Insulation detection circuit, charging pile and photovoltaic inverter

Abstract

The utility model discloses an insulation detection circuit, a charging pile and a photovoltaic inverter. In the insulation detection circuit, the first end of insulation monitoring equipment is connected with a direct current positive electrode through a direct current positive electrode switch, and the second end of the insulation monitoring equipment is connected with a direct current negative electrode through a direct current negative electrode switch. The first end of the direct-current anode switch branch is connected with the first end of the direct-current anode switch, and the second end of the direct-current anode switch branch is connected with the second end of the direct-current anode switch or the second end of the direct-current cathode switch; the first end of the direct-current cathode switch branch is connected with the first end of the direct-current cathode switch, and the second end of the direct-current cathode switch branch is connected with the second end of the direct-current cathode switch or the second end of the direct-current anode switch. And under the condition that the direct-current anode switch and the direct-current cathode switch are switched off, the states of the direct-current anode switch branch and the direct-current cathode switch branch are controlled, so that the insulation monitoring equipment obtains the insulation resistance of the input side of the insulation detection circuit.

Description

Technical Field

[0001] This utility model relates to the field of testing technology, and in particular to an insulation testing circuit, a charging pile, and a photovoltaic inverter. Background Technology

[0002] An insulation monitor device (IMD) is used to monitor the insulation impedance of ungrounded systems. When an insulation fault occurs in an ungrounded system, it promptly outputs an alarm signal to mitigate significant losses such as system instability, production interruptions, or fires caused by leakage current.

[0003] In related technologies, IMD (Insulation Damping) typically detects the insulation impedance of the device under test (DUT) when it is in standby mode. However, for DUTs in standby mode, IMD can usually only detect the output insulation impedance of the insulation detection circuit, and cannot obtain the input insulation impedance. Consequently, it cannot detect the leakage current status of the device connected to the input side of the insulation detection circuit. Utility Model Content

[0004] To address the aforementioned issues, this application provides an insulation detection circuit, a charging pile, and a photovoltaic inverter, which acquires the insulation impedance on the input side of the insulation detection circuit to detect the leakage current status of the input-side device of the insulation detection circuit.

[0005] The embodiments of this application disclose the following technical solutions:

[0006] In a first aspect, embodiments of this application provide an insulation detection circuit, including: an insulation monitoring device, a DC positive switch, a DC negative switch, a DC positive switch branch, a DC negative switch branch, and a processor;

[0007] The first end of the insulation monitoring device is connected to the DC positive terminal via a DC positive switch, and the second end of the insulation monitoring device is connected to the DC negative terminal via a DC negative switch.

[0008] The first end of the DC positive switch branch is used to connect to the DC positive terminal, and the second end of the DC positive switch branch is connected to the second end of the DC positive switch or the second end of the DC negative switch; the first end of the DC negative switch branch is used to connect to the DC negative terminal, and the second end of the DC negative switch branch is connected to the second end of the DC negative switch or the second end of the DC positive switch.

[0009] The control terminals of the DC positive switch branch, the DC negative switch branch, and the output terminal of the insulation monitoring equipment are connected to the processor.

[0010] Optionally, the processor controls the switching on and off of the DC positive and DC negative switch branches to enable the insulation monitoring device to acquire the insulation impedance of the input side DC positive terminal to ground and the insulation impedance of the input side DC negative terminal to ground of the insulation detection circuit.

[0011] Optionally, the DC positive switch branch includes a first resistor and a first switch connected in series, and the DC negative switch branch includes a second resistor and a second switch connected in series.

[0012] The processor is specifically used to control the conduction or deactivation of the first switch and the second switch when the DC positive switch and the DC negative switch are turned off, so that the insulation monitoring device can obtain the insulation impedance of the input side DC positive terminal to ground and the insulation impedance of the input side DC negative terminal to ground of the insulation detection circuit.

[0013] Optionally, the DC positive switch branch is connected in parallel across the DC positive switch, and the DC negative switch branch is connected in parallel across the DC negative switch.

[0014] The processor is specifically configured to, when the DC positive switch and the DC negative switch are turned off, control the DC positive switch branch and the DC negative switch branch to be turned on, so that the insulation monitoring device can obtain the first insulation impedance of the DC positive terminal to ground and the first insulation impedance of the DC negative terminal to ground; control the DC positive switch branch and the DC negative switch branch to be turned off, so that the insulation monitoring device can obtain the insulation impedance of the output side DC positive terminal to ground and the insulation impedance of the output side DC negative terminal to ground of the insulation detection circuit; obtain the insulation impedance of the input side DC positive terminal to ground based on the first insulation impedance of the DC positive terminal to ground and the insulation impedance of the output side DC positive terminal to ground; and obtain the insulation impedance of the input side DC negative terminal to ground based on the first insulation impedance of the DC negative terminal to ground and the insulation impedance of the output side DC negative terminal to ground.

[0015] Optionally, the DC positive switch branch is connected in parallel across the two ends of the DC positive switch, the first end of the DC negative switch branch is used to connect to the DC negative terminal, and the second end of the DC negative switch branch is connected to the second end of the DC positive switch.

[0016] The processor is specifically configured to, when the DC positive switch and the DC negative switch are turned off, control the DC positive switch branch to be turned on and the DC negative switch branch to be turned off, so that the insulation monitoring device can obtain the second insulation impedance of the DC positive terminal to ground; control the DC positive switch branch to be turned off and the DC negative switch branch to be turned on, so that the insulation monitoring device can obtain the third insulation impedance of the DC positive terminal to ground; control the DC positive switch branch and the DC negative switch branch to be turned off, so that the insulation monitoring device can obtain the insulation impedance of the output side DC positive terminal to ground of the insulation detection circuit; and obtain the insulation impedance of the input side DC positive terminal to ground and the insulation impedance of the input side DC negative terminal to ground based on the second insulation impedance of the DC positive terminal to ground, the third insulation impedance of the DC positive terminal to ground and the insulation impedance of the output side DC positive terminal to ground.

[0017] Optionally, the first end of the DC positive switch branch is used to connect to the DC positive terminal, the second end of the DC positive switch branch is connected to the second end of the DC negative switch branch, and the DC negative switch branch is connected in parallel across the two ends of the DC negative switch.

[0018] The controller is specifically used to: control the DC positive switch branch to turn off and the DC negative switch branch to turn on when the DC positive switch and the DC negative switch are off, so that the insulation monitoring device can obtain the second insulation impedance of the DC negative terminal to ground; control the DC positive switch branch to turn on and the DC negative switch branch to turn off, so that the insulation monitoring device can obtain the third insulation impedance of the DC negative terminal to ground; control the DC positive switch branch and the DC negative switch branch to turn off, so that the insulation monitoring device can obtain the insulation impedance of the output side DC negative terminal to ground of the insulation detection circuit; and obtain the insulation impedance of the input side DC positive terminal to ground and the insulation impedance of the input side DC negative terminal to ground based on the second insulation impedance of the DC negative terminal to ground, the third insulation impedance of the DC negative terminal to ground and the insulation impedance of the output side DC negative terminal to ground.

[0019] Optionally, the first end of the DC positive switch branch is used to connect to the DC positive terminal, the second end of the DC positive switch branch is connected to the second end of the DC negative switch branch, the first end of the DC negative switch branch is used to connect to the DC negative terminal, and the second end of the DC negative switch branch is connected to the second end of the DC positive switch.

