| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To appropriately output a voltage required for a constant current circuit without performing excessive boosting irrespective of a change of a constant current value of the constant current circuit used for driving a light emitting element. <P>SOLUTION: Differential voltage between a drain and a gate of a constant current control transistor 16 is detected by a constant voltage monitoring amplifier 1c and it is fed back to an error amplifier 11. Thus, output boosting voltage is kept to a voltage which can secure a normal operation of the constant current circuit 1b. Optimum power efficiency is maintainable without performing excessive boosting irrespective of the change of the constant current value of the constant current circuit 1b. <P>COPYRIGHT: (C)2009,JPO&INPIT</p> |
