Search

A quasi-Z-source inverter (qZSI) belongs to the group of single-stage boost inverters. The input dc voltage is boosted by utilizing an impedance network and so called shoot-through (ST) states. In pulse-width modulations utilized for the qZSI, the dead-time is commonly omitted. However, unintended ST states inevitably occur as a result of this action, due to the non-ideality of the switching devices, causing the unintended voltage boost of the inverter and an increase in the switching losses. Hence, the implementation of the dead-time is desirable with regard to both the controllability and efficiency of the qZSI. This paper deals with the calculation of semiconductor losses of the three- phase qZSI with implemented dead time. An algorithm available in the literature was utilized for that purpose. The algorithm in question was originally proposed and applied for the qZSI with omitted dead-time, where the occurrence of unintended, undetected ST states combined with the errors in the switching energy characteristics of the insulated gate bipolar transistor (IGBT) provided by a manufacturer led to errors in the obtained results. However, these errors were unjustifiably ascribed solely to the errors in the switching energy characteristics of the IGBT. In this paper, a new, corrected multiplication factor is experimentally determined and applied to the manufacturer-provided IGBT switching energies. The newly-determined multiplication factor is expectedly lower than the one obtained in the case of omitted dead time. The loss- calculation algorithm with the new multiplication factor was experimentally evaluated for different values of the qZSI input voltage, the duty cycle, and the switching frequency.

As third-generation semiconductors become commercial, SiC semiconductors are gradually becoming more widely used in LLC resonant converters. The efficiency of the LLC resonant converter is improved by employing soft switching. However, when designing LLC resonant converters, semiconductors are usually regarded as ideal devices, and their turn-on and turn-off times are neglected. Furthermore, the method of designing the dead time relies on engineering experience and lacks precise theoretical foundations. In order to overcome the shortcomings of the current empirical method and to improve the generality and practicality of the dead time design method, a novel method for calculating the dead time of full-bridge LLC converters is proposed through theoretical research based on the operating principle of full-bridge LLC converters and the conditions for implementing soft switching. The method takes into account the switching characteristics of semiconductors and the on-state delay time of their body diodes, stray inductance, drive circuits, and errors arising from the first harmonic approximation (FHA) and improves the accuracy of the dead time calculation. It can implement good soft switching with full-bridge LLC converters, reduce switching losses, and improve system efficiency. Finally, the simulation experiment and the 2 kW experimental prototype are built to verify the effectiveness of the proposed method.

It is essential to estimate stator inductance and rotor flux linkage online for fault diagnosis and high-performance control of surface-mounted permanent magnet synchronous machine (SPMSM). Current injection method is a popular way to estimate the two parameters. However, the dead-time influence of voltage-source-inverter (VSI) and the stator inductance variation caused by injected current could not guarantee the converge of the estimation. To solve the above two problems, a method of injecting square-wave angle for online parameter estimation is proposed in this paper. Firstly, the theory of eliminating dead-time influence with and without square-wave angle injection is analysed. Next, the least square algorithm is adopted to estimate stator inductance without injection. Then the rotor flux linkage is estimated with injecting square-wave angle. The saturation effect on estimation is also analyzed and both parameters are estimated without acquiring any nominal values. At last, the appropriate amplitude and frequency of square-wave angle are determined by the parameter error and convergence analysis. The proposed method is evaluated with simulation and extensive experiments under various speed and load conditions. It is noteworthy that not less than two parameters are estimated without the dead-time influence and the injection will not cause inductance variation, which is different from the previous work.

A Gallium nitride (GaN) field effect transistor (FET) can provide superior performance over a Si-MOSFET due to its low on-state resistance and low junction capacitances. However, a GaN-based converter exhibits higher dead-time loss during reverse conduction. Thus, to improve the efficiency, dead-time optimization is required. This paper proposes simple models for dead-time optimization in a GaN-based buck converter under different load conditions. The proposed models are analytical in nature compared to the conventional models available for Si-based converters. A buck converter prototype is designed using a 100 V GaN device (GS61008P from GaN Systems) and the proposed analytical model-based dead-time optimization techniques are validated experimentally. The proposed modeling techniques can be extended for other GaN-based DC-DC converters.

