Improved soft switching dual switch forward converter

In this study, a new zero-voltage transition (ZVT)–zero-current transition (ZCT) quasi-resonant buck converter, which ensures zero crossings at any time required for soft switching (SS) and provides ZVT turn-on and ZCT turn-off together for the main switch of active snubber cell in buck converter is presented. The proposed circuit combines the most of the advantageous features of the circuits presented previously and overcomes most of drawbacks of these circuits by using only one auxiliary switch with fewer other components. Consequently, new ZVT–ZCT quasi-resonant buck converter, which is verified by a prototype of a 0.4-kW and 100-kHz circuit, is analysed in detail. All semiconductor devices operate under SS, the main switch is subjected to no additional voltage and current stresses, and the stress on the auxiliary switch is very low in the proposed new converter.

In this paper, an improved Zero-Voltage-Transition (ZVT) two-cell interleaved boost Power Factor Correction (PFC) converter is proposed and investigated. A new auxiliary circuit is designed and added to two-cell interleaved boost converter to reduce the switching losses. Only one auxiliary switch is used in the active soft switching auxiliary circuit. The main advantage of this auxiliary circuit is that it not only provides ZVT in the boost switches but also provides soft switching in the auxiliary switch and passive diodes. Therefore, the switching losses of the converter can be reduced. Compared to the previous published soft switching interleaved boost converters, only one auxiliary switch is needed in the auxiliary unit, so the auxiliary unit and control circuit are simple. A 1kW, 50 kHz two-cell interleaved boost PFC converter with an improved ZVT auxiliary circuit has been simulated using average current control method and the results are presented. Simulation results show that the main switches, the auxiliary switch and passive diodes are operating under soft switching mode.

This paper is concerned with the design, construction and testing of a 3-phase to 3-phase soft switching matrix converter. Two auxiliary soft switching circuits are added to each output phase in order to achieve soft switching without significantly increasing the conduction losses. The converter operation is discussed with reference to theoretical waveforms. The distribution of the switching losses with respect to load current and commutation voltage is investigated. Using the proposed topology it is possible to disable the auxiliary switch when the current and/or voltage is low. This simplifies the design of the auxiliary circuit as the range of operating conditions is reduced, allowing better optimisation in terms of switching losses and commutation speed. We present results from a 3-phase to 3-phase prototype matrix converter showing switching waveforms for all commutation scenarios. Measurements of the overall power circuit losses are presented and comparisons are made with conventional hard switching matrix converters. The distribution of losses between the different loss mechanisms will be investigated for both converters. It is shown that the switching losses for the main switches is reduced by about 50% but this is compensated for by the losses in the auxiliary switches resulting in no significant increase in efficiency. Further research will be required to develop viable soft switching matrix converter structures.

Traditional phase-shift full-bridge converters are popular in industrial applications due to the advantages of simple design, fixed-frequency control and soft switching. However, a large duty cycle variation range is required in applications with a wide input voltage range, which can cause loss of soft switching range, excessive circulating currents and output current ripple. This article introduces a three-leg converter that is a hybrid combination of two full-bridges. The current and power of the two transformers in the converter are shared automatically by adopting the symmetrical structure and modulation, and output current ripple is suppressed by the superposition of the two transformer voltages. The circulating current is minimized in the proposed converter that the conduction loss is reduced. By adding two auxiliary switches on the secondary side, zero-voltage switching and zero-current switching of all switches can be achieved to maintain high efficiency in a wide range. An experimental prototype rated at 1 kW is designed to convert 220–460 V input to 100 V output. The experimental results show that the proposed converter can achieve high efficiency over a wide input voltage and load range.

In this paper, a new zero-voltage zero-current transition (ZVZCT) boost converter using coupled inductors is proposed. The feature of this topology is: the main switch can be switched on with ZVZCT, and off with zero-voltage switching, without any voltage and current stress. The auxiliary switch is turned on with zero-current switching. Other semiconductor devices can also achieve soft switching (SS). Due to the existence of the coupling effect, the current impact of the auxiliary switch is completely suppressed when it is turned off . Lower input current and output voltage in the interval of the switch- off for the auxiliary switch are just equivalent to running at a low power level, which is an additional advantage of the coupled inductor ZVZCT solution. Another advantage of the topology is that the SS condition of the main switch for each specific load can be effectively optimized just by setting the ratio of coupling inductance corresponding to the circuit design and application load. Thus, the topology design can be improved to adapt to different load types. A 100 kHz experimental prototype has been verified, different load for 1 and 0.4 kW optimization comparison has been presented, and the case without optimization is also observed.

