Diode Losses Research Articles

Investigation of networked SSHI configurations for plate-based piezoelectric energy harvesters

Piezo-patch energy harvesters attached to plate-like structures can be used to extract multimodal vibrational energy. For each piezo-patch, SSHI circuits can boost the harvested power compared to standard rectifier circuits. However, the effect of using different configurations of the SSHI network for multiple piezo-patches on plate structures has not yet been understood. This study aims to assess the performance of the networked SSHI configurations compared to networked rectifier configurations and investigate the optimum configurations for energy harvesting purposes. For this, three piezo-patches are bonded to an aluminum plate and connected to single and/or multiple circuits. The equivalent circuit model (ECM) of the electromechanical system is developed from the experimentally validated analytical model and utilized in simulation software LTspice. The performances of considered configurations are evaluated regarding peak power outputs, and the optimal load resistances are obtained. Based on the experimental findings, the best configuration is determined and verified by simulations. The results show that by using respective SSHIs, the power output can be improved by preventing charge cancellation despite the cost of increased diode loss. This study contributes to our understanding of optimal energy harvesting techniques by investigating the effectiveness of networked SSHI configurations for multiple piezo-patches on plate structures.

Research on Junction Temperature Smooth Control of SiC MOSFET Based on Body Diode Conduction Loss Adjustment

In a converter of actual working condition, the change in the current and voltage of the power device will cause the junction temperature to fluctuate greatly. This device is subjected to high thermal stress due to the change in the junction temperature. Therefore, it is necessary to adopt junction temperature control to reduce or smooth the junction temperature fluctuation, so as to realize the junction temperature control and improve the reliability of the device. At present, the methods for the junction temperature control of power devices have certain limitations and there are few active thermal management methods proposed for SiC device characteristics. In this paper, a method for realizing the smooth control of the junction temperature of a SiC device based on the conduction loss adjustment of the body diode for the SiC device has been proposed, considering that the conduction loss of the body diode is greater than the conduction loss of the SiC MOSFET. The conduction time of SiC MOSFET body diode was adjusted. By adjusting the conduction loss of the SiC MOSFET device, the fluctuation range of the junction temperature of the SiC MOSFET device was controlled, the smooth control of the junction temperature of the SiC device was realized, and the thermal stress of the device was reduced.

Analytical Determination of Majority Carrier Diode Losses in Power Switching and Perspective for Ultrawide Bandgap Semiconductors

Analytical Determination of Majority Carrier Diode Losses in Power Switching and Perspective for Ultrawide Bandgap Semiconductors

In-situ fabricated hexagonal PDMS microsphere arrays for substrate-mode light extraction in blue fluorescent organic light emitting diodes

To inhibit the total reflection in the substrate-mode light loss of organic light-emitting diodes (OLEDs) and fully take advantage of the excellent light converging and out-coupling effect of the hexagonal array of microsphere, we in-situ fabricated the hexagonal array of polydimethylsiloxane (PDMS) microsphere onto the substrate of OLEDs via the porous template for substrate-mode light extraction. Firstly, regular honeycomb porous polystyrene (PS) template was prepared via a self-assembly “breath figure” process. The PS molecular weight, solvent, and humidity play an important role on the uniformity of pore distribution and pore diameter according to Young-Laplace equation. Based on the optimized porous PS template, the PDMS microsphere array was fabricated by pattern transferring, which indicates more prominent light diffraction than the flat PDMS film. Finite-difference time-domain (FDTD) simulation denotes that higher duty ratio of the PDMS microsphere array contributes to higher light out-coupling efficiency. Therefore, a PDMS microsphere array with larger duty ratio of 84.0 % was applied in the extraction of external light for the blue fluorescent OLED device. The maximum luminance, current efficiency, and power efficiency are all improved, and the external quantum efficiency (EQE) is increased by 18.81 % with spectral stability.

