Negative impedance converter

About: Negative impedance converter is a research topic. Over the lifetime, 5801 publications have been published within this topic receiving 87636 citations.

Apparatus and method for regulating white LEDs

Abstract: The present invention is an apparatus for driving white LEDs. The apparatus includes a switchable current sink, a DC-DC converter and a reference circuit. The DC-DC converter provides a driving voltage to a plurality of LEDs. The switchable current sink regulates currents through the plurality of LEDs, and the switchable current sink further provides a first reference voltage and outputs a plurality of voltage drops. The reference circuit receives the first reference voltage and the plurality of voltage drops to provide a second reference voltage to the DC-DC converter. The DC-DC converter adjusts the driving voltage provided to the plurality of LEDs according to the second reference voltage. In this way, the driving voltage is regulated to a minimum possible value and consequently the voltage drops across the switchable current sink is minimized. Hence, the LED driving system maintains higher efficiency.

Small-signal impedance modelling of type-III wind turbine

Abstract: Impedance-based small signal analysis is a useful tool to examine resonance between type-III wind turbines and the grid, but no accurate and complete model of the turbine has been presented for the frequency range that covers from a few Hz to a few kHz Existing models either ignore the effects of the converters or do not model such effects correctly This paper presents positive- and negative-sequence impedance models of the turbine with and without phase-lock loop (PLL) This paper also gives an overview on the modelling approach taken to model the machine with PLL dynamics Finally, the models are validated with impedance sweeps using real-time simulation

Amplifier using a single polarity power supply and including depletion mode FET and negative voltage generator

Abstract: The present invention provides a power amplifier operating with a single power supply. The amplifier includes at least one depletion-mode FET for amplifying an ac signal and a negative voltage generator for providing a bias to the FET. Preferably the amplifier further includes a negative voltage regulator to provide a regulated bias to bias the FET for a class A, AB or B operation. The negative generator includes a multivibrator for producing two clock signals and a charge pump which receives the clock signals and produces a negative voltage. Advantageously the negative voltage is provided as a low reference potential to the multivibrator so that the clock signals it produced include a negative voltage period, which enables the charge pump to operate in a power efficient manner.

Switchgear voltage sensor

Abstract: A switchgear assembly which includes a vacuum interrupter, a current transformer, and a capacitive voltage sensor, all embedded within a cast epoxy housing mounted to a solidly grounded support structure. The voltage sensor includes a first capacitor, which is formed by an interrupter conductor stud, a plate, and the cast epoxy disposed therebetween, and a second capacitor, which is connected between the plate and a metal tube extending outside the housing. The tube is connected to ground through a conductive coating, applied to the housing, having an impedance which is very low in comparison to the impedance of the first capacitor. The voltage signal on the plate, which is proportional to the stud voltage, is supplied through the center conductor of a coaxial lead to one input of a voltage level sensing circuit, where it is amplified, rectified, and compared with a reference voltage to produce a positive output signal whenever the stud voltage exceeds a first value, and thereafter produce a negative output signal whenever the stud voltage decreases to less than a second value lower than the first value. The conductive shield of the coaxial lead has a first end connected to the metal tube and a second end connected to the ground terminal of the voltage level sensing circuit and to ground through a ground path having a low impedance in comparison to the impedance of conductive coating ground path between the metal tube and the grounded support structure.

Voltage supplying device, and semiconductor device, electro-optical device and electronic instrument using the same

Abstract: A voltage supplying device which supplies a voltage to a load capacitance to finish charging the load capacitance with a predetermined voltage within a predetermined charging period. The voltage supplying device comprises a digital-analogue converter (DAC) and a voltage follower circuit for performing the impedance conversion for a voltage from the DAC and outputting the converted voltage. A first switching element is provided between the output of the voltage follower circuit and the load capacitance. A bypass line is provided for supplying a voltage from the DAC to the load capacitance bypassing the impedance conversion circuit and the first switching element, and a second switching element is provided on the bypass line. In the first period of the charging period, the first switching element is turned on, and the second switching element is turned off, whereby the output of the voltage follower circuit is supplied to the load capacitance. In the second period of the charging period, the first switching element is turned off, and the second switching element is turned on, whereby the output of the DAC is supplied to the load capacitance instead of the output of the voltage follower circuit.