A voltage sampling circuit for a DC charging pile

Abstract

The present invention relates to a voltage sampling circuit for a DC charging pile, which includes a sampling module (1) and a processing module (2), and further includes a first-stage differential signal amplification module (3) connected to the output end of the sampling module (1) and having an isolation function, and a second-stage signal amplification module (4) connected to the output end of the first-stage differential signal amplification module (3); the processing module (2) is connected to the second-stage signal amplification module (4) and receives the DC voltage signal converted by the second-stage signal amplification module (4) from the differential signal output by the first-stage differential signal amplification module (3). This voltage sampling circuit has high sampling accuracy and high voltage resistance.

Description

Technical Field

[0001] The present invention relates to the field of charging piles, and particularly to a voltage sampling circuit for a DC charging pile. Background Art

[0002] With the development of new energy, charging piles play an increasingly important role in the charging of electric vehicles. Since the voltage required by the vehicle is direct current, DC charging piles are mainly used in actual applications.

[0003] Currently, the DC positive and negative voltages provided by DC charging piles are 200VDC - 1000VDC, while the DC voltage required by the charging vehicle is a specific value rather than a range. Moreover, different models of charging vehicles require different charging voltages. Therefore, before charging the vehicle, it is necessary for the DC charging pile to obtain the charging voltage of the current vehicle to be charged through an internal sampling circuit. At the same time, during charging, it is also necessary for the charging pile to sample the voltage it currently outputs to ensure that the output voltage matches the obtained vehicle charging voltage and guarantee the safety of the charging vehicle.

[0004] However, in the sampling circuit of existing DC charging piles, the working voltage of the chips used is generally about 5V, which is much lower than the output voltage of the DC charging pile or the charging voltage required by the vehicle. It is impossible to directly perform voltage sampling, otherwise it will cause equipment damage or the risk of electric shock to personnel, and the sampling accuracy of the existing sampling circuit is not high. Summary of the Invention

[0005] In view of the above problems, the purpose of the present invention is to provide a voltage sampling circuit for a DC charging pile with high sampling accuracy and good safety performance.

[0006] To achieve the above purpose, the technical solution of the present invention is: a voltage sampling circuit for a DC charging pile, including a sampling module and a processing module, characterized in that:

[0007] It further includes a first-stage differential signal amplification module with isolation function connected to the output end of the sampling module, and a second-stage signal amplification module connected to the output end of the first-stage differential signal amplification module;

[0008] The processing module is connected to the second-stage signal amplification module and receives the DC voltage signal converted by the second-stage signal amplification module from the differential signal output by the first-stage differential signal amplification module.

[0009] Furthermore, a filtering module is provided between the output end of the first-stage differential signal amplification module and the second-stage signal amplification module.

[0010] Further, the secondary signal amplification module includes an amplification module disposed at the output end of the primary differential signal amplification module and a micropower operational amplifier module connected to the amplification module, and the processing module is connected to the digital signal output end of the micropower operational amplifier module.

[0011] Further, the primary differential signal amplification module is an isolation operational amplifier module.

[0012] Further, the isolation operational amplifier module outputs two differential signals, the filtering module includes a first RC filter and a second RC filter respectively corresponding to and connected to the output ends where the two differential signals are located, and the amplification module is connected to the back ends of the first RC filter and the second RC filter.

[0013] Further, the amplification module includes a first resistor with one end connected to the back end of the first RC filter and the other end connected to the first analog signal input end of the micropower operational amplifier module, a second resistor with one end connected to the back end of the second RC filter and the other end connected to the second analog signal input end of the micropower operational amplifier module, a third resistor with one end connected between the first resistor and the first analog signal input end and the other end grounded, and a fourth resistor with one end connected between the second resistor and the second analog signal input end and the other end connected to the analog signal output end of the micropower operational amplifier module;

[0014] The amplification factor of the amplification module is the ratio between the third resistor and the first resistor, and the ratio between the third resistor and the first resistor is equal to the ratio between the fourth resistor and the second resistor.

