Wide Range Of Switching Frequencies Research Articles

Electrothermal Averaged Model of a Half-Bridge DC–DC Converter Containing a Power Module

This article proposes an electrothermal averaged model of a half-bridge DC–DC converter containing a power module. This kind of model enables the computation of characteristics of DC–DC converters using DC analysis. The form of the elaborated model is presented. Both the electrical and thermal properties of the analyzed DC–DC converter are included in this model. This is the first averaged electrothermal model of a DC–DC converter which makes it possible to compute the junction temperature of all the semiconductor devices and magnetic components. The accuracy of the model was experimentally verified in a wide range of switching frequencies and output currents. Particularly, the influence of mutual thermal couplings between the transistors contained in the considered module on the characteristics of the converter and the junction temperature of the transistors is analyzed.

Asymmetrical Six-phase GaN-based Drive Performance Analysis with Variable Switching Frequency Control

This paper analyses the performance ofa GaN-based multiphase drive when a variable switching frequency control is implemented for EV applications. The GaN-based inverters allow a wide switching frequency range, and the power losses of the inverter are reduced in comparison with other technologies such as Si. To be able to benefit from this wide switching frequency range, a variable switching frequency control with the objective of maintaining a ratio frequency ???????? = 17 is implemented. This control reduces the switching frequency losses above 30% in the three analysed speed points in comparison with maintaining a constant switching frequency. Hence, an efficiency improvement is achieved with the variable switching frequency control tackling one of the main problems of the EV.

A high-efficiency primary-side regulation control strategy for half-bridge LLC resonant converter with wide input voltage range

The requirement of the half-bridge LLC resonant converter with a wide input voltage range is becoming higher in photovoltaic applications because of its simple structure and low switching loss. Conventional frequency modulation (FM) requires a wide switching frequency range and a high-quality factor circuit design, leading to reduced efficiency and large component volumes at light loads. To solve the problems, a high-efficiency control strategy using adaptive pulse-width and frequency modulation (APWFM) is proposed. APWFM adjusts the gain by changing the switching frequency and duty cycle simultaneously. When the output power is below the reference value, the switching frequency decreases linearly as the output power decreases, and the duty cycle is simultaneously modulated to achieve constant output voltage, so the switching frequency variation range is smaller than FM. This results in improved light or medium load efficiency in a limited frequency range while keeping a small volume of magnetic components. Also, the proposed control strategy is realized with primary-side regulation (PSR) to eliminate the optocoupler and simplify the control circuit. Experimental results demonstrate a significant improvement in efficiency at medium and light loads compared to FM, and the average efficiency is improved by 5% based on low cost and simple operation.

A Simplified Sensorless Synchronous Rectification Method for Inner Phase Shift Control in CLLC Converters

The CLLC converter is a promising topology for bidirectional power conversion applications, such as vehicle-to-grid and battery energy storage systems. In these applications, wide output voltage range is needed. However, traditional pulse frequency modulation method is not suitable for wide output range because of wide switching frequency range. Inner phase shift (IPS) control is a good solution for this issue. In CLLC converters, to further increase the efficiency, synchronous rectification (SR) is required. In this paper, a simplified sensorless SR method is proposed for IPS control. A comprehensive operation mode analysis and an accurate operation mode model is established for IPS control in CLLC converters. With the operation mode model, waveform of secondary side current is simplified. As a result, only a standard quadratic-root formula needs to be calculated to generate SR drive signal, and no extra sensors are needed. The method is low cost and is suitable to implement in embedded systems. A prototype is built to verify the proposed simplified sensorless SR method. The proposed method achieves an obvious efficiency improvement (up to 1.88%) over uncontrolled rectification, and the effect of the proposed method is nearly the same as that of complete SR (maximum efficiency difference is 0.40%).

A Novel LCL Resonant Converter With Inherent CC-CV Output for On-Board Chargers of Plug-In Electric Vehicles

The <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> Resonant converter is widely used in on-board charger applications for its high efficiency. However, conventional <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> converter with pulse-frequency-modulation suffers from a wide switching frequency range for realizing constant current (CC) and constant voltage (CV) charges. To address this problem, different from the traditional solution, a novel <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCL</i> resonant converter operating at a fixed resonant frequency with inherent CC and CV output characteristics is proposed in this letter. In the proposed concept, the CC and CV charges are accomplished by the special <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCL</i> tank. With the increasing of battery voltage during charging process, the resonant tank of the proposed converter is equal to the conventional <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCL</i> tank and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> tank for CC mode and CV mode, respectively. Thus, the sensing and control circuits are canceled while the wide zero-voltage-switching operation for primary switches and zero-current-switching for secondary diodes still be maintained. Therefore, the fixed resonant frequency operation, high efficiency, high reliability, and low cost are key features of the proposed converter. A 1-kW prototype with 400 V input and 250–400 V output is built and tested. The full load efficiency of 96.7% and higher than 96% for the CC mode were both achieved. The experimental results demonstrate the advance and validity of the proposed converter.