[0020] The processor is specifically used to control the DC positive switch branch and the DC negative switch branch to conduct when the DC positive switch and the DC negative switch are turned off, so that the insulation monitoring device can obtain the fourth insulation impedance of the DC positive terminal to ground and the fourth insulation impedance of the DC negative terminal to ground; and to control the DC positive switch branch and the DC negative switch branch to turn off, so that the insulation monitoring device can obtain the insulation impedance of the output side DC positive terminal to ground and the insulation impedance of the output side DC negative terminal to ground of the insulation detection circuit; to obtain the insulation impedance of the input side DC negative terminal to ground based on the fourth insulation impedance of the DC positive terminal to ground and the insulation impedance of the output side DC positive terminal to ground; and to obtain the insulation impedance of the input side DC positive terminal to ground based on the fourth insulation impedance of the DC negative terminal to ground and the insulation impedance of the output side DC negative terminal to ground.

[0021] Optionally, the DC positive switch branch includes a first resistor, a third switch, and a fourth switch, and the DC negative switch branch includes a second resistor, a fifth switch, and a sixth switch; wherein, the first terminals of the third switch and the fourth switch are both connected to the first resistor, the second terminal of the third switch is connected to the second terminal of the DC positive switch, the second terminal of the fourth switch is connected to the second terminal of the DC negative switch, the second terminals of the fifth switch and the sixth switch are both connected to the second resistor, the second terminal of the fifth switch is connected to the second terminal of the DC negative switch, and the second terminal of the sixth switch is connected to the second terminal of the DC positive switch;

[0022] The processor is specifically used to control the conduction or deactivation of the third, fourth, fifth, and sixth switches when the DC positive and DC negative switches are turned off, so that the insulation monitoring equipment can obtain the insulation impedance of the input side DC positive terminal to ground and the insulation impedance of the input side DC negative terminal to ground of the insulation detection circuit.

[0023] Optionally, the DC positive switch branch includes a first resistor and a first single-pole double-throw switch connected in series, and the DC negative switch branch includes a second resistor and a second single-pole double-throw switch connected in series; wherein, the first moving terminal of the first single-pole double-throw switch is connected to the second terminal of the DC positive switch, the second terminal of the first single-pole double-throw switch is connected to the second terminal of the DC negative switch, the first moving terminal of the second single-pole double-throw switch is connected to the second terminal of the DC negative switch, and the second moving terminal of the second single-pole double-throw switch is connected to the second terminal of the DC positive switch;

[0024] The processor is used to control the conduction or deactivation of the first single-pole double-throw switch and the second single-pole double-throw switch when the DC positive switch and the DC negative switch are turned off, so that the insulation monitoring device can obtain the insulation impedance of the input side DC positive terminal to ground and the insulation impedance of the input side DC negative terminal to ground of the insulation detection circuit; wherein, the conduction of the first single-pole double-throw switch and the second single-pole double-throw switch both include: the first moving end is turned on and the second moving end is turned on.

[0025] Optionally, both the DC positive switch and the DC negative switch include either a contactor or a relay.

[0026] Optionally, the first switch, the second switch, the third switch, the fourth switch, the fifth switch, and the sixth switch all include any one of transistors, metal-oxide-semiconductor field-effect transistors, and relays, and the first single-pole double-throw switch and the second single-pole double-throw switch both include relays.

[0027] Secondly, this application provides a charging pile, including: a power conversion circuit, a controller, and an insulation detection circuit as described in any of the embodiments of the first aspect above; the first end of the insulation detection circuit is connected to the DC side of the power conversion circuit, and the second end of the insulation detection circuit is used to connect to the device to be charged;

[0028] The controller is used to detect the leakage current status of the power conversion circuit based on the insulation resistance of the input side DC positive terminal to ground and the insulation resistance of the input side DC negative terminal to ground when the DC positive and DC negative terminals are turned off.

[0029] Thirdly, embodiments of this application provide a photovoltaic inverter, including: a power conversion circuit, a controller, and an insulation detection circuit as described in any of the embodiments of the first aspect above; the first end of the insulation detection circuit is used to connect the DC positive terminal and the DC negative terminal of the photovoltaic module, and the second end of the insulation detection circuit is connected to the power conversion circuit;

[0030] The controller is used to detect the leakage current status of the photovoltaic module based on the insulation resistance of the input side DC positive terminal to ground and the insulation resistance of the input side DC negative terminal to ground when the DC positive and DC negative terminals are turned off.

[0031] Since the IMD can only detect the insulation impedance on the output side of the insulation detection circuit when the device under test is in standby mode, this application provides an insulation detection circuit, including: an insulation monitoring device, a DC positive switch, a DC negative switch, a DC positive switch branch, a DC negative switch branch, and a processor; the first terminal of the insulation monitoring device is connected to the DC positive terminal through the DC positive switch, and the second terminal of the insulation monitoring device is connected to the DC negative terminal through the DC negative switch; the first terminal of the DC positive switch branch is connected to the DC positive terminal, the second terminal of the DC positive switch branch is connected to the second terminal of the DC positive switch or the second terminal of the DC negative switch, and the first terminal of the DC negative switch branch is connected to the DC negative terminal, and the second terminal of the DC negative switch branch is connected to the second terminal of the DC negative switch or the second terminal of the DC positive switch; the control terminal of the DC positive switch branch, the control terminal of the DC negative switch branch, and the output terminal of the insulation monitoring device are connected to the processor. In this embodiment, both the DC positive switch branch and the DC negative switch branch include an on or off state. When the DC positive switch and the DC negative switch are off, the insulation impedance of the insulation detection input terminal to ground can be obtained by controlling the on and off states of the DC positive switch branch and the DC negative switch branch. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 A schematic diagram of an insulation detection circuit provided in an embodiment of this application;

[0034] Figure 2 A schematic diagram of another insulation detection circuit provided in an embodiment of this application;

[0035] Figure 3 A schematic diagram of yet another insulation detection circuit provided in an embodiment of this application;

[0036] Figure 4 A schematic diagram of another insulation detection circuit provided in an embodiment of this application;

[0037] Figure 5 A schematic diagram of an insulation detection circuit provided in an embodiment of this application;

[0038] Figure 6 A schematic diagram of another insulation detection circuit provided in an embodiment of this application;

[0039] Figure 7 A schematic diagram of yet another insulation detection circuit provided in an embodiment of this application;

[0040] Figure 8 This is a schematic diagram of the structure of a charging pile provided in an embodiment of this application;

[0041] Figure 9 This is a schematic diagram of the structure of a photovoltaic inverter provided in an embodiment of this application. Detailed Implementation

[0042] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] The terms "first" and "second," etc., used in the specification and claims of this application are used to distinguish different objects, not to describe a specific order of objects. For example, "first resistor" and "second resistor," etc., are used to distinguish different resistors, not to describe a specific order of resistors.

[0044] In the embodiments of this application, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design described as "exemplary" or "for example" in the embodiments of this utility model should not be construed as being more preferred or advantageous than other embodiments or design solutions. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0045] This application does not specifically limit the application scenarios of the insulation detection circuit, such as charging piles and photovoltaic inverters. For ease of understanding, the following will use the application scenario of charging piles as an example.

