Hard-switching Converter Research Articles

High-performance Cuk converter with turn-on switching at zero voltage and zero current

The soft-switching technique has the potential to significantly enhance the performance of the power converter. This is primarily because it allows for an increase in the switching frequency, which ultimately leads to improved modulation quality. This raises extra concerns, particularly in high-power applications, because in a standard hard-switching converter structure, components can often not function at frequencies higher than a few hundred hertz. This paper presents a high-efficiency soft switching CUK converter.When the main and auxiliary switches are turned on and off at zero voltage, the proposed converter yields zero voltage and zero current. The suggested method is ideal for a DC-DC converter based on IGBTs or MOSFETs. The recommended systems are described using theoretical analysis, the results of computer simulations, and experimental data derived from a prototype. The design parameters of the inductance and capacitor circuit for edge-resonant soft switching were obtained using the output power and the switching duty ratio. In the end, soft-switching is better than hard-switching in terms of efficiency, particularly when operating under full load.

Earthquake Algorithm-Based Voltage Referenced MPPT Implementation through a Standardized Validation Frame

This paper presents a new direct maximum power point tracking (MPPT) with a reference voltage (Vref) based on the metaheuristic earthquake algorithm (EA) where the optimization variable is the Vref for hard-switching converters. The efficiency and performance of EA-MPPT-Vref is compared with the perturb-and-observe (P&O) counterpart technique due to the fact that it is widely used for commercial products. Static and dynamic responses for both MPPT strategies are evaluated, which correspond to steady-state oscillations when they are near the maximum power point (MPP), and the tracking-speed, respectively. The efficiency was evaluated with the EN 50530 standard. The results show that the new MPPT proposed is a competitive method using the EA to obtain the optimal voltage reference. From static results, EA-MPPT VP presented a better efficiency of 5.13% and 3.23% for European and California energy commission (CEC) efficiency, respectively. Whereas, from dynamic results, MPPT-Vref techniques presented an efficiency from 95.13% to 99.91%, and 99.01% to 99.91% of the total power of the PV system for P&O and EA strategies, respectively.

Frequency-Based Active Ripple Compensation Technique to Reduce Bulk Capacitance in Integrated Offline LED Drivers

In order to increase the power density and the lifespan of LED drivers, several studies have proposed Active Ripple Compensation (ARC) techniques for minimizing the converter bulk capacitance. However, a common side-effect of the ARC method is the increase in the Total Harmonic Distortion (THD) of the converter input current. In this context, a frequency-based ARC technique is proposed as an alternative to the conventional ARC methodology, in which the duty-cycle is modulated. The analyses presented in this paper show that the frequency-based ARC approach applied to resonant converters has a better performance than the one used in hard-switching converters, since it allows for a huge capacitance reduction with a small THD increase. Furthermore, this paper presents a generalized analysis of ARC techniques applied to integrated off-line LED drivers, which reduce the number of components and the overall LED driver cost. The input current harmonic content and the output ripple reduction have been theoretically predicted for several converters. Experimental results gathered from a 96-W laboratory prototype supplied from a 127-V 60-Hz grid attested the superior performance of the frequency-based active ripple compensation, since a capacitance reduction of 66.6% has been obtained with an increase of only 0.9% in the THD.

Mitigation of Motor Overvoltage in SiC-Based Drives Using Soft-Switching Voltage Slew-Rate ($dv/dt$) Profiling

In silicon carbide (SiC) device based motor drives, the high-voltage slew-rate ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dv</i> / <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dt</i> ) associated with the fast-switching transitions results in excessive motor overvoltage, due to the reflected wave phenomenon, which increases the motor winding insulation stress and causes premature failure while raising electromagnetic interference (EMI) problems. This article proposes a soft-switching voltage slew-rate profiling approach to mitigate the motor overvoltage in SiC-based cable-fed drives. The proposed approach optimizes the rise/fall time of the output voltage according to the cable length, without altering the switching speed of the SiC devices. Since increasing the switching rise/fall time using conventional approaches, such as increasing the gate resistance, results in an increased switching power loss, the proposed profiling approach is implemented using a soft-switching inverter. The optimum rise/fall time that can significantly mitigate the overvoltage is derived using frequency- and time-domain analysis. The auxiliary resonant commutated pole inverter (ARCPI) is adopted as an example of the soft-switching inverter to experimentally verify the proposed slew-rate profiling approach for the overvoltage mitigation. The analysis and experimental results show that the motor overvoltage is fully mitigated when the output voltage rise/fall time is set as the cable antiresonance period, i.e., four times of the wave transmission time along the cable. Furthermore, the slew-rate profiling approach along with the ARCPI reduces the switching loss and improves the EMI performance at the high-frequency region, compared with the conventional hard-switching converter. Specifically, the maximum efficiency of the ARCPI is about 99%.

