WO2023048771A1

WO2023048771A1 - Power supply control for fuser temperature control

Info

Publication number: WO2023048771A1
Application number: PCT/US2022/023837
Authority: WO
Inventors: Jeongchul SONG; Juyeong JEONG; YoungHoon HAN
Original assignee: Hewlett-Packard Development Company, L.P.
Priority date: 2021-09-24
Filing date: 2022-04-07
Publication date: 2023-03-30
Also published as: KR20230043329A

Abstract

An example fuser includes a rotatable fusing member, a heater disposed inside the fusing member to receive power from an external power source to heat the fusing member, a temperature sensor to sense a temperature of a predetermined area of the fusing member, and a processor to control an operation of the heater to heat the fusing member to a predetermined temperature. The processor is to calculate a half-wave period of the external power source and select a control period to control power provided to the heater as a multiple of 6 of the half-wave period, calculate a total heating rate of the heater during the control period based on a temperature sensed through the temperature sensor at a time that the control period begins, and select a heating rate for each of a plurality of half-wave intervals included in the control period based on the calculated total heating rate.

Description

POWER SUPPLY CONTROL FOR FUSER TEMPERATURE CONTROL

BACKGROUND

[0001] An image forming apparatus may print an image on a printing medium and may include a printer, a copier, a fax, a scanner, a multifunction printer for integrating functions thereof, or the like. An electrophotographic image forming apparatus may form a developer image corresponding to print data on a print media and may use a fuser to fix the developer image on the print media by applying a predetermined heat and pressure to the developer image.

BRIEF DESCRIPTION OF THE DRAWINGS

[0002] FIG. 1 is a cross-sectional view schematically illustrating an image forming apparatus including a fuser according to an example;

[0003] FIG. 2 is a diagram illustrating a transverse surface of a fuser of a heating roller type according to an example;

[0004] FIG. 3 is a block diagram illustrating a fuser according to an example;

[0005] FIG. 4 is a diagram illustrating a method of controlling a power supply to control temperature of a fuser according to an example;

[0006] FIG. 5 is a diagram illustrating a period mismatch and a frequency mismatch which are factors affecting a selection of a control period according to an example;

[0007] FIG. 6 is a diagram illustrating a selection of a control period to correspond to a frequency of an input power according to an example;

[0008] FIG. 7 is a diagram illustrating an operation of supplying power to a heater with various power supply patterns according to an example;

[0009] FIG. 8 is a diagram illustrating that frequency components included in each power supply are different according to a power supply pattern based on there being a same heating rate for one control period according to an example;

[0010] FIG. 9 is a diagram illustrating a frequency band having a high flicker weight according to an example;

[0011] FIG. 10 is a diagram illustrating a harmonic component included in a supply power that is different based on to a power supply pattern according to an example;

[0012] FIG. 11 is a diagram illustrating a power supply pattern for heating a plurality of elements that are set differently according to an example; and

[0013] FIG. 12 is a flowchart illustrating a method of controlling a power supply to control a temperature of a fuser according to an example.

DETAILED DESCRIPTION

[0014] Hereinafter, various examples will be described with reference to the drawings. The examples described below may be modified and implemented in various different forms.

[0015] In the present disclosure, an element that is referred to as being “connected” with another element may include a case of being directly connected and also a case of being connected indirectly, for example with another element therebetween. Also, an element that is referred to as “including” another element may indicate that the element does not exclude another element and may further include additional elements, unless specifically stated otherwise.

[0016] Also, the term “image forming apparatus” may refer to an apparatus to print print data generated by a terminal apparatus such as a computer on a recording printable medium. Examples of such an image forming apparatus include a copier, a printer, a facsimile, a scanner, or a multi-function printer (MFP) that combines functions thereof through a single apparatus.

[0017] An image forming apparatus may include a developer, a transferring device, and a fuser. The developer is to form an image on a printing medium, such as paper. For example, the developer is to form an image by supplying a developing agent, such as toner, to a photosensitive body on which an electrostatic latent image is formed. The transferring device is to transfer the image formed on the photosensitive body to a printing medium, such as paper. The image transferred to the printing paper may be fixed to the printing paper while passing through the fuser.

[0018] In various examples, a power control method is described by which a temperature of a fuser affecting a printing quality of an image forming apparatus is maintained at an appropriate temperature, and flicker and harmonic frequency components affecting the quality of power supplied to the heater of the fuser may be minimized.

