High-voltage DC bus voltage isolation sampling circuit

Abstract

The invention relates to the technical field of voltage sampling, and discloses a high-voltage direct-current bus voltage isolation sampling circuit which comprises an isolation transformer, an N-MOS tube, a digital-to-analog converter and an MCU. The input end of the MCU is connected with the output end of the digital-to-analog converter, the driving output end of the MCU is connected with the grid electrode of the N-MOS tube, a rectangular wave signal with a preset frequency is output to the grid electrode of the N-MOS tube, and the N-MOS tube is controlled to be switched on at a high level and switched off at a low level, so that the N-MOS tube is switched off after being switched on in each period of the rectangular wave signal, and the output end of the MCU is connected with the grid electrode of the N-MOS tube. And the secondary side of the isolation transformer generates a secondary side coupling voltage, so that after the digital-to-analog converter converts and outputs the digital signal, the sampling voltage of the high-voltage direct-current bus is obtained based on the digital signal.

Description

Technical Field

[0001] The present invention relates to the technical field of voltage sampling, and in particular to a high-voltage direct current bus voltage isolation sampling circuit. Background Art

[0002] At present, in the fields of power system automation, new energy electric vehicles and high-voltage storage, it is often necessary to sample and detect the high-voltage DC bus voltage; generally, the high-voltage DC bus voltage may reach 100Vdc to 1000Vdc. Therefore, it is necessary to design a dedicated sampling circuit in combination with circuit cost and sampling accuracy.

[0003] Reference Figure 1 As shown in the figure, it is a schematic diagram of a traditional high-voltage DC sampling circuit; V+ is the positive pole of the high-voltage DC, V- is the negative pole of the high-voltage DC, R1, R2, R3, R4 and R5 are all sampling voltage-dividing resistors; the isolated high-voltage sampling dedicated chip is the core component, which is used to isolate the input and output, isolate V- and GND, to ensure that the high-voltage circuit will not damage the sampled circuit; the voltage across R5 is sampled and converted into an output voltage VF in proportion to add to the load R6. The traditional high-voltage DC sampling circuit can isolate the input and output, and use an isolated high-voltage sampling dedicated chip, which is expensive and difficult to purchase. And because the bus voltage is large, it is necessary to reasonably set the resistance value, divide the high-voltage DC into a voltage of several volts or even lower according to a certain proportion, and distribute it to each voltage-dividing resistor for processing by the sampling chip. Therefore, there are many sampling resistors in the circuit, and the actual use area in the circuit board is large, resulting in low circuit board utilization; at the same time, this method based on the resistor voltage-dividing method for detection has a large loss of sampling resistors, heat dissipation problems, and the selection of the resistance value of the voltage-dividing resistor will also affect the sampling accuracy of the high-voltage DC bus voltage. Summary of the invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the problems of high device cost and unstable sampling accuracy in the prior art when performing high-voltage DC bus voltage detection.

[0005] In order to solve the above technical problems, the present invention provides a high-voltage DC bus voltage isolation sampling circuit, comprising: An isolation transformer, wherein a first pin of a primary side is connected to a positive pole of a high-voltage DC bus voltage, and a fourth pin of a secondary side is grounded; An N-MOS tube, whose source is connected to the negative electrode of the high-voltage DC bus voltage, and whose drain is connected to the second pin of the primary side of the isolation transformer; Control unit, comprising: The digital-to-analog converter, whose input end is connected in parallel to the secondary side of the isolation transformer, couples the high-voltage DC bus voltage of the primary side of the isolation transformer to the secondary-side coupling voltage generated by the secondary side, and converts it into a digital signal output; The MCU has an input end connected to the output end of the digital-to-analog converter, and a driving output end connected to the gate of the N-MOS tube. The MCU outputs a rectangular wave signal of a preset frequency to the gate of the N-MOS tube, controls the N-MOS tube to be turned on at a high level and turned off at a low level, so that the N-MOS tube is turned on and then turned off in each cycle of the rectangular wave signal, so that the secondary side of the isolation transformer generates a secondary side coupling voltage, so that after the digital-to-analog converter converts and outputs the digital signal, the sampling voltage of the high-voltage DC bus is obtained based on the digital signal.

