Mark J. Scott

A Switched-Capacitor Voltage Tripler With Automatic Interleaving Capability

This paper presents a high-efficiency switched-capacitor voltage tripler topology aimed at high-power applications. A soft-switching scheme without the addition of extra components is adopted to minimize the switching loss and the electromagnetic interference noises. A two-step current charging method is used to enable the input current and output voltage interleaving functionality without adding an excessive number of components. The large loss on the input capacitor that exists in the traditional switched-capacitor topologies is eliminated by employing this interleaving scheme. The soft switching and interleaving results are analyzed in detail. The experimental results for a 2-kW prototype are demonstrated to verify the functionality of the proposed topology.

Switched-Capacitor-Cell-Based Voltage Multipliers and DC–AC Inverters

In this paper, several modular converter topologies based on a switched-capacitor-cell concept are introduced for high-power applications. Two types of switched-capacitor cells, including the full cell and the half-cell, are discussed. The full cell can be used for dc-ac inversion, and the half-cell is utilized in both dc-dc and dc-ac applications. A rotational charging scheme is adopted for the half-cell-based dc-dc voltage multiplier to eliminate the large output capacitor that exists in many traditional switched-capacitor topologies. A soft-switching scheme, which does not require extra components, is adopted to reduce the switching loss and electromagnetic interference. A variable switching frequency control scheme is proposed to realize soft switching for dc-ac inverters. The experimental results on a 2-kW prototype are presented to verify the proposed topologies.

Merits of gallium nitride based power conversion

Gallium nitride (GaN) based power electronics devices are actively being evaluated to determine if their theoretical advantages over silicon (Si) based switches can translate into improved performance of existing hardware as well as open the doors to new types of applications, such as high temperature implementations, or very high frequency power conversion. The following paper presents an overview of this activity. A brief summary about power electronics and the requirements of semiconductor devices used in this field is provided. Detailed analysis of the advantages and the challenges of using GaN devices is included along with a survey of demonstrations. This work also presents the test results from the evaluation of GaN devices from Efficient Power Conversion (EPC) and Transphorm. Included is a demonstration of EPCs devices in a high frequency, high efficiency, switched-capacitor voltage doubler. This circuit achieves an output of 480 W at a switching frequency of 893 kHz.

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 GaN transistor based 90W AC/DC adapter with a buck-PFC stage and an isolated Quasi-switched-capacitor DC/DC stage

This paper presents a GaN Transistor based 90W ac/dc adapter with a Buck-PFC stage and an isolated Quasi-Switched-Capacitor (QSC) dc/dc stage. In the dc/dc stage, two different QSC converters are proposed. Compared to Flyback and LLC resonant converters, the QSC converters feature: 1) reduced voltage stress on the primary-side switches to 2/3 of the input voltage; 2) reduced voltage stress on the transformer to 1/3 of the input voltage and a lower transformer turns ratio; 3) a wide range for soft-switching operation and high efficiency; 4) a simple control strategy. The operation principles and simulation results are presented. A 90 W, 85 V/19 V, 1 MHz QSC resonant converter is built, using 100 V EPC eGaN FETs for all switches. This prototype achieves: 1) a high power density of 10.5 W/cm3; 2) wide-range soft switching and a peak efficiency of 92.8% at 900 kHz in preliminary test results. A Buck-PFC evaluation module from TI is tested with a GaN HEMT and a SiC Schottky diode. The peak efficiency reached 97.1%, and the experimental results are compared with those from the Si based version.

A Gallium Nitride switched-capacitor power inverter for photovoltaic applications

A Gallium Nitride (GaN) based switched-capacitor module integrated inverter (MII) is presented in this paper. This two stage solution first employs a dc/dc quadrupler that utilizes an interleaving charging scheme. This strategy not only reduces the high frequency current ripple subjected to the photovoltaic panel, but also decreases the voltage ripple on the DC link between the two stages. The second stage is a five-level boost inverter that is responsible for both maximum power point tracking (MPPT) and minimizing reactive power flow. Both stages utilize a resonant soft-switching scheme in the capacitor charging current loops to increase the MIIs efficiency. Basic theoretical analysis and experimental results for the individual stages are included.

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.

Switched capacitor cell based Dc-dc and Dc-ac converters

This paper introduces a modular converter topology based on switched capacitor cells. Two types of cells are discussed in this paper. The full cell switched capacitor structure, which can be used in dc/ac inversion and the half cell structure that has applications in both dc/dc and dc/ac conversion. There are several merits to this converter topology; it has a modular structure, the capacitor count is minimized, and with dc/ac converter there is good redundancy. When utilized as a dc/dc converter, the required output capacitance is minimized and soft switching can be achieved. The basic analysis, simulation results and experimental results on a 1 kW cell prototype are presented.

Applications of Gallium Nitride in power electronics

The electrical properties of Gallium Nitride (GaN) offer several advantages over Silicon (Si) for creating switching devices for power electronics. Already this emerging technology is showing improvements in power density and efficiency in certain applications. The following paper reviews the current state of the art of GaN devices. It discusses challenges in implementation, such as the mistriggers that result from dV/dts across the miller capacitance. It examines third quadrant operation for negative gate to source voltages. A strategy for mounting devices from Efficient Power Conversion is provided. Finally, two switched capacitor circuits are presented with experimental results. The first is a voltage doubler operating at 893 kHz with a peak power of 480 W and an efficiency of 94.4 %. The second is a three-phase, three-level inverter with preliminary test results operating at 300 kHz.

Industry-Oriented Laboratory Development for Mixed-Signal IC Test Education

The semiconductor industry is lacking qualified integrated circuit (IC) test engineers to serve in the field of mixed-signal electronics. The absence of mixed-signal IC test education at the collegiate level is cited as one of the main sources for this problem. In response to this situation, the Department of Electrical and Computer Engineering at the Ohio State University, Columbus, has partnered with Texas Instruments to establish an IC test-engineering-oriented course. The course objectives are to familiarize students with industrial testing techniques and to help students obtain the fundamental skill sets required to be competent mixed-signal IC test engineers. A novel laboratory pedagogy is developed to achieve these objectives. The results of the classroom assignments and the feedback provided by students, faculty, and industry representatives indicate that the approach has successfully achieved these goals.