Patent Publication Number: US-2023160625-A1

Title: Refrigerator

Description:
BACKGROUND 
     Field of the Disclosure 
     The present disclosure relates to a refrigerator, and more particularly, to a refrigerator capable of improving defrosting efficiency and power consumption. 
     Description of the Related Art 
     For long-term storage of foods in a refrigerator, a refrigerator temperature is reduced using a compressor and an evaporator. For example, a freezer compartment in the refrigerator is maintained at a temperature of approximately −18° C. 
     Meanwhile, in order to improve refrigerator performance, it is desirable to remove frost which may be on the evaporator when the evaporator operates. 
     Korean Patent Application Laid-Open No. 10-2001-0026176 (hereinafter, referred to as Prior Document 1) relates to a method for controlling a defrost heater of a refrigerator, in which the defrost heater is turned on when a certain time for defrosting arrives, and turned off after the lapse of a certain period of time. 
     However, according to Prior Document 1, since the ON time and the OFF time of the defrost heater are based on a certain time or a predetermined time, defrosting is not performed according to the actual amount of frost of an evaporator. That is, when the amount of frost is large, defrosting is not performed properly, or when the amount of frost is small, unnecessary defrosting is performed, thereby unnecessarily consuming power. 
     U.S. Pat. No. 6,694,754 (hereinafter, referred to as Prior Document 2) relates to a refrigerator having a pulse-based defrost heater, disclosing that the On and off time of a defrost heater is determined based on time. 
     According to Prior Document 2, since the ON time and the OFF time of the defrost heater are determined based on time, defrosting is not performed according to the actual amount of frost of an evaporator. That is, when the amount of frost is large, defrosting is not performed properly, or when the amount of frost is small, unnecessary defrosting is performed, thereby unnecessarily consuming power. 
     Korean Patent Application Laid-Open No. 10-2016-0053502 (hereinafter, referred to as Prior Document 3) relates to a defrosting device, a refrigerator having the same, and a control method of the defrosting device, in which the On and off time of a defrost heater determined based on time or time and temperature. 
     According to Prior Document 3, since the ON time and the OFF time of the defrost heater are determined based on time or time and temperature, defrosting is not performed according to the actual amount of frost of an evaporator. That is, when the amount of frost is large, defrosting is not performed properly, or when the amount of frost is small, unnecessary defrosting is performed, thereby unnecessarily consuming power. 
     SUMMARY 
     An aspect of the present disclosure provides a refrigerator capable of improving defrosting efficiency and power consumption. 
     Another aspect of the present disclosure provides a refrigerator capable of performing a continuous operation mode again after a pulse operation mode of a defrost heater. 
     In an aspect, a refrigerator includes: an evaporator configured to perform heat exchange; a defrost heater configured to operate to remove frost formed on the evaporator; a temperature sensor configured to detect an ambient temperature of the evaporator; and a controller configured to control the defrost heater, wherein, in response to a defrosting operation start time point arriving, the controller is configured to perform a defrost operation mode, perform a continuous operation mode, in which the defrost heater is continuously turned on, and a pulse operation mode, in which the defrost heater is repeatedly turned on and off based on the defrost operation mode, and is configured to perform the continuous operation mode again after performing the pulse operation mode. 
     In response to a return condition to the continuous operation mode of the defrost heater arriving while performing the pulse operation mode, the controller may be configured to perform the continuous operation mode. 
     In response to a value related to the temperature detected by the temperature sensor doing not reach a reference value while performing the pulse operation mode, the controller may be configured to perform the continuous operation mode. 
     In response to the temperature detected by the temperature sensor being below a reference temperature while performing the pulse operation mode, the controller may be configured to perform the continuous operation mode. 
     In response to a change rate of the temperature detected by the temperature sensor being less than or equal to a change rate of the reference temperature while performing the pulse operation mode, the controller may be configured to perform the continuous operation mode. 
     In response to the temperature detected by the temperature sensor doing not reach a target temperature within a certain time while performing the pulse operation mode, the controller may be configured to perform the continuous operation mode. 
     In response to a sum of an ON time of the defrost heater while performing the pulse operation mode being greater than or equal to a reference level, the controller may be configured to perform the continuous operation mode. 
     In response to a sum of the number of opening times the defrost heater while performing the pulse operation mode being greater than or equal to the reference number of opening times, the controller may be configured to perform the continuous operation mode. 
     The sum of the ON time of the defrost heater while performing the pulse operation mode is greater than a sum of a continuous ON time of the defrost heater in the continuous operation mode, the controller may be configured to perform the continuous operation mode. 
     In response to a door open period being greater than or equal to an allowable period while performing the pulse operation mode, the controller may be configured to perform the continuous operation mode. 
     In response to humidity in the refrigerator being greater than or equal to reference humidity while performing the pulse operation mode, the controller may be configured to perform the continuous operation mode. 
     In response to a defrosting operation start time point arriving while performing a normal cooling operation mode, the controller may be configured to perform the defrost operation mode including a pre-defrost cooling mode, a heater operation mode, and a post-defrost cooling mode, and perform the continuous operation mode of the defrost heater, and the pulse operation mode, in which the defrost heater is repeatedly turned on and off, based on the heater operation mode. 
     The controller may be configured to continuously turn on the defrost heater based on the continuous operation mode, in response to a change rate of the ambient temperature of the evaporator detected by the temperature sensor being greater than or equal to a first reference value in an ON state of the defrost heater, enter the pulse operation mode and turn off the defrost heater, and in response to the change rate of the ambient temperature of the evaporator being less than or equal to a second reference value less than the first reference value in a state in which the defrost heater is turned off during the pulse operation mode, turn on the defrost heater. 
     The controller may be configured to continuously turn on the defrost heater based on the continuous operation mode, and repeatedly turn on and off the defrost heater for the change rate of the ambient temperature of the evaporator to be between the first reference value and the second reference value based on the pulse operation mode. 
     The controller may be configured to, as the number of opening times of the cooling compartment door increases, decrease a duration of the defrost operation mode. 
     The controller may be configured to control a peak temperature arrival time point of the evaporator in response to the continuous operation mode and the pulse operation mode being performed to be later than the peak temperature arrival time point of the evaporator in response to the defrost heater being only continuously turned on in the defrost operation mode. 
     The controller may be configured to control a size of a second section related to temperature versus time between a phase-change temperature and the defrost end temperature in response to the continuous operation mode and the pulse operation mode being performed in the defrost operation mode to be greater than a size of a first section related to temperature versus time between the phase-change temperature and the defrost end temperatures only in response to the defrost heater being continuously turned on in the defrost operation mode. 
     The controller may be configured to control an effective defrost in response to the continuous operation mode and the pulse operation mode being performed in the defrost operation mode to be greater than the effective defrost in response to the defrost heater being only continuously turned on in the defrost operation mode. 
     The controller may be configured to control a heater OFF time point in response to the continuous operation mode and the pulse operation mode being performed in the defrost operation mode to be later than the heater OFF time point in response to the defrost heater being only continuously turned on in the defrost operation mode. 
     In response to a defrosting operation start time point arriving, the controller may be configured to perform the defrost operation mode including a pre-defrost cooling mode, a heater operation mode, and a post-defrost cooling mode, in response to the temperature detected by the temperature sensor reaching the first temperature within a first period during the continuous operation mode in which the defrost heater is continuously turned on based on the heater operation mode, perform the pulse operation mode in which the defrost heater is repeatedly turned on and off, and in response to the period during which the temperature detected by the temperature sensor reaching the first temperature while performing the continuous operation mode is greater than or equal to a second period greater than the first period, continuously perform the continuous operation mode. 
     In another aspect, a refrigerator includes: an evaporator configured to perform heat exchange; a defrost heater configured to operate to remove frost formed on the evaporator; a temperature sensor configured to detect an ambient temperature of the evaporator; and a controller configured to control the defrost heater, wherein, in response to a defrosting operation start time point arriving, the controller is configured to perform a defrost operation mode, perform a continuous operation mode, in which the defrost heater is continuously turned on, and a pulse operation mode, in which the defrost heater is repeatedly turned on and off based on the defrost operation mode, and in response to a return condition to the continuous operation mode of the defrost heater arriving while performing the pulse operation mode, perform the continuous operation mode again. 
     In further another aspect, a refrigerator includes: an evaporator configured to perform heat exchange; a defrost heater configured to operate to remove frost formed on the evaporator; a temperature sensor configured to detect an ambient temperature of the evaporator; and a controller configured to control the defrost heater, wherein, in response to a defrosting operation start time point arriving, the controller is configured to perform the defrost operation mode including a pre-defrost cooling mode, a heater operation mode, and a post-defrost cooling mode, in response to the temperature detected by the temperature sensor reaching the first temperature within a first period during the continuous operation mode in which the defrost heater is continuously turned on based on the heater operation mode, perform the pulse operation mode in which the defrost heater is repeatedly turned on and off, and in response to the period during which the temperature detected by the temperature sensor reaching the first temperature while performing the continuous operation mode is greater than or equal to a second period greater than the first period, continuously perform the continuous operation mode. 
     In response to the temperature detected by the temperature sensor reaching a second temperature higher than the first temperature after arriving at the first temperature between the first period and the second period while performing the continuous operation mode, the controller may be configured to perform the pulse operation mode after the defrost heater is turned off. 
     The controller may be configured to control an OFF period of the defrost heater before performing the pulse operation mode in response to the temperature detected by the temperature sensor reaching a second temperature higher than the first temperature between the first period and the second period to be greater than the OFF period of the defrost heater before performing the pulse operation mode in response to the temperature detected by the temperature sensor reaching the first temperature within the first period. 
     In response to the temperature detected by the temperature sensor reaching the first temperature between the first period and the second period while performing the continuous operation mode, the controller may be configured to perform the pulse operation mode after the defrost heater is turned off. 
     The controller may be configured to control an OFF period of the defrost heater before performing the pulse operation mode in response to the temperature detected by the temperature sensor reaching the first temperature between the first period and the second period to be greater than the OFF period of the defrost heater before performing the pulse operation mode in response to the temperature detected by the temperature sensor reaching the first temperature within the first period. 
     The controller may be configured to, as the change rate of the temperature detected by the temperature sensor decreases while performing the continuous operation mode, increase a delay of a start time point of the pulse operation mode. 
     The controller may be configured to, as the change rate of the temperature detected by the temperature sensor decreases while performing the continuous operation mode, increase the duration of the pulse operation mode. 
     Effects of the Disclosure 
     A refrigerator according to an embodiment of the present disclosure includes: an evaporator configured to perform heat exchange; a defrost heater configured to operate to remove frost formed on the evaporator; a temperature sensor configured to detect an ambient temperature of the evaporator; and a controller configured to control the defrost heater, wherein, in response to a defrosting operation start time point arriving, the controller is configured to perform a defrost operation mode, perform a continuous operation mode, in which the defrost heater is continuously turned on, and a pulse operation mode, in which the defrost heater is repeatedly turned on and off based on the defrost operation mode, and is configured to perform the continuous operation mode again after performing the pulse operation mode. Accordingly, the present disclosure can improve a defrosting efficiency and reduce power consumption. In particular, since the defrosting is performed according to the amount of frost of the actual evaporator, it is possible to improve defrosting efficiency and power consumption. 
