LCL-T resonant network-based modular multi-channel constant-current LED driver analysis and design
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ORIGINAL ARTICLE
LCL‑T resonant network‑based modular multi‑channel constant‑current LED driver analysis and design Qingqing He1 · Quanming Luo1 · Jian Huang1 · Chi Cao1 · Pengju Sun1 · Xiong Du1 Received: 14 March 2020 / Revised: 9 August 2020 / Accepted: 23 August 2020 © The Korean Institute of Power Electronics 2020
Abstract Multiple output LED drivers are necessary to achieve better performance and higher reliability in street lighting, tunnel lighting and LCD background lighting applications. Based on LCL-T constant-current characteristics, a modular multiple output LED driver is proposed in this paper. The LCL-T rectifiers are connected to the same voltage bus and work like current sources. However, since there are much higher voltage harmonics in the AC square bus voltage, it is very important to quantitatively analyze how these harmonics influence the precision of the output currents. In addition, all of the switches can achieve Zero Voltage Switching (ZVS) by proper design of the LCL-T network. Finally, a 200-W prototype with five channels is established with an efficiency of 92.25%. Keywords LED driver · AC square voltage bus · Parameter design · Multi-channel constant current
1 Introduction LEDs have been widely applied in street lighting, tunnel lighting and LCD background lighting [1, 2]. In these high-power LED lighting applications, LED drivers need to realize the following three functions: power factor correction (PFC), multi-channel constant current and galvanic isolation [3]. Two-stage LED drivers are usually adopted to meet these requirements. These drivers contain the front PFC stage and the lag DC/DC stage working separately. The front PFC stage generally adopts a Boost converter to achieve PFC [4]. In addition, the lag DC/DC stage completes galvanic isolation with at least one transformer included and multiple constant-current output. This study focuses on the lag DC/DC stage since the PFC is relatively mature. According to the different methods of galvanic isolation, DC/DC LED drivers can be classified into three main types: multiple-converter schemes [5, 6], multiple-transformer schemes [7, 8], and single-transformer schemes [9–12]. The multiple-converter schemes are composed of as many isolated DC/DC converters as LED strings to achieve multiple * Quanming Luo [email protected] 1
State Key Laboratory of Power Transmission Equipment and System Security and New Technology, Chongqing University, Chongqing, China
outputs. Each converter, which includes a DC/AC unit, a transformer, and an AC/DC unit, is closed-loop controlled to achieve a constant-current output. They are modular schemes and a high efficiency can be realized by designing each converter optimally. However, each converter needs one power stage as well as a controller, which dramatically increases the cost of the driver with an increase of the LED strings. To simplify the circuit, a multiple-transformer scheme can be obtained by sharing the DC/AC unit of the converters. All of the transformers are connected in series from t
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