GaN and SiC Device Characterization by a Dedicated Embedded Measurement System

This work proposes a comparison among GaN and SiC device main parameters measured with a dedicated and low-cost embedded system, employing an STM32 microcontroller designed to the purpose. The system has the advantage to avoid the use of expensive laboratory measurement equipment to test the devices, allowing to obtain their behavior in operating conditions. The following KPIs (Key Performance Indicators) are measured and critically compared: threshold voltage, on-resistance and input capacitance. All the measurements are carried out in a short time interval and on a wide range of switching frequencies, ranging from 10 kHz to 1 MHz. This investigation is focused on the deviation of the figures of merit when the switching frequency changes, since it is crucial for wide-bandgap devices. The devised, low-cost, microcontroller unit allows high flexibility and system portability, while the employed equivalent-time sampling technique overcomes some issues related to the need of high sampling frequency. It allows good performances with common microcontroller embedded AD converters. To validate the proposed system, the obtained results have been compared with the time-domain waveforms acquired with a traditional laboratory oscilloscope and a study of the system’s measurement errors has been carried out. Results show that GaN devices achieve a higher efficiency with respect to SiC devices in the considered range of switching frequencies. The on-resistance exhibited by GaN devices shows, as expected, an increase with frequency, which happens to switching losses, too. On the other hand, GaN devices are more sensitive to parasitic effects and the high dV/dt, due to the reduced switching times, can excite unwanted ringing phenomena.

A Low Q Three-Phase Series Resonant Converter for PV Applications

In this paper, a soft-switched three-phase resonant converter with a low quality factor (Q) design is proposed for Photovoltaic (PV) energy harvesting systems with a very wide range of operating conditions. Due to the low quality factor (Q ≤ 1), the voltage stress across the capacitors is drastically reduced. However, a major challenge of using a low Q design is the wide switching frequency range required for operation over a wide range of load and input conditions. In order to reduce the switching frequency range, this paper introduces a hybrid modulation technique employing asymmetric pulse width modulation (APWM) along with variable frequency modulation. The proposed modulation scheme also substantially extends the soft-switching range of the converter from full-load upto 10–35% load condition over a wide range of line voltages. To sustain soft-switching in the entire operating region of the converter, the converter is operated in a hybrid structure with single-phase and burst modes at light load conditions. A comprehensive time-domain analysis of the proposed converter is presented, which greatly improves accuracy over conventional frequency-domain modeling. Experimental results from a 1 kW prototype are presented to verify the performance of the converter and validate the theoretical analysis.

Pulse Frequency Modulated Interleaved Boost-Integrated LC Series Resonant Converter With Frequency-Free Designed Transformer

In this article, we propose a novel interleaved boost-integrated <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> series resonant converter, in which the series resonant tank is located on the secondary side. Moreover, the input and output of the interleaved boost unit are in series directly, which is helpful to reduce the voltage stress of the output filter capacitor of boost unit. With the proposed pulse frequency modulation, except for that the output voltage can be controlled as constant under different input voltages, another feature is that the high-frequency transformer design is related to the series resonant frequency instead of the switching frequency. Hence, the proposed converter can operate under a very wide switching frequency range with a constant maximum magnetic flux density. The zero voltage switching and zero current switching can be achieved for all switches diodes. Finally, a 500-W prototype with a switching frequency range from 60 to 200 kHz is built to verify the operation principles of the proposed converter and modulation.

