JP2022191580A - Power supply unit, image forming apparatus, and electrical apparatus - Google Patents

Abstract

To provide a power supply unit for realizing electric shock prevention at a time of disconnection from an electrical apparatus, while suppressing power consumption.SOLUTION: A power supply unit 145 comprises an AC/DC power supply substrate 100 for generating a DC voltage Vout from an AC voltage supplied from a commercial power supply 101, and a support plate 135 to which the AC/DC power supply substrate 100 is attached. The AC/DC power supply substrate 100 comprises a smooth capacitor 110 for smoothing the AC voltage rectified by a diode bridge 109; a converter 30 for producing the DC voltage Vout from a voltage smoothed by the smooth capacitor 110; and a discharge mechanism 20 for discharging the smooth capacitor 110 by being disconnected from the smooth capacitor 110 when the AC/DC power supply substrate 100 is attached to the support plate 135, and by being connected to the smooth capacitor 110 when the AC/DC power supply substrate is removed from the support plate 135.SELECTED DRAWING: Figure 1

Description

The present invention relates to a power supply unit that converts an AC voltage supplied from a commercial power source into a DC voltage.

In general, electrical equipment is equipped with an AC/DC power supply that generates a DC voltage used to drive a built-in control board and a load from an AC voltage supplied from a commercial power supply. An AC/DC power supply rectifies an AC voltage supplied through an AC filter with a diode bridge, smoothes it with a smoothing capacitor, and then charges a capacitor connected to the secondary side of a transformer to convert it into a DC voltage. Generate. A circuit for detecting the voltage value of the DC voltage is provided on the secondary side of the transformer. Driving of a switching element provided on the primary side of the transformer is controlled based on the voltage value of the DC voltage on the secondary side of the transformer. As a result, the current flowing through the primary winding of the transformer is controlled so that the voltage value of the DC voltage becomes a predetermined voltage value.

An AC/DC power supply device often uses a large-capacity electrolytic capacitor of about 180 [μF] to 330 [μF] as a smoothing capacitor. If such a smoothing capacitor does not have a discharge mechanism, electric charge will remain for a while after the AC voltage is cut off.

2. Description of the Related Art An image forming apparatus or the like is equipped with an AC/DC power supply that generates a DC voltage of 5 [V], 12 [V], or 24 [V] used inside the apparatus from an AC voltage supplied from a commercial power source. The output of the AC/DC power supply is supplied to a plurality of control boards and loads arranged in the image forming apparatus. The control board controls the driving of the load. An AC/DC power supply may be determined to be out of order due to a load malfunction, communication failure between control devices, or the like. In this case, the service person removes the power supply unit including the AC/DC power supply from the image forming apparatus to investigate the cause of the failure, and visually checks and checks continuity using a tester or the like.

If the electric charge accumulated in the smoothing capacitor of the power supply unit is not discharged when AC voltage is not supplied from the commercial power supply, service personnel should If you touch it, you may get an electric shock. Therefore, there is a power supply device configured to discharge residual electric charges in a short period of time after cutting off the AC voltage from the commercial power supply by incorporating a discharge resistor in parallel with the smoothing capacitor from the beginning as a power supply circuit. However, in this configuration, constant power is always consumed by the discharge resistor in addition to the power used within the device.

Japanese Unexamined Patent Application Publication No. 2002-200001 discloses an image forming apparatus in which a power supply unit is configured to be slidably attachable/detachable in a predetermined direction. The power supply unit includes a capacitor electrically connected to an external power supply, a pair of wires connected to both ends of the capacitor, and a discharge mechanism for discharging the capacitor. When the power supply unit is slid and removed from the image forming apparatus, the discharge mechanism functions to discharge the capacitor.

JP 2013-61596 A

In a conventional slide-detachable power supply unit, it is necessary to convert voltage into heat with a resistor and consume it in order to discharge the smoothing capacitor. In other words, in order to discharge in a short period of time when the smoothing capacitor comes into contact with the discharge mechanism when it is pulled out while sliding, a discharge resistor with a small resistance value of several tens of watts that can instantaneously flow a large current is required. Become. Such a discharge resistor requires attention to heat generation. If the resistance value of the discharge resistor is set to a large value as a countermeasure against heat generation, a sufficient discharge effect cannot be obtained because the discharge mechanism does not have sufficient discharge time.

