Heating control circuit and baking machine

Abstract

The utility model discloses a heating control circuit and a baking machine, and the circuit comprises a drive circuit which is used for generating a first drive signal according to a heating control signal outputted by a main control circuit; the photoelectric coupling circuit is connected with the driving circuit and comprises a light-emitting sub-circuit, a zero-cross detection sub-circuit and a first switch sub-circuit; the light-emitting sub-circuit is used for generating a second driving signal according to the first driving signal, the zero-cross detection sub-circuit is used for outputting a trigger signal when detecting that an alternating current power supply for supplying power to the heating device is in a zero range, and the first switch sub-circuit is used for generating a switch control signal according to the second driving signal and the trigger signal; the switching circuit is connected with the photoelectric coupling circuit and the heating device; the switch circuit is used for conducting or disconnecting according to the switch control signal so as to control the working state of the heating device. According to the technical scheme, the impact current caused by the connection and disconnection operation is small, and the stability of the heating control circuit is improved.

Description

Technical Field

[0001] This application belongs to the field of digital printing technology, specifically relating to a heating control circuit and a baking machine. Background Technology

[0002] DTF (Direct to Film) technology is a printing technique that can transfer colorful or monochrome designs onto clothing, hats, and other objects made of various materials. It generally requires processes such as printing the design, applying hot melt adhesive powder, and heating for transfer.

[0003] During the baking process, the printing material typically needs to be moved to a specific area of ​​the baking machine for baking, which usually involves turning on the heating element. However, the baking heating process generates a large current surge, which in turn introduces significant harmonic interference to the power grid.

[0004] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this application, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0005] The purpose of this application is to provide a heating control circuit and a baking machine to reduce current surges and harmonic interference during the heating process.

[0006] Other features and advantages of this application will become apparent from the following detailed description, or may be learned in part from practice of this application.

[0007] According to one aspect of the embodiments of this application, a heating control circuit is provided for use in a baking machine, the baking machine including a main control circuit and a heating device, the heating device being used to generate heat to bake printing media; the heating control circuit includes:

[0008] A driving circuit is used to generate a first driving signal based on the heating control signal output by the main control circuit;

[0009] An optocoupler circuit, connected to the driving circuit, includes a light-emitting sub-circuit, a zero-crossing detection sub-circuit, and a first switching sub-circuit. The light-emitting sub-circuit generates a second driving signal based on the first driving signal. The zero-crossing detection sub-circuit outputs a trigger signal when it detects that the AC power supply to the heating device is within the zero-point range. The first switching sub-circuit generates a switching control signal based on the second driving signal and the trigger signal. The zero-point range indicates that the absolute value of the difference between the voltage of the AC power supply and zero is within a preset range.

[0010] A switching circuit is connected to the optocoupler circuit and to the heating device; the switching circuit is used to turn on or off according to the switching control signal to control the working state of the heating device.

[0011] In one embodiment of this application, the first switch sub-circuit includes a controlled terminal, a first path terminal, and a second path terminal. The controlled terminal of the first switch is used to receive the second driving optical signal and the trigger signal.

[0012] The optocoupler circuit further includes a first filter sub-circuit, wherein the first filter sub-circuit unit is connected in parallel with the light-emitting sub-circuit; and / or

[0013] The optocoupler circuit further includes a first current-limiting sub-circuit, one end of which is connected to the second path terminal of the first switching sub-circuit, and the other end is connected to the AC power supply; and / or,

[0014] The optocoupler circuit further includes a second current-limiting sub-circuit, one end of which is connected to the first path terminal of the first switching sub-circuit, and the other end is connected to the switching circuit; and / or,

[0015] The optocoupler circuit further includes a third current-limiting sub-circuit, one end of the resistor of the third current-limiting sub-circuit is connected to the driving circuit, and the other end is connected to the light-emitting sub-circuit.

[0016] In one embodiment of this application, the optocoupler circuit further includes a first filter sub-circuit, and the light-emitting sub-circuit includes a first terminal and a second terminal; the first filter sub-circuit includes a first filter capacitor and a first filter resistor, the first filter capacitor and the first filter resistor are connected in parallel, the first common connection terminal of the first filter capacitor and the first filter resistor is connected to the operating power supply and the first terminal of the light-emitting sub-circuit, and the second common connection terminal of the first filter capacitor and the first filter resistor is connected to the second terminal of the light-emitting sub-circuit.

[0017] In one embodiment of this application, the switching circuit includes a bidirectional thyristor switch;

[0018] The gate of the bidirectional thyristor switch is connected to the first path terminal of the first switch sub-circuit.

[0019] The first main electrode of the bidirectional thyristor switch is connected to the heating device;

[0020] The second main electrode of the bidirectional thyristor switch is connected to the AC power supply.

[0021] In one embodiment of this application, the switching circuit further includes an anti-interference circuit, which is disposed between the first main electrode and the second main electrode of the bidirectional thyristor switch.

[0022] The anti-interference circuit includes an anti-interference resistor and an anti-interference capacitor. One end of the anti-interference resistor is connected to the first main electrode of the bidirectional thyristor switch, and the other end is connected to one end of the anti-interference capacitor. The other end of the anti-interference capacitor is connected to the second main electrode of the bidirectional thyristor switch.

[0023] In one embodiment of this application, the driving circuit includes a second switching sub-circuit, which includes a controlled terminal, a first terminal, and a second terminal.

[0024] The controlled terminal of the second switch sub-circuit is connected to the main control circuit, the first terminal of the second switch sub-circuit is grounded, and the second terminal of the second switch sub-circuit is connected to the optocoupler circuit and the power supply, respectively.

[0025] In one embodiment of this application, the driving circuit further includes a second filter sub-circuit, the second filter sub-circuit being connected between the operating power supply and the second terminal of the driving switch transistor of the second switching sub-circuit; and / or,

[0026] The driving circuit further includes a third filter sub-circuit, which is connected between the first terminal and the controlled terminal of the second switching sub-circuit; and / or,

[0027] The driving circuit also includes the fourth current limiting sub-circuit, which is connected between the main control circuit and the controlled terminal of the driving switch tube of the second switching sub-circuit.

[0028] In one embodiment of this application, the heating control circuit further includes:

[0029] A temperature detection circuit, connected to the main control circuit, is used to detect the baking temperature and output a temperature detection signal, so that the main control circuit can generate the heating control signal based on the temperature detection signal.

[0030] In one embodiment of this application, the temperature detection circuit includes:

[0031] A temperature detection sub-circuit is used to detect the baking temperature and output a first temperature detection signal;

[0032] The fourth filtering sub-circuit, connected to the temperature detection sub-circuit, is used to filter the first temperature detection signal and output the second temperature detection signal.