[0046] The first end of the insulation monitoring device is connected to the positive output terminal of the DC side of the power conversion circuit via a DC positive switch, and the second end of the insulation monitoring device is connected to the negative output terminal of the DC side of the power conversion circuit via a DC negative switch. The first end of the DC positive switch branch is connected to the DC positive terminal, and the second end of the DC positive switch branch is connected to the second end of either the DC positive switch or the DC negative switch. The first end of the DC negative switch branch is connected to the DC negative terminal, and the second end of the DC negative switch branch is connected to either the second end of either the DC negative switch or the DC positive switch. The control terminals of the DC positive switch branch, the DC negative switch branch, and the output terminal of the insulation monitoring device are connected to the processor.

[0047] Therefore, when the charging pile is in standby mode (DC positive switch and DC negative switch are off), by controlling the conduction and cutoff of the DC positive switch branch and the DC negative switch branch, the insulation monitoring equipment can obtain the insulation impedance of the input side of the insulation detection circuit to determine the leakage status of the equipment connected to the input side of the insulation detection circuit, i.e., the power conversion circuit.

[0048] The technical content of this application will now be described in conjunction with embodiments.

[0049] See Figure 1 The figure is a schematic diagram of an insulation detection circuit provided in an embodiment of this application.

[0050] like Figure 1 As shown, the insulation detection circuit includes: an insulation monitoring device (IMD) 100, a DC positive switch Kp, a DC negative switch Kn, a DC positive switch branch 200, a DC negative switch branch 300, and a processor 400. The DC positive terminal DC1+ and the DC negative terminal DC1- serve as the input DC positive and input DC negative terminals of the insulation detection circuit, respectively, while the DC positive terminal DC2+ and the DC negative terminal DC2- serve as the output DC positive and output DC negative terminals of the insulation detection circuit, respectively. Dark lines (including solid and dashed lines) represent power lines, and light lines represent control lines.

[0051] The first terminal of the insulation monitoring device (IMD) 100 is connected to the positive DC terminal DC1+ via a positive DC switch Kp (the first terminal of the positive DC switch Kp is connected to the positive DC terminal DC1+, and the second terminal of the positive DC switch Kp is connected to the IMD). The second terminal of the insulation monitoring device 100 is connected to the negative DC terminal DC1- via a negative DC switch Kn (the first terminal of the negative DC switch Kn is connected to the negative DC terminal DC1-, and the second terminal of the negative DC switch Kn is connected to the IMD). The first terminal of the positive DC switch branch 200 is connected to the DC... The positive terminal DC1+ is connected to the second terminal of the positive DC switch branch 200, which is connected to the second terminal of the positive DC switch Kp or the second terminal of the negative DC switch Kn. The first terminal of the negative DC switch branch 300 is connected to the negative DC DC1-. The second terminal of the negative DC switch branch 300 is connected to the second terminal of the negative DC switch Kn or the second terminal of the positive DC switch branch Kp. The control terminals of the positive DC switch branch 200 and the negative DC switch branch 300 and the output terminal of the insulation monitoring device (IMD) 100 are connected to the processor 400.

[0052] In this embodiment, the types of DC positive switch Kp and DC negative switch Kn are not specifically limited. For example, both DC positive switch Kp and DC negative switch Kn can be either DC contactors or relays.

[0053] The processor 400 is used to control the state of the DC positive switch branch 200 and the DC negative switch branch 300 to be turned on or off, and to obtain the insulation resistance of the input side DC positive terminal DC1+ to ground and the insulation resistance of the input side DC negative terminal DC1- to ground of the insulation detection circuit.

[0054] In one embodiment, the DC positive switch branch 200 includes a first resistor R1 and a first switch K1 connected in series, and the DC negative switch branch 300 includes a second resistor R2 and a second switch K2 connected in series.

[0055] In this embodiment, the positional relationship between the first resistor R1 and the first switch K1 is not specifically limited. For example, the first resistor R1 may be located to the left of the first switch K1 or to the right of the first switch K1. Similarly, the positional relationship between the second resistor R2 and the second switch K2 is not specifically limited. For example, the second resistor R2 may be located to the left of the second switch K2 or to the right of the second switch K2.

[0056] In this embodiment, the types of the first switch K1 and the second switch K2 are not specifically limited. For example, the first switch K1 and the second switch K2 can both be any one of transistors, metal-oxide-semiconductor field-effect transistors and relays.

[0057] The processor 400 is specifically used to control the conduction or deactivation of the first switch K1 and the second switch K2 when the DC positive switch Kp and the DC negative switch Kn are turned off, so that the insulation monitoring device IMD can obtain the insulation impedance of the input side DC positive terminal to ground and the insulation impedance of the input side DC negative terminal to ground of the insulation detection circuit.

[0058] The embodiments of this application do not specifically limit the type of processor. For example, the processor can be any one of a digital signal processor (DSP) and a field programmable gate array (FPGA).

[0059] In this embodiment, by controlling the on and off of the DC positive switch branch and the DC negative switch branch, the insulation impedance of the input side DC positive terminal to ground and the insulation impedance of the input side DC negative terminal to ground can be obtained. The leakage current of the connected device on the input side of the insulation detection circuit is judged. When the insulation impedance of the input side DC positive terminal to ground and the insulation impedance of the input side DC negative terminal to ground are less than their respective preset thresholds, it can be determined that the device connected to the input side of the insulation detection circuit has leakage current, and an alarm signal is output for the device connected to the input side of the insulation detection circuit.

[0060] Typically, an IMD (Insulation Device) senses insulation resistance by detecting the closed-loop current between the device under test (DUT) and ground. Further, the IMD releases a low-voltage signal between the DUT and ground. When leakage current in the DUT causes a decrease in insulation resistance, the measurement circuit closes, generating a measurement current. This current value varies with the insulation resistance. The IMD measures and monitors this current value in real time and derives the insulation resistance based on the correlation between the current value and the insulation resistance.

[0061] Based on the two connection methods of the DC positive switch branch 200 (i.e., the second end of the DC positive switch branch 200 is connected to the second end of the DC positive switch Kp, and the second end of the DC positive switch branch 200 is connected to the second end of the DC negative switch Kn) and the two connection methods of the DC negative switch branch 300 (i.e., the second end of the DC positive and negative switch branch 300 is connected to the second end of the DC negative switch Kn, and the second end of the DC negative switch branch 300 is connected to the second end of the DC positive switch Kp), the following will introduce the methods for obtaining the insulation resistance of the DC positive terminal to ground and the insulation resistance of the DC negative terminal to ground of the insulation detection circuit for the four combination methods respectively.

[0062] The first method, the schematic diagram of the insulation detection circuit is as follows: Figure 2 As shown, the first end of the DC positive switch branch 200 is used to connect to the DC positive terminal DC1+, and the first end of the DC positive switch Kp is also connected to the DC positive terminal DC1+. The second end of the DC positive switch branch 200 is connected to the second end of the DC positive switch Kp (i.e., the DC positive switch branch 200 is connected in parallel across the two ends of the DC positive switch Kp). The first end of the DC negative switch branch 300 is used to connect to the DC negative terminal DC1-, and the first end of the DC negative switch Kn is also connected to the DC negative terminal DC1-. The second end of the DC negative switch branch 300 is connected to the second end of the DC negative switch Kn (the DC negative switch branch 300 is connected in parallel across the two ends of the DC negative switch Kn).