SUMMARY OF THE INVENTION In view of the above problems, the main object of the present invention is to provide a power supply unit capable of preventing an electric shock when being pulled out of an electrical device while suppressing power consumption.

A power supply unit of the present invention is a power supply unit comprising: a power supply board that generates a DC voltage from an AC voltage supplied from a commercial power supply; and a mounting member to which the power supply board is mounted, wherein the power supply board a smoothing capacitor for smoothing the AC voltage rectified by the rectifier; a converter for generating the DC voltage of a predetermined voltage value from the voltage smoothed by the smoothing capacitor; a discharging mechanism that is disconnected from the smoothing capacitor when the power supply board is attached to the mounting member, and is connected to the smoothing capacitor to discharge the smoothing capacitor when the power supply board is removed from the mounting member. and

ADVANTAGE OF THE INVENTION According to this invention, electric shock prevention at the time of pulling out from an electrical equipment can be implement|achieved, suppressing power consumption.

(a), (b) is a structure illustration figure of a power supply unit. (a) and (b) are external views of an image forming apparatus. 4A and 4B are explanatory views of a method of removing the power supply unit from the image forming apparatus; FIG. (a) to (c) are explanatory diagrams of a support plate. (a) and (b) are explanatory diagrams of an AC/DC power supply board attached to a support plate. (a) to (c) are explanatory diagrams of mounting states of spacers. (a), (b) is a structure illustration figure of the power supply unit of 2nd Embodiment. FIG. 4 is an exemplary view of the AC/DC power supply board removed from the support plate; (a) to (c) are explanatory diagrams of the third embodiment.

EMBODIMENT OF THE INVENTION Below, embodiment of this invention is described in detail, referring drawings. In the embodiments described below, a power supply unit to which the present invention is applied and an image forming apparatus, which is an example of an electric device including the power supply unit, will be described. Note that the electrical equipment is not limited to the image forming apparatus.

(First embodiment)
FIG. 1 is a diagram illustrating the configuration of a power supply unit according to this embodiment. This power supply unit 145 includes an AC/DC power supply board 100 covered with a cover 144 as a power supply. The AC/DC power supply board 100 converts an AC voltage supplied from a commercial power supply 101 into a DC voltage Vout and outputs the DC voltage Vout. FIG. 1(a) shows the circuit configuration of the AC/DC power supply substrate 100. FIG.

AC/DC power supply board 100 sends AC voltage supplied from commercial power supply 101 to diode bridge 109 via AC filter 108 . AC filter 108 is composed of X capacitor 102 , common mode choke coil 103 , X capacitor 104 , and Y capacitors 105 and 106 . Y capacitors 105 and 106 are connected to FG (Frame Ground) 107 that serves as a reference for commercial power supply 101 . It should be noted that the AC filter 108 can be changed in the number of constituent parts and in the order of construction as necessary. Diode bridge 109 is an example of a rectifier and rectifies the AC voltage supplied through AC filter 108 . A smoothing capacitor 110 is charged by the rectified current. A DC voltage is thus obtained from both ends of the smoothing capacitor 110 .

A DC voltage obtained from both ends of smoothing capacitor 110 is supplied to converter control section 114 via starting resistor 113 . The DC voltage supplied to converter control unit 114 is a voltage divided by starting resistor 113 and resistor 125 . Converter control unit 114 controls opening and closing of switching element 116 connected in series to primary winding 115 a of transformer 115 . An alternating current flows through the primary winding 115 a of the transformer 115 by opening/closing control of the switching element 116 . A voltage corresponding to the winding ratio of the transformer 115 is generated in the secondary winding 115b by the alternating current flowing through the primary winding 115a.

