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Wireless power transfer has significantly improved the user experience in device charging and is currently an area of active research. Some major limitations of wireless charging systems include size constraints due to low frequency operation, the need for close proximity and tight alignment for efficient power transfer, and limited use of the device while charging. This work proposes several techniques to passively boost the voltage harvested and decrease the size of the power module. The rectifier and DC-DC converter explored in this dissertation extend technology proposed in existing literature that uses a resonator as the high quality factor component in the antenna matching network and energy storage element, respectively. This project proposes further development of these technologies by multiplexing the resonator between the rectifier and converter to reduce power module size and decrease generated electromagnetic interference by eliminating the need for magnetics. Preliminary testing has shown a resonator is more effective than an inductor (by a maximum of 30 percent) in boosting the rectifier output voltage and can boost the rectifier output voltage by a maximum of 8 times compared to an unmatched rectifier at 18 MHz on a commercial-grade printed circuit board. Initial DC-DC converter simulations with NMOS switches and realistic diodes show a 100 kHz resonator can store energy in a boost DC-DC converter on the order of nanojoules for a 10 V to 14 V step up conversion with 68 percent efficiency. This is similar in performance to a simulated inductor-based converter, which has a 78 percent efficiency when operating with the same step up ratio. The resonator-based DC-DC converter was built on a printed circuit board (PCB) using discrete transistors and a 185 kHz ceramic resonator. Simulations and measurements both showed the proposed discrete transistors did not effectively boost a 5 V input voltage by 1.4 times as was shown previously. Different methods to address this issue such as a floating driver and PMOS switches were proposed. An integrated design was also implemented using the open-source SkyWater 130 nm CMOS process design kit (PDK). A magnetoelectric (ME) antenna is proposed to decrease the size of the antenna by operating at acoustic resonance. Another benefit is more lenient alignment rules, which provide more device usage flexibility while charging. The maximum voltage output from the fabricated ME antenna is 0.3 V with a Qi transmitter producing 0.8 W as the source. The size of the antenna is 2 cm by 1.5 cm, which is smaller than the commercial Qi receiving antennas of 4 cm by 4 cm. When used to harvest vibrational energy, a slightly larger antenna (3 cm by 1.5 cm) could provide a maximum output power of 0.3 uW for an input vibration acceleration of approximately +/- 8 g.

This paper proposes digitally controlled power management circuit (PMC) for vibration energy harvesting in vehicle suspension system. The PMC is tested with a mechanical motion rectifier based electromagnetic energy harvester that converts from bi-directional vibration to unidirectional rotation, with improved energy harvesting performance and efficiency. Topology of one-stage DC-DC converter is adapted, and it is digitally controlled while considering the uncertainty of vibration sources. In order to efficiently transfer the harvested power to the electrical load, the algorithm of digital controller is designed to have four operation modes, which are impedance matching mode, voltage regulation mode, generator protection mode, and low power mode, for increasing the PMC efficiency while reducing the power consumption of controller. Experimental results show that proposed circuit can successfully operate and switch between the four operation modes. In the evaluation of PMC performance with 2mm and 2Hz excitation, the efficiency of proposed one-stage power converter is 86%. The total power consumption of controller in active mode and low power mode are 109 mW and 2.52 mW respectively while harvesting about 3W vibration energy.

With the rapid and extensive development of wireless communication and low power electronics, electromagnetic wireless power harvesting (WPH) draws more and more attention. As the core component for RF-to-DC power conversion, its characteristics determine the performance of the overall system. To obtain as much DC energy as possible, ambient electromagnetic energy with various frequencies should be efficiently rectified. Therefore, its important to widen the operating bandwidth of the rectifier. According to the theoretical analysis of the Schottky diode, it can be found that if the harmonic components generated by the diode can be fed back through a specific approach for rectifying, the bandwidth of the rectifier will be effectively improved. Therefore, a broadband rectifier has been proposed based on the previous principle. For validation, a wideband rectifier based on Schottky diode SMS7630 had been designed, fabricated and measured. When the input power level is 0 dBm, the conversion efficiency of the implemented rectifier is larger than 40% from 0.4 GHz to 2.6 GHz within a relative bandwidth of 146.67%, exhibiting an ultra-wide bandwidth compared with existing state-of-the-art configurations.

This article presents an interleaved boost rectifier for power factor correction (PFC) that operate in the continuous conduction mode (CCM) and is grounded on the switching cell with switching frequency modulation (SC-SFM). The input current naturally follows the shape of the input voltage, which is a resistive input characteristic (voltage follower). In the proposed converter, only one output voltage control loop is required. Moreover, the proposed topology has a wide range of soft commutation and no reverse recovery when the diodes block. This article presents the operating principle, a mathematical analysis of the converter, and four topological variations. In addition, experimental results of a 1-kW rectifier prototype with four different switch technologies (MOSFET, CoolMOS, SiC and IGBT), are discussed and their operational characteristics are demonstrated.

