Blocking Capacitor Research Articles

A Wide Range Zero‐Voltage Switching Phase‐Shifted Full‐Bridge Converter With No Duty Cycle Loss and Low Rectifier Oscillation

ABSTRACTThe phase‐shifted full‐bridge (PSFB) converter has been widely used in DC/DC converters due to its soft‐switching characteristics. However, it still has many drawbacks. In order to solve the shortcomings of the PSFB converter, such as limited soft‐switching range, high loss of duty cycle, and high oscillating voltage of the secondary rectifier, a PSFB converter based on parallel variable inductor and series blocking capacitor is proposed in this study. A wide range of soft switching, low rectifier oscillation voltage, and no duty cycle loss can be realized by the auxiliary current‐controlled variable inductor and reasonable blocking capacitor design. In this study, the mechanism of soft switching and suppression of oscillation is discussed and some of the designs are given. Finally, the experimental results of a 200 W/50 kHz prototype are constructed in the laboratory to verify the feasibility and effectiveness of the proposed converter.

Optimal Asymmetric Duty Modulation for Dual Active Bridge Converters with DC Blocking Capacitors

Aiming at the optimization of current stress with low voltage ratio and full ZVS, a control method combining variable duty cycle and phase shift was proposed based on dual active bridge (DAB) converters with DC blocking capacitors. By adding DC bias to the DC blocking capacitors, asymmetric duty modulation (ADM) can adjust the bias as needed. Based on the theoretical analysis of steady-state operation, the operating modes can be divided into eight modes. According to the features of each mode, equivalent circuits are established. The transmission power and the boundary of zero-voltage-switching (ZVS) are deduced through a detailed analysis of each mode. Based on the theoretical deduction, ADM is more suitable for a low voltage ratio. Verified by experiment, optimized asymmetric duty modulation (OADM) can increase efficiency by 3.58%, 6.57%, 8.81%, and 10.33% compared with DPS when P is equal to 0.36 and m is equal to 0.4, 0.3, 0.2, and 0.1, respectively. Using this method, the current stress of the converter is lighter than that under regular modulation when the voltage ratio m ≤ 0.5 with full ZVS.

Hybrid-Type DAB Converter With DC Blocking Capacitor for Ultrawide Input-Voltage Range

In this letter, a hybrid-type dual active bridge topology with dc blocking capacitor for ultra-wide input voltage is proposed. The proposed topology can expand the gain range by introducing voltage offset across the dc blocking capacitor, and has the ability to operate in single-stage or two-stage mode. The control strategy is also designed, which adopts the minimum resistive loss under the premise of soft switching as the optimization object to derive the operating boundary of the optimal modes. The proposed methodology avoids the additional loss caused by the increased devices of the traditional two-stage converters, and also avoids the efficiency dip of traditional converters with dc blocking capacitor at non-optimal voltage matching points. The performance of the proposed scheme is verified by experimental results.

Open-Circuit Fault-Tolerant Control for a Three-Phase Current-Fed Dual Active Bridge DC–DC Converter

Fault-tolerant methods have been recognized for improving the reliability of multiphase bidirectional dc–dc converters, including current-fed and voltage-fed dual active bridge converters. Fault-tolerant research for voltage-fed dual active bridge converters has caught much attention recently. In this article, a new fault-tolerant method for current-fed dual active bridge (CF-DAB) converters with blocking capacitors is proposed. The operation of the CF-DAB converter when an open-circuit fault occurs is comprehensively presented and analyzed. A frozen-phase fault-tolerant method with additional blocking capacitors on both sides of the transformer is proposed. The aim of the use of blocking capacitors is to block the dc current component of the high-frequency transformer, which could avoid the core saturation of the transformer. Also, the dc blocking capacitors help isolate the faulty phase when a frozen-phase fault-tolerant method is applied. The proposed method is shown to be a practical, simple, low loss, and effective solution for not only open-circuit fault isolation but also for shedding capability of the multiphase converter. The proposed concept could be applied for general multiphase current-fed converters. The experiment of a 6-kW prototype is implemented to confirm the proposed concept.