Benefited from the fast switching speed, Gallium nitride (GaN) high electron mobility transistors (HEMTs) have been widely used in high switching frequency converters. However, due to the significant correlation between the turn-off time and operating conditions (more than 20 times difference of the turn-off time between the high load current and small load current for GaN HEMTs), using a fixed dead time will introduce extra dead-time losses in inverters where the output voltage and current are constantly varying. Therefore, this paper proposes a high-efficiency adaptive method to dynamically adjust the GaN-inverter dead-time with operating conditions. An improved transient model including the parasitic inductance and output voltage with bidirectional solution flow has been proposed for GaN HEMTs to increase the accuracy of dead-time adjustment. Based on this model, the dynamic dead-time adjustment can be realized without extra sensors for GaN-inverters. Using the dynamic dead-time adjustment, the experimental results show a peak efficiency of 98.25% in a 1200W inverter with triangular current mode modulation. Compared with using the fixed dead-time, the dynamic dead-time method can reduce the power loss by 26.7% under full load and 49.14% under light load.

This study presents a new dead-time measurement method using the gamma attenuation law and generalized dead-time models for nuclear gamma-ray detectors. The dead-time of the Nal(TI) detection system was obtained to validate the new dead-time determination method using very thin lead and polyethylene absorbers. Non-paralyzing dead-time was found to be 8.39 mu s, and paralyzing dead-time was found to be 8.35 mu s using lead absorber for Nal(TI) scintillator detection system. These dead-time values are consistent with the previously reported dead-time values for scintillator detection systems. The gamma build-up factor's contribution to the dead-time was neglected because a very thin material was used. (C) 2021 Korean Nuclear Society, Published by Elsevier Korea LLC.

In this paper, we present the first CMOS SPAD with performance comparable or better than that of the best custom SPADs, to date. The SPAD-based design, fully integrated in 180 nm CMOS technology, achieves a peak PDP of 55% at 480nm with a very broad spectrum spanning from NUV to NIF and a normalized DCR of 0.2cps/m2, both at 6V of excess bias. Thanks to a dedicated CMOS pixel circuit front-end, an afterpulsing probability of about 0.1% at a dead time of3ns were achieved. We designed three SPADs with a diameter of 25, 50, and 100m to study the impact of size on the timing jitter and to create a scaling law for SPADs. For these SPADs, a SPTR of 12.1ps, 16ps, and 27ps was achieved at 6V of excess bias, respectively. The SPADs operate in a wide range of temperatures, from -65C to 40C, reaching a normalized DCR of 1.6 mcps/m2 at 6V of excess bias. The proposed SPADs are ideal for a wide range of applications, including LiDAR, super-resolution microscopy, QRNGs, QKD, fluorescence lifetime imaging, time-resolved Raman spectroscopy, to name a few.

This paper proposes a driver integrated circuit (IC) for a GaN-based synchronous buck converter to minimized the dead-time loss of GaN devices and improve converter efficiency. The proposed adaptive control achieves minimized dead-time for any loading condition. A driver IC is fabricated in a 0.18 lm BCD process to verify the concept. The measurement result achieves only 0.7 ns and 0.8 ns dead-time at the minimum and maximum load condition, respectively. The efficiency improves 2.1% at 2 A full load compared to the fixed dead-time control counterpart.

In this article, the effect of the dead-time on a single-phase wireless power transfer (WPT) system is studied in detail. In practice, the dead-time is always placed between the complementary switching pulses of the inverter phase-leg. At higher operating frequencies, the dead-time issues in the resonant inverter become critical, especially as the power level increases. The detailed analysis of the dead-time on a WPT system is discussed for different operating conditions of the inverter duty-cycle and power factor. The switching characteristics of the WPT system inverter are analyzed, and the notch phenomenon that appears at the output of the inverter is also discussed. A notch equation based on the observations is derived to predict the notch occurrence during the system operation. Furthermore, the mathematical expressions are presented for different notch conditions. Subsequently, the effect of the notches on the sensitivity and the power transfer of the series–series compensated WPT system is analyzed. Finally, the approach is verified experimentally on an 8-kW WPT system prototype, and the results are compared with the theoretical analysis.

