Overcurrent protection circuit and electronic device

Abstract

The application relates to an overcurrent protection circuit and electronic equipment, which comprises a mechanical switch module, a first end of the mechanical switch module being used for connecting a first end of a load loop and being used for controlling conduction of the load loop; a second end of the mechanical switch module being used for connecting a first alternating current input end of an external alternating current power supply; a PTC module, one end of the PTC module being connected to a second alternating current input end of the external alternating current power supply; a switch circuit, a first end of the switch circuit being connected to the other end of the PTC module; a second end of the switch circuit being used for connecting a second end of the load loop; a control module, a first end of the control module being connected to the mechanical switch module, a second end of the control module being connected to the other end of the PTC module, and a third end of the control module being connected to a third end of the switch circuit; when the control module detects that a switch of the mechanical switch module is closed, the control module controls a switch of the switch circuit to be closed, so that the load loop is conducted; and when the control module further detects that the PTC module presents a preset high resistance state, the control module controls the switch of the switch circuit to be opened. The structure can improve the reliability of overcurrent protection.

Description

Technical Field

[0001] This application relates to the field of circuit protection technology, and in particular to an overcurrent protection circuit and electronic device. Background Technology

[0002] Positive temperature coefficient thermistors (PTCs) are widely used as overcurrent protection components in circuits because their resistance increases exponentially with temperature. PTCs have important applications in power adapters, battery packs, automotive electronics, and electric equipment, especially due to their "self-recovery" characteristic of automatically returning to a low resistance state after a fault is cleared.

[0003] To maintain the PTC in the protection state (high impedance state) after overcurrent triggering, traditional technology requires it to operate continuously in a high temperature range of 100-140℃, corresponding to a maintenance power consumption of 1.0W-2.5W.

[0004] However, during implementation, the applicant discovered that traditional technologies suffer from at least low reliability of overcurrent protection. Utility Model Content

[0005] Based on this, the purpose of this application is to at least solve one of the above-mentioned technical defects, especially the technical defect of low reliability of overcurrent protection in the prior art. This application provides an overcurrent protection circuit and electronic device.

[0006] In a first aspect, this application provides an overcurrent protection circuit for overcurrent protection of a load circuit, the circuit comprising:

[0007] The mechanical switch module has two terminals: the first terminal is used to connect to the first terminal of the load circuit to control the conduction of the load circuit; the second terminal of the mechanical switch module is used to connect to the first AC input terminal of an external AC power supply.

[0008] The PTC module has a second AC input terminal that connects to an external AC power source at one end.

[0009] The switching circuit has one end connected to the other end of the PTC module; the second end of the switching circuit is used to connect to the second end of the load circuit.

[0010] The control module has its first end connected to the mechanical switch module, its second end connected to the other end of the PTC module, and its third end connected to the third end of the switch circuit.

[0011] The control module is used to control the switch circuit to close when it detects that the mechanical switch module is closed, so as to make the load circuit conduct; the control module is also used to control the switch circuit to open when it detects that the PTC module presents a preset high resistance state.

[0012] In one embodiment, the overcurrent protection circuit further includes:

[0013] The PTC signal detection circuit has one end connected to the other end of the PTC module, and the other end connected to the second end of the control module. The PTC signal detection circuit is used to detect the signal level of the PTC module, and the signal level indirectly represents the impedance state of the PTC module.

[0014] In one embodiment, the overcurrent protection circuit further includes:

[0015] The mechanical switch detection circuit has its first terminal connected to the first terminal of the mechanical switch module, and its second terminal connected to the first terminal of the control module. The mechanical switch detection circuit is used to detect the on / off signal of the mechanical switch.

[0016] In one embodiment, the overcurrent protection circuit further includes:

[0017] The power module has an input terminal for connecting to an external AC power source, and its output terminals are connected to the power supply terminals of the control module and the switching circuit, respectively.

[0018] In one embodiment, the switching circuit includes:

[0019] The first switching unit has a first end connected to the other end of the PTC module, and a second end of the first switching unit is used to connect to the second end of the load circuit.

[0020] The second switch unit has its first end connected to the third end of the first switch unit, and its second end connected to the third end of the control module.

[0021] In one embodiment, the first switching unit includes:

[0022] The relay unit has its first normally open contact connected to the other end of the PTC module, and its second normally open contact connected to the second end of the load circuit.

[0023] The input terminal of the relay unit is used to connect to the power supply voltage, and the output terminal of the relay unit is connected to the first terminal of the second switch unit.

[0024] In one embodiment, the second switching unit includes:

[0025] The base of the transistor unit is connected to the third terminal of the control module, the collector of the transistor unit is connected to the third terminal of the first switching unit, and the emitter of the transistor unit is used for grounding.

[0026] In one embodiment, the mechanical switch module includes:

[0027] The diode, with its anode connected to the first terminal of the control module;

[0028] The first mechanical switch has a first end connected to the cathode of a diode, and a second end of the first mechanical switch is used to connect to the first AC input terminal of an external AC power supply.

[0029] The second mechanical switch is the first terminal of the first control module, and the second terminal of the second mechanical switch is used to connect to the first AC input terminal of an external AC power supply.

[0030] In one embodiment, the overcurrent protection circuit further includes:

[0031] The differential mode interference suppression circuit has a first AC input terminal for connecting to an external AC power supply, and is also connected to the second terminal of the mechanical switch module.