[0015] Further, the analog signal output end of the micropower operational amplifier module is connected to the first digital signal input end it includes, and the processing module is connected to the digital signal output end of the micropower operational amplifier module.

[0016] Further, the sampling module includes a sampling resistor located at the positive and negative ends of the DC voltage, m voltage-dividing resistors connected in series between the positive end of the DC voltage and the sampling resistor, and n voltage-dividing resistors connected in series between the sampling resistor and the negative end of the DC voltage;

[0017] The total resistance value of the n resistors is equal to the total resistance value of the m resistors.

[0018] Further, a third RC filter is provided between the sampling resistor and the input end of the isolation operational amplifier module;

[0019] The third RC filter includes a fifth resistor with one end connected to one end of the sampling resistor and the other end connected to the first differential signal input terminal of the isolation operational amplifier module, a sixth resistor with one end connected to the other end of the sampling resistor and the other end connected to the second differential signal input terminal of the isolation operational amplifier module, and a capacitor connected in parallel between the first differential signal input terminal and the second differential signal input terminal.

[0020] Further, the isolation operational amplifier module is AMC1200BDUB, the micropower operational amplifier module is oPA4330, and the amplification factor of the amplification module is 1.5.

[0021] Compared with the prior art, the advantages of the present invention are as follows: After the conventional sampling module, a first-stage differential signal amplification module with an isolation function and a second-stage signal amplification module capable of converting multiple differential signals into one signal are provided. Through multiple amplifications, the signal finally output to the processor will not be too small, thereby improving the sampling accuracy of the sampling circuit of the DC charging pile. At the same time, the isolation function can effectively prevent the back-end circuit from being affected by potential destructive voltages, improve the withstand voltage ability between the positive and negative poles of the DC charging pile, and ensure the safety of the DC charging pile. Description of the Drawings

[0022] Figure 1 It is a structural principle block diagram of the voltage sampling circuit for the DC charging pile of this application.

[0023] Figure 2 It is a circuit schematic diagram of the sampling module and the first-stage differential signal amplification module of the voltage sampling circuit for the DC charging pile of this application.

[0024] Figure 3 It is a circuit schematic diagram of the second-stage signal amplification circuit of the voltage sampling circuit for the DC charging pile of this application. Detailed Embodiments

[0025] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals denote the same or similar elements or elements with the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary and are only used to explain the present invention and should not be construed as a limitation of the present invention.

[0026] Such as Figures 1 to 3The figure shows a preferred embodiment of the voltage sampling circuit for a DC charging pile according to the present invention. The voltage sampling circuit for the DC charging pile includes a sampling module 1 and a processing module 2, and further includes a first-stage differential signal amplification module 3 connected to the output end of the sampling module 1 and having an isolation function, and a second-stage signal amplification module 4 connected to the output end of the first-stage differential signal amplification module 3. The processing module 2 is connected to the second-stage signal amplification module 4 and receives the DC voltage signal converted by the second-stage signal amplification module 4 from the differential signal output by the first-stage differential signal amplification module 3.

[0027] Since the differential signal output by the first-stage differential signal amplification module 3 may have clutter or oscillations, resulting in unstable signals. To facilitate the subsequent circuit to obtain high-quality signals, as an improvement, a filtering module 5 is provided between the output end of the first-stage differential signal amplification module 3 and the second-stage signal amplification module 4.

[0028] In this embodiment, the second-stage signal amplification module 4 includes an amplification module 41 provided at the output end of the first-stage differential signal amplification module 3 and a micropower operational amplifier module 42 connected to the amplification module 41. The processing module 2 is correspondingly connected to the digital signal output end of the micropower operational amplifier module 42. In this application, the micropower operational amplifier module 42 uses an OPA4330 chip. Therefore, the processing module 2 is connected to the digital signal output end OD of the OPA4330. As is well known to those skilled in the art, it is easy to think that the processing module is an MCU.