Two algorithms have been extensively studied for motor control: Field Oriented Control (FOC) and Direct Torque Control (DTC). Both control algorithms use a Voltage Source Inverter (VSI) to drive a Permanent Magnet Synchronous Motor (PMSM). To prevent short-arm short-circuit accidents when driving PMSM using VSI, a dead time is used to turn off the TOP and BOTTOM switches of each arm at the same time. However, this dead-time technique causes an unexpected pole voltage to be applied to the PMSM on the VSI output voltage, causing distortion and resulting in control nonlinearity. The disturbance voltage that causes nonlinearity is difficult to measure directly with the sensor. Therefore, this paper analyzes the nonlinearity of the controller due to the distorted voltage caused by the dead time during PMSM operation using the DTC algorithm and predicts the distorted output voltage using the extended Kalman Filter (EKF) to improve control stability. As a result, The algorithm proposed in this paper has verified the improvement of torque ripple and stator flux ripple through experiments and simulations.

The DC-link capacitor in power electronic systems is one of the most vulnerable components in terms of reliability. Since a reliable design of the DC-link capacitor depends on an accurate estimation of its current ripple, this paper proposes analytical equations to model the influence of dead-time on the input current ripple of a three-phase voltage source inverter. The effect of dead-time is modeled as a delay in the rising edges of the input current waveform. The proposed analytical equations are derived and then verified by simulations and experiments. The proposed equations generally provide better accuracy in predicting the input current ripple value compared to the benchmark equations. From the simulation and experimental results, the proposed equations are optimized for dead-time values more than 0.7 μs and modulation indices less than or equal to 0.7. Limitations of the proposed equations are also discussed. For small phase displacements and high modulation indices (0.8 to 1), the accuracy decreases because of the influence of AC output current ripple. For small modulation indices (less than 0.2) and a high value of dead-time (2 μs), the accuracy also decreases due to distortion in the phase current waveforms.

To avoid leg short-circuit in inverters, dead time must be introduced on leg gate signals. Dead time affects the inverter output voltage fundamental harmonic amplitude, voltage harmonic distortion and inverter efficiency by introducing additional voltage drops. In this regard, dead time effects have been widely investigated for traditional two-level three-phase voltage source inverters in the literature but not extensively for multilevel topology structures. This paper provides a detailed analysis of dead time impact on the harmonic distortion and efficiency of Cascaded H-Bridges Multilevel Inverters (CHBMIs). For this purpose, a general mathematical formulation to determine voltage drop due to dead time effects, also taking into account the adopted Multicarrier PWM strategy, has been provided and experimentally validated for a five-level three-phase CHBMI structure. As a comparison tool between expected and ideal inverter output voltage, the percentage voltage error e% is introduced. In most of the cases, e% is lower than 5%, and it starts increasing for very low amplitude modulation index or for specific working points where nonlinearities occur. Furthermore, several experimental investigations have been carried out to evaluate the CHBMI performance in terms of harmonic distortion and efficiency by changing, the values of dead time, modulation index and switching frequency for ten different multi-carried PWM strategies. Experimental results confirm the strong dependency between the dead time impact on the converter performance and the adopted Multi Carrier-PWM (MC-PWM) strategy: as a way of example, converter efficiency can be reduced from 80% to 60% when dead time is increased from 0.5 μs to 1.5 μs and Phase Shifted-PWM (PS-PWM) is adopted.

The four-level nested neutral point clamped (4L-NNPC) converter is a new multilevel converter with a simple structure and no power device in series, which is suitable for medium-voltage high-power applications. However, it experiences severe dead-time unexpected output levels problem in the output voltage when the low-output-frequency modulation method is applied. This article proposes a switching sequence optimization method (SSOM) on the basis of carrier-based 3 level (CB3L) PWM that can eliminate the dead-time unexpected levels and ensure the voltage balance of the flying capacitors at the low output frequency. The reasons for the unexpected levels generated by the state transition are first analyzed, and the relationship between the dead time and unexpected levels is investigated. Then, the basic principle and implementation of the proposed SSOM are elaborated in detail. Simulation and experimental results are presented to verify the effectiveness of the proposed method.

In this note we study discrete-time dead-time compensation from the viewpoint of the observer-based design procedure. We show that the discrete equivalent of the observer-predictor architecture can be derived ab initio via classical state-feedback and observer arguments under mild assumptions. The resulting observer is reduced order and we show that this choice is justifiable even if corresponding state measurement channels are noisy.

This paper emphasizes on the correction of a misconception among the students about the presence of negative dead time values determined by using a two-source method. To specify the importance of t...

