Patent Publication Number: US-9405261-B2

Title: Method and apparatus for detecting phase of input power

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority benefit of Korean Patent Application No. 10-2014-0111625, filed on Aug. 26, 2014, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. 
     BACKGROUND 
     1. Field 
     One or more exemplary embodiments relate to a method and apparatus for detecting a phase of input power. 
     2. Description of the Related Art 
     An image forming apparatus includes a fuser that fuses image onto printing paper by applying heat. Since a temperature of the fuser may affect printing quality, it is necessary to accurately adjust the temperature of the fuser. 
     In order to control the temperature of the fuser, the image forming apparatus may use a phase control method by detecting a phase of input power. In other words, the image forming apparatus may adjust electric power supplied to heat the fuser by using the phase control method. 
     SUMMARY 
     One or more exemplary embodiments include a method and apparatus for detecting a phase of input power for driving a fuser. 
     Also, one or more exemplary embodiments include a non-transitory computer-readable recording medium having recorded thereon a program, which, when executed by a computer, performs the method above. The technical goals are not limited thereto, and other technical goals may be derived from exemplary embodiments below. 
     According to one or more exemplary embodiments, a phase detector for detecting a phase of input power for driving a fuser of an image forming apparatus includes an alternating current (AC) input unit to which the input power is applied; a zero cross generator that outputs a zero cross signal at a zero cross point of the input power by using a photo coupler; and a zero cross detector that converts the zero cross signal to a pulse signal and detects the phase of the input power based on the pulse signal. A compensation capacitor is connected in parallel at a first side of the photo coupler. 
     According to one or more exemplary embodiments, an image forming apparatus for driving a fuser by controlling a phase includes a fuser driver board that outputs a zero cross signal at a zero cross point of input power by using a photo coupler; and a main board that converts the zero cross signal to a pulse signal and detects a phase of the input power based on the pulse signal. A compensation capacitor is connected in parallel at a first side of the photo coupler. 
     According to one or more exemplary embodiments, a phase detecting method of detecting a phase of input power for driving a fuser of an image forming apparatus includes outputting a zero cross signal at a zero cross point of the input power by using a photo coupler; converting the zero cross signal to a pulse signal; detecting the phase of the input power based on the pulse signal; and adjusting a magnitude of a capacitance of a compensation capacitor at a first side of the photo coupler according to a shape of the pulse signal. 
     According to one or more exemplary embodiments, an apparatus controlling a temperature of a fuser via a fuser heater in an image forming apparatus includes a zero cross generator to generate a zero cross signal at a zero cross point of power input to the image forming apparatus and a zero cross detector to convert the generated zero cross signal to a pulse signal, to detect a phase of the input power based on the converted pulse signal, and to control an electric power supplied to the fuser heater based on the detected phase of the power input. 
     The zero cross generator includes a compensation capacitor connected in parallel to a photo coupler. 
     In the zero cross generator, a magnitude of a capacitance of the compensation capacitor of the photo coupler is adjusted according to a shape of the converted pulse signal. 
     According to one or more exemplary embodiments, an apparatus for controlling a temperature of a fuser via a fuser heater in an image forming apparatus includes a zero cross generator to generate a zero cross signal at a zero cross point of power input to the image forming apparatus and a zero cross detector to convert the generated zero cross signal to a pulse signal, to detect a phase of the input power based on the converted pulse signal, and to control an electric power supplied to the fuser heater based on the detected phase of the power input. 
     The zero cross generator may include a compensation capacitor connected in parallel to a photo coupler. 
     A magnitude of a capacitance of the compensation capacitor of the photo coupler is adjusted according to a shape of the converted pulse signal. 
     According to one or more exemplary embodiments, a method of controlling a temperature of a fuser via a fuser heater in an image forming apparatus includes detecting a phase of AC power input to the image forming apparatus and controlling an electric power supplied to the fuser heater by adjusting a compensation capacitor in a photo coupler according to the detected phase of the AC power input to the image forming apparatus. 
