JPH04226480A - Power unit for image forming device - Google Patents

Abstract

PURPOSE:To make control easy, to attain overall cost-down, and to improve safety by providing an universal type power unit combining a DC power source part capable of being connected with both of the commercial power sources of an AC 100V system and an AC 200V system, and a heater power source part. CONSTITUTION:Whether an inputted commercial power source voltage is the AC 100V system or the AC 200V system, is detected, and the DC power source part 5 is changed over to double voltage rectification when the change-over rectifying circuit 2 of the power source part 5 is the AC 100V system, and to full wave rectification when the circuit 2 is the AC 200V system, so that DC electric power having a regular voltage is supplied to a DC-DC converter 4. The heater power source part 8 outputs a trigger signal so that a full wave current flows into a heater switch circuit 6 in series, with respect to the heater 25, when the fixing temp. control part 3 of the power source part 8 is the AC 100V system, and a half-wave current or a lagged current flows into the circuit 6, when the control part 3 is the AC 200V system, and electric power having less fluctuations is supplied to the heater 25.

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 an image forming apparatus that forms images on plain paper using electrostatic latent image technology.

0002

[Prior Art] Optical printers such as laser printers, LED (light emitting diode) printers, and LCA (liquid crystal array) printers, copying machines, digital copying machines, high-speed facsimile machines, electrostatic plotters, etc. use electrostatic latent image technology to print photoreceptors. There is an image forming apparatus that forms an electrostatic latent image thereon, transfers the toner image converted into a visible image by development onto plain paper, and then fixes the image using heat and pressure from a fixing roller heated by a heater.

FIG. 8 is a circuit diagram showing a conventional example of a power supply device for such an image forming apparatus. AC power from an AC commercial power supply connected to the AC input section 1 is supplied to a series circuit of the triac 91, heater 25, and thermal fuse 27 of the heater switch circuit 90 via the rectifier circuit 95 and the interlock switch 28. .

The heater switch circuit 90 switches the LE of the photocoupler 92 in response to a signal from a temperature control circuit (not shown).
When D92a lights up, the current flowing through the bridge rectifier 93 increases, so the voltage drop across the resistor 94 increases, turning on the triac 91, and when the LED92a goes out, the triac 91 turns off.

[0005] In this way, the AC power flowing to the heater 25 is controlled by turning on and off the triac 91. In addition, the AC power is converted into DC power by a rectifier circuit 95, and then is used as a stabilized constant voltage DC power source under feedback control by a DC-DC converter 96.
Output to L.

[0006] Worldwide, commercial AC power supplies have a standard supply voltage of 100V to 110V or 115V AC100V.
It is divided into 200V system and 200V to 220V AC200V system.
The frequency is divided into 50Hz and 60Hz and is not unified. Therefore, electrical equipment that uses commercial power
It was necessary to match the power supply voltage and frequency for each country and region in which it was used, making management extremely complex.

D using the above DC-DC converter
Since the C power source supplies stable DC power regardless of power supply voltage or frequency, it is used not only for control purposes but also for driving motors and the like that require a constant rotation speed.

However, although pure resistance elements such as heaters are unrelated to frequency, they are affected by the power supply voltage in a superlinear manner close to the square of the power supply voltage, so relatively strict temperature control is required, such as in the heater of the fixing roller. In some cases, the temperature control circuit alone may not be sufficient to cover the requirements, so depending on whether the system is AC100V or AC200V, there are two types of heaters 25, one for AC100V and one for AC200V, and depending on the power supply voltage, It was necessary to use them properly.

However, the fixing roller with a built-in heater needs to be replaced due to wear during use, and although the replacement work itself has been simplified so that it can be performed by the user, it is difficult to install a fixing roller with a different voltage specification. For example, if the temperature does not rise to a specified level, resulting in insufficient fusing, or if problems occur such as paper wrapping around the fusing roller even if there is no problem during normal use, this may lead to smoke and even fire accidents. There was a major problem in that the security of the device itself was compromised and the trust of users was lost.