[0032] The second terminal of the differential mode interference suppression circuit is used to connect to the second AC input terminal of the external AC power supply, and is also connected to one end of the PTC module;

[0033] The third terminal of the differential mode interference suppression circuit is used for grounding.

[0034] Secondly, this application also provides an electronic device, including a load circuit and an overcurrent protection circuit as described above; the overcurrent protection circuit is used to protect the load circuit from overcurrent.

[0035] As can be seen from the above technical solutions, the embodiments of this application have the following advantages:

[0036] The overcurrent protection circuit and electronic device provided in this application are configured such that the first terminal of a switching circuit is connected to the other terminal of a PTC module, and the second terminal of the switching circuit is connected to the second terminal of the load circuit. This structure allows control of the PTC module's connection state in the load circuit via the switching circuit. In other words, protection of the PTC module can be achieved by controlling the change in the PTC module's connection state in the load circuit. Furthermore, in the event of an overcurrent in the load circuit, compared to traditional technologies, the control module monitors the mechanical switch state and PTC resistance changes in real time. When an overcurrent occurs and the PTC module reaches a preset high resistance state, indicating that the PTC module's temperature is also relatively high, the circuit can be quickly cut off, preventing the PTC from being in a high-temperature, high-energy-consumption state for a prolonged period. This also prevents the temperature of electronic devices (especially handheld devices) from continuously rising, which would reduce user comfort. Therefore, this application improves the reliability of overcurrent protection. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 A schematic diagram of a conventional PCT overcurrent protection circuit provided in this application embodiment;

[0039] Figure 2 This is a schematic diagram of an overcurrent protection circuit provided in an embodiment of this application;

[0040] Figure 3 A schematic diagram of an overcurrent protection circuit with a detection circuit provided in an embodiment of this application;

[0041] Figure 4 A schematic diagram of an overcurrent protection circuit with a power supply module provided for an embodiment of the application;

[0042] Figure 5 This is a schematic diagram illustrating a specific circuit implementation of an overcurrent protection circuit provided in an embodiment of this application.

[0043] Figure label:

[0044] 210 Mechanical switch module; 220 PTC module; 230 Switching circuit; 240 Control module; 250 PTC signal detection circuit; 260 Mechanical switch detection circuit; 270 Power supply module; 30 External AC power supply; 40 Load circuit. Detailed Implementation

[0045] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0046] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0047] It is understood that the terms "first," "second," etc., used herein may be used to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another. For example, without departing from the scope of this application, a first resistor may be referred to as a second resistor, and similarly, a second resistor may be referred to as a first resistor. Both the first resistor and the second resistor are resistors, but they are not the same resistor.

[0048] It is understood that the term "connection" in the following embodiments should be understood as "electrical connection," "communication connection," etc., if the connected circuits, modules, units, etc., have electrical signal or data transmission with each other.

[0049] It is understandable that "at least one" can refer to one or more, while "multiple" can refer to two or more. "At least a part of an element" can refer to part or all of an element.

[0050] When used herein, the singular forms of “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that terms such as “comprising / including” or “having” specify the presence of the stated features, integrals, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, integrals, steps, operations, components, parts, or combinations thereof. Meanwhile, the term “and / or” as used in this specification includes any and all combinations of the associated listed items.

[0051] Positive temperature coefficient thermistors (PTCs) are widely used as overcurrent protection components in circuits because their resistance increases exponentially with temperature. PTCs have important applications in power adapters, battery packs, automotive electronics, and electric equipment, especially due to their "self-recovery" characteristic of automatically returning to a low resistance state after a fault is cleared.

[0052] To maintain the PTC in the protection state (high impedance state) after overcurrent triggering, traditional technology requires it to operate continuously in a high temperature range of 100-140℃, corresponding to a maintenance power consumption of 1.0W-2.5W.

[0053] The applicant's research revealed that the self-recovery characteristic of PTCs presents a significant technical bottleneck in overcurrent protection applications. Traditional PTCs need to maintain a temperature of 100-140℃ and a power consumption of 1.0W-2.5W to maintain high-resistance protection. This characteristic is particularly disadvantageous for handheld devices: continuous heat generation reduces user comfort and may even pose safety risks due to localized overheating.

[0054] Furthermore, in handheld device applications with stringent safety requirements, some designs employ a dual protection mechanism involving a mechanical switch connected in series in the load circuit. However, the PTC element in this solution still carries a risk of self-resetting. For example... Figure 1 As shown, Figure 1The schematic diagram of a conventional PCT overcurrent protection circuit provided in this application embodiment includes: fuse F1, thermistor PT1, varistor RV1, X capacitor C1, resistor R1, resistor R2, rectifier bridge DB1, diode D1, and rectifier bridge DB1, wherein ACL is the AC live wire input and CAN is the AC neutral wire input.

[0055] Traditional techniques typically place the PTC (Power Transmitter) before the X capacitor. When the PTC is in a low-impedance state, the X capacitor suppresses differential-mode interference in the circuit. When the PTC is in a high-impedance state due to overcurrent protection, the X capacitor acts as a voltage divider, utilizing its capacitive voltage divider characteristic to continuously provide current to the PTC to maintain the protection state. However, this approach has significant limitations in practical applications: in countries using 100-127V low-voltage mains standards (such as Japan and the United States), according to the voltage divider formula... (where U is the input voltage, R is the load resistance, f is the power supply frequency, and C is the step-down capacitor). A decrease in input voltage will directly lead to a proportional decrease in output current, making it difficult to meet the power consumption required for the PTC to maintain the protection state. Over time, the PTC will cool down due to heat dissipation, and its resistance will automatically return to a low resistance state, causing the overcurrent protection function to fail and failing to meet the stringent requirements for circuit safety and reliability of handheld devices.

