Input Voltage Changes Research Articles

A 2-MHz 60-W Zero-Voltage-Switching Synchronous Noninverting Buck–Boost Converter With Reduced Component Values

This brief presents a high-frequency high-efficiency zero-voltage-switching (ZVS) synchronous noninverting buck–boost converter for tens-of-Watt applications. By using two pairs of small auxiliary inductors and capacitors, the proposed converter can achieve ZVS under different load currents without increasing voltage stress across power field-effect transistors. The switching power loss is thus minimized to enable high-frequency operation of the converter. The proposed converter can be also configured into the boost mode or the buck mode with ZVS operation when the input voltage changes in order to maintain high power efficiency under different input voltages. The proposed noninverting buck–boost converter has been implemented to operate at 2 MHz and deliver 60-W output. The measured peak power efficiency achieves 94.3%, and the output capacitance and its volume can be reduced by at least 14 times and 4.8 times compared with other state-of-the-art counterparts.

Regulador de Voltaje -LDO- completamente integrado de baja caída de tensión, alta velocidad y bajo consumo de área

Este artículo presenta el diseño de un regulador de voltaje de baja caída de tensión, el cual presenta un bajoconsumo de potencia y área, así como una respuesta transitoria optimizada. La reducción en área se logra mediantela polarización del transistor de potencia en la región de triodo. Así mismo, se hace uso de una red de polarizacióndinámica con el propósito de reducir a 300ns el tiempo de establecimiento para cualquier cambio en la corriente decarga (desde 100μA hasta 100mA). El regulador es diseñado en la tecnología Silterra CMOS estándar de 0.18μm, yproporciona un voltaje regulado de 1.8V. Todo el circuito es polarizado únicamente con 2.3μA para cargas inferioresa 1mA, y puede recuperarse en 0.3μs para cualquier cambio en la carga y voltaje de entrada. Además, el reguladorno necesita de ningún capacitor externo para garantizar su estabilidad.

Design of Parallel-Operated SEPIC Converters Using Coupled Inductor for Load-Sharing

This study discusses the design of a parallel-operated DC-DC single-ended primary-inductor converter (SEPIC) for low-voltage application and current sharing with a constant output voltage. A coupled inductor is used for parallel-connected SEPIC topology. Generally, two separate inductors require different ripple currents, but a coupled inductor has the advantage of using the same ripple current. Furthermore, tightly coupled inductors require only half of the ripple current that separate inductors use. In this proposed work, tightly coupled inductors are used. These produce an output that is more efficient than that from separate inductors. Two SEPICs are also connected in parallel using the coupled inductors with a single common controller. An analog control circuit is designed to generate pulse width modulation (PWM) signals and to fulfill the closed-loop control function. A stable output current-sharing strategy is proposed in this system. An experimental setup is developed for a 18.5 V, 60 W parallel SEPIC (PSEPIC) converter, and the results are verified. Results indicate that the PSEPIC provides good response for the variation of input voltage and sudden change in load.

A novel dimmable LED driver with soft-start and UVLO circuits

A fully integrated LED driver based on a current mode PWM boost DC—DC converter with constant output current is proposed. In order to suppress the inrush of current and the overshoot voltage at the start up state, a soft-start circuit is adopted. Additionally, to adjust the LED brightness without color variation over the full dimming range and achieve high efficiency, a PWM dimming circuit is presented. Furthermore, to keep the loop stability of the LED driver, an internal slope compensation network is designed to avoid the sub-harmonic oscillation when the duty cycle exceeds 50%. Finally, a UVLO circuit is adopted to improve the reliability of the LED driver against the input voltage changing. The LED driver has been fabricated with a standard 0.5 μm CMOS process, and only occupies 1.21 × 0.76 mm2. Experimental results show that the brightness of the LED can be adjusted by an off-chip PWM signal with a wide adjusting range. The inductor current and output current increase smoothly over the whole load range. The chip is in the UVLO condition when the input voltage is below 2.18 V and has achieved about 137 μs typical start-up time.