[0063] The insulation impedance includes the insulation impedance of the input side to ground and the insulation impedance of the output side to ground of the insulation detection circuit. Specifically, the insulation impedance of the input side to ground further includes the insulation impedance of the input side DC positive terminal DC1+ to ground (Rdc1+) and the insulation impedance of the input side DC negative terminal DC1- to ground (Rdc1-), and the insulation impedance of the output side to ground further includes the insulation impedance of the output side DC positive terminal DC2+ to ground (Rdc2+) and the insulation impedance of the output side DC negative terminal DC2- to ground (Rdc2-).

[0064] With the DC positive switch Kp and DC negative switch Kn off, and the DC positive switch branch 200 and DC negative switch branch 300 on, the IMD obtains the first insulation resistance R1+ of the DC positive terminal to ground and the first insulation resistance R1- of the DC negative terminal to ground. The first insulation resistance R1+ of the DC positive terminal to ground and the first insulation resistance R1- of the DC negative terminal to ground are expressed by the following formulas (1) and (2):

[0065] R1 + =(Rdc1 + +R1) / / Rdc2 + (1)

[0066] R1 - = (Rdc1x + R2) / / Rdc2 - (2)

[0067] With the DC positive switch Kp and DC negative switch Kn turned off, and the DC positive switch branch 200 and DC negative switch branch 300 turned off, the IMD measures the insulation resistance Rdc2+ of the output side DC positive terminal to ground and the insulation resistance Rdc2- of the output side DC negative terminal to ground of the insulation detection circuit.

[0068] Combining the aforementioned formula (1), the insulation impedance Rdc1+ of the DC positive terminal to ground on the output side, the first insulation impedance R1+ of the DC positive terminal to ground, and the first resistance R1 are known. Combining the aforementioned formula (2), the insulation impedance Rdc1- of the DC negative terminal to ground on the input side is known.

[0069] The second method, the schematic diagram of the insulation detection circuit is as follows: Figure 3 As shown. The first end of the DC positive switch branch 200 is used to connect to the DC positive terminal DC1+, and the first end of the DC positive switch Kp is also connected to the DC positive terminal DC1+. The second end of the DC positive switch branch 200 is connected to the second end of the DC positive switch Kp (the DC positive switch branch 200 is connected in parallel across the two ends of the DC positive switch Kp). The first end of the DC negative switch branch 300 is used to connect to the DC negative terminal DC1-, and the second end of the DC negative switch branch 300 is connected to the second end of the DC positive switch Kp.

[0070] With the DC positive switch Kp and the DC negative switch Kn off, the DC positive switch branch 200 is turned on and the DC negative switch branch 300 is turned off, so that the insulation monitoring device IMD can obtain the second insulation resistance R2+ of the DC positive terminal to ground. The second insulation resistance R2+ of the DC positive terminal to ground is expressed as shown in the following formula (3):

[0071] R2 + =(Rdc1 + +R1) / / Rdc2 + (3)

[0072] The DC positive switch branch 200 is turned off, and the DC negative switch branch 300 is turned on, so that the insulation monitoring equipment can obtain the third insulation resistance R3+ of the DC positive terminal to ground. The third insulation resistance R3+ of the DC positive terminal to ground is expressed as shown in formula (4):

[0073] R3 + =(Rdc1 - +R2) / / Rdc2 + (4)

[0074] The DC positive switch branch 200 and the DC negative switch branch 300 are turned off so that the insulation monitoring device IMD can obtain the insulation impedance Rdc2+ of the DC positive terminal to ground of the insulation detection circuit.

[0075] Combining the above formulas (3) and (4), with the second insulation impedance R2+ of the DC positive terminal to ground, the third insulation impedance R3+ of the DC positive terminal to ground, the insulation impedance Rdc2+ of the DC positive terminal to ground on the output side, the first resistor R1, and the second resistor R2 known, we can obtain the insulation impedance Rdc1+ of the DC positive terminal to ground on the input side and the insulation impedance Rdc1- of the DC negative terminal to ground on the input side.

[0076] The third method, the schematic diagram of the insulation detection circuit is as follows: Figure 4 As shown. The first end of the DC positive switch branch 200 is used to connect to the DC positive terminal DC1+, and the first end of the DC positive switch Kp is also connected to the DC positive terminal DC1+. The second end of the DC positive switch branch 200 is connected to the second end of the DC negative switch Kn. The first end of the DC negative switch branch 300 is used to connect to the DC negative terminal DC1-, and the first end of the DC negative switch Kn is connected to the DC negative terminal DC1-. The second end of the DC negative switch branch 300 is connected to the second end of the DC negative switch Kn (the DC negative switch branch 300 is connected in parallel across the two ends of the DC negative switch Kn).

[0077] With the DC positive switch Kp and the DC negative switch Kn off, the DC positive switch branch 200 is turned off and the DC negative switch branch 300 is turned on, so that the insulation monitoring device IMD can obtain the second insulation impedance R2- of the DC negative terminal to ground. The second insulation impedance R2- of the DC negative terminal to ground is expressed as shown in the following formula (5):

[0078] R2 - =(Rdc1 - +R2) / / Rdc2 - (5)

[0079] The DC positive switch branch 200 is turned on, and the DC negative switch branch 300 is turned off, so that the insulation monitoring equipment can obtain the third insulation resistance R3- of the DC negative terminal to ground. The third insulation resistance R3- of the DC negative terminal to ground is expressed as shown in the following formula (6):

[0080] R3 - =(Rdc1 + +R1) / / Rdc2 - (6)

[0081] The DC positive switch branch 200 and the DC negative switch branch 300 are turned off so that the insulation monitoring device IMD can obtain the insulation impedance Rdc2- of the DC negative terminal to ground of the output side of the insulation detection circuit.

[0082] Combining the above formulas (5) and (6), with the second insulation impedance R2- of the DC negative terminal to ground, the third insulation impedance R3- of the DC negative terminal to ground, the insulation impedance Rdc2- of the output side DC negative terminal to ground, the first resistor R1, and the second resistor R2 known, the insulation impedance Rdc1+ of the input side DC positive terminal to ground and the insulation impedance Rdc1- of the input side DC negative terminal to ground are obtained.

[0083] The fourth method, the schematic diagram of the insulation detection circuit is as follows: Figure 5 As shown. The first terminal of the DC positive switch branch 200 is used to connect to the DC positive terminal DC1+, and the first terminal of the DC positive switch Kp is also connected to the DC positive terminal DC1+. The second terminal of the DC positive switch branch 200 is connected to the second terminal of the DC negative switch Kn, and the first terminal of the DC negative switch Kn is connected to the DC negative terminal DC1-. The first terminal of the DC negative switch branch 300 is used to connect to the DC negative terminal DC1-, and the second terminal of the DC negative switch branch 300 is connected to the second terminal of the DC positive switch Kp.

[0084] When the DC positive switch Kp and the DC negative switch Kn are off, and the DC positive switch branch 200 and the DC negative switch branch 300 are on, the insulation impedance obtained by the IMD includes the fourth insulation impedance R4+ of the DC positive terminal to ground and the fourth insulation impedance R4- of the DC negative terminal to ground. The fourth insulation impedance R4+ of the DC positive terminal to ground and the fourth insulation impedance R4- of the DC negative terminal to ground are expressed by the following formulas (7) and (8):

[0085] R4 + =(Rdc1 - +R2) / / Rdc2 + (7)

[0086] R4 - =(Rdc1 + +R1) / / Rdc2 - (8)

[0087] With the DC positive switch Kp and DC negative switch Kn off, and the DC positive switch branch 200 and DC negative switch branch 300 off, the IMD obtains the insulation resistance Rdc2+ of the output side DC positive terminal to ground and the insulation resistance Rdc2- of the output side DC negative terminal to ground of the insulation detection circuit.

