Zero-current Switching Condition Research Articles

Resonant Energy Carrier Base Active Charge-Balancing Algorithm

This paper presents a single LC tank base cell-to-cell active voltage balancing algorithm for Li-ion batteries in electric vehicle (EV) applications. EV batteries face challenges in accomplishing fast balancing and high balancing efficiency with low circuit and control complexity. It addresses that LC resonant tank uses an energy carrier to transfer the voltage from an excessive voltage cell to the lowest voltage cell. The method requires 2N - 4 bidirectional MOSFET switches and a single LC resonant circuit, where N is the number of cells in the battery strings. The balancing speed is improved by allowing a short balancing path for voltage transfer and guarantees a fast balancing speed between any two cells in the battery string, and power consumption is reduced by operating all switches in zero-current switching conditions. The circuit was tested for 4400 mAh Li-ion battery cells under static, cyclic, and dynamic charging/discharging conditions. Two battery cells at the voltage 3.93 V and 3.65 V were balanced after 76 min, and the balancing efficiency is 94.8%. The result of dynamic and cyclic charging/discharging conditions shows that the balancing circuit is applicable for the energy storage devices and Li-ion battery cells for EV.

Common‐ground non‐isolated high‐gain DC/DC converter for low powerdistributed generation photovoltaic systems

A high step-up/high-efficiency converter is one of the essential requirements of a low power grid-connected photovoltaic system that provides the maximum power point tracking ability and injects the low voltage extracted power to AC or DC distribution network. This study presents a common-ground non-isolated high-gain DC/DC converter whit a naturally wide range of soft-switching conditions. The proposed converter has two resonant loops, and a new simple structure consists of an active switch, three diodes, two inductors and two capacitors, work in two useful operation modes. In the optimum operation mode (OOM), the switch turns on/off in zero current switching (ZCS)/zero voltage switching condition, and at the sub-OOM, the switch turns on in ZCS condition and turns off in hard switching condition. The mathematical analysis and MATLAB/SIMULINK simulation results are described in detail. Also, a prototype 100 W converter is built and tested to validate the simulation analysis on a 100 W photovoltaic panel.

Hybrid resonant three‐level ZCS converter suitable for photovoltaic power MVDC distribution network

This study presents a hybrid resonant three-level (TL) zero-current-switching (ZCS) converter for distributed photovoltaic power applications accessing medium-voltage DC (MVDC) distribution network. The main constituents of the converter is a neutral point clamped TL circuit, an auxiliary circuit along with two transformers and six switches. The ZCS condition of the TL circuit is reached by operating the auxiliary circuit utilising pulse width modulation technique. It delivers the majority of the power and the switching loss is remarkably reduced. A section on the influence of the turn's ratio of the auxiliary transformer on the current is also presented. The piecewise linear electrical circuit simulation simulation results validate the designed parameter principles. For the sake of comparison, an experimental prototype is developed of 300–1500 V/1500 W to validate the performance of the proposed converter.

A Dual Active Clamp DC–DC Converter With High Voltage Gain

In this article, a novel dual active clamp converter with high voltage gain is proposed for dc-dc applications. The active clamps' switches turn on and off under zero-current switching (ZCS). In addition, the main switch turns on under ZCS condition, as well. Therefore, switching losses are significantly reduced. The converter is also capable of operating under quasi-resonance (QR) mode. In this mode, switching losses are reduced further by lowering the voltage and current, at which the main switch turns off. In comparison with the conventional interleaved converter, the voltage gain of the proposed converter is almost the same, but the number of semiconductors and switching loss are significantly reduced. The switching frequency of the active clamps' switches is half of the main switching frequency. The operation principles of the proposed converter are studied in both pulsewidth modulation and QR modes, and the advantages are investigated. A 200-W prototype is implemented to validate the desired functionality of the converter, and experimental results are compared in both modes.

Interleaved Ultrahigh Step-Down Converter With Low Component Count

An ultrahigh step-down converter with a low number of semiconductor devices is presented in this article. Important features of this converter are simple structure with low size and cost, low voltage and current stress on components, low output current ripple, and low conduction and switching losses. In this converter, the power switches are turned on under zero current switching (ZCS) condition, whereas the output diodes commutate under ZCS condition without any auxiliary circuit. Thereby, in addition to the converter efficiency improvement, the diodes reverse recovery problem is alleviated. The proposed topology has employed a two-phase interleaved structure to reduce current stress, three windings coupled inductors to further decrease the voltage gain, and two series capacitors to diminish the voltage stress on the semiconductors elements and recover the leakage inductances energy. The experimental results of an implemented prototype are provided to evaluate the effectiveness of the proposed topology at 100 kHz and 200 W, which converts a 400-V input voltage into a 12-V output voltage.

