Device comprising a power supply unit

Abstract

An apparatus including a power supply unit is disclosed. The apparatus provided with a power supply device including a switching unit includes a switching unit, a judging unit, and a controller. In the case where the judging unit judges that an overcurrent state occurs during operation of the power supply device in a first mode, the mode of operation of the power supply device is switched to a second mode by the switching unit, and then the occurrence of the overcurrent state is notified.

Description

Technical Field

[0001] The present invention relates to a device including a power supply, and to a configuration for protecting the power supply installed in an image forming apparatus (such as a copier, printer or fax machine) from overload / overcurrent conditions. Background Technology

[0002] Power supply devices are provided for image forming apparatuses (such as copiers, printers, or fax machines) that form images on recording material using electrophotographic processing, etc. These power supply devices generate DC voltage from AC voltage and supply the power necessary for feeding the recording material and image formation. In many cases, the power supply device outputs DC voltage for at least two systems. One is the relatively low voltage output necessary for control elements or control circuits such as CPUs / ASICs. The other is the relatively high voltage output supplied to a high-voltage power supply or an actuator such as a motor / solenoid, which is necessary for outputting the high voltage required for electrophotographic processing. Furthermore, as power supply devices, there are configurations that provide multiple AC-DC converters, a single system that provides only an AC-DC converter for outputting a relatively high voltage, and a configuration where the relatively low voltage necessary for the control circuit is generated from the relatively high voltage by a DC-DC converter, and similar configurations. Especially recently, in power supply devices with high cost reduction requirements, configurations where the number of expensive AC-DC converters is limited to a single system have been widely used, thus requiring further simplification and cost reduction.

[0003] Such power supplies are conventionally equipped with protection circuits to prevent malfunctions by stopping operation of the power supply in the event of an overcurrent condition at the output. In devices supplying power to the power supply, the power supply may experience an overcurrent condition if it consumes significantly more power than assumed or if a short circuit occurs in the power path. The power supply then detects the overcurrent condition and stops output to prevent malfunctions. For example, Japanese Patent Application Publication No. 2020-058166 discloses a power supply with a protection function that stops the switching control of the switching element by a primary-side control circuit in the event of an abnormality in which excessive current flows in the output due to a load short circuit.

[0004] However, particularly in configurations where only one AC-DC converter in the system is provided with a power supply, if the AC-DC converter is in an overcurrent state and the protection circuit activates and stops the output of the AC-DC converter, the following situation arises: The output of the DC-DC converter connected to the output also stops, causing the operation of the device including the power supply (e.g., the operation of an image forming apparatus) to completely cease. In this case, the following problem arises: the user cannot understand why the operation of the power supply of the image forming apparatus suddenly stops. Furthermore, if an overcurrent continues to flow to the extent that the overcurrent protection function has not activated despite the power supply being in an overload state, there is a possibility that components in the power supply may overheat due to the overload state and be damaged. Moreover, in this case, the power supply suddenly stops operating due to damage caused by the overcurrent. For this reason, the following problem arises: the user does not understand why the operation of the power supply of the image forming apparatus suddenly stops and then turns the main switch of the image forming apparatus back on, thus there is a possibility that the damage from the fault may further escalate. Summary of the Invention

[0005] Under the above circumstances, the present invention has been completed. The main objective of the present invention is to provide an apparatus including a power supply device that can change the state of the power supply device to a safe state before the power supply device reaches a damaged state and can notify the user of the occurrence of an anomaly.

[0006] According to one aspect of the present invention, an apparatus including a power supply device is provided, the power supply device including a conversion unit configured to convert AC voltage into DC voltage and operable in a first mode and a second mode, wherein in the first mode, a first DC voltage converted by the conversion unit is output, and in the second mode, a second DC voltage converted by the conversion unit and lower than the first DC voltage is output, the apparatus including: a switching unit configured to switch an operating mode of the power supply device between the first mode and the second mode; a discrimination unit configured to determine whether an overcurrent state has occurred in the conversion unit; and a controller configured to perform control such that, if the discrimination unit determines that an overcurrent state has occurred during operation of the power supply device in the first mode, the operating mode of the power supply device is switched by the switching unit to the second mode, and then the occurrence of the overcurrent state is notified.

[0007] Further features of the present invention will become clear from the following description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0008] Figure 1This is a schematic diagram showing the structure of the image forming apparatus of Embodiment 1.

[0009] Figure 2 This is a circuit diagram showing the power supply unit and engine controller in Embodiment 1.

[0010] Figure 3 This is a flowchart illustrating the control in Embodiment 1.

[0011] Figure 4 This is a circuit diagram showing the power supply unit and engine controller in Embodiment 2.

[0012] Figure 5 This is a flowchart illustrating the control in Embodiment 2. Detailed Implementation

[0013] In the following, embodiments of the invention will be specifically described with reference to the accompanying drawings.

[0014] [Example 1]

[0015] [Image forming apparatus]

[0016] In the following description, using the accompanying drawings, an embodiment 1 is described in which the apparatus, including the power supply device according to the invention, is operated as an image forming apparatus. Figure 1 This is a schematic cross-sectional view showing the structure of an image forming apparatus using electrophotographic processing. Incidentally, in Embodiment 1, a laser beam printer will be described as an example of an image forming apparatus, but another image forming apparatus (such as a copier, fax machine, or a multifunction machine with the functions of these machines) can be used.

