Switching Oscillations Research Articles

Gate Ringing Analysis and Driving Circuit Design of GaN HEMT

GaN HEMT can operate at a high switching frequency because of its characteristics, but there are also related problems. This paper analyzes the negative effects of switching oscillations of GaN HEMT, introduces the design criteria of its driving circuit, and analyzes the causes of the Miller effect and gate ringing under the influence of high-frequency parasitic parameters. Then, the corresponding suppression strategies for the above two phenomena are given, and the design of the driving circuit is introduced. Finally, the validity and rationality of the designed driving circuit are verified by experiments.

Online Monitoring of Lithium-Ion Battery Internal Temperature Using PWM Switching Oscillations

Online monitoring of Lithium-ion (Li-ion) battery internal temperature by electrochemical impedance spectrum (EIS) is important for the system safe and reliable operation. However, it is challenging in the high temperature region due to the limited thermal sensitivity. Moreover, additional signal injection or disturbance for online EIS measurement may interact with the operating system. To address these challenges, a Li-ion battery internal temperature continuous monitoring method using the self-excited ultrahigh frequency (UHF) PWM switching oscillations (e.g., several hundred kHz) is proposed in this article. First, the UHF EIS characteristics of a Li-ion battery are explored to find a novel thermal sensitive electric parameter applicable for high temperature measurement. Then, an PWM switching oscillation based online battery temperature monitoring scheme is presented, including the UHF oscillation sensor, resonance impedance extraction algorithm, and battery internal temperature estimation procedure. Finally, experimental work was carried out, and the results demonstrate an excellent performance, such as high sensitivity over 90 °C, ms-level fast response, and noncontract continuous monitoring.

Data-driven condition monitoring of stator winding terminal insulation for inverter-fed machine using enhanced switching oscillation signals

Data-driven condition monitoring of stator winding terminal insulation for inverter-fed machine using enhanced switching oscillation signals

Online Condition Monitoring of Line-End Coil Insulation for Inverter-Fed Machine by Switching Oscillation Mode Decomposition

Online condition monitoring of winding insulation has been proved to be an effective means to improve the reliability of an inverter-fed machine, but little work has been done on the insulation of line-end coil subjected to much higher transient voltage stress with a higher risk of premature insulation break down. In this article, the inverter self-excited high-frequency switching oscillations are utilized for the line-end coil insulation condition monitoring. To improve the condition monitoring sensitivity and its robustness to dynamic operating conditions, a switching oscillation mode decomposition method is proposed. First, the condition-sensitive mode, i.e., high-frequency common-mode (HFCM) current is selected and separated by the variation mode decomposition algorithm among three dominant modes in switching oscillation current. Then, the amplitude-frequency features of HFCM current are extracted for condition monitoring. Finally, the overall insulation condition of three-phase line-end coils and the degree of asymmetric degradation are quantitatively evaluated by the frequency and amplitude features respectively. Experimental work was carried out and the results demonstrate the good performance of high sensitivity, good robustness, and non-contract safety.

Failure quantitative assessment approach to MOSFET power device by detecting parasitic parameters

With the emerging wide bandgap (WBG) semiconductor development, the increasing power density and efficiency of power electronic converters may cause more switching oscillation, electromagnetic interference noise, and additional power loss, further increasing the probability of device failure. Therefore, determining and quantifying the failure of a metal-oxide-semiconductor-field-effect transistor (MOSFET), which assembled using WBG semiconductor in some applications, is crucial to improving the reliability of a power converter. This study proposes a novel failure quantitative assessment approach based on MOSFET parasitic parameters. According to the two-port network theory, MOSFET is equivalent to some second-order RLC circuits composed of independent inductances, capacitances, and resistances in series. Then, the frequency-domain impedance associated with the physical failure of MOSFET is identified through frequency domain reflectometry. Accelerated aging and bond wires cut-off experiments are employed to obtain various quality states of the MOSFET device. Result shows that the MOSFET quality level and its number of bond wire lift-offs can be quantified effectively. Drain-to-source on-resistance (RDS(on)) that normally represents the MOSFET quality shows a positive linear function relationship on drain-to-source parasitic resistance (RD + RS) during the quality degradation proceeding. This finding matches with the correlation established between RDS (on) and RD + RS in theory. Meanwhile, source parasitic inductance (LS) increases with the severity of bond wires faults, and even the slight fault shows a high sensitivity. The proposed approach would be an effective quality screening technology for power semiconductor devices without power on treatment, which can effectively avoid the impact of junction temperature and test conditions (current and voltage) on test results, and does not need to design additional test circuits. The test frequency range we used in this approach was 10–300 MHz, which to some extent is suitable for providing an on-line quality monitoring technology for high-frequency WBG power devices manufacturing.

