Insulation detection circuit, charging pile and photovoltaic inverter

Abstract

The utility model discloses an insulation detection circuit, a charging pile and a photovoltaic inverter. Wherein the first end of a first voltage sampling branch in the insulation detection circuit is connected with a direct current positive electrode, and the second end of the first voltage sampling branch is connected with the ground; the second end of the second voltage sampling branch is connected with the direct current negative electrode, and the second end of the second voltage sampling branch is grounded; the first end of the operational amplifier circuit is connected with the DC anode, and the second end of the operational amplifier circuit is grounded through a constant voltage source; the output end of the first voltage sampling circuit, the output end of the second voltage sampling circuit and the output end of the operational amplifier circuit are connected with the processor; the first voltage sampling circuit is used for obtaining a first voltage of the direct-current positive electrode to the ground; and the second voltage sampling circuit is used for obtaining a second voltage of the ground to the direct-current negative electrode. The insulation resistance is obtained by using the constant voltage source, the accuracy of the current and voltage sampling circuit is improved, and the stability of the power supply equipment is further improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of power electronics, especially to an insulation detection circuit, a charging pile and a photovoltaic inverter. BACKGROUND

[0002] Generally, the power supply equipment is installed outdoors, and with the alternation of different weather conditions such as high temperature and low temperature, the insulation of the power supply equipment may decrease. When the insulation of the power supply equipment decreases to a certain extent, leakage current may be generated in the process of use of the power supply equipment, which threatens personal safety. Therefore, the impedance value of the transmission system to the ground needs to be detected in the process of using the charging pile.

[0003] In the related art, the impedance value of the transmission system to the ground is obtained by injecting a signal with a fixed frequency and a voltage amplitude changing in a cycle into the ground. However, the above method brings voltage ripple to the ground of the charging system, affects the accuracy of the voltage and current acquisition circuit with the ground as a reference ground, and further affects the stability of the power supply equipment. SUMMARY

[0004] Based on the above problems, the utility model provides an insulation detection circuit, a charging pile and a photovoltaic inverter, which obtains insulation impedance through a constant voltage source, improves the accuracy of the current and voltage sampling circuit, and further improves the stability of the power supply equipment.

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

[0006] In a first aspect, the embodiments of the present application provide an insulation detection circuit, which comprises a first voltage sampling branch, a second voltage sampling branch, an operational amplifier circuit and a processor.

[0007] The first end of the first voltage sampling branch is connected to a direct current positive electrode, and the second end of the first voltage sampling branch is connected to the ground. The first end of the second voltage sampling branch is connected to a direct current negative electrode, and the second end of the second voltage sampling branch is connected to the ground. The first end of the operational amplifier circuit is connected to the direct current positive electrode, and the second end of the operational amplifier circuit is connected to the ground through a constant voltage source.

[0008] The output end of the first voltage sampling circuit, the output end of the second voltage sampling circuit and the output end of the operational amplifier circuit are connected to the processor.

[0009] Optionally, the operational amplifier circuit comprises a third resistor, a fourth resistor and an operational amplifier.

[0010] The first end of the third resistor is connected to the direct current positive electrode, the second end of the third resistor is connected to the first end of the fourth resistor, the second end of the fourth resistor is connected to the output end of the operational amplifier, the reverse input end of the operational amplifier is connected to the first end of the fourth resistor, and the forward input end of the operational amplifier is connected to the ground through the constant voltage source.

[0011] Optionally, the first voltage sampling branch comprises a first resistor and a first sampling resistor, and the second voltage sampling branch comprises a second resistor and a second sampling resistor;

[0012] A first end of the first resistor is connected to a positive pole of a direct current, a second end of the first resistor is connected to a first end of the first sampling resistor, and a second end of the second sampling resistor is used for connecting to a ground;

[0013] A first end of the second resistor is connected to a negative pole of the direct current, a second end of the second resistor is connected to a first end of the second sampling resistor, and a second end of the second sampling resistor is used for connecting to the ground.

[0014] Optionally, the operational amplifier circuit further comprises a first switching device;

[0015] A first end of the first switching device is connected to the positive pole of the direct current, and a second end of the first switching device is connected to a first end of a third resistor.