[0017] Alternatively, the power supply device of the present invention can also be installed in another electronic device. The main assembly 101 of the laser beam printer (hereinafter referred to as main assembly 101) includes a sheet (paper) feed cassette 104 for containing recording material S as a recording medium, a sheet feed roller 141 for feeding the recording material S from the sheet feed cassette 104, and a transfer roller pair 142. Additionally, the main assembly 101 includes a top sensor 143 provided downstream of the transfer roller pair 142 for detecting the leading edge of the recording material S, and an alignment roller pair 144 for synchronously transferring the recording material S. Furthermore, the main assembly 101 includes a cartridge unit 105 provided downstream of the alignment roller pair 144 for forming a toner image on the recording material based on a laser emitted from the laser scanner 106. The cartridge unit 105 includes a photosensitive drum 148, a primary charging roller 147, a developing roller 146, etc., which are known components required for electrophotographic processing as image carriers, and cooperates with the transfer roller 145 to form a toner image on the recording material S. Additionally, the main assembly 101 includes a thermal fixing apparatus 103 provided downstream of the cartridge unit 105 for thermal fixing the (unfixed) toner image formed on the recording material S. The thermal fixing apparatus 103 includes a fixing film 149, a pressure roller 150, and a heater 102 provided inside the fixing film 149.

[0018] The thermal fixing apparatus 103 includes a thermistor 109 provided adjacent to the heater 102 to detect the temperature of the heater 102 in the fixing film 149. Additionally, the main assembly 101 includes a discharge roller pair 151 provided downstream of the thermal fixing apparatus 103, and after the toner image is formed, the toner image is discharged by the recording material S thermally fixed thereon through the discharge roller pair 151.

[0019] The power supply unit 120, which serves as a power source (details of which will be described later), is capable of outputting either 24V or 5V in a suitable switching manner, and outputs 24V during operation in printing mode or standby mode. Here, printing mode refers to the state where an image can be formed on the recording material S, and standby mode refers to the state where power consumption is lower than in printing mode and the main component 101 awaits a printing command to switch to printing mode. Additionally, there is a sleep mode where the minimum function of the main component 101 is activated, thus achieving further power savings. The power supply unit 120 supplies 24V as the drive system voltage via the engine controller 123, which will be described later. The drive system voltage is the voltage supplied to drive units such as motors or clutches (not shown) and the drive portion (not shown) of the rotatable polygonal mirror included in the laser scanner 106.

[0020] The engine controller 123 controls the main component 101 and controls the feeding of the recording material S by controlling the operation of each roller via the aforementioned drive unit (not shown). Additionally, the engine controller 123 controls the laser scanner 106, cartridge unit 105, thermal fixing device 103, etc., and thus performs image forming operations (printing operations). Furthermore, the engine controller 123 houses a DC-DC converter 121, described later, which generates a 3.3V voltage, primarily used in the control system, based on the voltage supplied from the power supply unit 120. Incidentally, the DC-DC converter 121 can also be provided externally to the engine controller 123. The 3.3V voltage generated by the DC-DC converter 121 is supplied to the control circuitry (not shown) provided internally in the engine controller 123. The 3.3V voltage is also supplied to the circuitry of the control system, including the video controller 131, the laser emitting section of the laser scanner 106 (not shown), the top sensor 143, etc., described later. The video controller 131 is connected to the engine controller 123 via the engine interface 133 and to an external device 132, such as a personal computer, via a general interface 134 (e.g., USB).

[0021] In the power supply unit 120, the AC power supply 201, described later (see [link to power supply unit 120]), is detected. Figure 2 At the zero-crossing timing, a zero-crossing detection signal (not shown) is sent to the engine controller 123. Then, the engine controller 123 controls the heater switching unit (component) (not shown) so that power from the AC power supply 201 is provided synchronously with the zero-crossing timing with a duty cycle having a predetermined phase angle and a predetermined wave number, and thus performs control to change the temperature of the heater 102 to a predetermined temperature.

[0022] The video controller 131 receives printing information (e.g., number of pages to print and various settings) and printing data from the general interface 134. Additionally, the video controller 131 includes an image controller (not shown) mounted therein, through which the printing data is expanded into image data capable of being actually printed. Subsequently, the engine controller 123 receives the image data from the video controller 131 via the engine interface 133 at predetermined timings and sends the image data to the laser scanner 106. In the image forming operation, components that facilitate the formation of an image on the recording material S during image forming serve as image forming units (components).

[0023] [Power Supply Unit]

[0024] Figure 2This is a circuit diagram showing the configuration of the power supply unit 120 and engine controller 123 as power supply devices in Embodiment 1. An AC power supply 201 is connected to the power supply unit 120, and a voltage Vo2 is generated from the input AC voltage and output to the secondary side. Here, the DC voltage Vo2 includes at least two output voltage values, comprising 24V as a first DC voltage and 4V as a second DC voltage. For example, when the main component 101 is in printing mode or standby mode (in a standby state capable of instant printing), it outputs 24V as the DC voltage Vo2. Hereinafter, the state where the DC voltage Vo2 is 24V is referred to as the first output mode (first mode). On the other hand, when the main component 101 is in sleep mode (power saving mode), it outputs 5V as the DC voltage Vo2. Hereinafter, the state where the DC voltage Vo2 is 5V is referred to as the second output mode (second mode). The engine controller 123 includes a CPU 223 as a control unit (component), and the CPU 223 performs the switching of the DC voltage Vo2. CPU 223 serves as a switching unit (component) for switching the mode of the main component 101 between a first mode and a second mode. Incidentally, the power supply unit 120 may include CPU 223 by providing CPU 223 integrally with or in a similar manner to the power supply board (not shown) provided in the printer main component 101.

