Inductor Current Research Articles

Kv11 (ether-à-go-go-related gene) voltage-dependent K+ channels promote resonance and oscillation of subthreshold membrane potentials.

Key points Some ion channels are known to behave as inductors and make up the parallel resonant circuit in the plasma membrane of neurons, which enables neurons to respond to current inputs with a specific frequency (so‐called ‘resonant properties’).Here, we report that heterologous expression of mouse Kv11 voltage‐dependent K+ channels generate resonance and oscillation at depolarized membrane potentials in HEK293 cells; expressions of individual Kv11 subtypes generate resonance and oscillation with different frequency properties.Kv11.3‐expressing HEK293 cells exhibited transient conductance changes that opposed the current changes induced by voltage steps; this probably enables Kv11 channels to behave like an inductor.The resonance and oscillation of inferior olivary neurons were impaired at the resting membrane potential in Kv11.3 knockout mice.This study helps to elucidate basic ion channel properties that are crucial for the frequency responses of neurons. The plasma membranes of some neurons preferentially respond to current inputs with a specific frequency, and output as large voltage changes. This property is called resonance, and is thought to be mediated by ion channels that show inductor‐like behaviour. However, details of the candidate ion channels remain unclear. In this study, we mainly focused on the functional roles of Kv11 potassium (K+) channels, encoded by ether‐á‐go‐go‐related genes, in resonance in mouse inferior olivary (IO) neurons. We transfected HEK293 cells with long or short splice variants of Kv11.1 (Merg1a and Merg1b) or Kv11.3, and examined membrane properties using whole‐cell recording. Transfection with Kv11 channels reproduced resonance at membrane potentials depolarized from the resting state. Frequency ranges of Kv11.3‐, Kv11.1(Merg1b)‐ and Kv11.1(Merg1a)‐expressing cells were 2–6 Hz, 2–4 Hz, and 0.6–0.8 Hz, respectively. Responses of Kv11.3 currents to step voltage changes were essentially similar to those of inductor currents in the resistor–inductor–capacitor circuit. Furthermore, Kv11 transfections generated membrane potential oscillations. We also confirmed the contribution of HCN1 channels as a major mediator of resonance at more hyperpolarized potentials by transfection into HEK293 cells. The Kv11 current kinetics and properties of Kv11‐dependent resonance suggested that Kv11.3 mediated resonance in IO neurons. This finding was confirmed by the impairment of resonance and oscillation at –30 to –60 mV in Kcnh7 (Kv11.3) knockout mice. These results suggest that Kv11 channels have important roles in inducing frequency‐dependent responses in a subtype‐dependent manner from resting to depolarized membrane potentials.

Switching-Cell Four-Leg Current Source Inverter

Conventional current source inverter (CSI) suffers from open-circuit problem during switch transition. Thus, overlap-time should be inserted in the gate signals for safe commutation. The overlap-time distorts output current waveforms and increases total harmonic distortion of output current. Moreover, it reduces the current source utilization of the inverter. To solve these problems, this article proposes a new three-phase four-leg switching-cell (SC) CSI, abbreviated as H8-SC-CSI. With the help of the SC structure, the reliability of the proposed inverter is greatly enhanced as open-circuit concerns are eliminated. In addition, with the intrinsic voltage clamping action of the SC structure, switch voltage overshoot at turn-off is mitigated. In the proposed CSI, the switch overlap-time can be minimized or eliminated because the inductor current can flow through the SC capacitors. A 1.2 kW prototype inverter is designed and tested to verify the feasibility of the circuit.

Simulation and experimental study of induction heat treatment of titanium disks

During induction heat treatment (IHT) of titanium disks, the influence of the main electrotechnological parameters, in particular the inductor current, on the temperature of their surfaces was established at an exposure within t = 5 min. In the course of numerical simulation, i.e. when solving the self-consistent boundary value problem of electrodynamics and thermal conductivity for the "inductor – titanium disk" system, the influence of the inductor current in the range 2.7–4.5 kA on the average exposure temperature of the titanium disk was determined, which varied from 800–850°C to the melting temperature (about 1670°C) and above. In order to confirm numerical calculations, experimental studies on IHT in the same temperature range were performed. In addition to the inductor current IIND varying in the range from 2.7 to 4.5 kA, the influence of the corresponding value of the electric power PE in the range from 0.21 to 0.95 kW on the exposure temperature during IHT was considered. Changes in the surface morphology of the titanium disks were studied over a wide temperature range. The initial oxide coating was retained on the surfaces of the samples processed at a minimum exposure temperature of T = 800–850°C. A thick scale of titanium dioxide was also preserved on the surfaces of semi-molten titanium disks. In the IHT exposure range at temperatures from 1000–1050°C to 1500–1550°C, the scale was spontaneously separated from the surfaces of titanium disks; however, a high-strength oxide sublayer was formed under it.

