用一般脉宽调制器构造的变频式脉宽调制器

提出为直流变换器增加一个控制变量的概念,以弥补现行直流变换器只有一个调节变量引起的一些缺陷.本文选定的控制变量是直流变换器的运行频率f,将它与一次电源电压V联系起来,使f随V上升按预设的规律下降,以解决直流变换器以固定频率运行时这种情况下出现的许多问题,如开关管发热加剧等.实现这一设想的主要问题是将一般脉宽调制器构造成变频式脉宽调制器.现以脉宽调制器1842/3/4/5(简记为184X)和1842A/3A/4A/5A(简记为184XA)为例,给出了将它构造成变频式脉宽调制器的方法,示出了可实现的变频特性.设计了两个将一次电源电压转换为变频式脉宽调制器输入电压的线性转换电路,推导了计算这些电路中各元件参数的表达式.实验结果与设计一致.

A Variable Frequency Type of Pulse Width Modulator Constructed of Using General Pulse Width Modulator

In order to remedy some defects caused by only one regulating variable in the current DC/DC converters,a new concept to add a control variable in the converters is proposed.In this paper,the chosen control variable is the operating frequency f of the converter,and make f decrease according to a set law when the voltage of the primary power supply increases,so as to solve some problems such as severe heating of the switching transistors,etc.when the frequency is invariable.The main problem to realize the idea is to construct a variable frequency type of pulse width modulator(PWM) by a general PWM.Now taking the general modulator 1842/3/4/5 and 1842A/3A/4A/5A as examples to discuss how to construct the variable frequency type of PWM,and show the realizable frequency characters are given.Both of the linear transform circuits of voltages are designed to transform the voltage of the primary power supply to the input voltage of the PWM.The representations for calculating parameters of elements in these circuits are derived.The experiment results are consistent with designs.