Three-Phase Single-Stage Bidirectional CCM Soft-Switching AC–DC Converter With Minimum Switch Count

In this article, a three-phase single-stage bidirectional ac–dc converter with low component count is proposed. The single-stage structure is configured by integrating a three-phase ac–dc converter and a three-phase dual active bridge converter. The power factor correction and bidirectional power control are performed by adjusting the modulation index of sinusoidal pulse width modulation (SPWM) and phase-shift angle between the primary and secondary bridges. The low-frequency components generated by SPWM are absorbed by fundamental blocking capacitors connected in series with transformer windings, resulting in true high-frequency isolation. The proposed converter can achieve soft-switching of all switching devices even in continuous conduction mode. A 110 Vac, 3 kW, 100 kHz prototype is implemented to validate the proposed concept and demonstrated 95.34% peak efficiency.

A Dual-Polarization Scattering Probe for Modulated Scatterer Technique Measurements

A scattering probe for use in the modulated scatterer technique (MST) measurements was proposed. The proposed probe has dual-polarization capability and a high modulation depth (MD) for both polarizations. The high MD values are made possible by loading shorted transmission lines (STLs) at the center of dipoles, such that the integration of the dipole currents vanishes, resulting in an electrically invisible state for broadside observations. For the actual implementation of the dual-polarization MST probes, the scattering geometry on an FR-4 substrate was considered and the effects of the substrates, particularly in the invisible states, were studied. The dual-polarization scattering probes (DPSPs) were implemented on FR-4 substrates using 4 PIN diode switches, low-frequency blocking capacitors, and biasing structures to provide bias voltages to the PIN diode switches. The biasing structures were implemented using inductors and resistive wires. The locations of the blocking capacitors were offset from the ends of the dipoles to compensate for the nonideal characteristics of the PIN diodes and other parts. The performance of the implemented DPSPs was measured and demonstrated to have high MDs for both polarizations over a wide bandwidth indicating that the proposed probe may increase the sensitivity of the MST system.

Investigating the Effect of the DC Block Capacitor on Residual Current in a System-Level ESD-Protected Circuit

Investigating the Effect of the DC Block Capacitor on Residual Current in a System-Level ESD-Protected Circuit

A 24–40 GHz Differential SPDT Switch With an NMOS and PMOS Alternating Structure and Leakage-Canceling Capacitors

A 24–40 GHz CMOS differential SPDT switch that covers multiple frequency bands of millimeter-wave 5G communication is presented. The switch has a differential structure in which NMOS and PMOS are alternately connected, and leakage-canceling capacitors are cross-connected the two outputs of the switch. The differential structure allows it to have parasitic ground inductance robust characteristics. The opposite ON/OFF characteristics of NMOS and PMOS allow the gates of off-state NMOS/PMOS transistors to have lower/higher voltages than their source and drain without using DC block capacitors, improving both the power handling capability and the insertion loss. In the proposed SPDT structure, the resistors for source and drain biasing are eliminated, which resolves the trade-off between the ON/OFF time and the insertion loss. In addition, cross-connected capacitors in the differential structure are readily used as a leakage canceller, offering a high level of isolation at all frequency bands. The switch is implemented in a 65-nm RF CMOS process with a core area of only 0.016 mm2. Owing to the simple alternating structure, insertion losses lower than 1.6 dB and IP1dB higher than 24 dBm are achieved from 24 to 40 GHz. In addition, the isolation is improved by around 15 dB due to the proposed leakage-canceling capacitors. The measured isolation is higher than 30 dB from DC to 50 GHz.

A Hybrid Extended Phase Shift Modulation Strategy for DAB Converter With DC Blocking Capacitor to Extend ZVS Range and Reduce RMS Current

This article is aimed at enlarging the zero-voltage switching (ZVS) range and reducing current stress for the dual-active-bridge (DAB) converter with dc blocking capacitors (DCBCs). A hybrid extended phase shift modulation strategy (HEPSMS) is proposed, which makes the converter switch between the full-bridge mode and the half-bridge mode to obtain multivoltage matching operation points. Thus, the root mean square (rms) current and the burden of achieving full load range ZVS are reduced. In addition, the voltage–second of the leakage inductor is controlled to achieve equivalent voltage matching under wide voltage output, thereby simplifying the control law and achieving full load range ZVS under a wide voltage range. The operation principle, ZVS range, and rms current are analyzed and compared with the conventional modulation method. Finally, a 1-kW experimental prototype with a 200-V input and a 100–400-V output was built to verify the feasibility and effectiveness of the proposed method.

