Gary Mandrusiak

High Performance Silicon Carbide Power Block for Industry Applications

Silicone carbide (SiC) power devices have been optimized in performance over the past decade. However, wide industry adoption of SiC technology still faces challenges from system design perspective. This paper demonstrates an integrated air-cooled three-phase SiC power block for industry applications. The key design aspects, such as high performance gate driver, low parasitic layout, optimized thermal management, as well as flexible control platform are addressed. Experimental results are provided to demonstrate the superior performance of the design.

High performance SiC power block for industry applications

SiC power devices have been optimized in performance over the past decade. However, wide industry adoption of SiC technology still faces challenges from system design perspective. This paper demonstrates an integrated air-cooled three phase SiC power block for industrial applications comprising high performance gate driver, low parasitic layout, optimized thermal management, as well as a flexible control platform. Experimental results are provided to demonstrate the superior performance of the design.

Engineering Design of a near Junction Thermal Transport Heat Spreader

This paper describes a convection-based, self-contained heat spreader that provides device-level thermal management for GaN power amplifiers. The concept connects microchannels etched into the backside of the die to a liquid flow circuit that includes autonomous flow-balancing valves, a diaphragm pump, and a high-performance heat exchanger. The integrated system provides a heat spreading capability that reduces transistor gate heat fluxes by up to four orders of magnitude, enabling device-level temperature control using conventional cold plates. This paper will review the analysis used to design the key components in the assembly and to project their performance as part of an integrated system.

Impingement cooled embedded diamond multiphysics co-design

This paper describes engineering analysis and experimental evaluations used to design an innovative imbedded cooling concept for RF thermal management. The concept, called Impingement Cooled Embedded Diamond (ICED), uses liquid flowing through diamond-lined microchannels etched into the back of a GaN-on-SiC RF die to manage heat produced by the transistors. This approach combines the superior heat spreading of high-conductivity diamond with the outstanding convection capability of impinging jets to manage local heat fluxes as high as 30 kW/cm2. The first part of this paper presents the CFD analysis used to design the microfluidics, select diamond thickness, and understand the sensitivity of performance to component assembly, coolant temperature and composition, and channel dimensions. It also describes the structural analysis used to evaluate ICED mechanical stress levels, including those imposed by diamond growth and hardware assembly. The second part of this paper presents experimental measurements performed to validate the computer models and demonstrate the thermal management capability of the proposed design. These experiments confirmed the effectiveness of the impinging jets at drawing heat produced by the transistors directly to the coolant, reducing transistor mutual heating and enabling a four-fold increase in expected RF output power. They also showed the proposed cooling concept mitigates self-heating thermal limitations and enables aggressive design compaction not possible with existing conduction GaN-on-SiC cooling solutions.

On the Transient Thermal Characteristics of Silicon Carbide Power Electronics Modules

The transient performance of power semiconductor devices relates directly to their available power rating, reliability, and operating lifetime. This paper examines the transient thermal performance of liquid-cooled, silicon carbide power devices subjected to different unsteady electrical loads. The first part uses infrared thermography to examine an observed asymmetrical device thermal time constant when subjected to step-change increases and decreases in current. A theoretical analysis connects this behavior to the dependence of mosfet on-resistance on junction temperature. It also identifies three time constants that characterize junction transient response, one each for the die, the module, and the cold plate. The second part extends the transient thermal evaluation to half-sine wave periodic excitations that emulate real-application operating conditions. These experiments show that thermal ripple increases with increasing excitation amplitude but decreases with increasing excitation frequency. They also connect the observed thermal response to the time constants inferred from the step-change experiments. Both parts of the study show the importance of considering transient loads when designing power electronics cooling systems and the role that electrical properties play in determining unsteady thermal response.

Experimental development of a near junction microchannel heat spreader

This paper describes a convection-based alternative to conduction heat spreaders that uses liquid microchannels to remove heat directly from the transistors. The concept connects microchannels etched directly into the die with a hydraulic circuit that includes a piezo-diaphragm pump, thermally-regulated autonomous flow control valves, and a high-efficiency heat exchanger to create a stand-alone, hermetically-sealed cooling module. The first part of the paper reviews the experiments performed to develop the key components in the cooling package. It describes the flow tests that measured the pressure drop characteristics of different microchannel designs, reviews the bench tests used to design the piezo-diaphragm pump, and discusses the process followed to train the shape-memory alloy used for the autonomous flow control valves. The second part presents micro Raman spectroscopy experiments that measured gate temperatures in energized GaN-on-SiC dies cooled by different microchannel designs. These measurements show that the microchannels enable up to a 50% increase in device input power over conventional conduction cooling with no increase in gate temperature. They also quantify how cooling effectiveness varies with channel geometry and show how thermal performance plateaus with increasing coolant flow rate.

Development of Megawatt-Scale Medium-Voltage High Efficiency High Power Density Power Converters for Aircraft Hybrid-Electric Propulsion Systems

Hybrid-electric propulsion system is an enabling technology to make the aircrafts more fuel-saving, quieter, and lower carbide emission. In this paper, a megawatt-scale power converter based on a hybrid three-level active neutral-point-clamped (3L-ANPC) topology is developed. To achieve high efficiency, the switching devices operated at carrier frequency in the 3L-ANPC converter are configured by the emerging Silicon Carbide (SiC) Metal-Oxide Semiconductor Field-Effect Transistors (MOSFETs), while the conventional Silicon (Si) Insulated-Gate Bipolar Transistors (IGBTs) are selected for the switches modulated at the fundamental output frequency. The dc-bus voltage is increased from the conventional 270 V to 2.4 kV to reduce the power cable weight in the aircraft. Unlike the traditional 400 Hz aircraft electric systems, the rated fundamental output frequency of the inverter here is boosted to 1.4 kHz to drive the high-speed motor. Systematic hardware development and new PWM strategy for the 3L-ANPC inverter will be presented in this paper, and the associated experimental results are shown to verify the performance of this MW-scale medium-voltage inverter. It is shown that the 1-MW power inverter achieves an efficiency of99% and power density of 12 kVA/kg, which provides a promising solution to the realization of high-efficiency high-density aircraft hybrid propulsion systems.

Design of high-speed H-bridge converter using discrete SiC MOSFETs for solid-state transformer applications

The advancements in wide-band-gap (WBG) devices are enabling applications of power electronics converters coupled directly to medium voltage and incorporating galvanic insulation within the converter using high-frequency solid-state transformers. This paper presents the design and the characterization results of a SiC H-bridge converter suitable for up to 100 kVA single-phase ac-dc modular solid-state transformer comprised of a hard-switched ac-line interface and a resonant dc-dc stage switched at 175 kHz. To minimize the cost of switching elements per ampere and maximize design flexibility, the design uses multiple discrete SiC devices of, readily available, 1700 V ratings. The switching-cell layout concept together with the gate-drive solution is proposed to enable the design scalable for different power and voltage applications. The insulated metal substrate (IMS) is used to provide a simple but effective thermal management and mechanical packaging solution.

Comparison of 1.7kV, 450A SiC-MOSFET and Si-IGBT based modular three phase power block

A three phase power block based on novel 1.7 kV/450 A SiC-MOSFET is designed and tested. To benchmark the performance of the power block, a through comparison is done with currently standardized 1.7 kV/450 A Si-IGBT based three phase power block. Key performance indices, including power rating curves at different switching frequencies and power factors; temperature ripple at different fundamental frequencies, are examined. It is shown that the SiC based power block has very promising potentials in various applications. Simulation and experiment results are provided to support the claims for SiC-MOSFET based power block.