Showing papers on "Constant current published in 2005"

Analysis and design of an LCL-T resonant converter as a constant-current power supply

Abstract: An LCL-T resonant converter (LCL-T RC) is shown to behave as a current source when operated at resonant frequency. A detailed analysis of the LCL-T RC for this property is presented. Closed-form expressions for converter gain, component stresses, and the condition for converter design optimized for minimum size of resonant network is derived. A design procedure is illustrated with a prototype 200-W 20-A current-source power supply and experimental results are presented. The LCL-T RC as a current source offers many advantages such as easy parallel operation and low circulating currents at light load. Additionally, with appropriate phase shift in paralleled modules, the peak-peak ripple in output current is reduced and the ripple frequency is increased, reducing filtering requirements. The leakage inductance of a transformer can be advantageously integrated into the resonant network. These merits make the topology applicable in various applications such as magnet power supply, capacitor charging power supply, laser diode drivers, etc.

LED light source for backlighting with integrated electronics

Abstract: An LED backlight structure and technique for setting the voltages and currents for the LEDs are described. In one embodiment, red LEDs are connected in series between a first voltage regulator and a first controllable current source, green LEDs are connected in series between a second voltage regulator and a second controllable current source, and blue LEDs are connected in series between a third voltage regulator and a third controllable current source. The current sources may linear current regulators. After all the LEDs are mounted on a printed circuit board, each voltage regulator is controlled so that there is a minimum voltage drop across the current source to minimize energy dissipation by the current source. Also, after all the LEDs are mounted on the printed circuit board, the current sources are controlled to balance the three colors to achieve a target light output of the board using a light detection chamber. In another embodiment, a constant current source is connected to the series string of LEDs. PWM controllers control transistor switches connected in parallel across groups of LEDs, where the duty cycles set the average current through each group of LEDs. The control values used to achieve the target light characteristics are then stored in a memory on the board. With such a technique, LEDs do not need to be binned to match their efficiencies, since the controllable voltage and current sources compensate for the variety of LED efficiencies. Accordingly, all boards will have the same target light output using the particular values stored on each board. In other embodiments, not all the LEDs of a particular color are connected in series. The brightness levels of the LEDs may be further controlled by a PWM controller. The backlight may be for an LCD television or other color display.

Ultrasonic surgical apparatus with treatment modes selectable

Abstract: An ultrasonic surgical apparatus comprises a treatment device with an ultrasonic transducer driven to generate ultrasonic vibration, an operation device outputting a signal commanding the transducer to start driving in response to an operator's operation, and a driver driving the transducer by supplying current thereto. The apparatus further comprises a controller controlling the driver. The controller controls the driver using selectively a first output control pattern and a second output control pattern. The first output control pattern is set to supply the current of a first current value under control of constant current control in response to the signal from the operation device, while the second output control pattern is set to supply the current of a second current value in response to the signal from the operation device and then the current is reduced in amount as the time counted from starting the supply elapses.

Constant current driving device, backlight light source device, and color liquid crystal display device

Abstract: A constant current driving device for constant current driving of a plurality of elements connected in series with each other by a pulse width modulation constant current driving circuit includes: switching elements respectively connected in parallel with the plurality of elements connected in series with each other; a control circuit for performing control to bypass a driving current flowing through the other elements than an arbitrary element to be measured via the respective switching elements and pass a measuring driving current through only the element to be measured; and a detecting circuit for identifying an element at a faulty position by detecting the driving current flowing through the plurality of elements connected in series with each other.

Battery charger and method of charging a battery

Abstract: Stationary and on-board battery chargers, methods of charging batteries, electric-vehicle chargers, and vehicles with chargers, including electric vehicles and hybrid electric vehicles Chargers may automatically charge at the correct battery voltage for various types of batteries Chargers have variable AC power supplies controlled by digital controllers, isolation transformers, and rectifiers Transformers may be foil-type, and may have copper foil Power supplies may be variable-frequency generators and the controllers may control the frequency Use of the variable frequency generator supply facilitates reduced component size and weight and better battery charging performance Electric vehicle chargers may have card readers, and vehicles may have batteries and a charger Methods of charging include identifying the battery type and gradually increasing the charging at different rates of increase while monitoring charging voltage, charging current, or both, until a current lid is reached Charging may occur at constant current and then at constant voltage