[0033] The voltage follower sub-circuit, connected to the fourth filter sub-circuit, is used to amplify, buffer, and hold the second temperature detection signal, and output the third temperature detection signal.

[0034] In one embodiment of this application, the temperature detection sub-circuit includes a temperature sensor and a pull-up resistor, one end of the temperature sensor is connected to the operating power supply through the pull-up resistor, and the other end is grounded; and / or,

[0035] The fourth low-pass filter sub-circuit includes a fourth filter resistor and a fourth filter capacitor. One end of the fourth filter resistor is connected to the temperature detection sub-circuit, and the other end is shared with one end of the voltage follower sub-circuit and the fourth filter capacitor. The other end of the fourth filter capacitor is grounded; and / or

[0036] The voltage follower sub-circuit includes a voltage follower, which includes a positive input terminal, an inverting input terminal, and an output terminal. The positive input terminal is connected to the fourth low-pass filter sub-circuit, and the inverting input terminal is connected to the output terminal.

[0037] According to one aspect of the embodiments of this application, a baking machine is provided, comprising:

[0038] Multiple heating devices are provided to generate heat for baking the printing media.

[0039] Multiple heating control circuits are provided, wherein one of the heating devices is connected to one of the heating control circuits, and the heating control circuit is the heating control circuit provided in any embodiment of this application;

[0040] The main control circuit is connected to the plurality of heating control circuits and is used to output a plurality of heating control signals to the plurality of heating control circuits respectively.

[0041] In the technical solution provided in this application embodiment, the heating control circuit is applied to a baking machine, which includes a main control circuit and a heating device. The heating device generates heat to bake the printing medium. The heating control circuit includes a drive circuit for generating a first drive signal based on the heating control signal output by the main control circuit. An optocoupler circuit, connected to the drive circuit, includes a light-emitting sub-circuit, a zero-crossing detection sub-circuit, and a first switch sub-circuit. The light-emitting sub-circuit generates a second drive signal based on the first drive signal. The zero-crossing detection sub-circuit outputs a trigger signal when it detects that the AC power supply to the heating device is within the zero range. The first switch sub-circuit generates a switch control signal based on the second drive signal and the trigger signal. The zero range indicates that the absolute value of the difference between the voltage of the AC power supply and zero point is within a preset range. A switch circuit, connected to the optocoupler circuit and the heating device, is used to turn the heating device on or off according to the switch control signal to control the working state of the heating device. As can be seen, the switch control signal is generated when the AC power supply is in the zero range. Therefore, the switch circuit also performs conduction and disconnection operations when the AC power supply is in the zero range. Consequently, the working state of the heating device also changes when the AC power supply is in the zero range. The current when the AC power supply is in the zero range is usually small, which reduces the inrush current caused by the change in the working state of the heating device. This reduces harmonic interference to the AC power supply and helps improve the stability of the heating control circuit.

[0042] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0043] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0044] Figure 1 A schematic diagram of the structure of a baking machine applying the technical solution of this application is shown.

[0045] Figure 2 A schematic diagram of a heating control circuit provided in one embodiment of this application is shown.

[0046] Figure 3 A schematic diagram of a heating control circuit provided in one embodiment of this application is shown.

[0047] Figure 4 A schematic diagram of a heating control circuit provided in one embodiment of this application is shown.

[0048] Figure 5 A schematic diagram of a heating control circuit provided in one embodiment of this application is shown.

[0049] Figure 6 A schematic diagram of a heating control circuit provided in one embodiment of this application is shown.

[0050] Figure 7 A schematic diagram of a heating control circuit inside a baking machine provided in one embodiment of this application is shown.

[0051] Figure 8 A schematic block diagram of a heating control circuit provided in one embodiment of this application is shown.

[0052] Figure 9 A circuit diagram of a heating control circuit provided in one embodiment of this application is shown schematically.

[0053] Figure 10 A circuit diagram of a temperature detection circuit provided in one embodiment of this application is shown schematically.

[0054] Figure 11 A circuit diagram of a temperature detection circuit inside a baking machine provided in one embodiment of this application is shown schematically. Detailed Implementation

[0055] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided to make this application more comprehensive and complete, and to fully convey the concept of the exemplary embodiments to those skilled in the art.

[0056] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a thorough understanding of embodiments of this application. However, those skilled in the art will recognize that the technical solutions of this application can be practiced without one or more of the specific details, or other methods, components, apparatuses, steps, etc., can be employed. In other instances, well-known methods, apparatuses, implementations, or operations are not shown or described in detail to avoid obscuring various aspects of this application.

[0057] The block diagrams shown in the accompanying drawings are merely functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities can be implemented in software, in one or more hardware circuits or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.

[0058] Figure 1 A schematic diagram of the structure of a baking machine applying the technical solution of this application is shown.

[0059] like Figure 1 As shown, the baking machine includes a heating control circuit 100, heating devices 200, a baking zone 300, and a main control circuit 400. Multiple heating devices 200 are arranged within the baking zone 300. Each heating device 200 heats the printing media entering the baking machine to bake it. The printing media entering the baking machine is typically the media after the printer has completed its printing operation. Each heating device 200 is connected to a heating control circuit 100, which controls the heating operation of the heating device 200. The main control circuit 400 can output control signals to multiple heating devices 200 simultaneously, or it can output control signals to only one or some of the heating devices 200.

[0060] In this embodiment, the printing medium can be a medium with a printed pattern, such as a transfer film (PET film, PVC film, PS film, ABS film, PP film, etc.). The baking area 300 may have an annular path 310, allowing the printing medium to move along this path to achieve the baking operation. For example, the printing medium can... Figure 1 The vehicle enters the baking area 300 through the entrance shown, moves along the circular path 310 around the baking area 300 for thorough baking, and finally exits... Figure 1 The outlet shown exits from the baking area 300. By setting a ring path 310 and multiple heating devices 200 in the baking area 300, the printing medium can be baked at any position in the baking area 300, which not only effectively ensures the baking effect but also shortens the baking time and improves baking efficiency. The ring path 310 also reduces the area occupied by the baking area 300 in the baking machine while ensuring that the printing medium has a longer baking time, thus reducing the size of the baking machine while ensuring the baking effect, making the baking machine more compact and aesthetically pleasing. At the same time, each heating device 200 is connected to a heating control circuit 100, so that the heating operation of each heating device 200 can be controlled independently, which is beneficial for adjusting the baking temperature of local positions in the baking area 300, making the temperature adjustment in the baking area 300 more flexible and accurate, thereby improving the baking effect.

