RT&L FOCUS AREA(S): Directed energy
TECHNOLOGY AREA(S): Electronics; Ground / Sea Vehicles; Weapons
OBJECTIVE: Develop and demonstrate compact power electronics modules capable of supporting power combining of solid state High Power Microwave (HPM) sources. Develop bond wireless technology to enable ultra-high voltage silicon carbide metal-oxide semiconductor field-effect transistor (SiC MOSFET), insulated-gate bipolar transistor (IGBT), Thyristor, and diode modules capable of higher pulse repetition rate operation for burst mode operation. Develop specialized test beds that have the ability to characterize the maximum di/dt and dv/dt limitations of SiC devices while determining the safe operating area (SOA) of the modules. Advance and verify switch characteristics such as fast rise time and low impedance to be able to drive specific HPM sources. Develop a compact, less than 1 ft^3, packaged switch module capable of delivering 50-100 kV outputs that also has the ability to be combined to scale driver power. Demonstrate low jitter module operations to facilitate phased element design. This phased multi module system design will show the ability for scalable power and subsequent beam steering operations.
DESCRIPTION: Commercial grade SiC power electronic devices are available in the market; however, high voltage (HV) SiC devices have not been developed, tested, or packaged specifically for HPM applications. Research grade SiC MOSFET and IGBT dies have been packaged individually, but the maximum di/dt and narrow pulse capability have not been determined. In addition, HV IGBTs have not been packaged in modules. Ultra-high voltage SiC MOSFET, IGBT, Thyristor, and diode modules can be developed for narrow pulse fast rise time applications, while requiring unique drivers to optimize performance. The power density, long term reliability, efficiency, and control of directed energy systems can be improved through the utilization of novel SiC device modules. The fabrication of SiC has rapidly advanced in recent years with defect density and average carrier lifetime vastly improved, enabling stable and reliable operation. However, the device packaging has not been optimized for pulsed power switching that has very short times while being very high in voltage. The bond wires are a known failure point during high current switching that will need to be addressed.
Simulations show that SiC MOSFETs can be capable of up to 15 kV while SiC IGBTs are suitable from 15 kV to 35 kV, while higher voltages from 35 kV to 50 kV SiC gate turn off (GTO) Thyristors are the optimal choice [Ref 1]. Cree-Wolfspeed has developed a 15 kV SiC MOSFET and a 24 kV SiC IGBT as of 2016, though they are not in their standard product inventory [Refs 2, 3]. The rise-time of the MOSFET was 102 ns for an 8 kV, 28 A pulse while the IGBT had a switching speed of 46 kV/µs. Photoconductive semiconductor switches (PCSS) SiC have been developed to show switching voltages of 50 kV in experimental setups for a radial topology [Ref 4]. Behlke has developed HV solid state switching modules capable of switching 200 kV with a 1.6 kA current and a rise-time of 300 ns (HTS 2000-160). Behlke also has Thyristors capable of switching 150 kV with a 10 kA current and a rise-time of 35 µs (HTS 1500-1000-SCR).
PHASE I: Conceptualize, design, and model key elements for an innovative, all solid-state power modulator capable of a threshold 50 kV and objective 100 kV at pulse repetition rates of tens of kHz or higher. The design should establish realizable technological solutions for a module capable of driving various HPM sources that have certain requirements in rise-time and impedances.
• The technical solution should have a minimum pulse repetition rate on the order of tens of kHz or higher.
• The conceptual design should focus on rise times of 10’s of ns, <100 Ohm impedance, and jitter <1 ns to be able to drive specific HPM sources and accurately phase multiple modules.
• The proposed design should be an 80% complete solution and include all auxiliary systems associated with the control system for the power electronics, power buffer/energy magazines and thermal management.
• The design should include circuit modeling and analysis of the HV driver.
• The proposed brassboard system should be designed for both laboratory and limited open air testing with sufficient ruggedization to transport the hardware to test sites.
Perform additional modeling and simulation to determine predicted efficiency, prime power draw, and thermal management requirements. Provide an overview of the current state of the art for each of the key prototype elements along with manufacturer information, focusing on the solid state components required for this application, packaging and power density. Provide a cost analysis as well as material development to ascertain critical needs not yet fully developed or readily available given current technology. Develop a Phase II plan.
PHASE II: Refine the design of the proposed technology. Complete procurement, integration, assembly, and testing of a proof-of-concept brassboard prototype leveraging the Phase I effort. Requirements:
• The Phase II brassboard prototype will be capable of greater than 50 kV and a rep rate above 50 kHz, while being able to support low jitter (<1ns), fast rise-time (10’s of ns) operations.
• The brassboard system should be capable of operating in a laboratory environment, such as an anechoic chamber or Gigahertz Transverse Electromagnetic (GTEM) test cell.
• This brassboard prototype must demonstrate a clear path forward to a full scale concept demonstrator based on the selected technology.
PHASE III DUAL USE APPLICATIONS: A successful project will also showcase the ability of the technology to match evolving needs of commercial markets such as medical pulse power and sterilization. Recent progress in medical pulse power research, utilizing high voltage short pulses to increase immunology efficacy has driven the need of a low jitter, fast rep-rate, low impedance, solid-state HV pulse generator. Several medical areas benefiting from these HV modulators include wound healing, cancer treatment, and gene transfer. Various commercial markets ranging from environmental, sanitization, and food processing has also shown increased efficacy when utilizing short, high voltage pulses. These applications can be realized by the development of a reliable, long lifetime, solid-state HV modulator.
Within DOD, we seek to apply the knowledge gained during Phase I and II to further build, refine and demonstrate a full scale prototype device capable of transmitting an arbitrary waveform at power levels exceeding 10 MW and a rep-rate on the order of tens of kHz or more. To allow this, it is suggested to ensure that the prototype represents a complete power modulator with controls, thermal management, energy magazine or prime power buffer; and is ruggedized for, at a minimum, testing in an outdoor environment and be environmentally enclosed; and includes at least 2 or more modules that shows active control over phasing and power combining.
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