Analog voltage isolation circuit

Abstract

The utility model discloses an analog voltage isolation circuit, which belongs to the field of analog voltage isolation and comprises a first isolation unit and a second isolation unit, the first isolation unit and the second isolation unit are sequentially connected to the front end of a micro control unit (MCU), and a primary filter circuit is arranged between the first isolation unit and a voltage input end. An operational amplifier U3A is arranged between the second isolation unit and the micro-control unit MCU, a secondary filter circuit is arranged between the second isolation unit and the operational amplifier U3A, and the operational amplifier U3A is provided with a voltage output end connected with the micro-control unit MCU. The first isolation unit and the second isolation unit are arranged at the front end of the micro-control unit MCU, and the first-stage filter circuit, the second-stage filter circuit and the operational amplifier U3A are combined, so that the isolation degree and the anti-interference capability of analog voltage signals are remarkably improved, and it is ensured that signal transmission from the voltage input end to the micro-control unit is stable and safe.

Description

Technical Field

[0001] The utility model belongs to the field of analog voltage isolation, and specifically relates to an analog voltage isolation circuit. Background Art

[0002] In many application scenarios in the modern industrial field, the real-time acquisition and processing of analog voltages are key links for achieving precise control and automated operation. With the continuous improvement of industrial automation, the system needs to frequently and highly accurately process a large number of analog signals, which poses higher requirements for the processing ability and stability of the microcontroller unit (MCU). As the core control component of the system, the MCU not only has to efficiently execute complex control algorithms but also manage numerous analog inputs simultaneously, which often results in an extremely high operating load.

[0003] For example, the patent with the publication number CN109507466A discloses a high-precision linear isolation sampling device, which includes: a voltage-to-frequency module. Through the AD650 and its peripheral circuits, the input voltage is converted into an output frequency. After passing through a capacitor and an isolation transformer, the ground of the output circuit and the input circuit is isolated.

[0004] However, in the actual industrial environment, analog voltage signals are extremely vulnerable to various factors such as electromagnetic interference and power supply fluctuations. Once these external interferences are coupled into the sensitive analog circuit, they will not only reduce the accuracy of the signal but may even cause problems such as MCU misoperation, data processing errors, and even system crashes in severe cases, affecting the reliability and safety of the device. Relying solely on the voltage-to-frequency conversion module cannot cope with this situation. In view of this, it is particularly important to take effective isolation measures to protect the MCU from external analog voltage interference. Summary of the Utility Model

[0005] The technical problem to be solved by the utility model is to overcome the deficiencies of the prior art and provide an analog voltage isolation circuit.

[0006] To solve the defect of insufficient isolation effect in the prior art, the technical solution of the utility model is as follows:

[0007] An analog voltage isolation circuit includes a first isolation unit and a second isolation unit. The first isolation unit and the second isolation unit are sequentially connected to the front end of the microcontroller unit MCU. There is a primary filter circuit between the first isolation unit and the voltage input terminal. There is an operational amplifier U3A between the second isolation unit and the microcontroller unit MCU. There is a secondary filter circuit between the second isolation unit and the operational amplifier U3A. A voltage output terminal connected to the microcontroller unit MCU is provided on the operational amplifier U3A.

[0008] Preferably, the first isolation unit is an APC chip U1, the second isolation unit is an optocoupler U2, and the APC chip U1 and the optocoupler U2 are sequentially connected to the front end of an operational amplifier U3A.

[0009] Preferably, a voltage input terminal is connected to the 3rd pin of the APC chip U1, and a resistor R1 is provided between the 3rd pin of the APC chip U1 and the negative power supply terminal.

[0010] Preferably, the 4th pin of the APC chip U1 is connected to the positive power supply terminal. The first-stage filtering circuit includes a filtering capacitor C1 and a filtering capacitor E1 provided between the 4th pin of the APC chip U1 and the negative power supply terminal, and the filtering capacitor C1 and the filtering capacitor E1 are connected in parallel with each other.

[0011] Preferably, the 5th pin of the APC chip U1 is grounded, and the 8th pin of the APC chip U1 is grounded through a capacitor C2.

[0012] Preferably, the 6th pin of the APC chip U1 is connected to the A pole of the optocoupler U2 through a resistor R2.

[0013] Preferably, the K pole of the optocoupler U2 is grounded, the C pole of the optocoupler U2 is connected to the positive supply voltage terminal, and the E pole of the optocoupler U2 is connected to the second-stage filtering circuit.

[0014] Preferably, the 1st pin of the operational amplifier U3A is the voltage output terminal of the isolation circuit. The 2nd pin of the operational amplifier U3A is connected to the 1st pin of the operational amplifier U3A, and the 3rd pin of the operational amplifier U3A is connected to the optocoupler U2 through the second-stage filtering circuit.

