Power supply control device and image formation device

Abstract

To output a stable voltage in a period after changeover between normal mode and power saving mode.SOLUTION: A power supply control device of the present invention includes: a power supply control part; a power supply part for outputting a first voltage value in a first operation mode and outputting a second voltage value in a second operation mode; a DC voltage conversion circuit for converting the voltage of the first voltage value from the power supply part to the second voltage value and outputting it in the first operation mode; an output voltage stabilization circuit connected to a parallel circuit connected to the output side of the DC voltage conversion circuit; an operation part for forming a parallel circuit by connecting the power supply part and the output voltage stabilization part and supplying the voltage of the second voltage value in an output unstable period of the DC voltage conversion circuit when an operation mode is shifted; and a changeover supply part for supplying a voltage of the second voltage value by disconnecting the connection with the output voltage stabilization circuit connected by the operation part, after the lapse of the output unstable period of the DC voltage conversion circuit.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a power supply control device and an image forming apparatus, and is applicable to, for example, a power supply control device that controls an operation mode that operates with low power consumption, and an image forming apparatus that includes this power supply control device. [Background technology]

[0002] In the power supply control device described in Patent Document 1, in normal mode, the power supply generation unit supplies a first voltage (e.g., 24V) to a DC / DC converter, which then steps down the voltage to 5V and supplies it to the load, and in power saving mode, the power supply generation unit outputs a second voltage (e.g., 5V) that is lower than the first voltage, stops the DC / DC converter, and supplies the second voltage directly to the load. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-28201 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when switching from the power saving mode to the normal mode, if the input / output voltage difference of the DC / DC converter becomes small, the output of the DC / DC converter may decrease and fall below the reset detection voltage of the control unit.

[0005] In view of the above-mentioned problems, the present invention aims to provide a power supply control device and an image forming device that can output a stable power supply voltage during a period of unstable output voltage that can occur when switching between normal mode (first operating mode) and power saving mode (second operating mode). [Means for solving the problem]

[0006] In order to solve this problem, a first power supply control device according to the present invention is characterized by comprising: (1) a power supply control unit; (2) a power supply unit that outputs a voltage of a first voltage value in a first operating mode and a voltage of a second voltage value lower than the first voltage value in a second operating mode; (3) a DC voltage conversion circuit that converts the voltage of the first voltage value from the power supply unit to a second voltage value and outputs it in the first operating mode; (4) an output voltage stabilization circuit connected to a parallel circuit connected to the output side of the DC voltage conversion circuit; (5) an operation unit that, when the operating mode is switched, forms a parallel circuit connecting the power supply unit and the output voltage stabilization circuit based on a drive signal from the power supply control unit during an output unstable period of the DC voltage conversion circuit, and supplies a voltage of the second voltage value from the power supply unit; and (6) a switching supply unit that, when the operating mode is switched, after the output unstable period of the DC voltage conversion circuit has elapsed, cuts off the connection with the output voltage stabilization circuit based on a drive signal from the power supply control unit, and supplies a voltage of the second voltage value from the power supply unit.

[0007] The image forming apparatus according to the second aspect of the present invention is an image forming apparatus that forms an image on the surface of a medium, and is characterized by comprising: (1) a drive unit that transmits drive force to components involved in image formation; (2) a control unit that controls the image formation process; and (3) a power supply control device according to the first aspect of the present invention that supplies voltage to the drive unit and the control unit. [Effects of the Invention]

[0008] According to the present invention, a stable power supply voltage can be output during a period in which the output voltage is unstable, which may occur when switching between the normal mode and the power saving mode. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram illustrating an internal configuration of an image forming apparatus including a power supply control device according to an embodiment. [Figure 2] FIG. 2 is a configuration diagram showing the configuration of a control system of the image forming apparatus 1 according to the embodiment. [Figure 3] 1 is a circuit diagram illustrating a configuration of a power supply control device according to an embodiment. [Figure 4] 10 is a timing chart showing when the device transitions to a power saving mode and when the device returns to a normal mode in the embodiment. [Figure 5] FIG. 10 is a circuit diagram showing the configuration of a power supply control device according to a modified embodiment (part 1). [Figure 6] FIG. 10 is a circuit diagram showing the configuration of a power supply control device according to a modified embodiment (part 2). DETAILED DESCRIPTION OF THE INVENTION

[0010] (A) Main embodiment DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a power supply control device and an image forming apparatus according to embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0011] (A-1) Configuration of the embodiment FIG. 1 is a diagram showing the internal configuration of an image forming apparatus equipped with a power supply control device according to an embodiment.

