Aiming for converters with high efficiency and high power density demands converter topologies with zero-voltage switching (ZVS) capabilities. This letter shows that in order to determine whether ZVS is provided at a given operating point, the stored charge within the mosfet s has to be considered and the condition $L I^2 \geq 2Q_\text{oss} V_\text{DC}$ has to be fulfilled. In the case of incomplete soft switching, nonzero losses occur which are analytically derived and experimentally verified in this letter. Furthermore, the issue of nonideal soft-switching behavior of Si superjunction mosfet s is addressed.

ZVS of Power MOSFETs Revisited

An electromagnetic induction power transfer apparatus (100) comprises:an inductive power transmitter (102), comprising:a power supply with an active state and an inactive state, configured to switch between the active state and the inactive state at a selectable duty cycle; and a power-transmitting inductor (102-12) coupled to the power supply; and an inductive power receiver (104), comprising:a power-receiving inductor (104-12), positioned inductively proximate the power-transmitting inductor; a programmable load (104-12); and an impedance controller (104-6) coupled to the power receiving inductor and configured to increase or decrease an electrical impedance of the inductive power receiver in response to a change in a power requirement of the programmable load.

Impedance matching for inductive power transfer systems

This paper presents a compact battery-powered switched-reluctance motor (SRM) drive for an electric vehicle with voltage-boosting and on-board power-factor-corrected-charging capabilities. Although the boost-type front-end DC/DC converter is externally equipped, the on-board charger is formed by the embedded components of SRM windings and converter. In the driving mode, the DC/DC boost converter is controlled to establish boostable well-regulated DC-link voltage for the SRM drive from the battery. During demagnetization of each stroke, the winding stored energy is automatically recovered back to the battery. Moreover, the regenerative braking is achieved by properly setting the SRM in the regenerating mode. The controls of two power stages are properly designed and digitally realized using a common digital signal processor. Good winding current and speed dynamic responses of the SRM drive are obtained. In addition, the static operation characteristics are also improved. In the charging mode, the power devices that were embedded in the SRM converter and the three motor-phase windings are used to form a buck-boost switch-mode rectifier to charge the battery from utility with good power quality. All constituted circuit components of the charger are placed on board, and only the insertion of power cords is needed.

Development of a Compact Switched-Reluctance Motor Drive for EV Propulsion With Voltage-Boosting and PFC Charging Capabilities

This paper presents a combined phase-shift and frequency modulation scheme of a dual–active-bridge (DAB) ac–dc converter with power factor correction (PFC) to achieve zero voltage switching (ZVS) over the full range of the ac mains voltage. The DAB consists of a half bridge with bidirectional switches on the ac side and a full bridge on the dc side of the isolation transformer to accomplish single-stage power conversion. The modulation scheme is described by means of analytical formulas, which are used in an optimization procedure to determine the optimal control variables for minimum switch commutation currents. Furthermore, an ac current controller suitable for the proposed modulation scheme is described. A loss model and measurements on a 3.3-kW electric vehicle battery charger to connect to the 230  $\text{V}_\text{rms}$  / 50-Hz mains considering a battery voltage range of 280–420 V validate the theoretical analysis.

Combined Phase-Shift and Frequency Modulation of a Dual-Active-Bridge AC–DC Converter With PFC

A digital average-input current-mode control loop for a DC/DC power converter. The power converter may be, for example, a buck converter, boost converter, or cascaded buck-boost converter. The purpose of the proposed control loop is to set the average converter input current to the requested current. Controlling the average input current can be relevant for various applications such as power factor correction (PFC), photovoltaic converters, and more. The method is based on predicting the inductor current based on measuring the input voltage, the output voltage, and the inductor current. A fast cycle-by-cycle control loop may be implemented. The conversion method is described for three different modes. For each mode a different control loop is used to control the average input current, and the control loop for each of the different modes is described. Finally, the algorithm for switching between the modes is disclosed.

Digital Average Input Current Control in Power Converter

This paper presents a general method to measure the output capacitance (Coss) related energy loss per switching cycle in power MOSFETs used in zero-voltage-switched (ZVS) applications. It is shown that a simple model using Coss in series with a resistance Ross is inadequate for describing the observed energy loss and a different model is needed. This work also shows that the traditional hard-switched test methods for measuring the dynamic performance of power MOSFETs are inadequate for describing the dynamic performance of power MOSFETs used in ZVS applications. Finally, this study proposes a new power MOSFET figure of merit suitable for differentiating the performance of MOSFETs for use in ZVS applications.

C oss related energy loss in power MOSFETs used in zero-voltage-switched applications

In this work, a Sawyer-Tower circuit is employed to characterize the output capacitance (COSS) of advanced superjunction MOSFETs. It is shown that some of the most advanced superjunction MOSFETs exhibit significant hysteresis in their output capacitance which leads to unrecoverable power loss. This work shows that the conventional impedance analyzer method can only measure COSS accurately when hysteresis is not present while measurement of COSS with a Sawyer-Tower circuit gives accurate results regardless of whether hysteresis is present or not. Accurate measurement of COSS with a Sawyer-Tower circuit not only enables designers to more accurately calculate and predict power loss but even more importantly allows the power semiconductor industry to more effectively advance future generations of superjunction MOSFETs for optimum efficiency, especially for use in resonant converter applications.

COSS hysteresis in advanced superjunction MOSFETs

A three phase full resonant cyclo-converter suitable for converting a three phase AC supply to a DC output. In one embodiment the cycloconverter controls switching frequency to control converter output and adjusts phase on times for power factor correction. A switching sequence is employed which provides resonant switching to reduce losses and component ratings. The converter provides high conversion efficiency with a simple power component design.

Cyclo-converter and methods of operation

An apparatus, method, and system for measuring current within a converter. The converter including a resonant tank circuit with a capacitor, the resonant tank circuit is coupled to a DC input bridge and a first terminal of the capacitor is coupled to a ground of the DC input bridge. In addition, a voltage monitor coupled across the capacitor for measuring a voltage across the capacitor. The converter also includes a resonant current calculation module for computing a tank current value based on the voltage.

Method and apparatus for deriving current for control in a resonant power converter

Apparatus and system for powering an isolated gate driver. In one embodiment, the apparatus comprises a gate driver power supply unit (PSU), coupled to a transistor and to an isolated gate driver that couples control signals to the transistor, for (i) harnessing energy from commutation action across the transistor, and (ii) using the harnessed energy to power the isolated gate driver.

Michael J. Harrison

Papers

C oss related energy loss in power MOSFETs used in zero-voltage-switched applications

COSS hysteresis in advanced superjunction MOSFETs

Cyclo-converter and methods of operation

Method and apparatus for deriving current for control in a resonant power converter

Isolated gate driver auxiliary power supply