Closed Loop Simulation of an Active Buck- Boost Inverter

Renewable energy resources are gaining popularity now a days. Their input varies with changes in climatic conditions. So the output from them is not a constant value. The output of the energy sources have to be connected to grid. But the grid voltage is always constant. So the output from the renewable energy converters have to be constant. But the input of the renewable energy converters always varies with climatic and weather conditions. So the output of the converters also changes. To get a constant output voltage at the grid some power converters have to be connected in between the renewable energy converters and the grid. These converters maintain constant output voltage at constant frequency irrespective of changes in input voltage. This paper introduces the concept of an Active Buck- Boost Inverter (ABI). In this converter the passive elements from the conventional buck-boost converter is eliminated. Closed loop simulation of the proposed converter is done to show that the output voltage of the converter remains the same even if the input voltage changes.

High-Quality Sine Wave Generation Using a Differential Boost Inverter at Higher Operating Frequency

Buck-converter-based topologies are used to generate high-frequency sinusoidal outputs. Buck-based inversion circuits such as voltage source inverters or class-D amplifiers have inherent control-to-output linearity in large-signal sense. However, in these topologies, the instantaneous output is always smaller than the dc-input during linear modulation. A differential boost inverter (DBI) is a boost-based topology that is used to generate a sinusoidal output. In DBI, the instantaneous output can be higher or lower than the dc-input voltage. DBI exhibits nonlinear control-to-output behavior in large-signal dynamic sense. Therefore, generating a high-frequency sinusoidal output using this topology is a challenge. The issues associated with a DBI for high-frequency sine wave generation are characterized in this paper. Conventional linear and nonlinear control techniques fail to produce a high-quality sine wave output at higher operating frequency. A nonlinear feedback linearization technique is proposed, which forces the output to be linear with respect to the reference even at higher operating frequency. This leads to a high-frequency high-quality sine wave generation using a DBI. The proposed modulator is verified using a laboratory prototype to generate a sine wave up to 2 kHz. A triangular wave of 100-Hz frequency is also generated by the proposed technique. Superior dynamic responses of a dynamic linearizing modulator controlled DBI for a step change in frequency, load current, input voltage, and reference are also experimentally verified.

Design of high-performance integrated dimmable LED driver for high-brightness solid-state lighting applications

This paper presents a high-voltage buck-type dimmable LED driver for high-brightness solid-state lighting applications. A synchronous hysteretic current control (SHCC) scheme is developed to regulate the LED current with high accuracy under different input voltages and various numbers of output LEDs. With a low-power high-speed dynamic level shifter, the proposed HV gate driver achieves short propagation delays and enables high-frequency operation of the high-voltage SHCC LED driver with an on-chip high-side power pFET. Both peak and valley current sensors are also proposed for high-speed LED current monitoring. Without any power diode and sensing resistor in the power stage, the power efficiency of the proposed LED driver can be enhanced significantly. Implemented in a 0.35-µm HV-CMOS process, the proposed driver can take a high input voltage up to 50 V and deliver an average LED current of 1 A for 12 series-connected output LEDs with a maximum output power of about 46 W. When the input voltage changes from 15 to 50 V and the number of series-connected LEDs varies from 1 to 12, the proposed driver achieves peak power efficiency of 98.8 % and the average LED current error of <1.2 %. The proposed LED driver supports high operation frequency of up to 2.2 MHz and high PWM dimming frequency of 20 kHz with a wide duty ratio from 10 to 100 %. The proposed SHCC LED driver achieves significant improvements in power efficiency and current accuracy over state-of-the-art counterparts.

A Digital Parallel Current-Mode Control Algorithm for DC–DC Converters

This paper presents a novel digital current-mode control strategy for dc-dc converters. In the proposed algorithm, the required duty cycle is calculated directly by two parallel terms. With some simple operations in digital implementation, the resultant control system achieves rapid and precise output voltage regulation under the input voltage and output load change. Moreover, the implementation of the proposed algorithm with a digital controller is discussed in detail. Analysis shows that the parallel current-mode control does not exhibit subharmonic oscillation. A 400-kHz switching frequency buck converter based on field-programmable gate array implementation is built to verify the feasibility and advantages of the parallel current-mode control.

