Showing papers on "Voltage regulator published in 1996"

An improved voltage control on large-scale power system

Abstract: To achieve a better voltage-VAr control in the electric power transmission system, different facilities are used. Generators are equipped with automatic voltage regulators to cope with sudden and random voltage changes caused by natural load fluctuations or failures. Other devices like capacitors, inductors, transformers with on load tap changers are installed on the network. Faced with the evolution of the network and operating conditions, electricity utilities are more and more interested in overall and coherent control systems, automatic or not. These systems are expected to co-ordinate the actions of local facilities for a better voltage control (more stable and faster reaction) inside different areas of the network in case of greater voltage and VAr variations. They afford a better use of existing reactive resources. Also, installation of new devices can be avoided allowing economy of investment. With this in mind, EDF has designed a system called Co-ordinated Secondary Voltage Control (CSVC). It is an automatic closed loop system with a dynamic of a few minutes. It takes into account the network conditions (topology, loads), the voltage limits and the generator operating constraints. This paper presents improvements which allow the CSVC to control the voltage profile and different kinds of reactive means on a large-scale power system, Furthermore, this paper presents a solution to spread out investment costs over several years, considering a deployment gradually extended.

Performance-temperature optimization by cooperatively varying the voltage and frequency of a circuit

Abstract: A system and method using thermal feedback to cooperatively vary a voltage and frequency of a circuit to control heating while maintaining synchronization. Preferably, on-chip thermal sensors are used for feedback. A system having features of the invention includes: a thermal sensor coupled to the circuit, the thermal sensor generating a temperature signal which is a function of a temperature associated with the functional unit; a temperature decoder having an input and an output, the input coupled to the thermal sensor for decoding the temperature signal; a comparator having one input coupled to the decoder for comparing a decoded temperature signal with a predetermined temperature threshold signal coupled to a second input, the comparator enabling a voltage/clock control signal as a function of the decoded temperature signal and the predetermined temperature threshold; an adjustable voltage regulator coupled to the voltage/clock control signal; and a clock selector coupled to the voltage/clock control signal; wherein the voltage regulator and the clock selector are adapted to cooperatively vary the voltage and the frequency of the circuit to a predetermined voltage-frequency pair, responsive to the voltage/clock control signal and switching factor means, coupled to the comparator, for varying the switching factor of the circuit, wherein the switching factor is the fraction of clock cycles that the circuit is dissipating power.

Method and apparatus providing multiple voltages and frequencies selectable based on real time criteria to control power consumption

Abstract: A method and system for reducing power consumption in a processor core. A state machine is used to coordinate a frequency from a clock signal generator with a voltage from a voltage regulator which is sufficient to allow operation of the processor at that frequency. Both the clock signal generator and the voltage regulator must be able to generate at least two frequencies or voltages, respectively. A level of processor need is tracked and the lowest frequency/voltage pair that will allow the processor core to satisfy the need is selected. The level of processor need is monitored either periodically or continually such that a new frequency/voltage pair can be dynamically selected as the application mix changes.

Semiconductor wafer test and burn-in

Abstract: An apparatus and a method for simultaneously testing or burning in all the integrated circuit chips on a product wafer. The apparatus comprises a glass ceramic carrier having test chips and means for connection to pads of a large number of chips on a product wafer. Voltage regulators on the test chips provide an interface between a power supply and power pads on the product chips, at least one voltage regulator for each product chip. The voltage regulators provide a specified Vdd voltage to the product chips, whereby the Vdd voltage is substantially independent of current drawn by the product chips. The voltage regulators or other electronic means limit current to any product chip if it has a short. The voltage regulator circuit may be gated and variable and it may have sensor lines extending to the product chip. The test chips can also provide test functions such as test patterns and registers for storing test results.

