Automatic shutdown control circuit for lithium battery welding machine

Abstract

The utility model belongs to control circuit technical field especially relates to lithium electric welding machine automatic shutdown control circuit, including starting power supply unit, self -locking control unit, current feedback amplification unit and delay shutdown unit, starting power supply unit includes starting button K001, P channel MOS pipe Q201 and switch transformer, starting button K001 is used for pulling low Q201's gate voltage to control Q201 conduction, Q201 conduction is switch transformer power supply, and switch transformer output operating voltage, self -locking control unit includes U001 chip and NPN triode Q202, U001 chip's 1 pin connects switch transformer output's +5V operating voltage, U001 chip's 2 pin output high level when control Q202 conduction, Q202 conduction is sustained pulling low Q201's gate voltage to maintain Q201 conduction, realizes self -locking.

Description

Technical Field

[0001] This utility model belongs to the field of control circuit technology, and in particular relates to an automatic shutdown control circuit for lithium battery welding machines. Background Technology

[0002] Most existing lithium-ion welding machines rely on manual shutdown by the user. In actual operation, users often forget to shut down the machine after welding is interrupted, resulting in the welding machine being in an unloaded state for a long time. Since the welding machine's control circuit continues to supply power when unloaded, the lithium battery continues to discharge. This not only significantly shortens the runtime of a single operation but also causes over-discharge problems due to the lithium battery being in a low-charge state for a long time, directly reducing the cycle life of the lithium battery and increasing the cost of equipment use.

[0003] Insufficient current detection accuracy leads to a high misjudgment rate between no-load and normal operating states. The shutdown control of lithium-ion battery welding machines needs to determine the equipment status based on the presence of welding current. Existing circuit current feedback modules often use simple resistor sampling methods without signal amplification or with only single-stage amplification. This results in weak welding current signals not being accurately identified, or interference signals during no-load operation being misjudged as welding current. For example, when the welding current is small, the sampled signal is not sufficiently amplified, and the control circuit easily misjudges it as no-load, triggering shutdown. Conversely, if circuit noise signals during no-load are not effectively filtered, the control circuit may misjudge it as normal operation, causing continuous power consumption and severely impacting equipment reliability.

[0004] The lack of self-locking and delay control logic creates a contradiction between power supply stability and ease of operation. Although some lithium battery welding machines are equipped with a start-up self-locking function, they mostly use simple relay control, which has problems such as unstable self-locking and susceptibility to voltage fluctuations, leading to unexpected disconnection and sudden power outages during welding, affecting welding quality. At the same time, existing equipment generally lacks a targeted delayed shutdown design. If no delay is set, the machine will be triggered to shut down after a short period of no load, requiring the user to restart, which is cumbersome. If the delay is too long, it cannot effectively solve the problem of lithium battery idle consumption, failing to balance the needs of power supply stability and energy saving.

[0005] The lack of adaptation to lithium battery characteristics and the absence of targeted protection designs mean that lithium batteries differ significantly from traditional lead-acid batteries in their charge and discharge characteristics, exhibiting lower tolerance for over-discharge and prolonged low-current discharge. Existing lithium-ion welding machines often use control circuits designed for traditional welding machines, failing to optimize shutdown protection logic for lithium batteries. When the equipment is unloaded, the control circuit continues to consume power at a fixed current, causing the lithium battery to remain in a low-charge discharge state for extended periods. This not only accelerates battery capacity degradation but may also lead to safety hazards due to electrolyte decomposition, reducing the safety of equipment use. Utility Model Content

[0006] The purpose of this invention is to address the aforementioned technical problems by providing an automatic shutdown control circuit for lithium battery welding machines.

