Hysteresis Comparator Research Articles

Monolithic Comparator and Sawtooth Generator of AlGaN/GaN MIS-HEMTs With Threshold Voltage Modulation for High-Temperature Applications

This article demonstrates the integrated comparators, hysteresis comparators, and sawtooth generators based on aluminum-gallium-nitride/gallium-nitride (AlGaN/GaN) metal-insulator-semiconductor high-electron-mobility transistors (MIS-HEMTs). The integrated circuits (ICs) exhibit thermal stability from 25 °C to 250 °C in both static and transient performances. The threshold voltage ( V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> ) in depletion (D)-mode MIS-HEMT is modulated from -8.9 to -2.4 V to optimize the performance of integrated comparator circuits. The comparator can realize a large and stable comparison range of 3-9 V and a high voltage swing of 9.1 V, while the hysteresis comparator exhibits a good noise-immunity ability and stable hysteresis output. The sawtooth generator with the hysteresis comparator features a high amplitude (6.1 V) sawtooth signal at 500 kHz to realize a compact structure applicable to the high-voltage mixed-signal circuits. These results show the feasibility of MIS-HEMT monolithic comparator circuits in conversion systems.

Feedforward Neural Network-DTC of Multi-phase Permanent Magnet Synchronous Motor Using Five-Phase Neural Space Vector Pulse Width Modulation Strategy

In this work, the direct torque control (DTC) is applied to the five-phase permanent magnet synchronous motor (FP-PMSM). The DTC method based on classical space vector pulse width modulation (SVPWM) is a common solution used to overcome traditional problems; such as stator flux ripple, electromagnetic torque ripple and gives more total harmonic distortion (THD) of the stator current. The actual paper is based on improving the performance of DTC-SVPWM by using the feedforward neural networks (FNNs) instead of the proportional-integral (PI) regulators and hysteresis comparators (HCs) of the conventional SVPWM strategy. This algorithm can solve the traditional PI regulators and HCs problems which are represented in responses dynamic and reduce the torque ripple, flux ripple, and the THD of stator current of FP-PMSM drives. The proposed strategy was tested in different tests with simulation using Matlab software.

A BJT-Based CMOS Temperature Sensor With Duty-Cycle-Modulated Output and ±0.5°C (3σ) Inaccuracy From −40 °C to 125 °C

This brief presents a 0.65% relative inaccuracy CMOS temperature sensor with a duty-cycle-modulated (DCM) output. It uses a BJT-based front-end to generate a proportional to absolute temperature voltage ( V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">PTAT</sub> ) and a complementary to absolute temperature voltage ( V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CTAT</sub> ), which are then modulated to a digital-friendly duty-cycle output. Dynamic element matching with Kelvin connection (KC-DEM) is applied to improve the accuracy of V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">PTAT</sub> . To enhance the robustness of the sensor, a continuous-time dynamic single-threshold hysteresis comparator with high energy efficiency is proposed. Implemented in a standard 0.13- μm CMOS process, the sensor has an active area of 0.086 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and achieves an inaccuracy of ±0.54 °C ( 3σ) from -40 °C to 125 °C.

Comparison of Conventional and Modified Direct Torque Control of Three-Phase Induction Motor Using Three-Level Flying Capacitor Inverter

The work presented in this paper aims to compare the effectiveness of different control strategies to improve the performance of the three-phase Induction Motor (IM). The Conventional Direct Torque Control (CDTC) was employed as the first strategy for driving the IM. This control strategy causes high ripples in the IM's torque and speed due to the hysteresis comparators and a variable switching frequency due to the look-up table. A modified DTC strategy based on Space Vector Modulation (DTC-SVM) was chosen as a second strategy to enhance the performance of the IM using the two-level inverter. This method, which leads to the reduction of the torque and speed ripples and achieves constant switching frequency. As the multi-level inverter becomes most popular than the two-level inverter, the third strategy is devoted to adopting the three-level flying capacitor inverter (TLFCMLI) -based DTC-SVM. The third strategy uses the method of mapping the multi-level space vector based on basic two-level SVM. Matlab/Simulink software package is utilized to implement the suggested controllers. Simulation results show that the DTC-SVM based on TLFCMLI significantly enhances the IM's performance compared with the other two strategies from the voltage and current profiles, torque, and speed points of view.