[0025] The AC voltage input to the AC power supply 201 of the power supply unit 120 is rectified by the bridge diode 204 and then smoothed by the capacitor 210, thereby becoming a DC voltage with the DCL line as the negative terminal and the DCH line as the positive terminal. The DCH line is connected not only to one of the two terminals of the primary winding 205a of the power transformer 205, but also to the VH terminal of the power supply IC 222 through the resistor 230, thus supplying voltage.

[0026] The power supply IC 222 begins operation when a voltage is applied to the VH terminal. Incidentally, in Figure 2 In the transformer 205, one side of the primary winding 205a and the first auxiliary winding 205b is the primary side, and the side of the secondary winding 205c is the secondary side.

[0027] The field-effect transistor (FET) 243, serving as a switching element, includes a drain terminal connected in series to the other terminal of the primary winding 205a and a source terminal connected to the DCL line via a current-sensing resistor 241. Additionally, the gate terminal of the FET 243 is connected to the OUT terminal of the power supply IC 222 via a gate resistor 242. The power supply IC 222 performs on / off control of the FET 243, thereby allowing current to flow through the primary winding 205a. The current flowing through the primary winding 205a is converted into a voltage by the current-sensing resistor 241, and this voltage is input to the IS terminal of the power supply IC 222. The power supply IC 222 monitors the voltage at the IS terminal and performs control to ensure that the current flowing through the primary winding 205a and the FET 243 falls within a predetermined current range.

[0028] When current flows through the primary winding 205a, flyback voltages are induced in the primary auxiliary winding 205b and the secondary winding 205c to have opposite polarities. The voltage induced in the primary auxiliary winding 205b is rectified and smoothed by resistor 233, diode 234, and capacitor 235, and then output as voltage Vcc. This voltage Vcc is then supplied as the power supply voltage to the Vcc terminal of power IC 222. Meanwhile, the voltage induced in the secondary winding 205c is rectified by the secondary-side rectifier diode 251, which acts as a rectifier element, and then smoothed by the secondary-side smoothing capacitor 252, which acts as a smoothing unit (component), and then output as DC voltage Vo2. Bridge diode 204, capacitor 210, transformer 205, FET 243, power IC 222, secondary-side diode 251, and secondary-side smoothing capacitor 252 serve as a conversion unit (component) for converting AC voltage to DC voltage.

[0029] (Feedback circuit)

[0030] Next, the feedback circuit 224 will be described. The feedback circuit 224 consists of resistors 253, 254, 255, 256, 257, shunt regulator 258, FET 259, optocoupler 206, capacitor 207, etc.

[0031] Feedback circuit 224 monitors the DC voltage Vo2 and feeds it back as an FB signal from the secondary side circuit to the FB terminal of the primary side power supply IC 222 via optocoupler 206, causing the DC voltage Vo2 to become 5V or 24V. Power supply IC 222 performs on / off control of FET 243 based on the voltage dependent on the FB signal input to the FB terminal, causing the DC voltage Vo2 to become a predetermined voltage. Additionally, a 5V / 24V signal is input from engine controller 123 to feedback circuit 224, causing the output voltage to switch via the 5V / 24V signal, thereby changing the DC voltage Vo2 to 5V or 24V. Feedback circuit 224 performs feedback, causing the DC voltage Vo2 to become 5V when the 5V / 24V signal is high, and 24V when the 5V / 24V signal is low.

[0032] Resistors 253, 254, and 256 are connected in series between the DC voltage Vo2 and ground (“Gnd”), and FET 259 is connected in parallel to resistor 256. The drain terminal of FET 259 is connected to the junction between resistors 254 and 256, and the source terminal of FET 259 is connected to Gnd. Additionally, a 5V / V 24 signal is input from engine controller 123 to the gate terminal of FET 259.

[0033] The photodiode 206a of the optocoupler 206 includes an anode terminal connected to the DC voltage Vo2 via resistor 255, and a cathode terminal connected to the cathode terminal of the shunt regulator 258. Incidentally, the resistor 257 connected in parallel to the photodiode 206a of the optocoupler 206 is a resistor used to bypass the leakage current of the shunt regulator 258. The shunt regulator 258 includes an anode terminal connected to the DC voltage Vo2 (Gnd) and a reference terminal connected to the connection point between resistors 253 and 254. Additionally, the phototransistor 206b of the optocoupler 206 includes a collector terminal connected to the FB terminal of the power supply IC 222 as an FB signal and an emitter terminal connected to the DCL line. Here, capacitor 207 is a capacitor that provides the FB signal and is used for noise absorption, and is connected between the FB terminal of the power supply IC 222 and the DCL line.