A modular isolated battery‐integrated multiport step‐up DC–DC converter for hybrid energy applications

In this paper, a modular isolated battery-integrated multiport step-up dc–dc converter is designed for simultaneous energy transfer from multiple renewable energy sources (RESs) to a load. The proposed converter offers a plug-and-play capability of input sources where each input can be connected to and disconnected from the converter. The power generation shortage/surplus can be managed by a battery inserted into a bidirectional port. Also, charging/discharging durations of battery are independent of switching duty ratios for input sources. In the presented converter, inputs are connected in parallel with a common ground through individual step-up dc–dc cells while outputs are connected in series with voltage doubler rectifiers (VDRs) to achieve higher voltage gains and lower voltage stress on output capacitors. Moreover, the leakage inductances of the isolated transformers with dc blocking capacitors provide quasi-resonant operation to alleviate high turn-off currents of switches and hard-switching in VDR diodes. Due to interactions of converter control loops, a MIMO closed-loop control system is designed to regulate the output voltage and output power of input sources at references. The simulation and experimental results obtained for three inputs verify performance of the developed converter in different modes.

A compact frequency reconfigurable patch antenna with asymmetric armed U and reversed L slots for handheld wireless devices

Abstract A frequency reconfigurable microstrip patch antenna with a combination of an asymmetric armed U-slot and a reversed L-slot etched on a rectangular base patch of 6 GHz resonant frequency designed on an FR4 substrate (ɛr = 4.4) is presented in this paper. Three RF PIN diodes are positioned at inimitable sites of these slots to achieve frequency reconfiguration. A DC bias circuitry, which includes DC blocking capacitors and RF blocking inductors, is integrated with the antenna structure for switching (ON/OFF) the PIN diodes. Six reconfigurable modes with resonant frequencies at 4.33, 4.63, 5.24, 5.87, 5.96, and 6.29 GHz is obtained with different ON-OFF combinations of these PIN diodes. These reconfigurable resonant frequencies cover two continuous bands from 4.21 to 5.43 GHz and 5.69 to 6.6 GHz and is considered to be useful for the applications like aeronautical radio navigation (4.3 GHz), sub-6-GHz 5G (4.4–5 GHz), WLAN (5.2 and 5.8 GHz) and Wi-Fi 6E (5.925–6.425 GHz). Measured gain of the antenna for all the modes varies between 5.86 dBi and 8.72 dBi.

Interleaved high conversion ratio DC–DC converter with output self‐balancing and current auto‐sharing for DC nanogrid application

AbstractIn the application of bipolar DC bus configuration in the DC nanogrid, the unbalanced voltage of two outputs in bipolar DC bus, due to the unbalanced conditions of loads and/or energy sources, will cause deterioration of the power quality of the bus and may damage the switch, affecting the stability and safety of the system. In order to solve the problem of unbalanced voltage of two outputs, interleaved series capacitor based dual‐output converter with a high conversion ratio is presented in this paper. By applying negative current mode (NCM) to the main inductor, the character of two‐output self‐balancing and zero voltage switching (ZVS) of all switches for such this topology configuration is achieved. In the NCM mode, the parallel diodes of main switches are not conducted during dead time and guarantee the flowing path to load side. Thus, based on this condition, volt‐second balance of main inductor is obtained to get the character of two‐output self‐balancing. Furthermore, by adopting series capacitor in the proposed topology and based on the charge‐balance of the intermediate block capacitor, inductor current existed in the two phase could be auto‐sharing. Comprehensive operational principle analysis, loss analysis, and efficiency of the proposed converter under different load conditions have been given, and the comparison analysis of three operation modes and selection of negative current mode is clarified. Small signal model of the proposed converter is described to convenient for the controller design. Finally, simulation results and a 20–220 V prototype are built to verify the character analysis of the proposed converter.