[0006] Preferably, the control unit further includes a level conversion circuit, including: A level conversion chip, wherein the input pin thereof is connected to the driving output end of the MCU, the ground pin thereof is connected to the negative pole of the high-voltage DC bus voltage, the power pin thereof is connected to a stable voltage source, and the output pin thereof is connected to the gate of the N-MOS tube, so that based on the voltage difference between the ground pin and the input pin and the conduction voltage threshold of the N-MOS tube, the output voltage of the output pin is adjusted, so that the voltage difference between the output voltage of the output pin and the ground pin is greater than the conduction voltage threshold of the N-MOS tube, and the N-MOS tube is driven to conduct.

[0007] Preferably, the control unit further includes a level conversion circuit, including: An NPN transistor, whose base is connected to the driving output end of the MCU through a resistor, whose emitter is connected to the negative electrode of the high-voltage DC bus voltage, whose collector is connected to a stable voltage source through a pull-up resistor, and whose collector is connected to the gate of the N-MOS tube, so that the NPN transistor adjusts the collector potential based on the change of the driving voltage and the negative electrode voltage of the high-voltage DC bus voltage, so that the voltage difference between the collector and the emitter is greater than the conduction voltage threshold of the N-MOS tube, thereby driving the N-MOS tube to conduct.

[0008] Preferably, the sampled voltage of the high-voltage DC bus is obtained based on the digital signal, which is expressed as: ; in, Represents the sampling voltage of the high-voltage DC bus, Represents the binary value of a digital signal. Indicates the resolution of the digital-to-analog converter, Indicates the reference voltage of the digital-to-analog converter.

[0009] Preferably, after obtaining the sampled voltage of the high-voltage DC bus based on the digital signal, the method further includes: Based on the ratio of the primary and secondary turns ratios of the isolation transformer With sampling voltage , calculate the actual voltage of the high-voltage DC bus , expressed as: .

[0010] Preferably, the MCU is also used for: The absolute value of the difference between the actual voltage of the high-voltage DC bus and the rated voltage of the load connected to the positive and negative ends of the high-voltage DC bus is calculated. If the absolute value of the difference is not less than a preset threshold, an adjustment voltage value is generated and output from the feedback output end to control the voltage regulator to adjust the voltage between the positive and negative poles of the high-voltage DC bus.

[0011] Preferably, it also includes a voltage regulator, which is arranged between the positive electrode of the high-voltage DC bus voltage and the load, and its signal input end is connected to the feedback output end of the MCU to obtain the adjusted voltage value, including: If the actual voltage of the high-voltage DC bus is greater than the rated voltage of the load connected to the positive and negative ends of the high-voltage DC bus, the voltage of the high-voltage DC bus is controlled to decrease until the absolute value of the difference between the actual voltage of the high-voltage DC bus and the rated voltage of the load connected to the positive and negative ends of the high-voltage DC bus is less than a preset threshold; If the actual voltage of the high-voltage DC bus is less than the rated voltage of the load connected to the positive and negative ends of the high-voltage DC bus, the high-voltage DC bus voltage is controlled to increase until the absolute value of the difference between the actual voltage of the high-voltage DC bus and the rated voltage of the load connected to the positive and negative ends of the high-voltage DC bus is less than a preset threshold.

[0012] Preferably, based on the high-voltage DC bus voltage and the turns ratio between the primary and secondary sides of the isolation transformer, the amplitude range of the secondary coupling voltage is obtained, and a digital-to-analog converter having a rated voltage greater than the amplitude range of the secondary coupling voltage is selected.

[0013] Preferably, it also includes a rectifying and filtering unit, whose input end is connected in parallel to the two ends of the secondary side of the isolation transformer, and outputs the secondary side coupled voltage after rectification and filtering.

[0014] Preferably, the rectifying and filtering unit comprises: A rectifier diode, an anode of which is connected to the third pin of the secondary side of the isolation transformer, and a cathode of which is connected to the fourth pin of the secondary side of the isolation transformer; A filter capacitor, one end of which is connected to the cathode of the rectifier diode and the other end of which is grounded; A filter resistor, one end of which is connected to the cathode of the rectifier diode, and the other end of which is grounded.

