DC Blocking Capacitor Research Articles

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.

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.

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 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.

Novel High-Step-Up/Step-Down Three-Port Bidirectional DC/DC Converter for Photovoltaic Systems

This paper presents a novel three-port high-step-up/step-down bidirectional DC/DC converter with a coupled inductor for photovoltaic (PV) systems. The proposed converter combines a high-step-up converter, which is used to step-up the PV module to DC bus 200 V, and a battery charge/discharge bidirectional converter to form a three-port bidirectional converter. When sufficient energy is supplied from the PV modules, the converter can step-up the output of the PV modules and provide energy to the DC bus while charging the battery simultaneously. However, when no energy is supplied from the PV modules, the DC bus voltage is provided by the battery. Moreover, the energy stored in the leakage inductor is recycled to the DC-blocking capacitor, and synchronous rectification is conducted in the switch during the step-up mode to reduce switch loss and thereby increase the system’s overall efficiency. Finally, a 500 W three-port bidirectional converter is implemented to verify the feasibility and practicability of the proposed converter. The maximum efficiency of the proposed converter is 95.4%, 94.3%, and 94.7% when operated in the high-step-up mode, battery step-up mode, and step-down mode for the PV modules, respectively.

Design of compact highly matched broadband balanced low‐noise amplifier at X‐band using CRLH transmission lines

This article presents broadband balanced low-noise amplifier (LNA) operating at X-band, which uses composite right/left-handed (CRLH) transmission lines as input–output matching networks. Proposed LNA eliminates lumped DC-blocking capacitors and is combined with a hybrid coupler to achieve better stability and matching. Presented CRLH matching technique enhances the matching quality, reduces the overall size and considerably improves the bandwidth and noise performance. The matrix analysis of the CRLH structure is provided to determine the exact dimension of microstrip lines for the highest stable gain and the lowest noise figure (NF). The LNA structure uses a HJFET technology as an active device, which is simulated using an ADS momentum and small-signal scattering parameters provided by the manufacturer. This LNA offers an improved impedance matching and measured the 20 dB S11 band-width of 16% (8.3–9.7GHz), which is in good agreement with simulation. Total area occupied by the fabricated LNA is only 1.7 λ 0 × 0.9 λ 0 @ 8.3GHz. The LNA also provides <1.8 dB NF based on the IEEE standard temperature (16.85 Celsius), and 1 dB gain flatness throughout the entire band along with a 1 dB compression point of −1 dBm and an output third point intercept point of 19.5 dBm. The proposed CRLH-based LNA can be a good candidate for compact receivers and sensors.

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.

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.

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.

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.

High-performance class-E power amplifier integrated with a microstrip bandpass-filter for wireless applications

In this paper, a class-E power amplifier using a harmonic control network consisting of a bandpass filter and a harmonic control circuit is presented. The advantage of using the bandpass filter in the harmonic control network is the elimination of the DC-block capacitor between the transistor and the load. As a result, losses due to this capacitor are eliminated at operating frequencies. In this design, a new narrow bandpass filter is used with a practical central frequency of 2.4 GHz. The filter carries the maximum power to the load due to its low insertion loss. On the other hand, the harmonic control circuit comprises a tunable elliptic resonator, which resonated in the third harmonic and a quadratic wavelength line, which controls the even harmonics. The input impedance of the harmonic controller circuit is also controlled by a microstrip transmission line that minimizes the parasitic effects of the transistor output. This design is fabricated and measured on the RO4001 board. The maximum measured power output of this narrow-band amplifier is 24 dBm, with 72% power added efficiency.

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.

Reconfigurable broadband printed monopole antenna for portable smart IoT applications

SummaryThe proposed work presents a design of a smart printed monopole antenna separated from a Hexagonal Matching Load (HML) with an air gap. The patch is fed by a coplanar waveguide, while the HML is connected to the ground plane through two pin diodes to realize antenna reconfiguration through controlling the surface current motion. The antenna structure is mounted on FR‐4 epoxy substrate with size of 23 mm × 30 mm to fit the portable devices. After running four different switching scenarios, an observable change in the antenna performance is demonstrated. The proposed antenna provides a gain of 3.1 dBi at 2.45 GHz when the two diodes are switched ON. However, the antenna gain is changed to 1.6 dBi when the two diodes are set OFF. It is demonstrated that the proposed technique shows an effective approach to control the antenna performance without the need for DC blocking capacitor for RF choke. Nevertheless, the Specific Absorption Rate (SAR) effects are evaluated with respect to the human head tissues for all considered scenarios. Finally, the antenna radiation leakages to the human body are also tested numerically and experimentally for validation.

A Novel Suppression Method for Grounding Transformer Against Earth Current From Urban Rail Transit

Earth current generated by the operation of urban rail transit can enter into the neutral point of grounding transformer, which will result in the deterioration of transformer operation performance and cause electrical safety problems. In this article, the neutral current for 220 kV transformers has been measured in the real power system, the characteristics of dc and harmonic current are analyzed, and a novel suppression method for the dc and harmonic current simultaneously combining an active converter with a dc blocking capacitor is proposed, which solves not only the traditional dc bias problem but also the intrusion of the harmonic current from urban rail transit. The active converter is designed to compensate harmonic voltage to suppress harmonic current, and the capacitor provides blocking for the dc current. The protection scheme in case of the high fault current of the neutral point is presented. The improved control method is designed to control the neutral current and adjust the fundamental impedance for the requirements of relay protection. The effectiveness of the proposed method is verified by the digital simulations and the laboratory experiments based on the field working conditions, and the results demonstrate the satisfying performances.

