JP5037070B2 - Inrush current suppression device - Google Patents

Description

  The present invention relates to an inrush current suppressing device, and more particularly, to an inrush current suppressing device for an electric device including a unit to which power from a power supply is supplied through a power supply wiring and a capacitor connected in parallel to the power supply wiring.

  An image forming apparatus such as a printer or a multifunction peripheral includes various units for forming an image inside a main body, and the main body is covered with a cover member. Examples of the unit include an image forming unit that performs image formation, a paper transport path that transports paper to the image forming unit, and a medium-high voltage power supply device that supplies power to these units.

  An example of the power supply device is a switching power supply. The switching power supply mainly includes a rectifying / smoothing unit, a switching unit, and a transformer unit. When the AC voltage is rectified and smoothed and then switched at a high frequency to perform insulation and step-down, it is rectified and output again. However, since such a rectifying and smoothing unit of the switching power supply is mainly configured by using a capacitor, an inrush current flows through the capacitor when the switching power supply starts generating power.

Therefore, as a power supply device for preventing an inrush current, a device capable of appropriately setting the time for starting suppression of the inrush current (Patent Document 1), a booster circuit provided in the power supply device, and a multi-winding choke A device that uses a coil and supplies a drive voltage for a thyristor from one winding of the choke coil is known (Patent Document 2).
Japanese Patent Laid-Open No. 5-56631 JP 2001-178137 A

  By the way, in the image forming apparatus, in order to ensure the safety of the user even when the cover member is opened during the operation of forming an image, each unit is connected to the power source in conjunction with the operation of opening the cover member. Some units are provided with an interlock switch for cutting off the power supply wiring for supplying the power and stopping the operation of each unit. However, a capacitor for supplying a stable voltage to each unit is connected to the power supply wiring in parallel. For this reason, when the cover member is changed from the open state to the closed state, and the interlock switch is turned on and the power is supplied to each unit so that power is supplied to each unit, the capacitors are simultaneously connected to each capacitor. An inrush current of several tens of amperes flows. Then, a voltage drop in which the voltage in the electric power supplied to each unit drops sharply, or a phenomenon that the unit is malfunctioned due to the GND being shaken due to the inrush current flowing all at once into GND.

  Even if the power supply devices of Patent Documents 1 and 2 are used for such an image forming apparatus, Patent Documents 1 and 2 provide means for preventing a so-called primary side inrush current before the transformer section, that is, inside the power supply. Since it is provided, it is impossible to prevent a so-called secondary inrush current that flows when the interlock switch outside the power source, that is, the outside of the power supply is turned on.

  As a general method for suppressing the inrush current on the secondary side, a method of inserting a resistance element in series with the power supply wiring is known. However, since the inrush current to each capacitor flows continuously in the resistor element itself, it is necessary to use a resistor element having a large rated power. Such a resistive element is generally high in cost and has a large shape.

  Accordingly, an object of the present invention is to provide an inrush current suppressing device that can suppress the inrush current on the secondary side in a small size and at low cost.

  In order to solve the above-mentioned problems, the invention 1 is an inrush current suppressing device for an electric device comprising a unit to which power from a power supply is supplied through a power supply wiring, and a capacitor connected in parallel to the power supply wiring. And an interlock switch, a resistance element, and a resistance short-circuit element. The interlock switch is provided between the power source and the capacitor, and turns on and off the application of a predetermined voltage to the unit of the power source. The resistance element is provided in series between the power source and the interlock switch. The resistance short-circuit element is connected in parallel to the resistance element and can short-circuit the resistance element.

  In the following, the case where the resistance short-circuit element is a thyristor and the interlock switch is turned on in conjunction with the operation of the cover member when the cover member of the open electric device is closed will be taken as an example. The inrush current that flows from the power source to each capacitor at the moment when the interlock switch is turned on flows in the resistance element. This inrush current is suppressed by the impedance of this resistance element. Thereafter, the thyristor is turned on by the voltage after the interlock switch, and the power source and the resistance element are bypassed by the thyristor. As a result, the power from the power source can be supplied to the unit with reduced loss by using a small resistance element with a small rated power, and the inrush current on the secondary side after the insulating transformer in the power source can be changed to the inrush current. This can be suppressed as compared with the case where measures are not taken. Accordingly, it is possible to suppress a steep voltage drop caused by the inrush current.

  A second aspect of the present invention is the inrush current according to the first aspect, wherein the resistance short-circuit element is a thyristor, and further includes control means for controlling the thyristor so that the thyristor short-circuits the resistance element when the interlock switch is turned on. A suppression device is provided.