An Improved ZVS High Step-Up Converter Based On Coupled Inductor and Built-In Transformer

A high step-up dc-dc converter with multiple magnetic devices and switched-capacitor voltage multiplier cell (SC VMC) is proposed in this article. By simultaneous implementation of a coupled inductor (CI) and a built-in transformer (BIT), the voltage gain is flexibly increased with an additional degree of freedom in comparison with the converters with only BIT or CI. To further increase the voltage gain, the secondary winding of the CI is inserted in series with the primary winding of the BIT. This new architecture leads to multiplication of the turns ratios of the CI and BIT in the voltage gain expression, as well. The SC VMC not only extends the voltage gain but also reduces the voltage stress across the MOSFETs. To have a better device utilization, the blocking capacitor is participated in voltage gain improvement. Moreover, through active clamp circuit, the leakage energy of the magnetic devices is recycled and zero voltage switching (ZVS) performance is obtained for the main and auxiliary MOSFETs. In such a case, the switching frequency can be increased to reduce the volume of the converter. Finally, a 400-W laboratory prototype with 25- 400 V voltage conversion is fabricated to demonstrate the effectiveness of the proposed converter.

Adapting the Finetech-Brindley Sacral Anterior Root Stimulator for Bioelectronic Medicine.

The Finetech-Brindley Sacral Anterior Root Stimulator (SARS) is a low cost and reliable system. The architecture has been used for various bioelectric treatments, including several thousand implanted systems for restoring bladder function following spinal cord injury (SCI). Extending the operational frequency range would expand the capability of the system; enabling, for example, the exploration of eliminating the rhizotomy through an electrical nerve block. The distributed architecture of the SARS system enables stimulation parameters to be adjusted without modifying the implant design or manufacturing. To explore the design degrees-of-freedom, a circuit simulation was created and validated using a modified SARS system that supported stimulation frequencies up to 600 Hz. The simulation was also used to explore high frequency (up to 30kHz) behaviour, and to determine the constraints on charge delivered at the higher rates. A key constraint found was the DC blocking capacitors, designed originally for low frequency operation, not fully discharging within a shortened stimulation period. Within these current implant constraints, we demonstrate the potential capability for higher frequency operation that is consistent with presynaptic stimulation block, and also define targeted circuit improvements for future extension of stimulation capability.

Benchmarked and upgraded particle-in-cell simulations of a capacitive argon discharge at intermediate pressure: the role of metastable atoms

The capacitive argon discharge operated in the intermediate pressure regime is studied by performing one-dimensional particle-in-cell Monte Carlo collision simulations. First, the basic object-oriented plasma device code (oopd1-v1) is strictly benchmarked against the well-established xpdp1 code over a wide range of pressure (0.05–15 Torr) and varying blocking capacitor of the external circuit (5–105 nF), and excellent agreement is obtained. The oopd1-v1 is upgraded to oopd1-v2 and oopd1-v3, by adding excited atoms modeled as time- and space-evolving fluid species. The metastable Arm, the radiative Arr, and the Ar(4p) manifold, and their roles in discharge equilibrium are explored. It is found that the presence of the metastable Arm enhances the plasma density by a factor of 3 at 1.6 Torr and even higher at pressures up to 5 Torr. At low pressure (0.05 Torr), electron impact ionization from the ground state atom dominates the ionization over the whole discharge region, while metastable pooling and step-wise ionization has small contribution. The proportion of metastable pooling ionization and step-wise ionization increases with increasing pressure and becomes the dominant ionization source at 5–15 Torr.

A New MMC Sub-Module Topology with DC Fault Blocking Capability and Capacitor Voltage Self-Balancing Capability

A large number of modular multilevel converters (MMC) are connected to HVDC transmission systems nowadays. This paper aims at the short-circuit fault in the DC line of the HVDC transmission system and the problem of capacitor voltage imbalance in MMC, proposing a new type of MMC sub-module, which has both the DC fault self-clearing ability and the capacitor voltage self-balancing ability. This sub-module combines the topology of half bridge and full bridge. It uses the reverse capacitor voltage to forcibly turn off the conducting diode to block the fault current loop. At the same time, the two capacitances charge and discharge states are consistent by utilizing the operating mode of the sub-module. It is possible to directly achieve a self-balancing capacitor voltage without complex balancing voltage control. The MATLAB/Simulink simulation verifies the effectiveness of the DC fault blocking capability and capacitor voltage balance capability of the proposed sub-module.

