查询词典 pulse-time modulation

First, the paper reviews the development and research of AC transfer speed system, introduces the different control strategy of transfer speed system for asynchronous motor, and discusses the basic principle of vector control system for asynchronous motor in detail,including the mathematics model and coordinate transformation of asynchronous motor, the fundamental equation of vector control, the estimation method of rotor flux, the system structure of vector control etc. Then, the paper lays stress on the fundamental principle, control algorithm and realization method in TMS320LF2407 of space vector pulse width modulation technology.

本文首先简述了交流调速系统的发展和研究重点，介绍了异步电机调速系统的不同控制策略，详细论述了异步电机矢量控制系统的基本原理：异步电机的数学模型和坐标变换、矢量控制的基本方程式、转子磁链的观测方法、矢量控制的系统结构等，并重点分析了空间矢量脉宽调制技术的基本原理、控制算法以及在TMS320LF2407中的实现方法。

Based on CMOS technology and using Composer and Spectre tools of Cadence EDA, a type of single-chip controller is designed for the fly-back switching power supply of AC/DC. It works at 70KHz with current mode pulse width modulation; and the max duty is 75 percent.

本论文基于高压CMOS工艺，用Cadence EDA中的Composer包及Spectre仿真工具，设计了一种反激式AC/DC开关电源控制芯片。

In the voltage doubling rectifying circuit, the high voltage has been realized by the positive and negative way, and the voltage between the cathode and anode could reach 1700 V. In the fly-back switching high-voltage power supply, considering the requirements of each unit of the driving circuits on the power supply, the three-group voltage outputs including low-voltage outputs have been realized: 1600V/20mA,12V/500mA, 5V/50mA, in which UC3842 has been used to achieve pulse width modulation.

在倍压整流电路设计中，采用正、负电压方式实现高压，有效降低了阴阳极间所需的高压，最终两极间可产生1700V电压；在反激式开关电源电路设计中，利用UC3842芯片实现PWM调制，考虑到驱动电路各单元对电源的需求，设计了包括低压电源在内的三组电源输出：1600V/20mA，12V/500mA，5V/50mA。

Finally, simulation experiments on intra pulse frequency modulation signals verify the correctness and efficiency of the proposed method.

仿真实验结果证明了方法的正确性和有效性。

The objective of the thesis is to present newly developed AC driver and protection circuits for light emitting diode. The LED modules for each upper and low arm are with pulse-width modulation control in every half fundamental cycle. The indication and protection circuits act whenever short circuit and open circuit of LED module occur. Moreover, the current path is switched off when there is a short circuit of LED module.

目前一般白光发光二极体的驱动器，皆是使用直流电源驱动，本文利用发光二极体本身单向导通的特性，将发光二极体串接成桥式整流器的方式，只需控制流经中间路径的电流周期，就可达到调整发光二极体亮度之目的，并且增加发光二极体故障时的保护指示电路。

Sub-femtosecond pulse, molecular modulation, high harmonic generation, spectral synthesis

中文关键词：亚飞秒脉冲，分子调制受激拉曼散射，高次谐波，频谱合成

Basing on analyzing the work principle of the current control methods, it can be given the detailed derivation process basing on the grid and inverter pulse width modulation algorithm and the duty cycle of the instantaneous current control.

在分析了电流控制方法工作原理的基础上，给出了基于瞬时电流控制的并网逆变器的脉宽调制算法和占空比的详细推导过程。

The principle of the space vector pulse width modulation was studied. And the sectors were determined by using Karnaugh map simplification method of logic function.

研究了电压空间矢量脉宽调制技术，并利用逻辑函数的卡诺图化简法来判断扇区。

The servo control system combines position loop,speed loop,current loop with algorithm of space vector pulse width modulation.

系统采用位置、速度和电流环三环控制，并结合空间矢量脉宽调制算法。

Base on the principle, the main circuit and control circuit of 2-phase hybrid stepping motor systems are designed. The system can realize many functions such as fix-frequency pulse width modulation, current sampling, power magnifying, ring distribution, producing control signal, and so on.

完成了对二相混合式步进电动机微步驱动系统主电路及控制电路的具体设计，实现了恒频斩波、信号检测、环形分配、微步信号的产生等功能，并搭制了实验电路进行实验验证。

I didn't watch TV last night, because it .

昨晚我没有看电视，因为电视机坏了。

Since this year, in a lot of villages of Beijing, TV of elevator liquid crystal was removed.

今年以来，在北京的很多小区里，电梯液晶电视被撤了下来。