Active Clamp Circuit Research Articles

High-Voltage Gain Ripple-Free Resonant DC–DC Converter Using Active Voltage-Quadrupler

This paper presents a high-voltage gain ripple-free resonant DC/DC converter using an active voltage-quadrupler. By incorporating an active voltage-quadrupler at the secondary side of the transformer, the circuit achieved a very high-voltage gain. Without using extra input inductors, the inherent dual transformer plus interleaved active-clamped circuit operating with a fixed duty-ratio of 0.5 generate a ripple-free input current, which extends the lifetime of the fuel cell and shrinks the size of the input capacitive filter. This asymmetric structure of the active-clamp circuit requires an extra dead time for one of the secondary-side switches to achieve zero-voltage switching (ZVS) turn-on. After the extra dead time for one of the secondary-side switches is applied, all power components of the active voltage quadrupler cell are turned on and off with soft switching. The resonant capacitor voltages are unbalanced due to the extra dead time, but they are compensated by applying different secondary-side duty ratios. The operating principle and steady-state characteristics of the proposed converter were analyzed in detail. We built a 1-kW/700-V prototype that copes with 48-72 V inputs, and tested to verify the theoretical analysis.

Single Power-Conversion Active-Clamped AC/DC Converter Employing Si/SiC Hybrid Switch

This article proposes a single power-conversion voltage-fed active-clamped ac/dc converter that uses an Si IGBT/SiC MOSFET hybrid switch. By incorporating two switches at the primary side of the circuit, we removed the full-bridge diode rectifier, and thereby reduced the required number of power devices. Inherent bidirectional active-clamp circuit naturally limits the voltage spike at bottom switches and reuses the energy accumulated in the leakage inductor during both positive and negative grid half-cycles. Also, it offers dual-resonant power transfer paths, so it can deliver the high power with less circuit components. The alternating switching modulation makes one of the bottom switches turn off with hard switching per grid half-cycle while holding other bottom switch on to conduct the current. In contrast, top switches are softly switched with low root-mean-square current. Therefore, the converter with proposed switching modulation enables direct substitution of Si IGBT for an SiC MOSFET at the top on the primary side, and thereby which cuts down the circuit implementation cost. We built a 1 kW prototype converter and confirmed its validity.

A High-Efficiency Integrated Converter for LED Driver

Enhancing the efficiency in the light-emitting-diode (LED) drivers is a noteworthy issue as it not only helps saving energy but also causes the long life span of the drivers. In this paper, a new LED driver with improved efficiency is proposed. Efficiency improvement is achieved without using any active or passive component to perform soft switching conditions. In the proposed driver, buck and buck-boost converters are integrated. The freewheeling diodes and inductors - of the two converters - are replaced by one diode and one inductor. So, the proposed driver constitutes a single-stage driver with a simple structure that uses only one controlled switch, one freewheeling diode, and one inductor. Besides its simple structure, the driver works with a constant frequency, which leads to using a simple controller. Efficiency improvement is obtained by changing the inductor size and LEDs arrangement rather than using the active clamp or snubber circuits. To decrease the switching losses in the proposed driver, the average of the input current is kept constant while the peak of the pulsating input current - which passes from the switch and freewheeling diode - is decreased. Moreover, power losses of the semiconductor components in the proposed driver are investigated, and consequently decreased, leading to improvement in the system's overall efficiency. Finally, a 10 W experimental driver is built and tested. The experimental results are consistent with theoretical analysis.

Dynamic Neural-Based Model Predictive Voltage Controller for an Interleaved Boost Converter With Adaptive Constraint Tuning

in recent years, interleaved current-fed boost dc converters consisting of a voltage multiplier and an active clamp circuit have been interested because of their good features like low input currents, and output voltages ripple high voltage-gains. Then developing more effective modeling and control techniques is important to increase their performance. In modeling section, it has been tried to estimate system model using the real data and dynamic neural networks with reducing number of variables. In control section there are constraints on control signal and its changing rate and in the proposed dynamic neural-based model predictive control (NMPC) controller, control signal changes constraint has been calculated adaptively. The proposed NMPC has been applied on system in online form and experimental results have been compared to the basic NMPC and a PI controllers. The output voltage have been specified for two loads with different input voltage. The experimental results show that their current transient response has smaller current peak and output voltage has smaller overshoot when load and voltage change. Output voltage steady-state response also has smaller oscillations about 2 volts for using proposed NMPC.