[0015] The above technical solution of the present invention has the following beneficial effects compared with the prior art: In order to reduce the cost of the high-voltage DC bus voltage isolation sampling circuit, the present invention uses an isolation transformer to achieve voltage conversion and isolation. However, since the transformer works based on the principle of electromagnetic induction and requires a changing magnetic field to generate an induced electromotive force, the transformer cannot be directly applied to the collection of the high-voltage DC bus voltage. To solve this problem, the present invention provides a high-voltage DC bus voltage isolation sampling circuit based on an isolation transformer, wherein the primary side of the isolation transformer is connected to the positive and negative poles of the DC bus to be sampled, and by controlling the on and off of the N-MOS tube, the isolation transformer couples the DC bus voltage to the secondary side of the isolation transformer, and after digital-to-analog conversion, the DC bus voltage sensed by the primary side is sampled. The present invention abandons the traditional isolation high-voltage sampling dedicated chip, reduces the device cost, and gets rid of technical dependence; at the same time, there is no need to set too many voltage-dividing resistors, which reduces power consumption and reduces the area used for the circuit board. The present invention only uses the control of the N-MOS gate and the coupling effect of the isolation transformer to achieve high-voltage DC sampling and isolation, with a simple structure, easy maintenance, and a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein: Figure 1 It is a schematic diagram of a conventional high voltage DC sampling circuit; Figure 2 It is a schematic diagram of the high-voltage DC bus voltage isolation sampling circuit provided by the present invention; Figure 3 It is a complete structural diagram of the high-voltage DC bus voltage isolation sampling circuit. DETAILED DESCRIPTION

[0017] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0018] In order to reduce the cost of the high-voltage DC bus voltage isolation sampling circuit, the present invention uses an isolation transformer to achieve voltage conversion and isolation. However, since the transformer works based on the principle of electromagnetic induction and requires a changing magnetic field to generate an induced electromotive force, the transformer cannot be directly applied to the collection of the high-voltage DC bus voltage. To solve this problem, the present invention provides a high-voltage DC bus voltage isolation sampling circuit based on an isolation transformer, wherein the primary side of the isolation transformer is connected to the positive and negative poles of the DC bus to be sampled, and by controlling the on and off of the N-MOS tube, the isolation transformer couples the DC bus voltage to the secondary side of the isolation transformer, and the DC bus voltage sensed by the primary side is sampled after digital-to-analog conversion.

[0019] Reference Figure 2 As shown, the schematic diagram of the high-voltage DC bus voltage isolation sampling circuit of the present invention includes: An isolation transformer, wherein a first pin of a primary side is connected to a positive pole of a high-voltage DC bus voltage, and a fourth pin of a secondary side is grounded; An N-MOS tube, whose source is connected to the negative electrode of the high-voltage DC bus voltage, and whose drain is connected to the second pin of the primary side of the isolation transformer; Control unit, comprising: The digital-to-analog converter, whose input end is connected in parallel to the secondary side of the isolation transformer, couples the high-voltage DC bus voltage of the primary side of the isolation transformer to the secondary-side coupling voltage generated by the secondary side, and converts it into a digital signal output; The MCU has an input end connected to the output end of the digital-to-analog converter, and a driving output end connected to the gate of the N-MOS tube. The MCU outputs a rectangular wave signal of a preset frequency to the gate of the N-MOS tube, controls the N-MOS tube to be turned on at a high level and turned off at a low level, so that the N-MOS tube is turned on and then turned off in each cycle of the rectangular wave signal, so that the secondary side of the isolation transformer generates a secondary side coupling voltage, so that after the digital-to-analog converter converts and outputs the digital signal, the sampling voltage of the high-voltage DC bus is obtained based on the digital signal.

[0020] In this embodiment, in order to ensure that the rectangular wave output by the MCU can drive the N-MOS tube to conduct, a level conversion circuit is set in the control unit of this embodiment, so that the rectangular wave output by the MCU is output to the gate of the N-MOS tube after passing through the level conversion circuit. This embodiment uses a level conversion chip or an NPN transistor to realize the level conversion circuit.

[0021] When a level conversion chip is used, its input pin is connected to the driving output end of the MCU, its ground pin is connected to the negative pole of the high-voltage DC bus voltage, its power pin is connected to a stable voltage source, and its output pin is connected to the gate of the N-MOS tube, so that based on the voltage difference between the ground pin and the input pin and the conduction voltage threshold of the N-MOS tube, the output voltage of the output pin is adjusted, so that the voltage difference between the output voltage of the output pin and the ground pin is greater than the conduction voltage threshold of the N-MOS tube, driving the N-MOS tube to conduct.