[0056] Based on this, and addressing the problems of easy failure of overcurrent protection circuits and low reliability of overcurrent protection in traditional technologies, this application provides an overcurrent protection circuit and electronic device. By setting the first end of the switching circuit to connect to the other end of the PTC module, and the second end of the switching circuit to connect to the second end of the load circuit, this structure allows control of the PTC module's connection state in the load circuit via the switching circuit. That is, by controlling the change in the PTC module's connection state in the load circuit, protection of the PTC module can be achieved. Simultaneously, in the event of an overcurrent in the load circuit, compared to traditional technologies, this application uses a control module to monitor the mechanical switch state and PTC resistance changes in real time. After an overcurrent occurs, if the PTC module reaches a preset high resistance state, it indicates that the PTC module's temperature is also relatively high. At this point, the circuit can be quickly cut off, preventing the PTC from being in a high-temperature, high-energy-consumption state for a long time. This also prevents the temperature of electronic devices (especially handheld devices) from continuously rising, resulting in low user comfort. Thus, this application improves the reliability of overcurrent protection.

[0057] In one exemplary embodiment, such as Figure 2 As shown, Figure 2 This is a schematic diagram of an overcurrent protection circuit provided in an embodiment of this application. The overcurrent protection circuit includes a mechanical switch module 210, a PTC module 220, a switch circuit 230, and a control module 240, wherein:

[0058] The mechanical switch module 210 has a first end for connecting to the first end of the load circuit 40 and for controlling the conduction of the load circuit 40; the second end of the mechanical switch module 210 is used to connect to the first AC input terminal of the external AC power supply 30.

[0059] The mechanical switch module 210 refers to a device that enables circuit switching through physical contacts, such as a rocker switch or push-button switch. Its first contact can be connected to the load circuit 40, and its second contact can be connected to an AC power source. The load circuit 40 refers to a closed path in the circuit that supplies power to the electrical equipment (load), including the load itself; current flows through this circuit to make the load work. The external AC power source 30 refers to the input source of the power supply system (such as a mains socket), providing AC voltage, and may have a first AC input terminal / a second AC input terminal (i.e., live wire L and neutral wire N).

[0060] The PTC module 220 has one end connected to the second AC input terminal of the external AC power supply 30.

[0061] Among them, PTC module 220 can be a positive temperature coefficient thermistor module, which refers to a resistive element with positive temperature coefficient characteristics. For example, it can be made of polymer-based composite material, and its resistance increases exponentially with increasing temperature.

[0062] The first end of the switching circuit 230 is connected to the other end of the PTC module 220; the second end of the switching circuit 230 is used to connect to the second end of the load circuit 40.

[0063] The switching circuit 230 can refer to an electronic component that controls the conduction or interruption of the current path. For example, it can be implemented using a combination of relay and transistor circuits, and the conduction state can be changed by a control signal.

[0064] The control module 240 has its first end connected to the mechanical switch module 210, its second end connected to the other end of the PTC module 220, and its third end connected to the third end of the switch circuit 230.

[0065] The control module 240 can refer to a circuit unit with control functions. For example, it can be constructed using a microcontroller or logic gate circuit, and monitor the voltage change across the thermistor through a voltage comparator.

[0066] In practical applications, the control module 240 is used to control the switch circuit 230 to close when it detects that the mechanical switch module 210 is closed, so as to make the load circuit 40 conduct; the control module 240 is also used to control the switch circuit 230 to open when it detects that the PTC module 220 presents a preset high resistance state.

[0067] The preset high resistance state can refer to the trigger resistance value of the PTC protection state. When the PTC resistance value exceeds this threshold, it means that the PTC's heating temperature is not allowed to rise further. Thus, this application can reduce the power consumption and temperature of the PTC in maintaining the protection state, thereby protecting the life of the PTC module 220 and reducing the heating temperature of electronic devices, especially solving the problem of continuous heating after overcurrent protection of handheld devices.

[0068] For example, the live wire input terminal (second terminal) of the mechanical switch module 210 can be directly connected to the live wire (ACL) of the external AC power supply 30, and its load output terminal (first terminal) is connected to the input terminal of the load circuit 40, forming the main power channel from the mains power to the load. The physical switch contacts of the mechanical switch module 210 can be manually controlled by the user to realize the basic on / off operation of the load circuit 40.

[0069] The input terminal of the PTC module 220 can be connected to the neutral wire (ACN) of the external AC power supply 30, and its output terminal can be connected in series with the first terminal of the switching circuit 230. This connection allows the PTC to be directly embedded in the main current path, normally exhibiting a low-resistance state that allows current to flow, and in the event of overcurrent, it self-heats and triggers a high-resistance state, forming a protective barrier for the load circuit 40.

[0070] The load connection terminal (second terminal) of the switching circuit 230 can be connected to the output terminal of the load circuit 40, and the controlled terminal (third terminal) of the switching circuit 230 can be connected to the drive signal output terminal of the control module 240. The switching circuit 230 can be used as an electronic actuator, and can be a relay or a semiconductor switching device (such as a MOSFET) to physically disconnect or connect the load circuit 40 according to the control command.

