Power source substrate and image formation device

Abstract

To downsize a power source substrate by utilizing space not utilized on a substrate.SOLUTION: A winding transformer 105 has a first input terminal and a second input terminal to which input voltage is supplied, and is mounted on a mounting surface of a power source substrate 100. A solder surface 100s, which is the opposite side of the mounting surface, has a land P1 and a land P3 for soldering. The first input terminal is soldered to the land P1 and the second input terminal is soldered to the land P3. A snubber circuit 108 has a surface mounting component on at least one part. When viewed in an orthogonal direction with the solder surface 100s of the power source substrate 100, the winding transformer 105 and the snubber circuit 108 are overlapped and are connected to the lands P1 and P3.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a power supply board and an image forming apparatus including the same.

Background Art

[0002] An image forming apparatus includes a power supply board that generates a DC voltage from an AC voltage. The image forming apparatus is required to be miniaturized for improving user convenience, and the power supply board included in the image forming apparatus is also required to be miniaturized. In order to miniaturize the power supply board, it is necessary to efficiently utilize the unused space on the board and reduce the board area.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] A winding transformer that transforms the primary-side voltage into the secondary-side voltage is mounted on the power supply board, and the winding transformer is a relatively large-sized component among the electrical components constituting the power supply board. There is a space on the back side of the board surface where the winding transformer is mounted where electrical components can be arranged, and utilizing this space leads to miniaturization of the power supply board.

[0005] An object of the present invention is to miniaturize a power supply board by utilizing the unused space on the board.

Means for Solving the Problems

[0006] In order to solve the above-described problems, the present invention has the following configuration.

[0007] (1) A power supply board comprising a transformer having a primary winding and a secondary winding, a switching element connected to the primary winding and performing a switching operation, and a snubber circuit connected to the primary winding, for transforming an input voltage on the primary side and outputting an output voltage from the secondary side, wherein the transformer has a first input terminal and a second input terminal to which the input voltage is supplied, is mounted on a first surface of the power supply board, a second surface which is a surface opposite to the first surface has a first soldering portion and a second soldering portion for soldering, the first input terminal is soldered to the first soldering portion, the second input terminal is soldered to the second soldering portion, the snubber circuit has surface-mounted components at least in part, and when viewed in a direction orthogonal to the first surface of the power supply board, the transformer and the snubber circuit overlap and are connected to the first soldering portion and the second soldering portion.

[0008] (2) A power supply board comprising a transformer having a primary winding and a secondary winding, a switching element connected to the primary winding and performing a switching operation, a rectifying and smoothing circuit for rectifying and smoothing the voltage output from the secondary winding, and a control circuit for detecting the output voltage and performing feedback control, for transforming an input voltage on the primary side and outputting the output voltage from the secondary side, wherein the transformer has a first output terminal and a second output terminal from which a voltage is output from the secondary winding, is mounted on a first surface of the power supply board, a second surface which is a surface opposite to the first surface has a third soldering portion and a fourth soldering portion for soldering, the first output terminal is soldered to the third soldering portion, the second output terminal is soldered to the fourth soldering portion, the control circuit has surface-mounted components at least in part, and when viewed in a direction orthogonal to the first surface of the power supply board, the transformer and the control circuit overlap and a pattern of the control circuit passes between the third soldering portion and the fourth soldering portion.

[0009] (3) An image forming apparatus for forming an image on a recording material, characterized in that the power supply board according to (1) or (2) is used as a power supply for the image forming apparatus.

Advantages of the Invention

[0010] According to the present invention, the power supply board can be miniaturized by utilizing the unused space on the board.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Mode for Carrying Out the Invention

Examples

[0012] <Circuit Configuration of Power Supply Board> The configuration of the power supply board 100 (board) of Example 1 will be described with reference to the drawings. FIG. 1 is a power supply circuit diagram in Example 1. The power supply board 100 is a board on which a power supply circuit that transforms the primary-side input voltage and outputs the output voltage from the secondary side is mounted. Power is supplied to the power supply board 100 from an AC power supply via two power lines, a LIVE line 101 and a NEUTRAL line 102, through a filter circuit (not shown). The voltage (AC voltage) and frequency of the AC power supply are, for example, 115V / 60Hz or 230V / 50Hz. The AC voltage generated between the LIVE line 101 and the NEUTRAL line 102 is rectified and smoothed by a bridge diode 103 and a primary smoothing capacitor 104, and a DC voltage is generated.