Artificial Neural Networks Applied to a Wind Energy System

In this context, we are taking a close interest in the optimization of wind energy production. It consists in designing simple to implement control strategies of a wind energy conversion system, connected to the network based on the Double Fed Induction Generator (DFIG) driven by the Converter Machine Side (CSM) in order to improve the performance of Direct Torque Control (DTC) and Direct Power Control (DPC). For this purpose, the artificial neural networks (ANNs) is used. Hysteresis comparators and voltage vector switching tables have been replaced by a comparator based on artificial neural networks. The same structure is adopted to build the two neural controllers, for the DTC – ANN and for the DPC – ANN. The simulation results show that the combination of classical and artificial neural network methods permit a double advantage: remarkable performances compared to the DTC-C and DPC-C and a significant reduction of the fluctuations of the output quantities of the DFIG and especially the improvement of the harmonics rate currents generated by the machine.

Coordinated frequency regulation among asynchronous AC grids with an MTDC system

With the increasing penetration level of renewable power, the power systems’ inertias are decreasing. To ensure that the frequency is above the threshold of the under frequency load shedding, one effective way is to share the spinning reserves among asynchronous AC grids through HVDC systems. In this paper, a coordinated frequency regulation scheme that enables spinning reserves sharing is proposed for such hybrid AC/DC grids. This scheme is a communication-free method that consists of the droop control, the inertia emulation control and the frequency safety control. The combined response of the three controls can increase not only the frequency nadir but also the settled frequency of the disturbed grid. In addition, the hysteresis comparators and the power injection limits are adopted in the frequency regulation scheme to reduce the coupling effect among AC grids. Thus, under small and harmless disturbance, the frequency regulation scheme will be inactive; the disturbance in strong AC grids would not affect the weak AC systems. The frequency regulation scheme coordinates well with the automatic generation control of the grids. The feasibility and effectiveness of the proposed frequency regulation scheme are verified through simulation studies.

Modified LUT-based DTC of NPC 3-Level Inverter fed Sensorless IPMSM Drive with DC Link Voltage Balance

In the proposed work, a modified look-up table-based direct torque control (DTC) scheme is reported for a neutral point-clamped three-level inverter-fed interior permanent magnet synchronous motor drive. In the classical DTC scheme, there are significant torque and flux ripples in the drive due to low number of available switching states. To reduce the oscillations in torque and flux, a three-level inverter-operated IPMSM drive is discussed. In a three-level inverter, the increased count of active voltage vectors is results in more sinusoidal output waveforms. Moreover, stator flux plane has 12 sectors in the proposed work unlike classical DTC. Besides, the higher level of flux and torque hysteresis comparators is implemented. DC link capacitor voltage balancing scheme is also instigated to minimize voltage stress on semiconductor devices, improve stator current THD and increased capacitor life. Based on the sector information, flux and torque hysteresis output and capacitor voltage balance logic, an improved LUT is established and explained for a three-level DTC scheme. Consequently, improved stator current (THD) and decrement in torque and flux ripples are observed. To make the system robust, model reference adaptive control (MRAC) based sensorless speed estimation algorithm is realized. The proposed DTC scheme is compared with a two-level inverter-fed and a three-level-inverter-fed DTC scheme without DC link voltage balance strategy. To carry out the analysis, MATLAB/Simulink environment is utilized. Moreover, to validate the simulation results, experimental analysis of the proposed technique is carried out using dSPACE1104.

