Variable power dimming control circuit

A variable power dimming control circuit, for driving and linearly adjusting the illumination brightness of a plurality of light emitting diodes (LEDs) and the LEDs being electrically connected in series with each other or installed in parallel with each other on a light board module, comprising:

• a dimming unit, electrically coupled to an external power supply;
• a rectification unit, electrically coupled to the dimming unit, for receiving and rectifying an alternate current (AC) voltage of the external power supply and outputting an input current;
• a dimming stabilization unit, including a constant current device and a switch, and the constant current device being electrically coupled to the rectification unit and the switch for receiving the input current to generate a holding current;
• a driving unit, electrically coupled to the rectification unit, the constant current device and the light board module, for receiving the input current and supplying a driving current to the LEDs;
• and
• a control unit, having a detector, a controller, a current limiter and a feedback device, the detector electrically coupled to the rectification unit, the driving unit and the controller, and the controller being electrically coupled to the switch, the current limiter and the feedback device, and the current limiter being electrically coupled to the light board module and the feedback device, and the detector being provided for receiving and detecting the input current to produce a detection value, and the feedback device being provided for receiving and sensing the driving current to produce a feedback value, and the controller being provided for comparing the detection value with the feedback value and outputting a driving signal to drive the current limiter to adjust the current value of the driving current, such that the input current Iin and the driving current IL satisfy the relation of Iin=IL, the controller compares the feedback value with a reference value, and outputs a stable signal to conduct the switch and allow the dimming stabilization unit to output the holding current if the feedback value is smaller than the reference value, so that when the LEDs are adjusted to a minimum brightness or turned off, the input current Iin and the holding current Ihold satisfy the relation of Iin=Ihold for stabilizing the operating quality of the dimming unit and reducing unnecessary power consumption.