The main contribution of this study is to show the effect of light-emitting diode (LED) modelling in the design of offline drives. The authors propose the use of a source voltage and resistance model (SVRM), consisting of a threshold voltage source in series with the characteristic resistance, for the modelling of the LED. The offline drive used for the analysis is the flyback converter operating in discontinuous conduction mode. The equivalent circuit is analysed by superposition and the AC circuit is analysed with phasors. The analysis has proven that the flyback converter can be modelled as a current source feeding the output capacitor in parallel with the load. Likewise, the analysis demonstrated that the current ripple is always greater than the voltage ripple when an LED is used as a load. In order to validate the theoretical analysis, a design methodology for the flyback converter with the SVRM as a load was developed. The designed circuit was simulated in Spice and implemented in a prototype. Experimental results using an LED as load are compared with the same circuit using a simple resistance as load. The experimental results confirm the theoretical analysis with an error of <6.6%.

中文翻译：

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LED建模对功率转换器输出电容的影响

这项研究的主要贡献是展示了离线驱动器设计中发光二极管（LED）建模的效果。作者建议使用源电压和电阻模型（SVRM）进行建模，该模型由与特性电阻串联的阈值电压源组成。用于分析的离线驱动器是反激式转换器，它以不连续导通模式运行。通过叠加分析等效电路，并使用相量分析交流电路。分析证明，反激式转换器可以建模为与负载并联地为输出电容器供电的电流源。同样，分析表明，当将LED用作负载时，电流纹波始终大于电压纹波。为了验证理论分析，开发了一种以SVRM为负载的反激式转换器的设计方法。设计的电路在Spice中进行了仿真，并在原型中实现。将使用LED作为负载的实验结果与使用简单电阻作为负载的相同电路进行比较。实验结果证实了理论分析，误差＜6.6％。