JP2002084736A - Power control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power control device wherein, when power is supplied to a load of large capacity, such as a heater lamp for use in an image formation device or the like, voltage drop is effectively reduced without producing large distortion in current waveform or conductive noise. SOLUTION: The power control device is what supplies power from an alternating-current power supply to a load having a positive resistance characteristic to temperature. At start of energization, start control intervals containing a plurality of half-wave intervals in supply voltage waveform are provided, and intermittent control is exercised wherein specified half-wave intervals of the start control intervals are energization intervals when energization is performed by zero crossing control and the remaining half-wave intervals are quiescent intervals when energization is not performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to, for example, an electric power supply to a load such as a heater used in a heat fixing device provided in an image forming apparatus such as an electrophotographic copying machine, a printer or a facsimile. More specifically, the present invention relates to a power control device that controls supply, more specifically, a temporary drop in power supply voltage (voltage drop) due to an inrush current flowing to a load, and harmonic distortion (harmonics) of a current waveform generated due to power supply by phase control. The present invention relates to a power control device that takes into account generation of conduction noise and conduction noise (conduction noise).

[0002]

2. Description of the Related Art For example, in an image forming apparatus such as an electrophotographic copying machine, a printer or a facsimile,
The image signal is converted into an electric signal in accordance with the density of the image information of the document, and an electrostatic latent image is formed on the photosensitive member using a laser beam or the like. Then, the electrostatic latent image is transferred to a sheet after being formed into a developer image by development, and the developer image on the sheet is heated and melted by heat from a heater of a heat fixing device and fixed on the sheet. In such a fixing device that performs fixing by heat, a heater of the heat fixing device (hereinafter referred to as “fixing heater”)
Is provided as a load. In the fixing heater,
A heater lamp such as a halogen lamp, a heating resistor, or the like is used as a heat source, and these fixing heaters are built in a pair of fixing rollers for nipping and conveying a sheet to be fixed. In addition, one or more of these fixing heaters are incorporated in one or both of the fixing roller pairs, and one having several hundred watts to one thousand and several hundred watts is used. Further, a high-speed machine that forms an image at a very high speed uses an even larger-capacity machine. Further, according to the detection result of the temperature sensor disposed in contact with the surface of the fixing roller, an on / off signal of the fixing heater is generated, and the power supplied to the fixing heater is controlled, so that the fixing roller pair It is kept at a predetermined temperature.

[0003] When a load having a large positive characteristic with respect to temperature is provided as a control target for supplying electric power, such as a fixing heater in the above-described image forming apparatus, a large current (rush current) is applied to the load immediately after the supply of electric power is started. ) Flows. The state of the rush current flowing to the load and the state of the decrease in the power supply voltage at that time will be described with reference to FIG. 16 taking the halogen heater of the fixing device as an example.

In FIG. 16, when a heater signal is turned on as shown by a curve a, power supply to a halogen heater is started from a commercial power supply. The resistance value of the halogen heater has a positive characteristic with respect to the temperature, that is, the higher the temperature of the halogen heater itself, the higher the resistance. Are extremely small. Generally, the resistance value at such a low temperature is 1/10 of that at the time of glowing.
It is about. Since electric power is supplied to the halogen heater in the low resistance state, the rush current I1 (peak value of the half-wave waveform of the first current) immediately after the start of the supply as shown by the curve c.
Flows.

[0005] Then, a current flows through the halogen heater, and the halogen heater generates heat and the temperature rises, so that the resistance value of the halogen heater rises. As the resistance value increases, the current flowing through the halogen heater decreases, converges on the steady current I0, and enters a steady state. The ratio (I1 / I0) of the inrush current I1 to the steady current I0 is about several times to about ten times. In the case of the figure, since the halogen heater starts to be turned on at a substantially zero crossing point of the power supply voltage waveform, the rush current is suppressed to be slightly smaller.

On the other hand, when such an inrush current flows, the impedance around the outlet of the commercial power supply or other indoor wiring supplying power to the image forming apparatus is caused by its own impedance as shown by a curve b in FIG. A voltage drop ΔV1 occurs. The curve b in the figure shows the envelope of the voltage waveform when a voltage drop occurs. Thereafter, as the current flowing through the halogen heater converges to a steady state, the voltage drop converges to a small value ΔV2. When the supply of power to the halogen heater is cut off, the voltage returns to the original level V0.

The voltage drop caused by the inrush current described above is instantaneously large, and may affect surrounding equipment and lighting equipment. For example, when the voltage supplied to the lighting device is reduced, a flicker phenomenon (blinker) of the brightness of the lighting device may occur.

