Voltage Gain Curve Research Articles

Resonant step-down DC-DC converter based on GaN power integrated circuits and SiC diodes

In the paper results of the operation and efficiency of a DC-DC resonant converter with a switched capacitor topology, equipped with GaN transistors and SiC diodes are presented. Investigated problems are related to the optimization of the DC- DC power electronic converter in order to achieve miniaturization, a simplified design and high efficiency. The proposed system operates at a high frequency with low switching losses. The proposed design helps to achieve uniform heating of the transistors and diodes, as demonstrated by the results of the thermal imaging measurements. The GaN transistors are integrated in one package with dedicated gate drivers and used to simplify the drivers circuitry and increase the power density factor of the proposed device. In the high-frequency design presented in the paper, the converter is implemented without electrolytic capacitors. The results included in the paper contain waveforms recorded in the power circuit at ZVS operation when switching on the transistors. It occurs when the system operates above the frequency of current oscillations in the resonant circuit of the switched capacitor. Efficiency characteristics and a voltage gain curve of the converter versus its output power are presented as well. Results of efficiency and quality of waveforms are important because they allow to characterize the tested system for the implementation using WBG devices. The use of integrated GaN modules to minimize elements in the physical system is also unique to this model and it allows for very short dead-time use, operation in ZVS mode at low reverse-conduction losses.

A Family of Multilevel Class-DE Resonant Converters With Full-Range Regulation

This paper proposes a family of multilevel Class-DE resonant converters (RCs) paired with a full-range voltage regulation method. The proposed converters feature steep gain changes and are fully regulatable while maintaining zero-voltage switching (ZVS) and low voltage/current stresses. An extensive analysis provides the operation states, voltage-gain curves, voltage/current stresses, and comparisons with different methods. A 140W 2X Class-DE RC prototype was built to validate the analysis. The voltage gains are verified to be continuously adjustable for all load conditions within the 2X frequency range.

A Dual-Frequency-Detuning Method for Improving the Coupling Tolerance of Wireless Power Transfer

This letter proposes a dual-frequency-detuning method for wireless power transfer systems to gain a smooth power profile in large coupling variation ranges. The application of the detuning method in the dual-frequency resonant network is explored to adjust the equivalent impedance of each frequency channel at different coupling conditions. Accordingly, the proposed method can freely regulate the voltage gain and output power curves even under a square-wave voltage excitation with high-order harmonic components. By designing the system properly, both the fundamental and 3 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rd</sup> frequency channels alternately serve as the main power transfer channel under strong and weak coupling conditions, so less power fluctuation over a large coupling variation is realized. A 130W prototype is developed, and the experimental results show that the maximum power fluctuation is less than 6.8% against coupling coefficient variations from 0.35 to 0.74.

Accurate Analysis Method and Voltage Gain Curve Derivation Algorithm Based on Time-Domain Analysis for High-Efficiency LLC Resonant Converter Design

An accurate analysis method for an LLC resonant converter and a time-domain analysis (TDA)-based voltage gain curve derivation algorithm are proposed in this paper. When applied to an LLC resonant converter, the TDA method can obtain high-accuracy current and voltage waveforms by solving nonlinear equations for circuit parameters through operation-mode analysis. An LLC resonant converter operating mode classification algorithm was proposed based on the results of this analysis. The circuit voltage and current values in the steady state were quickly and precisely derived using this algorithm. An accurate power-loss analysis is required to design a high-efficiency converter. Therefore, TDA is a powerful tool for designing an LLC resonant network. The proposed TDA-based LLC resonant converter analysis and voltage gain curve derivation algorithm provides high-accuracy voltage, current value estimation and voltage gain curves for all switching-frequency ranges. The effectiveness of the proposed algorithm is verified using a 500 W LLC resonant converter prototype experiment.

