Protection circuit of alternating current hot bed and 3D printer

Abstract

The utility model discloses a protection circuit of an alternating current hot bed and a 3D printer. The circuit comprises a current detection circuit, a switching circuit, a hardware self-locking circuit and a controller, a power supply is connected with a power supply end of the alternating current hot bed through the current detection circuit and the switching circuit, and a signal output end of the current detection circuit is connected with an input end of the hardware self-locking circuit. The control end of the switching circuit is connected with the controller and the output end of the hardware self-locking circuit. The controller is used for outputting a hot bed power supply signal to control the switch-on or switch-off of the switching circuit, so that the alternating-current hot bed implements power supply or stops power supply; the current detection circuit is used for detecting the power supply current of the alternating-current hot bed when the switching circuit is switched on and outputting a current detection signal; and the hardware self-locking circuit is used for outputting an over-current detection signal to the switching circuit when the current detection signal is detected to reach a preset over-current detection value so as to control the switching circuit to be cut off, so that the alternating-current hot bed stops supplying power. The circuit can improve the use safety of the alternating-current hot bed.

Description

Technical Field

[0001] The present application relates to the technical field of three-dimensional printing, and in particular to a protection circuit for an AC heated bed and a 3D printer. Background Art

[0002] AC heated beds are currently widely used in 3D printers for their fast heating speeds and minimal power requirements on the power module. However, these beds are typically powered by 220V / 110V high voltage, which exceeds the safe voltage range for human body use. Furthermore, AC heated beds typically operate in rapid motion, placing extremely high demands on the bending life of the wire, posing significant safety risks.

[0003] To address these safety hazards, existing AC heated bed protection circuits primarily employ two methods to ensure power supply safety. The first involves installing protective devices such as temperature control switches within the heated bed to prevent overcurrent and other issues. The second involves monitoring the AC power supply current through a controller and promptly disconnecting the heated bed if a fault such as a short circuit or open circuit is detected.

[0004] However, the first method only protects the AC heated bed itself and cannot disconnect the wires connected to it, so there is still a safety hazard. In the second method, since any electronic device is subject to failure, if the controller fails, the protection function will not be activated, which also poses a safety hazard. Summary of the Invention

[0005] In view of this, the embodiments of the present application provide a protection circuit for an AC heated bed and a 3D printer, the main purpose of which is to solve the technical problem of potential safety hazards in the use of an AC heated bed.

[0006] According to one aspect of the present application, a protection circuit for an AC heated bed is provided. The protection circuit for the AC heated bed includes a current detection circuit, a switch circuit, a hardware self-locking circuit, and a controller, wherein:

[0007] The current input terminal of the current detection circuit is connected to the power supply, the current output terminal of the current detection circuit is connected to the input terminal of the switch circuit, the output terminal of the switch circuit is connected to the power supply terminal of the AC heated bed, the signal output terminal of the current detection circuit is connected to the input terminal of the hardware self-locking circuit, and the control terminal of the switch circuit is connected to the controller and the output terminal of the hardware self-locking circuit respectively;

[0008] The controller is used to output a power supply signal for the heated bed to control the switching circuit to be turned on or off, so that the AC heated bed is powered on or off; the current detection circuit is used to detect the power supply current of the AC heated bed and output a current detection signal when the switching circuit is turned on; the hardware self-locking circuit is used to output an overcurrent detection signal to the switching circuit when it detects that the current detection signal reaches a preset overcurrent detection value, so as to control the switching circuit to be turned off, so that the AC heated bed is powered off.

[0009] In one embodiment, the hardware self-locking circuit includes a comparator module and a signal driving module, wherein the input end of the comparator module is connected to the signal output end of the current detection circuit, the output end of the comparator module is connected to the input end of the signal driving module, and the output end of the signal driving module is respectively connected to the control end of the switch circuit and the input end of the comparator module; the comparator module is used to compare the current detection signal with a reference signal and output a current comparison signal; the signal driving module is used to generate an overcurrent detection signal when the current comparison signal indicates that the current detection signal is greater than or equal to the reference signal, and output the overcurrent detection signal to the switch circuit and the comparator module respectively, so as to cut off the switch circuit and keep the comparator module in a self-locking state, so that the AC heated bed continuously stops supplying power.

[0010] In one embodiment, the comparator module includes a first comparison unit, a second comparison unit, a first reference unit and a second reference unit, wherein the positive input terminal of the first comparison unit is connected to the signal output terminal of the current detection circuit, the negative input terminal of the first comparison unit is connected to the output terminal of the first reference unit, and the output terminal of the first comparison unit is connected to the input terminal of the signal driving module; the positive input terminal of the second comparison unit is connected to the output terminal of the second reference unit, the negative input terminal of the second comparison unit is connected to the signal output terminal of the current detection circuit, and the output terminal of the second comparison unit is connected to the input terminal of the signal driving module.

[0011] In one embodiment, the first comparison unit and the second comparison unit are integrated in a window comparator; and / or, the first reference unit and the second reference unit are voltage divider circuits composed of voltage divider resistors, wherein the first reference unit is used to generate a reference signal corresponding to the current detection signal in the positive half cycle, and the second reference unit is used to generate a reference signal corresponding to the current detection signal in the negative half cycle.

[0012] In one embodiment, the signal driving module includes a first switching tube, a second switching tube, a third switching tube and several resistors, wherein the control end of the first switching tube is connected to the output end of the comparator module through a current-limiting resistor, and the control end of the first switching tube is also connected to the power supply end through a pull-up resistor. The first end of the first switching tube is connected to the power supply end, and the second end of the first switching tube is connected to the control end of the second switching tube and the control end of the third switching tube respectively through current-limiting resistors; the first end of the second switching tube is connected to the input end of the comparator module, and the second end of the second switching tube is grounded; the first end of the third switching tube is connected to the control end of the switching circuit, and the second end of the third switching tube is grounded.

[0013] In one embodiment, the output end of the comparator module includes a first output end and a second output end, the first output end is used to output a current comparison signal corresponding to the current detection signal in a positive half cycle, and the second output end is used to output a current comparison signal corresponding to the current detection signal in a negative half cycle; the signal driving module includes a first diode, a second diode, a fourth switching transistor, a fifth switching transistor, and a plurality of resistors, wherein the anode end of the first diode is connected to the first output end of the comparator module, the anode end of the first diode is further connected to the power supply end via a pull-up resistor, and the cathode end of the first diode is respectively connected to the control end of the fourth switching transistor and the control end of the fifth switching transistor via a current-limiting resistor; the anode end of the second diode is connected to the second output end of the comparator module, the anode end of the second diode is further connected to the power supply end via a pull-up resistor, and the cathode end of the second diode is respectively connected to the control end of the fourth switching transistor and the control end of the fifth switching transistor via a current-limiting resistor; the first end of the fourth switching transistor is connected to the input end of the comparator module, and the second end of the fourth switching transistor is grounded; the first end of the fifth switching transistor is connected to the control end of the switch circuit, and the second end of the fifth switching transistor is grounded.