Therefore, in order to unify the heaters 25 to one type and to make the power supply device of the image forming apparatus a universal type that does not require human operation including the heater connection, for example, Japanese Patent Laid-Open No. 62-40482 discloses As shown, if the commercial power supply is an AC 100V system, the proposal is to supply it to the heater as is, or if it is an AC 200V system, it is supplied to the heater every half wave, or as shown in Japanese Patent Application Laid-Open No. 1-292388, the heater is supplied according to the voltage of the commercial power supply. There were proposals to control the phase of the applied voltage.

[0011]

[Problems to be Solved by the Invention] For example, a DC power supply unit using a high-frequency switching type DC-DC converter is small and efficient, and the commercial power supply including voltage fluctuations is
Lower limit 90V for C100V system to upper limit 2 for AC200V system
A constant voltage can be maintained even if the voltage changes up to 40V.

[0012] However, if the input voltage of the DC-DC converter changes so drastically, it is difficult to always maintain the highest designed efficiency.
It is designed to have the highest efficiency in the middle of the 00V system, and in actual commercial power supplies, it is used at a point where the efficiency is slightly lower, so components with sufficient performance margins such as withstand voltage and capacity are used. must be used.

[0013] The present invention has been made in view of the above points, and provides an efficient universal power supply including heater-related power supplies, and provides management of inventory parts, products, assembly departments, services, and users. The purpose of this invention is to reduce overall costs by making it easier to operate, and to improve the safety and reliability of image forming apparatuses.

[0014]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides image formation in which a visible image transferred onto plain paper by electrostatic latent image technology is fixed by heat and pressure from a heater of a fixing roller. In the power supply of the device,

001
5] Line switching means that switches to a voltage doubler rectifier circuit when AC 100V is input and to a full wave rectifier when AC 200V is input, depending on the voltage of the input commercial power supply, and the output of the rectifier circuit switched by the line switching means to a predetermined voltage. A DC power supply section consisting of a DC-DC converter that converts the DC power into output and outputs it, a bidirectional switch means that turns on in response to a trigger signal, and a full-wave A heater power supply section is provided, which includes a trigger control means for triggering the bidirectional switch means so as to pass a half-wave current when the current is inputted from an AC 200 V system.

Alternatively, depending on the voltage of the input commercial power supply, when the AC100V system is input, the voltage doubler rectifier circuit may be connected to AC200V.
A line switching means that switches to a full-wave rectifier circuit when the V system is input, and a DC-D that converts the output of the rectifier circuit switched by the line switching means into DC power of a predetermined voltage and outputs it.
A DC power supply section consisting of a C converter, a bidirectional switch means that is turned on in response to a trigger signal, and a full-wave current when an AC 100V system is input, and a half-wave current when an AC 200V system is input, depending on the voltage of the commercial power supply. A heater power supply section comprising trigger control means for triggering the bidirectional switch means so as to pass the second half current respectively is provided.

Furthermore, it is preferable to provide input voltage detection means for switching the operations of both the line switching means and the trigger control means.

[0018]

[Operation] According to the power supply device of the image forming apparatus configured as described above, the DC power supply section has a line switching means of AC10
Since the circuit switches to a voltage doubler rectifier circuit when inputting a 0V system and to a full-wave rectifier circuit when inputting a 200V AC system, the DC input voltage of the DC-DC converter becomes almost equal, and the DC voltage can always be converted with the highest efficiency. I can do it.

[0019] The heater power supply section has a trigger control means that includes:
When inputting AC100V system, it is full wave as it is, and AC200V is input.
Since the bidirectional switch means is controlled so that only a half wave or only the latter half of each half wave flows to the heater when the system is input, the heater can be used uniformly for the AC 100V system.

Furthermore, if the same input voltage detection means switches the operations of both the line switching means and the trigger control means, duplication can be avoided and costs can be reduced.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be specifically described below with reference to the drawings.

