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.

System and method for over-voltage protection in a photovoltaic system

Abstract: A photovoltaic array for use in an electrical power system includes multiple photovoltaic modules and a voltage converter coupled to at least one of the photovoltaic modules. The photovoltaic array also includes an over-voltage protection circuit. The over-voltage protection circuit includes an interface adapted to couple to an output of the voltage converter. The over-voltage protection circuit also includes a spike detector configured to detect a voltage spike in an output voltage of the voltage converter. The over-voltage protection circuit further includes a voltage control module configured to regulate an output voltage slew rate of the voltage converter in response to an over-voltage signal received from the spike detector.

Ac equivalent circuit analysis for high-frequency isolated dual-bridge series resonant dc/dc converter

Abstract: Bidirectional dual-bridge DC/DC converter with high-frequency isolation is gaining more attentions due to small size, high power density. In this paper, a dual-bridge series resonant DC/DC converter is analyzed with two simple ac equivalent circuit analysis methods for both voltage source load and resistive load. In both methods, only fundamental components of voltages and currents are considered. All the switches may work in either ZVS or ZCS for a wide changes in load or supply voltage allowing itpsilas use in a wide range of applications, such as renewable energy generation, regular battery charger/discharger, do motor control, etc. It is also shown in the second method that the load side circuit could be represented with an equivalent impedance. The polarity of cosine value of the load angle reveals the power flow direction. The analysis is verified with PSIM simulation results. Experimental results based on a 200 W prototype circuit are also included for validation purpose.

High efficiency bimodal power converter and method of operation thereof

Abstract: A bimodal power converter, having an input couplable to a voltage source, provides a charging current to at least one of first and second serially-coupled output energy storage devices. The bimodal converter includes power switching circuitry, coupled to the input, for controlling the charging current conducted through the power converter and a mode selection circuit. The mode selection circuit includes a voltage sensing circuit for sensing an input voltage at the input of the power converter and a mode switching circuit, coupled to the voltage sensing circuit, for selecting an alternative one of a first and second mode of operation. In the first mode of operation, the charging current concurrently flows through both of the first and second output energy storage devices when the input voltage exceeds a threshold voltage. In the second mode of operation, the charging current alternates flowing through the first and second output energy storage devices when the input voltage is less than the threshold voltage. The mode selection circuit thereby decreases losses associated with components of the power converter. Concurrently, a duty cycle of the power switching circuitry reduces to decrease conduction losses associated with the power converter.

Nonideal negative resistors and capacitors using an operational amplifier

Abstract: Negative impedance converters (NIC's) may be used to realize negative driving-point impedances. The effect of the nonideal characteristics of the operational amplifier such as finite frequencydependent gain and output impedance on the performance of the negative impedances is analyzed. Detailed equivalent circuits showing the additional positive or negative inductive impedances due to the nonideal characteristics are given for negative resistance and negative capacitance realizations, and their relative performances are compared. The experimental results confirm the validity of the equivalent circuits. The effect of the slew rate of the operational amplifier on the maximum signal-handling capability (SHC) of the negative impedances at high frequencies is studied. Practical design considerations for achieving wider bandwidth as well as improved SHC are discussed.

Impedance related blood flow measuring device

Abstract: A cardiac blood flow measuring method and apparatus including two current electrodes and two voltage pick-up electrodes positionable in direct contact with the subject, with a circuit for applying a high frequency, low voltage current to the current electrodes and a circuit for measuring the total impedance across the voltage pick-up electrodes by using a summing circuit for adding selectively either a resistive or a reactive voltage to the subject''s total impedance voltage to determine selectively either the subject''s resistive impedance or reactive impedance with the reactive impedance being employed to measure cardiac blood volume flow.