[0019] As used herein, the term "fusing member" refers to a device which is heated by a heater and used to transfer heat to a printing medium, such as paper on which an image is located. The fusing member may include a heating roller and a pressing roller according to various fusing methods, or may be composed of a fusing belt and a nip forming member. However, the example is not limited thereto, and may be implemented in any of various forms to transfer heat to a printing paper.

[0020] An example image forming apparatus may be implemented with various structures and functions depending on its size, performance, price, usage, model type, and the like. An example structure will be described with reference to FIG. 1.

[0021] FIG. 1 is a cross-sectional view schematically illustrating an image forming apparatus including a fuser according to an example.

[0022] Referring to FIG. 1 , an image forming apparatus 1 may include a main body 10, a feeder 20, a printer engine 30, a fuser 100, and an eject apparatus 40.

[0023] The main body 10 may form an outer portion of the image forming apparatus 1 and may support various components installed inside.

[0024] The feeder 20 may include a feeding tray 21 at a lower portion of the main body 10, a pick-up roller 23 to pick up printing paper P loaded on the feeding tray 21 one by one, a registration roller 25 to provide a conveying force to the picked-up printing paper P and to arrange the printing paper P so that an image may be transferred on a desired portion of the printing paper P, and a feeding roller 27 to feed the printing paper P between a photosensitive drum 31 and a transfer roller 35.

[0025] The printer engine 30 may form a predetermined image on the printing paper P provided by the feeder 20. The printer engine 30 may include the photosensitive drum 31 , a charger 32, an exposure device 33, a developer 34, and the transfer roller 35.

[0026] An electrostatic latent image may be formed on the photosensitive drum 31. For example, an image may be formed on the photosensitive drum 31 by operations of the charger 32 and the exposure device 33, examples of which will be described later.

[0027] For convenience of description, the printer engine 30 has been described as corresponding to one color. However, this is an example and in implementation, the printer engine may include a plurality of photosensitive drums 31 , a plurality of chargers 32, a plurality of exposure devices 33, a plurality of developers 34, an intermediate transferring belt, or the like.

[0028] The charger 32 may charge a surface of the photosensitive drum 31 to a uniform potential.

[0029] The exposure device 33 may form an electrostatic latent image on a surface of the photosensitive drum 31 by changing a surface potential of the photosensitive drum 31 in accordance with information of an image to be printed. [0030] The developer 34 is to accommodate a developing agent therein, and may supply the developing agent (for example, toner) to the electrostatic latent image and develop the electrostatic latent image into a visible image. The developer 34 may include a developing roller 37 to provide the developing agent to the electrostatic latent image.

[0031] The transfer roller 35 may face an outer circumference of the photosensitive drum 31 .

[0032] The fuser 100 is to apply heat and pressure while the printing paper P, on which the image has been transferred, passes in the printer engine 30, to fix the image with developing agent on the printer medium P. An example of the fuser 100 will be described below.

[0033] The eject apparatus 40 may include an eject roller 41 to discharge the printing paper P which passes the fuser 100 to an external discharging tray 42.

[0034] An example of an image forming apparatus 1 and a developing method have been described. However, the image forming apparatus 1 and the developing method are not limited thereto. Rather, in other examples, the image forming apparatus 1 and the developing method may be varied and changed.

[0035] There are several types of fusers. For example, there are a heating roller type fuser and a fusing belt type fuser. Hereinafter, an example in which the fuser is a heating roller type will be described. However, this is merely for convenience of description and not intended as limiting. Various examples according to the disclosure may also be applied to a fusing belt type fuser.

[0036] FIG. 2 is a diagram illustrating a transverse surface of a fuser in a heating roller type according to an example.

[0037] Referring to FIG. 2, the fuser 100 may include a heating roller 110 having a heater 130 disposed therein, and a pressing roller 120 disposed to be in contact with the heating roller 110 to form a nip.

[0038] The heating roller 110 may include the heater 130 and a release layer 133 disposed on an outer surface of a cylindrical substrate 131. An elastic layer 132 having a strong heat resistance may be further disposed between the substrate 131 and the release layer 133. In other examples, the release layer 133 may be provided without the elastic layer 132 having heat resistance.

[0039] The substrate 131 may include a metal core, and the heater 130 may be disposed inside a hollow of the metal core. The heater 130 may be disposed at substantially the same position as a rotary shaft of the heating roller 110. The heater 130 may be a halogen lamp or the like, and the heating roller 110 may be heated by heat generated from the heater 130.

