10281 results about "Current limiting" patented technology

A secondary power source system, includes a first unit receiving a primary power input and restricting a current used for charging to a predetermined amount, a second unit including a device providing capacitance, receiving a first output from the first unit with restricted current, a third unit generating a second output of a certain voltage, and a fourth unit performing a logical OR operation with the primary power input, first output from the first unit and second output from the second unit, to generate a single third output of a certain voltage.

Various embodiments provide compositions that exhibit positive temperature coefficient of resistance (PTCR) properties for use in thermal interactions with tissue—including thermal sensing and I2R current-limiting interactions. Embodiments also provide tissue-engaging surfaces having PTCR materials that provide very fast switching times between low resistance and high, current-limiting resistance. One embodiment provides a matrix for an electrosurgical energy delivery surface comprising a PTCR material and a heat exchange material disposed within an interior of the matrix. The PTCR material has a substantially conductive state and a substantially non-conductive state. The heat exchange material has a structure configured to have an omni-directional thermal diffusivity for exchanging heat with the PTCR material to cause rapid switching of the PTCR material between the conductive state and non-conductive state. Preferably, the structure comprises a graphite foam having an open cell configuration. The matrix can be carried by tissue contacting surfaces of various electrosurgical devices.

One embodiment of the invention provides a UPS including a precharge circuit and a battery pack sensor electrically coupled to the precharge circuit. The sensor senses the presence of an extra battery pack. The precharge circuit includes: a first precharge contact; a capacitor having first and second leads, the first lead electrically coupled to the first contact; a second precharge contact electrically coupled to the second lead of the capacitor; a current limiting circuit having first and second leads, the first lead of the current limiting circuit electrically coupled to the first lead of the capacitor; and a third precharge contact electrically coupled to the second lead of the current limiting circuit. The UPS can further include an enclosure having a housing and a battery connector integral to the housing, the battery connector adapted to receive the first, second and third precharge contacts.

This disclosure describes techniques for operating a corded electronic device in which a battery and a power control unit manage power draw from an external power source electrically coupled to the corded electronic device using a physical cord, such as a universal serial bus (USB) cable. The power control unit automatically supplements an electrical current continuously drawn by the corded electronic device from the external power source with an electrical current from the battery, when needed. Moreover, the power control unit operates to limit the current drawn from the external power source and the physical cord so as to ensure the current does not exceed any limitations or requirements associated with the external power source or the physical cord.

A ballast circuit is disclosed for inductively providing power to a load. The ballast circuit includes an oscillator, a driver, a switching circuit, a resonant tank circuit and a current sensing circuit. The current sensing circuit provides a current feedback signal to the oscillator that is representative of the current in the resonant tank circuit. The current feedback signal drives the frequency of the ballast circuit causing the ballast circuit to seek resonance. The ballast circuit preferably includes a current limit circuit that is inductively coupled to the resonant tank circuit. The current limit circuit disables the ballast circuit when the current in the ballast circuit exceeds a predetermined threshold or falls outside a predetermined range.

Embodiments of the invention include a method of forming a nonvolatile memory device that contains a resistive switching memory element that has improved device switching performance and lifetime, due to the addition of a current limiting component disposed therein. The electrical properties of the current limiting component are configured to lower the current flow through the variable resistance layer during the logic state programming steps by adding a fixed series resistance in the resistive switching memory element of the nonvolatile memory device. In some embodiments, the current limiting component comprises a varistor that is a current limiting material disposed within a resistive switching memory element in a nonvolatile resistive switching memory device. Typically, resistive switching memory elements may be formed as part of a high-capacity nonvolatile memory integrated circuit, which can be used in various electronic devices, such as digital cameras, mobile telephones, handheld computers, and music players.

A ballast circuit is disclosed for inductively providing power to a load. The ballast circuit includes an oscillator, a driver, a switching circuit, a resonant tank circuit and a current sensing circuit. The current sensing circuit provides a current feedback signal to the oscillator that is representative of the current in the resonant tank circuit. The current feedback signal drives the frequency of the ballast circuit causing the ballast circuit to seek resonance. The ballast circuit preferably includes a current limit circuit that is inductively coupled to the resonant tank circuit. The current limit circuit disables the ballast circuit when the current in the ballast circuit exceeds a predetermined threshold or falls outside a predetermined range.