Apparatus and method for maximizing power delivered by a photovoltaic array

Abstract: A method and apparatus for maximizing the electric power output of a photovoltaic array connected to a battery where the voltage across the photovoltaic array is adjusted through a range of voltages to find the voltage across the photovoltaic array that maximizes the electric power generated by the photovoltaic array and then is held constant for a period of time. After the period of time has elapsed, the electric voltage across the photovoltaic array is again adjusted through a range of voltages and the process is repeated. The electric energy and the electric power generated by the photovoltaic array is delivered to the battery which stores the electric energy and the electric power for later delivery to a load.

Power quality measurements performed on a low-voltage grid equipped with two wind turbines

Abstract: The power quality of a low-voltage grid with two wind turbines is investigated. Slow voltage variations as well as transients and harmonics are measured and analysed. Furthermore, the spectrum of the power is determined so that the presence of periodic power components can be investigated. Although periodic power fluctuations reaching 10% of the rated power are registered, voltage variations are lower than the prescribed IEC flicker limit at steady-state operation. As the turbines are put on-line, the voltage level is lowered by 3%, which exceeds the flicker limit. The risk for flicker increases if the X/R ratio of the grid is low and if turbines which have a tendency to produce large periodic power fluctuations are used.

A low power switching power supply for self-clocked systems

Abstract: This paper presents a digital power supply controller for variable frequency and voltage circuits. By using a ring oscillator as a method of predicting circuit performance, the regulated voltage is set to the minimum required to operate at a reference frequency which maximizes energy efficiency. Our initial test silicon, implemented with a fixed frequency controller is analyzed and reveals that the controller's power consumption is a major limitation for such a design. To make the controller power dissipation scale with the CV/sup 2/f power of the load, we introduce a new architecture with variable frequency control, which allows the controller's supply and frequency to scale along with the load device.

Input current modulation for power factor correction

Abstract: A nonlinear carrier controlled power factor correction circuit operates in the continuous and discontinuous conduction modes and provides unity power factor at the input of a power supply by only sensing the output voltage and the current flowing through a diode of a rectifier circuit. The power factor correction circuit monitors a level of current flowing through the diode and generates an integrated voltage signal representative of the level of current flowing through the diode. The integrated voltage signal is compared to a periodic, carrier waveform signal generated using a feedback signal corresponding to a level of an output voltage delivered to a load. A difference between the feedback signal and a reference signal determines the waveshape and characteristics of the carrier waveform. Preferably, leading edge modulation is used to control the duty cycle of a switch within the rectifier circuit. The switch is turned on when the integrated voltage signal reaches a level greater than the value of the carrier waveform. The switch is turned off at the leading edge of the clock reference signal. The duty cycle of the switch will vary as the level of the output voltage varies in reference to the reference signal and as the level of current through the diode varies.

Linearly regulated voltage multiplier

Abstract: A regulating circuit for the output voltage of a voltage booster, of the type which comprises a first charge transfer capacitor adapted to draw electric charges from the supply terminal and transfer them to the output terminal, through electronic switches controlled by non-overlapped complementary phase signals, and a second charge storage capacitor connected between the output terminal and ground, further comprises an error amplifier which generates, during one of the operational phases, a DC voltage corresponding to the difference between a reference voltage and a divided voltage of the output voltage of the voltage booster; this DC voltage is applied directly to one end of the transfer capacitor.

Neural Networks for Combined Control of Capacitor Banks and Voltage Regulators in Distribution Systems

Abstract: A neural network for controlling shunt capacitor banks and feeder voltage regulators in electric distribution systems is presented. The objective of the neural controller is to minimize total I/sup 2/R losses and maintain all bus voltages within standard limits. The performance of the neural network for different input selections and training data is discussed and compared. Two different input selections are tried, one using the previous control states of the capacitors and regulator along with measured line flows and voltage which is equivalent to having feedback and the other with measured line flows and voltage without previous control settings. The results indicate that the neural net controller with feedback can outperform the one without. Also, proper selection of a training data set that adequately covers the operating space of the distribution system is important for achieving satisfactory performance with the neural controller. The neural controller is tested on a radially configured distribution system with 30 buses, 5 switchable capacitor banks and a nine tap line regulators to demonstrate the performance characteristics associated with these principles. Monte Carlo simulations show that a carefully designed and relatively compact neural network with a small but carefully developed training set can perform quite well under slight and extreme variation of loading conditions.