[0016] Optionally, the insulation detection circuit further comprises a second switching device and a third switching device;

[0017] The second switching device is used for controlling conduction of the positive pole of the direct current;

[0018] The third switching device is used for controlling conduction of the negative pole of the direct current.

[0019] Optionally, a resistance value of the first resistor is equal to a resistance value of the second resistor, and a resistance value of the first sampling resistor is equal to a resistance value of the second sampling resistor.

[0020] Optionally, the first switching device comprises any one of a triode, a metal-oxide semiconductor field effect transistor and a relay.

[0021] Optionally, the processor is used for obtaining a first voltage of the positive pole of the direct current to the ground according to the first voltage sampling branch, obtaining a second voltage of the ground to the negative pole of the direct current according to the second voltage sampling branch, and obtaining the insulation impedance according to the first voltage, the second voltage, a voltage of the constant voltage source and an output voltage of the operational amplifier circuit.

[0022] In a second aspect, an embodiment of the present application provides a charging pile, comprising: a power conversion circuit, a controller and an insulation detection circuit according to any one of the first aspect;

[0023] A direct current side of the power conversion circuit is connected to a first end of the insulation detection circuit, and a second end of the insulation detection circuit is used for connecting to a device to be charged;

[0024] The controller is used for controlling a state of the charging pile according to the insulation impedance; wherein the state of the charging pile comprises a charging state and a prohibited charging state.

[0025] In a third aspect, the embodiments of the present application provide a photovoltaic inverter, comprising: a power conversion circuit, a controller and an insulation detection circuit as any of the embodiments of the first aspect;

[0026] The first end of the insulation detection circuit is configured to be connected to the photovoltaic module, and the second end of the insulation detection circuit is connected to the DC side of the power conversion circuit;

[0027] The controller is configured to control the state of the photovoltaic inverter according to the insulation impedance, and the state of the photovoltaic inverter comprises a power conversion state and a power conversion prohibited state.

[0028] The method of obtaining the insulation resistance by injecting a signal (with a fixed frequency and a voltage amplitude changing in a period) into the ground can cause voltage ripple, affecting the accuracy of the voltage and current acquisition circuit with the ground as a reference ground, and further affecting the stability of the power supply device. Therefore, in the embodiments of the present application, the insulation resistance is obtained by using a constant voltage source, which improves the accuracy of the voltage and current acquisition circuit and further improves the stability of the power supply device. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description. Obviously, the drawings described below are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0030] Figure 1 A schematic diagram of an insulation detection circuit provided by the embodiments of the present application is shown in the figure;

[0031] Figure 2 A schematic diagram of an operational amplifier circuit provided by the embodiments of the present application is shown in the figure;

[0032] Figure 3 A schematic diagram of another operational amplifier circuit provided by the embodiments of the present application is shown in the figure;

[0033] Figure 4 A schematic diagram of a voltage sampling circuit provided by the embodiments of the present application is shown in the figure;

[0034] Figure 5 A schematic diagram of another insulation detection circuit provided by the embodiments of the present application is shown in the figure;

[0035] Figure 6 A structural schematic diagram of a charging pile provided by the embodiments of the present application is shown in the figure;

[0036] Figure 7 A structural schematic diagram of a photovoltaic inverter provided by the embodiments of the present application is shown in the figure. DETAILED DESCRIPTION

[0037] In order to make the personnel in the technical field better understand the scheme of the present application, the technical scheme in the present embodiment will be clearly and completely described in combination with the drawings in the present embodiment. Obviously, the described embodiments are only some of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor belong to the scope of protection of the present application.

[0038] The terms "first" and "second" and the like in the specification and claims of the present application are used to distinguish different objects, not to describe a specific order of the objects. For example, the first resistor and the second resistor are used to distinguish different resistors, not to describe a specific order of the resistors.

[0039] In the present embodiment, the words such as "exemplary" or "for example" are used to mean an example, illustration, or description. Any embodiment or design scheme described as "exemplary" or "for example" in the present embodiment should not be interpreted as more preferred or more advantageous than other embodiments or design schemes. Rather, the words such as "exemplary" or "for example" are intended to present the relevant concept in a specific manner.

