Constant Current Characteristics Research Articles

An Economical DWPT System With Mutual Compensation of Segmented Power Supply Rails Based on LCL Topology

For high-power, long-mileage dynamic wireless power transfer (DWPT) system, its economy and adaptability to complex working conditions are the main factors limiting its popularization and application. In this paper, the compensation and power supply of segmented rails are studied, and a DWPT system with mutual compensation of segmented power supply rails based on LCL topology is constructed. By multiplexing components, the number, cost and volume of devices are reduced, and the economy of the system is improved. The power supply topology is optimized to achieve constant-current characteristics over a wide load range to generate a stable high-frequency magnetic field in space and avoid short-circuit current induced by mutual coupling of adjacent rail. The resonant control conditions of the system are derived, and a phase shift control method based on the three-leg inverter is proposed to realize the full range regulation of transmitter current and output power, and improve the adaptability of the system. The characteristics of the proposed DWPT system have been verified by an experimental prototype.

Modular Stacked Multiport Wireless Energy Interconnection System With Virtual AC Bus and Its Power Flow Control Strategy

This article proposes a modular stacked multiport wireless energy interconnection (WEI) system with a virtual ac bus for multisource and multiload wireless power transfer (WPT) applications, which has the following advantages. 1) It can serve as an interface for WPT among multiple sources and loads. 2) Bipolar coils are adopted to eliminate the undesired cross-coupling among multiple coils, which simplifies the complexity of system modeling and power flow control. 3) The relay coil with constant current characteristics is introduced as a virtual ac bus, from which the derived multicoil structure provides the bidirectional channel for power transfer between any two ports. 4) System applicability and scalability are greatly enhanced due to the modularization of coils, power converters, and compensation circuits. For power flow control, the hybrid phase-shifted control method matched with the WEI system is applied, in which the power flow direction is determined by the external phase-shifted angles between ports, whereas the power values are regulated by the internal phase-shifted angles. Furthermore, the peak value of the current of the virtual ac bus, as an intermediate control variable, is controlled to be constant; thus, distributed control can be further realized. Finally, a four-port experimental prototype was built and experiments were carried out under different operating conditions. The efficiency curves and loss distribution, as well as the tolerance analysis of coil misalignments, are given. From the experimental results, the effectiveness of the proposed system architecture and its power flow control strategy is verified.

A Self-Tuning S/S Compensation WPT System Without Parameter Recognition

In the application of wireless power transfer system, parameter drift of resonant tank is a general situation which induces natural frequency of primary side or secondary side deviates from switching frequency. This frequency deviation phenomenon will deteriorate load-independent constant current characteristics and decrease output power capacity for an S/S compensation system. This article illustrates the problems caused by frequency deviation through output characteristic analysis and addresses them by a self-tuning method based on switched capacitors (SCs). The proposed self-tuning method requires no resonant parameters such as compensation capacitance and coil self-inductance in advance. Primary and secondary natural frequencies can be both tuned to switching frequency continuously by SCs. The proposed method is verified by a simulation and a 500 W S/S compensation experimental prototype. After completion of self-tuning process, load-independent constant current characteristic is recovered and the output power capacity is boosted, which are in consistent with the theoretical analysis of system output characteristics. The proposed method is also applicable to <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC</i> /S and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC</i> / <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC</i> topologies.

출력 전류 평형을 위한 커플드 인덕터를 적용한 다중 출력 LED 조명용 LLC 공진형 컨버터 분석

LED(Light Emitting Diode) lighting with a long life span and high efficiency is a light source used in various fields. In order to drive these LED modules, a PFC converter and a DC-DC converter capable of controlling the current constant are required. Conventional single output LED converters can achieve high efficiency and high power density, but there is a problem that high capacity and low utilization make maintenance difficult. In order to output a plurality of LED lighting, constant current characteristics are maintained for each output, and an independent converter of an LED protection circuit is required for each channel. Also, Multi-output LED converters have a problem that other LED lighting does not operate normally when one of the output LED lighting fails. Therefore, in this paper, it is suggested that multiple LED lighting can be driven without problems by applying 4 coupled inductor to one LLC resonance converter, and that other LED lighting can operate normally even if the output LED lighting fails.

An Improvement of SNR for Simultaneously Wireless Power and Data Transfer System with Full-Duplex Communication Mode

The power interference is always inevitable in the simultaneous wireless power and data transfer (SWPDT) system resulting in the lower signal to noise rate (SNR) and may cause the failure of communication. Besides, the interference between bidirectional data source is also the problem during the full-duplex communication. To solve these problems, in this article, an improvement of SNR for SWPDT system with full-duplex communication mode is proposed. In the power transfer channel, the double-sided LCCL compensation topology is selected due to its good performance of blocking the power interference on data transmission. Besides, the constant current characteristic of primary coil could guarantee the stability of power transmission. In the data transfer channel, a novel data transmission based on the dual-resonant structure is proposed to suppress the ipsilateral interference, and the full-duplex communication is achieved by two different frequencies. An optimization method of power and data transfer channel to improve SNR further is proposed after the analysis on interferences of power transmission and ipsilateral data source. Finally, the feasibility of proposed topology and the correctness of the parameter design method are verified by the simulation and experimental results.

