Insulation detection circuit and charging pile

Abstract

The invention relates to the technical field of charging piles, in particular to an insulation detection circuit and a charging pile. The insulation detection circuit comprises a controller, a signal generation circuit, an analog insulation resistor and a sampling circuit, the controller is used for outputting a specified control signal in response to a target working mode, and the signal generation circuit is used for outputting a preset signal to the grounding end of the charging pile in response to the specified control signal. The analog insulation resistor is connected in parallel with a to-be-tested insulation resistor in a calibration mode, the sampling circuit is used for coupling a preset signal and outputting a sampling voltage, and the controller performs analog-to-digital conversion on the sampling voltage in the calibration mode to obtain a first conversion result and determines a calibration parameter according to the first conversion result and a preset insulation resistance value. And performing analog-to-digital conversion on the sampling voltage in the measurement mode to obtain a second conversion result, and detecting the resistance value of the to-be-detected insulation resistor according to the second conversion result and the calibration parameter. According to the embodiment, online insulation detection can be carried out on the charging pile, and the accuracy of insulation detection can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of charging piles, and particularly to an insulation detection circuit and a charging pile. Background Art

[0002] A charging pile is a device used to charge new energy vehicles. With the continuous popularization and application of new energy vehicles, the demand for charging piles is also growing rapidly. An insulating layer is usually provided between the charging busbar of the charging pile and the grounded housing, so that there is a large insulation resistance between the charging busbar and the grounded housing, ensuring the charging safety of new energy vehicles and personal safety. When the insulating layer fails, the insulation resistance between the charging busbar and the grounded housing decreases sharply, and thus the charging pile will output high voltage and large current, posing a great safety risk.

[0003] To avoid safety risks caused by insulation faults, it is usually necessary to perform insulation detection on the charging pile. The current insulation detection method is generally off-line detection, that is, when performing insulation detection, the power supply of the charging pile needs to be disconnected, a high voltage is applied between the charging busbar of the charging pile and the grounded housing through a detection device, and then the current value of the loop is measured to calculate the insulation resistance value. Since this insulation detection method requires disconnecting the power supply of the charging pile and cannot perform on-line detection, it is not convenient to perform real-time insulation detection on the charging pile. Summary of the Invention

[0004] An object of the present invention is to provide an insulation detection circuit and a charging pile to solve the technical problem in the related art that it is not convenient to perform real-time insulation detection on the charging pile.

[0005] In a first aspect, an embodiment of the present invention provides an insulation detection circuit, including:

[0006] A controller, configured to output a specified control signal in response to a target operating mode, where the target operating mode includes a calibration mode and a measurement mode;

[0007] A signal generation circuit, electrically connected to the controller and configured to be electrically connected to the grounded end of the charging pile, for outputting a preset signal to the grounded end in response to the specified control signal, where there is a to-be-tested insulation resistance between the charging busbar of the charging pile and the grounded end;

[0008] An analog insulation resistance, configured to be connected in parallel with the to-be-tested insulation resistance in the calibration mode;

[0009] A sampling circuit, electrically connected to the controller and configured to be electrically connected to the charging busbar, for coupling the preset signal and outputting a sampling voltage to the controller;

[0010] When the target working mode is the calibration mode, the controller performs analog-to-digital conversion on the sampled voltage to obtain a first conversion result, acquires a preset insulation resistance value, and determines a calibration parameter according to the first conversion result and the preset insulation resistance value; when the target working mode is the measurement mode, the controller performs analog-to-digital conversion on the sampled voltage to obtain a second conversion result, and detects the resistance value of the insulation resistance to be measured according to the second conversion result and the calibration parameter.

[0011] Optionally, the sampling circuit includes:

[0012] A signal coupling circuit, configured to be electrically connected to the charging bus, for coupling the preset signal and outputting a coupling voltage;

[0013] A signal conditioning circuit, electrically connected to the signal coupling circuit and the controller respectively, for providing a preset adjustment voltage and a preset gain, and outputting the sampled voltage in response to the coupling voltage, where the sampled voltage is determined by the coupling voltage, the preset adjustment voltage, and the preset gain.

[0014] Optionally, the signal conditioning circuit includes:

[0015] A low-pass filter, electrically connected to the signal coupling circuit, for providing a first gain and outputting a filtered voltage in response to the coupling voltage, where the first gain is the ratio of the filtered voltage to the coupling voltage;

[0016] An adder, electrically connected to the low-pass filter and the controller respectively, for providing a preset adjustment voltage and a second gain, and outputting the sampled voltage in response to the filtered voltage, where the sum of the preset adjustment voltage and the product of the filtered voltage and the second gain is equal to the sampled voltage, and the product of the first gain and the second gain is equal to the preset gain.

[0017] Optionally, the signal coupling circuit includes an equivalent coupling resistor connected in series with the insulation resistance to be measured in an equivalent manner;

[0018] The preset signal includes a first voltage and a second voltage, and the first conversion result includes a first conversion value corresponding to the first voltage and a second conversion value corresponding to the second voltage;

[0019] In the calibration mode, the controller acquires the resistance value of the equivalent coupling resistor and the preset insulation resistance value, determines a first total resistance to ground according to the resistance value of the equivalent coupling resistor and the preset insulation resistance value, and determines the calibration parameter according to the first total resistance to ground, the first conversion value, and the second conversion value.

[0020] Optionally, the second conversion result includes a third conversion value corresponding to the first voltage and a fourth conversion value corresponding to the second voltage;

[0021] In the measurement mode, the controller obtains the calibration parameter and the resistance value of the equivalent coupling resistance, determines a second total resistance value to the ground according to the calibration parameter, the third conversion value, and the fourth conversion value, and detects the resistance value of the insulation resistance to be measured according to the second total resistance value to the ground and the resistance value of the equivalent coupling resistance.

[0022] Optionally, the preset signal is a pulse signal;

[0023] The controller is further configured to start timing when the pulse signal output by the signal generation circuit in response to the specified control signal is a specified voltage, obtain a conversion result corresponding to the specified voltage, detect whether the specified voltage is in a stable state according to the conversion result, and if it is in a stable state, stop timing to obtain a target duration, and adjust the specified control signal according to the target duration to adjust the period of the pulse signal output by the signal generation circuit to the minimum period.

[0024] Optionally, the signal generation circuit includes:

[0025] A signal generator electrically connected to the controller for outputting an initial signal in response to a specified control signal;

[0026] A signal amplifier electrically connected to the signal generator and configured to be electrically connected to the ground terminal of the charging pile, for amplifying the initial signal and outputting a preset signal to the ground terminal.

[0027] Optionally, the insulation detection circuit further includes an isolation transmission circuit;

[0028] The isolation transmission circuit is configured to be electrically connected to the controller and an external device respectively, for transmitting the detection result of the insulation resistance to be measured output by the controller to the external device on the basis of satisfying electrical isolation.

[0029] Optionally, the insulation detection circuit further includes a switch circuit;

[0030] The switch circuit is configured to be electrically connected to the controller and the charging bus respectively, for disconnecting the charging bus in response to a switch control signal output by the controller, and the switch control signal is output when the controller determines that the resistance value of the insulation resistance to be measured is less than a preset resistance threshold.

[0031] In a second aspect, an embodiment of the present invention provides a charging pile, including the insulation detection circuit as described above.