PURPOSE To overcome limitations in the duration of RF excitation in zero-TE (ZTE) MRI by exploiting intrinsic encoding properties of RF pulses to retrieve data missed during the dead time caused by the pulse. METHODS An enhanced ZTE signal model was developed using multiple RF pulses, which enables accessing information hidden in the pulse-induced dead time via encoding intrinsically applied by the RF pulses. Such ZTE with pulse encoding was implemented by acquisition of two ZTE data sets using excitation with similar frequency-swept pulses differing only by a small off-resonance in their center frequency. In this way, the minimum scan time is doubled but each acquisition contributes equally to the SNR, as with ordinary averaging. The method was demonstrated on long-T2 and short-T2 phantoms as well as in in vivo experiments. RESULTS ZTE with pulse encoding provided good image quality at unprecedented dead-time gaps, demonstrated here up to 6 Nyquist dwells. In head imaging, the ability to use longer excitation pulses led to approximately 2-fold improvements in SNR efficiency as compared with conventional ZTE and allowed the creation of T1 contrast. CONCLUSION Exploiting intrinsic encoding properties of RF pulses in a new signal model enables algebraic reconstruction of ZTE data sets with large dead-time gaps. This permits larger flip angles, which can be used to achieve enhanced T1 contrast and significant improvements in SNR efficiency in case the Ernst angle can be better approached, thus broadening the range of application of ZTE MRI.

In field-oriented vector control of permanent magnet synchronous machine (PMSM) drives, the dead time will cause the 5th and 7th current harmonics in the stationary reference frame. They are mapped to the negative and positive 6th harmonic current in the synchronous reference frame (SynRF), resulting in torque ripple and deterioration of control performance. To solve this problem, a new dead-time compensation method is proposed in this article. First, a multiple complex coefficient filter is modified with a low-pass filter being paralleled to extract positive and negative sequence components of 6th harmonic from dq -axes currents. Then, based on the extracted harmonics, a voltage feedback path with variable gains is designed in SynRF to eliminate the dead-time effect. Finally, the proposed method is implemented in a prototyped PMSM drive to verify its effectiveness. Both the simulations and experiments indicate that the proposed method can significantly weaken the dead-time effect with no additional hardware. Besides, it is also proved robust to the variable machine parameters.

The distortion of an H-bridge inverter can originate from many nonlinear factors, of which the most dominant one is typically the dead-time. In previous research, analytical models have been proposed to calculate the output spectrum of the H-bridge inverter. However, the existing models have not fully explored the effects of soft-switching and discontinuous conduction mode, which might severely degrade their accuracy. In this article, the characteristics and the corresponding effects of these switching modes are analyzed. Constraint functions are proposed in order to determine the time position of each switching mode. Based on this analysis, a numerical model of the output spectrum of the H-bridge inverter is then introduced. The model is shown to have a significantly improved accuracy compared to the previous analytical models especially for large inductor current ripples. The accuracy improvement is confirmed by simulation and measurements on an experimental prototype.

In low output voltage and high output current LLC resonant converter applications, a synchronous rectification (SR) is essential component for high efficiency and high power density. However, stray inductances in MOSFET package and printed circuit board (PCB) pattern make premature turn- off of SR gate and large SR dead time. To compensate the stray inductance effect and increase system efficiency, a hysteresis band dead time regulation control method is proposed. In the proposed control method, SR dead time is regulated to predetermined dead time target regardless of the stray inductances by using a mixed signal, which includes instantaneous drain voltage information and previous cycle dead time information. As a result, the proposed control method can provide lower conduction losses by the dead time regulation and better transient characteristic by the instantaneous drain voltage information. To verify the validity of the proposed control method, 234-W prototype is built and experimented with the proposed controller, which is implemented with 0.25- μ m BCDMOS technology.

In a dual-bridge series resonant converter (DBSRC) working at a high switching frequency, the dead-time effect is a serious issue. When the minimum current trajectory (MCT) method is applied, the inductor current cannot be minimized due to the dead-time effect, and the range of the soft switching is reduced. Considering the dead-time, this paper first presents a theoretical analysis of the transmission power and the soft-switching characteristics based on the fundamental harmonic approximation (FHA) approach. Then, a minimum current trajectory method considering the dead-time (MCT-d) is proposed to achieve the minimum inductor current by compensating for the dead-time. This method can extend the soft-switching range as well. Finally, the experimental results validate the theoretical analysis and the improvement of the converter’s efficiency.