[0034] Next, the method by which feedback circuit 224 switches DC voltage Vo2 from 24V to 5V will be described. When the 5V / 24V signal output from engine controller 123 is high, FET 259 is turned on. At this time, the voltage divided from DC voltage Vo2 by resistors 253 and 254 is input to the reference terminal of shunt regulator 258. This voltage is then fed back to the FB terminal of power supply IC 222 via optocoupler 206, causing the voltage at the reference terminal of shunt regulator 258 to become the same as the internal reference voltage, resulting in DC voltage Vo2 being controlled to 5V. Conversely, when the 5V / 24V signal is low, FET 259 is turned off. At this time, the voltage divided from DC voltage Vo2 by resistors 253, 254, and 256 is input to shunt regulator 258. Then, the voltage is fed back to the FB terminal of the power IC 222 through the optocoupler 206, so that the voltage at the reference terminal of the shunt regulator 258 becomes the same as the internal reference voltage, resulting in the DC voltage Vo2 being controlled to 24V.

[0035] (Engine controller, etc.)

[0036] The engine controller 123 houses a CPU 223 and a DC-DC converter 121. The DC voltage Vo2 output from the power supply unit 120, along with a control signal (not shown) output from the CPU 223, is connected from the engine controller 123 to the aforementioned drive unit (not shown) or a high-voltage power supply, etc. Incidentally, in sleep mode operation, the DC voltage Vo2 becomes 5V. Therefore, to avoid unnecessarily supplying 5V to the drive unit, etc., a switch or similar device for cutting off the supply of DC voltage Vo2 can be provided during sleep mode operation.

[0037] A 5V / 24V signal is output from the engine controller 123 to the power supply unit 120. A 5V / 25V signal is output from the Port 201 terminal of the CPU 223 through resistor 264, allowing a high or low level to be input to the power supply unit 120. The CPU 223 switches the DC voltage Vo2 to 5V or 24V by switching the level of the Port 201 terminal to high or low.

[0038] The DC voltage Vo2 output from the power supply unit 120 is input to the engine controller 123. Also, the DC voltage Vo2 is input to the DC-DC converter 121 as a generating unit (component). The DC-DC converter 121 outputs a voltage Vo, which is a third DC voltage lower than the DC voltage Vo2 (Vo < Vo2). Here, the DC-DC converter 121 operates to output a predetermined voltage (e.g., 3.3V) even if the input DC voltage Vo2 is either 24V or 5V. In addition, the voltage Vo is supplied to the circuits of the control system including the CPU 223, a control circuit (not shown), a video controller 131, a laser emission part of the laser scanner 106 (not shown), a top sensor 143, etc. in the engine controller 123 as described above.

[0039] The thermistor 208 as a detection element (temperature detection unit (component)) is provided inside the power supply unit 120 and disposed in the vicinity of the transformer 205 (in this case, its secondary winding 205c) which is an element that generates heat due to an increase in load current and in the vicinity of the secondary side rectifier diode 251. The thermistor 208 includes one terminal connected to the secondary side Gnd and another terminal connected to the A / D 201 terminal of the A / D port of the CPU 223 on the engine controller 123 so as to input a TH signal to the A / D 201 terminal. Then, the TH signal is pulled up by the pull-up resistor 209 on the engine controller 123.

[0040] The CPU 223 monitors the TH signal in a state where the main unit 101 is in the standby mode or the print mode (low level state of the 5V / 24V signal), and determines whether the temperature detected by the thermistor 208 falls within the normal range. When the temperature as the detection result of the thermistor 208 is a predetermined temperature or less, the CPU 223 determines that the transformer 205 and the secondary side rectifier diode 251 are operating normally. The predetermined temperature is a threshold value for determining whether the state of the CPU 223 is normal or abnormal. At this time, the CPU 223 determines that the load current falls within the normal value.

[0041] On the other hand, if the temperature detected by the thermistor 208 is higher than a predetermined temperature, the CPU 223 determines that the load current of the power supply unit 120 has become abnormally high and the temperatures of the transformer 205 and the secondary-side rectifier diode 251 have risen to abnormally high temperatures. If the temperature detected by the thermistor 208 is higher than a predetermined threshold, the CPU 223 determines that the transformer 205 and the secondary-side rectifier diode 251 are in an overcurrent state. The CPU 223 serves as a discrimination unit (component) for determining that the power supply unit 120 is in an overcurrent state. In this case, the CPU 223 changes the level of the 5V / 24V signal from low to high. Then, the CPU 223 notifies the video controller 131 that the load state of the main component 101 is abnormal. The video controller 131 causes the display panel 160 of the main component 101 to display a message indicating an abnormal load state (i.e., overload state), for example, information roughly meaning that the power supply unit 120 has caused an error. Additionally, the video controller 131 notifies the external device 132 via the general interface 134 that the power supply unit 120 is in an overload state, and can cause the screen of the external device 132 to display a message that roughly means that.

[0042] Additionally, the main component 101 can print a message indicating that the power supply unit 120 is in an overload state on the recording material S, and then output the recording material S. Thus, the CPU 223 can notify the user that the power supply unit 120 is in an abnormal state. Therefore, in Embodiment 1, when the CPU 223 determines that the power supply unit 120 is in an overcurrent state, the CPU 223 switches the state of the DC voltage Vo2 to a second mode and performs control to notify the user of the overcurrent state of the power supply unit 120.