[0071] Specifically, when the mechanical switch is closed, the control module 240 receives a conduction signal and drives the switch circuit 230 to close, allowing AC current to flow through the thermistor module (PTC module 220) and the load circuit 40 to form a complete circuit. When an overcurrent fault occurs in the load, the thermistor heats up due to the increased current, and its resistance rises sharply to a preset threshold. The control module 240 detects the voltage change across the thermistor to determine whether it has entered a preset high-resistance state. If so, it can immediately cut off the switch circuit 230, interrupting the main circuit current. At this time, the thermistor cools down naturally due to the disappearance of current, avoiding continuous high-temperature operation.

[0072] Optionally, if the power supply to the entire circuit of the electronic device is interrupted, for example, by disconnecting the external power supply via a mechanical switch, and then the power is restored, the state of the control module 240 can be reset, and it can continue to detect the signal of the mechanical switch closing again and control the switching circuit 230 to close. In this way, a closed-loop cyclic control is formed to achieve normal operation of the electronic device and reliable overcurrent protection.

[0073] In this embodiment, the heat source is eliminated by actively cutting off the main circuit, and only the standby power consumption of the control module 240 needs to be maintained after the protection is triggered. Through this structure, the thermistor can remain in a normal temperature environment under protection conditions. This structural design avoids performance degradation caused by long-term high-temperature operation of the thermistor. Real-time monitoring of the thermistor's resistance state by the control module 240 ensures timely protection action, and the coordinated control of the mechanical and electronic switches achieves reliable switching operations. This embodiment maintains the self-recovery function while extending the service life of the protection element, thereby improving the reliability of overcurrent protection.

[0074] In one exemplary embodiment, such as Figure 3 As shown, Figure 3 This application provides a schematic diagram of an overcurrent protection circuit with a detection circuit as an embodiment of the present application; wherein the overcurrent protection circuit further includes:

[0075] The PTC signal detection circuit 250 has its first end connected to the other end of the PTC module 220, and its second end connected to the second end of the control module 240. The PTC signal detection circuit 250 is used to detect the signal level of the PTC module 220, and the signal level indirectly represents the resistance state of the PTC module 220.

[0076] The PTC signal detection circuit 250 can refer to a detection unit that converts the impedance change of the PTC module 220 into a recognizable electrical signal. For example, it can be implemented using a voltage divider circuit or a comparator circuit, generating a corresponding level signal by acquiring the voltage change across the PTC. The signal level can refer to a voltage amplitude parameter that corresponds to the PTC's resistance state. For example, it can be implemented by setting a threshold voltage comparison method. When the PTC is in a high-resistance state, its voltage division value exceeds the set threshold, which is determined to be an overcurrent state.

[0077] For example, when the load circuit 40 is operating normally, the PTC module 220 is in a low-resistance state, and the level signal output by the PTC signal detection circuit 250 is in the first voltage range. When an overcurrent fault occurs, the PTC module 220 enters a high-resistance state due to the temperature rise, and the voltage across its terminals increases significantly. The PTC signal detection circuit 250 converts this voltage change into a level signal exceeding a preset threshold and transmits it to the control module 240. The control module 240 can determine that an overcurrent state has been triggered based on this level signal and then cuts off the operating circuit of the switching circuit 230. In this way, the indirect detection method avoids the response delay caused by directly monitoring the PTC temperature, and also avoids the problem of decreased reliability of electronic components under high-temperature environments.

[0078] In this embodiment, by setting up an independent signal detection circuit, the resistance change is converted into an accurately identifiable level signal, enabling the control module 240 to make logical judgments based on stable electrical parameters. This effectively improves the anti-interference capability of state recognition and ensures that protection actions are triggered under real overcurrent conditions, thereby improving the reliability of overcurrent protection.

[0079] In one exemplary embodiment, such as Figure 3 As shown, the overcurrent protection circuit also includes:

[0080] The mechanical switch detection circuit 260 has its first end connected to the first end of the mechanical switch module 210, and its second end connected to the first end of the control module 240. The mechanical switch detection circuit 260 is used to detect the on / off signal of the mechanical switch.

[0081] The mechanical switch detection circuit 260 can refer to a signal conversion circuit used to acquire the on / off state of the mechanical switch module 210. For example, it can be implemented using an optocoupler isolation circuit or a voltage divider sampling circuit to convert the physical on / off action of the mechanical switch into an electrical signal output. The first terminal of the control module 240 can refer to an input port for receiving the mechanical switch status signal. For example, it can be implemented using a microcontroller's general-purpose input pin or a dedicated signal interface circuit to receive and process the level signal output by the mechanical switch detection circuit 260.

[0082] For example, the first terminal of the mechanical switch module 210 is connected to the first terminal of the load circuit 40. When the mechanical switch is closed, the external AC power supply 30 and the load circuit 40 form a conductive path. The mechanical switch detection circuit 260 can be connected in parallel with the mechanical switch module 210 through a voltage divider resistor network, generating a high-level signal when the mechanical switch is closed and a low-level signal when it is open. This signal is transmitted to the first terminal of the control module 240, where the internal logic circuit determines the switch state.

[0083] For example, when a high-level signal is detected, the control module 240 determines that the mechanical switch is closed and then sends a closing command to the switch circuit 230 to turn on the load circuit 40; when a low-level signal is detected, the control module 240 determines that the mechanical switch is in the open state and maintains the open state of the switch circuit 230.