[0012] 1, an image forming apparatus 1 according to the embodiment includes a paper feed cassette 102, a hopping roller 103, registration rollers 104 and 105, an image forming unit (ID unit) 111, a transfer roller 114, a fixing unit 116, and discharge rollers 119 and 120.

[0013] In this embodiment, the image forming device 1 is described as a monochrome printer, but this is not limited to this, and the invention can also be applied to image forming devices such as color printers, multifunction devices, scanners, etc., as long as they are capable of switching between multiple operating modes, such as normal mode and power saving mode.

[0014] The paper feed cassette 102 accommodates print media 101 such as paper. The hopping roller 103 feeds the print media 101 from the paper feed cassette 102 one sheet at a time onto a paper transport path.

[0015] The registration rollers 104 and 105 correct any skew in the print medium 101 fed onto the paper transport path, and send the print medium 101 to the transfer roller 114 at a predetermined timing.

[0016] The image forming unit 111 forms an image on one surface of the print medium 101, and is disposed opposite the transfer roller 114 across the paper transport path. The image forming unit 111 is an electronic LED printing mechanism that prints with K (black) toner.

[0017] The image forming unit 111 includes a photosensitive drum 106 , a detachable toner cartridge 122 , a charging roller 123 , an LED head 112 , a developing roller 124 , and a toner supply roller 125 .

[0018] The charging roller 123 charges the surface of the photosensitive drum 106 by applying a negative high voltage thereto.

[0019] The LED head 112 exposes the surface of the charged photosensitive drum 106 to light, and generates an electrostatic latent image for attaching a charged toner image to the exposed portion.

[0020] The developing roller 124 adheres toner to the electrostatic latent image formed on the surface of the photosensitive drum 106 by applying a negative high voltage thereto.

[0021] The toner supply roller 125 supplies the toner contained in the toner cartridge 122 to the developing roller 124 by applying a negative high voltage thereto.

[0022] The transfer roller 114 transfers the toner image formed on the surface of the photosensitive drum 106 onto the print medium 101 by applying a positive high voltage to the transfer roller 114 while transporting the print medium 101 to the image forming unit 111.

[0023] The fixing device 116 heats the print medium 101 onto which the toner image has been transferred, fusing the toner and fixing the toner onto the surface of the print medium 101. The fixing device 116 includes a fixing roller 117 having, for example, a halogen heater, and a backup roller 118, and the fixing roller 117 is heated to a temperature at which fixing is possible by power input to the halogen heater.

[0024] Discharge rollers 119 and 120 discharge the print medium 101 with the toner fixed thereon to the outside of the device.

[0025] FIG. 2 is a configuration diagram showing the configuration of a control system of the image forming apparatus 1 according to the embodiment.

[0026] 2, the image forming apparatus 1 has a printer control unit 201, a paper feed motor 202, an image formation (ID) motor 203, an LED head 112, a fixing motor 204, a high voltage circuit 205, a fixing control unit 206, and a toner sensor 210 as a control system.

[0027] When the image forming apparatus 1 acquires print data via an interface (not shown) (for example, USB, LAN (registered trademark), etc.), it starts a print operation.

[0028] The printer control unit 201 operates by receiving a power supply voltage from the power supply control device 300 .

[0029] In addition, the paper feed motor 202, image formation (ID) motor 203, LED head 112, fixing motor 204, and high-voltage circuit 205 are each components of a drive unit 307, and each component operates when power supply voltage is supplied from the power supply control device 300.

[0030] The printer control unit 201 controls the printing operation of the image forming apparatus 1. The printer control unit 201 is connected to a paper feed motor 202, an image formation (ID) motor 203, an LED head 112, a fixing motor 204, a high-voltage circuit 205, a fixing control unit 206, and a toner sensor 210, and controls the operation of these components.

[0031] The paper feed motor 202 is a stepping motor for feeding and transporting the print medium 101 based on a control signal from the printer control unit 201. The paper feed motor 202 drives the hopping roller 103 and the registration rollers 104 and 105 to rotate.

