Isolated voltage detection circuit

Abstract

The utility model provides an isolation type voltage detection circuit comprising an isolation module which is connected with a non-isolation bus circuit and an isolation weak current circuit and comprises an adjustable resistor; wherein at least part of the adjustable resistor is connected in series to the isolated weak current circuit, and the size of the adjustable resistor is changed through the change of the bus voltage of the non-isolated bus circuit. The technical problems that in the prior art, for the detection condition that weak current is isolated and strong current is non-isolated, isolation detection needs to be conducted through an isolation type linear optocoupler or an isolation type operational amplifier, the circuit is complex, interference is likely to happen, and reliability is low are solved.

Description

Technical Field

[0001] This utility model relates to the field of voltage detection technology, and more specifically, to an isolated voltage detection circuit. Background Technology

[0002] Current air conditioner controllers generally require DC bus voltage detection to achieve precise control of DC motors, compressors, or other functional logic. Conventional voltage detection methods involve using multiple resistors to divide and reduce the voltage, with the controller's MCU detecting the small voltage drop at the next stage to determine the overall voltage. This method requires a common ground for both high and low voltage circuits to measure the bus voltage. Specifically, the GND of the low-voltage components (such as the 5V or 3.3V-powered MCU on the controller) must be connected to the same ground as the high-voltage bus. This approach is unsuitable for scenarios where the low-voltage circuits are isolated while the high-voltage circuits are not, making a common ground impossible.

[0003] For situations where low-voltage circuits are isolated while high-voltage circuits are not, isolation voltage detection is typically achieved using isolated linear optocouplers or isolated operational amplifiers. This approach involves complex external circuitry, requires sophisticated component selection and calculations, demands high standards for layout and wiring, is susceptible to interference, has low reliability, and poor versatility.

[0004] Therefore, the relevant technologies have at least one of the following problems: In the prior art, for the detection of weak currents that are isolated while strong currents are not isolated, isolation detection is required through isolated linear optocouplers or isolated operational amplifiers, which results in complex circuits, susceptibility to interference, and low reliability. Utility Model Content

[0005] This invention addresses the technical problem in the prior art that, for situations where weak current is isolated but strong current is not, isolation detection requires the use of isolated linear optocouplers or isolated operational amplifiers, resulting in complex circuits, susceptibility to interference, and low reliability.

[0006] To address the aforementioned problems, this utility model provides an isolated voltage detection circuit, comprising: an isolation module, which connects a non-isolated bus circuit and an isolated low-voltage circuit, and the isolation module includes an adjustable resistor; wherein at least a portion of the adjustable resistor is connected in series in the isolated low-voltage circuit, and the magnitude of the adjustable resistor is changed by the change in the bus voltage of the non-isolated bus circuit.

[0007] Compared with existing technologies, the technical effects achieved by this solution are as follows: By changing the magnitude of the bus voltage in the non-isolated bus circuit, the adjustable resistor connected in series in the isolated low-voltage circuit is transformed into a change in resistance in the isolated low-voltage circuit. This converts the change in bus voltage on the non-isolated side into a change in low-voltage voltage on the isolated side, enabling electromagnetic isolation between strong and weak currents while detecting the bus voltage. This application can realize bus voltage detection between two circuits: a non-grounded isolated low-voltage circuit and a non-isolated bus circuit. It avoids the risk of electric shock to humans in existing strong and weak current common-ground detection schemes, improving safety and compatibility with safety regulations in various countries. Furthermore, compared with existing complex and interference-prone isolated detection circuits such as linear optocouplers and isolation amplifiers, it improves reliability.

[0008] In one embodiment of this utility model, the isolated low-voltage circuit is provided with a low-voltage terminal and an isolated ground terminal; the adjustable resistor is provided with a sliding contact and a fixed terminal, the sliding contact is connected to the low-voltage terminal, and the fixed terminal is connected to the isolated ground terminal; wherein, the position of the sliding contact is changed by the change of the bus voltage; the fixed terminal is also connected to the microcontroller through a voltage divider.