Buck converter IC for brushless DC motor drive using voltage‐mode PWM controller

This study proposes a buck converter IC with voltage-mode pulse-width modulation (PWM) controller to provide a stable bias voltage for the brushless DC motor drive. The proposed buck converter IC comprises an error amplifier, a hysteresis comparator, a linear ramp generator, a driving circuit, a non-overlapping circuit, a bootstrap circuit and a level shifter. By integrating these proposed circuits into a single chip, the performance of buck converter chip could be improved significantly. The PWM controlled signal was used to generate a suitable output voltage by modifying the duty cycle. The advantage of this method is that the control method of the feedback circuit can be implemented easily, has a short ON time, and has effective noise immunity. After verifying the designed functions, the proposed IC was fabricated using TSMC 0.25 μm 1P3M complementary metal oxide semi-mixed signal process. Measurement results illustrate that the output voltage, output current, line regulation, load regulation, output ripple voltage and peak power efficiency were 5 V, 200 mA, 13.33 mV/V, 18.5 mV/A, 30 mV, and 68%, respectively, at an input voltage of 15 V and a switching frequency of 100 kHz. The chip area was ∼1.480 × 0.999 mm 2 .

Twelve Sectors DPC Control Based on Neural Hysteresis Comparators of the DFIG Integrated to Wind Power

Twelve Sectors DPC Control Based on Neural Hysteresis Comparators of the DFIG Integrated to Wind Power

Sliding mode approach applied to sensorless direct torque control of cage asynchronous motor via multi-level inverter

To improve the robustness and performance of the dynamic response of a cage asynchronous motor, a direct torque control (DTC) based on sliding mode control (SMC) is adopted to replace traditional proportional-integral (PI) and hysteresis comparators. The combination of the proposed strategy with sinusoidal pulse width modulation (SPWM) applied to a three-level neutral point clamped (NPC) inverter brings many advantages such as a reduction in harmonics, and precise and rapid tracking of the references. Simulations are performed for a three-level inverter with SM-DTC, a two-level inverter with SM-DTC and the three-level inverter with PI-DTC-SPWM. The results show that the SM-DTC method achieves better performance in terms of reference tracking, while adoption of the three-level inverter topology can effectively reduce the ripples. Applying the SM-DTC to the three-level inverter presents the best solution for achieving efficient and robust control. In addition, the use of a sliding mode speed estimator eliminates the mechanical sensor and this increases the reliability of the system.

Low-voltage cold-start circuit for energy harvesting suitable for indoor sunlight

This paper proposes a low-voltage cold-start circuit suitable for indoor sunlight energy harvesting in TSMC 40nm CMOS process. The circuit can work normally when the input voltage is as low as 200mV and is compatible with a wide input power range. Pulse-skipping modulation (PSM) is used to control the circuit’s operation and sleep. The main structure includes a ring oscillator, a two-phase clock drive circuit, a linear charge pump, a low-power voltage reference, and a hysteresis comparator. Compared with other cold-start circuits, the structure proposed in this paper can realize the function of voltage rise without the aid of external machinery or voltage. Simulation results show that when the input voltage is in the range of 200mV to 700mV, the cold-start circuit can stably output 800mV to power the subsequent circuit.

Coordinate strategy of dual-pulse-width-modulation converter based on direct power control with load power feed-forward

The common dual-pulse-width-modulation converter adopts the independent method to control the rectifier and inverter, which has the defects including direct current voltage fluctuation, slow system response and so on. A coordinate strategy of dual-pulse-width modulation based on direct power control with load power feed-forward is proposed in this paper. The fixed switching frequency method with space vector pulse width modulation is provided to overcome the instability of power devices, caused by the hysteresis comparators in the conventional direct power control. With the analysis on the dynamic performance of load power feed-forward coordination, the principle of load power feed-forward is introduced to control the dual-pulse-width-modulation converter. According to the state variable of the alternating current motor, the load power is estimated to construct the feed-forward channel. The experimental results show that the proposed coordinate control method has rapid response, direct current bus voltage fluctuation minimization, lower capacity and unit power factor.

