Temperature control circuit and image forming apparatus

Abstract

The application provides a temperature control circuit and an image forming device, and relates to the technical field of imaging. The temperature control circuit comprises, in sequence, a temperature detection circuit, a state comparison circuit, a first temperature protection circuit and a first switch circuit. The temperature detection circuit is configured to output a temperature detection value to the state comparison circuit. The state comparison circuit is configured to compare the temperature detection value with a preset temperature threshold value, and output a first level signal to the first temperature protection circuit. The first temperature protection circuit is configured to output a second level signal to the first switch circuit according to the first level signal, and lock the second level signal in a target state. The first switch circuit is configured to switch to an off state according to the second level signal. Through the technical solution, the heating can be stopped when the heating temperature of a fuser is abnormal, and the state of stopping heating can be locked, so that the reliability and safety of the temperature control process are improved.

Description

[Technical Field]

[0001] This application relates to the field of imaging technology, and in particular to a temperature control circuit and an image forming apparatus. [Background Technology]

[0002] Printers, copiers, and other image forming devices all contain fusers, which include heaters. These heaters are used to fix printing media such as toner onto the paper by heating, thereby completing the image formation. To ensure the safety of the heating process, it is necessary to detect and control the heating temperature of the fuser so that it can be stopped promptly in case of abnormal temperature. [Summary of the Invention]

[0003] This application provides a temperature control circuit and an image forming apparatus, which can be used to control the heating to stop when the fuser heating temperature is abnormal, and lock it in the stopped heating state, thereby improving the reliability and safety of the temperature control process.

[0004] In a first aspect, embodiments of this application provide a temperature control circuit, the circuit comprising: a temperature detection circuit, a state comparison circuit, a first temperature protection circuit, and a first switching circuit connected in sequence; the temperature detection circuit is used to detect the heating temperature of a heater and output the detected temperature value to the state comparison circuit; the state comparison circuit is used to compare the detected temperature value with a preset temperature threshold and output a first level signal associated with the comparison result to the first temperature protection circuit; the first temperature protection circuit is used to output a second level signal to the first switching circuit according to the first level signal and lock the second level signal in a target state; the first switching circuit is used to switch to an off state in response to the second level signal.

[0005] In one possible implementation, the first temperature protection circuit includes: a trigger circuit, a charging / discharging circuit, a current-blocking circuit, and a state-locking circuit connected in sequence; the trigger circuit is used to trigger the charging / discharging circuit to enter a charging state according to the first level signal; the charging / discharging circuit is used to trigger the state-locking circuit to generate a second level signal and lock the second level signal at the target state after charging to the target voltage, and to trigger the current-blocking circuit to prevent voltage backflow of the state-locking circuit.

[0006] In one possible implementation, after the state locking circuit locks the second level signal in the target state, the triggering circuit is further configured to: trigger the charging and discharging circuit to enter the discharging state according to the first level signal.

[0007] In one possible implementation, the first switching circuit includes a relay.

[0008] In one possible implementation, the circuit further includes a second temperature protection circuit and a second switching circuit; the state comparison circuit is further configured to output the first level signal to the second temperature protection circuit; the second temperature protection circuit is configured to generate a third level signal associated with the first level signal and output the third level signal to the second switching circuit; the second switching circuit is configured to switch to an off state in response to the third level signal.

[0009] In one possible implementation, the second switching circuit includes a thyristor.

[0010] In one possible implementation, the circuit further includes a third temperature protection circuit and a control module; the state comparison circuit is further configured to output the first level signal to the third temperature protection circuit; the third temperature protection circuit is configured to generate a fourth level signal associated with the first level signal and output the fourth level signal to the control module; the control module is configured to control the first switching circuit and / or the second switching circuit to switch to the off state in response to the fourth level signal.

[0011] In one possible implementation, the circuit further includes a power control circuit; the first temperature protection circuit is also used to output the second level signal to the power control circuit; the power control circuit is used to cut off the power supply in response to the second level signal.

[0012] In one possible implementation, the power supply includes a first power supply and a second power supply, the first power supply being used to power the fuser and the second power supply being used to power the image forming apparatus; the power control circuit is specifically used to, in response to the second level signal, cut off the first power supply; or, in response to the second level signal, cut off both the first power supply and the second power supply.

[0013] In a second aspect, embodiments of this application provide an image forming apparatus, including the temperature control circuit described in the first aspect.