     Additional aspects and/or advantages will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the exemplary embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects will become apparent and more readily appreciated from the following description of the exemplary embodiments, taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a block diagram of an image forming apparatus according to an exemplary embodiment; 
         FIG. 2  is a block diagram of an image forming apparatus according to another exemplary embodiment; 
         FIG. 3  is a block diagram of an image forming apparatus according to another exemplary embodiment; 
         FIG. 4  is a diagram for describing a zero cross signal and a pulse signal; 
         FIG. 5  is a circuit diagram of an image forming apparatus according to another exemplary embodiment; 
         FIG. 6  is a circuit diagram of an image forming apparatus according to another exemplary embodiment; 
         FIG. 7  is a diagram of a first adaptive circuit according to an exemplary embodiment; 
         FIG. 8  is a circuit diagram of a first adaptive circuit according to an exemplary embodiment; 
         FIGS. 9A and 9B  are diagrams of a second adaptive circuit according to an exemplary embodiment; 
         FIG. 10  is a circuit diagram of an image forming apparatus according to another exemplary embodiment; and 
         FIG. 11  is a flowchart of a phase detecting method according to an exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     As the inventive concept allows for various changes and numerous exemplary embodiments, particular exemplary embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the inventive concept to particular modes of practice, and it is to be appreciated that all changes, equivalents, and substitutes that do not depart from the spirit and technical scope are encompassed in the inventive concept. In the description, certain detailed explanations of the related art are omitted when it is deemed that they may unnecessarily obscure the essence of the inventive concept. 
     While such terms as “first,” “second,” etc., may be used to describe various components, such components must not be limited to the above terms. The above terms are used only to distinguish one component from another. 
     The terms used in the present specification are merely used to describe particular embodiments, and are not intended to limit the inventive concept. An expression used in the singular encompasses the expression of the plural, unless it has a clearly different meaning in the context. In the present specification, it is to be understood that the terms such as “including,” “having,” and “comprising” are intended to indicate the existence of the features, numbers, steps, actions, components, parts, or combinations thereof disclosed in the specification, and are not intended to preclude the possibility that one or more other features, numbers, steps, actions, components, parts, or combinations thereof may exist or may be added. 
     Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. Like reference numerals in the drawings denote like elements, and thus their description will be omitted. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. 
       FIG. 1  is a block diagram of an image forming apparatus  100  according to an exemplary embodiment. Referring to  FIG. 1 , the image forming apparatus  100  may include, for example, a phase detector  110 , a phase controller  120 , a fuser heater  130 , and a fuser  140 . 
     The image forming apparatus  100  may detect a phase of input power and thereby control a temperature of the fuser  140 . In other words, the image forming apparatus  100  may adjust electric power supplied to heat the fuser by using a phase control method. 
     The image forming apparatus  100  may be an apparatus such as a printer, a fax machine, or a combination of both. Also, the image forming apparatus  100  may output images using a laser. 
     The input power may be alternating current (AC) signals of 110V or 220V that is supplied to the image forming apparatus  100 . 110V and 220V indicate magnitudes of a voltage that is generally supplied to the image forming apparatus  100 . However, input power having other voltage magnitudes may also be supplied to the image forming apparatus  100 . 
     The phase detector  110  detects the phase of the input power. In detail, the phase detector  110  detects a zero cross point of the input power. The zero cross point refers to a point where a magnitude of the input power is zero. When the zero cross point is detected, the phase detector  110  generates a pulse signal and outputs the pulse signal to the phase controller  120 . 
     The phase controller  120  detects the phase of the input power based on the pulse signal. Since a point when the pulse signal is detected is the zero cross point, the phase controller  120  may calculate the phase of the input power based on the zero cross point. 
     The phase controller  120  may control electric power supplied to the fuser heater  130  by performing a phase control operation, and thus, the fuser  140  may be heated. The phase controller  120  may perform the phase control operation based on the phase of the input power. That is, the phase controller  120  may determine electric power that is supplied to a lamp included in the fuser heater  130 , and estimate a start phase and an end phase of the input power to supply the determined electric power. The phase controller  120  uses the input power to control an on/off timing of a switch included in the fuser heater  130 , and thus, adjusts a temperature of the lamp. 
     The fuser heater  130  heats the fuser  140 . The fuser heater  130  heats the fuser  140  by controlling electric current that is supplied to the fuser  140  based on a control signal received from the phase controller  120 . 