[0029] To ensure the safety of the DC charging pile and protect the devices from interference, the first-stage differential signal amplification module is an isolation operational amplifier module. Specifically, in this embodiment, the isolation operational amplifier module uses an AMC1200BDUB chip. It should be noted that the inherent properties of this chip determine that this device can bring 8-fold signal amplification, that is, the chip has a built-in 8-fold output signal amplification function and can amplify the sampling signal from the sampling module 1 by 8 times. This chip can isolate 4KV and can meet the 2.5KV withstand voltage requirement between the positive and negative voltages of the DC charging pile.

[0030] Of course, this chip also requires a corresponding working voltage. However, due to the special nature of its isolation function, its working power supply needs to be provided by an isolation power supply circuit. For those skilled in the art, the isolation power supply circuit belongs to a conventional design and is well known to those of ordinary skill in the art. Therefore, it will not be elaborated here.

[0031] The AMC1200BDUB chip outputs two-way differential signals. To ensure the quality of the sampling signal, each two-way differential signal needs to be filtered. Therefore, in this application, the filtering module 5 includes a first RC filter 51 and a second RC filter 52 respectively corresponding to and connected to the output ends where the two-way differential signals are located, and the amplification module 41 is correspondingly connected to the back ends of the first RC filter 51 and the second RC filter 52.

[0032] As shown Figure 2 in the figure, the two differential signal output terminals of the isolation operational amplifier module AMC1200BDUB are pin 7 and pin 8 respectively. The first RC filter includes a resistor R187 and a capacitor C122 which are connected in parallel at the back end of pin 7. The second RC filter includes a resistor R194 and a capacitor C124 which are connected in parallel at the back end of pin 8. The resistor R187 and the resistor R194 are respectively packaged in 0603 and have a value of 1.2 KΩ. The capacitors C122 and C124 are respectively packaged in 0603 and have a capacitance value of 10 NF.

[0033] Continue to refer to Figure 3 , the amplification module 41 includes a first resistor R92 with one end connected to the back end of the first RC filter and the other end connected to the first analog signal input terminal of the micropower operational amplifier module, that is, connected to the non-inverting operational amplifier port +A of OPA4330, a second resistor R90 with one end connected to the back end of the second RC filter and the other end connected to the second analog signal input terminal of the micropower operational amplifier module, that is, connected to the inverting operational amplifier port -A of OPA4330, a third resistor R88 with one end connected between the first resistor R92 and the non-inverting operational amplifier port +A and the other end grounded, and a fourth resistor R86 with one end connected between the second resistor R90 and the inverting operational amplifier port -A of OPA4330 and the other end connected to the analog signal output terminal of OPA4330, that is, connected to the OA port. The amplification factor of the amplification module 41 is the ratio between the third resistor R88 and the first resistor R92, and the ratio between the third resistor R88 and the first resistor R92 is equal to the ratio between the fourth resistor R86 and the second resistor R90.

[0034] In other words, for the differential signals JY2P and JY2N output from the isolation operational amplifier module AMC1200BDUB chip, when entering the secondary signal amplification module, the amplification factor can be changed by adjusting the ratios between R88 and R92, and R86 and R90 according to the required amplification factor, so as to perform secondary signal amplification. In this embodiment, the third resistor R88 and the fourth resistor R86 are 15 KΩ resistors packaged in 0402, and the second resistor R90 and the first resistor R92 are 10 KΩ resistors packaged in 0402. In this way, there is R86 / R90 = R88 / R92 = 15K / 10K = 15K / 10K = 1.5, that is, the amplification factor of this circuit is 1.5 times.