     In response to a return condition to the continuous operation mode of the defrost heater arriving while performing the pulse operation mode, the controller may be configured to perform the continuous operation mode. Accordingly, it is possible to improve the defrosting efficiency while stably performing the defrosting. 
     In response to a value related to the temperature detected by the temperature sensor doing not reach a reference value while performing the pulse operation mode, the controller may be configured to perform the continuous operation mode. Accordingly, it is possible to improve the defrosting efficiency while stably performing the defrosting. 
     In response to the temperature detected by the temperature sensor being below a reference temperature while performing the pulse operation mode, the controller may be configured to perform the continuous operation mode. Accordingly, it is possible to improve the defrosting efficiency while stably performing the defrosting. 
     In response to a change rate of the temperature detected by the temperature sensor being less than or equal to a change rate of the reference temperature while performing the pulse operation mode, the controller may be configured to perform the continuous operation mode. Accordingly, it is possible to improve the defrosting efficiency while stably performing the defrosting. 
     In response to the temperature detected by the temperature sensor doing not reach a target temperature within a certain time while performing the pulse operation mode, the controller may be configured to perform the continuous operation mode. Accordingly, it is possible to improve the defrosting efficiency while stably performing the defrosting. 
     In response to a sum of an ON time of the defrost heater while performing the pulse operation mode being greater than or equal to a reference level, the controller may be configured to perform the continuous operation mode. Accordingly, it is possible to improve the defrosting efficiency while stably performing the defrosting. 
     In response to a sum of the number of opening times the defrost heater while performing the pulse operation mode being greater than or equal to the reference number of opening times, the controller may be configured to perform the continuous operation mode. Accordingly, it is possible to improve the defrosting efficiency while stably performing the defrosting. 
     The sum of the ON time of the defrost heater while performing the pulse operation mode is greater than a sum of a continuous ON time of the defrost heater in the continuous operation mode, the controller may be configured to perform the continuous operation mode. Accordingly, it is possible to improve the defrosting efficiency while stably performing the defrosting. 
     In response to a door open period being greater than or equal to an allowable period while performing the pulse operation mode, the controller may be configured to perform the continuous operation mode. Accordingly, it is possible to improve the defrosting efficiency while stably performing the defrosting. 
     In response to humidity in the refrigerator being greater than or equal to reference humidity while performing the pulse operation mode, the controller may be configured to perform the continuous operation mode. Accordingly, it is possible to improve the defrosting efficiency while stably performing the defrosting. 
     Meanwhile, in response to a defrosting operation start time point arriving while performing a normal cooling operation mode the controller may be configured to perform the defrost operation mode including a pre-defrost cooling mode, a heater operation mode, and a post-defrost cooling mode, and control the continuous operation mode of the defrost heater and the pulse operation mode, in which the defrost heater is repeatedly turned on and off, to be performed based on the heater operation mode. Accordingly, it is possible to improve the defrosting efficiency and reduce the power consumption. 
     Meanwhile, the controller may be configured to continuously turn on the defrost heater based on the continuous operation mode, and enter the pulse operation mode and turn off the defrost heater in response to the change rate of the ambient temperature of the evaporator detected by the temperature sensor being greater than or equal to the first reference value in the ON state of the defrost heater, and turn on the defrost heater in response to the change rate of the ambient temperature of the evaporator being less than or equal to the second reference value less than the first reference value in the state in which the defrost heater is turned off during the pulse operation mode. Accordingly, it is possible to improve the defrosting efficiency and reduce the power consumption. 
     Meanwhile, the controller may be configured to turn off the defrost heater based on the heater pulse operation end condition. Accordingly, it is possible to improve the defrosting efficiency and reduce the power consumption. 
     Meanwhile, the controller may be configured to continuously turn on the defrost heater based on the continuous operation mode, and repeatedly turn on and off the defrost heater for the change rate of the temperature around the evaporator being between the first reference value and the second reference value based on the pulse operation mode. Accordingly, it is possible to improve the defrosting efficiency and reduce the power consumption. 
     Meanwhile, in response to the temperature detected by the temperature sensor being a predetermined temperature, the controller may be configured to perform the pulse operation mode. Accordingly, the present disclosure can improve a defrosting efficiency and reduce power consumption. 
     Meanwhile, in response to the temperature detected by the temperature sensor being a predetermined temperature, and an execution period of the continuous operation mode being longer than a predetermined period, the controller may be configured to perform the pulse operation mode. Accordingly, it is possible to improve the defrosting efficiency and reduce the power consumption. 
     Meanwhile, when the execution period of the continuous operation mode is longer than a predetermined period, the controller may be configured to perform the pulse operation mode. Accordingly, it is possible to improve the defrosting efficiency and reduce the power consumption. 
     Meanwhile, the controller may be configured to perform the pulse operation mode based on the temperature change rate of the temperature detected by the temperature sensor. Accordingly, it is possible to improve the defrosting efficiency and reduce the power consumption. 
     Meanwhile, the controller may be configured to operate the heater with power inversely proportional to the temperature change rate of the temperature detected by the sensor during the pulse operation mode. Accordingly, it is possible to improve the defrosting efficiency and reduce the power consumption. 
     Meanwhile, the controller may be configured to, as the number of opening times of the cooling compartment door increases, decrease the duration of the defrost operation mode. Accordingly, it is possible to improve the defrosting efficiency and reduce the power consumption. 
     Meanwhile, the controller may be configured to control a peak temperature arrival point of the evaporator in response to the continuous operation mode and the pulse operation mode being performed in the defrost operation mode to be later than a peak temperature arrival point of the evaporator in response to the defrost heater being only continuously turned on in the defrost operation mode. Accordingly, defrosting efficiency may be improved and power consumption may be improved. 
     Meanwhile, the controller may be configured to control a size of a second section related to a temperature versus time between a phase-change temperature and a defrost end temperature in response to the continuous operation mode and the pulse operation mode being performed in the defrost operation mode to be greater than a size of a first section related to a temperature versus time between the phase-change temperature and the defrost end temperature in response to the defrost heater being only continuously turned on in the defrost operation mode. Accordingly, defrosting efficiency may be improved and power consumption may be improved. 
     Meanwhile, the controller may be configured to control an effective defrost in response to the continuous operation mode and the pulse operation mode being performed in the defrost operation mode to be greater than an effective defrost in response to the defrost heater being only continuously turned on in the defrost operation mode. Accordingly, defrosting efficiency may be improved and power consumption may be improved. 
     Meanwhile, the controller may be configured to control a heater OFF time point in response to the continuous operation mode and the pulse operation mode being performed in the defrost operation mode to be later than a heater OFF time point in response to the defrost heater being only continuously turned on in the defrost operation mode. Accordingly, defrosting efficiency may be improved and power consumption may be improved. 
     Meanwhile, in response to a defrosting operation start time point arriving, the controller may be configured to perform the defrost operation mode including a pre-defrost cooling mode, a heater operation mode, and a post-defrost cooling mode, in response to the temperature detected by the temperature sensor reaching the first temperature within a first period during the continuous operation mode in which the defrost heater is continuously turned on based on the heater operation mode, perform the pulse operation mode in which the defrost heater is repeatedly turned on and off, and in response to the period during which the temperature detected by the temperature sensor reaching the first temperature while performing the continuous operation mode is greater than or equal to a second period greater than the first period, continuously perform the continuous operation mode. Accordingly, it is possible to improve the defrosting efficiency and reduce the power consumption. 
     A refrigerator according to another embodiment of the present disclosure includes: an evaporator configured to perform heat exchange; a defrost heater configured to operate to remove frost formed on the evaporator; a temperature sensor configured to detect an ambient temperature of the evaporator; and a controller configured to control the defrost heater, wherein, in response to a defrosting operation start time point arriving, the controller is configured to perform a defrost operation mode, perform a continuous operation mode, in which the defrost heater is continuously turned on, and a pulse operation mode, in which the defrost heater is repeatedly turned on and off based on the defrost operation mode, and in response to a return condition to the continuous operation mode of the defrost heater arriving while performing the pulse operation mode, perform the continuous operation mode again. Accordingly, it is possible to improve the defrosting efficiency and reduce the power consumption. In particular, since the defrosting is performed according to the amount of frost of the actual evaporator, it is possible to improve defrosting efficiency and power consumption. 
     A refrigerator according to another embodiment of the present disclosure includes: an evaporator configured to perform heat exchange; a defrost heater configured to operate to remove frost formed on the evaporator; a temperature sensor configured to detect an ambient temperature of the evaporator; and a controller configured to control the defrost heater, wherein, in response to a defrosting operation start time point arriving, the controller is configured to perform the defrost operation mode including a pre-defrost cooling mode, a heater operation mode, and a post-defrost cooling mode, in response to the temperature detected by the temperature sensor reaching the first temperature within a first period during the continuous operation mode in which the defrost heater is continuously turned on based on the heater operation mode, perform the pulse operation mode in which the defrost heater is repeatedly turned on and off, and in response to the period during which the temperature detected by the temperature sensor reaching the first temperature while performing the continuous operation mode is greater than or equal to a second period greater than the first period, continuously perform the continuous operation mode. 
     Accordingly, it is possible to improve the defrosting efficiency and reduce the power consumption. In particular, since the defrosting is performed according to the amount of frost of the actual evaporator, it is possible to improve defrosting efficiency and power consumption. 
     Meanwhile, in response to the temperature detected by the temperature sensor reaching a second temperature higher than the first temperature after arriving at the first temperature between the first period and the second period while performing the continuous operation mode, the controller may be configured to perform the pulse operation mode after the defrost heater is turned off. Accordingly, it is possible to improve the defrosting efficiency and reduce the power consumption. 
     Meanwhile, the controller may be configured to control an OFF period of the defrost heater before performing the pulse operation mode in response to the temperature detected by the temperature sensor reaching a second temperature higher than the first temperature between the first period and the second period to be greater than the OFF period of the defrost heater before performing the pulse operation mode in response to the temperature detected by the temperature sensor reaching the first temperature within the first period. Accordingly, it is possible to improve the defrosting efficiency and reduce the power consumption. 
     Meanwhile, in response to the temperature detected by the temperature sensor reaching the first temperature between the first period and the second period while performing the continuous operation mode, the controller may be configured to perform the pulse operation mode after the defrost heater is turned off. Accordingly, it is possible to improve the defrosting efficiency and reduce the power consumption. 
     The controller may be configured to control an OFF period of the defrost heater before performing the pulse operation mode in response to the temperature detected by the temperature sensor reaching the first temperature between the first period and the second period to be greater than the OFF period of the defrost heater before performing the pulse operation mode in response to the temperature detected by the temperature sensor reaching the first temperature within the first period. Accordingly, it is possible to improve the defrosting efficiency and reduce the power consumption. 
     Meanwhile, the controller may be configured to, as the change rate of the temperature detected by the temperature sensor decreases while performing the continuous operation mode, increase a delay of a start time point of the pulse operation mode. Accordingly, it is possible to improve the defrosting efficiency and reduce the power consumption. 