Aiming at the issue of the sliding mode observer (SMO) being sensitive to the motor model parameters at low speeds, a rotor position observation method based on resistance adaptive SMO and considering the influence of inverter dead time is designed in this paper. In this method, the online resistance identification is introduced into the conventional SMO, the resistance parameters of the SMO are modified in real-time, and the online resistance identification algorithm is designed by using the Lyapunov function. An enhanced linear dead time compensation method is proposed to improve the resistance adaptive SMO and eliminate the voltage error between the estimated and the actual motor models in order to address the impact of inverter dead time on the voltage parameters in the estimation model at low speeds. Simulation results show that the online resistance identification and dead time compensation can significantly improve the accuracy of sensorless speed control at low speeds, and the dead time compensation can also improve the accuracy of online resistance identification.

In this work, we report the portable NMR system which provides solutions to the existing problems in miniature CMOS NMR systems. First, a higher IF of 50 kHz is achieved by exploiting separate frequencies for sample excitation and LO, thereby having higher immunity to 1/f noise. The proposed phase detector circuit aligns the experiment trigger with the constant phase difference between two frequencies. It maintains the constant RX output phase in every experiment, allowing the direct signal averaging without extra phase correction. In addition, 40X faster RX recovery with RX BW switching enables the signal acquisition with the dead time of 10 $\mu \text{s}$ . Fast settling improves the acquisition sensitivity. Lastly, a frequency calibration method based on signal peak detection is proposed. Combining the techniques with the fully integrated NMR transceivers, the system demonstrates the NMR experiments to measure the decaying time constant of less than 100 $\mu \text{s}$ . Furthermore, NMR diffusion experiments are performed with the echo spacing of $0.2\sim 8$ ms.

This paper aims to present an analysis of the performance and robustness characteristics of repeated-pole plus dead-time (RPPDT) model PID (Proportional Integral Derivative) regulatory control syst...

The simplicity of the proportional-integral controller makes it very popular in many practical engineering applications. In the literature, several approaches have been introduced for tuning proportional-integral controllers by calculating the centroid of the stability region. However, all those approaches depend on graphical plottings which are time-consuming. Also, the design procedure has to be redone as the transfer function changes. Here, two new analytical methods are proposed to obtain the centroid of the stability region for the proportional-integral controllers to control a time delay process which can be modeled by a stable or unstable first-order plus dead-time model. The methods introduced eliminate the compulsory procedure of plotting the stability region. The efficiency of the suggested methods has been studied by conducting a robustness analysis and studying several simulation examples.

Dead-time processes are common in industry and represent a challenge for feedback control. The use of predictor structures with the controllers can attenuate this. A predictor is proposed here based on the Kalman filter, the Kalman Predictor (KP), that has only one tuning parameter for SISO systems and can be used with non-minimum phase, open-loop unstable and integrative systems of any order, and is also capable of estimating many types of disturbances. It is shown that the KP implicitly defines a Filtered Smith Predictor (FSP), hence, all tools used to analyze the closed-loop properties of the FSP can be used, including robustness and disturbance rejection. Tuning guidelines are provided and simulation examples with comparisons with other predictor structures are used to illustrate the advantages of the proposed KF.

The photon counts (PC) signal of the lidar backscattered signal is affected by the dead time of the transient digitizer. The dead time relies on the photomultiplier (PMT) characteristics and high voltage settings which results in variation of the dead time over time. In this paper, the dead time of the Raman lidar system installed at remote atmospheric monitoring station of CSIR-National Physical Laboratory in Palampur, Himachal Pradesh, India, is estimated and reported. Two different methods proposed by Whiteman et al. and Newsom et al. are used to derive the dead time of the lidar system from June 2016 to June 2019 and the results of both the methods are statistically compared. The results show that the dead time values were found to be increasing from 4 ns to 5.8 ns over the study period. For comparison, one sample t-test and Bland–Altman analysis were used along with the correlation and regression analysis and the results suggest that both the methods were found to be in agreement and there was no statistically significant difference between both the methods. The dead time corrected data was used to obtain glued signal and from that aerosol optical properties have been derived. The optical properties derived from glued signal, dead time corrected and uncorrected signal have been compared and we observed significant difference at the lower altitudes.