[0014] In the above technical solution, the first temperature protection circuit can achieve circuit self-locking in the event of fuser overheating, thereby keeping the relay in the off state based on a stable output control signal. This improves the reliability of the temperature control process. Compared with the existing recoverable hysteresis protection circuit, the above technical solution can significantly improve the reliability and safety of fuser circuit protection. [Attached Image Description]

[0015] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the structure of a temperature control circuit provided in an embodiment of this application;

[0017] Figure 2 This is a schematic diagram of the structure of a state comparison circuit provided in an embodiment of this application;

[0018] Figure 3 This is a schematic diagram of the structure of a first temperature protection circuit provided in an embodiment of this application;

[0019] Figure 4 A schematic diagram of another first temperature protection circuit provided in an embodiment of this application;

[0020] Figure 5 A schematic diagram of another first temperature protection circuit provided in an embodiment of this application;

[0021] Figure 6 A schematic diagram of another first temperature protection circuit provided in an embodiment of this application;

[0022] Figure 7 This is a schematic diagram of another temperature control circuit provided in an embodiment of this application;

[0023] Figure 8 This is a schematic diagram of the structure of a second temperature protection circuit provided in an embodiment of this application;

[0024] Figure 9 This is a schematic diagram of another temperature control circuit provided in an embodiment of this application;

[0025] Figure 10 This is a schematic diagram of the structure of a third temperature protection circuit provided in an embodiment of this application;

[0026] Figure 11 This is a schematic diagram of another temperature control circuit provided in an embodiment of this application;

[0027] Figure 12 This is a schematic diagram of a power control circuit provided in an embodiment of this application;

[0028] Figure 13 This is a schematic diagram of another temperature control circuit provided in an embodiment of this application.

Detailed Implementation Methods

[0029] To better understand the technical solution of this application, the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0030] It should be understood that the described embodiments are merely some, not all, of the embodiments in this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0031] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0032] This application provides an image forming apparatus, which may include a fuser and a temperature control circuit for controlling the heating temperature of a heater in the fuser. The temperature control circuit provided in this application can detect the heating temperature of the heater in the fuser and control the heater to stop heating when the detected temperature value exceeds a set temperature threshold. Furthermore, the temperature control circuit provided in this application can lock the level signal, locking the fuser in a stopped heating state. Compared to a scheme that controls the fuser to automatically resume heating after a period of time following a stop heating period, this scheme offers higher reliability and safety.

[0033] The image forming apparatus provided in this application may be, for example, an inkjet printer, a laser printer, a light-emitting diode (LED) printer, a copier, or a multifunction printer, as well as a multi-function peripheral (MFP) that performs the above functions in a single device. This application does not impose any limitations on this.

[0034] The temperature control circuit provided in the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0035] Figure 1 This is a schematic diagram of a temperature control circuit provided in an embodiment of this application. Figure 1 As shown, the temperature control circuit provided in this application may include: a temperature detection circuit 11, a status comparison circuit 12, a first temperature protection circuit 13, and a first switching circuit 14 connected in sequence.

[0036] The temperature detection circuit 11 can be used to detect the heating temperature of the heater in the fuser and output the temperature detection value to the status comparison circuit 12.

[0037] Specifically, the temperature detection circuit 11 may include at least one temperature sensor, which may be in contact with the heating element of the fuser (such as a ceramic plate or halogen lamp). Each temperature sensor may output its detected temperature value to the state comparison circuit 12. In this embodiment, a smaller positive voltage at the temperature sensor indicates a higher detected temperature. In one feasible implementation, the temperature detection circuit 11 may include three temperature sensors, which may be positioned in the middle and on both sides of the heating element. Each of the three temperature sensors may output its detected temperature value to the state comparison circuit 12. Since the probability of all three temperature sensors failing simultaneously is almost zero, the reliability of the temperature detection process can be improved. Furthermore, since the three temperature sensors detect the heating temperature at different locations on the heating element, the accuracy of the temperature detection process can be improved. Understandably, the temperature sensors used in this application may employ conventional detection elements such as thermistors.

[0038] The state comparison circuit 12 can be used to compare the received temperature detection value with a preset temperature threshold and output a first level signal associated with the comparison result to the first temperature protection circuit 13.

[0039] Specifically, the state comparison circuit 12 may include at least one comparator, which may be connected to at least one temperature sensor and compare the temperature detection value output by the temperature sensor with a preset temperature threshold. When the temperature detection value is less than the threshold temperature, the first level signal output by the comparator may be a high level signal. When the temperature detection value is greater than the threshold temperature, the first level signal output by the comparator may be a low level signal. In this embodiment, when the comparison results of all comparators are that the temperature detection value is less than the threshold temperature, the first level signal output by the state comparison circuit 12 to the first temperature protection circuit 13 is, for example, a high level. When the comparison result of any comparator is that the temperature detection value is greater than the threshold temperature, the first level signal output by the state comparison circuit 12 to the first temperature protection circuit 13 is, for example, a low level.