     Meanwhile, the controller may be configured to, as the change rate of the temperature detected by the temperature sensor decreases while performing the continuous operation mode, increase the duration of the pulse operation mode. Accordingly, it is possible to improve the defrosting efficiency and reduce the power consumption. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view illustrating a refrigerator according to an embodiment of the present disclosure; 
         FIG.  2    is a perspective view of a door of the refrigerator of  FIG.  1   ; 
         FIG.  3    is a view schematically illustrating a configuration of the refrigerator of  FIG.  1   ; 
         FIG.  4    is a block diagram schematically illustrating the inside of the refrigerator shown in  FIG.  1   ; 
         FIG.  5 A  is a perspective view illustrating an example of an evaporator associated with the present disclosure; 
         FIG.  5 B  is a diagram referenced in the description of  FIG.  5 A ; 
         FIG.  6    is a flowchart illustrating a method of operating a refrigerator according to an embodiment of the present disclosure; 
         FIGS.  7 A to  13    are diagrams referenced in the description of  FIG.  6   ; 
         FIG.  14    is a flowchart illustrating a method of operating a defrost heater according to another embodiment of the present disclosure; 
         FIGS.  15 A to  15 D  are diagrams referenced in the description of  FIG.  14   ; 
         FIG.  16    is a flowchart illustrating a defrosting method according to another embodiment of the present disclosure; and 
         FIGS.  17 A to  17 D  are diagrams referenced in the description of  FIG.  16   . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, the present disclosure will be described in further detail with reference to the accompanying drawings. 
     The suffixes “module” and “unit” in elements used in description below are given only in consideration of ease in preparation of the specification and do not have specific meanings or functions. Therefore, the suffixes “module” and “unit” may be used interchangeably. 
       FIG.  1    is a perspective view illustrating a refrigerator according to an embodiment of the present disclosure. 
     Referring to the drawings, a refrigerator  100  according to an embodiment of the present disclosure forms a rough outer shape by a case  110  having an internal space divided, although not shown, into a freezer compartment and a refrigerating compartment, a freezer compartment door  120  that shields the freezer compartment, and a refrigerator door  140  to shield the refrigerating compartment. 
     In addition, the front surface of the freezer compartment door  120  and the refrigerating compartment door  140  is further provided with a door handle  121  protruding forward, so that a user easily grips and rotates the freezer compartment door  120  and the refrigerating compartment door  140 . 
     Meanwhile, the front surface of the refrigerating compartment door  140  may be further provided with a home bar  180  which is a convenient means for allowing a user to take out a storage such as a beverage contained therein without opening the refrigerating compartment door  140 . 
     In addition, the front surface of the freezer compartment door  120  may be provided with a dispenser  160  which is a convenient means for allowing the user to easily take out ice or drinking water without opening the freezer compartment door  120 , and a control panel  210  for controlling the driving operation of the refrigerator  100  and displaying the state of the refrigerator  100  being operated on a screen may be further provided in an upper side of the dispenser  160 . 
     Meanwhile, in the drawing, it is illustrated that the dispenser  160  is disposed in the front surface of the freezer compartment door  120 , but is not limited thereto, and may be disposed in the front surface of the refrigerating compartment door  140 . 
     The control panel  210  may include an input device  220  formed of a plurality of buttons, and a display device  230  for displaying a control screen, an operation state, and the like. 
     The display device  230  displays information such as a control screen, an operation state, a temperature inside the refrigerator, and the like. For example, the display device  230  may display the set temperature of the freezer compartment and the set temperature of the refrigerating compartment. 
     The display device  230  may be implemented in various ways, such as a liquid crystal display (LCD), a light emitting diode (LED), an organic light emitting diode (OLED), and the like. In addition, the display device  230  may be implemented as a touch screen capable of serving as the input device  220 . 
     The input device  220  may include a plurality of operation buttons. For example, the input device  220  may include a freezer compartment temperature setting button (not shown) for setting the freezer compartment temperature, and a refrigerating compartment temperature setting button (not shown) for setting the refrigerating compartment temperature. Meanwhile, the input device  220  may be implemented as a touch screen that may also function as the display device  230 . 
     Meanwhile, the refrigerator according to an embodiment of the present disclosure is not limited to a double door type shown in the drawing, but may be a one door type, a sliding door type, a curtain door type, and the like regardless of its type. 
       FIG.  2    is a perspective view of a door of the refrigerator of  FIG.  1   . 
     Referring to the drawing, a freezer compartment  155  is disposed inside the freezer compartment door  120 , and a refrigerating compartment  157  is disposed inside the refrigerating compartment door  140 . 
       FIG.  3    is a view schematically illustrating a configuration of the refrigerator of  FIG.  1   . 
     Referring to the drawing, the refrigerator  100  may include a compressor  112 , a condenser  116  for condensing a refrigerant compressed by the compressor  112 , a freezer compartment evaporator  122  which is supplied with the refrigerant condensed in the condenser  116  to evaporate, and is disposed in a freezer compartment (not shown), and a freezer compartment expansion valve  132  for expanding the refrigerant supplied to the freezer compartment evaporator  122 . 
     Meanwhile, in the drawing, it illustrated that a single evaporator is used, but it is also possible to use respective evaporators may be used in the refrigerating compartment and the freezer compartment. 
     That is, the refrigerator  100  may further include a refrigerating compartment evaporator (not shown) disposed in a refrigerating compartment (not shown), a three-way valve (not shown) for supplying the refrigerant condensed in the condenser  116  to the refrigerating compartment evaporator (not shown) or the freezer compartment evaporator  122 , and a refrigerating compartment expansion valve (not shown) for expanding the refrigerant supplied to the refrigerating compartment evaporator (not shown). 
     In addition, the refrigerator  100  may further include a gas-liquid separator (not shown) which separates the refrigerant passed through the evaporator  122  into a liquid and a gas. 
     In addition, the refrigerator  100  may further include a refrigerating compartment fan (not shown) and a freezer compartment fan  144  that suck cold air that passed through the freezer compartment evaporator  122  and blow the sucked cold air into a refrigerating compartment (not shown) and a freezer compartment (not shown) respectively. 
     In addition, the refrigerator  100  may further include a compressor driver  113  for driving the compressor  112 , and a refrigerating compartment fan driver (not shown) and a freezer compartment fan driver  145  for driving the refrigerating compartment fan (not shown) and the freezer compartment  144 . 
     Meanwhile, based on the drawing, since a common evaporator  122  is used for the refrigerating compartment and the freezer compartment, in this case, a damper (not shown) may be installed between the refrigerating compartment and the freezer compartment, and a fan (not shown) may forcibly blow the cold air generated in one evaporator to be supplied to the freezer compartment and the refrigerating compartment. 
       FIG.  4    is a block diagram schematically illustrating the inside of the refrigerator shown in  FIG.  1   . 
     Referring to the drawings, the refrigerator of  FIG.  4    includes a compressor  112 , a machine room fan  115 , the freezer compartment fan  144 , a controller  310 , a heater  330 , a temperature sensor  320 , and a memory  240 , and an evaporator  122 . 
     In addition, the refrigerator may further include a compressor driver  113 , a machine room fan driver  117 , a freezer compartment fan driver  145 , a heater driver  332 , a display device  230 , and an input device  220 . 
     The compressor  112 , the machine room fan  115 , and the freezer compartment fan  144  are described with reference to The input device  220  includes a plurality of operation buttons, and transmits a signal for an input freezer compartment set temperature or refrigerating compartment set temperature to the controller  310 . 
     The display device  230  may display an operation state of the refrigerator. Meanwhile, the display device  230  is operable under the control of a display controller (not shown). 
     The memory  240  may store data necessary for operating the refrigerator. 
     For example, the memory  240  may store power consumption information for each of the plurality of power consumption devices. In addition, the memory  240  may output corresponding power consumption information to the controller  310  based on the operation of each power consumption device in the refrigerator. 
     The temperature sensor  320  detects a temperature in the refrigerator and transmits a signal for the detected temperature to the controller  310 . Here, the temperature sensor  320  detects the refrigerating compartment temperature and the freezer compartment temperature respectively. In addition, the temperature of each chamber in the refrigerating compartment or each chamber in the freezer compartment may be detected. 
     In order to control an ON/OFF operation of the compressor  112 , the fan  115  or  144 , and the heater  330 , as shown in the drawing, the controller may control the compressor driver  113 , the fan driver  117  or  145 , the heater driver  332  to eventually control the compressor  112 , the fan  115  or  144 , and the heater  330 . Here, the fan driver may be the machine room fan driver  117  or the freezer compartment fan driver  145 . 
     For example, the controller  310  may output a corresponding speed command value signal to the compressor driver  113  or the fan driver  117  or  145  respectively. 
     The compressor driver  113  and the freezer compartment fan driver  145  described above are provided with a compressor motor (not shown) and a freezer compartment fan motor (not shown) respectively, and each motor (not shown) may be operated at a target rotational speed under the control of the controller  310 . 
     Meanwhile, the machine room fan driver  117  includes a machine room fan motor (not shown), and the machine room fan motor (not shown) may be operated at a target rotational speed under the control of the controller  310 . 
     When such a motor is a three-phase motor, it may be controlled by a switching operation in an inverter (not shown) or may be controlled at a constant speed by using an AC power source intactly. Here, each motor (not shown) may be any one of an induction motor, a Blush less DC (BLDC) motor, a synchronous reluctance motor (synRM) motor, and the like. 
     Meanwhile, as described above, the controller  310  may control the overall operation of the refrigerator  100 , in addition to the operation control of the compressor  112  and the fan  115  or  144 . 
     For example, as described above, the controller  310  may control the overall operation of the refrigerant cycle based on the set temperature from the input device  220 . For example, the controller  310  may further control a three-way valve (not shown), a refrigerating compartment expansion valve (not shown), and a freezer compartment expansion valve  132 , in addition to the compressor driver  113 , the refrigerating compartment fan driver  143 , and the freezer compartment fan driver  145 . In addition, the operation of the condenser  116  may also be controlled. In addition, the controller  310  may control the operation of the display device  230 . 
     Meanwhile, the cold air heat-exchanged in the evaporator  122  may be supplied to the freezer compartment or the refrigerating compartment by a fan or a damper (not shown). 
     Meanwhile, the heater  330  may be a freezer compartment defrost heater. For example, when only one freezer compartment evaporator  122  is used in the refrigerator  100 , the freezer compartment defrost heater  330  may operate to remove frost attached to the freezer compartment evaporator  122 . To this end, the heater driver  332  may control the operation of the heater  330 . Meanwhile, the controller  310  may control the heater driver  332 . 
     Meanwhile, the heater  330  may include a freezer compartment defrost heater and a refrigerating compartment defrost heater. For example, when the freezer compartment evaporator  122  and the refrigerating compartment evaporator (not shown) are separately used in the refrigerator  100 , the freezer compartment defrost heater  330  may operates to remove frost attached to the freezer compartment evaporator  122 , and the refrigerating compartment defrost heater (not shown) may operate to remove frost attached to the refrigerating compartment evaporator. To this end, the heater driver  332  may control the operations of the freezer compartment defrost heater  330  and the refrigerating compartment defrost heater. 