Ringing loss analysis and its influence on boost converter efficiency

Ringing of voltage and/or current waveforms is inevitable in hard-switching converters, especially when the operational frequency increases. The impact of ringing is increasing due to the development of high-speed switching devices. However, the extra loss introduced by ringing is not considered in the evaluation of the converter&apos;s total loss. This paper proposes detailed analysis of the ringing loss and its estimation method. It is shown that the ringing introduces extra loss, which is not included in the conventional method for loss estimation. The loss introduced by ringing is determined by its magnitude and the parasitic inductance in the power loop. In addition to the analysis, experiments are conducted on a boost converter with different ringing to evaluate the influence of ringing on the overall efficiency. It is shown that the ringing has a greater influence on efficiency under low current condition.

Current Collapse Conduction Losses Minimization in GaN Based PMSM Drive

The ever-increasing demands on the efficiency and power density of power electronics converters lead to the replacement of traditional silicon-based components with new structures. One of the promising technologies represents devices based on Gallium-Nitride (GaN). Compared to silicon transistors, GaN semiconductor switches offer superior performance in high-frequency converters, since their fast switching process significantly decreases the switching losses. However, when used in hard-switched converters such as voltage-source inverters (VSI) for motor control applications, GaN transistors increase the power dissipated due to the current conduction. The loss increase is caused by the current-collapse phenomenon, which increases the dynamic drain-source resistance of the device shortly after the turn-on. This disadvantage makes it hard for GaN converters to compete with other technologies in electric drives. Therefore, this paper offers a purely software-based solution to mitigate the negative consequences of the current-collapse phenomenon. The proposed method is based on the minimum pulse length optimization of the classical 7-segment space-vector modulation (SVM) and is verified within a field-oriented control (FOC) of a three-phase permanent magnet synchronous motor (PMSM) supplied by a two-level GaN VSI. The compensation in the control algorithm utilizes an offline measured look-up table dependent on the machine input power.

High-Frequency Operation of Series-Connected IGCTs for Resonant Converters

Series-connected integrated gate-commutated thyristors (IGCTs) find application in hard-switched commercial power converters at the megawatt power levels. Expanding the application of these devices to medium-voltage dc&#x2013;dc resonant converters is of great interest due to the IGCT&#x0027;s low conduction losses. This requires a deeper understanding of the device&#x0027;s behavior in series connection and under switching conditions different than those in hard-switched converters. In particular, the voltage sharing between series-connected IGCTs must be achieved with significantly reduced turn-<small>off</small> currents, typical for resonant converters. Relying on a versatile IGCT test setup, this article explores the operational performances of series-connected IGCT operation at very low turn-<small>off</small> current and with snubber capacitance in the range of a few tens of nanofarad. The results presented in this article are obtained from commercially available 4.5-kV 68-mm reverse-conducting IGCTs (with standard irradiation), as well as two customized engineering samples (high irradiated variants), optimized on their technology curve for high switching frequencies. The IGCTs are successfully operated in series connection at 5 kHz, with device voltage being effectively shared in resonant converter operation.

Analysis and Experimental Verification of an Isolated Half-Bridge Bidirectional DC−DC Converter

This article describes the analysis of a zero voltage switched isolated bidirectional half-bridge active-clamp current-fed push--pull converter for a power in the range of 1 kW. Combining the beneficial characteristics of active-clamping and advanced control scheme, this converter realizes soft-switching features for a hard-switching converter design. The technique utilizes the inductance and the clamp capacitor on the lower voltage (LV) side to create zero voltage switching conditions for the transistors on the higher voltage (HV) side. Additional overvoltage stress, voltage spikes, and reverse-recovery for the transistors on the LV side are reduced. By using the advanced control scheme, the effective turns ratio can be increased. The operating principles are analyzed in time-domain and validated by measurements.