FIG. 2 is a schematic diagram showing the internal mechanism of a laser printer according to an embodiment of the present invention. A charging charger 11, a writing unit 12, a developing unit 13, a transfer charger 14, and a cleaning unit 15 are arranged around the photoreceptor belt 10, which rotates counterclockwise as shown by the arrow, in the order of the rotational direction. .

The surface of the photoreceptor belt 10 is first uniformly charged by a charger 11, and then a beam modulated by image data from a writing unit 12 and deflected in the main scanning direction forms a spot. main scanned,
An electrostatic latent image is formed.

The electrostatic latent image is developed by the developing unit 13 and converted into a visualized toner image, and then the toner image is transferred by the transfer charger 14 onto the paper 16 that has been conveyed. The toner and charge remaining on the photoreceptor belt 10 are removed by a cleaning unit 15, and the removed toner is collected by the cleaning unit 15.

The paper 16 is fed by a paper feed roller 19 from a paper stack 18 on a paper feed cassette 17 and is temporarily stopped when it comes into contact with a pair of registration rollers 20. Then, the paper 16 is transferred to the photoreceptor on which writing is written by the writing unit 12. At a timing that matches the image on the belt 10, the toner image is transferred to the position of the transfer charger 14 by a pair of registration rollers 20. The paper 16 on which the toner image has been transferred is conveyed to a fixing unit 21, is pressed against a fixing roller 23 heated by a pressure roller 22, and is fixed by the heat and pressure, and then placed on a paper output tray 24. be discharged.

A hollow spiral heater 25 is provided close to the sleeve 23a of the fixing roller 23, and heats the fixing roller 23 from the inside. Heated fixing roller 23
The surface temperature of the sleeve 23a is detected by a temperature sensor 26 made of, for example, a thermistor, which is provided in pressure contact with the outside of the sleeve 23a, and is controlled by turning on and off the heater 25 to maintain the optimum temperature during standby and fixing operation. ing.

Further, a thermal fuse 27 connected in series to the heater 25 is provided near the temperature sensor 26, and if the heater 25 becomes uncontrollable and overheats, the thermal fuse 27 will melt. By turning off the heater 25, serious accidents such as smoke and fire can be prevented.

FIG. 3 is a block diagram showing an example of a control section of this laser printer. The controller 30 is a main microcomputer (hereinafter referred to as "MPU") 31
, a ROM 32 that stores necessary programs, constant data, character fonts, etc., a RAM 33 that stores temporary data and patterns, etc., an I/O 34 that controls input and output of commands and data, and an I/O 34 that stores the necessary programs, constant data, character fonts, etc. via MP
Consists of an operation panel 35 connected to U31 and an internal interface (I/F) 36, which are connected to each other by a data bus,
Connected via address bus, etc. Also, a host machine 38 that outputs print commands, character data, and image data.
is also connected to the MPU 31 via the I/O 34.

The engine driver 40 includes a sub microcomputer (hereinafter referred to as "CPU") 41 and a ROM 42 that stores necessary programs and constant data.
, a RAM 43 for storing temporary data, and an I/O 44 for controlling data input/output, and are connected to each other via a data bus, an address bus, etc.

The I/O 44 is connected to the internal interface 36 of the controller 30, and inputs video signals from the controller 30 and the states of various switches on the operation panel 35, and sends status signals such as image clock and paper end to the controller 30. Output to. Also, this I/
O44 is a printer engine 4 which is a printing means.
It is also connected to the writing unit 12 and other sequence equipment groups 46 constituting the writing unit 5, and various sensors 47 including a synchronous sensor.

The controller 30 receives print commands, character codes, and image data from the host machine 38, edits those codes and data, and stores the character codes in the ROM.
32 into a dot pattern necessary for image writing, and stores the dot patterns of those characters and images (hereinafter collectively referred to as "images") in a VRAM (video RAM) area in RAM 33. Leave it there.

When the image clock is input together with the ready signal from the engine driver 40, the controller 30
The dot pattern stored in the AM area is output to the engine driver 40 via the internal interface 36 serially or in parallel as a video signal synchronized with the image clock.