Harmonic Current Effect on Three Phase 100kVA Transformer Losses under Static Load and Dynamic Load

This paper describes the harmonic current effect under static and dynamic load on 3 phase 100kVA transformer model. The methodology that used to measure a harmonic current is using power analyzer with different excitation. The experiment is conducted by changing input voltage with different flux density. A waveform can be obtained by using the data collected. 3rdorder of harmonic gives a high impact to the complex waveform. At 0.6 Tesla, 50 Hz, the 3rdorder of harmonic current under static load and dynamic load is 0.00196A and 0.26746A respectively. Therefore, both static and dynamic load were give an effect to harmonic current effect on transformer. This is because when the transformer connected to the load, more current and voltage induced in order to energize the load. Moreover, the loads itself have their own harmonic effect because of the functional mechanism.

Differentiation of Harmonic Current Effect at T-Joint and Corner Joint on Three Phase 100kVA Transformer Losses

This paper describes the harmonic current effect at T-joint and corner joint on 3 phase 100kVA transformer model. The methodology that used to measure a harmonic current is using search coil connected to oscilloscope. The experiment is conducted by changing input voltage with different flux density. From the results obtained, the 3rdorder harmonic current shows the highest for both T – joint and corner joint. The highest harmonic occurred at T – joint. For in plane, the harmonic current is 0.237A at corner joint and 0.389A at T - joint. At normal condition, the harmonic current were 0.250A and 0.769A at corner joint and T – joint respectively. This happened because of more energy required for transferring the flux to the left and right of the core. The corner joint of harmonic is less since the flux direction is 90° thus smaller amount of energy is required for the movement.

High‐voltage boost quasi‐Z‐source isolated DC/DC converter

A high-voltage gain two-switch quasi-Z-source isolated DC/DC converter has been presented in this study. It consists of a quasi-Z-source network at its input, a push-pull square-wave inverter at its middle, and a voltage-doubler rectifier at its output. When coordinated appropriately, the new converter uses less switches, a smaller common duty cycle and less turns for the transformer when compared with existing topologies. Its size and weight are therefore smaller, whereas its efficiency is higher. It is therefore well-suited for applications, where a wide range of voltage gain is required like renewable energy systems, DC power supplies found in telecom, aerospace and electric vehicles. To demonstrate the performance of the proposed converter, a 400 V, 500 W prototype has been implemented in the laboratory. Efficiency of the prototype measured is found to vary from 89.0 to 97.4% when its input voltage changes from 44 to 82 V at full load.

Time Domain Based Digital Controller for Buck-Boost Converter

Design, Simulation and experimental analysis of closed loop time domain based Discrete PWM buck-boost converter are described. To improve the transient response and dynamic stability of the proposed converter, Discrete PID controller is the most preferable one. Discrete controller does not require any precise analytical model of the system to be controlled. The control system of the converter is designed using digital PWM technique. The proposed controller improves the dynamic performance of the buck-boost converter by achieving a robust output voltage against load disturbances, input voltage variations and changes in circuit components. The converter is designed through simulation using MATLAB/Simulink and performance parameters are also measured. The discrete controller is implemented, and design goal is achieved and the same is verified against theoretical calculation using LabVIEW.

Analysis, Design and Implementation of DC-DC Boost Converter Using H∞ Loop Shaping Controller

This paper proposes the H∞ loop shaping control scheme for DC-DC boost converter using Pulse-width modulation (PWM) techniques. The averaged linear model of the boost converter is developed for three controllers namely classical control (voltage mode), post modern control (H∞ control) and H∞ loop shaping using Ricatti equations which guarantee stability and the desired closed loop dynamic response. The experimental results are accomplished using DSP TMS320LF2407 validated with simulation results that shows the proposed H∞ loop shaping controller has better performances with good tracking and high rejection capability when disturbances are introduced due to changes of load and input voltage.