[0014] In one embodiment, the controller is further connected to the output end of the hardware self-locking circuit, and is further used to receive the overcurrent detection signal and generate an overcurrent alarm signal based on the overcurrent detection signal; and / or, the controller is further connected to the signal output end of the current detection circuit, and is further used to receive the current detection signal and generate the hot bed power supply signal based on the current detection signal.

[0015] In one embodiment, the current detection circuit includes a Hall current sensor and a voltage divider module, wherein the current input end of the Hall current sensor is connected to the power supply, the current output end of the Hall current sensor is connected to the input end of the switching circuit, the signal output end of the Hall current sensor is respectively connected to the input end of the hardware self-locking circuit and the input end of the voltage divider module, and the output end of the voltage divider module is connected to the input end of the controller.

[0016] In one embodiment, the switching circuit includes a sixth switching tube, a seventh switching tube, a photocoupler, a thyristor, and several resistors, wherein the control end of the sixth switching tube is respectively connected to the output end of the controller and the output end of the hardware self-locking circuit, the first end of the sixth switching tube is connected to the control end of the seventh switching tube through a current-limiting resistor, and the second end of the sixth switching tube is grounded; the control end of the seventh switching tube is also connected to the first end of the seventh switching tube through a current-limiting resistor, the first end of the seventh switching tube is connected to a power supply end, and the second end of the seventh switching tube is connected to the anode input end of the photocoupler; the cathode input end of the photocoupler is grounded through a current-limiting resistor, the first output end of the photocoupler is connected to the current output end of the current detection circuit through a current-limiting resistor, and the second output end of the photocoupler is connected to the control end of the thyristor; the first end of the thyristor is connected to the current output end of the current detection circuit as the input end of the switching circuit, and the second end of the thyristor is connected to the power supply end of the AC heated bed as the output end of the switching circuit.

[0017] According to another aspect of the present application, a 3D printer is provided, comprising the protection circuit of the AC heated bed as described in any one of the above embodiments.

[0018] By means of the above technical solution, the embodiment of the present application provides a protection circuit for an AC heated bed and a 3D printer. By setting a current detection module, a switch module, a hardware self-locking module and a controller in the circuit, the power supply current of the AC heated bed can be detected in real time. When an abnormal situation such as overcurrent is detected, the power supply is quickly cut off by hardware self-locking, thereby avoiding equipment failure or safety accidents caused by excessive current, ensuring the safe and stable use of the AC heated bed. The above circuit does not rely on the soft control of devices such as controllers, and can avoid safety hazards caused by failure of electronic devices. In addition, the above circuit can directly cut off the connection between the AC power and the heated bed wire, avoiding the occurrence of safety accidents such as wire fire and electric shock, greatly improving the safety of the use of the AC heated bed.

[0019] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0021] Figure 1 The figure shows a circuit structure diagram of a power supply circuit of an AC heated bed provided by the prior art;

[0022] Figure 2 A schematic diagram of the circuit structure of a protection circuit for an AC heated bed provided in an embodiment of the present application is shown;

[0023] Figure 3 A schematic diagram of the circuit structure of another protection circuit for an AC heated bed provided in an embodiment of the present application is shown;

[0024] Figure 4 A schematic diagram of the circuit structure of a comparator module provided in an embodiment of the present application is shown;

[0025] Figure 5 A schematic diagram of the circuit structure of a signal driving module provided in an embodiment of the present application is shown;

[0026] Figure 6 A schematic diagram of the circuit structure of another comparator module provided in an embodiment of the present application is shown;

[0027] Figure 7 A schematic diagram of the circuit structure of another signal driving module provided in an embodiment of the present application is shown;

[0028] Figure 8 A schematic diagram of the circuit structure of another protection circuit for an AC heated bed provided in an embodiment of the present application is shown;

[0029] Figure 9 A schematic diagram of the circuit structure of a current detection circuit and a switch circuit provided in an embodiment of the present application is shown;

[0030] Figure 10 A schematic structural diagram of the layout of a protection circuit of an AC heated bed provided in an embodiment of the present application on a circuit board is shown. DETAILED DESCRIPTION

[0031] The present application will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that, unless there is a conflict, the embodiments and features in the embodiments of the present application can be combined with each other.

[0032] Reference Figure 1 , provides a circuit structure diagram of the power supply circuit of the AC heated bed in the prior art. Figure 1 As shown, in the prior art, a switching device, such as a thyristor (SCR), is typically placed between the AC power supply and the AC heated bed. A controller sends control signals to the SCR to enable or disable power to the AC heated bed. Currently, to address potential safety hazards associated with AC heated beds, protective measures are typically implemented. For example, protective devices such as temperature-controlled switches are installed to prevent overcurrent and other issues. Alternatively, a controller monitors the AC power supply current and promptly disconnects the AC heated bed if a fault such as a short circuit or open circuit is detected. However, installing a temperature-controlled switch in the AC heated bed only protects the heated bed itself and does not de-energize the wires connected to it, thus presenting a potential safety hazard. Furthermore, since any electronic device is subject to failure, if the controller fails, the protective function will not activate, creating a significant safety hazard. In severe cases, this can even lead to serious safety incidents such as overcurrent and fire.

[0033] There is a big safety hazard in the use of AC heated bed. In one embodiment, Figure 2 As shown, a protection circuit for an AC heated bed is provided, which includes a current detection circuit 10, a switch circuit 20, a hardware self-locking circuit 30, and a controller 40. The current input terminal of the current detection circuit 10 is connected to a power supply, the current output terminal of the current detection circuit 10 is connected to the input terminal of the switch circuit 20, the output terminal of the switch circuit 20 is connected to the power supply terminal of the AC heated bed 50, the signal output terminal of the current detection circuit 10 is connected to the input terminal of the hardware self-locking circuit 30, and the control terminal of the switch circuit 20 is connected to the output terminals of the controller 40 and the hardware self-locking circuit 30, respectively. In this embodiment, the controller 40 can be used to output a heated bed power supply signal to control the switch circuit 20 to be turned on or off, thereby enabling or disabling power to the AC heated bed 50. The current detection circuit 10 can be used to detect the power supply current of the AC heated bed 50 when the switch circuit 20 is turned on, and output a current detection signal. The hardware self-locking circuit 30 can be used to output an overcurrent detection signal to the switch circuit 20 when it detects that the current detection signal reaches a preset overcurrent detection value, thereby controlling the switch circuit 20 to be turned off, thereby disabling power to the AC heated bed.

[0034] Specifically, when the system is powered on, the controller 40 typically does not control the switch circuit 20 to conduct. That is, in the initial state, the AC heated bed 50 is typically not set to a powered state. During operation of the AC device, the controller 40 can determine whether to power the AC heated bed 50 through a pre-set program or a control command sent by the user. Furthermore, if it is determined that the AC heated bed 50 needs to be powered, the controller 40 will issue a power supply signal to control the switch circuit 20 to conduct, thereby controlling the switch circuit 20 to conduct the AC power supply, thereby providing the AC heated bed 50 with the required AC power. During the power supply process, the current detection circuit 10 will monitor the current flowing through the AC heated bed in real time and send the detected current detection signal to the hardware self-locking circuit 30. If the hardware self-locking circuit 30 detects that the current detection signal exceeds a preset overcurrent detection value, it will immediately generate an overcurrent detection signal and send the overcurrent detection signal to the control terminal of the switch circuit 20 to control the switch circuit 20 to turn off, thereby quickly cutting off power to the AC heated bed, thereby preventing equipment damage or safety hazards caused by overcurrent. In this embodiment, the timing and manner of the controller 40 sending the hot bed power supply signal can be set according to actual conditions, and this embodiment does not specifically limit this.