The efficiency of a rectenna varies under the influences of receiving polarization tilt angle, operating frequency, input power, and load value in different applications. Yet, no reported rectenna can realize stable efficiency when all these factors vary within a wide range. To solve this problem, an all-polarized rectenna is proposed in this paper, composed of a dual-input rectifier and a dual-polarized antenna. By introducing a novel six-port coupler, the rectifier maintains stable efficiency at wideband, wide input power and dc load ranges. Moreover, the efficiency of the rectifier keeps stable when the antenna receives power at different polarization tilt angles. Accordingly, a dual-polarized antenna with extended bandwidth and 3-dB beamwidth is implemented. Finally, the rectenna is formed. The prototype can maintain beyond 70% of the peak efficiency from 1.7 to 2.5 GHz. At a power density as low as 1 W/cm2, efficiency can reach 24.4%. Furtherly, the rectenna is demonstrated by forming a battery-less digital clock. The clock can be powered wirelessly by a WiFi router or cellular base station with maximum distances of 1 or 70 m respectively. Besides, the clock can successfully function under significant transmitting-direction deviation or polarization misalignment between the power source and the rectenna.

In this paper, a novel zero-voltage switching (ZVS) full-bridge converter is proposed to overcome the disadvantages of traditional phase-shifted full-bridge (PSFB) converter. In the proposed converter, a half-bridge (HB) converter with center-tap rectifier (CTR) is integrated into the traditional PSFB converter by sharing the lagging-leg switches and output filter. The HB converter operates with full duty cycle to ensure continuous energy transmission and the output voltage is regulated by adjusting the phase-shifted time of FB converter. The proposed converter has many advantages such as reduced filter requirement, wide ZVS range and low primary circulating current. In addition, the rectifier in the proposed converter is composed of a full-bridge rectifier (FBR) section and a CTR section. This feature makes the proposed converter well appropriate for the medium output voltage applications. Key operation principle and characteristics are fully discussed in this paper. The effectiveness of proposed converter is verified using a 1.2-kW prototype circuit with 280 V input voltage and 60-120 V output voltage.

LLC and CLLC resonant converters are good candidates for the isolated dc-dc stage in EV on-board chargers due to their capability of achieving zero-voltage-switching (ZVS) at full load range. The synchronous rectifier (SR) is usually utilized to reduce the conduction loss and improve the system efficiency compared with the conventional diode bridge rectifier. In this paper, a high-dv/dt-immune, fine-controlled and parameter-adaptive gate driving scheme is presented for GaN-based synchronous rectifier in EV on-board chargers. A novel self-driven SR drain-to-source voltage sensing circuit is proposed. The circuit provides a low-impedance bypassing path for the displacement current induced by the high dv/dt, which addresses the over-voltage and oscillation issues for the controller input. The detailed operating principles and the design considerations of the novel sensing circuit are discussed as well. Moreover, the adaptive SR on-time tuning algorithm is implemented, which avoids the influence from the loop stray inductance and the propagation delay in the path and reaches the SR zero current turn-off moment with fine accuracy. A 3.3 kW, 500 kHz CLLC resonant converter prototype is built to validate the proposed SR gate driving scheme. With the employment of the proposed gate driving scheme, the SR almost achieves zero current turn-off for the whole operating frequency range. The prototype demonstrates the peak efficiency of 97.6% and the power density of 130 W/inch3.

This paper proposes a new bidirectional isolated LLC resonant converter, which is suitable for ultra-wide voltage gain range applications, such as electric vehicle charging systems. The inverter and rectifier of proposed topology both have two modes by reconfiguring different modulation schemes during bidirectional operation. This results in three voltage-gain ranges, allowing ultra-wide output voltage operation and narrow modulation frequency. The conversion ratio and resonant tank can be designed for only a quarter of the required output voltage range. Finally, the proposed topology and analysis are validated by experiments results obtained from the converter prototype built in the laboratory

This paper proposes a novel approach to the modelling of HTS transformer-rectifier flux pumps that can charge HTS magnet-ic loads without the need for bulky current leads or expensive cryogenic requirements. The model was built in MATLAB/Simulink for a flux pump with 2 HTS switches, an HTS transformer with a primary inductance of 15 mH, second-ary inductance of 50 H and an HTS magnetic load with an in-ductance of 2 mH. With a 5 A pk-pk triangular current wave-form at 2 Hz the system can load the HTS load to 34.63 A in 5 s. This incremental addition of flux to the load demonstrates the advantage of flux pumps as they can charge high-field magnets without the need for large power sources. The speed of flux pumping is improved by increasing the system frequency, the magnitude of the dynamic voltage developed in the HTS switches and by increasing the primary inductance of the trans-former. This has widespread industrial applicability in fields such as the charging of high-field magnets for MRI systems.

The existence of inrush current poses a significant problem during the start-up process within three-phase voltage-source rectifiers. To address this problem, this study proposes a strategy to suppress the inrush current effectively based on the virtual-resistor- control method, while preventing the increase in cost of the system and complexity of the algorithm. First, a mathematical model is established based on the dq coordinate frame, and the primary cause of the inrush current is analyzed. Then, the design process of the virtual-resistor-control method is detailed. Finally, the accuracy and effectiveness of the proposed method are verified by simulations and experiments. The results show that the inrush current can be more than two times the rated current before the addition of the virtual resistor. The start-up process can be realized without the inrush current after the addition of the virtual resistor, it does not need to increase hardware costs, there is no secondary inrush current, and the sensitivity of the parameters and the complexity of control are low.