A Multimode Control Scheme for Output Regulation and Voltage Balancing in a Stacked-Switch Resonant Converter With Extended High Efficiency for Wide Gain Range Applications

In this article, a new hybrid comprehensive multimode control system is proposed for a stacked-switch bidirectional CLLC resonant converter for wide voltage gain applications. By configuring the presented leg with different switching patterns, the presented leg in the converter can operate in different modes: full-wave (FW), half-wave (HW), or voltage-doubler (VD) through the converter’s built-in circuit redundancy. The proposed hybrid control scheme consists of different control modes: variable frequency modulation, pulse-width modulation (PWM), and asymmetric PWM (APWM) control. Correspondingly, four voltage gain curves are derived from the proposed converter. With the proposed approach, the converter is able to achieve constant voltage regulation while constraining the range of switching frequency, allowing very high efficiencies to be realized for a wide range of input voltages. Soft-switching is achieved for all the semiconductor devices for the entire operating range. The steady-state and dynamic performances of the proposed hybrid comprehensive control system are verified through a proof-of-concept 400-V <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim ~1$ </tex-math></inline-formula> -kV/ 700-V, 1-kW laboratory prototype. Results confirmed that the efficiency is maintained between 95.03% and 96.97% throughout the specified input voltage range.

Full-Range Regulation Method for Half-Bridge Series Resonant Converter

In this article, a fixed on-time modulation (FTM) method for half-bridge series resonate converters (SRCs) is proposed to achieve the full range regulation for all loads. Additionally, the proposed method features low current stresses, zero voltage switching turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> for transistors and zero current switching turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> for diodes. A comprehensive analysis of the operation principle, voltage gain curves, component stresses, and comparisons with other methods is given. Besides, the extension of the FTM method to a family of half-bridge SRCs is discussed and the voltage gains of different topologies are provided. A 200 W prototype of the half-bridge SRC was built and tested to verify the theoretical analysis.

Driving Circuit Design for Piezo Ceramics Considering Transformer Leakage Inductance

This paper presents the circuit and control method for piezo-ceramic drives. With the proposed method, a gap is imposed in the transformer core to increase the leakage inductance. This flattens the voltage gain curve of the piezo-ceramic driver over the resonant frequency range, so voltage gain changes are insensitive to frequency changes. In addition, resonant frequency tracking and power control methods are developed, while the circuit is capable of zero-voltage soft-switching such that the circuit operation efficiency can be improved. In order to solidify the practicality of the circuit design, mathematical analysis and experimental validations have been thoroughly performed. The test results help to confirm the effectiveness of the proposed method and demonstrate its practicality in industrial applications.

Seven Switching Techniques for the Ladder Resonant Switched-Capacitor Converters With Full-Range Voltage Regulation

Ladder resonant switched-capacitor converters (RSCCs) provide high step-up voltage gain, but the continuous regulation range is typically limited with an extremely wide switching frequency band. This article introduces a new full-range regulation method for step-up ladder RSCCs along with seven switching techniques. Each switching technique offers multiple possibilities for implementation. Furthermore, ladder RSCCs with the proposed switching techniques feature the merits of simple control, soft switching, and high efficiency. A comprehensive analysis of operation principle, voltage gain curves, device stress, active switch utilization, zero voltage switching range, output voltage ripple, and input current ripple is given for the proposed seven switching techniques. A 3X step-up Ladder RSCC prototype was built and tested to validate the theoretical results.

Equivalent Circuit Approach for Output Characteristic Design of Capacitive Power Transfer

A simple equivalent circuit of the capacitive coupler and the compensator topology is presented to provide a design procedure for a capacitive power transfer (CPT) system. After that, the voltage gain curve is plotted to analyze the output characteristic of the CPT. This approach is needed in the frequency-controlled CPT stage without any post-regulator, since the output has to be operated in some charging characteristics, such as the load-independent constant current (CC) and constant voltage (CV) outputs that strongly rely on the gain curve design. Therefore, the circuit derivation and the gain curve plot is presented in this brief. Finally, the four-plate compact CPT design with LCL-compensated topology with 100 V output voltage and 450 W output power is experimentally tested to verify the design approach. The plate air-gap distance is 50 mm, and the maximum efficiency of the proposed system is 72%.

