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.

DC-DC converter having protective function of over-voltage and over-current and led driving circuit using the same

Abstract: The invention relates to a DC-DC converter having over-current/over-voltage protection function and an LED driving circuit using the same. The DC-DC converter adjusts a width of a switching pulse outputted from a Pulse Width Modulation (PWM) controller to control on/off durations of a switch, thereby providing a controlled level of voltage to a load. The DC-DC converter includes a microcontroller for detecting a voltage, and if the detected voltage is greater than a reference voltage, generating an alarm signal. The DC-DC converter further includes a digital-analogue converter for outputting a voltage of 0V and an analogue dimmer for generating a control signal that changes an ‘on’ duration of the switching pulse outputted from the PWM controller to 0 and providing the control signal to the PWM controller.

Design and Analysis of Piezoelectric Metamaterial Beams With Synthetic Impedance Shunt Circuits

Abstract: We present an electromechanical modeling framework and a detailed numerical investigation for the design and analysis of piezoelectric metamaterial beams whose unit cells with segmented electrode pairs are shunted to synthetic impedance circuits. This framework aims to extend the well-studied locally resonant piezoelectric metamaterials and resulting finite metastructures with specified boundary conditions to novel concepts beyond bandgaps associated with simple inductive shunts. Overcoming the bandgap limitations of the locally resonant design requires more advanced considerations in the electrical domain. To this end, we bridge piezoelectric metamaterials and synthetic impedance shunts, and present a general design and analysis framework along with numerical case studies. A general procedure is implemented based on the root locus method for choosing the shunt circuit impedance, with an emphasis on vibration attenuation and practical design considerations. Case studies are presented for systems with locally resonant bandgaps with or without negative capacitance, as well as systems with multiple distinct bandgaps, and the necessary shunt admittance is derived for each case. Simulations are performed for a typical finite meta material beam with synthetic impedance shunts, accounting for the finite sampling rate and circuit dynamics. Time-domain simulations using these synthetic impedance circuits are compared to the ideal frequency-domain results with very good agreement.

Multi-Domain Negative Capacitance Effects in Metal-Ferroelectric-Insulator-Semiconductor/Metal Stacks: A Phase-field Simulation Based Study.

Abstract: We analyze the ferroelectric domain-wall induced negative capacitance (NC) effect in Metal-FE-Insulator-Metal (MFIM) and Metal-FE-Insulator-Semiconductor (MFIS) stacks through phase-field simulations by self-consistently solving time-dependent Ginzburg Landau equation, Poisson’s equation and semiconductor charge equations Considering Hf05Zr05O2 as the ferroelectric material, we study 180° ferroelectric domain formation in MFIM and MFIS stacks and their polarization switching characteristics Our analysis signifies that the applied voltage-induced polarization switching via soft domain-wall displacement exhibits non-hysteretic characteristics In addition, the change in domain-wall energy, due to domain-wall displacement, exhibits a long-range interaction and thus, leads to a non-homogeneous effective local negative permittivity in the ferroelectric Such effects yield an average negative effective permittivity that further provides an enhanced charge response in the MFIM stack, compared to Metal-Insulator-Metal Furthermore, we show that the domain-wall induced negative effective permittivity is not an intrinsic property of the ferroelectric material and therefore, is dependent on its thickness, the gradient energy coefficient and the in-plane permittivity of the underlying insulator Similar to the MFIM stack, MFIS stack also exhibits an enhanced charge/capacitance response compared to Metal-Oxide-Semiconductor (MOS) capacitor Simultaneously, the multi-domain state of the ferroelectric induces non-homogeneous potential in the underlying insulator and semiconductor layer At low applied voltages, such non-homogeneity leads to the co-existence of electrons and holes in an undoped semiconductor In addition, we show that with the ferroelectric layer being in the 180° multi-domain state, the minimum potential at the ferroelectric-dielectric interface and hence, the minimum surface potential in the semiconductor, does not exceed the applied voltage (in-spite of the local differential amplification and charge enhancement)

Negative dielectric constant manifested by static electricity

Abstract: Negative dielectric constant has long been pursued for a possible revolution in electronics and photonics. It is usually found in systems containing free electrons under high frequency oscillating field, but not involving static charges or insulating materials. Here, we report the observation of the phenomenon in an insulating polymer containing static electricity, which lasts for several weeks, where negative capacitance persists from <1 Hz up to MHz frequency, also presenting an unusual spiral curve in impedance spectrum, producing inductors without bulky magnetic coils.

Fast and noise-insensitive load status detection

Abstract: Method and apparatus for detecting whether load coils are attached to a telephone line. A stimulus waveform having multiple frequency components is applied to the line. The current and voltage at the near end of the line are coherently sampled and transformed to the frequency domain. The frequency spectra are used to compute auto and cross power spectra of the current and voltage. These power spectra are then used to compute the impedance on the line as well as a coherence function that indicates the extent to which the computed impedance was influenced by noise. If the coherence values indicate that the computed impedance is sufficiently reliable, load coils are detected by finding peaks in the magnitude of the impedance function or sign changes in the phase of the impedance function. Calibration, offset adjustments and ensemble smoothing are used to increase the accuracy of the results. The computation is fast because computing the spectra avoids the needs for individual measurements at multiple frequencies. The computation is accurate because it is not sensitive to noise.