Modelling of Power Semiconductor Devices Switching and Conduction Losses in a Power Electronic System

In power converters, power semiconductor devices, mainly Insulated-Gate Bipolar Transistor (IGBT), are generally used as they are less costly and capable of converting electrical energy into high frequency and voltage. It is critical to accurately determine the switching and conduction losses of power devices before they are assembled into an electronic system. The accurate values help to minimize power loss in a power converter system. With the aid of simulation, design problems are identified to help eliminate device destruction, and critical parameters are monitored. In addition, costly equipment for measuring purposes and testing prototypes is not required at the initial design stage. This research uses simulation work in a power converter system to predict IGBT and diode losses with varied frequencies and voltages. The predictive modelling is produced using regression analysis. The models have been validated by R square (R2) and Mean Absolute Percentage Error (MAPE) techniques. This work is aimed at providing a supervised learning technique mainly used in a machine learning environment, in line with the technological development in the semiconductor industry. With the simulation performed in this work, the efficiency of a boost converter system is enhanced as it shows the models have a good fit with an R2 value of almost 1, and MAPE values are noticed to be less than 5%.

A Novel Non-Isolated Bidirectional DC-DC Converter with Improved Current Ripples for Low-Voltage On-Board Charging

This paper presents a novel single-phase non-isolated bidirectional buck converter topology. The proposed converter uses a basic switching cell structure with a coupled inductor and an interleaving switching scheme. This article addresses a crucial challenge in bidirectional DC-DC conversion by prioritizing reducing output current ripples and minimizing filter inductor size. The employed method includes using MOSFETs with fast recovery diodes to mitigate reverse recovery and body diode losses. Furthermore, the optimization of the switching frequency of the output inductor to be twice the actual switching frequency contributes to reducing the component size of the converter. The coupled inductor also helps to reduce stress on components by distributing currents among its legs. The experimental result demonstrates the proposed converter has a very low ripple current as compared to the conventional converter. The low current ripples and smaller filter inductor size enabled by high-frequency operation have improved the efficiency and size of the converter. A common ground between input and output terminals ensures robust performance without common mode current concerns. Overall, the proposed converter represents a significant improvement in DC-DC converters, promising enhanced efficiency, reliability, and compactness in bidirectional DC-DC conversion systems. In order to verify the performance of the proposed converter, a 460 W buck converter prototype was built and tested.

Experimental Study on Glazing Impacts on Rectification Performance of Planar Thermal Diode Integrated Collector Storage Systems

Thermal diodes are innovative tools to rectify the heat transfer mechanism in integrated collector storage (ICS) solar water heating (ICSSWH) systems and reduce ambient heat losses. This study analyzes an innovative planar thermal diode ICSSWH and aims to determine how the glazing affects the efficiency and dynamics of planar diodes. Furthermore, the robust ability of planar diodes to rectify the heat transfer mechanism is proven. Hence, an experimental setup was fabricated and analyzed outdoors during the day to observe the planar diode’s dynamics comprehensively. The obtained results illustrate the strong effects of glazing on the dynamics and diodicity of the planar diode. The stored water obtains the highest temperature of 64 °C in the glazed scenario and 50 °C in the unglazed one. Hence the glazing improves collection and retention efficiencies in which the collection efficiency reaches 52.81% and 35.56%, while the retention efficiency has peak values of 11.04% and 3.22% in the glazed and unglazed scenarios. The partial vacuum is another crucial factor that slightly affects the stored water temperature and efficiencies compared to the glazing strategy. Hence the glazing significantly reduces ambient heat losses in the planar diode as a robust thermal rectifier.