Interleaved LCLC Resonant Converter With Precise Current Balancing Over a Wide Input Voltage Range

An interleaved LCLC resonant converter with accurate current balancing performance over a wide input voltage range is proposed. Resonant tank components have slight tolerances that can unbalance load sharing between paralleled phases. Because of the steep voltage gain curve of the LCLC resonant tank, most conventional current sharing approaches might not be effective. In the proposed converter, the impedances of the resonant tanks are matched by a switch-controlled capacitor (SCC) that is in series with the resonant capacitor resulting in precise load current balancing between phases. The impact of various unbalanced situations on the interleaved LCLC resonant converter is investigated, a minimum operating angle for the SCC circuit is identified, the basic accuracy of SCC current balancing via digital control is investigated, and a control strategy is proposed to perform the current sharing. Computer simulation results and experimental results from a GaN-based prototype validate the performance of the proposed interleaved LCLC converter with precise current sharing over a wide input voltage range from 250 to 400 V. Using enhancement mode GaN and benefiting from the interleaving feature, a high conversion efficiency is achieved on a two-phase 1 kW LCLC converter with peak efficiency of 96.7%.

A Leg Phantom Model Based on the Visible Human Data for Intra-Body Communication

Intra-body communication (IBC) is an alternative method for communication of devices in body area networks. The existing research is mainly focused on on-body (OB) channel modeling, transceiver design, and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in vivo</i> experiments. However, the difficulty arises in carrying out long-term <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in vivo</i> experiments for investigating the human channel characteristics in OB or in-body (IB) IBC channels, since the repeatability of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in vivo</i> experiments shows inconsistency. In this paper, a multi-layer leg model with realistic shape was designed based on visible human data (VHD) images. Then, novel mixtures with the approximate conductivities of leg tissues were designed and used to fabricate leg phantoms, via several pairs of 3D-printed molds. Finally, the efficiency of the leg phantoms was validated by <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in vivo</i> experiments through the high similarity of voltage gain versus distance characteristic of the OB channel. Both conditions featured the same trend, that is, they decreased first and then stabilized. The leg phantom was adopted to explore the channel characteristics of the IB channel. The results indicate that the voltage gain versus distance curve of the OB to IB channel was nearly reciprocal. In summary, the VHD-based leg phantom provides a reusable experiment platform for the IBC research, especially for the case of implantable channels.

Comparative evaluation of a family of isolated Ćuk DC/DC converter with step‐up techniques

In this study, a comparative evaluation of a family of isolated Cuk DC/DC converter with step-up techniques is presented. The voltage gain techniques are the reduced redundant power processing and the voltage multiplier. In addition, a detailed comparative analysis of the converters is showed. This comparison comprises features, such as the principle of operation, voltage gain curves, voltage and current stresses, design methodology, and estimated losses. By these comparisons, the main features and constraints of the analysed converters are identified. Four 200 W prototypes were constructed and evaluated in the laboratory. The isolated Cuk converter with voltage multiplier showed the best performance and a peak efficiency of 95.86%.

Differential Equation Model of the LLC Resonant Converter in the Ideal Case

The LLC resonant converter has been widely used in direct current (DC) power supply applications. However, fundamental harmonic approximation or other simplified analyses will introduce inevitable deviations. Therefore, the differential equation model with numerical solution of the LLC converter is proposed in this paper based on the operational principle of the ideal case. In order to solve the differential equation, initial values need to be substituted. The accurate LLC model based on time interval analysis is very complicated and cannot be used. In this paper, solution methods of the initial values corresponding to different switching frequencies are proposed. The initial values can be solved conveniently. Furthermore, the voltage gain curve is modified by the idealized analysis. Lastly, all the above research is verified by PSIM simulation. The work is helpful to understand the operational principle of the LLC resonant converter.

