− 136 − Honda R&D Technical Review April 2012 Power Circuit Technology using Next-generation SiC Power Semiconductors for Power Electronics Devices in Electric Powertrain Tomoyo EGOSHI* Sadao SHINOHARA* ABSTRACT Next-generation silicon carbide (SiC) power semiconductors are expected to offer size reductions and increased efficiency. Optimized design is necessary for the power circuits employing these semiconductors in order to exploit their performance potential. The identification of each circuit element related to transient response during high-speed switching, a characteristic of SiC power semiconductors, and the correlation of circuit simulation models with the results of actual measurements, made it possible to obtain voltage and current waveforms to within a 4% level of error. Using this circuit simulation technology, the most important circuit elements to power circuit design were identified. The employment of optimized values in sections of the circuit in which parasitic impedance affected efficiency and electromagnetic interference (EMI) performance was shown to reduce switching loss and noise. 1. Introduction With the transition to the use of higher levels of power, it becomes necessary to make the power electronics devices such as inverters and converters used in electric vehicles and similar vehicles smaller, more efficient, and less prone to electromagnetic interference (EMI). Power semiconductors are one of the key technologies employed in power electronics devices. Most semiconductors today are based on silicon (Si), but the performance limits of the material have been reached, and research and development efforts are proceeding in the area of SiC semiconductors, a type of next-generation power semiconductor expected to offer ultra-low levels of loss. However, because SiC power semiconductors are capable of high-speed switching, they present issues with regard to their use in automotive applications, including reduced efficiency and increased EMI, making optimal power circuit design essential. Parasitic impedance in power semiconductor chips, electrical wiring, and other components is an important parameter in realizing faithful reproduction of circuits by the circuit simulation technologies used at the design stage. The development of a circuit simulation technology that reflected this parameter would make it possible to (1) simulate a power circuit able to reproduce the high-speed switching operation of an SiC power semiconductor, and (2) analyze and evaluate the voltage and current when EMI originating in high-speed switching by an SiC power semiconductor occurs. This paper discusses the development of a circuit simulation that reproduces the high-speed switching operation of an SiC power semiconductor, the identification of areas of circuits with a significant effect on EMI due to voltage and current waveforms, and achieved noise reduction results. The achievement of good reproduction of voltage and current waveforms was an important factor in realizing this development, in respect of their relationship to loss in devices and the efficiency of the system as a whole. 2. SiC Power Semiconductors: Characteristics and Issues of Application Figure 1 shows the theoretical limit line for the on- resistance of Si and SiC. As this graph indicates, a dramatic increase in on-resistance performance can be expected from the use of SiC against Si. To provide an indication of projected performance increases, Table 1 shows a comparison of the characteristics of new semiconductor materials with those of the conventionally used Si (1). On-resistance, RonA, an important parameter for power semiconductors, can be expressed by Eq. (1)(2). 4VB2 Ec3 RonA =µε (1) * Automobile R&D CenterTechnical papers− 137 −Power Circuit Technology using Next-generation SiC Power Semiconductors for Power Electronics Devices in Electric Powertrain VB: Breakdown voltage µ: Bulk migration e: Permittivity Ec: Breakdown strength