Active Clamping Technique Research Articles

Zero voltage switching high step‐up boost converter with coupled inductor for renewable energy applications

AbstractThis paper proposes a zero‐voltage switching high step‐up boost converter with coupled inductor for renewable energy applications. In this proposed circuit, main and auxiliary switches are turned ON at zero voltage switching to reduce switching losses. The voltage gain of the converter is increased by varying the turns ratio between primary and secondary of the coupled inductor (CI). The voltage spikes at the main switch are mitigated by using active clamping technique. The reverse recovery problem in diodes is alleviated due to leakage inductance of the CI. Zero current switching turn OFF in output diode is achieved, which can enhance the efficiency of the converter. A real‐time model for 100 W proposed converter circuit is developed to verify the theoretical analysis.

High efficiency step‐up DC–DC converter for grid‐connected photovoltaic microinverter applications

This paper presents a resonant step-up DC–DC converter for the photovoltaic micro-inverter system and describes the converter's operation principle in detail. In the proposed converter, the active-clamp technique is used to reduce the high voltage spike of the main power switch during its turns-off. Meanwhile, the output rectifier diodes can operate in the zero-current-switching (ZCS) operation and the clamping power switch can operate in zero-voltage-switching (ZVS) condition with the series LC resonant circuit. Then, the design procedure for the key components of the proposed DC–DC converter is derived. Finally, experimental prototype with 300 W is established to verify the validity of the proposed topology, and the experimental results shows that the proposed topology processes the merits of few components, simple control, galvanic isolation and high conversion efficiency in a wide photovoltaic voltage input and power range.

A Novel Digital Control Method of Primary-Side Regulated Flyback With Active Clamping Technique

Because of the different working principles between conventional flyback and active-clamped flyback (ACF), the existing primary-side regulation (PSR) technology cannot be applied to ACF. And in order to achieve PSR of ACF, a low-cost digital sampling method based on the auxiliary winding of the transformer is proposed. In the conventional peak current mode (PCM) controlled ACF, the sampling resistor of primary current may introduce additional power loss, and high-frequency oscillations during sampling may reduce system's stability. Therefore, a digital feedback-feedforward control (FFC) method is proposed to eliminate the sampling resistor. The stability of the proposed control method and its influence on the dynamic response are studied. In addition, since GaN device has higher power loss during reverse conduction than its Si counterpart, design considerations of reverse conduction time of power switches are also discussed in this paper. All control methods and design considerations are verified on a GaN-based 12V-3A ACF, and the proposed control strategy is implemented by FPGA.

A Constant Current Digital Control Method for Primary-Side Regulation Active-Clamp Flyback Converter

Constant current controlled flyback converter is widely used in low power applications for its simple structure and low cost. In order to further improve the output power and the efficiency, active-clamp flyback converter with soft-switching technique is always used. To avoid the nonlinearity and temperature drift of opto-coupler in the feedback circuit, a constant current digital control method is proposed for a primary-side regulation active-clamp (PSRAC) flyback converter in this article. Soft-switching technique is realized in discontinuous conduction modulation mode with a modified active-clamp technique. To compensate the nonlinearity of the secondary diode current with primary-side regulation, a new output current estimation algorithm is put forward based on the charge balance principle. The output current is predicted from primary current and the auxiliary winding voltage, and constant output current control is realized with primary peak current control method. The cost is low as only one low speed digital-to-analog converter, three comparators and a digital controller are required. The proposed control scheme was verified by a field-programmable gate array controlled 5.4-10.8 V/1.80 A PSRAC flyback converter. The output current accuracy is within in 1.2% in different input and output condition and the peak efficiency is improved by 3.6% after active-clamp technique is used.

An Active-Clamping ZVS Interleaved Buck/Boost Bidirectional Converter With One Auxiliary Switch

This article introduces a zero voltage switching (ZVS) interleaved buck/boost bidirectional converter using the active-clamp technique. In the proposed converter, by utilizing a simple auxiliary circuit comprised of an auxiliary switch, an auxiliary inductor, and a clamp capacitor, ZVS condition is secured for both the boost and buck operation modes, regardless of the converter operating duty cycle or load condition. Furthermore, the converter can operate with the conventional fixed-frequency pulsewidth modulation (PWM) control procedure. The boost and buck modes of the proposed converter are analyzed in both conditions of D > 0.5 and D < 0.5. To confirm the theoretical analysis, the experimental results of a 350 W–100 kHz prototype are presented.