In recent years, in order to reduce this phenomenon, a device that consumes a large amount of power for a power supply has
Regulations have come to be regulated by a test called the flicker test. This flicker test is to test that the voltage on the power supply side does not become lower than a predetermined value due to a load in the device. Regarding the image forming apparatus, the flicker test is provided for each mode such as a copy mode (a flicker test in this mode is called a short flicker test) and a standby mode (a flicker test in this mode is called a long flicker test). Are tested with the regulation values provided corresponding to the respective modes.

In order to reduce such a problematic voltage drop, as described in Japanese Patent Application Laid-Open No. 6-242644, power is supplied by gradually changing the conduction angle when energizing a load. There is known a control method called phase control. However, when power is supplied to a load such as the above-described halogen heater by performing phase control, power supply is started at a position other than the zero cross point of the voltage waveform, and a large voltage is rapidly applied to the load. In addition, the current waveform is distorted, and the conductive noise is radiated over a wide frequency band. This distortion of the current waveform adversely affects other devices connected to an outlet around a commercial power supply or another indoor wiring connected to a device that supplies power to an internal load by phase control. In addition, there is a problem that the radiated conductive noise causes a malfunction or the like of a peripheral electronic device.

[0010] Because of such a problem, a regulation called a Harmonics Test has been regulated. This harmonic test is a test for examining how much the current waveform as shown in FIG. 17 is distorted from the original waveform. Actually, it tests whether or not the coefficient of each harmonic of each order when the current waveform is subjected to Fourier analysis falls within a predetermined regulation value. inspect. This harmonics test is performed on an image forming apparatus.
In a copy mode in which normal image formation is performed, it has been required by safety standards to be able to be kept within a predetermined regulation value.

[0011]

Various measures have been taken to satisfy such regulations. For example, Japanese Patent Application Laid-Open No. 6-242644 discloses a technique in which the conduction angle is gradually increased by a soft start circuit using a bidirectional thyristor (triac) to suppress generation of an inrush current. When this technique is used, it is very effective against a voltage drop, but since the same phase control is performed as in the past, the current waveform is greatly distorted and a large amount of conductive noise is generated. It is necessary to provide an expensive noise filter on the power supply line so that the conductive noise does not affect other devices, and there is a problem that the cost increases. Also, the distortion of the current waveform remains unresolved.

How the length of the phase control period generally affects the above-described voltage drop, distortion of the current waveform, and conductive noise will be described below with reference to Table 1 and FIG. .

[0013]

[Table 1] Now, when supplying power to the load, as shown in FIG.
For a predetermined period Tph from the start of energization, phase control is performed such that the power supply turns on after a predetermined period (delay time) from the zero cross point of the voltage waveform and turns off at the zero cross point. After that, the process shifts to the zero-cross control in which the current is continuously supplied.

In this case, as can be seen from Table 1, as for the voltage drop, the longer the phase control period is, the smaller the voltage drop is, and the shorter the phase control period is, the larger the voltage drop is. . On the other hand, with respect to the distortion of the current waveform and the conductive noise, the level increases as the phase control period becomes longer, and the level decreases as the phase control period becomes shorter.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to provide a large current waveform distortion and conductive noise when supplying power to a large capacity load such as a heater lamp used in an image forming apparatus or the like. It is an object of the present invention to provide a power control device capable of efficiently reducing a voltage drop without generating the power control.

[0016]

A power supply device according to the present invention is a device for supplying power from an AC power supply to a load having a positive resistance characteristic with respect to temperature. A start control section including a plurality of half-wave sections of the voltage waveform is provided. A predetermined half-wave section of the start control section is an energization section in which energization is performed by zero-cross control. It is characterized by performing intermittent control for a section.

The zero-crossing control is a control for energizing the entire half-wave section from the zero-crossing point to the next zero-crossing point.

By providing a pause section in which power is not supplied in the start control section at the start of power supply, it is possible to suppress the occurrence of the flicker phenomenon. Further, in the start control section at the start of energization, conduction is performed by the zero-cross control in the energization section, so that conductive noise generated in the case of the conventional phase control is not generated.

In the power control apparatus of the present invention, for example, voltages having opposite polarities are alternately applied in a continuous energizing section of the start control section.

If a voltage of the same polarity is continuously applied in a continuous energization section of the start control section at the start of energization, the possibility of occurrence of the flicker phenomenon increases. , The occurrence of the flicker phenomenon can be suppressed.

Further, in the power supply device of the present invention, for example, a period until the temperature of the load becomes a predetermined value or more is defined as a start control section.

Thus, the influence of the environment such as room temperature can be prevented.

Further, the power control device according to the present invention is a device for supplying power from an AC power supply to a load having a positive resistance characteristic with respect to temperature, wherein the power control device performs a return operation when the temperature of the load becomes lower than a predetermined value. A start control section including a plurality of half-wave sections of the supply voltage waveform is provided, a predetermined half-wave section of the start control section is an energization section in which energization is performed by zero-cross control, and the remaining half-wave section is energized. The present invention is characterized in that intermittent control is performed with no pause section.