A Novel Design Method for Resonance Network Parameters of Bi-directional CLLLC Resonance Converter

In order to solve the problem that there are many resonant elements and it is difficult to design the full bridge CLLLC resonant converter, an improved resonant network parameter design method combined with simulation analysis is proposed in this paper. Accurate DC voltage gain curves are obtained under different resonant parameters. A 3.5 kW simulation circuit is constructed based on the parameters of the proposed method. The simulation results confirm the correctness and feasibility of the proposed improved design method.

A Family of Step-Up Series–Parallel Dual Resonant Switched-Capacitor Converters With Wide Regulation Range

In this paper, a family of new step-up series–parallel dual resonant switched-capacitor converters (SP-DRSCs) is proposed to extend the conversion ratio for high step-up applications. The converters feature a wide gain range, continuously adjustable, and enhanced light-load voltage regulation. All flying capacitors operate in resonance, eliminating high transient current spikes and charge sharing losses. Thus, zero-current-switching (ZCS) turn- on for all transistors and ZCS turn- off for all diodes are achieved. A comprehensive analysis of the operation principle, voltage-gain curves, stable regulation range, and voltage and current stress is given. An analytical method to quantify the passive component volume for the group of step-up dual resonance switched-capacitor converters is presented. Further design considerations to optimize the passive component volume of the proposed SP-DRSC and the effect of bulky bypass capacitors on the volume are discussed.

A Novel Dual Integrated LLC Resonant Converter Using Various Switching Patterns for a Wide Output Voltage Range Battery Charger

This paper proposes a novel dual integrated LLC resonant converter (DI-LRC) with a wide output voltage range using various switching patterns. The primary side of the proposed DI-LLC converter consists of two resonant tanks and six switches, while the secondary side consists of a six-pulse diode rectifier. Depending on the switching pattern of the primary switch, the DI-LRC converter is performed by single full-bridge operation with a voltage gain of 1, series-connected full-bridge operation with a voltage gain of 0.5, series-connected half bridge operation with a voltage gain of 0.25, and parallel-connected full-bridge operation with a voltage gain of 2. Accordingly, the proposed DI-LRC converter has four voltage gain curves with different variations and achieves a wider output voltage range than the conventional single voltage gain curve in a given operating frequency range. In this paper, the equivalent circuits derived for each switching pattern are proposed to analyze the operating characteristics of the proposed converter according to each switching pattern, and each Q factor and voltage gain are calculated based on the analyzed equivalent circuit. The performance of the proposed converter and switching pattern is verified using the simulation and experimental results of the prototype battery charger, which is designed to be 4-kW class.

Multi-Resonance-Core-Based Dickson Resonant Switched-Capacitor Converters With Wide Regulation

The Cuk dual resonance core (DRC) realizes overlapped dual resonance to regulate its output voltage. However, the DRC configuration was only applied to the Fibonacci switched-capacitor converter (SCC), series–parallel SCC, and voltage doubler. In this paper, the Cuk DRC is modified and then is extended to the Dickson SCC to form a multi-resonance-core-based (MRC) Dickson resonant switched-capacitor converter. All charging and discharging loops achieve soft charging, and so the inherent capacitor charge sharing loss and the high current transient spikes are eliminated. The modular configuration makes the MRC Dickson easy to be extended to a higher voltage level. The on -time fixed frequency modulation is adopted, all transistors being turned on with zero-current-switching (ZCS) operation and all diodes being turned off with ZCS operation. Most importantly, the conversion ratio of the MRC Dickson can be regulated continuously, widely, and efficiently even at light load condition, which is a huge advantage over the traditional Dickson SCC with limited control headroom. A comprehensive analysis of the operation principle, voltage-gain curve, component stress analysis, and output characteristic is provided. The converter operation principle and regulation capability were verified by both simulation and experiment.