[0088] Combining the aforementioned formula (7), the insulation impedance R2dc+ of the output side DC positive terminal to ground, the fourth insulation impedance R4+ of the DC positive terminal to ground, and the second resistance R2 can be calculated. Combining the aforementioned formula (8), the insulation impedance Rdc1- of the input side DC negative terminal to ground can be calculated.

[0089] In this embodiment of the application, by obtaining the insulation impedance of the DC positive terminal to ground and the insulation impedance of the DC negative terminal to ground on the input side, the leakage current of the connected device on the input side of the insulation detection circuit can be judged. When the insulation impedance of the DC positive terminal to ground and the insulation impedance of the DC negative terminal to ground on the input side are less than their respective preset thresholds, it can be determined that the connected device on the input side of the insulation detection circuit has leakage current, and an alarm signal is output for the connected device on the input side of the insulation detection circuit.

[0090] In another embodiment, such as Figure 6As shown, the DC positive switch branch 200 includes a first resistor R1, a third switch K3, and a fourth switch K4, and the DC negative switch branch 300 includes a second resistor R2, a fifth switch K5, and a sixth switch K6; wherein, the first ends of the third switch K3 and the fourth switch K4 are both connected to the first resistor R1, the second end of the third switch K3 is connected to the second end of the DC positive switch Kp, the second end of the fourth switch K4 is connected to the second end of the DC negative switch Kn, the first ends of the fifth switch K5 and the sixth switch K6 are both connected to the second resistor R2, the second end of the fifth switch K5 is connected to the second end of the DC negative switch Kn, and the second end of the sixth switch K6 is connected to the second end of the DC positive switch Kp.

[0091] In addition, in the embodiments of this application, the DC positive switch branch 200 can also be in the form of a first branch and a second branch connected in parallel (the first branch includes a first resistor R1 and a third switch K3 connected in series, and the second branch includes a second resistor R2 and a fourth switch K4 connected in series); the DC negative switch branch 300 can also be in the form of a third branch and a fourth branch connected in parallel (the third branch includes a third resistor R3 and a fifth switch K5 connected in series, and the fourth branch includes a fourth resistor R4 and a sixth switch K6 connected in series).

[0092] The processor (not shown in the figure) is specifically used to control the conduction or deactivation of the third switch K3, the fourth switch K4, the fifth switch K5 and the sixth switch K6 when the DC positive switch Kp and the DC negative switch Kn are turned off, so that the insulation monitoring device IMD can obtain the insulation impedance of the input side DC positive terminal to ground and the insulation impedance of the input side DC negative terminal to ground of the insulation detection circuit.

[0093] Corresponding to the previous embodiments, this embodiment has four ways to obtain the insulation resistance of the DC positive terminal to ground and the insulation resistance of the DC negative terminal to ground of the input side of the insulation detection circuit, which will be described one by one below.

[0094] In the first method, with the DC positive switch Kp and the DC negative switch Kn off, the third switch K3 and the fifth switch K5 are turned on, and the IMD obtains the first insulation resistance R1+ of the DC positive terminal to ground and the first insulation resistance R1- of the DC negative terminal to ground. Their corresponding expressions are as described in the aforementioned formulas (1) and (2), respectively. The third switch K3, the fourth switch K4, the fifth switch K5 and the sixth switch K6 are turned off, and the IMD measures the insulation resistance Rdc2+ of the DC positive terminal to ground and the insulation resistance Rdc2- of the DC negative terminal to ground on the output side of the insulation detection circuit.

[0095] Combining the aforementioned formula (1), the insulation impedance Rdc1+ of the DC positive terminal to ground on the output side, the first insulation impedance R1+ of the DC positive terminal to ground, and the first resistance R1 are known. Combining the aforementioned formula (2), the insulation impedance Rdc1- of the DC negative terminal to ground on the input side is known.

[0096] In the second method, with the DC positive switch Kp and the DC negative switch Kn off, the third switch K3 is turned on so that the insulation monitoring device IMD can obtain the second insulation impedance R2+ of the DC positive terminal to ground, which is expressed as in the aforementioned formula (3); the sixth switch K6 is turned on so that the insulation monitoring device can obtain the third insulation impedance R3+ of the DC positive terminal to ground, which is expressed as in the aforementioned formula (4); the third switch K3, the fourth switch K4, the fifth switch K5 and the sixth switch K6 are turned off so that the insulation monitoring device IMD can obtain the insulation impedance Rdc2+ of the DC positive terminal to ground on the output side of the insulation detection circuit.

[0097] Combining the aforementioned formulas (3) and (4), with the second insulation impedance R2+ of the DC positive terminal to ground, the third insulation impedance R3+ of the DC positive terminal to ground, the insulation impedance Rdc2+ of the output side DC positive terminal to ground, the first resistor R1, and the second resistor R2 known, the insulation impedance Rdc1+ of the input side DC positive terminal to ground and the insulation impedance Rdc1- of the input side DC negative terminal to ground are obtained.

[0098] In the third method, with the DC positive switch Kp and the DC negative switch Kn off, the fifth switch K5 is turned on so that the insulation monitoring device IMD can obtain the second insulation impedance R2- of the DC positive and negative terminals to ground. The second insulation impedance R2- of the DC negative terminal to ground is expressed as in the aforementioned formula (5). The fourth switch K4 is turned on so that the insulation monitoring device can obtain the third insulation impedance R3- of the DC negative terminal to ground. The third insulation impedance R3- of the DC negative terminal to ground is expressed as in the aforementioned formula (6). The third switch K3, the fourth switch K4, the fifth switch K5 and the sixth switch K6 are turned off so that the insulation monitoring device IMD can obtain the insulation impedance Rdc2+ of the DC positive terminal to ground on the output side of the insulation detection circuit.

[0099] Combining the aforementioned formulas (5) and (6), with the second insulation impedance R2- of the DC negative terminal to ground, the third insulation impedance R3- of the DC negative terminal to ground, the insulation impedance Rdc2- of the DC negative terminal to ground on the output side, the first resistor R1, and the second resistor R2 known, the insulation impedance Rdc1+ of the DC positive terminal to ground on the input side and the insulation impedance Rdc1- of the DC negative terminal to ground on the input side are obtained.

[0100] In the fourth method, with the DC positive switch Kp and the DC negative switch Kn off, the fourth switch K4 and the sixth switch K6 are turned on, and the IMD obtains the fourth insulation resistance R4+ of the DC positive terminal to ground and the fourth insulation resistance R4- of the DC negative terminal to ground. Their corresponding expressions are as described in the aforementioned formulas (7) and (8), respectively. The third switch K3, the fourth switch K4, the fifth switch K5 and the sixth switch K6 are turned off, and the IMD measures the insulation resistance Rdc2+ of the DC positive terminal to ground and the insulation resistance Rdc2- of the DC negative terminal to ground on the output side of the insulation detection circuit.

[0101] Combining the aforementioned formula (7), the insulation impedance R2dc+ of the output side DC positive terminal to ground, the first insulation impedance R1+ of the DC positive terminal to ground, and the second resistance R2 can be calculated. Combining the aforementioned formula (8), the insulation impedance Rdc1+ of the input side DC positive terminal to ground can be calculated.

