JPH08237859A - Electronic equipment power supply - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a power supply device for an electronic device that is inexpensive and can use a miniaturized choke coil. [Structure] A power supply device for an electronic device that is used by being connected to a commercial power supply 9 includes a plurality of inductance elements L1 and L2.
And a DC for selecting an optimum inductance element among the plurality of inductance elements according to the current used by the electronic device.
The controller 2 and the switch SW that connects the inductance element selected by the DC controller 2 between the commercial power source and the current source (switching power source 1) of the electronic device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device for electronic equipment, and more particularly to a power supply device for electronic equipment such as a copying machine and a laser beam printer whose power consumption greatly differs depending on the operating state of the electronic equipment.

[0002]

2. Description of the Related Art In recent years, small and inexpensive switching power supplies have been widely used as power supply devices for computer equipment and household electronic equipment connected to a commercial power supply.

However, although the switching power supply has the above-mentioned advantages, it causes waveform distortion (power supply harmonic distortion) such that the input current to other electronic equipment is not a sine wave, and this power supply harmonic distortion is It is a cause of heating, burning, and abnormal noise of power capacitors and transformers of electric power systems and electronic devices, and causes of various operation failures such as malfunctions and malfunctions of electronic devices.

Therefore, in accordance with the amount of electric power used for electronic equipment, a standard or the like for controlling the amount of generation of power source harmonic distortion is set as a target value, and there is a movement to secure a clean commercial power source worldwide. Is coming out.

As one of the countermeasures on the electronic equipment side against the inconvenience caused by the harmonic distortion, there is a means for inserting and connecting one choke coil in series between the commercial power source and the input portion of the switching power source. According to this structure, the inductance of the choke coil inserted in series serves as a resistance against the harmonic component generated by the switching power supply, suppresses harmonic distortion, and can prevent adverse effects on the commercial power supply. .

[0006]

However, when a single choke coil is simply inserted in series to the input portion of the switching power source as in the prior art, a device whose load current changes significantly (for example, copying) In the copying operation of the machine and in the standby state), there is a drawback that the choke coil becomes large and expensive in order to cover all the large changes in the load current. In addition, the large choke coil causes large power loss in the coil portion, resulting in unnecessary power consumption.

Now, the cause of the increase in size of the choke coil will be described in detail with reference to FIG.

In the figure, the horizontal axis represents the current value (load current value) flowing in the choke coil, the left vertical axis represents the inductance value of the choke coil at the current value at each operating point (standby, copy), and the right. The vertical axis represents the inductance value required to clear the standard value.

(A) is the characteristic of the inductance required to clear the standard value at each load current value. As is clear from this characteristic (a), the inductance value required to suppress harmonics is gradually reduced as the load current flowing through the electronic device increases. Therefore, when the load current of the electronic device is small, a large inductance value is required to suppress harmonics, and when the current value is large, the inductance value may be small.

(B) is a superposition characteristic in which direct current and higher harmonics are superposed on the choke coil necessary for clearing the standard value with one inductance over the entire range of the load current. As is clear from this characteristic (b), the superposition characteristic is set to a high value over the entire range of the load current.

(C) is an operating point of a certain copying machine (the same copying machine as the copying machine in the embodiment described later) during standby, and (d) is an operating point of the copying operation of the copying machine. Is. Thus, in the copying machine, the load current greatly changes between the two operating points ((c) and (d)).

Therefore, in order to clear the standard value over the load current range of the operating point (c) and the operating point (d) with one choke coil, it is necessary to clear the standard value at the operating point (c). Therefore, a choke coil having a large inductance required for the above and a wide range of superposition characteristics shown in the characteristic (b) is required.

The inductance value of the choke coil corresponds to the number of turns on the core. Therefore, in order to clear the standard value at the operating point (c), it is necessary to set the number of turns to the maximum. On the other hand, at the operating point (d), a small inductance value is required, but it is necessary to use an expensive and small core material or a very large core material in order to guarantee the superposition characteristics. It is necessary to use thick wires to prevent voltage drop.