     The fuser heater  130  includes a lamp and a switch. The lamp generates heat according to electric power supplied to the lamp. The fuser heater  130  may control the electric power supplied to the lamp by turning the switch on and off according to the control signal. 
     The fuser  140  fuses an image by heating a printing paper. The temperature of the fuser  140  is adjusted by the fuser heater  130 . 
       FIG. 2  is a block diagram of an image forming apparatus  200  according to another exemplary embodiment. Referring to  FIG. 2 , the image forming apparatus  200  may include, for example, an AC input unit  210 , a zero cross generator  220 , a zero cross detector  230 , the fuser heater  130 , and the fuser  140 . The image forming apparatus  200  may control the fuser heater  130  by using a phase control method. 
     The AC input unit  210  receives input power. For example, the input power may be an AC current. 
     The zero cross generator  220  outputs a zero cross signal at a zero cross point of the input power, for example, by using a photo coupler. The photo coupler may be divided into a first side and a second side. The first side includes a light-emitting device and the second side includes a light-receiving device that operates by absorbing light generated by the first side. 
     A compensation capacitor is connected in parallel at the first side of the photo coupler. In other words, the light-emitting device and the compensation capacitor are connected to each other in parallel. The compensation capacitor may reduce the distortion of the zero cross signal caused by noise in the input power. When the compensation capacitor is connected to the photo coupler, an increasing speed (or rise time) of the zero cross signal measured by the light-receiving device of the photo coupler is slower than when the compensation capacitor is not connected. 
     The zero cross generator  220  may include a first adaptive circuit that includes at least one capacitor at the first side of the photo coupler. The first adaptive circuit may be connected to the compensation capacitor in series or in parallel. Alternatively, the first adaptive circuit may be connected to the photo coupler instead of the compensation capacitor. The first adaptive circuit may include a switch that controls an operation of the at least one capacitor. The switch in the first adaptive circuit may be controlled by the zero cross detector  230 . In other words, the zero cross detector  230  may control an on/off function of the switch, and the total capacitance of the first adaptive circuit may be determined according to whether the switch is on or off. 
     The zero cross detector  230  may convert the zero cross signal to the pulse signal, and detect a phase of the input power. When a pulse width of the pulse signal is less than a threshold value, the zero cross detector  230  may not detect the pulse signal and may not normally perform a phase control operation. When the zero cross signal is formed of triangular pulses, the zero cross detector  230  may clip the triangular pulses at a predetermined point and generate the pulse signal. If the zero cross detector  230  clips the zero cross signal at an excessively high point, a width of a pulse may be reduced, and if the zero cross signal is clipped at an excessively low point, the width of the pulse may be increased. Therefore, the zero cross detector  230  may adjust a point at which the zero cross signal is clipped by adjusting a ratio between resistors connected at the second side of the photo coupler. 
     The zero cross generator  220  may further include a second adaptive circuit for adjusting a ratio between resistors connected in series at the second side of the photo coupler. The zero cross detector  230  controls the second adaptive circuit according to a shape of the pulse signal. That is, the zero cross detector  230  monitors the pulse width of the pulse signal, and controls the second adaptive circuit to adjust the pulse width. 
     The zero cross detector  230  controls the first adaptive circuit according to the shape of the pulse signal and thus adjusts the total capacitance of the first adaptive circuit. For example, if the pulse width of the pulse signal is less than a threshold value, the zero cross detector  230  may control the first adaptive circuit such that the total capacitance of the first adaptive circuit is increased. Alternatively, if the pulse width of the pulse signal is greater than a threshold value, the zero cross detector  230  controls the first adaptive circuit such that the total capacitance of the first adaptive circuit is decreased. 
     At least two capacitors may be connected to the first adaptive circuit, and the first adaptive circuit may include switches that are respectively connected to the at least two capacitors. The zero cross detector  230  may control on/off of the switches so that a magnitude of the total capacitance of the first adaptive circuit is adjusted. 
       FIG. 3  is a block diagram of an image forming apparatus  300  according to another exemplary embodiment. Referring to  FIG. 3 , the image forming apparatus  300  may include, for example, a fuser driver board (FDB)  310 , a main board  320 , and the fuser  140 . 