[0032] Compared with the prior art, an embodiment of the present invention provides an insulation detection circuit and a charging pile. The insulation detection circuit includes a controller, a signal generation circuit, an analog insulation resistance, and a sampling circuit. The controller is configured to output a specified control signal in response to a target operating mode, and the target operating mode includes a calibration mode and a measurement mode. The signal generation circuit is electrically connected to the controller and is configured to be electrically connected to the grounding terminal of the charging pile, and is used to output a preset signal to the grounding terminal in response to the specified control signal. There is a to-be-detected insulation resistance between the charging bus of the charging pile and the grounding terminal. The analog insulation resistance is configured to be connected in parallel with the to-be-detected insulation resistance in the calibration mode. The sampling circuit is configured to be electrically connected to the charging bus and is used to couple the preset signal and output a sampling voltage. When the target operating mode is the calibration mode, the controller performs analog-to-digital conversion on the sampling voltage to obtain a first conversion result, and obtains a preset insulation resistance value, and determines a calibration parameter according to the first conversion result and the preset insulation resistance value. When the target operating mode is the measurement mode, the controller performs analog-to-digital conversion on the sampling voltage to obtain a second conversion result, and detects the resistance value of the to-be-detected insulation resistance according to the second conversion result and the calibration parameter. On the one hand, in this embodiment, by injecting a preset signal into the grounding terminal of the charging pile and performing signal coupling, and then detecting the resistance value of the to-be-detected insulation resistance based on the coupled sampling voltage, online insulation detection of the charging pile is realized, thereby improving the real-time performance of insulation detection. On the other hand, in this embodiment, before measurement, the sampling circuit is calibrated first, and then the calibrated calibration parameter is used for subsequent measurement, which is beneficial to improving the accuracy and reliability of insulation detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments of the present invention. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0034] Figure 1 FIG. is a schematic diagram of an application scenario of a charging pile provided by an embodiment of the present invention;

[0035] Figure 2 FIG. is a schematic diagram of the structure of a charging pile provided by an embodiment of the present invention;

[0036] Figure 3 FIG. is a schematic diagram of the structure of an insulation detection circuit provided by an embodiment of the present invention;

[0037] Figure 4 FIG. is a schematic diagram of the structure of an insulation detection circuit provided by another embodiment of the present invention;

[0038] Figure 5 FIG. is an equivalent circuit diagram provided by an embodiment of the present invention;

[0039] Figure 6 An equivalent circuit diagram provided for another embodiment of the present invention;

[0040] Figure 7 An equivalent circuit diagram provided for yet another embodiment of the present invention;

[0041] Figure 8 An equivalent circuit diagram provided for yet another embodiment of the present invention;

[0042] Figure 9 A structural schematic diagram of an insulation detection circuit provided for yet another embodiment of the present invention. Detailed implementation manners

[0043] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts fall within the protection scope of the present invention.

[0044] It should be noted that if there is no conflict, the various features in the embodiments of the present invention can be combined with each other and are all within the protection scope of the present invention. In addition, although the functional modules are divided in the device schematic diagram and the logical sequence is shown in the flowchart, in some cases, the steps shown or described can be executed in a different order from the module division in the device or the sequence in the flowchart. Furthermore, the terms "first", "second", "third", etc. used in the present invention do not limit the data and execution order, but only distinguish the same items or similar items with basically the same functions and effects.

[0045] Please refer to Figure 1 , Figure 1 which is a schematic diagram of an application scenario of a charging pile provided for an embodiment of the present invention. As Figure 1 shown, the application scenario includes a charging pile 100, a power grid 200 and an electric vehicle 300.

[0046] The power grid 200 is a power network that transmits the commercial power to the charging pile 100 through a transmission line to supply power to the electric vehicle 300. Among them, the commercial power is industrial frequency alternating current, and the industrial frequency alternating current is commonly characterized by voltage, current and frequency. Generally, the commercial power transmitted by the power grid 200 to the charging pile 100 is three-phase alternating current.

[0047] The charging station 100 is a device used to charge an electric vehicle 300 to replenish its power. Its operating principle is to receive electrical energy from the power grid 200 and then transmit the electrical energy to the electric vehicle 300 via a charging cable to charge the electric vehicle 300. The charging station 100 can be any type of charging station that supports AC charging, such as a DC charging station, an AC charging station, or an integrated AC / DC charging station.

[0048] The DC charging pile uses DC power to charge the power battery of the electric vehicle 300. This charging method is also called "fast charging." The DC charging pile is electrically connected to the power grid 200, and can receive three-phase 380V AC power input from the power grid 200 and convert the AC power into DC power. It is then transmitted to the power battery of the electric vehicle 300 for charging through a standard DC charging plug and charging socket, thereby achieving DC charging. The power supply characteristics of the DC charging pile itself determine that it can output sufficient charging power, and the adjustment range of voltage and current is relatively large, thereby achieving fast charging. The DC charging pile has a charger function, which can monitor and control the working status of the charged power battery in real time, and can also measure the charging power.

[0049] AC charging piles typically use a single or dual 220VAC / 380VAC AC output interface to provide power to the electric vehicle 300, which then uses an onboard charger to charge its power battery. This charging method is also known as "slow charging." The output power of an AC charging pile is typically 5kW (220VAC) / 20kW (380VAC), but the actual charging power is limited by the onboard charger. Generally, the onboard charging power of a small electric vehicle is between 2 and 3kW. The onboard charger of the electric vehicle 300 can convert the AC power into DC power through filtering and rectification, and then store the DC power in the power battery of the electric vehicle 300, thereby charging the electric vehicle 300. This charging method is mainly used in small pure electric vehicles.

[0050] The input voltage of the AC-DC integrated charging pile generally adopts three-phase four-wire 380VAC±15%, with a frequency of 50Hz. The AC-DC integrated charging pile includes a DC output port and an AC output port. Among them, the DC output port outputs adjustable direct current to charge the power battery of the electric vehicle 300, and the charging power is generally 10-40kW. The AC output port outputs 220VAC (5kW) / 380VAC (20kW) alternating current to provide a charging power supply for the on-board charger of the electric vehicle 300. The AC-DC integrated charging pile can provide a conventional charging method through the AC output port and a fast charging method through the DC output port. When there are many charging services during the day, the fast charging method is used for fast charging. When there are few users at the charging station at night, the conventional charging method can be used for slow charging. The AC-DC integrated charging pile can not only achieve AC and DC simultaneous charging, but also achieve interlocking charging, and adopts a modular design for convenient maintenance.

[0051] In some embodiments, the charging pile 100 is configured with one or more charging guns. The charging gun is an interface device connecting the charging pile and the electric vehicle 300, mainly used to transmit electric energy to the electric vehicle 300 for charging. The charging gun usually has a plug and a connecting wire, one end is connected to the charging pile, and the other end is inserted into the charging interface of the electric vehicle 300. According to different charging requirements and technical standards, the charging gun can be divided into a fast charging gun and a slow charging gun.

[0052] The fast charging gun is also called the DC fast charging gun, which is usually used in fast charging stations, has a large power output, and can quickly charge the power battery of the vehicle.

[0053] The slow charging gun is also called the AC charging gun, which is usually used in home charging piles, commercial charging piles and public charging piles, has a low power, is suitable for charging with ordinary household power supplies, and has a relatively slow charging speed.

[0054] The electric vehicle 300 can receive alternating current or direct current provided by the charging pile 100. When the electric vehicle 300 receives direct current, the electric vehicle 300 can store the direct current in the power battery of the electric vehicle 300, so as to charge the power battery of the electric vehicle 300. When the electric vehicle 300 receives alternating current, the electric vehicle 300 can convert the voltage, filter and rectify the alternating current to obtain direct current, and then store the modified direct current in the power battery of the electric vehicle 300, so as to charge the power battery of the electric vehicle 300. The electric vehicle 300 includes any vehicle that can be driven by electricity, including but not limited to pure electric vehicles, hybrid electric vehicles, fuel cell vehicles, etc.

