An automatic switching circuit for input reverse connection protection

Abstract

An automatic switching circuit for input reverse connection protection includes: an optocoupler (U1), a relay (K1), and a first diode (D1); a DC device is connected to the input terminal of the optocoupler (U1), the polarity of the input terminal of the optocoupler (U1) being opposite to the correct polarity of the DC device; the output terminal of the optocoupler (U1) is connected to the control terminal of the relay (K1); the input terminal of the relay (K1) is connected in parallel with the input terminal of the optocoupler (U1); both the normally closed contact and the normally open contact of the relay (K1) are connected to the output terminal of the relay (K1), but with opposite output polarities; the first diode (D1) is placed on the positive terminal line of the output terminal of the relay (K1), and the cathode side of the first diode (D1) is connected to the positive terminal of the output terminal of the relay (K1). By employing this circuit, damage to electronic components caused by reverse polarity is reduced, ensuring system safety, and allowing normal operation even under reverse polarity conditions.

Description

Technical Field

[0001] This utility model belongs to the field of circuit protection technology, and more specifically, relates to an automatic switching circuit for input reverse connection protection. Background Technology

[0002] With the development of the new energy industry, DC equipment is being used more and more widely. Reversed polarity of its input is a common problem. Once the polarity is reversed, it will not only cause the equipment to stop working, but may also damage the electronic equipment.

[0003] Prior art document 1 (CN119029819A) discloses a DC input reverse connection protection circuit, which uses a polarity detection control circuit for the input voltage located before the input relay to control the relay to activate and ensure the reliability of the circuit. However, this circuit uses transistors and NMOS transistors for operation, and the circuit stops working and cannot continue to operate after the polarity is reversed.

[0004] Prior art document 2 (CN119154241A) discloses a power reverse connection protection circuit, electronic device and method. When the power is reversed, the circuit can automatically switch to the correct power supply state to ensure that the circuit to be powered is powered. However, it uses multiple parallel transistor switching modules, which makes the circuit complex. If one of the transistors is damaged, the entire circuit cannot completely determine whether the polarity is reversed. Utility Model Content

[0005] To address the shortcomings of existing technologies, this utility model provides an automatic switching circuit for input reverse polarity protection. This circuit solves the problem of circuit malfunction or damage when the input polarity is reversed. It can automatically switch the circuit by controlling the relay's engagement through an optocoupler when the polarity of DC equipment is reversed, thus ensuring normal circuit operation and improving system safety.

[0006] This utility model adopts the following technical solution. This utility model provides an input reverse connection protection automatic switching circuit, characterized in that it includes: an optocoupler, a relay, and a first diode;

[0007] The DC device is connected to the input terminal of the optocoupler, and the polarity of the input terminal of the optocoupler is opposite to the correct polarity of the DC device. The output terminal of the optocoupler is connected to the control terminal of the relay.

[0008] The input terminal of the relay is connected in parallel with the input terminal of the optocoupler. The normally closed contact and normally open contact of the relay are both connected to the output terminal of the relay, but the output polarity is opposite.

[0009] The first diode is placed on the positive terminal of the relay output, and the cathode side of the first diode is connected to the positive terminal of the relay output.

[0010] Preferably, the input reverse connection protection automatic switching circuit further includes: a capacitor;

[0011] A capacitor is connected in parallel between the positive and negative terminals of the optocoupler's input.

[0012] Preferably, the input reverse connection protection automatic switching circuit further includes: a resistor;

[0013] A resistor is connected in series between the positive terminal of the optocoupler's input and the DC device.

[0014] Preferably, the optocoupler includes: pin 1, pin 2, pin 3, and pin 4;

[0015] Pins 1 and 2 are input terminals, with pin 1 being the positive terminal and pin 2 being the negative terminal. Pin 3 is connected to the power supply with the set voltage, and pin 4 is the output signal.

[0016] Preferably, the optocoupler includes: a light-emitting diode and a photodiode;

[0017] The anode of the light-emitting diode is connected to pin 1, and the cathode is connected to pin 2;

[0018] The anode of the photodiode is connected to pin 3, and the cathode is connected to pin 4;

[0019] When the light-emitting diode emits light, the photosensitive diode conducts.

[0020] Preferably, the input reverse connection protection automatic switching circuit further includes: a second diode;

[0021] The anode of the second diode is connected to the 4 pins of the optocoupler, and the cathode is grounded.