[0015] Preferably, the second-stage filtering circuit includes a resistor R4 and a resistor R5 connected in series between the optocoupler U2 and the 3rd pin of the operational amplifier U3A. The second-stage filtering circuit further includes a resistor R3, a capacitor C3, and a capacitor C4. One end of the resistor R3 is connected to the 4th pin of the operational amplifier U3A, and the other end is connected between the resistor R4 and the E pole of the optocoupler U2. One end of the capacitor C3 is connected to the 4th pin of the operational amplifier U3A, and the other end is connected between the resistor R4 and the resistor R5. One end of the resistor R3 is connected to the 4th pin of the operational amplifier U3A, and the other end is connected between the resistor R5 and the 3rd pin of the operational amplifier U3A.

[0016] Preferably, the 4th pin of the operational amplifier U3A is grounded, and the 8th pin of the operational amplifier U3A is connected to the positive supply voltage terminal.

[0017] After adopting the above technical solution, an analog voltage isolation circuit provided by the present utility model has the following beneficial effects compared with the prior art.

[0018] (1) By setting a first isolation unit and a second isolation unit at the front end of the microcontroller unit (MCU), combined with a first-stage and a second-stage filter circuit and operational amplifier U3A, the isolation degree and anti-interference ability of the analog voltage signal are significantly improved, ensuring stable and safe signal transmission from the voltage input terminal to the microcontroller unit. The design of two-stage filtering effectively filters out the noise of the acquisition line and the isolation circuit itself, improving the stability of the circuit.

[0019] (2) By using the APC chip U1 as the first isolation unit and the optocoupler U2 as the second isolation unit, efficient electrical isolation of the signals in the circuit is achieved, effectively preventing damage to the microcontroller unit caused by high voltage or abnormal voltage.

[0020] (3) By directly connecting the pin 3 of the APC chip U1 to the voltage input terminal and configuring the resistor R1 for current limiting protection, this design simplifies the circuit structure and provides preliminary voltage stabilization and protection measures for the input signal, ensuring the stability and durability of the circuit in the face of transient voltage impact.

[0021] The following further describes in detail the specific implementation manners of the present utility model in conjunction with the accompanying drawings. Description of the Drawings

[0022] The accompanying drawings, as a part of the present utility model, are used to provide a further understanding of the present utility model. The schematic embodiments of the present utility model and their descriptions are used to explain the present utility model, but do not constitute an improper limitation to the present utility model. Obviously, the accompanying drawings in the following description are only some embodiments, and those of ordinary skill in the art can obtain other drawings based on these drawings without creative efforts. In the drawings:

[0023] Figure 1 is a schematic diagram of the isolation circuit of the present utility model.

[0024] It should be noted that these drawings and text descriptions are not intended to limit the scope of the concept of the present utility model in any way, but to illustrate the concept of the present utility model to those skilled in the art by referring to specific embodiments. Specific Embodiments

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present utility model clearer, the technical solutions in the embodiments of the present utility model will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present utility model. The following embodiments are used to illustrate the present utility model, but are not used to limit the scope of the present utility model.

[0026] In the description of the present utility model, it should be noted that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present utility model.

[0027] In the description of the present utility model, it should be noted that unless otherwise clearly specified and limited, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood according to specific circumstances.

[0028] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present utility model, the meaning of "a plurality" is two or more unless otherwise clearly and specifically defined.

[0029] As Figure 1 shown, the present utility model provides an analog voltage isolation circuit, which includes a first isolation unit and a second isolation unit. The first isolation unit and the second isolation unit are sequentially connected to the front end of a microcontroller unit (MCU). A first-stage filtering circuit is provided between the first isolation unit and the voltage input terminal. An operational amplifier U3A is provided between the second isolation unit and the microcontroller unit (MCU). A second-stage filtering circuit is provided between the second isolation unit and the operational amplifier U3A. A voltage output terminal connected to the microcontroller unit (MCU) is provided on the operational amplifier U3A.

[0030] By providing the first isolation unit and the second isolation unit at the front end of the microcontroller unit (MCU), in combination with the first-stage and second-stage filtering circuits and the operational amplifier U3A, the isolation degree and anti-interference ability of the analog voltage signal are significantly improved, ensuring stable and safe signal transmission from the voltage input terminal to the microcontroller unit. The design of two-stage filtering effectively filters out the noise of the acquisition line and the isolation circuit itself, improving the stability of the circuit.

[0031] The first isolation unit is an APC chip U1, and the second isolation unit is an optocoupler U2. The APC chip U1 and the optocoupler U2 are sequentially connected to the front end of the operational amplifier U3A.