[0013] The generated DC voltage is supplied to a winding transformer 105 (transformer) having a primary winding 105a, an auxiliary winding 105b, and a secondary winding 105c. A MOSFET (metal-oxide-semiconductor field-effect transistor) 106 is connected in series to the primary winding 105a of the winding transformer 105. When the MOSFET 106, which is a switching element, performs a switching operation, an alternating magnetic field is generated in the winding transformer 105, and the energy stored in the primary winding 105a is transmitted to the secondary winding 105c.

[0014] The capacitor 107 is provided to suppress the surge voltage generated between the drain and source of the MOSFET 106. The power supply board 100 includes a snubber circuit 108, and the snubber circuit 108 is composed of a diode 108a, a capacitor 108b, a resistor 108c, a resistor 108d, and a resistor 108e. The snubber circuit 108 has a resistor composed of at least two or more components, and in the first embodiment, it has three resistors 108c, 108d, and 108e. The snubber circuit 108 is connected between the terminals of the primary winding 105a and is provided to suppress the surge voltage generated between the terminals of the primary winding 105a.

[0015] The resistor 109 is the gate resistor of the MOSFET 106, and the resistor 110 is the resistor for detecting the current flowing between the drain and source of the MOSFET 106. The AC voltage generated in the secondary winding 105c is rectified and smoothed by a rectifier smoothing circuit composed of a rectifier diode 111 and a secondary smoothing capacitor 112 (smoothing capacitor), and is output as the output voltage 113 of the power supply circuit. The voltage value of the output voltage 113 is, for example, +24V.

[0016] The feedback control circuit 121 as a control circuit is a circuit that performs constant-voltage feedback control to control the output voltage 113 to a constant voltage. The feedback control circuit 121 has surface mount components at least in part. The feedback control circuit 121 detects the output voltage 113 and controls the current flowing through the LED (light emitting diode) 122p of the photocoupler 122. The resistors 121a and 121b are resistors that detect the output voltage 113, and the voltage divided by the resistors 121a and 121b is supplied to the REF terminal of the shunt regulator IC 121c. The shunt regulator IC 121c controls the current of the cathode terminal (K terminal) according to the voltage of the REF terminal, and controls the current flowing through the LED 122p of the photocoupler 122. The resistors 121d, capacitor 121e, resistor 121f, and capacitor 121g are components provided for phase compensation. The resistor 121h is a shunt resistor, and the resistor 121i is a current limiting resistor.

[0017] The overvoltage detection circuit 131 is a circuit that detects that the output voltage 113 of the power supply circuit has become an overvoltage (abnormal state) and controls the current flowing through the LED 132p of the photocoupler 132. The overvoltage detection circuit 131 has surface mount components at least in part. A Zener diode 131b is selected as a component having a Zener voltage Vz that does not operate when the power supply circuit has a normal output voltage. For example, a component with a Zener voltage Vz of 27V is selected. When the output voltage 113 of the power supply circuit becomes an overvoltage (abnormal state) and the voltage across the Zener diode 131b exceeds the Zener voltage Vz, current flows as follows. That is, current flows through the diode 131a, Zener diode 131b, resistor 131c, resistor 131d, capacitor 131e, and resistor 131f, and the transistor 131g turns on. When the transistor 131g turns on, current flows through the LED 132p of the photocoupler 132. The resistor 131h is a shunt resistor, and the resistor 131i is a current limiting resistor.

[0018] The power supply IC 161 is a component that controls the power supply circuit. The VH terminal is a terminal for supplying the startup current and detecting brownout, and is connected to the line to which the plus terminal of the primary smoothing capacitor 104 is connected. The NC terminal is an unused terminal. The VCC terminal is a terminal to which power is supplied to the power supply IC 161, and a voltage obtained by rectifying and smoothing the AC voltage of the auxiliary winding 105b of the winding transformer 105 with the diode 162 and the capacitor 163 is supplied. The capacitor 164 is a bypass capacitor. The OUT terminal is a terminal from which a rectangular wave for switching the MOSFET 106 is output, and is connected to the gate terminal of the MOSFET 106 via the resistor 109.

