Power supply miswiring protection circuit

Abstract

The embodiment of the present invention discloses a power miswiring protection circuit, including: a power connection circuit for connecting an external power supply, the power connection circuit including a positive connection terminal, a negative connection terminal, a thermistor and a bidirectional transient diode; the first bidirectional transient diode is connected to the positive connection terminal and the negative connection terminal for clamping; the thermistor is connected in series between the positive connection terminal and the bidirectional transient diode; a DC circuit connection terminal; a first filter circuit arranged between the power connection circuit and the DC circuit connection terminal. The present invention can play a protective role when the AC 220V high voltage is connected to the power circuit of the line loss module, and the line loss module can resume normal operation after the wrongly connected high voltage AC signal is removed.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of circuits, and in particular to a power supply miswiring protection circuit. Background Art

[0002] The line loss module is a key component in the core equipment of distribution network automation (FTU and DTU). It is responsible for the energy metering of related lines and has the following functions:

[0003] Measuring three-phase voltage, three-phase current, total active power, total reactive power, active and reactive power of each phase, system frequency, etc.; four-quadrant energy measurement;

[0004] Power freeze function, including timed freeze, instantaneous freeze, daily freeze, hourly freeze, and assessment day freeze;

[0005] Built-in RTC with temperature compensation, the daily timing accuracy is better than 0.5s / day within the full temperature working range;

[0006] Supports DL / T634.5101-2002 communication protocol, supports balanced and unbalanced mode switching, power resolution adjustment (decimal places can be set), total call power, frozen quantity burst upload, telemetry change upload, remote signal change position (TCOS) upload and other functions.

[0007] The line loss module uses a wide voltage power supply, supports DC18-56V self-adaptation, and the system can maintain basic functions such as measurement and metering for more than 5s after power failure, avoiding the impact of power supply interruption on the continuity of the module sampling work. Since the line loss module is installed inside the FTU or DTU device, its structure is very compact. All power supply, communication and voltage and current sampling input signals are implemented using standard connectors with a spacing of 5.08. If the wiring operator is not properly trained during wiring, it is easy to connect the high-voltage sampling signal to the power supply line. The high-voltage sampling signal is up to AC 220V. Once the line is connected incorrectly, the power supply circuit of the line loss module will be burned, causing permanent damage to the equipment. The current common solution is to strengthen the training of on-site operators and try to reduce the rate of wrong wiring, but it is impossible to completely eliminate the situation of wrong wiring. Summary of the invention

[0008] The purpose of the embodiment of the present invention is to provide a power supply miswiring protection circuit to solve the problem that the existing line loss module is easily miswired, resulting in the burning of the power supply circuit and causing permanent damage to the equipment.

[0009] To achieve the above objectives, the embodiments of the present invention mainly provide the following technical solutions:

[0010] An embodiment of the present invention provides a power miswiring protection circuit, comprising: a power connection circuit, used to connect an external power supply, the power connection circuit comprising a positive connection terminal, a negative connection terminal, a thermistor and a first bidirectional transient diode; the first bidirectional transient diode is connected to the positive connection terminal and the negative connection terminal for clamping; the thermistor is connected in series between the positive connection terminal and the first bidirectional transient diode; a DC circuit connection terminal; and a first filter circuit arranged between the power connection circuit and the DC circuit connection terminal.

[0011] According to one embodiment of the present invention, the first filtering circuit includes a diode, a first resistor, an inductor and a first capacitor; the positive electrode of the diode is connected to the positive electrode connection end through the thermistor, and the negative electrode of the diode is connected to the DC circuit connection end through the first resistor; one end of the first capacitor is connected to a node between the first resistor and the DC circuit connection end, and the other end of the first capacitor is connected to the negative electrode connection end; the inductor is connected in parallel with the first resistor.

[0012] According to one embodiment of the present invention, it further includes: a second bidirectional transient diode for clamping the DC circuit connection terminal.

[0013] According to one embodiment of the present invention, it further includes: a second capacitor connected between the positive electrode of the DC circuit connection terminal and the ground terminal.