Therapy delivery mode selection

Abstract: Techniques for selectably providing either constant voltage or constant current stimulation are described. A programming device provides a user interface by which a user selects either constant voltage or constant current stimulation, and selects either a voltage or current amplitude based on the selected stimulation mode. The programming device configures a medical device to provide the selected mode of stimulation at the selected amplitude. For example, when a medical device has constant voltage stimulation circuitry, e.g., circuitry including a voltage source, and the user selects constant current stimulation, the programming device configures the medical device to adjust the voltage amplitude based on a measured impedance to provide substantially constant current amplitude.

Apparatus for Electrical Power Transmission

Abstract: A device for the transmission of electrical energy includes at least one current converter. Each current converter has phase elements with respective arrangements of circuit elements that comprise at least two switchable power semiconductors each and at least two free-wheeling diodes, each connected in parallel thereto, and energy storing means. The transfer properties in or between power distribution networks are improved with the novel device. The device is provided with means for controlling the current converter in such a manner that the zero crossing, the amplitude and/or the instantaneous values of an alternating current of a transfer network that can be connected to the device and/or the direct current of a direct current line that connects at least one current converter to a direct current source, and/or the direct voltage and the direct current of at least three interconnected current converters can be controlled.

Method and apparatus for generating temperature-compensated read and verify operations in flash memories

Abstract: Methods and an apparatuses for generating a word-line voltage are disclosed. A word-line voltage generator includes a first current source, an adjustable current source, adjustable current sink, and a voltage converter, all operably coupled to a current sum node. The first current source generates a first current having a temperature coefficient substantially equal to a temperature coefficient of at least one bit cell. The adjustable current source generates a second current that is substantially independent of a temperature change. The adjustable current sink sinks a third current that is substantially independent of a temperature change. The voltage converter is configured for generating a word-line signal having a word-line voltage proportional to a reference current, wherein the reference current comprises the first current, plus the second current, and minus the third current.

PWM controller with constant output power limit for a power supply

Abstract: A PWM controller has a line voltage input that allows using a start-up resistor for both start-up and power-limit compensations so that it can save the power consumption, ease the PCB layout, and shrink the power supply size. In the integrated circuit, a current switch used for both start-up and line voltage sensing is composed of a diode and a switch transistor. A current multiplier is used to improve the precise by canceling the impact of the integrated resistor's absolute value, which is composed of a transistor loop, a constant current and a reference current. Thus, by properly selecting the value of the start-up resistor, an identical output power limit for low line and high line voltage input can be achieved.

Primary side constant output current controller

Abstract: A lower-cost and more precise control methodology of regulating the output current of a Flyback converter from the primary side is provided. The methodology regulates the output current accurately in both continuous current mode (CCM) and discontinuous mode (DCM) and can be applied to most small, medium, and high power applications such as cell phone chargers, power management in desktop computers and networking equipment, and, generally, to a wide spectrum of power management applications. Two highly integrated semiconductor chips based on this control methodology are also described that require very few components to build a constant current Flyback converter.

Discharge lamp lighting device and projector

Abstract: A discharge lamp lighting apparatus comprising a d.c. power source section which rectifies and smoothes an a.c. voltage; a current detecting circuit which detects a current which flows through a discharge lamp; a power source ripple detecting circuit which detects a voltage change of power supplied from the d.c. power source section and outputs a voltage obtained by superimposing the detected voltage over a detected voltage which is available from the current detecting circuit; and a control circuit which controls, based on the output voltage from the power source ripple detecting circuit, an output voltage to the discharge lamp so that the current flowing through the discharge lamp becomes a constant current. A rate of superimposition of the output voltage from the power source ripple detecting circuit may be switched in accordance with the discharge lamp voltage.

Impedance measurement for an implantable device

Abstract: A method and an apparatus for determining an impedance experienced by a lead associated with the implantable device. A substantially constant current signal is provided through a first terminal and a second terminal of the lead. A voltage across the first and second terminals is measured. An impedance across the first and second terminals is determined based upon the constant current signal and the measured voltage.

