A hardware circuit for preventing DC power input

Abstract

The present invention discloses a hardware circuit for preventing DC power input, which includes a relay switch module, a switching power supply module, and an AC / DC judgment module. The AC / DC judgment module includes a resistor voltage division circuit, a waveform shaping circuit, and an AC / DC judgment circuit. The present invention provides a hardware circuit that supports AC power input and effectively prevents DC power input, protects the power supply interface of relay protection equipment in intelligent substations, and ensures the normal operation of some relay protection equipment that only supports AC power.

Description

Technical Field

[0001] The present invention relates to the technical field of power input protection devices for some relay protection devices in intelligent substations, and specifically relates to a hardware circuit for preventing DC power input. Background Art

[0002] With the rapid development of China's intelligent power grid, the application demand for micro relay protection devices is increasing, and the types of micro relay protection devices are also increasing. In the actual environment where micro relay protection devices are applied, there may be two power interfaces, namely 220V AC power and 220V DC power, at the same time. However, for some micro relay protection devices with built-in toroidal transformers, since a toroidal transformer is a device that works with AC power, these micro relay protection devices can only work under 220V AC power and cannot be connected to a 220V DC power interface.

[0003] In the actual working environment, due to improper operation, if a micro relay protection device with a built-in toroidal transformer is mistakenly connected to a 220V DC power supply, it will cause the relay protection device to malfunction, and even cause damage to the micro relay protection device, thus affecting the normal working efficiency. Therefore, in order to avoid damage to micro relay protection devices and improve the safety of micro relay protection devices, a device that can identify whether the input power is AC power or DC power, and can block DC power input while allowing AC power input is needed. Summary of the Invention

[0004] The purpose of the present invention is to solve the deficiencies in the prior art, and provide a hardware circuit for preventing DC power input, which can identify AC power and DC power, and can effectively block DC power while allowing AC power input.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A hardware circuit for preventing DC power input includes a relay switch module, and also includes an AC / DC judgment module.

[0007] The AC power supply is connected to the power supply end of the relay protection device through the switch part of the relay switch module.

[0008] The AC / DC judgment module includes a resistor voltage division circuit, a waveform shaping circuit, and an AC / DC judgment circuit.

[0009] The waveform shaping circuit includes a comparator. The AC power supply is connected to the input end of the resistor voltage division circuit, and both ends of the output end of the resistor voltage division circuit are respectively connected to the non-inverting input end and the inverting input end of the comparator.

[0010] The AC-DC judgment circuit includes a DC-blocking capacitor, an energy storage capacitor, a first current-limiting resistor, a second current-limiting resistor, a third diode, a fourth diode, and a crystal triode.

[0011] One end of the DC-blocking capacitor is connected to the output terminal of the comparator, and the other end of the DC-blocking capacitor is respectively connected to the cathode of the third diode and the anode of the fourth diode. The cathode of the fourth diode is respectively connected to one end of the energy storage capacitor, one end of the first current-limiting resistor, and one end of the second current-limiting resistor. The other end of the second current-limiting resistor is connected to the base of the crystal triode. The collector of the crystal triode is connected to one end of the driving coil of the relay switch module. The driving coil of the relay switch module is connected to the power supply terminal. The emitter of the crystal triode, the anode of the third diode, the other end of the energy storage capacitor, and the other end of the first current-limiting resistor are all connected to the power supply ground.

[0012] The non-inverting input terminal of the comparator as described above is respectively connected to the cathode of the first diode and the anode of the second diode; the inverting input terminal of the comparator is respectively connected to the anode of the first diode and the cathode of the second diode.

[0013] The resistor voltage division circuit as described above includes a first voltage division resistor, a second voltage division resistor, and a third voltage division resistor.

[0014] One end of the first voltage division resistor is connected to one end of the AC power supply. The other end of the first voltage division resistor is connected to one end of the third voltage division resistor. The other end of the third voltage division resistor is connected to one end of the second voltage division resistor. The other end of the second voltage division resistor is connected to the other end of the AC power supply. The two ends of the third voltage division resistor form the output terminal of the resistor voltage division circuit.