[0084] In this embodiment, the mechanical switch detection circuit 260 converts the physical switch state into a stable level signal, eliminating interference caused by poor contact or voltage fluctuations. For example, when using an optocoupler isolation circuit, the on / off action of the mechanical switch is transmitted through the coupling between the light-emitting diode and the phototransistor, achieving electrical isolation and signal shaping, thereby ensuring the reliability of the control command of the switch circuit 230, and thus ensuring the reliability of the overcurrent protection circuit.

[0085] In one exemplary embodiment, such as Figure 4 As shown, Figure 4 A schematic diagram of an overcurrent protection circuit with a power supply module 270 provided in this application embodiment is shown, wherein the overcurrent protection circuit further includes:

[0086] The power module 270 has an input terminal for connecting to the first AC input terminal of the external AC power supply 30, and the output terminals of the power module 270 are respectively connected to the power supply terminal of the control module 240 and the power supply terminal of the switching circuit 230.

[0087] The power supply module 270 refers to a conversion circuit that converts AC power to DC power. For example, it can be implemented using a combination of a rectifier bridge and a voltage regulator circuit to provide a stable operating voltage for the control module 240 and the switching circuit 230. The input terminal of the power supply module 270 is directly connected to the AC power supply, enabling independent power supply and preventing current fluctuations in the load circuit 40 from affecting the control circuit.

[0088] For example, the power module 270 converts AC power into pulsating DC power through a rectifier bridge, and then outputs a stable DC voltage after processing by a filter capacitor and a voltage regulator. This DC voltage is supplied to both the control module 240 and the switching circuit 230 simultaneously, ensuring that both operate under the same voltage reference. When the mechanical switch module 210 is closed, the control module 240 responds quickly based on the stable power supply, driving the switching circuit 230 to conduct the load circuit 40; when the PTC module 220 is in a high-impedance state, the control module 240 maintains the detection and judgment function through continuous power supply, accurately cutting off the switching circuit 230.

[0089] In this embodiment, self-powering can be achieved through the integrated power module 270. This simplifies the system structure and eliminates the impact of load current fluctuations on the control logic, ensuring that the control module 240 and the switching circuit 230 maintain stable operation under conditions such as AC power fluctuations and sudden load changes. This improves the accuracy and reliability of overcurrent protection. Simultaneously, the power module 270 can provide a low-voltage supply to the control module 240, maintaining power supply even after the PTC is disconnected. The control module 240 maintains protection lockout, preventing protection failure due to PTC self-recovery, significantly improving reliability.

[0090] In one exemplary embodiment, the switching circuit includes:

[0091] The first switching unit has a first end connected to the other end of the PTC module, and a second end of the first switching unit is used to connect to the second end of the load circuit.

[0092] The second switch unit has its first end connected to the third end of the first switch unit, and its second end connected to the third end of the control module.

[0093] The first switching unit can refer to a power switching device used to carry the main circuit current. For example, it can be implemented using a relay unit with normally open contacts, whose contacts are connected in series between the PTC module and the load circuit to achieve main current on / off control. The second switching unit can refer to a control switching device used to drive the first switching unit. For example, it can be implemented using a transistor unit, which is triggered to turn on or off by a level signal output by the control module.

[0094] For example, when the mechanical switch module is closed, the control module activates the second switching unit via a detection signal, causing the transistor to conduct and energize the relay coil, which in turn closes the normally open contacts of the relay to form a load circuit. When the PTC module reaches a critical temperature due to overcurrent heating, its resistance rises sharply, triggering the control module to cut off the operating current of the second switching unit. The relay coil then loses power, its contacts open, and the load circuit is disconnected. This hierarchical control structure separates the high-current switching function from the logic control function, avoiding a single switching device simultaneously undertaking the dual tasks of power switching and signal processing.

[0095] In this embodiment, by setting independent drive switches and main circuit switches, the control signal and power circuit can be electrically isolated. This allows for accurate disconnection of the main circuit current path in the event of an overcurrent, preventing the PTC module from remaining in a high-temperature state for extended periods, thereby improving the reliability of overcurrent protection. This structural design ensures timely overcurrent protection while reducing power loss in the control module and extending the lifespan of the relay contacts.

[0096] In one exemplary embodiment, the first switching unit includes:

[0097] The relay unit has its first normally open contact connected to the other end of the PTC module, and its second normally open contact connected to the second end of the load circuit.

[0098] The input terminal of the relay unit is used to connect to the power supply voltage, and the output terminal of the relay unit is connected to the first terminal of the second switch unit.

[0099] The relay unit refers to an electrical component that controls the on / off state of a circuit through electromagnetic effects. For example, it can be implemented using an electromagnetic relay with normally open contacts, where the contacts close to form a conductive path when the coil is energized. The normally open contact refers to the contact point of the relay in the open state when not energized; for example, it can be implemented using silver alloy contacts, where the contacts close to conduct current when the relay coil is energized. The power supply voltage input terminal refers to the interface that provides the operating voltage to the relay coil; for example, it can be implemented using a 12V DC power supply interface, where an external power module converts AC power to DC power to supply the relay.

[0100] For example, when the control module outputs a drive signal, the second switching unit is turned on, energizing the relay coil. The normally open contact closes, forming a current path between the PTC module and the load circuit. In the overcurrent protection triggered state, the PTC module presents a high-impedance state, causing the second switching unit to turn off. After the relay coil is de-energized, the normally open contact automatically resets and opens, cutting off the load circuit current. This structure achieves circuit isolation through the mechanical separation of the relay's physical contacts, avoiding leakage current problems in the semiconductor device's off state.