A secondary rectifier diode 117 and a secondary smoothing capacitor 118 are arranged on the secondary winding 115 b side of the transformer 115 . The voltage generated in secondary winding 115 b is rectified by secondary rectifier diode 117 and smoothed by secondary smoothing capacitor 118 . A DC voltage is obtained from both ends of the secondary side smoothing capacitor 118 . A DC voltage obtained across the secondary smoothing capacitor 118 is output as a DC voltage Vout generated by the AC/DC power supply board 100 .

Resistors 119 and 120, a shunt regulator 121, and a photocoupler are provided to stabilize the DC voltage Vout at a constant value. The photocoupler is configured by housing a light emitting diode 122a and a phototransistor 122b in the same package. The resistors 119 and 120, the shunt regulator 121, and the photocoupler function as the voltage detection section 10 that detects the voltage value of the DC voltage Vout. The detection result of the voltage value of DC voltage Vout by voltage detection unit 10 is fed back to converter control unit 114 as a detection signal.

A DC voltage Vout is divided by resistors 119 and 120 and input to a reference terminal of a shunt regulator 121 . The shunt regulator 121 increases the current flowing through the light emitting diode 122a when the voltage generated by dividing the DC voltage Vout by resistors is higher than the reference voltage, and increases the current flowing through the light emitting diode 122a when the voltage is lower than the reference voltage. Decrease the current. The light-emitting diode 122a emits light with an amount of light corresponding to the magnitude of the flowing current, and electrically insulates the phototransistor 122b. A current corresponding to the amount of received light flows through the collector of the phototransistor 122b. Converter control unit 114 detects the voltage value of DC voltage Vout according to the value of current flowing through the collector of phototransistor 122b. In this manner, the voltage value of the DC voltage Vout is fed back to the converter control section 114 via the photocoupler.

Converter control unit 114 controls the duty ratio of switching element 116 in accordance with the fed-back voltage value of DC voltage Vout so that DC voltage Vout is adjusted to a predetermined voltage value. For example, when the voltage value of DC voltage Vout decreases, converter control unit 114 increases the conduction time of switching element 116 to increase the current flowing through primary winding 115a of transformer 115 . As a result, more power is supplied to the secondary side of the transformer 115, and the voltage value of the DC voltage Vout increases. Transformer 115 , converter control section 114 , secondary smoothing capacitor 118 , and voltage detection section 10 constitute converter 30 .

An auxiliary winding 115c is wound around the same core as the primary winding 115a and the secondary winding 115b of the transformer 115 . When switching of the switching element 116 is started, a voltage is also generated in the auxiliary winding 115c at the same time. This voltage causes a current to flow through the diode 123 to charge the capacitor 124 , so that a DC voltage is obtained from both ends of the capacitor 124 . The voltage of capacitor 124 serves as a power supply source for converter control section 114 . As the DC voltage is supplied from both ends of capacitor 124 , converter control unit 114 cuts off the power supplied from smoothing capacitor 110 via starting resistor 113 .

FIG. 1(b) is an explanatory diagram of a mounting state of the AC/DC power supply board 100. FIG. The AC/DC power supply board 100 is screwed to the supporting plate 135 of the cover 144 . The supporting plate 135 is provided with screwing portions 136 , 137 , 138 , 139 , 140 , and 141 formed by cutting and bending a sheet metal to fix the AC/DC power supply board 100 with screws. FG 107 of AC/DC power supply board 100, ground 134 of DC voltage Vout, ground 128 of smoothing capacitor 110, ground 130, 131, 132, 133 are screwed to screwed portions 136, 137, 138, 139, 140, 141. Fixed. The grounds 130 , 131 , 132 , 133 are common on a ground pattern (not shown) of the AC/DC power supply board 100 . The AC/DC power supply board 100 and the support plate 135 are kept at a predetermined distance by insulating spacers 142 and 143 .

With regard to electric shock, permissible contact voltages are determined according to the circumstances in which people come into contact. The permissible contact voltage is defined as 25 [V] when the human body is extremely wet or when the human body is constantly in contact with metallic electrical equipment, etc., and 50 [V] in normal conditions. Since the power supply unit 145 of this embodiment is used indoors, it has an allowable contact voltage of 50 [V] and includes a discharge mechanism 20 composed of a discharge resistor 111 and a switch 112 .