[0015] The power supply terminal and the power supply ground as described above are provided by the output terminal of the switching power supply module. The input terminal of the switching power supply module is connected to the AC power supply.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The present invention effectively protects the micro relay protection device, ensures that the micro relay protection device can work on a normal AC input power supply, avoids the harm of the DC power supply to the micro relay protection device, and improves the safety of the micro relay protection device in use. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the circuit structure of the present invention;

[0019] Figure 2 It is a schematic diagram of the relay switch module of the present invention;

[0020] Figure 3 It is a schematic diagram of the switching power supply module of the present invention;

[0021] Figure 4 Schematic diagram of the AC-DC judgment module of the present invention;

[0022] Figure 5 Schematic diagram of the resistor voltage division circuit of the present invention;

[0023] Figure 6 Schematic diagram of the waveform shaping circuit of the present invention;

[0024] Figure 7 Schematic diagram of the AC-DC judgment circuit of the present invention;

[0025] Figure 8 Waveform diagram of key points in the AC-DC judgment circuit when an AC power supply is input;

[0026] Figure 9 Waveform diagram of key points in the AC-DC judgment circuit when a DC power supply is input.

[0027] Figure 8 and Figure 9 In [reference] and [reference], A, B, C, and D all refer to Figure 1 the voltages at A, B, C, and D in [reference], and INPUT is the voltage of the AC power supply. Detailed implementation manners

[0028] To facilitate the understanding and implementation of the present invention by those of ordinary skill in the art, the present invention will be further described in detail below in conjunction with embodiments. It should be understood that the embodiments described herein are only used to illustrate and explain the present invention and are not used to limit the present invention.

[0029] A hardware circuit for preventing DC power input includes a switching power supply module, an AC-DC judgment module, and a relay switch module.

[0030] The switching power supply module is a power supply device that can work on an AC power supply or a DC power supply and provides a constant DC power output to supply power to the AC-DC judgment module and the relay switch module.

[0031] The AC-DC judgment module includes a resistor voltage division circuit, a waveform shaping circuit, and an AC-DC judgment circuit.

[0032] The resistor voltage division circuit includes a first voltage division resistor R1, a second voltage division resistor R2, and a third voltage division resistor R3. One end of the first voltage division resistor R1 is connected to the live wire (L) of the power input, the other end of the first voltage division resistor R1 is connected to one end of the third voltage division resistor R3, the other end of the third voltage division resistor R3 is connected to one end of the second voltage division resistor R2, and the other end of the second voltage division resistor R2 is connected to the neutral wire (N) of the power input, thus forming a resistor voltage division circuit to reduce the measured input power supply voltage to a safe low voltage range.

[0033] The waveform shaping circuit includes a first diode D1, a second diode D2 and a comparator U1, wherein the anode of the first diode D1, the cathode of the second diode D2, the reverse input terminal of the comparator U1 and one end of the third resistor R3 are connected, the cathode of the first diode D1, the anode of the second diode D2, the non-inverting input terminal of the comparator U1 and the other end of the third resistor R3 are connected, and the output terminal of the comparator U1 is connected to one end of the DC blocking capacitor C1. The first diode D1 and the second diode D2 limit the voltage difference between the non-inverting input terminal and the reverse input terminal of the comparator U1 to within 0.7V, ensuring the normal operation of the comparator U1. If the input power supply is a DC power supply, the output of the comparator U1 is a continuous low-level signal or a continuous high-level signal, such as Figure 9 The waveform (A) shown in FIG. 1 is as follows; if the input power supply is an AC power supply, the comparator U1 outputs a square wave signal with an industrial frequency, such as Figure 8 The waveform shown is (A).

[0034] The AC / DC judgment circuit includes a DC blocking capacitor C1, an energy storage capacitor C2, a first current limiting resistor R4, a second current limiting resistor R5, a third diode D3, a fourth diode D4 and a transistor Q1. One end of the DC blocking capacitor C1 is connected to the output end of the comparator U1, the other end of the DC blocking capacitor C1 is connected to the cathode of the third diode D3 and the anode of the fourth diode D4, the cathode of the fourth diode D4 is connected to one end of the energy storage capacitor C2, one end of the first current limiting resistor R4 and one end of the second current limiting resistor R5, the other end of the second current limiting resistor R5 is connected to the base of the transistor Q1, the collector of the transistor Q1 serves as the output end of the AC / DC judgment circuit, the collector of the transistor Q1 is connected to one end of the driving coil of the relay switch module, the driving coil of the relay switch module is connected to the power supply end VCC of the switch power module, the emitter of the transistor Q1, the anode of the third diode D3, the other end of the energy storage capacitor C2, and the other end of the first current limiting resistor R4 are all connected to the power ground GND of the switch power module. According to the on / off state of the driving coil of the relay switch module, the switch of the relay switch module opens and closes the neutral line N and the live line L, thereby controlling the on / off state of the relay protection device. If the comparator U1 continuously outputs the same level, the waveform output by the DC blocking capacitor C1 is as follows: Figure 9 The waveform (B) shown in the figure will not output any signal. If the comparator U1 outputs a square wave with the power frequency, the waveform output by the DC blocking capacitor C1 will be as follows: Figure 8For the waveform (B) shown, a square wave with the same frequency will be output. During the high level within one frequency period, the energy storage capacitor C2 is charged, and at the same time, the crystal triode Q1 is driven to conduct to provide a driving signal for the driving coil of the relay switch module; during the low level within one frequency period, the energy storage capacitor C2 discharges, and the third diode D3 and the fourth diode D4 limit the direction of the discharge current, preventing the energy storage capacitor C2 from discharging to the blocking capacitor C1 and ensuring that the energy storage capacitor C2 can continuously drive the crystal triode Q1 during this half period, making the crystal triode Q1 continuously conduct, as Figure 8 shown in the waveform (C), the energy storage capacitor C2 continuously charges and discharges, causing the base of the crystal triode Q1 to always be at the conduction voltage of the crystal triode, as Figure 8 shown in the waveform (D).

