Abstract: This paper presents a voltage-power droop/frequency-reactive power boost (VPD/FQB) control scheme that allows multiple voltage source converters (VSCs) to operate in parallel in a VSC fed microgrid Each current controlled VSC in such a microgrid has its own VPD/FQB controller that sets its current references to regulate the voltage and frequency of a common microgrid bus By drooping the voltage reference of each controller against its real power output, multiple VPD/FQB controllers jointly regulate the microgrid voltage while sharing a common load power in proportion to a predetermined ratio Similarly, by boosting the frequency reference of each controller against its reactive power output, multiple VPD/FQB controllers jointly regulate the microgrid frequency while sharing the reactive load in proportion to a predetermined ratio The proposed control scheme can also operate in grid connected mode Experimental results are provided to validate the VPD/FQB control scheme

Abstract: A DC converter and a mode-switching method used in an electronic apparatus are included. The electronic apparatus includes a subsystem circuit. The DC power converter comprises a first voltage converting circuit electrically connected to the subsystem circuit, receiving a system voltage and a first reference voltage, and converting the system voltage to a first output voltage based on the first reference voltage; and a second voltage converting circuit electrically connected to the subsystem circuit and receiving the system voltage and a second reference voltage, and converting the system voltage to a second output voltage to the same output end of the first voltage converting circuit based on the second reference voltage; wherein the second voltage converting circuit outputs the second output voltage to the subsystem circuit when the first output voltage at the output end is smaller than a threshold.

Abstract: A new family of a single-switch three-diode dc-dc pulsewidth-modulated (PWM) converters operating at constant frequency and constant duty cycle is presented in this paper. The proposed converters are different from the conventional dc-dc step-up converters, and they posses higher voltage gain with small output voltage ripples. Other advantages of the proposed converters include lower voltage stress on the semiconductor devices, simple structure, and control. Moreover, the reduced voltage stress on the diodes allows using Schottky diodes for alleviating the reverse-recovery current problem, as well as decreasing the switching and conduction losses. The principle of operation, theoretical analysis, and experimental results of one prototype rated 40 W and operating at 94 kHz are provided in this paper to verify the performance of this new family of converters.

Abstract: A light emitting diode (LED) lighting system includes a PFC and output voltage controller and a LED lighting power system. The controller advantageously operates from an auxiliary voltage less than a link voltage generated by the LED lighting power system. The common reference voltage allows all the components of lighting system to work together. A power factor correction switch and an LED drive current switch are coupled to the common reference node and have control node-to-common node, absolute voltage that allows the controller to control the conductivity of the switches. The LED lighting system can utilize feed forward control to concurrently modify power demand by the LED lighting power system and power demand of one or more LEDs. The LED lighting system can utilize a common current sense device to provide a common feedback signal to the controller representing current in at least two of the LEDs.

Abstract: A resonant mode power converter is controlled with a control unit including a feedback circuit coupled to generate a first current representative of an output of the power converter. A current limiting circuit is coupled to receive the first current and a second current generated in response to a reference voltage. The current limiting circuit is coupled to limit the first current in response to the second current. An oscillator is coupled to receive the first current to generate a control signal having a control frequency in response to the first current. An output voltage of the power converter is controlled in response to the control frequency of the control signal.

Abstract: In this paper, a novel controller with fixed modulation index (MI) and variable dc capacitor voltage reference to minimize voltage and current harmonics is presented for a distribution static synchronous compensator (STATCOM). The STATCOM with the proposed controller consists of a three-phase voltage-sourced inverter and a dc capacitor and is used to provide reactive power compensation and regulate ac system bus voltage with minimum harmonics. A systematic design procedure based on pole-zero cancellation, root locus method, and pole assignment method has been developed to determine proper parameters for the current regulator, the dc voltage controller, and the ac voltage controller of the STATCOM. With the proposed STATCOM controller, harmonic distortions in the inverter output current and voltage can be reduced since the MI is held constant at unity in steady state. In addition, a fast adjustment in the STATCOM output reactive power is achieved to regulate the ac bus voltage through the adjustment of the dc voltage reference during the transient period. Simulation and experimental results for the steady-state operating condition and transient operating conditions for the system subjected to a reactive current reference step change, a three-phase line to neutral fault, and a step load change are presented to demonstrate the effectiveness of the proposed controller.