[0035] The AC heated bed protection circuit provided in the above embodiment, by providing a current detection module, a switch module, a hardware self-locking module, and a controller within the circuit, can detect the AC heated bed's supply current in real time. When an abnormality such as overcurrent is detected, the power supply is quickly cut off through a hardware self-locking mechanism. This prevents equipment failure or safety incidents caused by excessive current, thereby ensuring the safe and stable use of the AC heated bed. The above circuit does not rely on soft control of components such as a controller, thus avoiding safety hazards caused by electronic device failure. Furthermore, the above circuit can directly cut off the connection between the AC power and the heated bed wires, preventing safety incidents such as wire fires and electric shocks, greatly improving the safety of the AC heated bed.

[0036] It should be noted that the circuit connection method and component selection of each circuit module in the AC heated bed protection circuit can be determined based on actual circumstances and are not specifically limited in this embodiment. The circuit functions of the AC heated bed protection circuit provided in this embodiment are primarily implemented through the circuit connection relationships between the various circuit modules, and do not rely on the implementation of the program modules within a particular circuit module. Furthermore, each circuit module can be implemented using either analog or digital circuits, and for circuit modules that can be embedded with program modules, the module functions can be implemented using program modules provided by existing technologies.

[0037] In one embodiment, Figure 3As shown, the hardware self-locking circuit 30 includes a comparator module 31 and a signal driving module 32. The input end of the comparator module 31 is connected to the signal output end of the current detection circuit 10, the output end of the comparator module 31 is connected to the input end of the signal driving module 32, and the output end of the signal driving module 32 is respectively connected to the control end of the switch circuit 20 and the input end of the comparator module 31. In this embodiment, the comparator module 31 can be used to compare the current detection signal with the reference signal and output a current comparison signal; the signal driving module 32 can be used to generate an overcurrent detection signal when the current comparison signal indicates that the current detection signal is greater than or equal to the reference signal, and output the overcurrent detection signal to the switch circuit 20 and the comparator module 31 respectively, so as to turn off the switch circuit 20 and keep the comparator module 31 in the self-locking state, thereby keeping the AC heated bed 50 in a state of continuous power outage.

[0038] Specifically, the comparator module 31 in the hardware self-locking circuit 30 can receive the current detection signal output by the current detection circuit 10 and compare the current detection signal with a preset reference signal through hardware. When the comparator module 31 detects that the current detection signal is greater than or equal to the preset reference signal, it will output a corresponding current comparison signal to the signal driving module 32. Subsequently, the signal driving module 32 will generate an overcurrent detection signal through hardware and send the overcurrent detection signal to the switch circuit 20 and the comparator module 31. In this embodiment, the overcurrent detection signal not only causes the switch circuit 20 to immediately disconnect to cut off the power supply to the AC heated bed 50, but also causes the comparator module 31 to enter a self-locking state, thereby preventing the system from automatically restoring power or level jumps and other faults, thereby ensuring the safety of the AC heated bed.

[0039] It should be noted that the hardware method refers to a method of realizing a specific circuit function through physical circuits, electronic components and their mutual connection relationship. In this embodiment, it refers to a method of realizing the comparison of the current detection signal and the preset reference signal through physical circuits and their connection relationship. The implementation of the above-mentioned current comparison function does not rely on the instructions of the software program or controller to execute, that is, it does not rely on the soft control implementation of devices such as controllers, but relies on the design of the circuit itself and the characteristics of the components to automatically complete the predetermined operation. Compared with the soft control of devices such as controllers, the current comparison function is realized by hardware, which has a faster response speed and higher reliability, and does not rely on any software program, and is more suitable for application scenarios with high requirements for safety and stability.

[0040] The hardware self-locking circuit provided in the above embodiment, by providing a comparator module and a signal driver module, can quickly cut off the power supply to the AC heated bed through hardware when an overcurrent anomaly occurs, thereby preventing equipment damage or safety accidents that may be caused by current overload, and improving the stability and safety of the circuit. In addition, the hardware self-locking circuit does not rely on soft control of devices such as controllers and can directly cut off the power supply, thus avoiding safety hazards caused by electronic device failure. At the same time, the circuit can avoid abnormal issues such as power restoration or level jumps in the circuit, thereby further improving the safety and stability of the circuit.

[0041] In one embodiment, Figure 4 As shown, the comparator module includes a first comparison unit, a second comparison unit, a first reference unit, and a second reference unit. The positive input terminal LIMIT_IN of the first comparison unit is connected to the signal output terminal ADC1 of the current detection circuit and receives the current detection signal output by the current detection circuit. The negative input terminal of the first comparison unit is connected to the output terminal VREF1 of the first reference unit, and the output terminal LIMIT_OUT of the first comparison unit is connected to the input terminal of the signal driving module. The positive input terminal of the second comparison unit is connected to the output terminal VREF2 of the second reference unit, the negative input terminal LIMIT_IN of the second comparison unit is connected to the signal output terminal of the current detection circuit, and the output terminal LIMIT_OUT of the second comparison unit is connected to the input terminal of the signal driving module.

[0042] Specifically, in the comparator module, the current detection circuit can directly connect the current detection signal output from the ADC1 port to the positive input terminal LIMIT_IN of the first comparison unit. At the same time, the reference voltage VREF1 generated by the first reference unit can be connected to the negative input terminal of the first comparison unit to form a comparison reference. Subsequently, the first comparison unit can compare the current detection signal with the reference voltage, and its comparison result can be output to the signal driving module via the LIMIT_OUT port to control the subsequent signal driving module. Correspondingly, the positive input terminal of the second comparison unit can receive the reference voltage VREF2 from the second reference unit, while its negative input terminal LIMIT_IN is connected to the signal output terminal ADC1 of the current detection circuit to achieve signal multiplexing. The second comparison unit can also perform a comparison operation and output the comparison result to the signal driving module via the LIMIT_OUT port. In this embodiment, the first comparison unit and the second comparison unit can respectively compare the overcurrent conditions of the current detection signal in the positive half-cycle and the negative half-cycle, thereby comprehensively monitoring the power supply current throughout the entire cycle.

[0043] The comparator module provided in the above embodiment, by providing a first and second comparison unit, as well as first and second reference units corresponding to the first and second comparison units, can comprehensively monitor overcurrent conditions in the current detection signal throughout the entire cycle. This circuit improves the accuracy and reliability of AC power detection, enhances the protection capabilities of the AC heated bed, and ensures a timely response to any current anomalies within any half-cycle, thereby ensuring the safety of the AC heated bed.

