Charging pile alternating current sampling circuit and charging equipment

Abstract

The utility model relates to the technical field of charging equipment, in particular to a charging pile alternating current sampling circuit and charging equipment, which comprises an acquisition module for acquiring sampling voltage and / or sampling current, a rectification module and a signal output module connected with output equipment, an operational amplifier U2; a diode D1; a diode D2; and a resistor R3. When a negative signal is input into the rectifier module, the rectifier module is cut off by using the diode D1, and when a positive signal is input, the operational amplifier U2 plays a role of a buffer, so that a voltage signal at the in-phase input end of the operational amplifier U1 is equal to a voltage signal at the output end of the operational amplifier U2, thereby avoiding voltage drop caused by the diode D1 and improving the signal sampling precision.

Description

Technical Field

[0001] This utility model relates to the field of charging equipment technology, specifically to an AC sampling circuit for a charging pile. Background Technology

[0002] With the increasing popularity of electric vehicles, the demands on charging stations are also rising. In charging station applications, current sampling is frequently used for loop control, as well as for transient overcurrent and short-circuit protection. Therefore, the accuracy and timing of sampling play a crucial role in loop control. Typically, current sampling accuracy is required to be within 1%. Furthermore, current sampling often spans both the control unit and the power unit, which may pose a safety hazard during data acquisition, necessitating isolation of the current sampling process. Utility Model Content

[0003] The purpose of this utility model is to solve the problem of low accuracy in existing AC sampling circuits for charging piles and to provide a more accurate AC sampling circuit for charging piles.

[0004] The technical solution provided by this utility model is as follows:

[0005] A charging pile AC sampling circuit includes a sampling module for acquiring sampling voltage and / or sampling current, a rectifier module, and a signal output module connected to an output device. The rectifier module includes:

[0006] Operational amplifier U1 has its non-inverting input connected to the acquisition module and its inverting input coupled to the signal output module.

[0007] Diode D1, the positive terminal of diode D1 is connected to the output terminal of operational amplifier U1;

[0008] Diode D2, the positive terminal of diode D2 is connected to the inverting input terminal of operational amplifier U1, and its negative terminal is connected to the output terminal of operational amplifier U1;

[0009] Operational amplifier U2 has its inverting input coupled to its output, which is then coupled to a signal output module. Its non-inverting input is connected to the negative terminal of diode D1. Resistor R3 has one end grounded and the other end connected to the non-inverting input of operational amplifier U2.

[0010] When a positive signal is input, diode D1 is forward biased, and the positive signal is directly input to operational amplifier U2. Operational amplifier U2 acts as a buffer, and the positive signal will not flow into the high-impedance inverting input terminal of U1A. This makes the voltage signal at the non-inverting input terminal of operational amplifier U1 equal to the voltage signal at the output terminal of operational amplifier U2, thereby avoiding the voltage drop caused by diode D1 and improving the accuracy of signal sampling.

[0011] When a negative signal is input, diode D1 is reverse biased, so that no signal is sent to the non-inverting input of U2. Resistor R3 biases the non-inverting input of U2 to ground, and diode D2 is forward biased. Therefore, U1 drives U2 like a standard inverting amplifier, thus outputting a positive signal.

[0012] Preferably, the rectifier module further includes:

[0013] Resistor R5 is connected at both ends to the inverting input terminal and the output terminal of operational amplifier U2, respectively.

[0014] Resistor R4 is connected at both ends to the inverting input terminals of operational amplifier U1 and operational amplifier U2, respectively.

[0015] By adjusting the values ​​of resistors R4 and R5, the numerical relationship between the output voltage and the input voltage is adjusted, thereby achieving full-wave rectification. Resistors R4 and R5 are the gain resistors of the precision full-wave rectifier circuit. Appropriate resistance values ​​are selected to reduce thermal noise and minimize voltage drop caused by the reverse leakage current of the diodes. Furthermore, during negative input signal periods, these two resistors act as the load for operational amplifier U1.

[0016] Preferably, a compensation capacitor C5 is also coupled between the inverting input terminal and the output terminal of the operational amplifier U1 to provide a local high-frequency feedback path for U1, which helps to stabilize the output.

[0017] Preferably, the signal output module includes a filtering circuit, which comprises a resistor R2 and a capacitor C3. The resistor R2 and capacitor C3 are connected in series and grounded. One end of the resistor R2 is connected to the rectifier module, and the other end outputs the signal. Since the rectifier circuit outputs pulsating DC with a large AC component, the RC filter circuit composed of resistor R2 and capacitor C3 makes the output voltage smoother.

[0018] Preferably, the signal output module further includes a voltage follower circuit, which includes operational amplifier U3. The non-inverting input of operational amplifier U3 is connected to the filter circuit or rectifier module, and the inverting input and output of operational amplifier U3 are connected to each other. The output of operational amplifier U3 outputs a signal. By using operational amplifier U3 as a voltage follower circuit, the output impedance is reduced, thereby improving the signal output capability.

