| 摘要 |
PROBLEM TO BE SOLVED: To provide a constant current control circuit capable of maintaining stable accuracy even when base-emitter voltage of a transistor for switching electrical loads fluctuates.SOLUTION: A constant current control circuit in which serially connected light emitting diodes LED1, LED2, a bipolar transistor Q1 and a resistor R3 are connected in series and voltage-dividing resistors R1, R2 for setting a base electrical potential are connected to a base terminal of the bipolar transistor Q1, is configured to feedback a voltage drop signal across the resistor R3 corresponding to a current IE flowing through the light emitting diodes LED1, LED2 to an AD input terminal of a microcomputer 1. The microcomputer 1 performs PWM control based on the voltage drop signal coming in through the AD input terminal to keep an emitter voltage VE of the bipolar transistor Q1 approximately constant. |