[0061] The heating control circuit provided in this application is described below.

[0062] Figure 2 A schematic diagram of a heating control circuit provided in one embodiment of this application is shown.

[0063] like Figure 2 As shown, the heating control circuit 100 includes a drive circuit 110, an optocoupler circuit 120, and a switching circuit 130. One end of the drive circuit 110 is connected to the main control circuit 400 in the baking machine, and the other end is connected to the optocoupler circuit 120. One end of the switching circuit 130 is connected to the optocoupler circuit 120, and the other end is connected to the heating device 200 in the baking machine. The optocoupler circuit 120 includes a light-emitting sub-circuit 121, a zero-crossing detection sub-circuit 122, and a first switching sub-circuit 123. The light-emitting sub-circuit 121 is connected to the drive circuit 110. The zero-crossing detection sub-circuit 122 is connected to the AC power supply and the first switching sub-circuit 123. The first switching sub-circuit 123 is connected to the switching circuit 130, and the switching circuit 130 is connected to the AC power supply. In this circuit, the light-emitting sub-circuit 121 and the first switching sub-circuit 123 can transmit signals without physical connection. That is, the light-emitting sub-circuit 121 and the first switching sub-circuit 123 are physically isolated, but the first switching sub-circuit 123 can receive the first driving signal output by the light-emitting sub-circuit 121. For example, the first driving signal can be in the form of an optical signal, an ultrasonic signal, etc., so that signal transmission can be achieved without the light-emitting sub-circuit 121 and the first switching sub-circuit 123 forming a physical connection.

[0064] During the operation of the heating control circuit 100, the drive circuit 110 generates a first drive signal based on the heating control signal output by the main control circuit 400; the light-emitting sub-circuit 121 generates a second drive signal based on the first drive signal; simultaneously, the zero-crossing detection sub-circuit 122 detects the AC power supply. When the AC power supply is in the zero range, the zero-crossing detection sub-circuit 122 outputs a trigger signal; the zero range indicates that the absolute value of the difference between the AC power supply voltage and zero voltage is within a preset range. Both the first drive signal and the trigger signal are sent to the first switch sub-circuit 123, which generates a switch control signal based on these two signals; the switch circuit 130 turns on or off according to the switch control signal to control the working state of the heating device 200. Thus, the working state of the heating device 200 can be changed when the AC power supply is in the zero range. Since the current of the AC power supply is usually small when it is in the zero range, the inrush current caused by the change in the working state of the heating device 200 is small, thereby reducing harmonic interference to the AC power supply and improving the stability of the heating control circuit 100.

[0065] In one embodiment of this application, the operating state of the heating device 200 includes the connection and disconnection of the heating device 200 with the AC power supply. For example, the switching circuit 130 can control the connection path between the heating device 200 and the AC power supply. When the switching circuit 130 is off, it is equivalent to the heating device 200 being disconnected from the AC power supply; when the switching circuit 130 is on, it is equivalent to the heating device 200 being connected to the AC power supply. Since the switching circuit 130 performs on and off operations when the AC power supply is in the zero range, the heating device 200 is connected to or disconnected from the AC power supply when the AC power supply is in the zero range. It can be understood that when the heating device 200 is connected to the AC power supply, the heating device 200 is in a heating state; when the heating device 200 is disconnected from the AC power supply, the heating device 200 is in a stopped heating state.

[0066] In one embodiment of this application, the second driving signal generated by the light-emitting sub-circuit 121 can be an optical signal, and the first switching sub-circuit 123 can include a photosensitive element. Thus, when the first switching sub-circuit 123 senses the optical signal, it can trigger the generation conditions of the switching control signal. The generation conditions of the switching control signal also include the trigger signal output by the zero-crossing detection sub-circuit 122, so that the switching control signal can be generated when the AC power supply is in the zero range.

[0067] In one embodiment of this application, the zero-crossing detection sub-circuit 122 is used to detect and track the position and time of the alternating zero-crossing point of the positive and negative half-waves of the AC power supply. This alternating zero-crossing point, also known as the zero-position range, includes the transition from the positive half-wave to the negative half-wave and from the negative half-wave to the positive half-wave. In other words, the absolute value of the difference between the voltage of the AC power supply and the zero point is within a preset range. The zero-crossing detection sub-circuit 122 can be implemented using a voltage comparator, which compares the output signal of the AC power supply with a reference level. When the output signal of the AC power supply passes through the zero point, the output signal of the voltage comparator changes direction; this change point is the zero-crossing point. Furthermore, a rectification and filtering circuit can be added to the output of the voltage comparator to compare the rectified and filtered signal with the reference level to achieve zero-crossing detection.

[0068] In one embodiment of this application, the zero-crossing detection sub-circuit 122 and the first switching sub-circuit 123 can be implemented by a single component, such as a thyristor switch with zero-crossing detection function.

[0069] In one embodiment of this application, the light-emitting sub-circuit 121, the zero-crossing detection sub-circuit 122, and the first switching sub-circuit 123 can be implemented by a single component, such as a silicon controlled rectifier optocoupler.

[0070] The heating control signal is a signal generated by the baking machine when it needs to adjust the temperature in the baking zone 300. For example, when baking the printing media, when lowering the temperature of the baking zone 300, when raising the temperature of the baking zone 300, or in other temperature adjustment situations, the heating control signal can be generated. The heating control signal can be a PWM (Pulse Width Modulation) signal.

[0071] In the technical solution provided in this application embodiment, the heating control circuit is applied to a baking machine, which includes a drive circuit for generating a drive signal according to the heating control signal issued by the baking machine; an optocoupler circuit connected to the drive circuit and also connected to an AC power supply, including a light-emitting sub-circuit and a first switch; the light-emitting sub-circuit is used to generate a light signal according to the drive signal, and the first switch is used to generate a switch control signal according to the light signal when the AC power supply is in the zero range; the zero range means that the absolute value of the difference between the voltage of the AC power supply and zero voltage is within a preset range; a switch circuit connected to the optocoupler circuit and also connected to a heating device in the baking area of ​​the baking machine, the heating device being connected to the AC power supply; the switch circuit is used to turn on or off according to the switch control signal to control the connection or disconnection of the heating device and the AC power supply. As can be seen, the switch control signal is generated when the AC power supply is in the zero range. Therefore, the switch circuit also performs conduction and disconnection operations when the AC power supply is in the zero range. Consequently, the circuit containing the heating device also performs conduction and disconnection when the AC power supply is in the zero range. The current when the AC power supply is in the zero range is usually small, which reduces the inrush current caused by the conduction and disconnection operations, thereby reducing harmonic interference to the power grid and improving the stability of the heating control circuit.

