Low-voltage Semiconductor Research Articles

On the Practical Evaluation of the Switching Loss in the Secondary Side Rectifiers of LLC Converters

The switching loss of the secondary side rectifiers in LLC resonant converters can have a noticeable impact on the overall efficiency of the complete power supply and constrain the upper limit of the optimum switching frequencies of the converter. Two are the main contributions to the switching loss in the secondary side rectifiers: on the one hand, the reverse recovery loss (Qrr), most noticeably while operating above the series resonant frequency; and on the other hand, the output capacitance (Coss) hysteresis loss, not previously reported elsewhere, but present in all the operating modes of the converter (under and above the series resonant frequency). In this paper, a new technique is proposed for the measurement of the switching losses in the rectifiers of the LLC and other isolated converters. Moreover, two new circuits are introduced for the isolation and measurement of the Coss hysteresis loss, which can be applied to both high-voltage and low-voltage semiconductor devices. Finally, the analysis is experimentally demonstrated, characterizing the switching loss of the rectifiers in a 3 kW LLC converter (410 V input to 50 V output). Furthermore, the Coss hysteresis loss of several high-voltage and low-voltage devices is experimentally verified in the newly proposed measurement circuits.

Modeling and Control Design Based on Petri Nets Tool for a Serial Three-Phase Five-Level Multicellular Inverter Used as a Shunt Active Power Filter

In this work, we represent a shunt active power filter (SAPF) based on a serial three-phase flying capacitor multilevel inverter (FCMI) controlled by a Petri Nets representation (PNs). This structure is chosen for its significant performances. In fact, the use of the FCMI within the SAPF makes it possible to increase the apparent switching frequency of the structure in order to reduce the value then the volume and weight of the inductance of the output filter. Besides, the FCMI allows the synthesis of a high-voltage signal using low-voltage semiconductor components. Therefore, improving the reliability of this structure leads to the improvement of the dynamics of the SAPF. This paper deals with a new control methodology based on PNs to regulate the flying capacitor voltages and the reference currents issued by the instantaneous active and reactive power theory. Compared to a conventional SAPF composed by a classical two-level inverter and controlled by a simple PWM control, simulation results demonstrate that our proposed control enhances the dynamic system and the power quality by reducing the total harmonic distortion (THD) satisfying the limits of IEEE standards.

Multicell AFE Rectifier Managed by Finite Control Set–Model Predictive Control

Multicell converters, based on power cells that use low-voltage semiconductors, implement AC motor drives for medium-and high-voltage applications. These converters feature an input multipulse transformer, which performs low-frequency harmonics cancelation generated by three-phase diode rectifiers in the power cells. Despite this advantage, the multipulse transformer is bulky, heavy, expensive, and must be designed according to the number of power cells required by a specific case, limiting the modularity of the topology. This work proposes a multicell converter based on power cells that requires a standard input transformer and uses active front-end rectifiers controlled by employing a finite control set-model predictive control algorithm. The proposed approach emulates the multipulse transformer harmonic cancelation owing to the predictive algorithm operation combined with input current references that are phase-shifted for each active front-end rectifier. Simultaneously, the DC voltages of the power cells are regulated and equalized among the cells using PI regulators. Experimental results confirm the feasibility of the proposed system as input currents in each Multicell AFE rectifier with a unitary displacement factor, and a low THD of 1.87% was obtained. It is then possible to replace the input multipulse transformer with standard ones while reducing the copper losses, reducing the K factor, and extending the modularity of the power cell to the input transformer.

Interleaved current‐auto‐balance high step‐down converter with coupled inductors

This study presents a current-auto-balance non-isolated interleaved high step-down converter with a coupled inductor. The proposed converter achieves low-voltage gain by the turns ratio of the coupled inductor and capacitive voltage division which avoids low duty cycles. The voltage stress across the power MOSFETs is decreased and the voltage stress across the diodes is controlled by the turns ratio of the coupled inductors. Therefore, low voltage semiconductors are adopted reducing the switching and conduction losses. Meanwhile, the zero current switching (ZCS) turn-ON for MOSFETs and ZCS for whole switching transitions of diodes are provided by the leakage inductances that reduces the switching losses and alleviates the reverse recovery problems. Besides, by replacing the inductors with the coupled ones, the power density is improved. Due to the interleaved structure, the output current ripple is minimised and the thermal stress is distributed between the phases. All of these factors improve the conversion efficiency and overall performance of the proposed converter. Moreover, the auto-current-sharing performance is realised due to the charge balance of the blocking capacitors. Finally, a 400 W prototype with 400–25 V voltage conversion is fabricated to demonstrate the performance of the proposed converter.