[0040] Either of the heating roller 110 or the pressing roller 120 may be rotated. In that case, the other roller may be rotated by a driving force, and the printing paper P may be transferred by the rotation of the two rollers. By this operation, the heating and pressing of the printing paper P may be performed to fuse an image to the printing paper P.

[0041] As an example, the printing paper P may be introduced into the nip, which is a contacting part of the heating roller 110 and the pressing roller 120. A non-fused image on the printing paper P may be softened by the heat of the heating roller 110 and pressed by contact of the pressing roller 120 and the heating roller 110 to fuse the image on the printing paper.

[0042] FIG. 3 is a block diagram illustrating a fuser according to an example.

[0043] Referring to FIG. 3, the fuser 100 may include the heater 130, a temperature sensor 140, and a processor 150.

[0044] The heater 130 may receive power from an external power source to generate heat. The heater 130 may be disposed inside the heating roller 110 to heat the heating roller 110, so that a temperature of the nip area which is the contacting part of the heating roller 110 and the pressing roller 120 and through which the printing paper P passes may be controlled.

[0045] The temperature sensor 140 may sense a temperature of the fuser 100. In an example, the temperature of the fuser 100 may refer to a surface temperature of the fuser 100 to fuse the unfused image. For example, the temperature of the fuser 100 may refer to a temperature of the fusing member (e.g., the heating roller or the heating belt) included in the fuser 100.

[0046] The processor 150 may control an operation of the fuser 100. The fuser 100 is to maintain a certain temperature and pressure in order to maintain the fixing level or the fusing level of the toner on the printing paper P. In an example, the fuser 100 is to maintain a temperature and pressure above or equal to a predetermined level. The processor 150 may control the operation of the heater 130 so that the fuser 100 has a predetermined temperature.

[0047] The processor 150 may control an amount of power supplied to the heater 130 to control the heating amount of the heater 130. The power supplied to the heater 130 may be an alternating current (AC) power source. In that case, the processor 150 may control the power supplied to the heater 130 through phase control for adjusting a phase angle of an AC wave provided from the processor 150, wave control for adjusting a number of waves, or the like.

[0048] FIG. 4 is a diagram illustrating a method of controlling a power supply to control a temperature of the fuser according to an example.

[0049] Referring to FIG. 4, the fuser 100 may control an amount of current supplied to the heater 130 using a phase control or a wave control method. The phase control method may control the heating amount of the heater 130 by turning on the power source for a predetermined phase with respect to one half-wave interval of the AC power source as shown in screen (a). The wave control method may control the heating amount of the heater 130 by turning on or off each AC half-wave interval as shown in screen (b). The example methods shown in FIG.

4 illustrate that the heating rate is 50%. However, although the amount of heat generated by the heater 130 is the same, each waveform appears to be different from each other.

[0050] FIG. 5 is a diagram illustrating a period mismatch and a frequency mismatch which are factors affecting a selection of a control period according to an example.

[0051] The processor 150 may control power supplied to the heater 130 in units of a control period.

[0052] Referring to FIG. 5, based on the control period of the processor 150 not matching the period of the input power (AC power) or the number of waves of the control period and the number of waves of the input power not matching, the power supplied to the heater 130 may not be easily controlled. In that case, an unintended power supply may be generated.

[0053] In an example, the control period may be set to be an integer multiple of a half-wave period of the input power source. For example, the control period may be set as an even multiple (n = 2, 4, 6... ) to avoid a mismatch between the control period and the period of the input power.

[0054] In an example, the processor 150 may identify a frequency of an external power source supplying power to the heater 130 to calculate a half-wave period of the external power source. Based on the identified frequency of the external power source, the processor 150 may select the control period to be an even multiple of the half-wave period of the external power source. Here, the fuser 100 may calculate the half-wave period of the external power by detecting the time between the zero point of the AC power source detected through a zerocrossing detection unit to detect the zero point of the AC power source and the next zero point.

[0055] FIG. 6 is a diagram illustrating a selection of a control period to correspond to a frequency of an input power according to an example. [0056] Referring to FIG. 6, based on the frequency of the input power being 50 Hz or 60 Hz, each half-wave period, a minimum control period, and a control period applicable for the fuser 100 control may be identified.

[0057] Based on the frequency of the input power being 50 Hz or 60 Hz, each half-wave period is respectively 10ms or 25/3ms. Therefore, if the control period is to be selected as a multiple of 6 of the half-wave period of the input power source, it is possible to select the control period applicable for both the 50 Hz and 60 Hz input power sources so that the control period becomes an integer. At the same time, the control period becomes an even multiple of the half-wave period.