       FIG.  5 A  is a perspective view illustrating an example of an evaporator related to the present disclosure, and  FIG.  5 B  is a diagram referenced in the description of  FIG.  5 A . 
     First, referring to  FIG.  5 A , the evaporator  122  in the refrigerator  100  may be a freezer compartment evaporator as described above with reference to  FIG.  2   . 
     A sensor mounter  400  including a temperature sensor  320  may be attached to the evaporator  122  in the refrigerator  100 . 
     In the drawing, it is illustrated that a sensor mounter  400  is attached to an upper cooling pipe of the evaporator  122  in the refrigerator  100 . 
     The evaporator  122  includes a cooling pipe  131  extending from one side of the accumulator  134  and a support  133  supporting the cooling pipe  131 . 
     The cooling pipe  131  may be repeatedly bent in a zigzag manner to form multiple rows and may be filled with a refrigerant. 
     Meanwhile, the defrost heater  330  for defrosting may be disposed in the vicinity of the cooling pipe  131  of the evaporator  122 . 
     In the drawing, it is illustrated that the defrost heater  330  is disposed in the vicinity of the cooling pipe  131  in a lower region of the evaporator  122 . 
     For example, since frost ICE is formed from a lower region of the evaporator  122  and grows in an upward direction, and thus, preferably, the defrost heater  330  may be disposed in the vicinity of the cooling pipe  131  in the lower region of the evaporator  122 . 
     Accordingly, as shown in the drawing, the defrost heater  330  may be disposed in a shape surrounding the cooling pipe  131  of the lower region of the evaporator  122 . 
     Meanwhile,  FIG.  5 B  illustrates frost ICE is attached to the evaporator  122 . 
     In the drawing, it is illustrated that frost ICE is attached to a central portion and a lower portion of the evaporator  122 . 
     In particular, in the drawing, it is illustrated that frost ICE is formed on the defrost heater  330  to cover the defrost heater  330 . 
     Meanwhile, when the defrost heater  330  operates, frost ICE is removed from the lower region of the evaporator  122  and may be gradually removed in the direction of the central region. 
     Meanwhile, in the present disclosure, a method for improving defrosting efficiency and power consumption when removing frost ICE, that is, defrosting, is proposed. This will be described with reference to  FIG.  6    and the following drawings. 
       FIG.  6    is a flowchart illustrating a method of operating a refrigerator according to an embodiment of the present disclosure. 
     Referring to the drawings, the controller  310  of the refrigerator  100  according to an embodiment of the present disclosure determines whether a defrosting operation start time point for defrosting arrives (S 610 ). 
     For example, the controller  310  of the refrigerator  100  may determine whether a defrosting operation start time point arrives while performing a normal cooling operation mode Pga. 
     The defrosting operation start time point may vary according to a defrost cycle. 
     For example, when the number of opening times a door of the cooling compartment (the refrigerating compartment or the freezer compartment) increases, the amount of cold air supplied in the normal cooling operation mode increases, and accordingly, a rate at which frost is formed on the evaporator  122  may increase. 
     Accordingly, when the number of opening times the door of the cooling compartment (the refrigerating compartment or the freezer compartment) increases, the controller  310  of the refrigerator  100  may control such that a defrost cycle is shortened. 
     That is, when the number of opening times the door of the cooling compartment (the refrigerating compartment or the freezer compartment) increases, the controller  310  of the refrigerator  100  may control the defrosting operation start time point to be shortened. 
     Meanwhile, when a defrosting operation start condition is satisfied, for example, in response to a defrosting operation start time point arriving, the controller  310  of the refrigerator  100  may end the normal cooling operation mode, control to perform a defrost operation mode Pdf, and control the defrost heater  330  to be continuously turned on based on a heater operation mode PddT in the defrost operation mode Pdf (S 615 ). 
     Next, the controller  310  of the refrigerator  100  may be configured to perform a pulse operation mode in which the defrost heater  330  is repeatedly turned on and off by a heater pulse after the defrost heater  330  is continuously turned on (S 620 ). 
     For example, when the defrosting operation start condition is satisfied, the controller  310  of the refrigerator  100  may be configured to perform the defrost operation mode Pdf including a pre-defrost cooling mode Pbd, a heater operation mode PddT, and a post-defrost cooling mode pbf. 
     Also, based on the heater operation mode PddT, based on the defrost operation mode pdf, the controller may be configured to perform a continuous operation mode Pona in which the defrost heater  330  is continuously turned on and a pulse operation mode Ponb in which the defrost heater  330  is repeatedly turned on and off. 
     Meanwhile, the controller  310  controls the defrost heater  330  to be continuously turned on based on the continuous operation mode Pona, and in the ON state of the defrost heater  330 , when a change rate of an ambient temperature of the evaporator  122  detected by the temperature sensor  320  is equal to or greater than a first reference value ref 1 , the controller  310  may enter the pulse operation mode Ponb to control the defrost heater  330  to be turned off. Accordingly, defrosting efficiency and power consumption may be improved. 
     Meanwhile, the controller  310  of the refrigerator  100  may control the defrost heater  330  to be turned on and off based on a change rate of the temperature detected by the temperature sensor  320  when the pulse operation mode Ponb is performed. 
     For example, in response to performing the pulse operation mode Ponb, if the change rate of the temperature detected by the temperature sensor  320  is equal to or greater than the first reference value ref 1 , the controller  310  of the refrigerator  100  may control the defrost heater  330  to be turned off, and if the change rate of the temperature detected by the temperature sensor  320  is less than or equal to a second reference value ref 2  less than the first reference value ref 1 , the controller  310  may control the defrost heater  330  to be turned on. Accordingly, since defrosting may be performed based on a change rate ΔT of the temperature, defrosting efficiency and power consumption may be improved. 
     Next, the controller  310  of the refrigerator  100  determines whether a pulse operation mode end time point arrives (S 630 ), and if pulse operation mode end time point arrives, the controller  310  turns off the defrost heater  330  (S 640 ). 
     For example, the pulse operation mode end time point may be a time point at which the temperature detected by the temperature sensor  320  falls below a phase-change temperature Trf 1 . 
     As another example, the pulse operation mode end time point may be an end time point of the defrosting operation or an end time point of the heater operation mode. 
     As such, the continuous operation mode Pona in which the defrost heater  330  is continuously turned on and the pulse operation mode in which the defrost heater  330  is repeatedly turned on and off are controlled to be performed based on the change rate of the temperature detected by the temperature sensor  320 , defrosting efficiency and power consumption may be improved by performing defrosting based on the change rate ΔT of the temperature. 
     In particular, since defrosting is performed according to the actual amount of frost of the evaporator  122 , defrosting efficiency and power consumption may be improved. 
       FIGS.  7 A to  13    are diagrams referenced in the description of  FIG.  6   . 
     First,  FIG.  7 A  is a diagram illustrating a defrost heater HT and a switching element RL for driving a defrost heater when one evaporator and one defrost heater are used in the refrigerator  100 . 
     Referring to the drawing, when only one freezer compartment evaporator  122  is used in the refrigerator  100 , the freezer compartment defrost heater HT may operate to remove frost attached to the freezer compartment evaporator  122 . 
     To this end, the switching element RL in the heater driver  332  may control the operation of the defrost heater HT. In this case, the switching element RL may be a relay element. 
     That is, when the switching element RL is continuously turned on, the continuous operation mode Pona in which the defrost heater HT is continuously turned on may be performed, and when the switching element RL is switched On and off, the pulse operation mode Ponb in which the defrost heater HT is repeatedly turned on and off may be performed. 
     Next,  FIG.  7 B  is a diagram illustrating defrost heaters HTa and HTb and switching elements RLa and Rlb for driving the defrost heaters when two evaporators and two defrost heaters are used in the refrigerator  100 . 
     When a first defrost heater HTa is a freezer compartment defrost heater, a first switching element RLa in the heater driver  332  may control the operation of the first defrost heater HTa. In this case, the first switching element RLa may be a relay element. 
     That is, when the first switching element RLa is continuously turned on, the continuous operation mode Pona in which the first defrost heater HTa is continuously turned on may be performed, and when the first switching element RLa performs On and off switching, the pulse operation mode Ponb in which the first defrost heater HTa is repeatedly turned on and off may be performed. 
     When a second defrost heater HTb is a refrigerating compartment defrost heater, a second switching element RLb in the heater driver  332  may control the operation of the second defrost heater HTb. In this case, the second switching element RLb may be a relay element. 
     That is, when the second switching element RLb is continuously turned on, the continuous operation mode Ponb in which the second defrost heater HTb is continuously turned on may be performed, and when the second switching element RLb performs On and off switching, the pulse operation mode Ponb in which the second defrost heater HTb is repeatedly turned on and off may be performed. 
     Meanwhile, On and off timings of the first switching element RLa and the second switching element RLb may be different from each other. Accordingly, it is possible to perform the defrosting of the freezer compartment evaporator and the defrosting of the refrigerating compartment evaporator, separately. 
       FIG.  8 A  is a diagram illustrating an example of a pulse waveform indicating an operation of one defrost heater of  FIG.  7 A . 
     Referring to the drawings, the horizontal axis of the pulse waveform Psh may represent time and the vertical axis may represent a level. 
     When the defrosting cloud base start time To arrives, while performing the normal cooling operation mode Pga, the controller  310  of the refrigerator  100  may end the normal cooling operation mode Pga and control to perform the defrost operation mode pdf. 
     The defrost operation mode pdf may include a pre-defrost cooling mode Pbd between Toa and Ta, a heater operation mode PddT between Ta and Td, and a post-defrost cooling mode pbf between Td and Te. 
     Meanwhile, after the defrost operation mode pdf is ended, the normal cooling operation mode Pgb is performed again. 
     The defrost heater  330  is turned off in the normal cooling operation mode Pga and the normal cooling operation mode Pgb. 
     Meanwhile, the defrost heater  330  may be turned off in the pre-defrost cooling mode Pbd and the post-defrost cooling mode pbf of the defrost operation mode Pdf. 
     Meanwhile, the defrost heater  330  may be continuously turned on in the continuous operation mode Pona of the heater operation mode PddT, and may be repeatedly turned on and off in the pulse operation mode Ponb of the heater operation mode PddT. 
     The continuous operation mode Pona may be performed between Ta and Tb, and the pulse operation mode Ponb may be performed between Tb and Tc. 
     When only the continuous operation mode is performed and the defrost heater  330  is continuously turned on, if the amount of frost is large, defrosting may not be performed properly or if the amount of frost is small, unnecessary defrosting may be performed, and thus, unnecessary power consumption may be consumed. 
     Accordingly, in the present disclosure, the continuous operation mode Pona and the pulse operation mode Ponb are used in combination. Accordingly, defrosting efficiency and power consumption may be improved. 
       FIG.  8 B  is a diagram illustrating an example of a pulse waveform indicating an operation of two defrost heaters of  FIG.  7 B . 
