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.

Single-Stage Single-Switch Switched-Capacitor Buck/Buck-Boost-Type Converter

Abstract: A new dc-dc converter featuring a steep step-down of the input voltage is presented. It answers a typical need for on-board aeronautics modern power architectures: power supplies with a large conversion ratio able to deliver an output voltage of 1-1.2 V. The proposed structure is derived from a switched-capacitor circuit integrated with a buck converter; they share the same active switch. The proposed solution removes the electromagnetic interference (EMI) emission due to the large di/dt in the input current of the switched-capacitor power supplies. Compared with a quadratic buck converter, it presents a similar complexity, a smaller reduction in the line voltage at full load (but less conduction losses due to smaller input inductor current and capacitor voltage), lower voltage stresses on the transistor and diodes, lower current stresses in the diodes, and smaller size inductors. A similar structure using a buck-boost converter as the second stage is also presented. The experimental results confirm the theoretical developments.

Apparatus and method for performing impedance measurements

Abstract: An impedance module for calculating the impedance of a body part creates stimulus currents for injection into the body part and receives resulting voltages generated by the body part The impedance module includes a current generator for generating the stimulus currents, the stimulus currents including a current signal and a complementary current signal thereby forming a differential current signal. The impedance module also includes voltage processing circuitry for pre-processing the received voltages and amplifying the received voltages to generate a measured voltage signal; processing circuitry for creating a current control voltage signal for controlling parameters related to the stimulus currents, and for calculating an impedance value based on the stimulus current and the measured voltage signal, and interface circuitry for interconnecting the components of the impedance module.

Ferroelectric negative capacitance domain dynamics

Abstract: Transient negative capacitance effects in epitaxial ferroelectric Pb(Zr0.2Ti0.8)O3 capacitors are investigated with a focus on the dynamical switching behavior governed by domain nucleation and growth. Voltage pulses are applied to a series connection of the ferroelectric capacitor and a resistor to directly measure the ferroelectric negative capacitance during switching. A time-dependent Ginzburg-Landau approach is used to investigate the underlying domain dynamics. The transient negative capacitance is shown to originate from reverse domain nucleation and unrestricted domain growth. However, with the onset of domain coalescence, the capacitance becomes positive again. The persistence of the negative capacitance state is therefore limited by the speed of domain wall motion. By changing the applied electric field, capacitor area or external resistance, this domain wall velocity can be varied predictably over several orders of magnitude. Additionally, detailed insights into the intrinsic material properties of the ferroelectric are obtainable through these measurements. A new method for reliable extraction of the average negative capacitance of the ferroelectric is presented. Furthermore, a simple analytical model is developed, which accurately describes the negative capacitance transient time as a function of the material properties and the experimental boundary conditions.

A Survey on Switching Oscillations in Power Converters

Abstract: High-frequency power converters enabled by wide bandgap (WBG) and silicon semiconductor devices offer distinct advantages in power density and dynamic performance. However, switching oscillations are commonly observed in these circuits with undesirable consequences. This paper reviews the impacts, root causes, and mitigation techniques of switching oscillations through literature survey, modeling analysis, and experimental investigation. We categorize the following root causes for oscillations during switching transients: 1) damped oscillation triggered by high di/dt and/or dv/dt coupled with parasitic elements; 2) undamped oscillation of WBG devices as part of a negative resistance oscillator; and 3) semiconductor device physical mechanisms such as the negative capacitance phenomenon due to conductivity modulation in insulated gate bipolar transistors or impact ionization in MOSFETs, the plasma extraction transit-time effect in bipolar power devices, and the reverse conduction property of GaN HEMTs. Furthermore, this paper discusses various circuit techniques to suppress switching oscillations, and techniques of extracting parasitic inductances of power devices.

Single-inductor buck-boost converter with positive and negative outputs

Abstract: A single-inductor power converter with buck-boost capability provides regulated bipolar output voltage to a positive and a negative load. A five-switch bridge topology allows a controller to direct the inductor current to the appropriate outputs or circuit ground as needed to maintain regulation. The controller also adjusts the inductor current level for proper output voltage regulation. The five-switch bridge topology makes possible a wide range of ratios between the positive and negative output currents of the converter.