A novel on-chip step-dimmer for low cost AC-powered HV-LED driver

Abstract

This letter proposes a novel on-chip step-dimmer using an analog dimming method for a high PF AC-powered LED driver. The full AC LED driver can achieve a very high PF and a low THD by using a self-adaptive power processing circuit while delivering a best-in-class dimming performance with the proposed step-dimmer. Under the control of the dimming signal, the dimming voltage is step-adjusted from 1.0 V to 2.5 V, the average LED current can be changed from 40% to 100% of the nominal LED current value. To verify the feasibility of the proposed scheme, an 8-string 4.4 W AC-powered LED driver with the proposed step-dimmer was designed and simulated using a 0.35 um-700 V BCD Magnachip process. The gained results verify that the proposed step-dimmer can maintain a high performance of the AC LED driver under different dimming modes with a PF and a THD around 0.998 and 6%, respectively.