Showing papers on "Constant current published in 1997"

Method and apparatus for rapidly changing a magnetic field produced by electromagnets

Abstract: A method and apparatus for ramping current in an electromagnet in which a coil is used to generate the magnetic field provides rapid changes in the generated magnetic field. The method allows a change in current in the coil to be accomplished more rapidly than by applying a step change in voltage, when superconducting coils subject to quenching are used or when nonsuperconducting coils subject to other physical limitations are used. The method requires that both the current I(t) through the coil and the first derivative of the current vary with respect to time t during the ramping period, so that magnitude of the derivative of the current is higher when the magnitude of applied current is lower, lower when the magnitude of the applied current is higher. One variation of this method supplies (or removes) a constant amount of power from the magnetic field of the magnet, while another variation compensates for both self-generated eddy current losses and self-generated high field effects. The method can be used to guide a magnetic seed and in other applications. The apparatus includes, in its most general form, an electromagnetic coil, a generator for applying an initial current to the coil, and a processor controlling the generator that causes the current to ramp from an initial to a final value in accordance with the methods described above.

Measuring method of accumulator charged state

Abstract: The method involves applying a charging constant current pulse to the battery terminals. The voltage (Ut) at the terminals is measured at a pre-determined instant during application of the current pulse. An alternative is to measure the voltage (Ut) at a pre-determined instant immediately preceding the end of the application of the current pulse. The method may also involve measuring the current (I) passing through the battery at an instant close to the average of the start and the end of the current pulse.

Low-dropout voltage regulator incorporating a current efficient transient response boost circuit

Abstract: An improved low-dropout ("LDO") voltage regulator incorporates a transient response boost circuit which is added to the slew-rate limited node at the control terminal of the LDO voltage regulator output transistor and provides improved transient response performance to the application of various load current step stimuli while requiring no standby or quiescent current during zero output current load conditions. The transient boost circuit supplies current to the slew-rate limited node only upon demand and may be constructed as either a localized positive feedback loop or a number of switching devices which conduct current only during slew-rate conditions.

High efficiency switching regulator with adaptive drive output circuit

Abstract: Switching regulator circuits and methods are provided in which the output circuit is adaptable to maintain high efficiency over various load current levels. The regulator circuits generate one or more control signals in response to the load current and selectively route a switch driver control signal to one or more switches in the output circuit. The switches differ in their size, such that the most efficient switch can be used at a particular load current level. At low load current levels, the driver control signal is routed to output circuitry with smaller switch devices, which incur smaller driver current losses for a given frequency of operation, thereby increasing the regulator efficiency. At high load current levels, the driver control signal is routed to large switch devices, which incur greater driver current losses for a given frequency of operation, but which have a lower impedance. The regulator thus maintains high efficiency over a wide range of load currents while operating at a constant frequency.

Am improved tail current source for low voltage applications

Abstract: A new current source for low-voltage applications is proposed. This current source is well suited for biasing differential pairs and source followers. Measured compliance voltage is slightly smaller than that of a single transistor. Its output resistance is a factor of 25 larger than that of a single transistor current source and was measured to be 8 M/spl Omega/. The use of the new current source improves the common-mode input range and the common-mode rejection ratio of fully balanced and single-ended differential amplifiers.

CMOS current steering logic for low-voltage mixed-signal integrated circuits

Abstract: A quiet logic family-complementary metal-oxide-semiconductor (CMOS) current steering logic (CSL)-has been developed for use in low-voltage mixed-signal integrated circuits. Compared to a CMOS static logic gate with its output range of ΔV logic V dd , a CSL gate swings only ΔV logic V T + 0.25 V because the constant current supplied by the PMOS load device is steered to ground through either an NMOS diode-connected device or switching network. Owing to the constant current, digital switching noise is 100x smaller than in static logic. Another useful feature which can be used to calibrate CSL speed against process, temperature, and voltage variations is propagation delay that is approximately constant versus supply voltage and linear with bias current. Several CSL circuits have been fabricated using 0.8 and 1.2 μm high-V T n-well CMOS processes. Two self-loaded 39-stage ring oscillators fabricated using the 1.2 μm process (1.2 V power supply) exhibited power-delay products of 12 and 70 fJ with average propagation delays of 0.4 and 0.7 ns, respectively. High-V T and low-V T CSL ALU's were operational at V dd 0.70 V and V dd 0.40 V, respectively.