Center Clamped Forward Converter for High Current Applications

High current applications like Microprocessors, Fuel cells, Electric Hybrid Vehicles, Solar Cells etc., use interleaved isolated buck derived converter. Interleaving of converters for such high current applications converters is done to achieve reduced input capacitor ripple voltages, output capacitor ripple current cancellation and reduced peak currents of output inductors. Generally, interleaving requires a higher number of transformers through which distributed magnetics can be achieved. i.e., one bulky transformer can be replaced with low power profile transformers. The performance of forward converter depends on core resetting of the main transformer. The core’s magnetizing energy is recycled by resetting it. In the absence of core reset, the current builds up at each switching cycle, saturates the core, causes reverse recovery problem in the diode and the active clamp will no longer in zero voltage state during turn on of the main switch. The transformer secondary output is used as a gating pulse for Synchronous Rectifiers. These have very low forward drop which are most suitable for high current applications. Among various used clamping methods, the transformer core is optimized effectively by Active center clamp reset approach. The proposed method results in less number of switches and clamping capacitor, and lower cost compared to conventional forward converter. Reduction in voltage stress without losing duty-cycle ratio is also achieved by means of a series-parallel connected switch structure with Self Driven Synchronous Rectifiers. The proposed center clamp converter overcomes the Maximum Duty cycle limitation of 50%. This paper mainly focuses on active center clamp forward converter and is also compared with Active Positive Negative clamping techniques.

MATLAB SIMULINK Model for Flyback Inverter with Active Clamp Technique

3 Abstract: The interleaved flyback inverter is the proposed system.. Two flyback inverters are connected and the control strategy used is the active clamp technique. This technique reduces the voltage spikes across the main switch during resonance, and the switching losses are reduced along with voltage stress. The system is modified as an energy storage application. The efficiency is improved and The simulations are done using MATLAB .The explanations theories and results are discussed.

English

A new dual active-clamping dc-dc converter is proposed to obtain high efficiency. The proposed converter employs a dual active-clamping technique, while a resonant voltage doubler rectifier scheme controls the output voltage with the pulse width modulation technique. The dual active-clamping circuit serves to recycle the energy stored in the leakage inductor or the magnetizing inductor and provides zero-current turn-off switching. The voltage stresses of the main switches are clamped. The voltage transient spikes across the dual active-clamping circuit and the current stress of the current-fed side switches are limited by auxiliary dual active-clamping circuits on both sides, and zero-current switching is achieved. Also, to reduce the output voltage variation, a modified PI controller is suggested.

Design of Soft Switching Sepic Converter Fed DC Drive Applications

High efficiency DC-DC converters with high-voltage gain have been researched due to increasing demands. A softswitching single-ended primary inductor converter (SEPIC) is presented in this work. An auxiliary switch and a clamp capacitor are presented in this project. A coupled inductor and an auxiliary inductor are utilized to obtain ripple-free input current and achieve zero voltage-switching (ZVS) operation of the main and auxiliary switches. The voltage multiplier technique and active clamp technique are applied to the conventional SEPIC converter to increase the voltage gain, reduce the voltage stresses of the power switches and diode. Moreover, by utilizing the resonance between the resonant inductor and the capacitor in the voltage multiplier circuit, the zero-current-switching (ZVS) operation of the output diode is achieved and its reverse-recovery loss is significantly reduced. The converter achieves high efficiency due to soft switching commutation of the power semiconductor device. The circuit is simulated using MATLAB Simulink and output result is verified.

A Study on Implementing a Phase-Shift Full-Bridge Converter Employing an Asynchronous Active Clamp Circuit

The conventional Phase-Shift Full-Bridge (PSFB) converter has a serious voltage spike because of the ringing between the leakage inductance of the transformer and the parasitic output capacitance of the secondary side rectifier switches. To overcome this problem, an asynchronous active clamp technique employing an auxiliary DC/DC converter has been proposed. However, an exact analyses for designing the auxiliary DC/DC converter has not been presented. Therefore, the amount of power that is supposed to be handled in the auxiliary DC/DC converter is calculated through a precise mode analyses in this paper. In addition, this paper proposes a lossy snubber circuit with hysteresis characteristics to reduce the burden that the auxiliary DC/DC converter should take during the starting interval. This technique results in optimizing the size of the magnetic component of the auxiliary DC/DC converter. The operational principles and the theoretical analyses are validated through experiments with a 48V-to-30V/15A prototype.

