Constant current control circuit 3′ may include transistor Q1, resistor R2, and error amplifier EA2 for controlling transistor Q1. Transistor Q1 can connect between the LED load and resistor R2. One terminal of resistor R2 can connect to a source of transistor Q1, and the other terminal of resistor R2 can connect to ground. A gate of transistor Q1 can connect to an output terminal of error amplifier EA2. A non-inverting input terminal of error amplifier EA2 can receive load current reference signal Ref2, and an inverting input terminal of error amplifier EA2 can connect to the source of transistor Q1. Since a voltage at the inverting input terminal of error amplifier EA2 may indicate a current flowing through transistor Q1 due to a voltage drop across resister R2, the output signal of error amplifier EA2 may change with the load current, thus forming a current closed loop. Transistor Q1 controlled by the output signal of error amplifier EA2 can operate in the linear region and adjust the current flowing through transistor Q1 to be consistent with load current reference signal Ref2.