An improved coupled inductor‐based quadratic step‐up DC–DC converter with a high step‐up factor and reduced voltage overshoot on the power switch

AbstractMost coupled inductor‐based step‐up DC–DC converters encounter a significant voltage overshoot on their power switch due to the leakage inductance of the coupled inductor. So, they need additional bulky snubber circuits or a sophisticated procedure for coupled inductor design to reduce that effect. This paper proposes an improved coupled inductor‐based DC–DC converter, which provides a high quadratic voltage conversion ratio without excessive voltage stresses on the power switch. An active clamp circuit that operates with the zero‐voltage switching (ZVS) feature has been utilized for this aim. This feature allows the main power switch to be selected from low voltage ratings and low on‐resistance MOSFETs, which reduces conduction loss. The topology also benefits from continuous input current, high gain, high efficiency, and an appropriate number of components compared with the produced gain. In this article, the theory and operation of this converter are described by proposing the dc and small‐signal models, loss model, and continuous and discontinuous current modes (CCM and DCM) relations. Experimental results are represented to evaluate the performance of the proposed topology. For this purpose, a 240 V/240 W prototype has been designed and fabricated. Results confirm the above claims.

A Novel Pull-Up Active-Clamping Wireless Charging Circuit with Low Cost and Voltage Stress

The traditional single-switch circuit has the advantages of fewer components, no shoot-through problems, and suitability for high-frequency wireless charging applications. However, because of the high voltage stress of the switch, the bulky inductor, and the narrow soft-switching range, its power and applications have some limitations. To relieve this problem, this paper proposes a pull-up active-clamping circuit, which not only offers a low component count with no bulky inductors, but also greatly reduces the switch voltage stress. In addition, a wide range of soft switching can be achieved by designing a primary-side compensation capacitor. A detailed parametric design method is given and compared with existing circuits from the aspects of switch voltage stress, component count, efficiency, cost, and so on. Finally, a 1 MHz, 180 W active-clamping wireless charging system is built to verify the proposed circuit and design method.

A Current-Fed ZVS High Step-Up Boost Converter Integrated with Isolated SEPIC Converter

In this paper, the combination of a high step-up boost converter with extended voltage multiplier cell and isolated SEPIC converter with a series output module is presented. Since these converters use the same current source in their inputs, they can share the common parts, so the structure of the proposed converter is simple. In this converter, the high frequency transformer used in the SEPIC converter and the inductor of the extended voltage multiplier cell are coupled, so the volume of the magnetic parts is reduced. In addition, an active-clamp circuit is used to solve the problem of leakage inductor and achieve to Zero Voltage Switching (ZVS) turn on/off for switches and ZCS for diodes. Compared to its high step-up counterpart, the proposed converter has the following: (1) distributed voltage stress on the diodes and voltage of the output capacitors are fair. (2) Higher voltage gain. (3) Voltage stresses on the diodes are lower and the reverse-recovery problem of the diodes is eliminated. (4) Minimum root mean square (RMS) leakage inductor current. The operational principle and characteristics of the proposed converter are presented, and in order to verify the proposed converter, a 200 W, 20–400 V prototype converter is implemented and experimental results are provided.

High Step-Up Soft-Switching DC–DC Converter Integrated With Y-Source Network

High step-up dc-dc converter is generally used in micro grid, uninterruptible power supply, hybrid electric vehicle, and other applications. For attaining high boosting and high efficiency, a high step-up soft switching circuit topology with an integrated Y-Source network is presented. Its front end is a Boost structure with the strengths of continuous and low ripple input current. The active clamp circuit may store the energy of leakage inductance in the output capacitor, and then output with reuse. In addition, the switches achieve zero voltage conduction, thereby decreasing its switching loss. At the same time, the coupling inductor achieves zero dc bias, which reduces the core size and core loss. The converter may attain high step-up by selecting the proper turns ratio of the coupling inductor at a reasonable duty cycle. The paper elucidates the working mode of the converter in depth, builds the small signal model, and study the stability of the converter. Finally, an experimental prototype of 200 W 28-380 V 100 kHz is built, and the feasibility of the presented converter is demonstrated in both dynamic and static aspects of the experiment.

