Series Resonant Capacitor Research Articles

Development of 80-kW High-Voltage Power Supply for X-ray Generator

This paper describes the development of an 80kW high voltage power supply (HVPS) to drive an X-ray tube. Since the developed HVPS is based on an LCC resonant converter with a symmetrical bipolar voltage multiplier (SBVM), it shows many superior features such as soft switching capability and low voltage imbalance among stages. In addition, the proposed circuit has high power density because a series resonant capacitor is removed by using a method converting the SBVM into capacitors and the full-wave rectifier. Furthermore, a suggested transformer achieves high insulation performance and effective winding area utilization by applying half of the output voltage to the core. The detailed design based on the fundamental harmonic approximation (FHA) is presented for the practical use of the LCC resonant converter with the SBVM in high voltage and high power applications. Also, some significant issues in the implementation are addressed. The performance of the developed HVPS is verified by simulations and experimental results.

A Unified Common Inductor and Common Capacitor Current Sharing Method for Multiphase LLC Converter

The common inductor and common capacitor current sharing technologies with excellent current sharing capabilities and low-cost have attracted a lot of attention in recent years. However, these methods have certain limitations. To solve this problem, this paper proposes a unified common inductor common capacitor scheme. Firstly, the existing common inductor and common capacitor methods are reviewed. Based on the first harmonic approximation (FHA) analysis method, the limitations of these schemes are analyzed, and we find that the current sharing performance is not well when the multi-resonant parameters are mismatched, which will cause the one-phase to bear more power, even over-powered and damaged. To realize a better current sharing of multi-phase LLC modules, a unified common inductor common capacitor method is proposed in this article, where the series resonant inductors and resonant capacitors in each LLC converter are connected in parallel. The current sharing performance of the proposed method is analyzed by the FHA analysis method, and the proof-of-concept prototype with a 480W 24V two-phase LLC converter was built to verify the effectiveness of the proposed method. Simulation and experimental results show that the current sharing error of the proposed method is 2.1% under half load and 0.9% under full load.

Research on Phase-Shifted Full-Bridge Circuit Based on Frequency and Phase-Shift Synthesis Modulation Strategy

The full-bridge converters usually use transformer leakage inductance and parallel resonant capacitors to achieve smooth current commutation and soft switching functions, which can easily cause problems such as energy leakage and significant duty cycle loss. This paper designs a novel full-bridge zero-current (FB-ZCS) converter with series resonant capacitors and proposes a frequency and phase-shift synthesis modulation (FPSSM) control strategy based on this topology. Compared with the traditional parallel resonant capacitor circuit, the passive components used are significantly reduced, the structure is simple, and there is only a slight energy loss. By controlling the charging time of the capacitor, it can be achieved without additional switches or auxiliary circuits. The automatic control of capacitor energy based on input current addresses the low efficiency of the traditional control strategies. This paper introduces its principle in detail and verifies it through simulation. Finally, an experimental prototype was built further to demonstrate the feasibility of the theory through experiments. The module can be applied to a photovoltaic DC collection system using input parallel output series (IPOS) cascade to provide a new topology for large-scale, long-distance DC transmission.

The Partial Discharge Field Test of 1000kV Shunt Reactors

Aiming at the insulation performance field diagnosis of 1000kV shunt reactors, the series resonant withstand voltage test equipment is developed. The test equipment mainly consists of the frequency conversion power supply, the excitation transformer, the series resonant capacitor, the wave blocking resistor and the voltage divider. The resonant frequency is between 30 and 300 Hz, the rated voltage is 1200kV, and the capacity is 1000 kW. During the test, the discharge is monitored at the high voltage bushing terminal and the 1000kV reactor insulation is analyzed. By using the developed test equipment, the 1000kV reactor in 1000kV Xuyi Station is tested, which verifies the validity of the on-site partial discharge measurement test.