[0014] According to one embodiment of the present invention, the model of the thermistor is MZ11-08A100-200RM.

[0015] According to one embodiment of the present invention, the model of the first bidirectional transient diode is P6KE75CA.

[0016] According to one embodiment of the present invention, the clamping voltage of the second bidirectional transient diode is 70V.

[0017] According to an embodiment of the present invention, the capacitance of the second capacitor is 0.1 uF.

[0018] The technical solution provided by the embodiment of the present invention has at least the following advantages:

[0019] The power miswiring protection circuit provided in the embodiment of the present invention can prevent damage to the equipment when the high-voltage mains is connected to the low-voltage DC power supply line of the line loss module, and the equipment can resume normal operation after the miswiring is restored to normal. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 4 is a circuit diagram of a power supply miswiring protection circuit according to an embodiment of the present invention. DETAILED DESCRIPTION

[0021] The following is a description of the implementation of the present invention by means of specific embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0022] In the following description, specific details such as specific system structures, interfaces, and technologies are provided for illustration rather than limitation so that the present invention is thoroughly understood. However, it should be clear to those skilled in the art that the present invention may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present invention.

[0023] In the description of the present invention, it should be understood that the terms “first” and “second” are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0024] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0025] The inventor of this application conducted a lot of creative work on the normal power supply voltage range of the line loss module and the maximum voltage of the voltage sampling input line number and found that: the normal power supply voltage range required by the line loss module standard is DC18-56V, the maximum voltage of the voltage sampling input line number is AC220V, and the design working voltage range of the working power supply of the line loss module is 16V-75V.

[0026] Based on the above understanding, the present invention is proposed.

[0027] Figure 1 FIG. 1 is a circuit diagram of a power supply miswiring protection circuit according to an embodiment of the present invention. Figure 1 As shown, the power miswiring protection circuit of the embodiment of the present invention includes: a power connection circuit, a DC circuit connection terminal and a first filter circuit for filtering out high-frequency interference on the line.

[0028] The power connection circuit includes a positive connection terminal V+, a negative connection terminal V−, a thermistor RT1 and a first bidirectional transient diode VD1 .

[0029] When the power input is wired normally, the input voltage range between V+ and the negative connection terminal V- is 18-72V.

[0030] The first bidirectional transient diode VD1 is connected to the positive connection terminal V+ and the negative connection terminal V- for clamping. In one embodiment of the present invention, the model of the first bidirectional transient diode is P6KE75CA, the peak discharge power is 600W; the clamping voltage is 71.30V-78.80V, the clamping voltage at the maximum peak current is 103V, and the average clamping voltage is 75V; the maximum peak current is 5.9A, and the operating and storage temperature range is: -55-150℃.

[0031] The thermistor RT1 is connected in series between the positive connection terminal and the first bidirectional transient diode. In one embodiment of the present invention, the model of the thermistor is MZ11-08A100-200RM, with a resistance of 10-20Ω at room temperature, a non-operating current of 100MA, a maximum withstand voltage of 400V, and a normal operating temperature of -25-80°C.

[0032] When the power input is wired normally, the input voltage range is 18-72V. Within the normal working range of this power supply, the power consumption current of the subsequent power supply is within 50MA, which is lower than the operating current of thermistor RT1. The resistance value of the thermistor is 10-20 ohms. The power supply works normally. When the wiring is wrong, the input voltage can reach up to AC220V. Since the TVS tube VD1 is connected in parallel to the negative pole of the power supply at the back end of the thermistor, the clamping voltage of VD1 is 75V. After the input voltage passes through the thermistor, it is added to both ends of the TVS tube. The TVS tube is turned on instantly, and the voltage at both ends is clamped at about 75. At this time, the current flowing through the thermistor RT1 and the TVS tube is (220-75)V / 10 ohms = 3.5A (this current is less than the TVS tube allows to pass The maximum current that flows through the thermistor is far greater than the non-actuating current of the thermistor. The thermistor RT1 generates heat by itself and its resistance rises by 3-4 orders of magnitude in a short time, presenting a high-resistance state. The entire circuit enters an open circuit state, and the 220V voltage is basically applied to both ends of the thermistor. Since the withstand voltage of the thermistor is higher than 400V, the thermistor will not be damaged. Before the thermistor cuts off the circuit, due to the clamping effect of the TVS, the input voltage of the subsequent circuit is only about 75V at most, and the subsequent circuit is also well protected. Even if the 220V high voltage is continuously applied to this circuit for a long time, the circuit will not be damaged. When the incorrect external wiring is corrected, the current of the thermistor drops and the temperature returns to normal, its resistance returns to its original state, and the circuit resumes normal operation.