Single-Phase Five-Level Flying-Capacitor Rectifier Using Three Switches

In this paper, a unidirectional single-phase five-level PWM rectifier based on flying-capacitor topology operating as PFC is proposed. The main feature is the fact that the proposed converter has three active switches, therefore offering a cost reduction compared to traditional five-level topologies. The multilevel voltage operation reduces the weight and bulk of the magnetic devices. Moreover, 82% of the semiconductors are subject to one fourth to DC output voltage which allows the use of low voltage semiconductor devices. An extensive mathematical analysis, control-oriented modeling in addition to experimental results are presented in order to demonstrate the feasibility of the structure.

A Hybrid 7-Level Inverter Using Low-Voltage Devices and Operation With Single DC-Link

This paper proposes a new 7-level inverter topology for induction motor drives. It is a hybrid topology formed by cascading a 5-level active neutral-point-clamped inverter with a 3-level T-type converter. It is obtained using low-voltage semiconductor devices with voltage blocking capability of Vdc/3 and Vdc/6. The topology uses three floating capacitors per phase, which are balanced within a pulsewidth modulation (PWM) switching duration using switching-state redundancies for each pole-voltage level. Topology forms two stacks at the front-end, which requires individual symmetrical dc source. The analysis of switching loss and conduction loss is performed and compared with some of the existing 7-level multi-level inverters reported in various literatures to show the advantages of the proposed topology. Furthermore, the single dc source operation with two stacked capacitors and closed-loop control of neutral-point voltage using symmetrical six-phase induction motor is proposed. The voltage-control algorithms for floating capacitors and dc-link stacked capacitors are proposed, which are independent of load power factor and modulation index. Open-loop V / f and closed-loop rotor field oriented control are performed, and various results at steady and transient states are presented to validate the aforementioned claims.

A Very High Frequency Self-Oscillating Inverter Based on a Novel Free-Running Oscillator

This letter introduces a self-oscillating very high-frequency (VHF) class $\phi$ 2 inverter based on a free-running oscillator. The class $\phi$ 2 is a low-voltage semiconductor stress, fast-transient, single-transistor inverter topology suitable for VHF applications. With new advancements in GaN technology, the tendency to increase the switching frequency in power converters is on the rise. Switching at VHF (VHF: 30–300 MHz) allows for smaller passive components and more compact power converters. However, although GaN components are able to switch at 100 MHz and beyond, gate drivers available in the market struggle to provide the adequate switching signal at VHF. Hence, there is a need for an alternative to VHF converters using those gate drivers—self-oscillating topologies. To that end, a self-oscillating class $\phi$ 2 inverter switching at 30 MHz is presented and a design methodology is provided. A 30 MHz prototype with 30 V input voltage using a GaN Systems GS61004B is also built and tested, showing good matching between the simulation and experimental results.

HVDC shunt tap based on three single‐phase half‐bridge series‐connected MMCs operated under 2L modulation

In this study, a cost-effective HVDC shunt tap with low-number of relatively low-voltage semiconductor devices and small-sized passive components is proposed. The proposed architecture is based on employing three single-phase half-bridge Modular Multilevel Converters (MMCs), where the DC sides of MMCs are connected in series across the total DC-link voltage. The MMCs are adopted instead of conventional Two-Level Voltage Source Converters (2L-VSCs) to avoid the complications of series connection of Insulated Gate Bipolar Transistors (IGBTs). The involved MMCs in the suggested architecture are operated with the conventional 2L modulation, which results in insignificant arm inductors and Sub-Modules (SMs) capacitances (in range of µH and µF, respectively). This, in turn, affects positively the converter cost and footprint. Each arm of the involved MMCs can be considered as a high-voltage valve of a 2L-VSC. To maintain the balance of SMs capacitors, each arm of the involved (N + 1)-level MMC has an extra SM (a balancing SM) to select N out of N + 1 SMs during the turn-off condition. The operational concept, design, and assessment of the proposed architecture are presented in this study. Simulation results are provided for substantiation of the proposed concept. Finally, a scaled down single-phase prototype is used for experimental validation.

Wearable, Fiber-less, Multi-Channel System for Continuous Wave Functional Near Infrared Spectroscopy Based on Silicon Photomultipliers Detectors and Lock-In Amplification.