Characterization and Optimal Control of Totem-Pole PFC Converter With High Frequency GaN HEMTs and Low Frequency Si Diodes

A cost-effective totem-pole power factor correction converter with high-frequency gallium nitride high electron-mobility transistors and low-frequency Si diodes is investigated in this article. The reverse recovery characteristics of low-frequency diodes are evaluated experimentally. With the slow recovery characteristics, a negative current can flow through the low frequency diode, so that soft-switching and critical mode operation is achieved easily. However, if the duration of the negative current exceeds the reverse recovery time of the low-frequency diode, the diode will switch at high frequency, leading to severe losses and losing control of the inductor current. In order to avoid this issue, an adaptive off-time soft-switching strategy is adopted, and discontinuous conduction mode operation is suggested near the zero crossing of the grid voltage. Furthermore, since only the low-frequency grid current is sampled, this control strategy has the merits of low requirements on control resources and low cost. Experimental results of a 400W prototype are provided to verify the effectiveness of the proposed control strategy.

Modelling and Comparison of Conventional SEPIC Converter with Cascaded Boost–SEPIC Converter

A DC–DC cascaded structure is proposed which beats the classical single-ended primary inductor current (SEPIC) converter in terms of voltage gain, output power and efficiency. Conventional DC–DC converter requires a greater number of components, leading to increase in cost, space and complexity of the system. The proposed cascaded structure is a fusion of boost and SEPIC converter. The voltage gain, efficiency and the output power achieved by the cascaded boost–SEPIC converter are very high in comparison with the conventional converters. This paper includes detailed comparison between the conventional SEPIC and cascaded boost–SEPIC converter using Simulink model and fabricated model. MATLAB platform has been used for simulation of the circuit.

Pulse Coding Controlled Switching Converter with Notch Generation and its Conversion Voltage Ratio Analysis

This paper proposes an EMI spread spectrum technology with automatically setting the notch frequency using the pulse coding controlled method of the DC-DC switching converter. In the automatic notch generation method, by usage of the input frequency Fin, the clock frequency Fckand the coding pulses PH, PL are generated automatically using the equation (see formula in the paper). Here the conversion voltage ratio is given by (see formula in the paper) . If shifts, the balance of the inductor current is shifted and then the output voltage ripple is influenced. Moreover, as the power supply IC, it is necessary to automatically detect or set the conditions for Vin and Vout, and hence we also provide discussion about the conversion voltage ratio Do in many situations.

A switching frequency modulated DC-to-DC converter with reduced spurious noise for a RF power amplifier in microwatts transmitters

Varying a supply voltage using a DC-to-DC converter can significantly improve the efficiency of RF power amplifiers (PAs) for low-power RF transceivers. However, intrinsic switching noise from a conventional DC-to-DC converter operating in fixed Pulse-Width Modulation (PWM) can affect the system performance since the spectral components in the switching noise are confined in the fundamental switching frequency and its harmonics. This harmonic noise will have detrimental effects on the performance of the microwatt’s transmitter due to its low output power. Especially for microwatts systems, the minimized size of the inductor will increase the spurious noise due to increased peak-to-peak inductor current. By relocating the spurious noise and reducing peak noise from a switching converter, this paper proposes the technique to prevent high noise spurs in a microwatt transmitter, combining both pseudo-random frequency stepping and monotonic frequency stepping. Both modulation circuits are implemented in CMOS 0.18 µm process and incorporated to achieve the proposed DC-to-DC converter system. The measurement results indicate that the proposed PWM ramp signal modulator with random frequency modulation in a DC-to-DC converter can reduce the peak of the spurious noise-power by 22 dB. Monotonic frequency modulation with various frequency steps reduces the peak of the spurious noise-power by 18 dB.