Abstract: Classical discontinuous pulsewidth modulations (DPWMs) may not be efficiently applied in active power filters (APFs), because it is hard to predict the peak values of the inverter current, and consequently it is difficult to calculate the position of the clamped interval, that minimizes the switching losses in any operating point. This paper proposes a new DPWM strategy applied to shunt APFs. The proposed modulation strategy detects the current vector position relative to the inverter voltage reference and determines instantaneously the optimum clamped duration on each phase. It achieves a clamped voltage pattern, with variable lengths depending on the magnitude of the inverter current. This property adaptively reduces the current stress and minimizes the inverter switching losses, regardless of its application. The proposed modulation strategy is described, analyzed and validated on a three-phase voltage source inverter, rated at 7 kVA 400 V, controlled as an APF.

Abstract: A driver for driving a plurality of light emitting diodes (LEDs) is formed of a plurality of LED controllers connected in series between a power supply and a reference voltage Each controller drives one or more LEDs directly connected to it Each controller has a voltage input terminal coupled to an output terminal of an adjacent upstream controller, and an output terminal coupled to the voltage input terminal of an adjacent downstream controller Each controller has a normally-on bypass switch coupled between its voltage input terminal and the voltage input terminal of the adjacent upstream controller The bypass switch completely bypasses the adjacent upstream controller when the adjacent downstream controller detects that its input voltage is below a threshold insufficient to drive the LED in the adjacent upstream controller The bypass switch is turned off if the voltage is above the threshold

Abstract: A voltage control arrangement for a system of multiple windfarms with transmission lines. Voltage is regulated at a point of regulation on the system, such as a high voltage substation or other system bus. Regulation is achieved at the point of regulation by sensing the voltage, comparing to a reference voltage, and adjusting the reactive power output of the wind turbines and other equipment in the system. The regulation point may be shifted to another point if needed to respect voltage limits at that points of the system after attempting to shift reactive load to restore voltage within limits at the other points in the system. The reference voltage may be adjusted to minimize losses for the system of multiple windfarms and transmission lines. A loss optimizing algorithm is applied to the combined multiple windfarm and transmission line to shift reactive load among local windfarms to minimize losses and to shift reactive load among individual wind turbines within an individual windfarm.

Abstract: An LED driver is disclosed that boosts an input voltage to drive any number of LEDs in series. The driver includes a switch-mode current regulator that supplies regulated current pulses to the LEDs. No high voltage output capacitor is used to smooth the current pulses, so the LEDs are turned on any off at the switching frequency. Also, no blocking diode between the switching transistor and the LEDs is used. The cathode of the “bottom” LED in the string is connected to ground via a current sense resistor. In parallel with the sense resistor is connected an RC filter using a small, low voltage filter capacitor. The RC filter provides a substantially smooth feedback voltage for the current regulator to control the duty cycle of the switching transistor so that the feedback voltage matches a reference voltage.

Abstract: A semiconductor integrated circuit device formed by a trench dielectric isolation technique has input terminals connected to positive and negative terminals of secondary cells of an assembled battery and includes monitor circuits for respectively monitoring cell voltages of the cells. Each monitor circuit includes a cell voltage detection circuit, a reference voltage generation circuit, and a comparison circuit. The cell voltage detection circuit divides a voltage between the input terminals connected to the positive and negative terminals of a corresponding cell and detects the cell voltage based on the divided voltage. The reference voltage generation circuit generates a reference voltage from the cell voltage. The comparison circuit is powered by the cell voltage of the corresponding cell and compares the divided voltage with the reference voltage.

Abstract: An application-specific delay-line based windowed analog-to-digital converter (ADC) with programmable reference voltage, conversion time, and accuracy of voltage regulation, is introduced. The ADC can be fully implemented on a small silicon area and is suitable for implementation in various integrated digital controllers for high-frequency low-power switch-mode power supplies. The programmable characteristics are achieved through the utilization of the inherent averaging effect of the delay line and through the adjustments of delay cells' propagation times. The ADC is implemented in a standard 0.18 m CMOS technology, as a part of a high-frequency digital controller integrated circuit, and tested with a 1.5 MHz, 1 W buck dc-dc converter.