[0072] Figure 3 A schematic diagram of a heating control circuit provided in one embodiment of this application is shown.

[0073] like Figure 3 As shown, the heating control circuit 100 includes a driving circuit 110, an optocoupler circuit 120, and a switching circuit 130. The optocoupler circuit 120 includes a light-emitting sub-circuit 121, a zero-crossing detection sub-circuit 122, a first switching sub-circuit 123, and a first filtering sub-circuit 124. The connection relationship between the driving circuit 110, the switching circuit 130, the light-emitting sub-circuit 121, the zero-crossing detection sub-circuit 122, and the first switching sub-circuit 123 is the same as in the previous embodiment and will not be repeated here. Figure 3As shown, the first filter sub-circuit 124 is connected in parallel across the light-emitting sub-circuit 121, and is used to filter the received signal of the light-emitting sub-circuit 121. The first filter sub-circuit 124 can be implemented using any filtering method such as parallel capacitor, series inductor, π-type RC filter, π-type LC filter, electronic filter, etc. The filter circuit or filter sub-circuit provided in any embodiment of this application can be implemented using these filtering methods according to actual needs.

[0074] In one embodiment of this application, such as Figure 3 As shown, the optocoupler circuit 120 also includes a first current-limiting sub-circuit 125, which is connected between the first switching sub-circuit 123 and the AC power supply to limit the current in the loop containing the first switching sub-circuit 123. The first current-limiting sub-circuit 125 can be implemented using any circuit structure capable of limiting the current in the circuit. For example, it can be implemented by connecting a resistor in series in the circuit, constructing a current-limiting circuit based on a switching transistor (such as a bipolar transistor), or using a constant current source current-limiting circuit. It is understood that the current-limiting circuit or current-limiting sub-circuit provided in any embodiment of this application can be implemented using these methods according to actual needs.

[0075] In one embodiment of this application, such as Figure 3 As shown, the optocoupler circuit 120 also includes a second current limiting sub-circuit 126. The first current limiting sub-circuit 125 is connected between the first switching sub-circuit 123 and the switching circuit 130 to limit the current magnitude of the loops in which the first switching sub-circuit 123 and the switching circuit 130 are located.

[0076] In one embodiment of this application, such as Figure 3 As shown, the optocoupler circuit 120 also includes a third current limiting sub-circuit 127, which is connected between the first switching sub-circuit 123 and the driving circuit 110 to limit the current magnitude of the loop in which the first switching sub-circuit 123 and the driving circuit 110 are located.

[0077] Figure 4 A schematic diagram of a heating control circuit provided in one embodiment of this application is shown.

[0078] like Figure 4 As shown, the heating control circuit 100 includes a drive circuit 110, an optocoupler circuit 120, and a switching circuit 130. The connection relationship and specific structure of the drive circuit 110 and the optocoupler circuit 120 are the same as in the previous embodiment, and will not be repeated here. Figure 4As shown, the switching circuit 130 includes a bidirectional thyristor switch Q1. The gate of the bidirectional thyristor switch Q1 is connected to the first path terminal of the first switching sub-circuit 123. The first main electrode T1 of the bidirectional thyristor switch Q1 is connected to the heating device 200. The second main electrode T2 of the bidirectional thyristor switch Q1 is connected to the AC power supply. When the gate of the bidirectional thyristor switch Q1 receives a high-level signal, the first main electrode T1 and the second main electrode T2 of the bidirectional thyristor switch Q1 are turned on (referred to as the bidirectional thyristor switch Q1 being turned on). When the gate of the bidirectional thyristor switch Q1 receives a low-level signal, the first main electrode T1 and the second main electrode T2 of the bidirectional thyristor switch Q1 are turned off (referred to as the bidirectional thyristor switch Q1 being turned off). In this embodiment, the switch control signal is the signal received by the gate of the bidirectional thyristor switch Q1. When the switch control signal is high, the bidirectional thyristor switch Q1 is turned on, and the AC power supply is connected to the heating device 200, that is, the AC power supply supplies power to the heating device 200, causing the heating device 200 to generate heat. When the switch control signal is low, the bidirectional thyristor switch Q1 is turned off, and the AC power supply is disconnected from the heating device 200, that is, the power supply to the heating device 200 is cut off, causing the heating device 200 to stop generating heat. It can be understood that, under permissible conditions, the signal received by the gate of the bidirectional thyristor switch Q1 when it is turned on can also be a low-level signal, and the signal received by the gate of the bidirectional thyristor switch Q1 when it is turned off can also be a high-level signal.

[0079] In one embodiment of this application, such as Figure 4 As shown, the switching circuit 130 also includes an anti-interference circuit 131, which is located between the first main electrode T1 and the second main electrode T2 of the bidirectional thyristor switch Q1. Its main function is to attenuate and suppress interference signals in the circuit, such as suppressing voltage spikes and eliminating high-frequency oscillations. The anti-interference circuit provided in any embodiment of this application can employ circuit structures capable of achieving anti-interference effects, such as RC snubber absorption circuits, or isolation circuits.

[0080] Figure 5 A schematic diagram of a heating control circuit provided in one embodiment of this application is shown.

[0081] like Figure 5 As shown, the heating control circuit 100 includes a drive circuit 110, an optocoupler circuit 120, and a switching circuit 130. The connection relationship and specific structure of the drive circuit 110 and the optocoupler circuit 120 are the same as in the previous embodiment, and will not be repeated here. Figure 4As shown, the driving circuit 110 includes a second switch sub-circuit 111. The second switch sub-circuit 111 includes a controlled terminal, a first terminal, and a second terminal. The controlled terminal of the second switch sub-circuit 111 is connected to the main control circuit 400. The first terminal of the second switch sub-circuit 111 is grounded. The second terminal of the second switch sub-circuit 111 is connected to the optocoupler circuit 120 and the working power supply VCC, respectively.

