MOSFET Output Capacitance Research Articles

Implementation of class‐E/F3 power amplifiers based on the variations of the MOSFET grading coefficient, built‐in potential and output capacitance along with their roles in MOSFET selectivity

SummaryIn this paper, a theoretical analysis of the class‐E/F3 power amplifier based on the variation of the grading coefficient m1 and its vital role in MOSFET selectivity to operate safely under given design specifications is presented while the nonlinearity of the drain‐to‐source capacitance is considered. Moreover, the importance of Vbi and Cjo in designing the class‐E/F3 amplifier is investigated. To clarify how the grading coefficient m1 and the other mentioned parameters can directly influence the power amplifier performance and also its elements, these MOSFET parameters are considered as the independent variables of the calculated equations and consequently define the horizontal axis of the obtained plots. Accordingly, as the grading coefficient increases, the maximum switch voltage increases and values of the output power and output power capability decline. Moreover, to prove the reliability of the carried‐out analysis in selecting proper MOSFETs, the performances of three amplifier samples utilizing IRF510, IRFZ24N, and 2SK2504 MOSFETs with different grading coefficient m1 and almost similar Vbi and Cjo are studied. Then, by comparing the results of amplifiers with three MOSFETs, IRF510, IRF530, and IRF540, with similar grading coefficient and different values of Vbi and Cjo, the significance of considering the values of Vbi and Cjo is investigated. Eventually, three amplifiers with 2SK2504, IRF510, and IRF530 MOSFETs have been simulated, implemented, and tested and measurement results agreed well with the theoretical and simulation results.

Analysis of Intrinsic Switching Losses in Superjunction MOSFETs Under Zero Voltage Switching

Switching losses of power transistors usually are the most relevant energy losses in high-frequency power converters. Soft-switching techniques allow a reduction of these losses, but even under soft-switching conditions, these losses can be significant, especially at light load and very high switching frequency. In this paper, hysteresis and energy losses are shown during the charge and discharge of the output capacitance (COSS) of commercial high voltage Superjunction MOSFETs. Moreover, a simple methodology to include information about these two phenomena in datasheets using a commercial system is suggested to manufacturers. Simulation models including COSS hysteresis and a figure of merit considering these intrinsic energy losses are also proposed. Simulation and experimental measurements using an LLC resonant converter have been performed to validate the proposed mechanism and the usefulness of the proposed simulation models.

Interleaved Boost-Integrated <italic>LLC</italic> Resonant Converter With Fixed-Frequency PWM Control for Renewable Energy Generation Applications

This paper proposes a current-fed LLC resonant converter that is able to achieve high efficiency over a wide input voltage range. It is derived by integrating a two-phase interleaved boost circuit and a full-bridge LLC circuit together by virtue of sharing the same full-bridge switching unit. Compared with conventional full-bridge LLC converter, the gain characteristic is improved in terms of both gain range and optimal operation area, fixed-frequency pulsewidth-modulated (PWM) control is employed to achieve output voltage regulation, and the input current ripple is minimized as well. The voltage across the turned-off primary-side switch can be always clamped by the bus voltage, reducing the switch voltage stress. Besides, its other distinct features, such as single-stage configuration, and soft switching for all switches also contribute to high power conversion efficiency. The operation principles are presented, and then the main characteristics regarding gain, input current ripple, and zero-voltage switching (ZVS) considering the nonlinear output capacitance of MOSFET are investigated and compared with conventional solutions. Also, the design procedure for some key parameters is presented, and two kinds of interleaved boost integrated resonant converter topologies are generalized. Finally, experimental results of a converter prototype with 120–240 V input and 24 V/25 A output verify all considerations.