[0022] Preferably, the second diode is a light-emitting diode. If the second diode does not emit light when the DC equipment is reverse-connected, the optocoupler will be damaged.

[0023] Preferably, pin 3 is connected to the 24V positive terminal, and the relay control terminal activates when it receives a 24V voltage signal.

[0024] Compared to existing technologies where the circuit stops working after reverse polarity connection or where the anti-reverse polarity circuit structure is complex, the advantages of this invention include at least the following: when DC equipment is connected in reverse polarity, the circuit can be automatically switched by controlling the relay to activate via an optocoupler, thus ensuring normal circuit operation and improving system safety. Specifically, by using the circuit of this invention, damage to electronic components caused by reverse polarity connection is reduced, ensuring system safety while maintaining normal operation even under reverse polarity conditions. Attached Figure Description

[0025] Figure 1This is a schematic diagram of the basic principle of correct circuit polarity provided according to the embodiments of this utility model;

[0026] Figure 2 This is a schematic diagram of the basic principle of reverse polarity circuit connection provided in accordance with the embodiments of this utility model. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this utility model clearer, the technical solutions of this utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. The described embodiments are merely some embodiments of this utility model, not all embodiments. Based on the spirit of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0028] like Figure 1 , 2 As shown, Embodiment 1 of this utility model provides an automatic switching circuit for input reverse connection protection, comprising:

[0029] Optocoupler U1, relay K1, and first diode D1;

[0030] The DC device is connected to the input terminal of optocoupler U1, and the output terminal of optocoupler U1 is connected to the control terminal of relay K1. The polarity of the input terminal of optocoupler U1 is opposite to the correct polarity of the DC device. That is, when the input polarity of the DC device is correct, the output terminal of optocoupler U1 has no output signal; when the input polarity of the DC device is reversed, the output terminal of optocoupler U1 outputs a signal of a set magnitude, which serves as the starting voltage of relay K1. Relay K1 is activated, that is, the normally closed contact of the relay opens and the normally open contact closes.

[0031] The input terminal of relay K1 is connected in parallel with the input terminal of optocoupler U1. The normally closed contact and normally open contact of relay K1 are both connected to the output terminal of relay K1, but the output polarities are opposite.

[0032] The first diode D1 is placed on the positive terminal of the relay K1 output terminal, and the cathode side of the first diode D1 is connected to the positive terminal of the relay K1 output terminal.

[0033] like Figure 1 , 2 As shown, Embodiment 2 of this utility model provides an automatic switching circuit for input reverse connection protection. Compared with Embodiment 1, the automatic switching circuit for input reverse connection protection provided in Embodiment 2 further enhances the function of the circuit itself through structural design, specifically including: capacitor C1, resistor R1, optocoupler U1, relay K1, first diode D1 and second diode D2.

[0034] Optocoupler U1 has pins 1 and 2 as input terminals, with pin 1 being positive and pin 2 being negative. Capacitor C1 is connected between the positive and negative terminals to filter and maintain voltage stability. Resistor R1 is a current-limiting resistor connected to pin 1 of the optocoupler to prevent excessive current from damaging the optocoupler. Pin 3 of the optocoupler is connected to the 24V positive terminal, and pin 4 outputs a signal to provide the operating start voltage for the relay. Relay K1 includes contact 1 and contact 2. Contact 1 is a normally closed contact, meaning that relay K1 is normally closed and is energized at contact 1 under normal conditions. Contact 2 is a normally open contact; when relay K1 is activated, it will switch to contact 2. The outputs are connected in pairs to ensure correct output polarity. The cathode of the first diode D1 is connected to the positive terminal of the relay K1 output. The first diode D1 is used to prevent circuit damage caused by reverse polarity in case of optocoupler failure. The anode of the second diode D2 is connected to pin 4 of optocoupler U1, and the cathode is grounded. The second diode D2 will light up as a warning when the polarity of a DC device is reversed.

[0035] When the input polarity is correct, the current does not pass through optocoupler U1, and pin 4 of optocoupler U1 does not output. Relay K1 has no starting voltage. Since the relay is normally closed at contact 1, the input current is output through contact 1, which is equivalent to a resistor with very small internal resistance. The first diode D1 is forward-biased, and the subsequent circuit has input, so the system operates normally.