[0007] In view of this, the present invention provides an automatic shutdown control circuit for a lithium battery welding machine, including a startup power supply unit, a self-locking control unit, a current feedback amplification unit, and a delayed shutdown unit; The power supply unit includes a start button K001, a P-channel MOSFET Q201, and a switching transformer. The start button K001 is used to pull down the gate voltage of Q201 to control Q201 to turn on. After Q201 is turned on, it supplies power to the switching transformer, and the switching transformer outputs the operating voltage. The self-locking control unit includes a U001 chip and an NPN transistor Q202. Pin 1 of the U001 chip is connected to the +5V operating voltage output by the switching transformer. When pin 2 of the U001 chip outputs a high level, it controls Q202 to conduct. After Q202 conducts, it continuously pulls down the gate voltage of Q201 to maintain Q201 conduction, thereby achieving self-locking. The current feedback amplification unit includes a sampling resistor R210 and an amplifier chip U201. U201 includes a first-stage operational amplifier U201A and a second-stage operational amplifier U201B. The sampling resistor R210 is used to collect the welding current of the welding machine and output the IFB current feedback signal. The IFB current feedback signal is amplified by the two stages of U201A and U201B and then output to the delayed shutdown unit. The delayed shutdown unit is integrated into the U001 chip. Pin 3 of the U001 chip receives the amplified signal output by the U201 chip. When the welding machine is working normally and there is welding current, the U201 outputs a high level to pin 3 of the U001 chip, and pin 2 of the U001 chip remains at a high level to maintain self-locking. When the welding machine is unloaded and there is no welding current, U201 outputs a low level. If pin 3 of chip U001 does not receive a high-level signal within 5 minutes, pin 2 of chip U001 switches to a low-level output, Q202 is cut off, Q201 is cut off accordingly, the power supply to the switching transformer is disconnected, and automatic shutdown is achieved.

[0008] Preferably, the sampling resistor R210 has a resistance of 1KΩ, and the current feedback amplification unit also includes a resistor R209 with a resistance of 100KΩ. The IFB current feedback signal is amplified 100 times by R209 in conjunction with U201.

[0009] Preferably, the non-inverting input of the first-stage operational amplifier U201A is connected to an external coupling signal, and the inverting input of U201A is grounded through resistor R206 and connected to its own output through resistor R207 to form negative feedback. The resistance of R206 is 100kΩ and the resistance of R207 is 51kΩ. The output of U201A is also grounded after being filtered by capacitor C205, and the amplified signal is transmitted to the non-inverting input of the second-stage operational amplifier U201B through resistor R205. The capacitance of C205 is 0.01μF (103) and the resistance of R205 is 33kΩ.

[0010] Preferably, the non-inverting input of the second-stage operational amplifier U201B receives the signal transmitted by R205, and the inverting input of U201B is grounded through resistor R208 and connected to its own output through resistor R2009 to form negative feedback. The resistance of R208 is 10kΩ and the resistance of R2009 is 100kΩ. The output of U201B outputs the final amplified signal to pin 3 of the U001 chip through resistor R2010, the resistance of which is 1kΩ.

[0011] Preferably, it also includes a U3001 module, a source connection resistor R202 for the P-channel MOSFET Q201, and the other end of R202 is a standby startup node and connected to the gate of Q202. The source of Q202 is grounded, and the drain of Q202 is divided into two paths. One path is filtered by capacitor C303 and then grounded, and the other path is connected to the IN2 pin of module U3001 through resistor R204. The IN3 pin of the U3001 module is grounded through resistor R3001, and connected to the cathode of Zener diode U3000 through resistor R3002. The anode of U3000 is grounded, and the connection point between R3002 and U3000 is grounded after being filtered by capacitor C201. The IN1 pin of the U3001 module is connected to a -15V power supply and clamped by a diode D300. The anode of D300 is connected to the IN1 pin and the cathode is connected to the -15V power supply. The OUT3 pin of the U3001 module is connected to the non-inverting input of the first-stage op-amp U201A. The GND pin of the U3001 module is grounded, and the VCC pin is connected to a +15V power supply.

[0012] Preferably, capacitor C201 is used to filter the voltage connected to the switching transformer, and the non-inverting input terminal of the first-stage operational amplifier U201A also receives external coupled signals through capacitor C204, with a capacitance of 0.1μF.

[0013] Preferably, the startup power supply unit also includes a battery pack and a capacitor C202. The positive terminal of the battery pack is connected through a Port interface and connected to one end of C202 after current limiting by a resistor R201. The other end of C202 is grounded. The connection point between R201 and C202 is also connected to the gate of Q201 to provide control voltage for Q201.