  Invention 3 further includes a feedback wiring for feeding back a voltage downstream of the resistance short-circuiting element to the power supply in Invention 1 or 2, wherein the power supply is based on a voltage fed back through the feedback wiring. An inrush current suppressing device that adjusts and outputs the predetermined voltage is provided.

  When the thyristor is turned on, an on-voltage of the thyristor is generated, and a voltage obtained by dropping the voltage from the power supply by the on-voltage is given to the unit. However, this device feeds back the voltage from the power source that has dropped by the ON voltage, that is, the voltage downstream of the thyristor to the power source. The power supply performs, for example, PWM control based on the fed back voltage, and adjusts so that the voltage in the downstream portion of the thyristor becomes a predetermined voltage. As a result, a predetermined voltage is applied to the unit.

  According to the inrush current suppressing device of the present invention, the inrush current on the secondary side can be suppressed with a small size and low cost. Accordingly, it is possible to prevent a voltage drop of a voltage supplied to each unit and a phenomenon that the unit malfunctions. Further, since a voltage drop can be prevented, a capacitor having a small capacity can be used as a capacitor for supplying a stable voltage to each unit.

<Embodiment>
(1) Configuration of Image Forming Apparatus FIG. 1 is an external view of an image forming apparatus 101 in which the inrush current suppressing device according to the present embodiment is employed. The image forming apparatus 101 is a multifunction machine model having functions as a copying machine, a printer, a facsimile machine, and a scanner. An image forming apparatus 101 in FIG. 1 includes a document cover 102, a cover member 103, a main body 104, and a paper feed cassette 105.

  The document cover 102 is for pressing a document placed on a document placement table (not shown) provided in a portion of the main body 104 facing the document cover 102 and can be opened and closed with respect to the document placement table. Is attached to the main body 104.

  The cover member 103 is attached to the front portion of the main body portion 104 so as to be rotatable about the end portion 103 a of the cover member 103 with respect to the main body portion 104, and has an open posture that exposes the inside of the main body portion 104. A closed posture in which the inside of the main body 104 is separated from the outside can be adopted.

  The cover member 103 is provided with a protruding member 131. More specifically, as shown in FIG. 2, the protruding member 131 protrudes in the direction of the inside of the main body portion 104 with respect to the cover member 103, and the interlock switch 3 ( The cover member 103 is provided so as to correspond to a position described later.

  As shown in FIG. 3, the main body unit 104 includes units 141 a, 141 b, 141 c, capacitors 142 a, 142 b, 142 c, a power supply unit 143, and an inrush current suppression device 1.

  The units 141a to 141c are supplied with a predetermined voltage from a power supply unit 143 through a power supply wiring 2 (described later). For example, a communication unit that communicates with another terminal or an image forming unit that prints an image on a sheet. Etc.

  The capacitors 142a to 142c are for stabilizing a predetermined voltage supplied from the power supply unit 143 to the units 141a to 141c. The capacitors 142a to 142c are in the vicinity of the units 141a to 141c and are connected to the branch wirings 2a and 2b of the power supply wiring 2. , 2c (described later) are connected in parallel. Examples of the types of capacitors 142a to 142c include electrolytic capacitors as shown in FIG.

  The power supply unit 143 mainly includes a rectifying / smoothing unit 144, a SW control unit 145, and a transformer 146, and generates a predetermined voltage to be supplied to the units 141a to 141c. The rectifying / smoothing unit 144 rectifies and smoothes an AC voltage supplied from the outside of the image forming apparatus 101, for example. The SW control unit 145 performs PWM control on the voltage that has been rectified and smoothed by the rectifying and smoothing unit 144 based on a voltage input through the feedback wiring 7 (described later), and then performs switching at a high frequency. The transformer 146 steps down and insulates the voltage switched by the SW control unit 145.

  The inrush current suppressing device 1 is a device for suppressing an inrush current flowing in each of the capacitors 142a to 142c at the moment when a predetermined voltage generated by the power supply unit 143 is started to be supplied to each unit 141a to 141c through the power supply wiring 2. In this case, the power supply unit 143 is provided at a subsequent stage. The inrush current suppressing device 1 will be described later.

  The paper feed cassette 105 can store paper, and is provided in two stages below the main body 104 as shown in FIG.

(2) Configuration of Inrush Current Suppression Device Next, the configuration of the inrush current suppression device 1 will be described. As shown in FIG. 3, the inrush current suppressing device 1 includes a power supply wiring 2, an interlock switch 3, a resistance element 4, a thyristor 5, a thyristor driving unit 6 (corresponding to control means), and a feedback wiring 7.