As a result, it is possible to prevent the occurrence of the flicker phenomenon and the conductive noise even during the return operation.

Further, the power control device according to the present invention is a device for supplying power from an AC power supply to a plurality of loads having a positive resistance characteristic with respect to temperature. A start control section including a plurality of half-wave sections is provided so as not to overlap with each other. A predetermined half-wave section of the start control sections is an energization section in which energization is performed by zero-cross control, and the remaining half-wave sections are energized. The present invention is characterized in that intermittent control is performed for a pause section in which no operation is performed.

The flickering phenomenon can be prevented by preventing the start control sections for a plurality of loads from overlapping each other.

Further, the power control apparatus according to the present invention is an apparatus for supplying power from an AC power supply to a load having a positive resistance characteristic with respect to temperature in an image forming apparatus. Phase control is performed to set an energization time for a half-wave of the supply voltage waveform. At the beginning of energization in the copy mode, a start control section including a plurality of half-wave sections of the supply voltage waveform is provided. The wave section is an energization section in which energization is performed by zero-cross control, and the remaining half-wave section is characterized by performing intermittent control in which a non-energization section is a pause section.

By performing the above-described intermittent control at the start of energization, it is possible to prevent the occurrence of flickering and conductive noise. However, when supplying power to a load that uses high-output power, when the load temperature is low and the load is cold, the flicker phenomenon occurs by performing zero-cross control in which power is supplied over the entire half-wave section at the beginning of power supply. May occur.

At the initial stage of energization in the standby mode, the temperature of the load is often lowered and the load is cooled. At this time, phase control for setting the energization time for a half-wave of the supply voltage waveform should be performed. Thereby, the occurrence of the flicker phenomenon can be suppressed.

By providing a pause section in which no power is supplied in the start control section at the beginning of power supply in the copy mode, it is possible to suppress the occurrence of flickering. In the power supply section, power is supplied by zero-cross control. No conductive noise occurs in the case of the conventional phase control. In addition, since the load is not so cooled at the beginning of the energization in the copy mode, the flickering phenomenon does not occur even if the zero-cross control for energizing the entire half-wave section at the beginning of the energization is performed.

Therefore, according to the power control method of the present invention, when power is supplied to a large-capacity load such as a heater lamp used in an image forming apparatus, large current waveform distortion and conductive noise occur. And the voltage drop can be reduced efficiently.

For example, the number of continuous half-wave sections of the pause section in the start control section is reduced with time.

For example, the number of continuous half-wave sections of the energization section in the start control section is increased with time.

For example, the number of continuous half-wave sections in the pause section in the activation control section is reduced with time, and the number of continuous half-wave sections in the continuous energizing section is increased with time.

For example, the number of half-wave sections of the continuous energizing section in the start control section is odd or even, and the number of half-wave sections of the continuous pause section is even.

[0036]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a digital copying machine will be described below with reference to the drawings.

As shown in FIG. 1, the copying machine is roughly divided into a scanner unit (1), an image processing unit (not shown),
And a recording unit (2). The scanner unit (1) reads a document image, converts it into an electric signal corresponding to the document image, and transmits the electric signal as image data to the image processing unit. The image processing unit performs predetermined image processing on the transmitted image data.
The image data subjected to the image processing is irradiated by a laser writing device in the recording unit (2) onto a photoconductor provided in an electrophotographic image forming device in the recording unit (2), and the original is printed. An electrostatic latent image corresponding to the image is formed. The electrostatic latent image is developed by a developing device to be a developer image, and then transferred to a recording sheet. The sheet supporting the developer image is conveyed to a fixing device (3) disposed downstream of the image forming apparatus in the sheet conveying direction, and is fixed on the sheet.

Next, details of the fixing device (3) will be described with reference to FIG.
This will be described with reference to FIG.

As shown in FIG. 2, the fixing device (3) is provided with an upper fixing roller (4) and a lower fixing roller (5), and both rollers (4) and (5) are pressurizing means. They are pressed against each other by (6). The upper and lower fixing rollers (3) and (4) are rotatable by driving means (not shown), and are capable of pinching and conveying the sheet. Inside the upper fixing roller (3), a fixing heater (7) as a load is built. A fixing thermistor (8) and a fixing peeling claw (9) are arranged in contact with the outer peripheral surface of the upper fixing roller (3). A thermal fuse (10) is arranged apart from the upper fixing roller (3).

Next, the configuration of the power control device according to the present invention will be described with reference to FIG. FIG. 1 shows a configuration of a main part of a fixing heater control circuit as a power control device in a digital copying machine.