Quantitative Modeling and Analysis of Switching Oscillations of Cascode GaN Devices in Half-Bridge Converters

Having high efficiency and power density, the motor drives based on wide bandgap (WBG) devices can better meet the requirements for developing more electric aircraft (MEA). However, the fast switching characteristic of gallium nitride (GaN) devices has led to undesirable voltage and current oscillations during turn-ON and turn-OFF processes, thus decreasing the reliability of the electric drive system. The complicated structure of cascode GaN devices and various parasitic parameters in the device and the half-bridge converter make the switching oscillation modeling of cascode GaN device comparatively complex. In this article, an equivalent circuit approach in consideration of nonlinear characteristics in voltage-dependent junction capacitances is presented to model the switching oscillation for high-voltage (650 V) cascode GaN-based half-bridge converters. Quantitative mathematical models are derived to provide a theoretical analysis of the switching oscillation for turn-on and turn-off processes of cascode GaN devices. Furthermore, the influences of device and circuit parameters on the oscillation are investigated in detail, offering a reliable guidance to the gate driver and print circuit board design. Finally, experimental studies on the basis of cascode GaN and custom cascodes are carried out to validate the modeling approach. The results have proved that one of the root causes of the oscillations is how the different parasitics interact.

An integrated modelling and parameter design method for the RC snubber in novel cascode GaN‐based bridge convertors

The utilization of novel cascode GaN devices can significantly increase the power density and the efficiency of convertors. However, owing to high switching speed (high dv/dt or di/dt) and inevitable parasitic inductance in device packages and external circuits, cascode GaN devices are more prone to oscillate, resulting in voltage overshoot, electromagnetic interference (EMI), and even device breakdown, which reduces the reliability of the drive system. Therefore, effective suppression of the switching oscillation becomes highly critical. This paper presents an integrated modelling and a parameter design method for cascode GaN-based bridge convertors. Firstly, a high-frequency equivalent circuit model is derived for the switching oscillation of cascode GaN-based bridge convertors. Secondly, a quantitative RC snubber parameter design method is established based on root locus analysis, which makes up for defects of the previous trial-and-error empirical method. Then impacts of the RC snubber on power loss and EMI are also studied, with the optimal snubber resistance and capacitance obtained by minimizing power loss. Finally, the effect of oscillation suppression is verified by simulation and experiment, and results show good agreement with the theoretical analysis.

Analytical Method for RC Snubber Optimization Design to Eliminate Switching Oscillations of SiC MOSFET

The switching oscillations caused by the high-speed switching and low-damping characteristics of SiC <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> seriously deteriorate its high-reliability applications. By viewing from the terminals of both SiC <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> and diode for the turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> and turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> oscillation not only the two-port networks be formed to carry out more accurate analysis about the system characteristics but also the characteristic equations of the system can be deduced, thereby reliably guiding the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RC</i> snubber design. Since the oscillation is essentially caused by the imaginary part of poles, with the assistance of the two-port networks, an optimized design method of an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RC</i> snubber circuit is developed by the way of actively assigning poles. Different from existing analytical techniques, no necessity is needed to reduce the order of characteristic equations to yield the mathematical expressions of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RC</i> snubbers. Instead, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RC</i> snubber regions where oscillations can be completely suppressed are determined directly by an exhaustion method. An overlapping area is found, which means that both the turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> and turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> oscillation can be eliminated simultaneously by the same snubber circuit. Moreover, the related discussions about existence conditions of the snubber region, sensitivity to parameters, and the limitation in choosing <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RC</i> are illustrated in detail. Finally, standard double-pulse tests are conducted on both the LTspice simulation and the laboratory experiment to verify the effectiveness of the analysis and proposed method.

Observation of Transient Parity-Time Symmetry in Electronic Systems.

We demonstrate the transient parity-time (PT) symmetry in electronics. It is revealed by equivalent circuit transformation according to the switching states of electronic systems. With the phasor method and Laplace transformation, we derive the hidden PT-symmetric Hamiltonian in the switching oscillation, which are characterized by free oscillation modes. Both spectral and dynamic properties of the PT electronic structure demonstrate the phase transition with eigenmode orthogonality. Importantly, the observed transient PT symmetry enables exceptional-point-induced optimal switching oscillation suppression, which shows the significance of PT symmetry in electronic systems with temporary responses. Our work paves the way for breakthroughs in the PT symmetry theory and has essential applications such as anti-interference in switch-mode electronics.

