Voltage sampling circuit of direct-current high-voltage system
By using technical means such as voltage division circuit and multi-channel multiplexing analog switch chip U2 in DC high-voltage system, the problem of voltage offset at the voltage acquisition point is solved, efficient voltage signal sampling and isolation is achieved, and cost and the occupation of single board space is reduced.
Patent Information
- Application Number
- CN202411895684.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-19
- Publication Date
- 2025-03-14
AI Technical Summary
The existing DC high-voltage system voltage sampling scheme has the voltage offset of the voltage acquisition point because the power supply negative and high-voltage negative of the operational amplifier are not at the same potential, resulting in the problem of high voltage display at the sampling end without high voltage.
The voltage divider circuit is used to divide the multi-channel DC high voltage, divide the voltage through series of resistors R1 and R2, and use capacitor C1 filtering and diode D1 for clamping protection to ensure that the voltage negative acquisition point is consistent with the high voltage negative. At the same time, multi-channel multiplexed analog switch chip U2 and digital isolator U1 are used to reduce the use of optocouplers and realize efficient isolation of voltage signals and select output.
It effectively avoids the voltage offset problem at the voltage acquisition point, reduces the use of optocouplers, thereby reducing the area and cost of the single board, and improving the accuracy and efficiency of voltage sampling.
Smart Images
Figure CN119619615A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of voltage sampling of a direct current high voltage system, and in particular to a voltage sampling circuit of a direct current high voltage system. Background Art
[0002] The current mainstream voltage sampling scheme for DC high-voltage systems is to use resistors to divide the high-voltage positive and high-voltage negative voltages, input them into operational amplifiers for amplification, and then input them into DSPs for processing after optical coupler isolation. Generally, this scheme requires one optical coupler isolation for each sampling channel. When the number of voltage samples is large, the number of optical couplers used will also increase, and the area and cost of the single board will also increase.
[0003] In this solution, since the negative power supply and the negative high voltage of the operational amplifier are not at the same potential, when one part of the circuit has high voltage input and the other part does not, due to the resistor voltage division, the negative power supply potential of the operational amplifier will be offset relative to the negative high voltage, resulting in the sampling end operational amplifier without high voltage input still having output voltage, causing the sampling end that should show no high voltage to show high voltage. Summary of the invention
[0004] The object of the present invention is to provide a voltage sampling circuit for a DC high voltage system.
[0005] To achieve the above object, the present invention provides the following technical solution: a voltage sampling circuit of a DC high voltage system, comprising: A voltage divider circuit is used to divide the multiple DC high voltages and then output voltage sampling signals; A sampling channel selection circuit, used for isolating the voltage sampling signal and then selecting the output voltage signal; and The operational amplifier isolation circuit is used to reduce the output resistance of the voltage signal before outputting it.
[0006] Furthermore, the voltage divider circuit includes resistors R1 and R2, one end of the resistor R1 is connected to one end of the resistor R2 and then connected to negative high voltage of multiple DC high voltages, and the other end of the resistor R1 is connected to positive high voltage of multiple DC high voltages.
[0007] Furthermore, the voltage divider circuit further includes a capacitor C1, one end of the capacitor C1 is connected between the resistors R1 and R2, and the capacitor C1 is connected in parallel with the resistor R2.
[0008] Furthermore, the voltage divider circuit further includes a diode D1, wherein pin 1 of the diode D1 is connected to one end of the resistor R2, and pin 3 of the diode D1 is connected to the other end of the resistor R2.
[0009] Furthermore, the sampling channel selection circuit includes a digital isolator U1, a multi-channel multiplexed analog switch chip U2, and resistors R12, R13, R14, R15, R16, R17, R18, and R19. The resistors R12, R13, R14, R15, R16, R17, R18, and R19 are respectively connected to the digital isolator U1, and the digital isolator U1 is connected to the multi-channel multiplexed analog switch chip U2.
[0010] Furthermore, the operational amplifier isolation circuit includes an isolation optical coupler U4, operational amplifiers U3, U5, resistors R20, R21, R22, R23, R25, R26, R27, and a capacitor C3, one end of the resistor R20 is connected to the positive input end of the operational amplifier U3, the negative input end of the operational amplifier U3 is connected to the positive input end and then connected to the isolation optical coupler U4 through the resistor R22, one end of the resistor R21 is connected between the operational amplifier U3 and the resistor R22, the other end of the resistor R21 is connected to one end of the capacitor C3, and the resistor R21 is connected to the positive input end of the operational amplifier U3. The other end of capacitor C3 is connected between resistor R22 and isolation optocoupler U4, one end of resistor R23 is connected to isolation optocoupler U4, and the other end of resistor R23 is connected to the positive input end of operational amplifier U5 through one end of R25, one end of resistor R26 is connected to isolation optocoupler U4, and the other end of resistor R26 is connected to the output end of operational amplifier U5 through resistor R27, the negative input end of operational amplifier U5 is connected between resistors R26 and R27, and one end of resistor R28 is connected to the output end of operational amplifier U5.