[0009] Compared with existing technologies, the technical effects achieved by this technical solution are as follows: The adjustable resistor is equipped with a sliding contact and a fixed end, with the fixed end connected to the isolation ground. By changing the position of the sliding contact through the change of the bus voltage, the resistance value connected to the isolation low-voltage circuit is changed, and the voltage drop detected by the microcontroller also changes accordingly, thereby enabling the identification of the current value of the bus voltage.

[0010] In one embodiment of this utility model, the non-isolated bus circuit is provided with a bus voltage terminal and a non-isolated ground terminal. The isolation module further includes: an iron core with a coil wound around it, the two ends of which are respectively connected to the bus voltage terminal and the non-isolated ground terminal; a metal slider connected between a sliding contact and a low-voltage terminal; and a spring connected between the metal slider and the low-voltage terminal. When the non-isolated bus circuit is turned on, the coil generates a magnetic field, and the magnitude of the magnetic field is changed by the change of the bus voltage.

[0011] Compared with existing technologies, the technical effects achieved by this solution are as follows: When the non-isolated bus circuit is not connected, the metal slider is in its initial position; when the non-isolated bus circuit is connected, the coil is energized and generates a magnetic field, which attracts the metal slider. The magnitude of the attraction varies with the bus voltage. The metal slider slides to different positions of the adjustable resistor according to the different magnitudes of the attraction, thereby changing the length of the adjustable resistor connected in the isolated low-voltage circuit and changing the resistance value of the adjustable resistor connected in the isolated low-voltage circuit. A spring is set to connect the metal slider to control the range of movement of the metal slider, preventing the metal slider from making large displacements. At the same time, when the coil is de-energized, the spring force can be used to restore the metal slider to its initial position.

[0012] In one embodiment of this utility model, the axis of the iron core, the axis of the spring, and the center of the metal slider are located on the same straight line.

[0013] Compared with existing technologies, the technical effects achieved by this technical solution are as follows: the axis of the iron core, the axis of the spring, and the center of the metal slider are located on the same straight line, which enables the metal slider to move in a straight line and the spring to deform in the same straight line, thereby improving the stability of the movement of the metal slider and the spring.

[0014] In one embodiment of this utility model, the non-isolated bus circuit includes: a first current limiting structure, which is connected in series between the coil and the bus voltage terminal.

[0015] Compared with existing technologies, the technical effects achieved by adopting this technical solution are as follows: The first current limiting structure is used to limit the current in the non-isolated bus circuit to prevent excessive current from burning out or affecting normal operation.

[0016] In one embodiment of this utility model, the first current limiting structure includes a first resistor and a second resistor connected in series, and the bus voltage terminal is connected in sequence through the first resistor, the second resistor and the coil.

[0017] Compared with existing technologies, the technical effect achieved by adopting this technical solution is: the current in the non-isolated bus circuit is further limited by the first and second resistors connected in series.

[0018] In one embodiment of this utility model, the isolation low-voltage circuit further includes a freewheeling diode, which is connected in parallel to both ends of the coil.

[0019] Compared with existing technologies, the technical effect achieved by this technical solution is as follows: when the non-isolated bus circuit is cut off, the coil is de-energized, and its reverse electromotive force is eliminated through the freewheeling diode.

[0020] In one embodiment of this utility model, the isolation low-voltage circuit includes: a third resistor connected in series between the spring and the low-voltage terminal; and a fourth resistor connected in series between the isolation ground terminal of the fixed terminal.

[0021] Compared with existing technologies, the technical effects achieved by adopting this technical solution are as follows: the third resistor serves as the upper voltage divider resistor, and the fourth resistor serves as the lower voltage divider resistor. The third and fourth resistors are specifically used for voltage division in isolated low-voltage circuits.

[0022] In one embodiment of this utility model, the voltage divider includes: a fifth resistor connected between the fixed terminal and the microcontroller; and a first capacitor, one end of which is connected to the non-isolated ground terminal, and the other end of which is connected to the microcontroller.

[0023] Compared with the existing technology, the technical effects achieved by adopting this technical solution are as follows: In addition to being connected to the isolation ground terminal via the fourth resistor, the fixed terminal of the adjustable resistor is also connected to the microcontroller via the fifth resistor and the first capacitor. The fifth resistor is a current-limiting resistor used for current limiting; the first capacitor is a filter capacitor used for filtering.