     Referring to the drawing, (a) of  FIG.  8 B  shows a pulse waveform Psha indicating an operation of the freezer compartment defrost heater, and (b) of  FIG.  8 B  shows a pulse waveform Pshb indicating an operation of the refrigerating compartment defrost heater. 
     The pulse waveform Psha of (a) of  FIG.  8 B  may be the same as the pulse waveform Psh of  FIG.  8 A . 
     Meanwhile, since less frost may occur in the refrigerating compartment evaporator than in the freezer compartment evaporator, an operating section of the refrigerating compartment defrost heater may be less than an operating section of the freezer compartment defrost heater. 
     Referring to the pulse waveform Pshb of (b) of  FIG.  8 B , a period of continuously turning on in the continuous operation mode Pona in the heater operation mode PddT may be less than a period of the pulse waveform Psha of (a) of  FIG.  8 B . 
     In addition, referring to the pulse waveform Pshb of (b) of  FIG.  8 B , an ON/OFF repetition period of the pulse operation mode Ponb in the heater operation mode PddT may be less than the pulse waveform Psha of (a) of  FIG.  8 B . 
       FIG.  9    is a diagram illustrating an example of cooling power supply and a defrost heater operation in the defrost operation mode Pdf of  FIG.  8 A . 
     Referring to the drawing, the defrost operation mode pdf may include a pre-defrost cooling mode Pbd between To and Ta, a heater operation mode PddT between Ta and Td, and a post-defrost cooling mode pbf between Td and Te. 
     During a period To to T 1  of the pre-defrost cooling mode Pbd, a level of supplied cooling power may be an R level, and during a period T 1  to T 2 , a level of cooling power may be an F level greater than the R level. 
     Also, during a period T 2  to T 3  of the pre-defrost cooling mode Pbd, the cooling power supply may be stopped. 
     In addition, during a period T 3  to Ta in the pre-defrost cooling mode Pbd, a level of supplied cooling power may be the R level. 
     According to the pre-defrost cooling mode Pbd, cooling power supply for compensating for the stoppage of cooling power supply during the heater operation mode PddT is performed. 
     Meanwhile, the cooling power supply may be performed by a compressor, a thermoelectric element, or the like, and in the drawings, it is illustrated that the cooling power supply is performed by an operation of the compressor. 
     During a period To to T 2  and T 3  to Ta in which cooling power is supplied, the compressor operates, and during a period T 2  to T 3  in which cooling power is not supplied, the compressor is turned off. 
     Meanwhile, during a period To to T 1  in which the R level cooling power is supplied, the refrigerating compartment fan may operate and the freezer compartment fan may be turned off. 
     Meanwhile, during a period from a time point T 1 , at which the F level cooling power is supplied, to a time point Ta, at which the pre-defrost cooling mode Pbd is ended, the refrigerating compartment fan may be turned off and the freezer compartment fan may be operated. 
     Meanwhile, during the period T 2  to Ta, the defrost heater  330  should be maintained in an OFF state. 
     Next, the defrost heater  330  may operate during the period of Ta to Tc in the period of Ta to Td of the heater operation mode PddT. 
     As shown in  FIG.  8 A , the continuous operation mode Pona may be performed during the period of Ta and Tb of the heater operation mode PddT period, and the heater operation mode PddT may be performed during the Tb and Tc periods. 
     Meanwhile, the defrost heater  330  may be turned off from Tc, which is an end time point of the continuous operation mode Pona, to Td. 
     Meanwhile, during the period of the heater operation mode PddT, the compressor and the refrigerating compartment fan may be turned off. 
     Meanwhile, during the period of the heater operation mode PddT, the freezer compartment fan may be turned off. In particular, it is preferable that the freezer compartment fan is turned off from Tc, which is the end time point of the continuous operation mode Pona, to Td. 
     After the heater operation mode PddT, the post-defrost cooling mode Pbf is performed. 
     During the period of Td to T 4  in the post-defrost cooling mode Pbf, a level of the supplied cooling power may be an R+F level, and the largest level of cooling power may be supplied. 
     In addition, during the period of T 4  to T 6  in the post-defrost cooling mode Pbf, a level of the supplied cooling power may be F level, and the cooling power supply may be stopped during the period T 6  to Te. 
     According to the post-defrost cooling mode Pbf, the largest level of cooling power supply may be performed according to the stopping of the cooling power supply during the heater operation mode PddT. 
     During the period of Td to T 6  in which cooling power is supplied, the compressor operates, and the compressor is turned off during the period of T 6  to Te in which cooling power is not supplied. 
     Meanwhile, during the period of Td to T 4  in which the R+F level of cooling power is supplied, the refrigerating compartment fan and the freezer compartment fan may be turned off together. 
     Meanwhile, during the period of T 4  to T 6  in which the F level cooling power is supplied, the refrigerating compartment fan may be turned off and the freezer compartment fan may be operated. 
     Meanwhile, the level of power consumption in the heater operation mode PddT in  FIG.  9    may be greater than the level of power consumption of the R+F level cooling power. 
       FIG.  10    is a diagram illustrating temperature change waveforms of an evaporator in response to the defrost heater being operated only in the continuous operation mode and in response to the continuous operation mode and the pulse operation mode being mixed. 
     In particular, in (a) of  FIG.  10   , CVa represents a temperature change waveform in response to the defrost heater being operated only in the continuous operation mode, and CVb represents a temperature change waveform in response to the defrost heater being operated by mixing the continuous operation mode and the pulse operation mode. 
     According to CVa, the defrost heater  330  is continuously turned on, and may be turned off at a time point Tx, as shown in (b) of  FIG.  10   . 
     According to CVb, the defrost heater  330  operates during the Pohm period, as shown in (c) of  FIG.  10   . 
     That is, during the Ponm period including up to a Tpa time point, the continuous operation mode is performed, and the pulse operation mode is performed during a Pofn period from Tpa to Tpb. 
     Trf 1  represents a phase-change temperature, and may be, for example, 0° C. Meanwhile, Trf 2  represents a defrost end temperature, for example, may be 5° C. 
     Meanwhile, a region between Trf 1  and Trf 2  may indicate a defrosting region in which defrosting is actually performed, and a region exceeding Trf 2  may indicate an overheating region in which excessive defrosting is performed. 
     In order to actually effectively perform defrosting, it is preferable that a size of the overheating region is reduced and a size of the defrosting region is increased. 
     Accordingly, in the present disclosure, the continuous operation mode and the pulse operation mode of the defrost heater  300  are mixed in order to reduce the size of the overheating region and increase the size of the defrosting region. 
     Meanwhile, the controller  310  may be configured to control a peak temperature arrival point Qd of the evaporator  122  when the continuous operation mode Pona and the pulse operation mode Ponb are performed in the defrost operation mode Pdf to be later than a peak temperature arrival point Qc of the evaporator  122  when the defrost heater  330  is only continuously turned on in the defrost operation mode Pdf. Accordingly, it is possible to improve the defrosting efficiency and power consumption when the continuous operation mode Pona and the pulse operation mode Ponb are performed. 
     Meanwhile, the controller  310  may be configured to control a size of a second section Arbb related to a temperature versus time between a phase-change temperature Trf 1  and a defrost end temperature Trf 2  in response to the continuous operation mode and the pulse operation mode being performed in the defrost operation mode Pdf to be greater than a size of a first section Arab related to a temperature versus time between the phase-change temperature Trf 1  and the defrost end temperature Trf 2  in response to the defrost heater being only continuously turned on in the defrost operation mode Pdf. Accordingly, it is possible to improve the defrosting efficiency and power consumption when the continuous operation mode Pona and the pulse operation mode Ponb are performed. 
     Meanwhile, the controller  310  may be configured to control an effective defrost when the continuous operation mode Pona and the pulse operation mode Ponb are performed in the defrost operation mode Pdf to be greater than an effective defrost when the defrost heater  330  is only continuously turned on in the defrost operation mode Pdf. Accordingly, it is possible to improve the defrosting efficiency and power consumption when the continuous operation mode Pona and the pulse operation mode Ponb are performed. 
     Meanwhile, the controller  310  may be configured to control a heater OFF time point Tpb when the continuous operation mode Pona and the pulse operation mode Ponb are performed in the defrost operation mode Pdf to be later than a heater OFF time point Tx when the defrost heater  330  is only continuously turned on in the defrost operation mode Pdf. Accordingly, it is possible to improve the defrosting efficiency and power consumption when the continuous operation mode Pona and the pulse operation mode Ponb are performed. 
     Meanwhile, the controller  310  may be configured to control a period Tpb-Qd between the heater OFF time point Tpb and a peak temperature arrival time Qd of the evaporator  122  when the continuous operation mode Pona and the pulse operation mode Ponb are performed in the defrost operation mode Pdf to be greater than a period Tx-Qc between the heater OFF time point and the peak temperature arrival time Qc of the evaporator  122  when the defrost heater  330  is only continuously turned on in the defrost operation mode Pdf. Accordingly, it is possible to improve the defrosting efficiency and power consumption when the continuous operation mode Pona and the pulse operation mode Ponb are performed. 
     Meanwhile, the controller  310  may be configured to control a period Tpb-Qh during which a temperature maintains above the phase-change temperature Trf 1  when the continuous operation mode Pona and the pulse operation mode Ponb are performed in the defrost operation mode Pdf to be greater than a period Tx-Qg during which a temperature maintains above the phase-change temperature Trf 1  when the defrost heater  330  is only continuously turned on in the defrost operation mode Pdf. Accordingly, it is possible to improve the defrosting efficiency and power consumption when the continuous operation mode Pona and the pulse operation mode Ponb are performed 
     Meanwhile, the controller  310  may be configured to control a period Tpb-Qh between the heater OFF time point Tpb to a time point at which a temperature falls below a phase-change temperature Trf 1  when the continuous operation mode Pona and the pulse operation mode Ponb are performed in the defrost operation mode Pdf to be less than a period Tx-Qg between the heater OFF time point Tx to a time point Qg at which the temperature falls below the phase-change temperature Trf 1  when the defrost heater  330  is only continuously turned on in the defrost operation mode Pdf. Accordingly, it is possible to improve the defrosting efficiency and power consumption when the continuous operation mode Pona and the pulse operation mode Ponb are performed. 
     Meanwhile, the controller  310  may be configured to control a size of an overheat temperature region Arba equal to higher than the defrosting end temperature Trf 2  when the continuous operation mode Pona and the pulse operation mode Ponb are performed in the defrost operation mode Pdf to be less than an overheat temperature region Araa equal to higher than the defrosting end temperature Trf 2  when the defrost heater  330  is only continuously turned on in the defrost operation mode Pdf. Accordingly, it is possible to improve the defrosting efficiency and power consumption when the continuous operation mode Pona and the pulse operation mode Ponb are performed. 
     In  FIG.  10   , (d) shows a cooling power supply waveform COa in the case of only continuously turning on the defrost heater  330  and a cooling power supply waveform COb in the case of performing a continuous operation mode Pona and a pulse operation mode Ponb. 