In FIG. 3, the fixing heater control circuit is roughly divided into an AC power supply connection plug (11), a power supply unit (12), a control board (13), and a fixing unit (14). The power supply unit (12) includes a power transformer (15), a zero-cross detection circuit (16), and a bidirectional thyristor (17). The control board (13) has two input / output devices (18) (19) and a CPU (2
0), a ROM (21), a RAM (22), an A / D converter (23) and an amplifier (24). When the plug (11) is connected to the AC power supply, the power on the primary side is converted into the power on the secondary side by the power transformer (15), and a predetermined power is supplied to the electric components. The fixing unit (14) incorporates the above-mentioned temperature fuse (10), fixing heater (7), and fixing thermistor (8).

As described above, the fixing heater (7) is disposed inside the upper fixing roller (3), and the upper and lower rollers (3)
Supply heat to (4). Further, the fixing thermistor (8) detects the surface temperature of the fixing roller (3). The amplifier (24) processes the output signal of the fixing thermistor (8) and generates a heater operation signal E1.
Is sent to the CPU (20) via the A / D converter (23). The bidirectional thyristor (17) receives the heater control signal E4 from the CPU (20) via the input / output device (18), and supplies and shuts off power from the power supply to the fixing heater (7). That is, the supply voltage E5 from the power supply to the fixing heater (7) is controlled. The zero cross detection circuit (16)
The zero cross point of the power supply voltage E2 applied by the AC power supply is detected, and a zero cross signal E3 is sent to the CPU (20) via the input / output device (18). The thermal fuse (10) is provided to prevent the fixing heater (7) from being ignited when the fixing thermistor (8) or the bidirectional thyristor (17) fails and power is continuously supplied to the fixing heater (7). Are connected in series.
Switching means is constituted by the power supply unit (12) and the control board (13).

The CPU (20) manages the operation of the entire digital copying machine based on a control program stored in the ROM (21), and the switching means also operates according to a command from the CPU (20).

A control program for controlling the switching means is stored in the ROM (21).
(20) controls the switching means by reading the contents of the ROM (21) as appropriate. The ROM (21) also stores control data for controlling the operation of the switching means. This control data is also read out at appropriate times and used for controlling the switching means.

Next, the operation after the main switch of the copying machine whose power is off is turned on will be described.

First, when the main switch of the copying machine is turned on, power is supplied to the control circuit of the copying machine, and the copying machine can be controlled by the control circuit. The CPU (20) activates the driving means of the mechanism to perform a pre-processing process of the image forming unit and supplies power to the fixing heater (7) to make the copier usable. ) To a predetermined temperature.

Next, a first example of power supply control to the fixing heater 7 at the start of energization will be described with reference to FIGS.

In the first example, at the start of energization, a start control section including a plurality of half-wave sections of the supply voltage waveform is provided, and a predetermined half-wave section of the start control section is an energization section in which energization is performed by zero-cross control. In the remaining half-wave section, intermittent control is performed to set a pause section in which power is not supplied.

The time chart of FIG. 4 shows an example of intermittent control at the start of energization.

FIG. 4 shows a heater operation signal E1, a power supply voltage E2, a zero cross signal E3, a heater control signal E4, and a supply voltage E5 to the heater. As described above, the power supply voltage E2 is the voltage of the commercial power supply. The heater operation signal E1 is an output signal of the amplifier (24). Only when the heater operation signal E1 is on (L level), power is supplied to the fixing heater 7 as follows, and when it is off (H level), no power is supplied. The zero-cross signal E3 is an output signal of the zero-cross detection circuit (16) and is normally off (L
Level) at the zero crossing point of the power supply voltage E2 (H level). The heater control signal E4 is a signal for controlling the bidirectional thyristor (17). When the fixing heater (7) is not energized, the heater control signal E4 is off (H level). When the fixing heater (7) is energized, the heater control signal E4 is turned on when the zero-cross signal E3 is turned on. (L level). The supply voltage E5 to the heater is an output signal of the bidirectional thyristor (17). Heater control signal E
4 is on, the same voltage as the power supply voltage E2 is supplied to the fixing heater (7) over the entire half-wave section, and when the heater control signal E4 is off, the fixing heater (7) is supplied over the entire half-wave section. 7) Turn off the power to the unit.

While the heater operation signal E1 is off, it is a continuous pause section (D) in which no power is supplied to the fixing heater (7). In the section where the heater operation signal E1 is on, immediately after the heater is turned on, that is, the power supply voltage E at the start of energization.
A section including a plurality of 2 half-wave sections is referred to as a start control section, and a subsequent section is referred to as a continuous conduction section (C). In the activation control section, a predetermined half-wave section is an energization section (ON) in which energization is performed by zero-cross control, and the remaining half-wave section is a pause section (B) in which energization is not performed. In the power supply section (ON), a half-wave waveform of the power supply voltage E2 is supplied to the fixing heater (7). In the energizing section (ON), the section in which the positive voltage is applied is defined as a positive voltage applying section (+ A), and the section in which the negative voltage is applied is defined as a negative voltage applying section (-A). In the continuous energizing section, the power supply voltage E2 is energized as it is to the fixing heater (7).

