Voltage frequency detection circuit

Abstract

The application provides a voltage frequency detection circuit, and relates to the technical field of electronics.The voltage frequency detection circuit comprises a voltage acquisition circuit and a control circuit.The three-phase voltage is acquired by the voltage acquisition circuit, a sampling voltage is obtained, and the sampling voltage is transmitted to the control circuit, so that the control circuit can acquire the sampling voltage.Thus, the control circuit can obtain the voltage frequency according to the sampling voltage and a reference voltage.Thus, the voltage frequency detection circuit can detect the voltage frequency.

Description

Technical Field

[0001] This application relates to the field of electronic technology, and in particular to a voltage frequency detection circuit. Background Technology

[0002] Islanding refers to a situation where, when the power grid is interrupted due to electrical faults or human error, the photovoltaic (PV) system fails to detect the outage and disconnects from the grid, continuing to supply power to nearby systems. Together with the local load, it forms a self-sufficient power supply island uncontrolled by the public power grid. When a PV system is in islanding mode, it can affect power quality and even damage electrical equipment. The continued energization of the islanded lines can hinder the extinction of fault arcs, leading to reclosing failures and, in severe cases, endangering the safety of maintenance personnel. Therefore, timely and effective detection of islanding and disconnecting the PV system from the point of common coupling (PCC) triggers islanding protection.

[0003] However, since photovoltaic systems have very high requirements for voltage frequency, it is urgent to design a voltage frequency detection circuit to accurately detect the voltage frequency at the common coupling point. Utility Model Content

[0004] This application provides a voltage frequency detection circuit capable of detecting voltage frequency.

[0005] In a first aspect, this application provides a voltage frequency detection circuit, which includes: a voltage acquisition circuit and a control circuit; The input terminal of the voltage acquisition circuit is electrically connected to the three-phase voltage, and the output terminal of the voltage acquisition circuit is electrically connected to the control circuit. The voltage acquisition circuit is used to acquire the three-phase voltage, obtain the sampled voltage, and transmit the sampled voltage to the control circuit; The control circuit is used to obtain the voltage frequency based on the sampled voltage and the reference voltage.

[0006] The voltage frequency detection circuit provided in the first aspect acquires the three-phase voltage through a voltage acquisition circuit to obtain a sampled voltage, which is then transmitted to the control circuit so that the control circuit can obtain the sampled voltage. Thus, the control circuit can determine the voltage frequency based on the sampled voltage and a reference voltage. Therefore, the voltage frequency detection circuit can achieve voltage frequency detection.

[0007] In one possible design, the control circuit is specifically configured to trigger an interrupt and record the trigger time of the interrupt when the sampled voltage is detected to be greater than the reference voltage at the rising edge of the reference voltage. The control circuit is specifically used to calculate the voltage frequency based on the timing of two consecutive triggering events.

[0008] In one possible design, the control circuit is specifically used to determine the time difference between two adjacent trigger times, and to determine the reciprocal of the time difference as the voltage frequency.

[0009] In one possible design, the control circuit includes: a detection circuit; The detection circuit is electrically connected to the output terminal of the voltage acquisition circuit; The detection circuit is used to detect whether the sampled voltage is greater than the reference voltage at the rising edge of the reference voltage.

[0010] In one possible design, the detection circuit includes: a first selection switch, a second selection switch, a third selection switch, a fourth selection switch, a reference voltage generator, and a comparator; The input terminal of the first selection switch is electrically connected to the output terminal of the voltage acquisition circuit. The output terminal of the first selection switch is electrically connected to the first terminal of the second selection switch. The second terminal of the second selection switch is electrically connected to the non-inverting input terminal of the comparator. The third terminal of the second selection switch is electrically connected to the first terminal of the third selection switch. The second terminal of the third selection switch is electrically connected to the negative inverting input terminal of the comparator. The output terminal of the comparator is used to output a digital signal, which is used to characterize whether the sampled voltage is greater than the reference voltage. The third terminal of the third selection switch is electrically connected to the first terminal of the fourth selection switch. The second terminal of the fourth selection switch is electrically connected to the reference voltage generator. The third terminal of the fourth selection switch is electrically connected to the third terminal of the first selection switch.