[0040] In the description of the present embodiment, unless otherwise specified, "a plurality of" means two or more, for example, a plurality of processing units means two or more processing units, and the like; a plurality of elements means two or more elements, and the like.

[0041] In order to facilitate understanding of the technical scheme of the present application, the application scenario of the power supply equipment as a charging pile will be introduced below.

[0042] The charging pile is installed outdoors. With the alternation of different weather conditions such as high temperature and low temperature, the insulation performance of the charging pile may decrease. When the insulation performance decreases to a certain extent, leakage current will be generated in the process of using the charging pile, and the leakage current flows through the human body to the ground, which is dangerous to personal safety. Therefore, during the charging process of the new energy vehicle, the impedance value of the transmission system to the ground needs to be detected in real time. When low impedance is detected, the charging is disconnected in time to protect personal safety. In the related art, the impedance value of the transmission system to the ground is obtained by injecting a signal of a fixed frequency and a voltage amplitude changing in a cycle to the ground. However, the above method will bring voltage ripple to the ground of the charging system, which will affect the accuracy of the voltage and current acquisition circuit with the ground as a reference, and further affect the stability of the power supply equipment.

[0043] To this end, the embodiment of the present application provides an insulation detection circuit, which comprises a first voltage sampling branch, a second voltage sampling branch, an operational amplifier circuit and a processor; a first end of the first voltage sampling branch is connected to a direct current positive pole, and a second end of the first voltage sampling branch is connected to a ground; a second end of the second voltage sampling branch is connected to a direct current negative pole, and a second end of the second voltage sampling branch is connected to the ground; a first end of the operational amplifier circuit is connected to the direct current positive pole, and a second end of the operational amplifier circuit is connected to the ground through a constant voltage source; an output end of the first voltage sampling circuit, an output end of the second voltage sampling circuit and an output end of the operational amplifier circuit are connected to the processor; the first voltage sampling circuit is configured to obtain a first voltage of the direct current positive pole to the ground; the second voltage sampling circuit is configured to obtain a second voltage of the ground to the direct current negative pole; and the processor is configured to obtain an insulation impedance according to the first voltage, the second voltage, a voltage of the constant voltage source and an output voltage of the operational amplifier circuit.

[0044] The insulation detection circuit will be described below in combination with specific embodiments.

[0045] Referring to Figure 1 , the figure is a schematic diagram of an insulation detection circuit provided by the embodiment of the present application.

[0046] As Figure 1 indicated, the insulation detection circuit comprises a first voltage sampling branch 100, a second voltage sampling branch 200, an operational amplifier circuit 300 and a processor 400.

[0047] A first end of the first voltage sampling branch 100 is connected to a direct current positive pole DC1+, and a second end of the first voltage sampling branch 100 is connected to a ground PE; a second end of the second voltage sampling branch 200 is connected to a direct current negative pole DC1-, and a second end of the second voltage sampling branch 200 is connected to the ground PE; a first end of the operational amplifier circuit 300 is connected to the direct current positive pole DC1+, and a second end of the operational amplifier circuit 300 is connected to the ground PE through a constant voltage source; an output end of the first voltage sampling circuit 100, an output end of the second voltage sampling circuit 200 and an output end of the operational amplifier circuit 300 are connected to the processor 400.

[0048] It should be noted that Figure 1 DC1+ and DC1- in the above are used as input ends of the insulation detection circuit, and DC2+ and DC2- are used as output ends of the insulation detection circuit.

[0049] In a possible implementation manner, as Figure 2As shown, the operational amplification circuit 300 comprises a third resistor R3, a fourth resistor R4 and an operational amplifier OP. The first end of the third resistor R3 is connected to the direct current positive pole DC1+, the second end of the third resistor R3 is connected to the first end of the fourth resistor R4, the second end of the fourth resistor R4 is connected to the output end of the operational amplifier OP, the reverse input end of the operational amplifier OP is connected to the first end of the fourth resistor R4, and the forward input end of the operational amplifier OP is connected to the ground through the constant voltage source DC.