[0044] In one embodiment, Figure 4 As shown, the first comparison unit and the second comparison unit can be integrated into the window comparator U10. Furthermore, the first reference unit can be a voltage divider circuit composed of voltage divider resistors R12 and R13, and the second reference unit can be a voltage divider circuit composed of voltage divider resistors R14 and R15. The first reference unit can be used to generate a reference signal corresponding to the positive half-cycle of the current detection signal and output it through the output terminal VREF1 of the first reference unit; the second reference unit can be used to generate a reference signal corresponding to the negative half-cycle of the current detection signal and output it through the output terminal VREF2 of the second reference unit.

[0045] Specifically, the first comparison unit and the second comparison unit can be integrated into a window comparator U10 to achieve full-cycle comparison of the current detection signal. In this embodiment, the window comparator U10 can take up less space than using two comparator units to compare the reference signal, and is convenient for the design and line layout of the circuit module. Furthermore, the first reference unit can be formed by a voltage divider circuit composed of voltage divider resistors R12 and R13, and can generate a reference signal corresponding to the current detection signal in the positive half cycle, and then provide the reference signal to the first comparison unit through its output end. Similarly, the second reference unit is also formed by a voltage divider circuit composed of voltage divider resistors R14 and R15, and generates a reference signal corresponding to the current detection signal in the negative half cycle, and then provides the reference signal to the second comparison unit through the output end. In this way, whether in the positive half cycle or the negative half cycle of the current, a corresponding reference signal can be generated to compare with the current detection signal, thereby improving the accuracy and reliability of current detection.

[0046] The comparator module provided in the above embodiment can perform comprehensive and accurate comparison of current detection signals by providing a window comparator and a reference unit composed of voltage-dividing resistors in the comparator module. Accurate comparison can be performed using the corresponding reference signal in both the positive and negative half-cycles of the current, thereby improving the accuracy and reliability of current detection. Furthermore, the use of the window comparator reduces the volume occupied by the comparator module and improves the convenience of the design and layout of the comparator module.

[0047] In one embodiment, Figure 5 As shown, the signal driving module includes a first switch tube Q5, a second switch tube Q9, a third switch tube Q8 and several resistors. The control end of the first switch Q5 is connected to the output end LIMIT_OUT of the comparator module via a current-limiting resistor R16. The control end of the first switch Q5 is also connected to the power supply end 5V_LIMIT via a pull-up resistor R30. The first end of the first switch Q5 is connected to the power supply end 5V_DELAY. The second end of the first switch Q5 is connected to the control end of the second switch Q9 via a current-limiting resistor R32. The first end of the second switch Q9 is connected to the input end of the comparator module, and the second end of the second switch Q9 is grounded. The second switch Q9 can be used to output an overcurrent detection signal to the comparator module to cause the comparator module to self-lock. The second end of the first switch Q5 is also connected to the control end of the third switch Q8 via a current-limiting resistor R17. The first end of the third switch Q8 is connected to the control end of the switch circuit, and the second end of the third switch Q8 is grounded. The third switch Q8 can be used to output an overcurrent detection signal to the switch circuit to turn off the switch module, thereby stopping power supply to the AC heated bed.

[0048] Specifically, when the comparator module detects an overcurrent condition, it can output a low-level current comparison signal to the control end of the first switch tube Q5 through its output terminal LIMIT_OUT. After receiving the current comparison signal, the first switch tube Q5 will automatically turn on and transmit the voltage of the power supply end to the control end of the second switch tube Q9, so that Q9 is turned on. After Q9 is turned on, the overcurrent detection signal can be fed back to the input end of the comparator module to achieve a self-locking function. At the same time, the conduction of the first switch tube Q5 will also trigger the conduction of the third switch tube Q8. After the third switch tube Q8 is turned on, the overcurrent detection signal can be transmitted to the control end of the switch circuit, causing the switch module to be cut off, thereby quickly cutting off the power supply to the AC hot bed to prevent damage to the equipment due to overcurrent.

[0049] The signal driver module provided in the above embodiment, by providing first, second, and third switching transistors within the signal driver module, can rapidly detect and immediately respond to overcurrent comparison signals. When the comparator module detects an overcurrent, the signal driver module quickly self-locks the comparator module and cuts off power, thereby improving circuit safety and reliability, thereby ensuring the safe use of equipment such as AC heated beds.

[0050] In one embodiment, Figure 6As shown, the output end of the comparator module includes a first output end LIMIT_OUT_H and a second output end LIMIT_OUT_L, wherein the first output end LIMIT_OUT_H can be used to output a current comparison signal corresponding to the positive half cycle of the current detection signal, and the second output end LIMIT_OUT_L can be used to output a current comparison signal corresponding to the negative half cycle of the current detection signal. Figure 7 As shown, the signal driving module includes a first diode D83, a second diode D84, a fourth switch transistor Q13, a fifth switch transistor Q14, and several resistors. The anode terminal of the first diode D83 is connected to the first output terminal LIMIT_OUT_H of the comparator module and is also connected to the power supply terminal 5V_LIMIT via a pull-up resistor R48. The cathode terminal of the first diode D83 is connected to the control terminals of the fourth switch transistor Q13 and the fifth switch transistor Q14 via a current-limiting resistor R32. The anode terminal of the second diode D84 is connected to the second output terminal LIMIT_OUT_L of the comparator module and is also connected to the power supply terminal 5V_LIMIT via a pull-up resistor R49. The cathode terminal of the second diode D84 is connected to the control terminals of the fourth switch transistor Q13 and the fifth switch transistor Q14 via a current-limiting resistor R32. A first end of the fourth switch tube Q13 is connected to the input end of the comparator module, and a second end of the fourth switch tube Q13 is grounded. The fourth switch tube Q13 can be used to output an overcurrent detection signal to the comparator module to cause the comparator module to self-lock. A first end of the fifth switch tube Q14 is connected to the control end of the switch circuit, and a second end of the fifth switch tube Q14 is grounded. The fifth switch tube Q14 can be used to output an overcurrent detection signal to the switch circuit to turn off the switch module, thereby stopping power supply to the AC heated bed.

[0051] Specifically, the comparator module can output the current comparison signal corresponding to the positive half-cycle and the current comparison signal corresponding to the negative half-cycle of the current detection signal through its first output terminal LIMIT_OUT_H and second output terminal LIMIT_OUT_L, respectively. Among them, the first output terminal LIMIT_OUT_H of the comparator module can transmit the signal through the first diode D83, and the second output terminal LIMIT_OUT_L of the comparator module can transmit the signal through the second diode D84. In this embodiment, by providing the first diode D83 and the second diode D84 in the signal driving module, the current comparison signal corresponding to the positive half-cycle and the current comparison signal corresponding to the negative half-cycle can be effectively isolated, thereby avoiding crosstalk between the current comparison signals of the two half-cycles during the transmission process, thereby improving the stability and reliability of the signal, and enabling the subsequent circuit to more accurately receive and process the current comparison signals of the two half-cycles.