Three-pin buck and four-pin boost converter having open loop output voltage control

Abstract: A controlled output voltage is provided for a switching mode power converter operating in the continuous conduction mode without requiring a feedback path coupled to monitor the output voltage. Instead, a voltage related to the input voltage is monitored. The monitored voltage is compared to a periodic waveform for forming a switch control signal. In the case of a buck converter operating as a voltage regulator, over each period of the periodic waveform, the periodic waveform is representative of the inverse function. In the case of a boost converter operating as a voltage regulator or buck converter operating as a bus terminator or power amplifier, over each period of the periodic waveform, the periodic waveform has a linear slope. The switch control signal controls a duty cycle of the power switches. Therefore, switching is controlled in an open loop, rather than in a closed loop. By monitoring a voltage related to the input voltage, rather than the output voltage, an integrated circuit for controlling the buck converter or boost converter requires few pins and can sink or source current.

Indirect implementations of sliding-mode control law in buck-type converters

Abstract: Some practical methods for implementing the sliding-mode control law to control the buck-type converters are introduced The control equations are derived from the basic sliding-mode control law to accommodate the conventional fixed-frequency PWM control method As a result, the overall feedback control systems can be expressed under a form similar to state-feedback control where the voltage and current of the output capacitor are sensed and controlled With the switching frequency maintained to be constant (not varied over a wide range as in the original law), these control techniques are insensitive to power circuit parameter changes The output voltage errors in these implementations are proven to converge to zero exponentially similarly to the cases implementing the basic sliding-mode control equation These control implementations can be applied to both constant output voltage regulation (as in popular DC-DC converters) and to time-varying output voltage tracking (as in switching power amplifiers)

Switching voltage regulator circuit

Abstract: An integrated circuit for use in implementing a switching voltage regulator, the integrated circuit including a power switching transistor, driver circuitry and control circuitry, which is operable in a normal feedback mode or an isolated flyback mode. The integrated circuit includes shutdown circuitry for placing the regulator in a micro-power sleep mode, and can be packaged in a five-pin conventional power transistor package. The terminals of the integrated circuit regulator perform multiple functions. A compensation terminal is used for frequency compensation, current limiting, soft-start operation and shutdown. A feedback terminal is used as a feedback input when the integrated circuit is in feedback mode, and as a logic pin to program the regulator for isolated flyback operation. The feedback terminal is also used to trim the flyback reference voltage.

An active line conditioner to balance voltages in a three-phase system

Abstract: In this paper a new configuration for an active line conditioner is proposed to correct dynamically voltage unbalances in a three-phase AC system. In the proposed system it is shown that the injection of a correction voltage V/sub inj/ in one phase is sufficient to nullify the negative sequence voltage component in the incoming three phase supply. The resulting three phase voltages at the load terminals are essentially positive sequence voltages and hence are balanced. It is further shown that the kVA requirement of the proposed active line conditioner is small, typically 3% for a ten percentage unbalance in the input supply. The dynamic cancellation of the negative sequence voltage component by the proposed scheme drastically improves the performance of induction motor loads connected to a weak AC system. A thorough analysis of the scheme along with the suitable design guides are presented. Finally selected experimental results on a laboratory prototype active line conditioner are detailed.

Voltage regulator with load pole stabilization

Abstract: A voltage regulator with load pole stabilization is disclosed. The voltage regulator consists of an error amplifier, an integrator which includes a switched capacitor, a pass transistor, and a feedback circuit. In one embodiment, the integrator circuit includes an amplifier, a capacitor, and a switched capacitor which is driven by a voltage controlled oscillator. The voltage controlled oscillator changes its frequency of oscillation proportional to the output current. In another embodiment, the switched capacitor is driven by a current controlled oscillator whose frequency of oscillation is also proportional to the output current of the voltage regulator. When the output current demand is large, the controlled oscillators increase the frequency which decreases the effective resistance of the switched capacitor thereby changing the frequency of the zero to respond to the change in the load pole. Conversely, the effective resistance is increased as the current demand is decreased, also to respond to the decrease in load pole. The controlled oscillator may be coupled to a current sensing device that generates a scaled version of the load current and couples to the regulated voltage output. The controlled oscillator is restricted to operating voltages that are related to the regulated output voltage and a control current that is a scaled version of the load current. Consequently, the disclosed voltage regulator has high stability without consuming excess power.