[0011] In one possible design, the voltage acquisition circuit includes: a first voltage acquisition circuit, a second voltage acquisition circuit, and a third voltage acquisition circuit; The input terminals of the first voltage acquisition circuit, the second voltage acquisition circuit, and the third voltage acquisition circuit are all electrically connected to the three-phase voltage, and the output terminals of the first voltage acquisition circuit, the second voltage acquisition circuit, and the third voltage acquisition circuit are all electrically connected to the control circuit. The first voltage acquisition circuit is used to acquire the A-phase voltage of the three-phase voltage to obtain the first sampling voltage; The second voltage acquisition circuit is used to acquire the B-phase voltage of the three-phase voltage to obtain the second sampling voltage; The third voltage acquisition circuit is used to acquire the C-phase voltage of the three-phase voltage to obtain a third sampling voltage, which includes the first sampling voltage, the second sampling voltage and the third sampling voltage.

[0012] In one possible design, the first voltage acquisition circuit, the second voltage acquisition circuit, or the third voltage acquisition circuit includes: a voltage divider circuit; The input terminal of the voltage divider circuit is electrically connected to the three-phase voltage, and the output terminal of the voltage divider circuit is electrically connected to the control circuit. The voltage divider circuit is used to divide the A-phase voltage to obtain the first sampling voltage, or to divide the B-phase voltage to obtain the second sampling voltage, or to divide the C-phase voltage to obtain the third sampling voltage.

[0013] In one possible design, the voltage divider circuit includes at least two first resistors connected in series; The first ends of the at least two first resistors are electrically connected to the three-phase voltage, and the second ends of the at least two first resistors are electrically connected to the control circuit.

[0014] In one possible design, the first voltage acquisition circuit, the second voltage acquisition circuit, or the third voltage acquisition circuit further includes a filter circuit; The first terminal of the filter circuit is electrically connected to the output terminal of the voltage divider circuit, and the second terminal of the filter circuit is grounded. The filtering circuit is used to filter out interference signals in the first sampling voltage, or to filter out interference signals in the second sampling voltage, or to filter out interference signals in the third sampling voltage.

[0015] In one possible design, the filter circuit includes: a second resistor and a capacitor; The first end of the second resistor and the first plate of the capacitor are both electrically connected to the output end of the voltage divider circuit, and the second end of the second resistor and the second plate of the capacitor are both grounded.

[0016] The above description is merely an overview of the technical solutions of the embodiments of this application. In order to better understand the technical means of the embodiments of this application and to implement them in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the embodiments of this application more obvious and understandable, specific implementation methods of this application are described below. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of a voltage frequency detection circuit provided in one embodiment of this application; Figure 2 This is a schematic diagram of the control circuit in a voltage frequency detection circuit according to an embodiment of this application; Figure 3 This is a schematic diagram of the voltage acquisition circuit in a voltage frequency detection circuit according to an embodiment of the present application; Figure 4 This is a schematic diagram illustrating the working process of a voltage frequency detection circuit according to an embodiment of this application.

[0019] Explanation of reference numerals in the attached figures: 100. Voltage frequency detection circuit; 110. Voltage acquisition circuit; 111. First voltage acquisition circuit; 112. Second voltage acquisition circuit; 113. Third voltage acquisition circuit; 113-1. Voltage divider circuit; 113-2. Filtering circuit; 111. Discharge circuit; 120. Control circuit; 121. Detection circuit; 121-1. First selection switch; 121-2. Second selection switch; 121-3. Third selection switch; 121-4. Fourth selection switch; 121-5. Reference voltage generator; 121-6. Comparator. Detailed Implementation

[0020] In this application, "at least one" means one or more, and "more than one" means two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can mean: A alone, A and B simultaneously, or B alone, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c alone can mean: a alone, b alone, c alone, a combination of a and b, a combination of a and c, a combination of b and c, or a, b, and c, where a, b, and c can be single or multiple. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0021] The terms “center,” “longitudinal,” “lateral,” “up,” “down,” “left,” “right,” “front,” and “rear,” etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0022] The terms "connected" and "connected" should be interpreted broadly. For example, in circuit structures, "connected" or "connected" can refer not only to physical connections but also to electrical or signal connections. This could be a direct connection (physical connection) or an indirect connection via at least one intermediate component, as long as the circuit is connected. It could also refer to the internal connection between two components. Similarly, a signal connection can refer to a connection via a circuit or a medium, such as radio waves. Those skilled in the art will understand the specific meaning of these terms in this application based on the specific circumstances.

[0023] Reference Figure 1 , Figure 1 This is a schematic diagram of a voltage frequency detection circuit provided in one embodiment of this application. Figure 1 As shown, the voltage frequency detection circuit 100 may include a voltage acquisition circuit 110 and a control circuit 120.

