Abstract: In order to improve the load transient response speed of Buck LED constant current driver，a

capacitive current ripple-controlled（CCRC） Buck LED constant current driver was proposed. Based on the

operating principle of Buck LED constant current driver，the state space averaging model of Buck LED constant

current driver was established by using the state space averaging method. On this basis，combined with the operating principle of the CCRC Buck LED constant current driver，a small signal model of the driver was established. The control-output loop gain transfer function of the system was deduced，and the PI compensation parameters of the control circuit were designed. Comparing analysis with the load transient response speed of traditional voltage mode controlled（VMC）Buck LED constant current driver was presented by Bode diagram. The analysis results show that the CCRC Buck LED constant current driver has a faster load transient response speed compared with the VMC Buck LED constant current driver. Finally，the correctness of the theoretical analysis was verified by simulation and experimental results.

      Key words: Buck LED constant current driver；capacitive current ripple-controlled；small signal model；

compensation parameter；transient response