Quasi-Resonant Half-Wave Buck Converter with Non-Isolated High Side Switching Techniques

Power density of the power converters became one of the most important parameters in many applications. Power density is increased by reducing the losses through use of better performing components and circuit topologies. It can be increased further by reducing the size of filter components through increasing the switching frequency. In hard-switching converters however, losses due to switching will eventually render this method not applicable. Instead, resonant converters are utilized in many high-frequency switched power supplies. Soft-switching feature of these converters provide increased efficiency due to decreased switching losses. Such converters exploit the resonance of the specific inductors and capacitors in the circuit called as resonant tank elements. Resonance behavior is used in order to eliminate turn-on or turn-off losses. Existing power converter topologies can be modified to create the resonance during switching period. Such converters are called as quasi-resonant converters. This paper presents analysis and design of Zero Current Switching (ZCS) half-wave quasi-resonant buck converters. In this topology, high-side switching is required. Two different non-isolated high-side switching techniques are utilized. Experimental results are obtained for light load to full load operation. Both techniques are compared in detail.

An Energy Storage System Composed of Photovoltaic Arrays and Batteries with Uniform Charge/Discharge

The main purpose of this study was to develop a photovoltaic module array (PVMA) and an energy storage system (ESS) with charging and discharging control for batteries to apply in grid power supply regulation of high proportions of renewable energy. To control the flow of energy at the DC load and charge/discharge the battery uniformly, this work adapted a bidirectional buck–boost soft-switching converter and the maximum power point tracking (MPPT) technique of the photovoltaic module array. First, a boost converter is used with the perturb and observe (P&amp;O) method, so that the photovoltaic module array can work at the maximum power point (MPP) at any time. When the output power of the photovoltaic module array is greater than the load power, the excess power is used to charge the battery; on the contrary, if the output power of the photovoltaic module array is lower than the load power, the battery discharges for auxiliary power supply. This makes the voltage of the DC link maintain a constant value. The monitoring circuit sends the voltage and current signals to the TMS320F2809 digital signal processor (DSP) produced by Texas Instruments to control the battery charging/discharging voltage and current. The photovoltaic module array works at the MPP to improve the performance of the overall energy storage system. Finally, the actual test result shows that the soft-switching converter used in this work, when compared to the hard-switching converter, can improve efficiency by nearly 4% when the load power is above 125 W. When the photovoltaic power generation system operation is between 150 W and 400 W, the proposed uniform charging and discharging architecture can rapidly reach uniformity.

Enabling Resonant Commutated Pole in Parallel Power FET Bridge Legs

To meet the requirements of higher current ratings and lower thermal impedances, paralleling power field-effect transistor (FET) discretes or modules is often a cost-effective or even an unavoidable solution. While paralleling FETs allows for a significant reduction in conduction loss, the switching loss is increased in hard-switching applications. This article proposes a generic soft-switching modulation scheme for parallel power FET bridge legs. Part of the paralleled FET legs is chosen as an auxiliary leg that is turned on prior to the remaining main legs. A resonant commutated pole (RCP) mode is then created, which enables the high-side FET of the auxiliary leg to achieve zero-current switching (ZCS) or quasi-ZCS and the remaining FETs to achieve zero-voltage switching. Thus, we can significantly reduce the switching loss that normally dominates the total power loss of high-frequency hard-switching converters particularly at partial and light loads. Experimental results from three parallel GaN high-electron-mobility transistor legs validate the effectiveness of this RCP-enabled solution in reducing switching losses and improving power conversion efficiencies. This article is accompanied by supplementary JIF and PDF files demonstrating the operational details of the RCP mode.

Comparative Reliability Analysis for Resonant Converter Operation Under Component Ageing

This article is concerned with reliability analysis in relation to optimal switching of resonant power converters, aimed at minimizing their power loss and operational temperature and, thus, reducing their lifetime degradation. In most cases, high-performance resonant converter control requires a continuous adaptation of the power device switching instances depending on the power input source, load current, or parameter variation in passive components. If the resonant converter is switched before or after the resonant swing ends, more loss is added to the system, with effects in operating temperature rise and reliability deterioration. Even if the switching frequency is adjusted to keep the output voltage constant, it may influence the operational temperature. This article is quantifying this problem with a calculation of the lifetime implication for both cases of zero voltage transition (ZVT) and zero current transition (ZCT) buck converters. A broad range of parameter variation in passive components is considered due to ageing or aggravated stress. A thorough performance (lifetime/reliability) evaluation is achieved through a comparative analysis of results obtained for resonant converters with ideal operation, resonant converters with adjusted timing due to parameter variation, and hard-switched converters without any resonance. Conclusions are formulated in the end. The results reported in this article should be of high interests to the power electronics community, given that resonant converters are used in a wide range of applications due to their ability to reduce power semiconductor losses.

