Grounding detection circuit capable of self-adapting to input voltage

Abstract

The utility model relates to the technical field of grounding detection, and discloses a grounding detection circuit capable of self-adapting to input voltage, which is high in detection accuracy and reliable, and comprises a rectification module (100), a voltage division module (200), a filtering module (300), a voltage following module (400) and a main control module (500), the main control module (500) outputs a first signal according to a comparison result, when the first threshold signal is smaller than or equal to the voltage signal and the voltage signal is smaller than or equal to the second threshold signal, the main control module (500) outputs a second signal according to the comparison result, and when the voltage signal is larger than the second threshold signal, the main control module (500) outputs a third signal according to the comparison result.

Description

Technical Field

[0001] The utility model relates to the technical field of grounding detection, and more specifically to a grounding detection circuit with adaptive input voltage. Background Art

[0002] As a charging device that provides electric vehicles with energy, charging piles need to be connected to the mains to convert the mains into electricity for charging the subsequent vehicles. When the charging pile is connected to the mains, it must be grounded to ensure power supply safety. At present, in order to ensure reliable grounding of the charging pile, it is necessary to perform grounding detection on the charging pile, but the mains power type may have dual live wires or live and neutral wires.

[0003] However, the prior art generally only performs grounding detection on the live wire and the neutral wire, and is unable to perform grounding detection on different power supply types. The accuracy of the grounding detection is poor, such as when there is a wide input voltage or when the grid voltage is unstable, it is easy to misjudge. In addition, when dual live wires are used for power supply, accurate detection is impossible. Utility Model Content

[0004] The technical problem to be solved by the present invention is to provide a ground detection circuit with high detection accuracy and reliable adaptive input voltage, in view of the above-mentioned defects of the prior art that ground detection cannot be performed on different power supply types and the accuracy of ground detection is poor.

[0005] The technical solution adopted by the utility model to solve the technical problem is: constructing a ground detection circuit with adaptive input voltage, which has:

[0006] A rectifier module, whose input end is connected to the mains output end, is used to receive an AC voltage signal and perform rectification processing on the AC voltage signal;

[0007] A voltage divider module, whose input end is coupled to the output end of the rectifier module and is used to receive the rectified voltage signal;

[0008] A filter module, whose input end is coupled to the output end of the voltage divider module, for receiving the voltage signal and performing filtering processing on the voltage signal;

[0009] A voltage follower module, whose input end is connected to the output end of the filtering module, and is used to receive the voltage signal after filtering;

[0010] The main control module is provided with a first threshold signal and a second threshold signal, wherein:

[0011] The detection end of the main control module is connected to the output end of the voltage follower module, and is used to receive the voltage signal and compare the voltage signal with the first threshold signal or the second threshold signal.

[0012] When the voltage signal is less than the first threshold signal, the main control module outputs a first signal according to the comparison result.

[0013] When the first threshold signal is less than or equal to the voltage signal, and the voltage signal is less than or equal to the second threshold signal, the main control module outputs a second signal according to the comparison result.

[0014] When the voltage signal is greater than the second threshold signal, the main control module outputs a third signal according to the comparison result.

[0015] In some embodiments, the rectifier module includes a first diode and a second diode.

[0016] The anode of the first diode is connected to the live wire output end of the mains power.

[0017] The anode of the second diode is connected to the neutral line output terminal of the mains.

[0018] The cathodes of the first diode and the second diode are connected to the input end of the voltage divider module.

[0019] In some embodiments, the voltage dividing module includes a first voltage dividing branch and a second voltage dividing branch connected in series.

[0020] The input end of the first voltage dividing branch is coupled to the cathode of the first diode.

[0021] The input end of the second voltage dividing branch is coupled to the cathode of the second diode.

[0022] The output end of the first voltage dividing branch is connected to the input end of the filtering module.

[0023] In some embodiments, when the live wire and the neutral wire are correctly connected, the second voltage dividing branch does not participate in the voltage dividing output of the first voltage dividing branch.

[0024] When the live wire and the neutral wire are connected reversely, the second voltage-dividing branch participates in the voltage-dividing output of the first voltage-dividing branch.

[0025] In some embodiments, the first voltage dividing branch may be formed by a resistor or at least two resistors connected in series.

[0026] The second voltage dividing branch may be formed by one resistor or at least two resistors connected in series.

[0027] In some embodiments, the filter module includes a first capacitor and a voltage regulator connected in parallel.

[0028] One end of the first capacitor and the voltage regulator is connected to the output end of the first voltage dividing branch.

[0029] The other ends of the first capacitor and the voltage regulator are connected to a common end.