     The FDB  310  uses a photo coupler to output a zero cross signal to the main board  320  at a zero cross point of input power. The zero cross signal may be formed of triangular pulses and be generated at a point where a magnitude of the input power is zero. 
     The FDB  310  includes the photo coupler and a compensation capacitor. The photo coupler includes a light-emitting device and a light-receiving device. In the photo coupler, a portion that is connected to the light-emitting device is referred to as a first side and a portion that is connected to the light-receiving device is referred to as a second side. The compensation capacitor may be connected to the light-emitting device in parallel. The compensation capacitor may reduce the distortion of the zero cross signal caused by noise in the input power. 
     The FDB  310  may further include an adaptive circuit. The adaptive circuit may be connected in parallel to the compensation capacitor. The adaptive circuit includes at least one capacitor. The adaptive circuit may include a switch that is connected to the at least one capacitor in series. Operations of the switch of the adaptive circuit are controlled by the main board  320 . 
     The FDB  310  heats the fuser  140 . The FDB  310  may include a switch and a lamp. The switch is controlled by the main board  320 . The switch may supply electric power to the lamp or block the electric power. The main board  320  may calculate a phase of the input power and thus determine an on/off timing of the switch. An operation in which the main board  320  controls an on/off function of the switch is referred to as a phase control operation. 
     The main board  320  converts the zero cross signal to a pulse signal, and detects the phase of the input power based on the pulse signal. The main board  320  may determine a moment when the pulse signal is detected as a point when a magnitude of the input power is zero. Therefore, the main board  320  may determine the moment when the pulse signal is detected as the zero cross point, and may determine the phase of the input power based on the zero cross point. 
     The main board  320  may control the fuser heater  130  included in the FDB  310 . The main board  320  includes a central processing unit (CPU) and the CPU may control supply of electric power to a lamp included in the fuser heater  130  or block electric power so as to increase or decrease a temperature of the fuser  140 . The fuser heater  130  includes a switch that is connected to the lamp. The CPU may adjust a temperature of the lamp by adjusting an on/off timing or on/off periods of the switch. 
       FIG. 4  is a diagram for describing a zero cross signal and a pulse signal. Input power is a signal input to an image forming apparatus. 
     The zero cross signal is generated at a point where the input power meets a horizontal axis. For example, as shown in  FIG. 4 , the zero cross signal may be formed of triangular pulses. 
     The pulse signal is generated by clipping the zero cross signal. For example, the pulse signal may be formed of quadrilateral pulses. Therefore, the pulse signal may be detected as a digital signal by a CPU. That is, the CPU may determine a moment when the pulse signal is detected as a zero cross point. 
     A pulse width of the pulse signal is indicated by “d,” as illustrated in  FIG. 4 . “d” may vary according to a height at which the zero cross signal will be clipped. The image forming apparatus may monitor a size and a pulse width of the pulse signal, and adjust a ratio between resistors included in the main board  320  based on a monitoring result. That is, when the pulse signal is not detected due to its small size or pulse width, the CPU adjusts the ratio between the resistors included in the main board  320 . 
       FIG. 5  is a circuit diagram of an image forming apparatus  500  according to another exemplary embodiment.  FIG. 5  only illustrates a circuit for detecting zero crossing in the image forming apparatus  500 . 
     The FDB  310  includes a plurality of resistors R 1  to R 3 , a photo coupler  520 , and a compensation capacitor C 1   510 . The photo coupler  520  includes two diodes D 1  and D 2  and a transistor Q 1 . The two diodes D 1  and D 2  indicate light-emitting devices, and the transistor Q 1  indicates a light-receiving device. The compensation capacitor C 1   510  and the two diodes D 1  and D 2  are connected in parallel. The transistor Q 1  operates by absorbing light that is generated by the diodes D 1  and D 2 . The compensation capacitor C 1   510  affects operations of the transistor Q 1 . A zero cross signal applied to the main board  320  is generated according to the operations of the transistor Q 1 . 
