Electric vehicle charging anti-overcurrent circuit

Abstract

The utility model relates to an electric vehicle charging anti-overcurrent circuit, which belongs to the field of electric vehicle charging circuits and comprises a main charging circuit and an overcurrent circuit break circuit. The main charging circuit comprises an electric vehicle charger output interface, an electromagnet, a relay normally-closed contact switch J and an electric vehicle battery which are connected in series; an electric vehicle charger output interface, a resistor R1, a normally open reed switch K and a resistor R2 are connected in series to form a first path, and the electric vehicle charger output interface, a relay coil and an NPN triode are connected in series to form a second path; the relay coil is paired with the relay normally-closed contact switch J. The capacitor C is connected in parallel with two ends of the resistor R2. One end of the resistor R3 is connected with the base electrode of the NPN triode, and the other end of the resistor R3 is connected with the A end of the resistor R2. According to the circuit, a controller is abandoned, connection and disconnection of a second access are achieved through an electromagnet and a normally-open reed switch K, and the second access controls connection and disconnection of a main charging circuit.

Description

Technical Field

[0001] The utility model belongs to the field of electric vehicle charging circuits, and in particular relates to an electric vehicle charging overcurrent prevention circuit. Background Art

[0002] One of the situations in which a fire occurs when an electric vehicle is charged is that the electric vehicle battery short-circuits, causing the charging circuit to instantly generate a large current, which in turn generates sparks and burns the wire rubber to cause a fire.

[0003] Most current charging circuits for overcurrent protection use a controller as a logic element. When the circuit generates high current, the controller monitors the current and uses a threshold to control the circuit's on / off state. While this approach effectively disconnects the charging circuit when overcurrent occurs, it relies too heavily on the controller. If the controller is subject to external electromagnetic interference, its control capabilities may be reduced, resulting in delayed operation and even failure of the overcurrent protection circuit. Utility Model Content

[0004] The utility model provides an electric vehicle charging overcurrent protection circuit, which abandons a controller, avoids the influence of external electromagnetic interference on the controller, and ensures that the protection capability of the overcurrent protection circuit is not affected.

[0005] The utility model provides an electric vehicle charging overcurrent protection circuit, comprising a main charging circuit and an overcurrent circuit breaker circuit;

[0006] The main charging circuit includes: an electric vehicle charger output interface, an electromagnet, a relay normally closed contact switch J and an electric vehicle battery; the electric vehicle charger output interface, the electromagnet, the relay normally closed contact switch J and the electric vehicle battery are connected in series;

[0007] Overcurrent circuit breaker: resistor R1, normally open reed switch K, relay coil, NPN transistor, resistor R2, resistor R3 and capacitor C;

[0008] Among them, the electric vehicle charger output interface, resistor R1, normally open reed switch K and resistor R2 are connected in series to form a path 1, and the path 1 is connected in parallel with the main charging circuit; the normally open reed switch K is within the magnetic force range of the electromagnet;

[0009] The electric vehicle charger output interface, relay coil and NPN transistor are connected in series to form path 2, which is connected in parallel with path 1 and the main charging circuit. The relay coil is paired with the relay normally closed contact switch J. The pairing means: when the relay coil is energized, the relay normally closed contact switch J is open; when the relay coil is de-energized, the relay normally closed contact switch J is closed.

[0010] Capacitor C is connected in parallel across resistor R2;

[0011] Assume that one end of the resistor R2 connected to the negative pole of the electric vehicle charger output interface is terminal B, and the other end is terminal A; one end of the resistor R3 is connected to the base of the NPN transistor, and the other end is connected to terminal A of the resistor R2.

[0012] Furthermore, a diode D1 is connected in parallel to both ends of the relay coil, the anode of the diode D1 is connected to the collector of the NPN transistor G, and the cathode of the diode D1 is connected to the positive electrode of the electric vehicle charger output interface.

[0013] Diode D1 is mainly used to release the loop current in the relay coil and protect the relay coil.

[0014] Furthermore, the resistance values ​​of the resistor R1, the resistor R2 and the resistor R3 are all 3-10 kΩ.

[0015] In order to protect the circuit, the resistance value should not be too large, which will cause excessive circuit consumption. Therefore, it is more reasonable to set the resistance value of resistors R1, R2 and R3 to 3-10kΩ.

[0016] Furthermore, the capacitor C is a 63V electrolytic capacitor.