[0050] For example, the output voltage of the operational amplifier OP is U op , and the output voltage of the constant voltage source DC is Us. The insulation impedance R+ is calculated by using the "virtual short" and "virtual open" characteristics of the operational amplifier OP. The "virtual short" means that the reverse input end and the forward input end of the operational amplifier OP are at the same potential, and the "virtual open" means that the current flowing into the input end of the operational amplifier OP is zero. By using the "virtual short" and "virtual open" of the operational amplifier OP, the constant voltage source flows to the ground PE through the third resistor R3 (R3 belongs to the operational amplification circuit 300), the first resistor R1 (R1 belongs to the first voltage sampling branch 100), the first voltage sampling resistor r1 (r1 belongs to the first voltage sampling branch 100) and the insulation resistor R+, and the current flowing through the third resistor R3, the first resistor R1, the first voltage sampling resistor r1 and the insulation resistor R+ is equal to the current flowing through the fourth resistor R4, as shown in the following formula (1). Since the insulation resistor R+ and the resistors (R1 and r1) on the first voltage sampling branch are connected in parallel, the following formula (2) can be obtained:

[0051]

[0052] It should be understood that " / / " in the above formula represents a parallel relationship. Since the output voltage U op of the operational amplifier OP, the first resistor R1, the first voltage sampling resistor r1, the third resistor R3, the fourth resistor R4 and the voltage U s of the constant voltage source are known quantities, the insulation impedance R+ can be obtained by the above formula (1) and formula (2).

[0053] To meet the requirement of obtaining the insulation impedance in real time, i.e. updating the insulation impedance, the present embodiment provides another schematic diagram of an operational amplification circuit, as shown in Figure 3 .

[0054] As Figure 3As shown, the operational amplification circuit 300 includes a first switching device S1, a third resistor R3, a fourth resistor R4 and an operational amplifier OP. The first end of the first switching device S1 is connected to the direct current positive pole DC1+, the second end of the first switching device S1 is connected to the first end of the third resistor R3, the second end of the third resistor R3 is connected to the first end of the fourth resistor R4, the second end of the fourth resistor R4 is connected to the output end of the operational amplifier OP, the reverse input end of the operational amplifier OP is connected to the first end of the fourth resistor R4, and the forward input end of the operational amplifier OP is connected to the ground through the constant voltage source DC.

[0055] For example, the first switching device S1 can be any one of a triode, a metal-oxide semiconductor field effect transistor and a relay.

[0056] The embodiment of the present application can detect the insulation impedance in real time by controlling the conduction and turn-off of the first switching device S1, i.e., update the insulation impedance.

[0057] To improve the safety of the power supply device, the embodiment of the present application needs to obtain the insulation impedance R+ and R- at the same time.

[0058] The processor 400 is configured to obtain the insulation impedance R+ and R- according to the first voltage U1, the second voltage U2, the voltage Us of the constant voltage source DC and the output voltage Uop of the operational amplification circuit 300.

[0059] It should be understood that, in the foregoing embodiment, the embodiment of the present application obtains the insulation impedance R+ by using the "virtual short" and "virtual open" of the power amplifier based on the output voltage Uop of the operational amplification circuit and the voltage Us of the constant voltage source. The way of obtaining the insulation impedance R- will be introduced below.

[0060] In a possible implementation manner, as shown in Figure 4 The first voltage sampling circuit 100 includes a first resistor R1 and a first sampling resistor r1, and the second voltage sampling branch 200 includes a second resistor R2 and a second sampling resistor r2. The first end of the first resistor R1 is connected to the direct current positive pole DC1+, the second end of the first resistor R1 is connected to the first end of the first sampling resistor r1, the second end of the first sampling resistor r1 is connected to the ground PE; the first end of the second resistor R2 is connected to the direct current negative pole DC1-, the second end of the second resistor R2 is connected to the first end of the second sampling resistor r2, and the second end of the second sampling resistor is connected to the ground PE.

[0061] The embodiments of this application do not specifically limit the specific connection method of the first voltage sampling circuit 100 and the second voltage sampling circuit 200. For example, in the first sampling circuit 100, the first sampling resistor r1 is connected to the positive voltage terminal and the first resistor R1 is connected to ground; in the second sampling circuit 200, the second sampling resistor r2 is connected to the positive voltage terminal and the second resistor R2 is connected to ground.