Abstract: A multimode voltage regulator circuit includes a linear regulator sub-circuit configured to supply current to a load in a low-current mode, responsive to a first control signal from a first control path, as well as a switching regulator sub-circuit configured to supply current to the load in a high-current mode, responsive to a second control signal from a second control path. The circuit further comprises a shared error amplifier configured to generate an error signal based on the difference between a reference voltage and a feedback signal coupled from the load, and a switch configured to selectively route the error signal to the first control path in the low-current mode and to the second control path in the high-current mode.

Abstract: The application of a particular medium-voltage converter in a certain application depends on numerous criteria. However, in completely new installations, the choice of the system voltage is very often uninhibited of external constraints. Then, the voltage level shall be selected to enable the most efficient power conversion at the lowest cost. This paper is dedicated to help in finding the best voltage level for three-level neutral-point-clamped voltage source converters (3L-NPC VSCs) with respect to the power semiconductor devices. Three insulated-gate-bipolar-transistor-based 3L-NPC VSCs of different voltage levels (2.3, 3.3, and 4.16 kV) are investigated and compared regarding their maximum output power, semiconductor efficiency, and semiconductor cost per MVA output power. The effects of thermal cycling, the loss distribution within the converter, and switching frequencies from 300 to 1050 Hz are considered in the evaluation.

Abstract: A low power 6-bit ADC that uses reference voltage and common-mode calibration to improve linearity and reduce power dissipation is presented. The ADC occupies 0.13 mm2 in 65 nm CMOS. The ADC dissipates 4 mW at 100 MS/s and 12 mW at 800 MS/s from a 1.2 V supply.

Abstract: Embodiments of present invention provide a circuit including a voltage regulator, a phase frequency detector, a charge pump, a low pass filter a control-voltage generating circuit and a voltage controlled oscillator. In a first mode of operation the voltage controlled oscillator produces an output clock in accordance with a control voltage produced from the control-voltage generating circuit and the output voltage of the voltage regulator. In a second mode of operation, the voltage controlled oscillator produces an output clock in accordance with a control voltage from the low pass filter and the output voltage of the voltage regulator.

Abstract: A novel distributed control for uninterruptible power supply (UPS) modules in parallel operation is proposed in this paper, in which the voltage reference synchronization control and load current distribution control are decoupled by a local feedback. The voltage reference is presynchronized beyond the current distribution control with a microcontroller unit and a wired-and circuit. Both instantaneous current distribution and hot swapping of any module are allowed with all the UPS modules electrically isolated. The transfer function of the circulating current regulator is analyzed and equivalent to a first-order low-pass filter. The control characteristics of the root-mean-square voltage regulator (RMSVR) in each UPS module in parallel operation are researched, as well as the coupling effect between the RMSVR and the load balance performance. The RMSVR's impact on current distribution is compensated by introducing the amplitude of the output current or the circulating current into the amplitude adjustment of the sinusoidal voltage reference signal. As a result, both the current sharing and the output-voltage performance of the whole system are effectively improved. Theoretical analysis and experimental results are provided to demonstrate the validity and feasibility of the proposed control.

Abstract: In a circuit apparatus for transformerless conversion of an electric direct voltage of a two-pole direct voltage source ( 1 ) connected to ground having a first voltage pole (+) and a second voltage pole (−) into an alternating voltage, hazardous capacitive leakage currents are avoided by connecting the direct voltage source ( 1 ) to ground and the DC-AC converter ( 400 ) is operated at a controlled intermediate circuit voltage, a DC-DC converter stage ( 300 ) being connected between the direct voltage source ( 1 ) and the DC-AC converter ( 400 ), said DC-DC converter stage providing at its output a +/− voltage that is symmetrical with respect to the grounding point, two series-connected capacitors ( 41, 42 ) having the same polarity and being connected to ground at their connecting point (V) and controlled are charged by two buck-boost choppers ( 100, 200 ) connected one behind the other.