Development and in-vivo validation of a Continuous Wave (CW) functional Near Infrared Spectroscopy (fNIRS) system is presented. The system is wearable, fiber-less, multi-channel (16×16, 256 channels) and expandable and it relies on silicon photomultipliers (SiPMs) for light detection. SiPMs are inexpensive, low voltage and resilient semiconductor light detectors, whose performances are analogous to photomultiplier tubes (PMTs). The advantage of SiPMs with respect to PMTs is that they allow direct contact with the scalp and avoidance of optical fibers. In fact, the coupling of SiPMs and light emitting diodes (LEDs) allows the transfer of the analog signals to and from the scalp through thin electric cables that greatly increase the system flexibility. Moreover, the optical probes, mechanically resembling electroencephalographic electrodes, are robust against motion artifacts. In order to increase the signal-to-noise-ratio (SNR) of the fNIRS acquisition and to decrease ambient noise contamination, a digital lock-in technique was implemented through LEDs modulation and SiPMs signal processing chain. In-vivo validation proved the system capabilities of detecting functional brain activity in the sensorimotor cortices. When compared to other state-of-the-art wearable fNIRS systems, the single photon sensitivity and dynamic range of SiPMs can exploit the long and variable interoptode distances needed for estimation of brain functional hemodynamics using CW-fNIRS.

Different Switching Sequence Comparison Applied to Multimodular Matrix Converter using ISVM

This paper discusses the study of the indirect space vector modulation applied to the matrix multimodular converter (MMMC), a converter which connects the theory of matrix converters with the concepts of multilevel topologies, allowing the use of low voltage semiconductors in high power application due to voltage stress sharing between modules. During the theoretical studies and simulations, two topological variations of MMMC are compared, testing in each one two different switching sequences for the same modulation in order to measure the influence of the switching order in the total harmonic distortion of the converter. For the tests were simulated converters of 333 kVa and 1 MVA, using 4.16 kV as the line voltage input of the transformers, switched at 1.8 kHz. After the performed tests, one of the switching sequences showed a lower total harmonic distortion in the two converters studied, due to its characteristic of not inverting the times of vectors applications depending on the phase voltage, generating a potentially more symmetrical waveform.

Фотоконденсатор на основе нанокомпозита n-InSe<RbNO3>

The n-InSe<RbNO3> nanocomposite material was obtained by the method of intercalation of the InSe layered single crystal from a melt of RbNO3 ferroelectric salt, which can be used for the production of a high-specific capacitance photoconductor. X-ray analysis of the structure, AFM-imaging of the surface and measurement of dielectric frequency characteristics of the samples were carried out. It was found that the intercalated InSe<RbNO3> samples keeps the type of monocrystalline structure, and the spectrum of X-ray diffraction pattern indicates the implantation of the intercalant in the van der Waals gaps of layered InSe single crystal with an increase in the parameters of the crystal lattice. AFM images of the surface of nanocomposite material layers show the RbNO3 islands in the form of nanosized rings. The islands' height does not exceed the width of van der Waals gap for InSe, which is ≈ 0,35 nm, and the average outside diameter of the rings is ≈ 50 nm. The ensemble of nanorings is characterized by a high surface density in (0001) plane of the crystal layers (109—1010 cm–2). Thus, the physical phenomena of self-organization of nanostructures with ionic conductivity on the surfaces of layers with a molecular type of bond are used in the making of nanocomposite material for the proposed photoconductor. This allows us to obtain arrays of nanosized 2D inclusions with ionic conductivity and with given geometrical sizes, morphology and spatial distribution in a matrix of a layered crystal. The developed photoconductor has a high specific electrical capacity, a high coefficient of overlapping of the capacity (≈ 109) in the light, has the ability to accumulate electric charge, it can be used as a low-voltage semiconductor device in optoelectronic memory systems, in photoelectric sensors, in light energy converter and in the storage of electric energy.

Characterization of a fiber-less, multichannel optical probe for continuous wave functional near-infrared spectroscopy based on silicon photomultipliers detectors: in-vivo assessment of primary sensorimotor response.

We report development, testing, and in vivo characterization of a multichannel optical probe for continuous wave (CW) functional near-infrared spectroscopy (fNIRS) that relies on silicon photomultipliers (SiPMs) detectors. SiPMs are cheap, low voltage, and robust semiconductor light detectors with performances analogous to photomultiplier tubes (PMTs). In contrast with PMTs, SiPMs allow direct contact with the head and transfer of the analog signals through thin cables greatly increasing the system flexibility avoiding optical fibers. The coupling of SiPMs and light-emitting diodes (LEDs) made the optical probe lightweight and robust against motion artifacts. After characterization of SiPM performances, which was proven to provide a noise equivalent power below 3fW, the apparatus was compared through an in vivo experiment to a commercial system relying on laser diodes, PMTs, and optical fibers for light probing and detection. The optical probes were located over the primary sensorimotor cortex and the similarities between the hemodynamic responses to the contralateral motor task were assessed. When compared to other state-of-the-art wearable fNIRS systems, where photodiode detectors are employed, the single photon sensitivity and dynamic range of SiPMs can fully exploit the long and variable interoptode distances needed for correct estimation of brain hemodynamics using CW-fNIRS.