[0024] By adopting the technical solution of this utility model, the following technical effects can be achieved:

[0025] (1) This application can realize bus voltage detection between two circuits: isolated weak current circuit and non-isolated bus circuit, which avoids the risk of electric shock to the human body in the existing strong and weak current common ground detection scheme, improves safety and compatibility with safety regulations of various countries, and improves reliability compared with the existing linear optocoupler and isolation amplifier, which are complex and susceptible to interference.

[0026] (2) By changing the position of the sliding contact through the change of the bus voltage, the resistance value in the isolated weak current circuit is changed, and the voltage drop detected by the microcontroller also changes accordingly, so that the current value of the bus voltage can be identified.

[0027] (3) The axis of the iron core, the axis of the spring, and the center of the metal slider are on the same straight line, which enables the metal slider to move on a straight line and the spring to deform on the same straight line, thereby improving the stability of the movement of the metal slider and the spring. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings to be used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of an isolated voltage detection circuit provided in Embodiment 1 of this utility model;

[0030] Figure 2 for Figure 1 A schematic diagram of the structure of the isolation module.

[0031] Explanation of reference numerals in the attached figures:

[0032] 1. Isolation module; 2. Non-isolated bus circuit; 21. Bus voltage terminal; 22. Non-isolated ground terminal; 3. Isolation low-voltage circuit; 31. Low-voltage terminal; 32. Isolation ground terminal; 100. Adjustable resistor; 110. Sliding contact; 120. Fixed terminal; 200. Iron core; 210. Coil; 211. First terminal; 212. Second terminal; 300. Metal slider; 400. Spring. Detailed Implementation

[0033] To make the above-mentioned objectives, features, and advantages of this utility model more apparent and understandable, the technical solutions in the embodiments of this utility model are clearly and completely described. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0034] Example 1

[0035] See Figure 1 This utility model provides an isolated voltage detection circuit, which includes an isolation module 1, which is connected to a non-isolated bus circuit 2 and an isolated low-voltage circuit 3, and the isolation module 1 includes an adjustable resistor 100; wherein, at least a portion of the adjustable resistor 100 is connected in series to the isolated low-voltage circuit 3, and the value of the adjustable resistor 100 is changed by the change of the bus voltage of the non-isolated bus circuit 2.

[0036] In one specific embodiment, the magnitude of the bus voltage of the non-isolated bus circuit 2 is used to change the value of the adjustable resistor 100 connected in series in the isolated weak current circuit 3. This converts the voltage change of the bus voltage into a change in the resistance of the isolated weak current circuit 3, thereby converting the change in the non-isolated side bus voltage into a change in the isolated side weak current voltage. This enables electromagnetic isolation between strong and weak current circuits while detecting the bus voltage. This application can realize bus voltage detection between the isolated weak current circuit 3 and the non-isolated bus circuit 2, which are not grounded. It avoids the risk of electric shock to the human body in existing strong and weak current grounded detection schemes, improves safety and compatibility with safety regulations of various countries, and improves reliability compared with existing complex and interference-prone isolated detection circuits such as linear optocouplers and isolation amplifiers.

[0037] Furthermore, the isolated low-voltage circuit 3 is provided with a low-voltage terminal 31 and an isolated ground terminal 32; the adjustable resistor 100 is provided with a sliding contact 110 and a fixed terminal 120, the sliding contact 110 is connected to the low-voltage terminal 31, and the fixed terminal 120 is connected to the isolated ground terminal 32; wherein, the position of the sliding contact 110 is changed by the change of the bus voltage; the fixed terminal 120 is also connected to the microcontroller through a voltage divider section.

[0038] Specifically, the MCU is a microcontroller, and the adjustable resistor 100 can be a resistance wire wound on a ceramic cylinder. The length of the resistance wire determines the resistance value connected to the isolated low-voltage circuit 3. The adjustable resistor 100 is provided with a sliding contact 110 and a fixed end 120. The fixed end 120 is connected to the isolation ground end 32. By changing the position of the sliding contact 110 through the change of the bus voltage, the resistance value connected to the isolated low-voltage circuit 3 is changed, and the voltage drop detected by the MCU also changes accordingly, so that the current value of the bus voltage can be identified.