Voltage regulator for regulating an output voltage from a charge pump and method therefor

Abstract: An SRAM memory cell (10) is provided a boosted voltage by a charge pump (56) to reduce the soft error rate within the SRAM (10) and to improve bit cell stability. A voltage regulator (58) is coupled to the charge pump (56) to regulate the operation of the charge pump (56) and its outputted boosted voltage. The voltage regulator (58) regulates the boosted voltage over three operating states: low supply voltage, steady state operation, and burn-in.

An approach to harmonic current-free AC/DC power conversion for large industrial loads: the integration of a series active filter with a double-series diode rectifier

Abstract: This paper proposes a new harmonic-free AC/DC power converter characterized by the integration of a small-rated series active filter with a large-rated double-series diode rectifier. The DC terminals of the series active filter are directly connected in parallel with those of the double-series diode rectifier, thereby forming a common DC bus. The series active filter enables the diode rectifier to draw three-phase sinusoidal currents from the utility. In addition, it can provide the supplementary value-added function of regulating the common DC bus voltage to a limited extent of /spl plusmn/5%, with slightly increased RMS voltage rating but without increasing peak voltage rating. Experimental results obtained from a 5 kW laboratory system verify the practical viability and cost-effectiveness of the proposed AC/DC power converter.

Automatic voltage detection in multiple voltage applications

Abstract: A removable controller card comprised of a plurality of Flash EEPROM devices (24) and a controller device (20) is described. The controller device (20) is further comprised of voltage detection circuitry including a variable voltage detector (28) for determining the system voltage level provided by a power supply within a computer (25) and for appropriately enabling a voltage regulator circuit (30) for dividing the system voltage level to a level suited for operation by the Flash EEPROM devices (24) and applying this operational voltage level to the Flash EEPROM devices (24). Upon determining the system voltage level provided by the power supply to be appropriately suited for operation of the Flash EEPROM devices (24), disabling the voltage regulator circuit (30) and providing the system voltage level to the Flash EEPROM devices (24).

Harmonic correction of 3-phase rectifiers and converters

Abstract: An AC-DC converter for connecting an AC supply and a DC has a rectifier, and a harmonic correction circuit formed of (a) thyristor inverter legs connected at a common output point to form a Y switch, or separately at positive and negative terminals and (b) a voltage selection circuit for selecting a voltage derived from one of the positive and negative DC rails, or the AC lines, to control current shape and turn-off the thyristors. The thyristors are turned on by, and may also be turned off by, a controller. The voltage selection network may be a resonant circuit that uses ramping of the voltage at the outputs from the thyristors to turn the thyristors off or switches controlled by the controller. A converter for converting DC to AC power has an inverter bridge, a DC input line inductor on each DC rail, a generator for generating a waveshape output that has a frequency equal to the number of AC lines times the frequency of the AC supply; and a multiplexer for multiplexing the output of the generator onto the AC lines to reduce total harmonic distortion of current in the AC lines. The DC to AC converter may use the thyristor networks used for the AC to DC converter for the multiplexing function, under control of the controller. The generator may be a voltage selection network or switch network that selects a voltage source from one of the positive DC rail, the negative DC rail and a center tap on the DC rail.