[0102] In this embodiment, by using parallel branches, when it is necessary to obtain the insulation impedance of the input side DC positive terminal to ground and the insulation impedance of the input side DC negative terminal to ground, a convenient method can be selected, such as the first method, the second method, the third method and the fourth method described in the embodiment, thereby improving the diversity of ways to obtain the insulation impedance of the input side DC positive terminal to ground and the insulation impedance of the input side DC negative terminal to ground.

[0103] In yet another embodiment, such as Figure 7 As shown, the DC positive switch branch 200 includes a first resistor R1 and a first single-pole double-throw switch K7 connected in series, and the DC negative switch branch 300 includes a second resistor R2 and a second single-pole double-throw switch K8 connected in series; wherein, the first moving end (1) of the first single-pole double-throw switch K7 is connected to the second end of the DC positive switch Kp, the second moving end (2) of the first single-pole double-throw switch K7 is connected to the second end of the DC negative switch Kn, the first moving end (1) of the second single-pole double-throw switch K8 is connected to the second end of the DC negative switch Kn, and the second moving end (2) of the second single-pole double-throw switch K8 is connected to the second end of the DC positive switch Kp.

[0104] The processor (not shown in the figure) is specifically used to control the conduction or deactivation of the first single-pole double-throw switch K7 and the second single-pole double-throw switch K8 when the DC positive switch Kp and the DC negative switch Kn are turned off, so that the insulation monitoring device IMD can obtain the insulation impedance of the input side DC positive terminal to ground and the insulation impedance of the input side DC negative terminal to ground of the insulation detection circuit; wherein, the conduction of the first single-pole double-throw switch K7 and the second single-pole double-throw switch K8 both include the conduction of the first moving end and the conduction of the second moving end.

[0105] Corresponding to the previous embodiments, this embodiment has four ways to obtain the insulation resistance of the DC positive terminal to ground and the insulation resistance of the DC negative terminal to ground of the input side of the insulation detection circuit, which will be described one by one below.

[0106] In the first method, with the DC positive switch Kp and the DC negative switch Kn off, the first moving end of the first single-pole double-throw switch K7 and the first moving end of the second single-pole double-throw switch K8 are turned on. The IMD obtains the first insulation resistance R1+ of the DC positive terminal to ground and the first insulation resistance R1- of the DC negative terminal to ground, and their corresponding expressions are as described in the aforementioned formulas (1) and (2). The first single-pole double-throw switch K7 and the second single-pole double-throw switch K8 are turned off. The IMD measures the insulation resistance Rdc2+ of the DC positive terminal to ground and the insulation resistance Rdc2- of the DC negative terminal to ground on the output side of the insulation detection circuit.

[0107] Combining the aforementioned formula (1), the insulation impedance Rdc1+ of the DC positive terminal to ground on the output side, the first insulation impedance R1+ of the DC positive terminal to ground, and the first resistance R1 are known. Combining the aforementioned formula (2), the insulation impedance Rdc1- of the DC negative terminal to ground on the input side is known.

[0108] In the second method, with the DC positive switch Kp and the DC negative switch Kn off, the first moving terminal of the first single-pole double-throw switch K7 is turned on and the second single-pole double-throw switch K8 is turned off, so that the insulation monitoring device IMD can obtain the second insulation impedance R2+ of the DC positive terminal to ground, which is expressed as in the aforementioned formula (3); the first single-pole double-throw switch K7 is turned off and the second moving terminal of the second single-pole double-throw switch K8 is turned on, so that the insulation monitoring device can obtain the third insulation impedance R3+ of the DC positive terminal to ground, which is expressed as in the aforementioned formula (4); the first single-pole double-throw switch K7 and the second single-pole double-throw switch K8 are turned off, so that the insulation monitoring device IMD can obtain the insulation impedance Rdc2+ of the DC positive terminal to ground on the output side of the insulation detection circuit.

[0109] Combining the aforementioned formulas (3) and (4), with the second insulation impedance R2+ of the DC positive terminal to ground, the third insulation impedance R3+ of the DC positive terminal to ground, the insulation impedance Rdc2+ of the output side DC positive terminal to ground, the first resistor R1, and the second resistor R2 known, the insulation impedance Rdc1+ of the input side DC positive terminal to ground and the insulation impedance Rdc1- of the input side DC negative terminal to ground are obtained.

[0110] In the third method, when the DC positive switch Kp and the DC negative switch Kn are turned off, the first single-pole double-throw switch K7 is turned off and the first moving end of the second single-pole double-throw switch K8 is turned on, so that the insulation monitoring device IMD can obtain the second insulation impedance R2- of the DC positive and negative poles to ground. The second insulation impedance R2- of the DC negative pole to ground is expressed as in the aforementioned formula (5); the second moving end of the first single-pole double-throw switch K7 is turned on and the second single-pole double-throw switch K8 is turned off, so that the insulation monitoring device can obtain the third insulation impedance R3- of the DC negative pole to ground. The third insulation impedance R3- of the DC negative pole to ground is expressed as in the aforementioned formula (6); the first single-pole double-throw switch K7 and the second single-pole double-throw switch K8 are turned off, so that the insulation monitoring device IMD can obtain the insulation impedance Rdc2+ of the DC positive pole to ground on the output side of the insulation detection circuit.

[0111] Combining the aforementioned formulas (5) and (6), with the second insulation impedance R2- of the DC negative terminal to ground, the third insulation impedance R3- of the DC negative terminal to ground, the insulation impedance Rdc2- of the DC negative terminal to ground on the output side, the first resistor R1, and the second resistor R2 known, the insulation impedance Rdc1+ of the DC positive terminal to ground on the input side and the insulation impedance Rdc1- of the DC negative terminal to ground on the input side are obtained.

[0112] In the fourth method, when the DC positive switch Kp and the DC negative switch Kn are turned off, the second moving terminal of the first single-pole double-throw switch K7 and the second moving terminal of the second single-pole double-throw switch K8 are turned on, and the IMD obtains the fourth insulation resistance R4+ of the DC positive terminal to ground and the fourth insulation resistance R4- of the DC negative terminal to ground, and their corresponding expressions are as described in the aforementioned formulas (7) and (8), respectively; when the first single-pole double-throw switch K7 and the second single-pole double-throw switch K8 are turned off, the IMD measures the insulation resistance Rdc2+ of the DC positive terminal to ground on the output side and the insulation resistance Rdc2- of the DC negative terminal to ground on the output side of the insulation detection circuit.

[0113] Combining the aforementioned formula (7), the insulation impedance R2dc+ of the output side DC positive terminal to ground, the first insulation impedance R1+ of the DC positive terminal to ground, and the second resistance R2 can be calculated. Combining the aforementioned formula (8), the insulation impedance Rdc1+ of the input side DC positive terminal to ground can be calculated.

[0114] In this embodiment, by using a single-pole double-throw switch, when it is necessary to obtain the insulation impedance of the input side DC positive terminal to ground and the insulation impedance of the input side DC negative terminal to ground, a convenient method can be selected, such as the first method, the second method, the third method and the fourth method described in the embodiment, thereby improving the diversity of ways to obtain the insulation impedance of the input side DC positive terminal to ground and the insulation impedance of the input side DC negative terminal to ground.

