Challenges Regarding Parallel Connection of SiC JFETs

State-of-the-art silicon carbide switches have current ratings that are not sufficiently high to be used in high-power converters. It is, therefore, necessary to connect several switches in parallel in order to reach sufficient current capabilities. An investigation of parallel-connected normally ON silicon carbide JFETs is presented in this paper. The device parameters that play the most important role for the parallel connection are the pinch-off voltage, the gate-source reverse breakdown voltage, the spread in the on-state resistances, and the variations in static transfer characteristics of the devices. Moreover, it is experimentally shown that a fifth factor affecting the parallel connection of the devices is the parasitic inductances of the circuit layout. The temperature dependence of the gate-source reverse breakdown voltages is analyzed for two different designs of silicon carbide JFETs. If the spread in the pinch-off and gate-source reverse breakdown voltages is sufficiently large, there might be no possibility for a stable off-state operation of a pair of transistors without forcing one of the gate voltages to exceed the breakdown voltage. A solution to this problem using individual gate circuits for the JFETs is given. The switching performance of two pairs of parallel-connected devices with different combinations of parameters is compared employing two different gate-driver configurations. Three different circuit layouts are considered and the effect of the parasitic inductances is experimentally investigated. It is found that using a single gate circuit for the two mismatched JFETs may improve the switching performance and therefore the distribution of the switching losses significantly. Based on the measured switching losses, it is also clear that regardless of the design of the gate drivers, the lowest total switching losses for the devices are obtained when they are symmetrically placed.

[1]  Johann W. Kolar,et al.  SiC versus Si—Evaluation of Potentials for Performance Improvement of Inverter and DC–DC Converter Systems by SiC Power Semiconductors , 2011, IEEE Transactions on Industrial Electronics.

[2]  K. Acharya,et al.  Efficient, High-Temperature Bidirectional Dc/Dc Converter for Plug-in-Hybrid Electric Vehicle (PHEV) using SiC Devices , 2009, 2009 Twenty-Fourth Annual IEEE Applied Power Electronics Conference and Exposition.

[3]  P. Friedrichs,et al.  Silicon carbide power semiconductors — new opportunities for high efficiency , 2008, 2008 3rd IEEE Conference on Industrial Electronics and Applications.

[4]  P. Friedrichs.  Unipolar SiC devices - latest achievements on the way to a new generation of high voltage power semiconductors , 2006, 2006 CES/IEEE 5th International Power Electronics and Motion Control Conference.

[5]  I. Sankin,et al.  Power factor correction using an enhancement-mode SiC JFET , 2008, 2008 IEEE Power Electronics Specialists Conference.

[6]  Ronald Green,et al.  Performance of a dual, 1200 V, 400 A, silicon-carbide power MOSFET module , 2010, 2010 IEEE Energy Conversion Congress and Exposition.

[7]  J. Barbaroux,et al.  1 MHz power factor correction boost converter with SiC Schottky diode , 2004, Conference Record of the 2004 IEEE Industry Applications Conference, 2004. 39th IAS Annual Meeting..

[8]  L. Tolbert,et al.  Investigation on the parallel operation of discrete SiC BJTs and JFETs , 2011, 2011 Twenty-Sixth Annual IEEE Applied Power Electronics Conference and Exposition (APEC).

[9]  Michael S. Shur,et al.  High-transconductance beta -SiC buried-gate JFETs , 1989 .

[10]  I. Josifovic,et al.  SiC JFET switching behavior in a drive inverter under influence of circuit parasitics , 2011, 8th International Conference on Power Electronics - ECCE Asia.

[11]  J. Kolar,et al.  A SiC JFET driver for a 5 kW, 150 kHz three-phase PWM converter , 2005, Fourtieth IAS Annual Meeting. Conference Record of the 2005 Industry Applications Conference, 2005..

[12]  Dushan Boroyevich,et al.  A High-Power-Density Converter , 2010, IEEE Industrial Electronics Magazine.

[13]  Olivier Stalter,et al.  Advanced solar power electronics , 2010, 2010 22nd International Symposium on Power Semiconductor Devices & IC's (ISPSD).

[14]  Mietek Bakowski,et al.  Status and Prospects of SiC Power Devices , 2006, Materials Research Foundations.

[15]  T. Friedli,et al.  Design and Performance of a 200-kHz All-SiC JFET Current DC-Link Back-to-Back Converter , 2009, IEEE Transactions on Industry Applications.

[16]  Leon M. Tolbert,et al.  Impact of SiC Devices on Hybrid Electric and Plug-In Hybrid Electric Vehicles , 2008, IEEE Transactions on Industry Applications.

[17]  J. Kolar,et al.  Controllable dυ/dt behaviour of the SiC MOSFET/JFET cascode an alternative hard commutated switch for telecom applications , 2010, 2010 Twenty-Fifth Annual IEEE Applied Power Electronics Conference and Exposition (APEC).

[18]  Leon M. Tolbert,et al.  Characterization of a high temperature multichip SiC JFET-based module , 2011, 2011 IEEE Energy Conversion Congress and Exposition.

[19]  H. Hearne,et al.  A 1680-V (at 1 {mA/cm}(2) ) 54-A (at 780 {W/cm}(2) ) Normally ON 4H-SiC JFET With 0.143- {cm}(2) Active Area , 2008 .

[21]  Leon M. Tolbert,et al.  High temperature packaging of 50 kW three-phase SiC power module , 2011, 8th International Conference on Power Electronics - ECCE Asia.

[22]  Puqi Ning,et al.  A Novel High-Temperature Planar Package for SiC Multichip Phase-Leg Power Module , 2010, IEEE Transactions on Power Electronics.

[23]  D. Peftitsis,et al.  High-Power Modular Multilevel Converters With SiC JFETs , 2010, IEEE Transactions on Power Electronics.

[24]  Leon M. Tolbert,et al.  18 kW three phase inverter system using hermetically sealed SiC phase-leg power modules , 2010, 2010 Twenty-Fifth Annual IEEE Applied Power Electronics Conference and Exposition (APEC).

[25]  H. Mantooth,et al.  A Physics-Based Model for a SiC JFET Accounting for Electric-Field-Dependent Mobility , 2011, IEEE Transactions on Industry Applications.

[26]  J. Biela,et al.  SiC power semiconductors in HEVs: Influence of junction temperature on power density, chip utilization and efficiency , 2009, 2009 35th Annual Conference of IEEE Industrial Electronics.

[27]  J. Lutz,et al.  A first loss evaluation using a vertical SiC-JFET and a conventional Si-IGBT in the bidirectional matrix converter switch topology , 2005, 2005 European Conference on Power Electronics and Applications.