Performance Improvement Strategies for Discrete Wide Bandgap Devices: A Systematic Review

Wide bandgap (WBG) devices are becoming increasingly popular due to their excellent material properties. WBG devices are commercially available in discrete and module packages. Many studies have investigated the design, structure and benefits of module packages. However, a comprehensive and in-depth overview of the discrete package is lacking. Discrete package has the advantages of flexibility, scalability and reduced cost; however, challenges of severe switching oscillations and limited current capacity are associated with it. This review encompasses the switching oscillations and limited current capacity issues of discrete devices. Switching oscillations are categorized in terms of voltage. The underlying oscillation mechanisms are explored in detail. For the current imbalance, the types, root causes and adverse effects in parallel-connected discrete devices application are reviewed. Besides, the most recent techniques to extract stray parameters are also explored. Finally, state-of-the-art methods to mitigate the switching oscillations and the current imbalance are summarized and evaluated. The performance improvement strategies discussed in this paper can assist researchers to better use the discrete package and can stimulate them to come up with new solutions.

All-SiC ANPC Submodule for an Advanced 1.5 kV EV Charging System under Various Modulation Methods

This work is focused on the design and experimental validation of the all-SiC active neutral-point clamped (ANPC) submodule for an advanced electric vehicle (EV) charging station. The topology of the station is based on a three-wire bipolar DC bus (±750 V) connecting an ac grid converter, isolated DC-DC converters, and a non-isolated DC-DC converter with a battery energy storage. Thus, in all types of power converters, the same three-level submodule may be applied. In this paper, a submodule rated at 1/3 of the nominal power of the grid converter (20 kVA) is discussed. In particular, four different modulation strategies for the 1.5 kV ANPC submodule, exclusively employing fast silicon carbide (SiC) MOSFETs, are considered, and their impact on the submodule performance is analyzed. Moreover, the simulation study is included. Finally, the laboratory prototype is described and experimentally verified at a switching frequency of 64 kHz. It is shown that the system can operate with all of the modulations, while techniques PWM2 and PWM3 emerge as the most efficient, and alternating between them, depending on the load, should be considered to maximize the efficiency. Furthermore, the results showcase that the impact of the different PWM techniques on switching oscillations, including overvoltages, can be nearly fully omitted for a parasitic inductance optimized circuit, and the choice of modulation should be based on power loss and/or other factors.

A New Method to Measure the Parasitic Parameter Model of IGBT on Bias Voltage

With the increase in frequency, IGBT can generate serious electromagnetic interference (EMI) when it is turned on and off quickly. The variations in voltage and current produced by switching devices in the transient process are the main sources of high-frequency EMI. The ultrafast switching characteristics of IGBT (i.e., high du/dt or di/dt) will cause serious switching oscillation, EMI noise, and additional power loss. The speed of voltage and current variations in transient process is determined by the interelectrode capacitances of the semiconductor switch. Due to the structural characteristics of IGBT, the interelectrode capacitances will change based on the difference in external voltage. This article introduces an improved method to measure the parasitic inductance and resistance of IGBT. This method perfectly avoids the interference of ${Z}_{\text {ground}}$ which refers to the floating terminal impedance to the ground. The parasitic parameters of IGBT can be obtained by fitting the impedance of IGBT with genetic algorithm. The article also introduces a method to measure the parasitic parameters of IGBT on bias voltage with impedance analyzer and dc source. In the experiment, the capacitance is used to protect the impedance analyzer to avoid the dc current from the dc source. Finally, a double-pulse test circuit is used to verify the parasitic parameter model of IGBT measured in this article. By comparing the current and voltage waveforms when IGBT is turned on and off and the voltage frequency domain waveforms in multiple cycles, it is proved that the parasitic parameter model of IGBT is applicable to the circuit.

Online Monitoring of Incipient Turn Insulation Degradation for Inverter-Fed Machine Using Sensitive Tail Component in PWM Switching Oscillations

A failure of insulation is one of the main reasons for electric machine outage. Online condition monitoring (CM) of an incipient degradation of turn insulation could eliminate the potential fault at the early stage, which is attractive but challenging. To improve the sensitivity and availability of CM, a noninvasive technique is presented in this article for the inverter-fed electric machine utilizing the existing high-frequency (HF) switching oscillations during pulsewidth modulation operation. First, the tail component sensitive to turn insulation is selected among the dominant oscillation modes in switching current, which can penetrate the winding of machine within an adequate frequency band (e.g., several hundreds of kHz). Then, a noncontact and simple HF sensor is developed for switching oscillation current capture. The CM system, procedure, and turn insulation state indicator are devised. After that, experimental work is carried out on a 3-kW permanent magnet synchronous machine test rig. The results show good sensitivity (about 2%) to the local incipient degradation of turn insulation with insusceptibility to the operating conditions. Finally, further discussion is given to demonstrate the performance of the method.