High Output Power SOA Assisted Extended Reach EADFB Laser (AXEL) TOSA for 400-Gbit/s 40-km Fiber-Amplifier-Less Transmission

An AXEL sub-assembly and a 4-channel AXEL TOSA were designed and fabricated. The sub-assembly with a width of less than 0.65 mm was needed to make the width of TOSA applicable to QSFP-DD transceiver. On the other hand, the wire that connects between the terminator and the DC block capacitor must be 0.5 mm or longer to obtain 3-dB bandwidth of over 40 GHz which is enough for 50-Gbaud operation. To become that wire length 0.5 mm or more on the narrow sub-assembly, the AXEL chip was placed between the RF circuit board integrated with the terminator and the DC block capacitor. As a result, the AXEL sub-assembly with a width of only 0.65 mm and with a 3-dB bandwidth of more than 40 GHz was realized. Based on the designed sub-assembly, the 4-channel AXEL TOSA was fabricated. Size of the TOSA is only 18.2 × 6.2 × 5.4 mm (which is suitable for a QSFP-DD transceiver). Optical-modulation amplitudes (OMAs) of the fabricated TOSA exceed +4.7 dBm for all channels. 40-km SMF fiber-amplifier-less transmission of 4-channel × 100-Gbit/s/λ signals was successfully demonstrated by using the fabricated 4-channel AXEL TOSA, 4-channel APD ROSA, and a commercially available DSP. Loss budgets exceed 18 dB for all channels.

Frequency reconfigurable dual-band filtenna

In this paper, a compact size frequency reconfigurable dual-band filtenna (Filter + Antenna) is proposed for WLAN, WiMaX and C-band applications. The filtenna is designed by a switchable SRR (i.e. Two switches are used in inner and outer split rings) band pass filter (BPF) and a CSRR based antenna. In the process of filtenna design synthesis process is used. The advantages of the reconfigurable filtenna structure are to reduce undesired frequency interference to the system and controllable bandwidth. The antenna is resonated at three frequencies with the bandwidth @ S11 = −10 dB i.e. 2.4 GHz (2.05–2.86 GHz), 3.46 GHz (3.4–3.55 GHz) & 4.36 GHz (4.19–4.65 GHz), whereas the filter is resonated at two frequencies i.e. 2.42 GHz (2.36–2.48 GHz) and 4.41 GHz (4.16–4.77 GHz), When both the designs (i.e. antenna & filter) are combined (i.e. Filtenna), then the joint structure allow only two resonance frequencies i.e. 2.42 GHz (2.37–2.47 GHz) and 4.41 GHz (4.24–4.69 GHz) to pass through and 3.46 GHz frequency is rejected. The rejection is occurred due to dual band filter. Due to the filteration the in band gains are 2.14 dBi and 3.39 dBi, whereas the out of band gain is −4.23 dBi, which justify its rejection behavior and does not effect system performances. Furthermore, the resonances of the resonating structures (SRR and CSRR) are justified by the lump components of the structure.In order to make the filtenna operation re-configurable, PIN diodes with DC block capacitors are connected in the inner and outer split rings of the SRR band pass filter and appropriate dc bias is applied across the PIN diodes to perform either ‘ON’ or ‘OFF’ operation. When inner ring PIN diode is ‘ON’ and outer one is ‘OFF’ then filtenna operates at 2.58 GHz (2.5–2.67 GHz). Similarly, when outer ring PIN diode is ‘ON’ and inner one is ‘OFF’ then the frequency of operation is shifted to 4.45 GHz (4.26–4.85 GHz) band. The realized filtenna at each resonance frequency exhibits bi-directional radiation pattern in E-plane and omni-directional in the H-plane. The simulated performances of the proposed filtenna is verified using the experimental results.

An mm-Wave CMOS I–Q Subharmonic Resistive Mixer for Wideband Zero-IF Receivers

In this letter, we propose a novel wideband subharmonically pumped fully differential I–Q resistive mixer architecture, which eliminates the necessity for on-chip dc-blocking capacitors to integrate IF amplifiers. The proposed differential subharmonic mixer topology is verified by presenting a CMOS millimeter-wave monolithic integrated circuit (MMIC), which includes the mixer and two on-chip differential IF amplifiers at the mixer’s I- and Q-channels. The 3-dB IF frequency bandwidth is measured from 0.01 to 5 GHz with a peak conversion gain (CG) of −2 dB and an image rejection ratio (IRR) of more than 25 dB over the IF frequency range. The proposed mixer covers the input signal (RF) frequency from 170 to 185 GHz. The mixer has also been tested with an on-chip voltage-controlled oscillator (VCO) and shows −4.7-dB CG with a 3-dB IF bandwidth from 0.01 to 4.5 GHz.