[0062] The embodiments of this application do not specifically limit the resistance value of each resistor. For example, in the embodiments of this application, the resistance value of the first resistor R1 is equal to the resistance value of the second resistor R2, and the resistance value of the first sampling resistor r1 is equal to the resistance value of the second sampling resistor r2.

[0063] In this embodiment, the first voltage U1 between the DC positive terminal and ground is obtained through the first voltage sampling circuit 100, and the second voltage U2 between ground and DC negative terminal is obtained through the second voltage sampling circuit 200.

[0064] Wherein, the first resistor R1 is the voltage divider resistor in the first voltage sampling circuit 100, and the first voltage of the DC positive terminal to ground is expressed by the following formula (3):

[0065]

[0066] The second resistor R2 is the voltage divider resistor in the second voltage sampling circuit 200, and the second voltage between ground and the DC negative terminal is expressed by the following formula (4):

[0067]

[0068] Based on the first voltage U1, the second voltage U2, and the insulation resistance R+ obtained in the aforementioned embodiments, the following formula (5) can be obtained:

[0069]

[0070] It should be understood that, based on the above formula (5), combined with the insulation impedance R+, the first voltage U1 and the second voltage U2 obtained in the preceding steps, and the known parameters first resistance R1, second resistance R2, first sampling resistor r1 and second sampling resistor r2, the insulation impedance R- can be calculated. Therefore, the insulation detection circuit in this embodiment finally obtains the insulation impedances R+ and R-.

[0071] In addition, this application provides another insulation detection circuit, the corresponding schematic diagram of which can be found in [reference needed]. Figure 5 .

[0072] like Figure 5 As shown, the insulation detection circuit includes: a second switching device K2, a third switching device K3, a first voltage sampling branch 100, a second voltage sampling branch 200, an operational amplifier circuit 300, and a processor 400.

[0073] The first end of the second switching device K2 is used for connecting the direct current positive pole DC1+, the second end of the second switching device K2 is connected to the first end of the first voltage sampling branch 100, the second end of the first voltage sampling branch 100 is connected to the ground PE; the first end of the third switching device K3 is used for connecting the direct current negative pole DC1-, the second end of the third switching device K3 is connected to the first end of the second voltage sampling branch 200, the second end of the second voltage sampling branch 200 is connected to the ground PE; the first end of the operational amplifier circuit 300 is connected to the direct current positive pole DC1+, the second end of the operational amplifier circuit 300 is connected to the ground through the constant voltage source DC; the output end of the first voltage sampling circuit 100, the output end of the second voltage sampling circuit 200 and the output end of the operational amplifier circuit 300 are connected to the processor 400.

[0074] The operational amplifier circuit 300 comprises a first switching device S1, a third resistor R3, a fourth resistor R4 and an operational amplifier OP. The first end of the first switching device S1 is connected to the direct current positive pole DC1+, the second end of the first switching device S1 is connected to the first end of the third resistor R3, the second end of the third resistor R3 is connected to the first end of the fourth resistor R4, the second end of the fourth resistor R4 is connected to the output end of the operational amplifier OP, the reverse input end of the operational amplifier OP is connected to the first end of the fourth resistor R4, and the forward input end of the operational amplifier OP is connected to the ground through the constant voltage source DC.

[0075] The first voltage sampling circuit 100 comprises a first resistor R1 and a first sampling resistor r1, and the second voltage sampling branch 200 comprises a second resistor R2 and a second sampling resistor r2. The first end of the first resistor R1 is connected to the direct current positive pole DC1+, the second end of the first resistor R1 is connected to the first end of the first sampling resistor r1, and the second end of the first sampling resistor r1 is used for connecting the ground PE; the first end of the second resistor R2 is connected to the direct current negative pole DC1-, the second end of the second resistor R2 is connected to the first end of the second sampling resistor r2, and the second end of the second sampling resistor is used for connecting the ground PE.

[0076] Exemplarily, the second switching device K2 and the third switching device K3 can be contactors.