Resonant Frequency and Load Voltage in Voltage-Source Type Wireless Power Transfer Circuits using Series and Parallel Resonant Capacitors

Resonant Frequency and Load Voltage in Voltage-Source Type Wireless Power Transfer Circuits using Series and Parallel Resonant Capacitors

Active cell balancing of Li-Ion batteries using single capacitor and single LC series resonant circuit

In this paper a novel single series resonant tank and capacitor converter based voltage balancing circuit for series supercapacitor string and battery cells string is presented. It recognizes the balancing circuit which recovered the maximum energy and zero voltage gap between cells in a series supercapacitor system or battery system. This balancing circuit not only inherits the improvement of conventional single series resonant converter based balancing system, but also recovers the drawback of switching loss, conduction loss and voltage gap between cell strings. All MOSFET switches are controlled by a pair of complementary PWM signals. Also the resonant tank and parallel capacitor operate between the two mode of charging and discharging. This voltage balancing circuit has shown promising result to be used in battery management system.

Design of a 5.4 kJ/s three-phase resonant converter based on a lithium polymer battery

This paper describes the design and manufacture of a 5.4 kJ/s three-phase resonant converter based on a 22 and 44 V lithium polymer (LiPo) battery as a high density power supply. Using the low LiPo battery input voltage generates a relatively high current that causes problems such as a large current burden on the used components and high peak-to-peak noise when the switch is turned off. To resolve such problems, the three-phase resonant converter in this work is used to handle the high input current. In the three-phase inverter structure, the amount of current flowing in a single switch is smaller than that of a single-phase current. In addition, the delta-star structure is intentionally introduced to reduce the turns ratio which helps to decrease the current on the transformer's primary side when the same output power is required. Furthermore, components such as series and parallel resonant capacitors are placed on the secondary side of the transformer, which have a high voltage and low current. These voltage and current conditions of the secondary side are more appropriate for commercialized film capacitors, which normally use series and parallel resonant capacitors because the film capacitors have been manufactured with high voltage and low current rated capacity. In terms of the design procedure, the used delta-star three-phase resonant circuit is redrawn on the secondary side of the transformer as a single-phase resonant equivalent circuit for the three-phase resonant converter design. Based on the simplified design, the operating mode and simulation of the 22 and 44 V LiPo battery-based chargers were analyzed, and the comparison of the resistor and capacitor load test results for the two chargers verifies both the aforementioned features and the performance of the proposed chargers using 300 and 150 A of the LiPo battery. The advantages are confirmed, and the capacitor bank is charged to 600 V for 80 ms, achieving power efficiencies of 82 and 92.5% for the 22 and 44 V based capacitor chargers, respectively.

A Modularized IPT With Magnetic Shielding for a Wide-Range Ubiquitous Wi-Power Zone

A wide-range ubiquitous wireless power environment, called a ubiquitous Wi-power zone, where any electric devices can be charged by three-dimensional (3-D)-omnidirectional wireless charging, is newly proposed in this paper. By virtue of the proposed direct-quadrature (DQ) transmitting (Tx) coils composed of multiple Tx modules with same size, a ubiquitous Wi-power zone having the transmitting (Tx) coils can be provided over wide-range 3-D space. In this area, a number of electric devices can be simultaneously charged during operation. Therefore, the proposed IPT is expected to be the next generation of wireless power transfer (WPT), as the internet of things (IoT), mobile devices, and sensor technologies evolve. For magnetic shielding behind the Tx coils and high power efficient operation of the proposed DQ Tx coils, providing an evenly distributed magnetic field, a conductive plate is adopted, and the effects of the conductive plate for the dipole coil structure were thoroughly evaluated by a 3-D FEM simulation. To create the proposed ubiquitous Wi-power zone, simulation-based optimum design procedures are established based on four design considerations and the optimized number of modularizations for the DQ Tx coils can be found by an optimum point of figure of merit (FoM). The DQ Tx module composed of the DQ Tx coils and series resonant capacitors was adopted as a standard unit of the proposed IPT so that different sizes and shapes of 3-D space can be utilized for universal use of the proposed ubiquitous IPT; hence, a general solution to create the proposed ubiquitous IPT is provided in this paper. A prototype 5 × 5 modularized IPT composed of 25 DQ Tx modules having the same size of ${\text{10 cm}} \times {\text{10 cm}}\times {\text{2 cm}}$ was fabricated and experimentally verified for a ${\text{1 m}}\times {\text{1 m}}\times {\text{0.7 m}}$ ubiquitous Wi-power zone. Experimental results showed that 95.5%, 92.1%, and 98.8% of high magnetic field uniformity for $z_{1}= {\text{25}}$ cm, 50 cm, and 75 cm, respectively, and 3-D omnidirectional wireless power delivery have been achieved; thus, meeting essential requirements for the proposed ubiquitous Wi-power zone. Nine Rx coils can be simultaneously charged with 14.2 W of total received load power and 8.2% power efficiency at $z_{1}= {\text{70}}$ cm.

