| 摘要 |
PROBLEM TO BE SOLVED: To provide an LED drive circuit at low cost which can highly accurately equalize drive currents flowing in the LEDs of a plurality of LED strings connected in parallel to a constant current power supply.SOLUTION: A current dividing circuit 16 is composed of constant current circuits 18a to 18c provided one for each of LED strings 13 to 15, which are connected in ring form. The constant current circuits 18a to 18c are connected in series to the LED strings 13 to 15 and are provided with drive transistors Q1 to Q3 in which drive currents for LEDs 17 flow, so they control the currents flowing in the drive transistors Q1 to Q3 to make them constant, thereby driving the LEDs 17 of the LED strings 13 to 15 with constant current. Each of the constant current circuits 18a to 18c connected in ring form uses a current flowing in the drive transistor of the preceding one of the constant current circuits to set a current flowing in the drive transistor of the subsequent one of the constant current circuits. |