[0032] The image forming (ID) motor 203 is a brushless DC motor that drives the image forming unit 111 and the transfer roller 114 to rotate based on a control signal from the printer control unit 201 .

[0033] The LED head 112 exposes the surface of the photosensitive drum 106 under the control of the printer control unit 201 .

[0034] The high voltage circuit 205 is a circuit that generates a high voltage for charging, developing, and transferring in the image forming unit 111 .

[0035] The fixing control unit 206 controls the heating of the halogen heater of the fixing unit 116 and the rotational driving of the fixing roller 117 and the backup roller 118 under the control of the printer control unit 201 .

[0036] The toner sensor 210 is housed in the toner cartridge 122 and detects the amount of remaining toner.

[0037] FIG. 3 is a circuit diagram showing the configuration of the power supply control device according to the embodiment.

[0038] In FIG. 3, the power supply control device 300 has a low-voltage power supply 301 as a "power supply unit", a power supply control unit 302, a DC / DC converter 303 as a "DC voltage conversion circuit", a first FET (Field Effect Transistor) 304 (hereinafter also referred to as "FET #1"), a second FET 305 (hereinafter also referred to as "FET #2") as a "first switching element", a third FET 306 (hereinafter also referred to as "FET #3") as a "second switching element", a third resistor R3 309, and a shunt regulator circuit 310 as an "output voltage stabilization circuit".

[0039] The power supply control device 300 converts an alternating current (AC) voltage into a direct current (DC) voltage and supplies the DC voltage to a drive unit 307 and the printer control unit 201.

[0040] Here, the drive unit 307 functions as a drive unit within the image forming apparatus 1, and includes, for example, the paper feed motor 202, the ID motor 203, the LED head 112, the fixing motor 204, the high voltage circuit 205, and the like.

[0041] The power supply control device 300 operates in two operation modes: a "normal mode (also called a "first operation mode")" and a "power saving mode (also called a "second operation mode")."

[0042] The "normal mode" is an operation mode in which the power supply control device 300 supplies a specified voltage value so that the image forming apparatus 1 can perform various functions.

[0043] The "power saving mode" is an operation mode in which the power supply control device 300 supplies a voltage value that is lower than the specified voltage value in the normal mode in order to reduce power consumption.

[0044] In "normal mode," power supply control device 300 supplies a DC voltage of a first voltage value (e.g., 24 V) to drive unit 307, and supplies a DC voltage of a second voltage value (e.g., 5 V, within the operable voltage range of printer control unit 201, where reset is not detected) to printer control unit 201. In "power saving mode," power supply control device 300 does not supply power to drive unit 307, and supplies a DC voltage of a second voltage value (e.g., 5 V) to printer control unit 201.

[0045] It should be noted that the "power saving mode" is not limited to one type, but multiple types of power saving modes may be set, such as a "power saving mode" as a first power saving mode and a "standby mode" as a second power saving mode, and the voltage value supplied by the power supply control device 300 may be different for each type.

[0046] The low-voltage power supply 301 converts an input alternating current voltage (AC voltage) into a direct current voltage (DC voltage) and supplies the DC voltage according to a predetermined operation mode to the drive unit 307 and the printer control unit 201. For example, the low-voltage power supply 301 includes an AC / DC converter, which converts the input AC voltage into a DC voltage.

[0047] The low-voltage power supply 301 receives a switching signal from the power supply control unit 302 to switch the operating mode, and outputs a DC voltage of a first voltage value (e.g., 24 V) in normal mode and a DC voltage of a second voltage value (e.g., 5 V) in power-saving mode.

[0048] The first FET 304 (FET#1) is provided between the output side of the low-voltage power supply 301 and the input side of the drive unit 307, and switches the power supply voltage supplied from the low-voltage power supply 301 to the drive unit 307. The first FET 304 (FET#1) switches the power supply from the low-voltage power supply 301 to the drive unit 307 on and off based on a drive signal (drive voltage) from the power supply control unit 302.

[0049] DC / DC converter 303 is provided between the output side of low-voltage power supply 301 and the input side of printer control unit 201, and in normal mode converts a DC voltage of a first voltage value from low-voltage power supply 301 to a DC voltage of a second voltage value and supplies it to printer control unit 201, and stops in power saving mode when the voltage drops below the lower operating voltage limit of DC / DC converter 303.