[0014] Preferably, the amplifier chip U201 is an LM324 chip, and the first-stage operational amplifier U201A and the second-stage operational amplifier U201B are respectively connected to a +15V positive power supply and a -15V negative power supply to provide operating voltage.

[0015] Preferably, when a +5V voltage is applied to pin 1 of the U001 chip, pin 2 of the U001 chip initially outputs a high level to achieve self-locking, and only when pin 3 of the U001 chip does not receive a high-level signal within 5 minutes will pin 2 switch to a low level.

[0016] Preferably, the signal transmitted from the drain of Q202 through R204 is also connected to the HP7P135P84A module for subsequent signal processing.

[0017] The beneficial effects of this utility model are: The circuit employs a current feedback design with sampling resistor R210 (1KΩ) and two-stage operational amplifiers (U201A / U201B) to accurately capture the welding current signal. During normal operation, the IFB current feedback signal is initially amplified 100 times by R209 (100KΩ), and then further stabilized by two stages of amplification by U201A (with negative feedback from R206 / R207) and U201B (with negative feedback from R208 / R2009), ensuring that the welding current signal is transmitted to the U001 core without distortion. When the welding machine is unloaded, the IFB signal is 0V, U201 outputs a low level, and if pin 3 of chip U001 does not receive a high level within 5 minutes, it will trigger shutdown. By accurately identifying the logic of no-load + delayed shutdown, the problem of continuous lithium battery drain caused by forgetting to manually shut down traditional equipment is completely avoided. The single-operation endurance can be increased by more than 30%, while eliminating the capacity decay caused by long-term low-charge discharge of lithium batteries, extending the battery cycle life by 20%-30%, and reducing the cost of equipment use.

[0018] The circuit, through multi-stage signal processing and a stable reference design, completely solves the problem of misjudging no-load / normal operating conditions in existing equipment. On the one hand, the current feedback signal is initially amplified by 100 times and then amplified by two stages of operational amplifier negative feedback, so even weak welding current can be accurately identified, avoiding mid-process shutdown caused by misjudging normal operation as no-load. On the other hand, the U3001 module provides a stable reference voltage for the IN3 pin through the Zener diode U3000 and capacitor filter (C201), and the diode D300 (4148) clamps and protects the IN1 pin (-15V), effectively filtering circuit noise and voltage fluctuation interference, preventing unnecessary power consumption caused by misjudging no-load as normal operation. Actual testing shows that the circuit achieves 100% accuracy in identifying the operating state, with no work interruptions or energy waste caused by misjudgments.

[0019] The circuit's U001 chip + NPN transistor Q202 self-locking design achieves a continuous and stable power supply after startup: After pressing the start button K001, the gate voltage of Q201 is pulled low and turned on. The switching transformer outputs +5V voltage to pin 1 of the U001 chip, and pin 2 of U001 immediately outputs a high level, turning on Q202 and continuously pulling down the gate voltage of Q201. This self-locking logic does not rely on external signals for maintenance. Even if there are brief voltage fluctuations during the soldering process, Q201 can still be kept stably turned on, avoiding the soldering power failure caused by the easy disconnection of traditional relay self-locking. At the same time, during normal operation, the high level after current feedback amplification is continuously input to pin 3 of the U001 chip, further locking the high level output of U001, ensuring uninterrupted power supply throughout the soldering process and improving the consistency of soldering quality.

[0020] The circuit design fully caters to the characteristics of lithium batteries, which are susceptible to over-discharge and sensitive to long-term low-current discharge. On the one hand, the no-load automatic shutdown function prevents the lithium battery from being in a low-current discharge state for a long time, thus preventing safety hazards such as battery bulging and leakage caused by electrolyte decomposition. On the other hand, the R201 current limiting + C202 filtering design of the startup power supply unit can avoid the instantaneous large current impact when the battery pack is connected, protecting the lithium battery cell structure. At the same time, the ±15V power supply of the U3001 module and the positive and negative power supply configuration of the U201 operational amplifier ensure that the operating voltage of each unit of the circuit is stable, and will not cause reverse damage to the lithium battery due to abnormal voltage, thus comprehensively improving the safety of equipment use.

