Load Current Variation Research Articles

A Novel Efficient Sine Wave Inverter with Custom Programmed PWM and Intelligent Control

This article presents an efficient design of a pure sine wave inverter which results in an electronic design with reduced losses. The proposed design incorporates the generation of custom programmed pulse width modulation (CPPWM) waveforms; the gate drive signals that are customized for the harmonic elimination from the output voltage, maximizing the fundamental component and resulting in an efficient electronic circuit design as compared to the traditional techniques in terms of the switching losses and the filtering energy losses. The CPPWM signals are digitally programmed in a micro-controller. The inverter realization is followed by an intelligent compensator design for the regulation of output voltage amplitude. The proposed algorithm self-adjusts its parameters in response to the load current and voltage amplitude variations hence resulting in an improved performance. The simulation results of the control algorithm are presented. The experimental validation of the theoretically investigated controller is also presented by implementing a discrete time realization of the control algorithm using digital controller interfaced in real time with MATLAB®/Simulink®. The hardware results are elucidated. The feasibility of the proposed controller is theoretically and experimentally verified by its efficiency compared to the classical techniques, the available tunable parameters in the controller structure and the immense flexibility in the attainable closed loop dynamics.

A transient-enhanced NMOS low dropout voltage regulator with parallel feedback compensation

This paper presents a transient-enhanced NMOS low-dropout regulator (LDO) for portable applications with parallel feedback compensation. The parallel feedback structure adds a dynamic zero to get an adequate phase margin with a load current variation from 0 to 1 A. A class-AB error amplifier and a fast charging/discharging unit are adopted to enhance the transient performance. The proposed LDO has been implemented in a 0.35 μm BCD process. From experimental results, the regulator can operate with a minimum dropout voltage of 150 mV at a maximum 1 A load and IQ of 165 μA. Under the full range load current step, the voltage undershoot and overshoot of the proposed LDO are reduced to 38 mV and 27 mV respectively.

Numerical Thermal Analysis of Fuse Mounted on Fuse Holder

This paper presents a three-dimensional thermal model of an electric fuse mounted on its fuse holder. The proposed model can be used in steady-state conditions but also during transient operating conditions. A comparison at the same ambient temperature and load current, between the thermal model of the fuse with and without its fuse holder, has been performed. In the case of load current and ambient temperature variation, a thermal analysis at different voltage drop values on the fuse contacts has been done. For different thermal load on fuse contacts and current variation, the temperature distribution along the fuse link, has been investigated. The experimental tests led to the validation of the proposed three-dimensional thermal model of the fuse mounted on its fuse holder.

Frequency compensation circuit for adaptive on‐time control buck regulator

A novel frequency compensation circuit for adaptive on-time control buck regulator is presented in this study, which mainly applied to provide power supply for double data rate synchronous dynamic random access memory system. Typical ripple control regulator possesses the advantage of fast transient response and unconditional stability. However, it suffers significant steady-state switching frequency variation when the input voltage and output voltage are varied. The on-time is directly proportional to the output voltage and inversely proportional to the input voltage so that the regulator can dynamically adjust the turn-on time of power switches according to the changes of input voltage and output voltage in steady-state operation by adaptive on-time control. Finally, an approximately fixed switching frequency is achieved. However, the variation of the switching frequency with load current still exists. Through the implementation of the frequency compensation circuit, the switching frequency variation caused by the load current variation can be effectively reduced in order to obtaining a more fixed switching frequency. The adaptive on-time control regulator with frequency compensation has been successfully fabricated with 0.35 µm 30 V complementary double-diffused metal oxide semiconductor process and full chip test results are provided to verify the proposed method in this study.

Adaptive Gate Switching Control for Discontinuous Conduction Mode DC–DC Converter

This paper aims to develop a novel adaptive gate switching controller (AGSC) for discontinuous conduction mode (DCM) dc-dc converters, in an attempt to reduce the power losses caused by nonideal gate switching operations. The proposed AGSC employs a dead-time controller (DTC) and a zero-current detector (ZCD) to turn ON and OFF the synchronous switch, respectively. Both the DTC and the ZCD perform self-calibration according to the converter switching node voltage, allowing the AGSC achieves near-optimal gate switching control regardless of the operating frequency, process variation, power device variation, as well as source voltage and load current variation. The proposed AGSC can have useful applications in many DCM dc-dc converters, e.g., buck, boost, and buck-boost converters. For a proof of concept, in this paper, a boost converter was implemented with the proposed AGSC in a 0.18-μm 3.3-V CMOS process with an area of 1.5 mm 2 . The experimental results demonstrate precise control of the gate switching operations, and the boost converter at 1.2-V/2.5-V nominal input/output achieves a peak efficiency of 86% at 30-mA load current.