FIG. 2 is an external view of an image forming apparatus, which is an example of electrical equipment. 2A is a perspective view of the image forming apparatus 211 seen obliquely from the front, and FIG. 2B is a perspective view of the image forming apparatus 211 seen obliquely from the rear. The image forming apparatus 211 incorporates a power supply unit 145 . The power supply unit 145 supplies a DC voltage Vout to each part of the image forming apparatus 211 . The image forming apparatus 211 operates with a DC voltage Vout shared from the power supply unit 145 . The image forming apparatus 211 may include multiple power supply units 145 . In this case, each power supply unit 145 generates a DC voltage Vout of a predetermined voltage value.

The image forming apparatus 211 includes a printer unit 202, a document scanning unit 203, a document conveying unit 204, an operation unit 201, and a display unit 210 as components. When a plurality of power supply units 145 are provided, for example, one power supply unit 145 is provided for each of the printer section 202 , document scanning section 203 , document conveying section 204 , operation section 201 and display section 210 . Each part operates with a DC voltage Vout supplied from the corresponding power supply unit 145 .

The document conveying unit 204 is provided with a document stacking tray 205 on which the document is placed with the surface printed with the image facing up. The printer unit 202 is provided with a paper discharge unit 206 for discharging printed matter. The image forming apparatus 211 is provided with a main switch 207 on the back. The image forming apparatus 211 is connected to an outlet 212 via a plug 209 with a power cable 208 .

The originals placed on the original stacking tray 205 are separated and conveyed one by one by the original conveying unit 204 , and the images are read by the original scanning unit 203 . Image data representing the read image is transmitted from the document scanning unit 203 to the printer unit 202 . The printer unit 202 prints an image on a sheet based on the image data acquired from the document scanning unit 203 to generate a printed material. In the case of copy processing, the image forming apparatus 211 operates in this way.

The operation unit 201 and display unit 210 are user interfaces. An operation unit 201 includes various key buttons and a touch panel. A user uses the operation unit 201 to instruct printing and perform various settings. The display unit 210 has a display. The display unit 210 displays a print setting screen and a screen showing the state of the image forming apparatus 211 .

For example, the display unit 210 displays a message (service call) indicating a failure of the power supply unit 145 built in the image forming apparatus 211 . In this case, the user turns off the main switch 207 and pulls out the plug 209 from the outlet 212 after confirming that the image forming apparatus 211 has been shut down. After that, the user removes the failed power supply unit 145 from the image forming apparatus 211 and confirms the failure of the power supply unit 145 . 3A and 3B are explanatory diagrams of a method of removing the power supply unit 145 from the image forming apparatus 211. FIG.

FIG. 3A shows a state in which the back cover 301 of the image forming apparatus 211 is removed. 3B shows the power supply unit 145 taken out from the image forming apparatus 211. FIG. The power supply unit 145 is pulled out from the image forming apparatus 211 after the rear cover 301 is removed. When the cover 144 is removed from the power supply unit 145, the AC/DC power supply board 100 is exposed. As a result, the AC/DC power supply board 100 is removed from the screw-fixed support plate 135 .

4A and 4B are explanatory diagrams of the support plate 135. FIG. As shown in FIG. 4A, the support plate 135 has screw portions 136, 137, 138, 139, 140, and 141 to which the AC/DC power supply board 100 is screwed. be provided. Processed portions 401 and 402 obtained by burring the support plate 135 are provided at positions where the spacers 142 and 143 are fixed. The spacers 142 and 143 are configured so that the fixed portions of the spacers 142 and 143 do not protrude from the bottom surface of the support plate 135 when fixed to the processed portions 401 and 402 .