[0055] In some embodiments, please refer to Figure 2, the charging pile 100 includes an input filter circuit 10, an AC / DC circuit 20, a DC / DC circuit 30, an output filter circuit 40, an auxiliary power supply 50, a charging control module 60, an insulation detection circuit 70, a metering module 80, and a communication module 90.

[0056] The input filter circuit 10 is configured to be electrically connected to the power grid 200, and the input filter circuit 10 is used to filter out high-frequency interference signals, thereby reducing conducted interference.

[0057] The AC / DC circuit 20 is electrically connected to the input filter circuit 10 and is used to convert the alternating current of the power grid 200 into direct current. The AC / DC circuit 20 may include any circuit for converting alternating current into direct current, including but not limited to a three-phase active PFC (Power Factor Correction) circuit, a three-phase Vienna circuit without a neutral line, etc.

[0058] The DC / DC circuit 30 is electrically connected to the AC / DC circuit 20 and is used to convert the direct current output by the AC / DC circuit 20 into a voltage waveform required by the battery charging strategy. The DC / DC circuit 30 may be any circuit for converting the direct current output by the AC / DC circuit 20 into a voltage waveform required by the battery charging strategy, including but not limited to an LLC resonant circuit, a three-phase interleaved LLC resonant circuit, a DAB (Dual Active Bridge Converter), a bidirectional full-bridge CLLC resonant circuit, a three-phase interleaved CLLC resonant circuit, a phase-shifted full-bridge circuit, etc.

[0059] The output filter circuit 40 is electrically connected to the DC / DC circuit 30 and the electric vehicle 300 respectively. The output filter circuit 40 is used to filter out electromagnetic interference generated during the operation of the charging pile 100, ensure stable communication between the charging pile 100 and the electric vehicle 300, and avoid charging errors or safety problems caused by interference.

[0060] The auxiliary power supply 50 is electrically connected to the AC / DC circuit 20 and is used to convert the direct current output by the AC / DC circuit 20 and then output a power supply, and this power supply is used to supply power to the charging control module 60.

[0061] The charging control module 60 is electrically connected to the AC / DC circuit 20, the DC / DC circuit 30, and the auxiliary power supply 50 respectively, and is used to operate under the power supply of the auxiliary power supply 50 and control the voltage conversion of the AC / DC circuit 20 and the DC / DC circuit 30.

[0062] The insulation detection circuit 70 is electrically connected to the charging bus and the grounding end of the charging pile 100 respectively, and is used to detect the insulation resistance to be measured between the charging bus and the grounding end of the charging pile 100, so as to timely disconnect the charging circuit of the charging pile 100 for the electric vehicle 300 when the insulation resistance to be measured is abnormal, and avoid the situation of personal injury caused by the high-level large current output when the insulation layer between the charging bus and the grounding end fails.

[0063] The metering module 80 is electrically connected to the charging control module 60. The metering module 80 includes metering functions, monitoring functions and management functions. The metering function is responsible for accurately measuring parameters such as electric quantity, voltage, current, etc. during the charging process, and feeding back the data to the charging control module 60 to ensure the accurate metering of the charging electric quantity. The monitoring function is responsible for real-time monitoring of the operation status of the charging pile 100, including electric quantity, time, cost, etc., to ensure the normal operation of the charging pile 100. The management function is responsible for managing the charging pile 100, such as setting the charging price, counting the charging quantity and cost, etc., to provide data support and business basis for the operator.

[0064] The communication module 90 is electrically connected to the charging control module 60 and the electric vehicle 300 respectively, and is used to establish communication between the charging control module 60 and the electric vehicle 300. Based on the established communication, the charging pile 100 can interact with the electric vehicle 300. When the charging pile 100 interacts with the electric vehicle 300, various charging interaction information can be sent and received between the charging pile 100 and the electric vehicle 300. The interaction between the electric vehicle 300 and the charging pile 100 during the charging process can be roughly divided into a charging parameter configuration stage and a charging stage. After the charging pile 100 and the electric vehicle 300 are physically connected and powered on, and the voltage is checked to be normal, it enters the charging parameter configuration stage. During the charging stage, the charging pile 100 adjusts the charging voltage and charging current according to the charging requirements of the battery management system of the electric vehicle 300 to ensure the normal progress of the charging process.

[0065] In some embodiments, please refer to Figure 3 , the insulation detection circuit 70 includes a controller 71, a signal generation circuit 72, an analog insulation resistor 73 and a sampling circuit 74.

[0066] The controller 71 is used to output a specified control signal in response to the target working mode, and the target working mode includes a calibration mode and a measurement mode.

[0067] The calibration mode is an operating mode for calibrating the component parameters inside the insulation detection circuit 70. Since when the insulation detection circuit is operating, the component parameters inside the insulation detection circuit 70 may deviate from the design values due to increased operating time or process errors, therefore, calibrating the component parameters inside the insulation detection circuit 70 is beneficial to reliably and accurately detect the resistance value of the insulation resistance to be measured between the charging bus and the ground terminal in the measurement mode.

[0068] The measurement mode is a mode for actually detecting the resistance value of the insulation resistance to be measured.

[0069] The controller 71 can obtain the target operating mode through any suitable means such as button input, keyboard input, screen touch, receiving externally transmitted signals, etc. The specified control signals output by the controller 71 in response to different operating modes can be the same or different. For example, the controller 71 outputs a first control signal in response to the calibration mode, and the controller 71 outputs a second control signal in response to the measurement mode. The first control signal and the second control signal are different control signals.

[0070] In some embodiments, the controller 71 is configured with an analog-to-digital conversion circuit. Among them, the analog-to-digital conversion circuit is used to convert analog signals into digital signals for the controller 71 to perform signal processing.

[0071] The controller 71 can include any general-purpose processor, digital signal processor (DSP), application-specific integrated circuit (ASIC), field-programmable gate array (FPGA), single-chip microcomputer, ARM (Acorn RISC Machine), or other programmable logic devices, discrete gate or transistor logic, discrete hardware components, or any combination of these components. Additionally, the controller 71 can also include any conventional processor, controller, microcontroller, or state machine. The controller 71 can also be implemented as a combination of computing devices. For example, a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors combined with a DSP and / or any other such configuration.

[0072] In some embodiments, the model of the controller 71 is ATMEGA649. ATMEGA649 has an 8-channel 10-bit analog-to-digital converter with a reference voltage source, which enables the chip to convert analog signals into digital signals with high precision, facilitating the microcontroller to perform processing and analysis, and is suitable for various application scenarios that require acquisition and processing of analog quantities, such as sensor data acquisition, audio signal processing, etc.

[0073] The signal generation circuit 72 is electrically connected to the controller 71 and is configured to be electrically connected to the ground terminal of the charging pile 100, and is used to output a preset signal to the ground terminal in response to the specified control signal.

[0074] The preset signal can be a voltage signal of any suitable type, such as a pulse signal, etc. In some embodiments, the preset signal includes a first voltage and a second voltage, and the voltage amplitudes of the first voltage and the second voltage are different. The first voltage can be a positive voltage or a negative voltage, and the second voltage can be a positive voltage or a negative voltage. In some embodiments, when the first voltage is a positive voltage, the second voltage is a negative voltage, and when the first voltage is a negative voltage, the second voltage is a positive voltage. For example, when the first voltage is +48V, the second voltage is -48V, and when the first voltage is -48V, the second voltage is +48V.