Effects of Secondary Leakage Inductance on the LLC Resonant Converter

It is quite often to utilize the transformer leakage inductance in the resonant tank of the LLC resonant converter to allow for a drastic reduction in the converter cost, weight, size, and volume. The effects of the secondary leakage inductance on the operation of the LLC resonant converter are not well discussed in the relevant literature, and it is the purpose of this paper to give an insight into these effects. The contribution of this paper lies in the following: first, highlighting that it is not always an accurate assumption to consider that the values of the primary and secondary leakage inductance are identical, specifically in asymmetric magnetic core structures. Second, it has been disclosed that the well-known coupling factor ( k 12) cannot properly express the unequalized leakage inductance distribution in the proposed asymmetric transformer. Therefore, the authors bring the primary coupling factor ( k 1) and secondary coupling factor ( k 2) into practice to appropriately express the unequalized leakage distribution on the primary and secondary windings, which can be controlled by the allocation of the relevant winding with respect to the air gap, utilizing the noise absorber, and changing the distance between the winding. Several transformer prototypes had been built and experimentally tested to validate these hypotheses. Third, it has been observed that the transformer voltage gain and efficiency can be improved when the transformer leakage inductance is concentrated on the secondary side to avoid the voltage drop inflicted by the relatively large value of the magnetizing current $(i_{m})$ , especially at the light load condition. Fourth, it has been reported that in a transformer structure with a concentrated value of leakage on the secondary side would decrease the resonant tank input impedance, vertically widen the voltage–gain curve of the converter, and eventually increase the frequency control bandwidth with respect to the load variation. Transformer prototypes had been constructed and tested in a 390 V/12 V–220 W LLC resonant converter to evaluate the proposed analysis.

A Family of Step-Up Resonant Switched-Capacitor Converter With a Continuously Adjustable Conversion Ratio

In this paper, a family of step-up resonant switched-capacitor converters (RSCs) with a continuously adjustable conversion ratio is proposed based on the Cuk dual-resonance core (DRC) featuring two resonant paths. By adopting the on-time fixed frequency modulation, the two resonant paths can conduct simultaneously and satisfy the charge balance of the flying capacitor during the overlapping period. As a result, the conversion ratio—upper bounded by two determined by the circuit configuration—can vary continuously and efficiently even at the light load condition (1/10 of the rated power). A comprehensive analysis—the operation principle, voltage-gain curve, and voltage/current stresses—about the DRC is given. In addition, the Cuk DRC was extended to the series–parallel switched-capacitor converter (SCC), Fibonacci SCC, and voltage doubler to form a family of step-up RSCs, whose voltage-gain curves of different topologies are derived. Moreover, a characteristic comparison between the Cuk DRC and the traditional “direct” and “indirect” resonant core is given. Then, a 48 to 62–94.6 V resonant core with peak efficiency 97.8% and maximum power 120 W under the open loop condition was built. The analyses were verified by both experimental and simulation results.

A Novel D-CLT Multi-Resonant DC-DC Converter with Reduced Voltage Stresses for Wide Frequency Variation Applications

In this paper, a dual-capacitor-inductor-transformer (CLT) (D-CLT) soft-switching dc–dc converter has been proposed. Combining the multiresonant technology, the converter employs two high-frequency transformers in the resonant tank and exhibits desirable characteristics. The fundamental and the third-order harmonics can be utilized to transfer active power simultaneously. The share of third harmonic is larger than first component. Thus, the converter can use the 100-kHz controlling signals to mainly transfer the 300-kHz active power, which makes it easier to realize high power density. Moreover, the available range for the third power delivery is expanded as well. A resonant zero point is introduced into the voltage gain curves. It ensures broadened voltage gain range (from zero to the maximum) and good protection for overcurrent issue. Then, improved soft-switching performances have been achieved: All the switches achieve the zero-voltage-switching (ZVS) turn- on , whereas all the diodes obtain the zero-current-switching (ZCS) turn- on and quasi-ZCS turn- off . Switching losses are constrained to the minimum. To verify the feasibility of the proposed converter, a 330-W prototype is established and tested. The results demonstrate the experiments match well with the theoretical analyses. The peak efficiency has reached 95.2%, although a high-loss diode bridge is adopted.