This paper presents the application of “ripple correlation control (RCC)” maximum power point tracking (MPPT) algorithm for photovoltaic (PV) system employing dc-dc Cuk converter to maximize the output power of PV module. Soft switching commutation of the main and auxiliary switches at zerovoltage using active clamp technique allows the operation of the Cuk converter at very high switching frequencies with reduced size of reactive elements and electromagnetic interference. The combination of auxiliary switch, clamp capacitor and resonant inductor is used to exploit the advantage of high efficiency with zero switching losses. RCC technique uses the high frequency signal ripple, which makes it to converge asymptotically to the maximum power point independent of module configuration and parameters. The operating modes of converter for different switching time intervals are analyzed and design considerations are presented. The simulated performance of the converter with RCC MPPT over conventional MPPT algorithms is presented. The MPPT methods are compared on the basis of the time taken to track the maximum power point (MPP), steady state oscillations about MPP and dependence on array parameters. To evaluate the viability of ZVS Cuk converter with RCC MPPT, the entire system is simulated using MATLAB/SIMULINK platform for an 87 Wp solar PV system.

This paper proposes the analysis and design methodology of lossless, passive soft switching methods for PWM converters. The emphasis of the design and analysis is for PWM converters that use nonminimum voltage stress (non-MVS) circuit cells to provide soft switching. PWM converters with non-MVS circuit cells have several distinct advantages over converters that use minimum voltage stress (MVS) cells. With the same relative size of the inductor and capacitor added for soft switching, the non-MVS cells have a substantially larger duty ratio range where soft switching is guaranteed. In addition, the overcurrent stress of the main switch, under most conditions, will be lower and an optimum value of inductor and capacitor added for soft switching can be used. Therefore, with proper design, the non-MVS cells provide higher efficiency. These advantages are obtained with the price of higher switching voltage stress and one additional inductor. The loss model for a MOSFET and optimum capacitor and inductor values are utilized in the design procedure. Examples of the design procedure are given for PFC and DC-DC applications. Experimental results backup the claim of higher efficiency.

This paper proposes a new high-gain soft-switching dc–dc topology based on a switched inductor boost converter (SIBC). A conventional SIBC as a high gain boost topology has the issues of high conduction loss in switching diodes and high switching loss in the main switches. Also, it has severe electromagnetic interference (EMI) issue due to high-frequency ringing formed by parasitic inductance and diode junction capacitors. The new topology is derived with the objective of achieving zero voltage switching (ZVS) turn on of the main switch. Instead of adding extra active clamp zero voltage transition (ZVT) path at the switching node, the proposed topology augments the auxiliary ZVT path to the switching diode path. This is achieved by replacing the switching diodes with synchronous switches. The new topology can achieve soft switching for all the switches and alleviate the EMI issue. All the diodes achieve zero current switching (ZCS) turn off without reverse recovery. Auxiliary switches have ZCS turn on and ZVS turn off , and the main switches have ZVS turn on . The soft-switching SIBC also reduces the conduction loss in the switching diodes. A numerical simulation in PLECS and a prototype hardware are built corresponding to a micro-inverter application with 100 kHz switching frequency. Peak power conversion efficiency of 94.76% is achieved in the hardware prototype with Si devices.

This paper proposes a high-gain, highly efficient nonisolated bidirectional dc–dc converter with soft-switching capabilities. An intermediate energy storage cell enables the converter to generate high gain in the continuous current mode. Two auxiliary resonant networks, each consisting of a low-power switch, a capacitor, and an inductor, are integrated to provide the soft switching [zero-voltage switching (ZVS)] for the main switches. The dedicated resonant networks ensure the ZVS is sustained over a wide operating range of duty cycle and power. The auxiliary switches are also soft switched to boost the efficiency further. Additionally, the reverse recovery loss is eliminated by optimizing the resonant capacitors. The validity of the design is verified by a 200 W prototype converter. A maximum gain of 17.8 is observed at a duty cycle ratio of 0.8. At 30 kHz, a full load efficiency of 97.5% and 95.5% is recorded in the boost and buck modes, respectively. On the other hand, at 100 kHz, these efficiencies are 97.0% and 94.5%, respectively. Consequently, the experimental results validate the proposed concept and design procedures. This performance exceeds that of high gain topologies published in the recent literature.