[0052] Furthermore, the cathode terminals of both diodes are connected to the control terminals of the fourth switch tube Q13 and the fifth switch tube Q14 via a current-limiting resistor R32. When the comparator module detects that the current detection signal exceeds a preset reference signal, it can output a high-level current comparison signal, turning on D83 or D84, thereby driving the fourth switch tube Q13 and the fifth switch tube Q14 to turn on via the current-limiting resistor R32. After the fourth switch tube Q13 turns on, an overcurrent detection signal can be fed back to the comparator module to achieve self-locking protection. After the fifth switch tube Q14 turns on, an overcurrent detection signal can be fed back to the switch circuit to turn off the switch module, thereby quickly cutting off the power supply to the AC heated bed. In this embodiment, the type of signal output by the comparator module in the overcurrent state (high-level signal or low-level signal) can be set by the reference signal in the comparator module. This embodiment does not specifically limit the setting method of the reference signal.

[0053] The signal driver module provided in the above embodiment, by incorporating components such as diodes, current-limiting resistors, and switching transistors, can rapidly control the cutoff of the switching circuit, thereby effectively implementing overcurrent protection for the AC heated bed. This circuit effectively prevents damage to the device caused by excessive current, improving circuit safety and reliability, and ensuring the safe use of the AC heated bed. Furthermore, by isolating the current comparison signals between the two half-cycles and outputting them, crosstalk between signals can be avoided, improving signal stability.

[0054] In one embodiment, Figure 8 As shown, the controller 40 is also connected to the output end of the hardware self-locking circuit 30, and the controller 40 is also used to receive the overcurrent detection signal and generate an overcurrent alarm signal according to the overcurrent detection signal. Further, the controller 40 is also connected to the signal output end of the current detection circuit 10, and the controller 40 is also used to receive the current detection signal and generate a hot bed power supply signal according to the current detection signal. Specifically, referring to Figure 9 The controller's input terminal ADC can receive the current detection signal output by the current detection chip U7 through the interface J1, so as to identify the working state of the circuit through the current detection signal, such as the open circuit state, the normal working state and the abnormal high current state. Figure 5 、 Figure 7 and Figure 9 The controller can also receive the overcurrent detection signal output by the hardware self-locking circuit through the same interface J1 to identify whether the circuit is currently in an overcurrent state. In other words, the controller can use the same input port to identify whether the circuit is open, normal operation, abnormally high current, or overcurrent, and respond accordingly.

[0055] Specifically, the controller 40 can also be connected to the output terminal of the hardware self-locking circuit 30 to receive the overcurrent detection signal output by the hardware self-locking circuit 30 in real time. Based on this, it generates an overcurrent alarm signal to drive devices such as a buzzer and display to output an abnormal overcurrent condition, thereby prompting the user to disconnect the power supply and ensure safe use of the device. Furthermore, the controller 40 can also be connected to the signal output terminal of the current detection circuit 10 and receive the current detection signal from the current detection chip U7 via an interface. The current detection signal can be used to identify various operating states of the circuit, including open circuit, normal operation, and abnormally high current. In this embodiment, the controller can receive the overcurrent detection signal output by the hardware self-locking circuit 30 and the current detection signal output by the current detection circuit 10 through the same interface to monitor whether the circuit is in an open circuit, normal operation, abnormally high current, or overcurrent state. Through this design, the controller can accurately identify various circuit states in real time and respond accordingly, such as controlling the switch circuit to cut off to stop powering the AC heated bed. Moreover, by multiplexing the ports, the number of ports provided by the controller in the protection circuit can also be reduced.

[0056] The AC heated bed protection circuit provided in the above embodiment, by providing a controller to receive current detection signals and overcurrent detection signals, can monitor the circuit operating status in real time and can quickly identify various abnormal conditions in the circuit, such as open circuit, abnormally high current, and overcurrent, so that corresponding responses can be made accordingly, thereby avoiding equipment damage and safety accidents and ensuring stable operation of the equipment.

[0057] In one embodiment, Figure 9 As shown, the current detection circuit includes a Hall current sensor U7 and a voltage divider module composed of voltage divider resistors R11 and R25. The current input of the Hall current sensor U7 is connected to the AC power supply via power supply interfaces U1, U2, and U3. The current output of the Hall current sensor U7 is connected to the input of the switching circuit. The signal output ADC1 of the Hall current sensor U7 is connected to the input of the hardware self-locking circuit and the input of the voltage divider module, respectively. The output of the voltage divider module is connected to the input ADC of the controller via interface J1.

[0058] Specifically, the Hall current sensor U7 can receive AC power through the power supply interfaces U1, U2, and U3, and connect the AC power to the input of the switching circuit. When the switching circuit is on, the Hall current sensor U7 can output AC power to the power supply of the AC heated bed through the heated bed interfaces U8, U4, and U9, thereby powering the AC heated bed and monitoring the power supply current of the AC heated bed in real time. Furthermore, the signal output terminal ADC1 of the Hall current sensor U7 can be connected to the input terminal of the hardware self-locking circuit and the input terminal of the voltage divider module, thereby achieving dual utilization of the signal. That is, the current detection signal output by the Hall current sensor U7 can be used as the input signal of the hardware self-locking circuit for overcurrent detection, and can also be input into the controller through the voltage divider module to ensure that the detection signal input to the controller is within the appropriate level range.

[0059] The current detection circuit provided in the above embodiment can efficiently and accurately detect AC current by providing a Hall current sensor and a voltage divider module within the current detection circuit. The Hall sensor ensures real-time and accurate current detection, while the voltage divider module improves signal stability and reliability, ensuring that the current detection signal can be accurately recognized by the controller.

[0060] In one embodiment, Figure 9 As shown, the switching circuit includes a sixth switch tube Q3, a seventh switch tube Q4, a photocoupler U5, a thyristor U6, and several resistors. The control terminal of the sixth switch tube Q3 is connected to the output terminal GPIO of the controller and the output terminal OCP of the hardware self-locking circuit, respectively. The first terminal of the sixth switch tube Q3 is connected to the control terminal of the seventh switch tube Q4 via a current-limiting resistor R8. The second terminal of the sixth switch tube Q3 is grounded. The control end of the seventh switch tube Q4 is also connected to the first end of the seventh switch tube Q4 through a current limiting resistor R9 and a filter capacitor C3. The first end of the seventh switch tube Q4 is connected to the power supply end 5V_IN. The second end of the seventh switch tube Q4 is connected to the anode input end of the photoelectric coupler U5. The cathode input end of the photoelectric coupler U5 is grounded through a current limiting resistor R4. The first output end of the photoelectric coupler is connected to the current output end of the current detection circuit (i.e., the current output end of the current detection chip U7) through a current limiting resistor R6. The second output end of the photoelectric coupler U5 is connected to the control end of the thyristor U6. The first end of the thyristor U6 is connected to the current output end of the current detection circuit (i.e., the current output end of the current detection chip U7) as the input end of the switching circuit. The second end of the thyristor U6 is connected to the power supply end of the AC hot bed through ports U8, U4 and U9 and the AC wire as the output end of the switching circuit.