Abstract: An LED driving module suitable to drive a plurality of LED strings in parallel connection is disclosed. The LED driving module includes a voltage converting apparatus, a conduction voltage detecting apparatus, a reference voltage generating apparatus and a current-adjusting apparatus. The voltage converting apparatus produces a driving voltage according to a conduction voltage. The conduction voltage detecting apparatus detects the conducting states of the LED strings for producing a conduction voltage and an enabling signal. The reference voltage generating apparatus generates a first reference voltage according to the enabling signal. The current-adjusting apparatus produces a plurality of driving currents according to the first reference voltage, and the driving currents flow through the LED strings.

Abstract: This paper presents a digital current regulator for an H-bridge PWM converter, having a sampling frequency equal to quadruple of the switching frequency. The current regulator detects the current and manipulates the voltage reference not only at the upper and lower peaks of the PWM triangle carrier but also at its zero crossings. This paper theoretically discusses the switching sequence of the H-bridge PWM converter and reveals the amount of the voltage error and the condition where the voltage error occurs. A modified deadbeat current regulator is proposed to suppress the current oscillation induced by the voltage error, based on the theoretical analysis. Experimental results are shown to verify the control performance of the proposed current regulator. Moreover, a proposed current regulator is applied to a single-phase active power filter to demonstrate the effectiveness in harmonic compensation.

Abstract: A low-power (21 muW ) bandgap reference source that is operable from a nominal supply voltage of 1.4 V is described. The circuit provides an output voltage equal to the bandgap voltage having a low output resistance and allows resistive loading. It does not use resistors or operational amplifiers. Thus, the design is suitable for fabrication in any digital CMOS technology. The circuit uses a current conveyor and current mirrors to convert the proportional to absolute temperature voltage into a current using a MOSFET. The current is converted back to a voltage by using the functional inverse of the FET v-i characteristics. This makes the voltage gain linear and temperature independent. The absence of back-gate bias is the reason for achieving the low supply voltage of operation. Simulation results using the transistor models for the 0.18-mum TSMC process show that the voltage-variation over the temperature range 0 to 100degC is <1 mV.

Abstract: We describe a compact programmable CMOS reference, where the reference is determined by the charge difference between two floating-gate transistors, thereby making the reference insensitive to temperature and other environmental effects. Using floating-gate transistors adds programmability making a wide range of reference voltages possible with negligible long-term drift. A prototype circuit has been implemented in a 0.35-mum CMOS process, and reference voltages ranging from 50 mV to 0.6 V have been achieved. We demonstrate a voltage reference programming accuracy of plusmn40 muV . Experimental results indicate a temperature sensitivity of approximately 53 muV/degC for a nominal reference voltage of 0.4 V over a temperature range of -60degC-140degC.

Abstract: A dual-mode input voltage modulation (IVM) control scheme for a three-phase zero current switching series resonant (SR) inverter-fed three-phase voltage-multiplier based X-ray power supply is proposed to achieve a quick rise of output voltage. In this control scheme, a quasi-resonant control circuit is connected at the lower arm of the three-phase inverter to control the effective input voltage across the inverter by raising or lowering the voltage level at the lower arm of the inverter. At the startup of the power supply, the quasi-resonant control circuit shorts the lower arm of the three-phase SR inverter to ground, causing the inverter to see maximum voltage and the output voltage to rise with maximum speed toward the target voltage. As the output voltage reaches 90% of the target voltage, the effective input voltage across the inverter is reduced to a value that corresponds to the target output voltage by raising the voltage level at the lower arm of the inverter. As a result, the rise rate of the output voltage slows down and overshoot is prevented. Experimental results based on the scaled-down laboratory prototype are presented to verify the effectiveness of the proposed dual-mode IVM control scheme.