In FIG. 4, as indicated by numerals in each half-wave section of the power supply voltage E2 and the supply voltage E5 to the heater, the half-wave sections of the activation control section and the continuous energization section are sequentially arranged from the first one at the start of energization. , 0th section, 1st section, ...
Thus, section numbers are assigned.

In the example of FIG. 4, the section corresponding to the 12 half-wave sections at the start of energization from the 0th section to the 11th section is the start control section, and the subsequent half-wave section from the 12th section onward. The section is a continuous energizing section (C).

In the start control section, the 0th, 1st, and 6th
The seventh section is an energizing section (ON), and when the zero-cross signal E3 is turned on at the beginning of each section, the heater control signal E4 is turned on, and the entire half-wave section of each section is performed. The same voltage as the power supply voltage E2 is supplied. As a result, for the 0th section and the 1st section which are continuous energizing sections (ON), the 0th section becomes a positive voltage energizing section (+ A) and the 1st section becomes a negative voltage energizing section (-A), Alternating polarity voltages are applied alternately. The same applies to the sixth section and the seventh section, which are continuous power supply sections (ON). The second, third, fourth, fifth, eighth, ninth, tenth, and eleventh sections are pause sections (B), and even if the zero-cross signal E3 is turned on at the beginning of each of these sections, The heater control signal E4 remains off, and the energization is stopped over the entire half-wave section of each of these sections.

In the continuous energizing section (C) after the twelfth section, the heater control signal E4 is always turned on every time the zero-cross signal E3 is turned on at the beginning of the entire section, and the power supply voltage E2 is energized as it is.

The energization control in such a start control section is performed based on the contents of the start control data table stored in the ROM (21). FIG. 5 shows the start control data table corresponding to the example of FIG. One example of the content is shown.

In the example of FIG. 5, for the start control section from the 0th section to the 11th section and the first twelfth section of the continuous energizing section (C), whether or not to energize or to pause is shown for each section. Data is stored. Wave number counter (0 to 1
2) corresponds to the section number of the section from the 0th section to the 12th section, and “1” of the data indicates the energized section (ON),
“0” indicates a pause section (B). Therefore, the data corresponding to the wave number counters 0, 1, 6, 7 and 12 is “1”, and the wave number counters 2, 3, 4, 5, 8, 9, 10
The data corresponding to and 11 is "0".

Next, referring to the flowchart of FIG.
An example of the control process of FIG. 4 based on the start control data of FIG. 5 will be described.

When the process for the start control starts, first,
It is checked whether the heater operation signal E1 is on (L level) (S1), and if it is off (H level), the value of the wave number counter F for counting the number of half-wave sections is reset to 0 ( After S2), turn off the heater control signal E4 (H level)
(S3), and returns to S1 to repeat the above processing. As a result, in the continuous pause section (D) in which the heater operation signal E1 is off, power is not supplied, and the value of the counter F remains 0. If the heater operation signal E1 is turned on in S1, the process proceeds to S4 and waits until the rising edge at which the zero-cross signal E3 changes from off (L level) to on (H level) is detected. When the rising edge of the zero-cross signal E3 is detected in S4, the process proceeds to S5, and the data of the activation control data table corresponding to the counter F at that time is read into the register R. Next, it is checked whether or not the content of the register R is 0 (S6). If it is 0, the process proceeds to S7, and the heater control signal E4 is kept off (H level). Then, the heater control signal E4 is turned on (L level). As a result, power is not supplied to a half-wave section in which the data of the activation control data table is 0, and power is supplied to a half-wave section in which the data is 1. When the processing in S7 or S8 is completed, the value of the counter F is incremented by 1 (S9), and it is checked whether the value of the counter F is smaller than a predetermined value N (12 in this example) (S10). . If the value of F is smaller than N, the process returns to S4 and the above processing is repeated. When the value of F becomes equal to or more than N, the process ends. As a result, for the entire start control section, the energization is not performed in the half-wave section in which the data of the start control data table is 0, and the energization is performed in the half-wave section in which the data is 1, as shown in FIG. Results are obtained.

In the example shown in FIG. 4, voltages having opposite polarities are alternately applied in successive energization sections of the activation control section (two sections of the 0th to 1st sections and 2 sections of the 6th and 7th sections). Therefore, the occurrence of the flicker phenomenon can be suppressed.