High Efficient Soft Switching Cuk Converter with Ripple Correlation Control MPPT for PV Applications

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.

DC-DC Converters Using PID Controller and Pulse Width Modulation Technique

This paper presents a boost converter along with a flyback converter. The Zero Voltage Switching (ZVS) technique is used to achieve soft switching. A bidirectional boost converter is connected with an output module as a Parallel Input Serial Output configuration. The flyback converter with Voltage Doubler Rectifier (VDR) acts as an output module. This connection makes a bidirectional boost converter an active clamp circuit which is connected to the output side in order to extend the step up ratio. A converter with active clamp technique is used to recycle the leakage energy, to eliminate voltage spike due to coupled inductors and also to provide a mechanism to achieve ZVS. To overcome the efficiency degradation during light load due to load dependent soft switching of the ZVS, a control method using Pulse Width Modulation (PWM) proportional to the load current is used.

Analysis of Soft-Switching Isolated Time-Sharing Multiple-Input Converters for DC Distribution Systems

This paper explores the feasibility of active clamping techniques in isolated time-sharing (TS) multiple-input converters (MICs). Additional losses caused by energy transfer from the leakage inductance in the isolating coupled-inductor into the input switches are addressed with a common active clamping leg for all input legs. An active clamping technique is applied to isolated TS-MIC to minimize the additional switching losses and voltage stresses on input legs. This paper also conducts an operational analysis of an isolated time-sharing dual-input single-ended primary-inductor converter (I-TS-DI-SEPIC) with the discussed active clamping technique. Zero-voltage switching can be achieved on the first-turned-on input leg and the active clamping leg with a proper driving strategy and well-chosen circuit parameter settings. Discussions on the effect of the active clamping technique to an MIC and the components stresses of the I-TS-DI-SEPIC with the active clamping technique have also been made to assist in the design of TS-MICs. Prototypes of the I-TS-DI-SEPIC with the active clamping technique have been built to demonstrate the performance in the application of split-phase dc distribution systems. Converter efficiency and voltage stresses are experimentally verified, showing that the active clamping technique achieves noticeable efficiency gains and component stress reduction.

A ZVS-PWM Three-Phase Current-Fed Push–Pull DC–DC Converter

In this paper, a ZVS-PWM three-phase current-fed push-pull dc-dc converter is proposed. When compared to single-phase topologies, the three-phase dc-dc conversion increases the power density, uses the magnetic core of the transformer more efficiently, reduces the stress on switches, and requires smaller filters since the frequency for its design is higher. The proposed converter employs an active clamping technique by connecting the primary side of the transformer to a three-phase full bridge of switches and a clamping capacitor. This circuit allows the energy from the leakage inductances to be reused, increasing the efficiency of the converter. If appropriate parameters are chosen, soft-commutation of the switches (ZVS) can also be achieved. The soft-commutation improves the efficiency even further, allows higher switching frequencies to be used, and reduces the electromagnetic interference significantly. Applications such as fuel cell systems, transportation, and uninterruptable power supplies are some examples that can benefit from the advantages presented by this converter. The theoretical analysis, a design example, and the experimental results for a prototype implementing this topology are presented. The prototype was designed to process 4 kW at full load with an input voltage of 120 V, an output voltage of 400 V, and a switching frequency of 40 kHz.

Soft-Switching SEPIC Converter With Ripple-Free Input Current

A soft-switching single-ended primary inductor converter (SEPIC) is presented in this paper. An auxiliary switch and a clamp capacitor are connected. A coupled inductor and an auxiliary inductor are utilized to obtain ripple-free input current and achieve zero-voltage-switching (ZVS) operation of the main and auxiliary switches. The voltage multiplier technique and active clamp technique are applied to the conventional SEPIC converter to increase the voltage gain, reduce the voltage stresses of the power switches and diode. Moreover, by utilizing the resonance between the resonant inductor and the capacitor in the voltage multiplier circuit, the zero-current-switching operation of the output diode is achieved and its reverse-recovery loss is significantly reduced. The proposed converter achieves high efficiency due to soft-switching commutations of the power semiconductor devices. The presented theoretical analysis is verified by a prototype of 100 kHz and 80 W converter. Also, the measured efficiency of the proposed converter has reached a value of 94.8% at the maximum output power.