[0033] The most critical components of this protection circuit are the PTC thermistor and the high-power TVS tube. The matching of the index parameters between the two is very critical. They must not only play a protective role in the circuit, but also not be damaged under continuous high-voltage conditions.

[0034] In one embodiment of the present invention, the first filtering circuit includes a diode D, a first resistor R1, an inductor L1 and a first capacitor C1.

[0035] The anode of the diode D is connected to the anode connection terminal V+ through the thermistor RT1, and the cathode of the diode D is connected to the DC circuit connection terminal VSR through the first resistor R1. The diode D is used to achieve unidirectional conduction.

[0036] One end of the first capacitor C1 is connected to a node between the first resistor R1 and the DC circuit connection terminal VSR, and the other end of the first capacitor C1 is connected to the negative electrode connection terminal V-. The inductor is connected in parallel with the first resistor.

[0037] In one embodiment of the present invention, the source miswiring protection circuit also includes: a second bidirectional transient diode VD2 for clamping the DC circuit connection end, the second bidirectional transient diode VD2 is a bidirectional TVS tube with a clamping voltage of 70V, and is used to clamp short-term surge impact voltage.

[0038] In one embodiment of the present invention, the power supply miswiring protection circuit further includes: a second capacitor C2 connected between the positive electrode of the DC circuit connection terminal and the ground terminal, and the capacitance of the second capacitor is 0.1uF.

[0039] In addition, other structures and functions of the power miswiring protection circuit in the embodiment of the present invention are known to those skilled in the art, and will not be described in detail to reduce redundancy.

[0040] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made on the basis of the technical solution of the present invention should be included in the scope of protection of the present invention.

Claims

1. A power supply miswiring protection circuit, characterized in that: include: A power connection circuit, used to connect an external power supply, the power connection circuit comprising a positive connection terminal, a negative connection terminal, a thermistor and a first bidirectional transient diode; the first bidirectional transient diode is connected to the positive connection terminal and the negative connection terminal for clamping; the thermistor is connected in series between the positive connection terminal and the first bidirectional transient diode; DC circuit connection terminal; A first filter circuit disposed between the power supply connection circuit and the DC circuit connection terminal; The first filtering circuit includes a diode, a first resistor, an inductor and a first capacitor; The positive electrode of the diode is connected to the positive electrode connection end through the thermistor, and the negative electrode of the diode is connected to the DC circuit connection end through the first resistor; One end of the first capacitor is connected to a node between the first resistor and the DC circuit connection end, and the other end of the first capacitor is connected to the negative electrode connection end; The inductor is connected in parallel with the first resistor; Also included: a second bidirectional transient diode for clamping the DC circuit connection terminal; It also includes: a second capacitor connected between the positive electrode of the DC circuit connection terminal and the ground terminal.

2. The power supply miswiring protection circuit according to claim 1, characterized in that: The model of the thermistor is MZ11-08A100-200RM.

3. The power supply miswiring protection circuit according to claim 1, characterized in that: The model of the first bidirectional transient diode is P6KE75CA.

4. The power supply miswiring protection circuit according to claim 1, characterized in that: The clamping voltage of the second bidirectional transient diode is 70V.

5. The power miswiring protection circuit according to claim 1, characterized in that: The capacitance of the second capacitor is 0.1uF.

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