[0043] [Exception detection and notification processing]

[0044] Next, we will use Figure 3 The control of Embodiment 1 is described. When the main component 101 is powered on, step (S) 102 and subsequent steps are executed. In S102, the power supply unit 120 is started when a voltage is applied to the VH terminal of the power supply IC 222 in the power supply unit 120.

[0045] At this time, the 5V / 24V signal is at a low level. For this reason, the power supply unit 120 is initially in the state of outputting a 24V DC voltage Vo2 (first voltage-current mode), and thus supplies the 24V DC voltage Vo2 to the engine controller 123.

[0046] In S103, the engine controller 123 is activated by being supplied with DC voltage Vo2 in S102, and the DC-DC converter 121 starts operating and outputs voltage Vo. This voltage Vo is then supplied to the CPU 223, causing the CPU 223 to start operating. In S104, the CPU 223 continues operation in print mode or standby mode (“STBY / PRINT M”) while the 5V / 24V signal is at a low level due to the voltage Vo supplied in S103. In S105, the CPU 223 monitors the state of the thermistor 208 and determines whether the temperature detected by the thermistor 208 falls within the normal range. Specifically, the CPU 223 determines that the power supply unit 120 is normal when the detected temperature is at or below a predetermined temperature, and determines that it is abnormal when the detected temperature is above the predetermined temperature.

[0047] If CPU 223 determines in S105 that the detected temperature is within the normal range, CPU 223 advances the sequence to S106. If CPU 223 determines in S105 that the detected temperature is not within the normal range, CPU 223 advances the sequence to S108. In S106, CPU 223 determines whether it can transition to sleep mode. If CPU 223 determines in S106 that it cannot transition to sleep mode, CPU 223 returns the sequence to S104. If CPU 223 determines in S106 that it can transition to sleep mode, CPU 223 advances the sequence to S107. In S107, CPU 223 sets the 5V / 24V signal to a high level, thus transitioning to sleep mode, and then returns the sequence to S106.

[0048] In S108, CPU 223 switches the 5V / 24V signal to a high level, thus switching the DC voltage Vo2 from 24V to 5V (5V output). The decrease in DC voltage Vo2 significantly reduces the load current, resulting in a lower temperature. As a result, damage to the components of power supply unit 120 is avoided, and DC voltage Vo2 is continuously and safely output. In S109, CPU 223 causes a user interface such as display panel 160 to display information indicating an abnormality (i.e., an overload) in the output line of power supply unit 120, including the main components, and notifies the user of the output line abnormality. Then, CPU 223 causes power supply unit 120 to stop its operation, ending the sequence. Incidentally, before operation of power supply unit 120 stops, operation can continue when CPU 223 monitors the state of the thermistor 208 and the temperature returns to the normal range.

[0049] In Embodiment 1, the thermistor 208 is deployed near components that are prone to heat generation when the secondary-side components are under overcurrent load conditions (such as the secondary winding 205c of transformer 205 and the secondary-side rectifier diode 251).

[0050] However, the configuration of the thermistor 208 is not limited to... Figure 2 The configuration shown can also be placed near components whose temperature rises more easily due to load current (such as the primary-side FET 243 and the primary winding 205a of the transformer 205). However, in the case of detecting primary-side components, for safety, insulation between the primary and secondary sides needs to be considered. That is, an insulated transmission unit (component) such as an optocoupler is needed to transmit the detection result of the primary-side temperature detection unit (component) to the secondary-side engine controller 123. Therefore, the thermistor 208 can also detect the temperature of at least one of the primary winding 205a, secondary winding 205c, FET 243, and secondary-side rectifier diode 251. In addition, the component whose temperature is detected is not limited to the above-mentioned components; it may be required that the component heats up due to the flow of current (hereinafter referred to as the heating element). For example, a load switch (not shown) provided on the secondary side, a resistor for detecting current, etc., are included in the heating element.

[0051] Furthermore, in Embodiment 1, the case of using two modes with DC voltage Vo2 of 24V and 5V was described, but the present invention is not limited thereto. The present invention can also be applied to systems that include output voltages of more than and different from the two modes of DC voltage, depending on the structure and purpose of the associated equipment. That is, it may be necessary to require the power supply device to output two or more different voltages. In this case, depending on the heat generated, the operation of switching the voltage to a lower voltage can be repeated multiple times, and the switching voltage can be selected based on the heat generated. Additionally, depending on the value of the switched DC voltage Vo2, the threshold used to detect anomalies (such as the normal temperature range) can be changed. For example, when DC voltage Vo2 is 5V, anomalies can be detected at temperatures lower than when DC voltage Vo2 is 24V. In this case, it may be necessary to require the CPU 223 to monitor the state of the thermistor 208, even when the power supply unit 120 outputs 5V as DC voltage Vo2 (e.g., in…). Figure 3 (After processing S107).

[0052] As described above, in Embodiment 1, the load state of the power supply unit 120 is monitored by the thermistor 208, and a determination is made based on the detection result of the thermistor 208 whether an abnormal load has been generated. Then, if a determination is made that an abnormal load has been generated, damage to the components of the power supply unit 120 is prevented, making it possible to switch the voltage to a voltage that creates a safe state by changing the mode. Furthermore, the abnormal load state of the power supply unit 120 can be notified to the user. Therefore, even if an abnormality occurs in the image forming apparatus and its connected devices, and the load current of the power supply device becomes excessive, the components provided in the power supply device can be maintained in a safe state while utilizing the existing structure, and the user can be notified of the occurrence of the abnormality.