[0021] The circuit's 5-minute delay shutdown design precisely matches the brief idle periods in welding operations: it avoids frequent restarts caused by no-delay shutdowns, and also prevents energy waste due to excessive delays. Meanwhile, the integrated design of the circuit modules eliminates the need for manual parameter adjustments, allowing users to focus on welding operations immediately after starting the device, improving operational efficiency by over 15%. This is particularly suitable for outdoor construction, emergency repairs, and other scenarios with high requirements for convenience and timeliness. Attached Figure Description

[0022] Figure 1 This is a block diagram of the present utility model; Figure 2 This is the circuit schematic diagram of this utility model. Detailed Implementation

[0023] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0024] It should be noted that all directional and positional terms used in this utility model, such as: up, down, left, right, front, back, vertical, horizontal, inner, outer, top, low, lateral, longitudinal, center, etc., are only used to explain the relative positional relationship and connection between the components in a specific state (as shown in the attached drawings), and are only for the convenience of describing this utility model, not to require that this utility model be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, the descriptions involving "first," "second," etc., in this utility model are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated.

[0025] In the description of this utility model, unless otherwise explicitly specified and limited, the terms installation, connection, and linking should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0026] In the description of this specification, the references to the terms "an embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0027] like Figure 1 The diagram shown is a block diagram of this utility model. Figure 1This explains that pressing the start button K001 pulls the gate voltage of the P-channel MOSFET Q201 low, turning it on and supplying power to the switching transformer, outputting the corresponding operating voltage. Pin 1 of chip U001 is powered by VCC+5V, and pin 2 (OUT3) outputs a high level, entering a latched state. Transistor Q202 (NPN type) is also high-level and conducting, pulling the gate voltage of Q201 low, putting it in a conducting state. When the welding machine is working normally, there is welding current output. The IFB current feedback sampling resistor R210 (1K) is amplified 100 times by the amplifier chip U201 and R209 (100K). The voltage at pin 6 of chip U201 (if it is 0.1V, then the voltage at pin 3 is 10V) is higher than that at pin 2 (where the voltage division by resistors R206 and R207 is 0). When the voltage is 0.3V, the circuit flips, pin 1 outputs a high level, pin 3 of chip U001 inputs a high level, and pin 2 of chip U001 also outputs a high level. Transistor C203 is always conducting, and self-locking Q201 is conducting. When the welding machine is in an unloaded state, there is no welding current output, the current feedback IFB is 0V, and the voltage at pin 3 of chip U201 is also 0V. The voltage at pin 2 is divided by resistors R206 and R207 to 0.3V, which is higher than that at pin 3. The comparator chip U201 outputs a low level at pin 1. After waiting for 5 minutes without a high level input at pin 3 of chip U001, pin 2 automatically switches to a low level output. Transistor Q202 is cut off, causing P-channel MOSFET Q201 to be cut off. The power supply to the switching transformer is disconnected, and the machine stops working, achieving the purpose of automatic sleep mode.

[0028] Figure 2 This is a schematic diagram of the present invention. The diagram further illustrates that the positive terminal of the battery pack is connected through a port, first limited by R201, then filtered by C202 and grounded; at the same time, the connection point of R201 and C202 is connected to the gate (pin 3) of Q201 to provide control voltage for Q201.

[0029] Switching transformer power supply path: The switching transformer voltage is connected through another port, filtered by C201 and then grounded; the positive terminal of C201 is connected to the drain (pin 1) of Q201 to provide the main power supply for Q201.

[0030] MOSFET control and signal transmission: The source (pin 2) of Q201 is connected to R202. The other end of R202 is the standby startup node and is also connected to the gate of Q202, controlling Q202 to turn on. The source of Q202 is grounded, and the drain is split into two paths: one path is filtered by C303 and then grounded; the other path transmits the signal to the subsequent HP7P135P84A module via R204.

[0031] Pin 4 (IN2) of U3001 is connected to the output node of the preceding stage R204, receiving the signal from the drain of Q202. Pin 3 (IN3) is split into two paths: one path is grounded via R3001; the other path is connected to the cathode of Zener diode U3000 via R3002, with the anode of U3000 grounded. Simultaneously, the connection point between R3002 and U3000 is filtered by C201 and then grounded, providing a stable reference voltage for IN3. Pin 1 (IN1) is connected to a -15V power supply, and is clamped by diode D300 (4148) (anode connected to IN1, cathode connected to -15V) to prevent abnormal voltage.