No dead-time is contained in the existing dead-time elimination pulsewidth modulation (PWM) for three-phase three-level T-type converters, where complementary drive pulses are allocated alternatively according to polarities of output currents. Consequently, the dead-time effect can be inherently avoided. However, the dependency on current polarities seriously limits its widespread application. Wrong current polarities, e.g., in a dynamic process, will lead to the output-voltage disappearance, thus aggravating the possible “algebraic loop” issue and impairing the stability of the system. In this article, in order to reduce the dependency on current polarities while retaining the characteristic of dead-time-effect elimination, a double-modulation-wave PWM is proposed by modifying the dead-time elimination PWM. Two modulation waves with a magnitude difference are adopted for generating underlap periods between complementary drive pulses, which can avoid the shoot-through failure and no dead-time effect will be generated. And to further simplify the implementation process, the two modulation waves are decomposed by introducing a magnitude-adjustment factor related to the current polarity. Whereas it is also due to the employment of two modulation waves, extra issues of overmodulation, single drive pulses, and a shorter underlap period may occur, which are analyzed in detail and the negative effect can be avoided. Finally, the proposed PWM is experimentally verified, showing the effectiveness on harmonic suppression and the reduced dependency on current polarities.

This article presents an accurate model of a digitally controlled voltage-source inverter with the dead-time effect. The impact of two nonlinear behaviors of digital sinusoidal pulsewidth modulation and dead time on the output waveform is analyzed in the time domain. The problematic waveform with sinusoidal pulsewidth modulation is displayed, which highlights the necessity of establishing a new model. In the frequency domain, considering the dead-time effect on the current double Fourier transform is used to give a harmonic expression without a current sign function. Furthermore, this avoids the error caused by the measurement of the current polarity, so the exact amplitude of each harmonic of the output voltage can be accurately calculated, which is important for eliminating specific harmonics and improving power quality. Moreover, the problem caused by the current zero crossing is solved. The result of the analysis is verified by simulation and experiment on DSP and SIC platform. And the result shows that the harmonics and their amplitudes are in good agreement with our formula.

In order to improve the speed regulation performance of induction motors, a multimodulation times space vector pulsewidth modulation (MMT-SVPWM) is proposed for the three-level neutral point clamped (NPC) converter. This method can eliminate the dead-time effect (DTE), which is caused by the addition of the dead time (DT) in the SVPWM. This article first analyzes the deviation of the output voltage that is caused by the DTE in the SVPWM, and then proposed the MMT-SVPWM. The generation of driving signals in this method is different from the ideal SVPWM. According to the directions of three-phase currents, the driving signals of a pair of complementary power switches are obtained by comparing a pair of multiple modulation times with the triangular carrier. Thus, this method directly eliminate the DTE, which is different from the SVPWM with DT. The output voltage vector is the same as that of the ideal SVPWM, and there is no zero-current clamping effect. Finally, the simulation and experimental results show that the proposed method effectively eliminates the DTE and improves the output currents of the three-level NPC converter.

For the dual three‐phase permanent magnet synchronous motor(dual‐PMSM), the deadtime can introduce fifth and seventh current harmonics, and they are only constrained by the small stator leakage impedance, which means even if there are only small fifth and seventh voltage harmonics, the resulting fifth and seventh current harmonics will be very large. The harmonic current will make an increment of the system loss, thus lead to an reduce of the efficiency of the speed control system. This paper proposes a harmonic current suppression strategy for dual‐PMSM based on least mean square (LMS) adaptive notch filter. This strategy suppresses the fifth and seventh harmonic currents by introducing four LMS adaptive notch filters in the subspace. The proposed algorithm has good dynamic performance and is insensitive to motor parameters that are offset within a certain range. The effectiveness of proposed method is verified by a set of comparative simulations and experiments.

This paper provides analytical equations to model the influence of dead-time and diode's reverse recovery on the input current ripple of a three-phase voltage source inverter. Analytical equations are derived and then verified by simulation and experiments. The influence of dead-time is also modeled heuristically as a linear relationship between the dead-time and the input current ripple values. A comparative analysis shows that the analytical equations proposed here are more accurate in predicting the input current ripple value than the heuristic method.

This paper presents an adaptive dead-time control circuit for a maximum work frequency 20 MHz, maximum voltage level 90 V GaN gate driver. The dead-time is set to prevent straight-through of the upper and lower power transistors of the bridge arm structure and ensure the reliability of the motor driver. For GaN drivers on the market today, fixed or configurable dead-time is widely used in more-than-10 MHz application scenarios. However, the switching loss caused by insufficient dead-time and reverse turn-on loss caused by excessive dead-time of GaN devices have a hazardous influence on the efficiency of drivers, which fixed or configurable dead-time cannot avoid. The gate driver with the proposed adaptive dead-time control circuit has been implemented in a 0.18 um BCD process. The proposed adaptive control circuit dissipates 56.3 uA quiescent current in a simulation situation and is able to provide maximum 5 ns dead-time error for a GaN gate driver.