A ballast circuit is disclosed for inductively providing power to a load. The ballast circuit includes an oscillator, a driver, a switching circuit, a resonant tank circuit and a current sensing circuit. The current sensing circuit provides a current feedback signal to the oscillator that is representative of the current in the resonant tank circuit. The current feedback signal drives the frequency of the ballast circuit causing the ballast circuit to seek resonance. The ballast circuit preferably includes a current limit circuit that is inductively coupled to the resonant tank circuit. The current limit circuit disables the ballast circuit when the current in the ballast circuit exceeds a predetermined threshold or falls outside a predetermined range.

A system for heat ablation of tissue in a patient comprises a plurality of electrodes operatively connected to a source of radiofrequency energy and configured to apply RF energy to tissue at a patient site, a plurality of RF current restricting circuits, each circuit coupled between one of the plurality of electrodes and the source of radiofrequency energy, and configured to restrict RF energy to the electrode when the current restricting circuit is enabled and not restrict RF energy to flow to the electrode when the current restricting circuit is disabled, at least one return electrode adapted to contact the patient and configured to return RF energy to the RF source; and a switching mechanism configured to selectively enable each of the plurality of RF current restricting circuits, in one of a sequential and non sequential fashion, wherein the switching mechanism is isolated from each of the current restricting circuits.

Secondary resonant pickup coils (102) used in loosely coupled inductive power transfer systems, with resonating capacitors (902) have high Q and could support large circulating currents which may destroy components. A current limit or "safety valve" uses an inductor designed to enter saturation at predetermined resonating currents somewhat above normal working levels. Saturation is immediate and passive. The constant-current characteristic of a loosely coupled, controlled pickup means that if the saturable section is shared by coupling flux and by leakage flux, then on saturation the current source is terminated in the saturated inductor, and little detuning from resonance occurs. Alternatively an external saturable inductor (1101, 1102) may be introduced within the resonant circuit (102 and 902), to detune the circuit away from the system frequency. Alternatively DC current may be passed through a winding to increase saturation of a saturable part of a core. As a result, a fail-safe pickup offering a voltage-limited constant-current output is provided.

The present invention discloses a primary-side feedback switching power supply that uses a sample-and-hold circuit to obtain a corner voltage of a harmonic wave voltage while the primary-side auxiliary winding is operating at a discontinuous mode as a feedback control, and provides both voltage regulation and current limit functions. A stable voltage output is provided within the nominal input voltage and nominal output load, such that when the output reaches a current limit, the output voltage drops but the output current is controlled to remain unchanged, so as to provide an over-current protection.

A system may regulate voltage supplied from a power source to an integrated circuit and / or an inertial device. A minimal voltage may be maintained in the integrated circuit by temporarily cutting off current to the inertial device to supply surges of voltage to the controller. Optionally voltage may be smoothed between said surges for example by adding capacitance and / or a current restrictor.

An electronically commutated brushless DC motor primarily for fractional horsepower applications of the type where at any instant one motor winding is unpowered and used to detect back EMF zero-crossings which information is used to initiate winding commutations. The duration of the pulse produced in this winding due to dissipation of stored energy by free-wheel diodes in parallel with the commutation devices after supply of current has been removed from this winding is used to provide a measure of motor current. This allows for simplified commutation device current limiting circuits and is available for control purposes which are a function of motor torque. There is also disclosed a method for maximizing useful power output by reducing the phase angle between the motor current and the back EMF. This is accomplished by introducing a delay in commutating the motor windings beyond the occurrence of each back EMF zero-crossing, with the delay being a function of the time between commutations.