[0036] When the input polarity is reversed, current flows through optocoupler U1, the internal LED of optocoupler U1 lights up, the photodiode receives the signal, pins 4 and 3 conduct, pin 4 OUT is pulled to 24V+, and then the relay receives the starting voltage. The relay K1 contact changes from normally closed contact 1 to normally open contact 2. The input current is output through contact 2. Since the outputs of contact 1 and contact 2 are connected in pairs, the direction of the output current remains unchanged. The first diode D1 conducts in the forward direction, the second diode D2 lights up, the subsequent circuit has input, and the system operates normally.

[0037] When the input polarity is reversed, if the second diode D2 does not light up, there will be no input to the subsequent circuit and the system will not run. This indicates that the optocoupler U1 may be damaged, the relay K1 is working at contact 1, the first diode D1 is reverse cut off, and the circuit has no output.

[0038] It is worth noting that the input reverse connection protection automatic switching circuit provided by this utility model does not require complex control logic and devices. It can complete the input reverse connection protection automatic switching by simply improving the structure and using the external characteristics of optocoupler U1 and relay K1. The structural innovation alone has achieved the beneficial technical effect of reducing the damage to electronic components caused by polarity reversal, ensuring the safety of the system, and ensuring normal operation under polarity reversal conditions.

[0039] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of this utility model and not to limit it. Although the utility model has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of this utility model. Any modifications or equivalent substitutions that do not depart from the spirit and scope of this utility model should be covered within the protection scope of the claims of this utility model.

Claims

1. An input reverse connection protection automatic switching circuit, characterized in that, include: Optocoupler (U1), relay (K1), and first diode (D1); The DC device is connected to the input terminal of the optocoupler (U1), and the polarity of the input terminal of the optocoupler (U1) is opposite to the correct polarity of the DC device. The output terminal of the optocoupler (U1) is connected to the control terminal of the relay (K1). The input terminal of relay (K1) is connected in parallel with the input terminal of optocoupler (U1). The normally closed contact and normally open contact of relay (K1) are both connected to the output terminal of relay (K1), but the output polarities are opposite. The first diode (D1) is placed on the positive terminal of the relay (K1) output terminal, and the cathode side of the first diode (D1) is connected to the positive terminal of the relay (K1) output terminal.

2. The input reverse connection protection automatic switching circuit according to claim 1, characterized in that: The input reverse connection protection automatic switching circuit also includes: a capacitor (C1); A capacitor (C1) is connected in parallel between the positive and negative terminals of the input of the optocoupler (U1).

3. The input reverse connection protection automatic switching circuit according to claim 1, characterized in that: The input reverse connection protection automatic switching circuit also includes: a resistor (R1); A resistor (R1) is connected in series between the positive terminal of the input of the optocoupler (U1) and the DC device.

4. An input reverse connection protection automatic switching circuit according to any one of claims 1 to 3, characterized in that: The optocoupler (U1) includes: pin 1, pin 2, pin 3, and pin 4; Pins 1 and 2 are input terminals, with pin 1 being the positive terminal and pin 2 being the negative terminal. Pin 3 is connected to the power supply with the set voltage, and pin 4 is the output signal.

5. The input reverse connection protection automatic switching circuit according to claim 4, characterized in that: The optocoupler (U1) includes: a light-emitting diode and a photodiode; The anode of the light-emitting diode is connected to pin 1, and the cathode is connected to pin 2; The anode of the photodiode is connected to pin 3, and the cathode is connected to pin 4; When the light-emitting diode emits light, the photosensitive diode conducts.

6. The input reverse connection protection automatic switching circuit according to claim 4, characterized in that: The input reverse connection protection automatic switching circuit also includes: a second diode (D2); The anode of the second diode (D2) is connected to the 4 pins of the optocoupler (U1), and the cathode is grounded.

7. The input reverse connection protection automatic switching circuit according to claim 6, characterized in that: The second diode (D2) is a light-emitting diode. If the DC equipment is reverse-connected, the second diode (D2) will not emit light, and the optocoupler (U1) will be damaged.

8. An input reverse connection protection automatic switching circuit according to claim 5 or 6, characterized in that: Pin 3 is connected to the 24V positive terminal. The relay (K1) control terminal activates when it receives a 24V voltage signal.

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