Multiplexed Active Clamp High-Frequency Link Inverter With De–Re-Coupling Frequency Doubling Modulation

In this paper, a multiplexed active clamp high-frequency link inverter (MACHFLI) with de-re-coupling frequency doubling modulation (DFDM) is proposed. The proposed MACHFLI consists of a primary inverter, high-frequency transformer, multiplexed active clamp (MAC) circuit, and cycloconverter. MAC recycles leakage inductance energy and eliminates voltage spikes caused by leakage inductance. Overlapping commutation is designed in the DFDM to ensure the safe commutation of the output filter inductor current and realize the ZVS of the cycloconverter. The ZVS of the primary inverter can be realized utilizing magnetizing current, and full-range ZVS of MAC can also be realized with turn-on delay. The operating principle and ZVS conditions of the proposed MACHFLI are analyzed, and the design of the transformer and clamp capacitor is discussed in this paper. Finally, a 1kW prototype is made to verify the analysis results. Experimental results show that MACHFLI has Four-quadrant operation capability, good dynamic response, high efficiency over a wide load range, and peak efficiency reaches 95.4%.

Applying a Multiple-Input Single-Output Interleaved High Step-Up Converter with a Current-Sharing Device Having Different Input Currents to Harvest Energy from Multiple Heat Sources

In this paper, a thermoelectric conversion system for multiple heat sources is proposed. For design convenience, the overall system employs only a single-stage converter. Such a converter uses coupling inductors and switched capacitors to increase the voltage gain. In order to reduce the high-frequency voltage oscillation of the turn-off of the main switches created from leakage inductors, two active clamp circuits with zero voltage switching (ZVS) turn-on are employed. By doing so, although the current-sharing device with interleave control is embedded in the proposed converter, the input currents can be unequal. Therefore, the inputs of the converter can operate under individual maximum power points and transfer the energy from different thermoelectric generators (TGs) to a single load. Furthermore, the main switches have low voltage stress during the turn-off period. As for the maximum power point tracking (MPPT) method, it utilizes a three-point-weighting method to improve the tracking stability. In addition, the number of inputs of this converter can be extended. The MPPT simulation is presented to verify the feasibility as well as several experimental waveforms to demonstrate the effectiveness. The field programmable gate array (FPGA) is used as a digital control kernel to control the thermoelectric conversion system.

Performance improvement of a zero‐voltage switching interleaved high step‐up DC–DC converter with low‐voltage stresses

AbstractThis paper proposes a novel interleaved ultra‐large gain zero‐voltage switching (ZVS) DC–DC converter for renewable energy systems. By using coupled inductor (CI) and built‐in transformer (BIT), a high‐voltage gain is achieved. The secondary windings of the CIs are connected in series with the primary winding of the BIT and the secondary winding of the BIT is inserted in voltage multiplier cell (VMC). In such a case, the voltage gain is proportional to the multiplication of the turn's ratios of the CI and BIT. To increase the devices’ utilization, the active clamp circuit not only provide ZVS performance for the metal‐oxide‐semiconductor field‐effect transistor (MOSFETs) and recycles the leakage energy, but also participates in voltage gain enhancement. The voltage stress across the switches is considerably decreased and the low duty cycle reduces the conduction and switching losses. Low input current ripple, equal current sharing without a dedicated controller and common ground are the other merits of the proposed converter. Steady‐state analyses are presented and through a fair comparison, the superiority of the proposed converter over the state‐of‐the‐art is guaranteed. Finally, a 500‐W laboratory prototype with 20‐ to 400‐V voltage conversion is built to demonstrate the effectiveness of the proposed converter.