Electrical scooter having an equalization circuit for charging multiple batteries

Abstract: An electric scooter employs an equalization circuit for charging a plurality of series connected batteries used to power the scooter. The equalization circuit has a number of cell circuits, each connected across the terminals of a corresponding battery. Each cell circuit includes two voltage detectors, a first implemented as a modular voltage monitor for detecting a low voltage across the battery terminals, and the second implemented as a Zener diode to detect a high voltage across the battery terminals. Both voltage monitors are enabled by an optocoupler switch. When the switch is turned on and either a low or a high voltage condition is detected, the cell circuit outputs a signal reflective of this condition through a second optocoupler. During a constant current charging phase, a high voltage condition causes the cell circuit to cause a portion of the charging current to bypass that battery, thus achieving equalization. A controller, which selectively enables the first optocoupler, also receives outputs from logic circuitry which tells whether any of batteries have low voltage and also whether the series connected batteries are fully charged. The scooter monitors the batteries for low voltage conditions during starting and also during quiescent states, i.e., low or no current draw, when it is being operated.

Driver circuit device

Abstract: In the constant current drive type driver used for an LVDS (low voltage differential signal) interface, the parasitic capacitance of the package pins is charged and discharged sufficiently at a high speed to secure the high speed signal transmission operation. Further, the AC differential amplitude large enough to be received by the receiver can be obtained. The driver circuit device comprises: a transmit circuit composed of transistors (52, 53, 56, 57) for transmitting a signal by switching the signal current direction flowing through a pair of transmission lines (8, 9) connected between two output terminals (13 and 13B); and a constant current source composed of transistors (54, 75) for controlling the current value of the transmit circuit. In the idle state, only one of the two transistors (54 and 75) of the constant current source is turned on to limit the signal current flowing through the output terminals (13 and 13B). On the other hand, in the high speed signal transmission, both the transistors (54, 75) are turned on to increase the signal current flowing through the output terminals (13, 13B) to obtain a signal current of high DC LVDS level.

Circuit arrangement for producing a d.c. current

Abstract: A description is given of a circuit arrangement for producing a D.C. current, comprising a current-source stage, which is supplied on one input with a measuring current led via an input resistor, and which comprises a current source transistor whose base-emitter path is arranged in parallel with the input resistor and whose collector electrode forms an output of the current-source stage, on which output an output current is offered, a current mirror stage for mirror-inverting the output current of the current-source stage to a working impedance, on which working impedance a control voltage is produced in response to this output current, a current bank having a control input which is supplied with a control voltage, and having at least two outputs simultaneously controlled by the control voltage, on which outputs mutually proportional currents are offered of which a first current forms the measuring current. As a result, a current reference is created which can be used for very low supply voltages, preferably around 0.9 volt, is simple, shows a stable operating behavior and produces a reference current that has a negative temperature coefficient.

The effect of dc offset on current ope

Abstract: When a fault occurs on a power system, one or more phases will experience dc offset. This dc component, which will decay dependent on the L/R time constant of the system, can produce saturation in the current transformers, as well as the input current transformers of the protective relays sensing the fault. In addition, when the fault current is interrupted, the resulting dc tail can maintain the current above the relay's pickup setting for a time dependent on the CT secondary circuit L/R time constant. This paper discusses this phenomenon and how it can affect the operation of two types of current operated relays.

Electrical system having a clear conductive composition

Abstract: An electrical system, or a trigger circuit for use in connection with an electrical system, is disclosed. The electrical system includes a circuit element responsive to applied current, a power source for providing current to the circuit element, a substrate, and a substantially clear conductive composition arranged on or in associatin with the substrate for providing an electrical current path between the power source and the responsive circuit element.