[0040] It should be understood that the descriptions of high and low levels in this application are merely examples and are not intended to limit the scope of this application. In practical scenarios, high and low levels can be adaptively changed based on hardware design.

[0041] The first temperature protection circuit 13 is used to output a second level signal to the first switching circuit according to the first level signal, and lock the second level signal in the target state.

[0042] Specifically, the first temperature protection circuit 13 may include a self-locking circuit. When the first temperature protection circuit 13 receives a high-level first-level signal, the first temperature protection circuit 13 is inactive. When the first temperature protection circuit 13 receives a low-level first-level signal, the first temperature protection circuit 13 can generate a second-level signal and, based on the self-locking circuit, lock the second-level signal in a target state, such as a high-level state. The first temperature protection circuit 13 can also send the locked second-level signal to the first switching circuit 14.

[0043] In this embodiment, the first switching circuit 14 can be a relay. The first switching circuit 14 can be turned off upon receiving a second level signal and locked in the off state, thereby reliably stopping the fuser heating. Furthermore, based on the technical solution of this embodiment, when the locked state needs to be released, it can only be done by powering off and restarting, preventing the fuser from resuming heating, thus improving safety. Also, in the self-locking state, if the circuit malfunctions, it will not affect the downstream circuitry.

[0044] Figure 2 This is a schematic diagram of a state comparison circuit provided in an embodiment of this application. Figure 2 As shown, the state comparison circuit may include three comparators, namely U31A, U31B, and U32A. The three comparators can respectively receive temperature detection values ​​FUSER_FTH_READ, FUSER_RTH_READ, and FUSER_CTH_READ sent by three temperature sensors. For any first comparator, when the positive terminal voltage is higher than the negative terminal voltage (associated with a preset temperature threshold), the first level signal HW_OVER_TEMP output by the comparator is high, and the first temperature protection circuit 13 is not activated. When the positive terminal voltage is lower than the negative terminal voltage, the temperature detection value is higher than the preset temperature threshold. At this time, the level flips, the first level signal HW_OVER_TEMP output by the comparator is low, and the first temperature protection circuit 13 is activated.

[0045] Figure 3 This is a structural diagram of a first temperature protection circuit provided in an embodiment of this application. Figure 3 As shown, the first temperature protection circuit may include: a trigger circuit 31, a charging and discharging circuit 32, a current-blocking circuit 33, and a state-locking circuit 34 connected in sequence.

[0046] The input terminal of the trigger circuit 31 can be connected to the output terminal of the state comparison circuit 12. When the heating temperature of the fuser exceeds the set temperature threshold, the state comparison circuit 12 can send a first-level signal in a low-level state to the trigger circuit 31. In response to the first-level signal sent by the state comparison circuit 12, the trigger circuit 31 can trigger the charging / discharging circuit 32 to enter the charging state.

[0047] The charge / discharge circuit 32 can be used to trigger the state-locking circuit 34 to generate a second-level signal after charging to the target voltage, and lock the second-level signal in the target state, such as a high-level state. Additionally, the charge / discharge circuit 32 can trigger the current-blocking circuit 33 to prevent voltage backflow into the state-locking circuit 34, thereby maintaining a stable locked state cycle.

[0048] The aforementioned first temperature protection circuit allows it to enter a self-locking state after controlling the first switching circuit to turn off, thereby outputting a level signal with an unchanged state, keeping the first switching circuit in the off state. Furthermore, based on the self-locking function of the first temperature protection circuit, once the first switching circuit enters the off state, it can only be restored by power-off restart, thus preventing the fuser from continuing to heat after the temperature recovers, resulting in higher safety.

[0049] After the fuser resumes normal heating, the first level signal is set to a high level. At this time, the trigger circuit 31 can trigger the charging and discharging circuit 32 to enter the discharging state based on the first level signal until all electrical energy is lost.

[0050] In the above implementation scheme, the first temperature protection circuit can achieve circuit self-locking in the event of overheating of the fuser, thereby keeping the relay in the off state based on a stable control signal. Furthermore, the structure of the first temperature protection circuit is simpler than that of common self-locking circuits, saving components and reducing hardware costs.