System and method for driving light-emitting diodes (LEDs)

Abstract: System and method for improving efficiency in driving LEDs. A preferred embodiment comprises a switch current regulator coupled to a current control signal input, the switch current regulator to control an amount of current provided to the LED based upon a magnitude of a voltage on the current control signal input, a switching voltage regulator coupled to the switch current regulator and the LED, the switching voltage regulator to provide current to the LED, and a sensor coupled to the switch current regulator, the LED, and a signal feedback circuit, the sensor to measure status information regarding the switch current regulator and the LED and provides the information to a controller, wherein the status information can be used to adjust the current on the current control signal input.

A Full-Wave Rectifier using a Current Conveyor and Current Mirrors with Improved Efficiency

Abstract: A full-wave rectifier using a current conveyor and current mirrors proposed by Monpapassorn e/ al. (2001) is improved. The improved rectifier uses two voltage sources in place of two transistordiodes and three constant current sources of the original rectifier. The improvement yields better performance in view of device number, power consumption and operation frequency. Simulation results that agree with theory are included.

Light emitting element drive device and display system

Abstract: A light emitting element drive circuit and a display system able to simultaneously perform constant current control and PWM control and able to perform a stable adjustment of luminance over a wide dynamic range, including a constant voltage source having an output voltage adjustment unit able to be changed in output voltage according to a signal from the outside, a switch circuit connected to the cathode side of the LED and ON/OFF controlled in accordance with a PWM signal from the outside, a current detection unit for detecting the current flowing in the circuit, and a sample and hold circuit for maintaining the current input value from the current detection unit for a constant period, and the output voltage adjustment unit receives as input the output of the sample and hold circuit, that is, the current value when the switch circuit is ON, and adjusts the output of the constant voltage source so that this value becomes a previously determined set value, to thereby make the current flowing in the LED constant.

Step-up circuit and portable device using it

Abstract: According to the invention, as an input voltage of a certain step-up unit of a plurality of stages of step-up units, a stepped-up output of a step-up unit in a stage preceding the certain step-up unit is inputted. This makes it possible to increase the level of a voltage stepped up by each step-up unit, and reduce the number of units. Furthermore, according to the invention, when an output voltage of a step-up unit that performs stepping-up operation according to a reference constant current is lower than a reference voltage, a reference constant current is produced; when the output voltage thereof exceeds the reference voltage, the reference constant current is stopped. This makes it possible to provide stable output of an output voltage at a predetermined level, and reduce an inrush current during start-up to a predetermined current level.

Boost controller capable of step-up ratio control

Abstract: A charge pump circuit boosts a voltage of a battery so as to generate a drive voltage for an LED. A constant current circuit generates a constant current to feed through the LED. A monitoring circuit monitors a cathode potential of the LED, i.e., a voltage across the constant current circuit. A control circuit receives a result of monitoring from the monitoring circuit 110 and increases a step-up ratio of the charge pump circuit when the voltage across the constant current circuit drops below a minimum voltage that guarantees a constant current. The control circuit sets an externally requested constant current value in the constant current circuit. When a change from a large current to a small current is requested, the control circuit returns the step-up ratio of the charge pump circuit to 1.0.

Signal line driving circuit and light emitting device

Abstract: Dispersion occurs in the characteristics of the transistors. The invention is a signal line driving circuit having a first and a second current source circuits corresponding to each of a plurality of signal lines, a shift register, and a constant current source for video signal, in which the first current source circuit is disposed in a first latch and the second current source circuit is disposed in a second latch. The first current source circuit includes capacitive means for converting the current supplied from the constant current source for video signal into a voltage, according to a sampling pulse supplied from the shift register, and supplying means for supplying the current corresponding to the converted voltage. The second current source circuit includes capacitive means for converting the current supplied from the first latch into a voltage, according to a latch pulse, and supplying means for supplying the current corresponding to the converted voltage.

