Control circuit of light emitting diodes and operation method of a control circuit of light emitting diodes

An operation method of a control circuit of light emitting diodes, wherein the control circuit comprises a current setting pin, an adjuster, a regulator circuit, and a driving current generator, and the control circuit is used for driving at least one series of light emitting diodes, the operation method comprising:

• setting a reference current according to an external resister coupled to the current setting pin, wherein the reference current flows through the current setting pin;
• the driving current generator generating a driving current flowing through the series of light emitting diodes according to the reference current;
• the adjuster generating an adjustment voltage according to the reference current;
• and
• the regulator circuit regulating a voltage of a first terminal of the series of light emitting diodes at a target voltage and generating a supply voltage to drive the series of light emitting diodes according to the adjustment voltage;
• wherein when the driving current is less than a first predetermined current, the target voltage is increased with decrease of the driving current.