[0019] Preferably, the acquisition module includes a current transformer and a sampling resistor RI. The two ends of the current transformer are connected in parallel with the resistor RI, one end of the resistor RI is grounded, and the other end is connected to the rectifier module. The current transformer, by using windings around various types of magnetic cores, can provide accurate measurements within the target current range and bandwidth in conjunction with the resistor RI, separating the control unit from the power unit and isolating the current sampling.

[0020] A charging device comprising any of the above-mentioned charging pile AC sampling circuits.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] When a positive signal is input, diode D1 is forward biased, and the positive signal is directly input to operational amplifier U2. Operational amplifier U2 acts as a buffer, and the positive signal will not flow into the high-impedance inverting input terminal of U1A. This makes the voltage signal at the non-inverting input terminal of operational amplifier U1 equal to the voltage signal at the output terminal of operational amplifier U2, thereby avoiding the voltage drop caused by diode D1 and improving the accuracy of signal sampling.

[0023] When a negative signal is input, diode D1 is reverse biased, so that no signal is sent to the non-inverting input of U2. Resistor R3 biases the non-inverting input of U2 to ground, and diode D2 is forward biased. Therefore, U1 drives U2 like a standard inverting amplifier, thereby outputting a positive signal. By adjusting the values ​​of resistors R4 and R5, the numerical relationship between the output voltage and the input voltage can be adjusted, thereby achieving full-wave rectification.

[0024] Resistors R4 and R5 are gain resistors for the precision full-wave rectifier circuit. By selecting appropriate resistance values, thermal noise can be reduced and the voltage drop caused by the reverse leakage current of the diode can be minimized, and they also serve as the load for op-amp U1.

[0025] Current transformers, by using windings around various types of magnetic cores, can provide accurate measurements within the target current range and bandwidth in conjunction with resistors RI, separating the control unit from the power unit and isolating current sampling. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the overall circuit of Embodiment 1 of this utility model;

[0027] Figure 2 This is a simplified circuit diagram of the rectifier module when the input is a positive signal, as shown in Embodiment 1 of this utility model.

[0028] Figure 3 This is a simplified circuit diagram of the rectifier module when the input is a negative signal, as shown in Embodiment 1 of this utility model. Detailed Implementation

[0029] The specific embodiments of this utility model will be further described below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the scope of this utility model.

[0030] The term "coupled" in the specification and claims of this utility model includes both direct and indirect connections, such as connections via an electrical conduction medium, like a conductor, which may contain parasitic inductance or capacitance. It may also include connections via other active or passive devices that achieve the same or similar functional purpose, such as connections via switches, follower circuits, or other circuits or components.

[0031] Example 1, as Figure 1 As shown, an AC sampling circuit for a charging pile includes a sampling module for acquiring sampling voltage and / or sampling current, a rectifier module, and a signal output module connected to an output device. The rectifier module includes:

[0032] Operational amplifier U1 has its non-inverting input connected to the signal input of the acquisition module, and its inverting input coupled to the signal output module.

[0033] Diode D1, the positive terminal of diode D1 is connected to the output terminal of operational amplifier U1;

[0034] Diode D2, the positive terminal of diode D2 is connected to the inverting input terminal of operational amplifier U1, and its negative terminal is connected to the output terminal of operational amplifier U1;

[0035] Operational amplifier U2, the inverting input terminal of operational amplifier U2 is coupled to the output terminal of operational amplifier U2, the output terminal is coupled to the signal output module, and the non-inverting input terminal is connected to the negative terminal of the diode D1;

[0036] Resistor R3 has one end grounded and the other end connected to the non-inverting input of op-amp U2;

[0037] Resistor R5 is connected at both ends to the inverting input terminal and the output terminal of operational amplifier U2, respectively.

[0038] Resistor R4 is connected at both ends to the inverting input terminals of operational amplifier U1 and operational amplifier U2, respectively.

[0039] When the acquisition module outputs a positive signal, such as Figure 2 As shown, diode D1 is reverse biased and diode D2 is forward biased. The positive signal is directly input to the non-inverting input of operational amplifier U2. Operational amplifier U2 acts as a buffer, and the positive signal will not flow into the high-impedance inverting input of U1A. This makes the voltage signal at the non-inverting input of operational amplifier U1 equal to the voltage signal at the output of operational amplifier U2, thereby avoiding the voltage drop caused by diode D1 and improving the accuracy of signal sampling.

[0040] When a negative signal is input, such as Figure 3As shown, diode D1 is reverse biased, ensuring no signal reaches the non-inverting input of U2. Resistor R3 biases the non-inverting input of U2 to ground, while diode D2 is forward biased. Therefore, U1 drives U2 like a standard inverting amplifier, outputting a positive signal. By adjusting the values ​​of resistors R4 and R5, the relationship between the output and input voltages is adjusted, thus achieving full-wave rectification. Resistors R4 and R5 are gain resistors in the precision full-wave rectifier circuit. Appropriate values ​​are chosen to reduce thermal noise and minimize voltage drop caused by the reverse leakage current of the diodes. Furthermore, during negative input signal periods, these two resistors act as the load for operational amplifier U1.