The time chart of FIG. 7 shows another example of the intermittent control at the start of energization.

In this case, ten half-wave sections from the 0th section to the 9th section are the start control sections, and the 0th, 1st, 6th and 7th sections are the energizing sections (ON). ,
The second, third, fourth, fifth, eighth, and ninth sections are the pause sections (B).

In the case of the example of FIG. 7, as in the case of FIG. 4, in the continuous energization section of the activation control section (two sections of the 0th to the 1st sections and 2 sections of the 6th to the 7th sections), it is alternately performed. A voltage of the opposite polarity is applied.

Further, the number of continuous half-wave sections in the start control section (four sections of the second to fifth sections and two sections of the eighth to ninth sections) decreases with time.

The time chart of FIG. 8 shows still another example of the intermittent control at the start of energization.

In this case, ten half-wave sections from the 0th section to the ninth section are the start control sections, of which the 0th, 1st, 4th, 5th, 6th and 7th sections are set. Indicates an energized section (ON), and the second, third, eighth, and ninth sections are idle sections (B).

In the case of the example of FIG. 8, as in the case of FIG. 4, in the continuous energizing section of the activation control section (two sections of the 0th to 1st sections and 4 sections of the 4th to 7th sections), it is alternately performed. A voltage of the opposite polarity is applied.

Further, the number of continuous half-wave sections in the activation control section (two sections from the 0th to the 1st section and 4 sections from the 4th to the 7th section) increases with time.

The time chart of FIG. 9 shows another example of the intermittent control at the start of energization.

In this case, the twelve half-wave sections from the 0th section to the 11th section are the start control sections, of which the 0th, 1st, 6th, 7th, 8th and 9th sections are set. Indicates an energizing section (ON), and the second, third, fourth, fifth, tenth, and eleventh sections are idle sections (B).

In the case of the example of FIG. 9, similarly to the case of FIG. 4, in the continuous energizing section of the activation control section (two sections of the 0th to the 1st sections and 4 sections of the 6th to the 9th sections), they are alternately performed. A voltage of the opposite polarity is applied.

In addition, the number of half-wave sections in continuous pause sections (four sections of the second to fifth sections and two sections of the tenth to eleventh sections) in the start-up control section decreases with time and continuous energization is performed. The number of half-wave sections in the sections (two sections from the 0th to the 1st section and 4 sections from the 6th to the 9th section) increases with time.

The time chart of FIG. 10 shows another example of the intermittent control at the start of energization.

In this case, four half-wave sections from the 0th section to the 3rd section are the start control sections, of which the 0th and 1st sections are the energizing sections (ON), and the 2nd and 3rd sections. Is a pause section (B).

Next, referring to FIGS. 11 to 13, at the start of energization to the fixing heater, the above-mentioned conventional uncontrolled continuous energization control X and the conventional phase control Y and Y will be described. A description will be given of the results of some tests performed on the sample Z in which the above-described intermittent control according to the present invention is performed. In the “Judgment” column of these drawings, “○” indicates that there is a sufficient margin within the regulation value (standard value), “△” indicates that the margin is just below the regulation value, and “×” indicates that the regulation value is out of the regulation value. It represents that.

FIG. 11 is a table showing the results of the flicker test. The short column shows the results of the short flicker test, and the long column shows the results of the long flicker test. As is clear from the results of FIG. 11, the result of the conventional continuous energization control X for both short and long is out of the regulation value, whereas the result of the intermittent control of the present invention Z is the conventional one. It is almost the same as that in which the phase control is performed, and is within the regulation value.

FIG. 12 is a graph showing the results of the harmonics test. The horizontal axis represents the order of harmonics, and the vertical axis represents the harmonic current. As is clear from the results of FIG. 12, the control Z in which the intermittent control of the present invention is performed is equivalent to the control X in which the conventional continuous energization control is performed and the control Y in which the phase control is performed, and is within the regulation value.

FIG. 13 is a graph showing the results of the conducted noise test, in which the horizontal axis represents the frequency and the vertical axis represents the noise terminal voltage. As is clear from the results of FIG. 13, the result of the conventional phase control Y is almost at the limit value, whereas the result of the intermittent control of the present invention Z is the result of the conventional continuous energization control. X and within the regulation value.

In the above intermittent control, both the number of half-wave sections in the continuous energization section and the number of half-wave sections in the continuous pause section in the start-up control section are even, but the energization section is odd or even. The pause section may be an even number.

In the above intermittent control, a predetermined number of half-wave sections at the start of energization are set as the start control sections.
A period until the load temperature becomes equal to or higher than a predetermined value may be set as the start control section. In such a case, for example, for a half-wave section larger than the number of half-wave sections predicted to be necessary for the load temperature to be equal to or higher than a predetermined value, a startup control data table similar to that in FIG. 5 is prepared. In addition, while monitoring the temperature of the load using this table, the same processing as in the case of FIG. 6 is performed, and the processing is terminated when the temperature of the load becomes a predetermined value or more.

