高压变压器寄生电容对串联谐振变换器特性的影响

高压串联谐振变换器广泛应用于电容器充电、静电除尘等系统中。然而,高压变压器寄生电容的存在,使得客观上并不存在理想的高压串联谐振变换器。定量分析了高压高频变压器的寄生电容对工作于断续谐振电流模式(discontinuous current mode,DCM)的串联谐振变换器特性的影响,这些特性包括临界断续谐振频率、归一化输出电流和软开关。当考虑高压变压器寄生电容后,串联谐振变换器实际上已经演变为LCC串并联谐振变换器。通过对DCMLCC谐振变换器在不同工作阶段的数学分析、推导和归一化处理,得到了具有封闭形式的电路特性的表达式。通过分析发现,随着等效电压增益的增加,DCM LCC谐振变换器的正向和反向谐振过程均由两元件谐振向三元件谐振过程转变,临界断续频率升高。以图形曲线的方式给出了量化的分析结果。通过比较两类典型的控制方法可知,第二类典型控制方法具有更高的电流输出能力和能量传输效率,是一种优化的控制方法。所得分析结果可为工作于断续谐振电流模式的高压串联谐振变换器的设计提供参考,特别对电容充电和静电除尘电源具有工程应用价值。

Effects of the Parasitic Capacitance on Characteristics of Series Resonant Converters

High voltage series resonant converters are widely used in capacitor charging,electrostatic precipitators(ESP) systems,etc.However,ideal high voltage series resonant converters do not exist due to the parasitic capacitance of the high voltage transformers.Accurate analysis of the parasitic capacitance effects on characteristics of series resonant converters is given in this article,including normalized critical discontinuous resonant frequency,normalized output current and soft switching.When parasitic capacitance of the high voltage transformer is considered,discontinuous current mode(DCM) series resonant converters have become DCM series and parallel resonant converters.Closed-form expressions reflecting the characteristics of the system can be got by mathematical analysis of the circuit.As the equivalent voltage gain increases,the positive and negative resonant process changes from LC to LCC resonant process and the normalized critical discontinuous resonant frequency increases.Quantitative results are given by figures and curves.From the comparison of two typical control methods,the second one has higher output current ability and energy transmission efficiency;hence it is an optimal control method.The results provide the theoretical basis and guidance for the analysis,design and control of the high voltage series resonant converters with parasitic capacitance,which especially presents a good application value for engineering of capacitor charging and electrostatic precipitator power supply.