Theoretical research on hydroviscous speed-adjusting clutch in soft-start of belt conveyor

Through research on the application of hydroviscous speed-adjusting clutch in belt conveyor, this paper concluded that hydroviscous speed-adjusting clutch has many advantages such as controllable start and stop, overload protection and multi-motor power equilibrium. But its theory when used in large power fan and pump could not meet the needs of belt conveyor soft-start operation. Focusing on the theo- retical analysis of the lubrication oil flow needed by the transmission procedure to form the oil-film. Put forward concrete calculation methods of lubrication flow and how to de- cide number of oil-films used in belt conveyor.

探讨SOFT-START光聚合技术对光固化复合树脂充填后边缘微渗漏的影响

目的探讨SOFT-START光聚合技术对光固化复合树脂充填后边缘微渗漏的影响。方法选取患者80例,并按照随机数字法分为观察组和对照组,各40例,观察组患者采用SOFT-START光聚合模式处理,对照组患者使用传统高强度光聚合模式,比较两组干预前后微渗漏值情况,并统计两组的临床效果。结果通过比较两组干预前后微渗漏值情况发现,在进行干预前,观察组的微渗漏值为(0.8±0.2)分,对照组的微渗漏值为(1.8±0.3)分,经过治疗后,观察组微渗漏值得分显著低于对照组(t=17.541,P<0.05)。而观察组治疗成功率为92.5%,对照组治疗成功率为65.0%,经比较,观察组治疗成功率显著高于对照组(X^2=7.470,P<0.05)。结论采用SOFT-START光聚合技术对患者进行干预,可以显著减小光固化复合树脂充填后边缘微渗漏情况,并能有效促进光固化复合树脂聚合收缩反应,提高填充边缘封闭性,进而提高患者的治愈率。因此,采用SOFT-START光聚合模式对患者牙齿进行处理,具有较好的临床治疗效果,值得大力推广。

Fuzzy-immune control strategy of a hydro-viscous soft start device of a belt conveyor

Considering the control difficulties of a hydro-viscous trol algorithm was derived. A fuzzy-immune PID controller was soft start （HVSS） device of a belt conveyor, a fuzzy-immune con- designed based on immune feedback regulations and adaptability of the fuzzy logic inference. Using MATLAB software, we simulated the controller and compared the HVSS device with a conven- tional PID controller and a fuzzy PID controller. The simulation results show that the controller is not only very reliable as a PID controller, robust and requires only a short adjustment time of fuzzy control, but possesses also capacity of global optimization of the immune algorithm. To verify our theoretical analysis and simulation, a HVSS test-bed was developed. The experimental results demonstrate that the fuzzy-immune PID controller managed to start the belt conveyor softly and to follow an S-shaped curve while the output speed correctly followed the preset speed with only small fluctuations in speed.

A fast novel soft-start circuit for peak current-mode DC-DC buck converters

A fully integrated soft-start circuit for DC-DC buck converters is presented. The proposed high speed soft-start circuit is made of two sections： an overshoot suppression circuit and an inrush current suppression circuit. The overshoot suppression circuit is presented to control the input of the error amplifier to make output voltage limit increase in steps without using an external capacitor. A variable clock signal is adopted in the inrush current suppression circuit to increase the duty cycle of the system and suppress the inrush current. The DC-DC converter with the proposed soft-start circuit has been fabricated with a standard 0.13 um CMOS process. Experimental results show that the proposed high speed soft-start circuit has achieved less than 50 us start-up time. The inductor current and the output voltage increase smoothly over the whole load range.

Thorough Validation of a Rotor Fault Diagnosis Methodology in Laboratory and Field Soft-Started Induction Motors

Induction motors are the most widespread rotating electrical machines in industry.Predictive maintenance of the motors is of crucial importance due to the fact that unexpected faults in those machines can lead to huge economic losses for the corresponding companies.Over recent years,there is an increasing use of industrial induction motors operated by different types of drives,which have different functionalities.Among them,the use of soft-starters has proliferated due to the inherent benefits provided by these drives:they damp the high starting currents,enabling the soft startup of the motors and avoiding undesirable commutation transients introduced by other starting modalities.In spite of these advantages,they do not avoid the possible occurrence of rotor damages,one of the most common faults in this type of motors.Few works have proposed predictive maintenance techniques that are aimed to diagnose the rotor condition in soft-started machines and even fewer have demonstrated the validity of their methods in real motors.This work presents,for the first time,the massive validation of a rotor fault diagnosis methodology in soft-started induction motors.Industrial and laboratory and induction motors started under different types of soft-starters and with diverse rotor fault conditions are considered in the work.The results prove the potential of the approach for the reliable assessment of the rotor condition in such machines.

