Douglas Hopkins

Institute Fellow

Key words:

Power electronics, High voltage engineering

Unlisted key words: Packaging, Pulsed power, Capacitors

Research description:

HIGH DENSITY AND HIGH TEMPERATURE CIRCUITS PACKAGING -The use of electronics at higher temperatures (200C+) for automotive and space environments opens avenues of higher density power electronic systems for general applications. Evaluation of Power Hybrid Structures which use Copper Clad Ceramics. Thermal performance of highly thermally conductive substrate materials is evaluated with consideration toward high temperature operation. Several publications outline a continuous research in this area. Development of high temp modules and capacitors proven to 240C and operation to 6kV. Serial Operation of Zero-Voltage-Switched Semiconductor Devices. As the rated breakdown voltage of a semiconductor device decrease the operating temperature can be increased. This increase allows temperatures to reach well above 200C. To compensate for the low voltage rating, devices must be in series and have high frequency switching techniques altered. HIGH POWER PULSE THYRISTOR - The worlds highest di/dt testing has been performed with capability of >110kA/us @ 3kV and >40kA. The PPT SELF-limited 4.3kA/us from 3kV into 1ohm. RECIRCULATING ENERGY SYSTEMS-Concept of returning output energy from a converter to its input for the purpose of supplying large energy flows from a nominal supply. In Situ Testing of Power Semiconductors and High Power Converters. The output energy for a cascade of converters is recirculated to the source. Therefore, the only energy supplied is for losses in the switching devices and components. Dynamic Cell Equalization During Serial Charging of a Long Battery String. (Invited Paper at 1991 APEC). Controlled shunting of energy from serial cells allows each cell to be charged at an optimum rate. The shunted energy is returned to the charging source effectively making higher charging rates available to selected cells. Battery life and charge time are significantly affected by the type of charge profile and scheme used. Pulse (Reflex) Charging of batteries can be combined with the aforementioned Dynamic Equalization scheme to provide natural commutation current patterns that cause positive/negative pulse charging.

Laboratory Facilities:

Capability to test to 400kV, pulsed to 100kA. Packaging lab to 10kV, pulsed to 110kA/us to 40kA; high temp to 300C; continuous current from a battery bank: 130V, 300A. Expertise in Megahertz switching power electronics; high speed scopes and full lab of instrumentation, including LabView controllers.

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