That is, in the conventional choke coil for suppressing the harmonics for the switching power source of the copying machine, when an inexpensive core material is used, the choke coil becomes large and an expensive core material is used. In that case, the choke coil was expensive. Further, in order to increase the inductance value and reduce the voltage drop in the range where the load current is small, a large number of expensive thick windings are wound. Furthermore, since the number of windings of the winding is large, the winding time is increased and the cost is increased.

In the above description, the switching power supply of the copying machine is taken as an example. However, in an electronic device equipped with a source of discontinuous current in addition to the switching power supply,
The same can be said.

Therefore, an object of the present invention is to provide a power supply device for electronic equipment which is inexpensive and can use a miniaturized choke coil.

[0017]

In order to achieve the above object, the invention according to claim 1 is a direct-current power supply for generating a direct-current voltage from a commercial power supply in a power supply device for an electronic device which operates using the commercial power supply. And a plurality of inductance elements connectable between the commercial power source and the DC power source, and a selection switching unit that selects and switches an optimum inductance element from the plurality of inductance elements according to an operating state of an electronic device. It is characterized by having and.

Preferably, the plurality of inductance elements are different from each other in at least one of an inductance value, a wire diameter, a core material, and a core size corresponding to a load current of an electronic device.

More preferably, the plurality of inductance elements are choke coils.

[0020]

In the power supply device for electronic equipment of the present invention having the above structure,
The selection switching means selects and uses the optimum one of the plurality of inductance elements according to the operating state of the electronic device. Preferably, an inductance element having an inductance value, wire diameter, core material, or core size suitable for the load current is selected and used.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a power supply device for electronic equipment according to the present invention will be described in detail below with reference to FIGS.

FIG. 1 is a block diagram showing a schematic configuration of a power supply and a control unit of the copying machine when the present invention is applied to the copying machine. This copying machine is an electrophotographic system, and an optical system guides an original image placed on a platen glass onto a photosensitive drum to form an original image, and an electrostatic process forms a latent image on the photosensitive drum. It is a type that transfers and fixes to the recording paper that has been conveyed.

As shown in FIG. 1, a voltage of 100 V with an AC frequency of 50 Hz or 60 Hz (in the case of Japan,
Commercial power supply of 115V in the US and 220V in Europe) 9
A series circuit composed of a fixing heater 7 for melting and fixing the toner on the recording paper and a semiconductor control element 8 formed of a triac or the like is connected between both terminals.

Further, a movable terminal of a switch SW, which is an inductance element connecting means, is connected to one terminal of the commercial power supply 9, one end of a first choke coil L1 is connected to one fixed terminal of the switch SW, and the other terminal. One end of the second choke coil L2 is connected to the fixed terminal of. The other ends of the first and second choke coils L1 and L2 are connected to each other and the switching power supply 1 serving as a current generation source is connected.
Connected to one of the input terminals. The other input terminal of the switching power supply 1 is connected to the other terminal of the commercial power supply 9.

The first choke coil L1 is used when the copying machine is in a standby state and the load current value is small. The input current to the switching power supply 1 is small and the inductance is required to clear the standard value. The value is set high (see reference numeral (c) in FIG. 2), and the superposition characteristic is set high (see reference numeral (b-1)). Further, since the input current to the switching power supply 1 is small (because the 24V power supply such as the drive source 4 and the actuator 3 which will be described next is not operating), the wire diameter of the choke coil winding is thin and sufficient, and the size can be reduced. It is configured.

The second choke coil L2 is used when the load current during the copying operation of the copying machine is large,
The inductance value may be a low inductance value (see symbol (d) in FIG. 2) to clear the standard value, and the superposition characteristic may be set low (see symbol (b-2)). Also,
Since the input current to the switching power supply 1 is large (because the 24V power supply of the driving source 4 and the actuator 3 is operating), the thickness of the choke coil winding is configured to have a large wire diameter so as not to cause current loss. ing. However, since the inductance value is small, the number of turns can be reduced, and the cost and size can be reduced.

