Switch value input voltage control circuit

Abstract

The invention discloses a switch value input voltage control circuit. The circuit comprises a positive electrode input end input1, a negative electrode input end input 2, an output end DI1, an optical coupler H1, a current regulative diode D1, a voltage regulator diode Z1, a rectifier diode D2, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a capacitor C1 and a capacitor C2; the positive electrode input end input1 is electrically connected with the resistor R1, and the second end of the resistor R1 is electrically connected with the first end of the current regulative diode D1, the first end of the capacitor C1 and the first end of the resistor R2. According to the scheme, by utilizing the characteristics of the voltage regulator diode, it is guaranteed that the optical coupler is connected when the Ui is increased to a certain value, and therefore the optical coupler can work after reaching a certain voltage; meanwhile, by means of the characteristics of the current regulative diode, it is guaranteed that the front-end current IF of the optical coupler is limited within a certain range and cannot be increased along with rising of the input voltage, and therefore the low power consumption requirement is met; accordingly, it is guaranteed that the maloperation condition cannot occur when the switch value is used in the industrial field.

Description

technical field [0001] The invention relates to the field of industrial automation control, in particular to a switching value input voltage control circuit. Background technique [0002] In the process of industrial control, the digital input signal often needs to be provided by an external power supply Ui, so as to realize industrial control according to the change of the state of the digital value. In order to ensure the reliability and stability of the control, it is usually required to isolate the input circuit from the processing unit of the single-chip microcomputer to prevent damage to the single-chip microcomputer by high voltage, so optocoupler isolation is usually used. [0003] Existing technical solutions mainly adopt such as figure 1 The circuit shown is realized, and its working principle is: the voltage drop of the input voltage Ui on the resistance of R1 generates the conduction current If of the optocoupler, which drives the optocoupler H1. When the volta...

AI Technical Summary

Problems solved by technology

[0004] The industrial control site has strong interference, and the interference voltage on the switch input line normally reaches tens of volts. Since the optocoupler is a current-sensitive device, that is, the value of If directly affects the level of the optocoupler’s secondary side. figure 1 If the judgment circuit is used, the circuit may be unreliable due to the interference voltage on site.

In addition, If increases with the increase of Ui, there is no restriction on If, so the power consumption of the judgment circuit will also rise rapidly

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