Simple High Efficiency Full-Bridge DC-DC Converter using a Series Resonant Capacitor

This paper presents a simple high efficiency full-bridge DC-DC converter using a series resonant capacitor. The proposed converter achieves the zero voltage switching of the primary switches under a wide range of load conditions and reduces the high circulating current in the freewheeling mode using the leakage resonant inductance and the series resonant capacitor. Thus, the proposed converter overcomes the drawbacks of the conventional full-bridge DC-DC converter and improves its overall system efficiency. Its structure is simplified by using the leakage inductance of the transformer as the resonant inductance and omitting the DC output filter inductance. Also it can operate over a wide range of input voltages. In this paper, the operational principle, analysis and design example are described in detail. Finally, the experimental results from a 650W (24V/27A) prototype are demonstrated to confirm the operation, validity and features of the proposed converter.

High-Efficiency Contactless Power Transfer System for Electric Vehicle Battery Charging Application

In this paper, a contactless charging system for an electric vehicle (EV) battery is proposed. The system consists of three parts: 1) a high-frequency power supply from a full-bridge inverter with frequency modulation; 2) a loosely coupled transformer that utilizes series resonant capacitors for both the primary and secondary windings; and 3) a rectification output circuit that uses a full-bridge diode rectifier. With carefully selected compensation network parameters, zero-voltage switching can be ensured for all the primary switches within the full range of an EV battery charging procedure, which allows the use of low ON-state resistance power MOSFETs to achieve high-frequency operation and system efficiency. The design of loosely coupled transformer is simulated and verified by finite element analysis software. For a 4-kW hardware prototype, the peak dc–dc efficiency reaches 98% and 96.6% under 4- and 8-cm air gap conditions, respectively. The prototype was tested with an electronic load and a home-modified EV to verify the performance of constant current and constant voltage control and their transitions.

Analysis and Design Considerations of LLCC Resonant Multioutput DC/DC LED Driver With Charge Balancing and Exchanging of Secondary Series Resonant Capacitors

A new rectifier for multioutput LED driver is proposed based on a charge exchanging and balancing principle in the secondary resonant capacitors. Combined with common ground rectifier and LLCC resonant topology, a four-output dc-dc LED driver is proposed with minimum quantity of secondary charge balancing capacitors. In the LLCC topology, the secondary side resonant capacitors can be used as dc blocking and charge balancing capacitors. The proposed LED driver can automatically share the average output currents by the charge balancing and exchanging among secondary resonant capacitors. The operating principle and the brief design guidelines for the four-output LLCC resonant dc-dc converter are presented. The guaranteed current sharing capability of the proposed four-output LED driver is also analyzed thoroughly. Finally, a 150 W four outputs LLCC resonant dc-dc LED driver is built-up to verify the theoretical analysis.

Bang-Bang Charge Control for LLC Resonant Converters

This paper proposes a Bang-Bang Charge Control (BBCC) method for LLC resonant converters. Instead of switching frequency control, the BBCC method utilizes the series resonant capacitor voltage level to trigger the MOSFETs' switching actions. Advantages of the proposed method include fast dynamic performance and simple implementations. Small-signal analysis shows that the loop bandwidth can achieve around 1/6 of the switching frequency in all operating conditions. Experimental results show that 5 to 25 A load step transients are completed within only seven switching cycles at both 400- and 300-V input-voltage conditions. Practical considerations are also discussed in detail.