     Referring to the drawing, the controller  310  may be configured to control a cooling power supply time point Tcb according to a normal cooling operation mode Pga when the continuous operation mode Pona and the pulse operation mode Ponb are performed in the defrost operation mode Pdf to be later than a cooling power supply time point Tca according to the normal cooling operation mode Pga when the defrost heater  330  is only continuously turned on in the defrost operation mode Pdf. 
     Accordingly, it is possible to improve the defrosting efficiency and power consumption. Accordingly, it is possible to improve the defrosting efficiency and power consumption when the continuous operation mode Pona and the pulse operation mode Ponb are performed. 
       FIG.  11    is a diagram illustrating an operating method in a pulse operation mode according to an embodiment of the present disclosure. 
     Referring to the drawing, the controller  310  controls the defrost heater  330  to be turned on based on the heater operation mode, in particular, based on the continuous operation mode (S 1115 ). 
     Next, the controller  310  calculates a change rate ΔT of a temperature detected by the temperature sensor  320  during the operation of the defrost heater  330 , and determines whether the change rate ΔT of the temperature is equal to or greater than a first reference value ref 1  (S 1120 ). 
     For example, when the change rate ΔT of the temperature during the continuous operation of the defrost heater  330  is less than the first reference value ref 1 , the controller  310  may control the defrost heater  330  to continuously operate. 
     Meanwhile, when the change rate ΔT of the temperature during the continuous operation of the defrost heater  330  is equal to or greater than the first reference value ref 1 , the controller  310  may temporarily turn off the defrost heater  330  (S 1125 ). 
     Next, the controller  310  calculates the change rate ΔT of the temperature detected by the temperature sensor  320  after the defrost heater  330  is temporarily turned off, and determine whether the change rate ΔT of the temperature is less than or equal to a second reference value ref 2  (S 1128 ). 
     When the change rate ΔT of the temperature detected by the temperature sensor  320  is less than or equal to the second reference value ref 2  after the defrost heater  330  is temporarily turned off, the controller  310  is configured to turn on the defrost heater. That is, the controller  310  controls to perform step S 1115 . 
     As such, when steps  1115  to  1128  are repeated, the pulse operation mode of the defrost heater  330  is performed. 
     Meanwhile, in step S 1128 , after the defrost heater  330  is temporarily turned off, when the change rate ΔT of the temperature exceeds the second reference value ref 2 , the controller  310  determines a pulse operation mode end condition is met. When the pulse operation mode end condition is met (S 1130 ), the controller  310  ends the pulse operation mode and controls the heater to be turned off (S 1140 ). 
     The pulse operation mode end condition may correspond to the pulse operation mode time point. 
     For example, the pulse operation mode end time point may be a time at which the temperature detected by the temperature sensor  320  falls below the phase-change temperature Trf 1 . 
     As another example, the pulse operation mode end time point may be an end time point of the defrosting operation or an end time point of the heater operation mode. 
     Meanwhile, when the defrosting operation start time point To arrives, the controller  310  controls to perform the defrost operation mode Pdf and controls to perform the continuous operation mode Pona in which the defrost heater  330  is continuously turned on and the pulse operation mode Ponb in which the defrost heater  330  is repeatedly turned on and off based on the defrost operation mode Pdf, and in response to performing the pulse operation mode Ponb, the controller controls the defrost heater  330  to be turned on and off based on the change rate ΔT of the temperature detected by the temperature sensor  320 . Accordingly, since defrosting may be performed based on the change rate ΔT of the temperature, it is possible to improve defrost efficiency and power consumption. 
     In particular, since defrosting is performed according to the actual amount of frost ICE of the evaporator  122 , it is possible to improve defrost efficiency and power consumption. 
     Meanwhile, the controller  310  may be configured to perform the continuous operation mode Pona or the pulse operation mode Ponb based on the change rate ΔT of the temperature detected by the temperature sensor  320 . Accordingly, it is possible to improve the defrosting efficiency and power consumption. 
     Meanwhile, the controller  310  may be configured to operate the heater with power inversely proportional to the change rate ΔT of the temperature detected by the sensor during the pulse operation mode Ponb. Accordingly, it is possible to improve the defrosting efficiency and power consumption. 
     Meanwhile, the controller  310  may be configured to decrease a period of performing the defrost operation mode Pdf as the number of opening times the cooling compartment door increases. Accordingly, it is possible to improve the defrosting efficiency and power consumption. 
       FIG.  12 A  is a diagram showing a temperature waveform of the evaporator when there is a large amount of frost formation. 
     In  FIG.  12 A , (a), CVma represents a temperature change waveform in response to the defrost heater being operated only in the continuous operation mode, and CVmb represents a temperature change waveform in response to the defrost heater being operated by mixing the continuous operation mode and the pulse operation mode. 
     According to CVma, the defrost heater  330  may be continuously turned on, and may be turned off at a time point Tmg, as shown in (b) of  FIG.  12 A . 
     According to CVmb, as shown in (c) of  FIG.  12 A , the defrost heater  330  is continuously turned on during a Tma period and turned off during Tma and Tmb, during Tmc and Tmd, during Tme and Tmf, and during Tmg and Tmh, and the defrost heater  330  is turned on during Tmb and Tmc, during Tmd and Tme, during Tmf and Tmg, and during Tmh and Tmi. 
     That is, from Tma to Tmi, the defrost heater  330  operates in the pulse operation mode. 
     Meanwhile, the controller  310  controls the defrost heater  330  to be continuously turned on based on the continuous operation mode Pona, and in the ON state of the defrost heater  330 , when the change rate ΔT of the ambient temperature of the evaporator  122  detected by the temperature sensor  320  is equal to or greater than the first reference value ref 1 , the controller  310  may enter the pulse operation mode Ponb and control the defroster heater  330  to be turned off. Accordingly, it is possible to improve the defrosting efficiency and power consumption. 
     Meanwhile, when the defrost heater  330  is turned off during the pulse operation mode Ponb and the change rate ΔT of the temperature around the evaporator  122  is equal to or less than the second reference value ref 2  less than the first reference value ref 1 , the controller  310  may control the defrost heater  330  to be turned on. Accordingly, it is possible to improve the defrosting efficiency and power consumption. 
     Meanwhile, when the defrost heater  330  is turned on during the pulse operation mode Ponb and the change rate ΔT of the temperature around the evaporator  122  is equal to or greater than the first reference value ref 1 , the controller  310  may control the defrost heater  330  may to be turned on. Accordingly, it is possible to improve the defrosting efficiency and power consumption. 
     Meanwhile, the controller  310  may control the defrost heater  330  to be continuously turned on based on the continuous operation mode Pona, and based on the pulse operation mode Ponb, the controller  310  may repeatedly turned on and off the defrost heater  320  so that the change rate ΔT of the temperature around the evaporator  122  may be between the first reference value ref 1  and the second reference value ref 2 . Accordingly, it is possible to improve the defrosting efficiency and power consumption. 
       FIG.  12 B  is a diagram showing a temperature waveform of the evaporator when the amount of frost formation is less than that of  FIG.  12 A . 
     In (a) of  FIG.  12 B , CVna represents a temperature change waveform in response to the defrost heater being operated only in the continuous operation mode, and CVnb represents a temperature change waveform in response to the defrost heater being operated by mixing the continuous operation mode and the pulse operation mode. 
     According to CVna, the defrost heater  330  may be continuously turned on and may be turned off at a time point Tng, as shown in (b) of  FIG.  12 B . 
     According to CVnb, as shown in (c) of  FIG.  12   b   , the defrost heater  330  is continuously turned on during a period of Tna, and the defrost heater  330  is turned off during Tna and Tnb, during Tnc and Tnd, during Tne and Tnf, and during Tng and Tnh, and turned on during Tnb and Tnc, during Tnd and Tne, during Tnf and Tng, and during Tnh and Tni. 
     That is, from Tna to Tni, the defrost heater  330  operates in the pulse operation mode. 
       FIG.  13    is a view showing a region requiring cooling power supply and a region requiring defrosting according to temperatures of the refrigerating compartment and the freezer compartment. 
     Referring to the drawing, the horizontal axis may indicate a temperature of the refrigerating compartment, and the vertical axis may indicate a temperature of the freezer compartment. 
     When a temperature is equal to or lower than a reference temperature of the freezer compartment refma, it may indicate that a freezing capacity is sufficient, and when the temperature is equal to or lower than a reference temperature of the refrigerating compartment refmb, it may indicate that cooling capacity of the refrigerating compartment is sufficient. 
     An Arma region in the drawing is a region in which freezing capacity of the freezer compartment and cooling capacity of the refrigerating compartment are sufficient, and may be a region requiring defrosting. 
     Accordingly, when the defrosting required region is satisfied based on the temperature of the refrigerating compartment and the freezer compartment, the controller  310  may be configured to perform the continuous operation mode and the pulse operation mode described above. In particular, ON/OFF of the defrost heater  330  in the pulse operation mode may be controlled based on a temperature change rate around the evaporator  122 . 
     Meanwhile, the Armb region in the drawing may be a region in which both cooling power of the freezer compartment and cooling power of the refrigerating compartment are insufficient, and may be a cooling power supply requiring region requiring cooling power supply. 
     Accordingly, the controller  310  may control supply of cooling power. For example, a compressor may be operated or a thermoelectric element may be operated to control supply of cooling power. 
       FIG.  14    is a flowchart illustrating a method of operating a defrost heater according to another embodiment of the present disclosure, and  FIGS.  15 A to  15 D  are diagrams referenced in the description of  FIG.  14   . 
     First, referring to  FIG.  14   , the controller  310  of the refrigerator  100  according to an embodiment of the present disclosure determines whether a defrosting operation start time point arrives for defrosting (S 610 ). 
     For example, the controller  310  of the refrigerator  100  may determine whether a defrosting operation start time point arrives, while performing the normal cooling operation mode Pga. The defrosting operation start time point may vary according to a defrost cycle. 
     Meanwhile, when a defrosting operation start condition is satisfied, for example, in response to a defrosting operation start time point arriving, the controller  310  of the refrigerator  100  may end the normal cooling operation mode and control to perform the defrost operation mode Pdf. 
     Meanwhile, the defrost operation mode Pdf may include a pre-defrost cooling mode Pbd, a heater operation mode PddT, and a post-defrost cooling mode pbf. 
     Meanwhile, the heater operation mode PddT may include a continuous operation mode Pona in which the defrost heater  330  is continuously turned on, and a pulse operation mode Ponb in which the defrost heater  330  is repeatedly turned on and off. 
     Meanwhile, the controller  310  of the refrigerator  100  may control the defrost heater  330  to be continuously turned on based on the heater operation mode PddT in the defrost operation mode Pdf (S 615 ). 
     In particular, the controller  310  may control the defrost heater  330  to be continuously turned on based on the continuous operation mode Pona in the heater operation mode PddT. 
     Next, the controller  310  of the refrigerator  100  may control the pulse operation mode Ponb, in which the defrost heater  330  is repeatedly turned on and off, to be performed by a heater pulse after the defrost heater  330  is continuously turned on (S 620 ). 