A Buck-Boost Transformerless DC–DC Converter Based on IGBT Modules for Fast Charge of Electric Vehicles

A transformer-less Buck-Boost direct current–direct current (DC–DC) converter in use for the fast charge of electric vehicles, based on powerful high-voltage isolated gate bipolar transistor (IGBT) modules is analyzed, designed and experimentally verified. The main advantages of this topology are: simple structure on the converter’s power stage; a wide range of the output voltage, capable of supporting contemporary vehicles’ on-board battery packs; efficiency; and power density accepted to be high enough for such a class of hard-switched converters. A precise estimation of the loss, dissipated in the converter’s basic modes of operation Buck, Boost, and Buck-Boost is presented. The analysis shows an approach of loss minimization, based on switching frequency reduction during the Buck-Boost operation mode. Such a technique guarantees stable thermal characteristics during the entire operation, i.e., battery charge cycle. As the Buck-Boost mode takes place when Buck and Boost modes cannot support the output voltage, operating as a combination of them, it can be considered as critically dependent on the characteristics of the semiconductors. With this, the necessary duty cycle and voltage range, determined with respect to the input-output voltages and power losses, require an additional study to be conducted. Additionally, the tolerance of the applied switching frequencies for the most versatile silicon-based powerful IGBT modules is analyzed and experimentally verified. Finally, several important characteristics, such as transients during switch-on and switch-off, IGBTs’ voltage tails, critical duty cycles, etc., are depicted experimentally with oscillograms, obtained by an experimental model.

ЦИФРОВІ КОМПАРАТОРИ ЧАСТОТИ ТА ФАЗИ В СКЛАДІ СИСТЕМИ СТАБІЛІЗАЦІЇ ПОЛОЖЕННЯ РУХОМОЇ ПЛАТФОРМИ

Urgency of the research. A dual-range, four-quadrant position stabilization system (PSS) of a brushless direct current motor (BLDC) as a part of movable platform (MP), in which the power stage is based on a quasi-resonant pulse converter (QRPC), has the better speed and accuracy characteristics in comparison with hard-switching PWM-based converters. Target setting. The BLDC PSS can be built on the basis of the classic multi-loop control system (MLCS), or on the pulse-frequency (PF-) domain. In PF-domain the task of speed control is transformed into the frequency comparing and matching task, and the position control is transformed into the phasecomparing and matching between the reference signal and the feedback signal. The development of specialized digital blocks of a frequency comparator (FK) and a phase comparator (PC) to perform the above tasks is a non-trivial task. Actual scientific researches and issues analysis. The earliest solutions of the FC, which should be correctly called the ‘frequency detector’ (FD), were implemented mixed-signal (contained both analog and digital nodes) due to their usage in a high-frequency phase-locked loop (PLL) system. A full-featured FC consists of two counters, comparator, a FD block, control finite-state machine (FSM), and a specialized combinational circuit. Uninvestigated parts of general matters defining. Existing FC blocks do not return a quantitative relation between measured frequencies, which can be used to predict dynamics, and are insensitive to the detection of small misalignments between frequencies, that, in turn, creates instability of determining the frequencies equality state. Existing PC blocks are unstable when the frequency of one of the measured signals reaches the system clock frequency, and also do not take into account the edges incoming order of the measured signals. The research objective. The article is devoted to the study and development of the structure of pure-digital FC and PC blocks, which will eliminate the disadvantages of existing solutions and are oriented for integration into PSS with QRPC in the power stage and MLCS operates in a PF-domain. The statement of basic materials. A novel technical solutions is proposed, developed and tested for pure-digital blocks of the FC and PC built on the basis of the field-programmable gate array (FPGA) by means of the hardware description language (VHDL). They allow not only to measure the sign of the inequality of frequency and phase between two periodic signals, but also to obtain the difference numerical values between them. Conclusions. The installation of the FC and PC blocks into the BLDC PSS leads to a significant reducing of FPGA hardware resources utilization and to the high reliability and noise immunity of the MLCS through the unruptured (continiously) nature of the signals. Both the proposed blocks are novel and have eliminated the inherent disadvantages of the existing blocks of the FC and PC due to the installation of additional digital nodes − synchronizers (pulse shorters and edge detectors), and also a hysteresis node that leads to increase the stability and solve the problem of detection near-to-equal frequencies and phases.