Driver circuit of light-emitting device

Abstract: A driver circuit of a light-emitting device that is able to reduce the current consumption. This circuit includes a reference current source for generating a reference current, a cascode current source circuit for generating a driving current for the light-emitting device with the use of the reference current, and an input circuit for switching the driving current according to a data signal. The cascode current source circuit has a first current mirror formed by first and second transistors and a second current mirror formed by third and fourth transistors. The first transistor is supplied with a first constant current proportional to the reference current, and controls the second transistor so that the driving current flows through the second transistor. The third transistor is supplied with a second constant current proportional to the reference current, and generates a mirror current with respect to the second constant current. The second mirror current flows through the second transistor as the driving current. The input circuit serves to turn on and off the fourth transistor according to the data signal, thereby controlling the output of the driving current to the light-emitting device.

Battery charging apparatus and method with charging mode convertible function

Abstract: A battery charging apparatus for use with batteries that require charging in a constant current mode and/or constant voltage mode. The charging apparatus includes a constant current charging control circuit converting the charging current supplied with the battery into a voltage signal and applying the voltage signal to a feedback input terminal of a switching regulator in response to a charging speed control signal F -- Q, and a constant voltage charging control circuit providing a control signal to the feedback input terminal for controlling constant voltage charging if the battery voltage level has reached a preset voltage level, whereby a constant voltage charging is possible during the charging operation in response to a charging mode selection signal CHG -- MOD. A microcomputer produces the charging mode selection signal CHG -- MOD when it is detected the charging voltage of the battery in the constant current mode and the detected voltage reached to a preset level in order to convert the charging mode into the constant voltage mode. Further, a charging speed control signal F -- Q is produced to enable the switching regulator to perform quick charging operation. With this arrangement, the constant voltage (CV) charging mode can be performed when the battery is in the preset condition, regardless of type of batteries. In addition, by provision of a protection circuit, possible damage of the CV charging control circuit due to the excessive static or surge is effectively prevented.

Degradation judging device of battery

Abstract: PROBLEM TO BE SOLVED: To determine deterioration objectively and accurately by detecting the terminal voltage of a battery at the time of recharging it with a constant charging current and detecting recharge time that the terminal voltage reaches the second voltage from the first voltage by a timer. SOLUTION: Recharge time tt required for the predetermined first voltage value V1 to reach the second voltage value V2 is detected by a timer, and the deterioration of a battery is determined on the basis of the recharge time tt. The first voltage value V1 is set somewhat higher than the voltage value Vs corresponding to a remaining capacity assumed at the time of the start of the recharging of the battery. The second voltage value V2 is set at a voltage value (a voltage value of constant voltage recharging) Vc which is a criterion of the completion of constant current recharging or somewhat lower than this. The recharge time tt is corrected according to a battery temperature and a current value at the time of constant current recharging, and deterioration is judged by comparing the corrected recharge time with a recharge time characteristic value stored in advance.

The effect of DC offset on current operated relays

Abstract: When a fault occurs on a power system, one or more phases will experience DC offset. This DC component, which will decay dependent on the L/R time constant of the system, can produce saturation in the current transformers, as well as the input current transformers of the protective relays sensing the fault. In addition, when the fault current is interrupted, the resulting DC tail can maintain the current above the relay's pickup setting for a time dependent on the current transformer secondary circuit L/R time constant. This paper discusses this phenomenon and how it can affect the operation of two types of current-operated relays.

In-rush current reduction circuit for boost converters and electronic ballasts

Abstract: An electronic power supply circuit (50) that includes a rectifying circuit (14), a boost converter (16), an in-rush current reduction circuit (52), and a bulk capacitor (18). The in-rush current reduction circuit (52) includes an in-rush current limiting resistor (54) and a bypass capacitor (56) that are connected in parallel with each other. An improved version of the in-rush current reduction circuit (52) includes a bypass diode (58) connected in parallel with the in-rush current limiting resistor (54) and bypass capacitor (56) which is oriented to provide a path for current flowing out of bulk capacitor (18). One particular application of the disclosed circuit is for use in an electronic ballast for fluorescent lamps.

Voltage-controlled oscillator resistant to supply voltage noise

Abstract: A voltage-controlled oscillator (VCO) generates an oscillating signal that is substantially resistant to noise fluctuations in the supply voltage. The VCO is a delay-based VCO which preferably includes a compensation circuit for each delay cell and a noise-immune reference current generator for providing a noise-immune bias current to the conditioning circuit of the VCO. The compensation circuit preferably adjusts the capacitance of the delay cell to compensate for the variations in current caused by the supply noise. The noise-immune reference current generator preferably utilizes a configuration of transistors which maintains through at least one transistor a substantially constant current which is used to bias the conditioning circuit.