     The main board  320  includes a CPU, transistors Q 2  and Q 3 , resistors R 21  to R 25 , and capacitors C 21  and C 22 . A collector of the transistor Q 3  is connected to the CPU, and a pulse signal is output via the collector. A shape of the pulse signal may vary according to a ratio between the resistors R 21  and R 22 . Therefore, the CPU may change the shape of the pulse signal by changing the ratio between the resistors R 21  and R 22  according to the shape of the pulse signal. 
       FIG. 6  is a circuit diagram of an image forming apparatus  600  according to another exemplary embodiment. Referring to  FIG. 6 , the image forming apparatus  600  further includes a first adaptive circuit  610  and a second adaptive circuit  620 . 
     The first adaptive circuit  610  may be connected to a first side of the photo coupler  520  in parallel and may include at least one capacitor and a switch. A CPU may control on/off of the switch included in the first adaptive circuit  610  so that a magnitude of a total capacitance of the first adaptive circuit  610  is changed. When a pulse width of a pulse signal decreases or the pulse signal is not detected for a predetermined amount of time, the CPU may increase the magnitude of the total capacitance of the first adaptive circuit  610 . 
     The second adaptive circuit  620  may be connected to a second side of the photo coupler  520 . The second adaptive circuit  620  may include at least one resistor and a switch. The CPU may control on/off of the switch included in the second adaptive circuit  620  so that a magnitude of a total resistance of the second adaptive circuit  620  is changed. 
     The CPU may compare the pulse width of the detected pulse signal and a reference value. When the pulse width of the pulse signal less than the reference value, the CPU may control the first adaptive circuit  610  or the second adaptive circuit  620  so that the pulse width of the pulse signal is increased. 
       FIG. 7  is a diagram of the first adaptive circuit  610  according to an exemplary embodiment. Referring to  FIG. 7 , the first adaptive circuit  610  includes two capacitors C 11  and C 12  and two switches S 1  and S 2 . The two capacitors C 11  and C 12  are connected in parallel. The capacitor C 11  is connected to the switch S 1  in series and the capacitor C 12  is connected to the switch S 2  in series. 
     The switches S 1  and S 2  are controlled by the CPU. The CPU controls on/off of the switches S 1  and S 2  so that a total capacitance of the first adaptive circuit  610  is changed. 
     The first adaptive circuit  610  is connected to a light-emitting device  521  of the photo coupler  520 . The photo coupler  520  includes the light-emitting device  521  and a light-receiving device  522 . A first terminal of the first adaptive circuit  610  is connected to a first terminal of the photo coupler  520 , and a second terminal of the first adaptive circuit is connected to a second terminal of the photo coupler  520 . 
     Although  FIG. 7  illustrates an example in which the first adaptive circuit  610  includes two capacitors, the first adaptive circuit  610  may include more than two capacitors. The capacitors may be connected in series, in parallel, or by using any other method. Each capacitor may be connected to a switch so that the capacitor is connected to or disconnected from another capacitor. 
       FIG. 8  is a circuit diagram of the first adaptive circuit  610  according to an exemplary embodiment. The circuit diagram of  FIG. 8  is an embodiment of the first adaptive circuit  610  of  FIG. 7 . Therefore, details of the first adaptive circuit  610  described with reference to  FIG. 7  may also applied to the first adaptive circuit  610  of  FIG. 8 . 
     Referring to  FIG. 8 , the first adaptive circuit  610  includes the two capacitors C 11  and C 12 . A connection status of the capacitors C 11  and C 12  is determined by a CPU. The capacitors C 11  and C 12  are connected in parallel, and transistors connected to the capacitors C 11  and C 12  function as switches under the control of the CPU. 
     The CPU controls the first adaptive circuit  610  via a photo coupler  810 . Since the first adaptive circuit  610  is electrically insulated from the CPU, the CPU outputs a control signal to the first adaptive circuit  610  via the photo coupler  810 . 
       FIGS. 9A and 9B  are diagrams of the second adaptive circuit  620  according to an exemplary embodiment. Referring to  FIGS. 9A and 9B ,  FIG. 9A  is a conceptual view of the second adaptive circuit  620  and  FIG. 9B  is a circuit diagram of the second adaptive circuit  620 . 