Study and analysis of a DC–DC soft‐switched buck converter

In this study, a soft-switched buck converter is proposed and analysed. In this structure, by adding an auxiliary inductor and two auxiliary capacitors, zero-voltage switching condition for switch's turn on and near to soft-switching condition for switch's turn off are provided. Furthermore, the power diode turns off under zero-current switching condition. As a result, switching losses and reverse recovery losses have been eliminated, and the proposed converter can provide high efficiencies. To prove the mentioned advantages, a 200 W laboratory prototype of the proposed converter is built and its results are investigated completely. On the basis of these results, the proposed converter can provide 96.1% experimental efficiency at 200 W output power, which proves the 96.78% theoretical efficiency. Also, in comparison results, it is shown that this converter not only provides higher efficiency in comparison with other structures, but also it has less components and simpler structure than other related buck converters.

Modelling and Controlling of Induction Heating Unit for Induction Cooking Application

A study on the control methodology of voltage source inverter (VSI) fed series resonant circuit for induction heating has been done in this work with the goal that converter can be worked at about unity power factor. In this work, phase locked loop (PLL) has been accustomed to bring the converter’s switching frequency near to the natural frequency of series coil and capacitor branch of induction heater. Using this control method, the effectiveness of induction heater can be improved and necessity of input power is turned out to be less when compare to the fixed frequency operation. This control technique gives reliable operation of voltage source inverter fed circuit for varying load. Controlled phase locked loop gives increment or decrement in resonance frequency corresponding to the phase difference in voltage and current of resonant circuit. The coil of the induction heater is utilized as load in the resonant circuit of inverter. This power control procedure enables the inverter to operate near to the natural frequency for controlling power at all level. In this work, ZVS (zero-voltage switching) and ZCS (zero-current switching) condition has been obtained, and the switching losses are minimized. Pulse density modulated (PDM) power control method has been simulated to control the output power of a half bridge VSI fed induction heater.

A new lossless snubber for DC-DC converters with energy transfer capability

In this paper, a new passive lossless snubber circuit with energy transfer capability is proposed. The proposed lossless snubber circuit provides Zero-Current Switching (ZCS) condition for turn-on instants and Zero-Voltage Switching (ZVS) condition for turn-off instants. In addition, its diodes operate under soft switching condition. Therefore, no significant switching losses occur in the converter. Since the energy of the snubber circuit is transferred to the output, there are no significant conduction losses. The proposed snubber circuit can be applied on isolated and non-isolated converters. To verify the operation of the snubber circuit, a boost converter using the proposed snubber is implemented at 70W. Also, the measured conducted Efficiency Electromagnetic Interference (EMI) of the proposed boost converter and conventional ones are presented which show the effects of proposed snubber on EMI reduction. The experimental results confirm the presented theoretical analysis.

A New Soft Switching DC–DC Converter With High Voltage Gain Capability

In this article, a new high step-up dc-dc converter with zero voltage switching (ZVS) capability is presented for renewable energy applications. In order to achieve high voltage gain without extreme duty cycles or a high turns ratio, a combination of a coupled inductor and switched diode-capacitor voltage multiplier cells is used. In the presented converter, only an auxiliary winding with a diode that operates under zero current switching (ZCS) is utilized to realize ZVS for two power switches, and an active clamp circuit is utilized to reach ZVS for the other power switches. The leakage inductance of the coupled inductor controls the current falling rate of the voltage multiplier and output diodes, and also they turn-on under ZCS condition. Hence, reverse recovery losses of the diodes are reduced. The voltage stress on the power switches is low, and low voltage rating switches can be adapted to reduce the losses of their conduction. Finally, a 1-kW experimental prototype setup with 50 V input voltage and 470 V output voltage is built to verify the converter performance.

Wide Load Range ZVS Three-level DC-DC Converter: Modular Structure, Redundancy Ability, and Reduced Filters Size

In future dc distributed power systems, high performance high voltage dc-dc converters with redundancy ability are welcome. However, most existing high voltage dc-dc converters do not have redundancy ability. To solve this problem, a wide load range zero-voltage switching (ZVS) three-level (TL) dc-dc converter is proposed, which has some definitely good features. The primary switches have reduced voltage stress, which is only Vin/2. Moreover, no extra clamping component is needed, which results simple primary structure. Redundancy ability can be obtained by both primary and secondary sides, which means high system reliability. With proper designing of magnetizing inductance, all primary switches can obtain ZVS down to 0 output current, and in addition, the added conduction loss can be neglected. TL voltage waveform before the output inductor is obtained, which leads small volume of the output filter. Four secondary MOSFETs can be switched in zero-current switching (ZCS) condition over wide load range. Finally, both the primary and secondary power stages are modular architecture, which permits realizing any given system specifications by low voltage, standardized power modules. The operation principle, soft switching characteristics are presented in this paper, and the experimental results from a 1 kW prototype are also provided to validate the proposed converter.