[0011] It can be seen from the above technical solution that the present invention has the following beneficial effects: The voltage sampling circuit of the DC high voltage system first obtains the signal through the series voltage division of resistors R1 and R2, uses capacitor C1 for filtering, and diode D1 for clamping protection. Since the negative voltage acquisition point of this voltage division method is directly connected to the negative high voltage, the potentials of the two will always be consistent. This method can avoid the situation in which the voltage of the negative voltage acquisition point is offset relative to the negative high voltage voltage in traditional voltage sampling, resulting in the sampling end that should not display no high voltage displaying high voltage; After the multi-channel voltage obtains the signal through the resistor series voltage division method, the signal is input to the multi-channel multiplexing analog switch chip U2. The DSP sends the control signal, which is isolated by the digital isolator U1 and then sent to the multi-channel multiplexing analog switch chip U2 for channel selection. The control signal rotates and cycles according to a fixed period, thereby realizing 8-channel voltage signal input and 2-channel voltage signal output. In this way, the 8 optocouplers required for traditional voltage sampling are reduced to two optocouplers, which greatly reduces the use of optocouplers. With the reduction in the use of optocouplers, the area and cost of the single board can be greatly reduced; The two voltage signal outputs of the multi-channel multiplexing analog switch chip U2 are first followed by the operational amplifier U3 and then input to the isolation optocoupler U4. The isolation optocoupler U4 isolates the output signal to the operational amplifier U5. The operational amplifier U5 performs differential amplification on the signal and then passes the signal to the DSP for internal calculation and processing to obtain the voltage sampling value. This method of voltage sampling solves the voltage deviation problem of traditional voltage sampling very well, and greatly saves costs and single board space. BRIEF DESCRIPTION OF THE DRAWINGS
[0012] Figure 1 This is a voltage divider circuit diagram of the present invention; Figure 2 A circuit diagram for selecting a sampling channel of the present invention; Figure 3 This is the operational amplifier isolation circuit diagram of the present invention. DETAILED DESCRIPTION
[0013] In the description of the present invention, it should be noted that the terms "upper", "lower", "inner", "outer", "front end", "rear end", "two ends", "one end", "the other end" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.
[0014] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "provided with", "connected", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.
[0015] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0016] See also Figure 1-3 The present invention provides a voltage sampling circuit for a DC high voltage system, including a voltage divider circuit, a sampling channel selection circuit and an operational amplifier isolation circuit. Figure 1 As shown, the voltage divider circuit includes resistors R1 and R2, one end of the resistor R1 is connected to one end of the resistor R2, the high voltage positive is input through U1_P1, and the high voltage negative is input through GND1. Since R1 and R2 are in series relationship in the circuit, according to the voltage divider formula of the series circuit: V1_SEN=R2*(U1_P1) / R1+R2, the value of V1_SEND after voltage division can be obtained.
[0017] A capacitor C1 is also provided in the voltage divider circuit. One end of the capacitor C1 is connected between the resistors R1 and R2. The capacitor C1 is connected in parallel with the resistor R2. To reduce the interference of external interference signals on the circuit, the capacitor C1 is connected in parallel to the V1_SEN network to reduce the interference of external interference signals.
[0018] The voltage divider circuit also includes a diode D1. Pin 1 of the diode D1 is connected to one end of the resistor R2, and pin 3 of the diode D1 is connected to the other end of the resistor R2. In order to prevent the value of V1_SEN from exceeding the safe input range of the subsequent circuit due to external voltage fluctuations, the diode D1 is added as a clamping circuit.
[0019] The DC high voltage is first divided in series by resistors R1 and R2 to obtain the signal, and then filtered by capacitor C1 and clamped by diode D1. Since the negative voltage collection point of this voltage division method is directly connected to the negative high voltage, the potentials of the two will always remain consistent. This method can avoid the situation in which the voltage of the negative voltage collection point is offset relative to the negative voltage of the high voltage in traditional voltage sampling, resulting in the sampling end that should not display no high voltage displaying high voltage.