Shared External Driver for VHF Converter With a Synchronous Rectifier Based on Matching Network Parameters Optimization

In order to reduce the conduction loss of diode, synchronous rectification is usually adopted in very-high-frequency (VHF) converters, in which the rectifier diode is replaced by a MOSFET with very low on-state resistance. And to ensure normal operation of the synchronous rectifier switch, it is necessary to design a suitable driver with accurate timing. The widely used self-oscillating resonant drive circuit has a limited range of duty cycle adjustment, and the body diode of synchronous rectifier switch has long on-state time and a large conduction loss. Therefore, based on the analysis and parameters optimization of matching network, a shared external drive circuit is put forward. That is, the drive signals of the inverter switch and the synchronous rectifier switch come from the same external oscillation signal. On the premise of ensuring accurate drive timing, it can improve the drive signal's duty cycle of synchronous rectifier switch, reduce the conduction loss of body diode, and improve the efficiency of converter. Then on the basis of the proposed drive circuit, a VHF converter prototype with operating frequency of 10 MHz, 13 V input and 8 V/10 W output is designed, and the feasibility of the proposed drive circuit is verified by simulations together with experiments.

High-Performance Light Emitting Diode Lighting Circuits and Their Interior Design Applications

This study explores the application of the half-bridge Inductor-Inductor-Capacitor (LLC) resonant converter in Light Emitting Diode (LED) lighting driver power supplies, with a specific focus on improving efficiency and dimming capabilities. The investigation begins with an analysis of the sliding mode control (SMC) method, utilizing a constant-current design with a fixed switching frequency (FWF). A novel fuzzy frequency-selective SMC dimming strategy is proposed to recognize the challenge of significant output voltage ripple during dimming under a FSF. To address the ripple issue during dimming, an electromagnetic filtering circuit is designed, and a zero-voltage turn-on Metal—Oxide—Semiconductor (MOS) tube is introduced, incorporating a synchronous rectification scheme to mitigate losses in the secondary-side rectification diode. The study comprehensively considers a current-mode self-driven method, specifically tailored to the LLC circuit’s different operating modes. The LLC resonant circuit, along with the subsequent synchronous rectification circuit, is meticulously designed for a 252 W LED driver power supply prototype. A closed-loop simulation circuit model is developed using PSIM software in experimental validation. The feasibility of SMC based on a FSF is affirmed through a comparative analysis of SMC signal waveforms, steady-state output current (OC) models, and resonant tank current waveforms. The investigation into the OC under various SMC conditions demonstrates the half-bridge LLC resonant converter’s ability to achieve stable output with minimal ripple. The designed LED lighting circuit is applied to indoor design, providing adjustable LED brightness and switch status at different power levels. Although obstacles slightly impact the communication quality of the circuit, it remains suitable for the majority of users’ needs.

A Novel Integrated Electronic Lighting Driver Circuit for Supplying an LED Projection Lamp with High Power Factor and Soft Switching Characteristics

The traditional light source of projection lamps adopts a halogen lamp, which has the advantages of high brightness, but its luminous efficiency is not good and consumes energy. A light-emitting diode (LED) has the characteristics of high luminous efficiency and energy savings and can be used as a new light source for projection lamps. The conventional two-stage electronic lighting driver circuit for supplying an LED projection lamp is composed of an AC-DC converter with power factor correction (PFC) as the first stage and a DC-DC converter for providing rated lamp voltage and current as the second stage. The conventional LED projection lamp driver circuit has more circuit components, a higher cost and limited efficiency. Therefore, this paper proposes a novel electronic lighting driver circuit for supplying an LED projection lamp with PFC function, which integrates a modified stacked dual boost converter and a half-bridge LLC resonant converter into a single-stage power-conversion circuit. The inductor inside the modified stacked boost converter is designed to operate at discontinuous conduction mode (DCM) for the driver circuit achieving PFC. Wide bandgap semiconductor devices silicon carbide (SiC)-based Schottky diodes are utilized to reduce power diode losses, and soft switching is implemented in the proposed LED projector lamp driver circuit to reduce the switching losses of the power switches and thus improve circuit efficiency. This paper has completed a single-stage prototype driver circuit for an LED projection lamp with PFC function, and the prototype circuit has a high power factor (PF > 0.98), low input current total-harmonic-distortion (THD < 6%) and high efficiency (>89%) in the case of an AC input power supply with an RMS value of 110 volts, and both power switches have the characteristics of soft switching.

