| 摘要 |
PURPOSE:To reduce power consumption which does not contribute to an optical output, to decrease power cost and to prevent a device from deteriorating due to heat generation by connecting a plurality of LEDs and one constant-current circuit in series. CONSTITUTION:Two LEDs 1, 2 emit green and red lights. The LEDs 1, 2 and one constant-current circuit 3 are connected in series. A constant-current circuit 4 is connected to the anode of the LED 1. A constant-current circuit 5 is connected to the connecting point of the LED 1 to the LED2. A transistor TR4 is connected between the connecting point of the LEDs 1, 2 and a GND. An output S1 is applied as a switching signal to the circuit 3. An output S2 is applied as a switching signal to the circuit 5. An output S3 is applied as a switching signal to the transistor TR4. When both the LEDs 1, 2 are lit, both inputs G, R are set to '1', the two LEDs 1, 2 are supplied with the constant current from the circuit 3 to be lit. When only the LED1 is lit, the input G is set to '1', and the input R is set to '0'. Thus, a constant current is supplied from the circuit 4 to the LED1, which is lit, and the it is fed to the GND through the transistor TR4. |