A modified seven-level cross-connected PUC boost multilevel inverter with reduced cost factor and device count

Abstract The device count (dC) and cost factor (CF) with the boosting feature are the main challenges in the packed u-cell multilevel inverters as the number of levels are increased in the output voltage. In this paper, to mitigate these problems, a new topology of a 7-level modified packed u-cell boost multilevel inverter (PUC-BMLI) is designed to improve the cost factor and device count. Further, it can be used for a wide range of switching frequencies since only one capacitor is required and the voltage across the capacitor is balanced. To generate a 7-level stepped-up voltage across the load, the PUC-BMLI needs only eight power switches and one capacitor. The proposed topology can boost the input voltage by 1.5 times. To generate a 7-level stepped-up voltage across the output multicarrier phase-disposition pulse width modulation (PD-PWM) has been used. To prove the superior performance of the PUC-BMLI, a comparative analysis with existing single DC source boost MLI has been done. The device count (dC) and cost factor (CF) are the lowest compared to the recently proposed topology employing one dc source and producing 7-level across the output. The dC and CF are 10 and 22.33. All the switches are two-quadrant switches, thus reducing the cost of the overall circuit. THD is found to be 4.10% for output current. The feasibility of the 7-level modified topology is evaluated by Matlab/Simulink simulation and verified by an experimental study using the OPAL-RT 4510 real-time platform.

Efficiency Optimization of PWM-Induced Power Losses in Traction Drive Systems With IPM Machines Using Wide Bandgap-Based Inverters

This article investigates the total PWM-induced power losses in interior permanent magnet (IPM) machines excited by wide bandgap (WBG)-based voltage-source inverters with different pulsewidth modulation (PWM) schemes and a wide range of switching frequencies. The PWM current ripple characteristics are predicted and compared using an accurate analytical model. Three enhanced power loss estimation models are utilized to estimate the PWM-induced power losses in each of three major machine materials: the stator form-wound windings, the stator and rotor iron cores, and the permanent magnets in the rotor cavities. The variation trend of each loss component versus PWM frequency and modulation scheme is provided. Experiments have validated the model accuracy in two IPM machines designed for traction applications. Both measured and predicted results suggest that increasing the PWM frequency is beneficial for suppressing the PWM-induced power losses in IPM machines. In conjunction with the reduction in machine-related power losses, it has also been demonstrated that a higher PWM frequency in IPM drives with WBG-based inverter exhibits the appealing potential for improving the system-level efficiency in traction applications.

A Resistor-Network Model of Dickson Charge Pump Using Steady-State Analysis

This paper presents a new average behavioral model, named a resistor-network (RN) model, that accurately predicts the electrical characteristics of the Dickson charge pump (DCP) circuit in the slow-switching limit and the fast-switching limit regions based on steady-state analysis. The RN model describes the steady-state behavior of a single-stage DCP using a network of resistors, which can then be cascaded to model N-stage DCP, taking into account the top- and bottom-plate parasitic capacitances. The RN model provides a comprehensive insight into various design parameters of the DCP, including the input/output current, output voltage, load characteristics, losses caused by parasitics, and power efficiency. Simulation results show that the proposed RN model accurately predicts the output voltage and power efficiency of the DCP over a wide range of switching frequencies, from 0.1 Hz to 1 GHz, with an error of less than 2% at the maximum power efficiency. The RN model provides designers with a simple and effective model to design DCP quickly and efficiently for a broad spectrum of applications, including energy harvesting and flash memory applications.

Adaptive Deep-Learning-Based Steady-State Modeling and Fast Control Strategy for CLLC DC-DC Converter in Highly Renewable Penetrated System

The CLLC DC-DC converter offers highly efficient DC voltage conversion for the highly renewable penetrated system. The modeling significantly influences the performance of CLLC DC-DC converters. However, both the current FHA-based and time-domain analysis methods are incapable to incorporate different switching frequencies and load conditions. Moreover, due to the inevitable non-monotonic voltage gain, the PI controller with these models leads to the uncontrolled steady-state voltage deviation. As a novel modeling method, deep learning implicitly builds extensively accurate and arbitrary mappings, which can solve the aforementioned modeling problems. This paper proposes an adaptive steady-state modeling method for the CLLC converter based on deep learning. Precise voltage gain can be provided over a wide range of switching frequencies and load conditions. Besides, a fast control strategy based on the proposed modeling method is developed. This strategy searches the optimal operating point using particle swarm optimization, which rapidly adjusts voltage gain and suppresses the steady-state voltage deviation even in non-monotonic situations. Finally, a 400V/300V, 2.4kW SiC-based CLLC converter prototype with distributed heterogeneous controllers is implemented to verify the proposed methods. The experimental results show the accuracy of the proposed adaptive modeling and the effectiveness of the fast control strategy. The proposed method improves the stability and extends the operating range of the CLLC converter, which benefits the development of highly renewable penetrated systems.