[0115] The previous section provided a detailed introduction to insulation detection circuits. The following section will introduce several application products of insulation detection circuits.

[0116] See Figure 8 The figure is a schematic diagram of the structure of a charging pile provided in an embodiment of this application.

[0117] like Figure 8 As shown, the charging pile includes: a power conversion circuit 3000 and an insulation detection circuit 1000 in any of the aforementioned embodiments; the first end of the insulation detection circuit 1000 is used to connect to the DC side of the power conversion circuit 3000, and the second end of the insulation detection circuit 1000 is used to connect to the device to be charged.

[0118] This application does not specifically limit the type of the power conversion circuit 3000. For example, the power conversion circuit 3000 may include a DC-DC power conversion circuit and an AC-DC power conversion circuit, or it may be an AC-DC power conversion circuit. When the power conversion circuit 3000 includes both a DC-DC power conversion circuit and an AC-DC power conversion circuit, the AC side of the AC-DC power conversion circuit is used to connect to the power grid, the DC side of the AC-DC power conversion circuit is connected to the first terminal of the DC-DC power conversion circuit, and the second terminal of the DC-DC power conversion circuit is connected to the first terminal of the insulation detection circuit. The second terminal of the insulation detection circuit is used to connect to the device to be charged.

[0119] The controller (not shown in the figure) is used to detect the leakage current status of the power conversion circuit based on the insulation impedance of the input side of the insulation detection circuit.

[0120] Specifically, the controller is used to ensure that the power conversion circuit is normal when the insulation impedance of the DC positive terminal to ground on the input side of the insulation detection circuit is greater than or equal to a preset threshold, and the insulation impedance of the DC negative terminal to ground on the input side is greater than or equal to a preset threshold; when the insulation impedance of the DC positive terminal to ground on the input side is less than a preset threshold, and the insulation impedance of the DC negative terminal to ground on the input side is less than a preset threshold, the power conversion circuit is leaking current and an alarm signal is issued.

[0121] For example, the input-side insulation resistance is Rdc1+ and Rdc1-, and the output voltage of the charging pile is U. When both U / Rdc1+ and U / Rdc1- are greater than the preset threshold, the power conversion circuit is normal; when U / Rdc1+ and / or U / Rdc1- are less than the preset threshold, the power conversion circuit leaks current and issues an alarm signal.

[0122] In this embodiment, when the DC positive switch and DC negative switch are turned off, the insulation detection circuit is connected to the DC positive switch branch and the DC negative switch branch, so that the insulation monitoring device can measure the insulation impedance on the input side of the insulation detection circuit, thereby improving the safety of the charging pile.

[0123] See Figure 9 The figure is a schematic diagram of the structure of a photovoltaic inverter also provided in this application embodiment.

[0124] like Figure 9 As shown, the photovoltaic inverter includes: a power conversion circuit 2000 and an insulation detection circuit 1000 in any of the aforementioned embodiments; the first end of the insulation detection circuit 1000 is used to connect to the photovoltaic module (PV+ and PV-), and the second end of the insulation detection circuit 1000 is connected to the DC side of the power conversion circuit 2000.

[0125] The controller (not shown in the figure) is used to detect the leakage current status of the photovoltaic module based on the insulation impedance on the input side of the insulation detection circuit.

[0126] In this embodiment of the application, the insulation detection circuit in the photovoltaic inverter detects the DC side insulation impedance in real time. When the insulation impedance on the input side of the insulation detection circuit is greater than a preset threshold, the photovoltaic module is normal; when the insulation impedance is less than or equal to the preset threshold, the photovoltaic module leaks current and sends an alarm signal.

[0127] The embodiments of this application do not specifically limit the type of power conversion circuit 2000. For example, the power conversion circuit 2000 is a DC-DC power conversion circuit or a DC-AC power conversion circuit.

[0128] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0129] The above description of the disclosed embodiments enables those skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An insulation detection circuit, characterized by comprising: The application relates to an insulation monitoring device, a direct-current positive electrode switch, a direct-current negative electrode switch, a direct-current positive electrode switch branch, a direct-current negative electrode switch branch and a processor. A first end of the insulation monitoring device is connected with a direct-current positive electrode through the direct-current positive electrode switch, and a second end of the insulation monitoring device is connected with a direct-current negative electrode through the direct-current negative electrode switch. A first end of the direct-current positive electrode switch branch is used for connecting the direct-current positive electrode, and a second end of the direct-current positive electrode switch branch is connected with a second end of the direct-current positive electrode switch or a second end of the direct-current negative electrode switch; a first end of the direct-current negative electrode switch branch is used for connecting the direct-current negative electrode, and a second end of the direct-current negative electrode switch branch is connected with the second end of the direct-current negative electrode switch or the second end of the direct-current positive electrode switch. Control ends of the direct-current positive electrode switch branch and the direct-current negative electrode switch branch and an output end of the insulation monitoring device are connected with the processor. The processor is used for controlling the conduction and the turn-off of the direct-current positive electrode switch branch and the direct-current negative electrode switch branch, so that the insulation monitoring device obtains the insulation impedance of the input side direct-current positive electrode to the ground and the insulation impedance of the input side direct-current negative electrode to the ground.

2. The insulation detection circuit according to claim 1, characterized by The direct-current positive electrode switch branch comprises a first resistance and a first switch connected in series, and the direct-current negative electrode switch branch comprises a second resistance and a second switch connected in series.

3. The insulation detection circuit according to claim 2, characterized in that, The processor is specifically used for controlling the conduction or the turn-off of the first switch and the second switch under the condition that the direct-current positive electrode switch and the direct-current negative electrode switch are turned off, so that the insulation monitoring device obtains the insulation impedance of the input side direct-current positive electrode to the ground and the insulation impedance of the input side direct-current negative electrode to the ground. The direct-current positive electrode switch branch is connected in parallel at two ends of the direct-current positive electrode switch, and the direct-current negative electrode switch branch is connected in parallel at two ends of the direct-current negative electrode switch.

4. The insulation detection circuit according to claim 2 or 3, characterized in that, The processor is specifically used for controlling the conduction of the direct-current positive electrode switch branch and the direct-current negative electrode switch branch under the condition that the direct-current positive electrode switch and the direct-current negative electrode switch are turned off, so that the insulation monitoring device obtains the first insulation impedance of the direct-current positive electrode to the ground and the first insulation impedance of the direct-current negative electrode to the ground, controlling the turn-off of the direct-current positive electrode switch branch and the direct-current negative electrode switch branch, so that the insulation monitoring device obtains the insulation impedance of the output side direct-current positive electrode to the ground and the insulation impedance of the output side direct-current negative electrode to the ground; the insulation impedance of the input side direct-current positive electrode to the ground is obtained according to the first insulation impedance of the direct-current positive electrode to the ground and the insulation impedance of the output side direct-current positive electrode to the ground, and the insulation impedance of the input side direct-current negative electrode to the ground is obtained according to the first insulation impedance of the direct-current negative electrode to the ground and the insulation impedance of the output side direct-current negative electrode to the ground. The direct-current positive electrode switch branch is connected in parallel at two ends of the direct-current positive electrode switch, and the first end of the direct-current negative electrode switch branch is used for connecting the direct-current negative electrode, and the second end of the direct-current negative electrode switch branch is connected with the second end of the direct-current positive electrode switch.