Influence of a charging current with a sinusoidal perturbation on the performance of a lead-acid battery

Abstract: The effects of the battery current created by a charger operating in power factor correction (PFC) mode is investigated. In this case, the charging current contains a sinusoidal perturbation. This could deteriorate the performance of the charge compared to the classic charging technique, which uses a constant current. A dynamical model of the battery is proposed which facilitates an explaination of the contribution of the sinusoidal perturbation on the performances of a lead-acid battery. This theoretical facilitates the supposition that the DC component of the charging current is at the origin of the charge. This assumption is validated by the experimental results which show that the sinusoidal perturbation has no effect on the electrical performance of a lead-acid battery.

Power supply system and electronic device

Abstract: An output from a generator section is controlled by a current converter section to be a constant current. Charging and discharging of a power storage section is controlled by a charge/discharge control circuit. Thereby, even in a case where a current value required by a load is high, the case can be dealt with in the manner that, while an output current from the generator section is being maintained constant, the output from the generator section and an output from the power storage section can be caused to function in cooperation with each other. Further, charging and discharging of the power storage section can be performed by a simplified device.

Effect of current waveforms on metal transfer in pulsed gas metal arc welding

Abstract: With new types of welding power supply based on higher performance power electronic devices and digital control techniques, advanced pulse waveforms can be produced to offer more characteristics that can be fine tuned to optimize the welding process. In this paper, pulsed current waveforms with four basic parameters and six secondary parameters are used to study the effect of waveform parameters on the mode of metal transfer in pulsed gas metal arc welding (GMAW-P). An experimental system is developed to sense, observe and analyse the images of droplet/wire, and the transient data of welding current and arc voltage. Experiments are conducted to study the influence of the ratio of the pulsing-current time to the droplet-detachment time as well as the droplet-detachment current level on the mode of metal transfer. Appropriate sets of welding conditions including pulse waveform and parameters are obtained to achieve the ideal transfer mode of one-droplet-per-pulse in GMAW-P.

Balanced circuit for multi-LED driver

Abstract: A driving circuit uses a plurality of transformers to provide currents for driving a plurality of LEDs associated with a plurality of current paths. Each transformer has two induction coils with a coil turn ratio between to the number of turns in each induction coil. One induction coil is used to provide an output current to a different current path and the other induction coil is connected to the corresponding induction coil of other transformers for forming a current loop. The output current of each transformer has a relationship with the output current of the other transformers depending on the coil turn ratios of the connected transformers. LEDs in red, blue and green colors can be connected to different current paths so that the brightness of the LEDs in each color can be determined by the current in a current path.

Analysis, design and experimental results of a high-frequency power supply for spark erosion

Abstract: The LC/sub s/C/sub p/ resonant converter finds a new application in an electrical discharge machining (EDM) power supply, which is designed for the purpose of developing small size EDM systems. The switching frequency is tuned to the natural resonant frequency where the converter tends to act as a current source. In this way, three effects are achieved: 1) the necessary over-voltage is generated, first to ionize the dielectric and then to establish the electric discharge, 2) a constant current is supplied during the machining of the workpiece, providing the circuit with inherent protection under short circuit conditions, and 3) overall stability is guaranteed despite the equivalent negative resistance of the dielectric breakdown. The proposed control achieves an optimum and stable operation using tap water as dielectric fluid preventing the generation of undesired impulses and keeping the distance between the electrode and the workpiece within the optimum stable range. The EDM power supply has been validated to perform operations in a nuclear power plant application.

Led drive circuit and led drive method

Abstract: PROBLEM TO BE SOLVED: To provide an LED drive circuit which can be applied to a lighting device that uses a commercial power supply, has a long service life and is high in efficiency. SOLUTION: The LED drive circuit includes an LED circuit composed of unit circuits that are connected in series. The unit circuit is composed of LED series circuits 10 to 13 consisting of two or more LEDs connected in series, and electronic switching circuits 15 to 18 connected in parallel with the LED series circuits 10 to 13. Further, the LED drive circuit includes a constant current circuit 19 connected in series with the LED circuit, a rectifying circuit 21 which applies a pulsating flow obtained by rectifying a commercial power supply, and a controller which detects an applied voltage and controls the electronic switching circuits 15 to 18 so as to turn the LEDs ON as many as possible. The number of the LEDs may be any of n-th powers of m×2. The LEDs can be efficiently driven, a useless power consumed by a part other than the LEDs can be reduced to an irreducible minimum, and a power necessary for obtaining the same luminance can be reduced. COPYRIGHT: (C)2007,JPO&INPIT