[0019] The LAT terminal is a terminal for detecting an abnormality and stopping the operation of the power supply IC 161, and is connected to the phototransistor 132t of the photocoupler 132 via a circuit composed of the capacitor 165, the diode 166, the resistors 167 and 168, and the capacitor 169. The FB terminal is a terminal for detecting the feedback signal from the secondary-side feedback control circuit 121, and is connected to the capacitor 170 and the phototransistor 122t of the photocoupler 122. The power supply IC 161 controls the frequency and duty (DUTY) of the rectangular wave output from the OUT terminal according to the voltage level of the FB terminal, and controls the switching operation of the MOSFET 106, thereby controlling the secondary-side output voltage 113 to be constant. The CS terminal is a terminal for detecting the current flowing between the drain and source of the MOSFET 106, and is connected to one end of the resistor 110 via a filter circuit composed of the resistor 171 and the capacitor 172. The GND (ground) terminal is connected to the line to which the minus terminal of the primary smoothing capacitor 104 is connected.

[0020] <Pattern Configuration of Power Supply Substrate> Figure 2 is a pattern diagram of the power supply board 100 in Embodiment 1. It shows the solder side 100s of the single-sided board (the second side opposite to the first side), and also shows the area on the back side of the board surface (the first side) where the winding transformer 105 is mounted. The dotted line of S105 indicates the outer shape of the winding transformer 105, and the winding transformer 105 is mounted on the component surface on the back side of the solder side 100s. Here, the outer shape of the winding transformer 105 refers to the outer shape of the area where the winding transformer 105 is projected onto the power supply board 100 when viewed from the direction (normal direction) perpendicular to the power supply board 100 in the state where the winding transformer 105 is mounted on the power supply board 100. The same applies when using "outer shape" for other components. P1, P2, and P3 are lands where the terminals of the primary winding 105a are soldered, and P2 is the land to which the intermediate terminal of the primary winding 105a is connected. Specifically, the winding transformer 105 has a first input terminal and a second input terminal to which an input voltage is supplied. The solder side 100s of the power supply board 100 has a land P1 as a first solder part for soldering and a land P3 as a second solder part. The first input terminal of the winding transformer 105 is soldered to the land P1, and the second input terminal is soldered to the land P3.

[0021] The area of the snubber circuit 108 is shown by a dashed line, and the pattern where the diode 108a, capacitor 108b, resistors 108c, 108d, and 108e are mounted is also shown. The snubber circuit 108 is at least partially composed of surface-mounted components. The snubber circuit 108 is arranged on the back side of the board surface where the winding transformer 105 is mounted and is connected to the lands P1 and P3 of the winding transformer 105. Also, the lands P1 and P3 are connected in a pattern to primary-side components not shown in FIG. 2. In this way, the snubber circuit 108 has surface-mounted components at least partially, is mounted within the projection range (within S105), which is the area projected onto the solder side 100s when the winding transformer 105 is mounted on the board surface, and is connected to the lands P1 and P3. That is, when viewed in the direction perpendicular to the solder side 100s of the power supply board 100, the winding transformer 105 and the snubber circuit 108 overlap. Thereby, the space on the board that has not been utilized conventionally can be utilized.

[0022] P4 and P5 are lands where the terminals of the auxiliary winding 105b are soldered. The land P4 and the land P5 are connected in a pattern to a primary-side component (not shown in FIG. 2). P6 and P7 are lands where the output terminals of the secondary winding 105c are soldered, and P8 and P9 are lands where the GND terminals of the secondary winding 105c are soldered. More specifically, the winding transformer 105 has a first output terminal and a second output terminal from which a voltage is output from the secondary winding 105c. The solder surface 100s of the power supply board 100 has lands P6 and P7 as a third soldering part for soldering and lands P8 and P9 as a fourth soldering part. The first output terminal of the winding transformer 105 is soldered to the land P6 or the land P7, and the second output terminal is soldered to the land P8 or the land P9.

[0023] The dotted line of S111 indicates the outer shape of the rectifying diode 111, and the rectifying diode 111 is mounted on the component surface on the back side of the solder surface 100s. 111a and 111c are lands where the anode terminal of the rectifying diode 111 is soldered, and are connected in a pattern to the lands P6 and P7 of the winding transformer 105. 111b is a land where the cathode terminal of the rectifying diode 111 is soldered.