[0017] The larger the capacity of the capacitor, the longer the conduction time of path 2 will be extended. It is more reasonable to use a 63V electrolytic capacitor to control the conduction time of path 2. Beneficial effects

[0018] This circuit uses an electromagnet to attract the normally open reed switch K when the main charging circuit overcurrents, connecting paths one and two. The relay coil in path two then controls the normally closed relay switch J to disconnect the main charging circuit. Capacitor C also delays the reclosing of the main charging circuit to avoid multiple reconnections within a short period of time. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The present invention is a circuit diagram of an electric vehicle charging overcurrent protection circuit. DETAILED DESCRIPTION

[0020] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0021] An electric vehicle charging overcurrent protection circuit comprises a main charging circuit and an overcurrent disconnecting circuit.

[0022] The main charging circuit includes: the electric vehicle charger output interface, electromagnet, relay normally closed contact switch J and electric vehicle battery. The electric vehicle charger output interface, electromagnet, relay normally closed contact switch J and electric vehicle battery are connected in series.

[0023] Because the output interface of the electric vehicle charger outputs direct current, which has positive and negative poles, the current flow direction in the main charging circuit is: the current flows from the positive pole of the electric vehicle charger output interface, through the electromagnet and the normally closed contact switch J of the relay, and then flows to the electric vehicle battery, and then flows back from the negative pole of the electric vehicle battery to the negative pole of the electric vehicle charger output interface.

[0024] The overcurrent cut-out circuit includes:

[0025] Resistor R1, normally open reed switch K, relay coil, NPN transistor G, resistor R2, resistor R3 and capacitor C.

[0026] The electric vehicle charger output port, resistor R1, normally open reed switch K, and resistor R2 are connected in series to form path 1, which is connected in parallel with the main charging circuit. Resistor R1 is connected to the positive terminal of the electric vehicle charger output port, while resistor R2 is connected to the negative terminal of the electric vehicle charger output port.

[0027] The normally open reed switch K is within the magnetic field of the electromagnet. Only when the main charging circuit experiences an overcurrent, and the electromagnet generates a strong suction force due to the high current, will the normally open reed switch K transition from the normally open state to the closed state under the magnetic attraction of the electromagnet. In other situations, the normally open reed switch K remains normally open. Reed switch K is a magnetic reed switch.

[0028] When the internal contacts of the normally open reed switch K close, path 1 is connected. The current in path 1 flows from the positive terminal of the electric vehicle charger output interface, through resistor R1, the closed normally open reed switch K, and resistor R2, to the negative terminal of the electric vehicle charger output interface. Capacitor C is connected in parallel across resistor R2; when path 1 is connected, capacitor C charges. Capacitor C uses a 63V electrolytic capacitor.

[0029] The electric vehicle charger output interface, relay coil and NPN transistor G are connected in series to form path 2, which is connected in parallel with path 1 and the main charging circuit. In this embodiment, a 9013 transistor is used.

[0030] One end of the relay coil is connected to the positive terminal of the electric vehicle charger output interface, and the other end is connected to the collector of NPN transistor G; the emitter of NPN transistor G is connected to the negative terminal of the electric vehicle charger output interface. Let the end of resistor R2 connected to the negative terminal of the electric vehicle charger output interface be terminal B, and the other end be terminal A; one end of resistor R3 is connected to the base of NPN transistor G, and the other end is connected to terminal A of resistor R2. In this embodiment, the resistance values ​​of resistors R1, R2, and R3 are 3-10kΩ. When path one is turned on, the base of NPN transistor G is forward biased, causing path two to be turned on simultaneously.

[0031] The relay also includes a diode D1, connected in parallel across the relay coil. The anode of diode D1 is connected to the collector of NPN transistor G, and the cathode of diode D1 is connected to the positive terminal of the electric vehicle charger output interface. Diode D1 is used to discharge the loop current in the relay coil and protect the relay's normally closed contact switch J. In this embodiment, a 4007 diode is used. The relay coil and normally closed contact switch J are paired in this embodiment. This pairing means that when the relay coil is energized, the normally closed contact switch J is open; when the relay coil is de-energized, the normally closed contact switch J is closed.

[0032] The use of this circuit

[0033] When the main charging circuit is normally free of overcurrent, only the main charging circuit is conducting, while both path 1 and path 2 are closed. That is, the current flows from the positive terminal of the electric vehicle charger output interface, through the electromagnet, the normally closed relay switch J, and the battery, back to the negative terminal of the electric vehicle charger output interface, achieving the purpose of charging the battery through the electric vehicle charger output interface.