[0082] In this embodiment, the controlled terminal of the second switch sub-circuit 111 is used to receive the heating control signal output by the main control circuit 400, and the second terminal of the second switch sub-circuit 111 is used to output the first drive signal. When the controlled terminal of the second switch sub-circuit 111 receives a high-level signal, the first and second terminals of the second switch sub-circuit 111 are turned on (hereinafter referred to as the second switch sub-circuit 111 being turned on); when the controlled terminal of the second switch sub-circuit 111 receives a low-level signal, the first and second terminals of the second switch sub-circuit 111 are turned off (hereinafter referred to as the second switch sub-circuit 111 being turned off). It can be understood that, under permissible conditions, the signals received by the controlled terminal corresponding to the on and off states can also be reversed, that is, the controlled terminal of the second switch sub-circuit 111 is turned on when it is low-level and turned off when it is high-level. Thus, when the heating control signal is a high-level signal, the first and second terminals of the second switch sub-circuit 111 are turned on. Since the first terminal of the second switch sub-circuit 111 is grounded, the second terminal of the second switch sub-circuit 111 outputs a low-level signal, i.e., the first drive signal is a low-level signal. When the heating control signal is a low-level signal, the first and second terminals of the second switch sub-circuit 111 are turned off. Since the second terminal of the second switch sub-circuit 111 is connected to the working power supply VCC, the second terminal of the second switch sub-circuit 111 outputs a high-level signal, i.e., the first drive signal is a high-level signal.

[0083] The second switch sub-circuit 111 can be any circuit structure capable of achieving the above-mentioned conduction and cutoff functions. For example, the second switch sub-circuit 111 can be a switching element such as a transistor, MOSFET, or IJBT, or it can be a switching circuit composed of multiple identical or different switching elements.

[0084] In one embodiment of this application, such as Figure 5 As shown, the drive circuit 110 also includes a second filter sub-circuit 112, which is connected between the operating power supply VCC and the second terminal of the second switch sub-circuit 111.

[0085] In one embodiment of this application, such as Figure 5 As shown, the driving circuit 110 also includes a third filter sub-circuit 113, which is connected between the first terminal and the controlled terminal of the second switch sub-circuit 111.

[0086] In one embodiment of this application, such as Figure 5 As shown, the drive circuit 110 also includes a fourth current limiting sub-circuit 114, which is connected between the main control circuit 400 and the controlled terminal of the second switch sub-circuit 111.

[0087] The heating control circuit provided by this application is illustrated below with a specific embodiment.

[0088] Figure 6 A schematic diagram of a heating control circuit provided in one embodiment of this application is shown.

[0089] like Figure 6 As shown, the heating control circuit includes a drive circuit 110, an optocoupler circuit 120, and a switching circuit 130. It should be noted that... Figure 6 In this context, AC_L represents the live wire of AC power supply AC, and AC_N represents the neutral wire of AC power supply AC. Both the live wire and the neutral wire belong to AC power supply AC. Unless otherwise specified, AC power supply AC in the following text refers to the live wire AC_L.

[0090] The optocoupler circuit 120 includes a light-emitting sub-circuit 121, a zero-crossing detection sub-circuit 122, a first switching sub-circuit 123, a first filtering sub-circuit 124, a first current-limiting sub-circuit 125, a second current-limiting sub-circuit 126, and a third current-limiting sub-circuit 127. The light-emitting sub-circuit 121 includes a light-emitting diode (LED) D. The zero-crossing detection sub-circuit 122 and the first switching sub-circuit 123 are implemented by a zero-crossing detection SCR switch Q, which will be referred to as the zero-crossing detection SCR switch Q thereafter. The LED D includes a first terminal (Anode) and a second terminal (Cathode). The zero-crossing detection SCR switch Q includes a controlled terminal (Ga), a first path terminal (Terminal1), and a second path terminal (Terminal2).

[0091] Furthermore, such as Figure 6 As shown, the first filter sub-circuit 124 includes a first filter capacitor C39 and a first filter resistor R23. The first filter capacitor C39 and the first filter resistor R23 are connected in parallel. The first common connection terminal of the first filter capacitor C39 and the first filter resistor R23 is connected to the first terminal Anode of the light-emitting diode D and the working power supply VCC. The second common connection terminal of the first filter capacitor C39 and the first filter resistor R23 is connected to the second terminal Cathode of the light-emitting diode D.

[0092] Furthermore, such as Figure 6 As shown, the first current limiting sub-circuit 125 includes a first current limiting resistor R21. One end of the first current limiting resistor R21 is connected to the second path terminal Teminal2 of the zero-crossing detection thyristor switch Q, and the other end is connected to the AC power supply AC.

[0093] Furthermore, such as Figure 6 As shown, the second current limiting sub-circuit 126 includes a second current limiting resistor R26. One end of the second current limiting resistor R26 is connected to the first path terminal Teminal1 of the zero-crossing detection thyristor switch Q, and the other end is connected to the switching circuit 130.

[0094] Furthermore, such as Figure 6 As shown, the third current limiting sub-circuit 127 includes a third current limiting resistor R25. One end of the third current limiting resistor R25 is connected to the first terminal Anode of the light-emitting diode D, and the other end is connected to the driving circuit 110.

[0095] Furthermore, such as Figure 2 As shown, the switching circuit 130 includes a bidirectional thyristor switch Q1 and an anti-interference circuit 131. The bidirectional thyristor switch Q1 includes a gate, a first main electrode T1, and a second main electrode T2. The gate of the bidirectional thyristor switch Q1 is connected to the first path terminal Terminal1 of the zero-crossing detection thyristor switch Q. The first main electrode T1 of the bidirectional thyristor switch Q1 is connected to the second current-limiting resistor R26 and the heating device 200, respectively. The second main electrode T2 of the bidirectional thyristor switch Q1 is connected to the first current-limiting resistor R21 and the AC power supply AC, respectively. The anti-interference circuit 131 is connected in parallel between the first main electrode T1 and the second main electrode T2 of the bidirectional thyristor switch Q1.

[0096] In one embodiment of this application, the switching circuit 130 can be connected to the heating device 200 via a connector. Any device in the heating control circuit that needs to be connected to the heating device 200 can first be connected to the connector, and then connected to the heating device 200 via the connector. This simplifies the wiring complexity between the heating control circuit and the heating device 200.

[0097] Furthermore, such as Figure 6 As shown, the anti-interference circuit 131 includes an anti-interference resistor R24 ​​and an anti-interference capacitor C40. One end of the anti-interference resistor R24 ​​is connected to the first main electrode T1 of the bidirectional thyristor switch Q1, and the other end is connected to one end of the anti-interference capacitor C40. The other end of the anti-interference capacitor C40 is connected to the second main electrode T2 of the bidirectional thyristor switch Q1.

[0098] Furthermore, such as Figure 6 As shown, the drive circuit 110 includes a second switching sub-circuit 111, a second filtering sub-circuit 112, a third filtering sub-circuit 113, and a fourth current limiting sub-circuit 114. The second switching sub-circuit 111 includes a switching transistor Q2, and the second filtering sub-circuit 112 includes...