In this paper, a series-series wireless power transfer (WPT) system combined with an inverse coupled current-doubler rectifier (ICCDR) is proposed, as a very appropriate WPT topology for high current applications. The ICCDR uses an autotransformer to reduce the losses on the rectifier stage, which is suitable for high current low voltage output applications. Furthermore, a comprehensive comparison between the proposed WPT system with ICCDR and the traditional WPT system with diode rectifier is presented. In the proposed WPT system, the primary parameter configuration and circuit behavior keep the same, while the secondary side altered, contributing to a volume reduction on the resonant capacitor. The system overall efficiency and power density are improved significantly. Accordingly, a 10kW 400V/48V WPT prototype for battery charging is constructed and tested to validate this proposal. The output voltage is in the range between 38 Vdc and 55 Vdc, and the rated output current is 200A. The overall efficiency of the proposed system reaches 94%, improving 2% efficiency with 220W energy saving with respect to the traditional diode-rectifier system, when 9.5kW output power is delivered. Theoretical analysis and experimental results have verified that the proposed system shows great advantages in high power WPT applications.

As for bidirectional LLC converter, conventional pulse frequency modulation is typically adopted in the reverse mode resulting in a low voltage gain of reverse LLC. Then the bus voltage may be lower than peak grid voltage, which causes the buck-type inverter cannot output 220 Vac and poses series challenge for bidirectional operation. A bidirectional synchronous / asynchronous rectifier control is proposed for wide battery voltage applications in LLC converter. In the forward mode, the secondary-side switching devices are regulated as synchronous rectifiers (SRs) and a simplified model is built to calculate the SR on-time. In the reverse mode, with the same conduction time, the turn-on instants of primary-side and secondary-side switches are asynchronous and controlled with a delay angle. The proposed control not only achieves the forward LLC SR function with low microcontroller calculation resources, but also helps the reverse LLC obtain high voltage gain. A 6.6-kW SiC bidirectional LLC charger was built. By using the proposed control, the forward LLC efficiency improves 0.2% compared to conventional SR method. In the reverse mode, the LLC voltage gain is up to 1.33 so that the charger can output 220 Vac in the wide battery voltage range of 200 V~500 V.

Nowadays, the scale of power grid is remarkably increasing and there is a continuous reinforcement of AC–DC hybrid systems. Thus, the single-phase grounding fault currents on the AC grid-side of rectifier and inverter stations increase significantly, which may exceed the capacity limit of the circuit breakers. The large short-circuit currents would result in problems during equipment selection and threaten the safety of equipment and personnel. To solve such issue, the effect of the converter transformer on the single-phase grounding fault current on the grid-side is analyzed. The mechanism of high short-circuit current in DC near region is revealed. Also, the feasibility of neutral point earthing via small reactor at HVDC converter transformer to suppressing the single-phase grounding fault current is verified. In addition, the principle of selecting the suitable small reactor is summarized. The results show that the neutral point earthing via small reactor at converter transformer can effectively limit the single-phase grounding fault current on the AC-side. However, it would lead to an increase of overvoltage at the neutral point of HVDC transformer. Therefore, neutral grounding by small reactor might be implemented when the insulation level is satisfied.

This paper proposes a novel three-phase hybrid rectifier topology and control method for high power electrolytic hydrogen production application. It is composed of a primary rectifier, i.e., a 6-pulse silicon controlled rectifier (SCR) and an auxiliary converter, including a pulse width modulation (PWM) voltage source converter (VSC) and a phase-shift-full-bridge (PSFB) converter. SCR undertakes most of the power consumed by electrolysis cell (EC), and the auxiliary converter can compensate dc current ripples and absorb ac current harmonics of primary rectifier simultaneously. Compared with high power PWM rectifier, the proposed hybrid rectifier can keep the main benefits of PWM rectifier, such as the low dc current ripple to realize improved efficiency of electrolytic hydrogen production and high grid current quality at ac side, while significantly reducing the cost. The effectiveness of proposed hybrid rectifier is verified by the simulation as well as experimental results.

Vibration energy harvesting using multiple piezoelectric transducers (multi-PZTs) can increase its output power and environmental adaptability. At present, there are still few researches on multi-input interface circuits for multi-PZTs, especially those using the parallel synchronized switching harvesting on inductor (PSSHI) technique. Therefore, this article presents a self-powered dual-inductor MI-PSSHI-VDR interface circuit. It can process multi-PZT voltages with arbitrary phases input. The measurements demonstrate that the prototyped MI-PSSHI-VDR circuit can extract a peak power of 1.93 mW from four PZTs under an excitation of 1.5 g and 75.5 Hz. The energy integration efficiency and energy extraction efficiency of the prototyped circuit are 93.2% and 75.1%. Compared with a multi-input full-bridge rectifier, the proposed circuit can achieve 3.22 power improvement and 3.58 voltage improvement, which grasps a good balance between the indexes of peak output power and load voltage range. Additionally, the MI-PSSHI-VDR circuit is easy to implement and shows a good scalability, which can be an alternative solution for multi-PZTs energy harvest

This paper presents an improved full-bridge converter with a five-diode rectifier. The primary side circuit is composed of a full bridge with two transformers and two split capacitors. On the secondary side, five diodes are employed in the rectifier stage. By using the asymmetrical PWM signals, this converter can realize the ZVS of all switches and reduce the circulating current. The two transformers share the load power equally in whole load range. Compared with the other dual-transformer-isolated-full-bridge converters, the transformers in the proposed converter are easy to optimize because of the load power equal sharing. Furthermore, the output filter inductance is reduced, which reduces the loss and volume. According to the loss analysis, the proposed converter has higher efficiency compared with some other DC-DC converters. The experimental results of a prototype with 300-400V input voltage and 250V/4A output verify the performance of the proposed converter.

