关键词: LED调光, 非对称脉宽调制, 分段混合控制, 脉冲频率调制

Abstract:

In order to achieve wide range dimming of high power LED driver power supplies,the gain offset problem of LLC resonant converters under light load needs to be solved.A novel segmented hybrid control dimming strategy is proposed,which combines the characteristics of the LLC resonant converter controlled by the constant frequency variable duty cycle asymmetric pulse width modulation (APWM) with the voltage reduction control region.When heavy load,pulse frequence modulation (PFM ) control is adopted for LLC resonant converter.When light load,APFM control with duty cycle less than 0.5 is adopted for LLC resonant converter.A high power LED driving power supply prototype with a rated output power of 1 440 W and an output voltage of 30~48 V is built.The experiments show that the prototype had a wide dimming range,fast dimming speed,small current ripple at light load,and stable work,which can verify the correct effectiveness of the new strategy.

Key words: LED dimming, asymmetric pulse width modulation (APWM), segmented hybrid control, pulse frequence modulation (PFM)