[0050] The DC / DC converter 303 converts the voltage value of the DC voltage if a control signal (enable (EN) signal) indicating a DC / DC enable signal from the power supply control unit 302 is active, and does not perform conversion if the enable signal is inactive.

[0051] The second FET 305 (FET#2) is turned ON when the shunt regulator circuit 310 is used. For example, the second FET 305 (FET#2) is provided between the output side of the low-voltage power supply 301 and the input side of the printer control unit 201, and switches ON / OFF the power supply from the low-voltage power supply 301 to the printer control unit 201 based on a drive signal (drive voltage) from the power supply control unit 302.

[0052] The third resistor R3 (309) is provided between the output side of the second FET 305 (FET#2) and the printer control unit 201.

[0053] When the operating mode is changed, the second FET 305 (FET#2) and the third resistor R3 (309) function as an "operating unit" that connects the low-voltage power supply and the shunt regulator circuit 310 based on a drive signal from the power supply control unit 302 and supplies a voltage of the second voltage value from the low-voltage power supply during an unstable output period of the DC / DC converter 303 in which the input from the low-voltage power supply 301 to the DC / DC converter 303 drops below the lower limit operating voltage.

[0054] The third FET 306 (FET#3) is turned ON when the output of the low-voltage power supply 301 is supplied directly to the printer control unit 201. For example, the third FET 306 (FET#3) is provided between the output side of the low-voltage power supply 301 and the input side of the printer control unit 201, and switches ON / OFF the power supply from the low-voltage power supply 301 to the printer control unit 201 based on a drive signal (drive voltage) from the power supply control unit 302.

[0055] When the low-voltage power supply 301 outputs a second voltage value that is within the operable voltage range of the printer control unit 201, the third FET 306 (FET#3) functions as a "switching supply unit" that supplies the second voltage value from the low-voltage power supply 301 based on a drive signal from the power supply control unit 302.

[0056] The shunt regulator circuit 310 is a circuit that keeps the input DC voltage constant, and is provided in a parallel circuit that is connected to the output side of the DC / DC converter 303 .

[0057] Here, when transitioning from the power saving mode to the normal mode, the voltage suddenly increases from the second voltage value (e.g., 5 V) to the first voltage value (e.g., 24 V), so the voltage output by the DC / DC converter 303 to the printer control unit 201 becomes unstable.

[0058] Therefore, in this embodiment, a shunt regulator circuit 310 is provided which is connected to a parallel circuit connected to the output side of the DC / DC converter 303 and is activated when switching between the power saving mode and the normal mode. This makes it possible to stabilize the voltage between the DC / DC converter 303 and the printer control unit 201 at a constant level.

[0059] The shunt regulator circuit 310 includes a shunt regulator 313, a first resistor R1 (311), and a second resistor R2 (312).

[0060] The third resistor R3 (309) provided between the second FET 305 (FET#2) and the shunt regulator 313 is a limiting resistor that limits the current flowing through the shunt regulator 313.

[0061] The first resistor R1 (311) and the second resistor R2 (312) are voltage dividing resistors for determining the target voltage. When the shunt regulator 313 is used, the second FET #2 (305) is turned ON, and when the output of the low-voltage power supply 301 becomes higher than the second voltage value and falls outside the operable voltage range of the printer control unit 201, the third FET #3 (306) is turned OFF.

[0062] The power supply control unit 302 is connected to the low-voltage power supply 301, first FET 304 (FET#1), second FET 305 (FET#2), third FET 306 (FET#3), and DC / DC converter 303, and performs ON / OFF control. The power supply control unit 302 also has an input terminal connected to an AD conversion circuit (not shown) that converts analog voltages into digital values, and is capable of monitoring the output voltage of the low-voltage power supply 301 as a digital value. The AD conversion circuit may be replaced by a comparison unit (comparator) that compares the magnitude of a threshold voltage.

[0063] (A-2) Operation of the embodiment Next, the processing of the power supply control method in the power supply control device 300 according to the embodiment will be described with reference to the drawings.