[0020] Diode D1 is connected to the positive pole of the 5V power supply and the negative pole of the high voltage. When the voltage signal is negative, diode D1 is turned on to limit the voltage through the negative pole of the high voltage. When the voltage signal is higher than 5V, diode D1 is turned on to limit the voltage through the positive pole of the 5V power supply. This ensures that the voltage range of V1_SEN will not damage the subsequent circuits. By arranging multiple circuits above, voltage sampling signals of multiple DC high voltages after voltage division can be obtained.
[0021] The sampling channel selection circuit includes a digital isolator U1, a multi-channel multiplexing analog switch chip U2, resistors R12, R13, R14, R15, R16, R17, R18, and R19. The sampling channel selection circuit isolates the voltage sampling signal and selects the output voltage signal. The resistors R12, R13, R14, R15, R16, R17, R18, and R19 are respectively connected to the digital isolator U1, and the digital isolator U1 is connected to the multi-channel multiplexing analog switch chip U2. The voltage sampling signal is input to the multi-channel multiplexing analog switch chip U2 after passing through the current limiting resistors R12, R13, R14, R15, R16, R17, R18, and R19. The multi-channel multiplexing analog switch chip U2 can switch the connectivity between the input pin and the output pin according to the levels of the two control pins. According to the chip manual, when the level of the 9th and 10th pins (SO2, SO1) of the multi-channel multiplexing analog switch chip U2 is 00, the 12th and 13th pins of the multi-channel multiplexing analog switch chip U2 are connected, and the 1st and 3rd pins are connected. When the level of the 10th and 9th pins (SO1, SO2) of the multi-channel multiplexing analog switch chip U2 is 01, the 14th and 13th pins of the multi-channel multiplexing analog switch chip U2 are connected, and the 5th and 3rd pins are connected. When the level of the 10th and 9th pins (SO1, SO2) of the multi-channel multiplexing analog switch chip U2 is 10, the 15th and 13th pins of the multi-channel multiplexing analog switch chip U2 are connected, and the 2nd and 3rd pins are connected. When the level of the 10th and 9th pins (SO1, SO2) of the multi-channel multiplexing analog switch chip U2 is 11, the 11th and 13th pins of the multi-channel multiplexing analog switch chip U2 are connected, and the 4th and 3rd pins are connected. After DSP sends the control signal, since the ground used by the DSP power supply must be a low-voltage ground, the control signal is isolated by the digital isolator U1 and then transmitted to the high-voltage ground system of the multi-channel multiplexed analog switch chip U2. The control signal sent by DSP switches state every 2ms, and it takes a total of 8ms to complete a cycle of state switching. In this way, 8 voltage sampling signals can be integrated into 2 channels.
[0022] After the multi-channel voltage obtains the signal through the resistor series voltage division method, the signal is input to the multi-channel multiplexing analog switch chip U2. The DSP sends the control signal, which is isolated by the digital isolator U1 and then sent to the multi-channel multiplexing analog switch chip U2 for channel selection. The control signal rotates and cycles according to a fixed period, thereby realizing 8-channel voltage signal input and 2-channel voltage signal output. In this way, the 8 optocouplers required for traditional voltage sampling are reduced to two optocouplers, which greatly reduces the use of optocouplers. With the reduction in the use of optocouplers, the area and cost of the single board can be greatly reduced.
[0023] The operational amplifier isolation circuit includes an isolation optical coupler U4, operational amplifiers U3, U5, resistors R20, R21, R22, R23, R25, R26, R27, and a capacitor C3. One end of the resistor R20 is connected to the positive input end of the operational amplifier U3. The negative input end of the operational amplifier U3 is connected to the positive input end and then connected to the isolation optical coupler U4 through the resistor R22. One end of the resistor R21 is connected between the operational amplifier U3 and the resistor R22. The other end of the resistor R21 is connected to one end of the capacitor C3. The other end is connected between the resistor R22 and the isolation optocoupler U4, one end of the resistor R23 is connected to the isolation optocoupler U4, and the other end of the resistor R23 is connected to the positive input terminal of the operational amplifier U5 through one end of R25, one end of the resistor R26 is connected to the isolation optocoupler U4, and the other end of the resistor R26 is connected to the output terminal of the operational amplifier U5 through the resistor R27, the negative input terminal of the operational amplifier U5 is connected between the resistors R26 and R27, and one end of the resistor R28 is connected to the output terminal of the operational amplifier U5.