[0032] By adopting the APC chip U1 as the first isolation unit and the optocoupler U2 as the second isolation unit, efficient electrical isolation of signals in the circuit is achieved, effectively preventing damage to the microcontroller unit caused by high voltage or abnormal voltage.

[0033] Furthermore, the 3rd pin of the APC chip U1 is connected to a voltage input terminal, and a resistor R1 is provided between the 3rd pin of the APC chip U1 and the negative power supply terminal.

[0034] The 3rd pin of the APC chip U1 is directly connected to the voltage input terminal, and the resistor R1 is configured for current limiting protection. The resistor R1 is a pull-down resistor with a relatively large resistance value, providing a high impedance for the external input, generally above 10k, providing preliminary voltage regulation and protection measures for the input signal, and ensuring the stability and durability of the circuit in the face of transient voltage impacts.

[0035] The 4th pin of the APC chip U1 is connected to the positive power supply terminal. The first-stage filtering circuit includes a filtering capacitor C1 and a filtering capacitor E1 provided between the 4th pin of the APC chip U1 and the negative power supply terminal, and the filtering capacitor C1 and the filtering capacitor E1 are connected in parallel with each other.

[0036] The first-stage filtering circuit added on the power supply line of the APC chip U1, which is composed of the filtering capacitors C1 and E1 in parallel, can effectively suppress power supply ripple, ensure that the chip works in a cleaner power supply environment, and further improve the anti-interference performance and long-term working stability of the circuit.

[0037] The 5th pin of the APC chip U1 is grounded, and the 8th pin of the APC chip U1 is grounded through a capacitor C2.

[0038] Specifically, the chip model of the APC chip U1 is GP9301B. Its 3rd pin is the input signal pin, responsible for processing external analog voltage or current signals, including functions such as filtering and amplification to ensure the purity and amplitude of the signal are suitable for subsequent processing. It can convert the analog signal into a low-frequency PWM signal, convert different voltage values into PWM signals with different duty cycles, and also integrate an LDO inside to supply power to the optocoupler.

[0039] The 6th pin of the APC chip U1 is connected to the internal PWM generator of the chip, used to generate an accurate pulse width modulation signal, used to control the switching frequency and duty cycle of the switching power supply, thereby adjusting the output voltage or current.

[0040] Preferably, the 6th pin of the APC chip U1 is connected to the A pole of the optocoupler U2 through a resistor R2.

[0041] The K pole of the optocoupler U2 is grounded, the C pole of the optocoupler U2 is connected to the positive power supply voltage, and the E pole of the optocoupler U2 is connected to the second-stage filtering circuit.

[0042] Specifically, the specific model of optocoupler U2 is TLP291. It has an isolation function, and the highest transmission frequency can reach 1Mhz. It mainly consists of two parts: the transmitting part (input side) and the receiving part (output side). The receiving part is a light-emitting diode, and the transmitting part is a phototransistor. These two parts achieve isolated transmission of electrical signals through the transmission of light without generating direct electrical connection. The transmitting part includes the A pole and the K pole, that is, the anode and cathode of the light-emitting diode. When receiving the signal sent from pin 6 of APC chip U1, the light-emitting diode will be lit. The transmitting part includes the collector (C pole), the emitter (E pole), and the base (not directly exposed). The base does not appear as an external pin but is internally connected to the photodiode and is used to receive the optical signal emitted by the light-emitting diode and transmitted through the isolation medium, thereby controlling the on or off state of the phototransistor.

[0043] When a sufficient forward voltage is applied to the input side, the LED emits light, and the generated light passes through the insulating material (usually epoxy resin or other light-conducting materials) inside the optocoupler. This process achieves electrical isolation because light energy is not affected by electromagnetic interference and does not conduct electricity. The change in current on the input side will cause the transistor on the output side to conduct or cut off, thereby forming a change in high and low levels in the output circuit and realizing the transmission of logic signals. Its working state depends on the magnitude of the input current. By adjusting the input current, the conduction degree of the transistor on the output side can be controlled, and thus the intensity or threshold of the output signal can be controlled.

[0044] Preferably, pin 1 of operational amplifier U3A is the voltage output terminal of the isolation circuit. Pin 2 of operational amplifier U3A is connected to pin 1 of operational amplifier U3A. Pin 3 of operational amplifier U3A is connected to optocoupler U2 through a secondary filtering circuit.

[0045] Preferably, the secondary filtering circuit includes resistor R4 and resistor R5 connected in series between optocoupler U2 and pin 3 of operational amplifier U3A. The secondary filtering circuit also includes resistor R3, capacitor C3, and capacitor C4. One end of resistor R3 is connected to pin 4 of operational amplifier U3A, and the other end is connected between resistor R4 and the E pole of optocoupler U2. One end of capacitor C3 is connected to pin 4 of operational amplifier U3A, and the other end is connected between resistor R4 and resistor R5. One end of resistor R3 is connected to pin 4 of operational amplifier U3A, and the other end is connected between resistor R5 and pin 3 of operational amplifier U3A.