[0053] As described above, according to Embodiment 1, the power supply device can be switched to a safe state before it fails and the user is notified of the occurrence of the anomaly.

[0054] [Example 2]

[0055] [Power Supply Unit]

[0056] Next, Embodiment 2 will be described using the accompanying drawings. In Embodiment 1 above, an example was described in which the overcurrent of the power supply unit 120 was detected by a thermistor 208, which is a temperature sensing element.

[0057] In Embodiment 2, an example of detecting overcurrent in power supply unit 420 by overcurrent detection circuit 424 (current detection unit (component)) for detecting current flowing through transformer 205 will be described.

[0058] Incidentally, the main structure and operation are the same as described in Embodiment 1, and therefore descriptions will be omitted by adding the same reference numerals or symbols. Similarly, power supply unit 120 and engine controller 123 are read as power supply unit 420 and engine controller 423, respectively. These will be described in detail below.

[0059] Figure 4 This is a circuit diagram showing the configuration of the power supply unit 420 and the engine controller 423. Figure 2 In contrast, power supply unit 120, engine controller 123, power supply IC 222, and CPU 223 are replaced by power supply unit 420, engine controller 423, CPU 422, and CPU 323, respectively. These CPUs 422 and 323 are power controllers. However, the main operation of these components is essentially the same as that in Embodiment 1. On the other hand, Embodiment 2 differs from Embodiment 1 in that the thermistor 208 and pull-up resistor 209 are removed, and an overcurrent detection circuit 424 is added. The differences will be mainly described below.

[0060] Power supply unit 420 generates DC voltage Vo2 from the input AC voltage and outputs DC voltage Vo2 to the secondary side. In embodiment 2, the control of DC voltage Vo2 is performed by power supply CPU 422 provided on the primary side. Furthermore, the switching of DC voltage Vo2 between 5V and 24V is performed by CPU (control unit (component)) installed in engine controller 423. The AC voltage input to power supply unit 420 is rectified and smoothed by bridge diode 204 and capacitor 210 and becomes DC voltage for the DCL and DCH lines. The voltage is divided by resistors 430, 431, and 432. Zener diode 436 is connected in parallel to resistor 432 and clamped by voltage Vcc before being supplied to the Vcc terminal. Power supply CPU 422 begins operation when a voltage is applied to the Vcc terminal.

[0061] The resistor CPU 422 includes a Port 403 terminal connected to the gate terminal of the FET 243 via a gate resistor 242, and performs on / off control of the FET 243 by setting the Port 403 terminal to a high or low level. Then, when current flows through the primary winding 205a, the current is converted into a voltage by the current sensing resistor 241, and this voltage is input to the A / D 401 terminal, which serves as the A / D port of the power supply CPU 422. The power supply CPU 422 monitors the voltage at the A / D 401 terminal and performs control to ensure that the current flowing through the primary winding 205a and the FET 243 falls within a predetermined current range. Incidentally, when a voltage is induced in the primary winding 205b by the startup of the power supply CPU 422 and the initiation of the switching operation of the FET 243, and this voltage begins to be output to the capacitor 235, the voltage Vcc is switched and supplied from the primary winding 205b. Additionally, the FB signal output from the feedback circuit 224 is input to the A / D 402 terminal of the A / D port of the power supply CPU 422.

[0062] (Overcurrent detection circuit)

[0063] Next, the overcurrent detection circuit 424 will be described. The output stage of the DC voltage Vo2 is provided with a current detection resistor 408 for detecting the current flowing through the engine controller 423. The voltage of the current detection resistor 408 on the primary side is divided by the resistor 410 and the resistor 411 provided on the engine controller 423, and the voltage Vc obtained by the voltage division is input to the inverting input terminal (- terminal) of the comparator 412 similarly provided on the engine controller 423. The voltage of the current detection resistor 408 on the output side (DC voltage Vo2) is input to the non-inverting input terminal (+ terminal) of the comparator 412 through the resistor 413 similarly provided on the engine controller 423. The output terminal of the comparator 412 is not only input to the Port 401 terminal of the CPU 323, but is also pulled up to the voltage Vo by the resistor 409.

[0064] When the current flowing through the engine controller 423 falls within the normal range, the voltage drop of the resistor 408 is small, and the resulting DC voltage Vo2 is higher than the voltage Vo divided by the resistor 410 and the resistor 411 (Vo2 > Vo). Therefore, the output of the comparator 412 is at a high level and is input to the CPU 323. When the current flowing through the engine controller 423 exceeds the normal range and is large, the voltage drop of the resistor 408 becomes larger, so that the DC voltage Vo2 becomes lower than the voltage Vc (Vo2 < Vc). Therefore, the output of the comparator 412 is inverted to a low level and is input to the Port 401 terminal of the CPU 323. When the DC voltage Vo2 is lower than the voltage Vc, in other words, when the current detected by the overcurrent detection circuit 424 is greater than a predetermined threshold, the CPU 323 determines that an overcurrent state has been formed. The CPU 323 monitors the level of the Port 401 terminal and thus determines the normality or abnormality of the current value.