A Soft-Switching Non-Inverting Buck–Boost Converter With Efficiency and Performance Improvement

This letter proposed a new soft-switching non-inverting buck–boost converter (NIBBC) by introducing the magnetic coupling effect to an existing soft-switching dc/dc converter. The new NIBBC obtains two superiorities: one magnetic core is removed to improve the efficiency; the magnetic coupling effect can give an adjustable soft-switching range. Operating principles and converter characteristics of the new NIBBC are presented. An experimental prototype of the new NIBBC is built, and switching waveforms and the efficiency are measured. Experimental results show that the new NIBBC can obtain soft-switching conditions and has efficiency improvement comparing to hard-switching converter and another soft-switching dc/dc converter.

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.

A PWM Switch Model of Isolated Battery Charger in Constant-Current Mode

In this paper, the pulsewidth modulation switch method was used to investigate the effect of the transformer leakage inductance on the small-signal model in isolated full-bridge converter. A galvanic isolated hard-switching full-bridge converter that operates in constant-current mode is analyzed, confirming that leakage inductance significantly affects the small-signal model, and the influence of leakage inductance can be equivalent to a resistance in series with the converter's output LC filter just as that in phase-shifted full-bridge converter. However, the same leakage inductance in these both converters will lead to different equivalent resistance due to different operating principles. Results of the modified model, simulations, and the experiments are compared to verify the correctness of the model. Moreover, this paper also shows that the Norton equivalent circuit of the charger operates in constant current mode, which can be used to estimate the dynamic behavior of the system.

Analysis and Design of a ZVT Resonant Boost Converter Using an Auxiliary Resonant Circuit

In this paper, a new zero voltage transition (ZVT) resonant boost converter is proposed. A typical boost converter generates switching losses at turning on and turning off, and these losses cause a reduction in the efficiency of the whole system. This proposed ZVT resonant boost converter utilizes a soft switching method, using an auxiliary circuit with a resonant inductor, capacitor, and two auxiliary switches. Therefore, it can reduce switching losses more so than the conventional hard switching converter. Also, the conduction period of the resonant inductor current is reduced by using a modified circuit. An experiment is conducted with the converter, which steps up the voltage from 200 V to 380 V and its switching frequency and output power are 30 kHz and 4 kW, respectively. It is confirmed that the experimental results and simulation results are the same and the validity of this proposed converter is verified. The conventional converter and proposed converter are analyzed by comparing the experimental results of two converters under the same conditions. It is confirmed that all switches can achieve soft switching and the proposed converter improves on the conventional converter by measuring the efficiency of two converters.

Using low‐cost microcontrollers to implement variable hysteresis‐width comparators for switching power converters

Hysteretic comparators are often used to implement sliding-mode controllers or other type of discontinuous regulators for power switching converters. Their design is usually performed analogically yielding robust and fast controllers that can even allow converter operation with high values of duty cycle. A new analogue implementation based on a low-cost microcontroller is described in this study showing the mentioned advantages plus the flexibility of a programmable digital system. The proposed comparator employs some microcontroller peripherals without consuming execution time of the control algorithm and without requiring interruption management. It provides variable hysteresis width to obtain constant switching frequency in sliding-mode strategies and can be used in any type of hard switching converter. The dynamic performance of the method is verified experimentally in a boost converter-based rectifier with power factor correction and output voltage regulation in one single stage. The boost converter operates in sliding mode with constant switching frequency and results in a total harmonic distortion of the input current <1%.

Half‐bridge flyback converter with lossless passive snubber and interleaved technique

Hard-switching flyback converters are widely used in the low power application but suffer from high electromagnetic emissions, current ripples, and low efficiency. To overcome these problems, a half-bridge flyback converter with a new lossless passive snubber is proposed using an interleaved structure. All switches of the proposed converter turn on under zero current switching and turn off under zero voltage switching which decreases the switching losses and electromagnetic interference (EMI). Theoretical analysis of the proposed converter is presented and verified by the experimental results of a 200 W prototype. In addition to the 7% efficiency improvement, the proposed converter has lower EMI in comparison with its hard-switching converter.