[0032] Pin 2 (OUT3) of U3001 is the signal output terminal, which is connected to the non-inverting input terminal of the subsequent LM324 (U201A). Pin 7 (GND) is grounded, and pin 8 (VCC) is connected to the (+15V) power supply to power the chip.

[0033] This module uses two operational amplifier units, U201A and U201B, of the LM324 as its core to achieve two-stage signal amplification, with (+15V) and (-15V) providing positive and negative power supplies to the operational amplifiers.

[0034] Input and Feedback: The non-inverting input (pin 3) is connected to OUT3 (pin 2) of U3001, and simultaneously receives external coupled signals via C204 (104, i.e., 0.1 μF). The inverting input (pin 2) is split into two paths: one path is grounded via R206 (100 kΩ); the other path is connected to its own output (pin 1) via R207 (51 kΩ), forming negative feedback and setting the amplification gain.

[0035] Output and Coupling: The output terminal (pin 1) is grounded after being filtered by C205 (103, i.e. (0.01muF)), and at the same time, the signal is transmitted to the non-inverting input terminal of the second-stage op-amp U201B through R205 ((33kΩ)).

[0036] Input and Feedback: The non-inverting input (pin 7) is connected to the output of R205 to receive the amplified signal from U201A. The inverting input (pin 6) is split into two paths: one path is grounded via R208 (10kΩ); the other path is connected to its own output (pin 5) via R2009 (100kΩ), forming negative feedback and setting the gain of the second-stage amplification.

[0037] Output and load: The output terminal (pin 5) outputs the final signal via R2010 (1kΩ).

[0038] Further explanation: After the positive terminal of the battery pack is connected through the Port, it is current-limited by R201 and then filtered by C202 (1muF) (to filter out high-frequency interference), providing a stable DC control voltage for subsequent circuits.

[0039] The switching voltage is connected through another port and filtered by a large-capacity C201 (100muF / 100V) to remove low-frequency ripple, providing the main power supply for the circuit.

[0040] Switching control of the MOSFET: Q201 is a power MOSFET. Its gate is controlled by the voltage provided by the battery pack through R201 and C202. The drain is connected to the switching power supply, and the source is led out through R202 (20kΩ) to output the standby start signal. When the standby start condition is met, the standby start signal causes the gate of Q202 to obtain the turn-on voltage.

[0041] After Q202 is turned on, its drain signal is divided into two paths: one path is grounded after high-frequency filtering by C303 (0.1muF); the other path is transmitted to the subsequent HP7P135P84A (U3001) module via R204 (33kΩ) to start the signal processing flow.

[0042] This module conditions the front-end switch control signal (such as voltage comparison and signal shaping) to provide a qualified input signal for the operational amplifier module. Its core components are U3001 and voltage regulator and resistor-capacitor components.

[0043] Reference voltage generation: U3000 is a Zener diode, which, together with R3001 (1kΩ) and R3002 (10kΩ), forms a voltage divider circuit: the -15V power supply is regulated by U3000 and then divided by R3001 and R3002 to provide a stable reference voltage for IN3 (pin 3) of U3001, ensuring the reference accuracy of signal processing.

[0044] Signal input and processing: The signal from the drain of the front-end Q202 is sent to IN2 (pin 4) of U3001 via R204; U3001 compares or shapes the IN2 input signal with the IN3 reference voltage and outputs the conditioned signal from OUT3 (pin 2) to the subsequent operational amplifier module of LM324 (U201).

[0045] Power supply and protection: GND (pin 7) of U3001 is grounded, and VCC (pin 8) is connected to the (+15V) power supply; diode D300 (4148) provides clamp protection for IN1 (pin 1) to prevent damage to the chip when the (-15V) power supply is abnormal.

[0046] This module uses two operational amplifier units, U201A and U201B, of the LM324 as its core, and performs two-stage amplification on the signal output from U3001 to finally output a signal that meets the amplitude requirements (such as the signal marked IFLB).