In this paper, a high-input power (> 30dBm) rectifier circuit for 2.45 GHz microwave wireless power transmission is presented. To overcome the shortcomings of traditional Schottky rectifier circuit, the novel rectifier circuit is designed based on a GaAs field effect transistor (FET) and a Schottky diode are together as the rectification part. A system-level verification demonstrates that the novel rectifier circuit has a potential application value for microwave wireless power transmission system. Measurement results show that higher input power range and MW-DC power conversion efficiency are realized at the same time by this design scheme. The maximum MW-DC conversion efficiency of the novel rectifier circuit can reach 74.42% when the input power is 30 dBm, and it is 20% higher than the peak conversion efficiency of traditional rectifier who without FET. In addition, the proposed rectifier circuit can operate with over 50% efficiency when the input power varies from 16 to 31 dBm, and has a good performance with the value of load ranging from 70 to 730, it is mean that the novel rectifier circuit is able to provide power for some electronic devices with different impedance.

To integrate large-scale islanded onshore wind power with different sizes, this paper proposes an integration system based on the cascaded hybrid HVDC transmission system, which consists of LCC and several MMCs in series connection at the DC side of the rectifier. A large-scale wind farm is connected with one LCC and one MMC while several medium-scale wind farms are connected with MMCs directly. Owing to the hierarchical integration arrangement, the operating flexibility can be improved with reduced capacity and the number of step-up interfacing transformers. A resilient DC voltage control is proposed for the integration system to adaptively redistribute power among the converters during wind power fluctuations. Firstly, the topology and operating characteristics of the wind power integration system are introduced. Then, a resilient DC voltage control is proposed to ensure stable operation during wind power curtailments. Finally, a simulation model of the hybrid cascaded HVDC transmission system is built in PSCAD/EMTDC to verify the effectiveness. The research results show that the system provides a new option for long-distance transmission of large-scale islanded wind power.

In this paper, a single-stage rectifier-less boost converter circuit (SSRBC) for piezoelectric energy harvesting from ambient vibration was proposed. The proposed rectifier-less circuit acted as a boost converter to extract energy from a piezoelectric device (PD). It combined the conventional boost, buck-boost methods using two split inductors and single filter capacitor. The proposed integrated circuit topology functioned in both positive and negative half cycles generated by the PD. In the proposed topology, inductors were invigorated by being enveloped with the current, which was produced by the PD through the switches. This facilitated active rectification of ultra-low AC (amplitude < 0.5 VP). Theoretical analysis, control strategies, simulation and experimental study, were presented. The proposed circuit was capable of converting a low amplitude AC voltage of 0.5 VP into 5.1 Vdc. The highest output power extracted by the proposed circuit was 281.1 µW, which outperformed existing circuits. It could potentially facilitate the advancement of vibration-based energy harvesting system for low power demand applications such as sensors, quartz watches and portable charging devices.

The aim of this paper is to analyze the influence of adding serial inductance in AC side of the 3ph -6 pulse bridge rectifier on the reduction of harmonic distortion rate. A simulated model with serial inductance was analyzed. The 3-phase 6-pulse diode bridge rectifier was chosen because it corresponds to the operation of the 6-pulse thyristor bridge rectifier at maximum load (while keeping the angle α = 0). Both the total harmonic distortion (THDi) and the power factor (PF) for the circuit have been measured. The results obtained of the THDi has been recorded for four values of serial inductance and results was compared with the (IEEE 519-1992) standard. Comparison results indicates that for values of inductive reactance (Xi) up to 67% cause a reduction of THDi which is above the standard values, while for (Xi) more than 67% cause a reduction in THDi within the acceptable standard level. Analyzing of results prove that the adding of serial inductance at the AC side leads to good reduction in harmonic distortion rate, but with some reduction in power factor value, which results in some energy losses.

Wound field synchronous machines (WFSMs) are an attractive alternative to permanent magnet synchronous machines (PMSMs) given their competitive power/torque density and direct field excitation control for easy weakening. Here, a design process is presented for a low cost and contactless capacitive power coupler (CPC) for WFSM rotor winding excitation using only simple printed circuit boards (PCBs). These PCBs are an extension of the machine’s rotating rectifier. Experimental verification of the design shows 675 W power transfer at 90.3% efficiency to the rotor field of a 30/55 kW (continuous/peak) WFSM operating as a generator. A GaN inverter switching at 2 MHz reduces passive component sizes and keeps CPC voltages within safe limits. Parasitic loss minimization design rules for trace layout in the CPC PCB structure are established for high frequency operation along with a partial capacitance approach for the coupling matrix. Tank inductor loss was reduced by use a cored design while a buck converter integrated into the rotating rectifier matches the load impedance of the rotor to the CPC system, reducing the complexity of the tank compensation circuit. Finally, the CPC as a platform for position self-sensing is introduced conceptually via two methods. First, a phase locked loop (PLL) tracks the resonant tank frequency of the CPC, whose saliency is spatially tied to the rotation of the machine. Second, the rotating buck converter effectively injects high frequency content into the field that can be tracked by the stator drive controls.