능동 클램프 전류원 하프 브릿지 기반 태양광 모듈 집적형 전력변환장치에 대한 연구

태양광 발전 시스템이 대용량화됨에 따라 태양전지 어레이 구성 시 부정합(mismatch) 문제가 대두되는 가운데, 태양전지 모듈을 직접 계통에 연계하는 AC 모듈형 태양광 모듈 집적형 전력변환장치(PV-MIC)에 관한 연구가 지속되고 있다. PV-MIC는 수명 및 고효율이 가장 큰 문제이며 이 문제를 해결하기 위해서 본 논문에서는 ZVS 동작을 통하여 스위칭 손실을 저감시키고 입력전류 리플감소를 통하여 입력 커패시턴스를 저감할 수 있는 능동 클램프 전류원 하프 브릿지 컨버터를 적용한 PV-MIC를 제안하고, 이에 관한 제어분담 및 설계에 대하여 고찰한다. In this paper, photovoltaic module integrated converter (MIC) based on active clamp current-fed half-bridge converter is proposed. The converter stage operates in zero-voltage condition using active clamp technique. The theoretical study and circuit design for proposed inverter are confirmed with PSIM simulator and experimental reusult.

A High Efficiency Flyback Converter With New Active Clamp Technique

This paper proposes a flyback converter with a new noncomplementary active clamp control method. With the proposed control method, the energy in the leakage inductance can be fully recycled. The soft switching can be achieved for the main switch and the absorbed leakage energy is transferred to the output and input side. Compared to the conventional active clamp technique, the proposed methods can achieve high efficiency both for heavy-load and light-load condition, and the efficiency is almost not affected by the leakage inductance. The detailed operation principle and design considerations are presented. Performance of the proposed circuit is validated by the experimental results from a 16 V/4 A prototype.

Analysis of a new ZVS converter with output voltage doubler

A novel zero voltage switching (ZVS) converter with output voltage doubler is presented. The output voltage doubler is used on the output side to achieve the boost type of voltage conversion ratio. Active-clamping technique is adopted to realise the ZVS turn-on of all switches, release the energy stored in the transformer leakage inductance and limit the voltage stresses on power switches. The ZVS function is achieved at the commutation stage of two complementary switches. The proposed circuit has no large output inductor such that the adopted circuit has a simpler structure, lower cost and no effective duty loss. The voltage stresses on output diodes are clamped at the output voltage. The circuit configuration, operation principles and design consideration are presented. Finally, experimental results based on a 300 W prototype are provided to verify the effectiveness of the proposed converter.

Analysis of an integrated flyback and zeta converter with active clamping technique

An integrated converter with active clamping technique to achieve zero voltage switching (ZVS) is presented. In the proposed converter, the flyback and zeta topologies are used in the input and output sides to achieve the following features: to share the power switches in the transformer primary side, to achieve the partial magnetising flux reset and to share the load current. The input power is delivered to the load by the interleaved operation. The active clamping circuit, besides contributing to reduce commutation losses, resets the energy stored in the leakage inductances of both converters and the magnetising inductance of the zeta converter. The magnetising inductance of the flyback converter is reset by the load. Based on the resonance with the resonant inductance and output capacitance of switches, switches can be turned on at ZVS during the transition interval. Experimental results, taken from a laboratory prototype rated at 360 W, input voltage of 200 V, output voltage of 12 V and switching frequency of 125 kHz, are presented to demonstrate the converter performance.

Analysis and implementation of a zero voltage switching bi-forward converter

The system analysis and the circuit implementation of a zero voltage switching (ZVS) bi-forward converter is presented here. Two forward converters are adopted in the circuit with the active clamp technique to achieve interleaved PWM operation and load current sharing. Only two switches are used in the proposed converter instead of the four switches in the conventional parallel ZVS converter. Thus, the circuit components and conduction losses are reduced in the proposed converter. In the proposed circuit, the PWM signals of two switches are complementary to each other with a small delay time in order to realise the ZVS turn-on of the switches at the transition interval. Thus, the switching losses and thermal stresses of semiconductors are reduced since the interleaved PWM scheme is used to control two forward converters such that the output ripple currents are partially cancelled out. The sizes of the output chokes and capacitor are reduced. Experiments based on a 300 W prototype are provided to verify the theoretical analysis and the effectiveness of the proposed converter.