This paper aims to present two approaches for repeated-pole plus dead-time (RPPDT) models identification procedures for highorder processes based. First approach is based on using two or three poin...

Average switch simulation has the advantage of being much faster to simulate than the switching simulation but it lacks any harmonics or distortion on the converter current waveform. In a hardware converter, the current distortion is caused by the dead-time between high side and low side switching devices provided to avoid switch shoot-through. To improve the fidelity of average switch simulation, this paper provides a simple method to induce the distortion resulting from the dead-time. The result of average switch simulation can thus closely resemble the result of switching simulation in a fraction of the simulation time. To validate the accuracy of this average switch simulation, the result of this simulation is compared with the detail switching simulation and the waveform from actual hardware measurement.

Based on the ring-down signal generation principle of nuclear magnetic resonance (NMR), we presented here a design scheme of transmitting and receiving separated short dead-time radio frequency (RF) coil composed of loop-gap resonator (LGR) coil and solenoid coil in low-field NMR system, to improve transmission efficiency by optimizing tuning and matching network. We also designed a fast RF switch and driver to fulfill the requirement of the RF coil. Based on the simulation results, the short dead-time RF coil was fabricated and applied to a self-developed 9.51 MHz portable low-field NMR spectrometer. The NMR experiments showed that the dead-time was reduced to less than 10 μs, which verified the feasibility of the design scheme.

In order to improve the current steady-state control performance of the model predictive control (MPC), a dead-time voltage-vector based MPC method is proposed in this article. First, the effect of the dead-time on MPC is introduced, and the formation process of the dead-time voltage vector existed in MPC is analyzed. Furthermore, the beneficial dead-time voltage vector and nonbeneficial dead-time voltage vector for the current steady-state control performance of MPC is distinguished, and the advantage of the beneficial dead-time voltage vector is analyzed. Then, the MPC method based on dead-time voltage vector is presented, which optimizes the action time of dead-time. Finally, the experimental results prove that the current steady-state control performance of the proposed MPC method is better than the conventional MPC method without increasing the switching frequency.

Accurate current polarity detection is a major issue for successful compensation of dead-time distortion in pulse-width-modulated (PWM) voltage source inverter. The present study is concerned with the concept of shift in current-zero-crossing due to dead-time distortion compensation that results in error in current polarity detection and thus causes a problem with regard to the successful continuation of compensation. The phenomenon is analysed in detail, along with its dependence on different factors. The proposed concept is validated in digital simulation and also through experimental verification. The study also recommends the possible correction to be incorporated in view of such zero-crossing shift for achieving proper compensation, especially in case of current-sensor-less compensation techniques.

This paper proposed a dead-time compensation method with fractional-order proportional integral (FOPI) error voltage control. The disturbance voltages caused by the power devices’ dead time and non-ideal switching characteristics are compensated for with the FOPI controller and fed to the reference voltage. In this paper, the actual error voltage is calculated based on the model and actual voltage of the permanent magnet synchronous motor. Considering the parameter error of the permanent magnet synchronous motor and the voltage error caused by the dead-time effect, a FOPI controller is used to calculate the compensation voltage. An improved particle swarm optimization (PSO) algorithm is utilized to design the parameters of the FOPI controller in order to eliminate the dead-time effect, and the optimal fitness function is designed. Compared with other optimization algorithms, the improved PSO algorithm can achieve faster convergence speed in the error voltage controller parameter design. The proposed dead-time compensation method can improve the performance of the current response and eliminate the dead-time effect. This method also eliminates all harmonic disturbances and has a good suppression effect on high-frequency harmonics. The simulation and experimental results show that the dead-time compensation method using optimal FOPI error voltage control makes the current ripple smaller and the response speed faster than that of the traditional optimal integer-order PI control, thus demonstrating the effectiveness and advantages of the proposed method.