[0064] (A-2-1) Operation in normal mode The low-voltage power supply 301 outputs a DC voltage of a first voltage value (for example, 24 V). At this time, FET#1 is turned ON and the DC / DC converter 303 is turned ON. On the other hand, FET#2 and FET#3 are both turned OFF.

[0065] Therefore, a DC voltage of a first voltage value (for example, 24 V) is supplied from the low-voltage power supply 301 to the drive unit 307 .

[0066] Furthermore, DC / DC converter 303 converts a DC voltage of a first voltage value (e.g., 24 V) from low-voltage power supply 301 into a DC voltage of a second voltage value (e.g., 5 V) and outputs the DC voltage of the second voltage value (e.g., 5 V). As a result, the DC voltage of the second voltage value (e.g., 5 V) is supplied to printer control unit 201.

[0067] (A-2-2) Operation when switching to power saving mode FIG. 4 is a timing chart showing transition to the power saving mode and return to the normal mode in this embodiment.

[0068] When switching from the normal mode to the power saving mode, the power supply control unit 302 sends a switching signal from the normal mode to the power saving mode to the low voltage power supply 301 and switches FET#1 OFF (S1). Upon receiving the switching signal, the low voltage power supply 301 outputs a DC voltage stepped down from a first voltage value (e.g., 24 V) to a second voltage value (e.g., 5 V).

[0069] At this time, when the output voltage of the low-voltage power supply 301 falls below the lower limit voltage (e.g., 7V) at which the DC / DC converter 303 can output 5V, FET#2 turns ON (S2), the DC / DC converter 303 turns OFF (S3), and FET#3 turns OFF (S4).

[0070] In this way, by turning on FET#2, the voltage from the low-voltage power supply 301 is supplied to the shunt regulator circuit 310, and the shunt regulator 313 is put into an operating state. This stabilizes the voltage between the low-voltage power supply 301 ⇒ FET#2 ⇒ resistor R3 ⇒ shunt regulator circuit 310 ⇒ printer control unit 201, and a DC voltage of the second voltage value is supplied to the printer control unit 201.

[0071] When the output voltage of the low-voltage power supply 301 drops to a second voltage value (for example, 5V) that is within the operable voltage range of the printer control unit 201, FET#2 turns OFF (S5) and FET#3 turns ON (S6).

[0072] In this way, when FET#3 is turned on, a DC voltage of the second voltage value is supplied from the low voltage power supply 301 to the FET#3 to the printer control unit 201 without passing through the resistor R3.

[0073] In other words, the power supply from the low-voltage power supply 301 to the drive unit 307 is cut off by FET #1, and a DC voltage of the second voltage value (5V) is supplied to the printer control unit 201 from the low-voltage power supply 301 via FET #3.

[0074] If the voltage value of the input voltage to printer control unit 201 (for example, the upper limit of the operable voltage range of printer control unit 201) is made equal to the target voltage value of shunt regulator 313, the current draw of shunt regulator 313 will decrease, and the cathode current will also decrease.

[0075] (A-2-3) When returning to normal mode When returning from the power saving mode to the normal mode, the power supply control unit 302 provides the low-voltage power supply 301 with a switching signal from the power saving mode to the normal mode.

[0076] Upon receiving the switching signal, the low-voltage power supply 301 outputs a DC voltage converted from the second voltage value (for example, 5 V) to the first voltage value (for example, 24 V).

[0077] Here, FET#2 is kept ON (S8), DC / DC converter 303 is kept OFF (S9), and FET#3 is kept OFF (S10) until the output voltage value of the low-voltage power supply becomes equal to or greater than the 5V output voltage (e.g., 7V) that DC / DC converter 303 can output.

[0078] This turns FET#2 ON, causing the shunt regulator circuit 310 to operate, stabilizing the path from low-voltage power supply 301 ⇒ FET#2 ⇒ resistor R3 ⇒ shunt regulator circuit 310 ⇒ printer control unit 201, and allowing a DC voltage of the second voltage value to be supplied to the printer control unit 201.

[0079] When the output voltage value of the low voltage power supply becomes equal to or greater than the 5V output voltage (for example, 7V) of the DC / DC converter 303, the FET#2 turns OFF (S11) and the DC / DC converter 303 turns ON (S12).