[0077] In the embodiment of the application, the insulation impedance R+ is obtained when the second switching device K2, the third switching device K3 and the first switching device S1 are closed, and the insulation impedance R- is obtained when the first switching device S1 is disconnected (i.e. the flow path of the constant voltage source is disconnected).

[0078] In the embodiment of the application, the insulation impedance can be obtained by using the constant voltage source, and the constant voltage source signal will not affect the accuracy of the voltage and current collection circuit with the ground as the reference ground, thereby improving the stability of the power supply equipment.

[0079] In addition, the application further provides a charging pile, a corresponding structural schematic diagram of which is shown in Figure 6 .

[0080] As shown in Figure 6 , the photovoltaic inverter comprises a power conversion circuit 3000, a controller (not shown in the figure) and the insulation detection circuit 1000 in any one of the foregoing embodiments; a first end of the insulation detection circuit 1000 is used for connecting a direct current side of the power conversion circuit 2000, and a second end of the insulation detection circuit 1000 is used for connecting a device to be charged.

[0081] The application does not specifically limit the type of the power conversion circuit 3000, for example, the power conversion circuit 3000 can comprise a direct current-direct current (DC-DC) power conversion circuit and an alternating current-direct current (AC-DC) power conversion circuit, and can also be an AC-DC power conversion circuit. In the case where the power conversion circuit 3000 comprises a DC-DC power conversion circuit and an AC-DC power conversion circuit, an alternating current side of the AC-DC power conversion circuit is used for connecting a power grid, a direct current side of the AC-DC power conversion circuit is connected to a first end of the DC-DC power conversion circuit, a second end of the DC-DC power conversion circuit is connected to the first end of the insulation detection circuit, and a second end of the insulation detection circuit is used for connecting the device to be charged.

[0082] The controller is configured to control a state of the charging pile according to the insulation impedance; wherein the state of the charging pile comprises a charging state and a forbidden charging state.

[0083] For example, the insulation impedance is R+ and R-, and the output voltage of the charging pile is U. In the case where U / R+ and U / R- are both greater than a first threshold value, the state of the charging pile is the charging state, that is, the charging pile is normal to charge the device to be charged; in the case where U / R+ or U / R- is less than the first threshold value and greater than a second threshold value, the charging pile issues an insulation warning; and in the case where U / R+ or U / R- is less than the second threshold value, the state of the charging pile is the forbidden charging state.

[0084] The charging pile provided in the application improves the safety of the charging pile by configuring the insulation detection circuit. The insulation detection circuit can obtain the insulation impedance in the case of using a constant voltage source, and the constant voltage source signal will not affect the accuracy of the voltage and current acquisition circuit with the ground as the reference ground, thereby improving the stability of the charging pile.

[0085] In addition, the application further provides a photovoltaic inverter, a corresponding structural schematic diagram of which is shown in Figure 7 .

[0086] As shown in Figure 7As shown, the photovoltaic inverter comprises: a power conversion circuit 2000, a controller (not shown in the figure) and the insulation detection circuit 1000 in any of the foregoing embodiments; the first end of the insulation detection circuit 1000 is used for connecting the photovoltaic assembly (PV+ and PV-), and the second end of the insulation detection circuit 1000 is connected to the direct current side of the power conversion circuit 2000.

[0087] A controller is configured to control a state of the photovoltaic inverter according to the insulation impedance; the state of the photovoltaic inverter comprises a power conversion state and a power conversion prohibited state.

[0088] In the embodiments of the present application, the insulation detection circuit in the photovoltaic inverter detects the insulation impedance R+ and R- of the direct current side of the power conversion circuit in real time, controls the photovoltaic inverter to perform power conversion when the insulation impedance is greater than a first preset threshold, prohibits the photovoltaic inverter to perform power conversion when the insulation impedance is less than a second preset threshold, and the first preset threshold is greater than the second preset threshold. In addition, a warning signal is sent to remind the operation and maintenance personnel to take timely measures when the insulation impedance is less than the first preset threshold and greater than the second preset threshold, thereby improving the safety of the photovoltaic inverter.

