Parasitic capacitance

About: Parasitic capacitance is a research topic. Over the lifetime, 10029 publications have been published within this topic receiving 110331 citations.

A Multiphase, Modular, Bidirectional, Triple-Voltage DC–DC Converter for Hybrid and Fuel Cell Vehicle Power Systems

Abstract: Electrical power systems in future hybrid and fuel cell vehicles may employ three voltage [14 V, 42 V, and high voltage (HV)] nets. These will be necessary to accommodate existing 14-V loads as well as efficiently handle new heavy loads at the 42-V net and a traction drive on the HV bus. A low-cost DC-DC converter was proposed for connecting the three voltage nets. It minimizes the number of switches and their associated gate driver components by using two half-bridges and a high-frequency transformer. Another salient feature is that the half bridge on the 42-V bus is also utilized to provide the 14-V bus by operating at duty ratios around an atypical value of 1/3. Moreover, it makes use of the parasitic capacitance of the switches and the transformer leakage inductance for soft switching. The use of half bridges makes the topology well suited for interleaved multiphase modular configurations as a means to increase the power level because the capacitor legs can be shared. This paper presents simulation and experimental results on an interleaved two-phase arrangement rated at 4.5 kW. Also discussed are the benefits of operating with an atypical duty ratio on the transformer and a preferred multiphase configuration to minimize capacitor ripple currents.

Electrosurgical safety circuit and method of using same

Abstract: An improved electrosurgical safety circuit where the currents in the active and patient leads are monitored, the monitored currents being respectively rectified and then subtracted from one another. Whenever the active current exceeds the patient or return current by an amount corresponding to a dynamically variable threshold, an appropriate measure is taken such as the sounding of an alarm and/or the de-energization of the electrosurgical generator. The dynamic threshold varies in accordance with the level of the signal applied to the patient and compensates for leakage current through stray capacitance from the active lead to ground. The patient lead is substantially grounded at radio frequencies through a frequency sensitive network. The frequency sensitive network may include a capacitor, the value of which is such as to provide the foregoing frequency response. Since as small a capacitor as possible must be used to provide a high impedance at low frequencies, and since the radio frequency voltage across the capacitor must be kept low to thereby keep the voltage patient low at radio frequencies, a further network is employed to enable the use of a small capacitor while at the same time decreasing the effective voltage thereacross whereby protection of the patient is enhanced.

Capacitive fingerprint acquisition sensor

Abstract: An apparatus for detecting topographic variations on an object such as a finger includes an array of sensing elements disposed on a substrate which each have a parasitic capacitance. An insulating receiving surface is disposed over the array of sensing elements and is adapted to receive the object such that a sensing element and a portion of the object located thereabove creates a measurable change in capacitance with respect to the parasitic capacitance. An electronic circuit is coupled to the array of sensing elements for measuring the measurable change in capacitance.

P-N Junction Charge-Storage Diodes

Abstract: The design theory for a new range of p-n junction applications is presented. The applications include pulse generation, wave shaping, and harmonic generation. The diodes are characterized by a very abrupt interruption of reverse current in the turn-off transient and are approximately ideal nonlinear capacitors. The abrupt interruption of current in the reverse transient is related to the impurity profile in the junction. An estimate is given of the duration of the abrupt phase. In addition, the role of parasitic elements such as inductance, capacitance, and series resistance is discussed in relation to a particular representative circuit. In typical cases, the abrupt turn-off phase lasts for a time of the order of 10-9 sec. Transitions in excess of 100 v or an ampere are readily obtained.

Digital Control of Actual Grid-Connected Converters for Ground Leakage Current Reduction in PV Transformerless Systems

Abstract: The design of a photovoltaic (PV) grid-connected converter usually comprehends a galvanic isolation between the grid and the photovoltaic panels. Recently, in low power systems, the galvanic isolation has been removed with the aim to increase efficiency and reduce the cost of the converter. Due to the presence of a parasitic capacitance between the photovoltaic cells and the metal frame of the PV panel, usually connected to earth, a high value of common mode current (i.e., ground leakage current) can arise. In order to limit the ground leakage current (which deteriorates the power quality and generates EMI), new converter topologies have been proposed. Their effectiveness is based on the symmetrical (ideal) commutations of the power switches and some of them adopt a further voltage level derived from a capacitive divider of the DC bus voltage. Unfortunately, in actual implementations, asymmetrical power switches transients and variations of this added voltage lead to higher ground leakage current with respect to the ideal case. After a review of the state of the art this paper investigates these two issues and presents a particular solution (based on digital control and PWM strategy) that, in conjunction with a compensation strategy of power switches actual commutations, guarantees low ground leakage current regardless the parameters tolerance of the power circuit. Simulation and experimental results confirm the effectiveness of the proposed solution.