Analysis of the Charging Characteristics of High Voltage Capacitor Chargers Considering the Transformer Stray Capacitance

In this paper, the charging characteristics of series resonant type high voltage capacitor chargers considering the transformer stray capacitance have been studied. The principles of operation for the four operational modes and the mode changes for the four different switching frequency sections are explained and analyzed in the range of switching frequency below the resonant frequency. It is confirmed that the average charging currents derived from the above analysis results have non-linear characteristics in each of the four modes. The resonant current, resonant voltage, charging current, and charging time of this capacitor charger as variations of the switching frequency, series parallel capacitance ratio (<TEX>$k=C_p/C_s$</TEX>), and output voltage are calculated. From the calculation results, the advantages and disadvantages arising from the parallel connection of this stray capacitance are described. Some methods to minimize charging time of this capacitor charger are suggested. In addition, the results of a comparative test using two transformers whose stray capacitances are different are described. A 1.8 kJ/s prototype capacitor charger is assembled with a TI28335 DSP controller and a 40 kJ, 7 kV capacitor. The analysis results are verified by the experiment.

10 kW Contactless Power Transfer System for Rapid Charger of Electric Vehicle

A contactless power transfer system for charging electric vehicles requires a high efficiency, a large air gap, and a good tolerance to lateral misalignment and needs to be compact and lightweight. A double-sided winding 10 kW transformer based on a 1.5 kW H-shaped core transformer was developed for a rapid charger. Even though the transformer capacity was increased, the dimensions of the 10 kW transformer were almost the same as those of the 1.5 kW transformer. In this paper, the design concept for this 10 kW transformer and the results of experimental are described. The transformer was found to exhibit more than 94% efficiency with a mechanical gap of 70mm. Even for gap change and position change, an efficiency of over 92% was maintained. In a contactless power transfer system with a series resonant capacitor, the primary terminal voltage increases with increasing power. This overvoltage may lead to the problem of breakdown voltage of capacitor and the breakdown of winding insulation. To prevent such an overvoltage occurring, it is suggested that the primary winding and the series capacitor are split into two pieces or more respectively, and the split windings and capacitors are alternately connected in a series. Electric vehicles using a contactless power transformer for rapid charging would also uses normal charging. Therefore, the 10 kW transformer was designed to be compatible with the 1.5 kW transformer. Consequently, electric vehicles equipped with the 10 kW transformer can charge even using a 1.5 kW ground transformer, without decrease efficiency.

Moving pick‐up‐type contactless power transfer systems and their efficiency using series and parallel resonant capacitors

AbstractThe equivalent circuit, the efficiency, and the important characteristics of moving pick‐up type contactless power transfer systems are described. If the primary series capacitor and the secondary parallel capacitors are chosen correctly and the winding resistances are ignored, the equivalent circuit of the transformer with these capacitors becomes the same as an ideal transformer at the resonant frequency. This simple approximation helps to understand the phenomena occurring with load changes. Because the circuit analysis becomes simple, the approximate value of the power transfer efficiency can be derived. This paper describes the determination of the capacitor values, the derivation of the equivalent circuit and the efficiency, and test results. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 172(2): 47–54, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20970

Moving Pick-Up Type Contactless Power Transfer Systems and their Efficiency Using Series and Parallel Resonant Capacitors

The equivalent circuit, the efficiency, and the important characteristics of moving pick-up type contactless power transfer systems are described. If the primary series capacitor and the secondary parallel capacitors are chosen correctly and the winding resistances are ignored, the equivalent circuit of the transformer with these capacitors becomes the same as an ideal transformer at the resonant frequency. This simple approximation helps to understand the phenomena occurring with load changes. Because the circuit analysis becomes simple, the approximate value of the power transfer efficiency can be derived. This paper describes the determination of the capacitor values, the derivation of the equivalent circuit and the efficiency, and test results. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 172(2): 47–54, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20970