Spacers 142 and 143 are used for different purposes. Relatively heavy parts such as a common mode choke coil 103 and a transformer 115 are mounted on the AC/DC power supply board 100 . Therefore, the AC/DC power supply substrate 100 may be damaged due to resonance with the screw fixing portion as a fulcrum due to factors such as vibration. A spacer 143 that prevents the AC/DC power supply board 100 from bending is used to suppress damage to the AC/DC power supply board 100 due to resonance. The AC/DC power supply board 100 is fixed by the spacer 143 without using screws. Spacer 142 constitutes switch 112 side of discharge mechanism 20 (discharge resistor 111 and switch 112 ) configured to connect both electrodes of smoothing capacitor 110 .

4(b) and 4(c) show how the spacer 142 is attached to the AC/DC power supply substrate 100. FIG. The AC/DC power supply board 100 is provided with an opening 403 through which the spacer 142 passes. When attaching the AC/DC power supply substrate 100 to the support plate 135 , the spacer 142 attached to the support plate 135 is inserted into the opening 403 of the AC/DC power supply substrate 100 .

The spacer 142 inserted into the opening 403 protrudes from the surface of the AC/DC power supply board 100 (component mounting surface). The spacer 142 of this embodiment does not suppress vibration of the AC/DC power supply substrate 100 like the spacer 143 for preventing bending. In this embodiment, it is necessary for the spacer 142 to come off from the opening 403 without stress in order to prevent electric shock. Therefore, the diameter 405 of the thickest portion of the spacer 142 passing through the opening 403 is set smaller than the diameter 404 of the opening 403 . For example, the diameter 405 of the spacer 142 and the diameter 404 of the opening 403 are designed to satisfy the following relational expression.
(Diameter 404 of opening 403)-(Diameter 405 of spacer 142)>1 [mm]

FIG. 5 is an explanatory diagram of the AC/DC power supply board 100 when attached to the support plate 135. As shown in FIG. FIG. 5( a ) shows the state when the AC/DC power supply board 100 is attached to the support plate 135 . FIG. 5(b) shows the state when the AC/DC power supply board 100 is removed from the support plate 135. FIG.

5A shows the state when the AC/DC power supply board 100 is incorporated in the image forming apparatus 211. FIG. The AC/DC power supply board 100 converts the AC voltage supplied from the commercial power supply 101 and outputs a DC voltage Vout. The AC/DC power supply board 100 is a single-sided board, and a smoothing capacitor 110 , a discharge resistor 111 , a conductive spring member 501 which is a constituent part of the switch 112 , and a jumper wire 504 are mounted on the surface. A copper foil pattern 502 connected to the positive terminal of the smoothing capacitor 110 and a copper foil pattern 503 connected to the negative terminal of the smoothing capacitor 110 are wired on the back surface of the AC/DC power supply board 100. .

The members to which the spring member 501 connects are the jumper wire 504 mounted on the copper foil pattern 503 and the discharge resistor 111 . The jumper wire 504 is mounted so as to be raised from the surface of the AC/DC power supply board 100 by about 1 [mm] to 2 [mm], considering the plastic deformation of the spring member 501 . The spacer 142 holds the spring member 501 in a pushed state, thereby holding the switch 112 in an off state (blocking state) (FIG. 5(a)). Even if the stress of the spring has weakened due to aging, the switch 112 is turned on (conducting state) by extracting the spacer 142 from the AC/DC power supply substrate 100 (FIG. 5(b)). Residual charge of the smoothing capacitor 110 is discharged by the switch 112 being turned on (conducting state).

FIG. 6 is an explanatory diagram of the mounting state of the spacers 142 and 143. As shown in FIG. FIG. 6A is a cross-sectional view illustrating a case where the AC/DC power supply board 100 is attached to the spacer 143 mounted on the support plate 135. FIG. The diagram on the left side of FIG. 6A shows the process of attaching the AC/DC power supply board 100 . The diameter 602 of the opening 403 to which the spacer 143 of the AC/DC power supply board 100 is attached is smaller than the width of the board supporting portion 601 of the spacer 143 . Therefore, when the AC/DC power supply board 100 is pushed in the direction of the arrow 603 , the board support portion 601 of the spacer 143 is compressed, so that the spacer 143 passes through the opening 403 . By passing through the opening 403, the shape of the substrate supporting portion 601 returns to its original shape as shown in the right diagram of FIG. With such a configuration, even if vertical vibration 604 occurs, the vibration of the AC/DC power supply board 100 is suppressed.

