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Posted on 05 July 2019

Silicon Carbide Power Electronics Modules for High Temperature Applications (> 200 °C)

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The efficient high temperature capability makes passive cooling possible

Power electronics systems are becoming increasingly important for weight sensitive applications such as hybrid electric/full electric vehicles and more electric aircraft. These particular applications are redefining the standard of performance, size, weight, and power density required from power electronic systems. Silicon Carbide (SiC) power devices have emerged as the ideal solution to meet the performance requirements conventional switch technologies cannot meet.

By Edgar Cilio and Alex Lostetter APEI, Inc. USA

 

SiC power electronics have capabilities to operate at high temperatures and high switching frequencies [1-4]. High temperature of operation can significantly reduce the size and complexity of the cooling system. High switching frequency enables size reduction of passive filter components further rendering the overall power converter system smaller and lighter.

In order to capture the capabilities innate to SiC power electronics, innovative power packaging technologies are needed. The packaging technology ultimately limits the high temperature and high frequency operation of SiC devices. Arkansas Power Electronics International, Inc. (APEI, Inc.) has been performing research on SiC power packaging and SiC applications for several years and is now quickly moving its prototypes into the market. Two of APEI’s most recent developments on SiC power module packaging and SiC power systems are presented, highlighting their revolutionary high temperature/high power density capabilities. First, we want to introduce our award winning 250 °C, 1200V, 150 A, SiC power module with integrated gate drive board [5-6]. And second, we demonstrate our 200 °C, 50 kHz, 300 VDC/5 kVA SiC-based three phase inverter operating under representative and relevant requirements to an aircraft power electronics system.

250 °C, 1200V, 150 A, SiC Power Modules with Integrated Gate Drive Boards

Selected as one of the top 100 global technology breakthroughs for 2009 by R&D Magazine, this high-temperature silicon carbide power module is the world’s first commercial high-temperature SiC-based power electronics module. The 50 kW (1200 V /150 A peak) SiC power modules are rated up to 250°C junction temperature and include integrated high-temperature gate drivers. Jointly developed by APEI, Inc., the University of Arkansas, Rohm Co., LTD, and the U.S. Department of Energy, these modules usher in a new era for power electronics. The increased temperature of operation gives the power electronics designer unprecedented thermal design freedom, yielding greatly reduced cooling/heat removal requirements.

The module implements a half-bridge power topology (up to eight parallel power transistors per switch position), integrates a high-temperature silicon-on-insulator (HTSOI) gate driver board, and is packaged in a high-temperature plastic housing. The module can be built and is functional with SiC MOSFETs, JFETs, or BJTs. Figure 1 is a photograph of the high temperature silicon carbide power module product and the promotional translucent display module.

Photographs of the high temperature silicon carbide power module

Figure 2 illustrates a thermal image of the high temperature SiC power module driving a DC motor load in a demonstration setup. The demonstration operated an un-lidded SiC power module (utilizing Rohm SiC DMOS power transistors) with the gate drive control board in a separate module. With this arrangement, the SiC power switches can be exposed and thermally imaged for clear illustration of high temperature operation.

Photograph of the un-lidded high temperature SiC power module

In the demonstration setup, the high-side power switching position is operating at 80% duty cycle, while the low-side power switching position is operating at 20% duty cycle. The 250 °C steady-state junction temperature in this demo is reached through the elimination of the heat-sink and operating the module under self-heating conditions in a room-temperature ambient environment.

Figure 3 illustrates a scope capture of the high-temperature SiC power module operating under high power conditions in a switching test. The operating conditions for this test are as follows: 300 V DC bus, 15 kHz switching frequency, 1 kHz output current frequency (required by application), ~90 Arms output current, and 250 °C power device junction temperature. In Figure 3, Channel 4 shows DC bus, Channel 2 shows the output current (~160 A peak), and Channel 3 shows the drain to source voltage across one of the switch positions.

Operation of the module under full-current condition

This module’s high temperature capability is removing previous thermal limitations and enabling high power density design options for the power electronics designer.