[0035] In summary, when the input power supply is a DC power supply, the switch part of the relay switch module is in the open state, and the micro relay protection device cannot obtain the input power supply, thus ensuring the safety of the micro relay protection device and avoiding damage to the micro relay protection device by the DC power supply; when the input power supply is an AC power supply, the switch part of the relay switch module is in the closed state, and the micro relay protection device operates under a normal AC power supply.

[0036] The specific embodiments described herein are merely illustrative of the spirit of the present invention. Those skilled in the art to which the present invention pertains can make various modifications or supplements to the described specific embodiments or use similar ways to replace them, but will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. A hardware circuit for preventing DC power input, including a relay switch module, characterized in that, It further includes an AC / DC judgment module. The AC power supply is connected to the power supply terminal of the relay protection device through the switch part of the relay switch module. The AC / DC judgment module includes a resistor voltage division circuit, a waveform shaping circuit, and an AC / DC judgment circuit. The waveform shaping circuit includes a comparator (U1). The AC power supply is connected to the input end of the resistor voltage division circuit. One end of the output end of the resistor voltage division circuit is connected to the non-inverting input end of the comparator (U1), and the other end of the output end of the resistor voltage division circuit is connected to the inverting input end of the comparator (U1). The AC / DC judgment circuit includes a DC blocking capacitor (C1), an energy storage capacitor (C2), a first current limiting resistor (R4), a second current limiting resistor (R5), a third diode (D3), a fourth diode (D4), and a bipolar junction transistor (Q1). One end of the DC blocking capacitor (C1) is connected to the output end of the comparator (U1), and the other end of the DC blocking capacitor (C1) is respectively connected to the cathode of the third diode (D3) and the anode of the fourth diode (D4). The cathode of the fourth diode (D4) is respectively connected to one end of the energy storage capacitor (C2), one end of the first current limiting resistor (R4), and one end of the second current limiting resistor (R5). The other end of the second current limiting resistor (R5) is connected to the base of the bipolar junction transistor (Q1). The collector of the bipolar junction transistor (Q1) is connected to one end of the driving coil of the relay switch module. The driving coil of the relay switch module is connected to the power supply terminal (VCC). The emitter of the bipolar junction transistor (Q1), the anode of the third diode (D3), the other end of the energy storage capacitor (C2), and the other end of the first current limiting resistor (R4) are all connected to the power supply ground (GND). The non-inverting input end of the comparator (U1) is respectively connected to the cathode of the first diode (D1) and the anode of the second diode (D2); the inverting input end of the comparator (U1) is respectively connected to the anode of the first diode (D1) and the cathode of the second diode (D2). The resistor voltage division circuit includes a first voltage division resistor (R1), a second voltage division resistor (R2), and a third voltage division resistor (R3). One end of the first voltage division resistor (R1) is connected to one end of the AC power supply. The other end of the first voltage division resistor (R1) is connected to one end of the third voltage division resistor (R3). The other end of the third voltage division resistor (R3) is connected to one end of the second voltage division resistor (R2). The other end of the second voltage division resistor (R2) is connected to the other end of the AC power supply. Both ends of the third voltage division resistor (R3) form the output end of the resistor voltage division circuit.

2. The hardware circuit for preventing DC power input according to claim 1, wherein The power supply terminal (VCC) and the power supply ground (GND) are provided by the output end of the switching power supply module. The input end of the switching power supply module is connected to the AC power supply.

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