  The power supply wiring 2 is for supplying a predetermined voltage generated by the power supply unit 143 to each unit 141a to 141c, and connects between the power supply unit 143 and each unit 141a to 141c. Specifically, one power supply wiring 2 extending from the connection side with the power supply unit 143 branches at a branch point A to become branch wirings 2a to 2c, and is connected to the units 141a to 141c.

  The interlock switch 3 is provided in the middle of the power supply wiring 2 and between the power supply unit 143 and the branch point A of the power supply wiring 2, and is turned on and off in conjunction with a change in posture that the cover member 103 can take. Specifically, the interlock switch 3 turns on and off the application of a predetermined voltage to the units 141a to 141c of the power supply unit 143. Examples of the type of the interlock switch 3 include an electromagnetic lock type constituted by an actuator and a solenoid, a magnet type that is turned on when a magnetic field of a magnet is detected by a sensor, and a push type that is turned on when pressed directly. However, in this embodiment, a case where a push-down interlock switch is used is taken as an example. That is, in the present embodiment, when the cover member 103 changes from the open state to the closed state, the protruding member 131 of the cover member 103 presses the interlock switch 3. Thereby, the pressed interlock switch 3 is turned on, and a predetermined voltage from the power supply unit 143 is supplied to each of the units 141a to 141c.

  The resistance element 4 is provided in series in the middle of the power supply wiring 2 and between the power supply unit 143 and the interlock switch 3.

  The thyristor 5 is connected in parallel to the resistance element 4 so that the resistance element 4 can be short-circuited.

  The thyristor driving unit 6 is for controlling the thyristor 5 so that the thyristor 5 is turned on to short-circuit the resistance element 4 at the moment when the interlock switch 3 is turned on. The thyristor is driven using the voltage from the connection point B on the wiring 2.

  The feedback wiring 7 is used to feed back the voltage on the downstream side of the thyristor 5 to the SW control unit 145 in the power supply unit 143. Of the power supply wiring 2, the resistance element 4, the thyristor 5, the interlock switch 3, And the SW control unit 145 are connected to each other.

(3) Operation of Inrush Current Suppressing Device Next, the operation of the inrush current suppressing device 1 will be described.

  First, it is assumed that the image forming apparatus 101 has already been turned on and the cover member 103 of the image forming apparatus 101 is open as shown in FIG. In this case, the power supply unit 143 generates a predetermined voltage, but since the protruding member 131 is separated from the interlock switch 3, the interlock switch 3 is turned off. Therefore, each unit 141a-141c is in the state where the predetermined voltage from the power supply part 143 is not supplied. In the image forming apparatus 101 in such a state, it is assumed that the user rotates the cover member 103 in the direction of arrow A with the end portion 103a of the cover member 103 as a rotation axis.

  Then, the interlock switch 3 is pressed by the protruding member 131 of the cover member 103 and turned on. At this moment, a predetermined voltage from the power supply unit 143 is applied to the power supply wiring 2. The thyristor driving unit 6 turns on the thyristor 5 by supplying, for example, a current to the gate terminal of the thyristor 5 when a predetermined voltage is applied to the connection point B of the power supply wiring 2.

  At this time, an inrush current flows from the power supply unit 143 to the capacitors 142a to 142c through the power supply wiring 2 and the branch wirings 2a to 2c. The inrush current is a resistance element at the moment when the interlock switch 3 is turned on. 4 is suppressed by the impedance. Then, after the thyristor 5 is turned on by the thyristor driving unit 6, the inrush current flows to the thyristor 5 side having a lower impedance than the resistance element 4. Thereby, the period during which the inrush current flows through the resistance element 4 is a short period from when the interlock switch 3 is turned on until the thyristor 5 is turned on. Therefore, the power loss due to the resistance element 4 is smaller than when the inrush current suppression device 1 is not provided.

  On the other hand, in the thyristor 5 that has been turned on, after a rush current flows through the capacitors 142a to 142c, the current further flows continuously, so that a so-called ON voltage is generated. For this reason, the predetermined voltage output from the power supply unit 143 drops by the ON voltage of the thyristor 5.

  However, the voltage dropped by the ON voltage is fed back from the connection point C on the power supply wiring 2 to the SW control unit 145 of the power supply unit 143 through the feedback wiring 7. The SW control unit 145 of the power supply unit 143 adjusts a predetermined voltage output from the power supply unit 143 based on the fed back voltage. For example, since the value of the fed back voltage is less than a predetermined voltage value, the SW control unit 145 performs PWM so that the voltage value output from the power supply unit 143 is increased from the predetermined value by the ON voltage of the thyristor 5. Take control. As a result, a voltage higher than the predetermined voltage value by the on-voltage of the thyristor 5 is output from the power supply unit 143. Since this voltage drops through the thyristor 5 by the on-voltage, each unit 141a to 141c has a predetermined voltage. A voltage having a value of is supplied.