[0058] Hereinafter, an example is provided in which a control period is selected to be a multiple of 6 of the half-wave period of the external power source. [0059] FIG. 7 is a diagram illustrating an operation of supplying power to a heater with various power supply patterns according to an example.

[0060] The processor 150 may calculate an amount of heat to be supplied during a control period based on a sensed temperature at a start point of the control period to maintain a temperature of the fuser 100 at a target temperature, and calculate a heating rate of the power to be supplied during the control period. The heating rate refers to a ratio of the power supplied to the heater 130 of the fuser 100 out of the total supply power of the input power in a specific time interval by controlling the ON/OFF time (or phase) of the input power.

[0061] In an example, the processor 150 may sense the temperature of a particular region (e.g., a region corresponding to the nip) of the heating roller 110 at the start point of the control period through the temperature sensor 140. The processor 50 may calculate the heating rate of the power to be supplied during the control period by calculating the amount of heat used to reach the target temperature at the end of the control period.

[0062] Referring to FIG. 7, a power supply pattern available based on the total heating rate being 50% is illustrated as an example.

[0063] The processor 150 may select the heating rate in each of the plurality of half-wave intervals included in the control period.

[0064] The half-wave period refers to a period in which the control period is divided by the half-wave period of the input power. For example, if the previously selected control period is six times the input power half-wave period, it may be divided into six half-wave intervals having the same period as the halfwave period of the input power. The average of the heating rates of each of the plurality of half-wave intervals may be set to be a total heating rate during a control period, and various power supply patterns may be formed according to the heating rate set in each half-wave interval.

[0065] Referring to FIG. 7, each power supply pattern has a total heating rate of 50% during a control period and thus is the same. However, the heating rate set in each half-wave interval may be different. Accordingly, the frequency components included in each supply power may be different.

[0066] FIG. 8 is a diagram illustrating that frequency components included in each power supply are different according to a power supply pattern based on there being a same heating rate for one control period according to an example.

[0067] In FIG. 8, a frequency component included in each power supply pattern may be identified through an inverse Fourier transform, for a first power supply pattern (heating rates of the half-wave interval are 100%, 0%, 100%, 0%, 100%, 0%, respectively) and a second power supply pattern (heating rates of the half-wave interval are 50%, 50%, 50%, 50%, 50%, 50%, respectively), as shown in FIG. 7.

[0068] Referring to FIG. 8, the heating rates of both power supply patterns are the same as 50%, but the frequency components included in each supply power are different.

[0069] Accordingly, the processor 150 may analyze the frequency component according to the power supply pattern to select the heating rate for each of the plurality of half-wave intervals to minimize frequency components that adversely affect the power quality.

[0070] The processor 150 may select a heating rate for each of a plurality of half-wave intervals so that a frequency component included in the power supplied to the heater 130 is composed of a frequency component of a band having a low flicker weight and a frequency component avoiding a harmonic component corresponding to an integer multiple of the external power source frequency.

[0071] FIG. 9 is a diagram illustrating a frequency band having a high flicker weight according to an example.

[0072] Flicker weights refer to factors that may be harmful to the human body. For example, flicker weight may be caused by power variation and may be identified by an intensity and frequency of the supply power. Referring to FIG. 9, the flicker weight increases as it approaches a specific frequency band, in this case 6Hz to 12Hz. Accordingly, the processor 150 may select a heating rate for each of a plurality of half-wave intervals that avoids the frequency band of 6Hz to 12Hz, which are frequency bands having the high flicker weight.

[0073] FIG. 10 is a diagram illustrating a harmonic component included in a supply power that is different based on a power supply pattern according to an example.

[0074] Harmonics refer to a physical electricity amount that is generated by a non-linear load connected to the input power. In more detail, harmonics refer to a voltage and a current corresponding to an integer multiple, such as twice, three times, four times, etc. of the basic frequency of the input power, and may be up to a level of about 50 orders. Harmonics of an odd number order, such as third, fifth, seventh, etc., among all harmonics, may be undesirable in that it may cause a communication line failure, device overheating, device failure, device malfunction, etc., as compared to an even number order.

[0075] The processor 150 may select a heating rate for each of a plurality of half-wave intervals by setting a weight to avoid harmonic components corresponding to an odd multiple of the external power source frequency to be higher than a weight to avoid harmonic components corresponding to an even multiple of the external power source frequency.

