I^(2)控制单电感双输出Buck LED驱动电源交叉影响分析

Cross Regulation Analysis of I~2-Controlled Single-Inductor Dual-Output Buck LED Driver

单电感双输出(single-inductor dual-output,SIDO) Buck LED驱动电源有LED_(1)和LED_(2) 2条输出支路,2条输出支路间存在交叉影响.为减小工作于电感电流连续导电模式(continuous conduction mode,CCM)的SIDO Buck LED驱动电源的输出交叉影响,提出电流-电流(current-current,I^(2))控制SIDO Buck LED驱动电源.基于SIDO Buck LED驱动电源的工作原理和开关状态,采用状态空间平均法建立状态空间平均模型和小信号模型;在此基础上,分析I^(2)控制SIDO Buck LED驱动电源的电路结构和工作原理;基于电感电流纹波和输出电流纹波,推导占空比的小信号表达式,获得交叉影响传递函数;通过交叉影响传递函数Bode图,对比分析其与电压控制SIDO Buck LED驱动电源输出支路间的交叉影响.研究结果表明:当电压控制SIDO Buck LED驱动电源LED_(1)输出支路的参考信号分别从1.6 V突变至0.8 V和从2.4 V突变至1.2 V时,其LED1输出支路对LED_(2)输出支路的交叉影响分别为0.250 A和0.365 A;反之,LED_(2)输出支路的参考信号分别从3.2 V突变至1.6 V和从2.4 V突变至1.2 V时,LED_(2)输出支路对LED1输出支路的交叉影响分别为0.06 A和0.04 A.参考信号相同变化条件下,I^(2)控制SIDO Buck LED驱动电源LED_(1)输出支路对LED_(2)输出支路的交叉影响分别为0.090 A和0.115 A,相反,LED_(2)输出支路对LED_(1)输出支路的交叉影响分别为0.030 A和0.015 A.相比电压控制SIDO Buck LED驱动电源,I^(2)控制SIDO Buck LED驱动电源减小了输出支路间的交叉影响.

The single-inductor dual-output(SIDO) Buck LED driver has two output branches,namely LED_(1) and LED_2.Between these two output branches,there is cross regulation.In order to reduce the output cross regulation of a SIDO Buck LED driver operating in continuous conduction mode(CCM) of the inductive current,the current-current(I~2)-controlled SIDO Buck LED driver was proposed.The operating principle and switch modes of the SIDO Buck LED driver were analyzed,and its state space average model and small signal model were established with the state space averaging method.Then,the circuit structure and operating principle of the I~2-controlled SIDO Buck LED driver were analyzed.Based on inductive current ripple and output current ripple,the small signal expressions of duty cycle and cross regulation transfer functions were obtained.The Bode plots of the cross regulation transfer functions were employed to analyze the cross regulation compared with the output branches of the voltage-controlled SIDO Buck LED driver.The study results show that when the reference signal of LED_(1) of the voltage-controlled SIDO Buck LED driver steps down from 1.6 V to 0.8 V and 2.4 V to 1.2 V respectively,the cross regulation between LED_(1) and LED_(2) is 0.250 A and 0.365 A,and that of the I~2-controlled SIDO Buck LED driver is 0.09 A and 0.115 A.When the reference signal of LED_(2) steps down from 3.2 V to 1.6 V and 2.4 V to 1.2 V respectively,the cross regulation between LED_(2) and LED_(1) is 0.06 A and 0.04 A,and that of I~2-controlled SIDO Buck LED driver is 0.03 A and 0.015 A.It illustrates that the cross regulation between output branches of the I~2-controlled SIDO Buck LED driver has been reduced compared with that of the voltagecontrolled SIDO Buck LED driver.