[0024] The input terminal of the voltage acquisition circuit 110 is electrically connected to the three-phase voltage, and the output terminal of the voltage acquisition circuit 110 is electrically connected to the control circuit 120.

[0025] The voltage acquisition circuit 110 and the control circuit 120 can be integrated or set separately, depending on actual needs. This application does not impose specific limitations on this.

[0026] The voltage acquisition circuit 110 can acquire three-phase voltages to obtain sampled voltages. Furthermore, the voltage acquisition circuit 110 can transmit the sampled voltages to the control circuit 120, enabling the control circuit 120 to acquire the sampled voltages.

[0027] Thus, the control circuit 120 can obtain the voltage frequency based on the sampled voltage and the reference voltage. Consequently, the voltage frequency detection circuit 100 can detect the voltage frequency.

[0028] For example, the control circuit 120 is a microcontroller unit (MCU).

[0029] The reference voltage can be a sinusoidal alternating current (AC) or a pulse voltage; this application does not specifically limit this.

[0030] After obtaining the voltage frequency, the control circuit 120 can display the voltage frequency in real time through a display circuit electrically connected to the control circuit 120, or, when the voltage frequency exceeds the preset voltage frequency, the control circuit 120 can issue an alarm through an alarm circuit electrically connected to the control circuit 120.

[0031] In some examples, the control circuit 120 can trigger an interrupt when the rising edge of the reference voltage is detected and the sampled voltage is greater than the reference voltage. Furthermore, the control circuit 120 can record the interrupt trigger time.

[0032] Thus, the control circuit 120 can calculate the voltage frequency based on the time between two adjacent triggering events.

[0033] For example, the control circuit 120 can determine the time difference between two adjacent trigger times. Furthermore, the control circuit 120 can determine the voltage frequency as the reciprocal of the time difference, allowing the control circuit 120 to calculate the voltage frequency based on two adjacent trigger times.

[0034] The time difference is the period of the voltage, and therefore, the reciprocal of the time difference is the voltage frequency.

[0035] Because the minimum unit time of the triggering time is small, the control circuit 120 obtains a highly accurate voltage frequency, enabling the voltage frequency detection circuit 100 to accurately capture minute changes in the voltage frequency. Simultaneously, because the voltage acquisition circuit 110 can acquire three-phase voltages at a period of, for example, 20ms, the voltage frequency detection circuit 100 can achieve high-frequency dynamic monitoring of the voltage frequency.

[0036] Therefore, the control circuit 120 can obtain the voltage frequency based on the sampled voltage and the reference voltage.

[0037] Furthermore, compared to related technologies that use comparators, phase-locked loops, and frequency counters for voltage frequency detection, this application uses the cooperation of voltage acquisition circuit 110 and control circuit 120 to detect voltage frequency, which has the advantages of higher flexibility and adaptability, as well as lower cost.

[0038] The voltage frequency detection circuit provided in this application acquires the three-phase voltage through a voltage acquisition circuit to obtain a sampled voltage, and transmits the sampled voltage to a control circuit so that the control circuit can acquire the sampled voltage. Thus, the control circuit can obtain the voltage frequency based on the sampled voltage and a reference voltage. Therefore, the voltage frequency detection circuit can achieve voltage frequency detection.

[0039] Based on the description of the above embodiments, an exemplary possible implementation of the control circuit 120 is provided. (Refer to...) Figure 2 , Figure 2 This is a schematic diagram of the control circuit in a voltage frequency detection circuit according to an embodiment of this application. Figure 2 As shown, the control circuit 120 may include a detection circuit 121.

[0040] The detection circuit 121 is electrically connected to the output terminal of the voltage acquisition circuit 110.

[0041] At the rising edge of the reference voltage, the detection circuit 121 can detect whether the sampled voltage is greater than the reference voltage. Therefore, the control circuit 120 can trigger an interrupt and record the interrupt trigger time when the sampled voltage is detected to be greater than the reference voltage at the rising edge of the reference voltage.

[0042] Based on the description of the above embodiments, an exemplary possible implementation of the detection circuit 121 is provided. For example... Figure 2 As shown, the detection circuit 121 may include: a first selection switch 121-1, a second selection switch 121-2, a third selection switch 121-3, a fourth selection switch 121-4, a reference voltage generator 121-5, and a comparator 121-6.