[0089] The embodiments of the present application do not specifically limit the type of the power conversion circuit 2000, for example, the power conversion circuit 2000 is a direct current-direct current DCDC power conversion circuit or a direct current-alternating current DCAC power conversion circuit.

[0090] The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the difference from other embodiments, and the same or similar parts between various embodiments can be referred to each other.

[0091] The above description of the disclosed embodiments enables a person skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to 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 detection circuit. The first voltage sampling branch, the second voltage sampling branch, the operational amplifier circuit and the processor are connected. The first end of the first voltage sampling branch is connected with a direct current positive electrode, and the second end of the first voltage sampling branch is connected with the ground; the first end of the second voltage sampling branch is connected with a direct current negative electrode, and the second end of the second voltage sampling branch is connected with the ground; the first end of the operational amplifier circuit is connected with the direct current positive electrode, and the second end of the operational amplifier circuit is connected with the ground through a constant voltage source. The output end of the first voltage sampling circuit, the output end of the second voltage sampling circuit and the output end of the operational amplifier circuit are connected with the processor.

2. The insulation detection circuit according to claim 1, characterized by The operational amplifier circuit comprises a third resistor, a fourth resistor and an operational amplifier. The first end of the third resistor is connected with the direct current positive electrode, the second end of the third resistor is connected with the first end of the fourth resistor, the second end of the fourth resistor is connected with the output end of the operational amplifier, the reverse input end of the operational amplifier is connected with the first end of the fourth resistor, and the forward input end of the operational amplifier is connected with the ground through the constant voltage source.

3. The insulation detection circuit according to claim 1, characterized by The first voltage sampling branch comprises a first resistor and a first sampling resistor, and the second voltage sampling branch comprises a second resistor and a second sampling resistor. The first end of the first resistor is connected with the direct current positive electrode, and the second end of the first resistor is connected with the first end of the first sampling resistor; the second end of the second sampling resistor is used for connecting the ground. The first end of the second resistor is connected with the direct current negative electrode, and the second end of the second resistor is connected with the first end of the second sampling resistor; the second end of the second sampling resistor is used for connecting the ground.

4. The insulation detection circuit according to claim 2, characterized by The operational amplifier circuit further comprises a first switching device. The first end of the first switching device is connected with the direct current positive electrode, and the second end of the first switching device is connected with the first end of the third resistor.

5. The insulation detection circuit according to any one of claims 1 to 4, characterized in that, The insulation detection circuit further comprises a second switching device and a third switching device. The second switching device is used for controlling the conduction of the direct current positive electrode. The third switching device is used for controlling the conduction of the direct current negative electrode.

6. The insulation detection circuit according to claim 3, characterized by The resistance value of the first resistor is equal to the resistance value of the second resistor, and the resistance value of the first sampling resistor is equal to the resistance value of the second sampling resistor.

7. The insulation detection circuit according to claim 4, characterized by The first switching device comprises any one of a triode, a metal-oxide semiconductor field effect transistor and a relay.

8. The insulation detection circuit of claim 1, wherein The processor is used for obtaining a first voltage of the direct current positive electrode to the ground according to the first voltage sampling branch and obtaining a second voltage of the ground to the direct current negative electrode according to the second voltage sampling branch; the processor is further used for obtaining an insulation impedance according to the first voltage, the second voltage, the voltage of the constant voltage source and the output voltage of the operational amplifier circuit.

9. A charging post, characterized in that The application further relates to a power conversion circuit, a controller and the insulation detection circuit. The direct current side of the power conversion circuit is connected with the first end of the insulation detection circuit, and the second end of the insulation detection circuit is used for connecting a device to be charged. The controller is used for controlling the state of the charging pile according to the insulation impedance; wherein the state of the charging pile comprises a charging state and a forbidden charging state. The application further relates to a charging pile.

10. A photovoltaic inverter, characterized by ​ The power conversion circuit, the controller and the insulation detection circuit according to any one of claims 1-8; The first end of the insulation detection circuit is used for connecting the photovoltaic module, and the second end of the insulation detection circuit is connected to the DC side of the power conversion circuit; The controller is used for controlling the state of the photovoltaic inverter according to the insulation impedance; the state of the photovoltaic inverter includes a power conversion state and a power conversion prohibited state.

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