Duty cycle adjusting circuit of a lighting system and method thereof

A duty cycle adjusting circuit of a lighting system, adjusting illuminating intensity of at least one light emitting device of a first color and at least one light emitting device of a second color according to a plurality of intensity values respectively, comprising:

• a driving unit, producing a first driving current and a second driving current wherein the first driving current comprises a first duty cycle, the second driving current comprises a second duty cycle, the driving unit drives the light emitting device of the first color to emit light of the first color in the first duty cycle, and the second duty cycle drives the light emitting device of the second color to emit light of the second color;
• a sensing unit, respectively sensing the light of the first color and the light of the second color to produce the intensity values correspondingly;
• a controlling unit, calculating a first pulse width correcting value and a second pulse width correcting value according to the intensity values, wherein the first pulse width correcting value corresponds to the light emitting device of the first color, the second pulse width correcting value corresponds to the light emitting device of the second color;
• a pulse width adjusting unit, adjusting the first duty cycle and the second duty cycle according to the first pulse width correcting value and the second pulse width correcting value respectively;
• and
• a timing sampling unit providing the driving unit a plurality of driving timings for generating the first driving current and the second driving current,
• wherein the controlling unit controls the timing sampling unit according to a plurality of reference timings.