[0080] In this way, when FET#2 is turned OFF, the operation of the shunt regulator circuit 310 is reduced, and when the DC / DC converter 303 is turned ON, a DC voltage of the second voltage value is supplied to the printer control unit 201 via the path of the low-voltage power supply 301 ⇒ DC / DC converter 303 ⇒ printer control unit 201.

[0081] Then, when the output voltage of the low-voltage power supply 301 rises to a first voltage value (for example, 24 V), the FET #1 is turned ON (S13), and power supply to the drive unit 307 begins.

[0082] Instead of the shunt regulator 313, a Zener diode having a Zener voltage as the target voltage value may be provided, and the resistors 311 and 312 may be omitted.

[0083] (A-3) Modification of power supply control device (part 1) FIG. 5 is a circuit diagram (part 1) showing the configuration of a power supply control device according to a modified embodiment.

[0084] In FIG. 5, the power supply control device 300A includes a low-voltage power supply 301, a power supply control unit 302, a DC / DC converter 303, a first FET 304 (hereinafter also referred to as "FET#1"), a second FET 305 (hereinafter also referred to as "FET#2"), a third resistor R3 309, a shunt regulator circuit 310, and a switch unit 320.

[0085] 5, a power supply control device 300A according to the modified embodiment includes a switch section 320 instead of the third FET 306 (FET#3) in FIG.

[0086] The switch unit 320 is provided between the output side of the third resistor R3, which serves as a limiting resistor, and the input side of the printer control unit 201, and switches the connection with the shunt regulator 313 based on a switch switching signal from the power supply control unit 302.

[0087] When the switch unit 320 is switched to the contact C1, a bypass of the third resistor R3 (390) is formed. When the switch unit 320 is switched to the contact C2, a connection to the shunt regulator 313 is made.

[0088] (A-3-1) When switching to power saving mode The power supply control unit 302 provides a switching signal from the normal mode to the power saving mode to the low-voltage power supply 301, and switches FET #1 OFF. Upon receiving the switching signal, the low-voltage power supply 301 outputs a DC voltage stepped down from a first voltage value (e.g., 24 V) to a second voltage value (e.g., 5 V).

[0089] At this time, the power supply control unit 302 instructs the switch unit 320 to connect to the contact C2, and the switch unit 320 connects to the shunt regulator 313.

[0090] When the output voltage of low-voltage power supply 301 falls below the 5V output voltage (for example, 7V) of DC / DC converter 303, FET #2 turns ON and DC / DC converter 303 turns OFF. This activates shunt regulator 313, supplying a voltage of the second voltage value to printer control unit 201.

[0091] When the output voltage of the low-voltage power supply 301 drops to a second voltage value (for example, 5 V), the FET #2 is turned ON, the DC / DC converter 303 is turned OFF, and the switch section 320 switches the connection to the contact C1.

[0092] (A-3-2) When returning to normal mode When returning to the normal mode, the power supply control unit 302 provides the low-voltage power supply 301 with a switching signal to switch from the power saving mode to the normal mode.

[0093] Upon receiving the switching signal, the low-voltage power supply 301 outputs a DC voltage converted from the second voltage value (for example, 5 V) to the first voltage value (for example, 24 V).

[0094] The power supply control unit 302 keeps the DC / DC converter 303 OFF, turns FET #2 ON, and switches the switch unit 320 to contact C2 to connect to the shunt regulator 313 until the output voltage value of the low-voltage power supply becomes equal to or greater than the 5V output voltage (for example, 7V) that the DC / DC converter 303 can output. Then, when the output voltage value of the low-voltage power supply 301 becomes equal to or greater than the 5V output voltage (for example, 7V) that the DC / DC converter 303 can output, the DC / DC converter 303 is turned ON, turns FET #2 OFF, and switches the switch unit 320 to contact C1 to disconnect from the shunt regulator 313.

[0095] Then, when the output voltage of the low-voltage power supply 301 rises to a first voltage value (for example, 24 V), the FET #1 is turned on, and power supply to the drive unit 307 begins.

[0096] Instead of the shunt regulator 313, a Zener diode having a Zener voltage as the target voltage value may be provided, and the resistors 311 and 312 may be omitted.

[0097] (A-4) Modification of power supply control device (part 2) FIG. 6 is a circuit diagram (part 2) showing the configuration of a power supply control device according to a modified embodiment.