Design Considerations of Multi-Phase Buck DC-DC Converter

The main objective of this article is to propose a rational methodology for designing multi-phase step-down DC-DC converters, which can find applications both in engineering practice and in power electronics education. This study discusses the main types of losses in the multi-phase synchronous buck converter circuit (transistors’ conduction losses, high-side MOSFET’s switching losses, reverse recovery losses in the body diode, dead time losses, output capacitance losses in the MOSFETs, gate charge losses in MOSFETs, conduction losses in the inductor, and losses in the input and output capacitors) and provides analytical dependencies for their calculation. Based on the control examples for applications characterized by low voltage and high output current, the multi-phase buck converter’s output and input current ripples are analyzed and compared analytically and graphically (3D plots). Furthermore, graphical results of the converter efficiency at different numbers of phases (N = 2, 4, 6, 8, and 12) are presented. An analysis of the impact of various parameters on power losses is conducted. Thus, a discussion on assessing the factors influencing the selection of the number of phases in the multi-phase synchronous buck converter is presented. The proposed systematized approach, which offers a fast and accurate method for calculating power losses and overall converter efficiency, reduces the need for extensive preliminary computational procedures and achieves optimized solutions. Simulation results for investigating power losses in 8-phase multi-phase synchronous buck converters are also presented. The relative error between analytical and simulation results does not exceed 4%.

SiC Three-Level Neutral-Point-Clamped Converter With Clamping Diode Volume Reduction Using Quasi-Two-Level Operation

Medium voltage (MV) SiC MOSFETs have recently garnered considerable attention in the medium-voltage high-power areas like high-frequency solid-state transformers and multilevel converters. While direct series connection of these MOSFETs is an option for higher voltage levels, it requires complex voltage balancing approaches for device voltage balancing during fast switching transients. Alternatively, converter-level solutions such as the three-level (3L) neutral-point-potential (NPC) converter can be used. This paper proposes a new modulation strategy, combining 3L and Quasi-two-level (Q2L) modulations, to minimize the rating and volume of clamping diodes by tightly controlling the thermal stress on the diodes. This approach achieves better efficiency, higher power density, and a simpler converter bus-structure to stack two SiC MOSFETs effectively in series. We present a real-time clamping diode loss estimation to improve the effectiveness of the proposed modulation strategy. To verify the proposed converter-level approach and modulation strategy, we test a 20 kV rated phase-leg with two 10 kV SiC MOSFETs and 3.3 kV SiC diodes.

A Comparative Evaluation of Wide-Bandgap Semiconductors for High-Performance Domestic Induction Heating

This paper presents a comparative evaluation of wide-bandgap power semiconductor devices for domestic induction heating application, which is currently a serious alternative to traditional heating techniques. In the induction heating system, the power transferred to the output depends on the equivalent resistance of the load, and the resistance depends on the operating frequency. Due to the switching characteristics of wide-bandgap power semiconductor devices, an induction heating system can be operated at higher operating frequencies. In this study, SiC and Si semiconductor devices are used in the comparison. These devices are compared according to different evaluation issues such as the turn-off energy losses, turn-off times, current fall time, the power losses of the internal diodes, and the conduction voltage drops issues. To perform the proposed evaluation, the series-resonant half-bridge inverter, which is frequently used in state-of-the-art induction heating systems, has been selected. The device suitability in an induction heating system is analyzed with the help of a test circuit. A comparison is made in terms of criteria determined by using the selected switches in the experimental circuit, which is operated in the 200 W to 1800 W power range and 45 kHz to 125 kHz switching frequency range. System efficiency is measured as 97.3% when Si IGBT is used. In the case of using SiC cascode JFET, the efficiency of the system is increased up to 99%.

