| 摘要 |
<P>PROBLEM TO BE SOLVED: To detect a cathode-side voltage of a light-emitting element without requiring a high breakdown voltage element. <P>SOLUTION: A voltage detection circuit 40 in a driving system 10 for a light-emitting element has a function of detecting a cathode voltage V<SB POS="POST">C</SB>of a light-emitting element 12 and outputting the voltage to an LED driving circuit 20. The voltage detection circuit 40 includes a control transistor 46, a resistor 48, a differential amplifier 42, and a luminance control switch 50. Moreover, the voltage detection circuit 40 includes a setting unit 52 which, when the voltage level of an output terminal of the differential amplifier 42 is at the H level for turning on the control transistor 46, turns off a measurement switch element 54 to connect a measurement current source 60 to the other end of the resistor 48. When the voltage of the output terminal of the differential amplifier 42 is at the H level by the setting unit 52, a voltage detection unit 70 detects the voltage at a measurement position 18 and outputs this as the cathode voltage V<SB POS="POST">C</SB>of the light-emitting element 12. <P>COPYRIGHT: (C)2012,JPO&INPIT |
