This paper presents a soft-switched buck converter using Autonomous Gate Drivers (AGDs) for power electronic converters. Operating at a 400 V DC-link, typical of Electric Vehicles (EVs) and industrial systems, the converter achieves Zero Voltage Switching (ZVS) during turn-on and turn-off via AGD circuitry and optimized snubber capacitance. Operating in Triangular Current Mode (TCM), the converter utilizes inductor current ripple to enable ZVS. Experimental results confirm reliable soft-switching and suppression of voltage overshoot under realistic conditions. While the validation uses a buck converter, the proposed AGDs are directly applicable to more complex converters, including three-phase inverters with sinusoidal reference currents, relevant to EVs, renewable energy, and industrial drives. This work demonstrates a scalable solution for reducing switching losses and improving efficiency in advanced high-voltage converters.

The utilization of soft-switching inverters is essential for achieving high efficiency and low electromagnetic interference (EMI) in electric vehicle (EV) drive systems. However, inductor design for such converters presents significant challenges. In triangular current mode (TCM)-based zero voltage switching (ZVS) inverters, inductors experience large current ripple and variable switching frequency, leading to excessive core and winding losses. This paper presents a design methodology for a high-power filter inductor specifically suited for TCM-based ZVS inverters. A ferrite pot core was selected, and three winding techniques—Litz wire, copper foil, and solid copper wire—were evaluated. The inductance of the three inductors was determined both experimentally and via simulation using FEMM and ANSYS, while power losses were estimated using FEM-based simulations in ANSYS. Experimental determination of 3C91 core loss coefficients was also performed. The optimal configuration required two parallel inductors per phase, resulting in a final three-phase inverter design with six inductors, each 57 mm high and 66 mm in diameter. By integrating experimental measurements with simulation-based loss estimation, the proposed approach reduces core and copper losses, improves thermal management, and enhances power density, making it suitable for next-generation EV powertrains and renewable energy conversion systems.

The electrification of transportation demands power conversion systems that are highly efficient, compact, reliable, and exhibit low electromagnetic interference (EMI). In electric vehicle (EV) drive applications, the two-level three-phase traction inverter is a key component that should exhibit high efficiency across varying loads and reliable operation at elevated switching frequencies.

This thesis presents a scalable, high-performance inverter design that combines autonomous gate drivers (AGDs) with optimized magnetic components. It incorporates snubber capacitors across each SiC MOSFET and a compact LC low-pass filter between the inverter output and motor terminals to enable effective soft switching and reduce EMI. This approach addresses key challenges in EV power conversion, offering a path toward compact, efficient, and EMI-compliant traction inverters for next-generation electric mobility.

The novel AGD design achieves zero-voltage switching (ZVS) under triangular current mode (TCM) control by continuously monitoring the switch voltage and current to determine optimal switching instants in real time. Direct sensing of switch conditions removes communication delays and ensures efficient ZVS at both turn-on and turn-off. The turn-off timing is set by an externally defined reference current transmitted through a galvanically isolated amplifier.

Simulation of a 10 kW two-level, three-phase inverter employing the proposed AGDs demonstrates over 99 % efficiency, sinusoidal current waveforms, and fast torque response with minimal overshoot and EMI. The integrated LC filter improves the output waveform quality while supporting soft-switching operation.

Experimental validation of the AGD concept was performed using a buck converter prototype. The AGDs operated independently of a central controller, initiating turn-on based on negative voltage detection and enabling lossless turn-off through a snubber capacitor. The system achieved ZVS at both transitions, confirming the practicality and scalability of the proposed gate-driving approach. For current sensing, the AGD employs the on-state resistance (Rds(on)) of SiC MOSFETs, eliminating the need for external shunt resistors. This reduces component count, avoids parasitic effects, and potentially increases reliability.

The thesis also investigates the design of filter inductors suitable for TCM-based ZVS inverters. Three prototypes were constructed using ferrite pot cores with Litz wire, copper foil, and solid round copper wire windings. Inductance was measured experimentally, and power losses were evaluated through Ansys Maxwell simulations under high ripple current and variable frequency conditions. Litz wire demonstrated superior performance in minimizing both copper and core losses. A dual-inductor configuration per phase—six inductors in total—is recommended for effective current handling and thermal management.