DESIGN AND DEVELOPMENT OF HIGH FREQUENCY RESONANT TRANSITION CONVERTER

The demand for higher switching frequencies in order to achieve higher power conversion densities and efficiencies has made resonant mode conversion [1] techniques to be used nowadays to improve pulse width modulated dc- dc converters which can operate at higher switching frequencies upto 1 MHz. Since the parasitic elements that normally present in a power circuit can be very significant at this frequency, most of the work is focused on resonant topologies. The topology [2] enables to advantageously employ transformer leakage inductance, MOSFET output capacitance and the MOSFET body diode, to easily move their designs upwards in frequency. The topology offers additional advantages like zero voltage switching at a constant switching frequency, which substantially reduces switching losses. The ability to use higher switching frequency will ultimately reduce the overall size of the power supply. A resonant transition converter is selected for developing a compact 30W power supply. The switching frequency considered is 500 kHz for achieving the required power conversion density. At this switching frequency it is possible to take advantage of lead inductances and parasitic capacitance of switching MOSFETs to either eliminate or substantially reduce the resonant tank elements required for achieving a resonant transition conversion to improve efficiency.

A New ZVS DC/DC Converter With Three APWM Circuits

This paper presents a new soft-switching dc/dc converter with series-connected transformers to implement the features of zero-voltage switching (ZVS), load current sharing, low voltage stress for MOSFETs, and low current rating for the rectifier diodes and the output inductors. The proposed converter includes two half-bridge circuits connected in series to limit the voltage stress of MOSFETs at one-half of the input voltage. The output sides of the two circuits are connected in parallel to reduce the current rating on the rectifier diodes and the output inductors and to achieve load current sharing. In order to balance two output inductor currents, series-connected transformers at the low-voltage side are adopted. Thus, the output power is equally distributed by the two half-bridge circuits. The output capacitances of MOSFETs and the resonant inductances are resonant at the transition instant such that MOSFETs can be turned on at ZVS. Finally, experiments based on a laboratory prototype with 1-kW rated power are provided to demonstrate the performance of the proposed converter.

Soft-Switching Converter With Two Series Half-Bridge Legs to Reduce Voltage Stress of Active Switches

This paper presents a new soft-switching dc/dc converter for high-input-voltage applications. Two half-bridge converters connected in series with interleaved asymmetric pulsewidth modulation (PWM) are adopted to limit the voltage stress of each power switch at one-half of the input dc bus voltage. In each half-bridge converter, two asymmetrical dc/dc circuits with the same active switches are connected in parallel at the output side to share the load current and reduce the current stresses of the secondary windings and rectifier diodes. Since two half-bridge converters are operated with interleaved PWM, the output ripple currents partially cancel each other so that the resultant ripple current at the output side is reduced. Active switches in the proposed circuit can be turned on at zero-voltage switching during the transition interval due to the resonant behavior by the output capacitance of MOSFETs and the leakage inductance of transformers. Experiments based on a laboratory prototype with 960-W rated power are provided to demonstrate the performance of the proposed converter.

Zero‐voltage switching full‐bridge DC/DC converter with parallel‐connected output and without output inductor

This study presents a soft-switching converter without output inductor. The features of the proposed converter are zero-voltage switching (ZVS) for all power switches, load current sharing and high circuit efficiency. Full-bridge converter with phase-shift pulse-width modulation (PWM) is adopted to regulate the output voltage. Based on the resonant behaviour by the output capacitance of MOSFETs and the resonant inductance, active switches can be turned on at ZVS during the transition interval. Thus, the switching losses of power MOSFETs are reduced. The voltage stress of power switches is clamped to DC bus voltage. Four transformers are connected in series in the primary side. Each transformer can be operated as an inductor to smooth the output current or a transformer to achieve electric isolation and power transfer from input side to output side. Therefore no output inductor is needed in the secondary side. Two centre-tapped rectifiers connected in parallel are used in the secondary side to achieve load current sharing. Finally, experiments based on a 960 W (48 V/20 A) laboratory prototype are provided to demonstrate the performance of proposed converter.