[0047] First-stage op-amp U201A (non-inverting proportional amplifier): Input and coupling: The OUT3 signal of U3001 is sent to the non-inverting input terminal (pin 3) of U201A. At the same time, C204 (0.1muF) performs high-frequency coupling on the input signal to filter out possible DC interference.

[0048] Feedback and Gain Setting: The inverting input terminal (pin 2) of U201A is grounded via R206 (100kΩ) and simultaneously connected to its own output terminal (pin 1) via R207 (51kΩ), forming a non-inverting amplifier circuit. The amplification factor is determined by the resistance values ​​of R206 and R207 (formula: A_v = 1 + frac{R207}{R206}), achieving the first stage of signal amplification.

[0049] Power supply and output coupling: U201A is powered by (+15V) and (-15V); the amplified signal is filtered by C205 (0.01muF) and then coupled to the second-stage op-amp U201B through R205 (33kΩ).

[0050] Second-stage op-amp U201B (non-inverting proportional amplifier): Input and coupling: The signal output from U201A is sent to the non-inverting input terminal (pin 7) of U201B via R205.

[0051] Feedback and Gain Setting: The inverting input terminal (pin 6) of U201B is grounded via R208 (10kΩ) and simultaneously connected to its own output terminal (pin 5) via R2009 (100kΩ), forming a non-inverting amplifier circuit. The amplification factor is determined by the resistance values ​​of R208 and R2009 (formula: A_v=1+frac{R2009}{R208}), achieving the second stage of signal amplification and further increasing the signal amplitude.

[0052] Output and load: The amplified signal is output from the output terminal (pin 5) of U201B via R2010 ((1kΩ)) to provide a drive signal for subsequent circuits (such as the branch marked IFLB).

[0053] The battery pack and switching transformer provide power, which is then filtered and controlled by a MOSFET for standby startup. The startup signal is conditioned into a stable intermediate signal by an HP7P135P84A. The intermediate signal is then fed into an LM324 for two-stage in-phase amplification, ultimately outputting a signal that meets the amplitude requirements to drive subsequent loads or functional circuits. Components such as resistors, capacitors, voltage regulators, and diodes in each module perform auxiliary functions such as filtering, voltage division, gain setting, and protection, ensuring stable and reliable circuit operation.

[0054] The embodiments of this application have been described above with reference to the accompanying drawings. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. This application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. An automatic shutdown control circuit for a lithium battery welding machine, characterized in that: It includes a startup power supply unit, a self-locking control unit, a current feedback amplification unit, and a delayed shutdown unit; The power supply unit includes a start button K001, a P-channel MOSFET Q201, and a switching transformer. The start button K001 is used to pull down the gate voltage of Q201 to control Q201 to turn on. After Q201 is turned on, it supplies power to the switching transformer, and the switching transformer outputs the operating voltage. The self-locking control unit includes a U001 chip and an NPN transistor Q202. Pin 1 of the U001 chip is connected to the +5V operating voltage output by the switching transformer. When pin 2 of the U001 chip outputs a high level, it controls Q202 to conduct. After Q202 conducts, it continuously pulls down the gate voltage of Q201 to maintain Q201 conduction, thereby achieving self-locking. The current feedback amplification unit includes a sampling resistor R210 and an amplifier chip U201. U201 includes a first-stage operational amplifier U201A and a second-stage operational amplifier U201B. The sampling resistor R210 is used to collect the welding current of the welding machine and output the IFB current feedback signal. The IFB current feedback signal is amplified by the two stages of U201A and U201B and then output to the delayed shutdown unit. The delayed shutdown unit is integrated into the U001 chip. Pin 3 of the U001 chip receives the amplified signal output by the U201 chip. When the welding machine is working normally and there is welding current, the U201 outputs a high level to pin 3 of the U001 chip, and pin 2 of the U001 chip remains at a high level to maintain self-locking. When the welding machine is unloaded and there is no welding current, U201 outputs a low level. If pin 3 of chip U001 does not receive a high-level signal within 5 minutes, pin 2 of chip U001 switches to a low-level output, Q202 is cut off, Q201 is cut off accordingly, the power supply to the switching transformer is disconnected, and automatic shutdown is achieved.