Elektrifieringen av transport kräver effektomvandlingssystem som är mycket effektiva, kompakta, pålitliga och som uppvisar låg elektromagnetisk störning (EMI). I elfordonsapplikationer (EV) är den tvånivåiga trefasiga drivomvandlaren en nyckelkomponent som måste ha hög effektivitet över varierande belastningar och pålitlig drift vid höga switchfrekvenser.

Denna avhandling presenterar en skalbar och högpresterande omvandlardesign som kombinerar autonoma gate-drivare (AGD) med optimerade magnetiska komponenter. Den inkluderar snubber-kondensatorer över varje SiC MOSFET och ett kompakt LC-lågpassfilter mellan omvandlarens utgång och motorterminalerna för att möjliggöra effektiv mjukomkoppling och minska EMI. Denna metod tar itu med viktiga utmaningar inom EV-effektomvandling och banar väg för kompakta, effektiva och EMI-kompatibla drivomvandlare för nästa generations elektriska mobilitet.

Den nya AGD-designen uppnår nollspänningsomkoppling (ZVS) under triangulär strömmode (TCM) styrning genom att kontinuerligt övervaka switchens spänning och ström för att bestämma optimala omskiftningstidpunkter i realtid. Direkt avkänning av switchförhållanden eliminerar kommunikationsförseningar och säkerställer effektiv ZVS vid både på- och avslagning. Avslagnings-tidpunkten styrs av en externt definierad referensström som överförs via en galvaniskt isolerad förstärkare.

Simulering av en 10kW tvånivåig trefasomvandlare med de föreslagna AGD:erna visar över 99% verkningsgrad, sinusformade strömvågor och snabb momentrespons med minimal överslängning och EMI. Det integrerade LC-filtret förbättrar utgångsvågformen samtidigt som det stödjer mjukomkopplingsdrift.

Experimentell validering av AGD-konceptet utfördes med en buck- omvandlarprototyp. AGD:erna fungerade oberoende av en central styrenhet, initierade påslagning baserat på negativ spänningsdetektion och möjliggjorde förlustfri avslagning genom en snubber-kondensator. Systemet uppnådde ZVS vid båda övergångarna, vilket bekräftar praktikaliteten och skalbarheten i den föreslagna gate-drivningsmetoden. För strömmätning använder AGD:erna SiC MOSFET:arnas påslagsresistans (Rds(on)), vilket eliminerar behovet av externa shuntmotstånd. Detta minskar komponentantalet, undviker parasitiska effekter och ökar potentiellt tillförlitligheten.

Avhandlingen undersöker även utformningen av filterinduktorer lämpliga för TCM-baserade ZVS-omvandlare. Tre prototyper konstruerades med ferritpotkärnor och lindningar av Litz-tråd, kopparfolie och solida runda koppartrådar. Induktansen mättes experimentellt och effektförluster utvärderades med Ansys Maxwell-simuleringar under höga ripple-strömmar och varierande frekvenser. Litz-tråden visade överlägsen prestanda vad gäller minimering av både koppar- och kärnförluster. En dubbelinduktor-konfiguration per fas — totalt sex induktorer — rekommenderas för effektiv strömhantering och termisk kontroll.

This study focuses on analyzing and optimizing LC filter components for the triangular current mode (TCM)-based zero voltage switching (ZVS) inverter. The integration of ZVS and TCM control techniques in TCM-based ZVS two-level three-phase inverters significantly reduces switching losses, enhances overall system efficiency and power density, and mitigates electromagnetic interference (EMI) issues. An LC filter is essential for operating the inverter in TCM-based ZVS mode, ensuring soft switching throughout. Optimized LC filters play a crucial role by providing ZVS at turn-on and turn-off, enhancing motor efficiency by achieving sinusoidal waveforms and minimizing harmonics. Additionally, the design increases copper space in motor winding slots, enabling lower temperature operation, extended lifespan, and reduced reliance on cooling systems. Performance analysis, including output waveform examination, fast fourier transform (FFT), total harmonic distortion (THD) evaluation, and EMI highlights the superior effectiveness of this LC filter-optimized TCM-based ZVS inverter configuration over conventional hard-switched inverters.