An advanced photovoltaic array regulator module

Abstract: Current trends in satellite design are focused on developing small, reliable, and inexpensive spacecraft. To that end, a modular power management and distribution system is proposed which will help transition the aerospace industry towards an assembly line approach to building spacecraft. The modular system is based on an innovative DC voltage boost converter called the series connected boost unit (SCBU). The SCBU uses any isolating DC-DC power converter and adds a unique series connection. This simple modification provides the SCBU topology with many advantages over existing boost power converters. Efficiencies of 94-98%, power densities above 1,000 W/kg and inherent fault tolerance are just a few of the characteristics presented. Limitations of the SCBU technology are presented and it is shown that the SCBU makes an ideal photovoltaic array regulator. A set of photovoltaic power system requirements are presented that can be applied to almost any low Earth orbit satellite. Finally, a modular design based on the series connected boost unit is outlined and functional descriptions of the components are given.

Design considerations for 12-pulse diode rectifier systems operating under voltage unbalance and pre-existing voltage distortion with some corrective measures

Abstract: In this paper, design considerations for twelve-pulse diode rectifier systems operating under utility voltage unbalance and pre-existing harmonic voltage distortion are discussed. For a twelve-pulse diode rectifier system connected in parallel to feed a common DC link via an interphase transformer, it is shown that a small amount of impedance mismatch, utility voltage unbalance or pre-existing voltage distortion drastically affects the current sharing capability of the rectifier bridges. This, in turn, generates additional uncharacteristic and characteristic harmonics thereby increasing the THD. In order to mitigate these effects and ensure proper operation of diode rectifiers, specially designed line reactors termed harmonic blocking reactors (HBRs) are introduced. Analysis and design procedures for HBRs are discussed. Simulation results illustrate improved performance. Experimental results from a laboratory prototype system show close agreement with theory.

An improved control scheme for a series capacitive reactance compensator based on a voltage source inverter

Abstract: Power utilities have traditionally used series capacitors to increase the power transfer capability of transmission lines, but their widespread use has been limited by concerns for the harmful effects of series resonances. An advanced, controllable series VAr compensator has the potential to avoid such problems and, therefore, allow more efficient use of existing transmission plant. This paper describes a modified control scheme for an advanced series VAr compensator based on a single voltage source inverter. Practical results from a working prototype demonstrate the ability of the compensator to provide a rapidly controllable magnitude of compensation.

Constant on-time architecture for switching regulators

Abstract: A switching voltage regulator whose switching frequency decreases with reduced load currents is disclosed. The switching voltage regulator includes a current-controlled oscillator that varies the frequency of switching by changing the off-time of the switch and maintaining a constant on-time. The lower frequency as a result of the constant on-time switching reduces switching loss and power consumption at lower load currents. The constant on-time architecture of the present invention significantly improves the overall efficiency of the switching voltage regulator, while reducing component count and die size.

Frequency compensation for a low drop-out regulator

Abstract: A low drop-out voltage regulator is compensated by providing a compensation capacitor across an output terminal of the regulator and an output lead of an input stage which compares a reference voltage and a voltage derived from a regulated output signal at the output terminal. The output from the input stage is inverted without gain before being provided to an output stage. This inversion allows Miller compensation with the compensation capacitor.

Bi-directional voltage translator

Abstract: A bi-directional voltage translator (102) includes a first port (300/302), a second port (302/300), and a switch circuit (310). The first port (300/302) communicates a first signal at a first voltage or a second voltage (V1/V2). The second port (302/300) communicates a second signal at the first voltage or a third voltage (V2/V1). The second and third voltages (V1, V2) are different. The switch circuit (310) is coupled to the first port (300/302) and the second port (302/300). The switch circuit (310), responsive to the first signal at the first voltage and the second signal at the third voltage (V2/V1), communicates to the second port (302/300) the second signal at the first voltage. The switch circuit (310), responsive to the second signal at the first voltage and the first signal at the second voltage (V1/V2), communicates to the first port (300/302) the first signal at the first voltage.