[0024] The dotted line of S112 indicates the outer shape of the secondary smoothing capacitor 112, and the secondary smoothing capacitor 112 is mounted on the component surface on the back side of the solder surface 100s. 112a is a land where the plus terminal of the secondary smoothing capacitor 112 is soldered, and is connected in a pattern to the land 111b of the rectifying diode 111. Also, the land 112a is connected in a pattern to a secondary-side component (not shown). 112b is a land where the minus terminal of the secondary smoothing capacitor 112 is soldered, and is connected in a pattern to the lands P8 and P9 of the winding transformer 105. Also, the land 112b is connected in a pattern to a secondary-side component (not shown).

[0025] The dotted line area of A121 indicates the area where the feedback control circuit 121 is implemented. It is composed of surface mount components and is arranged on the solder side 100s, which is the back side of the substrate surface where the winding transformer 105 is implemented. The illustration of individual components is omitted. The power line of the feedback control circuit 121 is wired through between the lands P7 and P8 of the winding transformer 105 from the land 112a of the secondary smoothing capacitor 112. Also, the GND line of the feedback control circuit 121 is wired through between the lands P7 and P8 of the winding transformer 105 from the land 112b of the secondary smoothing capacitor 112. That is, the feedback control circuit 121 is implemented within the projection range (within S105), which is the area projected onto the solder side 100s when the winding transformer 105 is implemented on the substrate surface. That is, when viewed in the direction orthogonal to the solder side 100s of the power supply substrate 100, the winding transformer 105 and the feedback control circuit 121 overlap. And the wiring (pattern) of the power line and the GND line of the feedback control circuit 121 passes between the lands P7 and P8.

[0026] The dotted-line area of A131 indicates the area where the overvoltage detection circuit 131 is implemented. It is composed of surface-mounted components and is arranged on the solder side 100s, which is the back side of the substrate surface where the winding transformer 105 is implemented. The illustration of individual components is omitted. The power line of the overvoltage detection circuit 131 is wired from the land 112a of the secondary smoothing capacitor 112, similar to the feedback control circuit 121. The power line of the overvoltage detection circuit 131 passes between the lands P7 and P8 of the winding transformer 105 and branches off to the line to the feedback control circuit 121 on the way. Also, the GND line of the overvoltage detection circuit 131 is wired from the land 112b of the secondary smoothing capacitor 112, similar to the feedback control circuit 121. The GND line of the overvoltage detection circuit 131 passes between the lands P7 and P8 of the winding transformer 105 and branches off to the line to the feedback control circuit 121 on the way. In this way, the overvoltage detection circuit 131 is also implemented within the projection range (S105), which is the area projected onto the solder side 100s when the winding transformer 105 is implemented on the substrate surface. That is, when viewed in the direction orthogonal to the solder side 100s of the power supply substrate 100, the winding transformer 105 and the overvoltage detection circuit 131 overlap. And the wiring (pattern) of the power line and GND line of the overvoltage detection circuit 131 also passes between the lands P7 and P8. In this way, by arranging the feedback control circuit 121 and the overvoltage detection circuit 131 within S105 on the solder side 100s, the space on the substrate that has not been utilized conventionally can be utilized.

[0027] The dotted line of S122 indicates the outer shape of the photocoupler 122, and the photocoupler 122 is implemented on the component side on the back side of the solder side 100s. 122a and 122b are the lands where the primary-side terminals are soldered and are connected in pattern to a primary-side component (not shown). 122c and 122d are the lands where the secondary-side terminals are soldered. The land 122c is connected in pattern to the feedback control circuit 121, and the land 122d is connected in pattern to the power line of the feedback control circuit 121 and the power line of the overvoltage detection circuit 131.

[0028] The dotted line of S132 indicates the outer shape of the photocoupler 132, and the photocoupler 132 is mounted on the component surface on the back side of the solder surface 100s. 132a and 132b are lands where the primary side terminals are soldered, and are connected in a pattern to a primary side component (not shown). 132c and 132d are lands where the secondary side terminals are soldered, and are connected in a pattern to the overvoltage detection circuit 131.