Research on Constant Current Technology of High Current Power Amplifier for Relay Protection Test Device

In order to provide more accurate and consistent reference current for power system under different loads, the constant current performance of the high-current power amplifier is studied. This paper presents a circuit topology suitable for high-current power amplifier circuits, and analyses the key factors that affect its constant current characteristics. It is found that resistance matching plays a decisive role in the constant current characteristics. Through quantitative analysis and verification, the boundary conditions of the output resistance of the high-current power amplifier under the specified resistance accuracy are also found. Then based on Monte Carlo analysis and worst-case analysis, the previous theoretical derivation afterwards is conducted. Finally, an effective method of resistance matching is brought forward, which is authenticated in the contrast test later.

LCL-T resonant network-based modular multi-channel constant-current LED driver analysis and design

Multiple output LED drivers are necessary to achieve better performance and higher reliability in street lighting, tunnel lighting and LCD background lighting applications. Based on LCL-T constant-current characteristics, a modular multiple output LED driver is proposed in this paper. The LCL-T rectifiers are connected to the same voltage bus and work like current sources. However, since there are much higher voltage harmonics in the AC square bus voltage, it is very important to quantitatively analyze how these harmonics influence the precision of the output currents. In addition, all of the switches can achieve Zero Voltage Switching (ZVS) by proper design of the LCL-T network. Finally, a 200-W prototype with five channels is established with an efficiency of 92.25%.

Analysis and design of modular open‐loop LED driver with multi‐channel output currents

In view of some applications for red green blue (RGB) light-emitting diodes (LEDs), a modular multi-channel constant-current LED driver is getting more important to obtain desirable colour and brightness. A multi-channel constant-current LED driver is proposed according to the constant-current characteristics of the passive LCL-T resonant network, which is composed of one high-frequency half-bridge inverter and as many passive LCL-T resonant rectifiers as the number of output channels. Only one passive resonant rectifier is added to increase a constant-current output channel, thus, it is easy to achieve multi-channel constant-current output as needed. In practical applications, the control can be simplified and the reliability can be improved in the open-loop mode. However, any change of input and output voltage would cause a certain fluctuation in the output current considering the high-order harmonic components in the open-loop mode. To this end, the precise solution of the actual output current is obtained in the paper. The quantitative parameter design has been completed according to the desirable current to meet the output constant-current accuracy within the given input and output. Finally, a 120-W prototype with three different constant-current outputs is built to verify the correctness of theoretical analysis.

Enhanced Howland-based constant current source for soil EC&lt;SUB align="right"&gt;a measurement

In the present work, enhanced Howland current source-based voltage controlled current source (VCCS), used in four probe Wenner array technique to measure apparent electrical conductivity (ECa) of soil is reported. The distortion in the output signal is negligible and current is maintained constant. To check circuit reliability for constant current characteristics across varying standard load resistance, voltages were measured to calculate value of current, which was then compared with theoretically calculated value. The performance of proposed circuit was studied using TINA-TI software simulations and it was found that proposed source is capable of providing a constant current over the entire range of resistance (0.5 Ω to 20 kΩ) within very low frequency range; with an error less than 5%, and an average error of 0.9466%, which is within acceptable tolerance in present application.

A Voltage-Feed High-Frequency Resonant Inverter With Controlled Current Output as a High-Frequency AC Power Source

A current-based power distribution is presented for the applications of high-frequency ac power distribution system (PDS). Comparing with the traditional voltage-based counterpart, the current-based system can be applied into some specific applications, such as high-voltage gate-driving system, contactless power transmission, etc. A modified resonant topology based on LCL-T tank is proposed to implement high-frequency current source. The effective magnitude control and high conversion efficiency are both achieved. First, the proposed topology is examined with circuit principle, operational cycle analysis, and soft-switching description. Second, the phase-shifted control scheme is explored to calculate the equivalent resonant capacitor of LCL-T resonant tank, as well as the relations between current gain ratio and phase-shifted angle control are discussed in depth. Finally, the simulation model and experiment prototype are implemented with rated peak current of 2 A, rated output frequency of 30 kHz, and rated output power of 50 W. The experimental results in accordance with simulation prove that the constant current characteristics are maintained with high conversion efficiency. Hence, the proposed circuit topology and control scheme are a feasible realization of current source that is used to feed high-frequency PDS.