[0099] Furthermore, such as Figure 2As shown, the driving circuit 110 includes a second switching sub-circuit 111, a second filtering sub-circuit 112, a third filtering sub-circuit 113, and a fourth current-limiting sub-circuit 114. The second switching sub-circuit 111 includes a driving switch Q2, which includes a controlled terminal G, a first terminal S, and a second terminal D. The third filtering sub-circuit 113 includes a third filtering capacitor C41 and a third filtering resistor R28. The fourth current-limiting sub-circuit 114 includes a fourth current-limiting resistor R27.

[0100] The controlled terminal G of the driving switch Q2 is connected to one end of the fourth current-limiting resistor R27, and the other end of the fourth current-limiting resistor R27 is connected to the main control circuit 400 to receive heating control signals; one end of the third filter capacitor C41 and the third filter resistor R28 are both connected to the controlled terminal G of the driving switch Q2, and the other end is grounded; the first terminal S of the driving switch Q2 is grounded, and the second terminal D of the driving switch Q2 is connected to the optocoupler circuit 120, specifically to the third current-limiting resistor R25.

[0101] Furthermore, such as Figure 6 As shown, the second filter sub-circuit 112 includes a second filter capacitor C38 and a second filter resistor R22. The second filter capacitor C38 and the second filter resistor R22 are connected in parallel. The first common connection terminal of the second filter capacitor C38 and the second filter resistor R22 is connected to the working power supply VCC. The second common connection terminal of the second filter capacitor C38 and the second filter resistor R22 is connected to the first terminal Cathode of the light-emitting diode D of the light-emitting sub-circuit 221.

[0102] In this embodiment, Figure 6 The driving switch Q2 shown is a MOSFET. The controlled terminal G of Q2 is the MOSFET gate, the first terminal S is the MOSFET source, and the second terminal D is the MOSFET drain. In practical applications, the driving switch Q2 can be other types of switching transistors, such as bipolar transistors (BJTs) or IGBTs.

[0103] exist Figure 6In the heating control circuit shown, the heating control signal PWM is input from one end of the fourth current-limiting resistor R27. When a high level reaches the controlled terminal G of the driving switch Q2, the first terminal S and the second terminal D of the driving switch Q2 are turned on, thus making the end of the first current-limiting resistor R25 connected to the driving switch Q2 low level. The operating voltage VCC can make the light-emitting diode D conduct and emit light. The controlled terminal Ga of the zero-crossing detection thyristor switch Q receives the light signal and, when the AC power supply AC is within the zero range, turns on the first path terminal Tenminal1 and the second path terminal Tenminal2. At this time, the gate of the bidirectional thyristor switch Q1 receives a high-level signal, turning on the first main electrode T1 and the second main electrode T2. Thus, the AC power supply AC forms a loop connection with the heating device 200, and the heating device 200 generates heat. When the low level of the heating control signal PWM reaches the controlled terminal G of the drive switch Q2, the drive switch Q2 cannot be turned on, the light-emitting diode D1 cannot be turned on and emit light, the zero-crossing detection thyristor switch naturally cannot be turned on, and the bidirectional thyristor switch Q1 cannot be turned on either. Then the AC power supply AC is disconnected from the heating device 200, and the heating device 200 stops heating.

[0104] In the above control process, when the AC power supply is in the positive half-wave, the optocoupler circuit 120 is turned on. At this time, the voltage VG-VT1 between the gate of the bidirectional SCR switch Q1 and the first main electrode T1 is negative, and the voltage VT2-VT1 between the second main electrode T2 and the first main electrode T1 is also negative. Therefore, the bidirectional SCR switch Q1 operates in the third quadrant. When the AC power supply is in the negative half-wave, the optocoupler circuit 120 is turned on. At this time, the voltage VG-VT1 between the gate of the bidirectional SCR switch Q1 and the first main electrode T1 is positive, and the voltage VT2-VT1 between the second main electrode T2 and the first main electrode T1 is also positive. Therefore, the bidirectional SCR switch Q1 operates in the first quadrant. It can be seen that the bidirectional SCR switch Q1 operates in both the first and third quadrants. In practical applications, a three-quadrant or four-quadrant SCR switch can be selected to replace the bidirectional SCR switch Q1.

[0105] Zero-crossing detection of a thyristor involves turning the thyristor on or off near its zero-crossing position. Specifically, when the thyristor is near zero, the load (heating device 200) should be quickly connected to or disconnected from the circuit. This is because, when the current is high, turning the circuit on or off can cause a significant impact on the load and power supply; the higher the current, the greater the impact, which can introduce numerous harmonic interferences into the power grid. Therefore, connecting or disconnecting the load when the current is zero minimizes the impact, thus avoiding the negative effects of frequent load disconnections.

[0106] In one embodiment of this application, when the baking machine is equipped with multiple heating devices 200, multiple heating control circuits 100 can be simultaneously configured, with each heating control circuit 100 connected to one heating device 200, enabling individual control of each heating device 200. For example, when the baking machine is equipped with three heating devices 200, the corresponding heating control circuits are as follows: Figure 7 As shown, Figure 7 The diagram shows three heating control circuits 100: heating control circuit 100_1, heating control circuit 100_2, and heating control circuit 100_3. Each heating control circuit 100 has the same circuit structure.

[0107] Figure 8 A schematic block diagram of a heating control circuit provided in one embodiment of this application is shown.

[0108] like Figure 8 As shown, the heating control circuit 100 provided in this embodiment includes a driving circuit 110, an optocoupler circuit 120, a switching circuit 130, and a temperature detection circuit 140. The structure and function of the driving circuit 110, the optocoupler circuit 120, and the switching circuit 130 can be referred to the description in the foregoing embodiments, and will not be repeated here.

[0109] The temperature detection circuit 140 is used to detect the temperature of the baking area and output a temperature detection signal. The temperature detection circuit 140 is connected to the main control circuit 400. The temperature detection circuit 140 sends the temperature detection signal to the main control circuit 400, and the main control circuit 400 generates a heating control signal based on the temperature detection signal.

[0110] In one embodiment of this application, the main control circuit 400 includes a comparator circuit 410 and a PID circuit 420. The comparator circuit 410 is connected to the temperature detection circuit 140 and is used to generate temperature difference information based on the temperature detection signal and the target signal corresponding to the target temperature. The PID circuit 420 is connected to both the comparator circuit 410 and the drive circuit 110 and is used to generate a heating control signal based on the temperature difference information. In short, the temperature detection circuit 140 realizes feedback regulation of the baking zone temperature.

