Circuit signal reference ground potential difference detection circuit

Abstract

The utility model discloses a detection circuit for a circuit signal reference ground potential difference, which relates to a detection circuit and comprises a resistor R1, a resistor R2, a voltage comparator UA and a voltage follower UB. One end of the resistor R2 is a free end, the other end of the resistor R2 is respectively connected with one end of the resistor R1 and a normal phase input end of the voltage comparator UA, the other end of the resistor R1 is connected with an output end of the voltage comparator UA, and the voltage follower UB is connected with the voltage comparator UA. The inverted input end of the voltage comparator UA is connected with the output end of the voltage follower UB and the inverted input end of the voltage follower UB, and the normal input end of the voltage follower UB is connected with the zero potential point PE. According to the utility model, the occupied resources are few, the realization is simpler and the cost is low; a hysteresis comparator is adopted to prevent false triggering, and the response speed of an operational amplifier is faster than that of a conventional optocoupler isolation scheme; and a voltage follower is adopted to prevent PE from introducing interference.

Description

Technical Field

[0001] The utility model relates to a detection circuit, in particular to a detection circuit for a circuit signal reference ground potential difference. Background Art

[0002] In the charging control pilot circuit of the charging pile, according to the national standard documents, the reference ground of its output signal CP is the protective ground PE. To ensure that the output signal CP meets the standard requirements, it is necessary to use the protective ground PE as the reference ground for level conversion.

[0003] To this end, the reference ground GND of the power circuit and the reference ground PE of the CP need to be short-circuited to achieve equal potential. And for EMC considerations, a magnetic bead will be inserted between PE and GND to suppress interference and prevent signal distortion.

[0004] The use of magnetic beads will introduce a problem of component failure. When the magnetic beads fail, PE and GND are equivalent to an open circuit. At this time, the CP signal based on the reference ground GND will produce a certain voltage fluctuation relative to the protective ground PE. This fluctuation will cause the CP signal to be unable to be correctly identified, and in severe cases, it will damage the circuit.

[0005] The existing technology mainly adopts the following three solutions:

[0006] Solution 1: Short-circuit the reference ground GND of the power supply circuit and the reference ground PE of the CP, without any technical processing of the signal, to achieve the same potential of GND and PE.

[0007] Solution 2: Short-circuit the reference ground GND of the power circuit and the reference ground PE of the CP to achieve equal potential. And for EMC considerations, a magnetic bead L1 is inserted between PE and GND to suppress interference and prevent signal distortion.

[0008] Solution 3: Use optocouplers, isolation chips and other components to build an isolated power supply circuit.

[0009] The disadvantages of the above three solutions are as follows:

[0010] Disadvantages of Solution 1: susceptible to interference and severe signal distortion.

[0011] Disadvantages of Solution 2: When the magnetic bead fails, PE and GND are equivalent to an open circuit, which will cause the output signal to change, and the CP signal cannot be correctly identified. In severe cases, the circuit may be damaged.

[0012] Disadvantages of Solution 3: high cost, occupies more hardware resources, and is not very practical. Utility Model Content

[0013] The utility model aims to provide a circuit signal reference ground potential difference detection circuit which not only utilizes magnetic beads to suppress interference from the outside world, but also avoids circuit failure caused by magnetic bead failure, so as to solve the problems raised in the above background technology.

[0014] In order to achieve the above purpose, the utility model provides the following technical solutions:

[0015] A detection circuit for a circuit signal reference ground potential difference, comprising a resistor R1, a resistor R2, a voltage comparator UA and a voltage follower UB, wherein one end of the resistor R2 is a free end, the other end of the resistor R2 is respectively connected to one end of the resistor R1 and a positive input end of the voltage comparator UA, the other end of the resistor R1 is connected to an output end of the voltage comparator UA, an inverting input end of the voltage comparator UA is respectively connected to an output end of the voltage follower UB and an inverting input end of the voltage follower UB, and a positive input end of the voltage follower UB is connected to a zero potential point PE

[0016] As a further solution of the utility model: the MCU controller samples the signal signal_PE output by the voltage comparator UA. When the signal is valid, the system can perform fault protection, stop outputting the CP signal, and prohibit charging.

[0017] As a further solution of the utility model: the output signal signal_PE of the voltage comparator UA can be connected in series with an LED light as a simple alarm prompt, which can not occupy the resources of the MCU controller and realize the alarm prompt.

[0018] The output end of the voltage comparator UA is connected to the signal input end of the MCU controller.

[0019] Compared with the prior art, the beneficial effects of the utility model are:

[0020] 1. It takes up less resources, is simpler to implement, and has low cost;

[0021] 2. The hysteresis comparator is used to prevent false triggering, and the operational amplifier responds faster than the conventional optocoupler isolation solution;

[0022] 3. Use a voltage follower to prevent interference from PE. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The circuit diagram of the detection circuit for the circuit signal reference ground potential difference.