Optimum Number of Cascaded Cells for High-Power Medium-Voltage AC–DC Converters

For power electronic systems to interface medium-voltage grids, e.g., in future electric ships, usually cascaded cells converters need to be employed, whereby either few cells featuring power semiconductors with high blocking voltage capability or a larger number of cells using low-voltage (LV) semiconductors can be used. As shown in this paper, physics-inspired empirical models of the dependence of Insulated-Gate Bipolar Transistor (IGBT) power modules' loss-relevant characteristics on the blocking voltage enable an analytic optimization of the efficiency of a cascaded H-bridges (ac-dc) converter, which is complemented by a full efficiency versus power density ηρ-Pareto optimization. For a 10-kV grid, 1200V or 1700V are identified as optimum blocking voltages, resulting in a suitable trade-off between efficiency and power density. Significant efficiency and power density gains can be realized by replacing silicon IGBTs by LV silicon carbide (SiC) devices in multi-cell systems, whereas single-cell designs based on high-voltage SiC devices suffer from the high dv/dt and di/dt values required to limit switching losses. Reliability is analyzed considering redundancy, showing that the reliability of designs based on lower blocking voltages can be comparable with that of designs using higher blocking voltages, and hence fewer cells, if similar effort concerning additionally installed power capability is considered.

Input‐series and output‐series connected modular single‐switch flyback converter operating in the discontinuous conduction mode

This study proposes a modular isolated dc–dc converter, based on the input-series and output-series connection of flyback converters operating in discontinuous conduction mode, as an alternative to provide higher voltage capability for medium-voltage applications (1–10 kV), from low-voltage semiconductors and passive components. The proposed architecture allows the modular system to operate with a simplified control scheme thanks to an intrinsic voltage-balancing mechanism. The voltage-balancing mechanism is investigated by theoretical analysis, both for steady-state and dynamic operations. A small-signal ac modelling of the architecture is developed to design the total output-voltage controller. To experimentally verify the proposed technique, a laboratory prototype system with three single-switch flyback converters, with 3 kW output power, 600 V dc input and output voltages, and 40 kHz of switching frequency was built.

Naturally Clamped Zero-Current Commutated Soft-Switching Current-Fed Push–Pull DC/DC Converter: Analysis, Design, and Experimental Results

The proposed converter has the following features: 1) zero-current commutation (ZCC) and natural voltage clamping (NVC) eliminate the need for active-clamp circuits or passive snubbers required to absorb surge voltage in conventional current-fed topologies. 2) Switching losses are reduced significantly owing to zero-current switching of primary-side devices and zero-voltage switching of secondary-side devices. Turn-on switching transition loss of primary devices is also negligible. 3) Soft switching and NVC are inherent and load independent. 4) The voltage across primary-side device is independent of duty cycle with varying input voltage and output power and clamped at rather low reflected output voltage enabling the use of low-voltage semiconductor devices. These merits make the converter good candidate for interfacing low-voltage dc bus with high-voltage dc bus for higher current applications. Steady state, analysis, design, simulation, and experimental results are presented.

Novel Interleaved Bidirectional Snubberless Soft-Switching Current-Fed Full-Bridge Voltage Doubler for Fuel-Cell Vehicles

This paper presents a novel interleaved soft-switching bidirectional snubberless current-fed full-bridge voltage doubler (dc/dc converter) for an energy storage system in fuel cell electric vehicles. A novel secondary modulation technique is also proposed to clamp the voltage across the primary-side switches naturally with zero-current commutation. It, therefore, eliminates the necessity for an external active-clamped circuit or passive snubbers to absorb the switch turn-off voltage spike, a major challenge in current-fed converters. Zero-current switching of primary-side devices and zero-voltage switching of secondary-side devices are achieved, which significantly reduce switching losses. An interleaved design is adopted over a single cell to increase the power handling capacity obtaining merits of lower input current ripple, reduction of passive components' size, reduced device voltage and current ratings, reduced conduction losses due to current sharing, and better thermal distribution. Primary device voltage is clamped at rather low-reflected output voltage, which enables the use of low-voltage semiconductor devices having low on-state resistance. Considering input current is shared between interleaved cells, conduction loss of the primary side, a considerable part of total loss, is significantly reduced and higher efficiency can be achieved to obtain a compact and higher power density system. Steady-state operation, analysis, and design of the proposed topology have been presented. Simulation is conducted over software package PSIM 9.0.4 to verify the accuracy of the proposed analysis and design. A 500-W prototype has been built and tested in the laboratory to validate the converter performance.

