Isolated pulse output circuit with overload protection function and implementation method

Abstract

The invention discloses an isolated pulse output circuit with an overload protection function and an implementation method. The circuit comprises an MCU, an isolation pulse output optocoupler, a current-limiting resistor, an overload protection execution optocoupler, a current sampling resistor, an overload control triode, an external analog load and an external power supply. When the MCU needs tocarry out isolation pulse output, the isolation output pulse optocoupler light emitting diode is conducted; a collector and an emitter of a photoelectric triode of the isolation pulse output optocoupler are conducted; when the voltage drop on the sampling resistor reaches 0.7 V, the voltage drop is reduced to 0.7 V, the overload control triode is conducted, a collector and an emitter of the photoelectric triode are conducted; the anode of the light emitting diode of the isolation pulse output optocoupler is pulled down, the diode of the isolation pulse output optocoupler is not conducted anymore, the collector and the emitter of the photoelectric triode of the isolation pulse output optocoupler are not conducted, and external current cannot form a loop, so that an isolation pulse outputcircuit is effectively protected, and the circuit is prevented from being damaged due to overload.

Description

technical field [0001] The invention relates to an automatic control or instrumentation circuit, in particular to an isolated pulse output circuit with overload protection function and its realization method. Background technique [0002] In automatic control or instrumentation circuits, optocoupler isolation is often used to achieve pulse isolation output. This typical conventional circuit is shown in image 3 middle. Including pulse output control MCU, isolated pulse output optocoupler U1, current limiting resistor R1, external analog load R, and external power supply; when the MCU needs to perform isolated pulse output, the I / O pin becomes low, and the isolation connected to it The cathode of the light-emitting diode of the pulse output optocoupler U1 becomes low, and the light-emitting diode is turned on. Since there is current flowing through the light-emitting diode of the isolated pulse output optocoupler U1, the collector and emitter of the phototransistor of U1 are ...

AI Technical Summary

Problems solved by technology

[0004] 1. In actual use, both the analog load R and the external power supply vary greatly. Sometimes, during the process of forming pulses on the load R, the loop current is too large, resulting in damage to

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