FIG. 6B is a cross-sectional view of the AC/DC power supply board 100 attached to the spacer 142 mounted on the support plate 135. FIG. The diameter 404 of the opening 403 to which the spacer 142 of the AC/DC power supply board 100 is attached is larger than the maximum width of the tip 605 of the spacer 142 .

As shown in FIGS. 6A and 6B, the support plate 135 has processed portions 401 and 402 that protrude toward the spacers 142 and 143 . The spacers 142 , 143 are provided with locking portions 610 , 611 of similar shape to the substrate support portion 601 . The locking portions 610 and 611 protrude toward the processed portions 401 and 402 and are locked to the support plate 135 .

FIG. 6C is an explanatory diagram of the switch 112. As shown in FIG. The spacer 142 pushes the spring member 501 when the AC/DC power supply board 100 is incorporated in the image forming apparatus 211 . As a result, the jumper wire 504 mounted on the copper foil pattern 503 connected to the smoothing capacitor 110 and the spring member 501 are brought into a non-contact state. By being in the non-contact state, current does not flow through the discharge resistor 111 and power is not consumed.

When the AC/DC power supply board 100 is pulled out from the image forming apparatus 211 and the AC/DC power supply board 100 is removed from the support plate 135 , the spacer 142 is pulled out from the AC/DC power supply board 100 . Therefore, the spring member 501 comes into contact with the jumper wire 504 . Thereby, the smoothing capacitor 110 is discharged. One end of the spring member 501 is fixed to the AC/DC power supply board 100 by a fixing portion 606 , and is electrically connected to the copper foil pattern 607 through the AC/DC power supply board 100 .

Although the AC/DC power supply board 100 in FIG. 6(c) exemplifies a single-sided board, the AC/DC power supply board 100 can have a similar configuration even if it is a double-sided board. Instead of the jumper wire 504, the screw head for grounding the AC/DC power supply board 100 and the spring member 501 may be connected. With such a configuration, the residual charge of the smoothing capacitor 110 can be discharged to the ground of the AC/DC power supply board 100 to obtain the same effect.

An AC voltage is supplied from a commercial power supply 101 to the AC/DC power supply board 100 . Therefore, it is necessary to secure a safe distance for each circuit component and copper foil pattern on the primary side of the transformer 115 . By using a material (insulating material) made of resin for the spacers 142 and 143 described above, it is possible to facilitate board design in consideration of the creepage distance.

In the case of the AC/DC power supply board 100 of the present embodiment, in the case of a 100 [V] (141 [V] charge) system, by using a discharge resistor 111 of 10 [kΩ] and 2 [W], about 3.5 seconds can be discharged up to 50 [V]. The discharge time can be shortened by reducing the resistance value of the discharge resistor 111 . However, short-time discharge leads to an increase in power consumption, so the resistance value of the discharge resistor 111 is selected to be an optimum value as necessary. The discharge resistor 111 is intended to discharge in a short period of time, and power consumption increases momentarily. Therefore, for the discharge resistor 111, it is preferable to select a resistor that can withstand a rush current and several hundreds [mA] of current discharge when the discharge mechanism 20 starts to function. For example, the discharge resistor 111 may be a wire-wound resistor, a square wire-wound resistor, a square metal oxide film resistor, or the like, which has excellent pulse characteristics.

(Second embodiment)
FIG. 7 is an exemplary configuration diagram of a power supply unit according to the second embodiment. This power supply unit 145a has a configuration in which a light emitting diode 701 is added as a light emitting element to the configuration of the discharge mechanism 20 of the power supply unit 145 of the first embodiment (see FIG. 1). The light emitting diode 701 is provided between the discharge resistor 111 and the switch 112 to constitute the discharge mechanism 20a. Other configurations of the power supply unit 145a are the same as those of the power supply unit 145 of the first embodiment.