Simplified sustain driver with low-voltage semiconductor devices and low-voltage power supply for AC plasma display panel

Two types of novel sustain drivers with low cost and high performance are proposed for plasma display panels (PDPs). One is based on switching scan integrated circuit (IC) to realize high-efficient and cost-effective PDP drives with low-cost and low-voltage-rating circuit devices. Since the proposed driver is designed in such a way to utilize the switching operation of the scan IC as well as the common resonant circuit, the developed sustain driver can be implemented with considerably less number of circuit devices than the prior cascaded Weber-type driver. In addition, the proposed driver can employ a power supply board based on switching devices with reduced voltage rating and costeffectiveness. The other sustain driver is developed with a compromise of high efficiency and fast energy transfer speed for the PDP. In this driver, the resonant network is energized by the sustain voltage level and the half sustain voltage level in charging and discharging the panel capacitor, respectively. The energy transferred into the panel from the power supply is twice as fast as the conventional Weber-type driver, during every up-commutation of the panel voltage. On the other hand, the proposed driver recovers the panel energy using the resonant circuit biased by the half sustain voltage. This operation results in lower displacement current during the down-commutation period than during the up-commutation period, which can yield enhanced energy recovery and energy efficiency. Furthermore, this proposed driver is realized with reduced number of circuit devices, leading to the costeffectiveness.

Analysis of a modular generator for high-voltage, high-frequency pulsed applications, using low voltage semiconductors (<1kV) and series connected step-up (1:10) transformers

This article discusses the operation of a modular generator topology, which has been developed for high-frequency (kHz), high-voltage (kV) pulsed applications. The proposed generator uses individual modules, each one consisting of a pulse circuit based on a modified forward converter, which takes advantage of the required low duty cycle to operate with a low voltage clamp reset circuit for the step-up transformer. This reduces the maximum voltage on the semiconductor devices of both primary and secondary transformer sides. The secondary winding of each step-up transformer is series connected, delivering a fraction of the total voltage. Each individual pulsed module is supplied via an isolation transformer. The assembled modular laboratorial prototype, with three 5 kV modules, 800 V semiconductor switches, and 1:10 step-up transformers, has 80% efficiency, and is capable of delivering, into resistive loads, -15 kV1 A pulses with 5 micros width, 10 kHz repetition rate, with less than 1 micros pulse rise time. Experimental results for resistive loads are presented and discussed.

Diode Laser-Driven Microthrusters: A New Departure for Micropropulsion

We developed an entirely new type of orientation thruster for micro- and nanosatellites. The laser plasma thruster is based on the recent commercial availability of diode lasers with sufficient brightness and 100% duty cycle to produce a repetitively pulsed or continuous vapor or plasma jet on a surface in vacuum. A low-voltage semiconductor switch can drive the laser. A lens focuses the laser diode output on the ablation target, producing a miniature jet that provides the thrust. Single-impulse dynamic range is nearly five orders of magnitude, and the minimum impulse bit is 1 nN/s in a 100-„s pulse. Even with diffraction-limited focusing optics, at least 0.5-W optical power is needed to produce thrust from selected ablator materials. Thrust-to-power ratio Cm is 50 to 100„N/W and specific impulse Isp is 200‐500 s with a 1-W laser, depending partially on the illumination mode. Transmission and reflection (R) illumination modes are discussed. R mode gives about 50% better Isp and two times better Cm. Improved results are anticipated from higher laser power in the reflection mode. The prototype engine we are developing is intended to provide lifetime on-orbit steering for a 5-kg satellite, as well as reentering it from low Earth orbit.

4412142 Integrated circuit incorporating low voltage and high voltage semiconductor devices

An integrated circuit incorporating high voltage semiconductor devices which are controlled by low voltage semiconductor devices is disclosed, including a method for making the same. The low voltage devices which are capable of realizing complex logic functions on the same chip are realized with only one simple extra step in the fabrication process as compared with the process used to fabricate discrete high voltage power transistors. The process addition to implant the low voltage device does not significantly degrade the original capability associated with discrete power transistors. Both laterally developed and vertically developed devices are described. The integrated circuit combines I2 L logic with power Darlington transistors. A large area ion implantation permits one to fabricate both low and high voltage devices on one substrate. The resulting integrated circuit permits a plurality of loads to be controlled by a simple or complex control function.