High-Q Switched Oscillator With Capacitive Voltage Divider for Generating Mesoband High-Power Microwave Pulses

The switched oscillator (SWO) is a quarter-wave oscillator capable of generating mesoband high-power microwave (HPM) pulses. This paper presents a novel high-quality factor ( Q) SWO with a capacitive voltage divider (CVD). Unlike conventional SWOs, the transmission line energy of the proposed SWO is gradually coupled with the output load through the CVD. Thus, the proposed SWO can produce a mesoband pulse with a much higher power spectral density within the coupling bandwidth of a target in HPM effect testing. The frequency-domain output-voltage equation of the proposed SWO was obtained through a theoretical analysis of the equivalent circuit of the SWO. Through a numerical analysis, the time-domain output waveform of the proposed SWO was demonstrated to have a high quality factor, and the circuit parameters of the equivalent circuit of the SWO were set to achieve a high quality factor. The circuit parameters selected in the numerical analysis were used in an electromagnetic simulation to determine the design parameters of the parallel-plate transmission line (PPTL)-based SWO with the CVD built on a printed circuit board. The proposed SWO was fabricated and its performance was assessed. For a breakdown voltage of 8.7 kV, the output voltage of the fabricated SWO showed a quality factor of 25, which is more than two times larger than the quality factors of conventional SWOs. Thus, the proposed SWO was demonstrated to produce high- Q mesoband HPM pulses, and it has the potential to be applied in HPM effect testing. Moreover, the proposed SWO improves operator safety by preventing the output load from being charged by a high-voltage power supply.

Investigation of Switching Oscillations for Silicon Carbide MOSFETs in Three-Level Active Neutral-Point-Clamped Inverters

This article investigates the multifrequency switching oscillations of silicon carbide (SiC) MOSFETs in three-level active neutral-point-clamped (3L-ANPC) inverters under three typical commutation modes (i.e., the full mode, outer mode, and inner mode). Multiple switching-oscillation components with various frequencies are identified theoretically for both the full- and outer-mode commutations, due to their switching-loop diversities. Oppositely, the inner mode exhibits a single oscillation component as only one switching loop is involved. Three types of double-pulse tests (DPTs) are conducted on a 3L-ANPC inverter demonstrator with SiC MOSFETs, and the switching-oscillation components are extracted accordingly, which match well with the theoretical derivations. Moreover, other switching characteristics closely related, i.e., the oscillation peaks, current overshoots, capacitive charges, and switching energies, are studied and benchmarked according to the DPT results. It is concluded that the full- and outer-mode commutations share similarities in terms of switching oscillations, current overshoots, capacitive charges, and turn-on energies. The theoretical findings from this work provide a comprehensive knowledge of the multifrequency oscillation mechanisms associated with fast-switched 3L-ANPC inverters. Accordingly, the critical parasitic components are identified, and specific design considerations are proposed to achieve switching-performance improvements.

Switched Oscillator With Quarter-Wave, Open-Circuited Stub for Generating Mesoband High-Power Microwave Pulses

This article presents a high-voltage switched oscillator (SO) with a quarter-wave open-circuited stub (OCS) for generating mesoband high-power microwave (HPM) pulses. Unlike the conventional SO, the proposed SO generates mesoband HPM pulses whose dc offset is greatly reduced because the OCS inserted between a charged transmission line and an antenna blocks the flow of the electric energy from a high-voltage power supply to the antenna. Thus, the proposed SO allows the insulation capability of the antenna to be increased and ground-loop-integrated-wideband antennas to be employed. The transient response of the proposed SO is theoretically analyzed to understand its operation mechanism. The results prove that the proposed SO is capable of producing mesoband HPM pulses with a damped rectangular pulse waveform without a high-voltage dc offset. Also, the amplitude and quality factor are discussed. Compared with the conventional SO, the proposed SO has a larger output amplitude and smaller quality factor. Here, the difference between the quality factors is negligible. In addition to the theoretical analysis, we simulated and fabricated the proposed SO. Consequently, the results of the circuit simulation and experiment demonstrated the validity of the proposed design concept.