The power supply unit 145a of the second embodiment notifies the serviceman that the smoothing capacitor 110 remains charged, that is, that the residual charge is being discharged by causing the light emitting diode 701 to emit light. As a result, the power supply unit 145a can prompt the serviceman to prevent electric shock.

The serviceman removes the AC/DC power supply board 100 a from the support plate 135 while looking at the component side of the AC/DC power supply board 100 . The serviceman notices the existence of the residual charge by removing the spacer 142 and operating the discharge mechanism 20a. The serviceman can recognize that the residual charge of the smoothing capacitor 110 has been discharged by confirming the state in which the light amount (brightness) of the light emitting diode 701 rapidly decreases. In the second embodiment, the light-emitting diode 701 can more reliably notify the serviceman of the residual charge.

FIG. 8 is an exemplary view of the AC/DC power supply board 100a removed from the support plate 135. FIG. When the AC/DC power supply board 100a is removed from the support plate 135, the switch 112 (spring member 501) of the discharge mechanism 20a is closed. In this state, the operation is the same as in FIG. 5(b), so the explanation is omitted. Note that the light emitting element is not limited to the light emitting diode 701, and may be any element that emits light when the switch 112 (spring member 501) is closed. Also, instead of the light-emitting element, a sound-producing element may be used for notification. The sound generating element outputs a sound to notify that the smoothing capacitor 110 is discharging the residual charge.

(Third embodiment)
FIG. 9 is an explanatory diagram of the third embodiment. The configuration of the power supply unit of the third embodiment is the same as that of the first embodiment (see FIG. 1). In order to make the structure more resistant to electric shock than in the first embodiment, the power supply unit 145 of the third embodiment discharges the residual charge of the smoothing capacitor 110 when the cover 144 of the power supply unit 145 is removed. . The same effect can be obtained by using the power supply unit 145a of the second embodiment as the power supply unit of the third embodiment.

FIG. 9A shows a state in which the AC/DC power supply board 100 is attached to the support plate 135. FIG. In FIG. 9A, spacers 143 are attached to each of the burred processed portions 401 and 402 of the supporting plate 135 . With the two spacers 143, the bending of the AC/DC power supply substrate 100 can be suppressed more than the configuration of the eleventh embodiment (see FIG. 4).

The AC/DC power supply board 100 is a single-sided board, and a smoothing capacitor 110, a discharge resistor 111, and the like are mounted on the front surface (first surface). A spring member 901 that is a component of the switch 112 is mounted on the back surface side (second surface side) of the AC/DC power supply board 100 . A copper foil pattern 502 connected to the positive terminal of the smoothing capacitor 110 and a copper foil pattern 503 connected to the negative terminal of the smoothing capacitor 110 are provided on the back surface of the AC/DC power supply board 100 .

The members to which the spring member 901 as a component of the switch 112 is connected are the copper foil pattern 904 and the copper foil pattern 902 extending from the copper foil pattern 503 . The copper foil pattern 902 mounts the discharge resistor 111 on the fulcrum side of the spring member 901 . The AC/DC power supply board 100 is provided with an opening 903 near the center of the spring member 901 into which the spacer 142 is inserted.

9B illustrates the cover 144 of the power supply unit 145. FIG. FIG. 9C illustrates a cross-sectional view of the cover 144 when the AC/DC power supply board 100 is mounted. The cover 144 has a notch 905 bent inward, and an opening 906 into which the spacer 142 is inserted is provided. The spacer 142 inserted from the opening 906 toward the AC/DC power supply board 100 pushes the spring member 901 through the opening 903 of the AC/DC power supply board 100 when the cover 144 is attached. As a result, the switch 112 is turned off (blocked state) when the cover 144 is attached. When the cover 144 is removed when the power supply unit 145 is disassembled, the switch 112 is turned on (conducting state), and discharging of the residual charge of the smoothing capacitor 110 is started.