[0101] In this embodiment, the relay unit achieves complete isolation through physical contacts, eliminating the risk of leakage current in the open state. This structural design enables physical isolation control of the load current path, completely cutting off the current path after overcurrent protection is triggered, without relying on the PTC module to maintain a continuously high-impedance state. This structure retains the self-recovery characteristics of the PTC module while reducing maintenance power consumption through the relay unit's dual protection mechanism. It also avoids the overheating and aging problems caused by long-term conduction of semiconductor switching devices, significantly improving the long-term operational stability of the overcurrent protection system.

[0102] In one exemplary embodiment, the second switching unit includes:

[0103] The base of the transistor unit is connected to the third terminal of the control module, the collector of the transistor unit is connected to the third terminal of the first switching unit, and the emitter of the transistor unit is used for grounding.

[0104] Among them, the transistor unit refers to a current-controlled device made of semiconductor material. For example, it can be implemented using an NPN bipolar junction transistor, where the base receives the control signal and the collector and emitter form the main current path.

[0105] For example, when the control module detects that the PTC module is in a high-impedance state, it outputs a low-level signal to the base of the transistor unit, causing the transistor to enter the cutoff state. At this time, no conductive path can be formed between the collector and emitter, the relay unit's coil loses its drive current, and the normally open contact opens. The load circuit is thus cut off, the PTC module stops heating up and gradually cools down to return to a low-impedance state. During this process, the transistor unit only needs to withstand a milliamp-level drive current to complete the relay control, without needing to maintain continuous power consumption.

[0106] In this embodiment, the drive circuit is directly constructed using a transistor unit. The transistor's fast switching characteristic allows the relay to disconnect within microseconds, effectively shortening the duration of the fault state. This structure simplifies the design of the relay drive circuit, reduces overall system power consumption, and improves the determinism of overcurrent protection operation.

[0107] In one exemplary embodiment, the mechanical switch module includes:

[0108] The diode, with its anode connected to the first terminal of the control module;

[0109] The first mechanical switch has a first end connected to the cathode of a diode, and a second end of the first mechanical switch is used to connect to the first AC input terminal of an external AC power supply.

[0110] The second mechanical switch is the first terminal of the first control module, and the second terminal of the second mechanical switch is used to connect to the first AC input terminal of an external AC power supply.

[0111] Here, diode refers to a semiconductor device with unidirectional conductivity, such as a rectifier diode made of silicon or germanium, used to prevent reverse current from interfering with the input of the control module. First and second mechanical switches refer to devices that achieve circuit switching through physical contacts, such as rocker switches or push-button switches. The two are connected in parallel to form a redundant structure for multi-position mechanical switch control.

[0112] For example, when the mechanical switch module is in the closed state, the first AC input terminal of the external AC power supply transmits a conduction signal to the control module through the first or second mechanical switch. The presence of the diode blocks the reverse current during the negative half-cycle of the AC power supply, preventing the control module input terminal from experiencing reverse voltage. The parallel design of the two mechanical switches ensures that closing either switch can trigger the detection signal of the control module. After overcurrent protection is triggered, the control module can disconnect the load circuit by detecting the open state of the mechanical switch module.

[0113] In this embodiment, a parallel dual mechanical switch structure can be used to achieve multi-level mechanical switch control, and even if a single contact fails, the other contact can still maintain signal transmission, thus improving detection reliability.

[0114] In one exemplary embodiment, the overcurrent protection circuit further includes:

[0115] The differential mode interference suppression circuit has a first AC input terminal for connecting to an external AC power supply, and is also connected to the second terminal of the mechanical switch module.

[0116] The second terminal of the differential mode interference suppression circuit is used to connect to the second AC input terminal of the external AC power supply, and is also connected to one end of the PTC module;

[0117] The third terminal of the differential mode interference suppression circuit is used for grounding.

[0118] The differential-mode interference suppression circuit refers to a filter circuit used to suppress high-frequency noise between AC power lines. For example, it can be implemented using a combination of a common-mode inductor and an X-capacitor, where the common-mode inductor suppresses common-mode interference and the X-capacitor absorbs differential-mode interference. Grounding the third terminal of the differential-mode interference suppression circuit refers to connecting the neutral point of the filter circuit to ground. This can be achieved, for example, through a Y-capacitor or a metal casing, forming a discharge path for high-frequency interference.

[0119] For example, a differential-mode interference suppression circuit is configured between the AC power input terminal and the mechanical switch module and PTC module. It suppresses common-mode noise in the two power lines using a common-mode inductor, and absorbs inter-line voltage fluctuations using an X capacitor. When transient voltage spikes or high-frequency interference exist in the AC power supply, this circuit effectively reduces the impact of interference signals on the detection circuit of the mechanical switch module and the resistance detection circuit of the PTC module, preventing the control module from making erroneous decisions due to interference signals. After the neutral point of the differential-mode interference suppression circuit is grounded, residual interference signals can be directed to ground through the Y capacitor, further reducing the system's sensitivity to ground potential fluctuations.