This research analyzes the asymmetric control strategies in multilevel inverters, including asymmetric techniques in space vector modulation of power converters. Modulation parameters such as reference voltage vector (Vref), switching time, and duty cycle are derived in the three-dimensional spatial vector geometry formulation. Asymmetric space vector pulse width modulation (SVPWM) is unique in specifying modulation parameters, has unequal tetrahedron patterns, accompanied by application examples for the upper and lower sector pairs of a tetrahedron. The combination of the switch in the form of an inclined cylinder produces twelve pairs of asymmetric tetrahedrons where the voltage vector positions are in the other twenty-four tetrahedrons. The calculation shows processing dead-time in switching, which is used for current compensation in three-phase power converters.

This article proposes a three-stage dead-time adjustment scheme for the leading-leg and lagging-leg switches of phase-shift full-bridge converter (PSFBC) according to the load conditions to enhance the conversion efficiencies at light loads. This article also investigates an iterative rigorous loss calculation for light loads under dead-time adjustment. The proposed iterative calculation can be used to modify the duty ratio of the transition region and estimate the operating currents more accurately; therefore, the losses of a PSFBC at light loads and under the dead-time adjustments can be effectively estimated. A PSFBC prototype with an input voltage of 380 V, an output voltage of 48 V, and a rated output power of 480 W is designed and implemented in this article. Experimental results show that comparing with the PSFBC without the dead-time adjustment and with the conventional dead-time adjustment, the conversion efficiency enhancements of 12.13% and 5.97% can be achieved by the proposed three-stage dead-time adjustment scheme at about 5% load condition, respectively. For a small-scale data center with 100 designed PSFBCs, simulated results indicate that about 3.21 MWh of electricity and 1.03 tons of carbon dioxide emission can be saved and reduced per year, respectively, by the proposed dead-time adjustment scheme.

Industrial processes of unstable/integrating nature having a dead time and inverse response characteristics are challenging to control. For controlling such processes, double-loop control structures have proven to be more efficient than conventional PID controllers in a unity feedback configuration. Therefore, a new design method to obtain PI-PD controller settings is proposed for a set of unstable/integrating plant models with dead time and inverse response. The stabilizing proportional–derivative (PD) controller is designed using maximum sensitivity considerations and Routh–Hurwitz stability criteria. The PI controller settings are obtained by comparing the first and second derivatives of expected and actual closed-loop transfer functions about the origin of the s-plane. Adjustable parameters of the inner and outer loops are selected such that the desired value of maximum sensitivity is achieved. Simulation studies are conducted on some benchmark linear and nonlinear plant models used in literature. Robustness of the proposed design is analyzed with perturbed plant models, and quantitative performance measures are computed. It is found that the proposed design yields enhanced and robust closed-loop response than some contemporary works.

A current-mode four-phase synchronous buck converter with a dynamic dead-time control (DDTC) method is presented in this work. A brief analysis of the multiphase buck converter power efficiency in both continuous conduction mode (CCM) and discontinuous conduction mode (DCM) is performed to provide design guidelines for minimizing power losses. In synchronous converters, the power efficiency can always be improved by optimizing the dead-time. Therefore, a gate driver with DDTC is designed to optimize the dead-time in every switching cycle, thereby improving power efficiency particularly under heavy load conditions. The proposed buck converter has the ability to deliver a maximum load current of 6.0 A at a typical output voltage of 1.2 V from a power supply of 3.0 V. A power efficiency improvement of over 1.0% is achieved when the load current is over 2.0 A, and an improvement of about 2.4% is obtained at a load current of 4.0 A. A peak power efficiency of 92.8% is measured at an output voltage of 1.8 V.

A dynamic model of surface-mounted permanent magnet synchronous motors (SPMSMs) is constructed to include the dead-time disturbance voltage of the voltage-source inverter and SPMSM parameter uncertainty. The constructed model reveals that both the disturbance voltage and the parameter uncertainty degrade the SPMSM stator current control performance. Based on this notion, a nonlinear damping compensator is designed to simultaneously compensate for the dead-time disturbance voltage and parameter uncertainty in a unified structure. The designed compensator is advantageous because it is implemented with only the static feedback of available system variables with a low computational load, which enables the compensation signal to be calculated within one sampling period without requiring a specific calculation cycle. A rigorous analysis using a Lyapunov function shows that the designed compensator achieves the global exponential ultimate boundedness of the stator current errors with arbitrarily small bounds and fast decay rates in the presence of both the dead-time disturbance voltage and parameter uncertainty. The designed compensator performance is demonstrated by performing experiments using a 750-W laboratory SPMSM drive and comparing the experimental results with those of a conventional proportional-integral controller with a feedforward compensator.