Analogue quantity output circuit

Abstract

The invention discloses an analogue quantity output circuit, comprising a photoelectric coupler, a singlechip and a filter circuit which are connected in series. PWN signals output by the singlechip are respectively transmitted to the operational amplifiers of a voltage output circuit and a current output circuit after being output by the filter circuit; an assistant power circuit comprises a serial voltage stabilizing circuit composed of a first triode and a reference voltage chip and a silicon diode; the negative voltage output end of the serial voltage stabilizing circuit is connected withthe positive pole of the silicon diode; the serial voltage stabilizing circuit provides a +5V stable power supply for the singlechip and the photoelectric coupler; and the negative pole of the silicon diode and the negative power supply ends of the operational amplifiers of the voltage output circuit and the current output circuit are connected. The invention can output high-precision positive-negative power supply circuits, lower cost for isolated power and further realizes zero point linear output.

Description

technical field [0001] The invention relates to an analog quantity output circuit, which belongs to the field of industrial automation. Background technique [0002] In the power transmission and distribution system, in order to facilitate remote monitoring and control, many electrical parameters need to be transmitted through analog quantities. At present, the analog output circuit is divided into two types: isolation mode and non-isolation mode in terms of hardware structure. [0003] Among them, the isolation method can be divided into two types: one is to use a high-speed photocoupler to transmit the PWM signal sent by the main CPU, and then output it through the operational amplifier after filtering the circuit; the other is to use an ordinary photocoupler to transmit the main CPU control and The data signal is analyzed by the single-chip microcomputer and then output as a PWM signal, and then output through the operational amplifier after passing through the filter ci...

AI Technical Summary

Problems solved by technology

[0004] The use of high-speed optocoupler transmission has the following disadvantages: In order to ensure the output accuracy, it has high requirements for the transmission speed of high-speed optocoupler, and the transmission speed is directly related to the cost, so the actual circuit cost is relatively high; using high-speed optocoupler transmission The resource usage of the main CPU is high

However, conventional photocouplers are used to complete signal transmission. Although the cost of single-chip microcomputers is far lower than that of high-speed photocouplers, its output accuracy is difficult to meet actual production needs.

[0005] The current main problem of the non-isolation method is that it occupies a lot of resources of the main CPU, and multiple output groups cannot be directly connected to the negative end, which not only reduces the design flexibility, but also increases the system cost.

[0006] From the design of the auxiliary power supply, the analog output circuit can be divided into two types: positive and negative dual power supply and single power supply: the design of positive and negative dual power supply is mainly used in non-isolated circuits, multiple sets of output use the same auxiliary power supply, and the operational amplifier can be Guaranteed linear output; single power supply is mainly used in isolation circuits, and independent power supply is used between multiple groups. The advantage of this single power supply is that the analog output circuit is electrically isolated from the main CPU, and multiple groups of negative terminals can be directly connected. The disadvantage is that the calculation The amplifier is powered by a single supply and cannot achieve a linear output at zero

Therefore, none of the existing analog output circuits of the above two isolation methods can achieve zero-point linear output

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