[0075] In some embodiments, the preset signal is a low-voltage pulse signal. By injecting the low-voltage pulse signal into the ground terminal, the interference of the signal to the charging bus can be reduced.

[0076] As described above, the specified control signals output by the controller 71 in response to different operating modes may be different, and thus the preset signals output by the signal generation circuit 72 in response to the specified control signals may also be different. For example, when the specified control signal is the first control signal, the signal generation circuit 72 outputs a first pulse signal in response to the first control signal, and when the specified control signal is the second control signal, the signal generation circuit 72 outputs a second pulse signal in response to the second control signal. The pulse periods or voltage amplitudes of the first pulse signal and the second pulse signal are different.

[0077] In some embodiments, please refer to Figure 4 , the signal generation circuit 72 includes a signal generator 721 and a signal amplifier 722.

[0078] The signal generator 721 is electrically connected to the controller 71 and is configured to output an initial signal in response to the specified control signal. In some embodiments, the signal type of the initial signal is the same as the signal type of the preset signal. For example, when the preset signal is a pulse signal, the initial signal is also a pulse signal.

[0079] The signal amplifier 722 is electrically connected to the signal generator 721 and is configured to be electrically connected to the ground terminal of the charging pile 100, and is used to amplify the initial signal and then output the preset signal to the ground terminal, so that the voltage amplitude of the preset signal injected into the ground terminal meets the established requirements.

[0080] The analog insulation resistance 73 is configured to be connected in parallel with the insulation resistance to be measured in the calibration mode. The insulation resistance to be measured is the inherent resistance between the ground terminal and the charging bus. When the analog insulation resistance 73 is connected in parallel with the insulation resistance to be measured, the analog insulation resistance 73 is electrically connected to the ground terminal and the charging bus respectively. In some embodiments, as Figure 3 and Figure 4 shown, the charging bus includes a first-phase bus L1 and a second-phase bus L2.

[0081] In some embodiments, please refer to Figure 5 , the insulation resistance to be measured includes a first resistor R1 and a second resistor R2, and the simulated insulation resistance 73 includes a third resistor R3 and a fourth resistor R4. In the calibration mode, the first resistor R1 and the third resistor R3 are connected between the ground terminal E and the first-phase busbar L1, and the second resistor R2 and the fourth resistor R4 are connected between the ground terminal E and the second-phase busbar L2. Therefore, the first resistor R1 and the third resistor R3 are connected in parallel, and the second resistor R2 and the fourth resistor R4 are connected in parallel. It can be understood that the resistance value of the insulation resistance to be measured is the total resistance value of the first resistor R1 and the second resistor R2, and the resistance value of the simulated insulation resistance 73 is the total resistance value of the third resistor R3 and the fourth resistor R4. It can also be understood that in the measurement mode, the simulated insulation resistance 73 is not switched in, that is, the simulated insulation resistance 73 is not connected in parallel with the insulation resistance to be measured. Please refer to Figure 6 , the first resistor R1 is connected between the ground terminal E and the first-phase busbar L1, and the second resistor R2 is connected between the ground terminal E and the second-phase busbar L2.

[0082] Under normal circumstances, in order to ensure the effectiveness of the internal and external insulation structures of the charging pile 100, the designed resistance value of the insulation resistance to be measured is generally relatively large, reaching the megohm level, and the simulated insulation resistance 73 can select a resistor with a relatively small resistance value. In some embodiments, the resistance value of the simulated insulation resistance 73 is much smaller than the designed resistance value of the insulation resistance to be measured, that is, the designed resistance value of the insulation resistance to be measured is more than two orders of magnitude larger than the resistance value of the simulated insulation resistance 73. It can be understood that since the resistance value of the insulation resistance to be measured is more than two order values larger than the resistance value of the simulated insulation resistance 73, when the simulated insulation resistance 73 is connected in parallel with the insulation resistance to be measured, the parallel resistance value can be approximately equivalent to the resistance value of the simulated insulation resistance 73.

[0083] The sampling circuit 74 is electrically connected to the controller 71 and is configured to be electrically connected to the charging busbar for coupling a preset signal and outputting a sampling voltage to the controller 71.

[0084] When the target operating mode is the calibration mode, the controller 71 performs analog-to-digital conversion on the sampling voltage to obtain a first conversion result, and obtains a preset insulation resistance value, and determines a calibration parameter according to the first conversion result and the preset insulation resistance value.

[0085] The preset insulation resistance value is the parallel resistance value of the insulation resistance to be measured and the simulated insulation resistance 73. As mentioned above, the parallel resistance value can be approximately equivalent to the resistance value of the simulated insulation resistance 73. Therefore, the preset insulation resistance value only needs to be determined according to the resistance value of the simulated insulation resistance 73.

[0086] The calibration parameter is a parameter used to calibrate the component parameters inside the sampling circuit 74. Components such as resistors inside the sampling circuit 74 may have differences between their component parameters and the design values due to increased working hours or process errors. If the design values are directly used for calculating the resistance value of the insulation resistance to be measured, it is likely to cause a large deviation between the calculated resistance value of the insulation resistance to be measured and the actual resistance value. The calibration parameter is a parameter with a comprehensive influence and does not need to consider the deviation between the actual value and the design value of a certain component inside the sampling circuit 74. Therefore, using the calibration parameter for calculating the resistance value of the insulation resistance to be measured is beneficial to improving the reliability and accuracy of the calculation of the resistance value of the insulation resistance to be measured.

[0087] When the target working mode is the measurement mode, the controller 71 performs analog-to-digital conversion on the sampling voltage to obtain a second conversion result, and detects the resistance value of the insulation resistance to be measured according to the second conversion result and the calibration parameter.

[0088] Since the parameters of each component inside the sampling circuit 74 and the calibration parameter remain unchanged regardless of whether the target working mode is the calibration mode or the measurement mode, the calibration parameter determined in the calibration mode can be used for calculating the resistance value of the insulation resistance to be measured and achieving error compensation. Therefore, the controller 71 performs analog-to-digital conversion on the sampling voltage to obtain a second conversion result, and then detects the resistance value of the insulation resistance to be measured according to the second conversion result and the calibration parameter, which can improve the reliability and accuracy of the detection of the insulation resistance to be measured.

[0089] Therefore, on the one hand, in this embodiment, by injecting a preset signal at the grounding end of the charging pile 100 and performing signal coupling, and then detecting the resistance value of the insulation resistance to be measured based on the coupled sampling voltage, the on-line insulation detection of the charging pile 100 is realized, thereby improving the real-time performance of the insulation detection. On the other hand, before measurement in this embodiment, the sampling circuit 74 is calibrated first, and then the calibrated calibration parameter is used in subsequent measurements, which is beneficial to improving the accuracy and reliability of the insulation detection.

[0090] In some embodiments, in the calibration mode, the controller 71 can perform multiple calibrations. Each calibration can configure an analog insulation resistance with a different resistance value to be connected in parallel with the insulation resistance to be measured, so as to obtain the calibration parameter corresponding to the analog insulation resistance of each resistance value. The controller 71 can average these calibration parameters to obtain an average value, and then use this average value as the final calibration parameter.

[0091] Therefore, by performing multiple calibrations in the calibration mode, it is possible to avoid the one-sidedness of the calibration parameter determined by using an analog insulation resistance with a single resistance value, which is beneficial to improving the reliability of the calibration parameter.

[0092] In some embodiments, please continue to refer to Figure 4, the sampling circuit 74 includes a signal coupling circuit 741 and a signal conditioning circuit 742.