Integrated high voltage boost converter with LC filter and charge pump

Purpose – The paper aims to design of dual-mode boost converter with integrated low-voltage control circuit is introduced in this paper. The paper aims to discuss these issues. Design/methodology/approach – The converter is operated either with LC filter or with charge pump circuit by the switch control. The control stage with error amplifier, comparator, and oscillator is designed with the supply voltage of 3.3 V and the operating frequency of 5.5 MHz. The compensator circuit exploits a pole compensation for a stable operation. Findings – The simulation test in 0.35 μm CMOS process shows that the charge pump regulator and DC-DC boost converter are accurately controlled with the variation of number of stages and duty ratio. The output-voltage is obtained to be 6-15 V within the ripple ratio of 5 percent. Maximum power consumption is about 0.65 W. Originality/value – This dual-mode is useful in the converter with a wide load-current variation. The advantage of the dual-mode converter is that it can be used in either high or low load current with a simple switch control. Furthermore, in charge pump regulator, there is no degradation of output voltage because of the feedback control circuit.

A novel quasi‐Z‐source indirect matrix converter

SummaryA new type of three‐phase quasi‐Z‐source indirect matrix converter (QZS‐IMC) is proposed in this paper. It uses a unique impedance network for achieving voltage‐boost capability and making the input current in continuous conduction mode (CCM) to eliminate the input filter. The complete modulation strategy is proposed to operate the QZS‐IMC. Meanwhile, a closed‐loop DC‐link peak voltage control strategy is proposed, and the DC‐link peak voltage is estimated by measuring both the input and capacitor voltages. With this proposed technique, a high‐performance output voltage control can be achieved with an excellent transient performance even if there are input voltage and load current variations. The controller is designed by using the small‐signal model. Vector control scheme of the induction motor is combined with the QZS‐IMC to achieve the motor drive. A QZS‐IMC prototype is built in laboratory, and experimental results verify the operating principle and theoretical analysis of the proposed converter. The simulation tests of QZS‐IMC based inductor motor drive are carried out to validate the proposed converter's application in motor drive. Copyright © 2013 John Wiley & Sons, Ltd.

A current-mode DC—DC buck converter with adaptive zero compensation

To achieve fast transient response for a DC—DC buck converter, an adaptive zero compensation circuit is presented. The compensation resistance is dynamically adjusted according to the different output load conditions, and achieves an adequate system phase margin under the different conditions. An improved capacitor multiplier circuit is adopted to realize the minimized compensation capacitance size. In addition, analysis of the small-signal model shows the correctness of the mechanism of the proposed adaptive zero compensation technique. A current-mode DC—DC buck converter with the proposed structure has been implemented in a 0.35 μm CMOS process, and the die size is only 800 × 1040 μm2. The experimental results show that the transient undershoot/overshoot voltage and the recovery times do not exceed 40 mV and 30 μs for a load current variation from 100 mA to 1 A.

Fast transient DC–DC converter with adaptive compensation zero technique

This letter is to present an adaptive compensation zero circuit to achieve good transient response in current-mode DC---DC buck converter. The proposed structure introduces an adaptive resistance dynamically adjusted according to the different output load conditions, which achieves an adequate system phase margin. A monolithic DC---DC buck converter using the proposed structure was fabricated with 0.35 μm CMOS process. Measurement results show that the transient undershoot/overshoot voltage and the recovery time do not exceed 60 mV and 20 μs for a load current variation from 0 to 1 A.