[0098] In FIG. 6, the power supply control device 300B includes a low-voltage power supply 301, a power supply control unit 302, a DC / DC converter 303, a first FET 304 (hereinafter also referred to as "FET#1"), a second FET 305 (hereinafter also referred to as "FET#2"), a third resistor R3 309, a shunt regulator circuit 310, a switch unit 340, and a diode 330.

[0099] The third resistor R3 (309) is provided between the shunt regulator 313 and the contact C2 of the switch section 340.

[0100] The diode 330 has a cathode connected to the FET#2 control output side of the power supply control unit 302 and operates as a wired OR, and an anode connected to the cathode side of the shunt regulator 313.

[0101] The output for controlling FET#2 of the power supply control section 302 is capable of three-state output of high, low and high impedance, and is connected in pull-down by a resistor (not shown).

[0102] The switch unit 340 is provided between the output side of the second FET 305 (FET#2) and the input side of the printer control unit 201, and switches the connection with the shunt regulator 313 based on a switch switching signal from the power supply control unit 302.

[0103] When the switch section 320 switches to the contact C2, it is connected to the shunt regulator 313, and when it switches to the contact C1, it is disconnected from the shunt regulator 313.

[0104] (A-4-1) When switching to power saving mode The power supply control unit 302 provides a switching signal from the normal mode to the power saving mode to the low-voltage power supply 301, and switches FET #1 OFF. Upon receiving the switching signal, the low-voltage power supply 301 outputs a DC voltage stepped down from a first voltage value (e.g., 24 V) to a second voltage value (e.g., 5 V).

[0105] At this time, the power supply control unit 302 instructs the switch unit 340 to connect to the contact C2, and the switch unit 340 connects to the shunt regulator 313.

[0106] When the output voltage of low-voltage power supply 301 falls below the 5V output voltage (for example, 7V) of DC / DC converter 303, the control output for FET#2 from power supply control unit 302 goes into a high impedance state, FET#2 goes into OFF / ON control linked to the current draw / stop operation of shunt regulator 313 connected in wired OR, and DC / DC converter 303 turns OFF. This activates shunt regulator 313 to supply a voltage of the second voltage value to printer control unit 201.

[0107] When the output voltage of the low-voltage power supply 301 drops to a second voltage value (e.g., 5 V), the DC / DC converter 303 is turned OFF, and FET#2 is turned ON using the FET#2 control output from the power supply control unit 302 (which is connected in a wired OR fashion regardless of the operation of the shunt regulator 313), and the switch unit 340 switches the connection to contact C1, thereby cutting off the connection with the shunt regulator 313.

[0108] (A-4-2) When returning to normal mode When returning to the normal mode, the power supply control unit 302 provides the low-voltage power supply 301 with a switching signal to switch from the power saving mode to the normal mode.

[0109] Upon receiving the switching signal, the low-voltage power supply 301 outputs a DC voltage converted from the second voltage value (for example, 5 V) to the first voltage value (for example, 24 V).

[0110] Until the output voltage value of the low-voltage power supply reaches or exceeds the 5V output voltage (e.g., 7V) of the DC / DC converter 303, the DC / DC converter 303 is turned OFF, the FET#2 control output from the power supply control unit 302 is set to a high impedance state, and FET#2 is turned OFF / ON in conjunction with the current draw / stop operation of the wired-OR connected shunt regulator 313, and the switch unit 340 switches the connection to contact C2 to connect to the shunt regulator 313.

[0111] When the output voltage value of the low-voltage power supply becomes equal to or greater than the 5V output voltage (for example, 7V) of the DC / DC converter 303, the DC / DC converter 303 is turned ON, the switch unit 340 switches the connection to contact C1, disconnects the connection with the shunt regulator 313, and turns FET#2 OFF using the FET#2 control output from the power supply control unit 302 (which is connected in a wired OR regardless of the operation of the shunt regulator 313).

[0112] Then, when the output voltage of the low-voltage power supply 301 rises to a first voltage value (for example, 24 V), the FET #1 is turned ON, and power supply to the drive unit 307 begins.

[0113] (A-5) Effects of the embodiment As described above, according to this embodiment, by operating the shunt regulator 313 connected in parallel with the DC / DC converter 303 during the unstable period when transitioning from the power saving mode to the normal mode, it is possible to stably supply the second voltage value (5V) to the printer control unit.