[0029] The primary side circuit and the secondary side circuit need to ensure an insulation distance defined by safety standards. Note that the primary side circuit includes the lands P1, P2, P3, P4, P5 of the winding transformer 105 and the snubber circuit 108, and the secondary side circuit includes the lands P6, P7, P8, P9 of the winding transformer 105, the feedback control circuit 121, and the overvoltage detection circuit 131. In the first embodiment, since the snubber circuit 108 is composed of surface mount components and the resistors are divided into three, namely 108c, 108d, and 108e, and mounted, the degree of freedom of the component mounting layout is increased. Therefore, even if components are arranged on the back side (solder surface 100s) of the substrate surface on which the winding transformer 105 is mounted, the necessary insulation distance can be ensured.

[0030] <Circuit Loop of Feedback Control Circuit> FIG. 3 is a diagram showing a circuit loop L1 as a first circuit loop in the pattern diagram of FIG. 2. Since the content other than the circuit loop L1 is the same as that in FIG. 2, the description thereof is omitted. The circuit loop L1 indicates a circuit loop formed by wiring a power line and a GND line from the secondary smoothing capacitor 112 to the feedback control circuit 121. The winding of the winding transformer 105 is wound so that a circle is formed on a plane parallel to the substrate surface, and the magnetic flux generated when a current flows through the winding is generated in a direction perpendicular to the substrate surface. The main magnetic flux passes through the core provided in the winding transformer 105, but the leakage magnetic flux generated outside the core is generated in a direction penetrating the substrate surface. When the leakage magnetic flux is generated inside the circuit loop existing on the substrate surface, an induced current flows through the circuit loop due to electromagnetic induction, which causes circuit malfunction. In order to reduce the influence of the leakage magnetic flux of the winding transformer 105, it is necessary to reduce the circuit loop and the induced current. The feedback control circuit 121 has components arranged on the back side of the substrate surface on which the winding transformer 105 is mounted. At the same time, in order to reduce the influence of the leakage magnetic flux of the winding transformer 105, the feedback control circuit 121 is arranged in the vicinity of the lands P7 and P8 of the winding transformer 105 so that the circuit loop L1 is minimized. Here, the circuit loop formed by wiring the power line and the GND line from the secondary smoothing capacitor 112 to the feedback control circuit 121 is not limited to one pattern of the circuit loop L1, and a plurality of patterns are conceivable. In the first embodiment, the circuit loop L1 is such that the area of the region formed by the circuit loop is the smallest among the areas of the regions formed by a plurality of circuit loops that can be arranged on the solder surface 100s.

[0031] <Circuit Loop of Overvoltage Detection Circuit> FIG. 4 is a diagram showing a circuit loop L2 as a second circuit loop in the pattern diagram of FIG. 2. Since the content other than the circuit loop L2 is the same as that in FIG. 2, the description thereof is omitted. The circuit loop L2 shows a circuit loop formed by wiring a power line and a GND line from the secondary smoothing capacitor 112 to the overvoltage detection circuit 131. Compared with the circuit loop L1 in FIG. 3, the circuit loop L2 has a larger loop. That is, the overvoltage detection circuit 131 is arranged within the projection range such that the circuit loop L2 formed by the overvoltage detection circuit 131 and the secondary smoothing capacitor 112 is larger than the circuit loop L1. Also, the component mounting area A131 of the overvoltage detection circuit 131 is farther from the lands P7 and P8 of the winding transformer 105 than the component mounting area A121 of the feedback control circuit 121. More specifically, the entire component mounting area A121 of the feedback control circuit 121 is arranged near the lands P7 and P8. In contrast, the component mounting area A131 of the overvoltage detection circuit 131 is elongated compared to the component mounting area A121 and extends in a direction away from the lands P7 and P8. The component mounting area A131 of the overvoltage detection circuit 131 is an example where it is not arranged near the lands P7 and P8 of the winding transformer 105 so that the circuit loop L2 is minimized.

[0032] As described above, the feedback control circuit 121 is arranged near the lands P7 and P8 so that the circuit loop L1 formed by the feedback control circuit 121 and the secondary smoothing capacitor 112 is minimized among the patterns that can be arranged on the solder surface 100s. Comparing the feedback control circuit 121 and the overvoltage detection circuit 131, since the feedback control circuit 121 is more susceptible to noise, the feedback control circuit 121 is arranged near the lands P7 and P8 of the winding transformer 105.

[0033] As described above, according to the first embodiment, the power supply board can be miniaturized by utilizing the unused space on the board.

Embodiment

[0034] The configuration of the power supply board 200 in Example 2 will be described with reference to the drawings. In Example 1, an example in which the snubber circuit 108 is composed of a diode, a resistor, and a capacitor was described. In Example 2, a configuration using a power clamp will be described.