5. The insulation detection circuit according to claim 2 or 3, characterized in that, ​ The processor is specifically configured to: in the case that the DC positive electrode switch and the DC negative electrode switch are turned off, control the DC positive electrode switch branch to be turned on and the DC negative electrode switch branch to be turned off, so that the insulation monitoring device obtains a second insulation impedance of the DC positive electrode to ground; control the DC positive electrode switch branch to be turned off and the DC negative electrode switch branch to be turned on, so that the insulation monitoring device obtains a third insulation impedance of the DC positive electrode to ground; and control the DC positive electrode switch branch and the DC negative electrode switch branch to be turned off, so that the insulation monitoring device obtains an insulation impedance of the output side DC positive electrode to ground; and obtain an insulation impedance of the input side DC positive electrode to ground and an insulation impedance of the input side DC negative electrode to ground according to the second insulation impedance of the DC positive electrode to ground, the third insulation impedance of the DC positive electrode to ground and the insulation impedance of the output side DC positive electrode to ground.

6. The insulation detection circuit according to claim 2 or 3, characterized by The first end of the DC positive electrode switch branch is configured to be connected to the DC positive electrode, the second end of the DC positive electrode switch branch is connected to the second end of the DC negative electrode switch branch, and the DC negative electrode switch branch is connected in parallel between the two ends of the DC negative electrode switch. The processor is specifically configured to: in the case that the DC positive electrode switch and the DC negative electrode switch are turned off, control the DC positive electrode switch branch to be turned off and the DC negative electrode switch branch to be turned on, so that the insulation monitoring device obtains a second insulation impedance of the DC negative electrode to ground; control the DC positive electrode switch branch to be turned on and the DC negative electrode switch branch to be turned off, so that the insulation monitoring device obtains a third insulation impedance of the DC negative electrode to ground; and control the DC positive electrode switch branch and the DC negative electrode switch branch to be turned off, so that the insulation monitoring device obtains an insulation impedance of the output side DC negative electrode to ground; and obtain an insulation impedance of the input side DC positive electrode to ground and an insulation impedance of the input side DC negative electrode to ground according to the second insulation impedance of the DC negative electrode to ground, the third insulation impedance of the DC negative electrode to ground and the insulation impedance of the output side DC negative electrode to ground.

7. The insulation detection circuit according to claim 2 or 3, characterized by The first end of the DC positive electrode switch branch is configured to be connected to the DC positive electrode, the second end of the DC positive electrode switch branch is connected to the second end of the DC negative electrode switch branch, the first end of the DC negative electrode switch branch is configured to be connected to the DC negative electrode, and the second end of the DC negative electrode switch branch is connected to the second end of the DC positive electrode switch. The processor is specifically configured to control the DC positive electrode switch branch and the DC negative electrode switch branch to be turned on in the case that the DC positive electrode switch and the DC negative electrode switch are turned off, so that the insulation monitoring device obtains a fourth insulation impedance of the DC positive electrode to ground and a fourth insulation impedance of the DC negative electrode to ground, and controls the DC positive electrode switch branch and the DC negative electrode switch branch to be turned off, so that the insulation monitoring device obtains an insulation impedance of the output side DC positive electrode to ground and an insulation impedance of the output side DC negative electrode to ground of the insulation detection circuit; obtains an insulation impedance of the input side DC negative electrode to ground according to the fourth insulation impedance of the DC positive electrode to ground and the insulation impedance of the output side DC positive electrode to ground, and obtains an insulation impedance of the input side DC positive electrode to ground according to the fourth insulation impedance of the DC negative electrode to ground and the insulation impedance of the output side DC negative electrode to ground.

8. The insulation detection circuit according to claim 2, characterized by The DC positive electrode switch branch comprises a first resistor, a third switch and a fourth switch, and the DC negative electrode switch branch comprises a second resistor, a fifth switch and a sixth switch; wherein the first ends of the third switch and the fourth switch are connected to the first resistor, the second end of the third switch is connected to the second end of the DC positive electrode switch, the second end of the fourth switch is connected to the second end of the DC negative electrode switch, the first ends of the fifth switch and the sixth switch are connected to the second resistor, the second end of the fifth switch is connected to the second end of the DC negative electrode switch, and the second end of the sixth switch is connected to the second end of the DC positive electrode switch. The processor is specifically configured to control the third switch, the fourth switch, the fifth switch and the sixth switch to be turned on or turned off in the case that the DC positive electrode switch and the DC negative electrode switch are turned off, so that the insulation monitoring device obtains an insulation impedance of the input side DC positive electrode to ground and an insulation impedance of the input side DC negative electrode to ground of the insulation detection circuit.

9. The insulation detection circuit according to claim 2, characterized by The DC positive electrode switch branch comprises a first resistor and a first single-pole double-throw switch connected in series, and the DC negative electrode switch branch comprises a second resistor and a second single-pole double-throw switch connected in series; wherein the first movable terminal of the first single-pole double-throw switch is connected to the second end of the DC positive electrode switch, the second movable terminal of the first single-pole double-throw switch is connected to the second end of the DC negative electrode switch, the first movable terminal of the second single-pole double-throw switch is connected to the second end of the DC negative electrode switch, and the second movable terminal of the second single-pole double-throw switch is connected to the second end of the DC positive electrode switch. The processor is specifically configured to control the first single-pole double-throw switch and the second single-pole double-throw switch to be turned on or turned off in the case that the DC positive electrode switch and the DC negative electrode switch are turned off, so that the insulation monitoring device obtains an insulation impedance of the input side DC positive electrode to ground and an insulation impedance of the input side DC negative electrode to ground of the insulation detection circuit; wherein the turning on of the first single-pole double-throw switch and the second single-pole double-throw switch comprises turning on the first movable terminal and turning on the second movable terminal.

10. The insulation detection circuit of claim 1, wherein The DC positive electrode switch and the DC negative electrode switch each comprise any one of a contactor and a relay.

11. The insulation detection circuit according to claim 3, characterized by The first switch and the second switch each include any one of a triode, a metal-oxide semiconductor field effect transistor, and a relay.

12. The insulation detection circuit of claim 8, wherein The third switch, the fourth switch, the fifth switch, and the sixth switch each include any one of a triode, a metal-oxide semiconductor field effect transistor, and a relay.

13. The insulation detection circuit of claim 9, wherein The first single-pole double-throw switch and the second single-pole double-throw switch each include a relay.

14. A charging post, characterized by The application further discloses a power conversion circuit, a controller, and an insulation detection circuit. The first end of the insulation detection circuit is connected to a direct current side of the power conversion circuit, and the second end of the insulation detection circuit is used for connecting a device to be charged. The controller is used for detecting a leakage state of the power conversion circuit according to insulation impedances of a direct current positive electrode to ground and a direct current negative electrode to ground at an input side of the insulation detection circuit when the direct current positive electrode switch and the direct current negative electrode switch are turned off. The application further discloses a power conversion circuit, a controller, and an insulation detection circuit.

15. A photovoltaic inverter, characterized by The first end of the insulation detection circuit is connected to a direct current side of the power conversion circuit, and the second end of the insulation detection circuit is used for connecting a device to be charged. The controller is used for detecting a leakage state of the power conversion circuit according to insulation impedances of a direct current positive electrode to ground and a direct current negative electrode to ground at an input side of the insulation detection circuit when the direct current positive electrode switch and the direct current negative electrode switch are turned off. ​ ​

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