Self-inspection circuit of digital input circuit based on pulse injection method

Abstract

Disclosed is an on-off input loop self-checking circuit based on a pulse injection method. A spike self-checking pulse is generated through control of an IO pin of a CPU and is injected to an on-off input loop, and, after the spike self-checking pulse goes through an optical coupler, the spike self-checking pulse is acquired by an ADC analog-to-digital conversion pin of the CPU and is judged; the IO pin of the CPU is connected with an input end of the optical coupler, an output end of the optical coupler is connected with an input end of an optical MOS tube, a source electrode of the optical MOS tube is connected with a common anode of a power supply, a drain electrode of the optical MOS tube is connected with one end of a safety capacitor, and the other end of the safety capacitor is accessed into the on-off input loop. After a spike self-checking pulse signal generated due to drive of the IO pin of the CPU is injected to the on-off input loop, the ADC analog-to-digital conversion pin of the CPU acquires a waveform of a secondary side of the optical coupler, processing, analyses and comparison are performed, and then a self-checking judgment for integrity of the on-off input loop is achieved; and a self-checking mode can be applied no matter an on-off signal is in any state, and the self-checking loop has the extremely high isolation capability and reliability.

Description

technical field [0001] The invention belongs to the technical field of electric power systems, and relates to a switching value input circuit self-test circuit based on a pulse injection method and a device using the method, and is especially suitable for switching value input collection and input circuits in the fields of power system substation automation and industrial control automation. Self-checking protection control and automation device. Background technique [0002] In power system substation automation and industrial control automation devices, digital input acquisition loops are usually set to obtain the status of some important digital signal quantities, providing the necessary basis for subsequent protection and control operations. For the realization of the open-in circuit, the electric energy of the open-in signal is usually used to drive the primary side of the optocoupler of the input circuit, and the state change of the open-in signal is converted into a v...

AI Technical Summary

Problems solved by technology

[0005] There is no effective electrical isolation between the self-inspection input circuit and the open-in acquisition circuit, and the interference signal introduced by the open-in circuit can easily cause damage to the self-inspection circuit, which in turn leads to failure to realize the self-inspection function normally

[0006] The self-test signal output by the CPU IO port is a square wave signal, which is easy to be confused with the normal input signal, resulting in misjudgment of self-test or malfunction of the input

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