[0035] <Circuit Configuration of Power Supply Board> FIG. 5 is a power circuit diagram mounted on the power supply board 200 in Example 2. The snubber circuit 123 in Example 2 has a power clamp. More specifically, it is configured such that two power clamps 123a and 123b are connected in series. The power clamps 123a and 123b are, for example, those with a DC reverse voltage of 120V. The snubber circuit 123 is connected between the terminals of the primary winding 105a, similar to the snubber circuit 108 in Example 1, and is provided to suppress the surge voltage generated between the terminals of the primary winding 105a. Since the other components are the same as those in FIG. 1 described in Example 1, the description will be omitted.

[0036] <Pattern Configuration of Power Supply Board> FIG. 6 is a pattern diagram in Example 2. Two power clamps, the power clamp 123a and the power clamp 123b, are connected in series and are composed of surface-mounted components. The power clamps 123a and 123b are arranged on the solder side 200s, which is the back side of the substrate surface on which the winding transformer 105 is mounted, and are connected to the lands P1 and P3 of the winding transformer 105. Since the other components are the same as those in FIG. 2 described in Example 1, the description will be omitted. The same also applies to the circuit loops L1 and L2 described in FIGS. 3 and 4.

[0037] As described above, according to Example 2, the power supply board can be miniaturized by utilizing the unused space on the board.

Example

[0038] <Configuration of Image Forming Apparatus> In Example 3, an example in which the power supply board 100 or 200 described in Example 1 and Example 2 is applied to an image forming apparatus will be described. FIG. 7 is a schematic cross-sectional view showing the configuration of an image forming apparatus 201 that forms an image on a recording material. The configuration of the image forming apparatus 201 will be described with reference to FIG. 7.

[0039] In the paper feed cassette 202, sheets S, which are recording materials, are stacked. Various types of paper such as plain paper, thin paper, thick paper, OHT sheets, and rough paper can be used for the sheet S. The sheet S is fed by a paper feed roller 203 and is separated by the frictional force of a separation pad 204, and only one sheet S is fed to a pair of conveyance rollers 205. Thereafter, the sheet S passes through the pair of conveyance rollers 205 and the pair of registration rollers 206 and is conveyed to a transfer nip portion where the photosensitive drum 209 and the transfer roller 208 are in contact with each other. The process cartridge 210 is a detachable unit in which the photosensitive drum 209, the charging roller 211, and the developing roller 212 are integrated. The photosensitive drum 209 rotates in the direction of the arrow in the figure and is an image carrier that carries an electrostatic latent image and a toner image. The charging roller 211 is a member that charges the surface of the photosensitive drum 209 to a uniform potential, and a charging voltage is applied from a high-voltage power supply (not shown). The laser scanner unit 213 irradiates the photosensitive drum 209 with a laser beam 214 according to image data, exposes the surface of the photosensitive drum 209 charged to a uniform potential, and forms an electrostatic latent image on the surface of the photosensitive drum 209. The developing roller 212 develops the electrostatic latent image by attaching toner to the electrostatic latent image formed on the photosensitive drum 209 and forms a toner image. A developing voltage is applied to the developing roller 212 from a high-voltage power supply (not shown).

[0040] The transfer roller 208 transfers the toner image on the photosensitive drum 209 to the sheet S. A transfer voltage is applied to the transfer roller 208 from a high-voltage power source (not shown). The sheet S onto which the toner image has been transferred is heated and pressed by the fixing film 215 and the pressure roller 216, and the unfixed toner on the sheet S is melted and fixed to the sheet S. The sheet S conveyed by the fixing film 215 and the pressure roller 216 is conveyed by the discharge roller pair 217, 218, 219 and loaded onto the discharge tray 220. The door 221 that also serves as the exterior cover of the image forming apparatus 201 can be opened and closed by rotating about the fulcrum 222. Further, the opening and closing of the door 221 is performed by an operator or a user for the attachment and detachment of the process cartridge 210, the jam processing of the sheet S, the maintenance work of the image forming apparatus 201, etc.