[0043] The input terminal of the first selection switch 121-1 is electrically connected to the output terminal of the voltage acquisition circuit 110. The output terminal of the first selection switch 121-1 is electrically connected to the first terminal of the second selection switch 121-2. The second terminal of the second selection switch 121-2 is electrically connected to the positive input terminal of the comparator 121-6. The third terminal of the second selection switch 121-2 is electrically connected to the first terminal of the third selection switch 121-3. The second terminal of the third selection switch 121-3 is electrically connected to the negative input terminal of the comparator 121-6. The output terminal of the comparator 121-6 is used to output a digital signal, which is used to characterize whether the sampled voltage is greater than the reference voltage. The third terminal of the third selection switch 121-3 is electrically connected to the first terminal of the fourth selection switch 121-4. The second terminal of the fourth selection switch 121-4 is electrically connected to the reference voltage generator 121-5. The third terminal of the fourth selection switch 121-4 is electrically connected to the third terminal of the first selection switch 121-1.

[0044] in, Figure 2The input terminals of the first selector switch 121-1 refer to the first pin COMPx_IN0+, the second pin COMPx_IN1+, and the third pin COMPx_IN2+ of the first selector switch 121-1.

[0045] When the digital signal is high, it means that the sampling voltage is greater than the reference voltage. When the digital signal is low, it means that the sampling voltage is less than the reference voltage.

[0046] In some examples, the reference voltage generator 121-5 is a reference voltage generator that integrates an 8-bit digital-to-analog converter (DAC). Specifically, after receiving the reference value DACCODE0, the reference voltage generator 121-5 converts the reference value DACCODE0 into a reference voltage and transmits it to the comparator 121-6 via the fourth selection switch 121-4 and the third selection switch 121-3.

[0047] Based on the description of the above embodiments, an exemplary possible implementation of the voltage acquisition circuit 110 is provided. (Refer to...) Figure 3 , Figure 3 This is a schematic diagram of the voltage acquisition circuit in a voltage frequency detection circuit provided in one embodiment of this application. Figure 3 As shown, the voltage acquisition circuit 110 may include: a first voltage acquisition circuit 111, a second voltage acquisition circuit 112, and a third voltage acquisition circuit 113.

[0048] The input terminals of the first voltage acquisition circuit 111, the second voltage acquisition circuit 112, and the third voltage acquisition circuit 113 are all electrically connected to the three-phase voltage. The output terminals of the first voltage acquisition circuit 111, the second voltage acquisition circuit 112, and the third voltage acquisition circuit 113 are all electrically connected to the control circuit 120.

[0049] The input terminals of the first voltage acquisition circuit 111, the second voltage acquisition circuit 112, and the third voltage acquisition circuit 113 are all input terminals of the voltage acquisition circuit 110, and the output terminals of the first voltage acquisition circuit 111, the second voltage acquisition circuit 112, and the third voltage acquisition circuit 113 are all output terminals of the voltage acquisition circuit 110.

[0050] The first voltage acquisition circuit 111 can acquire the A-phase voltage of the three-phase voltage to obtain the first sampling voltage VA.

[0051] The second voltage acquisition circuit 112 can acquire the B-phase voltage of the three-phase voltage to obtain the second sampling voltage VB.

[0052] The third voltage acquisition circuit 113 can acquire the C-phase voltage of the three-phase voltage to obtain the third sampling voltage VC.

[0053] The sampling voltage may include: a first sampling voltage VA, a second sampling voltage VB, and a third sampling voltage VC.

[0054] Therefore, the voltage acquisition circuit 110 can acquire three-phase voltages and obtain the sampled voltage.

[0055] Based on the description of the above embodiments, an exemplary possible implementation of the first voltage acquisition circuit 111, the second voltage acquisition circuit 112, or the third voltage acquisition circuit 113 is provided. Figure 3 As shown, the first voltage acquisition circuit 111, the second voltage acquisition circuit 112, or the third voltage acquisition circuit 113 may include a voltage divider circuit 113-1.

[0056] The input terminal of the voltage divider circuit 113-1 is electrically connected to the three-phase voltage, and the output terminal of the voltage divider circuit 113-1 is electrically connected to the control circuit 120.

[0057] The voltage divider circuit 113-1 can divide the voltage of phase A to obtain the first sampling voltage VA, so that the first voltage acquisition circuit 111 can acquire the voltage of phase A in the three-phase voltage to obtain the first sampling voltage VA.

[0058] The voltage divider circuit 113-1 can divide the B-phase voltage to obtain the second sampling voltage VB, so that the second voltage acquisition circuit 112 can acquire the B-phase voltage in the three-phase voltage to obtain the second sampling voltage VB.