Steady-State Analysis of Class-E Shunt Inductor Inverter Outside ZCS and ZDCS Conditions

The class-E shunt inductor inverter (SII) topology typically operates based on zero-current switching (ZCS) and zero-derivative current switching (ZDCS) conditions. Based on these terms, the peak switch voltage and load resistance are eliminated as the major limitation parameters to implement the class-E SII with the desired design specifications. This paper introduces the design and analysis of the class-E SII with the specified deviation from both ZCS and ZDCS conditions. Therefore, 2 degrees of the design freedom are obtained. Two new parameters that are normalized by the dc-supply current are defined in terms of the deviation from ZCS, i.e., $\alpha $ and ZDCS, i.e., $\beta $ . This operation mode of class-E SII is named as the nonzero current. The performance characteristics and design relationships are obtained in terms of the phase shift between the input and output voltages. The demonstration of the proposed operation mode is proven by fabrication of a prototype circuit with output power 10 W at 4-MHz operating frequency and close agreement between experimental outcomes with the simulation and theoretical results.

A Plug-Play Active Resonant Soft Switching for Current-Auto-Balance Interleaved High Step-Up DC/DC Converter

In high gain voltage conversion applications, the low-side switches usually suffer large current stress, resulting in dominate switching loss. In this paper, a general soft-switching method based on an advanced interleaved high-step-up converter, which features excellent performance but works in hard-switching, is presented to combat this issue by using a plug-play resonant circuit. Under this soft-switching method, the main switches reach zero-voltage switching (ZVS) turn- on and ZVS turn- off , and the soft-switching condition is derived. Meanwhile, the added auxiliary switches could be turned off under ZVS condition and turned on under zero-current switching condition as well. More importantly, due to its location out of the energy transferring path, the auxiliary circuit will never lead gain lost to the converter and maintain its other existing merits, such as current auto-balancing and diode inverse-recovery well. A 1-kW prototype is built and tested to verify the significant efficiency improvement and merits maintenance for the proposed converter considering active resonant soft switching.

Zero Voltage Switching Control Method for MHz Boundary Conduction Mode Converters

Boundary conduction mode or critical conduction mode is characterized by an inductor current that operates in the boundary between continuous conduction modes (CCM) and discontinuous conduction modes, making the converter switching frequency dependent on the converter operating conditions. The advantage of this operation mode versus CCM is achieving zero current switching (ZCS) conditions for the converter rectifier, which makes it possible to use silicon diode rectifiers without having a penalty due to reverse recovery issues. Moreover, the main switch turn- on loss is decreased due to ZCS conditions and valley switching operation. However, the penalty is an increased current stress in the circuit and an increased main switch turn- off energy loss. Implementation of the synchronous rectifier in boundary conduction mode (BCM) converters makes it possible to achieve zero voltage switching (ZVS) conditions by extending the synchronous rectifier conduction time after zero current condition in the inductor. High power density and high-efficiency MHz implementations have already been demonstrated in the literature; however, none of the proposed solutions solves the controllability issues of the synchronous rectifier switch. This paper proposes and validates a ZVS self-regulating control method for BCM converters operating in the MHz switching frequency range.

Analysis and experimental verification of a single‐switch high‐voltage gain ZCS DC–DC converter

This study proposes and analyses the integration of soft-switching technique with a single switch, non-isolated, coupled inductor DC–DC converter to achieve high efficiency and high step-up conversion ratio. The topology optimally integrates the coupled inductor and soft-switching technique using a parallel LC resonant tank circuit to maintain zero-current switching (ZCS) for on/off switching. The leakage inductance of the coupled inductor alleviates the reverse-recovery issue of diodes, and diodes can operate under ZCS condition. Moreover, the converter operates in a lower frequency range due to high step-up voltage gain. The principle of operation and steady-state analyses of the proposed converter are presented. A prototype validates the theoretical analysis and demonstrates a higher peak efficiency of 96.43% than the corresponding hard-switched converter.