     Meanwhile, while performing the pulse operation mode Ponb, the controller  310  may determine whether the return condition to the continuous operation mode is satisfied (S 623 ), and if so, control the continuous operation mode to be performed again. 
     For example, when the switching element RL of  FIG.  7 A  is continuously turned on and off, the possibility of loss of the switching element RL may increase. Accordingly, the controller  310  may control the pulse operation mode to end, and the continuous operation mode to be performed again. 
     Accordingly, even in the pulse operation mode Ponb, when the defrosting of the frost is not smoothly performed, the defrosting may be stably performed. 
     Next, the controller  310  of the refrigerator  100  determines whether it is the pulse operation mode end time point (S 630 ), and if so, turns off the defrost heater  330  (S 640 ). 
     For example, the pulse operation mode end point time may be a time point at which the temperature detected by the temperature sensor  320  falls below the phase change temperature Trf 1 . 
     As another example, the pulse operation mode end time point may be a defrost operation end time point or a heater operation mode end time point. 
     Meanwhile, without determining the return condition to the continuous operation mode in step  623 , after performing the pulse operation mode Ponb, it is also possible to re-perform the continuous operation mode Ponc. 
     For example, the controller  310  may control the continuous operation mode Ponc to be performed again after performing the pulse operation mode Ponb for stable defrosting. Accordingly, it is possible to improve the defrosting efficiency and reduce the power consumption. In particular, since the defrosting is performed according to the amount of frost of the actual evaporator, it is possible to improve defrosting efficiency and power consumption. 
     Meanwhile, while performing the pulse operation mode Ponb in step  623 , a method of determining whether the return condition to the continuous operation mode is satisfied, various examples are possible. 
     For example, when the value related to the temperature detected by the temperature sensor  320  does not reach the reference value while performing the pulse operation mode Ponb, the controller  310  may determine that the defrosting is not smooth, and control the continuous operation mode Ponc to be performed for quick defrosting. Accordingly, it is possible to improve the defrosting efficiency while stably performing the defrosting. 
     Meanwhile, when the temperature detected by the temperature sensor  320  is below the reference temperature while performing the pulse operation mode Ponb, the controller  310  may control the continuous operation mode Ponc to be performed for quick defrosting. Accordingly, it is possible to improve the defrosting efficiency while stably performing the defrosting. 
     Meanwhile, when the change rate □T of the temperature detected by the temperature sensor  320  is below the reference temperature □T while performing the pulse operation mode Ponb, the controller  310  may determine that the defrosting is not smooth, and control the continuous operation mode Ponc to be performed for quick defrosting. Accordingly, it is possible to improve the defrosting efficiency while stably performing the defrosting. 
     Meanwhile, when the temperature detected by the temperature sensor  320  does not reach the target temperature within a certain time while performing the pulse operation mode Ponb, the controller  310  may determine that the defrosting is not smooth, and control the continuous operation mode Ponc to be performed for quick defrosting. Accordingly, it is possible to improve the defrosting efficiency while stably performing the defrosting. 
     Meanwhile, when a sum Ma+Mb+ . . . Mn of the ON time of the defrost heater  330  is above the reference level while performing the pulse operation mode Ponb, the controller  310  may determine that the defrosting is not smooth, and control the continuous operation mode Ponc to be performed for quick defrosting. Accordingly, it is possible to improve the defrosting efficiency while stably performing the defrosting. 
     Meanwhile, when a sum of the number of opening times of turn on of the defrost heater  330  is above the reference level while performing the pulse operation mode Ponb, the controller  310  may determine that the defrosting is not smooth, and control the continuous operation mode Ponc to be performed for quick defrosting. Accordingly, it is possible to improve the defrosting efficiency while stably performing the defrosting. 
     Meanwhile, when the sum Ma+Mb+ . . . , Mn of the ON time of the defrost heater  330  is greater than the sum Mo of the continuous ON time of the defrost heater  330  of the continuous operation mode while performing the pulse operation mode Ponb, the controller  310  may determine that the defrosting is not smooth, and control the continuous operation mode Ponc to be performed for quick defrosting. Accordingly, it is possible to improve the defrosting efficiency while stably performing the defrosting. 
     Meanwhile, when the open period is greater than or equal to the allowable period while performing the pulse operation mode Ponb, the controller  310  may determine that the defrosting is not smooth, and control the continuous operation mode Ponc to be performed for quick defrosting. Accordingly, it is possible to improve the defrosting efficiency while stably performing the defrosting. 
     Meanwhile, when the humidity in the refrigerator is greater than or equal to the reference humidity while performing the pulse operation mode Ponb, the controller  310  may determine that the defrosting is not smooth, and control the continuous operation mode Ponc to be performed for quick defrosting. Accordingly, it is possible to improve the defrosting efficiency while stably performing the defrosting. 
       FIG.  15 A  is a diagram illustrating an example of a pulse waveform indicating an operation of a defrost heater according to an embodiment of the present disclosure. 
     Referring to the drawing, a horizontal axis of a pulse waveform Pshm may indicate time, and a vertical axis may indicate a level. 
     When a defrosting operation start time point To arrives while performing the normal cooling operation mode Pga, the controller  310  of the refrigerator  100  may control the normal cooling operation mode Pga to end and the defrost operation mode Pdf to be performed. 
     The defrost operation mode Pdf may include the pre-defrost cooling mode Pbd between Toa and Ta, the heater operation mode PddT between Ta and Td, and the post-defrost cooling mode pbf between Td and Te. 
     Meanwhile, after the defrost operation mode Pdf ends, the normal cooling operation mode Pgb is performed again. 
     The defrost heater  330  is turned off in the normal cooling operation mode Pga and the normal cooling operation mode Pgb. 
     Meanwhile, the defrost heater  330  may be turned off in the pre-defrost cooling mode Pbd and the post-defrost cooling mode pbf of the defrost operation mode Pdf. 
     Meanwhile, the defrost heater  330  may be continuously turned on in the continuous operation mode Pona in the heater operation mode PddT, may repeat the turn on and off in the pulse operation mode Ponb in the heater operation mode PddT, and may be continuously turned on in the continuous operation mode Ponc in the heater operation mode PddT. 
     Unlike  FIG.  8 A , according to  FIG.  15 A , after the pulse operation mode Ponb, there is a difference in that the continuous operation mode Ponc is further performed. 
     As described in the description of  FIG.  14   , when the return condition to the continuous operation mode Ponc of the defrost heater  330  arrives while performing the pulse operation mode Ponb, the controller  310  may control the continuous operation mode Ponc to be further performed. 
     The continuous operation mode Pona may be performed between Ta and Tb, and the pulse operation mode Ponb may be performed between Tb and Tc. 
     An additional continuous operation mode Ponc may be performed between Tcm and Td. In the drawing, it is exemplified that the period during which the additional continuous operation mode Ponc is performed is Mz. 
     By this additional continuous operation mode Ponc, it is possible to improve the defrosting efficiency while stably performing the defrosting. 
       FIG.  15 B  is a diagram illustrating another example of a pulse waveform indicating an operation of a defrost heater according to an embodiment of the present disclosure. 
     A pulse waveform Pshn of  FIG.  15 B  is similar to the pulse waveform Pshm of  FIG.  15 A , but the additional continuous operation mode Ponc is different in that it is performed between Tcm and Tcn. 
     In the drawing, it is exemplified that My, which is the duration of the additional continuous operation mode Ponc, is less than Mz of  FIG.  15 A . 
     The controller  310  may vary the period during which the continuous operation mode Ponc is performed based on the difference between the value related to the temperature detected by the temperature sensor  320  and the reference value. For example, as the difference decreases, it is possible to control the period during which the continuous operation mode Ponc is performed to decrease. By this additional continuous operation mode Ponc, it is possible to improve the defrosting efficiency while stably performing the defrosting. 
     Meanwhile, the controller  310  may vary the period during which the continuous operation mode Ponc is performed based on the difference between the temperature detected by the temperature sensor  320  and the reference temperature while performing the pulse operation mode Ponb. For example, as the difference decreases, it is possible to control the period during which the continuous operation mode Ponc is performed to decrease. 
     Meanwhile, the controller  310  may vary the period during which the continuous operation mode Ponc is performed based on the difference between the change rate □T of the temperature detected by the temperature sensor  320  and the change rate □T of the reference temperature while performing the pulse operation mode Ponb. For example, as the difference decreases, it is possible to control the period during which the continuous operation mode Ponc is performed to decrease. 
     Meanwhile, the controller  310  may vary the period during which the continuous operation mode Ponc is performed based on the difference between the temperature detected by the temperature sensor  320  and the target temperature while performing the pulse operation mode Ponb. For example, as the difference decreases, it is possible to control the period during which the continuous operation mode Ponc is performed to decrease. 
     Meanwhile, the controller  310  may vary the period during which the continuous operation mode Ponc is performed based on the difference between the reference level and the sum Ma+Mb+ . . . Mn of the on time of the defrost heater  330  while performing the pulse operation mode Ponb. For example, as the difference decreases, it is possible to control the period during which the continuous operation mode Ponc is performed to decrease. 
     Meanwhile, the controller  310  may vary the period during which the continuous operation mode Ponc is performed based on the difference between the reference number of opening times and the sum of the number of opening times of turn on of the defrost heater  330  while performing the pulse operation mode Ponb. For example, as the difference decreases, it is possible to control the period during which the continuous operation mode Ponc is performed to decrease. 
     Meanwhile, the controller  310  may vary the period during which the continuous operation mode Ponc is performed based on the difference between the sum Mo of the continuous ON time and the sum Ma+Mb+ . . . Mn of the ON time of the defrost heater  330  while performing the pulse operation mode Ponb. For example, as the difference decreases, it is possible to control the period during which the continuous operation mode Ponc is performed to decrease. 
     Meanwhile, the controller  310  may vary the period during which the continuous operation mode Ponc is performed based on the difference between the humidity in the refrigerator and the reference humidity while performing the pulse operation mode Ponb. For example, as the difference decreases, it is possible to control the period during which the continuous operation mode Ponc is performed to decrease. 
       FIG.  15 C  is a diagram illustrating another example of a pulse waveform indicating an operation of a defrost heater according to an embodiment of the present disclosure. 
     A pulse waveform Psho of  FIG.  15   c    is similar to the pulse waveform (Pshm) of  FIG.  15 A , but there is a difference in that after the pulse operation mode Ponb, an additional continuous operation mode Ponab and an additional pulse operation mode ponbb are further performed. 
     In the drawing, it is exemplified that after Tc, an additional continuous operation mode Ponab is performed between Ta′ and Tb′, and an additional pulse operation mode ponbb is performed between Tb′ and Tc′. 
     Meanwhile, the duration of the additional continuous operation mode Ponab is preferably less than the duration of the continuous operation mode Pona. 
     Meanwhile, the duration of the additional pulse operation mode ponbb is preferably less than the duration of the continuous operation mode Ponb. Accordingly, it is possible to improve the defrosting efficiency while stably performing the defrosting. 
       FIG.  16    is a flowchart illustrating a defrosting method according to another embodiment of the present disclosure, and  FIGS.  17 A to  17 D  are diagrams referenced in the description of  FIG.  16   . 