[0051] Figure 4 A structural diagram of another first temperature protection circuit provided in an embodiment of this application is shown below. Figure 4 The working mechanism of the first temperature protection circuit in the embodiments of this application will be explained.

[0052] like Figure 4 As shown, when the fuser overheats, the first level signal HW_OVER_TEMP flips to a low level. At this time, transistor Q61 in the first temperature protection circuit is turned on. Since resistor R332 is a 100K resistor, it is in a high-resistance state and does not conduct. Consequently, capacitor C267 enters the charging state.

[0053] When capacitor C267 is charged to the forward voltage drop of diode D23 and transistor Q62, the path between diode D23 and transistor Q62 is turned on, and the base of transistor Q58 (PNP) is pulled down to ground, resulting in a low level and turn-on. Then, the second level signal LOCK_OVER_TEMP goes high. The first switching circuit can then be turned off based on this second level signal.

[0054] Furthermore, based on the unidirectional conduction characteristic of diode D23, the current will not flow back. The second level signal LOCK_OVER_TEMP can keep transistor Q62NPN conducting when it is in a high level state, and transistor Q58PNP will also conduct at the same time, so that the circuit achieves a self-locking state.

[0055] Once the circuit enters a self-locking state, it can only be released by power-off restart after confirming that the fuser has returned to normal. Specifically, after power-off restart, the power supply EC_3.3V is de-energized, and after being pulled down by the pull-down resistor R323, the first switching circuit returns to a controllable state.

[0056] Furthermore, after the first level signal HW_OVER_TEMP returns to a high level, transistor Q61 (PNP) is turned off, and capacitor C267 discharges rapidly through diode D24 and resistor R337. When the energy stored in capacitor C267 reaches the voltage drop across diode D24, diode D24 stops conducting, and capacitor C267 discharges slowly through resistors R33 and R337 until the energy is completely dissipated.

[0057] Figure 5 This is a structural diagram of another temperature control circuit provided in an embodiment of this application. Figure 5 As shown, in another embodiment of this application, the first temperature protection circuit may include a state locking circuit 35. The state locking circuit 35 may receive a control signal output by the state comparison circuit 12, and output a signal based on the control signal, thereby locking the output signal.

[0058] Specifically, when the fuser heating temperature exceeds a set temperature threshold, the state comparison circuit 12 can send a first-level signal in a low-level state to the state locking circuit 35. The state locking circuit 35 can generate a second-level signal output based on the first-level signal in a low-level state and lock the second-level signal in a high-level state.

[0059] Figure 6 A structural diagram of another first temperature protection circuit provided in an embodiment of this application is shown below. Figure 6 The working mechanism of the first temperature protection circuit in the above embodiments of this application will be explained.

[0060] like Figure 6 As shown, when the fuser overheats, the first level signal HW_OVER_TEMP toggles to a low level. At this time, transistor Q26 conducts, which in turn conducts transistor Q60, outputting the second level signal LOCK_OVER_TEMP, which is in a high level state. Due to the presence of diode D25, current does not flow back, keeping transistor Q26 in the conducting state, and the second level signal LOCK_OVER_TEMP remains in a high level state, thus forming a state lock.

[0061] Once the circuit enters a self-locking state, it can only be released by powering off and restarting after confirming that the fuser has returned to normal. Specifically, after powering off and restarting, the power supply EC_3.3V drops, is pulled down to ground through transistor Q26, and then returns to a controllable state.

[0062] Figure 7 This is a structural diagram of another temperature control circuit provided in an embodiment of this application. Figure 7 As shown, another embodiment of this application provides a temperature control circuit that may further include a second temperature protection circuit 15 and a second switching circuit 16. The second temperature protection circuit 15 is a hardware-based temperature protection circuit. The input terminal of the second temperature protection circuit 15 is connected to the output terminal of the state comparison circuit, and the output terminal of the second temperature protection circuit 15 is connected to the second switching circuit 16. The second switching circuit 16 may be a silicon controlled rectifier (SCR).

[0063] In this embodiment, the state comparison circuit 12 can also output a first-level signal to the second temperature protection circuit 15. The second temperature protection circuit 15 can generate a third-level signal based on the first-level signal and output the third-level signal to the second switching circuit 16. The second switching circuit 16 can be used to switch to an off state according to the third-level signal, thereby terminating the heating of the fuser.

[0064] Based on the above technical solution, two hardware protection channels can be set up simultaneously. One channel controls the relay switch based on the self-locking circuit, and the other channel controls the thyristor switch. This can prevent hardware failure from causing temperature control failure and further improve the reliability of the temperature control circuit.