Improvement of the floating probe method for ion density and electron temperature measurement without compensation due to voltage reduction across the sheath

The floating probe method (FPM) applicable for processing plasma diagnostics was developed for the measurement of ion density and electron temperature (J. Appl. Phys. 101 033305). When an AC voltage is applied to a floating probe, harmonic currents are generated due to the nonlinearity of the sheath. The electron temperature and ion density are obtained using the harmonic currents and the voltage across the sheath. However, in the FPM, when the sensing resistance becomes similar to the sheath resistance, iterative calculations must be performed to compensate for the voltage reduction across the sheath due to the sensing resistor. In this paper, the voltage across a DC blocking capacitor is measured to directly obtain the voltage across the sheath. Therefore, it is not necessary to compensate for the voltage reduction across the sheath through iterative calculations. The electron temperature was increasingly overestimated as the capacity of the DC blocking capacitor became smaller. This overestimation was caused by the capacitive load effect and was compensated for using a correction for the second harmonic current. The measured electron temperature and ion density were compared with those from electron energy distribution functions (EEDFs) in an inductively coupled plasma, and they were in good agreement.

Single-Phase Symmetric-Bipolar-Type High-Frequency Isolated Buck-Boost AC–AC Converter With Continuous Input and Output Currents

A single-phase symmetric-bipolar-type high-frequency isolated buck-boost ac–ac (SBT-HFI-BBAC) converter is proposed. The converter is composed of two full-bridge inverter modules, input/output <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> filters, and a high-frequency transformer (HFT) with series capacitors. It can provide identical noninverting and inverting buck-boost output voltages with symmetric-bipolar voltage gains of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ \pm D/({1 - D})$</tex-math></inline-formula> . The frequency of the output voltage can also be adjusted in discrete steps, similar to single-phase matrix converters (MCs). It supplies continuous input and output currents and works well with nonunity power factor loads. The magnetizing current of the HFT has no line frequency component due to the presence of the series blocking capacitors. Moreover, due to the absence of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ac</i> switches, the converter has a simple commutation process, unlike conventional ac-ac/MCs. Two switching strategies are proposed; Strategy-I with fewer high-frequency switches and Strategy-II with reduced switch currents, providing more flexibility in switch power loss optimization. The proposed SBT-HFI-BBAC converter is well suited for application as a dynamic voltage restorer, compensating a wide range of grid voltage sags and swells, without the need for a low-frequency voltage injection transformer. Its step-changed frequency operation can also find use in various applications, such as high-gain ac–dc converters, traction systems, etc. A comprehensive description of circuit operation is presented along with component design guidelines and appropriate comparisons. Experimental verification results are provided using a 400-W laboratory test circuit.

Control of the spatial distribution of ion flux in dual inductively coupled plasmas

The effects of external discharge parameters (applied RF power, operating pressure, and gas flow rate) on ion flux uniformity are investigated in a dual inductively coupled plasma. The ion fluxes and electron temperatures are measured using a Langmuir probe floated by a DC blocking capacitor based on the floating harmonic method. The RF power applied to the top antenna focuses on the total ion flux control throughout the chamber, while the power introduced to the bottom antenna can control the ion flux uniformity in the diffusion chamber. At high pressures, the local electron heating in the vicinity of the bottom antennas results in local maximum ionization, thereby increasing the ion flux near the chamber wall. Furthermore, the ion flux uniformity also can be affected by the gas flow rate and pressure because they are associated with the gas residence time and the electron heating region. A physical understanding of the effects of external discharge parameters on plasma uniformity is useful for optimizing plasma processes.

Fuzzy self-tuning PID control of MC3 LLC resonant LED drivers

An MC3 LLC resonant light-emitting diode (LED) driver is a multi-channel constant current (MC3) output solution based on LLC resonance. Through an effective combination of multiple transformers and a DC block capacitor, this driver allows constant current outputs in multiple channels when the LED channels are unbalanced. This study considers a fuzzy self-tuning proportional integral derivative (PID) control strategy that allows for the self-tuning of PID parameters according to fuzzy inference rules designed using the relationship between the current gain and the switching frequency. Thus, when LED channels are unbalanced, the system allows a constant current output for each of the channels and controls the input voltage disturbances well. Simulation and experimental verifications are carried out, and a 20 W 4-channel constant current power supply design based on LLC resonance is obtained for the LED driver. This realizes soft-switching of the switching device, which reduces system loss and improves system efficiency. Moreover, the adjustment time of the proposed method is half that of fixed-parameter control methods, and the overshoot of the proposed method is smaller than that of fixed-parameter control methods. When compared with PID controllers with fixed parameters, the proposed method is more robust. When a system is disturbed, it recovers faster and has a smaller range of current fluctuation with the proposed method.