SU1288904A1 - Pulse=width modulator - Google Patents

Abstract

The invention relates to a pulse technique and can be used in measurement technology and automatic control systems. The purpose of the invention, the simplification of a pulse width modulator, is achieved by using code set blocks and programmable frequency dividers to set the current operating characteristics of the modulator. The device contains counters 1, 2 and 3 pulses, triggers 4 and 10, block 5 comparison of codes, key 6, programmable frequency dividers 7 and 8, element 9, delay element 11, blocks 12 and 13 of the set of codes, inputs 14 and 15 and output 16 modulator. In the modulator, an operative change of the modulation characteristic is provided in the process of tuning the loop of automatic control systems with pulse-width modulation, 2 Il. yu (L

Description

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The invention relates to a pulse technique and can be used in measurement technology and automatic control systems.

The purpose of the invention is to expand the functionality and simplify the pulse width modulator by using code set blocks and programmable frequency dividers to set the current operating characteristics of the modulator.

FIG. 1 shows a functional diagram of the device; in fig. 2 - the form of the output voltage of the modulator (a), and possible modulation characteristics of the device (b, c).

The device contains the first 1, second 2 and third 3 pulse counters, the first trigger 4, block 5 compare codes, key 6, the first 7 and second 8 programmable frequency dividers, element 9, second trigger 10, delay element 1, first 12 and second 13 blocks of dialing code, the first 14 and second 15 inputs of the modulator, the output 15 of the modulator. FIG. 2 denoted f, is the modulating frequency; f - reference frequency; tp is the modulated pulse duration; about - the repetition period of the output pulse sequence

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body; t is the current time; f, the dead zone of the modulation response; A ,, A,.,, A, 2 are the initial values of the modulation characteristics 1, 1-1 and 1-2 (Fig. 2b) with a constant slope; 1, 2 and 3 (fig, 2c) - with different steepness characteristics.

The device works as follows.

At the output of the first programmable frequency divider 7, a sequence of pulses with a period is formed. These pulses allow successively changing cycles of measuring the input frequency f and converting the result obtained in this way into a pulse-width form, namely: when a next pulse is attenuated, counter 3 records the contents of counter 1, which is a code N, value which is equal to the number of periods of the input frequency f (for the time interval c;). At the same time, unit 5 compares the value of this code with the code command of the code set unit 12 installed on the output bus and representing the selected value of the deadband of the modulator f (Fig. 26, c). If N, N, at the output of block 5 an electrical signal is formed, corresponding to logical 1, which is fed to the input

And 9 and allows passage of the strobe pulse from the output of the programmable divider 7 to the first input of the trigger 4. The trigger 4 switches to the unit state and a voltage appears on its output, which is the output signal of the modulator.

In addition, a gate trigger 10 is set to one by a gate pulse from the output of the programmable divider 7, by connecting the subtraction input of counter 3 directly to the second input 15 of the modulator, and the set code of the code set block 13 is written to counter 2. Then, after a time interval equal to the setting of the delay element 11, the counter 1 is zeroed, after which the cycle of counting the pulses of the input frequency is repeated

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The initial setting of counter 2 determines how much the duration of each output pulse decreases outside the deadband of the modulator. This numerical value is selected from O to N, which corresponds to the points,. 35 modular torus characteristics

(Fig. 26). When the contents of counter 2 decrease to zero, a voltage pulse is generated at its output, which sets the trigger 10 to the positive state, while the output of the key 6 is the voltage from the output of the programmable divider 8. The same value ranges from 0 to N ,, the content of the counter 45 of the chuck 3 is reduced, the input of which, before changing the state of the trigger 10, was connected to the second input 15 of the device in parallel with the analogous input of the counter 2. Read intensity

The 50 residual contents of the counter 3, and, consequently, the duty ratio of the modulated pulses generated by the trigger 4, depend on the set coefficient of the programmable divide 55 frequency B bodies. When the content of the counter 3 decreases to zero, a voltage pulse is generated at its output, which is fed to the second input

trigger 4 and switches it to the zero state, thereby ending the formation of the output pulse.

Thus, the duration tp of pulses (Fig. 2a) generated at the output of flip-flop 4 is proportional to the current values of the input frequency ff (this relationship for different values of the parameters of the output signal is shown in Fig. 26, c). With the help of the code comparison unit 5 and the code dialing unit 12, the dead band of the modulator is established, within which its output signal is zero. By means of counter 2 and block 13 of the code set, the minimum required duration of modulated impulses excited by trigger 4 at the threshold of the dead zone of the modulator (A, -A, Fig. 2b) is selected. Setting the programmable divisor counting ratio. 8 frequency determines the steepness of the operating characteristics of the modulator, as well as the duty cycle of modulated pulses (Fig. 2c). In addition, by changing the count rate of the programmable frequency divider 7, you can set the required measurement cycle duration -t.

The introduction of programmable frequency dividers and code set blocks allows you to simplify the pulse-width modulator and promptly change the modulation characteristic of the device in the process of setting the loop of automatic control systems with PWM.

Claims (1)

Invention Formula Pulse width modulator containing the first and second pulse counters, the inputs of which are connected to the first and second input buses modulator, respectively, and the first group of outputs of the first counter is connected to the first group of inputs of the code comparison unit, and the first trigger output of which is the modulator output, characterized in that, in order to extend the functionality by providing an operational tuning of the output signal parameters, he entered the third counter, the first and second blocks of the code, key, element And, the second trigger, the delay element, the first and second programmable frequency dividers, the inputs of which are connected to the first input The key is connected to the second input bus of the modulator, the first input of the second trigger is connected to the output of the second counter, and the output of the first programmable frequency divider is connected to the code write inputs of the second and third counters, to the second input of the second Both with the input of the delay element, the output of which is connected to the input of the code entry of the first counter, the output of the second programmable frequency divider is connected to the second input of the key, the input of which is connected to the output of the second trigger, and The key is connected to the subtractive input of the third counter, the output of which is connected to the first input of the first trigger connected by its second input to the output of the element I, the second input of which is connected to the output of the code comparison unit, the second group of inputs of which and the group of inputs of the preset code of the second counter are connected to groups of outputs of the first and second blocks of dialing code, respectively, and the group of inputs of the preset code of the third counter is connected to the first group of outputs of the first counter. I fex const } fe 6} ow FIG. 2 Editor A. Petrov Compiled by S. Telemohin Tehred L. Serdyukova Order 7823/58 Circulation 922 Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raz-Shska nab., 4/3 Production and printing company, Uzhgorod, st. Project, 4 Proofreader N. King