| 摘要 |
PROBLEM TO BE SOLVED: To provide such a power LED driving circuit also used as battery indicator as being capable of preventing the flickering of a brightness due to the fluctuation of power voltage to drive a power LED and ensuring light-off of the power LED when the power voltage becomes prescribed voltage or below. SOLUTION: A power LED driving circuit has a power LED, a protecting resistor R1 provided in series to the power LED to determine a current flowing in the power LED, a driving power control transistor Q1 to which constant voltage is supplied from a power supply via a constant voltage circuit to control driving power supply to the power LED and a power voltage monitoring transistor Q2 operated when power voltage becomes prescribed voltage or above determined by a resistor R2 and a resistor R3. When the power voltage becomes the prescribed voltage or blow, the power voltage monitoring transistor Q2 is turned off and so the driving power control transistor Q1 is also turned off to cut off power supply to the power LED. |