[0030] One end of the voltage regulator is also connected to the input end of the voltage follower module.

[0031] In some embodiments, the voltage follower module includes at least an operational amplifier and a first resistor.

[0032] The in-phase terminal of the operational amplifier is connected to one end of the voltage regulator tube.

[0033] The inverting terminal of the operational amplifier is connected to its output terminal,

[0034] The output end of the operational amplifier is connected to one end of the first resistor,

[0035] The other end of the first resistor is connected to the detection end of the main control module.

[0036] In some embodiments, the main control module includes a main controller,

[0037] The detection end of the main controller is connected to the output end of the operational amplifier through the first resistor.

[0038] In the grounding detection circuit of the adaptive input voltage described in the utility model, the main control module is provided with a first threshold signal and a second threshold signal. When the voltage signal is less than the first threshold signal, the main control module outputs the first signal according to the comparison result. When the first threshold signal is less than or equal to the voltage signal, and the voltage signal is less than or equal to the second threshold signal, the main control module outputs the second signal according to the comparison result. When the voltage signal is greater than the second threshold signal, the main control module outputs the third signal according to the comparison result. Compared with the prior art, the voltage divider module processes the input single or dual AC signals and then outputs them to the main control module, which outputs the corresponding indication signal (such as correct grounding, incorrect grounding or L, N reverse connection) according to the comparison result, which can solve the problem that the prior art cannot perform grounding detection on different power supply types, and the accuracy of its grounding detection is poor, such as when the input voltage is wide or when the grid voltage is unstable, it is easy to misjudge; in addition, when the dual live wires are powered, the problem of inability to accurately detect. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0040] Figure 1 It is a principle diagram of an embodiment of a ground detection circuit with adaptive input voltage provided by the utility model;

[0041] Figure 2a The utility model provides an AC single-phase power supply waveform diagram;

[0042] Figure 2b The utility model provides a waveform diagram of AC single-phase power supply after half-wave rectification;

[0043] Figure 3a This utility model provides a North American dual live wire power supply waveform diagram;

[0044] Figure 3b The utility model provides a waveform diagram of North American AC single-phase power supply after half-wave rectification. DETAILED DESCRIPTION

[0045] In order to have a clearer understanding of the technical features, purposes and effects of the present utility model, the specific implementation methods of the present utility model are now described in detail with reference to the accompanying drawings.

[0046] like Figure 1 As shown, in the first embodiment of the adaptive input voltage grounding detection circuit of the utility model, the adaptive input voltage grounding detection circuit 10 includes a rectifier module 100, a voltage divider module 200, a filter module 300, a voltage follower module 400 and a main control module 500;

[0047] The rectifier module 100 is configured at the front end of the load circuit, and is used to receive the AC voltage signal input from the AC side, and convert the input signal into a unidirectional DC signal by blocking the passage of the negative half-cycle signal, and a signal wave containing the positive half-cycle can be obtained at its output end;

[0048] like Figure 2a and Figure 2b As shown, when the input current signal is a single-phase voltage, the output end of the rectifier module 100 outputs a positive half-cycle signal wave.

[0049] like Figure 3a and Figure 3b As shown, when the input current signal is a double-live-wire power supply, the output end of the rectifier module 100 outputs a positive half-cycle signal wave;

[0050] The voltage divider module 200 is a circuit that uses resistor voltage divider to realize voltage reduction or voltage distribution of electrical signals. It includes at least one or more resistors, usually including a larger resistor and a smaller resistor. The input signal passes through resistors with different resistance values ​​in the resistor network, thereby realizing the adjustment of the output voltage signal value;

[0051] The filter module 300 performs filtering processing on the rectified and divided voltage signal, that is, to reduce the AC component in the pulsating DC voltage as much as possible, retain its DC component, reduce the output voltage ripple coefficient, and make the waveform become a smoother DC voltage signal;

[0052] The voltage follower module 400 is used to buffer and isolate the input voltage signal, does not amplify or attenuate the signal, and provides sufficient voltage signal for the subsequent circuit;

[0053] The main control module 500 is provided with a plurality of threshold signals, which has the functions of receiving, comparing, calculating and outputting indication signals according to the comparison results;

[0054] Specifically, the rectifier module 100 is configured at the mains output side, and its input end is connected to the mains output end, for receiving an AC voltage signal, rectifying the AC voltage signal, and then outputting the rectified voltage signal to the voltage divider module 200;

[0055] The input end of the voltage divider module 200 is coupled to the output end of the rectifier module 100, and is used to receive the rectified voltage signal, perform voltage division processing on the input voltage signal, and then output the voltage signal after voltage division processing to the filter module 300;