Indirect Rotational Energy Harvesting System to Enhance the Power Supply of the Quadcopter

This paper presents a simple energy harvesting system using unpowered freewheeling propellers mounted on the quadcopter without changing its actual design. Different layout configurations have been analysed and its thrust variation also tested to place the harvesting system in a suitable place in the quadcopter. The same and different size freewheeling propellers running coordination and its speed ratio are examined at various speed. To know the flow performance the freewheeling propellers Reynolds number is calculated. The freewheeling propellers rotational energy which creates an electrical power by means of micro BLDC generator. The harvested energy from the BLDC generator is maximized using three-phase MOSFET enabled controlled rectifier with hysteresis comparator. To meet the requirement of powering the quadcopter the output voltage from the generator is boosted and regulated using single DC-DC SEPIC boost converter with high voltage and current range. This energy can be directly charge secondary battery or power the other electronic payloads. The freewheeling propeller energy harvesting system has been implemented and tested in the laboratory at static condition which gives 51 per cent of harvested current.

DTC-ANN-2-level hybrid by neuronal hysteresis with mechanical sensorless induction motor drive using KUBOTA observer

In this paper, DTC is applied for two-level inverter fed IM drives based on neuronal hysteresis comparators and The Direct Torque Control (DTC) is known to produce quick and robust response in AC drive system. However, during steady state, torque, flux and current ripple. An improvement of electric drive system can be obtained using a DTC method based on ANNs which reduces the torque and flux ripples, the estimated the rotor speed using the KUBOTA observer method based on measurements of electrical quantities of the motor. The validity of the proposed methods is confirmed by the simulation results.The THD (Total Harmonic Distortion) of stator current, torque ripple and stator flux ripple are determined and compared with conventional DTC control scheme using Matlab/Simulink environment.

Direct torque control of IM using PID controller

Direct torque control "DTC" technique is one of a high performance control system of an AC motor drive, which was proposed after the vector oriented control scheme during the resent 25 years. It has been developed rapidly for its concise system scheme, transient and dynamic performance. The DTC mechanism consists of voltage vector selection table, two hysteresis comparators and two estimators one for stator flux and another for electromagnetic torque. DTC is directly control torque and flux by using Voltage Source Inverter VSI, space vector and stator flux orientation and indirect speed regulated. A several control techniques can be used for improving the torque and flux performance.&#x0D; In this paper, the DTC with Proportional-Integral-Derivative (PID) controller used to improve the starting and dynamic performance of asynchronous motor AM, which gives good torque and flux response, best speed control and also minimize the unacceptable torque ripple. The mathematical model of DTC with PID controller of 3-phase induction motor IM are simulated under Matlab-Simulink. Therefore, the DTC based on PID controller has good performance of IM compared to classical DTC for starting, running state and also during change in load.

ANFIS-based hysteresis comparators with intelligent dual observer and speed controller of a direct torque control

This article presents the adaptive-network-based fuzzy inference system (ANFIS)-based direct torque control (DTC) for induction motor (IM). DTC is distinguished by merging a simple structure with a good dynamic behavior. Despite these cited advantages, some disadvantages are also present. For this aim, which consists of reducing the ripples in electromagnetic torque, flux and current; and to improve the IM response characteristics, the conventional hysteresis comparators of the torque, flux and the proportional integral (PI) speed controller are replaced by others based on ANFIS technique. Furthermore, an intelligent dual observer is implemented to achieve sensorless control; merging a Luenberger observer (LO) based on ANFIS to insure the adaptation mechanism in order to estimate the rotor speed, and a Kalman filter (KF) to insure the flux components estimation. The proposed sensorless ANFIS-DTC shows a robust performance; reduced ripples, decreased overshoots, short time of rising and settling, and high resistance to perturbations.