The switching power supply 1 performs high-frequency switching on a high-voltage DC voltage obtained by rectifying an AC commercial power supply, insulates it with a transformer, and supplies a DC voltage (for example, 5
V, 24V) is output. The switching power supply 1 uses a large-capacity electrolytic capacitor 1a for rectification in the input section, and therefore the input current waveform is not a sine wave but a distorted waveform.

A DC controller 2 is connected to the output side of the switching power supply 1 to connect the switching power supply 1 to 5V, 2V.
4V is supplied. The DC controller 2 is a CPU, R
It is composed of an AM, a ROM, a driver IC and the like, and various sensors, drivers, actuators, operating parts and the like described below are sequence-controlled by a program stored in the ROM.

The DC controller 2 is connected to the control terminal of the semiconductor control element 8, the control terminal of the switch SW, the actuator 3, the drive source 4, the operating section 5, various sensors 6 and the like.

The actuator 3 is composed of a clutch, a solenoid, etc. for turning on / off a drive source for transporting copy paper, and performs paper feed, start of transport, and stop of transport in accordance with a sequence. DC24V is used for this actuator 3, and a load current flows during the copying operation.

The drive source 4 is composed of a driving DC motor 4a and a driver 4b for driving the motor, and is a source of the rotational force of the drum and the conveying force of the paper. The driver 4b controls the rotation speed to be constant in order to keep the speed constant. 24V DC is also used for the driver 4b, and the maximum load current flows during the copying operation. A similar motor and driver are also used in the original scanning system of an optical device (not shown), DC24V is used, and the maximum load current flows during the copying operation.

The operation section 5 is a key input section for inputting the number of copies, copy density, copy mode for changing magnification, copy start, etc. when the operator makes a copy, and a copy acceptance state for the operator. Alternatively, it is composed of an LED lamp or the like that displays an unacceptable state due to a jam or the like.

The various sensors 6 are composed of a light quantity sensor, a light position detecting sensor, a thermistor temperature sensor and the like. The light amount sensor detects the original density according to the amount of light reflected on the original,
The optical position detection sensor detects the position of the paper on the paper conveyance path to detect the abnormality of the conveyed paper, and the thermistor temperature sensor detects the surface temperature of the fixing roller.

The DC controller 2 controls ON / OFF of the fixing heater 7 via the semiconductor control element 8 based on the information detected by the thermistor temperature sensor, and controls the temperature inside the fixing device to a target value. Since the fixing heater 7 is on / off controlled and does not generate harmonics, even if the fixing heater 7 is inserted at a position directly connected to the commercial power source 9,
Will not be adversely affected.

Next, the operation of the embodiment thus constructed will be described with reference to FIG.

When the main power switch of the copying machine is turned on, the copying machine enters the standby state, and the DC controller 2 recognizes this standby state and switches the switch SW to the first choke coil L1 side (step S1). Eventually, the user tries to start copying, sets a mode such as the number of copies and a scaling factor for the operation unit 5, and presses the copy start key (step S2). Then, the depression of the copy start key is recognized by the DC controller 2, and the DC controller 2 issues an instruction to switch the switch SW to the second choke coil L2 side, and the second
Switch to the choke coil L2 (step S3). In this state, the drum is rotated, the paper is conveyed, the copying operation is started (step S4), and when the sequence of a series of electrophotographic processes such as exposure, latent image formation, transfer, fixing, and paper discharge is completed ( Step S5), DC controller 2
Recognizes the end of the sequence, switches the switch SW to the side of the first choke coil L1 (step S6), and the copying machine goes into the standby state again.