Resonant Tank Switch Methodologies for Narrow Switching Frequency Range in Wide Output Range LCC Converter

Wide switching frequency range is required for LCC resonant converter with wide gain and load ranges which will lead to low power density and slow dynamic responses. Resonant tank switch is an effective approach to limit the operation frequency range without sacrificing the power transistor’s zero-voltage switching (ZVS) switching and system complexity too much. However, the current approach of resonant tank switch failed to provide a generalized and engineering practicability methodology. In this article, a new resonant tank design method is first proposed considering voltage and current stress for higher efficiency and improved design feasibility. Resonant tank switch methodologies are developed with a single switch parameter ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$C_{s}$ </tex-math></inline-formula> -Switch, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$L_{s}$ </tex-math></inline-formula> -Switch, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$L_{s}$ </tex-math></inline-formula> -Parallel) and a multi-switch parameter (full range, fixed slope, and fixed inflection point). Operation range divisions for different tanks are further proposed under gain and load covariations. A 5 kW LCC converter with gain variations of 0.3–1.2 and an output current range of 0.3–18 A is built to verify the tank switch approaches. The targeted frequency range is 400–500 kHz. Under constant load, the switching frequency range can be limited to 25% with one primary tank and one compensated tank, compared with 66.7% frequency variation with one resonant tank. It is also found that the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$L_{s}$ </tex-math></inline-formula> -Switch approach achieves desired gain range with the smallest switching frequency range, moderate voltage stress, and smallest current stress under constant load, and variable gain.With three resonant tanks, full gain, and load range can be covered under required frequency ranges. The switching frequency range is limited to 25% compared with 78.6 % variation with one resonant tank. Soft switching is also achieved under the full operation range.

Identification of DC Thermal Steady-State Differential Inductance of Ferrite Power Inductors

In this paper, we propose a method for the identification of the differential inductance of saturable ferrite inductors adopted in DC–DC converters, considering the influence of the operating temperature. The inductor temperature rise is caused mainly by its losses, neglecting the heating contribution by the other components forming the converter layout. When the ohmic losses caused by the average current represent the principal portion of the inductor power losses, the steady-state temperature of the component can be related to the average current value. Under this assumption, usual for saturable inductors in DC–DC converters, the presented experimental setup and characterization method allow identifying a DC thermal steady-state differential inductance profile of a ferrite inductor. The curve is obtained from experimental measurements of the inductor voltage and current waveforms, at different average current values, that lead the component to operate from the linear region of the magnetization curve up to the saturation. The obtained inductance profile can be adopted to simulate the current waveform of a saturable inductor in a DC–DC converter, providing accurate results under a wide range of switching frequency, input voltage, duty cycle, and output current values.

Full-bridge resonant converter with hybrid control for wide input voltage range applications

This paper proposes a hybrid control strategy for a full-bridge resonant converter. In the applications with a wide input voltage, a resonant converter with variable frequency control (VFC) has to modulate the converter operating in a wide switching frequency range to satisfy gain requirements, which results in some problems such as difficulty in optimizing the design of magnetic components, increased power loss and deteriorated electromagnetic interference. By use of VFC, primary-side phase shift control and secondary-side phase shift control, the frequency variable range can be greatly reduced and the conversion efficiency can be increased, which make the converter appropriate for a wide input voltage range. With this hybrid control strategy, the converter can automatically convert to the corresponding control mode according to variations of the input voltage and load, which has a good transient performance. The working principle, gain characteristics and design considerations of a hybrid controlled CLL resonant converter are introduced in detail. Experimental results are shown to demonstrate its validity and feasibility.

SiC-MOSFET and Si-IGBT-Based dc-dc Interleaved Converters for EV Chargers: Approach for Efficiency Comparison with Minimum Switching Losses Based on Complete Parasitic Modeling

Widespread dissemination of electric mobility is highly dependent on the power converters, storage systems and renewable energy sources. The efficiency and reliability, combined with the emerging and innovative technologies, are crucial when speaking of power converters. In this paper the interleaved dc–dc topology has been considered for EV charging, due to its improved reliability. The efficiency comparison of the SiC-MOSFET and Si-IGBT-based converters has been done on wide range of switching frequency and output inductances. The interleaved converters were considered with the optimal switching parameters resulting from the analysis done on a detailed parasitic circuit model, ensuring minimum losses and maintaining the safe operating area. The analysis included the comparison of different inductors, and for the selected ones the complete system efficiency and cost were conducted. The results indicate the benefits when SiC-MOSFETs are applied to the interleaved dc–dc topology for wide ranges of output inductances and switching frequencies, and most importantly, they offer lower total volume but also total cost. The realistic and dynamic models of power devices obtained from the manufacturer’s experimental tests have been considered in both LTspice and PLECS simulation tools.