High Step-Up IPOS DC/DC Converter Based Efficiency Optimization Control Strategy

This article introduces a symmetrical, high step-up, input-parallel output-serial (IPOS), dc–dc converter based on voltage multiplier (VM) cells and active clamp circuits to obtain a very high voltage conversion ratio. The VM using a switched capacitor and the coupled inductor makes high voltage gain achievable, which results in reduced voltage stress on power switches. Meanwhile, the IPOS structure also makes great improvements in the above aspects. Importantly, by incorporating active clamp circuits, not only voltage spikes caused by leakage inductance are restrained but also the clamped circuit plays a role in energy transfer to boost the gain. Especially, zero voltage switching for all switches can be obtained. Furthermore, the optimization control strategy is proposed to further improve the overall efficiency. A detailed mathematical analysis of the proposed converter is conducted for systematizing its design. Finally, a prototype of 768 W output power and the 480 V output voltage is implemented to verify the excellent performance of the proposed converter.

Fully soft switched high step‐up/down bidirectional buck/boost converter with reduced switch voltage stress

AbstractA 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.

IGBT Overvoltage Protection Based on Dynamic Voltage Feedback and Active Clamping

In view of the stability of the unmanned aerial vehicle (UAV) power system, this paper found that the voltage spike generated by IGBT mainly occurs when the IGBT is turned off in the study of the power system interior and IGBT drive and overvoltage protection, and an excessive voltage spike will lead to IGBT damage. To eliminate this serious threat to the safe operation of the circuit, an IGBT overvoltage protection circuit combining dynamic voltage feedback and active clamping is proposed. In this method, active clamping and dynamic voltage feedback circuits are operated alternately, and the drive circuit is controlled by the feedback of capacitor’s the dynamic voltage rise rate. The gate current output of the IGBT is directly compensated to control the signal delay of the gate, combined with improving the lifting effect of the active clamp circuit on the gate voltage and suppressing the peak of the turn-off voltage. According to the IGBT turn off process, combined with SABER simulation, this paper finally builds IGBT turn off experimental circuit to prove that the proposed method suppresses the size of the turn off voltage spike, further analyzes the effect of key circuit parameters on the suppression of the turn off voltage spike, thereby ensuring the safe operation of the IGBT, and improving the stability of the UAV power system.

A Soft-Switched Single-Stage Single-Phase PFC Converter for Bidirectional Plug-In EV Charger

This paper proposes a novel zero-current assisted soft-switching bidirectional single-stage single-phase isolated power factor correction (PFC) based converter for plug-in EV charger. An isolated topology consists of a current-fed full-bridge converter with bidirectional switches on the ac-side that is connected with a full-bridge converter on the dc-side of a high-frequency transformer (HFT). HFT offers galvanic isolation for safety and high power density, and it is the most desired specification for a battery charger. The converter enables zero current switching (ZCS) of ac-side switches and zero current turn-ON for dc-side switches without any active clamp circuit or passive snubbers, which significantly reduced switching losses, footprints, and cost. The proposed modulation strategy and control technique are presented for promising the soft-switching operation of all semiconductor devices throughout the range for all modes with bidirectional power flow capability. These merits make the converter more feasible, robust, and reliable with high power density for an EV application. A comprehensive study of proposed steady-state operation, design, and simulation results is reported. A proof-of-concept hardware laboratory prototype rated at 1.5 kW is established and tested to validate the claims and proposed converter performance.

An active clamp coupled inductor‐based soft‐switched quadratic boost converter

SummaryThis paper proposes a novel active clamp‐based quadratic boost converter to achieve a high gain output voltage. The converter combines a quadratic boost converter with a voltage doubler circuit using a coupled inductor. An active clamp circuit with an auxiliary switch is used to utilize the usually wasted energy of leakage inductance and clamp the voltage to a certain limit. The combination of leakage inductance and parasitic capacitance of the main switch provides the benefit of zero voltage switching (ZVS) in both MOSFETs. Similarly, output diodes operating under zero current switching (ZCS) improve the overall efficiency of the converter. Voltage doubler and active clamp circuitry reduce the voltage stress on solid‐state devices; hence, a low Rds,on device is selected. The converter model is simulated using PSIM software and calculated maximum efficiency of ~95% for 200 W and measured maximum efficiency of ~93% for 190 W power level including various parasitic elements.

