14119 results about "Constant current" patented technology

An electroporation device which may be used to effectively facilitate the introduction of a macromolecule into cells of a selected tissue in a body or plant. The electroporation device comprises an electro-kinetic device (“EKD”) whose operation is specified by software or firmware. The EKD produces a series of programmable constant-current pulse patterns between electrodes in an array based on user control and input of the pulse parameters and allows the storage and acquisition of current waveform data. The electroporation device also comprises a replaceable electrode disk having an array of needle electrodes, a central injection channel for an injection needle, and a removable guide disk.

A light-emitting diode (LED) driver is adapted to control either the magnitude of the current conducted through a LED light source or the magnitude of a voltage generated across the LED light source. The LED driver comprises a power converter circuit for generating a DC bus voltage, and an LED drive circuit for receiving the bus voltage and adjusting the magnitude of the current conducted through the LED light source. The LED driver is operable to dim the LED light source using either a pulse-width modulation technique or a constant current reduction technique. The LED drive circuit may comprise a controllable-impedance circuit, such as a linear regulator. The LED driver may be operable to control the magnitude of the bus voltage to optimize the efficiency and reduce the power dissipation in the LED drive circuit, as well ensuring that the load voltage and current do not have any ripple.

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.

A light-emitting diode (LED) driver according to the present invention consists of a voltage pre-regulator and multiple linear current regulators with an adaptively-controlled drive voltage. In this LED driver, the efficiency maximization is achieved by eliminating the sensing of the voltage drops across the linear regulators, i.e., by removing the external voltage feedback for the adjustment of the output voltage of the pre-regulator. In the LED driver of the present invention, the self-adjustment of drive voltage is achieved by relying on a relatively strong dependence between the gate-to-source and drain-to-source voltages of a current-regulating transistor, e.g., a MOSFET, operating in the linear region. The driver powers all LEDs in a string with a constant current and provides consistent illumination and optimum operating efficiency at low cost over a wide range of input/output voltage and temperature.

A current source generates, with high efficiency, a current that is substantially constant over a wide range of output voltages. This current is injected into the first end of a series-connected string (hereinafter referred to as string) of LEDs, with the second end of the string connected through a resistor to ground. The voltage developed across this resistor, which is a measure of current flow in the series string, is fed back to the current source, wherein feedback maintains nearly constant current output over a wide range of output voltages. A switch, such as a field effect transistor (FET) is placed in parallel with each LED in the string. A level shift gate driver couples a pulse width modulated control signal to the gate of each FET. When the FET across a particular LED is on, substantially all the current flows through the FET rather than the LED, and little or no light is emitted. Because the one resistance of the FET is very low, the power dissipated in the FET (current squared times resistance) is also very low. With the FET turned on, the forward voltage drop of the LED it is controlling drops to near zero, since little current is flowing through the LED. However, because the current source is designed to provide constant current over a wide range of output voltages, the current flow through the other LEDs in the series string changes little. When the FET is turned off, substantially all of the current flows through the associated LED, turning it on. By modulating the duty cycle of each FET, the brightness of each associated LED may be varied smoothly over its full range.

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. 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.

A dimmer circuit applicable for LED device and control method thereof is disclosed in the embodiments of the present invention. The dimmer circuit is applicable for controlling at least a LED device. The dimmer circuit includes a rectifier, a bleeder, a phase angle detect circuit, a constant current circuit and a programmable micro controller. The phase angle detect circuit couples to the programmable micro controller. The constant current circuit couples to the LED device The programmable micro controller generates a PWM signal according to the output signal of the phase angle detect circuit to adjust current of the constant current circuit.

A charging apparatus for electrically charging a capacitor storage type power source comprises a switching circuit for turning on/off the charge current, a current detection circuit for detecting the charge current, a voltage detection circuit for detecting the voltage of power source, a constant current control circuit for outputting an error amplifying signal according to the current value, a power control circuit for outputting an error amplifying signal according to the current value, the voltage value-and a power reference value, a constant voltage control circuit for outputting an error amplifying signal according to the voltage value and a voltage reference value, an OR circuit for selecting one of the error amplifying signals and a control circuit for generating a pulse width modulation signal according to the error amplifying signal output from the OR circuit to turn on/off the switching circuit and control the charge current.

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.

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.

An active matrix type EL display device is provided, which is capable of suppressing the unevenness of luminance display due to the unevenness of the characteristics of TFTs which constitute pixels, or due to variations in the environmental temperature at which the display device is used. The active matrix type EL display is driven by a time gray scale method, and is capable of keeping the drain current of each of its EL driving TFTs constant by operating each of the EL driving TFTs in a saturation region in an ON state. Accordingly, constant current can be made to flow in each of the EL elements, whereby it is possible to provide an active matrix type EL display device with accurate gray scale display and high image quality.

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.

System and method for regulating a power converter. The system includes a first signal generator configured to receive at least an input signal and generate at least a first output signal associated with demagnetization and a second output signal associated with sampling. Additionally, the system includes a sampling component configured to receive at least the input signal and the second output signal, sample the input signal based on at least information associated with the second output signal, and generate at least a third output signal associated with one or more sampled magnitudes. Moreover, the system includes an error amplifier configured to receive at least the third output signal and a first threshold voltage and generate at least a fourth output signal with a capacitor, the capacitor being coupled to the error amplifier.

A light emitting diode lighting device and system that can be used for illuminating the interior and/or exterior of vehicles, aircraft, watercraft, signage or buildings is provided. It includes a voltage feedback constant current power supply circuitry and high power LEDs. The printed circuit assemblies are firmly mounted onto a continuous or semi-continuous mounting channel case that also works as a heat sink. By this means, it not only increases the reliability of the LED lighting tube but also it provides sufficient heat dissipation capability for the heat generated by the LEDs. Since the operating temperature of the LEDs is controlled and stays in cool condition, it dramatically increases the LED's lifetime and efficiency. The end caps of this LED lighting device are fully compatible with existing conventional fluorescent light fixtures and can directly replace those fluorescent lighting tubes in vehicles, mass-transit, watercrafts, aircrafts, signage or buildings with minimal modifications.

A primary-side flyback power converter supplies a constant voltage and a constant current output. To generate a well-regulated output voltage under varying load conditions, the power converter includes a PWM controller. The PWM controller generates a PWM signal to control a switching transistor in response to a flyback voltage detected from the first primary winding of the power supply transformer. To reduce power consumption, the flyback energy of the first primary winding is used as a DC power source for the PWM controller. The flyback voltage is sampled following a delay time to reduce interference from the inductance leakage of the transformer. To generate a more accurate DC output voltage, a bias current is pulled from the detection input to form a voltage drop across a detection resistor for compensating for the voltage drop of the output rectifying diode.

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.

A switching power converter detects low load conditions based on the ratio of a first peak current value for peak current switching in constant voltage regulation mode to a second peak current value for peak current switching in constant current regulation mode. The power supply load is considered to have a low load if the ratio is lower than a predetermined threshold. Once a low load condition is detected, the switching frequency of the switching power converter is reduced to a level that minimizes switching loss in the power converter. In addition, the switching power converter also adjusts the switching frequency according to the sensed input line voltage. An offset is added to the switching period to reduce the switching frequency of the switching power converter, as the input line voltage is increased.