Universal Transient DC-Bias Current Suppression Strategy in Dual-Active-Bridge Converters for Energy Storage Systems

The dc-bias current may result in the magnetic flux saturation and endanger the safe operation of switching devices. By regulating the inductor current slope during the transient, this article proposes a novel transient phase shift control (TPSC) to suppress the dc-bias current in dual-active-bridge (DAB) converters, which is universal for different phase shift control strategies. First, the dc-bias current models under different transient scenarios are built. Then, the optimal switching transient is determined so that the proposed TPSC is able to achieve the possible maximum inductor current slope and the shortest settling time. Furthermore, the settling time is independent of the specific circuit parameters, such as inductance, which improves the universality of the proposed TPSC algorithm. With the TPSC, the inductor current slope, which depends on the appropriate combination of bridge voltages in DAB converters, becomes the sole variable in the practical algorithm implementation. Moreover, the inductor current can be changed linearly rather than in a piecewise linear way. Thus, the implementation of the TPSC becomes straightforward and the complicated calculations in conventional methods are avoided. The proposed TPSC was compared with other advanced dc-bias eliminating strategies experimentally under different transient scenarios. The results show that the TPSC can successfully eliminate the dc-bias current, and the transient process can be accelerated within 12% of a switching cycle.

Quadrilateral Current Mode Paralleling of Power MOSFETs for Zero-Voltage Switching

This article proposes a generic zero-voltage switching (ZVS) scheme for parallel power MOSFETs. Uncoupled or inversely coupled differential-mode commutation inductors are added to the midpoints (ac terminals) of parallel MOSFET half-bridges, and a time-delay-based control scheme is applied, generating a circulating current flowing through these commutation inductors. Thus, the inductor currents are reshaped as quadrilaterals, which enable all the parallel transistors to achieve ZVS. The mode of operation of the proposed paralleling technique is entitled quadrilateral current mode (QCM) due to the quadrilateral-shaped commutation inductor currents. The operating principle of the QCM-paralleling technique is detailed mathematically, yielding accurate closed-form analytical expressions for modulation parameters. Finally, simulations and experimental results of a QCM-enabled synchronous buck dc-dc converter are presented to validate the theoretical considerations.

Calculation of Semiconductor Power Losses of a Three-Phase Quasi-Z-Source Inverter

This paper presents two novel algorithms for the calculation of semiconductor losses of a three-phase quasi-Z-source inverter (qZSI). The conduction and switching losses are calculated based on the output current-voltage characteristics and switching characteristics, respectively, which are provided by the semiconductor device manufacturer. The considered inverter has been operated in a stand-alone operation mode, whereby the sinusoidal pulse width modulation (SPWM) with injected 3rd harmonic has been implemented. The proposed algorithms calculate the losses of the insulated gate bipolar transistors (IGBTs) and the free-wheeling diodes in the inverter bridge, as well as the losses of the impedance network diode. The first considered algorithm requires the mean value of the inverter input voltage, the mean value of the impedance network inductor current, the peak value of the phase current, the modulation index, the duty cycle, and the phase angle between the fundamental output phase current and voltage. Its implementation is feasible only for the Z-source-related topologies with the SPWM. The second considered algorithm requires the instantaneous values of the inverter input voltage, the impedance network diode current, the impedance network inductor current, the phase current, and the duty cycle. However, it does not impose any limitations regarding the inverter topology or switching modulation strategy. The semiconductor losses calculated by the proposed algorithms were compared with the experimentally determined losses. Based on the comparison, the correction factor for the IGBT switching energies was determined so the errors of both the algorithms were reduced to less than 12%.

A Novel Trapezoidal Wave Control Method for a Single-Phase Grid-Tied T-Type Inverter

Triangular conduction mode (TCM) is used in grid-tied inverters to achieve high efficiency by its soft switching feature. However, it suffers from a wide switching frequency variation over the whole power range, which impacts the weighted efficiency. To address this issue, this article proposes a novel trapezoidal wave control method for a single-phase grid-tied T-type inverter. By the proposed method, the inductor current is divided into three stages in a switching cycle, so it looks like trapezoidal wave rather than triangular wave. The proposed trapezoidal wave has two independent conduction times. In order to simplify the control, the proportion between the two conduction times is controlled as a variable. As a result, only one conduction time needs to be calculated, and the derived equation is easy to be calculated in digital controllers. Furthermore, this article proposes a design consideration for the value selection of the proportion between the two conduction times, which ensures proper operation of the circuit. The proposed scheme has three advantages. First, it realizes soft switching in every switching cycle. Second, it reduces the switching frequency and related losses compared to the full-bridge inverter in TCM operation and thus improves efficiency. Third, it can be applied over the whole line cycle as a uniform operation mode. Therefore, mode transitions are avoided, which improves the quality of the grid-injected current. A prototype has been built and the experimental results verify the feasibility of the proposed scheme.