[0111] When the heating device 200 starts working for the first time, the target signal (i.e., the set value, usually converted from temperature to voltage) corresponding to the target temperature is input to the comparison circuit 410. At this time, the detection signal can be set to a null value, and the temperature difference information at this time is the target signal itself. The comparison circuit 410 can directly input the target signal into the PID circuit 420. After processing by the PID circuit 420, a heating control signal is generated, which is then transmitted through the drive circuit 110, the optocoupler circuit 120, and the switching circuit 130 to control the heating device 200. After the heating device 200 has been working for a period of time, the temperature of the baking area changes. At this time, the actual temperature of the baking area can be detected by the temperature detection circuit 140, converted into a temperature detection signal, and fed back to the comparison circuit 410. Then, the comparison circuit 410 and the PID circuit 420 process the signal to generate a new heating control signal, which controls the heating device 200 so that the actual temperature of the baking area can approach the target temperature under the heating operation of the heating device 200.

[0112] Figure 9 A circuit diagram of a heating control circuit provided in one embodiment of this application is shown schematically.

[0113] like Figure 9 As shown, the heating control circuit 100 includes a drive circuit 110, an optocoupler circuit 120, a switching circuit 130, and a temperature detection circuit 140. The structure and function of the drive circuit 110, optocoupler circuit 120, and switching circuit 130 can be referred to the description in the preceding embodiments, and will not be repeated here. The temperature detection circuit 140 includes a temperature detection sub-circuit 141, a fourth filter sub-circuit 142, and a voltage follower sub-circuit 143. The temperature detection sub-circuit 141 detects the temperature of the baking area and converts the detected temperature information into a first temperature detection signal for output. The fourth filter sub-circuit 142 is connected to the temperature detection sub-circuit 141 and filters the first temperature detection signal to output a second temperature detection signal. The voltage follower sub-circuit 143 is connected to the fourth filter sub-circuit 142 and amplifies, buffers, and holds the second temperature detection signal to output a third temperature detection signal. The final output third temperature detection signal is the temperature detection signal input to the main control circuit 400.

[0114] Figure 10 A circuit diagram of a temperature detection circuit provided in one embodiment of this application is shown schematically.

[0115] like Figure 10As shown, the temperature detection circuit includes a temperature detection sub-circuit 141, a fourth filter sub-circuit 142, and a voltage follower sub-circuit 143. The temperature detection sub-circuit 141 includes a temperature sensor NTC and a pull-up resistor R308. One end of the temperature sensor NTC is connected to the operating power supply VCC (which can be the operating power supply MCU_3V3 provided by the microcontroller inside the baking machine, and the microcontroller can be the first part of the main control circuit 400) through the pull-up resistor R308, and the other end is grounded.

[0116] In one embodiment of this application, such as Figure 10 As shown, the fourth filter sub-circuit 142 includes a fourth filter resistor R309 and a fourth filter capacitor C216. One end of the fourth filter resistor R309 is connected to the temperature detection sub-circuit 141 (specifically, it is connected to the common connection terminal of the temperature sensor NTC and the pull-up resistor R308), and the other end is connected to the voltage follower sub-circuit 143. One end of the fourth filter capacitor C216 is connected to the common connection terminal of the fourth filter resistor R309 and the voltage follower sub-circuit 143, and the other end is grounded.

[0117] In one embodiment of this application, such as Figure 10 As shown, the voltage follower sub-circuit 143 includes a voltage follower U20A, which has a positive input terminal + (pin 3), an inverting input terminal - (pin 2), and an output terminal o (pin 1). The positive input terminal + is connected to the fourth filter resistor R309, and the inverting input terminal - is connected to the output terminal o. It can be understood that in practical applications, the voltage follower sub-circuit 143 can also employ other circuit structures to achieve signal current amplification, buffering, and signal holding processing.

[0118] In one embodiment of this application, the temperature sensor NTC is connected to the fourth filter sub-circuit 142 via a connector, such as... Figure 10 As shown, one end of the temperature sensor NTC is connected to pin 6 of connector J35. Pin 6 of connector J35 is connected to pull-up resistor R308 and fourth filter resistor R309, thus connecting the temperature sensor NTC to pull-up resistor R308. The other end of the temperature sensor NTC is connected to pin 5 of connector J35, which is grounded. An anti-static diode D97 is also connected between pins 6 and 5 of connector J35 to prevent electrostatic damage.

[0119] The resistance of an NTC temperature sensor changes with temperature; therefore, the function of an NTC temperature sensor can be considered as... Figure 10A variable resistor M is connected between node A and ground. The resistance of the variable resistor M is determined based on the temperature detected by the temperature sensor NTC. The voltage of node A changes with the resistance of the variable resistor M. Therefore, the voltage of node A can be regarded as a first temperature detection signal generated by the detected temperature of the baking area. This first temperature detection signal is low-pass filtered by the fourth filter resistor R309 and the fourth filter capacitor C216 to obtain a second temperature detection signal, which is then input to the positive input terminal + of voltage follower U20A. After processing the second temperature detection signal, voltage follower U20A outputs a third temperature detection signal through its output terminal o and sends the third temperature detection signal to the next stage circuit (such as the main control circuit 400). Voltage follower U20A effectively isolates the temperature sensor NTC from the main control circuit 400.

[0120] In one embodiment of this application, when the baking machine is equipped with multiple heating devices 200, multiple heating control circuits can be simultaneously configured, naturally including multiple temperature detection circuits. For example, when the baking machine is equipped with three heating devices 200, the corresponding temperature detection circuits are as follows: Figure 11 As shown, Figure 11 The diagram shows three temperature detection circuits 140: temperature detection circuit 140_1, temperature detection circuit 140_2, and temperature detection circuit 140_3. Each temperature detection circuit 140 has the same circuit structure. Specifically, the voltage follower U20A in temperature detection circuit 1 and the voltage follower U20B in temperature detection circuit 2 belong to the same chip. This chip contains two pairs of input / output ports, equivalent to having two operational amplifiers, one of which can function as a voltage follower. The three temperature detection circuits correspond to an NTC temperature sensor. Figure 11 All (not shown) are connected to the same connector J35, which has 6 interfaces. The temperature sensor NTC corresponding to each temperature detection circuit occupies two of these interfaces.

[0121] In some embodiments, the baking machine provided in this application may further include components such as a conveying component and / or a powder dispensing component to convey the printing medium and dispense hot melt adhesive powder.