In this letter, a compact broadband RF rectifier is proposed and tested for ambient RF energy harvesting (EH). An uncomplicated impedance matching network with multistage transmission lines (quasi T-shaped) is presented. Quasi T-shaped network performs three different functions to complete the broadband matching process. The novel matching network widens working bandwidth using fewer transmission lines without via hole so that it has low loss and high conversion efficiency. After theoretical analysis and simulation, the rectifier is manufactured, and the measured results are consistent with the simulation results. The rectifier shows good broadband performance. The frequency range of rectifier efficiency over 50% is from 0.85 to 2.05 GHz (a bandwidth of 82.7%) at 5 dBm. The rectifier shows a bandwidth of 101.5% (0.8-2.45 GHz) with a power conversion efficiency (PEC) greater than 50% for an 8 dBm input power. In addition, the maximum conversion efficiency of the circuit is as high as 73.1% at the input power of 8 dBm.

Radio frequency energy harvesting (RFEH) is very attractive for the Internet of things (IoT) and self-powered micro-systems such as wearable biomedical devices and wireless sensor networks. This paper proposes, analyzes, and implements a new RF-DC converter in standard 130 nm CMOS technology. The developed converter is designed and optimized for ultra-low-power IoT and wearable biomedical applications using the 900 MHz ISM band. The proposed 10-stage cross-connected rectifier compensates the transistors threshold voltage by using both dynamic and static bias compensation techniques. An analytical model of the rectifier based on the MOSFET transistor equations is presented, allowing optimization of the rectifier as a function of the number of stages and transistors sizing, improving the sensitivity and the input power range of the converter. The measurement results demonstrate a sensitivity of -25.5 dBm for 1 V output across a 5-MΩ resistive load and -29 dBm for a 100 MΩ load, which is better than the best previously reported results. The measured peak end-to-end efficiency of the proposed harvester is 42.4% at -16 dBm input power, delivering 2.19 V to a 450 kΩ load.

This article proposes a condition monitoring scheme for the dc-link capacitors used in ac/dc/ac pulsewidth-modulation converters based on the signal injection, which can estimate capacitance in real time when both the rectifier and the inverter are in normal operation. First, a low-frequency signal is injected into the dc-link voltage, and its effects on the total harmonic distortion (THD) of the input current are analyzed. Accordingly, a suitable injection frequency is selected to keep the THD of input current within limits prescribed by the IEEE standard. Then, a novel calculation method of capacitor current without any dc-link current sensor is given, where the converter system is still in normal operation and different inverter operations are both taken into consideration. Finally, capacitance estimation based on the slide discrete Fourier transform is introduced. At the end of this article, experiments have been done to validate the correctness of the conclusion and effectiveness of the proposed scheme.

A backpack energy harvester converts mechanical energy associated with the oscillation of the backpack during human walking, into electric energy. It can be a very promising solution for supplying portable devices, especially in outdoor activities, disaster relief, and military applications. In this article, a backpack energy harvesting system that is able to self-adapt its operating condition to maximize the extracted power while supplying a dc load is presented and studied, analytically and experimentally. It is based on a mechanical motion rectifier that converts the up-and-down oscillation of the backpack into a unidirectional rotation of a dc generator. The generator output voltage is regulated by a power electronic interface implementing a maximum power point tracking technique to maximize the extracted power. Experimental results confirm the tracking ability of the proposed system and show the advantages with respect to other wearable energy harvesting systems published in the literature.

Universal serial bus power delivery fast chargers equipped with wide-bandgap devices are driven to higher power density and efficiency. The indispensable high-voltage bulk capacitors used to smooth the rectifier output could take 40% of the total system volume due to the large capacitance value required. This letter discussed a capacitor reduction method using a self-driven thyristor scheme comprised of only three components in total. No extra control circuit is needed. Circuit analysis and design equations are presented, and the design results are implemented in a 60-W GaN-based active-clamp flyback converter. The measurement results on the prototype show a 36.4% reduction of the bulk-capacitor size with similar efficiency compared to the conventional solution.

Rectifier is the most critical block of the power conditioning circuit designed for the Piezoelectric Energy Harvester (PZEH). Maintaining high rectification efficiency under the variable ambient conditions is the major design challenge. This paper presents a novel topology of self tuned Synchronized Switch Harvesting on Inductor (SSHI) based rectifier circuit for PZEH which provides high power extraction efficiency over a wide range of frequency and magnitude of input vibrations available. The high rectification efficiency is maintained for different PZ devices also. The synchronization of SSHI block under different ambient conditions is achieved by an adaptively controlled pulse generator circuit which uses internal voltage sensing. An active diode circuit to reduce the conduction loss in SSHI block and forward voltage drop of rectifier is used. The proposed circuit is working from 100 to 350 Hz with flipping efficiency above 90% and power extraction efficiency around 50%. A maximum power conversion efficiency of 58 % and maximum flipping efficiency of 93.6% is obtained with a figure of merit of 467% and output power of $$72.6\,\mu \hbox {W}$$ .