The power supply units 145 and 145a of the first to third embodiments as described above are removed from the electrical equipment such as the image forming apparatus 211 after the power is turned off. At that time, the power supply units 145 and 145a are removed from the mounting members such as the support plate 135 and the cover 144. FIG. When the power supply units 145 and 145a are removed from the mounting member, the electric charge accumulated in the smoothing capacitor 110 can be consumed and discharged by the discharge resistor 111 . Therefore, the serviceman can safely remove the AC/DC power supply board 100 without being electrocuted. No current flows through the discharge resistor 111 while the power supply unit 145, 145a is attached to the electrical equipment. Therefore, the power supply units 145, 145a do not consume power unnecessarily during operation.

An electrical device such as an image forming apparatus equipped with such power supply units 145 and 145a can eliminate power consumption by the discharge resistor 111 during operation. When the power supply units 145 and 145a are removed after the power is cut off, the charge accumulated in the smoothing capacitor 110 is consumed and discharged by the discharge resistor 111. FIG. Therefore, the serviceman can safely remove the AC/DC power supply board 100 without being electrocuted.

Claims (12)

A power supply unit comprising: a power supply board that generates a DC voltage from an AC voltage supplied from a commercial power supply; and a mounting member to which the power supply board is mounted,
The power board,
a rectifier that rectifies the AC voltage;
a smoothing capacitor for smoothing the AC voltage rectified by the rectifier;
a converter that generates the DC voltage of a predetermined voltage value from the voltage smoothed by the smoothing capacitor;
a discharging mechanism that is disconnected from the smoothing capacitor when the power supply board is attached to the mounting member, and is connected to the smoothing capacitor to discharge the smoothing capacitor when the power supply board is removed from the mounting member; characterized by comprising
Power supply unit. The discharge mechanism includes a discharge resistor connected to the smoothing capacitor and a conductive switch,
The mounting member is provided with an insulating spacer,
When the power supply board is attached to the mounting member, the spacer cuts off the switch so that the discharge mechanism is cut off from the smoothing capacitor,
When the power supply board is removed from the mounting member, the spacer causes the switch to be in a conductive state, thereby connecting the discharge mechanism to the smoothing capacitor,
The power supply unit according to claim 1. When the power supply board is attached to the mounting member, the spacer puts the switch into a cut-off state by pushing the switch,
3. The power supply unit according to claim 2. The mounting member is a support plate that supplies grounding of the power supply substrate,
The power supply board is provided with an opening,
The spacer is attached at a position where the switch is pushed through the opening when the power supply board is attached to the support plate,
4. The power supply unit according to claim 2 or 3. The switch is provided on the same surface of the power supply substrate as the surface on which the smoothing capacitor is mounted,
The spacer pushes the switch through the opening from the back side of the surface on which the smoothing capacitor is mounted when the power supply board is attached to the support plate.
The power supply unit according to claim 4. The mounting member is a cover that covers the power supply board,
The power supply board is provided with an opening,
The spacer is attached to a position where the switch is pushed through the opening when the cover is attached to the power supply board,
4. The power supply unit according to claim 2 or 3. The switch is provided on the surface on the back side of the surface on which the smoothing capacitor of the power supply substrate is mounted,
The spacer pushes the switch through the opening from the surface on which the smoothing capacitor is mounted when the cover is attached to the power supply board,
The power supply unit according to claim 6. The discharge mechanism is characterized by comprising a notification means for notifying that the smoothing capacitor is discharging,
The power supply unit according to any one of claims 1-7. The notification means is a light emitting element that is connected to the smoothing capacitor and emits light when the power supply board is removed from the mounting member,
The power supply unit according to claim 8. The notification means is a sound generating element that is connected to the smoothing capacitor and outputs a sound when the power supply board is removed from the mounting member,
The power supply unit according to claim 8. A power supply unit according to any one of claims 1 to 10;
A printer that operates with a DC voltage supplied from the power supply unit and prints an image on a sheet,
Image forming device. A power supply unit according to any one of claims 1 to 10;
and a component that operates with a DC voltage supplied from the power supply unit,
electrical equipment.

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