[0033] The engine driver 40 is connected to the controller 3
0, the writing unit 12 of the printer engine 45 and the sequence equipment group 46 are controlled,
Video signals necessary for image writing are input from the controller 30 and output to the writing unit 12, and signals indicating the status of each part of the engine are input from the synchronous sensor and other sensors 47 for processing, and necessary information and An error signal is output to the controller 30.

FIG. 1 is a circuit diagram showing a first embodiment of the power supply device. This first embodiment is based on AC100V system or A
an AC input section 1 connected to a C200V commercial power supply;
A DC system consisting of a switching rectifier circuit 2 equipped with line switching means and a high frequency switching type DC-DC converter 4.
A heater power supply section 8 consisting of a power supply section 5, a heater switch circuit 6 consisting of a three-pole bidirectional thyristor, such as a triac 60, which is a bidirectional switching means, and its trigger circuit, and a fixing temperature control section 3, which is also a trigger control means.
and an input AC detection circuit 9.

The AC input section 1 consists of a fuse 51, a power switch 52, and a noise filter 53.
After passing through, the external noise contained therein is grounded and removed by a noise filter 53.

The AC power from which the noise has been removed is passed through the switching rectifier circuit 2 on one side and the normally closed interlock switch 28 on the other side to the thermal fuse 27, heater 25,
They are respectively supplied to heater circuits in which heater power supply units 6 are connected in series. This interlock switch 28 cuts off power supply to the heater circuit when the cover of the laser printer is opened for repair or inspection, thereby preventing electric shock or burns during work.

The switching rectifier circuit 2 includes a bridge rectifier 70 for full-wave rectification of power from an AC power source, and its DC output terminal c.
, d, connected in series to smooth the rectified output, and a bridge rectifier 7.
Fuses 7 provided on the AC input terminals a and b sides of 0
1, a noise filter 72 consisting of a noise cut transformer and two bypass capacitors, and a switching circuit 73 which is a line switching means provided between the input terminal b of the bridge rectifier 70 and the connection point of the capacitors C1 and C2. It is configured.

When the switching circuit 73 is off, the switching rectifier circuit 2 acts as a normal full-wave rectifier circuit, and the DC power smoothed by the series-connected capacitors C1 and C2 is used as the load DC-DC. It is supplied to converter 4. When the switching circuit 73 is turned on, the switching rectifier circuit 2 acts as a voltage doubler rectifier circuit, and a voltage twice that of full-wave rectification is obtained on the output side.

That is, in a cycle where terminal a is positive with respect to terminal b of the bridge rectifier 70, current flows from terminal a to terminal b through terminal c, capacitor C1, and switching circuit 73, charging capacitor C1, and In a cycle where a is negative, current flows from terminal b through switching circuit 73, capacitor C2, and terminal d to terminal a, charging capacitor C2.

Therefore, if the switching circuit 73 is turned on when the AC 100V system is input and the switching circuit 73 is turned off when the AC 200 system is input, the output side of the switching rectifier circuit 2 always has the full-wave rectified voltage DC when the AC 200V system is input. Electric power is obtained and supplied to the DC-DC converter 4.

FIG. 4 is a partial circuit diagram of the switching rectifier circuit 2 for explaining an example of the switching circuit 73, and the same parts as in FIG. A
Two lines connecting the C power supply line and the switching circuit 73 are added. The switching circuit 73 includes a three-pole bidirectional thyristor, so-called a triac 65, and a trigger circuit 68, which includes a voltage detection section 66 and a transistor 67 that triggers the triac 65 in accordance with its output.

The voltage detection section 66 is connected to the A of the bridge rectifier 70.
The AC voltage input to the C input terminals a and b is detected to determine whether it is an AC100V system or an AC200V system, and if it is an AC100V system, a trigger circuit 68 triggers the triac 65 via a transistor 67. If it is an AC200 system, the switching circuit 73 is turned off without triggering. Therefore, as already explained, a rectified voltage generated when the AC 200V power source is full-wave rectified is always generated across the series circuit of the capacitors C1 and C2.