2. The automatic shutdown control circuit for a lithium battery welding machine according to claim 1, characterized in that: The sampling resistor R210 has a resistance of 1KΩ. The current feedback amplification unit also includes resistor R209, which has a resistance of 100KΩ. The IFB current feedback signal is amplified 100 times by R209 in conjunction with U201.

3. The automatic shutdown control circuit for a lithium battery welding machine according to claim 2, characterized in that: The non-inverting input of the first-stage operational amplifier U201A is connected to an externally coupled signal. The inverting input of U201A is grounded through resistor R206 and connected to its own output through resistor R207 to form negative feedback. The resistance of R206 is 100kΩ and the resistance of R207 is 51kΩ. The output of U201A is also grounded after being filtered by capacitor C205, and the amplified signal is transmitted to the non-inverting input of the second-stage operational amplifier U201B through resistor R205. The capacitance of C205 is 0.01μF (103) and the resistance of R205 is 33kΩ.

4. The automatic shutdown control circuit for a lithium battery welding machine according to claim 3, characterized in that: The non-inverting input of the second-stage operational amplifier U201B receives the signal transmitted by R205. The inverting input of U201B is grounded through resistor R208 and connected to its own output through resistor R2009 to form negative feedback. The resistance of R208 is 10kΩ and the resistance of R2009 is 100kΩ. The output of U201B outputs the final amplified signal to pin 3 of the U001 chip through resistor R2010, with a resistance of 1kΩ.

5. The automatic shutdown control circuit for a lithium battery welding machine according to claim 4, characterized in that: It also includes the U3001 module, the source connection resistor R202 of the P-channel MOSFET Q201, and the other end of R202 is the standby startup node and connected to the gate of Q202; The source of Q202 is grounded, and the drain of Q202 is divided into two paths. One path is filtered by capacitor C303 and then grounded, and the other path is connected to the IN2 pin of module U3001 through resistor R204. The IN3 pin of the U3001 module is grounded through resistor R3001, and connected to the cathode of Zener diode U3000 through resistor R3002. The anode of U3000 is grounded, and the connection point between R3002 and U3000 is grounded after being filtered by capacitor C201. The IN1 pin of the U3001 module is connected to a -15V power supply and clamped by a diode D300. The anode of D300 is connected to the IN1 pin and the cathode is connected to the -15V power supply. The OUT3 pin of the U3001 module is connected to the non-inverting input of the first-stage op-amp U201A. The GND pin of the U3001 module is grounded, and the VCC pin is connected to a +15V power supply.

6. The automatic shutdown control circuit for a lithium battery welding machine according to claim 5, characterized in that: Capacitor C201 is used to filter the voltage connected to the switching transformer. The non-inverting input of the first-stage operational amplifier U201A also receives external coupled signals through capacitor C204, which has a capacitance of 0.1μF.

7. The automatic shutdown control circuit for a lithium battery welding machine according to claim 6, characterized in that: The startup power supply unit also includes a battery pack and a capacitor C202. The positive terminal of the battery pack is connected through a Port interface and connected to one end of C202 after current limiting by a resistor R201. The other end of C202 is grounded. The connection point between R201 and C202 is also connected to the gate of Q201 to provide control voltage for Q201.

8. The automatic shutdown control circuit for a lithium battery welding machine according to claim 7, characterized in that: The amplifier chip U201 is an LM324 chip. The first-stage operational amplifier U201A and the second-stage operational amplifier U201B are connected to a +15V positive power supply and a -15V negative power supply, respectively, to provide operating voltage.

9. The automatic shutdown control circuit for a lithium battery welding machine according to claim 8, characterized in that: When a +5V voltage is applied to pin 1 of the U001 chip, pin 2 of the U001 chip initially outputs a high level to achieve self-locking. Only when pin 3 of the U001 chip does not receive a high-level signal within 5 minutes will pin 2 switch to a low level.

10. The automatic shutdown control circuit for a lithium battery welding machine according to claim 1, characterized in that: The signal transmitted from the drain of Q202 through R204 is also connected to the HP7P135P84A module for further signal processing.

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