[0056] The input end of the filter module 300 is coupled to the output end of the voltage divider module 200, and is used to receive the voltage signal after the voltage division process, and filter and limit the voltage of the input voltage signal, and then output the processed voltage signal to the voltage follower module 400;

[0057] The input end of the voltage follower module 400 is connected to the output end of the filter module 300, and is used to receive the filtered voltage signal and then output it to the main control module 500;

[0058] Specifically, the main control module 500 is provided with a first threshold signal and a second threshold signal, wherein:

[0059] The detection end (corresponding to the PE-C end) of the main control module 500 is connected to the output end of the voltage follower module 400, and is used to receive the voltage signal isolated by the voltage follower module 400, and compare the input voltage signal with the first threshold signal or the second threshold signal.

[0060] When the input voltage signal is less than the first threshold signal, the main control module 500 outputs a first signal according to the comparison result, wherein the first signal indicates correct grounding.

[0061] When the first threshold signal is less than or equal to the voltage signal, and the voltage signal is less than or equal to the second threshold signal, the main control module 500 outputs a second signal (or an abnormal signal) according to the comparison result, wherein the second signal indicates that the grounding is not correct.

[0062] When the voltage signal is greater than the second threshold signal, the main control module 500 outputs a third signal (or another abnormal signal) according to the comparison result, wherein the third signal indicates that the live wire and the neutral wire are reversely connected.

[0063] Specifically, the MCU (belonging to the main control module 500) determines that the detection end of the MCU (corresponding to the PE-C end) obtains the voltage value u1 after voltage division, and combines it with the input Uin to obtain the ratio K. The ratio K is used to determine whether the input is grounded or reversely connected to meet the compatibility of different input voltages, and eliminate misjudgment caused by grid voltage fluctuations, and correct the impact of the input voltage. The relationship between the input voltage, the voltage division value, and the ratio K is K=Uin / u1;

[0064] Among them, when grounding is measured, the constant is K1,

[0065] When the actual measurement is not grounded, the constant is K2.

[0066] When the actual reverse connection is measured, the constant is K3.

[0067] Take the middle value K1+(K2-K1) / 2 between K1 and K2 as the threshold for judging whether the grounding is on or off;

[0068] Take the middle value of K2 and K3, K2+(K3-K2) / 2, as the judgment threshold for reverse connection and disconnection.

[0069] That is: when K<(K1+(K2-K1( / 2), it indicates correct grounding;

[0070] When (K1+(K2-K1) / 2(≤K≤(K2+(K3-K2) / 2), it means that the grounding is not correct;

[0071] When K>(K2+(K3-K2) / 2), it means L and N are reversely connected.

[0072] By using the technical solution, the input single or dual AC signal is divided and processed by the voltage divider module 200, and then output to the main control module 500, which can output a corresponding indication signal (such as correct grounding, incorrect grounding or L and N reverse connection) according to the comparison result. This can solve the problem that the prior art cannot perform grounding detection on different power supply types, and the accuracy of grounding detection is poor. For example, when the input voltage is wide or when the grid voltage is unstable, it is easy to misjudge; in addition, when dual live wires are used for power supply, it cannot be accurately detected.

[0073] In some embodiments, in order to improve the reliability of current signal detection, a first diode D101 and a second diode D102 may be provided in the rectifier module 100.

[0074] The anode of the first diode D101 is connected to the live wire (corresponding to L) output end of the mains.

[0075] The anode of the second diode D102 is connected to the output terminal of the neutral line (corresponding to N) of the mains.

[0076] The cathodes of the first diode D101 and the second diode D102 are connected to the input end of the voltage dividing module 200 .

[0077] Specifically, the input current signal is half-wave rectified by the first diode D101 and the second diode D102, and the positive half-wave of the AC power is taken, so that both single-phase power supply and dual-live power supply can be detected. When the power supply is single-phase power and dual-live power supply, the waveform after taking the positive half-wave is as follows: Figure 2a-Figure 3b shown.

[0078] In some embodiments, in order to improve the flexibility and adaptability of current signal detection, a first voltage dividing branch 210 and a second voltage dividing branch 220 connected in series may be provided in the voltage dividing module 200.

[0079] The input end of the first voltage dividing branch 210 is coupled to the cathode of the first diode D101, and is used to receive the voltage signal through the first diode D101, that is, the voltage signal when the live wire and the neutral wire are not connected reversely.

[0080] The input end of the second voltage dividing branch 220 is coupled to the cathode of the second diode D102 for receiving the voltage signal through the second diode D102, that is, the voltage signal when the live wire and the neutral wire are connected reversely.