[0120] In this embodiment, by setting a differential-mode interference suppression circuit at the power input terminal, conducted interference signals can be effectively filtered out, ensuring the accuracy of mechanical switch on / off detection and PTC resistance detection. Thus, through the above structural design, the impact of high-frequency interference conducted from the AC power line on the overcurrent detection circuit can be significantly reduced, avoiding false disconnection or delayed operation of the switching circuit due to transient voltage fluctuations, thereby improving the reliability of the overcurrent protection system in electromagnetic interference environments.

[0121] In one exemplary embodiment, such as Figure 5 As shown, Figure 5The present invention provides a schematic diagram of a specific circuit implementation of an overcurrent protection circuit. The overcurrent protection circuit may include, for example, a mechanical switch module 210, a mechanical switch detection circuit 260, a PTC module 220, a PTC signal detection circuit 250, a switch circuit 230, a control module 240, a power supply module 270, a differential mode interference suppression circuit, and a fuse F1.

[0122] The load circuit 40 may include a charging diode D2 and a rectifier bridge DB1.

[0123] The mechanical switch module 210 may include mechanical switch K1, mechanical switch K2, and diode D1, thus forming a two-position mechanical switch.

[0124] The mechanical switch detection circuit 260 may include resistors R1, R2, and R3.

[0125] The differential mode interference suppression circuit may include a capacitor C2, a resistor R5, a resistor R7, a resistor R4, a varistor RV1, and a surge protection module.

[0126] The power module 270 is a non-isolated electronic power supply, which may include a power conversion module, capacitor EC1, and resistor R6 to form a low-voltage power supply.

[0127] PTC module 220 may include a thermistor PT1 as a PTC protection element.

[0128] The PTC signal detection circuit 250 may include resistors R8 and R9.

[0129] The switching circuit 230 may include a relay RLY1, a diode D3, a transistor Q1, a resistor R10, and a resistor R11.

[0130] The control module 240 may include an MCU module U1 and a capacitor C1.

[0131] For example, a specific connection structure can be as follows: Figure 5 As shown, each pin of the MCU module U1 is connected to the port of the relevant module. For example, the K-START pin is connected to the K-START port to realize signal detection of the mechanical switch module 210.

[0132] It is understood that this embodiment can be used as a specific implementation of the overcurrent protection circuit in the above embodiments. Therefore, this embodiment can be used to explain the above embodiments, and will not be repeated here.

[0133] Optionally, the circuit integrates a differential-mode interference suppression circuit, combined with an electronic power supply, MCU, PTC, and dual-state detection circuit. When the MCU identifies the high-impedance protection state through the PTC state detection circuit, it immediately triggers the protection lockout logic: disconnecting the load drive circuit from the relay circuit, putting the PTC in a zero-current open-circuit state, and retaining only the detection circuit for low-power operation. This lockout state is maintained by the MCU program until power is restored, completely eliminating the risk of self-recovery.

[0134] Specifically, when the mechanical switch is triggered, the MCU can determine whether the mechanical switch has been triggered by the level change of the mechanical switch detection circuit 260, and control the switching circuit 230. The relay RLY1 of the switching circuit 230 is energized, making the load circuit 40 conduct. The PTC element PT1 is connected in series in the load circuit 40. When the load current is abnormally large, the current of the PTC element PT1 rises sharply and causes the PTC element PT1 to heat up to above 100°C. Due to the characteristics of PTC, the PTC element PT1 will be in a high-impedance state. The MCU can detect the signal level through the PTC signal detection circuit 250. After digital filtering by the program (about 100ms), it is determined that the PTC protection element has been protected and is in a high-impedance state. The MCU can turn off the drive level of the switching circuit 230, so that the entire load circuit 40 is disconnected, the PTC protection element is de-energized, and the MCU program enters the holding lock state. The entire product cannot continue to work without being powered off.

[0135] The differential-mode interference suppression circuit can effectively resist transient surge voltages and high-frequency interference in the power grid, maintaining stable circuit operation. Simultaneously, this module can also suppress electromagnetic interference generated during the operation of the load circuit 40 from flowing back into the power grid, meeting electromagnetic compatibility (EMC) requirements and preventing pollution to the power grid and other electrical equipment.

[0136] In this embodiment, when the MCU (control module 240) is locked, the PTC draws zero current, and the surface temperature gradually decreases, resolving the issue of continuous overheating after overcurrent protection in handheld devices. A wide-voltage power supply is used, adapting to voltages from 85-264V, and it can still stably maintain the protected state in low-voltage scenarios of 100-127V. MCU-controlled protection locking prevents protection failure due to PTC self-reset, significantly improving reliability. Integrated differential-mode interference suppression and surge protection meet EMC requirements and reduce circuit safety risks.

[0137] In one exemplary embodiment, an electronic device is provided, including a load circuit and an overcurrent protection circuit as described above; the overcurrent protection circuit is used to protect the load circuit from overcurrent.

[0138] In this context, "electronic equipment" refers to devices that include electric drive functions and require current protection. Examples include household appliances, industrial equipment, or vehicle systems. These devices must have an internal load circuit with a conductive path. The load circuit is a closed current path consisting of a power source, wires, and electrical components. It can be implemented using a series or parallel structure, and its current carrying capacity must match the equipment's power requirements. "Overcurrent protection circuit" refers to a protection device that disconnects the circuit by detecting abnormal current conditions. It can be implemented using a composite circuit structure including a mechanical switch module, a PTC module, and a control module, achieving a dual protection mechanism through the coordinated control of mechanical contacts and semiconductor switches.