[0065] Figure 8 This is a structural diagram of a second temperature protection circuit provided in an embodiment of this application. Figure 8 As shown, the second temperature protection circuit may include comparator U32B. When the fuser heating temperature is normal, the first level signal HW_OVER_TEMP is high, the voltage at the positive terminal of comparator U32B is higher than the voltage at the negative terminal, and the output third level signal is high. At this time, the second switching circuit is active. When the fuser overheats, the first level signal HW_OVER_TEMP is low, the voltage at the positive terminal of comparator U32B is lower than the voltage at the negative terminal, and the output third level signal is low. At this time, the second switching circuit is off, and fuser heating stops.

[0066] Figure 9 This is a structural diagram of another temperature control circuit provided in an embodiment of this application. Figure 9 As shown, in Figure 7Based on this, another embodiment of the temperature control circuit provided in this application may further include a third temperature protection circuit 17 and a control module 18. The input terminal of the third temperature protection circuit 17 may be connected to the output terminal of the state comparison circuit 12, and the output terminal of the third temperature protection circuit 17 may be connected to the control module 18. The control module 18 may be system firmware.

[0067] The third temperature protection circuit 17 can receive a first-level signal output by the state comparison circuit 12. Then, the third temperature protection circuit 17 can generate a fourth-level signal associated with the first-level signal and output the fourth-level signal to the control module 18. The control module 18 can then perform software-based control on the first and second switching circuits according to the fourth-level signal, thereby shutting off the first switching circuit 14 and / or the second switching circuit 16.

[0068] Based on the above technical solution, a software-based protection path can be added to the two hardware protection paths to further improve the reliability of the solution.

[0069] Figure 10 This is a structural diagram of a third temperature protection circuit provided in an embodiment of this application. Figure 10 As shown, when the fuser overheats, the first level signal HW_OVER_TEMP is low, the transistor Q23PNP is turned on, and the generated fourth level signal is in a low state. The fourth level signal is sent to the control module, which can control the first switching circuit and / or the second switching circuit to turn off based on the fourth level signal.

[0070] Figure 11 This is a structural diagram of another temperature control circuit provided in an embodiment of this application. Figure 11 As shown, the temperature control circuit provided in this embodiment may further include a power control circuit 19. The output terminal of the first temperature protection circuit 13 may also be connected to the input terminal of the power control circuit 19. When the fuser overheats, the first temperature protection circuit 13 may also output a second level signal to the power control circuit 19. Subsequently, the power control circuit 19 may shut off the power supply according to the second level signal.

[0071] In one specific implementation, the power supply may include a first power supply and a second power supply. The first power supply powers the fuser, and the second power supply powers the image forming apparatus. The power control circuit 19 can cut off the first power supply according to a second level signal. In this case, the scanning function of the image forming apparatus can be used normally, but functions requiring the fuser, such as printing and copying, cannot be used. Alternatively, the power control circuit 19 can simultaneously cut off both the first and second power supplies. In this case, the image forming apparatus cannot be used.

[0072] The above technical solution allows for direct disconnection of the power supply in case of abnormal heating temperature in the fuser, preventing further temperature increases.

[0073] Figure 12 This is a structural diagram of a power control circuit provided in an embodiment of this application. Figure 12 As shown, the second-level signal LOCK_OVER_TEMP output by the first temperature protection circuit can be connected to both the first power supply EC_PWR_EN and the second power supply PSU_24V_EN.

[0074] In one possible implementation, when the fuser overheats, the second level signal LOCK_OVER_TEMP goes high, which can cut off the first power supply EC_PWR_EN.

[0075] In another possible implementation, when the fuser overheats, the second level signal LOCK_OVER_TEMP goes high, which can simultaneously cut off the first power supply EC_PWR_EN and the second power supply PSU_24V_EN.

[0076] Figure 13 This is a structural diagram of another temperature control circuit provided in an embodiment of this application. Figure 13 As shown, the temperature control circuit provided in this application embodiment may include a heating device 10, a temperature detection circuit 11, a state comparison circuit 12, a first temperature protection circuit 13, a second temperature protection circuit 15, a third temperature protection circuit 17, a power control circuit 19, and an insertion detection circuit 20.

[0077] The temperature detection circuit 11 has its input connected to the heating device 10, and its output connected to the input of the state comparison circuit 12. The output of the state comparison circuit 12 can be connected to the first temperature protection circuit 13, the second temperature protection circuit 15, and the third temperature protection circuit 17, respectively. The temperature detection circuit 11 can detect the heating temperature of the heating device and output a level signal associated with the heating temperature to the state comparison circuit 12.