Abstract: PROBLEM TO BE SOLVED: To reduce the overshoot of an output voltage arising from a sudden change of a load with regard to a switching power supply that stabilizes the output voltage by switching SOLUTION: This switching power supply detects an output voltage that is impressed to a load Ro to compare it with a first reference voltage Vref1 by an error amplifier EA, controls the ON/OFF periods of switching elements (Q1, Q2) by a pulse width control circuit PWM and a drive circuit DRV corresponding to an output signal of the error amplifier EA, and stabilizes the output voltage that is impressed to the load Ro A comparator COMP is provided that compares an output signal of the amplifier EA with a second reference voltage Vref2, and that, if the output signal of the amplifier EA arising from sudden fluctuation of the load exceeds the second reference voltage Vref2, adds a comparison output signal to the terminals of the amplifier EA that detects and inputs an output voltage that is impressed to the load Ro COPYRIGHT: (C)2006,JPO&NCIPI

Abstract: A self-tracking analog-to-digital converter includes a digital-to-analog converter (DAC) adapted to provide a variable reference voltage, a windowed flash analog-to-digital converter (ADC) adapted to provide an error signal e k corresponding to a difference between an input voltage V i and the variable reference voltage, and digital circuitry adapted to generate suitable control signals for the DAC based on the error signal e k . More particularly, the digital circuitry includes a first digital circuit adapted to provide a first function value f(e k ) in response to the error signal e k , the first function value f(e k ) representing an amount of correction to be applied to the variable reference voltage. A second digital circuit is adapted to provide a counter that combines the first function value f(e k ) with a previous counter state N k to provide a next counter state N k+1 , the next counter state N k+1 being applied as an input to the digital-to-analog converter. A third digital circuit is adapted to scale the previous counter state N k by a factor M and combine the scaled counter state M·N k with the error signal e k to provide a digital output value D k representing the input voltage V i .

Abstract: A determination of the memory state of a resistive n-level memory cell is described. The determination includes charging or discharging a read capacity of the memory cell by applying a voltage between a first electrode and a second electrode of the resistive memory cell. A voltage at the second electrode is compared to a reference voltage to obtain a comparison signal. The comparison signal is sampled at, at least, (n−1) time instants during the charge or discharge of the read capacity to obtain sampling values. The memory state of the memory cell can be determined based upon the sampling values.

Abstract: In this paper an optimum design and control of three-phase grid-connected PV system has been proposed and analyzed. Also, a developed maximum power point tracking (MPPT) controller that uses the PV array differential power to voltage (dP/dV) as an index to provide the reference voltage of maximum power point (MPP) quickly and accurately is presented. The control scheme of a three phase current-controlled space vector pulse-width modulation (SVPWM) inverter in rotating synchronous coordinate d-q with the proposed MPPT algorithm and feed-forward compensation is discussed. The PV grid-connected system controller employs multi-loop control with the filter inductor current of the inverter in the inner loop to achieve fast dynamic response and the outer loop to control dc bus voltage for MPPT. The design method provided in the paper for the controller parameters and filter proved to be very practical and effective. Both the power quality into the grid and power factor correction comply with standards IEEE 929-2000. Good agreement is obtained between simulation and experimental results which illustrated the high performance of the proposed approach.

Abstract: An A/D converter compares one or more analog voltages to be converted with a reference voltage given by a voltage change value of ramp voltage whose voltage value changes monotonically for a certain period or a voltage proportional to the voltage change value, converts each analog voltage to a digital value corresponding to the reference voltage, and outputs it, the A/D converter comprising an arithmetic unit for comparison between the analog voltage and reference voltage with respect to each analog voltage, the arithmetic unit having a first power supply line for receiving a power supply voltage, wherein the first power supply line is provided as another power supply line not affected by voltage fluctuation of a second power supply line for supplying a system power supply voltage by providing a MOS transistor whose gate terminal is connected to a stabilized voltage source between the first and second power supply lines.

Abstract: An image sensor formed of an array of pixels, each pixel including a photodiode coupled between a first reference voltage and a first switch, the first switch being operable to connect the photodiode to a first node; a capacitor arranged to store a charge accumulated by the photodiode, the capacitor being coupled between a second reference voltage and a second node; a second switch coupled between the first and second nodes, the second switch being operable to connect the capacitor to the first node; and read circuitry coupled for reading the voltage at the second node.