Boost circuit capable of step-up ratio control

Abstract: When a step-up ratio control circuit sets a step-up ratio of a charge pump circuit to 1.0 to enable a short mode, a path inside the charge pump circuit is short-circuited and a first transistor is completely turned on. This produces an inrush current derived from a battery voltage of a lithium ion battery flowing into the charge pump circuit. To address this, a constant current circuit is operated so that the first transistor is turned on slowly. Further, the operation of an oscillator and an operational amplifier is suspended when the short mode is enabled.

Current prediction in a switching power supply

Abstract: A high efficiency switching power supply including an analog front end, a battery control circuitry portion, a display and equalization circuitry portion, field effect transistor (FET) drivers, an isolated power supply transformer circuitry (and three associated sets of tap circuitry), microcontroller circuitry, oscillator circuitry, overcharge protection circuitry, programmable logic circuitry portion, and a zero current predictor. Overbiasing of the FET power supply switches, and/or other various circuitry features disclosed herein, helps achieve electrical power efficiencies of preferably greater than 95%, even more preferably greater than 98% and even more preferably greater than 99%. Preferably, the switching power supply has one or more of the following: (1) high electrical power efficiency (>95%. >98%, >99%); (2) overbiasing of a gate of a power supply switch; (3) a power supply switch with a low gate capacitance ratio; (4) multiple modes of operation; and (5) current prediction wherein an inductor voltage is used to control a constant current capacitor whose voltage indicates the level of current in the inductor.

Equalizing circuit for lithium ion power accumulator

Abstract: This invention relates to a Li ionic power storage battery balance circuit. Every battery module has a set of balance circuit, at least two units of battery modules are serial, positive and negative ends of the battery module V are connected with a relay, serially connected with a self-restoring fuse and connected and a constant current DCDC converter with a discharge resistor switches separately. In the entire battery set by two conversions, the battery is charged or discharged according to the target balance voltage, balanced maximum volume difference or the maximum voltage difference designed by the module, the relay network switches the charge or discharge of the resistor of the constant current DCDC converter.

Fan motor with digital controller for applying substantially constant driving current

Abstract: An improved fan arrangement features a radial or diagonal fan ( 370 ) with which a direct current motor ( 32 ) is associated as its drive motor, further comprising a digital control element ( 23, 24 ) which executes a program, for controlling the current flowing through the direct current motor ( 32 ), which program is so configured that it applies a substantially constant current in the motor ( 32 ) in the working rotation speed range of the fan.

Charge pump circuit and PLL circuit using same

Abstract: A charge pump circuit able to enhance the rising and falling characteristics of a current output, drive the current output with a short pulse, reduce leakage current at the OFF time when a current is not output, and realize a reduction of a power consumption and a PLL circuit using same. By outputting a charge current or a discharge current in accordance with an up signal or a down signal and turning on a third transistor (PC, NC) at the OFF time when the current is not output, an inverse bias voltage is supplied between a gate and a source of the second transistor (PA, NA), whereby a reduction of the leakage current can be realized. When the second or third transistor is switched in accordance with the up signal or the down signal, the timing of the control signal is appropriately controlled, simultaneous turning on of the second and third transistors can be avoided, release or injection of charges from and to the output terminal of the charge pump circuit can be prevented, and the stability of an oscillation frequency of a VCO can be improved.

LED driving semiconductor circuit and LED driving apparatus including the same

Abstract: A LED driving semiconductor circuit of the present invention includes a first input terminal connected to a light-emitting diode, a switching device block having a first FET and a first switching device, a reference voltage terminal which is connected to the first FET and outputs the reference voltage, a start/stop circuit which outputs a start signal when the reference voltage is equal to or larger than a predetermined value and outputs a stop signal when the reference voltage is less than the predetermined value, a current detection circuit which detects the current flowing through the first switching device, and a control circuit which controls ON/OFF of the first switching device intermittently at the predetermined frequency based on the output signal of the start/stop circuit and the output signal of the current detection circuit so that the constant current flows through the light-emitting diode.