Abstract: An over-voltage protection circuit clamps an output voltage of a light source driving circuit. The over-voltage protection circuit includes a transistor and two resistors. When the load of the light source driving circuit is broken, the over-voltage protection circuit utilizes the current generated from the error amplifier in order to enter the transistor into saturation region and accordingly generates a fixed gate voltage. The fixed gate voltage is utilized to clamp the output voltage of the light source driving circuit through the two resistors.

Abstract: A dimming control device is disclosed for controlling a switch of a voltage boosting circuit to output voltage or not so as to control the lumen of the set of LEDs utilizing the voltage boosting circuit. The dimming control device includes a switch. The switch of the dimming control device receives a dimming signal and accordingly controls “ON” or “OFF” states of the switch of the voltage boosting circuit. In this way, the period of a predetermined current flowing through the set of the LEDs can be adjusted and the lumen of the set of the LEDs is adjusted.

Abstract: An LED driver circuit comprises a buck-boost converter circuit and a resistor. The cathode terminal of the LED is connected to the output terminal of the buck-boost converter circuit. The anode terminal of the LED is connected to a reference voltage. The resistor connects the anode terminal of the LED to a power input.