Patent ID: 8164276
Filing Date: 2012-04-24
Classification: H05B

Abstract:
1. An LED drive device for driving a plurality of series-connected LEDs, comprising: a first switching element which drives at least one of the LEDs; a second switching element which drives at least one of other LEDs different from the at least one of the LEDs driven by the first switching element; and a control circuit which controls the first switching element so that the sum of the value of a current flowing in the first switching element and the value of a current flowing in the second switching element is kept constant; wherein the control circuit includes: a current setting circuit which outputs a current setting value for setting the current flowing in the first switching element; a current regulating circuit which outputs a current regulating signal for regulating the first switching element so that the current flowing in the first switching element is made coincident with the current setting value; the LED drive device further comprising: a third switching element which drives at least one of other LEDs different from the LEDs driven by the first and second switching elements; and a break circuit which outputs a signal for interrupting outputting of the current regulating signal to the first switching element in accordance with the value of a current flowing in the third switching element and the value of a voltage set in advance; a fourth switching element which drives at least one of other LEDs different from the LEDs driven by the first, second and third switching elements; a second current setting circuit which outputs a second current setting value for setting the current flowing in the second switching element; a second switching element break circuit which outputs a signal for interrupting outputting of the current regulating signal for regulating the second switching element in accordance with the value of a current flowing in the fourth switching element and the voltage value; and a logic circuit which supplies the signal output from at least one of the break circuit and the second switching element break circuit, to the first switching element.