[0041] The image forming apparatus 201 described above includes electric circuits such as a high-voltage power source, a motor, a solenoid, and a sensor. As the operation source of these electric circuits, the output voltage of a power supply circuit that generates a predetermined DC voltage from an AC power source is used. By applying the configuration of the power supply board 100 or 200 described in the first embodiment and the second embodiment to this power supply circuit, the present invention can be applied to the image forming apparatus 201. Further, in the third embodiment, although a monochrome image forming apparatus that forms a single-color image formed by one process cartridge has been described, the present invention is also applicable to a color image forming apparatus having a plurality of process cartridges.

[0042] As described above, according to the third embodiment, the power supply board can be miniaturized by utilizing the unused space on the board.

[0043] The disclosure of this embodiment includes the following configurations. (Configuration 1) A transformer having a primary winding and a secondary winding, A switching element connected to the primary winding and performing a switching operation, A snubber circuit connected to the primary winding, A power supply board that includes the above and transforms the input voltage on the primary side and outputs an output voltage from the secondary side, The transformer has a first input terminal and a second input terminal to which the input voltage is supplied, and is mounted on the first surface of the power supply substrate. The second surface, which is the surface opposite to the first surface, has a first solder portion and a second solder portion for soldering. The first input terminal is soldered to the first solder portion. The second input terminal is soldered to the second solder portion. The snubber circuit has at least some surface-mounted components. When viewed in a direction orthogonal to the first surface of the power supply substrate, the transformer and the snubber circuit overlap, and the power supply substrate is characterized in that it is connected to the first solder portion and the second solder portion. (Configuration 2) The snubber circuit has a diode, a resistor, and a capacitor, and the power supply substrate according to Configuration 1 is characterized in that. (Configuration 3) The resistor is composed of at least two or more components, and the power supply substrate according to Configuration 2 is characterized in that. (Configuration 4) The snubber circuit has a power clamp, and the power supply substrate according to Configuration 1 is characterized in that. (Configuration 5) A rectifying and smoothing circuit for rectifying and smoothing the voltage output from the secondary winding; A control circuit for detecting the output voltage and performing feedback control; and is provided with The transformer has a first output terminal and a second output terminal from which a voltage is output from the secondary winding. The second surface has a third solder portion and a fourth solder portion for soldering. The first output terminal is soldered to the third solder portion. The second output terminal is soldered to the fourth solder portion. The control circuit has at least some surface-mounted components. When viewed in a direction orthogonal to the first surface of the power supply substrate, the transformer and the control circuit overlap. The pattern of the control circuit passes between the third solder part and the fourth solder part, and is the power supply board according to any one of Configurations 1 to 4 characterized by this. (Configuration 6) A transformer having a primary winding and a secondary winding, A switching element connected to the primary winding and performing a switching operation, A rectifying and smoothing circuit that rectifies and smooths the voltage output from the secondary winding, A control circuit that detects the output voltage and performs feedback control, A power supply board that includes these, steps up the input voltage on the primary side, and outputs the output voltage from the secondary side, The transformer has a first output terminal and a second output terminal from which a voltage is output, and is mounted on the first surface of the power supply board, The second surface, which is the surface opposite to the first surface, has a third solder part and a fourth solder part for soldering, The first output terminal is soldered to the third solder part, The second output terminal is soldered to the fourth solder part, The control circuit has surface mount components at least in part, and when viewed in a direction orthogonal to the first surface of the power supply board, the transformer and the control circuit overlap, The pattern of the control circuit passes between the third solder part and the fourth solder part, and is the power supply board characterized by this. (Configuration 7) The rectifying and smoothing circuit has a smoothing capacitor, The control circuit is arranged so as to pass between the third solder part and the fourth solder part, and is the power supply board according to Configuration 6 characterized by this. (Configuration 8) A power supply board according to Configuration 7, further comprising an overvoltage detection circuit that detects that the output voltage is an overvoltage, The overvoltage detection circuit has surface mount components at least in part, and when viewed in a direction orthogonal to the first surface of the power supply board, the transformer and the overvoltage detection circuit overlap, The pattern of the overvoltage detection circuit passes between the third solder part and the fourth solder part, and is the power supply board characterized by this. (Configuration 9) When the circuit loops of the power supply line and the GND line formed by the control circuit and the smoothing capacitor are defined as the first circuit loop, the overvoltage detection circuit is arranged such that the second circuit loop of the power supply line and the GND line formed by the overvoltage detection circuit and the smoothing capacitor is larger than the first circuit loop, according to the power supply board of Configuration 8. (Configuration 10) The power supply board is a single-sided board, according to the power supply board of any one of Configurations 1 to 9. (Configuration 11) An image forming apparatus that forms an image on a recording material, characterized in that the power supply board of any one of Configurations 1 to 10 is used as the power supply of the image forming apparatus.