In addition, instead of the voltage detection section 66 directly detecting the AC voltage of the commercial power source, the line connected from the switching circuit 73 to the AC terminal a of the bridge rectifier 70 is connected to the - terminal d, that is, the - terminal of the capacitor C2. Connect and capacitor C
By detecting the DC voltage between the two terminals, it is also possible to indirectly detect whether the commercial power source is an AC 100V system or an AC 200V system.

That is, at the time of initial setting when the power switch 52 is turned on, the triac 65 is turned on and the switching rectifier circuit 2 is set to the voltage doubler rectification mode, and the voltage between the terminals of the capacitor C2 is detected and it is determined that the half wave)
If the upper limit of the rectified voltage is not exceeded, the triac 65 is kept on, and if the upper limit is exceeded, the triac 65 is immediately turned off and the switching rectifier circuit 2 is switched to full-wave rectification mode.

[0045] In this way, the rectification mode can be switched without the output voltage of the switching rectifier circuit 2 exceeding the upper limit of the (full wave) rectification voltage of the AC 200V system,
It is only necessary to detect the smoothed DC voltage, so Figure 4
The configuration of the switching circuit 73 is simpler than directly detecting the AC voltage shown in FIG.

FIG. 5 is a circuit diagram showing an example of the DC-DC converter 4. The primary side of the step-down transformer 75 having three coils L1, L2, and L3 is connected in series with the primary coil L1 and receives DC input from the switching rectifier circuit 2.
F is a switching element that turns power on and off at high speed.
ET76, a snubber circuit 77 consisting of a CR series circuit connected in parallel between the source and drain of the FET76 to absorb surge voltage due to switching, and a transformer 7.
A pulse width control circuit 7 that controls the pulse width applied to the gate of the FET 76 according to the DC voltage obtained on the secondary side of the FET 76.
8, and a rectifier circuit 79 consisting of a rectifier diode and a smoothing capacitor that rectifies and smoothes the pulse power induced in the tertiary coil L3 of the transformer 75 and supplies it to the pulse width control circuit 78.
It is composed of.

The secondary side of the transformer 75 includes a rectifier diode 80 that rectifies and smoothes the pulse power induced in the secondary coil L2 when the FET 76 is turned on and current flows through the primary coil L1 of the transformer 75. Smoothing capacitor 8
1, an error voltage detection section 83 that divides its DC output voltage, compares it with a predetermined reference voltage, and outputs a difference signal according to the difference, and outputs a difference signal with a pulse width. It is composed of a photocoupler 84 that relays to the control circuit 78, and a load RL is connected to its output terminal 85.

As is already known, the DC-DC converter 4 converts the DC power input to the primary coil L1 of the transformer 75 into several hundred kilograms using the switching element (FET 76).
The transformer 75 turns on and off at high frequencies from Hz to several MHz.
The pulsed power that is lowered (or boosted) and induced in the secondary coil L2 is rectified and smoothed by the main rectifier circuit 82 and output to the load RL.

The DC output voltage is detected by the error voltage detection section 83 and fed back to the pulse width control circuit 78 via a photocoupler 84 for insulating the primary side and the secondary side. The pulse width control circuit 78 changes the pulse width applied to the gate of the FET 76 so that the on-time of the FET 76 becomes shorter when the output voltage is higher than a predetermined voltage, and becomes longer when the output voltage is lower than a predetermined voltage. Load R
The DC voltage across L is held constant.

Since the pulse width can be controlled over a relatively wide range, the voltage of the AC commercial power supply connected to the AC input section 1 can vary from the lower limit of 90 V for 100 V AC systems to the upper limit of 240 V for 200 V AC systems, including voltage fluctuations. Even if the range changes, the DC voltage between the output terminals 85 can be sufficiently maintained at a constant voltage, but as explained above, the switching rectifier circuit 2 can control the input voltage fluctuation width of the DC-DC converter 4. Since the fluctuation range is within the same voltage system, it is possible to set the performance and conditions of each component constituting the DC-DC converter 4 most efficiently, eliminate waste, and reduce costs.