[0035] The analog signal output terminal OA of the micropower operational amplifier module OPA4330 is connected to its first digital signal input terminal +D. The processing module MCU is connected to the digital signal output terminal OD of the micropower operational amplifier module OPA4330. That is, OPA4332 outputs a DC signal through single-ended output of JY2S, and then returns to OPA4332. The DC signal amplified by the front end is input to the MCU through the pin code M_PF6-JY2SI_YC3_C by OPA4332. The MCU processes the obtained information to inversely deduce the current DC input voltage value. However, the specific process of the inverse deduction and the algorithm or formula used are set according to the specific requirements of each product. Anyway, for those skilled in the art, this belongs to a conventional choice that can be made according to actual needs, and the specific inverse deduction calculation method is not the focus of protection of this application. Therefore, it will not be elaborated in detail here.

[0036] According to Figure 3 it can be known that this micropower operational amplifier chip supports two-channel sampling. That is, the ports JY3P and JY3N can also convert the differential signals from the front-end isolation operational amplifier module and output them to the MCU like JY2P and JY2N. Whether to use this port specifically depends on the actual circuit design requirements.

[0037] Refer to again Figure 2 This sampling module 1 includes a sampling resistor R188 located between the positive DC voltage terminal DC+ and the negative DC voltage terminal DC-, m voltage-dividing resistors connected in series between the positive DC voltage terminal DC+ and the sampling resistor R188, and n voltage-dividing resistors connected in series between the sampling resistor R188 and the negative DC voltage terminal DC-. Obviously, when the positive terminal DC+ and the negative terminal DC- form a loop, the currents on the two paths are equal. To ensure the accurate consistency of the two-channel differential signal sampling, the sum of the resistances of the n resistors must be equal to the sum of the resistances of the m resistors. In this embodiment, m = n = 5, and the resistances of the five voltage-dividing resistors are equal. That is, the voltage-dividing resistors R332, R182, R183, R184, R185, R192, R191, R190, R189, and R333 are 0204 packaged, 1 / 4W, 200KΩ power resistors, which mainly bear the input voltage between DC+ and DC-, and at the same time form a voltage division with the sampling resistor R188. The sampling resistor R188 is a 1206 packaged, 1 / 4W, 300Ω resistor, and forms a voltage division network circuit with the aforementioned 10 200KΩ resistors.

[0038] Similarly, to ensure the stability and accuracy of signal acquisition, a third RC filter 6 is provided between the sampling resistor R188 and the input terminal of the isolation operational amplifier module AMC1200BDUB. The third RC filter 6 includes a fifth resistor R186 with one end connected to one end of the sampling resistor R188 and the other end connected to the first differential signal input terminal VINP of the isolation operational amplifier module AMC1200BDUB, a sixth resistor R193 with one end connected to the other end of the sampling resistor R188 and the other end connected to the second differential signal input terminal VINN of the isolation operational amplifier module AMC1200BDUB, and a capacitor C123 connected in parallel between the first differential signal input terminal VINP and the second differential signal input terminal VINN. In this embodiment, the fifth resistor R186 and the sixth resistor R193 are 0603 packaged, 1 / 10W, 10Ω resistors, and the capacitor C123 is a 0402 packaged, 50V, 220PF capacitor to form a filtering circuit at the input end, that is, the third RC filter.

[0039] In this application, power resistors with equal resistance values are used for voltage division at both ends of DC + and DC-. Then, a differential signal that meets the design requirements is obtained through the sampling resistor. The differential signal is amplified by a high-voltage isolation device, and then amplified twice by a dedicated signal amplification device. Finally, through the AD sampling of the MCU, the current externally input DC voltage value is calculated by reverse deduction. This isolation device can provide good voltage isolation and protection for the internal components of the DC charging pile, improving the safety of the charging pile. At the same time, through multi-stage amplification, the sampling accuracy is improved.

[0040] Although the embodiments of the present invention have been shown and described, those skilled in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and purposes of the present invention. The scope of the present invention is defined by the claims and their equivalents.