[0081] The output end of the first voltage-dividing branch 210 is connected to the input end of the filter module 300 for receiving the voltage signal obtained by voltage-dividing the first voltage-dividing branch 210 or the second voltage-dividing branch 220 and the first voltage-dividing branch 210 .

[0082] Specifically, the AC mains is half-wave rectified by the first diode D101 and the second diode D102, connected via the second voltage dividing branch 220, and then divided by the first voltage dividing branch 210 to PE (earth), and then input into the filter module 300.

[0083] When the live wire and the neutral wire are correctly connected, the second voltage dividing branch 220 does not participate in the voltage dividing output of the first voltage dividing branch 210.

[0084] When the live wire and the neutral wire are connected reversely, at this time, the second voltage-dividing branch 220 participates in the voltage-dividing output of the first voltage-dividing branch 210 .

[0085] In some embodiments, Figure 1 As shown, the first voltage dividing branch 210 may be formed by one resistor or at least two resistors connected in series.

[0086] The first voltage dividing branch 210 may be formed by connecting a second resistor R102, a third resistor R103, a fourth resistor R104, a fifth resistor R105 and a seventh resistor R107 in series.

[0087] The second voltage dividing branch 220 may be formed by a single resistor or at least two resistors connected in series.

[0088] The second voltage dividing branch 220 may be formed by connecting a sixth resistor R106 and an eighth resistor R108 in series.

[0089] Specifically, after L and N are rectified, they are connected through the sixth resistor R106 and the eighth resistor R108. When L and N are correctly connected, the sixth resistor R106 and the eighth resistor R108 do not participate in voltage division.

[0090] When L and N are reversed, the sixth resistor R106 and the eighth resistor R108 will also participate in the voltage division, so that the voltage signal obtained by the detection end (corresponding to the PE-C end) of the main control module 500 is different, thereby judging whether L and N are reversed; among them, the second resistor R102, the third resistor R103, the fourth resistor R104, the fifth resistor R105 and the seventh resistor R107 are ground voltage-dividing resistors, which obtain a small voltage signal by voltage division while meeting the requirements of ground impedance and safety distance.

[0091] In some implementations, in order to improve the output of a smoother waveform, a first capacitor C101 and a voltage regulator tube TVS1 connected in parallel may be provided in the filter module 300.

[0092] The first capacitor C101 is used for filtering.

[0093] The voltage regulator tube TVS1 is used to absorb the transient voltage to protect the voltage follower module 400;

[0094] Specifically, the first capacitor C101 and one end of the voltage regulator tube TVS1 (corresponding to pin 2) are connected to the output end of the first voltage dividing branch 210.

[0095] The first capacitor C101 and the other end of the voltage regulator tube TVS1 (corresponding to pin 1) are connected to the common end, and one end of the voltage regulator tube TVS1 (corresponding to pin 2) is also connected to the input end of the voltage follower module 400 .

[0096] In some embodiments, the voltage follower module 400 includes at least an operational amplifier U1A and a first resistor R101, wherein the operational amplifier U1A buffers and isolates the voltage signal.

[0097] Among them, the in-phase terminal of the operational amplifier U1A (corresponding to pin 3) is connected to one end of the voltage regulator tube TVS1 (corresponding to pin 2) to obtain the filtered voltage signal (corresponding to u1).

[0098] The inverting terminal of the operational amplifier U1A (corresponding to pin 2) is connected to its output terminal (corresponding to pin 1).

[0099] The output terminal (corresponding to pin 1) of the operational amplifier U1A is connected to one end of the first resistor R101.

[0100] The other end of the first resistor R101 is connected to the detection end of the main control module 500 .

[0101] In some embodiments, the main control module 500 includes a main control unit MCU, wherein the main control unit MCU is provided with a plurality of threshold signals, and has the functions of receiving, comparing, calculating, and outputting an indication signal according to the comparison result;

[0102] Specifically, the detection terminal (PE-C) of the main controller MCU is connected to the output terminal (corresponding to pin 1) of the operational amplifier U1A through the first resistor R101, and the voltage signal output by the operational amplifier U1A is input into the main controller MCU through the first resistor R101.

[0103] The first capacitor C101 converts the rectified and divided steamed bun wave into a smooth DC voltage signal, and the voltage regulator TVS1 is used to absorb the transient voltage to protect the operational amplifier U1A.

[0104] Because the second resistor R102, the third resistor R103, the fourth resistor R104, the fifth resistor R105 and the seventh resistor R107 need to meet the ground impedance requirements, resistors above megohms need to be selected, so that the voltage driving capability obtained after voltage division is very weak and the anti-interference capability is poor. The driving capability and anti-interference capability can be effectively improved through the voltage following of the operational amplifier U1A.