[0076] For example, referring to FIG. 10, it is possible to identify that the harmonic components of the odd order (indicated as a black bar in the graph) included in the frequency component decreases from pattern 1 to pattern 4.

[0077] The processor 150 may select a heating rate of each of the plurality of half-wave intervals so that power may be supplied to the heater 130 through a power supply pattern that minimizes flicker and odd multiple harmonic frequency components.

[0078] FIG. 11 is a diagram illustrating a power supply pattern for heating a plurality of elements that are set differently according to an example.

[0079] Referring to FIG. 11 , based on a power supply pattern supplied to a plurality of heating elements being the same, the frequency components included in the supply power due to the overlap may include some low frequency components having a high flicker weight.

[0080] In an example, the processor 150 may select a heating rate for each of the plurality of half-wave intervals according to a number of driven heating elements among the plurality of heating elements.

[0081] For example, the processor 150 may select a power supply pattern for each heating element so that the power supply pattern according to the selected heating rate for each of the plurality of half-wave intervals is set differently for each of the plurality of heating elements.

[0082] The processor 150 may select a number of the driven heating elements according to information of a paper supplied to the fuser. As an example, the information of the paper may include information about at least one of a type, a size, a thickness, etc. of the paper. For example, the power supply pattern of each heating element may be selected according to the number of heating elements, since there is a case where two or more heating elements are driven to perform an image forming operation in the case of a relatively large size of paper (e.g., A3 or more).

[0083] FIG. 12 is a flowchart illustrating a method of controlling a power supply to control a temperature of a fuser according to an example.

[0084] Referring to FIG. 12, a method for controlling a power supply to control a temperature of a fuser includes calculating a half-wave period of an external power source by identifying a frequency of the external power source in operation S1210. In operation S1220, a control period for controlling power provided to the heater is selected as a multiple of 6 of the half-wave period of the external power source. In operation S1230, a total heating rate of the heater during the control period is calculated based on a temperature sensed through the temperature sensor at a time at which the control period begins. In operation S1240, a heating rate for each of a plurality of half-wave intervals included in the control period is selected based on the calculated total heating rate.

[0085] In operation S1210, the fuser may check a frequency of power supplied from an external power source to a heater of the fuser to calculate a halfwave period of an external power source. For example, the fuser may calculate the half-wave period of the external power by identifying the time between the zero point of the AC power source detected through a zero-crossing detector to detect the zero point of the AC power source.

[0086] In operation S1220, the fuser may set the control period for controlling the power supplied to the heater to be a multiple of 6 of the half-wave period of the external power source. For example, the control period may be set to be six times the half-wave period of the external power.

[0087] In operation S1230, the fuser may calculate the total heating rate of the heater during the control period based on the temperature sensed through the temperature sensor at the time that the control period starts. The temperature sensor may sense the temperature of the fusing nip area formed in the fuser. The total heating rate of the heater may be calculated based on the amount of heat that the fixing nip should generate during the control period so that the temperature of the fusing nip at the point of ending the control period reaches a predetermined target temperature.

[0088] In operation S1240, the fuser may select a heating rate for each of the plurality of half-wave periods included in the control period based on the calculated total heating rate. The half-wave period is a period in which the control period is divided by the half-wave period of the input power. For example, if the previously selected control period is 6 times the input power half-wave period, it may be divided into six half-wave intervals having the same period as the halfwave period of the input power. The average of the heating rates of each of the plurality of half-wave intervals may be set to be a total heating rate during a control period, and various power supply patterns may be selected according to the heating rate set in each half-wave interval.

[0089] The fuser may control the power supplied to the heater by selecting the power supply pattern in which the frequency component (e.g., the frequency component of the high frequency band, the harmonic components, etc.), which affects the power quality supplied to the heater, is minimized. Based on a heater including a plurality of heating elements being operated, a power supply pattern for each heating element may be selected so that the power supply pattern supplied to each heating element is not overlapped, thereby controlling power supply.

[0090] By setting the temperature of the fuser to a predetermined temperature, printing quality of the image forming apparatus may be improved and the quality of power supplied to the heater of the fuser may be improved.

[0091] The disclosure has been described according to various examples. The terminology used herein is for the purpose of description and should not be construed as limiting. Various modifications and variations are possible in accordance with the above teachings. Therefore, unless stated otherwise, the disclosure may be practiced freely within the scope of the claims.