[0024] Figure 2 The circuit diagram of the detection circuit for the circuit signal reference ground potential difference is the detection object circuit diagram.

[0025] Figure 3 This is the equivalent circuit diagram of the detection circuit for the circuit signal reference ground potential difference when the detection object fails.

[0026] Figure 4 It is a circuit diagram of the prior art solution 1 in the background technology of the present invention.

[0027] Figure 5 It is a circuit diagram of prior art solution 2 in the background technology of the present invention.

[0028] Figure 6 It is a circuit diagram of prior art solution 3 in the background technology of the present invention. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0030] Figure 2 Circuit module diagram of the detection object of this detection circuit. When the magnetic bead L1 works normally, PE and GND are at the same potential. Due to the existence of the reference level Vref, the Signal_PE signal outputs a high level. When the magnetic bead L1 fails, it can be equivalent to Figure 3 At this time, PE and GND are no longer at the same potential, but a certain potential difference is formed.

[0031] See also Figure 1 In an embodiment of the utility model, a detection circuit for a circuit signal reference ground potential difference includes a resistor R1, a resistor R2, a voltage comparator UA and a voltage follower UB, one end of the resistor R2 is a free end, the other end of the resistor R2 is respectively connected to one end of the resistor R1 and a positive input end of the voltage comparator UA, the other end of the resistor R1 is connected to an output end of the voltage comparator UA, an inverting input end of the voltage comparator UA is respectively connected to an output end of the voltage follower UB and an inverting input end of the voltage follower UB, and the positive input end of the voltage follower UB is connected to a zero potential point PE.

[0032] Use the utility model as Figure 1 The circuit shown detects the potential difference formed, wherein VCC is a positive power supply, VSS is a negative power supply, and the reference grounds of Vref, VCC, and VSS are all GND.

[0033] Define the voltage difference between PE and GND as U G , then:

[0034] U G =Upe-Ugnd,

[0035] Since PE is a constant zero potential point, then U G ≤0,

[0036] Therefore, the op amp used in the figure is a dual-channel differential operational amplifier.

[0037] U G The voltage follower (UB) circuit is used for level conversion to avoid interference from PE.

[0038] The voltage is then detected and compared through the voltage comparator (UA) circuit.

[0039] The figure shows the hysteresis range determined by the resistors R1, R2 and the power supplies VCC and VSS.

[0040] According to the threshold width requirement, the ratio and impedance of R1 and R2 can be determined, and then the parameters of the entire circuit can be determined.

[0041] The threshold width calculation formula of the hysteresis interval is as follows:

[0042]

[0043] Because U G ≤0 must exist, then Vref must also be <0, otherwise the circuit will fail.

[0044] Vref can be obtained by dividing the VSS voltage.

[0045] The above circuit realizes the detection of reference ground potential difference, ensuring that the potential of protective ground PE and common ground GND can maintain the same potential during normal use.

[0046] Preferably, the utility model can also adopt an MCU controller to sample the output signal signal_PE of the voltage comparator UA. When the signal is valid, the system can perform fault protection, stop outputting the CP signal, and prohibit charging.

[0047] Preferably, in the present invention, the output signal signal_PE of the voltage comparator UA can be connected in series with an LED light as a simple alarm prompt, which does not occupy the resources of the MCU controller and can achieve the alarm prompt.

[0048] In summary, the utility model occupies less resources, is simpler to implement, and has low cost; a hysteresis comparator is used to prevent false triggering, and the response speed of the operational amplifier is faster than that of the conventional optocoupler isolation solution; a voltage follower is used to prevent interference introduced by PE.

[0049] It is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be regarded as exemplary and non-restrictive from any point of view, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention. Any reference numeral in a claim should not be regarded as limiting the claim to which it relates.

[0050] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A circuit for detecting a circuit signal reference ground potential difference, characterized in that: It includes a resistor R1, a resistor R2, a voltage comparator UA and a voltage follower UB, one end of the resistor R2 is a free end, the other end of the resistor R2 is respectively connected to one end of the resistor R1 and the positive input end of the voltage comparator UA, the other end of the resistor R1 is connected to the output end of the voltage comparator UA, the inverting input end of the voltage comparator UA is respectively connected to the output end of the voltage follower UB and the inverting input end of the voltage follower UB, and the positive input end of the voltage follower UB is connected to the zero potential point PE.

2. The circuit signal reference ground potential difference detection circuit according to claim 1, characterized in that: The output end of the voltage comparator UA is connected to an LED lamp.

3. The circuit signal reference ground potential difference detection circuit according to claim 1, characterized in that: The output end of the voltage comparator UA is connected to the signal input end of the MCU controller.

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