A current-mode switching regulator uses adaptive current sensing to reliably monitor an inductor current in a cost-efficient and power-efficient manner. A semiconductor switch periodically turns on to conduct the inductor current. A voltage drop across the semiconductor switch is monitored when the semiconductor switch is on. A variable gain amplifier with an automatic gain control loop generates a feedback signal from the voltage drop of the semiconductor switch when conducting to provide an indication of the inductor current to a controller. The automatic gain control loop compensates for any variations in the on-resistance of the semiconductor switch.

A method and system for providing and magnetic element is disclosed. In one aspect, the magnetic element includes at least a pinned layer, a free layer, and a current confined layer residing between the pinned layer and the free layer. The pinned layer is ferromagnetic and has a first magnetization. The current confined layer has at least one channel in an insulating matrix. The channel(s) are conductive and extend through the current confined layer. The free layer is ferromagnetic and has a second magnetization. The pinned layer, the free layer, and the current confined layer are configured to allow the magnetization of the free layer to be switched using spin transfer. The magnetic element may also include other layers, including layers for spin valve(s), spin tunneling junction(s), dual spin valve(s), dual spin tunneling junction(s), and dual spin valve / tunnel structure(s).

The present invention provides a drive and control apparatus provides a desired switched current to a load including a string of one or more electronic devices. A voltage conversion means, based on an input control signal converts the magnitude of the voltage from the power supply to another magnitude that is desired at the high side of the load. A dimming control means provides control for activation and deactivation of the load and may further provide a means for current limiting. A feedback means is coupled to the voltage conversion means and a current sensing means and provides a control signal to the voltage conversion means that is indicative of voltage drop across the current sensing means which represents the current flowing through the load. Based on the control signal received, the voltage conversion means can subsequently adjust its output voltage such that a constant switched current is provided to the load.

A highly reliable, high voltage AC / DC LED device with integrated protection mechanism is disclosed. The protection element can be a current-limiting resistor, monolithically integrated on LED chip, or a discrete resistor assembled in the lamp package or submount. The protection elements may also include other parts integrated on a submount.

The present invention takes the form of a current limiting apparatus and method for limiting current flow, induced when the level of an external signal is greater than an external signal threshold signal level, in a conductive loop formed by a medical device implanted within a living organism having electrically excitable tissue. The system includes an implantable pulse generator (IPG) system having a housing, a signal generator disposed in the housing that generates an electrical signal, and at least one lead extending from the housing to convey electrical signal to the patient. To limit the induced current flow, the IPG includes current limiting componentry, an impedance increasing element, and / or alternating current blocking elements. These components provide an alternating current impedance path to the electrical ground from a lead coupled to the capacitive element. Also disclosed are techniques for reducing the effective surface area of the current inducing loop caused by the IPG system.

One embodiment of the present invention includes a memory element having a composite free layer including a first free sub-layer formed on top of the bottom electrode, a nano-current-channel (NCC) layer formed on top of the first free sub-layer, and a second free sub-layer formed on top of the NCC layer, wherein when switching current is applied to the memory element, in a direction that is substantially perpendicular to the layers of the memory element, local magnetic moments of the NCC layer switch the state of the memory element.

A power supply including a regulation circuit that maintains an approximately constant load current with line voltage. An example circuit includes a switch including first, second and third terminals. The first terminal is coupled or decoupled to the second terminal in response to a control signal received at the third terminal. Voltage sense circuitry is included and is coupled to sense a voltage drop across the switch. The voltage drop is representative of a current in the switch during an on time of the switch. The voltage sense circuitry has a variable current limit threshold that increases between a first level and a second level during the on time of the switch. The control signal is responsive to the variable current limit threshold to regulate a power supply with an output characteristic having an approximately constant output voltage below an output current threshold and an approximately constant output current below an output voltage threshold.

A protection circuit for a boost power converter provides input under-voltage protection and output over-voltage and over-current protection. The protection circuit includes a control power MOSFET connected in series between the ground of the boost power converter and the ground of the load. The arrangement of the circuit makes it easy to drive the gate of an N-channel power MOSFET and is ideal for current-limiting control, which utilizes the Rds-on of the MOSFET as a current sensing element. Neither a specific gate-driver nor a current sensing resistor is required, and thus high efficiency can be achieved. Furthermore, the slow slew-rate at the gate of the MOSFET provides a soft-start to the load. The protection circuit includes a temperature compensation circuitry to offset the variation of the Rds-on. A time delay circuit prevents the switching elements and protection elements from overload damage.