Controller for an electric power assisted steering system and an electric power assisted steering system

Abstract: A controller for an electric power assisted steering system comprises a drive circuit (2) for controlling current to a motor (1) and a data processor (8) for controlling the motor current and hence assistance torque. A circuit (9) generates a current limit which is a monotonically decreasing function of vehicle speed. A comparator (6) compares motor current with the current limit and switches off the drive circuit (2) if the current limit is exceeded.

Simple constant frequency constant current load-resonant power supply under variable load conditions

Abstract: A power supply incorporating a load-resonant converter operating at a fixed frequency and capable of efficient operation with a constant current characteristic, independent of the load conditions, is presented. The simple resonant circuit is designed so that at one of its multiple resonant frequencies both the load current and the resonant frequency are independent of the value of the load. A power supply is designed and constructed which delivers over 1 kW to a variable load at a constant switching frequency of 82 kHz.

Apparatus for powering television cameras via camera transmission lines

Abstract: An apparatus for powering one or more television cameras through an information signal transmission line wherein the television camera is operated by a constant DC current and outputs multiplexed electrical information signals is provided with a constant current supply unit and a rechargeable battery for powering the television camera when the constant DC current is cut off. A transmission line connects the television camera with the constant current supply means for feeding the television camera with the constant DC current and feeding the current supply unit with the multiplexed electrical information signals. The constant DC current provided by the constant DC current supply unit is equal to the sum of a constant current required for operating the television camera and a constant current required to charge the rechargeable battery.

Method and device for the modulation of the intensity of fluorescent lamps

Abstract: The invention describes a method for the modulation of the light intensity of fluorescent lamps via the supply main by modification of the form and/or the amplitude of the power supply provided. An electronic control element, provided as a component of the logical circuit, temporarily blocks current flow after at least every second zero-crossing of the voltage, dependent upon time and/or voltage. Blocking of the current flow occurs only during the time period in which there is no flow of charging current for the downstream direct-current mains supply circuit. The advantage thus obtained is that the control pulses for the logical circuit do not influence the electric current flowing through the fluorescent lamps.

Bi-direction current control circuit for monitoring charge/discharge of a battery

Abstract: A battery-monitoring circuit includes a bidirectionally current-controllable means disposed between a secondary battery and a charging circuit or a load circuit for monitoring the charge or discharge of the secondary battery to prevent undesirable charging. The current control means has characteristics as an active diode, which is constituted by an error amplifier to which a predetermined voltage and voltage between both terminals of the current control means are supplied. The current control means supplies an output to the current-controllable means, such that the output of the current-controllable means is controlled constant, equal to the predetermined voltage.

Method for measuring particles in gas flow e.g. vehicle exhaust

Abstract: The method generates an electrical field between a hollow electrode (7,12), through which the gas flows, and an internal electrode (9,6) within the hollow electrode by the application of a constant d.c. voltage. The charging current required for maintaining a constant voltage between the electrodes is measured. The d.c. voltage required can be 2 to 3 kV and the charging current can be measured using a high value series resistance (8) in the current circuit as a shunt.

Output buffer driver with load compensation

Abstract: A circuit for producing a buffered output includes a power source, a ground, a circuit input, a circuit output, a voltage reference source, a current control pre-driver and an output driver. The circuit input receives an input signal. The circuit output produces an output signal. The voltage reference source generates a reference voltage. The current control pre-driver includes a first current source, a second current source, and control logic. The first current source is connected to the power source and has a first control input. The second current source is connected to the ground and has a second control input. The control logic is connected to the circuit input, to the voltage reference source, to the first control input of the first current source and to the second control input of the second current source. In response to a first voltage value of the input signal on the circuit input, the control logic turns off the second current source and turns on the first current source. The first current source is turned on by connecting the reference voltage to the first control input of the first current source. In response to a second voltage value of the input signal on the circuit input, the control logic turns off the first current source and turns on the second current source. The second current source is turned on by connecting the reference voltage to the second control input of the second current source. The output driver includes driver circuitry and a feedback capacitance. The driver circuitry is connected to the circuit output. The feedback capacitance includes a first end and a second end. The first end is connected to the first current source and to the second current source. The second end is connected to the circuit output.