The above-described intermittent control is a method of stopping power supply to the load when the temperature of the load has exceeded a predetermined value and then restarting power supply to the load when the temperature of the load has dropped below the predetermined value. It can be applied to control.

The above-described intermittent control can also be applied to a case where power is supplied from an AC power supply to a plurality of loads having positive resistance characteristics with respect to temperature. In that case, for each load, a startup control section including a plurality of half-wave sections of the supply voltage waveform is provided, and a predetermined half-wave section of the startup control section is
An energizing section in which energization is performed by zero-cross control, a remaining half-wave section is a pause section in which energization is not performed, and the start control sections of the loads do not overlap with each other in terms of time.

Next, a second example of power supply control to the fixing heater 7 at the start of energization will be described with reference to FIGS.

In the second example, the fixing device (3) is in a cold state (a state before the power is turned on at a temperature lower than the feasible temperature, or a state in a standby mode in which the fusing device is on standby at a temperature lower than the feasible temperature). )), When power is supplied to the fixing device (3) that uses high output power, the flicker phenomenon may occur if intermittent control is performed at the beginning of energization. In the state where the fixing device (3) is cold, the phase control drive for performing the conventional phase control is performed at the beginning of energization, and otherwise, the intermittent control drive for performing the intermittent control is performed at the beginning of energization. Is what you do. By doing so, the fixing heater
When supplying power to a large capacity load such as (7),
Without generating large current waveform distortion or conductive noise,
The voltage drop can be reduced efficiently.

For this reason, the above-described phase control is carried out at the beginning of energization when the main switch is turned on and the power is turned on, and at the beginning of energization in the standby mode. It is supposed to do. In any case, after the initial stage of the energization after the phase control or the zero-cross control is performed, the continuous energization for energizing the entire half-wave section is performed for all the half-wave sections.

The phase control drive is described in Japanese Patent Laid-Open No.
Since a known method described in, for example, the method of No. 242644 can be adopted, the description is omitted.

For the intermittent control drive, the examples shown in FIGS. 4 to 10 can be employed.

Next, the above power control procedure will be described with reference to FIG.
With reference to the flowchart of FIG. 4, an example of the processing involved in the transition from turning on the power of the copying machine to printing and to the power saving mode will be described.

In FIG. 14, when the main switch of the copying machine is turned on and the power is turned on, first, the pre-processing step of S20 is performed, and then the phase control drive processing of S21 is performed. It waits until these processes are completed. When the phase control drive processing is completed in S22,
After the timer T is initialized to 0, it is checked in S24 whether the print switch is on. In S24, if the print switch is on, the mode is the copy mode.
Print processing by print control is performed, and intermittent control drive processing in S26 is performed. Then, in S27, it is checked whether or not the copy has been completed. If the copy has not been completed, the processes in S25 to S26 are repeated. In S27, when the copy is completed,
Returning to step 23, the above operation is repeated.

If the print switch is not turned on in S24, the operation is in the standby mode, so that the process proceeds to S28, where the timer T is counted up. In S29, it is checked whether or not the timer T is 30 minutes or less. In S29, if the timer T is 30 minutes or less, the process proceeds to S30, performs a phase control drive process, and returns to S24. If the timer T has exceeded 30 minutes in S29, the process proceeds to S31, where the power is turned off and the apparatus enters the power saving mode.

By performing such processing, the fixing device (3) is cooled below the copyable temperature (standby state at 100 ° C. or lower), such as before power-on or in a standby mode state.
When the energization is performed in step S21 and S30, the phase control drive is performed as in steps S21 and S30. When the energization is performed in another state (standby state at 180 ° C.) such as the copy mode state, step S26 is performed.
The intermittent control drive is performed as described above. Thereby, the flicker phenomenon is prevented, and the voltage drop can be reduced efficiently.

FIG. 15 is a table showing the results of the flicker test. The short column shows the results of the short flicker test (copy mode), and the long column shows the results of the long flicker test (standby mode). In the second example described above, phase control is performed at the beginning of energization in the standby mode corresponding to the long mode, and intermittent control is performed at the beginning of energization in the copy mode corresponding to the short mode.
It can be seen that even with a power supply of 700 W, the test result is within the regulation value with a sufficient margin, and only the advantage of power control using only phase control or only intermittent control can be obtained.

The present invention can be applied to a case where power is supplied from an AC power source to any load other than a fixing roller of a copying machine or the like, which has a positive resistance characteristic against temperature.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a digital copying machine which is an image forming apparatus to which the present invention is applied.