Claims

1. A fuser comprising: a rotatable fusing member; a heater disposed inside the fusing member to receive power from an external power source to heat the fusing member; a temperature sensor to sense a temperature of a predetermined area of the fusing member; and a processor to control an operation of the heater to heat the fusing member to a predetermined temperature, wherein the processor is to: calculate a half-wave period of the external power source by identifying a frequency of the external power source and select a control period to control power provided to the heater as a multiple of 6 of the halfwave period of the external power source, calculate a total heating rate of the heater during the control period based on a temperature sensed through the temperature sensor at a time that the control period begins, and select a heating rate for each of a plurality of half-wave intervals included in the control period based on the calculated total heating rate.

2. The fuser of claim 1 , wherein the processor is to select the heating rate for each of the plurality of half-wave intervals so that a frequency component included in the power supplied to the heater includes a frequency component avoiding a band having a high flicker weight and a harmonic component corresponding to an integer multiple of the external power source frequency.

3. The fuser of claim 2, wherein the processor is to select the heating rate for each of the plurality of half-wave intervals to avoid a frequency of 6Hz to 12Hz which are frequency bands having a high flicker weight.

4. The fuser of claim 2, wherein the processor is to select the heating rate for each of the plurality of half-wave intervals by setting a weight to avoid the harmonic component corresponding to an odd multiple of the external power source frequency to be higher than a weight to avoid the harmonic component corresponding to an even multiple of the external power source frequency.

5. The fuser of claim 1 , wherein the processor is to control a phase of power supplied to the heater in each of the plurality of half-wave intervals based on the total heating rate during the selected control period.

6. The fuser of claim 1 , wherein the heater comprises a plurality of heating elements, and wherein the processor is to select the heating rate for each of the plurality of half-wave intervals according to a number of driven heating elements among the plurality of heating elements.

7. The fuser of claim 6, wherein the processor is to select a power supply pattern for each heating element so that the power supply pattern according to the selected heating rate for each of the plurality of half-wave intervals is set differently for each of the plurality of heating elements.

8. The fuser of claim 6, wherein the processor is to select a number of the driven heating elements according to information of a paper supplied to the fuser.

9. The fuser of claim 8, wherein the information of the paper comprises information about at least one of a type, a size, or a thickness of the paper.

10. A method for controlling a power supply to control a temperature of a fuser, the method comprising: calculating a half-wave period of an external power source by identifying a frequency of the external power source; selecting a control period for controlling power provided to a heater as a 16 multiple of 6 of the half-wave period of the external power source; calculating a total heating rate of the heater during the control period based on a temperature sensed through a temperature sensor at a time that the control period begins; and selecting a heating rate for each of a plurality of half-wave intervals included in the control period based on the calculated total heating rate.

11. The method of claim 10, wherein the selecting of the heating rate for each of the plurality of half-wave intervals comprises selecting the heating rate for each of the plurality of half-wave intervals so that a frequency component included in the power supplied to the heater includes a frequency component avoiding a band having a high flicker weight and a harmonic component corresponding to an integer multiple of the external power source frequency.

12. The method of claim 11 , wherein the selecting of the heating rate for each of a plurality of half-wave intervals comprises selecting the heating rate for each of the plurality of half-wave intervals to avoid a frequency of 6Hz to 12Hz which are frequency bands having a high flicker weight.

13. The method of claim 11 , wherein the selecting of the heating rate for each of a plurality of half-wave intervals comprises selecting the heating rate for each of the plurality of half-wave intervals by setting a weight to avoid the harmonic component corresponding to an odd multiple of the external power source frequency to be higher than a weight to avoid the harmonics component corresponding to an even multiple of the external power source frequency.

14. The method of claim 10, further comprising: controlling a phase of power supplied to the heater in each of the plurality of half-wave intervals based on the total heating rate during the selected control period.

15. A non-transitory computer-readable storage medium storing 17 instructions to control a power supply to control a temperature of a fuser, the non- transitory computer-readable storage medium comprising: instructions to calculate a half-wave period of an external power source by identifying a frequency of the external power source; instructions to select a control period for controlling power provided to a heater as a multiple of 6 of the half-wave period of the external power source; instructions to calculate a total heating rate of the heater during the control period based on a temperature sensed through a temperature sensor at a time that the control period begins; and instructions to select a heating rate for each of a plurality of half-wave intervals included in the control period based on the calculated total heating rate.