[0022] When an NPN transistor is used, its base is connected to the driving output end of the MCU through a resistor, its emitter is connected to the negative electrode of the high-voltage DC bus voltage, its collector is connected to a stable voltage source through a pull-up resistor, and its collector is connected to the gate of the N-MOS tube, so that the NPN transistor adjusts the collector potential based on the change of the driving voltage and the negative electrode voltage of the high-voltage DC bus voltage, so that the voltage difference between the collector and the emitter is greater than the conduction voltage threshold of the N-MOS tube, thereby driving the N-MOS tube to conduct.

[0023] When using NPN transistors, when the drive signal output by the MCU is high, the base potential of the transistor increases and the transistor is turned on; at this time, the collector potential is close to the ground potential (the negative pole of the bus voltage), and the voltage difference between the collector and the emitter is small; if the negative pole of the bus voltage decreases, the emitter potential of the transistor decreases, and since the base potential is relatively stable, the conduction degree of the transistor will deepen, and the collector potential will further decrease, increasing the voltage difference between the gate and the source of the N-MOS tube. Conversely, if the negative pole of the bus voltage increases, the conduction degree of the transistor will weaken, the collector potential will increase, and the voltage difference between the gate and the source of the N-MOS tube will decrease, thereby automatically adjusting the output voltage to maintain the difference between the drive voltage and the negative pole of the bus voltage stable.

[0024] In the embodiment of the present invention, the calculation of the actual voltage of the high-voltage DC bus includes: The sampled voltage of the high-voltage DC bus is obtained based on the digital signal, which is expressed as: ; Based on the ratio of the primary and secondary turns ratios of the isolation transformer With sampling voltage , calculate the actual voltage of the high-voltage DC bus , expressed as: ; in, Represents the sampling voltage of the high-voltage DC bus, Represents the binary value corresponding to the digital signal, Indicates the resolution of the digital-to-analog converter, Indicates the reference voltage of the digital-to-analog converter.

[0025] Specifically, after obtaining the actual voltage of the high-voltage DC bus, the MCU is also used to: calculate the absolute value of the difference between the actual voltage of the high-voltage DC bus and the rated voltage of the load connected to the positive and negative ends of the high-voltage DC bus; if the absolute value of the difference is not less than a preset threshold, generate an adjustment voltage value and output it from the feedback output end, so as to control the voltage regulator to adjust the voltage between the positive and negative poles of the high-voltage DC bus.

[0026] The voltage regulator is arranged between the positive pole of the high-voltage DC bus voltage and the load, and its signal input terminal is connected to the feedback output terminal of the MCU to obtain the adjusted voltage value, including: If the actual voltage of the high-voltage DC bus is greater than the rated voltage of the load connected to the positive and negative ends of the high-voltage DC bus, the voltage of the high-voltage DC bus is controlled to decrease until the absolute value of the difference between the actual voltage of the high-voltage DC bus and the rated voltage of the load connected to the positive and negative ends of the high-voltage DC bus is less than a preset threshold; If the actual voltage of the high-voltage DC bus is less than the rated voltage of the load connected to the positive and negative ends of the high-voltage DC bus, the high-voltage DC bus voltage is controlled to increase until the absolute value of the difference between the actual voltage of the high-voltage DC bus and the rated voltage of the load connected to the positive and negative ends of the high-voltage DC bus is less than a preset threshold.

[0027] Based on the above embodiments, the embodiments of the present invention further include a rectifying and filtering unit, whose input end is connected in parallel to the two ends of the secondary side of the isolation transformer, and rectifies and filters the secondary side coupled voltage before outputting it.

[0028] Specifically, the rectification and filtering unit includes: A rectifier diode, an anode of which is connected to the third pin of the secondary side of the isolation transformer, and a cathode of which is connected to the fourth pin of the secondary side of the isolation transformer; A filter capacitor, one end of which is connected to the cathode of the rectifier diode and the other end of which is grounded; A filter resistor, one end of which is connected to the cathode of the rectifier diode, and the other end of which is grounded.