[0046] Pin 4 of operational amplifier U3A is grounded, and pin 8 of operational amplifier U3A is connected to the positive pole of the supply voltage. Operational amplifier U3A forms a voltage follower, providing a high input impedance for the previous stage, and the output can be directly introduced into the MCU.

[0047] In the description of this specification, the descriptions referring to terms such as "one embodiment", "some embodiments", "examples", "specific examples", or "some examples", etc., mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present utility model. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0048] The above are only the preferred embodiments of the present utility model, and do not impose any form of limitation on the present utility model. Although the present utility model has been disclosed above with the preferred embodiments, it is not intended to limit the present utility model. Any person skilled in the art of this patent, without departing from the scope of the technical solution of the present utility model, can make some changes or modifications using the technical content prompted above to be equivalent embodiments of equivalent changes. The implementation schemes in the above embodiments can also be further combined or replaced. However, as long as the content does not depart from the technical solution of the present utility model, any simple modification, equivalent change, and modification made to the above embodiments according to the technical essence of the present utility model still fall within the scope of the present utility model's solution.

Claims

1. An analog voltage isolation circuit, characterized in that: It includes a first isolation unit and a second isolation unit, which are connected to the front end of a microcontroller unit MCU in sequence, a primary filtering circuit is provided between the first isolation unit and the voltage input terminal, an operational amplifier U3A is provided between the second isolation unit and the microcontroller unit MCU, a secondary filtering circuit is provided between the second isolation unit and the operational amplifier U3A, and a voltage output terminal connected to the microcontroller unit MCU is provided on the operational amplifier U3A.

2. The analog voltage isolation circuit according to claim 1, characterized in that: The first isolation unit is an APC chip U1, and the second isolation unit is an optical coupler U2. The APC chip U1 and the optical coupler U2 are sequentially connected to the front end of the operational amplifier U3A.

3. The analog voltage isolation circuit according to claim 2, characterized in that: Pin No. 3 of the APC chip U1 is connected to a voltage input terminal, and a resistor R1 is provided between pin No. 3 of the APC chip U1 and the negative electrode of the power supply.

4. The analog voltage isolation circuit according to claim 2, characterized in that: Pin No. 4 of the APC chip U1 is connected to the positive pole of the power supply, and the primary filtering circuit includes a filter capacitor C1 and a filter capacitor E1 arranged between pin No. 4 of the APC chip U1 and the negative pole of the power supply, and the filter capacitor C1 and the filter capacitor E1 are arranged in parallel with each other.

5. The analog voltage isolation circuit according to claim 2, characterized in that: Pin 5 of the APC chip U1 is grounded, and pin 8 of the APC chip U1 is grounded via a capacitor C2.

6. The analog voltage isolation circuit according to claim 2, characterized in that: Pin 6 of the APC chip U1 is connected to the A pole of the optocoupler U2 via the resistor R2.

7. The analog voltage isolation circuit according to claim 6, characterized in that: The K pole of the optical coupler U2 is grounded, the C pole of the optical coupler U2 is connected to the positive pole of the power supply voltage, and the E pole of the optical coupler U2 is connected to the secondary filtering circuit.

8. The analog voltage isolation circuit according to claim 7, characterized in that: Pin 1 of the operational amplifier U3A is the voltage output terminal of the isolation circuit, pin 2 of the operational amplifier U3A is connected to pin 1 of the operational amplifier U3A, and pin 3 of the operational amplifier U3A is connected to the optocoupler U2 through a secondary filtering circuit.

9. The analog voltage isolation circuit according to claim 8, characterized in that: The secondary filtering circuit includes a resistor R4 and a resistor R5 which are arranged in series between the optocoupler U2 and the pin No. 3 of the operational amplifier U3A. The secondary filtering circuit also includes a resistor R3, a capacitor C3 and a capacitor C4. One end of the resistor R3 is connected to the pin No. 4 of the operational amplifier U3A and the other end is connected to the resistor R4 and the E pole of the optocoupler U2. One end of the capacitor C3 is connected to the pin No. 4 of the operational amplifier U3A and the other end is connected to between the resistor R4 and the resistor R5. One end of the resistor R3 is connected to the pin No. 4 of the operational amplifier U3A and the other end is connected to between the resistor R5 and the pin No. 3 of the operational amplifier U3A.

10. The analog voltage isolation circuit according to claim 8, characterized in that: Pin 4 of the operational amplifier U3A is grounded, and pin 8 of the operational amplifier U3A is connected to the positive pole of the power supply voltage.

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