直列および並列共振コンデンサを用いた非接触給電システム

A new contactless power transfer system using series and parallel resonant capacitors is described. If the primary series resonant capacitor and the secondary parallel resonant capacitor are chosen appropriately, the equivalent circuit of the transformer with these capacitors becomes very simple at the resonant frequency. Ignoring the winding resistance and the core loss, the equivalent circuit is the same as an ideal transformer. Therefore, the circuit analysis is easy, and if the input voltage is constant, the output voltage is also constant regardless the output current. Fig. 1 shows the configuration of our contactless power transfer system. The ferrite-core transformer with 10~20 mm gap is drived by 10 kHz rectangular waveform inverter. As the winding resistance and the ferrite-core loss are very small, the simplified equivalent circuit of Fig. 2 can be used. The parallel capacitor Cp at the secondary winding and the series capacitor Cs at the primary winding are determined as following values. 1 ω0CP = xP = x0 + x2 · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · (1)

A Novel Type of Series Load Resonant High Frequency Soft Switching Inverter with Phase Shift Control Scheme

The voltage source full bridge series load resonant high frequency soft switching inverter using pulse phaseshift modulation (PSM) strategy is proposed, which can operate ZVS in the left hand side bridge leg and ZCS in the right side bridge leg. This inverter using IGBTs employs two passive components and does not need any additional auxiliary circuit for the active power switch to achieve soft switching commutation, and it has wide soft switching operation region from full power to 3% light power. Furthermore, constant frequency power regulation that is required for induction-heating power applications is introduced on the basis of PSM. In this paper, steady state switching modes of the inverter treated here and its power regulation scheme by PSM are described under a soft switching scheme. Because the proposed inverter can operate at series resonant frequency of series resonant circuit under soft switching condition, it is easy to design the value of series resonant capacitor. The design methods of loss-less snubbing circuit components for soft switching are described to reduce switching losses effectively. The feasible experiment of the proposed inverter is implemented to demonstrate the power regulation performance of proposed high frequency inverter, high efficiency 97.6% at full power condition is obtained.

Extended-range linear magnetostrictive motor with double-sided three-phase stators

The authors have developed a novel extended-range linear magnetostrictive motor using the peristaltic motion of a laminated Terfenol-D (Tb/sub 0.3/Dy/sub 0.7/Fe/sub 2/) element. This element migrates in the opposite direction of the traveling magnetic field generated by prevailing three-phase armature commutation. The actuator mechanical design is in an open structure in order to allow easy assembly and access to internal actuator components. Eight sets of Belleville washers guarantee uniform squeeze preload in spite of wear, thermal expansion, or motion of the moving element. We incorporated a laminated Terfenol-D slab in this actuator to reduce the eddy current, leading to high-frequency high-speed operation. We have also designed and constructed the power electronics and control units for the magnetostrictive actuator's open-loop and closed-loop operations. With a series-resonant capacitor, we were able to achieve a near-unity power factor and decrease the reactive power requirement by a factor of 20. The magnetostrictive motor has demonstrated 12-mm/s speed at excitation frequency of 1600 Hz, and shown 140-N load capacity. The effective travel range of the present motor is 25 mm, and can be extended further. This linear magnetostrictive motor shows great potential in high-force precision positioning applications such as automotive actuators, robotics, and flight control surface actuators.

Class E resonant rectifier with a series capacitor

An analysis and experimental results are given for a Class E resonant low dv/dt rectifier with a series resonant capacitor. The circuit contains two resonant components: a capacitor and an inductor. It is driven by a sinusoidal voltage source whose amplitude must be controlled to obtain a constant-voltage output. The rectifier exhibits a peculiar behavior because its equivalent input reactance changes discontinuously from inductive to capacitive when the load varies from infinity to zero. Design equations are derived using Fourier series techniques. The theory is compared with experimental results obtained for the rectifier operating at 1 MHz ac input and 5 V dc output.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>