[0029] Specifically, in the isolated high-voltage sampling circuit, the secondary-side coupling voltage is a voltage signal after rectification and filtering. If the input voltage range of the digital-to-analog converter is smaller than the amplitude of the secondary-side coupling voltage, then the part of the signal that exceeds the range will not be converted correctly, resulting in distorted sampling results. For example, if the amplitude of the secondary-side coupling voltage is between 0-5V, and the selected digital-to-analog converter input voltage range is 0-3V, then the part of the signal that exceeds 3V will be cut off and cannot accurately reflect the actual voltage value. If the secondary-side coupling voltage exceeds the maximum input rated voltage of the digital-to-analog converter, the digital-to-analog converter chip may be damaged. The circuit structure inside the digital-to-analog converter is designed according to a certain voltage range. Excessive input voltage may cause components such as transistors inside the chip to break down, thereby preventing the digital-to-analog converter from working properly. Therefore, when selecting a digital-to-analog converter, it is necessary to ensure that its input voltage range can withstand the maximum amplitude of the secondary-side coupling voltage.

[0030] Therefore, in an embodiment of the present invention, when selecting a digital-to-analog converter, the present invention obtains the amplitude range of the secondary coupling voltage based on the high-voltage DC bus voltage and the turns ratio between the primary and secondary sides of the isolation transformer, and selects a digital-to-analog converter whose rated voltage is greater than the amplitude range of the secondary coupling voltage.

[0031] The present invention abandons the traditional isolation high-voltage sampling dedicated chip, reduces the device cost, and gets rid of technical dependence; at the same time, it does not need to set too many voltage-dividing resistors, reduces power consumption and reduces the circuit board usage area. The present invention only uses the control of the N-MOS gate and the coupling effect of the isolation transformer to achieve high-voltage DC sampling and isolation, with a simple structure, easy maintenance, and a wide range of applications.

[0032] Reference Figure 3As shown, it is a complete structural diagram of the high-voltage DC bus voltage isolation sampling circuit; in this embodiment, on the basis of the isolation transformer and the control unit, a rectifier filter unit is deployed to achieve more accurate voltage sampling. Among them, V+ represents the positive pole of the high-voltage DC, V- represents the negative pole of the high-voltage DC, Z is an N-MOS tube, T is an isolation transformer, D is a rectifier diode, C is a filter capacitor, and R1 and R2 are resistors. Pin 1 of the isolation transformer is connected to V+, and pin 2 of the isolation transformer is connected to V-; the source of the N-MOS tube is connected to V-, and the gate of the N-MOS tube is connected to the control unit; pin 3 of the isolation transformer is connected to the anode of the diode D, and the cathode of the diode D is connected to one end of the capacitor C, connected to one end of the resistor R1, and connected to the control system at the same time, that is, VF1; the other end of the capacitor C and the resistor R1 is connected to pin 4 of the isolation transformer, and connected to the control unit at the same time, that is, GND; the two ends of the resistor R2 are respectively connected to the control unit, and the voltage at both ends of the resistor R2 is the sampling voltage of the control unit. The control unit controls the gate of the N-MOS tube and outputs a driving waveform with a fixed frequency and a fixed duty cycle, so that the N-MOS tube works in a switching state; after the N-MOS tube is turned on, the voltage at both ends of the positive and negative poles of the high-voltage DC is added between the 1st and 2nd pins of the isolation transformer, and a voltage V+ appears between the 1st and 2nd pins of the isolation transformer; after the N-MOS is turned off, a voltage of 0 appears between the 1st and 2nd pins of the isolation transformer, that is, a pulse waveform with the same frequency, the same duty cycle, and an amplitude of V+ appears on the 1st and 2nd pins of the isolation transformer as the control unit; the turns ratio of the primary side (1st and 2nd pins) to the secondary side (3rd and 4th pins) of the isolation transformer is N:1, and the secondary side of the isolation transformer is coupled to a pulse waveform with the same frequency, the same duty cycle, and an amplitude of (V+ / N) as the control unit, which is rectified and filtered by a diode and a capacitor C to become a voltage VF1; the control unit analyzes and calculates VF1 and outputs a sampling voltage VF.