A novel embedded soft-start circuit for SOC power supply

To improve the power sequencing performance of the system-on-a-chip（SOC）,a novel embedded soft-start circuit is presented.A seamless soft-start reference voltage is obtained with 7 bits DAC,which can not only restrain the turning point overshoot,but also improve the output accuracy and the poor loading capability,reduce the pin number and save PCB area.The whole DC-DC converter has been fabricated in a 0.35μm CMOS process.The measurement results show that the chip starts up successfully with 250μs soft-start time under conditions of 400 kHz switching frequency,2.5 V DC-DC output and 1.8 V LDO output.Stable operation after soft-start is also shown.

A novel dimmable LED driver with soft-start and UVLO circuits

A fully integrated LED driver based on a current mode PWM boost DC-DC converter with constant output current is proposed. In order to suppress the inrush of current and the overshoot voltage at the start up state, a soft-start circuit is adopted. Additionally, to adjust the LED brightness without color variation over the full dimming range and achieve high efficiency, a PWM dimming circuit is presented. Furthermore, to keep the loop stability of the LED driver, an internal slope compensation network is designed to avoid the sub-harmonic oscillation when the duty cycle exceeds 50%. Finally, a UVLO circuit is adopted to improve the reliability of the LED driver against the input voltage changing. The LED driver has been fabricated with a standard 0.5/xm CMOS process, and only occupies 1.21 × 0.76 mm^2. Experimental results show that the brightness of the LED can be adjusted by an off- chip PWM signal with a wide adjusting range. The inductor current and output current increase smoothly over the whole load range. The chip is in the UVLO condition when the input voltage is below 2.18 V and has achieved about 137 μs typical start-up time.

A Novel Soft-start Method for SVG Based on D-axis Orientation

In this paper,a novel method for shock-free soft-start is proposed.The novel method can realize the aim of no-overshoot and inrush of current during the entire soft-start process,thus the start process is safe,stable,and reliable.When the uncontrolled rectification stage ends,a sinusoidal signal synchronized with the grid voltage is generated through dq coordinate transformation and D-axis orientation,then the signal is transmitted to the three-phase inverter bridge.The AC voltage output of the inverter bridge is superimposed on both ends of the soft-start resistor along with the grid.The open-loop control method is adopted to gradually reduce the modulation ratio of the sinusoidal PWM wave until the capacitor voltage on the DC side reaches the rated voltage value,then the soft-start resistor is removed,which means the shock-free soft-start process is completed.Experimental results prove the effectiveness and feasibility of the control strategy proposed in this paper.

Design of high efficiency dual-mode buck DC-DC converter

A buck DC-DC switching regulator with high efficiency is implemented by automatically altering the modulation mode according to load current,and it can operate with an input range of 4.5 to 30 V.At light load current,the converter operates in skip mode.The converter enters PWM mode operation with increasing load current.It reduces the switching loss at light load and standby state,which results in prolonging battery lifetime and stand-by time.Meanwhile, externally adjustable soft-start minimizes the inrush supply current and avoids the overshoot of output voltage at initial startup.The regulator is fabricated by a 0.6μm CDMOS process.The test results show that,under the condition of 3.3 V output,the efficiency is up to 64%at 5 mA and the maximum efficiency is 95.5%.

A wide load range,multi-mode synchronous buck DC-DC converter with a dynamic mode controller and adaptive slope compensation

A synchronous buck DC-DC converter with an adaptive multi-mode controller is proposed.In order to achieve high efficiency over its entire load range,pulse-width modulation（PWM）,pulse-skip modulation（PSM） and pulse-frequency modulation（PFM） modes were integrated in the proposed DC-DC converter.With a highly accurate current sensor and a dynamic mode controller on chip,the converter can dynamically change among PWM, PSM and PFM control according to the load requirements.In addition,to avoid power device damage caused by inrush current at the start up state,a soft-start circuit is presented to suppress the inrush current.Furthermore,an adaptive slope compensation（SC） technique is proposed to stabilize the current programmed PWM controller for duty cycle passes over 50%,and improve the degraded load capability due to traditional slope compensation.The buck converter chip was simulated and manufactured under a 0.35μm standard CMOS process.Experimental results show that the chip can achieve 79%to 91%efficiency over the load range of 0.1 to 1000 mA.

