Switching value acquisition insulating circuit

Abstract

The invention discloses a switching value acquisition insulating circuit.The switching value acquisition insulating circuit comprises a reverse protection unit, a current fixing unit, a voltage measurement unit and a photoelectric insulation unit, wherein a switching value signal is input into the reverse protection unit which is connected with the current fixing unit, a circuit is not damaged under the protection of the reverse protection unit after the switching value signal input and the ground are reversely connected, and the current fixing unit fixes the input current of a circuit after meeting a voltage opening condition. The voltage measurement unit is connected with the current fixing unit and controls the threshold voltage so as to reach a voltage signal condition for opening the circuit. The photoelectric insulation unit is connected with the voltage measurement unit and insulates an external input signal and an internal control signal so as to avoid the interference of external input signals and avoid the damage to an inner circuit caused by external fault. The invention can ensure the constancy of the input current in the acquisition process of a switching value input signals, ensures the photoelectric coupler to work reliably and has the advantages of simple circuit calculation, low power and low heating value.

Description

technical field [0001] The invention relates to a switch quantity acquisition isolation circuit, in particular to a switch quantity acquisition isolation circuit with constant front-end input current. Background technique [0002] As a basic input circuit, the switching value input acquisition circuit is to complete the state information acquisition and processing of the on-site switching value, convert the external electrical signal into a low-voltage digital signal used by the internal circuit, and cooperate with the field equipment to complete the corresponding control. The physical layout is closest to the on-site actuator, the working environment is harsh, and the reliability requirements are high. [0003] The existing circuit of this type adopts the form of resistive voltage division, the input current changes with the change of the input voltage, the parameter calculation process is more complicated, and it is not conducive to the stable operation of related devices,...

AI Technical Summary

Problems solved by technology

[0006] (1) In the past, the input circuit used the method of resistive voltage division to collect the voltage on the voltage dividing resistor to complete the conduction of the circuit. The current of the circuit changes with the change of the external switch voltage, and the calculation is complicated, the accuracy is low, and the power consumption is low. Larger, which is not conducive to the long-term stable operation of the optocoupler;

[0007] (2) The calculation of the circuit is complicated. It is necessary to calculate the voltage to meet the conditions, and then to calculate the current to meet the conditions. It is also necessary to calculate the conditions to be satisfied by the current transmission ratio of the photocoupler, and the circuit derating should also be considered;

[0008] (3) The power consumption of the circuit is relatively high

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