Illuminating system and control method thereof

The invention discloses an illumination system and a control method of the illumination system. The illumination system comprises a light modulator, a rectifier, a driver and a variable current source. The input end of the rectifier is connected with the light modulator and the output end of the rectifier is connected with the driver and the variable current source. The method comprises the steps that a PWM signal is transmitted to the driver, a current signal related to a line current of the output end of the rectifier is detected, and currents of the variable current source are increased when it is determined that the line current is smaller than a given value for keeping the current of the light modulator according to the current signal.