[0061] Specifically, under normal operating conditions, the controller can output a hot bed power supply signal through the GPIO port to control the switching circuit. At this time, the sixth switch Q3 turns on, thereby triggering the seventh switch Q4 to turn on. After the seventh switch Q4 turns on, the voltage at the power supply terminal can be supplied to the anode of the photocoupler U5 through the seventh switch Q4. At the same time, the cathode of the photocoupler U5 is grounded through the current-limiting resistor R4 to form a loop. The voltage difference between the anode and cathode of the photocoupler U5 turns on the internal phototransistor, connecting the two output terminals of the photocoupler, thereby transmitting the AC power output by the current detection chip U7 to the control terminal of the thyristor U6 through the current-limiting resistor R6. When the thyristor U6 receives a control signal that meets the conditions, a low-resistance path is formed within it, thereby transmitting the AC power output by the current detection circuit to the power supply terminal of the AC hot bed, achieving on-off control of the AC hot bed. In the overcurrent state, the overcurrent detection signal will act on the control end of the sixth switch tube Q3, so that the sixth switch tube Q3, the seventh switch tube Q4, the photoelectric coupler U5 and the thyristor U6 are turned off in sequence, thereby controlling the AC heated bed to stop powering, thereby achieving overcurrent protection for the AC heated bed and ensuring the safety of the AC heated bed.

[0062] The switching circuit provided in the above embodiment utilizes cascade control of the sixth and seventh switching transistors, combined with the electrical isolation and signal transmission capabilities of the optocoupler and the switching characteristics of the thyristor (SCR), to achieve precise control of the power supply to the AC heated bed. Furthermore, real-time monitoring of the current signal by the current sensing chip and overcurrent detection by the hardware self-locking circuit ensure circuit safety and stability, effectively preventing abnormal conditions such as overcurrent and ensuring the safe use of the AC heated bed.

[0063] In one embodiment, Figure 10 As shown, the multiple circuit modules of the AC heated bed's protection circuit can be separately arranged on multiple circuit boards and connected via interfaces, allowing for flexible placement of the protection circuit within AC devices such as 3D printers. Specifically, the controller 40 can be separately arranged on a single circuit board, facilitating the deployment of complex control circuits. The current detection circuit 10, switch circuit 20, and hardware self-locking circuit can be co-located on another circuit board and connected to the AC power supply and the AC heated bed's power supply via AC cables and interfaces, respectively, to achieve the AC heated bed's power supply and protection functions.

[0064] Specifically, in the above protection circuit, the controller 40 can be independently deployed on a circuit board to optimize the layout of the control circuit. Simultaneously, the current detection circuit 10, the switch circuit 20, and the hardware self-locking circuit can be integrated on another circuit board to form a compact power management module. The two circuit boards can then be connected via an interface to ensure smooth signal and power transmission.

[0065] The modular design of the above embodiment divides the AC heated bed protection circuit into multiple independent yet collaborative modules, and utilizes interfaces to achieve seamless integration between the modules. This not only simplifies the circuit installation process and reduces maintenance costs, but also makes each circuit module easier to replace and upgrade.

[0066] In another embodiment, a 3D printer is provided, comprising the AC heated bed protection circuit described in any of the above embodiments. The specific implementation process and technical effects of the AC heated bed protection circuit can be referenced to any of the above embodiments and will not be further described here.

[0067] Furthermore, as a refinement and expansion of the specific implementation of the above embodiment, in order to fully illustrate the specific implementation process of this embodiment, a protection circuit of an AC heated bed is provided, such as Figure 2 As shown, the protection circuit of the AC heated bed includes a current detection circuit 10, a switch circuit 20, a hardware self-locking circuit 30, and a controller 40. The current input of the current detection circuit 10 is connected to the power supply, the current output of the current detection circuit 10 is connected to the input of the switch circuit 20, the output of the switch circuit 20 is connected to the power supply of the AC heated bed 50, the signal output of the current detection circuit 10 is connected to the input of the hardware self-locking circuit 30, and the control terminal of the switch circuit 20 is connected to the controller 40 and the output of the hardware self-locking circuit 30, respectively. In this embodiment, the controller 40 can be used to output a heated bed power supply signal to control the switch circuit 20 to be turned on or off, thereby enabling or disabling power to the AC heated bed 50. The current detection circuit 10 can be used to detect the power supply current of the AC heated bed 50 when the switch circuit 20 is turned on, and output a current detection signal. The hardware self-locking circuit 30 can be used to output an overcurrent detection signal to the switch circuit 20 when the current detection signal reaches a preset overcurrent detection value, thereby controlling the switch circuit 20 to be turned off, thereby disabling power to the AC heated bed.

[0068] In this embodiment, if Figure 3As shown, the hardware self-locking circuit 30 includes a comparator module 31 and a signal driving module 32. The input end of the comparator module 31 is connected to the signal output end of the current detection circuit 10, the output end of the comparator module 31 is connected to the input end of the signal driving module 32, and the output end of the signal driving module 32 is respectively connected to the control end of the switch circuit 20 and the input end of the comparator module 31. In this embodiment, the comparator module 31 can be used to compare the current detection signal with the reference signal and output a current comparison signal; the signal driving module 32 can be used to generate an overcurrent detection signal when the current comparison signal indicates that the current detection signal is greater than or equal to the reference signal, and output the overcurrent detection signal to the switch circuit 20 and the comparator module 31 respectively, so as to turn off the switch circuit 20 and keep the comparator module 31 in the self-locking state, thereby keeping the AC heated bed 50 in a state of continuous power outage.

[0069] In this embodiment, if Figure 4 As shown, the comparator module includes a first comparison unit, a second comparison unit, a first reference unit, and a second reference unit. The positive input terminal LIMIT_IN of the first comparison unit is connected to the signal output terminal ADC1 of the current detection circuit and receives the current detection signal output by the current detection circuit. The negative input terminal of the first comparison unit is connected to the output terminal VREF1 of the first reference unit, and the output terminal LIMIT_OUT of the first comparison unit is connected to the input terminal of the signal driving module. The positive input terminal of the second comparison unit is connected to the output terminal VREF2 of the second reference unit, the negative input terminal LIMIT_IN of the second comparison unit is connected to the signal output terminal of the current detection circuit, and the output terminal LIMIT_OUT of the second comparison unit is connected to the input terminal of the signal driving module.

[0070] In this embodiment, if Figure 4 As shown, the first comparison unit and the second comparison unit can be integrated into the window comparator U10. In addition, the first reference unit can be a voltage divider circuit composed of voltage divider resistors R12 and R13, and the second reference unit can be a voltage divider circuit composed of voltage divider resistors R14 and R15.

[0071] Among them, the first reference unit can be used to generate a reference signal corresponding to the current detection signal in the positive half cycle, and output it through the output terminal VREF1 of the first reference unit; the second reference unit can be used to generate a reference signal corresponding to the current detection signal in the negative half cycle, and output it through the output terminal VREF2 of the second reference unit.

