高带宽差分电压探头:模型、设计与评测

High Bandwidth Differential Voltage Probe:Model,Design,and Assessment

SiC和GaN等宽禁带功率器件的开关速度非常快,可以提升功率器件的开关频率及电气装备的功率密度。然而,其开关速度已逼近测量仪器的探测极限,难以准确表征功率器件的开关特性。商业化高性能测试仪器,存在经济性差、透明度低、定制化难等问题,成为制约宽禁带器件大规模应用的一大关键技术难题。高速、高频、高压开关信号具有波的传播特征,无法采用现有集总参数模型与分析方法。此外,差分电压探头面临带宽约束机制不明、高频设计模型缺乏、测试表征方法匮乏等基础问题,给高性能电压探头的设计、研发和应用,带来了严峻挑战,亟待技术突破。基于高频传输线理论,文中揭示差分电压探头的结构–带宽机制,提出基于平行板传输线的高带宽分压器新结构,建立宽频范围适用的分压电路模型,分析分压器尺寸对探头带宽的影响规律,并给出一种最大化探头带宽的回路补偿方法。实验结果表明:多层陶瓷电容的等效串联电感及PCB平面耦合的传输线效应,是制约差分电压探头带宽的瓶颈问题,采用基于平行板传输线的高带宽分压结构、优化承压臂长度、高频回路补偿等新结构和新方法,可突破差分探头的带宽极限到500MHz,为高带宽差分电压探头和宽禁带器件的设计研发、测试表征、标准制定,提供有益的参考。

The SiC-and GaN-based wide bandgap(WBG)power devices perform very fast switching speeds,which effectively boosts the switching frequency and power density of the device and equipment,respectively.However,the ultra-high switching speed challenges the cutting-edge specification of the measurement instruments and results in the inaccurate assessment of the switching behavior.Besides,the commercial and advanced measurement instruments cannot satisfy the cost-efficient,open-source,and customized requirements,which restricts the massive development of wide bandgap devices.Furthermore,high-speed,high-frequency,and high-voltage switching signals have the characteristics of the electromagnetic wave;thus,the traditional lumped parameter model is inappropriate to model and design the high bandwidth voltage probe.Therefore,due to the unclear mechanism of the bandwidth limitation,the overlooked model of high-frequency desi gn,and lacked characterization of asse ssment measurement,the design,development,and application of the high bandwidth voltage probe remain obstacles.In this paper,based on the high-frequency transmission line theory,the mechanism of the structure-bandwidth of the differential voltage(DV)probe was revealed.Moreover,a novel high bandwidth voltage divider was proposed,by using the parallel-plate-based transmission line.A universe highfrequency circuit model was created for the proposed voltage divider.Besides,the bandwidth principle of the voltage divider affected by its size was observed.Additionally,a loop compensation approach was proposed to maximize the bandwidth of the DV probe.Comparative experiments were demonstrated to confirm the validity of the proposed models and analyses.It can be found that the equivalent series inductance of the multilayer ceramic capacitors(MLCC),as well as the transmission line effect of the printed circuit board(PCB),are the barriers for the high bandwidth DV probe.The maximum bandwidth of the DV probe can be propelled to 500MHz by employing innovative structures and methodologies,such as employing the parallel-plate-based transmission line structure,reducing the divider size,and optimizing the compensation loop,etc.These findings are extremely significant for the development,characterization,and standardization of advanced DV probes and promising WBG power devices.