High Power Factor Light-emitting Diode Driver on Digital Signal Processor Without Electrolytic Capacitor for High-power Lighting

—Electrolytic capacitor is a key factor that limits the life-time of the driver in a high-power light-emitting diode (LED) lighting. This article presents a high-power LED lighting driver on a digital signal processor without an electrolytic capacitor. The driver is composed of three stage circuits. The first stage is the boost power factor correction converter to achieve a high power factor. As it does not use an electrolytic capacitor, the output voltage ripple is larger, which directly affects the overall performance of the LED driver. Consequently, it must be optimized through the second and third stages. The second stage is the two-output LLC (Double inductance and capacitance) resonant converter, which is driven by a digital signal processor. This stage provides galvanic isolation and reduces voltage. The third stage is the two-input buck converter based on digital signal processor control that reduces the low-frequency ripple generated from the first two stages. Moreover, the regulation of each LED string current is achieved at this stage. The simulation and experimental results show that this LED lighting driver can achieve a high power factor and good constant current characteristics.

Double-Switch Equalizer Using Parallel- or Series-Parallel-Resonant Inverter and Voltage Multiplier for Series-Connected Supercapacitors

A double-switch cell voltage equalizer using a parallel-resonant-inverter (PRI) or series-parallel-resonant inverter (SPRI) and voltage multiplier is proposed for series-connected supercapacitors (SCs), such as electric double-layer capacitors (EDLCs) and lithium-ion capacitors. The double-switch operation without the need for a multiwinding transformer offers simpler circuitry as well as better modularity than conventional equalizers requiring multiple switches and/or a multiwinding transformer. Furthermore, the inherent constant current characteristic of the PRI/SPRI at a fixed frequency, not only removes the need for feedback control to limit currents under desired levels but the proposed equalizer can also operate safely, even when some cell voltage is 0 V. Detailed operation analyses were separately performed for the voltage multiplier and PRI/SPRI, and a dc equivalent circuit for the proposed equalizer was mathematically derived. A 10-W prototype for 12 cells connected in series was built, and an experimental equalization test was performed for EDLCs from an initially voltage imbalanced condition. Voltage imbalance of the series-connected EDLCs was successfully eliminated by the equalizer, demonstrating the equalization performance of the proposed equalizer.

SOI CMOS Voltage Multiplier Circuits with Body Bias Control Technique for Battery-Less Wireless Sensor System

Voltage multiplier (VM) circuits for RF (2.45GHz)-to-DC conversion are developed for battery-less sensor nodes. Converted DC power is charged on a storage capacitor before driving a wireless sensor module. A charging time of the storage capacitor of the proposed VM circuits is reduced 1/10 of the conventional VM circuits, because they have constant current characteristics owing to self-control of body bias in diode-connected SOI MOSFETs. The wireless sensor system composed of the fabricated VM chip and a commercially available sensor module is operated using an RF signal of a wireless LAN modem (2.45GHz) as a power source.

GMA welding of 9% Ni steel in pure argon shielding gas using coaxial multilayer solid wire

A coaxial multilayer solid wire was developed to perform stable gas metal arc welding of 9% Ni steel in pure argon shielding gas. This wire has a double structure consisting of an inner and outer part with different compositions. The average composition of this wire is similar to that of the wire for solid welding wire of 9% Ni steel. A potassium compound was added to the area between the inner part (center wire) and the outer part (hoop) of the wire to stabilize the welding in pure argon shielding gas. First, the wire melting behavior was observed with a high-speed video camera system. Then, the effect of potassium was confirmed experimentally. Next, the relation between the amount of potassium and the length of the column of liquid molten metal (CLM) was analyzed. The coaxial multilayer solid wire which contained more than 0.001 wt% potassium was able to shorten the CLM. Lastly, the welding was carried out in the V-groove to assess the ductility and strength of joints. The optimized coaxial multilayer solid wire that was developed and a constant current characteristics power source were used to obtain acceptable weld joints in pure Ar shielding gas.

高圧水銀ランプ同相形点灯回路の定電流特性に関する考察

高圧水銀ランプ同相形点灯回路の定電流特性に関する考察

Atomic force and scanning tunneling microscopy study of current-voltage properties of TiB2 microcontacts

Scanning probe microscopy was used to investigate electrical microcontacts in the nanometer range. With the atomic force microscope current flowing through the contact as well as current-voltage characteristics of the contact as a function of the force acting on the contact itself were recorded. With the scanning tunneling microscope current-voltage characteristics and voltage at constant current characteristics were measured as a function of the contact position. From these experiments we conclude that a TiB2 microcontact can sustain a maximum voltage of about 0.1–1 V before melting. These results were confirmed by a theoretical model. The implications for the functioning of so-called positive temperature coefficient current limiting devices based on filled polymers is discussed.