Soft-Switching High Step-Up DC–DC Converter Based on Switched-Capacitor and Autotransformer Voltage Multiplier Cell for PV Systems

This article introduces a nonisolated, high step-up voltage multiplier cell (VMC)-based dc–dc converter for applications such as module-integrated converter and power optimizers. The VMC combines switched capacitor with autotransformer techniques and active clamp circuit. The autotransformer tertiary winding is employed to increase voltage gain without operating the main switch under extreme duty cycle condition, to reduce the current through the main switch before it turns <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> and to ensure its zero-voltage switching (ZVS) operation on a wide operation range. The auxiliary switch in the clamp circuit provides ZVS for the main switch and vice-versa. Thus, both switches are turned <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> with zero voltage and there is no switching loss. Hence, high switching frequency is used to reduce the passive components’ volume and weight. Besides, the low dc-bias and bidirectional magnetizing current allows a smaller magnetizing inductance in the autotransformer to further minimizing the dimensions of the magnetic core. The leakage inductances are used to provide zero-current switching condition for the diodes, eliminating their reverse-recovery losses. The operation principle, steady-state analysis, and design guidelines are depicted and validated through experimental results obtained from a 350-W prototype of the proposed converter. Efficiency of 96.5% at full load is also reported.

A Hybrid Dynamic Voltage Sharing Scheme for Series-connected SiC MOSFETs with Single Gate Drive

At present, the voltage level of a commercial SiC MOSFET can hardly meet the requirements of high-voltage field. For the sake of achieving the application of MOSFETs in high-voltage fields, the method of series-connected MOSFETs has become a practical and effective solution. However, multiple series-connected SiC MOSFETs face the problem of voltage unbalance, especially dynamic voltage unbalance. Generally, the problem of dynamic unbalance could be solved using load side voltage sharing schemes or the methods of gate side. This paper uses a hybrid dynamic voltage sharing scheme for the single-driven series-connected SiC MOSFETs. That is to say, based on a sequential lagging single gate drive topology, combining active clamping circuits with RCD snubber circuits are introduced to solve the problem of dynamic voltage unbalancing of the whole module in this paper. Compared to the circuit without any dynamic voltage sharing scheme, the dynamic voltage imbalance degree of the circuit with a hybrid dynamic voltage sharing scheme is decreased to 3.75% during the switching-on and switching-off periods. The equalization effect would be verified through the simulation under clamped inductive load in LTspice.

A high step‐up soft‐switched DC‐DC converter with reduced voltage stress for DC micro‐grid applications

SummaryThis article proposes a non‐isolated soft switched high gain DC‐DC converter with reduced voltage stress across switches and diodes. This converter is suitable for renewable energy and DC micro‐grid applications. High gain is obtained at lower duty and turns ratio using a voltage multiplier and two coupled inductors. An active clamp circuit is incorporated to reduce the voltage stress across the main switch and also to achieve zero voltage switching (ZVS) of both switches. Zero current switching (ZCS) of diodes during turn off is also achieved. As a result, switching losses between switches and diodes are reduced, and efficiency is improved. The working principle and theoretical analysis in continuous conduction mode (CCM) is presented. A 500 W (24 V/400 V) prototype with a high voltage gain is built up, and an efficiency of 94.87% is observed. The hardware results are in close agreement with the simulation results.

Novel Quadratic High Gain Boost Converter With Adaptive Soft-Switching Scheme and Reduced Conduction Loss

In this article, an improved soft-switching quadratic boost converter is proposed. Instead of inserting an additional active clamp or auxiliary zero-voltage transition circuit at the switching node, the proposed topology connects the high-voltage switching node to the input diode node by replacing one of the input diodes with a low-rated switch. The proposed topology can attain soft-switching condition for all the switches and input diode turns- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> under zero-current switching (ZCS). The operation of input-side switch not only aids zero-voltage switching (ZVS) turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> for the main switch but also helps in reducing the conduction loss. Also, the input-side switch operates under ZCS turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> and ZVS turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> , making it a loss economical solution. An adaptive timing scheme for driving the input switch is proposed, which can ensure soft-switching condition under varying gain and load range. The detailed operational modes, analysis, and design considerations of the proposed topology are presented. A 250 W hardware prototype is built to validate the performance of the proposed converter operating at 100 kHz switching frequency. Results with adaptive soft-switching scheme shows that the converter is modulated to achieve its best efficiency condition under various system conditions. A peak efficiency of 96.1% at 155 W and efficiencies above 95.75% over a wide load range are achieved using all Si devices.