阅读说明：本技术 一种通用输入接口电路 (Universal input interface circuit ) 是由 杨晨飞 唐世悦 张光宇 曹桂平 于 2021-09-23 设计创作，主要内容包括：本发明公开了一种通用输入接口电路,属于接口电路技术领域,包括：输入接口、阈值电压产生模块、差分接收模块和开关模块,所述差分接收模块的差分输入正、负端分别连接至输入接口的输出和阈值电压产生模块的输出,开关模块的输出连接至阈值电压产生模块。通过控制开关模块的闭合/断开状态的切换,实现对阈值电压产生模块输出电压的动态调整,且电路结构简单可靠。(The invention discloses a universal input interface circuit, belonging to the technical field of interface circuits, comprising: the differential receiving module comprises an input interface, a threshold voltage generating module, a differential receiving module and a switch module, wherein the positive and negative differential input ends of the differential receiving module are respectively connected to the output of the input interface and the output of the threshold voltage generating module, and the output of the switch module is connected to the threshold voltage generating module. The dynamic adjustment of the output voltage of the threshold voltage generation module is realized by controlling the switching of the on/off state of the switch module, and the circuit structure is simple and reliable.)

1. A universal input interface circuit, comprising: the differential receiving module comprises an input interface, a threshold voltage generating module, a differential receiving module and a switch module, wherein the positive and negative differential input ends of the differential receiving module are respectively connected to the output of the input interface and the output of the threshold voltage generating module, and the output of the switch module is connected to the threshold voltage generating module.

2. The universal input interface circuit as claimed in claim 1, wherein the threshold voltage generating module comprises a voltage adjustable power supply unit and a dc power supply, the dc power supply input is connected to the voltage adjustable power supply unit, the output of the voltage adjustable power supply unit is connected to one of the positive differential input terminal and the negative differential input terminal of the differential receiving module, and the input of the voltage adjustable power supply unit is connected to the output of the switching module.

3. The universal input interface circuit as claimed in claim 2, wherein the adjustable voltage power supply unit comprises a low dropout linear power supply chip, an input pin of the low dropout linear power supply chip is connected to the dc power supply input, an output pin of the low dropout linear power supply chip is connected to a first resistor, a feedback pin of the low dropout linear power supply chip is connected in series to a second resistor and a third resistor, the first resistor is connected to the second resistor, the input pin of the low dropout linear power supply chip is connected to a ground pin and then connected to the third resistor, and an output of the switch module is connected to a connection line between the second resistor and the third resistor.

4. The universal input interface circuit as claimed in claim 1, wherein the switch module employs a field effect transistor, a source of the field effect transistor is grounded, a drain of the field effect transistor is connected to the threshold voltage generation module, and a gate of the field effect transistor is used as a control terminal of the field effect transistor.

5. The universal input interface circuit as claimed in any of claims 1-4, wherein the logic level of the output of the differential receiving module is:

VI is the voltage value of the input interface, X is an unstable logic level, and TH is a differential input threshold of the differential receiving module.

Technical Field

The invention relates to the technical field of interface circuits, in particular to a universal input interface circuit.

Background

The general input interface used in the industrial field has complex and diversified level formats, and the threshold voltages of the interface circuits required by different level formats have great difference. For example, the logic low level voltage range of the universal input signal in the LVCMOS18 level format is 0V-0.6V, and the logic high level voltage range is 1.2V-1.8V, and the interface circuit threshold required by the level format should be between 0.6V-1.2V; for example, a general input signal in a PLC24V level format, which has a logic low level voltage range of 0V-4V and a logic high level voltage range of 20V-24V, should have an interface circuit threshold value between 4V-20V. If threshold voltages of multiple compatible level formats exist in an overlapping region, the interface circuit threshold voltage is set in the overlapping region, so that the interface circuit can adapt to multiple different level formats, but noise tolerance of input signals of different level formats is reduced, large noise interference often exists in an industrial production environment, and the low noise tolerance can cause frequent error jump of the logic level of an output end of the input interface circuit to influence the performance of a later-stage circuit.

The general input interface circuit designed based on the prior art can not adjust the threshold voltage, a plurality of sets of different interface circuits are required to be designed to receive general input signals with different level formats, and even if a single set of circuit is compatible with a plurality of interfaces, the noise tolerance is low; or the threshold voltage can be adjusted, but the circuit structure is complex, and the circuit cost and power consumption are large.

Disclosure of Invention

The invention aims to provide a universal input interface circuit, which aims to solve the problem that the existing input interface circuit cannot adjust the threshold voltage.

To achieve the above object, there is provided a general input interface circuit including: the differential receiving module comprises an input interface, a threshold voltage generating module, a differential receiving module and a switch module, wherein the positive and negative differential input ends of the differential receiving module are respectively connected to the output of the input interface and the output of the threshold voltage generating module, and the output of the switch module is connected to the threshold voltage generating module.

Optionally, the threshold voltage generating module includes a voltage-adjustable power supply unit and a dc power supply, the dc power supply input is connected to the voltage-adjustable power supply unit, the output of the voltage-adjustable power supply unit is connected to one of the positive differential input terminal and the negative differential input terminal of the differential receiving module, and the input of the voltage-adjustable power supply unit is connected to the output of the switch module.

Optionally, the voltage-adjustable power supply unit includes a low-dropout linear power supply chip, an input pin of the low-dropout linear power supply chip is connected to the input of the dc power supply, an output pin of the low-dropout linear power supply chip is connected to a first resistor, a feedback pin of the low-dropout linear power supply chip is connected in series to a second resistor and a third resistor, the first resistor is connected to the second resistor, the input pin of the low-dropout linear power supply chip is connected to a ground pin and then connected to the third resistor, and an output of the switch module is connected to a connection line between the second resistor and the third resistor.