Smooth reference modulation based protection of fault current limiting DC/DC converters

Low voltage DC microgrids have been gaining great attention for the integration of renewable energy source and energy storage units, and electronic loads. DC microgrids are commonly controlled using the hierarchical control strategy (HCS) to provide flexible operation in both grid-connected and islanded modes. The HCS relies on proportional-integral (PI) controllers and employs the droop control strategy. To improve the fault ride-through of HCS based extra low voltage DC microgrids, this paper proposes a simple, accurate, and cost-effective current limiting strategy. The proposed control system based scheme modulates the current reference of the primary control level of HCS during an overcurrent condition using the smooth set point automatic adjustment with correction enabled technique. It properly protects the semiconductor switches of interface voltage-sourced DC-DC converters by accurate limiting their inductor currents. The main advantage of the proposed scheme is that it is implemented in the available PI controller based primary control level of the HCS. Also, it does not require the converter and load data. Several case studies performed in MATLAB/Simulink environment are presented to demonstrate the superior ability of this scheme for limiting fault current in different scenarios compared to conventional current limiters.

Analysis and Transition Techniques for a Bidirectional DC–DC Converter

This article proposes two new pulsewidth modulation (PWM) schemes, namely, asynchronous PWM scheme (APS) and synchronous PWM scheme (SPS), for a nonisolated fourth-order bidirectional dc-dc converter (FOBDC), which are implemented to achieve a smooth start-up operation and mode transition to reverse the direction of power flow. The presented FOBDC is reported already in the literature as a unidirectional boost converter, the functionality of which is modified in this work, to enable bidirectional power flow. The FOBDC can operate in either discharging (Mode-I) or charging (Mode-II) mode. The overshoot/undershoot of inductor currents in the FOBDC occur during converter start-up operation in either of the modes and while transitioning modes (from charging to discharging and vice-versa). To eliminate the overshoot/undershoot of inductor current, two effective transition techniques are developed for smooth start-up operation and mode transition, thereby reducing the delay time significantly. The FOBDC is modeled using the state-space modeling technique, and duty ratio-to-inductor current transfer function is derived, which is validated for resistive load and battery load. Two different compensators are designed for these two transfer functions to achieve an average current-mode control (ACMC) during the charging and discharging modes of operation. The performance of the compensators is evaluated by introducing perturbations. A 12-48-V FOBDC converter, controlled by these PWM techniques with the aforementioned features, is designed, analyzed, and experimentally verified for low-power applications.

Time-domain modeling analysis of pulsed eddy current testing on ferromagnetic casing.

Pulsed eddy current has attracted increasing attention to ferromagnetic metal material evaluation since it possesses low power consumption and abundant frequency spectrum advantages. However, when a current source is applied to generate the pulse excitation signal in eddy current testing, the inductance of driver coil induces a large reverse electromotive force in the excitation circuit, which distorts the pulse excitation signal as the excitation circuit hardly satisfies the severe power and stability requirements for counteracting the reverse induced electromotive force. Therefore, a pulsed eddy current field excited by a voltage-driven coil placed concentrically to a ferromagnetic casing is studied, and the analytic solutions of it are formulated in this paper. In contrast to current source based pulsed eddy current testing methods, the electromotive force induced by the coil's inductance and eddy current is analyzed. Furthermore, a new pulse excitation function is adopted and induced electromotive force equations of pick-up coils are formulated based on the superposition principle of magnetic field. Finally, the theoretical results are verified by experiments.

A hybrid control strategy for quadratic boost converters with inductor currents estimation

This paper deals with a control strategy for a DC–DC quadratic boost converter. In particular, a hybrid control scheme is proposed to encompass a control law and an observer for the estimation of the system states, based only on the measurements of the input and output voltages. Differently from classical control methods, where the controller is designed from a small-signal model, here the real model of the system is examined without considering the average values of the discrete variables. Using hybrid dynamical system theory, asymptotic stability of a neighborhood of the equilibrium point is established, ensuring practical stability of the origin, which contains estimation and tracking errors. Experimental results show the effectiveness of the proposed approach.

Adaptive Control of Four-Quadrant DC-DC Converters in Both Discontinuous and Continuous Conduction Modes

The inherently different dynamics of a DC-DC converter while operating in both continuous conduction mode (CCM) and discontinuous conduction mode (DCM) necessitate an advanced controller to control the inductor current. A conventional PI controller cannot be used across both modes since it does not guarantee a smooth transition between both modes. Furthermore, in time-varying input-output voltage applications of the four-quadrant converter such as in battery charging applications, the location of the boundary between the CCM and the DCM changes dynamically, creating an uncertainty. Therefore, a robust controller is required to accurately track the inductor current in the presence of uncertainties. Thus, an adaptive controller is proposed in this work, which is based on the general inverse model of the four-quadrant converter in both modes. Moreover, gain scheduling is used to switch the parameters of the controller as the converter transits between the DCM and the CCM. The adaptability and effectiveness of the controller in ensuring a smooth transition is validated by numerical simulations conducted on various converter topologies. Experimental results are also presented for a buck converter.