A dual energy scanning densitometry system for imaging and measuring bone density maintains acceptable flux by adjusting the x-ray current or scan speed according to preceding scan line data. The amount of acceptable flux is maintained within limits modified by information about the region of the body being scanned so that different precisions may be maintained for different body regions. Scan speed and current may be controlled so that scan speed is maximized within the current limits. Essentially continuous flux control can be achieved.

The invention provides a combined estimation method for lithium ion battery state of charge, state of health and state of function. The combined estimation method comprises the steps that the state of he---alth of a battery is estimated online: open circuit voltage and internal resistance are identified online by adopting a recursive least square method with a forgetting factor, the state of charge is indirectly acquired according to a pre-established OCV-SOC corresponding relation, and then the size of battery capacity is estimated according to cumulative charge and discharge electric charge between two SOC points; the state of charge of the battery is estimated online: the state of charge of the battery is estimated by adopting the Kalman filter algorithm based on a two-order RC equivalent circuit model, and the battery capacity parameter in the Kalman filter algorithm is updated according to the estimation result of battery capacity; and the state of function of the battery is estimated online: the maximum chargeable and dischargeable current is calculated based on the voltage limit and the current limit of the battery according to internal resistance obtained by online identification, and then the maximum chargeable and dischargeable function can be obtained through further calculation.

A solid-state light engine comprised of light emitting diodes (LEDs) configured into a bridge rectifier with a current limiting module coupled to the LED bridge rectifier. The light engine may be packaged for high temperature operation. Optionally, the LEDs comprise wavelength-converting phosphors with a persistence that is a multiple of the peak to peak current period, to smooth and mask ripple frequency pulsation of emitted light.

A method and apparatus of powering components on a network by using a load-share technique and by using over-voltage and current-limiting circuitry. The power subsystem for a component in a network is designed in a load-share manner whereby the power subsystem will supply power to the network bus and to the component load. Under normal operation of the power subsystem, the load will be powered directly from the power subsystem. In the event of a failure, the load will immediately pull power from the bus and thereby maintain network operation. The power subsystem and the power supply are protected from disruptions due to voltage or current surges. Further, the power subsystem is in compliance with the IEEE 1394 specifications in terms of recommended current levels and galvanic isolation of the power sources.

The present invention provides a drive and control apparatus provides a desired switched current to a load including a string of one or more electronic devices. A voltage conversion means, based on an input control signal converts the magnitude of the voltage from the power supply to another magnitude that is desired at the high side of the load. A dimming control means provides control for activation and deactivation of the load and may further provide a means for current limiting. A feedback means is coupled to the voltage conversion means and a current sensing means and provides a control signal to the voltage conversion means that is indicative of voltage drop across the current sensing means which represents the current flowing through the load. Based on the control signal received, the voltage conversion means can subsequently adjust its output voltage such that a constant switched current is provided to the load.

A primary side sensing power control system and method that controls the current limit such that it is maintained within a small range for any acceptable input voltages and causes the output voltage of a PWM controller to drop as the output load increases when the current limit is reached.

A layer of nanopaiticles having a dimension on the order of 10 nm is employed to form a current constricting layer or as a hardmask for forming a current constricting layer from an underlying insulator layer. The nanoparticles are preferably self-aligning and / or self-planarizing on the underlying surface. The current constricting layer may be formed within a bottom conductive plate, within a phase change material layer, within a top conductive plate, or within a tapered liner between a tapered via sidewall and a via plug contains either a phase change material or a top conductive material. The current density of the local structure around the current constricting layer is higher than the surrounding area, thus allowing local temperature to rise higher than surrounding material. The total current required to program the phase change memory device, and consequently the size of a programming transistor, is reduced due to the current constricting layer.