Analog signal control circuit for motor protector

Abstract

The invention provides an analog signal control circuit for a motor protector, which is characterized in that a micro-control unit of the motor protector is connected with an optical coupling isolation circuit, the optical coupling isolation circuit is connected with a filter circuit, the filter circuit is connected with an operational amplifier, and the operational amplifier is connected with a direct current analog quantity output module; the direct current analog quantity output module is connected with a sampling receiving end of a motor protector extension module, a micro-control unit of the motor protector sends out a PWM control signal, a PWM signal with the same waveform and duty ratio is outputted through the optical coupler isolation circuit, the PWM signal is amplified and outputted through the filter circuit and the operational amplifier, an analog quantity output signal is generated, and signals are sent to the motor protector expansion module for sampling and communication. According to the circuit, a DAC analog-to-digital converter is cancelled, the cost is saved, the MCU generates PWM for data conversion, controllability of analog quantity is enhanced, and optical coupler isolation is adopted, so electrical safety isolation is realized, the anti-interference capability of the product is improved, and the wrong line protection capability is achieved.

Description

technical field [0001] The invention relates to the technical field of motor protector signal control, in particular to an analog signal control circuit for a motor protector. Background technique [0002] In practical applications, motor protectors are generally used in industrial products, the control line is relatively long, the longer the digital signal transmission distance, the greater the external interference, and the digital signal is easy to penetrate into the interference. In industrial scenarios, the transmission effect of digital signals is far from ideal; on the other hand, in the long-distance transmission process of analog quantities, the anti-interference ability is obviously stronger than that of digital signals. Therefore, PWM control is often used to generate analog as a long-distance control signal, and the analog output signal is generally required to be 4-20ma. In the prior art, the digital signal is generally sent by the MCU, and then converted by th...

AI Technical Summary

Problems solved by technology

The cost of the existing circuit is high, the controllability of the analog quantity is low, there is no electrical safety isolation, and the product's anti-interference ability and miswire protection ability are low

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