FIG. 2 is a schematic configuration diagram illustrating a fixing device in the copying machine of FIG. 1;

FIG. 3 is a block diagram showing a schematic configuration of a fixing heater control circuit in the copying machine of FIG. 1;

FIG. 4 is a time chart illustrating an example of power control by intermittent control at the start of energization to a fixing heater.

FIG. 5 is an explanatory diagram illustrating an example of a start control data table;

FIG. 6 is a flowchart illustrating an example of power control processing by intermittent control at the start of energization of the fixing heater.

FIG. 7 is a time chart illustrating another example of power control by intermittent control at the start of energization to the fixing heater.

FIG. 8 is a time chart showing still another example of power control by intermittent control at the start of energization to the fixing heater.

FIG. 9 is a time chart showing still another example of power control by intermittent control at the start of energization to the fixing heater.

FIG. 10 is a time chart showing still another example of power control by intermittent control at the start of energization to the fixing heater.

FIG. 11 is an explanatory diagram showing a result of a flicker test.

FIG. 12 is an explanatory diagram showing the results of a harmonics test.

FIG. 13 is an explanatory diagram showing a result of a conductive noise test.

FIG. 14 is a flowchart illustrating an example of power control processing after power is turned on.

FIG. 15 is an explanatory diagram showing a result of a flicker test.

FIG. 16 is an explanatory diagram showing a state of a voltage drop and a current waveform when the conventional continuous energization control is performed.

FIG. 17 is an explanatory diagram showing distortion of a current waveform when conventional continuous energization control is performed.

FIG. 18 is an explanatory diagram showing a state of a voltage drop and a current waveform when the conventional phase control is performed.

[Explanation of symbols]

 (3) Fusing device (7) Fusing heater (8) Fusing thermistor (12) Power supply unit (13) Control board (14) Fusing unit (16) Zero cross detection circuit (17) Bidirectional thyristor (20) CPU (21) ROM

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Manabu Ito 22-22, Nagaikecho, Abeno-ku, Osaka, Osaka Inside Sharp Corporation (72) Inventor Suehiro Ueda 22-22, Nagaikecho, Abeno-ku, Osaka, Osaka Inside (72) Inventor Noya Sato 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Sharp Corporation (72) Inventor Hiroshi Takaya 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Sharp Corporation F-term (reference) 2H033 AA41 BA25 BB18 CA28 CA30 CA45 CA46 CA47 3K058 AA46 BA18 CA07 CB04 CB06 CB09 CB19 5H420 BB02 CC04 DD03 EA05 EA39 EA42 EB02 EB03 EB16 EB26 EB38 FF14 LL07 5H740 BA03 BC03 JA03

Claims (6)

[Claims] An apparatus for supplying power from an AC power supply to a load having a positive resistance characteristic with respect to temperature, comprising: a start control section including a plurality of half-wave sections of a supply voltage waveform at the start of energization; A power control device, wherein a predetermined half-wave section of a control section is an energization section in which energization is performed by zero-cross control, and the remaining half-wave section is an intermittent control in which a non-energization section is a pause section. 2. The power control apparatus according to claim 1, wherein voltages having opposite polarities are alternately applied in a continuous energization section of the start control section. 3. The power control device according to claim 1, wherein a start control section is set until the temperature of the load becomes equal to or higher than a predetermined value. 4. A device for supplying power from an AC power supply to a load having a positive resistance characteristic with respect to temperature, wherein a half-wave section of a supply voltage waveform is provided during a return operation when the temperature of the load becomes lower than a predetermined value. An intermittent control in which a predetermined half-wave section of the start control section is an energization section in which energization is performed by zero-cross control, and the remaining half-wave section is a pause section in which energization is not performed. A power control device characterized by performing: 5. An apparatus for supplying electric power from an AC power supply to a plurality of loads having a positive resistance characteristic with respect to temperature, wherein at the start of energization, each load includes a plurality of half-wave sections of a supply voltage waveform. Intermittent control in which the control sections are provided so as not to overlap each other, a predetermined half-wave section of the activation control section is an energization section in which energization is performed by zero-cross control, and the remaining half-wave section is a pause section in which energization is not performed. A power control device. 6. An image forming apparatus for supplying power from an AC power supply to a load having a positive resistance characteristic with respect to temperature, wherein power is supplied to a half-wave of a supply voltage waveform at the beginning of power supply in a standby mode. Phase control for setting the time is performed. At the beginning of energization in the copy mode, a start control section including a plurality of half-wave sections of the supply voltage waveform is provided, and a predetermined half-wave section of the start control section is energized by zero-cross control. The power control apparatus performs an intermittent control in which a current-carrying section is performed and the remaining half-wave section is a pause section in which no current is supplied.