[0034] If the electric vehicle battery shorts, the current in the main charging circuit will suddenly increase. This surge in current will cause the electromagnet to generate a strong magnetic force. The electromagnet exerts a strong magnetic force on the normally open reed switch K, causing it to close.

[0035] After the normally open reed switch K is closed, both path 1 and path 2 are connected.

[0036] Current in Path 1: Current flows from the positive terminal of the electric vehicle charger output interface, through resistor R1, the closed normally open reed switch K, and resistor R2, back to the negative terminal of the electric vehicle charger output interface. Because capacitor C is connected in parallel across R2, capacitor C begins to charge when path 1 is connected.

[0037] Current in Path 2 flows from the positive terminal of the electric vehicle charger output port, through the relay coil, through NPN transistor G, and back to the negative terminal of the electric vehicle charger output port. Because Path 1 is conductive, the base of NPN transistor G is forward biased, allowing NPN transistor G to conduct. When the relay coil is energized, the normally closed relay switch J opens. Once the normally closed relay switch J opens, the main charging circuit is immediately disconnected, and charging of the electric vehicle battery is no longer possible.

[0038] When the normally closed relay J opens, the main charging circuit is immediately disconnected, and the electromagnet loses its magnetic force. Although the normally open reed switch K immediately returns to the normally open state after losing the electromagnet's magnetic force, causing path one to immediately disconnect, due to the previously charged capacitor C, the electrons within capacitor C can continue to forward bias the base of the NPN transistor G. Therefore, path two remains conductive at this time and will not disconnect immediately. If path two does not disconnect, the normally closed relay J will remain normally open, and the main charging circuit will remain disconnected. Until the capacitor C is depleted of power, the base of the NPN transistor G is no longer forward biased, and path two is disconnected. After the relay coil is depleted of power, the normally closed relay J recloses, and the main charging circuit is reconnected. If the main charging circuit still has overcurrent at this time, the above process will repeat.

[0039] Based on the above-mentioned ideal embodiment of the present invention, and in accordance with the above description, relevant personnel can make various changes and modifications without departing from the technical scope of the present invention. The technical scope of the present invention is not limited to the content of the specification, but must be determined according to the scope of the claims.

Claims

1. An electric vehicle charging overcurrent protection circuit, characterized in that: Including main charging circuit and overcurrent cut-off circuit; The main charging circuit includes: an electric vehicle charger output interface, an electromagnet, a relay normally closed contact switch J and an electric vehicle battery; the electric vehicle charger output interface, the electromagnet, the relay normally closed contact switch J and the electric vehicle battery are connected in series; Overcurrent circuit breaker: resistor R1, normally open reed switch K, relay coil, NPN transistor, resistor R2, resistor R3 and capacitor C; Among them, the electric vehicle charger output interface, resistor R1, normally open reed switch K and resistor R2 are connected in series to form a path 1, and the path 1 is connected in parallel with the main charging circuit; the normally open reed switch K is within the magnetic force range of the electromagnet; The electric vehicle charger output interface, relay coil and NPN transistor are connected in series to form path 2, which is connected in parallel with path 1 and the main charging circuit. The relay coil is paired with the relay normally closed contact switch J. The pairing means: when the relay coil is energized, the relay normally closed contact switch J is open; when the relay coil is de-energized, the relay normally closed contact switch J is closed. Capacitor C is connected in parallel across resistor R2; Assume that one end of the resistor R2 connected to the negative pole of the electric vehicle charger output interface is terminal B, and the other end is terminal A; one end of the resistor R3 is connected to the base of the NPN transistor, and the other end is connected to terminal A of the resistor R2.

2. The electric vehicle charging overcurrent protection circuit according to claim 1, characterized in that: A diode D1 is connected in parallel to both ends of the relay coil, the anode of the diode D1 is connected to the collector of the NPN transistor G, and the cathode of the diode D1 is connected to the anode of the electric vehicle charger output interface.

3. The electric vehicle charging overcurrent protection circuit according to claim 1, characterized in that: The resistance values ​​of the resistor R1 , the resistor R2 and the resistor R3 are all 3-10 kΩ.

4. The electric vehicle charging overcurrent protection circuit according to claim 1, characterized in that: Capacitor C is a 63V electrolytic capacitor.

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