Adaptive switching frequency buck DC-DC converter with high-accuracy on-chip current sensor

A current-mode PWM buck DC-DC converter is proposed. With the high-accuracy on-chip current sen- sor, the switching frequency can be selected automatically according to load requirements. This method improves efficiency and obtains an excellent transient response. The high accuracy of the current sensor is achieved by a simple switch technique without an amplifier. This has the direct benefit of reducing power dissipation and die size. Additionally, a novel soft-start circuit is presented to avoid the inrush current at the starting up state. Finally, this DC-DC converter is fabricated with the 0.5μm standard CMOS process. The chip occupies 3.38 mm2. The accuracy of the proposed current sensor can achieve 99.5% @ 200 mA. Experimental results show that the peak efficiency is 91.8%. The input voltage ranges from 5 to 18 V, while a 2 A load current can be obtained.

Load adaptive start-up scheme for synchronous boost DC–DC converter

This paper presents a load adaptive soft-start scheme through which the inductor current of the synchronous boost DC-DC converter can trace the load current at the start-up stage. This scheme effectively eliminates the inrush-current and over-shoot voltage and improves the load capability of the converter. According to the output voltage, the start-up process is divided into three phases and at each phase the inductor current is limited to match the load. In the precharge phase, a step-increasing constant current gives a smooth rise of the output voltage which avoids inrush current and ensures the converter successfully starts up at different load situations. An additional ring oscillator operation phase enables the converter to start up as low as 1.4 V. When the converter enters into the system loop soft-start phase, an output voltage and inductor current detection methods make the transition of the phases smooth and the inductor current and output voltage rise steadily. Effective protection circuits such as short-circuit protection, current limit circuit and over-temperature protection circuit are designed to guarantee the safety and reliability of the chip during the start-up process. The proposed start-up circuit is implemented in a synchronous boost DC-DC converter based on TSMC 0.35μm CMOS process with an input voltage range 1.4-4.2 V, and a steady output voltage 5 V, and the switching frequency is 1 MHz. Simulation results show that inrush current and overshoot voltage are suppressed with a load range from 0-2.1 A, and inductor current is as low as 259 mA when the output shorts to the ground.

Research and design of the protection circuits in LD controller

According to the parameters and applications of laser diode （LD）, three protection circuits were designed： the time-delay soft-start protection circuit, the power-on impulse protection circuit and the limit-current protection circuit. In this article, the structure and the principle of every protection circuit have been detailed. From several tests and feedbacks from customers, the expected goals have been completed.

Effects of light curing modes and ethanol-wet bonding on dentin bonding properties

Objective： This study explored the effects of different light curing modes and ethanol-wet bonding on dentin bonding strength and durability. Methods： A total of 54 molars were randomly divided into three groups： Single Bond 2, Gluma Comfort Bond, and N-Bond. Based on the three light-curing modes and presence or absence of eth- anol pretreatment, the samples were assigned to six subgroups： high-light mode, ethanol pretreatment＋high-light mode, soft-start mode, ethanol pretreatment＋soft-start mode, standard mode, and ethanol pretreatment＋standard mode. All samples were bonded with resin based on the experimental groups. After 24 h and 6 months of water storage, a universal testing machine was used to measure microtensile bond strength. Scanning electron microscopy （SEM） was applied to observe mixed layer morphology. Results： The 24-h and 6-month microtensile bond strengths of the ethanol pretreatment groups were significantly higher than those of the non-ethanol pretreatment groups at the same light modes （P〈0.05）. With or without ethanol pretreatment, the microtensile bond strengths of the high-light modes were significantly lower than those of the soft-start modes and standard modes （P〈0.05）. The microtensile bond strengths of samples from the 6-month water storage group significantly decreased compared with those of samples from the 24-h water storage group （P〈0.05）. The soft-start groups and standard groups formed better mixed layers than the high-light mode groups, whereas the ethanol pretreatment groups formed more uniform mixed layers than those without ethanol pretreatment. Conclusions： Ethanol-wet bonding technique, soft-start, and standard modes could improve dentin bonding properties.