[0114] In power-saving mode, the step-down circuit is not used, eliminating losses due to voltage conversion and enabling further reductions in power consumption.

[0115] (B) Other embodiments Although various modified embodiments have been mentioned in the above-described embodiment, the present invention can also be applied to the following modified embodiments.

[0116] In the embodiment, an example in which the invention is applied to a monochrome printer has been described, but the invention can also be applied to a color printer or a multifunction machine. [Explanation of symbols]

[0117] 300 (300A, 300B): power supply control device, 301: low voltage power supply, 302: power supply control section, 303: DC / DC converter, 304: first FET, 305: second FET, 306: third FET, 307: drive section, 310: shunt regulator circuit, 313: shunt regulator, 320: switch section, 330: diode, 340: switch section, C1: contact, C2: contact, R1: first resistor, R2: second resistor, R3: third resistor, 1: image forming apparatus, 101: printing medium, 102: paper feed cassette, 103: hopping roller, 104: registration roller, 106: photosensitive drum, 111: image forming unit, 112: LED head, 114: transfer roller, 116: fuser, 117: fuser roller, 118: backup roller, 119: discharge roller, 122: toner cartridge, 123: charging roller, 124: developing roller, 125: toner supply roller, 201: printer control unit, 202: paper feed motor 203: Image formation (ID) motor, 204: Fixing motor, 205: High voltage circuit, 206: Fixing control unit, 210: Toner sensor.

Claims

1. a power supply control unit; a power supply unit that outputs a voltage of a first voltage value in a first operation mode and a voltage of a second voltage value lower than the first voltage value in a second operation mode; a DC voltage conversion circuit that converts the first voltage value from the power supply unit into the second voltage value and outputs the converted voltage in the first operation mode; an output voltage stabilization circuit connected to a parallel circuit connected to the output side of the DC voltage conversion circuit; an operating unit that, when the operation mode is changed, forms the parallel circuit by connecting the power supply unit and the output voltage stabilization circuit based on a drive signal from the power supply control unit during an output unstable period of the DC voltage conversion circuit, and supplies a voltage of the second voltage value from the power supply unit; when the operation mode is changed, after an output unstable period of the DC voltage conversion circuit has elapsed, a switching supply unit that cuts off the connection between the operation unit and the output voltage stabilization circuit based on a drive signal from the power supply control unit and supplies a voltage of the second voltage value from the power supply unit; A power supply control device comprising:

2. The operating unit is a first switching element connected in parallel with the DC voltage conversion circuit and turned on / off based on a drive signal from the power supply control unit; a resistor connected in series between the first switching element and the output voltage stabilization circuit; and The switching supply unit has a second switching element that is connected in parallel with the first switching element and that is turned on / off based on a drive signal from the power supply control unit.

2. The power supply control device according to claim 1.

3. The operating unit is a first switching element connected in parallel with the DC voltage conversion circuit and capable of switching between on and off based on a drive signal from the power supply control unit; a resistor connected in series with the first switching element connected to the output voltage stabilization circuit; and The switching supply unit is a switch unit that is provided at a subsequent stage of the resistor and that switches the connection to the output voltage stabilization circuit during an output unstable period of the DC voltage conversion circuit, and switches the connection to the output side of the first switching element after the output unstable period of the DC voltage conversion circuit has elapsed.

2. The power supply control device according to claim 1.

4. the operating unit includes a first switching element connected in parallel to the DC voltage conversion circuit and capable of switching between on and off based on a drive signal from the power supply control unit, The switching supply unit a switch unit provided in a subsequent stage of the first switching element, which switches the connection to a resistor connected in series with the output voltage stabilization circuit during an output unstable period of the DC voltage conversion circuit, and disconnects the connection after the output unstable period of the DC voltage conversion circuit has elapsed; a rectifier that causes a current to flow through the first switching element after a period of unstable output from the DC voltage conversion circuit has elapsed; 2. The power supply control device according to claim 1, further comprising:

5. In an image forming apparatus for forming an image on a surface of a medium, a driving unit that transmits driving force to components related to image formation; a control unit for controlling image forming processing; A power supply control device according to any one of claims 1 to 4, which supplies voltage to the drive unit and the control unit. An image forming apparatus comprising:

Images