In this article, a single-stage wireless power receiver featuring continuous dc output current, good output regulation, and high conversion efficiency is presented. The topology is achieved via the integration of a diode rectifier circuit into a pair of interleaved buck converters, of which overlapped components are removed. With this, component count (diode's number) reduction is achieved without affecting the combined operation of rectification and voltage regulation. Moreover, its output inductor pair can be conveniently incorporated in integrated-magnetics form to reduce magnetic size. For control, it adopts an ac-input-current-synchronized modulation scheme, which hybridizes phase-shift modulation (PSM) and pulse-width modulation (PWM) control. The PSM enables consistently zero-voltage-switching turn- on of switches and zero-current switching turn- off of diodes for mitigating switching loss, while the PWM modulation performs good regulation of the output voltage of the rectifier. Experimental results of our constructed 100-kHz, 12-V output voltage, 35-W output power prototype show a fairly constant dc output current with 71% current ripple reduction as compared with that of a regular single-phase buck converter, good output regulation with less than 1% regulation error, and efficient ac–dc conversion with a peak efficiency of 96%.

A phase-shift modulated converter with two full bridges at primary side and rectifier diodes in hybrid combination at secondary side is proposed in this article. Due to the proposed symmetrical modulation strategy, two full-bridges always equally share the total system power rating, and thus the VA rating of two transformers is minimized. The circulating currents decay to zero in the zero state, contributing to reduce the conduction loss and duty-cycle loss. Zero-voltage or zero-current switching is achieved for all switches over whole input voltage range with an auxiliary inductor. The rectifier output voltage is synthesized of two controlled transformer secondary voltages all the time, which achieves the same output current ripple suppression effect as the conventional input-parallel output-parallel full-bridge converters with interleaved control scheme, and reduces the voltage stress of rectifier diodes. These advantages make the converter suitable for wide input voltage range applications. In this article, the operation principle and steady-state analysis of the proposed converter are illustrated in detail. Experimental results with 220–460 V input voltage are demonstrated to verify the advantages.

The article overviews residential and building-integrated photovoltaic (PV) module types. It demonstrates that existing dc–dc converter technologies do not allow building a universal interface microconverter because of wide dispersion of the parameters. However, the absence of universal microconverters limits the widespread adoption of PV modules despite great benefits for energy-efficient buildings and restrains the deployment of residential PV-based dc microgrids. Based on the design requirements formulated, a new approach utilizing a boost half-bridge front-end inverter and a three-mode reconfigurable rectifier (RR) is proposed. The article describes the operating principle of the derived converter. The RR allows keeping the duty cycle of the input side within a favorable range of acceptable efficiencies. An experimental prototype rated for 360 W was assembled and tested in the entire operating range. The experimental results prove the ultrawide input voltage range of over 1:20 and demonstrate the capability of the proposed concept to interface different PV module types while enabling their shade-tolerant operation.

In LLC -based plug-in electric vehicle (PEV) charging system, light-load condition occupies a large portion of the charging process. However, at light load, the parasitic capacitance of full-bridge LLC converter leads to poor voltage regulation. Besides, the magnetic core loss and circulating loss are load-independent and jeopardize the light-load efficiency. To resolve those two issues in a coupled manner, a light-load performance enhancement technique is proposed in this article. At light load, the primary side is reconfigured as a half-bridge inverter and the secondary side is reconfigured as a voltage doubler rectifier, while the voltage gain is roughly unchanged. Therefore, both the equivalent resistance and capacitance of the secondary resonant network are effectively reduced, which contributes to an enhanced voltage-regulation capability. Moreover, the core loss and circulating current-induced conduction loss are both effectively reduced, which contributes to a boosted efficiency. A 2-A rated, which converts 390-V input to 250–450-V output, converter prototype is designed and tested to validate the concept. The light-load mode exhibits an obvious efficiency improvement. The frequency regulation range is also effectively squeezed.

In this article, a 10 MHz dc/dc converter based on three-dimensional air core transformer with zero-phase difference synchronous driving signals is designed. By using the characteristics of no leakage inductance in the inner winding of the nested toroidal air core transformer, the phase difference between the output voltage of the inverter and the input voltage of the rectifier can be regarded as zero, so that the rectifier and the inverter can use the same driving signal, which simplifies the control of the synchronous rectifier switches, and realizes the reliable and efficient synchronous rectification control at 10 MHz. The prototypes with primary and secondary compensation are proposed and the experimental results verify the feasibility of the proposed control method and numerical design method.

In this article, we describe the research and development of a 3 kV active rectifier for a 4 MW aerospace generator drive system demonstrator. The converter is fed by a multiphase high-speed/high-frequency permanent magnet generator. The main aim of the work is to demonstrate for the first time the feasibility of an MW-class generator system meeting future hybrid-electric propulsion requirements. A concept with multiple and isolated three-phase systems feeding different power buses is proposed to meet the availability requirements. Multiple converters (one for each three-phase system) are connected in series and/or in parallel to achieve the rated power and dc-link voltage. This article describes the key design concepts and the development and testing of the converter to meet the challenging application requirements. Reduced power tests are carried out on a full-scale 4 MW converter prototype, validating the proposed design. The work represents a step forward in terms of voltage, power, and output frequency with respect to the state-of-the-art.