Returning to FIG. 1, the noise filter 72 is for preventing high-frequency switching noise generated by the downstream DC-DC converter 4 from leaking to the AC power supply side.

[0052] The heater power supply section 8 supplies AC flowing through a heater circuit formed by connecting a heater 25 and a thermal fuse 27 in series.
It is composed of a heater switch circuit 6 that controls on/off of current, that is, a waveform, and a fixing temperature control section 3 that outputs a trigger signal to the heater switch circuit 6.

If the trigger signal from the fixing temperature control section 3 is not input, the LED 6 which is the light emitting section of the photocoupler 61
2 does not emit light, the phototriac 63, which is its light receiving section, is off, and since the voltage drop across the resistor R2 is 0, the triac 60 is also off, and no AC current flows through the heater circuit. When the trigger signal from the fixing temperature control section 3 is input, the LED 62 emits light and the photo triac 63 is turned on, so a voltage drop divided by the resistors R1 and R2 occurs in the resistor R2, and the triac 60 is triggered. The heater circuit turns on and AC current flows through the heater circuit.

The trigger signal relayed by the photocoupler 61 is generated by inputting the voltage signal of the commercial power supply detected by the input AC detection circuit 9 and the zero cross signal that occurs twice per cycle, and the fixing temperature control section 3 Determine phase and width. That is, when AC 100V is input, the trigger signal is always turned on, and a full-wave AC current flows through the heater circuit.

[0055] Figure 6 shows the input AC when inputting 200V AC.
This is a waveform diagram showing an example of voltage, trigger signal, and AC current flowing through the heater circuit. A in the diagram shows only the positive or negative half-wave, and B in the diagram shows the current flowing only in the second half of each half-wave. An example of each case is shown.

The trigger signal shown in FIG. 6A may be the output of a flip-flop circuit that is inverted by a zero-cross signal, for example, as it is. The trigger signal shown in FIG.
It is sufficient to generate a pulse that rises with a delay of 0° to 120°. By doing this, even when inputting AC100V, AC2
When using the 00V system input, almost the same amount of heat can be obtained using the same heater.

Further, the fixing temperature control section 3 operates according to a signal from a temperature sensor 26 that detects the surface temperature of the fixing roller 23 heated by the heater 25 and the mode of whether the laser printer is on standby or printing. , if the surface temperature of the fixing roller 23 is higher than a predetermined temperature set depending on the mode, the trigger signal is not output, and if it is lower than the predetermined temperature, it is always on, or by outputting a trigger signal with the waveform shown in FIG. , controls the temperature of the fixing roller 23. Therefore, the fluctuation range within the same AC voltage system is not a problem.

As explained above, by switching the rectification method of the DC power supply section and the current waveform of the heater power supply section according to the AC input voltage system, it is possible to obtain an efficient universal power supply including the heater-related power supply. It will be done.

In the second embodiment shown in FIG. 7, instead of the switching rectifier circuit 2 equipped with the switching circuit 73 shown in FIGS. 1 and 4,
A switching rectifier circuit 2a equipped with a triac 74 is provided, and other identical parts are given the same reference numerals and explanations will be omitted. A trigger electrode of the triac 74 is connected to the power supply control section 7 , and the triac 74 is held on or off in response to a trigger signal from the power supply control section 7 , which is also a trigger control means for the heater power supply section 8 .

That is, the power supply control section 7, which is integrated with the triac 74 and also serves as a line switching means,
The heater power supply section 6
AC1 is controlled by the voltage signal.
When 00V is input, by triggering the triac 74 and turning it on, the switching rectifier circuit 2a becomes a voltage doubler rectifier circuit.
When C200V is input, the triac 74 is always turned off and switched to a full-wave rectifier circuit for operation.