As described above, when the load current is small such as in the standby state of the copying machine, the first choke coil in which an inexpensive thin electric wire is wound many times to increase the inductance value as a choke coil for suppressing harmonics Use L1. Further, when the load current is large, such as during the copying operation of the copying machine, the second choke coil L2 having a low inductance value in which a thick electric wire is wound a few times is used. Therefore,
The choke coil for suppressing harmonics can be inexpensively and compactly constructed. Further, since it is only necessary to design a choke coil having a narrow load current range, the degree of freedom in design is widened.

In this embodiment, the case where two choke coils are used has been described. However, when the load current covers a wider range, the number of choke coils may be three or more.

In the copying machine of this embodiment, the switch SW is switched based on the depression of the copy start key, but in the case of the laser beam printer, the switch SW can be switched based on the print start command signal (print command). Good.

In the present embodiment, the DC controller 2 switches the switch SW by judging the start of the operation, but the switch SW is switched by detecting a sudden increase in the load current of 24V DC. May be taken.

In the present embodiment, the case where the switching power supply is used as the source of the higher harmonic wave has been described. For example, in a phase control device using a triac, it is possible to switch two or more choke coils as in the present embodiment. In addition, the same configuration as in the present embodiment may be applied to a device that uses both a switching power supply and a phase control device that uses a triac.

In the present embodiment, the choke coil is inserted at the stage before the AC current is rectified, but it goes without saying that the choke coil may be inserted at the position after the AC current is rectified.

Further, in this embodiment, when the switch SW is switched, the fixed terminal side temporarily becomes neutral and the voltage is interrupted, but a terminal (transfer contact) of the type in which the fixed terminals simultaneously contact at the time of switching may be used. In a normal switching power supply, even if the input voltage is temporarily interrupted, there is no problem because the input capacitor holds the voltage for a certain period of time.

Further, in the present embodiment, a circuit for preventing the generation of the voltage stored in the choke coil at the time of switching the switch SW is not provided, but if a varistor or the like is connected in parallel with the choke coil, the generation of the voltage can be prevented. it can.

In the above embodiment, the case where the present invention is applied to the copying machine is described, but it may be applied to other electronic equipment, for example, a printer such as a laser printer (LBP). In this case, the operation is performed. Instead of the operator pressing the copy key, the printer interface signal is used to communicate between the LBP and the external device, and a print start command signal called a print command serves as a machine operation start signal. The switching of the SW1 of the LBP may be controlled.

[0046]

As described above, according to the present invention, a plurality of inductance elements are prepared, and the optimum inductance element is selected according to the operating state of the electronic device, and the inductance element is connected between the commercial power source and the DC source. The inductance value, wire diameter, etc. corresponding to the magnitude of the load current can be set, and the choke coil can be inexpensively and compactly configured.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration around a power supply and a control unit according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram when different choke coils are applied according to the magnitude of load current according to the embodiment.

FIG. 3 is a flowchart showing a general operation of the embodiment.

FIG. 4 is a characteristic diagram in the case where one choke coil covers the entire range regardless of the magnitude of load current in a conventional copying machine.

[Explanation of symbols]

 L1 First choke coil (inductance element) L2 Second choke coil (inductance element) SW switch (inductance element connecting means) 1 Switching power supply 2 DC controller (inductance element selecting means) 3 Actuator 4 Drive source 5 Operation part 6 Various sensors 9 Commercial power supply

Claims (3)

[Claims] 1. A power supply device for an electronic device that operates using a commercial power supply, wherein a DC power supply that generates a DC voltage from the commercial power supply, and a plurality of inductances that are connectable between the commercial power supply and the DC power supply. A power supply device for an electronic device, comprising: an element; and a selection switching unit that selects and switches an optimal inductance element from among the plurality of inductance elements according to an operating state of the electronic apparatus. 2. The plurality of inductance elements are different from each other in at least one of an inductance value, a wire diameter, a core material, and a core size corresponding to a load current of an electronic device. Power supply device for electronic equipment. 3. The power supply device for electronic equipment according to claim 1, wherein the plurality of inductance elements are choke coils.