Electronic controller for linear cryogenic coolers

Abstract: A highly efficient motor driver circuit of an electronic controller for linear cryogenic coolers operates directly from a variable power supply, such as a battery, without the need for the voltage regulator control circuit of the prior art. Elimination of the prior art voltage regulator ensures a higher efficiency motor driver circuit of the electronic controller. Both open-loop and closed-loop controllers electronically control the motor driver circuit. The open-loop controller protects against temperature sensor failure, and will limit maximum motor power as a function of system ambient temperature. The closed-loop controller regulates the temperature of the cold finger accurately to a preset value, using feedback from a temperature sensor along with a novel pulse-width modulation concept for modifying motor drive waveforms. The motor driver circuit provides the advantages of increased efficiency, operation from a variable power source, tight control of temperature regulation, a fail-safe mode of temperature sensor feedback, and a small envelope space enabling electronic controller mounting internal to the cooler motor/compressor assembly of a linear cryogenic cooler.

Neutral point clamped (NPC) inverter control system

Abstract: A neutral point clamped (NPC) inverter control system including a DC power source to output DC voltage having a neutral point, an NPC inverter to convert the DC voltage into AC voltage in three phases through a PWM control, a mode selecting unit to decide a first and a second PWM modes by comparing amplitude of voltage reference with a prescribed value that is defined by a minimum pulse width, a first voltage reference conversion means to add a prescribed bias value at which a polarity changes to positive/negative within a fixed period to secure the minimum pulse width to voltage references in respective phases in a first PWM mode, a second voltage reference conversion means to fix the voltage reference in one phase by a value that secures the minimum pulse width when voltage reference in one phase is smaller than a prescribed value that is defined by the minimum pulse width in a second PWM mode and correct voltage references of other two phases so as to make line voltage to a value corresponding to the voltage reference, and a modulation frequency change-over means to lower PWM control modulation frequency in the first PWM mode and to suppress power loss caused by switching in the first PWM mode

Programmable bandwidth voltage regulator

Abstract: A method for reducing the transient response time of a voltage regulator when the load attached to it is entering or exiting a lower power consumption level by changing the bandwidth of the voltage regulator without compromising its stability, and a bandwidth regulator for implementing such a method are disclosed, wherein the bandwidth of the voltage regulator is changed based on a signal sent by a control device when it senses that the component is about to change power consumption levels.

On-board voltage regulators with automatic processor type detection

Abstract: An embodiment of the present invention provides a voltage comparator that senses the type of processor, unified or split voltage plane coupled to a mother board. Under the control of at least one multiplexer, voltage regulators supply voltage to the processor. If the processor is a unified voltage plane type, the voltage regulators are coupled together in a master/slave configuration to supply a single voltage to the processor. If the processor is a split voltage plane type, the voltage regulators are coupled to together in a master/master configuration where a core voltage regulator supplies a core voltage to the processor, and an I/O voltage regulator supplies an I/O voltage to the processor. This will allow each regulator to be set at a different voltages to accommodate processor types with different core and I/O voltages.

Three-pin buck converter and four-pin power amplifier having closed loop output voltage control

Abstract: A circuit for providing a regulated output voltage from a buck converter without directly monitoring the output voltage. The buck converter includes a switch having a first terminal coupled to a supply voltage and a second terminal coupled to a first terminal of an inductor and to a first terminal of a resistive divider. A second terminal of the inductor is coupled to a first capacitor for forming the output voltage across the first capacitor. A voltage formed by the resistive divider is applied to an inverting input of a transconductance amplifier, while a reference voltage is applied to a non-inverting input of the transconductance amplifier. An output of the transconductance amplifier is coupled to a second capacitor for forming an error signal across the second capacitor. The error signal is representative of a difference between the output voltage and a desired output voltage because an average of the voltage formed by the resistive divider is representative of the output voltage. The error signal is compared to a periodic ramp signal by a comparator for forming a switch control signal. Therefore, circuit regulates the output voltage in a feedback loop by monitoring a voltage on the first terminal of the inductor rather than directly monitoring the output voltage. When the circuit is implemented in an integrated circuit package, this results in a savings of one pin. In another aspect, a variable signal is added to, or replaces, the reference voltage such that the circuit functions as a power amplifier.