[0078] The first temperature protection circuit 13 includes a self-locking circuit, which is a hardware-based temperature protection channel that can control the relay to turn off based on the received level signal.

[0079] The second temperature protection circuit 15 is also a hardware-based temperature protection channel, which can control the turn-off of the thyristor based on the received level signal.

[0080] The third temperature protection circuit 17 is a software-based temperature protection channel that can send the received level signal to the system firmware, so that the system firmware can control the relay or thyristor to turn off from the software level.

[0081] The output of the first temperature protection circuit 13 can also be connected to the power control circuit 19. The first temperature protection circuit 13 can send a control level to the power control circuit 19 based on the received level signal. Then, the power control circuit 19 can control the first power supply to disconnect according to the control level, or simultaneously control the first power supply and the second power supply to disconnect.

[0082] The heating device 10 can also be connected to an insertion detection circuit 20, which can be used to detect the insertion status of the fuser socket. The relay can only work normally when the fuser is inserted.

[0083] The above implementation scheme sets up a multi-layer temperature protection circuit to protect the fuser from over-temperature, which improves the safety of the fuser heating process. When one layer of protection fails, other temperature protection circuits can be used for protection, which is more reliable.

[0084] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0085] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing custom logic functions or processes, and the scope of the preferred embodiments of this application includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as should be understood by those skilled in the art to which embodiments of this application pertain.

[0086] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0087] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or in a combination of hardware and software functional units.

[0088] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A temperature control circuit, characterized in that, include: A temperature detection circuit, a status comparison circuit, a first temperature protection circuit, and a first switch circuit are connected in sequence. The temperature detection circuit is used to detect the heating temperature of the heater and output the temperature detection value to the state comparison circuit. The state comparison circuit is used to compare the temperature detection value with a preset temperature threshold and output a first level signal associated with the comparison result to the first temperature protection circuit. The first temperature protection circuit is used to output a second level signal to the first switching circuit according to the first level signal, and lock the second level signal in the target state; The first switching circuit is used to switch to the off state according to the second level signal; The first temperature protection circuit includes: a trigger circuit, a charging and discharging circuit, a current blocking circuit, and a state locking circuit connected in sequence; The triggering circuit is used to trigger the charging and discharging circuit to enter the charging state according to the first level signal; The charging and discharging circuit is used to trigger the state locking circuit to generate a second level signal and lock the second level signal in the target state after charging to the target voltage, and to trigger the current blocking circuit to prevent the voltage backflow of the state locking circuit.

2. The circuit according to claim 1, characterized in that, After the state locking circuit locks the second level signal to the target state, the triggering circuit is further used for: Based on the first level signal, the charging and discharging circuit is triggered to enter the discharging state.

3. The circuit according to claim 1, characterized in that, The first switching circuit includes a relay.

4. The circuit according to claim 1, characterized in that, The circuit also includes a second temperature protection circuit and a second switching circuit; The state comparison circuit is also used to output the first level signal to the second temperature protection circuit; The second temperature protection circuit is used to generate a third level signal associated with the first level signal and output the third level signal to the second switching circuit; The second switching circuit is used to switch to the off state in response to the third level signal.

5. The circuit according to claim 4, characterized in that, The second switching circuit includes a silicon controlled rectifier (SCR).

6. The circuit according to claim 4 or 5, characterized in that, The circuit also includes a third temperature protection circuit and a control module; The state comparison circuit is also used to output the first level signal to the third temperature protection circuit. The third temperature protection circuit is used to generate a fourth level signal associated with the first level signal and output the fourth level signal to the control module; The control module is used to control the first switching circuit and / or the second switching circuit to switch to the off state in response to the fourth level signal.

7. The circuit according to claim 1, characterized in that, The circuit also includes a power control circuit; The first temperature protection circuit is also used to output the second level signal to the power control circuit; The power control circuit is used to cut off the power supply in response to the second level signal.

8. The circuit according to claim 7, characterized in that, The power supply includes a first power supply and a second power supply. The first power supply is used to power the fuser, and the second power supply is used to power the image forming apparatus. The power control circuit is specifically used to, in response to the second level signal, cut off the first power supply; or, in response to the second level signal, cut off both the first power supply and the second power supply.

9. An image forming apparatus, characterized in that, Includes the temperature control circuit as described in any one of claims 1 to 8.

Images