Enhanced Switching Frequency Control in FCS-MPC for Power Converters

Finite control set model predictive control (FCS-MPC) chooses at each sampling period the input control vector state without using a modulator. Therefore, it belongs to the direct control family. As a consequence, the conventional implementation of FCS-MPC presents variable switching frequency. This makes difficult the design of the output filter. This article investigates the period control approach (PCA-MPC) to achieve a fixed switching pattern, similar to that of modulated strategies placed at a desired frequency. PCA-MPC cannot reach a reference switching frequency without a steady-state error. Nonetheless, it is more than capable of reaching a fixed switching pattern, with clean spectrum at a wide range of switching frequencies. This feature is used here to design an embedded control objective to reach the desired switching frequency. The implementation of the cost function is done through modification of PCA-MPC measurements. These modifications allow one to obtain fast and precise estimates of the switching frequency, which, in turn, permits a fast control. The performance of this control strategy is evaluated through simulation and corroborated by experimental validation on a two-level three-phase, power converter.

High-Efficiency Switched-Capacitor DC-DC Converter with Three Decades of Load Current Range Using Adaptively-Biased PFM

A fully-integrated switched-capacitor (SC) DC-DC converter that steps down 2.0 V to 0.9 V with a peak efficiency of 80% is implemented in a 0.18 μ m CMOS process. An ultra-low-power voltage-controlled oscillator that generates a wide range of switching frequencies is proposed to extend battery runtime. An efficiency &gt;70% for load currents in the range of 12 μ A to 17.8 mA is achieved by implementing a novel adaptively-biased pulse frequency modulation (ABPFM) technique in the controller. A symmetric charge-discharge topology with two-phase time interleaving is used as a power stage to reduce the output voltage ripple to &lt;72 mV over the entire load current range.

Coupled Magnetic Field-Circuit Analysis of Inductive Power Transfer in High-Potential Transformers

Inductive power transfer grew to be a hot topic as reflected by monographs and thousands of articles published mainly last decade. We complement the bulk of research by harnessing the power of coupled magnetic field (MF)-circuit simulations on examples of virtually air-core high-potential (HP) transformers. Easiness of reliable insulation design is greatly facilitated by their open magnetic systems. Circuit analysis on the basis of simplified equivalent circuits is performed. A comparison is made to Tesla transformer. Major impediment here is modeling ferromagnetic parts of the system. Thus, circuit analysis is mostly helpful for a qualitative grasp of the problem. The design is greatly simplified by coupling the MF of the transformer to external circuitry. We do it on a COMSOL platform. Sweeping number of turns, height of the windings, values of resonant capacitors, and so on, we can arrive at an optimal design point. Most of the simulations were done in the frequency domain. Following this procedure, we built and extensively characterized several 20-kV, 1-kW transformers with high-potential insulation sized to 150 kV in a wide range of switching frequencies centered around 50 kHz. A transformer of choice was tested at high voltage (HV) and nominal power in ambient air. The transformer efficiency was >92%, with the largest overheat of 50 °C being on the primary winding.

Simulink Model for PWM-Supplied Laminated Magnetic Cores Including Hysteresis, Eddy-Current, and Excess Losses

A new implementation of an iron-loss model for laminated magnetic cores in the MATLAB/Simulink environment is proposed in this paper. The model is based on numerically solving a one-dimensional diffusion problem for the eddy currents in the core lamination and applying an accurate hysteresis model as the constitutive law. An excess loss model is also considered. The model is identified merely based on the catalog data provided by the core material manufacturer. The implementation is validated with analytical and finite-element models and experimentally in the case of a toroidal inductor supplied from a GaN FET full-bridge inverter with 5–500 kHz switching frequencies and a deadtime of 300 ns. Despite the simple identification, a good correspondence is observed between the simulated and measured iron losses, the average difference being 3.3% over the wide switching frequency range. It is shown that accounting for the skin effect in the laminations is significant, in order to correctly model the iron losses at different switching frequencies. Some differences between the measured and simulated results at high switching frequencies are also discussed. The model is concluded to be applicable for designing and analyzing laminated magnetic cores in combination with power-electronics circuits. The Simulink models are openly available.