A Review of Switching Oscillations of Wide Bandgap Semiconductor Devices

Wide bandgap (WBG) devices offer the advantages of high frequency, high efficiency, and high power density to power converters due to their excellent performance. However, their low parasitic capacitance and fast switching speed also make them more susceptible to switching oscillations. The switching oscillations can cause voltage and current overshoots, shoot-through, electromagnetic interference, additional power loss, and even device damage, which can seriously affect the performance of power converters and systems. However, a comprehensive and in-depth overview is lacking on this topic. This article reviews the types, the causes and negative effects, the effects of parasitic parameters and suppression methods of these switching oscillations, which is helpful for practical engineering. First, the switching oscillations are divided into different types, and their causes and negative effects are reviewed. Then, the effects of different parasitic parameters on the switching oscillations are overviewed. It is found that due to the different physical structures of silicon carbide metal-oxide-semiconductor field-effect transistors, enhancement-mode gallium nitride high-electron mobility transistors (eGaN HEMTs), and cascode GaN HEMTs, the effects are also different. Finally, the main methods of suppressing the switching oscillations are summarized, and the advantages and disadvantages of these methods are presented. Furthermore, future research works on this topic and the conclusion of this paper are drawn, which will help readers deepen their understanding of the switching oscillations of WBG devices, and inspire readers to better use WBG devices for high-frequency and high-efficient power conversion.

Impact of $RC$ Snubber on Switching Oscillation Damping of SiC MOSFET With Analytical Model

As the most popular wide bandgap (WBG) power device, the silicon carbide (SiC) metal–oxide–semiconductor field-effect transistor (MOSFET) has been widely adopted in the power electronics applications and brings in the benefits, including reduced switching losses, enhanced switching frequency, and improved power density. However, the switching oscillation and the electromagnetic interference (EMI) become more serious due to the rapid switching speed of SiC MOSFET. Thus, adding $RC$ snubber branch is considered as an effective method to suppress such unwanted oscillation in the early works. In this article, the switching transient of SiC MOSFET with $RC$ snubber is investigated with an analytical model based on the finite-state machine (FSM). The accuracy of the proposed analytical model can be verified by comparisons between the calculated and measured waveforms during the switching transition. In addition, the impacts of the $RC$ snubber on switching oscillation, switching loss, and high-frequency (HF) EMI noise have been comprehensively investigated based on the model, which shows that the added $RC$ snubber can effectively avoid the switching oscillation and reduce the level of HF EMI without increasing switching loss.

Analysis and Modeling of SiC MPS Diode and Its Parasitic Oscillation

SiC merged p-i-n Schottky (MPS) diodes have great potential in the construction of multiple power electronic circuits for their excellent static and dynamic characteristics. The ultrafast switching speed is unfortunately accompanied by undesirable parasitic oscillations, which have direct impact on the stability and reliability of these circuits. The wide use of SiC diodes is still limited by their uncertain reliability and a comprehensive diode physical model, which can be used to describe the device characteristics, including parasitic oscillations during reverse recovery, is still missing for the device safe operation. In this article, an accurate dynamic physical model based on the lumped-charge technique which can accurately estimate the switching oscillations is first developed for an SiC MPS diode considering all parasitic elements. Furthermore, the original static model is improved and many important semiconductor physical phenomenon are also included. In the end, simulation and experiments are carried out by a CETC WCSD60D330F19P SiC MPS diode to verify the proposed model.

A feedback loop of conditionally stable circuits drives the cell cycle from checkpoint to checkpoint

We perform logic-based network analysis on a model of the mammalian cell cycle. This model is composed of a Restriction Switch driving cell cycle commitment and a Phase Switch driving mitotic entry and exit. By generalizing the concept of stable motif, i.e., a self-sustaining positive feedback loop that maintains an associated state, we introduce the concept of a conditionally stable motif, the stability of which is contingent on external conditions. We show that the stable motifs of the Phase Switch are contingent on the state of three nodes through which it receives input from the rest of the network. Biologically, these conditions correspond to cell cycle checkpoints. Holding these nodes locked (akin to a checkpoint-free cell) transforms the Phase Switch into an autonomous oscillator that robustly toggles through the cell cycle phases G1, G2 and mitosis. The conditionally stable motifs of the Phase Switch Oscillator are organized into an ordered sequence, such that they serially stabilize each other but also cause their own destabilization. Along the way they channel the dynamics of the module onto a narrow path in state space, lending robustness to the oscillation. Self-destabilizing conditionally stable motifs suggest a general negative feedback mechanism leading to sustained oscillations.