Analysis of Subharmonic Oscillation and Slope Compensation for a Differential Boost Inverter

This paper focuses on the steady-behavior of a differential boost inverter used for generating a sinewave AC voltage in rural areas. The analysis of its dynamics will be performed using an accurate approach based on discrete time models and Floquet theory and adopting a quasi-static approximation. In particular, the undesired subharmonic oscillation exhibited by the inverter will be analyzed and its boundary in the parameter space will be predicted and delimited. Combining analytical expressions and computational procedures to determine the quasi-static duty cycle, subharmonic oscillation is accurately predicted. It is found that subharmonic oscillation takes place at critical values of the sinewave voltage reference cycle, which can cause distortion to the input current and degrade the harmonic content of the output voltage. The results provide useful information for the design of the boost inverter to avoid distortion caused by subharmonic oscillation. Namely, the minimum value of the compensation slope and the maximum proportional gain of the AC output voltage controller guaranteeing a pure sinewave voltage and clean inductor current during the entire AC cycle will be determined. Numerical simulations performed on the switched model implemented using PSIM© software confirm the theoretical predictions.

A High-Voltage Dual-Input Buck Converter With Bidirectional Inductor Current for Triboelectric Energy-Harvesting Applications

This article presents a high-voltage (HV) dual-input buck converter with a bidirectional inductor current (IL) and a fully integrated maximum power point tracking circuit for triboelectric (TE) energy-harvesting applications. The proposed converter regulates HV inputs through a single shared inductor, and HV inputs can be isolated without using an additional HV protection circuit. In addition, the proposed diode-based HV sampling circuit can accomplish high ac voltage sampling and peak detection to perform the fractional open-circuit voltage method without any external components. Fabricated using a 180-nm bipolar-CMOS-DMOS (BCD) process, the proposed system with a self-manufactured polytetrafluroethylene (PTFE)based TE nanogenerator can regulate two HV inputs up to 70 V and achieve a power conversion efficiency of 84.7% and an endto-end efficiency of 75.6%, which are 30.2% and 22.7% better than prior work, respectively.

Decoupled Average Current Control of Coupled Inductor Single-Input Dual-Output Buck Converter

Multiple-output dc–dc converters are compact and cost effective as compared to multiple parallel dc–dc converters. This article focuses on a coupled-inductor single-input dual-output (CI-SIDO) buck converter. For the CI-SIDO converter, achieving independent regulation of output voltages and maintaining good dynamic performance are difficult due to cross-regulation and cross-coupling problems. In addition, tuning of controller parameters is challenging. Thus, this article proposes a decoupled average current control (ACC) to suppress cross-coupling and cross-regulation in CI-SIDO buck. It also demonstrates the method of decoupling of inductor currents and the stability issue that exists in ACC of CI-SIDO buck. The analysis shows that decoupling of inductor currents makes the design of controllers independent and simplifies the closed-loop transfer functions. Based on the conditions of decoupling and stability, a systematic design procedure for a Type-II compensator is developed. The proposed control method is compared with the voltage-mode control by using MATLAB/Simulink results. The comparison shows that the proposed ACC exhibits better dynamic performance. Finally, the proposed method is validated using experimental results.

Signal flow graph model and control of dual input boost converter with voltage multiplier cell

The dual input boost converter (DIBC) with dual boost and integrated voltage multiplier cell (VMC) operating in continuous conduction mode (CCM) at duty cycles larger than 0.5 is a necessity to deliver a high voltage gain for energy systems possessing two independent renewable energy resources (RES). However, the modelling of this higher order converter is challenging due to the overlapping switching signals, multi-stage operation and the parasitic elements. Thus this paper aims to develop the small-signal transfer function model by applying the signal flow graph (SFG) approach. In addition, to handle the output voltage regulation of this converter with unknown load values this paper presents the design of adaptive current-mode (ACM) control using an adaptive law to estimate the uncertain load resistance in terms of load conductance to compute the reference inductor currents. Two independent input inductor reference currents are considered to ensure the decoupling among the interacting loops. The dynamic performance of the ACM controller to handle unknown load and an improved version of a traditional control, the feedforward plus feedback controller for known values of load resistance are designed and assessed. A 200W converter model is built, and the controls are implemented using FPGA.