[0065] When the DC voltage Vo2 is 5V, the difference ΔV5V between the voltage Vc divided by the resistors 410 and 411 and the DC voltage Vo2 becomes smaller than the difference ΔV24V when the DC voltage Vo2 is 24V (ΔV5V < ΔV24V). That is, when the DC voltage Vo2 is 5V, the output of the comparator 412 is inverted due to an output current lower than when the DC voltage Vo2 is 24V, and notifies the CPU 323 of an abnormality. When a low level is input to the Port 401 terminal when the DC voltage Vo2 is 24V, the CPU 323 changes the level of the Port 201 terminal from a low level to a high level, so that the DC voltage Vo2 is switched from 24V to 5V. In addition, when a low level is input to the Port 401 terminal when the DC voltage Vo2 is 5V, the CPU 323 changes the level of the Port 402 terminal from a low level to a high level, thus changing the level of the Pstop signal.

[0066] (Pstop signal)

[0067] The Pstop signal, output from Port 402 of CPU 323, is input from engine controller 423 to power supply unit 420, and then through resistor 455 to the anode terminal of photodiode 406a of optocoupler 406. The cathode terminal of photodiode 406a is connected to the secondary side Gnd. The phototransistor 406b of optocoupler 406 includes a collector terminal, which is not only input to Port 404 of power supply CPU 422, but is also pulled up to voltage Vcc by resistor 456. The emitter terminal of phototransistor 406b is connected to the DCL line. When the Pstop signal is low, photodiode 406a of optocoupler 406 is turned off. The collector terminal of phototransistor 406b of optocoupler 406 becomes high, causing Port 404 of power supply CPU 422 to become high. Because Port 404 is high, power supply CPU 422 determines that power supply unit 420 is normal and continues its operation.

[0068] On the other hand, when the Pstop signal goes high, the photodiode 406a of the optocoupler 406 is turned on, causing the collector terminal of the phototransistor 406b of the optocoupler 406 to go low. When the power supply CPU 422 detects a transition from the level of the Port 404 terminal to a low level, the power supply CPU 422 determines that an abnormality has occurred, and the operation of the power supply CPU 422 stops. In Embodiment 2, if the CPU 323 determines that an overcurrent state has occurred during operation in the second mode, the CPU 323 stops the operation of the power supply CPU 422.

[0069] [Exception detection and notification processing]

[0070] Next, we will use Figure 5 The control of Embodiment 2 is described. When the main component 101 is powered on, S202 and subsequent processing are executed. In S202, the power supply unit 420 is started when a voltage is applied to the VH terminal of the power supply CPU 422 in the power supply unit 420.

[0071] At this time, the 5V / 24V signal is at a low level, therefore, the DC voltage Vo2, which is the output voltage of the power supply unit 120, is 24V, so that the DC voltage Vo2 is supplied to the engine controller 423. In S203, the engine controller 423 is started by being supplied with the DC voltage Vo2 in S202, and the DC-DC converter 121 starts operating and outputs voltage Vo, causing the CPU 323 to start operating. In S204, the CPU 323 continues to operate in printing mode or standby mode while the 5V / 24V signal is at a low level.

[0072] In S205, CPU 323 monitors the status of overcurrent detection circuit 424 and determines whether current 208 falls within the normal range. Specifically, CPU 323 determines that power supply unit 420 is normal when DC voltage Vo2 is equal to or greater than voltage Vc, and determines that it is abnormal when DC voltage Vo2 is lower than voltage Vc.

[0073] If CPU 323 determines in S205 that the current is within the normal range, CPU 323 advances the sequence to S206. If CPU 323 determines in S205 that the current is not within the normal range, CPU 323 advances the sequence to S209. In S206, CPU 323 determines whether it can transition to sleep mode. If CPU 323 determines in S206 that it cannot transition to sleep mode, CPU 323 returns the sequence to S204. If CPU 323 determines in S206 that it can transition to sleep mode, CPU 323 advances the sequence to S207. In S207, CPU 323 sets the 5V / 24V signal to a high level, thus transitioning to sleep mode. In S208, CPU 323 determines whether the current is within the normal range by monitoring the state of the overcurrent detection circuit 424. If the CPU 323 determines in S208 that the current falls within the normal range, the CPU 323 returns the sequence to S206. If the CPU 323 determines in S208 that the current does not fall within the normal range, the CPU 323 advances the sequence to S209.

[0074] In the judgment process of S205 or S209, if the CPU 323 determines that the current exceeds the normal range and is abnormal, in S209, the CPU 323 switches the 5V / 24V signal to a high level, and thus switches the DC voltage Vo2 from 24V to 5V (5V output). By reducing the DC voltage Vo2 from 24V to 5V, the load current is significantly reduced, resulting in a decrease in temperature. In S210, the CPU 323 displays a message indicating an abnormality in the output line of the power supply unit 420, including the main component, on a user interface such as the display panel 160, and notifies the user of the formation of an overload condition. In S211, the CPU 323 determines whether the current has fallen back within the normal range by monitoring the state of the overcurrent detection circuit 424. If CPU 323 determines in S211 that the current is within the normal range, CPU 323 returns the sequence to S211. If CPU 323 determines in S211 that the current exceeds the normal range and is abnormal, CPU 323 moves the sequence to S212. In S212, CPU 323 changes the level of the Pstop signal from low to high (because although the output of DC voltage Vo2 changes to 5V, the overcurrent condition is not eliminated), causing the operation of power supply CPU 422 to stop, and therefore the operation of power supply unit 420 to stop.