Optionally, the switch module adopts a field effect transistor, a source electrode of the field effect transistor is grounded, a drain electrode of the field effect transistor is connected with the threshold voltage generation module, and a grid electrode of the field effect transistor is used as a control end of the field effect transistor.

Optionally, the logic level of the output end of the differential receiving module is:

VI is a voltage value of the general input interface, X is an unstable logic level, and TH is a differential input threshold of the differential receiving module.

Compared with the prior art, the invention has the following technical effects: the input interface circuit provided by the invention is provided with an input interface, a threshold voltage generation module, a differential receiving module and a switch module, wherein the positive and negative differential input ends of the differential receiving module are respectively connected to the output of the input interface and the output of the threshold voltage generation module, and the output of the switch module is connected to the threshold voltage generation module. The output voltage of the threshold voltage generation module is adjusted by switching the on/off state of the switch module, so that the dynamic adjustment of the threshold voltage is realized.

Drawings

The following detailed description of embodiments of the invention refers to the accompanying drawings in which:

FIG. 1 is a block diagram of a universal input interface circuit according to the present invention;

FIG. 2 is a block diagram of a universal input interface circuit according to the present invention.

In the figure:

10-a differential receiving module; 20-an input interface; 30-a threshold voltage generation module; 40-a switch module.

Detailed Description

To further illustrate the features of the present invention, refer to the following detailed description of the invention and the accompanying drawings. The drawings are for reference and illustration purposes only and are not intended to limit the scope of the present disclosure.

As shown in fig. 1, the present embodiment discloses a universal input interface circuit, which includes: the differential receiving module 10 comprises an input interface 20, a threshold voltage generating module 30, a differential receiving module 10 and a switch module 40, wherein the positive and negative differential inputs of the differential receiving module 10 are respectively connected to the output of the input interface 20 and the output of the threshold voltage generating module 30, and the output of the switch module 40 is connected to the threshold voltage generating module 30.

It should be noted that, in this embodiment, the dynamic adjustment of the output voltage of the threshold voltage generation module 30 is realized by controlling the on/off state switching of the switch module 40, and the circuit structure is simple.

Further, the threshold voltage generating module 30 includes a voltage-adjustable power supply unit and a dc power supply, wherein an input of the dc power supply is connected to the voltage-adjustable power supply unit, an output of the voltage-adjustable power supply unit is connected to one of a positive differential input terminal and a negative differential input terminal of the differential receiving module 10, and an input of the voltage-adjustable power supply unit is connected to an output of the switch module 40.

Further, as shown in fig. 2, the voltage-adjustable power supply unit includes a low-dropout linear power supply chip, an input pin 1 of the low-dropout linear power supply chip is connected to the dc power supply input VIN, an output pin 3 of the low-dropout linear power supply chip is connected to a first resistor R1, a feedback pin 4 of the low-dropout linear power supply chip is connected in series to a second resistor R2 and a third resistor R3, the first resistor R1 is connected to the second resistor R2, the input pin 1 of the low-dropout linear power supply chip is connected to a ground pin 2 and then connected to a third resistor R3, and an output of the switch module is connected to a connection line between the second resistor R2 and the third resistor R3; the output pin 3 of the low-dropout linear power supply chip is also connected with a first capacitor Cout, and a second capacitor Cin is connected in series between the input pin of the low-dropout linear power supply chip and the third resistor R3.

It should be noted that the present embodiment adjusts the output voltage by providing a resistor network composed of resistors R1, R2, and R3.

Further, the switch module 40 is a field effect transistor, and an N-type MOSFET field effect transistor is used, and includes three electrodes, namely a gate (G), a drain (D), and a source (S), where the source is connected to Ground (GND), the drain is used as an output of the switch module 40, and is connected to a connection between the second resistor R2 and the third resistor R3, and the gate is used as a control terminal of the switch module 40.

It should be noted that when the gate voltage value is greater than the switching voltage threshold of the MOSFET, D to S are turned on, the fet is in a closed state, the voltage-adjustable power supply unit outputs Vout ═ Vadj (R1+ R2)/R2, where Vadj is a reference voltage of the low dropout linear power supply chip, and when the gate voltage value is less than the switching voltage threshold of the MOSFET, D to S are turned off, the fet is in an open state, and the voltage-adjustable power supply unit outputs Vout ═ Vadj (R1+ R2+ R3)/(R2+ R3), so as to implement the adjustable voltage output Vout.

Further, the differential input threshold of the differential receiving module 10 is TH, and when the voltage value of the positive differential input terminal is higher than the voltage value of the negative differential input terminal by TH, the output terminal outputs a logic level 1; when the voltage value of the positive end of the differential input is lower than the voltage value of the negative end of the differential input by TH, the output end outputs a logic level 0. I.e. the output of the threshold voltage generating module 30 is connected to the other end.

The logic level of the output end of the differential receiving module 10 is:

where VI is the voltage value of the input interface 20 and X is the unstable logic level.

It should be noted that, in the embodiment, when the gate voltage value is greater than the switching voltage threshold of the MOSFET field effect transistor, the switch module 40 is in the on state, and when the gate voltage value is less than the switching voltage threshold of the MOSFET field effect transistor, the switch module 40 is in the off state, by controlling the on/off state switching of the switch module 40, the dynamic adjustment of the output voltage of the threshold voltage generation module 30 is realized, and the circuit structure is simple and reliable.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.