Low Switching Loss Built-In Diode of High-Voltage RC-IGBT with Shortened P+ Emitter

In this paper, a low switching loss built-in diode of a high-voltage reverse-conducting insulated gate bipolar transistor (RC-IGBT) is proposed without deteriorating IGBT characteristics. It features a particular shortened P+ emitter (SE) in the diode part of RC-IGBT. Firstly, the shortened P+ emitter in the diode part can suppress the hole injection efficiency resulting in the reduced carriers extracted during the reverse recovery process. The peak of the reverse recovery current and switching loss of the built-in diode during reverse recovery is therefore lowered. Simulation results indicate that the diode’s reverse recovery loss of the proposed RC-IGBT is lowered by 20% compared with that of the conventional RC-IGBT. Secondly, the separate design of the P+ emitter prevents the performance of IGBT from deteriorating. Finally, the wafer process of the proposed RC-IGBT is almost the same as that of conventional RC-IGBT, which makes it a promising candidate for manufacturing.

A Series-Connected 24-Pulse AC–DC Converter With Double-Diode Harmonic Suppression Circuit

A series-connected 24-pulse ac–dc converter with a double-diode harmonic suppression circuit (DDHSC) is presented in this article. The DDHSC is installed at the dc side of the ac–dc converter, and it consists of several passive devices. The DDHSC generates a specific current at the dc link to modulate and increase the operating modes of this ac–dc converter. Then, the series-connected 12-pulse ac–dc converter is extended to a novel 24-pulse ac–dc converter, and total harmonic distortion of the input line current is reduced to the acceptable levels (less than 5%). The maximum current through the auxiliary diodes in the DDHSC is only 6.8% of the load current, which means the current rating and conduction losses of the auxiliary diodes are low. The proposed DDHSC scheme is more suitable for high-current occasions. Given that only a low capacity (2.06% of the output power) DDHSC is sufficient to double the number of pulse of the 12-pulse ac–dc converter, the proposed scheme is simple and cost effective. The detailed theoretical analysis is provided, and an experimental prototype is established to demonstrate the performance of the proposed converter.

RESEARCH THE ACCURACY OF MODELING POWER LOSSES IN POWER DIODES AND TRANSISTORS

The methodology for modeling static and dynamic power losses in power IGBT and MOSFET transistors in the Matlab and Multisim software environments is given. It is shown that when modeling switching processes in power transistors, Matlab / Simulink does not allow determining the dynamic components of power losses, namely, the energy of turning on the transistor, the energy of turning off the transistor, as well as the recovery energy of power diodes. At the same time, the simulation of static power losses of power diodes and transistors in Matlab/Simulink is carried out with a significant error due to incorrect representation of the current-voltage characteristics. It is shown that for a more correct and accurate simulation of the operation of power transistors, including power losses in power switches, it is more appropriate to conduct simulations in the Multisim software environment, which takes into account more than 47 parameters during simulation, including temperature characteristics, parasitic input and output capacitances and inductances, nonlinearities of current-voltage characteristics and others. In Multisim, a circuit of a half-bridge inverter with power MOSFETs controlled by the IR2104PBF driver has been developed. It is shown that the switching of power transistors is significantly influenced by the parameters of the driver microcircuit, namely the size of the storage capacitor of the driver, as well as the value of the active resistance of the gate resistor. It is shown that the simulation in Multisim correctly displays the transient processes of turning on and off power transistors and reverse recovery of diodes, which allows determining the dynamic losses of power transistors and power diodes.

Double loops power management circuit of pulsed triboelectric nanogenerator with enhanced efficiency at low operating voltage and its application in self-powered flue gas monitoring system

