DRIVE CIRCUIT OF LIGHT EMITTING ELEMENT, LIGHT EMITTING DEVICE USING THE SAME, AND ELECTRONIC DEVICE

摘要

PROBLEM TO BE SOLVED: To provide a control circuit capable of reducing power consumption, while securely protecting a circuit.

SOLUTION: The drive circuit supplies drive voltage and drive current to an LED string 6. A first detection resistance R1 is provided on the path of the LED string 6. A voltage source 20 outputs a control voltage VDIMhaving a level according to a target luminance of the LED string 6 and a first threshold voltage VTH1proportional to the control voltage VDIM. A controller 10 generates a gate pulse signal G1 where a duty ratio is adjusted so that a voltage drop VR1of the first detection resistance R1 can coincide with the control voltage VDIM. A first driver DR1 drives a switching transistor M1 of a DC/DC converter on the basis of the gate pulse signal G1. A first comparator CMP1 stops switching operation of the switching transistor M1 when the voltage drop VR1of the first detection resistance R1 exceeds the first threshold voltage VTH1.

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