High-efficiency power-feed equipment using a series-resonant constant-current converter for use in submarine optical-fiber transmission systems

The saturable-reactor constant-current converter is widely used in cable transmission systems. It has excellent constant-current characteristics, but it is difficult to realize high efficiency due to the large loss in the switching element and the large driving loss of the saturable reactor. Consequently, it cannot be applied to submarine optical-fiber transmission systems, where a large current feed is required. For a constant-current converter to be used instead of the forementioned device in the submarine optical-fiber transmission system, the current variation must be less even in the transient state (the constant-current characteristic must be realized without the control) in addition to achieving high efficiency. This study describes a new constant-current converter design, a series-resonant converter based on the discontinuous current mode, which has excellent constant-current characteristics as well as small driving loss and switching loss. The series-resonant converter is analyzed first, and it is shown that a constant-current characteristic is realized without control. An approach to improvement of efficiency which decreases the on-period loss is described. The proposed high-efficiency technique is applied to the submarine optical-fiber constant-current converter. A technique of reducing the effective current, which is useful in reducing loss in the on-period, is considered. A design method for the maximum normalized frequency ratio is presented. In addition, in the current-feedback driving circuit, which is considered to minimize the loss of the transistor, the minimum-loss driving condition for the transistor is described. As a result, the efficiency of the main circuit of the constant-current converter is improved to 93 percent. © 1997 Scripta Technica, Inc. Electron Comm Jpn Pt 1, 80 (5): 87–97, 1996

High‐efficiency power‐feed equipment using a series‐resonant constant‐current converter for use in submarine optical‐fiber transmission systems

The saturable-reactor constant-current converter is widely used in cable transmission systems. It has excellent constant-current characteristics, but it is difficult to realize high efficiency due to the large loss in the switching element and the large driving loss of the saturable reactor. Consequently, it cannot be applied to submarine optical-fiber transmission systems, where a large current feed is required. For a constant-current converter to be used instead of the forementioned device in the submarine optical-fiber transmission system, the current variation must be less even in the transient state (the constant-current characteristic must be realized without the control) in addition to achieving high efficiency. This study describes a new constant-current converter design, a series-resonant converter based on the discontinuous current mode, which has excellent constant-current characteristics as well as small driving loss and switching loss. The series-resonant converter is analyzed first, and it is shown that a constant-current characteristic is realized without control. An approach to improvement of efficiency which decreases the on-period loss is described. The proposed high-efficiency technique is applied to the submarine optical-fiber constant-current converter. A technique of reducing the effective current, which is useful in reducing loss in the on-period, is considered. A design method for the maximum normalized frequency ratio is presented. In addition, in the current-feedback driving circuit, which is considered to minimize the loss of the transistor, the minimum-loss driving condition for the transistor is described. As a result, the efficiency of the main circuit of the constant-current converter is improved to 93 percent. © 1997 Scripta Technica, Inc. Electron Comm Jpn Pt 1, 80 (5): 87–97, 1996

Characteristics on PWM CSI-induction motor drive system with utility interactive photovoltaic generation

This paper proposes a PWM current source inverter-induction motor drive system with photovoltaic generation. Solar cells are inserted in dc link to obtain constant current characteristics and they are connected to the utility system by using a PWM converter. The PWM converter is controlled to obtain the maximum output photovoltaic (PV) power. The PWM inverter supplies sinusoidal currents for an induction motor which is driven by constant V/f control. A pulsewidth control is utilized in the inverter section because of constant dc link current caused by a peculiar V-I characteristics of solar cells. In the presented system, the PV power is not only used for the inverter-induction motor drive but also flowed into the utility system. The experimental results in the steady state show that the proposed system has sinusoidal current with unity power factor in the utility system, the maximum output PV power, and sinusoidal current/voltage for a motor. The demonstrated results for the separation of the utility system or the motor from the converter-PV-inverter system are given.

Characteristics on PWM CSI-Induction Motor Drive System with Utility Interactive Photovoltaic Generation.

This paper proposes a PWM current source inverter-induction motor drive system with photovoltaic generation. Solar cells are inserted in dc link to obtain constant current characteristics and they are connected to the utility system by using a PWM converter. The PWM converter is controlled to obtain the maximum output photovoltaic (PV) power. The PWM inverter supplies sinusoidal currents for an induction motor which is driven by constant V/f control. A pulsewidth control is utilized in the inverter section because of constant dc link current caused by a peculiar V-I characteristics of solar cells. In the presented system, the PV power is not only used for the inverter-induction motor drive but also flowed into the utility system. The experimental results in the steady state show that the proposed system has sinusoidal current with unity power factor in the utility system, the maximum output PV power, and sinusoidal current/voltage for a motor. The demonstrated results for the separation of the utility system or the motor from the converter-PV-inverter system are given.