To solve issues like complex control

large grid-side harmonics

low efficiency

high cost and large volume in step-down two-stage LED driver for small and medium power application

a single-stage step-down Cuk/two input ( TI) Buck LED driver and its power conversion control strategy integrated with visible light communication ( VLC ) modulation were proposed. The operating principle

process and steady-state characteristics of the proposed driver were analyzed in detail

circuit variable relationships was derived

and key parameters was analyzed and designed. Based on VLC quadrature amplitude modu-lation ( QAM) strategy

output current ripple’s amplitude

frequency and phase was served as constella-tion axes; the communication data was modulated via output current AC components superimposed on LED DC current

combined with the average lighting current constant-current control simultaneously. Computer simulation was fully carried out. The dynamic response characteristics of input and load switc-hing are satisfied through digital closed-loop control. Finally

a prototype (185 -265 V/50 Hz AC in-put

1 A/50 W full-load output) was developed. The prototype is tested and the VLC can be achieved 10-15 kbps data rate in 30% -100% dimming range; power factor 0. 97 (meeting IEC61000-3-2 Class C harmonic limits)

with the efficiency 83% at full-load (85. 1% can be obtained) . The effec-tiveness of the proposed single-stage driver and the proposed combined modulation strategy is verified by computer simulation and experimental results.