     First, referring to  FIG.  16   , the controller  310  of the refrigerator  100  according to an embodiment of the present disclosure determines whether a defrosting operation start time point arrives for defrosting (S 610 ). 
     For example, the controller  310  of the refrigerator  100  may determine whether it is the defrosting operation start time point, while performing the normal cooling operation mode Pga. The defrosting operation start time point may vary according to a defrost cycle. 
     Meanwhile, when a defrosting operation start condition is satisfied, for example, in response to a defrosting operation start time point arriving, the controller  310  of the refrigerator  100  may end the normal cooling operation mode and control the defrost operation mode Pdf to be performed. 
     Meanwhile, the defrost operation mode Pdf may include a pre-defrost cooling mode Pbd, a heater operation mode PddT, and a post-defrost cooling mode pbf. 
     Meanwhile, the heater operation mode (PddT) may include a continuous operation mode Pona in which the defrost heater  330  is continuously turned on, and a pulse operation mode Ponb in which the defrost heater  330  is repeatedly turned on and off. 
     Meanwhile, the controller  310  of the refrigerator  100  may control the defrost heater  330  to be continuously turned on based on the continuous operation mode Pona in the heater operation mode PddT of the defrost operation mode Pdf (S 615 ). 
     Next, the controller  310  of the refrigerator  100  determines whether the temperature detected by the temperature sensor  320  reaches a first temperature Tm 1  within a first period Pm 1  while performing the continuous operation mode Pona (S 1616 ). 
     If so, the controller  310  of the refrigerator  100  may control the pulse operation mode, in which the defrost heater  330  is repeatedly turned on and off, to be performed by the heater pulse after the defrost heater  330  is continuously turned on (S 1620 ). 
     (a) of  FIG.  17 A  illustrates an example of a temperature waveform Tcva around the evaporator  122 , and (b) of  FIG.  17 A  illustrates an example of an operating waveform Psh of the defrost heater  330 . 
     Referring to the drawing, based on the heater operation mode Pon, the continuous operation mode (Pona) is performed during the Pm 1  period between Ta and Tb. 
     Meanwhile, when the temperature detected by the temperature sensor  320  reaches the first temperature Tm 1  within the first period Pm 1 , or as illustrated in the drawing, at Tb, which is the end time of the first period Pm 1 , while performing the continuous operation mode Pona, the controller  310  of the refrigerator  100  may control the pulse operation mode Ponb to be performed after Tb. 
     That is, after the time Tb, the controller  310  of the refrigerator  100  may control the defrost heater  330  to be turned off during the period pf 1  and then the defrost heater  330  to be repeatedly turned on and off. 
     As such, when the amount of frost formed on the evaporator  122  is small, after the continuous operation mode Pona is performed, by controlling the pulse operation mode Ponb to be performed, it is possible to improve the defrosting efficiency and reduce the power consumption. 
     Next, the controller  310  of the refrigerator  100  determines whether it is the pulse operation mode end time point (S 1630 ), and if so, turns off the defrost heater  330  (S 1640 ). 
     For example, the pulse operation mode end point time may be a time point at which the temperature detected by the temperature sensor  320  falls below the phase change temperature Trf 1 . 
     As another example, the pulse operation mode end time point may be a defrost operation end time point or a heater operation mode end time point. 
     Meanwhile, in step S 1616 , when the temperature detected by the temperature sensor  320  does not reach the first temperature Tm 1  within the first period Pm 1  while performing the continuous operation mode Pona, step S 1617  may be performed. 
     That is, when the temperature detected by the temperature sensor  320  does not reach a first temperature Tm 1  within the first period Pm 1  while performing the continuous operation mode Pona, the controller  310  of the refrigerator  100  determines whether the first temperature Tm 1  arrival period is greater than or equal to the second period (S 1617 ). 
     If so, it is determined that the amount of frost formed on the evaporator  122  is large, and the continuous operation mode Pona may be controlled to be continuously performed (S 1623 ). 
     (b) of  FIG.  17 A  illustrates another example of a temperature waveform Tcvb around the evaporator  122 , and (b) of  FIG.  17 B  illustrates another example of an operating waveform Pshb 1  of the defrost heater  330 . 
     Referring to the drawing, based on the heater operation mode Pon, the continuous operation mode Pona is performed during the period Pm 1  between Ta and Tb. 
     Meanwhile, when the temperature detected by the temperature sensor  320  does not reach a first temperature Tm 1  within the first period Pm 1  while performing the continuous operation mode Pona 1 , the controller  310  of the refrigerator  100  determines whether the first temperature Tm 1  arrival period is greater than or equal to the second period pm 2 . 
     In the drawing, it is exemplified that the temperature detected by the temperature sensor  320  reaches the end time of the second period pm 2 . 
     Accordingly, the controller  310  of the refrigerator  100  may control the continuous operation mode Pona 1  to be performed during the periods Ta and Tc. 
     In addition, the controller  310  of the refrigerator  100  may control that, during the heater operation mode Pon, only the continuous operation mode Pona 1  is performed and the pulse operation mode (Ponb) is not performed. Accordingly, when the amount of frost formed on the evaporator  122  is large, it is possible to control to efficiently perform defrosting. 
     Meanwhile, unlike the drawing, the controller  310  of the refrigerator  100  may control the continuous operation mode Pona 1  to be performed during a predetermined period after the period Tc. 
     Meanwhile, after the continuous operation mode Pona 1  of  FIG.  17 B , step S 1622  may be performed again. 
     Meanwhile, in step  1617 , when the first temperature Tm 1  arrival period of the temperature detected by the temperature sensor  320  is not greater than or equal to the second period but is between the first period and the second period while performing the continuous operation mode Pona, step S 1618  may be performed 
     That is, the controller  310  of the refrigerator  100  determines whether the temperature detected by the temperature sensor  320  reaches the second temperature Tm 2  between the first period and the second period while performing the continuous operation mode Pona (S 1618 ). If so, the defrost heater is turned off (S 1619 ), and the defrost heater may be controlled to be turned on and off based on the pulse operation mode (S 1621 ). 
     (a) of  FIG.  17 C  illustrates another example of a temperature waveform Tcvc around the evaporator  122 , and (b) of  FIG.  17 C  illustrates another example of an operating waveform Pshb 2  of the defrost heater  330 . 
     Referring to the drawing, based on the heater operation mode Pon 2 , the continuous operation mode is performed during the period Pm 1  between Ta and Tb. 
     Meanwhile, when the temperature detected by the temperature sensor  320  does not reach the first temperature Tm 1  within the first period Pm 1  while performing the continuous operation mode, the controller  310  of the refrigerator  100  determines whether the first temperature Tm 1  arrival period is greater than or equal to the second period pm 2  or between the first period pm 1  and the second period pm 2 . 
     In the drawing, it is exemplified that the temperature detected by the temperature sensor  320  reaches the first temperature Tm 1  in Tk between the first period pm 1  and the second period pm 2 , and the temperature detected by the temperature sensor  320  reaches the second temperature Tm 2  in Tm between the first period pm 1  and the second period pm 2 . 
     Accordingly, the controller  310  of the refrigerator  100  may be configured to perform the continuous operation mode until the time point Tm at which a temperature reaches the second temperature Tm 2   
     In addition, after the first OFF of the defrost heater  330  after the time point Tm, the pulse operation mode Ponb 2  may be controlled to be performed. 
     Meanwhile, as the continuous operation mode continues, in consideration of the heat of the switching element RL of  FIG.  7 A , tit is preferable that the first OFF period psf 2  of the defrost heater  330  after the time point Tm is greater than the OFF period during the On and off of the pulse operation mode Ponb 2 . 
     Meanwhile, it is preferable that the first OFF period psf 2  of the defrost heater  330  after the time point Tm when the pulse operation mode Ponb 2  is performed is greater than the first OFF period pof 1  of the defrost heater  330  after the time point Tb when the pulse operation mode Ponb of  FIG.  17 A  is performed. Accordingly, it is possible to protect the switching element RL of  FIG.  7 A  and the like. 
     Meanwhile, according to  FIGS.  17 A to  17 C , the controller  310  may be configured to, as the change rate of the temperature detected by the temperature sensor  320  decreases while performing the continuous operation mode Pon, increase a delay of the start time point of the pulse operation mode Ponb. 
     That is, compared to  FIG.  17 A , in the case of  FIG.  17 C , the change rate of the temperature detected by the temperature sensor  320  is smaller, and accordingly, the start time point of the pulse operation mode is further delayed. 
     Meanwhile, compared to  FIG.  17 C , in the case of  FIG.  17 B , the change rate of the temperature detected by the temperature sensor  320  is smaller, and accordingly, the pulse operation mode may not start at all. 
     Meanwhile, the controller  310  may be configured to, as the change rate of the temperature detected by the temperature sensor decreases while performing the continuous operation mode Pona, increase the duration of the pulse operation mode Pona. 
     For example, compared to  FIG.  17 A , in the case of  FIG.  17 C , the change rate of the temperature detected by the temperature sensor  320  is smaller, and accordingly, the duration of the continuous operation mode is a period between Ta and Tm, and is greater than the period between Ta and Tb of  FIG.  17 A . 
     Meanwhile, compared to  FIG.  17 C , in the case of  FIG.  17 B , the change rate of the temperature detected by the temperature sensor  320  is smaller, and accordingly, the duration of the continuous operation mode is a period between Ta and Tc, and is greater than the period between Ta and Tm of  FIG.  17 B . Accordingly, it is possible to efficiently perform the defrosting. 
     Meanwhile, unlike  FIGS.  17 A to  17 C , when the temperature detected by the temperature sensor  320  reaches the first temperature Tm 1  between the first period Pm 1  and the period Pm 2  while performing the continuous operation mode, the controller  310  may control the pulse operation mode Ponb to be performed after the defrost heater  310  is turned off without determining whether the second period Pm 2  arrives. 
     The controller  310  may be configured to control the OFF period of the defrost heater  310  before the pulse operation mode Ponb is performed when the temperature detected by the temperature sensor  320  reaches the first temperature Tm 1  between the first period Pm 1  and the second period Pm 2  to be greater than the OFF period of the defrost heater  310  before the pulse operation mode Ponb is performed when the temperature detected by the temperature sensor  320  reaches the first temperature Tm 1  within the first period Pm 1 . Accordingly, it is possible to efficiently perform the defrosting. 
     In the refrigerator according to the present disclosure, the configuration and the method of the embodiments as described above are not restrictively applied. Rather, all or some of the embodiments may be selectively combined with each other so that the embodiments may be variously modified. 
     In addition, although the preferred embodiments of the present disclosure have been illustrated, the present disclosure is not limited to the specific embodiments described above, and can be variously modified by those skilled in the art to which the present disclosure pertains without departing from the gist of the present disclosure claimed in the claims, and these modifications should not be understood individually from the technical ideas or prospects of the present disclosure. 
     INDUSTRIAL APPLICABILITY 
     The present disclosure can be applied to a refrigerator, and more particularly, can be applied to a refrigerator capable of improving defrosting efficiency and power consumption.