[0093] The signal coupling circuit 741 is configured to be electrically connected to the charging bus, and is used for coupling a preset signal and outputting a coupling voltage.

[0094] In some embodiments, please continue to refer to Figure 5 or Figure 6 , the signal coupling circuit 741 includes a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, and an eighth resistor R8. The first end of the fifth resistor R5 is electrically connected to the first-phase bus L1, and the second end of the fifth resistor R5 is electrically connected to the first ends of the sixth resistor R6, the seventh resistor R7, and the eighth resistor R8 respectively. The second end of the sixth resistor R6 is electrically connected to the second-phase bus L2, and the second ends of the seventh resistor R7 and the eighth resistor R8 are grounded. The coupling voltage V1 is output at the connection node of the fifth resistor R5, the sixth resistor R6, the seventh resistor R7, and the eighth resistor R8.

[0095] After the preset signal is injected into the grounding terminal E, a voltage difference is formed between the grounding terminal E and the ground GND. As described above, when the first voltage is +48V, the voltage difference between the grounding terminal E and the ground GND is 48V, and when the first voltage is -48V, the voltage difference between the grounding terminal E and the ground GND is -48V.

[0096] It can be understood that in the measurement mode, the first resistor R1 and the second resistor R2 that make up the insulation resistance to be measured need to be measured together. Therefore, only the total resistance value of the first resistor R1 and the second resistor R2 (i.e., the resistance value of the insulation resistance to be measured) needs to be measured. Therefore Figure 6 the equivalent circuit diagram shown can be equivalent to Figure 7 the equivalent circuit diagram shown. In Figure 7 , the resistance value of R12 is the resistance value of the insulation resistance to be measured.

[0097] Similarly, in the calibration mode, if the resistance value of the simulated insulation resistance 73 is represented by the total resistance value of the third resistor R3 and the fourth resistor R4, then Figure 5 the equivalent circuit diagram shown can be equivalent to Figure 8 the equivalent circuit diagram shown. In Figure 8 , the resistance value of R34 is the resistance value of the simulated insulation resistance 73.

[0098] Please combine Figure 6 and Figure 7 , the fifth resistor R5 and the sixth resistor R6 can be equivalent to a first equivalent resistor R56, and the seventh resistor R7 and the eighth resistor R8 can be equivalent to a second equivalent resistor R78. The first equivalent resistor R56 and the second equivalent resistor R78 form an equivalent coupling resistor that is equivalently connected in series with the insulation resistance to be measured.

[0099] As described above, when the preset voltage is +48V, the following formula can be obtained:

[0100]

[0101] Among them, V1a is the coupling voltage, R_34 is the resistance value of the first equivalent resistance, R_56 is the resistance value of the second equivalent resistance. If the simulated insulation resistance 73 is connected in parallel with the insulation resistance to be measured, then R_0 represents the parallel resistance value of the simulated insulation resistance 73 and the insulation resistance to be measured. If the simulated insulation resistance 73 is not connected in parallel with the insulation resistance to be measured, then R_0 represents the resistance value of the insulation resistance to be measured.

[0102] When the preset voltage is -48V, the following formula can be obtained:

[0103]

[0104] Among them, V1b is the coupling voltage, and the meanings of other symbols can be referred to the above formula and will not be elaborated here.

[0105] The signal conditioning circuit 742 is electrically connected to the signal coupling circuit 741 and the controller 71 respectively, and is used to provide a preset adjustment voltage and a preset gain, and output a sampling voltage in response to the coupling voltage. The sampling voltage is determined by the coupling voltage, the preset adjustment voltage and the preset gain.

[0106] The preset gain is used to amplify or reduce the coupling voltage to obtain a scaled voltage, and the preset adjustment voltage is used to raise or lower the scaled voltage to obtain a sampling voltage.

[0107] Therefore, in this embodiment, by scaling, raising or lowering the coupling voltage, it can be ensured that the sampling voltage meets the measurement range of the analog-to-digital conversion, avoiding problems such as sampling cut-off, which is beneficial to improving the conversion accuracy and accuracy when the subsequent controller 71 performs analog-to-digital conversion on the sampling voltage.

[0108] In some embodiments, the calculation formula of the sampling voltage is as follows:

[0109] V2 = Vx + K * V1

[0110] Among them, V2 is the sampling voltage, Vx is the preset adjustment voltage, K is the preset gain, and V1 is the coupling voltage.

[0111] In some embodiments, please continue to refer to Figure 4 , the signal conditioning circuit 742 includes a low-pass filter 7421 and an adder 7422.

[0112] The low-pass filter 7421 is electrically connected to the signal coupling circuit 741, and is used to provide a first gain and output a filtered voltage in response to a coupling voltage. The first gain is the ratio of the filtered voltage to the coupling voltage.

[0113] The first gain is the amplification factor for amplifying the coupling voltage into the filtered voltage, and the first gain can be set according to actual needs. For example, the first gain can be set to be greater than 1, equal to 1, or less than 1. It can be understood that when the first gain is greater than 1, the absolute value of the filtered voltage is greater than the absolute value of the coupling voltage; when the first gain is equal to 1, the filtered voltage is equal to the coupling voltage; when the first gain is less than 1, the absolute value of the filtered voltage is less than the absolute value of the coupling voltage.

[0114] The low-pass filter 7421 can be any suitable type of filter, including but not limited to Butterworth filters, Chebyshev filters, Bessel filters, etc. The order of the low-pass filter 7421 can be set according to actual needs. In some embodiments, the order of the low-pass filter 7421 is 2.

[0115] The adder 7422 is electrically connected to the low-pass filter 7421 and the controller 71 respectively, and is used to provide a preset adjustment voltage and a second gain, and output a sampled voltage in response to the filtered voltage. The sum of the preset adjustment voltage and the product of the filtered voltage and the second gain is equal to the sampled voltage, and the product of the first gain and the second gain is equal to the preset gain.

[0116] The first gain is the amplification factor for amplifying the coupling voltage into the filtered voltage, and the first gain can be set according to actual needs. For example, the first gain can be set to be greater than 1, equal to 1, or less than 1.

[0117] In some embodiments, the controller 71 can calculate the sampled voltage according to the following formula:

[0118] V2 = Vx + (K1 * V1) * K2

[0119] where V2 is the sampled voltage, Vx is the preset adjustment voltage, K1 is the first gain, K2 is the second gain, and V1 is the coupling voltage.

[0120] In some embodiments, please refer to Figure 9 , the low-pass filter 7421 includes a first operational amplifier OPA1, a ninth resistor R9, a tenth resistor R10, a first capacitor C1, and a second capacitor C2.

[0121] The first end of the ninth resistor R9 is electrically connected to the signal coupling circuit 741. The second end of the ninth resistor R9 is respectively electrically connected to the first end of the first capacitor C1, the first end of the second capacitor C2, the first end of the tenth resistor R10, and the inverting input terminal of the first operational amplifier OPA1. The second end of the first capacitor C1 and the non-inverting input terminal of the first operational amplifier OPA1 are grounded. The output terminal of the first operational amplifier OPA1 is respectively electrically connected to the second end of the second capacitor C2, the second end of the tenth resistor R10, and the adder 7422.

[0122] In this embodiment, R_10 / R_9 = K1, where R_10 is the resistance value of the tenth resistor R10, R_9 is the resistance value of the ninth resistor R9, and K1 is the first gain. Therefore, the first gain can be adjusted by adjusting the resistance values of the tenth resistor R10 and the ninth resistor R9.