200 °C, 50 kHz, 300 VDC/5 kVA SiC Three Phase Inverter for Aircraft Applications

A second power module has been developed with the capability of high temperature and high frequency switching operation while delivering high efficiency power processing. This module and its related experimental performance are presented next.

A brazed metal package has been selected for the housing. The base material is copper for efficient thermal operation. These style of packages allow for high flexibility in design and cost effectiveness while providing sufficient space for multiple paralleled devices. The selected 26- pin package is shown in Figure 4. Each package contains a two-switch-position totem-pole, phase leg arrangement. Each switch position consists of eight SJEP120R100 SemiSouth SiC JEFTs and one antiparallel CPW2-1200S010 SiC Cree diode.

Side view (top) and corresponding thermal image (bottom) of the prototype

In order to illustrate the benefits of the developed module at the system level, a 300V/5kW, 50 kHz switching frequency, 200°C (device junction temperature) fully functional three phase inverter was implemented using three of the modules shown in Figure 4. With an electrical motor drive system for an aircraft platform in mind, the design philosophy aimed to take advantage of the low input capacitance, high switching frequency, and high temperature capability of the SiC JFET in order to obtain a high power-density capable inverter.

26-pin power package

Figure 5 shows a side view photograph (top) and a thermal image (bottom) of the three phase SiC inverter processing ~4.3 kW at 180 °C base plate temperature and an estimated > 200 °C die temperature. This high temperature, high switching frequency operation was achieved while simultaneously operating at ~97 % efficiency. Figure 6 shows the relevant output voltage and output current waveforms. Compared to the 97.8 % efficiency at 30 °C base plate temperature at a similar power level, there is only an approximate 0.8% efficiency drop when operating at 180 °C base plate. The efficient high temperature capability of the SiC system makes passive cooling possible. In the context of a weight sensitive application such as an aircraft, passive cooling would not only reduce complexity and increase system reliability but also enable further critical weight savings.

Phase voltages and currets at 180 degrees celcius base plate

Availability and Pricing

Power electronics modules are the core components of power electronics systems and, arguably, the single most important component ultimately impacting the overall systems power density and performance. Currently, APEI, Inc. is gearing resources and facilities towards reliability studies and will have a formal line of products in the near future. However, recognizing the importance for early adopters and for evaluation purposes, APEI, Inc. is making its power modules available as engineering samples. For more information and pricing, please contact as at jhornbe@apei.net. For the latest developments please visit us at our website.

 

References:

[1] B. McPherson, J. Hornberger, J. Bourne, A. Lostetter, R. Schupbach, R. Shaw, B. Reese, B. Rowden, K. Okumura, T. Otsuka, A. Mantooth, S. Ang, J. Balda, "Packaging of High Temperature 50 kW SiC Motor Drive Modules for Hybrid-Electric Vehicles", IMAPS 2009, Pages 663-670 San Jose, CA, November 2009.
[2] A. Lostetter, J. Hornberger, B. McPherson, B. Reese, R. Shaw, M. Schupbach, B. Rowden, A. Mantooth, J. Balda, T. Otsuka, K. Okumura, and M. Miura, “High-Temperature Silicon Carbide and Silicon on Insulator Based Integrated Power Modules”, 2009 IEEE Vehicle Power and Propulsion Conference, Dearborn, Michigan, September 7-11, 2009.
[3] J.W. Palmour, R. Singh, R.C. Glass, O. Kordina, C.H. Carter, Jr, "Silicon Carbide for Power Devices", IEEE Symposium on Power Semiconductor Devices and ICs, 1997.
[4] T. Funaki, J.C. Balda, J. Junghans, A.S. Kashyap, H.A. Mantooth, F. Barlow, T. Kimoto, T. Hikihara, "Power Conversion with SiC Devices at Extremely High Ambient Temperatures", IEEE Transactions on Power Electronics, Vol. 22, No. 4, July 2007.
[5] http://www.rdmag.com/RD100-Awards-Silicon-Carbide-Powers-Higher-Temperatures/
[6] http://www.sandia.gov/mission/ste/r&d100/2009winners/SIC_Power_Module.pdf

 

 

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