[0041] A compensation capacitor C5 is also coupled between the inverting input and output terminals of op-amp U1, providing a local high-frequency feedback path for U1, which helps to stabilize the output.

[0042] The signal output module includes a filter circuit, which consists of resistor R2 and capacitor C3. Resistor R2 and capacitor C3 are connected in series and grounded. One end of resistor R2 is connected to the rectifier module, and the other end is connected to the MCU (Microcontroller Unit) to output the signal. Since the rectifier circuit outputs pulsating DC with a large AC component, the RC filter circuit composed of resistor R2 and capacitor C3 makes the output voltage smoother.

[0043] The signal output module also includes a voltage follower circuit, which comprises operational amplifier U3. The non-inverting input of operational amplifier U3 is connected to a filter circuit or rectifier module, and the inverting input and output of operational amplifier U3 are interconnected. The output of operational amplifier U3 is connected to the MCU to output signals. By using operational amplifier U3 as a voltage follower circuit, the output impedance is reduced, thereby improving the signal output capability.

[0044] The output of op-amp U3 is directly connected to the MCU's AD port. The positive power supply terminal of op-amp U3 is connected to a 3.3V power supply and grounded through capacitor C2, while the negative power supply terminal is grounded. Op-amp U3 is powered by 3.3V to avoid excessive voltage burning out the MCU's AD port.

[0045] The acquisition module includes a current transformer and a sampling resistor RI. The two ends of the current transformer are connected in parallel with the resistor RI. One end of the resistor RI is grounded, and the other end is connected to the rectifier module. The current transformer, by using windings around various types of magnetic cores, can provide accurate measurements within the target current range and bandwidth in conjunction with the resistor RI. It separates the control unit from the power unit and isolates the current sampling. The current transformer outputs a small current proportional to the primary side current; typical current transformer ratios are 1000:1, 2000:1, etc. When the current transformer output current flows through the resistor RI, a sampling voltage is formed. Since the current transformer samples AC current, the output current is a 50Hz sine wave based on GND.

[0046] Example 2: A charging device, including the AC sampling circuit of the charging pile in Example 1.

[0047] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

Claims

1. A charging pile AC sampling circuit, comprising a sampling module for acquiring sampling voltage and / or sampling current, a rectifier module, and a signal output module connected to an output device, characterized in that, The rectifier module includes: Operational amplifier U1 has its non-inverting input connected to the signal input of the acquisition module, and its inverting input coupled to the signal output module. Diode D1, the positive terminal of diode D1 is connected to the output terminal of operational amplifier U1; Diode D2, the positive terminal of diode D2 is connected to the inverting input terminal of operational amplifier U1, and its negative terminal is connected to the output terminal of operational amplifier U1; Operational amplifier U2, the inverting input terminal of operational amplifier U2 is coupled to the output terminal of operational amplifier U2, the output terminal is coupled to the signal output module, and the non-inverting input terminal is connected to the negative terminal of the diode D1; Resistor R3 has one end grounded and the other end connected to the non-inverting input terminal of operational amplifier U2.

2. The AC sampling circuit for a charging pile according to claim 1, characterized in that, The rectifier module also includes: Resistor R5 is connected at both ends to the inverting input terminal and the output terminal of operational amplifier U2, respectively. Resistor R4 is connected at both ends to the inverting input terminals of operational amplifier U1 and operational amplifier U2, respectively.

3. The AC sampling circuit for a charging pile according to claim 1 or 2, characterized in that, A compensation capacitor C5 is also coupled between the inverting input terminal and the output terminal of the operational amplifier U1.

4. The AC sampling circuit for a charging pile according to claim 1 or 2, characterized in that, The signal output module includes a filtering circuit, which includes a resistor R2 and a capacitor C3. The resistor R2 and capacitor C3 are connected in series and then grounded. One end of the resistor R2 is connected to the rectifier module, and the other end outputs a signal.

5. The AC sampling circuit for a charging pile according to claim 4, characterized in that, The signal output module also includes a follower circuit, which includes an operational amplifier U3. The non-inverting input of the operational amplifier U3 is connected to the filter circuit, and the inverting input and output of the operational amplifier U3 are connected to each other. The output of the operational amplifier U3 outputs a signal to the outside.

6. The AC sampling circuit for a charging pile according to claim 1 or 2, characterized in that, The acquisition module includes a current transformer and a sampling resistor RI. The two ends of the current transformer are connected in parallel with the resistor RI. One end of the resistor RI is grounded, and the other end is connected to the rectifier module.

7. A charging device, characterized in that, Includes the AC sampling circuit for the charging pile as described in any one of claims 1-6.

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