A Comparison of Soft-Switched DC-to-DC Converters for Electrolyzer Application

An electrolyzer is part of a renewable energy system and generates hydrogen from water electrolysis that is used in fuel cells. A dc-to-dc converter is required to couple the electrolyzer to the system dc bus. This paper presents the design of three soft-switched high-frequency transformer isolated dc-to-dc converters for this application based on the given specifications. It is shown that LCL-type series resonant converter (SRC) with capacitive output filter is suitable for this application. Detailed theoretical and simulation results are presented. Due to the wide variation in input voltage and load current, no converter can maintain zero-voltage switching (ZVS) for the complete operating range. Therefore, a two-stage converter (ZVT boost converter followed by LCL SRC with capacitive output filter) is found suitable for this application. Experimental results are presented for the two-stage approach which shows ZVS for the entire line and load range.

Design and characterization of a multi-frequency bioimpedance measurement prototype

A multi-frequency bioimpedance measurement prototype is proposed, validated and characterized. It consists of an Improved Howland Current Source controlled by voltage, a load voltage sensing scheme through a discrete 3-opamp instrumentation amplifier, a phase and quadrature demodulation setup through analog multipliers, and digitization and processing of the signals using a digital benchtop multimeter. The electrical characterization of the measurement channel was done for resistive loads only, on four different circuits. Measurements were made on 10 frequencies, from 100 kHz to 1 MHz, with 10 load resistances, from 100 Ω to 1 kΩ, to obtain linearity, absolute error and frequency response. The best performance among the four circuits was a maximum absolute error of 5.55 %, and −1.93 % of load current variation at the worst case scenario.

A new humidification and heat control method of cathode air for a PEM fuel cell stack

A new method of humidification and heat controls for a PEM fuel cell stack using non-contact laser absorption spectroscopy is presented in this study. The focus of this experiment is to follow the load current variation and its effect on the resistance and performance. Optimal relative humidity gases not only decrease the total losses in the membrane-electrode-assembly (MEA), but also eliminate channel flooding. By controlling humidified air and heat, it is shown that the tested stack has an improvement in performance as compared to fully humidified gases especially under a heavy-load condition. In this paper, a proposed humidification and temperature control strategy based on humidifiers and gas heaters is presented and discussed in detail. The results indicate that the humidification and temperature control strategy suggested in this experimental study can precisely control the air relative humidity, temperature and flow rate, and increase overall power output by 16% from PEM fuel cell stack.

Improved transient response based adaptive compensation zero for DC–DC buck converter

An adaptive compensation zero circuit for a DC–DC buck converter is presented. The compensation resistance of the proportional compensator is dynamically adjusted according to the different output load conditions, and achieves an adequate system phase margin under different load conditions. In the experimented load-transient response, the dip voltage of 50 mV and a maximum settling time of 25 µs are observed with the proposed circuit for a load current variation from 0 to 1 A.

Load compensation using DSTATCOM in three-phase, three-wire distribution system under various source voltage and delta connected load conditions

This paper deals with a Distribution STATic COMpensator (DSTATCOM) for balancing of source currents, power factor correction and harmonic mitigation in three-phase, three-wire distribution system supplying delta connected load under various source voltage conditions. The control strategy applied to the DSTATCOM play a major role in its performance. A novel approach based on an improved instantaneous active and reactive current component (IARCC) theory is proposed for generation of three-phase reference currents for DSTATCOM. A three-phase voltage source converter with a dc bus capacitor is employed as DSTACOM which will track the reference currents in a hysteresis band scheme. The performance of DSTATCOM is evaluated under sinusoidal, unbalanced sinusoidal and unbalanced distorted source voltage conditions. Variation in load current, variation in magnitude and harmonic content in source voltage has been considered. Delta connected linear as well as non-linear load conditions have been considered. The performance of the DSTATCOM using the proposed control strategy is demonstrated using simulation results in MATLAB/SIMULINK software. Simulation results demonstrate the feasibility of proposed scheme for the control of DSTACOM.

A DSP-Based Dual-Loop Peak DC-link Voltage Control Strategy of the Z-Source Inverter

This paper proposes a direct dual-loop peak dc-link voltage control strategy, with outer voltage loop and inner current loop, of the Z-source inverter (ZSI). The peak dc-link voltage is estimated by measuring both the input and capacitor voltages. With this proposed technique, a high-performance output voltage control can be achieved with an excellent transient performance including input voltage and load current variations with minimized nonminimum phase characteristics caused by the right half-plane zero in the control to peak dc-link voltage transfer function. Both controllers are designed based on a third-order small-signal model of the ZSI using the direct digital control method. The performance of the proposed control strategy is verified by simulation and experimental results of a 30-kW ZSI prototype.