A novel dual-switch forward converter with input current ripple reduction, one of Taiwan Tech converters, is derived from a tertiary-winding forward converter by inserting a clamping capacitor between two identical primary windings and modifying with two series-connected MOSFETs and diodes. Lossless snubbing, voltage clamping, voltage sharing, and input current ripple reduction features are obtained under steady-state and transient conditions. Moreover, low voltage rating MOSFET accompanied with lower equivalent RDS(on) results in the reduction of the conduction losses. Furthermore, the reduced EMI filter components can be used to meet the EMI regulation due to the reduction of the pulsating input current-ripple. Consequently, it is suitable for high input-voltage, high efficiency, and high power density power conversion applications. To demonstrate its feasibility, the operation principle and the experimental results of the proposed converter with 300–400 V input and 50V/5A output power are described.

The paper vastly predicts the sizeable prediction between the hard and soft switching flyback converters operating under the discontinuous conduction mode (DCM) of operations. The soft switching flyback converters improve the performance compared to hard switching skills. The paper also highlights the merits and demerits of the both switching techniques of the converters with a common gate drive of the auxiliary and main switch using the PWM techniques. Outstanding challenges are also elucidated to assess for the additional soft switching.

In this paper, a new modular‐isolated‐forward‐based active snubber cell (SC) for power switches is designed. In the proposed new SC, the zero voltage transition (ZVT) technique is implemented with a forward converter although the current counterparts generally use a flyback converter. In the converter with the new SC, the main switch is turned on with ZVT (full zero voltage switching [ZVS]) and turned off with ZVS, the main diode is turned off with zero current switching (ZCS), the auxiliary switch is turned on with ZCS and turned off with ZVS, and the parasitic capacitor energies are recovered. In addition, thanks to the forward converter, it has been possible to minimize the transformer leakage inductance and greatly reduce the current values of devices in the new SC. The new cell is applied to a single‐phase, grid‐connected, T‐type three‐level inverter (T2‐3LI) as an example. A detailed steady‐state analysis of this inverter was made, and the theoretical analysis was confirmed with measurement results taken from a prototype with 100 kHz and 3.3 kW values. Compared to its hard switching (HS) equivalent, in the converter with soft switching (SS) cell, the total circuit loss was reduced from about 248 W to 86 W, thus achieving an increase in the total efficiency from 92.5% to 97.4%.

This article presents an efficient interleaved soft switching dc-dc converter for high step-up applications. In the proposed converter, two multifunction coupled inductors are employed to increase the voltage gain, accomplish soft switching operation for all semiconductors in a wide range of load variations, and smooth the input current. Besides, the leakage inductance energy is recovered to enhance the voltage gain and efficiency while assisting soft switching condition for the switches and diodes. In addition, no auxiliary switch or extra magnetic element is employed in the proposed converter while the voltage stress of switches and diodes is rather low. These have led to simple structure, high density, low cost, and improved efficiency. Theoretical analysis and design considerations for the proposed converter are presented. Moreover, the experimental results of a 48 to 500 V laboratory prototype approve the effectiveness of the proposed topology.

A soft switching boost converter that uses an auxiliary switch and resonant circuit is proposed in this paper. The main switch performs soft switching under zero voltage condition by using a resonant capacitor and an inductor, auxiliary switch and diode. The conventional boost converter generates switching losses at turn on and off and this reduces the whole system efficiency. But the soft switching boost converter reduces the switching losses more than the conventional boost converter. The efficiency is increased to 96% in this soft switching converter. This converter is suitable for applications such as high-efficiency converters, photovoltaic dc/dc converters, a power-factor-correction circuit, and battery chargers.

A fully soft switched high step‐up/down bidirectional converter is presented in this paper. The high voltage conversion ratio is achieved by a pair of coupled inductors along with a switched capacitor while all active switches operate at zero voltage switching. To provide soft switching condition for the main switches and absorb the leakage inductance energy of coupled inductors, active clamp circuits are utilized for both operating modes. Furthermore, all active switches body diodes which are utilized as converter diodes turn off at zero current switching (ZCS) and thus, the reverse recovery problem is eradicated. Additionally, the voltage stress of the main switches is reduced in comparison with the basic bidirectional buck/boost converter and thus, their drain‐source resistance is relatively lower which leads to considerably lower conduction loss. All the mentioned advantages along with relatively low number of components contribute to the converter efficiency. Theoretical analysis of the proposed converter is presented in detail for both operating modes and the experimental results from the implementation of a 300 W prototype circuit confirm the validity of the converter performance. A comprehensive comparison table between the proposed converter and the recent counterpart bidirectional converters is presented to demonstrate the converter advantages.