[0122] It should be noted that although several circuits or units for the device of action execution have been mentioned in the detailed description above, this division is not mandatory. In fact, according to the embodiments of this application, the features and functions of two or more circuits or units described above can be embodied in one circuit or unit. Conversely, the features and functions of one circuit or unit described above can be further divided and embodied by multiple circuits or units.

[0123] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein.

[0124] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is limited only by the appended claims.

Claims

1. A heating control circuit, characterized by, The application is applied to a baking machine, the baking machine comprises a main control circuit and a heating device for generating heat to bake a printing medium; the heating control circuit comprises: a driving circuit for generating a first driving signal according to a heating control signal output by the main control circuit; a photoelectric coupling circuit connected with the driving circuit, comprising a light-emitting sub-circuit, a zero-crossing detection sub-circuit and a first switch sub-circuit; the light-emitting sub-circuit is used for generating a second driving signal according to the first driving signal, the zero-crossing detection sub-circuit is used for outputting a trigger signal when an alternating current power supply for supplying power to the heating device is in a zero position range, and the first switch sub-circuit is used for generating a switch control signal according to the second driving signal and the trigger signal; the zero position range represents that an absolute value of a difference between a voltage of the alternating current power supply and zero is within a preset range; a switch circuit connected with the photoelectric coupling circuit and the heating device; the switch circuit is used for conducting or disconnecting according to the switch control signal to control a working state of the heating device.

2. The heating control circuit of claim 1, wherein, The first switch sub-circuit comprises a controlled end, a first passage end and a second passage end, and the controlled end of the first switch is used for receiving the second driving signal and the trigger signal; the photoelectric coupling circuit further comprises a first filter sub-circuit, and the first filter sub-circuit is connected with the light-emitting sub-circuit in parallel; and / or, the photoelectric coupling circuit further comprises a first current limiting sub-circuit, one end of the first current limiting sub-circuit is connected with the second passage end of the first switch sub-circuit, and the other end of the first current limiting sub-circuit is connected with the alternating current power supply; and / or, the photoelectric coupling circuit further comprises a second current limiting sub-circuit, one end of the second current limiting sub-circuit is connected with the first passage end of the first switch sub-circuit, and the other end of the second current limiting sub-circuit is connected with the switch circuit; and / or, the photoelectric coupling circuit further comprises a third current limiting sub-circuit, one end of the third current limiting sub-circuit is connected with the driving circuit, and the other end of the third current limiting sub-circuit is connected with the light-emitting sub-circuit.

3. The heating control circuit of claim 2, wherein, The light-emitting sub-circuit comprises a first end and a second end; the first filter sub-circuit comprises a first filter capacitor and a first filter resistor, the first filter capacitor and the first filter resistor are connected in parallel, a first common connection end of the first filter capacitor and the first filter resistor is connected with a working power supply and the first end of the light-emitting sub-circuit, and a second common connection end of the first filter capacitor and the first filter resistor is connected with the second end of the light-emitting sub-circuit.

4. The heating control circuit of claim 2, wherein, The switch circuit comprises a bidirectional thyristor switch; a gate of the bidirectional thyristor switch is connected with the first passage end of the first switch sub-circuit; a first main electrode of the bidirectional thyristor switch is connected with the heating device; a second main electrode of the bidirectional thyristor switch is connected with the alternating current power supply.

5. The heating control circuit of claim 4, wherein, The switch circuit further comprises an anti-interference circuit, and the anti-interference circuit is arranged between the first main electrode and the second main electrode of the bidirectional thyristor switch. The anti-interference circuit comprises an anti-interference resistor and an anti-interference capacitor, one end of the anti-interference resistor is connected to the first main electrode of the bidirectional thyristor switch, the other end is connected to one end of the anti-interference capacitor, and the other end of the anti-interference capacitor is connected to the second main electrode of the bidirectional thyristor switch.

6. The heating control circuit according to any one of claims 1 to 5, characterized in that, The driving circuit comprises a second switch sub-circuit, and the second switch sub-circuit comprises a controlled end, a first end and a second end. The controlled end of the second switch sub-circuit is connected to the main control circuit, the first end of the second switch sub-circuit is grounded, and the second end of the second switch sub-circuit is respectively connected to the photoelectric coupling circuit and the working power supply.

7. The heating control circuit of claim 6, wherein, The driving circuit further comprises a second filter sub-circuit, which is connected between the working power supply and the second end of the second switch sub-circuit; and / or, The driving circuit further comprises a third filter sub-circuit, which is connected between the first end and the controlled end of the second switch sub-circuit; and / or, The driving circuit further comprises a fourth current limiting sub-circuit, which is connected between the main control circuit and the controlled end of the second switch sub-circuit.

8. The heating control circuit according to any one of claims 1 to 5, characterized in that, The heating control circuit further comprises: a temperature detection circuit connected to the main control circuit, for detecting the baking temperature and outputting a temperature detection signal, so that the main control circuit generates the heating control signal based on the temperature detection signal.

9. The heating control circuit of claim 8, wherein, The temperature detection circuit comprises: a temperature detection sub-circuit for detecting the baking temperature and outputting a first temperature detection signal; a fourth filter sub-circuit connected to the temperature detection sub-circuit, for filtering the first temperature detection signal and outputting a second temperature detection signal; a voltage follower sub-circuit connected to the fourth filter sub-circuit, for current amplification, buffering and signal holding processing of the second temperature detection signal, and outputting a third temperature detection signal.

10. The heating control circuit of claim 9, wherein, The temperature detection sub-circuit comprises a temperature sensor and a pull-up resistor, one end of the temperature sensor is connected to the working power supply through the pull-up resistor, and the other end is grounded; and / or, The fourth filter sub-circuit comprises a fourth filter resistor and a fourth filter capacitor, one end of the fourth filter resistor is connected to the temperature detection sub-circuit, the other end is connected to the voltage follower sub-circuit and one end of the fourth filter capacitor, and the other end of the fourth filter capacitor is grounded; and / or The voltage follower sub-circuit comprises a voltage follower, and the voltage follower comprises a forward input end, a reverse input end and an output end, the forward input end is connected to the fourth filter sub-circuit, and the reverse input end is connected to the output end.

11. A roaster, characterized by, It comprises: a plurality of heating devices for generating heat to perform baking treatment on a printing medium; a plurality of heating control circuits, wherein one of the heating devices is connected to one of the heating control circuits, and the heating control circuit is the heating control circuit of any one of claims 1 to 10; a main control circuit connected to the plurality of heating control circuits, for outputting a plurality of heating control signals to the plurality of heating control circuits respectively.

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