Fast transient capacitor-less LDO regulator using low-power output voltage detector

An output-capacitor-less low-dropout regulator (LDO) with a low-power output voltage detector (OVD) is proposed. The OVD is based on an R/C highpass filter which is able to detect the fast-changing voltage at the LDO output and activate an additional path to control the power transistor. The OVD consumes only additional quiescent current to monitor the variation in output voltage in the steady state. In the simulated load-transient response, a maximum undershoot of 1.2 V and a settling time (Δt2) of 67 ns are observed with the proposed OVD for a load current variation from 1 to 50 mA at a rise time of 1 ns. These results are 0.2 V and 473 ns better than the results obtained without the proposed OVD.

Neuro-Fuzzy based Controller for a Three- Phase Four-Wire Shunt Active Power Filter

This paper describes the application of a novel neuro-fuzzy based control strategy which is used in order to improve the Active Power Filter (APF) dynamics to minimize the harmonics for wide range of variations of load current under various conditions. To improve dynamic behavior of a three phase four-wire shunt active power filter and its robustness under range of load variations, adaptive hysteresis band with instantaneous p-q theory is used with the inclusion of neural network filter for reference current generation and fuzzy logic controller for DC voltage control. The proposed control scheme for “split-capacitor” converter topology is simple and also capable of maintaining the compensated line currents balanced, irrespective of unbalancing in the source voltages & deviation in the capacitor voltages. The results presented in MATLAB-SIMULINK software in this paper clearly reflect the effectiveness of the proposed APF to meet the IEEE-519 standard recommendations on harmonic levels. DOI: http://dx.doi.org/10.11591/ijpeds.v1i2.93

Analysis and design of a low power regulator for a fully integrated HF-band passive RFID tag IC

We present a design for a low-dropout regulator suitable for use as a radio-frequency identification (RFID) tag IC that offers low power consumption while accommodating large load current variations using a small on-chip storage capacitor. Because of the low power design constraint, both the input and output impedances of the embedded current buffer are included for regulator stability analysis. A damping factor control technique is employed to ensure stability for the regulator with a small on-chip capacitor. Our analysis shows that the regulator provides a phase margin of greater than 45° over the full load current variation from 1 to 500 μA. Measurements show that the output voltage variation is less than 110 mV when the input voltage changes from 2.5 to 4 V under the same conditions of load current change, which indicates that the performance of the regulator is suitable for the RFID tag IC. The regulator consumes 10 μA of current and generates a nominal output of 1.8 V. The regulator design technique was successfully implemented in a fully-integrated HF-band passive RFID tag IC that satisfies the ISO-14443 type-B protocol. The tag chip is fabricated in a 1-poly 6-metal low-power 0.18 μm CMOS technology with a CoSi2-Schottky diode and EEPROM process.

Adaptive Droop Resistance Technique for Adaptive Voltage Positioning in Boost DC–DC Converters

In this paper, an adaptive droop resistance (ADR) technique can compensate for the adaptive voltage positioning (AVP) control in a boost dc-dc converter. A loop analysis is derived with the AVP technique to show the effects of the right-half-plane (RHP) zero. When the value of RHP zero is above the equivalent series resistance (ESR) zero, constant output impedance can be guaranteed by the proposed compensation method. Once the value of RHP zero is below five times of ESR zero, the proposed ADR technique can vary the droop resistance to track the variation of the load current to increase the system stability. In case of load current variation, the output impedance is proven constant due to the implementation of the AVP technique in the boost converter. The transient response time is 22 μS when a 200-mA load current step occurs, which is faster than that of a conventional boost converter. Even at heavy loads, the ADR technique can ensure a fast and stable transient response without being affected by the RHP zero. The experimental results demonstrate that the proposed method can increase system stability and guarantee a fast transient response in the design of a boost converter with the AVP technique.

Extracting Load Current Influence From Infrared Thermal Inspections

This paper presents some difficulties encountered when evaluating information obtained from infrared thermal inspections conducted in uncovered power substations. Technical, physical, and environmental factors are the main influences that have been identified. Based on field data and laboratory tests, mathematical models were derived to understand the load current variation influence on the thermal behavior of electrical components, which are suitable either to extract its influence or forecast the system behavior under specified conditions of interest.