[0033] The present invention does not need to use too many voltage-dividing resistors, thus reducing power consumption and circuit board usage area; at the same time, it avoids the use of isolated high-voltage sampling dedicated chips, which are mainly produced by a few foreign manufacturers and are inconvenient to import. The present invention greatly improves the domestic production rate of components and reduces costs.

[0034] The high-voltage DC bus voltage isolation sampling circuit provided by the present invention can be applied to various scenarios of electric vehicles. During the operation of the electric vehicle, the voltage of the high-voltage DC bus needs to be monitored in real time, and the various controllers on the vehicle will perform calculations and logic protection judgments based on the detected voltage values. For example: the battery management system BMS will perform pre-charging actions and total voltage overvoltage protection judgments based on the high-voltage DC bus voltage; the insulation detection circuit IMD will calculate the positive and negative DC bus insulation resistances based on the high-voltage DC bus voltage; the on-board charger OBC will adjust the charging current output according to the high-voltage DC bus voltage; the VCU, DC / DC and MCU will perform input voltage over-limit alarm judgments based on the high-voltage DC bus voltage, etc.

[0035] In order to reduce the cost of the high-voltage DC bus voltage isolation sampling circuit, the present invention uses an isolation transformer to achieve voltage conversion and isolation. However, since the transformer works based on the principle of electromagnetic induction and requires a changing magnetic field to generate an induced electromotive force, the transformer cannot be directly applied to the collection of the high-voltage DC bus voltage. To solve this problem, the present invention provides a high-voltage DC bus voltage isolation sampling circuit based on an isolation transformer, wherein the primary side of the isolation transformer is connected to the positive and negative poles of the DC bus to be sampled, and by controlling the on and off of the N-MOS tube, the isolation transformer couples the DC bus voltage to the secondary side of the isolation transformer, and after digital-to-analog conversion, the DC bus voltage sensed by the primary side is sampled. The present invention abandons the traditional isolation high-voltage sampling dedicated chip, reduces the device cost, and gets rid of technical dependence; at the same time, there is no need to set too many voltage-dividing resistors, which reduces power consumption and reduces the area used for the circuit board. The present invention only uses the control of the N-MOS gate and the coupling effect of the isolation transformer to achieve high-voltage DC sampling and isolation, with a simple structure, easy maintenance, and a wide range of applications.

[0036] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present application may adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes.

[0037] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0038] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0039] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0040] Obviously, the above embodiments are merely examples for the purpose of clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A high-voltage DC bus voltage isolation sampling circuit, characterized in that: include: An isolation transformer, wherein a first pin of a primary side is connected to a positive pole of a high-voltage DC bus voltage, and a fourth pin of a secondary side is grounded; An N-MOS tube, whose source is connected to the negative electrode of the high-voltage DC bus voltage, and whose drain is connected to the second pin of the primary side of the isolation transformer; Control unit, comprising: The digital-to-analog converter, whose input end is connected in parallel to the secondary side of the isolation transformer, couples the high-voltage DC bus voltage of the primary side of the isolation transformer to the secondary-side coupling voltage generated by the secondary side, and converts it into a digital signal output; The MCU has an input end connected to the output end of the digital-to-analog converter, and a driving output end connected to the gate of the N-MOS tube. The MCU outputs a rectangular wave signal of a preset frequency to the gate of the N-MOS tube, controls the N-MOS tube to be turned on at a high level and turned off at a low level, so that the N-MOS tube is turned on and then turned off in each cycle of the rectangular wave signal, so that the secondary side of the isolation transformer generates a secondary side coupling voltage, so that after the digital-to-analog converter converts and outputs the digital signal, the sampling voltage of the high-voltage DC bus is obtained based on the digital signal.

2. The high-voltage DC bus voltage isolation sampling circuit according to claim 1, characterized in that: The control unit also includes a level conversion circuit, including: A level conversion chip, wherein the input pin thereof is connected to the driving output end of the MCU, the ground pin thereof is connected to the negative pole of the high-voltage DC bus voltage, the power pin thereof is connected to a stable voltage source, and the output pin thereof is connected to the gate of the N-MOS tube, so that based on the voltage difference between the ground pin and the input pin and the conduction voltage threshold of the N-MOS tube, the output voltage of the output pin is adjusted, so that the voltage difference between the output voltage of the output pin and the ground pin is greater than the conduction voltage threshold of the N-MOS tube, and the N-MOS tube is driven to conduct.