Analysis and implementation of a soft switching DC/DC converter with three asymmetric PWM circuits

SUMMARYThis paper presents a soft switching converter with three buck‐type active clamp circuits (or asymmetric half‐bridge circuits) to achieve the functions of the low power rating on the transformers and power semiconductors and low current rating on the rectifier diodes and output inductors. Three half‐bridge circuits are stacked at the high voltage side to reduce the voltage stress of each power switch at one‐half of input voltage and connected in parallel at the low voltage side to share load current and reduce the current rating on each magnetic component and the rectifier diode. Thus, the size of the output chokes is reduced. In each half‐bridge converter, the asymmetric pulse‐width modulation is adopted to control power switches. Power MOSFETs can be turned on with zero voltage during the transition interval due to the resonant behavior by the output capacitance of MOSFETs and the leakage inductance (or external inductance) of transformers. Experiments based on a laboratory prototype with 1 kW rated power are provided to demonstrate the performance of proposed converter. Copyright © 2012 John Wiley & Sons, Ltd.

Implementation of a Soft Switching Converter with High Input Voltage

SUMMARYThis paper presents an interleaved zero voltage switching (ZVS) DC/DC converter with high input voltage applications. In order to reduce the voltage stress of MOSFETs, two half‐bridge zeta converters are connected in series at high voltage side. Thus, the voltage stress of MOSFETs can be clamped at one‐half of input voltage. Asymmetric pulse‐width modulation (APWM) is adopted to control power switches. With the resonant behavior by the leakage inductance of transformer and the output capacitance of MOSFET at the transition interval, MOSFETs can be turned on at ZVS. For each half‐bridge zeta converter, two series transformers are connected in series at the primary side and in parallel at the secondary side in order to reduce the current stress of secondary windings for high load current applications. Interleaved PWM scheme is used to control two half‐bridge converters in order to reduce the size of output filter inductor and capacitor due to the partial ripple current cancellation. Experimental results, taken from a laboratory prototype rated at 1 kW, are presented to demonstrate the converter performance. Copyright © 2012 John Wiley & Sons, Ltd.

Analysis and Implementation of an Interleaved ZVS Converter with High Input Voltage

ABSTRACTAn interleaved half‐bridge converter is presented for high input voltage application. The features of the proposed converter are zero voltage switching (ZVS) turn‐on for all active switches, ripple current reduction at output side, load current sharing and load voltage regulation. Two half‐bridge converters connected in series and two split capacitors are used to limit the voltage stress of each power switch at one‐half of input DC bus voltage. Thus, active switches with low voltage stress can be used at high input voltage application. On the other hand, the output sides of two half‐bridge converters are connected in parallel to share the load current and reduce the current stresses of the secondary windings and the rectifier diodes. Since two half‐bridge converters are operated with interleaved pulse‐width modulation (PWM), the output ripple current can partially cancel each other such that the resultant ripple current at output side is reduced and the size of output inductors can be reduced. In each half‐bridge converter, asymmetrical PWM scheme is used to regulate the output voltage. Based on the resonant behavior by the output capacitance of MOSFETs and the leakage inductance (or external inductance) of transformers, active switches can be turned on at ZVS during the transition interval. Thus, the switching losses of power MOSFETs are reduced. The proposed converter can be applied for high input voltage applications such as three‐phase 380‐V utility system. Finally, experiments based on a laboratory prototype with 960‐W rated power are provided to demonstrate the performance of proposed converter. Copyright © 2012 John Wiley & Sons, Ltd.

An Analysis of the ZVS Two-Inductor Boost Converter under Variable Frequency Operation

The two-inductor boost converter has been previously presented in a zero-voltage switching (ZVS) form where the transformer leakage inductance and the MOSFET output capacitance can be utilized as part of the resonant elements. In many applications, such as maximum power point tracking (MPPT) in grid interactive photovoltaic systems, the resonant two-inductor boost converter is required to operate with variable input output voltage ratios. This paper studies the variable frequency operation of the ZVS two-inductor boost converter to secure an adjustable output voltage range while maintaining the resonant switching transitions. The design method of the resonant converter is thoroughly investigated and explicit control functions relating the circuit timing factors and the voltage gain for a 200-W converter are established. The converter has an input voltage of 20V and is able to produce a variable output voltage from 169V to 340V while retaining ZVS with a frequency variation of 1MHz to 407kHz. Five sets of theoretical, simulation and experimental waveforms are provided for the selected operating points over the variable load range at the end of the paper and they agree reasonably well. The converter has achieved part load efficiencies above 92% and an efficiency of 89.6% at the maximum power of 200W