This article presents a pulsewidth modulation (PWM) controlled series resonant converter (SRC) for a universal EV charger. This article focuses on the boost mode of a SRC. By adapting two PWM boost switches with a full bridge rectifier, it is possible for a SRC to cover a very wide range of gain with a high and flat efficiency curve. As the output voltage increases, the secondary side rectifier of the proposed converter gradually converts from a full bridge rectifier to a voltage doubler rectifier. Since the switching frequency is fixed to the resonant frequency in boost mode, the proposed converter naturally achieves “two peak efficiency points” with full bridge and voltage doubler rectifiers. Two peak efficiency points limit the efficiency drop over a wide range of gain, and that is the reason the proposed converter achieves a high and flat efficiency curve. The effectiveness of the proposed converter and control has been verified on an 800 V input and 200–950 V/3.3 kW output prototype.

Rectifiers used in cathodic protection (CP) applications convert ac voltage to variable dc output. This article proposes a switching converter for CP, mostly to enhance the efficiency in low to medium output powers, where the duty cycle is less than 30%. This device is composed of two parts, an ac–dc converter and a dc–dc full-bridge converter. The ac–dc converter is a single-phase boost-type power factor correction converter with emphasis on high efficiency, thus resulting in an almost unity power factor and fixed dc output voltage. The dc–dc full-bridge converter operates under pulsewidth modulation with the simultaneous change of frequency and duty-cycle (SCFD) control method responding to the user output power demand. The SCFD control strategy, in this converter, increases overall efficiency of the proposed rectifier. Finally, a 1875 W prototype is implemented and tested to verify the nearly fixed high efficiency for the converter in a wide operating range of the output power.

There is an increasing attention on wireless power transfer (WPT) technology in many applications. However, for WPT systems, the changing coils distance and variable load make the output power fluctuant. In this article, a switched-capacitor-based half-wave rectifier with active impedance matching ability is proposed in the WPT system to solve the issue. Different from typical half-wave rectifier, the conducting time of the diode in the proposed topology becomes adjustable, making the equivalent impedance controllable. Compared with the universal methods, where an additional dc–dc converter located at the end of the rectifier for power adjustment, fewer components are employed and soft-switching is achieved for the rectifier switch in the proposed topology, leading to lower cost, higher power density, and higher efficiency. In the theoretical analysis, the operation principle is given and the relationship between the diode conducting time and the equivalent load is obtained. A prototype was built to verify the performance of the proposed topology, the experiments agree with the calculation well.

In this article, a dual active bridge (DAB)–LLC–DCX dc–dc converter with integrated magnetics and shared rectifier is proposed for point of load applications, which is able to achieve tight voltage regulation, zero-voltage switching (ZVS) operation for all switches and zero-current switching operation for rectifier. The challenge of the proposed converter is the realization of ZVS operation for all the switches within full power range to achieve high efficiency and high reliability, which is beneficial for light load efficiency improvement of microprocessors. Therefore, with different input voltage range, a hybrid control strategy is proposed to realize ZVS operation for all switches of the proposed converter within full power range in this article. When at high input voltage, extended phase shift control is applied to extend the ZVS range. When at low input voltage, variable gain LLC converter is designed to regulate the voltage distribution among DAB converter and LLC converter for the ZVS operation of DAB converter. Besides, the charging/discharging of junction capacitors are added into consideration of ZVS analysis. The operating principle, design considerations, and control schemes are presented. Finally, the experimental results of an 80-W prototype verified the theoretical analysis.

The paper deals with the realization of a simple and novel topology of a voltage-mode full-wave rectifier with easy arrangements of a voltage follower, a current follower, two diodes and two resist...

The RF to dc conversion efficiency of a rectenna often varies dramatically with the operating frequency, input power, and polarization tilt angle. To stabilize the efficiency, this article presents a polarization-independent rectifier, which employs a novel six-port Lange-based coupler with a grounded isolation point, as well as four subrectifiers. By the adoption of the novel six-port Lange-based coupler, the rectifier not only achieves stable efficiency at varied polarization tilt angles, but also widens operating frequency and input power ranges. In this case, when developing a dual-polarized rectenna with such a rectifier, the rectenna can receive incident energy at any polarization tilt angles with stable efficiency. For verification, the mechanism of the proposed rectifier is analyzed and a prototype is implemented. Measured results show that the rectifier operates efficiently at a frequency band from 1 to 2.7 GHz and an input power range beyond 18.5 dB. Furthermore, when the polarization tilt angle varies from 0° to 90°, the rectifier can work stably.

This work presents a wide-range, submicrowatt CMOS rectifier, which is designed to efficiently work at input power levels down to −31 dBm. The designed rectifier uses a novel threshold voltage compensation design, namely, the design of a custom-built single-stage rectifier that supplies a nanowatt current reference circuit. The generated bias current is mirrored to the core rectifier in order to precharge its CMOS diodes. The rectifier was optimized for a minimum number of gain stages while trying to minimize the overall input parasitic capacitance of the rectifier. The proposed CMOS rectifier was designed in an in-house 130-nm CMOS technology and includes a 1.6-kV human body level ESD protection at the input terminals. Measurements reveal a high 30% power conversion efficiency (PCE) over a wide input power range from −23 to −13 dBm for a 1- ${\mathrm{ M}}\Omega $ output load at 868 MHz. PCE of over 10% is achieved for a 1- ${\mathrm{ M}}\Omega $ load at an input power of −28 dBm. The enhanced startup at submicrowatt input power levels of the CMOS rectifier enables the design of an ultralow-power passive wake-up receiver. The measured sensitivity of −31 dBm for a 1-V output voltage across a capacitive load is the lowest reported in the literature so far.

