Chingchi Chen

Power cycling reliability of IGBT power modules

The goal of this study was to understand the power cycling reliability of IGBT power modules. These power modules are made up of multi-layer stacks and consist of multiple power dice in parallel. The interconnection schemes within the module include leadframes soldered to substrate, die attachment using solder and wirebonds. Thermal and power cycling fatigues material interfaces because of the CTE mismatch between dissimilar materials. In addition, wirebonds on the dice are prone to debonding because of the thermally induced stresses. Tests were designed to understand the power cycling reliability of these large transistor modules. Results from the tests are summarized in this paper.

A gallium-nitride switched-capacitor circuit using synchronous rectification

The promise of wide band-gap materials has the potential to usher in a new era of power electronics not seen since the introduction of the Silicon (Si) Metal Oxide Semiconductor Field Effect Transistor (MOSFET) and Bipolar Junction Transistor (BJT). The physical characteristics of Gallium Nitride (GaN) make it theoretically superior to Si in such aspects as temperature of operation, switching speed, and efficiency. While much research has been conducted on the High Electron Mobility Transistor (HEMT) made of GaN and Aluminum Gallium Nitride (AlGaN), the discussion of third quadrant operation is sparse. Furthermore, the merits of the AlGaN/GaN HEMT, in particular its switching speed, make it suitable for switched-capacitor circuits. Thus, this paper focuses on the AlGaN/GaN HEMTs third quadrant operation and demonstrates this functionality in a switched capacitor circuit.

A high frequency battery model for current ripple analysis

In applications where batteries work together with power electronic circuits, the current ripple generated by the power electronics will be shared by both the battery and passive components in the circuit. The amount of ripple absorbed by the battery depends on its impedance at the switching frequency of power electronics. This paper presents an impedance based high frequency battery model derived from test results of a NiMH battery using a novel battery impedance tester. The possible reasons for the battery impedance characteristics in high frequency region, including skin effect and proximity effect, are also discussed. This battery model can be directly used in current ripple analysis, passive components design and control strategy optimization of power electronic circuits. The effect of the passive component values on the battery current ripple is analyzed using the ac equivalent circuit of the test setup.

A Gallium Nitride Switched-Capacitor Circuit Using Synchronous Rectification

The physical characteristics of gallium nitride (GaN) make it theoretically superior to silicon (Si) in such aspects as the temperature of operation, switching speed, breakdown voltage, and efficiency. While much research has been conducted on GaN devices, the discussion of third-quadrant operation is limited. Furthermore, the merits of GaN transistors, particularly their fast switching speed and low on-resistance, make them suitable for switched-capacitor circuits. This paper demonstrates the ability of a GaN transistor to function as a synchronous rectifier in a switched-capacitor circuit. A 500 W GaN-based voltage doubler capable of achieving zero-current switching is presented with supporting experimental results. This circuit achieves peak efficiencies of 97.6% and 96.6% while switching at frequencies of 382 and 893 kHz, respectively.

Loss-less and cost-effective cable terminator topologies with no voltage overshoot

This paper proposes a series of cable terminator topologies to totally eliminate the voltage overshoot across the load of a power electronics system with fast switching edges and long cables. Potentially without power loss, the proposed terminators improve the system efficiency and with significantly reduced package size. Also, diagnostic capability can be built-in with little additional cost to remotely monitor the operation of the terminator. Detailed analysis and test results are included in the paper.

Characterizing the generation & coupling mechanisms of electromagnetic interference noise from an electric vehicle traction drive up to microwave frequencies

This paper proposes empirical strategies to characterize traditionally difficult electromagnetic compatibility (EMC) problems of power electronic motor drives, up to hundreds of MHz with high accuracy and providing better understanding to the root causes. Very simple concepts and block diagrams are used in this paper. Straightforward equations are then developed to predict or confirm important system-level features. By treating the noise sources and distribution paths separately, complicated EMC problems are conceptually divided into smaller and easier sub-issues, yielding more insightful perception and pave the road to better mitigation results. To confirm the proposed methodology, solid test results are shown in the paper, and followed by thorough discussions. Finally, a concise summary is appended to conclude this paper.

Auxiliary Power Supply for Hybrid Electric Vehicles

This paper is the first paper to systemically address issues related with HEV auxiliary power supply. Requirements and problems are identified. Basic and traditional power electronics circuit solutions are summarized. New circuit structures are proposed. Circuit design example and comparison between the new circuit and traditional circuit are also shown.

A hybrid inverter/cycloconverter-based variable-speed three-phase induction motor drive for single-phase inputs

This paper presents a simple converter topology for driving a three-phase induction motor with a single-phase AC supply. Using only two active switches and a triac, the converter can start the motor with high starting torque and low input current, and can bring the motor up to full speed using a very cost-effective, single-phase field-oriented control strategy. The converter supplies balanced output voltages at rated frequency with virtually no output distortion and with very high input power factor. In this paper, the capability contours for different speed ranges and various operating modes are addressed; the trade-offs between output torque, torque ripple, input current distortion, and inverter rating are also explained, and the proposed control approaches are supported by simulation and test results. >

A power loss characterization method for semiconductor switching devices based on inverter-level DC measurements

This paper presents an inverter-level power loss measurement method for semiconductor switching devices in real inverter operation conditions. This method employs an H-bridge dc-dc convertor topology and a low-loss inductive load to improve the loss measurement accuracy. Since only dc measurement is involved, it is simpler and more accurate compared to traditional inverter-level loss measurement methods. Both switching and conduction loss can be estimated with this method. Experimental results on a traction-drive inverter show that, the difference between the estimated results with the proposed method and the results from traditional component-level methods is within 4% in the normal operation range of the inverter.

Electromagnetic noise coupling and mitigation for fast response on-die temperature sensing in high power modules

A heavy low pass filter is usually applied to an on-die temperature sensors output to filter out the strong noises during switching transients. Aiming at high bandwidth junction temperature sensing, this paper evaluates the electromagnetic noise coupling of an on-die temperature sensing diode in a high power module. Challenges of fast response on-die temperature sensing are reviewed first. Noise coupling mechanisms are analyzed under different grounding configurations and operating conditions. Based on the analysis, a method is proposed to estimate the parasitic capacitance between the sensor and the power device. Special attention has been paid to achieve a high bandwidth and noise immunity test setup. With that, the sensor coupled noises are evaluated in experiments and compared with the model. Noise propagation impedance compensation is applied and verified by experiment. Considerations of sensing circuit design are also discussed. A 100 kHz low pass filter is used to deal with the residual noises during switching transients. With the designed sensing circuitry, short circuit tests are conducted to demonstrate sensors dynamic response.