[0072] In this embodiment, if Figure 5As shown, the signal driving module includes a first switch tube Q5, a second switch tube Q9, a third switch tube Q8 and several resistors. The control end of the first switch Q5 is connected to the output end LIMIT_OUT of the comparator module via a current-limiting resistor R16. The control end of the first switch Q5 is also connected to the power supply end 5V_LIMIT via a pull-up resistor R30. The first end of the first switch Q5 is connected to the power supply end 5V_DELAY. The second end of the first switch Q5 is connected to the control end of the second switch Q9 via a current-limiting resistor R32. The first end of the second switch Q9 is connected to the input end of the comparator module, and the second end of the second switch Q9 is grounded. The second switch Q9 can be used to output an overcurrent detection signal to the comparator module to cause the comparator module to self-lock. The second end of the first switch Q5 is also connected to the control end of the third switch Q8 via a current-limiting resistor R17. The first end of the third switch Q8 is connected to the control end of the switch circuit, and the second end of the third switch Q8 is grounded. The third switch Q8 can be used to output an overcurrent detection signal to the switch circuit to turn off the switch module, thereby stopping power supply to the AC heated bed.

[0073] In this embodiment, if Figure 6 As shown, the output end of the comparator module includes a first output end LIMIT_OUT_H and a second output end LIMIT_OUT_L, wherein the first output end LIMIT_OUT_H can be used to output a current comparison signal corresponding to the positive half cycle of the current detection signal, and the second output end LIMIT_OUT_L can be used to output a current comparison signal corresponding to the negative half cycle of the current detection signal. Figure 7As shown, the signal driving module includes a first diode D83, a second diode D84, a fourth switch transistor Q13, a fifth switch transistor Q14, and several resistors. The anode terminal of the first diode D83 is connected to the first output terminal LIMIT_OUT_H of the comparator module and is also connected to the power supply terminal 5V_LIMIT via a pull-up resistor R48. The cathode terminal of the first diode D83 is connected to the control terminals of the fourth switch transistor Q13 and the fifth switch transistor Q14 via a current-limiting resistor R32. The anode terminal of the second diode D84 is connected to the second output terminal LIMIT_OUT_L of the comparator module and is also connected to the power supply terminal 5V_LIMIT via a pull-up resistor R49. The cathode terminal of the second diode D84 is connected to the control terminals of the fourth switch transistor Q13 and the fifth switch transistor Q14 via a current-limiting resistor R32. A first end of the fourth switch tube Q13 is connected to the input end of the comparator module, and a second end of the fourth switch tube Q13 is grounded. The fourth switch tube Q13 can be used to output an overcurrent detection signal to the comparator module to cause the comparator module to self-lock. A first end of the fifth switch tube Q14 is connected to the control end of the switch circuit, and a second end of the fifth switch tube Q14 is grounded. The fifth switch tube Q14 can be used to output an overcurrent detection signal to the switch circuit to turn off the switch module, thereby stopping power supply to the AC heated bed.

[0074] In this embodiment, if Figure 8 As shown, the controller 40 is also connected to the output end of the hardware self-locking circuit 30, and the controller 40 is also used to receive the overcurrent detection signal and generate an overcurrent alarm signal according to the overcurrent detection signal. Further, the controller 40 is also connected to the signal output end of the current detection circuit 10, and the controller 40 is also used to receive the current detection signal and generate a hot bed power supply signal according to the current detection signal. Specifically, referring to Figure 9 The controller's input terminal ADC can receive the current detection signal output by the current detection chip U7 through the interface J1, so as to identify the working state of the circuit through the current detection signal, such as the open circuit state, the normal working state and the abnormal high current state. Figure 5 、 Figure 7 and Figure 9 The controller can also receive the overcurrent detection signal output by the hardware self-locking circuit through the same interface J1 to identify whether the circuit is currently in an overcurrent state. In other words, the controller can use the same input port to identify whether the circuit is open, normal operation, abnormally high current, or overcurrent, and respond accordingly.

[0075] In this embodiment, if Figure 9As shown, the current detection circuit includes a Hall current sensor U7 and a voltage divider module composed of voltage divider resistors R11 and R25. The current input of the Hall current sensor U7 is connected to the power supply via power supply interfaces U1, U2, and U3. The current output of the Hall current sensor U7 is connected to the input of the switching circuit. The signal output ADC1 of the Hall current sensor U7 is connected to the input of the hardware self-locking circuit and the input of the voltage divider module, respectively. The output of the voltage divider module is connected to the input ADC of the controller via interface J1.

[0076] In this embodiment, if Figure 9 As shown, the switching circuit includes a sixth switch tube Q3, a seventh switch tube Q4, a photocoupler U5, a thyristor U6, and several resistors. The control terminal of the sixth switch tube Q3 is connected to the output terminal GPIO of the controller and the output terminal OCP of the hardware self-locking circuit, respectively. The first terminal of the sixth switch tube Q3 is connected to the control terminal of the seventh switch tube Q4 via a current-limiting resistor R8. The second terminal of the sixth switch tube Q3 is grounded. The control end of the seventh switch tube Q4 is also connected to the first end of the seventh switch tube Q4 through a current limiting resistor R9 and a filter capacitor C3. The first end of the seventh switch tube Q4 is connected to the power supply end 5V_IN. The second end of the seventh switch tube Q4 is connected to the anode input end of the photoelectric coupler U5. The cathode input end of the photoelectric coupler U5 is grounded through a current limiting resistor R4. The first output end of the photoelectric coupler is connected to the current output end of the current detection circuit (i.e., the current output end of the current detection chip U7) through a current limiting resistor R6. The second output end of the photoelectric coupler U5 is connected to the control end of the thyristor U6. The first end of the thyristor U6 is connected to the current output end of the current detection circuit (i.e., the current output end of the current detection chip U7) as the input end of the switching circuit. The second end of the thyristor U6 is connected to the power supply end of the AC hot bed through ports U8, U4 and U9 and the AC wire as the output end of the switching circuit.

[0077] In this embodiment, if Figure 10 As shown, the multiple circuit modules of the AC heated bed's protection circuit can be separately arranged on multiple circuit boards and connected via interfaces, allowing for flexible placement of the protection circuit within AC devices such as 3D printers. Specifically, the controller 40 can be separately arranged on a single circuit board, facilitating the deployment of complex control circuits. The current detection circuit 10, switch circuit 20, and hardware self-locking circuit can be co-located on another circuit board and connected to the AC power supply and the AC heated bed's power supply via AC cables and interfaces, respectively, to achieve the AC heated bed's power supply and protection functions.

[0078] In this embodiment, a 3D printer is further provided, and the 3D printer includes the protection circuit of the AC heated bed.

[0079] By applying the technical solution of this embodiment, when an overcurrent fault occurs, the power supply can be quickly cut off by hardware self-locking, thereby avoiding equipment failure or safety accidents caused by excessive current, ensuring the safe and stable use of the AC heated bed. In addition, the above circuit can cut off the connection between the AC power and the heated bed wire, avoiding the occurrence of safety accidents such as wire fire and electric shock to personnel, greatly improving the safety of the use of the AC heated bed. In addition, the above circuit can perform circuit break protection and abnormal high current protection by setting a controller to receive the current detection signal, and through the hardware self-locking circuit, extremely abnormal overcurrent protection can be performed, so that the safe use of the AC heated bed can be ensured through both soft protection and hard protection, thereby avoiding equipment damage and safety accidents, and ensuring the stable operation of the equipment.

