According to the following design theory : the dsp calculates in real time and produces three phases spwm waves to control the on or off of the 6 igbts in ipm respectively . ipm then inverts the commutated single phase direct current ( insulated gate bipolar transistor ) into three phases alternating current . when modulated signals of spwm are changed , the on - off time of switches also changes , so as to the voltage and frequency of output signals 本文提出了一种基于dsp (数字信号处理器tms320f240 )的通用的三相间接变频电源系统，利用分段同步调制法和混合查表法，实时计算不同频率下的采样周期、电压幅值、输出脉宽，产生双极性spwm波形，经驱动放大后用于ipm ( intelligentpowermodule )中的绝缘栅双极型晶体管栅级驱动，以控制电源的输出电压和频率，实现变频电源的智能数字控制。
This paper realized frequency modulation using the video signal to directly control the resonance loop ' s diode of the vco at the early stages , and then through using radio frequency bipolar junction transistor , designed a lc voltage controlled oscillator which was emulated by advance design system . in addition , it also implemented the design and debugged the hardware circuit 本文第一次实验采用视频信号直接控制vco谐振回路变容二极管的方式实现频率调制,并且利用射频双极性晶体管( bjt )设计了一种lc压控振荡器,通过ads软件进行了参数仿真,最后进行了硬件电路的制作和调试。
According to the test conditions , the double polarity inputting mode is adopted in the circuit of voltage - frequency converting part ; storage batteries are used in the optical emission part of optical fibre isolating and transmitting device , that can guarantee isolation between the main circuit and the testing system ; the 89c51 singlechip is used in the singlechip testing - controlling unit , the peripheral circuits are extended , data are transmitted through the serial port in this part ; the p opular software delphi5 . 0 is used in the pc part , the communication between singlechip and pc by serial port , plotting of current wave , regulation of data ; the optical - electrical isolating and triggering are used in the controlling part , this can guarantee the veracity and reliability of breakers triggered , this triggering mode is also used in the triggering of the main closing breaker , the tested breaker and the assistant breaker , the triggering signals are sent out by a singlechip 压频转换部分电路中根据实际情况采用了双极性输入方式；光纤隔离传输装置的光发射部分电源采用了蓄电池供电，确保了主回路与测试回路的完全隔离；单片机测控部分采用了89c51单片机，扩充了外围电路，通过串口向pc机传送数据； pc机与单片机之间的串口通讯、波形绘制、数据管理等都采用了软件delphi5 . 0编写。该测试系统中预留了输出口，可以对合成回路中的主合闸开关、被试开关、辅助开关进行触发，信号由单片机发出，控制部分采用了光电耦合隔离触发的方法。软件设计主要集中在对电流信号的数据采集、数据处理、数据传送、人机界面、波形绘制和数据管理，软件部分又可分为单片机和pc机程序设计两大部分。
In order to eliminate the influences caused by temperature , electrode - polarization and autoeciousness - capacitance , the traditional instrument has added complicated circuits so that it cause such shortcomings as big error , time - retardation and a relatively small scope . through the problems caused by 2 - probe electrode and ac current source , a new measuring circuit based on the excitation of bi - directional voltage pulse and the sensor of 4 - probe electrode is proposed , using single - chip to achieve auto - temperature compensation 作者在参阅国内外大量相关参考文献的基础上,从电导测试技术的原理性研究出发,分析了采用交流激励源、两电导电极为传感器的传统电导测试系统所面临的种种问题,提出并研制了一种基于双极性脉冲电压激励、以四电导电极为探头、运用单片机进行温度自动补偿的新型电导率测量系统。
The components , working principle , advantages and defects of pwm power amplifier are introduced briefly in the dissertation . the working characteristics of h - bridge pwm power amplifier in double - polarity mode is analyzed qualitatively and qualitatively and the conclusion that fluctuant magnitude and continuousness of armature current are the essential parameters which can be used to evaluate pwm control modes 论文简要介绍pwm功率放大器的组成、工作原理、特点及存在问题；对常见h型双极性模式pwm功率放大器的工作特性作了定性和定量的分析，指出了电枢电流脉动量和电枢电流连续与否是衡量pwm控制方案优劣的两个本质参数。