The power management circuits (PMCs) of triboelectric nanogenerators (TENGs) play a key role in developing self-powered sensing system with high energy storage efficiency. However, when the operating voltage (Vop) of PMCs meets the voltage requirement of electronic equipment (generally around 5 V), PMCs have a reduced efficiency less than 36%. Here, based on analyzing the factors affecting the efficiency of PMCs, the general methods have been proposed to improve the efficiency at a lower Vop. It is found that energy loss of diodes in PMCs is the main part in total energy loss, reaching a ratio of 61.7% at a 5 V Vop. By using rectifier diodes with lower threshold voltage and developing double loops power management circuit (DL-PMC) with less operating diodes number, the energy loss of diodes is reduced from 38.6 to 17.0 μJ, and its ratio in total energy loss at a 5 V Vop is reduced to 47.1%. Moreover, it is found that in PMCs with varied open-circuit voltage (Voc) of TENG, the increasing trend of diodes energy loss (∝Voc) is slower than that of TENG’s output energy (∝Voc2), resulting in a reduced energy loss ratio from 62.7% to 26.1% as Voc increasing from 200 to 1000 V. Finally, the measured optimal energy storage efficiency of 48.9% at 5 V Vop, the record reported so far, has been reached as using a DL-PMC with rectifier diodes and Pulsed-TENG with a Voc of 1000 V. A self-powered flue gas monitoring system consisting of Pulsed-TENG, DL-PMC, and gas sensor is developed for detecting operating status of boiler, which can transmit data every 2.5 min and will have broad applications in industry. The proposed general methods are suitable for other PMCs and will promote the development of self-powered sensing systems.

A Lossless Soft-Switching Boost Converter with Passive Auxiliary Circuit

Based on boost topology, a lossless soft-switching passive circuit with a single switch is proposed in this paper. The proposed circuit's power switch achieves approximately zero voltage switching (ZVS) and zero current switching (ZCS) without increasing the number of switches. Due to an auxiliary inductor, the reverse recovery loss of the rectifier diode is significantly reduced. Besides, all auxiliary circuit energy is returned to the power supply without additional energy consumption. Therefore, by using a traditional control method, simple design, and appropriate auxiliary circuit parameters, soft-switching can be realized in a wide voltage and full load range. Moreover, the number of components used in the auxiliary circuit is minimal. This method makes circuit design more manageable and achieves 95.39% high efficiency since the increase of voltage stress is relatively small.

Multidentate Molecule Anchoring Halide Perovskite Surface and Regulating Crystallization Kinetics toward Efficient Light-Emitting Diodes.

Functional passivators are conventionally utilized in modifying the crystallization properties of perovskites to minimize the non-radiative recombination losses in perovskite light-emitting diodes (PeLEDs). However, the weak anchor ability of some commonly adopted molecules has limited passivation ability to perovskites and even may desorb from the passivated defects in a short period of time, which bring about plenty of challenges for further development of high-performance PeLEDs. Here, a multidentate molecule, formamidine sulfinic acid (FSA), is introduced as a novel passivator to perovskites. FSA has multifunctional groups (S≐O, C≐N and NH2 ) wherethe S≐O and C≐N groups enable coordination with the lead ions and the NH2 interacts with the bromide ions, thus providing the most effective chemical passivation for defects and in turn the formation of highly stable perovskite emitters. Moreover, the interaction between the FSA and octahedral [PbBr6 ]4- can inhibit the formation of unfavorable low-n domains to further minimize the inefficient energy transfer inside the perovskite emitters. Therefore, the FSA passivated green-emitting PeLED exhibits a high external quantum efficiency (EQE) of 26.5% with fourfold enhancement in operating lifetime as compared to the control device, consolidating that the multidentate molecule is a promising strategy to effectively and sustainably passivate the perovskites.

Multi-resonant DC-DC Converter Based on Switched Capacitor Pre-voltage Reduction

This paper proposes a multi-resonant DC-DC converter based on switched capacitor pre-buck. The converter can realize soft switching in the full load range and has good voltage gain characteristics. In order to effectively reduce the voltage stress on the device, the front stage of the converter adopts a stacked structure of switched capacitors. This structure realizes the function of high step-down ratio by pre-stepping the bus voltage. After reasonable parameter design and frequency matching, the third harmonic is superimposed on the high-order resonant link of the latter stage during the energy transmission process. This will significantly reduce the loss of the secondary side rectifier diode and increase the efficiency. This paper introduces the working principle of the converter, proposes a five-element parameter design scheme, and analyzes the parameter dispersion to assist the parameter design scheme to make it more reasonable, and finally conducts experimental verification. A 100 W prototype with 400 V input and 12 V output was built in the laboratory to verify the correctness of the theoretical analysis.