English

The recent upsurge in the demand of PV systems is due to the fact that they produce electric power without hampering the environment by directly converting the solar radiation into electric power. However the solar radiation never remains constant. It keeps on varying throughout the day. The need of the hour is to deliver a constant voltage to the grid irrespective of the variation in temperatures and solar insolation. In this paper I have designed a circuit such that it delivers constant and stepped up dc voltage to the load. I have studied the open loop characteristics of the PV array with variation in temperature and irradiation levels. Then coupled the PV array with the buck boost converter in such a way that with variation in load, the varying input current and voltage to the converter follows the open circuit characteristic of the PV array closely. At various insolation levels, the load is varied and the corresponding variation in the input voltage and current to the boost converter is noted. It is noted that the changing input voltage and current follows the open circuit characteristics of the PV array closely.

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.

The Design of a New-Type LED Switching Power Supply Circuit

A new-type LED switching power supply circuit using flyback converter is designed based on current-mode PFC controller chip L6562. The circuit has some characteristics such as simple structure, wide input voltage range, output stability and reliable operation. The experimental results show that the system efficiency is up to 89.46% when the input voltage changes from 85V to 265V(AC), meanwhile the system works stably with constant current and constant voltage output.

Time Domain Based Digital Controller for Sepic Converter

This paper presents a discrete PWM controller for SEPIC (Single ended Primary Inductor Converter) converter. SEPIC is chosen since it has positive voltage gain and higher characteristics than any other converter. To improve the transient response and dynamic stability of the proposed converter, Discrete PID controller is the most preferable one. The proposed controller improves the dynamic performance of the SEPIC converter by achieving a robust output voltage against load disturbances, input voltage variations and changes in circuit components. The converter is designed through simulation using MATLAB / Simulink and performance parameters are also measured. The discrete controller is implemented, design goal is achieved and the same is verified against theoretical calculation using LabVIEW. Keywords: SEPIC converter, Discrete PID Controller, Analog to Digital Converter (ADC), Digital Pulse Width Modulator (DPWM).

Trajectory prediction control for digital control DC–DC converters with fast transient response

A novel trajectory prediction control algorithm for digital control DC–DC converters has been presented in this paper. The proposed trajectory prediction control algorithm can provide an accurate prediction of the duty ratio of the next several switching cycles, so as to overcome the inherent time delay of the digital control loop, and to improve the transient response of digital control DC–DC converters, including load response, line response and reference tracking response. A digital control buck DC–DC converter was implemented to verify the effectiveness of the proposed prediction control algorithm. The recovery time is about 8μs and 4μs respectively, when the load current changes from a full load to a 17% load and the input voltage changing between 5V to 6V. The fastest reference tracking speed is about 26.7μs/V.

A Dynamic Model of Switched-Capacitor Power Converters

Switched-capacitor (SC) converters are frequently used for low-power applications that require little or no output regulation. Previous work has established static SC converter models, essentially composed of an ideal transformer (with turns ratio determined by the topology) and an output resistance that varies with component choices, switching frequency, and duty ratio. In this paper, the static model is expanded to include the dynamic response to the input voltage and output current changes. The dynamic model is particularly important in systems that experience large output power transients, such as low-power systems that enter and exit sleep modes. For applications that are only concerned with input-output behavior, a reduced-order model that neglects internal dynamics is derived. The dynamic model is validated with both simulations and experimental results.

Single ADC Digital PFC Controller Using Precalculated Duty Cycles

Traditional digital power factor correction (PFC) uses three sensors to measure the input and output voltages and the input current. Each sensor, especially the input current one, increases the cost of the system and generates power losses in case of resistive sensors. This paper presents a controller for boost PFC converters. It uses precalculated duty cycles generated offline, and applies them to the switch. In order to control the converter with nonnominal conditions, just one analog-to-digital converter (ADC) is used, which measures the output voltage. Measuring the average and the ripple of the output voltage with this ADC, the controller takes compensation action for changes in the input voltage but also in the load of the converter. The average value is used to control the input voltage changes, while the ripple value is used to control load changes. These two loops present low frequency bandwidth, so the ADC and the whole system can be low cost. Finally, a comparator is used to detect the zero-crossing of the input voltage, so the precalculated values are synchronized with the ac mains. In this way, the converter only uses one ADC and one comparator, both with low bandwidth. Results show that high power factor and normative compliance are reached, even under nonnominal conditions.