[0075] As described above, in Embodiment 2, by having a two-level protection function, damage to the components of the power supply unit 420 can be avoided and the DC voltage Vo2 can be completely stopped. Incidentally, in Figure 5 In step S209, if an overcurrent is detected when the DC voltage Vo2 is outputting at 24V, the DC voltage Vo2 is switched from 24V to 5V. However, the operation of the power supply CPU 422 can be stopped without switching the DC voltage Vo2 from 24V to 5V. In this case, compared to the case where the DC voltage Vo2 is 24V, the overcurrent threshold used to stop the operation of the power supply CPU 422 can be set to a low level when the DC voltage Vo2 is 5V. Therefore, in embodiment 2, the predetermined threshold in the second mode of operation can be set to a value lower than the predetermined threshold in the first mode of operation.

[0076] As described above, in Embodiment 2, the voltage level of the power supply unit 420 is monitored, and in the event of an abnormal increase in load, damage to the components of the power supply unit 420 can be prevented, and the voltage state can be switched to a safe state. Furthermore, when the DC voltage Vo2 of the power supply unit 420 becomes 5V for operation in power-saving mode (low voltage mode), the point (threshold) for overcurrent detection is set to a low level. Thus, even if the voltage decreases but the overcurrent value does not decrease, operation is safely stopped, preventing damage to the components.

[0077] As described above, according to Embodiment 2, the power supply device is switched from a state to a safe state before it is damaged, and the user can be notified of the occurrence of the anomaly.

[0078] While the invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be given the broadest interpretation in order to cover all such modifications and equivalent structures and functions.

Claims

1. An apparatus including a power supply device, the power supply device including a conversion unit configured to convert AC voltage into DC voltage and operable in the first mode and the second mode, wherein in the first mode, a first DC voltage converted by the conversion unit is output, and in the second mode, a second DC voltage converted by the conversion unit and lower than the first DC voltage is output, the apparatus comprising: A switching unit configured to switch the mode of operation of the power supply device between a first mode and a second mode; A discrimination unit is configured to determine whether an overcurrent state occurs in the conversion unit; The display section is configured to display information; A controller is configured to perform control such that, if the discrimination unit determines that an overcurrent condition has occurred in the conversion unit during operation of the power supply device in the first mode, the operation mode of the power supply device is switched by the switching unit to the second mode, and then the controller causes the display portion to display information related to the overcurrent condition in the conversion unit. as well as A generation unit configured to generate a third DC voltage lower than the DC voltage from the DC voltage output by the conversion unit. The generating unit supplies the third DC voltage to the controller.

2. The apparatus according to claim 1, wherein, The power supply device includes: A heating element configured to generate heat due to the flow of an electric current; and A temperature detection unit, configured to detect the temperature of the heating element. When the temperature detected by the temperature detection unit is higher than a predetermined threshold, the discrimination unit determines that an overcurrent state has occurred.

3. The apparatus according to claim 2, wherein, The conversion unit includes: A transformer, the transformer comprising a primary winding and a secondary winding; A switching element, which is connected in series to the primary winding and configured to perform a switching operation by being turned on or off; A power controller configured to control the switching operation of the switching element; A rectifier element configured to rectify the voltage induced in the secondary winding; and A smoothing unit is configured to smooth the voltage rectified by the rectifier element as the DC voltage. The heating element includes at least one of the primary winding, the secondary winding, the switching element, and the rectifier element.

4. The apparatus according to claim 1, wherein, The conversion unit includes: A transformer, the transformer comprising a primary winding and a secondary winding; A switching element, which is connected in series to the primary winding and configured to perform a switching operation by being turned on or off; A power controller configured to control the switching operation of the switching element; A rectifier element configured to rectify the voltage induced in the secondary winding; A smoothing unit, configured to smooth the voltage rectified by the rectifying element as the DC voltage; and A current detection unit configured to detect the current flowing due to the DC voltage. When the current detected by the current detection unit is higher than a predetermined threshold, the discrimination unit determines that an overcurrent state has occurred.

5. The apparatus according to claim 4, wherein, When the discrimination unit determines that an overcurrent condition has occurred during operation in the second mode, the controller causes the power controller to stop its operation.

6. The apparatus according to claim 5, wherein, In the second mode of operation, the predetermined threshold is set to a value lower than the predetermined threshold in the first mode of operation.

7. The apparatus according to any one of claims 1 to 6, wherein the apparatus is connected to an external device including a display portion configured to display information. in, The controller notifies the external device that an overcurrent condition has occurred, and then causes the display portion of the external device to display information indicating the occurrence of the overcurrent condition.

8. The apparatus according to any one of claims 1 to 6, further comprising an image forming unit configured to form an image on a recording material. in, The controller causes the image forming unit to print information indicating the occurrence of an overcurrent state on the recording material.

9. The apparatus according to any one of claims 1 to 6, wherein the apparatus is an image forming apparatus configured to form an image on a recording material.

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