[0123] In some embodiments, the low-pass filter 7421 is further configured to filter out the 50 Hz power frequency signal in the coupled voltage and output a stable filtered voltage.

[0124] In some embodiments, the frequency point of the low-pass filter 7421 is below 10 Hz.

[0125] It can be understood that the frequency point of the low-pass filter 7421 can be flexibly adjusted by adjusting the capacitance value of the second capacitor C2 and the resistance value of the tenth resistor R10. In some embodiments, the capacitance value of the second capacitor C2 and the resistance value of the tenth resistor R10 satisfy the following relationship:

[0126]

[0127] where C_2 is the capacitance value of the second capacitor C2, and R_10 is the resistance value of the tenth resistor R10.

[0128] In some embodiments, as Figure 9 shown, the adder 7422 includes a second operational amplifier OPA2, an eleventh resistor R11, a twelfth resistor R13, a thirteenth resistor R14, and a fourteenth resistor R15.

[0129] The first end of the eleventh resistor R11 is electrically connected to the low-pass filter 7421. The first end of the twelfth resistor R13 can be applied with an external voltage V3. The second end of the eleventh resistor R11 and the second end of the twelfth resistor R13 are respectively electrically connected to the inverting input terminal of the second operational amplifier OPA2 and the first end of the thirteenth resistor R14. The output terminal of the second operational amplifier OPA2 and the second end of the thirteenth resistor R14 are electrically connected to the controller 71. The non-inverting input terminal of the second operational amplifier OPA2 is electrically connected to the first end of the fourteenth resistor R15. The second end of the fourteenth resistor R15 is grounded.

[0130] In this embodiment, R_14 / R_11 = K2, and K2 * V3 = Vx, where R_14 is the resistance value of the thirteenth resistor R14, R_11 is the resistance value of the eleventh resistor R11, K2 is the second gain, and Vx is the preset adjustment voltage. Therefore, by adjusting the resistance values of the thirteenth resistor R14 and the eleventh resistor R11, the second gain can be adjusted. On this basis, by flexibly configuring the voltage value of the external voltage V3, the preset adjustment voltage can be adjusted.

[0131] In some embodiments, the resistance value of the eleventh resistor R11 is equal to the resistance value of the twelfth resistor R13. The resistance values of the eleventh resistor R11 and the twelfth resistor R13 can be freely set according to actual needs.

[0132] It can be understood that the external voltage V3 can be selected according to the input voltage range of the analog-to-digital conversion circuit. Generally speaking, it is more appropriate for the external voltage V3 to be near the midpoint voltage of the input voltage range of the analog-to-digital conversion circuit. For example, when the input voltage range is 0 - 4.5V, the external voltage V3 can be selected as 2.0V.

[0133] When the controller 71 performs analog-to-digital conversion on the sampled voltage, assuming that the analog-to-digital conversion circuit of the controller 71 outputs a 10-bit (bit) conversion value and the conversion reference voltage of the analog-to-digital conversion circuit is Vref, when the preset voltage is +48V, the following formula can be obtained:

[0134]

[0135] Among them, V2a is the sampled voltage, VALa is the conversion value, and Vref is the conversion reference voltage.

[0136] When the preset voltage is -48V, the following formula can be obtained:

[0137]

[0138] Among them, V2b is the sampled voltage, VALb is the conversion value, and Vref is the conversion reference voltage.

[0139] As mentioned above, V2a = Vx + K * V1a, V2b = Vx + K * V1b. Therefore, V2a - V2b = K * (V1a - V1b).

[0140] Substitute the relevant formulas of V1a and V1b into the formula V2a - V2b = K * (V1a - V1b), and we can get:

[0141]

[0142] Further simplifying this formula can obtain:

[0143]

[0144] Substituting the relevant formulas of V2a and V2b into this formula, we can get:

[0145]

[0146] Further simplifying this formula can obtain:

[0147]

[0148] Let the parameter M = (96 * R_78 * K * 1024) / Vref, and the parameter N = R_56 + R_78. Then, further simplifying this formula can obtain:

[0149]

[0150] Both the parameter M and the parameter N can be pre - stored in the preset storage area of the controller 71. Therefore, after the controller 71 obtains the conversion values VALa and VALb, it can retrieve the parameter M and the parameter N from the preset storage area, and thus calculate the value of R_0 according to the conversion values VALa and VALb, the parameter M, and the parameter N.

[0151] It can be understood that in the parameter M, the value of K is determined by the first gain K1 provided by the low - pass filter 7421 and the second gain K2 provided by the adder 7422. The first gain K1 is determined by the resistance design values of the ninth resistor R9 and the tenth resistor R10, and the second gain K2 is determined by the resistance design values of the eleventh resistor R11 and the thirteenth resistor R14. However, these resistors may have a difference between the actual value and the design value due to the increase in working hours or process errors, resulting in a certain error between the pre - configured parameter M and the actual value. Therefore, if the pre - configured parameter M is directly used to calculate the resistance value of the to - be - measured insulation resistor, the calculation result of the resistance value of the to - be - measured insulation resistor may have a large deviation from the actual resistance value of the to - be - measured insulation resistor, which is likely to cause misdetection.

[0152] Therefore, in some embodiments, the controller 71 can first calibrate the parameter M, update the parameter M before calibration with the calibrated parameter M as the calibration parameter, and then use the calibration parameter for calculating the resistance value of the to - be - measured insulation resistor, so as to improve the detection reliability and accuracy of the resistance value of the to - be - measured insulation resistor.

[0153] It can also be understood that by injecting a pulse signal composed of a positive voltage (such as +48V) and a negative voltage (such as -48V) into the ground terminal, and using the conversion value corresponding to the positive voltage (such as VALa) and the conversion value corresponding to the negative voltage (such as VALb) to calculate the resistance value of the insulation resistance to be measured, the software calculation process can be simplified, the calculation efficiency can be improved, and thus the insulation detection efficiency can be improved.

[0154] In some embodiments, please continue to refer to Figure 7 , the signal coupling circuit 741 includes an equivalent coupling resistor connected in series with the insulation resistance to be measured equivalently, that is, the first equivalent resistor R56 and the second equivalent resistor R78.

[0155] It can be understood that the resistance value R_741 of the equivalent coupling resistor = R_56 + R_78, where R_56 is the resistance value of the first equivalent resistor R56, and R_78 is the resistance value of the second equivalent resistor R78.

[0156] In some embodiments, the first conversion result includes a first conversion value corresponding to a first voltage and a second conversion value corresponding to a second voltage. The first conversion value corresponding to the first voltage refers to the digital conversion value obtained by the analog-to-digital conversion circuit of the controller 71 for the sampling voltage output by the sampling circuit 74 when the pulse signal injected into the ground terminal is the first voltage in the calibration mode, and the second conversion value corresponding to the second voltage refers to the digital conversion value obtained by the analog-to-digital conversion circuit of the controller 71 for the sampling voltage output by the sampling circuit 74 when the pulse signal injected into the ground terminal is the second voltage in the calibration mode.

[0157] In some embodiments, in the calibration mode, the controller 71 acquires the resistance value of the equivalent coupling resistor and the preset insulation resistance value, determines the first total resistance value to the ground according to the resistance value of the equivalent coupling resistor and the preset insulation resistance value, and determines the calibration parameter according to the first total resistance value to the ground, the first conversion value and the second conversion value.

[0158] In this embodiment, the first total resistance value to the ground is the total resistance value between the ground terminal and the ground.

[0159] In some embodiments, the controller 71 determines the first total resistance value to the ground according to the following formula:

[0160] R_100 = N + R_73

[0161] Wherein, R_100 is the first total resistance value to the ground, N is the resistance value of the equivalent coupling resistor, and R_73 is the preset insulation resistance value.