[0105] The technical solution achieves compatibility with dual live wire power supply by adding a first diode D101 and a second diode D102 to the detection input end and taking the positive half-wave of the alternating current. The ratio of the input voltage to the divided voltage is introduced to eliminate the influence of different input voltages on different divided voltage values, thereby achieving adaptation to different input voltages and effectively solving the problems of easy misjudgment in a wide input voltage or when the grid voltage is unstable and inability to accurately detect when dual live wire power supply is in place.

[0106] The above technical solution has the following advantages:

[0107] 1. Eliminates the influence of input voltage, and will not misjudge when there is wide input voltage or voltage fluctuation;

[0108] 2. Compatible with single-phase and dual-live-wire power input;

[0109] 3. The circuit is simple and the cost is low.

[0110] The embodiments of the utility model are described above in conjunction with the accompanying drawings, but the utility model is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the enlightenment of the utility model, ordinary technicians in this field can also make many forms without departing from the scope of protection of the utility model and the claims, which all fall within the protection of the utility model.

Claims

1. A ground detection circuit with adaptive input voltage, characterized in that: have: A rectifier module, whose input end is connected to the mains output end, is used to receive an AC voltage signal and perform rectification processing on the AC voltage signal; A voltage divider module, whose input end is coupled to the output end of the rectifier module and is used to receive the rectified voltage signal; A filter module, whose input end is coupled to the output end of the voltage divider module, for receiving the voltage signal and performing filtering processing on the voltage signal; A voltage follower module, whose input end is connected to the output end of the filtering module, and is used to receive the voltage signal after filtering; The main control module is provided with a first threshold signal and a second threshold signal, wherein: The detection end of the main control module is connected to the output end of the voltage follower module, and is used to receive the voltage signal and compare the voltage signal with the first threshold signal or the second threshold signal. When the voltage signal is less than the first threshold signal, the main control module outputs a first signal according to the comparison result. When the first threshold signal is less than or equal to the voltage signal, and the voltage signal is less than or equal to the second threshold signal, the main control module outputs a second signal according to the comparison result. When the voltage signal is greater than the second threshold signal, the main control module outputs a third signal according to the comparison result.

2. The ground detection circuit with adaptive input voltage according to claim 1, characterized in that: The rectifier module includes a first diode and a second diode. The anode of the first diode is connected to the live wire output end of the mains power. The anode of the second diode is connected to the neutral line output terminal of the mains. The cathodes of the first diode and the second diode are connected to the input end of the voltage divider module.

3. The ground detection circuit with adaptive input voltage according to claim 2, characterized in that: The voltage dividing module comprises a first voltage dividing branch and a second voltage dividing branch connected in series, The input end of the first voltage dividing branch is coupled to the cathode of the first diode. The input end of the second voltage dividing branch is coupled to the cathode of the second diode. The output end of the first voltage dividing branch is connected to the input end of the filtering module.

4. The ground detection circuit with adaptive input voltage according to claim 3, characterized in that: When the live wire and the neutral wire are correctly connected, the second voltage-dividing branch does not participate in the voltage-dividing output of the first voltage-dividing branch. When the live wire and the neutral wire are connected reversely, the second voltage-dividing branch participates in the voltage-dividing output of the first voltage-dividing branch.

5. The ground detection circuit with adaptive input voltage according to claim 3 or 4, characterized in that: The first voltage dividing branch may be formed by a resistor or at least two resistors connected in series. The second voltage dividing branch may be formed by one resistor or at least two resistors connected in series.

6. The ground detection circuit with adaptive input voltage according to claim 3, characterized in that: The filter module includes a first capacitor and a voltage regulator connected in parallel. One end of the first capacitor and the voltage regulator is connected to the output end of the first voltage dividing branch. The other ends of the first capacitor and the voltage regulator are connected to a common end. One end of the voltage regulator is also connected to the input end of the voltage follower module.

7. The ground detection circuit with adaptive input voltage according to claim 6, characterized in that: The voltage follower module at least includes an operational amplifier and a first resistor. The in-phase terminal of the operational amplifier is connected to one end of the voltage regulator tube. The inverting terminal of the operational amplifier is connected to its output terminal, The output end of the operational amplifier is connected to one end of the first resistor, The other end of the first resistor is connected to the detection end of the main control module.

8. The ground detection circuit with adaptive input voltage according to claim 7, characterized in that: The main control module includes a main controller, The detection end of the main controller is connected to the output end of the operational amplifier through the first resistor.

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