     In  FIG. 9A , the second adaptive circuit  620  includes two resistors R 21  and R 22  and two switches S 11  and S 12 . The two resistors R 21  and R 22  are connected in parallel. The resistor R 21  is connected to the switch S 11  in series and the resistor R 22  is connected to the switch S 12  in series. 
     The switches S 11  and S 12  are controlled by a CPU. The CPU controls on/off of the switches S 11  and S 12  so that a magnitude of a total resistance of the second adaptive circuit  620  is changed. 
     Although  FIG. 9A  illustrates an example in which the second adaptive circuit  620  includes two resistors, the second adaptive circuit  620  may include more than two resistors. The resistors may be connected in series, in parallel, or by using any other method. 
     In  FIG. 9B , the second adaptive circuit  620  includes the two resistors R 21  and R 22 . A connection status of the resistors R 21  and R 22  is determined by the CPU. The resistors R 21  and R 22  are connected in parallel, and transistors connected to the resistors R 21  and R 22  function as switches under the control of the CPU. 
     First and second terminals of  FIG. 9A  and first and second terminals of  FIG. 9B  are respectively connected to both sides of the resistor R 21  of  FIG. 5 . 
       FIG. 10  is a circuit diagram of an image forming apparatus  1000  according to another exemplary embodiment. Referring to  FIG. 10 , the image forming apparatus  1000  may include, for example, a rectifying circuit  1010  and a one-way photo coupler  1020 . 
     The rectifying circuit  1010  converts AC to a direct current (DC) using a diode. The rectifying circuit  1010  includes at least one diode and may be a full-wave rectifying circuit that converts all waveforms of positive and negative poles of AC to DC. The rectifying circuit  1010  rectifies input power and outputs the rectified input power to the one-way photo coupler  1020 . 
     The one-way photo coupler  1020  operates by receiving DC from the rectifying circuit  1010 . The one-way photo coupler  1020  may include a diode and operate according to a magnitude of the received DC. 
     The image forming apparatus  1000  may further include the first adaptive circuit  610  or the second adaptive circuit  620 . The first adaptive circuit  610  may be connected in parallel to a first side of the one-way photo coupler  1020  and may include at least one capacitor and a switch. A CPU may control on/off of the switch included in the first adaptive circuit  610  such that a magnitude of a total capacitance of the first adaptive circuit  610  is changed. 
     The second adaptive circuit  620  may be connected to a second side of the one-way photo coupler  1020 . The second adaptive circuit  620  may include at least one resistor and a switch. The CPU may control on/off of the switch included in the second adaptive circuit  620  such that a magnitude of a total resistance of the second adaptive circuit  620  is changed. 
       FIG. 11  is a flowchart of a phase detecting method according to an exemplary embodiment. The phase detecting method of  FIG. 11  may be executed by any of the image forming apparatuses  100  to  300  of  FIGS. 1 to 3  or by other apparatuses not described herein. Therefore, whether omitted or not, elements and features described with reference to the image forming apparatuses  100  to  300  are also applied to the phase detecting method of  FIG. 11 . 
     In operation  1110 , an image forming apparatus outputs a zero cross signal at a zero cross point of input power using a photo coupler. 
     In operation  1120 , the image forming apparatus converts the zero cross signal to a pulse signal. The image forming apparatus generates the pulse signal by clipping the zero cross signal. 
     In operation  1130 , the image forming apparatus detects a phase of the input power based on the pulse signal. The image forming apparatus detects the pulse signal, and then determines the zero cross point of the input power. 
     In operation  1140 , the image forming apparatus adjusts a magnitude of a capacitance of a compensation capacitor that is included at a first side of the photo coupler, according to a shape of the pulse signal. After adjusting the magnitude of the capacitance, the image forming apparatus may adjust the magnitude of the capacitance again based on the pulse signal. If a pulse width of the pulse signal is less or greater than a reference value, the image forming apparatus may not detect the pulse signal. If the image forming apparatus does not detect the pulse signal, the image forming apparatus does not detect the zero cross point of the input power, and thus, a phase control operation may not be performed. In other words, although the image forming apparatus needs to control a fuser at a certain phase based on the zero cross point, a phase to be controlled may be modified due to an error, and thus, the image forming apparatus may not be able to accurately control a temperature of the fuser. 