[0061] In this way, unlike the switching circuit 73 of the first embodiment, there is no need to provide means for the DC power supply section 5 to detect the commercial power supply voltage separately from the heater power supply section 8, and the circuit can be simplified. It is possible to reduce the number of parts and lower costs.

As explained above, the power supply device for an image forming apparatus according to the present invention does not require any manual operation that may lead to an accident due to erroneous operation, and the power supply device including the heater connection, which can be switched according to the voltage of the commercial power supply, Since it is a universal type power supply device, there is no need to separately manage products and parts depending on the country or region in which it is used, and users do not have to consider power supply voltage or its fluctuations. In addition, a replacement fusing roller (
Since only one type is required (or heater), there is no need for the user to make a mistake when replacing the product.

[0063]

[Effects of the Invention] As explained above, according to the present invention, it is possible to provide an efficient universal power supply including heater-related power supplies, and to reduce inventory parts, products, assembly departments, services, and users. In addition to facilitating comprehensive management and reducing costs, it is possible to improve the safety and reliability of the image forming apparatus.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a first embodiment of a power supply device for a laser printer, which is an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram showing an example of an internal mechanism of a laser printer.

FIG. 3 is a block diagram showing an example of a control unit of a laser printer.

4 is a circuit diagram showing an example of the switching circuit 73 of the first embodiment shown in FIG. 1. FIG.

FIG. 5 is a circuit diagram showing an example of the DC-DC converter 4. FIG.

FIG. 6 is a waveform diagram showing an example of voltage and current at each part of the heater power supply section 8. FIG.

FIG. 7 is a circuit diagram showing a second embodiment of the power supply device according to the present invention.

FIG. 8 is a circuit diagram showing an example of a conventional power supply device.

[Explanation of symbols]

1 AC input section
2, 2a Switching rectifier circuit 3 Fixing temperature control section (trigger control means) 4 DC-
DC converter 5D
C power supply section 6 Heater switch circuit
7 Power supply control section (trigger control means) 8 Heater power supply section 9 Input AC detection circuit (input voltage detection means) 23
Fuser roller
25 Heater 60 Triac (bidirectional switch means) 65, 74 Triac
70 Bridge rectifier 73 Switching circuit (line switching means)

Claims (3)

[Claims] 1. A power supply device for an image forming apparatus that fixes a visible image formed by electrostatic latent image technology and transferred onto plain paper using heat and pressure from a heater of a fixing roller,
A line switching means that switches to a voltage doubler rectifier circuit when an AC 100V input is input and a full wave rectifier circuit when an AC 200V input is input according to the voltage of the input commercial power supply, and a line switching means that switches the output of the rectifier circuit switched by the line switching means to a DC voltage of a predetermined voltage.
A DC power supply section consisting of a DC-DC converter that converts into electric power and outputs it, a bidirectional switch means that turns on in response to a trigger signal, and an AC1
An image characterized in that a heater power supply section is provided, which includes a trigger control means for triggering the bidirectional switch means so as to pass a full-wave current when a 00V system is input, and a half-wave current when an AC 200V system is input. Forming equipment power supply. 2. A power supply device for an image forming apparatus that fixes a visible image formed by electrostatic latent image technology and transferred onto plain paper using heat and pressure from a heater of a fixing roller,
A line switching means that switches to a voltage doubler rectifier circuit when an AC 100V input is input and a full wave rectifier circuit when an AC 200V input is input according to the voltage of the input commercial power supply, and a line switching means that switches the output of the rectifier circuit switched by the line switching means to a DC voltage of a predetermined voltage.
A DC power supply section consisting of a DC-DC converter that converts into electric power and outputs it, a bidirectional switch means that turns on in response to a trigger signal, and an AC1
and a heater power supply section that triggers the bidirectional switch means to pass a full-wave current when inputting a 00V system, and a second half of the current every half wave when inputting an AC 200V system. A power supply device for an image forming apparatus. 3. The power supply device for an image forming apparatus according to claim 1, further comprising input voltage detection means for switching the operation of both the line switching means and the trigger control means. Device power supply.