Explanation of Reference Numerals

[0044] 100 Power supply board 105 Winding transformer 106 MOSFET 108 Snubber circuit P1, P3 Lands S105 Outer shape of winding transformer

Claims

1. A transformer having a primary winding and a secondary winding, A switching element connected to the primary winding and performing a switching operation, A snubber circuit connected to the primary winding, A power supply board that steps down the input voltage on the primary side and outputs an output voltage from the secondary side, The transformer has a first input terminal and a second input terminal to which the input voltage is supplied, and is mounted on the first surface of the power supply board, The second surface, which is the surface opposite to the first surface, has a first solder portion and a second solder portion for soldering, The first input terminal is soldered to the first solder portion, The second input terminal is soldered to the second solder portion, The snubber circuit has at least some surface-mounted components, and when viewed in a direction orthogonal to the first surface of the power supply board, the transformer and the snubber circuit overlap and are connected to the first solder portion and the second solder portion. A power supply board characterized by this.

2. The power supply board according to claim 1, wherein the snubber circuit has a diode, a resistor, and a capacitor.

3. The power supply board according to claim 2, wherein the resistor is composed of at least two or more components.

4. The power supply board according to claim 1, wherein the snubber circuit has a power clamp.

5. A rectifying and smoothing circuit that rectifies and smooths the voltage output from the secondary winding, A control circuit that detects the output voltage and performs feedback control, Comprising, The transformer has a first output terminal and a second output terminal from which a voltage is output from the secondary winding, The second surface has a third solder portion and a fourth solder portion for soldering, The first output terminal is soldered to the third solder portion, The second output terminal is soldered to the fourth solder portion, The control circuit has at least some surface-mounted components, and when viewed in a direction orthogonal to the first surface of the power supply board, the transformer and the control circuit overlap, The pattern of the control circuit passes between the third solder portion and the fourth solder portion. The power supply board according to claim 1, characterized by this.

6. A transformer having a primary winding and a secondary winding, A switching element connected to the primary winding and performing a switching operation, A rectifying and smoothing circuit that rectifies and smooths the voltage output from the secondary winding, A control circuit that detects the output voltage and performs feedback control, A power supply board that includes a transformer for transforming the input voltage on the primary side and outputting the output voltage from the secondary side, wherein the transformer has a first output terminal and a second output terminal from which a voltage is output from the secondary winding, and is mounted on a first surface of the power supply board, a second surface, which is a surface opposite to the first surface, has a third solder portion and a fourth solder portion for soldering, the first output terminal is soldered to the third solder portion, the second output terminal is soldered to the fourth solder portion, the control circuit has surface-mounted components at least in part, and when viewed in a direction orthogonal to the first surface of the power supply board, the transformer and the control circuit overlap, a pattern of the control circuit passes between the third solder portion and the fourth solder portion, characterized in that it is a power supply board.

7. The rectifying and smoothing circuit has a smoothing capacitor, the control circuit is arranged so as to pass between the third solder portion and the fourth solder portion, characterized in that it is the power supply board according to claim 6.

8. It includes an overvoltage detection circuit for detecting that the output voltage is an overvoltage, the overvoltage detection circuit has surface-mounted components at least in part, and when viewed in a direction orthogonal to the first surface of the power supply board, the transformer and the overvoltage detection circuit overlap, a pattern of the overvoltage detection circuit passes between the third solder portion and the fourth solder portion, characterized in that it is the power supply board according to claim 7.

9. When a circuit loop of a power supply line and a GND line formed by the control circuit and the smoothing capacitor is defined as a first circuit loop, the overvoltage detection circuit is arranged such that a second circuit loop of a power supply line and a GND line formed by the overvoltage detection circuit and the smoothing capacitor is larger than the first circuit loop, characterized in that it is the power supply board according to claim 8.

10. The power supply board is a single-sided board, characterized in that it is the power supply board according to any one of claims 1 to 9.

11. An image forming apparatus that forms an image on a recording material, characterized in that the power supply board according to any one of claims 1 to 9 is used as the power supply of the image forming apparatus.

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