Claims

1. A voltage sampling circuit for a DC charging pile, comprising a sampling module (1) and a processing module (2), Characterized in that: It further includes a first - order differential signal amplification module (3) connected to the output end of the sampling module (1) and having an isolation function, and a second - order signal amplification module (4) connected to the output end of the first - order differential signal amplification module (3); The processing module (2) is connected to the second - order signal amplification module (4) and receives the DC voltage signal converted by the second - order signal amplification module (4) from the differential signal output by the first - order differential signal amplification module (3); The second - order signal amplification module (4) includes an amplification module (41) arranged at the output end of the first - order differential signal amplification module (3) and a micro - power consumption operational amplifier module (42) connected to the amplification module (41), and the processing module (2) is connected to the digital signal output end of the micro - power consumption operational amplifier module (42); A filtering module (5) is provided between the output end of the first - order differential signal amplification module (3) and the second - order signal amplification module (4). The first - order differential signal amplification module (3) is an isolation operational amplifier module, and the isolation operational amplifier module outputs two - way differential signals. The filtering module (5) includes a first RC filter (51) and a second RC filter (52) respectively corresponding to and connected to the output ends where the two - way differential signals are located, and the amplification module (41) is connected to the back ends of the first RC filter (51) and the second RC filter (52); The amplification module (41) includes a first resistor (R92) with one end connected to the back end of the first RC filter (51) and the other end connected to the first analog signal input terminal (+A) of the micro - power consumption operational amplifier module (42), a second resistor (R90) with one end connected to the back end of the second RC filter (52) and the other end connected to the second analog signal input terminal (-A) of the micro - power consumption operational amplifier module (42), a third resistor (R88) with one end connected between the first resistor (R92) and the first analog signal input terminal (+A) and the other end grounded, and a fourth resistor (R86) with one end connected between the second resistor (R90) and the second analog signal input terminal (-A) and the other end connected to the analog signal output terminal (OA) of the micro - power consumption operational amplifier module (42); The amplification factor of the amplification module is the ratio between the third resistor (R88) and the first resistor (R92), and the ratio between the third resistor (R88) and the first resistor (R92) is equal to the ratio between the fourth resistor (R86) and the second resistor (R90); The analog signal output terminal (OA) of the micro - power consumption operational amplifier module (42) is connected to its included first digital signal input terminal (+D), and the processing module (2) is connected to the digital signal output terminal (OD) of the micro - power consumption operational amplifier module (42); The sampling module (1) includes a sampling resistor (R188) located between the positive terminal (DC+) and the negative terminal (DC-) of the DC voltage, m first voltage-dividing resistors connected in series between the positive terminal (DC+) of the DC voltage and the sampling resistor (R188), and n second voltage-dividing resistors connected in series between the sampling resistor (R188) and the negative terminal (DC-) of the DC voltage; The sum of the resistances of the n second voltage-dividing resistors is equal to the sum of the resistances of the m first voltage-dividing resistors.

2. The voltage sampling circuit for a DC charging pile according to claim 1, characterized in that: A third RC filter (6) is provided between the sampling resistor (R188) and the input terminal of the isolation operational amplifier module; The third RC filter (6) includes a fifth resistor (R186) with one end connected to one end of the sampling resistor (R188) and the other end connected to the first differential signal input terminal (VINP) of the isolation operational amplifier module, a sixth resistor (R193) with one end connected to the other end of the sampling resistor (R188) and the other end connected to the second differential signal input terminal (VINN) of the isolation operational amplifier module, and a capacitor (C123) connected in parallel between the first differential signal input terminal (VINP) and the second differential signal input terminal (VINN).

3. The voltage sampling circuit for a DC charging pile according to claim 1, characterized in that: The isolation operational amplifier module is an AMC1200BDUB, the micropower operational amplifier module is an OPA4330, and the amplification factor of the amplification module is 1.5.

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