Dimming circuit and lighting device using the same

A lighting device free of flickering, comprising:

• an LED:
• a driving circuit for controlling the LED to emit a light;
• a dimming circuit, comprising:
• an interface trigger unit for obtaining an on-time of each pulse width from a plurality of periods of a first PWM signal;
• an average duty cycle calculation unit coupled to the interface trigger unit for calculating a ratio of the on-time to the periods, wherein the on-time are outputted from the interface trigger unit;
• a control voltage calculation unit coupled to the average duty cycle calculation unit for calculating a desired voltage according to the ratio obtained by the average duty cycle calculation unit;
• and
• a comparison unit coupled to the control voltage calculation unit for calculating a differential voltage between the desired voltage and a feedback voltage of the LED and sending the desired voltage and the differential voltage to the driving circuit;
• wherein the driving circuit compensates a control voltage outputted to the LED according to the differential voltage, wherein the control voltage is generated according to a second PWM signal, and a frequency of the second PWM signal is higher than that of the first PWM signal.