Control features of a four channel resonant buck converter

This study presents the steady-state behaviour of a new four channel resonant DC/DC buck converter in symmetrical operation both in continuous current conduction mode (CCM) and in discontinuous current conduction mode (DCM). Having two inputs and four outputs, one of the most important advantages of this converter is its capability to provide four identical or arbitrarily different output voltages, while power exchange between the input channels facilitates the smooth operation even when one of the inputs falls out (security power supply). The converter can be operated in zero-current switching and zero-voltage switching conditions that results in enhanced efficiency. The quasi-sinusoidal waveforms help to lower electromagnetic interference. The analysis revealed the relations among input and output voltages as well as the effect of control variables on the steady-state operation. The obtained theoretical results are verified by both computer simulations and measurements on a recently built experimental prototype. The analytical results and control characteristics are devoted to design such converters and develop control strategies for them.

A Single Switch High Step-Up DC/DC Converter with Zero Current Switching Condition

A Single Switch High Step-Up DC/DC Converter with Zero Current Switching Condition

High-Frequency Resonant ZVS Boost Converter With Grounded Switches and Continuous Input Current

In this paper, a new high-frequency resonant boost converter is presented. Zero-voltage switching (ZVS) for the switches and zero-current switching (ZCS) for the rectifying diode are attained. The provided ZVS conditions reduce switching losses considerably, and ZCS conditions for the diode decrease voltage oscillations. Both switches are grounded which simplifies the gate-drive circuit and enhances the converter potential for high-frequency operation. All passive elements are high-frequency resonant type and thereby the converter power density is enhanced. The resonant inductor placed in front of the converter can operate in continuous conduction mode and smoothens the converter input current. Experimental results from a 160 W/500 kHz laboratory discrete prototype with an almost high-voltage conversion ratio of 100 to 300 V confirm the integrity of the proposed converter operation.

Switched-Capacitor-Based Single-Source Cascaded H-Bridge Multilevel Inverter Featuring Boosting Ability

Cascaded multilevel inverter (CMI) is one of the most popular multilevel inverter topologies. This topology is synthesized with some series-connected identical H-bridge cells. CMI requires several isolated dc sources which brings about some difficulties when dealing with this type of inverter. This paper addresses the problem by proposing a switched-capacitor (SC)-based CMI. The proposed topology, which is referred to as switched-capacitor single-source CMI (SCSS-CMI), makes use of some capacitors instead of the dc sources. Hence, it requires only one dc source to charge the employed capacitors. Usually, the capacitor charging process in a SC cell is companied by some current spikes which extremely harm the charging switch and the capacitor. The capacitors in SCSS-CMI are charged through a simple auxiliary circuit which eradicates the mentioned current spikes and provides zero-current switching condition for the charging switch. A computer-aid simulated model along with a laboratory-built prototype is adopted to assess the performances of SCSS-CMI, under different conditions.

Steady-State Analysis and Modified Control Technique of a Capacitor Voltage Clamped Dual Half-Bridge Series Resonant Inverter

The paper discusses the technical problems, which are related to the application of the inverter configurations for electrotechnological purpose with power-limiting property. The examined capacitor voltage clamped dual half-bridge series-resonant inverter (CVCDHB-SRI) is a part of the class of inverters with improved load characteristics, which are characterized by stability in the operation of the power circuit, the power consumption is constant and independent from changes in the load. The present paper extends the investigation of the electromagnetic processes in steady-state mode of CVCDHB-SRI that supplies two different loads. A unified approach is introduced in the analysis of processes in steady-state mode, as well as, expressions for determination of the currents through the power devices and the resonant circuit components are obtained. A modified control technique for operating loads with different frequency and power is also discussed. Thus, the additional current overload of some of the transistors in the circuit is avoided. The commutation mechanism of the transistors enables zero-voltage and zero-current switching conditions. This results in increases the efficiency of the system and improves power quality and reduces the overall cost. The results of the analysis are confirmed by simulating with OrCad Pspice.

Analysis and implementation of a new zero current switching flyback inverter

SummaryIn this paper, a novel zero current switching (ZCS) flyback inverter in discontinuous conduction mode (DCM) is proposed. In the proposed flyback inverter, the ZCS for the primary switch is achieved by adding a simple auxiliary circuit to the conventional flyback inverter. Also, the auxiliary switch is turned on and turned off at ZCS condition. Therefore, the switching losses of the switches are negligible, which increases the efficiency and allows higher switching frequency and more compact design. The resonant auxiliary cell is activated only in short transition times that makes its conduction losses negligible. Furthermore, the voltage overshoot of the main switch is limited during the turn‐off process, which allows utilization of lower voltage metal‐oxide semiconductor field‐effect transistors (MOSFETs) with low conduction losses and low cost. The detailed operation of the flyback inverter with auxiliary circuit and design considerations are presented. Simulation and experimental results are presented to verify the performance of the proposed inverter.