  The voltage having the predetermined value is supplied again from the connection point C on the power supply wiring 2 to the SW control unit 145 of the power supply unit 143 through the feedback wiring 7. However, since this voltage is not less than the predetermined value, the SW control unit 145 maintains the current control.

(4) Effect According to this inrush current suppressing device 1, the inrush current flowing from the power supply unit 143 to each of the capacitors 142 a to 142 c at the moment when the interlock switch 3 is turned on is suppressed by the impedance of the resistance element 4. Then, after the thyristor 5 is turned on based on the voltage on the downstream side of the interlock switch 3, a current flows through the thyristor 5 having a lower impedance than the resistance element 4. From this, the period in which the current flows through the resistance element 4 is from the time when the interlock switch 3 is turned on until the thyristor 5 is turned on, so that the power loss in the resistance element 4 is reduced. As a result, a small element with a small rated power can be used as the resistance element 4 and the total amount of inrush current on the so-called secondary side outside the power supply unit 143 is suppressed as compared with a case where no countermeasure against inrush current is taken. be able to. Therefore, a steep voltage drop caused by the inrush current can be suppressed, and a small switch with a low rated current can be used as the interlock switch. In addition, since the voltage drop is suppressed, capacitors having a small capacity can be used for the capacitors 142a to 142c.

  Further, the inrush current suppression device 1 feeds back the voltage dropped by the ON voltage of the thyristor 5 to the power supply unit 143. The power supply unit 143 performs, for example, PWM control based on the fed back voltage and adjusts the voltage on the downstream side of the thyristor 5 to be a predetermined voltage, whereby a predetermined voltage is applied to each of the units 141a to 141c. Applied.

<Other embodiments>
(A) In the above embodiment, the case where a push-down interlock switch is used has been described. However, other types of interlock switches such as an electromagnetic lock type and a magnet type may be used.

  (B) In the above embodiment, the cover member in the front part of the main body of the image forming apparatus has been described as an example, but the present invention is not limited to this. For example, the present invention can be applied to a cover member on a side portion of the main body.

  (C) Although the case where a thyristor is used as an element for short-circuiting the resistance element has been described in the above embodiment, the element for short-circuiting the resistance element is not limited to the thyristor. Examples of the element for short-circuiting the resistance element include a diode other than the thyristor.

  The inrush current suppressing device according to the present invention may be employed in various types of copiers, printers, and facsimile machines, multifunctional image forming apparatuses that have a scanner function in addition to these functions, and electrical equipment such as finishers. it can. In other words, the inrush current suppressing device of the present invention includes any cover device provided with a cover member that covers the inside of the main body and provided with an interlock switch in order to ensure the safety of the user. It can also be adopted.

1 is an external view of an image forming apparatus in which an inrush current suppressing device according to an embodiment is employed. The figure which looked at the image forming apparatus from the top. The figure which showed the connection of the structure of an inrush current suppression apparatus, and the function part of the periphery of an inrush current suppression apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inrush current suppression apparatus 2 Power supply wiring 3 Interlock switch 4 Resistance element 5 Thyristor 6 Thyristor drive part 7 Feedback wiring 141a-141c Unit 142a-142c Capacitor 143 Power supply part

Claims (2)

An inrush current suppressing device for an electrical device comprising: a unit to which power from a power source is supplied through power wiring; and a capacitor connected in parallel to the power wiring.
An interlock switch that is provided between the power source and the capacitor and turns on and off the application of a predetermined voltage to the unit of the power source;
A resistance element provided in series between the power source and the interlock switch;
A resistance short-circuit element connected in parallel to the resistance element and capable of short-circuiting the resistance element;
A feedback wiring for feeding back a voltage at a connection point between the resistance element and the interlock switch to the power source;
When the interlock switch is turned on, control means for controlling the resistance short-circuit element so that the resistance short-circuit element short-circuits the resistance element using a voltage at a connection point between the interlock switch and the capacitor; Including
The power supply is an inrush current suppressing device that adjusts and outputs the predetermined voltage based on a voltage fed back through the feedback wiring . The resistance short-circuit element is a thyristor,
2. The inrush current suppression device according to claim 1 , wherein when the interlock switch is turned on , the control unit controls the thyristor so that the thyristor short-circuits the resistance element.

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