Abstract: A control circuit of an LED lamp includes a voltage regulator, at least a photo resistor and a feedback circuit. The voltage regulator includes an output terminal and a feedback terminal. The feedback circuit includes an amplifier having a first input end, a second input end and an output end. The LED lamp is connected between the first input end of the amplifier and the output terminal of the voltage regulator. The at least a photo resistor can sense a change of brightness level of an environment surrounding the LED lamp and a resistance of the at least a photo resistor increases along with a decrease of the brightness level. The change of resistance of the photo resistor is fed back to the voltage regulator via the amplifier, to thereby control an electric current flowing through the LED lamp.

Abstract: An LED illumination system includes an LED lamp, a voltage stabilizing circuit and a control circuit. The LED lamp includes an LED string which has a plurality of LEDs connected in series. The voltage stabilizing circuit connects the LED lamp for supplying an electric current to the LED string. The control circuit includes an MCU and a MOSFET connected between the MCU and the LED string. The MCU detects the electric current flowing through the LED string and outputs a PWM signal which has a frequency within a range from 60 Hz to 500 Hz to the MOSFET. The MOSFET receives the PWM signal from the MCU and turns on and off repeatedly under a control of the PWM signal, to make a flicker frequency of the LEDs of the LED string be within a predetermined range.

Abstract: An LED illumination system includes an LED lamp, a voltage stabilizing circuit and a control circuit. The LED lamp includes an LED string which has a plurality of LEDs connected in series. The voltage stabilizing circuit connects the LED lamp for supplying an electric current to the LED string. The control circuit includes an MCU and a MOSFET connected between the MCU and the LED string. The MCU detects the electric current flowing through the LED string and outputs a PWM signal which has a frequency within a range from 60 Hz to 500 Hz to the MOSFET. The MOSFET receives the PWM signal from the MCU and turns on and off repeatedly under a control of the PWM signal, to make a flicker frequency of the LEDs of the LED string be within a predetermined range.

Abstract: A control circuit of an LED lamp includes a voltage regulator, at least a photo resistor and a feedback circuit. The voltage regulator includes an output terminal and a feedback terminal. The feedback circuit includes an amplifier having a first input end, a second input end and an output end. The LED lamp is connected between the first input end of the amplifier and the output terminal of the voltage regulator. The at least a photo resistor can sense a change of brightness level of an environment surrounding the LED lamp and a resistance of the at least a photo resistor increases along with a decrease of the brightness level. The change of resistance of the photo resistor is fed back to the voltage regulator via the amplifier, to thereby control an electric current flowing through the LED lamp.

Abstract: A protecting circuit for an LED unit includes first, second, third and fourth diodes. A cathode of the second diode couples to an anode of the first diode, and a cathode of the third diode couples to a cathode of the first diode. The fourth diode includes an anode coupling to the anode of the second diode and a cathode coupling to the anode of the third diode. A first junction is formed between the first and second diodes, a second junction is formed between the third and fourth diodes, a third junction is formed between the second and fourth diodes, and a fourth junction is formed between the first and the third diodes. The first and the second junctions are connected to the LED unit. The third and fourth junctions are connected to a power source for supplying electric current to the LED unit.