[0162] It can be understood that since the equivalent coupling resistance N is the sum of the first equivalent resistance R56 and the second equivalent resistance R78, the first equivalent resistance R56 is obtained by equivalent of the fifth resistor R5 and the sixth resistor R6, and the second equivalent resistance R78 is obtained by equivalent of the seventh resistor R7 and the eighth resistor R8. Therefore, in order to ensure that the resistance value N of the equivalent coupling resistance is accurate enough, the fifth resistor R5, the sixth resistor R6, the seventh resistor R7, and the eighth resistor R8 can all use precision resistors with an accuracy of 1%.

[0163] In some embodiments, the controller 71 determines the calibration parameter according to the following formula:

[0164] M = (VALa1 - VALb1) * R_100

[0165] Where M is the calibration parameter, VALa1 is the first conversion value, and VALb1 is the second conversion value.

[0166] In some embodiments, the second conversion result includes a third conversion value corresponding to the first voltage and a fourth conversion value corresponding to the second voltage. The third conversion value corresponding to the first voltage refers to the digital conversion value obtained by the analog-to-digital conversion circuit of the controller 71 for the sampling voltage output by the sampling circuit 74 when the pulse signal injected into the ground terminal in the measurement mode is the first voltage. The fourth conversion value corresponding to the second voltage refers to the digital conversion value obtained by the analog-to-digital conversion circuit of the controller 71 for the sampling voltage output by the sampling circuit 74 when the pulse signal injected into the ground terminal in the measurement mode is the second voltage.

[0167] In some embodiments, in the measurement mode, the controller 71 obtains the calibration parameter and the resistance value of the equivalent coupling resistance, determines the second total resistance value to the ground according to the calibration parameter, the third conversion value, and the fourth conversion value, and detects the resistance value of the insulation resistance to be measured according to the second total resistance value to the ground and the resistance value of the equivalent coupling resistance.

[0168] In some embodiments, the controller 71 determines the second total resistance value to the ground according to the following formula:

[0169] R_200 = M / (VALa2 - VALb2)

[0170] Where R_200 is the second total resistance value to the ground, M is the calibration parameter, VALa2 is the third conversion value, and VALb2 is the fourth conversion value.

[0171] In some embodiments, the controller 71 determines the resistance value of the insulation resistance to be measured according to the following formula:

[0172] R_12 = R_200 - N

[0173] Wherein, R_12 is the resistance value of the insulation resistance to be measured, R_200 is the total resistance value of the second pair to the ground, and N is the resistance value of the equivalent coupling resistance.

[0174] In some embodiments, the preset signal is a pulse signal. It can be understood that when the preset signal is a pulse signal, the voltage amplitude of the pulse signal generally needs to take a certain time to stabilize. For example, the pulse signal is a positive and negative pulse with a period of 2 seconds, the voltage in the first second is the first voltage, and the voltage in the second second is the second voltage. Assuming the first voltage is +48V and the second voltage is -48V, the +48V voltage is not always stable within the first second but will stabilize after a certain time. The situation of the -48V voltage in the second second is similar. When the voltage amplitude of the pulse signal is unstable, the conversion value after the controller 71 performs analog-to-digital conversion on the sampled voltage is also unstable. If the unstable conversion value is used to calculate the calibration parameter in the calibration mode and the resistance value of the insulation resistance to be measured in the measurement mode, it is likely to cause inaccurate calculation results. Therefore, the controller 71 can determine when the voltage amplitude of the pulse signal is in a stable state. When it is determined that the voltage amplitude is in a stable state, the controller 71 can use the conversion value obtained by converting the sampled voltage when the voltage amplitude is in a stable state to calculate the calibration parameter in the calibration mode and the resistance value of the insulation resistance to be measured in the measurement mode, so as to improve the accuracy of the calculation result.

[0175] During the period when the voltage amplitude of the pulse signal is +48V or -48V, the controller 71 generally needs to perform analog-to-digital conversion 500 - 1000 times. Therefore, the controller 71 can, in the measurement mode, calculate the resistance value of the insulation resistance to be measured according to the conversion value obtained in real time, and determine whether the resistance value of the insulation resistance to be measured is stable. If the resistance value of the insulation resistance to be measured is stable, it can be considered that the voltage amplitude of the pulse signal is +48V and is also in a stable state at this time. In some embodiments, the controller 71 can calculate multiple resistance values of the insulation resistance to be measured obtained in sequence and take the average of these multiple resistance values to obtain an average value. According to the average value, the fluctuation range of the resistance value is determined. If the fluctuation range is less than the preset threshold, the controller 71 can determine that the voltage amplitude of the pulse signal is in a stable state.

[0176] In some embodiments, the controller 71 is further configured to start timing when the pulse signal output by the signal generation circuit 72 in response to the specified control signal is the specified voltage, obtain the conversion result corresponding to the specified voltage, detect whether the specified voltage is in a stable state according to the conversion result. If it is in a stable state, stop timing to obtain the target duration, and adjust the specified control signal according to the target duration to adjust the period of the pulse signal output by the signal generation circuit to the minimum period.

[0177] For example, the controller 71 marks the specified control signal output. For example, when the specified control signal enables the signal generation circuit 72 to generate a +48V voltage, the controller 71 can mark the specified control signal as 1. When the specified control signal enables the signal generation circuit 72 to generate a -48V voltage, the controller 71 can mark the specified control signal as 0. Then, when the controller 71 recognizes that the current mark is 1, it starts timing, or when the controller 71 recognizes that the current mark is 0, it starts timing. Assuming that when the timer reaches 0.5 seconds, the controller 71 detects that the +48V voltage is in a stable state according to the conversion value corresponding to the +48V voltage, it stops timing and determines that the target duration is 0.5 seconds. Thereafter, the controller 71 can output a pulse signal with a larger period for controlling the signal generation circuit 72, and determine the duration during which the signal generation circuit 72 generates a +48V voltage, and compare the duration with the target duration. If the duration is greater than the target duration, the controller 71 adjusts the specified control signal to downward adjust the duration until the duration is equal to or slightly greater than the target duration. The adjustment of the duration during which the signal generation circuit 72 generates a -48V voltage is the same. Thus, when the controller 71 controls the signal generation circuit 72 to generate a pulse signal according to the adjusted specified control signal, the period of the pulse signal can be the minimum period that can ensure the specified voltage is in a stable state. Since the period of the pulse signal is the minimum period, in the measurement mode, the controller 71 can obtain the detection result of the insulation resistance to be measured more quickly, which is beneficial to improving the detection efficiency.

[0178] In some embodiments, please refer to Figure 9 , the insulation detection circuit 70 further includes an isolation transmission circuit 75.

[0179] The isolation transmission circuit 75 is configured to be electrically connected to the controller 71 and an external device respectively, and is used to transmit the detection result of the insulation resistance to be measured output by the controller 71 to the external device on the basis of satisfying electrical isolation.

[0180] Therefore, by transmitting the detection result of the insulation resistance to be measured to the external device on the basis of satisfying electrical isolation, the anti-interference performance of the signal can be maximally improved, and the communication data can be ensured to be correct.

[0181] In some embodiments, the external device is the central processing unit of the charging pile 100.

[0182] In some embodiments, as Figure 9 shown, the isolation transmission circuit 75 includes a signal isolation circuit 751 and a communication circuit 752.

[0183] The signal isolation circuit 751 is electrically connected to the controller 71 and the communication circuit 752 respectively, and the communication circuit 752 is also configured to be electrically connected to the external device.