[0059] The voltage divider circuit 113-1 can divide the C-phase voltage to obtain the third sampling voltage VC, so that the third voltage acquisition circuit 113 can acquire the C-phase voltage in the three-phase voltage to obtain the third sampling voltage VC.

[0060] Based on the description of the above embodiments, an exemplary possible implementation of the voltage divider circuit 113-1 is provided. Figure 3 As shown, the voltage divider circuit 113-1 may include at least two first resistors R1 connected in series.

[0061] The first ends of at least two first resistors R1 are electrically connected to the three-phase voltage, and the second ends of at least two first resistors R1 are electrically connected to the control circuit 120.

[0062] in, Figure 3 The diagram illustrates a voltage divider circuit 113-1 comprising four first resistors R1 connected in series. These four first resistors R1 connected in series are first resistor R1-1, first resistor R1-2, first resistor R1-3, and first resistor R1-4.

[0063] Based on the description of the above embodiments, another possible implementation of the first voltage acquisition circuit 111, the second voltage acquisition circuit 112, or the third voltage acquisition circuit 113 is provided, for example. Figure 3 As shown, the first voltage acquisition circuit 111, the second voltage acquisition circuit 112, or the third voltage acquisition circuit 113 may further include a filter circuit 113-2.

[0064] The first terminal of the filter circuit 113-2 is electrically connected to the output terminal of the voltage divider circuit 113-1, and the second terminal of the filter circuit 113-2 is grounded.

[0065] The filter circuit 113-2 can filter out interference signals in the first sampling voltage VA, thereby improving the accuracy of the first sampling voltage VA.

[0066] The interference signal can be an interference voltage, an interference current, or a combination of interference voltage and interference current. This application does not specifically limit this.

[0067] The filter circuit 113-2 can filter out interference signals in the second sampling voltage VB, thereby improving the accuracy of the second sampling voltage VB.

[0068] The filter circuit 113-2 can filter out interference signals in the third sampling voltage VC, thereby improving the accuracy of the third sampling voltage VC.

[0069] Based on the description of the above embodiments, an exemplary possible implementation of the filter circuit 113-2 is provided. Figure 3 As shown, the filter circuit 113-2 may include: a second resistor R2 and a capacitor C.

[0070] The first end of the second resistor R2 and the first plate of the capacitor C are both electrically connected to the output of the voltage divider circuit 113-1, and the second end of the second resistor R2 and the second plate of the capacitor C are both grounded.

[0071] Based on the description of the above embodiments, another possible implementation of the first voltage acquisition circuit 111, the second voltage acquisition circuit 112, or the third voltage acquisition circuit 113 is provided, for example. Figure 3 As shown, the first voltage acquisition circuit 111, the second voltage acquisition circuit 112, or the third voltage acquisition circuit 113 may further include: a bidirectional transient voltage diode VD and a third resistor R3.

[0072] The first terminal of the bidirectional transient voltage diode VD and the first terminal of the third resistor R3 are both electrically connected to the control circuit 120, and the second terminal of the bidirectional transient voltage diode VD and the second terminal of the third resistor R3 are both electrically connected to the power supply voltage VAD.

[0073] The following is combined Figure 4 , Figure 4 This application provides a schematic diagram of the working process of a voltage frequency detection circuit 100 according to an embodiment of the present application. The working principle of the voltage frequency detection circuit 100 is explained in detail below: After starting operation, the voltage and frequency detection circuit initializes. The voltage acquisition circuit then samples the three-phase voltage, obtaining the sampled voltage, and transmits it to the detection circuit in the control circuit. At the rising edge of the reference voltage, the detection circuit checks whether the sampled voltage is greater than the reference voltage, triggering an interrupt in the control circuit and recording the interrupt trigger time.

[0074] When the sampled voltage is detected to be greater than the reference voltage, the control circuit determines the time difference between two adjacent trigger times and uses the reciprocal of the time difference as the voltage frequency. Thus, the voltage frequency detection circuit can detect the voltage frequency.

[0075] When the sampled voltage is detected to be less than the reference voltage, the voltage acquisition circuit continues to acquire the three-phase voltage, that is, it continues to continuously detect the three-phase voltage until the voltage frequency is determined.

[0076] Finally, it should be noted that the above embodiments are merely specific implementations of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions within the technical scope disclosed in this application should be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A voltage frequency detection circuit, characterized in that, The voltage frequency detection circuit includes: a voltage acquisition circuit and a control circuit; The input terminal of the voltage acquisition circuit is electrically connected to the three-phase voltage, and the output terminal of the voltage acquisition circuit is electrically connected to the control circuit. The voltage acquisition circuit is used to acquire the three-phase voltage, obtain the sampled voltage, and transmit the sampled voltage to the control circuit; The control circuit is used to obtain the voltage frequency based on the sampled voltage and the reference voltage.