Control method for snow-melting device using solar cell

Abstract: PROBLEM TO BE SOLVED: To make it possible to detect when snow has been melted at a preset value or above, by stopping a power conditioner for a short time at constant time interval, or stopping the power conditioner when the power conditioner is brought into constant current control state, and checking the output voltage from solar cell power generation. SOLUTION: A power conditioner 61 pauses at constant time intervals, or at constant timer intervals after the power conditioner is brought out of constant voltage control state. That is, if a voltage equal to or above a preset value, it is judged that snow has been melted. Then, the power conditioner 61 is stopped, and switched to the power generation side. If the generation voltage is lower than the set value, the power conditioner 61 is restarted and directcurrent power is supplied. Thus, it is possible to let reverse power flow perform through solar cell generation when the sun is shining, and bring the power conditioner in forward conversion operation to melt snow through temperature rise in the solar cell when it is snowing or the snow lies. COPYRIGHT: (C)1998,JPO

Output stage with switchable constant current modes

Abstract: An output circuit is provided for delivering output pulses in either a constant voltage or constant current mode. The output circuit has a simple architecture built around a pair of area-ratioed transistors which operate in a linear range carrying a ratio of currents corresponding to the area ratio. The circuit is mode controlled by a switch network which connects to a constant current source, which constant current source controls the pulse amplitude, either current or voltage. As used in a pacemaker embodiment, the circuit is controllable to control the mode and/or amplitude of the pulse following a cyclical decision to deliver a pulse, and with an amplitude derived from pacemaker data and controllable during delivery of the pulse. The circuit has high speed control which enables amplitude modulation of the pulse, for transmitting encoded data to an external device adapted to receive the data.

Charge regulator for a radio telephone

Abstract: An electronic device, such as a radiotelephone, is connectable to a variable-level power source. The electronic device includes a rechargeable power source which is repowered responsive to application of operative power generated by the variable-level power source. The electronic device provides a constant charge current regulator for converting operative power of a constant voltage into operative power of a constant current to be applied to the rechargeable power source to recharge the rechargeable power source. The constant charge current regulator is made up of a series connected diode and resistor pair. According to a further aspect of the invention, when the rechargeable power source becomes fully recharged, application of the operative power can be reduced.

High power output stage with temperature stable precisely controlled quiescent current and inherent short circuit protection

Abstract: An output stage driver circuit comprising two parallel class AB stages running at slightly different quiescent currents, the difference of which is scaled up through a current mirror is disclosed which provides a temperature stable precisely controlled quiescent current for the output stage. A current limited voltage source is provided to ensure inherent short circuit protection with instantaneous response to short circuit or excessive load current conditions.

Output driver circuit with switched current source

Abstract: A driver circuit is presented for producing particular output voltage levels at high speeds using a current switching technique. The circuit employs driver transistors connected in series between switchable current sources. The driver transistors switch current within the current sources through a resistor coupled between an output of the driver circuit and a reference terminal voltage. Switching the current occurs in rapid fashion within an opened loop arrangement. The switchable current sources are configured so that current is present through the current sources whenever a corresponding driver transistor is turned on. Current through the current sources, as switched through the resistor separating the reference terminal voltage and the driver output, is regulated by a closed loop replica circuit. The replica circuit may include an opamp whose output operably produces the regulated current via feedback from the current path to an input of the opamp. Output from the driver circuit may include differential output levels. Those levels are preferably controlled by regulating the current sources providing current to the driver transistors, and using a replica circuit to duplicate the driver transistors from current sources. The replica circuit may therefore be two replica circuits in scaled form. Feedback from a node within a replica circuit may be used along with a high or low reference signal to control current sources in one or both of the replica circuits and one or both of the current sources feeding the driver transistors. In one embodiment, opamps within the feedback circuits can have differential outputs feeding transistors which differentially control the regulated current which is then replicated through a driver transistor.