generates a second control signal to keep the switch element OFF if determining that a current equal to or over a predetermined value passes through the switch element when a predetermined time elapses after the timing at which the switch element changes its state from ON to OFF, and a driver of the switch element that drives the switch element and keeps the switch element OFF in case of a disconnection according to the second control signal in priority to the first control signal.

Abstract: An LED drive circuit for driving an LED includes a reactor L1, a switch element, a current detection resistor R1 to detect a current of the switch element, a constant current circuit 2 that generates a first control signal to control a current of the switch element to be constant, a disconnection detection circuit 4a that generates a second control signal to keep the switch element OFF if determining that a current equal to or over a predetermined value passes through the switch element when a predetermined time elapses after the timing at which the switch element changes its state from ON to OFF, and a driver of the switch element that drives the switch element and keeps the switch element OFF in case of a disconnection according to the second control signal in priority to the first control signal.

Abstract: A device for detecting disconnection for use in a stepping motor driver is provided having a driver circuit 3 which comprises a pair of windings 21, 22 wound in a bifilar turn arrangement; a pair of MOSFETs 1, 2 connected to the other end of each winding 21, 22; a common current detecting resistor 4 connected between MOSFETs 1, 2 and ground; a first reference voltage generator 34 for producing a first reference voltage Vt1; a second reference voltage generator 40 for producing a second reference voltage Vt2 lower than first reference voltage Vt1; a decision circuit 8, 8b for comparing the detection voltage on current detecting resistor 4 with second reference voltage Vt2 to produce an alarm signal when detection voltage is higher than second reference voltage Vt2; and a disconnection detector 11 for receiving an alarm signal from decision circuit 8, 8b after comparator 8 produces a chopper signal 17 to produce a disconnection signal upon occurrence of line-disconnection in winding 21 or 22.

Abstract: A device for detecting disconnection for use in a stepping motor driver is provided having a driver circuit 3 which comprises a pair of windings 21, 22 wound in a bifilar turn arrangement; a pair of MOSFETs 1, 2 connected to the other end of each winding 21, 22; a common current detecting resistor 4 connected between MOSFETs 1, 2 and ground; a first reference voltage generator 34 for producing a first reference voltage Vt1; a second reference voltage generator 40 for producing a second reference voltage Vt2 lower than first reference voltage Vt1; a decision circuit 8, 8b for comparing the detection voltage on current detecting resistor 4 with second reference voltage Vt2 to produce an alarm signal when detection voltage is higher than second reference voltage Vt2; and a disconnection detector 11 for receiving an alarm signal from decision circuit 8, 8b after comparator 8 produces a chopper signal 17 to produce a disconnection signal upon occurrence of line-disconnection in winding 21 or 22.