[0139] For example, when the mechanical switch module is closed, the control module is triggered and drives the switching circuit to conduct, forming a complete current path in the load circuit. When the load current exceeds the threshold, causing the PTC module temperature to rise, its resistance increases to a preset high-resistance state. At this point, the control module detects this resistance change and immediately cuts off the switching circuit, forcibly interrupting the current path. During this process, the mechanical switch module remains closed, but the disconnection of the switching circuit causes the load circuit to lose its conductive path, thereby achieving overcurrent protection.

[0140] In this embodiment, the protection mechanism is activated only briefly upon overcurrent triggering, significantly reducing the PTC operating temperature. Through the above technical solution, this application quickly cuts off the conductive path when an overcurrent occurs, avoiding the performance degradation problem caused by long-term high-temperature operation of the PTC in traditional solutions. By coordinating the control of mechanical and semiconductor switches, the high current-carrying capacity of the mechanical contacts is preserved while achieving the fast response characteristics of electronic control. This composite protection mechanism effectively improves the response speed and operational reliability of overcurrent protection while ensuring current carrying capacity.

[0141] The aforementioned overcurrent-included circuit can be applied to handheld devices or similar devices with load loops, such as mobile phones, tablets, or video game devices.

[0142] In the description of this specification, the references to terms such as "some embodiments," "other embodiments," "specific implementation," and "another implementation" refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example that are included in at least one embodiment or example of this application. In this specification, the illustrative descriptions of the above terms do not necessarily refer to the same embodiments or examples.

[0143] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, article, or apparatus that includes said element.

[0144] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The various embodiments can be combined as needed, and the same or similar parts can be referred to each other.

[0145] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An overcurrent protection circuit, characterized in that, The circuit is used for overcurrent protection of the load circuit and includes: The mechanical switch module has a first end for connecting to the first end of the load circuit and for controlling the conduction of the load circuit; the second end of the mechanical switch module is for connecting to the first AC input terminal of an external AC power supply. The PTC module is connected at one end to the second AC input terminal of the external AC power supply; A switching circuit, with its first terminal connected to the other terminal of the PTC module; and its second terminal connected to the second terminal of the load circuit. The control module has a first terminal connected to the mechanical switch module, a second terminal connected to the other terminal of the PTC module, and a third terminal connected to the third terminal of the switch circuit. The control module is used to control the switch circuit to close when it detects that the mechanical switch module is closed, so as to make the load circuit conduct; the control module is also used to control the switch circuit to open when it detects that the PTC module presents a preset high resistance state.

2. The overcurrent protection circuit according to claim 1, characterized in that, The overcurrent protection circuit also includes: The PTC signal detection circuit has a first terminal connected to the other terminal of the PTC module, and a second terminal connected to the second terminal of the control module. The PTC signal detection circuit is used to detect the signal level of the PTC module, and the signal level indirectly represents the impedance state of the PTC module.

3. The overcurrent protection circuit according to claim 1, characterized in that, The overcurrent protection circuit also includes: A mechanical switch detection circuit has a first terminal connected to the first terminal of the mechanical switch module, and a second terminal connected to the first terminal of the control module; the mechanical switch detection circuit is used to detect the on / off signal of the mechanical switch.

4. The overcurrent protection circuit according to claim 1, characterized in that, The overcurrent protection circuit also includes: The power module has an input terminal for connecting to the first AC input terminal of the external AC power supply, and the output terminals of the power module are respectively connected to the power supply terminal of the control module and the power supply terminal of the switching circuit.

5. The overcurrent protection circuit according to claim 1, characterized in that, The switching circuit includes: The first switching unit has a first end connected to the other end of the PTC module, and a second end of the first switching unit is used to connect to the second end of the load circuit. The second switching unit has its first end connected to the third end of the first switching unit, and its second end connected to the third end of the control module.

6. The overcurrent protection circuit according to claim 5, characterized in that, The first switching unit includes: The relay unit has a normally open contact whose first end is connected to the other end of the PTC module, and a normally open contact whose second end is used to connect to the second end of the load circuit. The input terminal of the relay unit is used to connect to the power supply voltage, and the output terminal of the relay unit is connected to the first terminal of the second switch unit.

7. The overcurrent protection circuit according to claim 5 or 6, characterized in that, The second switching unit includes: The base of the transistor unit is connected to the third terminal of the control module, the collector of the transistor unit is connected to the third terminal of the first switching unit, and the emitter of the transistor unit is grounded.

8. The overcurrent protection circuit according to claim 1, characterized in that, The mechanical switch module includes: The diode, with its anode connected to the first terminal of the control module; A first mechanical switch, with its first end connected to the cathode of the diode, and its second end used to connect to the first AC input terminal of the external AC power supply; The second mechanical switch is the first terminal of the control module, and the second terminal of the second mechanical switch is used to connect to the first AC input terminal of the external AC power supply.

9. The overcurrent protection circuit according to claim 1, characterized in that, The overcurrent protection circuit also includes: The differential mode interference suppression circuit has a first terminal for connecting to the first AC input terminal of the external AC power supply, and is also connected to the second terminal of the mechanical switch module; The second terminal of the differential mode interference suppression circuit is used to connect to the second AC input terminal of the external AC power supply, and is also connected to one end of the PTC module; The third terminal of the differential mode interference suppression circuit is used for grounding.

10. An electronic device, characterized in that, It includes a load circuit and an overcurrent protection circuit as described in any one of claims 1-9; the overcurrent protection circuit is used to provide overcurrent protection for the load circuit.

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