[0184] The signal isolation circuit 751 is used to achieve electrical isolation between the controller 71 and the communication circuit 752, and the communication circuit 752 is used to transmit the detection result of the insulation resistance to be measured to an external device.

[0185] The signal isolation circuit 751 can be built with any suitable isolation device such as an optocoupler.

[0186] In some embodiments, the communication circuit 752 can adopt any suitable communication method, including but not limited to RS485, RS232, USB (Universal Serial Bus), etc.

[0187] In some embodiments, as Figure 9 shown, the insulation detection circuit 70 further includes a switch circuit 76.

[0188] The switch circuit 76 is configured to be electrically connected to the controller 71 and the charging bus respectively, and is used to disconnect the charging bus in response to the switch control signal output by the controller. The switch control signal is output when the controller 71 determines that the resistance value of the insulation resistance to be measured is less than a preset resistance threshold.

[0189] It can be understood that after the controller 71 detects the resistance value of the insulation resistance to be measured, it will compare the resistance value with the preset resistance threshold. If the resistance value is less than the preset resistance threshold, it indicates that there may be an insulation fault in the charging pile 100. At this time, the controller 71 outputs a switch control signal to the switch circuit 76, and the switch circuit 76 responds to the switch control signal to disconnect the charging bus to ensure charging safety and personal safety. It can also be understood that the preset resistance threshold can be set according to actual needs and is not limited here.

[0190] In some embodiments, as Figure 9 shown, the insulation detection circuit 70 further includes a display module 77.

[0191] The display module 77 is electrically connected to the controller 71 and is used to display the detection result of the insulation resistance to be measured.

[0192] The display module 77 can be any suitable type of display screen, including but not limited to LED (Light Emitting Diode) digital tubes, LCD (Liquid Crystal Display) monitors, OLED (Organic Light-Emitting Diode) monitors, TFT (Thin Film Transistor)-LCD display screens, etc.

[0193] Finally, it should be noted that the present invention can be implemented in many different forms and is not limited to the embodiments described in this specification. These embodiments do not serve as additional limitations to the content of the present invention. The purpose of providing these embodiments is to make the understanding of the disclosed content of the present invention more thorough and comprehensive. And under the concept of the present invention, the above technical features continue to be combined with each other, and there are many other variations in different aspects of the present invention as described above, all of which are regarded as within the scope described in the specification of the present invention. Further, for those of ordinary skill in the art, improvements or modifications can be made according to the above description, and all such improvements and modifications should fall within the protection scope of the appended claims of the present invention.

Claims

1. An insulation detection circuit, characterized in that: A controller, configured to output a specified control signal in response to a target operating mode, where the target operating mode includes a calibration mode and a measurement mode; A signal generation circuit, electrically connected to the controller and configured to be electrically connected to the ground terminal of a charging pile, for outputting a preset signal to the ground terminal in response to the specified control signal. There is a to-be-tested insulation resistance between the charging bus of the charging pile and the ground terminal; An analog insulation resistance, configured to be connected in parallel with the to-be-tested insulation resistance in the calibration mode; A sampling circuit, electrically connected to the controller and configured to be electrically connected to the charging bus, for coupling the preset signal and outputting a sampling voltage to the controller; When the target operating mode is the calibration mode, the controller performs analog-to-digital conversion on the sampling voltage to obtain a first conversion result, and obtains a preset insulation resistance value, and determines a calibration parameter according to the first conversion result and the preset insulation resistance value; when the target operating mode is the measurement mode, the controller performs analog-to-digital conversion on the sampling voltage to obtain a second conversion result, and detects the resistance value of the to-be-tested insulation resistance according to the second conversion result and the calibration parameter.

2. The insulation detection circuit according to claim 1, wherein The sampling circuit includes: A signal coupling circuit, configured to be electrically connected to the charging bus, for coupling the preset signal and outputting a coupling voltage; A signal conditioning circuit, electrically connected to the signal coupling circuit and the controller respectively, for providing a preset adjustment voltage and a preset gain, and outputting the sampling voltage in response to the coupling voltage. The sampling voltage is determined by the coupling voltage, the preset adjustment voltage and the preset gain.

3. The insulation detection circuit according to claim 2, wherein, The signal conditioning circuit includes: A low-pass filter, electrically connected to the signal coupling circuit, for providing a first gain and outputting a filtered voltage in response to the coupling voltage. The first gain is the ratio of the filtered voltage to the coupling voltage; An adder, electrically connected to the low-pass filter and the controller respectively, for providing a preset adjustment voltage and a second gain, and outputting the sampling voltage in response to the filtered voltage. The sum of the preset adjustment voltage and the product of the filtered voltage and the second gain is equal to the sampling voltage. The product of the first gain and the second gain is equal to the preset gain.

4. The insulation detection circuit according to claim 2, characterized in that: The signal coupling circuit includes an equivalent coupling resistance connected in series with the to-be-tested insulation resistance equivalently; The preset signal includes a first voltage and a second voltage. The first conversion result includes a first conversion value corresponding to the first voltage and a second conversion value corresponding to the second voltage; In the calibration mode, the controller obtains the resistance value of the equivalent coupling resistance and the preset insulation resistance value, determines a first total resistance value to the ground according to the resistance value of the equivalent coupling resistance and the preset insulation resistance value, and determines the calibration parameter according to the first total resistance value to the ground, the first conversion value and the second conversion value.

5. The insulation detection circuit according to claim 4, characterized in that, The second conversion result includes a third conversion value corresponding to the first voltage and a fourth conversion value corresponding to the second voltage; In the measurement mode, the controller obtains the calibration parameter and the resistance value of the equivalent coupling resistor, determines a second total resistance value to the ground according to the calibration parameter, the third conversion value, and the fourth conversion value, and detects the resistance value of the to-be-tested insulation resistor according to the second total resistance value to the ground and the resistance value of the equivalent coupling resistor.

6. The insulation detection circuit according to claim 1, wherein The preset signal is a pulse signal; The controller is further configured to start timing when the pulse signal output by the signal generation circuit in response to the specified control signal is a specified voltage, obtain a conversion result corresponding to the specified voltage, detect whether the specified voltage is in a stable state according to the conversion result, and if it is in a stable state, stop timing to obtain a target duration, and adjust the specified control signal according to the target duration to adjust the period of the pulse signal output by the signal generation circuit to a minimum period.

7. The insulation detection circuit according to claim 1, wherein The signal generation circuit includes: A signal generator, electrically connected to the controller, for outputting an initial signal in response to a specified control signal; A signal amplifier, electrically connected to the signal generator and configured to be electrically connected to the ground terminal of the charging pile, for amplifying the initial signal and outputting a preset signal to the ground terminal.

8. The insulation detection circuit according to any one of claims 1 to 7, characterized in that The insulation detection circuit further includes an isolation transmission circuit; The isolation transmission circuit is configured to be electrically connected to the controller and an external device respectively, and is used for transmitting the detection result of the to-be-tested insulation resistor output by the controller to the external device on the basis of satisfying electrical isolation.

9. The insulation detection circuit according to any one of claims 1 to 7, characterized in that The insulation detection circuit further includes a switch circuit; The switch circuit is configured to be electrically connected to the controller and the charging bus respectively, and is used for disconnecting the charging bus in response to a switch control signal output by the controller, and the switch control signal is output when the controller determines that the resistance value of the to-be-tested insulation resistor is less than a preset resistance threshold.

10. A charging pile, characterized in that, Including the insulation detection circuit according to any one of claims 1 to 9.

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