[0039] Furthermore, the non-isolated bus circuit 2 is provided with a bus voltage terminal 21 and a non-isolated ground terminal 22, see [reference]. Figure 2 The isolation module 1 also includes: an iron core 200, a metal slider 300, and a spring 400. The iron core 200 is wound with a coil 210, and the two ends of the coil 210 are respectively connected to the bus voltage terminal 21 and the non-isolated ground terminal 22. The metal slider 300 is connected between the sliding contact 110 and the weak voltage terminal 31. The spring 400 is connected between the metal slider 300 and the weak voltage terminal 31. When the non-isolated bus circuit 2 is turned on, the coil 210 generates a magnetic field, and the magnitude of the magnetic field is changed by the change of the bus voltage.

[0040] Specifically, the coil 210 has a first end 211 and a second end 212. The first end 211 is connected to the bus voltage terminal 21 of the non-isolated bus circuit 2, and the second end 212 is connected to the non-isolated ground terminal 22 of the non-isolated bus circuit 2. When the non-isolated bus circuit 2 is not connected, the metal slider 300 is in the initial position. When the non-isolated bus circuit 2 is connected, the coil 210 is energized and generates a magnetic field, which attracts the metal slider 300. The spring 400 is deformed and stretched. The magnitude of the attraction changes with the bus voltage. The metal slider 300 slides to different positions of the adjustable resistor 100 according to different magnitudes of attraction, thereby changing the length of the adjustable resistor 100 connected to the isolated weak current circuit 3 and changing the resistance value of the adjustable resistor 100 connected to the isolated weak current circuit 3. The spring 400 is connected to the metal slider 300 to control the range of movement of the metal slider 300, so as to avoid large displacement of the metal slider 300. At the same time, when the coil 210 is de-energized, the spring force of the spring 400 can be used to restore the metal slider 300 to its initial position.

[0041] Furthermore, the axis of the iron core 200, the axis of the spring 400, and the center of the metal slider 300 are located on the same straight line.

[0042] Specifically, the iron core 200 can be cylindrical, and the axis of the iron core 200, the axis of the spring 400, and the center of the metal slider 300 are located on the same straight line, which enables the metal slider 300 to move in a straight line and the spring 400 to deform in the same straight line, thereby improving the stability of the movement of the metal slider 300 and the spring 400.

[0043] Furthermore, the non-isolated bus circuit 2 includes: a first current limiting structure connected in series between the coil 210 and the bus voltage terminal 21.

[0044] Specifically, the first current limiting structure is connected in series between the bus voltage terminal 21 and the first terminal 211 of the coil 210 to limit the current in the non-isolated bus circuit 2, preventing excessive current from burning out or affecting normal operation.

[0045] Furthermore, the first current limiting structure includes a first resistor and a second resistor connected in series, with the bus voltage terminal 21 connected in sequence through the first resistor, the second resistor and the coil 210.

[0046] Specifically, R1 is the first resistor and R2 is the second resistor, which further limits the current in the non-isolated bus circuit 2.

[0047] Furthermore, the isolation low-voltage circuit 3 also includes a freewheeling diode, which is connected in parallel to both ends of the coil 210.

[0048] Specifically, D1 is a freewheeling diode. The cathode of D1 is connected to the first end 211 of the coil 210, and the anode of D1 is connected to the second end 212 of the coil 210. It can also be regarded as the non-isolated ground terminal 22 connected to the non-isolated bus circuit 2. When the non-isolated bus circuit 2 is cut off, the coil 210 is de-energized, and its reverse electromotive force is eliminated through the freewheeling diode.

[0049] Furthermore, the isolation low-voltage circuit 3 includes a third resistor and a fourth resistor. The third resistor is connected in series between the spring 400 and the low-voltage terminal 31; the fourth resistor is connected in series between the isolation ground terminal 32 of the fixed terminal 120.