[0080] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0081] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined by the appended claims.

Claims

1. A protection circuit for an AC heated bed, characterized in that: The protection circuit of the AC heated bed includes a current detection circuit, a switch circuit, a hardware self-locking circuit and a controller, wherein: The current input terminal of the current detection circuit is connected to the power supply, the current output terminal of the current detection circuit is connected to the input terminal of the switch circuit, the output terminal of the switch circuit is connected to the power supply terminal of the AC heated bed, the signal output terminal of the current detection circuit is connected to the input terminal of the hardware self-locking circuit, and the control terminal of the switch circuit is connected to the controller and the output terminal of the hardware self-locking circuit respectively; The current detection circuit includes a Hall current sensor and a voltage divider module, the current input end of the Hall current sensor is connected to the power supply, the current output end of the Hall current sensor is connected to the input end of the switching circuit, the signal output end of the Hall current sensor is respectively connected to the input end of the hardware self-locking circuit and the input end of the voltage divider module, and the output end of the voltage divider module is connected to the input end of the controller; The controller is used to output a power supply signal for the heated bed to control the switching circuit to be turned on or off, so that the AC heated bed is powered on or off; the current detection circuit is used to detect the power supply current of the AC heated bed and output a current detection signal when the switching circuit is turned on; the hardware self-locking circuit is used to output an overcurrent detection signal to the switching circuit when it detects that the current detection signal reaches a preset overcurrent detection value, so as to control the switching circuit to be turned off, so that the AC heated bed is powered off.

2. The protection circuit of the AC heated bed according to claim 1, characterized in that: The hardware self-locking circuit includes a comparator module and a signal driving module, wherein: The input end of the comparator module is connected to the signal output end of the current detection circuit, the output end of the comparator module is connected to the input end of the signal driving module, and the output end of the signal driving module is connected to the control end of the switch circuit and the input end of the comparator module respectively; The comparator module is used to compare the current detection signal with a reference signal and output a current comparison signal; the signal driving module is used to generate an overcurrent detection signal when the current comparison signal indicates that the current detection signal is greater than or equal to the reference signal, and output the overcurrent detection signal to the switch circuit and the comparator module respectively, so as to cut off the switch circuit and keep the comparator module in a self-locking state, so that the AC heated bed continuously stops supplying power.

3. The protection circuit of the AC heated bed according to claim 2, characterized in that: The comparator module includes a first comparison unit, a second comparison unit, a first reference unit and a second reference unit, wherein: The positive input terminal of the first comparison unit is connected to the signal output terminal of the current detection circuit, the negative input terminal of the first comparison unit is connected to the output terminal of the first reference unit, and the output terminal of the first comparison unit is connected to the input terminal of the signal driving module; The positive input terminal of the second comparison unit is connected to the output terminal of the second reference unit, the negative input terminal of the second comparison unit is connected to the signal output terminal of the current detection circuit, and the output terminal of the second comparison unit is connected to the input terminal of the signal driving module.

4. The protection circuit of the AC heated bed according to claim 3, characterized in that: The first comparison unit and the second comparison unit are integrated into a window comparator; and / or, The first reference unit and the second reference unit are voltage divider circuits composed of voltage divider resistors, wherein the first reference unit is used to generate a reference signal corresponding to the current detection signal in the positive half cycle, and the second reference unit is used to generate a reference signal corresponding to the current detection signal in the negative half cycle.

5. The protection circuit of the AC heated bed according to claim 2, characterized in that: The signal driving module includes a first switch tube, a second switch tube, a third switch tube and several resistors, wherein: The control end of the first switching tube is connected to the output end of the comparator module via a current-limiting resistor, and the control end of the first switching tube is also connected to the power supply end via a pull-up resistor. The first end of the first switching tube is connected to the power supply end, and the second end of the first switching tube is connected to the control end of the second switching tube and the control end of the third switching tube respectively via current-limiting resistors. The first end of the second switch tube is connected to the input end of the comparator module, and the second end of the second switch tube is grounded; the first end of the third switch tube is connected to the control end of the switch circuit, and the second end of the third switch tube is grounded.

6. The protection circuit of the AC heated bed according to claim 2, characterized in that: The output end of the comparator module includes a first output end and a second output end, the first output end is used to output the current comparison signal corresponding to the current detection signal in the positive half cycle, and the second output end is used to output the current comparison signal corresponding to the current detection signal in the negative half cycle; the signal driving module includes a first diode, a second diode, a fourth switch tube, a fifth switch tube and several resistors, wherein, An anode terminal of the first diode is connected to the first output terminal of the comparator module, and an anode terminal of the first diode is also connected to the power supply terminal via a pull-up resistor, and a cathode terminal of the first diode is respectively connected to the control terminal of the fourth switching tube and the control terminal of the fifth switching tube via a current-limiting resistor; An anode terminal of the second diode is connected to the second output terminal of the comparator module, and an anode terminal of the second diode is further connected to the power supply terminal via a pull-up resistor, and a cathode terminal of the second diode is respectively connected to the control terminal of the fourth switching tube and the control terminal of the fifth switching tube via a current-limiting resistor; The first end of the fourth switch tube is connected to the input end of the comparator module, and the second end of the fourth switch tube is grounded; the first end of the fifth switch tube is connected to the control end of the switch circuit, and the second end of the fifth switch tube is grounded.

7. The protection circuit of the AC heated bed according to any one of claims 1 to 6, characterized in that: The controller is further connected to the output end of the hardware self-locking circuit, and is further configured to receive the overcurrent detection signal and generate an overcurrent alarm signal according to the overcurrent detection signal; and / or, The controller is also connected to the signal output end of the current detection circuit, and is further used to receive the current detection signal and generate the hot bed power supply signal according to the current detection signal.

8. The protection circuit of the AC heated bed according to claim 1, characterized in that: The switch circuit includes a sixth switch tube, a seventh switch tube, a photoelectric coupler, a thyristor and several resistors, wherein: The control end of the sixth switch tube is connected to the output end of the controller and the output end of the hardware self-locking circuit respectively, the first end of the sixth switch tube is connected to the control end of the seventh switch tube via a current-limiting resistor, and the second end of the sixth switch tube is grounded; The control end of the seventh switch tube is further connected to the first end of the seventh switch tube through a current limiting resistor, the first end of the seventh switch tube is connected to the power supply end, and the second end of the seventh switch tube is connected to the anode input end of the photoelectric coupler; The cathode input terminal of the photoelectric coupler is grounded through a current limiting resistor, the first output terminal of the photoelectric coupler is connected to the current output terminal of the current detection circuit through a current limiting resistor, and the second output terminal of the photoelectric coupler is connected to the control terminal of the thyristor; The first end of the thyristor is connected to the current output end of the current detection circuit as the input end of the switch circuit, and the second end of the thyristor is connected to the power supply end of the AC heated bed as the output end of the switch circuit.

9. A 3D printer, comprising the protection circuit for the AC heated bed according to any one of claims 1 to 8.

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