An inductive-power-transferred LED driver with constant-current compensation tanks

Abstract

电磁感应式非接触能量传输(inductive power transfer,IPT)的半导体发光二极管(light-emitting diode,LED)照明系统具有便利、灵活、安全等优点。为提高IPT的传输效率,IPT松耦合变压器两边需引入补偿网络。补偿后的IPT变换器输出特性十分复杂,其输出电压或电流与变压器参数、补偿结构和参数、开关频率和负载均有关。而LED负载的等效阻抗易随温度变化,松耦合变压器的磁场并不均匀,难以设计,这些问题使得IPT LED驱动器难以直接输出LED需要的驱动电流。针对此问题,该文提出一种基于恒流源补偿网络的IPT LED驱动电路,恒流源补偿网络使得IPT输出恒流,解耦电流与负载阻抗的关系,通过提出的变压器参数和补偿参数设计方法,采用定频占空比控制,可直接输出LED所需的电流,避免使用后级变换器,避免频率控制带来的频率分叉问题。该文还提出在给定变压器尺寸、气隙、负载范围、效率下的IPT系统综合设计方案。最后,搭建了一台20 W的IPT LED驱动电路,实验结果证明所提出的补偿网络可以准确实现与负载无关的恒流输出,避免无功环流,实现较高的传输效率。 The inductive-power-transferred (IPT) light emitting diode (LED) lighting system is convenient, flexible and safe in many applications. To improve the transfer efficiency, compensation tanks are introduced. But output characteristics of the compensated IPT system are complex, having relations with transformer parameters, tank topologies and parameters, switching frequency, and load values. It is known that the equivalent resistances of LED loads readily vary with temperature. Moreover, the loosely coupled transformer is hard to design due to non-uniform magnetic field. These problems challenge the design of an IPT LED driver to provide the required LED current directly. To solve them, this paper proposed an IPT LED driver with the constant-current compensation tank, which decouples the effect of load resistance. With well-designed transformer and compensation tanks, the IPT LED driver can directly generate the required LED current via duty cycle control at the fixed frequency. This paper also gave design steps under the given specifications. The analysis, implementation and verification were detailed in this paper.