2. The circuit according to claim 1, characterized in that, The control circuit is specifically used to trigger an interrupt and record the trigger time of the interrupt when the rising edge of the reference voltage is detected and the sampled voltage is greater than the reference voltage. The control circuit is specifically used to calculate the voltage frequency based on the timing of two consecutive triggering events.

3. The circuit according to claim 2, characterized in that, The control circuit is specifically used to determine the time difference between two adjacent trigger times, and to determine the voltage frequency as the reciprocal of the time difference.

4. The circuit according to claim 2, characterized in that, The control circuit includes: a detection circuit; The detection circuit is electrically connected to the output terminal of the voltage acquisition circuit; The detection circuit is used to detect whether the sampled voltage is greater than the reference voltage at the rising edge of the reference voltage.

5. The circuit according to claim 4, characterized in that, The detection circuit includes: a first selection switch, a second selection switch, a third selection switch, a fourth selection switch, a reference voltage generator, and a comparator; The input terminal of the first selection switch is electrically connected to the output terminal of the voltage acquisition circuit. The output terminal of the first selection switch is electrically connected to the first terminal of the second selection switch. The second terminal of the second selection switch is electrically connected to the non-inverting input terminal of the comparator. The third terminal of the second selection switch is electrically connected to the first terminal of the third selection switch. The second terminal of the third selection switch is electrically connected to the negative inverting input terminal of the comparator. The output terminal of the comparator is used to output a digital signal, which is used to characterize whether the sampled voltage is greater than the reference voltage. The third terminal of the third selection switch is electrically connected to the first terminal of the fourth selection switch. The second terminal of the fourth selection switch is electrically connected to the reference voltage generator. The third terminal of the fourth selection switch is electrically connected to the third terminal of the first selection switch.

6. The circuit according to any one of claims 1-5, characterized in that, The voltage acquisition circuit includes: a first voltage acquisition circuit, a second voltage acquisition circuit, and a third voltage acquisition circuit; The input terminals of the first voltage acquisition circuit, the second voltage acquisition circuit, and the third voltage acquisition circuit are all electrically connected to the three-phase voltage, and the output terminals of the first voltage acquisition circuit, the second voltage acquisition circuit, and the third voltage acquisition circuit are all electrically connected to the control circuit. The first voltage acquisition circuit is used to acquire the A-phase voltage of the three-phase voltage to obtain the first sampling voltage; The second voltage acquisition circuit is used to acquire the B-phase voltage of the three-phase voltage to obtain the second sampling voltage; The third voltage acquisition circuit is used to acquire the C-phase voltage of the three-phase voltage to obtain a third sampling voltage, which includes the first sampling voltage, the second sampling voltage and the third sampling voltage.

7. The circuit according to claim 6, characterized in that, The first voltage acquisition circuit, the second voltage acquisition circuit, or the third voltage acquisition circuit includes: a voltage divider circuit; The input terminal of the voltage divider circuit is electrically connected to the three-phase voltage, and the output terminal of the voltage divider circuit is electrically connected to the control circuit. The voltage divider circuit is used to divide the A-phase voltage to obtain the first sampling voltage, or to divide the B-phase voltage to obtain the second sampling voltage, or to divide the C-phase voltage to obtain the third sampling voltage.

8. The circuit according to claim 7, characterized in that, The voltage divider circuit includes at least two first resistors connected in series; The first ends of the at least two first resistors are electrically connected to the three-phase voltage, and the second ends of the at least two first resistors are electrically connected to the control circuit.

9. The circuit according to claim 7, characterized in that, The first voltage acquisition circuit, the second voltage acquisition circuit, or the third voltage acquisition circuit further includes: a filter circuit; The first terminal of the filter circuit is electrically connected to the output terminal of the voltage divider circuit, and the second terminal of the filter circuit is grounded. The filtering circuit is used to filter out interference signals in the first sampling voltage, or to filter out interference signals in the second sampling voltage, or to filter out interference signals in the third sampling voltage.

10. The circuit according to claim 9, characterized in that, The filter circuit includes: a second resistor and a capacitor; The first end of the second resistor and the first plate of the capacitor are both electrically connected to the output end of the voltage divider circuit, and the second end of the second resistor and the second plate of the capacitor are both grounded.

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