[0024] After the multi-channel multiplexing analog switch chip U2 outputs the selected voltage signal, the voltage signal first reaches the operational amplifier U3. The operational amplifier U3 forms a voltage follower through the resistor R20 and the wiring. Since the operational amplifier has the characteristics of high input impedance and low output impedance, the output resistance of the voltage signal can be reduced through this characteristic, and the voltage loss in the back-end circuit can be reduced, thereby ensuring the signal quality. The operational amplifier U3 outputs the voltage signal, which is input to the isolation optocoupler U4 after passing through the pull-down resistor R21, the current limiting resistor R22, and the filter capacitor C3. After being isolated and converted to a low-voltage ground by the isolation optocoupler U4, it is transmitted to the input end of the operational amplifier U5. The operational amplifier U5 forms a differential operational amplifier through resistors R23, R25, R26, R27 and wiring, thereby reducing the output resistance of the voltage signal and ensuring the signal quality. After the final voltage signal is output by the operational amplifier U5, it is transmitted to the DSP voltage signal detection pin, and the DSP performs the corresponding conversion operation.
[0025] The two voltage signal outputs of the multi-channel multiplexing analog switch chip U2 are first followed by the operational amplifier U3 and then input to the isolation optocoupler U4. The isolation optocoupler U4 isolates the output signal to the operational amplifier U5. The operational amplifier U5 performs differential amplification on the signal and then passes the signal to the DSP for internal calculation and processing to obtain the voltage sampling value. This method of voltage sampling solves the voltage deviation problem of traditional voltage sampling very well, and greatly saves costs and single board space.
[0026] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.
Claims
1. A voltage sampling circuit for a DC high voltage system, characterized in that: include: A voltage divider circuit is used to divide the multiple DC high voltages and then output voltage sampling signals; A sampling channel selection circuit is used to isolate the voltage sampling signal and then select the output voltage signal; as well as The operational amplifier isolation circuit is used to reduce the output resistance of the voltage signal before outputting it.
2. The voltage sampling circuit of a DC high voltage system according to claim 1, characterized in that: The voltage divider circuit includes resistors R1 and R2. One end of the resistor R1 is connected to one end of the resistor R2 and then connected to negative high voltage of multiple DC high voltages. The other end of the resistor R1 is connected to positive high voltage of multiple DC high voltages.
3. The voltage sampling circuit of a DC high voltage system according to claim 2, characterized in that: The voltage divider circuit further includes a capacitor C1 , one end of which is connected between the resistors R1 and R2 , and the capacitor C1 is connected in parallel with the resistor R2 .
4. The voltage sampling circuit of a DC high voltage system according to claim 3, characterized in that: The voltage divider circuit further includes a diode D1 , wherein pin 1 of the diode D1 is connected to one end of the resistor R2 , and pin 3 of the diode D1 is connected to the other end of the resistor R2 .
5. The voltage sampling circuit of a DC high voltage system according to claim 1, characterized in that: The sampling channel selection circuit includes a digital isolator U1, a multi-channel multiplexing analog switch chip U2, and resistors R12, R13, R14, R15, R16, R17, R18, and R19. The resistors R12, R13, R14, R15, R16, R17, R18, and R19 are respectively connected to the digital isolator U1, and the digital isolator U1 is connected to the multi-channel multiplexing analog switch chip U2.
6. The voltage sampling circuit of a DC high voltage system according to claim 1, characterized in that: The operational amplifier isolation circuit includes an isolation optical coupler U4, operational amplifiers U3 and U5, resistors R20, R21, R22, R23, R25, R26, R27, and a capacitor C3. One end of the resistor R20 is connected to the positive input end of the operational amplifier U3. The negative input end of the operational amplifier U3 is connected to the positive input end and then connected to the isolation optical coupler U4 through the resistor R22. One end of the resistor R21 is connected between the operational amplifier U3 and the resistor R22. The other end of the resistor R21 is connected to one end of the capacitor C3. The capacitor C3 The other end of the resistor R23 is connected between the resistor R22 and the isolation optocoupler U4, one end of the resistor R23 is connected to the isolation optocoupler U4, and the other end of the resistor R23 is connected to the positive input terminal of the operational amplifier U5 through one end of R25, one end of the resistor R26 is connected to the isolation optocoupler U4, and the other end of the resistor R26 is connected to the output terminal of the operational amplifier U5 through a resistor R27, the negative input terminal of the operational amplifier U5 is connected between the resistors R26 and R27, and one end of the resistor R28 is connected to the output terminal of the operational amplifier U5.