This article presents a highly-efficient radio frequency energy harvester that utilizes an extra matching network to produce a passively-amplified adaptive compensation voltage. The compensation voltage produced on the gate of the transistors reduces the transistors’ conduction loss by increasing the gate-source voltage when transistors are on and reduces the leakage current by producing a negative gate-source voltage when the transistors are off. This is the first work that produces an adaptive compensation voltage without using active components, resulting in a significantly higher conversion efficiency if passive components of high quality are utilized. The mathematical derivations show that the forward conduction loss and the leakage current of the transistors are minimized by utilizing the proposed technique, increasing the overall efficiency. The proposed rectifier is fabricated in a TSMC 130 nm standard CMOS process, and measurement results and simulation results are in good agreement. Measurement results show that the rectifier achieves the maximum efficiency of 61% and 63.4% for battery load of 1.2 V and 1.5 V, respectively, which is at least 20 % larger than the efficiency of the conventional Dickson’s rectifiers.

This article proposes a solid-state transformer (SST) based power electronic architecture for fast charging three categories of plug-in electric vehicle with batteries of vastly different voltage and power ratings. The SST accomplishes integration to a medium-voltage grid and isolation to the charging ports without the use of an LFT. Delta connected cascaded H-bridge (CHB) is used as the active front-end rectifier and quad active bridges (QABs) are utilized for the isolated dc–dc conversion stage. In the proposed architecture, an additional winding called balancing winding is provided in each of the medium-frequency transformers of the QAB. The balancing winding of the transformers are paralleled such that a circulating current flows among the transformers of the three phases, which eventually reduces the unbalance in the delta-connected clusters. Hence, the magnitude of zero-sequence current required to balance the cluster powers for a certain level of unbalance is also reduced. As a result, the total current in the devices of the CHB decreases and devices with a lesser current rating can be used. The control philosophy and detailed analysis of the system are given in the article. Experimental results with a scaled-down prototype are presented to verify the claims.

This paper demonstrates the analysis of a long-distance high-power microwave wireless power transmission (MWPT) system based on asymmetrical resonant magnetron and cyclotron-wave rectifier. In the system, the novel magnetron with the asymmetrical resonant cavity, the straps, and the output loop coupling circuit can effectively promote the beam–wave interaction, suppress the mode competition, and enhance the output coupling, which results in a 400 kW output microwave power with a conversion efficiency of 45%. The transceiver Cassegrain antenna system with its simple structure, high conversion efficiency, and high power capacity can attain an integral power transmission efficiency of 2.6% at 10 km distance. The cyclotron-wave rectifier with high efficiency and single-tube high power capacity can achieve 85% microwave to DC conversion efficiency. Finally, the long-distance high-power MWPT system can achieve 8.5 kW DC power with about 1% DC–DC transmission efficiency at the operating 2.45 GHz frequency and for the 10 km distance. Such a system is likely a potential and attracting solution to remotely power the fuel-free aerial vehicle from the ground, can also provide electrical power to an isolated mountain top or an island, and even an alternative to transmit the power from space solar power satellite in geostationary orbit to the ground.

This paper aims to build a smart lighting system with applications such as remote for controlling power supply and optimizing heat management in the metal body of the semiconductor diode and with a printed circuit board for agriculture. The semiconductor diode strips with multiple colors are lined up and configured as a LED lamp with proper casing and heat sink. It has a driver circuit with required power regulation that is able to control the intensity of light for photosynthesis and plant growth requirements. The system uses hydroponics to plant the water, thus decreasing the usage of fertilizers. The entire system is controlled remotely using necessary communication interface application.

There has been a significant increase in the number of total knee replacement (TKR) surgeries over the past few years, particularly among active young and elderly people suffering from knee pain. Continuous and optimal monitoring of the load on the knee is highly desirable for designing more reliable knee implants. This paper focuses on designing a smart knee implant consisting of a triboelectric energy harvester and a frontend electronic system to process the harvested signal for monitoring the knee load. The harvester produces an AC signal with peak voltages ranging from 10 V to 150 V at different values of knee cyclic loads. This paper demonstrates the measurement results of a PCB prototype of the frontend electronic system fabricated to verify the functionality and feasibility of the proposed approach for a small range of cycling load. The frontend electronic system consists of a voltage processing unit to attenuate high peak voltages, a rectifier and a regulator to convert the input AC signal into a stabilized DC signal. The DC voltage signal provides biasing for the delta-sigma analog-to-digital converter (ADC). Thus, the output of the triboelectric harvester acts as both the power signal that is rectified/regulated and data signal that is digitized. The power consumption of the proposed PCB design is approximately $5.35~\mu \text{W}$ . Next, the frontend sensor circuitry is improved to accommodate a wider range of cyclic load. These results demonstrate that triboelectric energy harvesting is a promising technique for self-monitoring the load inside knee implants.