The demand for highly efficient and dynamic electric vehicles (EVs) has increased dramatically. The traction inverter, a pivotal component in an EV powertrain, plays a crucial role. This study is dedicated to designing a traction inverter with focus on achieving high efficiency and elevated power density and mitigating electromagnetic interference (EMI) issues. To realize these objectives, autonomous gate drivers (AGDs) are proposed and designed using LTspice simulation software. The aim is to achieve zero voltage switching (ZVS) at both turn-on and turn-off through the utilization of triangular current mode (TCM) control on the gate driver. The AGDs implement a current modulation scheme by sensing the current and voltage and generating gate-source voltage signals with minimal delays. The implemented current modulation scheme by the AGDs results in an efficiency exceeding 99% for a 10 kW power rating. The sinusoidal output waveforms not only contribute to extending the motor lifespan by mitigating sharp-edge voltages but also bring advantages such as reduced switch stress, decreased EMI, and simplified thermal management.

This study compares shunt-based and SiC MOSFET Rds(on)-based autonomous gate drivers (AGDs) for triangular current mode (TCM)-based zero voltage switching (ZVS) two-level three-phase inverters for electric vehicle (EV) drive systems. Integrating ZVS and TCM control techniques significantly reduces switching losses, enhances overall system efficiency, and mitigates electromagnetic interference (EMI) issues. The AGDs, based on a current modulation scheme, sense switch voltage for turn-on at ZVS and switch current for turn-off, using either a shunt or SiC MOSFET Rds(on). When the switch current exceeds a predefined value, the AGD facilitates ZVS turn-off with external snubber capacitance. Performance evaluation includes gate-source voltage generation, optimum blanking time, ZVS turn-on/off, and efficiency supported by simulation results. The discussion covers the advantages, limitations, and impact of the proposed inverter design on EVs, providing valuable insights for the selection and implementation of AGDs in EV drive systems.

This paper introduces a novel triangular-current mode (TCM), zero-voltage switching (ZVS) two-level three-phase inverter, specifically designed to enhance the performance of the electric vehicle (EV) drive system. The primary objective is to enhance the inverter efficiency by minimizing turn-on and turn-off switching losses while mitigating electromagnetic interference (EMI) by generating sinusoidal output waveforms. The distinctive feature of this inverter lies in its gate driver, which executes the current modulation scheme. Achieving ZVS during turn-on involves the gate driver sensing the switch voltage and turning it on at zero voltage, utilizing TCM. For turn-off ZVS, the gate driver monitors the switch current, turning it off when it exceeds a predefined reference value. With a carefully placed snubber capacitor, turn-off ZVS is achieved. The implemented current modulation scheme yields an efficiency exceeding 99% for a 10 kW power rating. The sinusoidal output waveforms not only enhance motor lifespan by safeguarding against sharp-edge voltages but also offer benefits like reduced switch stress and simplified thermal management.

This paper investigates the performance and applicability of a triangular current mode (TCM)–based zero voltage switching (ZVS) three-phase inverter, incorporated with novel autonomous gate drivers (AGDs), for electric vehicle (EV) drive systems. By integrating the controller into the gate driver, delays are minimized, enabling ZVS during the turn-on and turn-off operations. Sinusoidal output waveforms aid in reducing electromagnetic interference (EMI). This study examines the potential interference of the LC filter with torque control and evaluates the inverter’s ability to respond quickly and accurately to torque commands without introducing delays, overshoots, or oscillations. The proposed 10 kW inverter achieved over 99% efficiency without including filter inductor losses. Torque steps were executed significantly faster than required for practical applications. No delays or oscillations were observed, indicating the inverter’s suitability for EV drive systems.

This paper introduces a novel approach to designing autonomous gate drivers for soft-switched buck converters. The objective is to reduce switching losses, enhance converter efficiency, and reduce electromagnetic interference (EMI). The uniqueness of this converter is that the pulse-width modulation is performed autonomously on the gate driver. The gate driver makes quick decisions on switching times, capitalizing on the minimal time delay between measurements and switching. In the proposed buck converter configuration, the gate driver senses both the current and voltage across the switches to avoid delay. When a slightly negative voltage is detected across the switch, it rapidly turns on, resulting in a zero-voltage switching (ZVS). With an external snubber capacitor placed across the switches, the turn-off switching losses are zero (ZVS). Hence, both the turn-on and turn-off of the switch are soft. To enable the switch to turn off, a reference value of the switch current needs to be sent out to the gate driver using a galvanically isolated current sensor. Through this approach, the efficiency of the 7 kW buck converter has been calculated to exceed 99% without including the filter losses. Additional benefits include reduced switch stresses, diminished electromagnetic interference (EMI), and simplified thermal management.