     The image forming apparatus may monitor a size, a pulse width, etc. of the pulse signal, and affect the size, the pulse width, etc. of the pulse signal by controlling a first adaptive circuit or a second adaptive circuit. Therefore, even when noise is included in the input power, the image forming apparatus may detect the zero cross point. 
     The device described herein may comprise a processor, a memory for storing program data and executing it, a permanent storage unit such as a disk drive, a communications port for handling communications with external devices, and user interface devices, including a touch panel, keys, buttons, etc. When software modules or algorithms are involved, these software modules may be stored as program instructions or computer-readable codes executable on a processor on a computer-readable medium. Examples of the computer-readable recording medium include magnetic storage media (e.g., ROM, floppy disks, hard disks, etc.), and optical recording media (e.g., CD-ROMs, or DVDs). The computer-readable recording medium can also be distributed over network coupled computer systems so that the computer-readable code is stored and executed in a distributive manner. This media can be read by the computer, stored in the memory, and executed by the processor. 
     The inventive concept may be described in terms of functional block components and various processing steps. Such functional blocks may be realized by any number of hardware and/or software components configured to perform the specified functions. For example, the inventive concept may employ various integrated circuit (IC) components, e.g., memory elements, processing elements, logic elements, look-up tables, and the like, which may carry out a variety of functions under the control of one or more microprocessors or other control devices. Similarly, where the elements are implemented using software programming or software elements, the inventive concept may be implemented with any programming or scripting language such as C, C++, Java, assembler language, or the like, with the various algorithms being implemented with any combination of data structures, objects, processes, routines or other programming elements. Functional aspects may be implemented in algorithms that are executed on one or more processors. Furthermore, the inventive concept could employ any number of conventional techniques for electronics configuration, signal processing and/or control, data processing and the like. The words “mechanism,” “element,” “means,” and “configuration” are used broadly and are not limited to mechanical or physical embodiments, but can include software routines in conjunction with processors, etc. 
     The particular implementations shown and described herein are illustrative examples of the inventive concept and are not intended to otherwise limit the scope of the inventive concept in any way. For the sake of brevity, conventional electronics, control systems, software development and other functional aspects of the systems may not be described in detail. Furthermore, the connecting lines, or connectors shown in the various figures presented are intended to represent exemplary functional relationships and/or physical or logical couplings between the various elements. It should be noted that many alternative or additional functional relationships, physical connections or logical connections may be present in a practical device. 
     The use of the terms “a” and “an” and “the” and similar referents in the context of describing the inventive concept (especially in the context of the following claims) are to be construed to cover both the singular and the plural. Furthermore, recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. Also, the steps of all methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The inventive concept is not limited to the described order of the steps. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the inventive concept and does not pose a limitation on the scope of the inventive concept unless otherwise claimed. Numerous modifications and adaptations will be readily apparent to one of ordinary skill in the art without departing from the spirit and scope. 
     As described above, a phase detecting circuit according to the one or more of the above exemplary embodiments may accurately measure a phase of input power. The phase detecting circuit according to the one or more of the above exemplary embodiments may include a compensation capacitor connected in parallel at a first side of a photo coupler, and thus, distortion of a zero cross signal may be reduced. The phase detecting circuit according to the one or more of the above exemplary embodiments may adjust a capacitance of the first side of the photo coupler according to a shape of a pulse signal. The phase detecting circuit according to the one or more of the above exemplary embodiments may adjust the capacitance of the first side of the photo coupler such that a pulse width of the pulse signal is adjusted. The phase detecting circuit according to the one or more of the above exemplary embodiments may adjust a ratio between resistors connected at a second side of the photo coupler according to a shape of the pulse signal. The phase detecting circuit according to the one or more of the above exemplary embodiments may adjust the pulse width of the pulse signal by adjusting the ratio between the resistors connected at the second side of the photo coupler. 
     It should be understood that the exemplary embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each exemplary embodiment should typically be considered as available for other similar features or aspects in other exemplary embodiments. 
     While one or more exemplary embodiments have been described with reference to the figures, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope as defined by the following claims.