[0050] Specifically, R3 is the third resistor, serving as the upper voltage divider resistor. The low-voltage terminal 31 is connected to the upper voltage divider resistor R3 and then connected to the metal slider 300 (i.e., connected to the sliding contact 110 of the adjustable resistor 100); R4 is the fourth resistor, serving as the lower voltage divider resistor. The fixed terminal 120 of the adjustable resistor 100 is connected to the lower voltage divider resistor R4 and then connected to the isolation ground terminal 32; the third and fourth resistors are specifically used for voltage division in the isolated low-voltage circuit 3.

[0051] Furthermore, the voltage divider section includes a fifth resistor and a first capacitor. The fifth resistor is connected between the fixed terminal 120 and the microcontroller. One end of the first capacitor is connected to the non-isolated ground terminal 22, and the other end of the first capacitor is connected to the microcontroller.

[0052] Specifically, R5 is the fifth resistor, C1 is the first capacitor, and the fixed terminal 120 of the adjustable resistor 100 is connected to the isolation ground terminal 32 via the lower voltage divider resistor R4, and also to the microcontroller via the fifth resistor R5 and the first capacitor C1. R5 is a current limiting resistor used for current limiting; C1 is a filter capacitor used for filtering.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and not to limit it. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this utility model.

Claims

1. An isolated voltage detection circuit, characterized in that, The isolated voltage detection circuit includes: An isolation module (1) is provided, which connects a non-isolated bus circuit (2) and an isolated low-voltage circuit (3), and the isolation module (1) includes an adjustable resistor (100). At least a portion of the adjustable resistor (100) is connected in series to the isolated low-voltage circuit (3), and the magnitude of the adjustable resistor (100) is changed by the change of the bus voltage of the non-isolated bus circuit (2).

2. The isolated voltage detection circuit according to claim 1, characterized in that, The isolated low-voltage circuit (3) is provided with a low-voltage terminal (31) and an isolated ground terminal (32); The adjustable resistor (100) is provided with a sliding contact (110) and a fixed end (120). The sliding contact (110) is connected to the low voltage terminal (31), and the fixed end (120) is connected to the isolation ground terminal (32). The position of the sliding contact (110) is changed by the change of the bus voltage; the fixed end (120) is also connected to the microcontroller via a voltage divider.

3. The isolated voltage detection circuit according to claim 2, characterized in that, The non-isolated bus circuit (2) is provided with a bus voltage terminal (21) and a non-isolated ground terminal (22), and the isolation module (1) further includes: Iron core (200), with a coil (210) wound around the iron core (200), the two ends of the coil (210) being connected to the bus voltage terminal (21) and the non-isolated ground terminal (22), respectively; A metal slider (300) is connected between the sliding contact (110) and the low voltage terminal (31); A spring (400) is connected between the metal slider (300) and the low voltage terminal (31); When the non-isolated bus circuit (2) is turned on, the coil (210) generates a magnetic field, and the magnitude of the magnetic field is changed by the change of the bus voltage.

4. The isolated voltage detection circuit according to claim 3, characterized in that, The axis of the iron core (200), the axis of the spring (400), and the center of the metal slider (300) are on the same straight line.

5. The isolated voltage detection circuit according to any one of claims 3-4, characterized in that, The non-isolated bus circuit (2) includes: A first current limiting structure is connected in series between the coil (210) and the bus voltage terminal (21).

6. The isolated voltage detection circuit according to claim 5, characterized in that, The first current limiting structure includes: The first resistor and the second resistor are connected in series, and the bus voltage terminal (21) is connected in sequence through the first resistor, the second resistor and the coil (210).

7. The isolated voltage detection circuit according to any one of claims 3-4, characterized in that, The isolated low-voltage circuit (3) also includes: A freewheeling diode is connected in parallel to both ends of the coil (210).

8. The isolated voltage detection circuit according to claim 3, characterized in that, The isolated low-voltage circuit (3) includes: A third resistor is connected in series between the spring (400) and the weak voltage terminal (31); A fourth resistor is connected in series between the fixed terminal (120) and the isolation ground terminal (32).

9. The isolated voltage detection circuit according to claim 3, characterized in that, The pressure-sharing section includes: The fifth resistor is connected between the fixed terminal (120) and the microcontroller; A first capacitor, one end of which is connected to the non-isolated ground terminal (22), and the other end of which is connected to the microcontroller.

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