3. The high-voltage DC bus voltage isolation sampling circuit according to claim 1, characterized in that: The control unit also includes a level conversion circuit, including: An NPN transistor, whose base is connected to the driving output end of the MCU through a resistor, whose emitter is connected to the negative electrode of the high-voltage DC bus voltage, whose collector is connected to a stable voltage source through a pull-up resistor, and whose collector is connected to the gate of the N-MOS tube, so that the NPN transistor adjusts the collector potential based on the change of the driving voltage and the negative electrode voltage of the high-voltage DC bus voltage, so that the voltage difference between the collector and the emitter is greater than the conduction voltage threshold of the N-MOS tube, thereby driving the N-MOS tube to conduct.

4. The high-voltage DC bus voltage isolation sampling circuit according to claim 1, characterized in that: The sampled voltage of the high-voltage DC bus is obtained based on the digital signal, which is expressed as: ； in, Represents the sampling voltage of the high-voltage DC bus, Represents the binary value corresponding to the digital signal, Indicates the resolution of the digital-to-analog converter, Indicates the reference voltage of the digital-to-analog converter.

5. The high-voltage DC bus voltage isolation sampling circuit according to claim 4, characterized in that: After obtaining the sampled voltage of the high-voltage DC bus based on the digital signal, it also includes: Based on the ratio of the primary and secondary turns ratios of the isolation transformer With sampling voltage , calculate the actual voltage of the high-voltage DC bus , expressed as: 。 6. The high-voltage DC bus voltage isolation sampling circuit according to claim 5, characterized in that: MCU, also used for: The absolute value of the difference between the actual voltage of the high-voltage DC bus and the rated voltage of the load connected to the positive and negative ends of the high-voltage DC bus is calculated. If the absolute value of the difference is not less than a preset threshold, an adjustment voltage value is generated and output from the feedback output end to control the voltage regulator to adjust the voltage between the positive and negative poles of the high-voltage DC bus.

7. The high-voltage DC bus voltage isolation sampling circuit according to claim 6, characterized in that: It also includes a voltage regulator, which is arranged between the positive pole of the high-voltage DC bus voltage and the load, and its signal input end is connected to the feedback output end of the MCU to obtain the adjusted voltage value, including: If the actual voltage of the high-voltage DC bus is greater than the rated voltage of the load connected to the positive and negative ends of the high-voltage DC bus, the voltage of the high-voltage DC bus is controlled to decrease until the absolute value of the difference between the actual voltage of the high-voltage DC bus and the rated voltage of the load connected to the positive and negative ends of the high-voltage DC bus is less than a preset threshold; If the actual voltage of the high-voltage DC bus is less than the rated voltage of the load connected to the positive and negative ends of the high-voltage DC bus, the high-voltage DC bus voltage is controlled to increase until the absolute value of the difference between the actual voltage of the high-voltage DC bus and the rated voltage of the load connected to the positive and negative ends of the high-voltage DC bus is less than a preset threshold.

8. The high-voltage DC bus voltage isolation sampling circuit according to claim 1, characterized in that: Based on the high-voltage DC bus voltage and the turns ratio between the primary and secondary sides of the isolation transformer, the amplitude range of the secondary coupling voltage is obtained, and a digital-to-analog converter with a rated voltage greater than the amplitude range of the secondary coupling voltage is selected.

9. The high-voltage DC bus voltage isolation sampling circuit according to claim 1, characterized in that: It also includes a rectifying and filtering unit, whose input end is connected in parallel to the two ends of the secondary side of the isolation transformer, and outputs the secondary side coupled voltage after rectification and filtering.

10. The high-voltage DC bus voltage isolation sampling circuit according to claim 9, characterized in that: Rectification and filtering unit, including: A rectifier diode, an anode of which is connected to the third pin of the secondary side of the isolation transformer, and a cathode of which is connected to the fourth pin of the secondary side of the isolation transformer; A filter capacitor, one end of which is connected to the cathode of the rectifier diode and the other end of which is grounded; A filter resistor, one end of which is connected to the cathode of the rectifier diode, and the other end of which is grounded.

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