ANFIS-based hysteresis comparators with intelligent dual observer and speed controller of a direct torque control

This article presents the adaptive-network-based fuzzy inference system (ANFIS)-based direct torque control (DTC) for induction motor (IM). DTC is distinguished by merging a simple structure with a good dynamic behavior. Despite these cited advantages, some disadvantages are also present. For this aim, which consists of reducing the ripples in electromagnetic torque, flux and current; and to improve the IM response characteristics, the conventional hysteresis comparators of the torque, flux and the proportional integral (PI) speed controller are replaced by others based on ANFIS technique. Furthermore, an intelligent dual observer is implemented to achieve sensorless control; merging a Luenberger observer (LO) based on ANFIS to insure the adaptation mechanism in order to estimate the rotor speed, and a Kalman filter (KF) to insure the flux components estimation. The proposed sensorless ANFIS-DTC shows a robust performance; reduced ripples, decreased overshoots, short time of rising and settling, and high resistance to perturbations.

Technique of control PMSM powered by PV panel using predictive controller of DTC-SVM

The present paper is a part of the study of Direct Torque Control based (DTC) on space vector modulation using predictive controller (Predictive SVM) of a permanent magnet synchronous motor (PMSM) powered by a photovoltaic (PV) source. In the conventional direct torque control (DTC) of a permanent magnet synchronous motor (PMSM), hysteresis controllers are used to choose the proper voltage vector resulting in large torque ripples. The direct torque control can accelerate the torque responses but increases the torque ripple at same time. Nowadays, exist some other alternative approaches to reduce the torque ripples based on (Predictive SVM) technique. This method is based on the replacement of hysteresis comparators (used in conventional DTC) by Proportional Integral (PI) regulators and the selection table by space vector modulation (SVM). The simulation results confirm that this proposed method where the control of the switching frequency is well controlled, allows us to reduce the oscillations of the electromagnetic torque and flux by 20 % and 30%, respectively with a good dynamic response compared with conventional DTC.

A 2.4 GHz ISM Band OOK Transceiver With High Energy Efficiency for Biomedical Implantable Applications.

This article presents a high energy efficiency, high-integrated, and low-power on-off keying transceiver for a 2.4 GHz industrial scientific medical band. The proposed receiver includes an input matching network, a low-noise amplifier, a novel single-to-differential envelope detector, a level shifter, cascaded baseband amplifiers, and a hysteresis comparator. The proposed transmitter includes a bias-stimulating circuit, a current-reused self-mixing voltage controlled oscillator, and a quadruple-transconductance power amplifier. Numerous proposed techniques implemented in the mentioned circuits improve the energy per bit and power efficiency. Therefore, the proposed receiver for short-distanced propagation can achieve a sensitivity of -46 dBm with a carrier frequency of 2.45 GHz and a high data rate of 2 Mbps. The proposed transmitter achieves an output power of -17 dBm with a high data rate of 20 Mbps. This work is fabricated in a TSMC 0.18 μm CMOS process and consumes 160 μW and 0.6 mW in the receiver and transmitter, respectively, from a 1.2 V supply voltage. The energy per bit of 80 pJ/bit in the receiver part and the figure of merit of 9 in the transmitter part are better than those of existing state-of-the-art transceivers.

An Improved Open-Switch Fault Diagnosis Technique of a PWM Voltage Source Rectifier Based on Current Distortion

Numerous studies show that power semiconductors are significant contributors to the overall failure rate of pulsewidth modulation (PWM) voltage source rectifier (VSR) systems. Aimed at this problem, this paper presents an improved diagnosis system for open-circuit faults of a three-phase PWM VSR based on ac current distortion characteristics, which consists of a diagnosis module, a register module, and a decision module. The diagnostic module employs a hysteresis comparator to judge the change trend of the currents, and thereby diagnoses the single open-circuit (OC) faults. The register module is employed to achieve multi-switch OC fault diagnosis, and the decision module is used to output the final result. The proposed method extends the previous work to multi-switch OC fault conditions as well as improves the diagnosis accuracy. The experimental results show that the proposed method can correctly achieve fault diagnosis, including 6 kinds of single-switch faults and 15 kinds of different double-switch faults. Additionally, the proposed method also shows superior anti-interference performance and high robustness under abrupt load transient conditions, different power factor conditions, unbalanced and/or distorted grid voltage conditions, and different ac filter structure conditions. Furthermore, the average diagnostic time of this method is only 3.68 ms.