Patent Publication Number: US-2021164152-A1

Title: Laundry treatment machine

Description:
BACKGROUND OF THE DISCLOSURE 
     1. Field of the Disclosure 
     The present disclosure relates to a laundry treatment machine, and more particularly, to a laundry treatment machine capable of changing a dewatering entry period after drainage is completed, based on a lift. 
     In addition, the present disclosure relates to a laundry treatment machine capable of shortening a dewatering entry period after drainage is completed. 
     In addition, the present disclosure relates to a laundry treatment machine capable of minimizing a decrease in drainage performance according to installation conditions. 
     In addition, the present disclosure relates to a laundry treatment machine capable of shortening a drainage time. 
     In addition, the present disclosure relates to a laundry treatment machine capable of being driven in a sensorless manner. 
     2. Description of the Related Art 
     A drain pump driving apparatus drives a motor during drainage to discharge water introduced into a water introduction part to the outside. 
     In order to drive a drain pump, the motor is generally driven in a constant speed operation using an input alternating current (AC) power. 
     For example, when a frequency of the input AC power is 50 Hz, the motor for the drain pump rotates at 3000 rpm, and when the frequency of the input AC power is 60 Hz, the motor for the drain pump rotates at 3600 rpm. 
     In this way, when the drain pump is operated at a constant speed by the input AC power, when the laundry treatment machine performs dewatering after the completion of the drainage, the motor driven in the constant speed operation is severely heated, and thus the motor for the drain pump is to be stopped for a considerable period, and then driven, and accordingly, in the laundry treatment machine, there is a limitation in that the entire operation period as well as the dewatering period thereof is prolonged. 
     Korean Patent Publication No. 10-2006-0122562 discloses that speed control is performed by operating a pump in a constant-speed mode or in an inverter mode after checking a current water-pumped amount using a pressure sensor and a water level sensor. 
     In addition, Japanese Patent Publication No. 2004-135491 discloses details of speed control according to a speed command for driving a motor. 
     For the speed control, however, it is required that a power supplied to the pump be changed according to a change in the level of the lift, and accordingly, a converter need to output a wide range of power levels. As a result, the stability of the converter is reduced. 
     SUMMARY 
     An object of the present disclosure is to provide a laundry treatment machine capable of changing a dewatering entry period after drainage is completed based on a lift. 
     Another object of the present disclosure is to provide a laundry treatment machine capable of shortening a dewatering entry period after drainage is completed. 
     Still another object of the present disclosure is to provide a laundry treatment machine capable of driving a converter stably even if a lift is changed during drainage. 
     Still another object of the present disclosure is to provide a laundry treatment machine capable of minimizing a decrease in drainage performance according to installation conditions. 
     Still another object of the present disclosure is to provide a laundry treatment machine capable of shortening a drainage time. 
     Still another object of the present disclosure is to provide a laundry treatment machine capable of being driven in a sensorless manner. 
     According to an embodiment of the present disclosure, a laundry treatment machine includes a controller configured to start dewatering after a first period from completion of drainage when a lift is at a first level, and to start the dewatering after a second period from the completion of the drainage when the lift is at a second level greater than the first level, wherein the second period is longer than the first period, wherein the lift is a difference between a water level of the water introduction part through which water flows into the drain pump and a water level of a water discharge part through which the water is discharged out of the drain pump. 
     In the laundry treatment machine according to an embodiment of the present disclosure, the controller may be configured to perform the dewatering after the first period when the water level in the washing tub is equal to or less than a first water level and the lift is at the first level, during the drainage before the dewatering. 
     In the laundry treatment machine according to an embodiment of the present disclosure, the controller may be configured to perform the dewatering after the first period when a level of the output current is equal to or less than a reference level, the water level in the washing tub is equal to or less than a first water level, and the lift is at the first level. 
     In the laundry treatment machine according to an embodiment of the present disclosure, the controller may be configured to drive the motor with a first power when the lift is at the first level during the drainage, and the controller may be configured to perform the dewatering after the first period when a power supplied to the motor is out of a first allowable range based on the first power. 
     In the laundry treatment machine according to an embodiment of the present disclosure, the controller may be configured to drive the motor with the first power when the lift is at the second level during the drainage, and the controller may be configured to perform the dewatering after the second period when the power supplied to the motor is out of the first allowable range based on the first power. 
     In the laundry treatment machine according to an embodiment of the present disclosure, when the lift is at the first level during the drainage, the controller may be configured to drive the motor with a power within the first allowable range based on the first power, without decreasing over time, from a first time point after the drainage is started until the completion of the drainage, and when the lift is at the second level, the controller may be configured to drive the motor with a power within the first allowable range based on the first power, without decreasing over time, from the first time point until the completion of the drainage. 
     In the laundry treatment machine according to an embodiment of the present disclosure, when the power supplied to the motor reaches the first power, the controller may control a speed of the motor to be constant. 
     In the laundry treatment machine according to an embodiment of the present disclosure, when the speed of the motor is increased, the controller may control the output current to be constant. 
     In the laundry treatment machine according to an embodiment of the present disclosure, the controller may be configured to decrease a water-pumped amount by an operation of the drain pump, during the drainage as the level of the lift increases. 
     In the laundry treatment machine according to an embodiment of the present disclosure, the controller may control the decrease in the water-pumped amount by the operation of the drain pump according to the increase in the level of the lift to be smaller when the power control is performed with respect to the motor than when speed control is performed with respect to the motor. 
     In the laundry treatment machine according to an embodiment of the present disclosure, the controller may control the power supplied to the motor, during the drainage, to be constant without decreasing over time. 
     In the laundry treatment machine according to an embodiment of the present disclosure, the controller may be configured to perform the power control when the drainage is started and to terminate the power control when a residual water level is reached. 
     In the laundry treatment machine according to an embodiment of the present disclosure, the controller may calculate a power based on the output current and the DC terminal voltage and output a voltage command value based on the calculated power, and a second controller may output a switching control signal to the inverter based on the voltage command value. 
     In the laundry treatment machine according to an embodiment of the present disclosure, the controller may be configured to increase the voltage command value and a duty of the switching control signal as level of the output current decreases. 
     In the laundry treatment machine according to an embodiment of the present disclosure, the second controller may output voltage information of the motor to the controller based on the voltage command value or the switching control signal. 
     In the laundry treatment machine according to an embodiment of the present disclosure, the controller may include: a speed calculator to calculate a speed of the motor based on voltage information of the motor; a power calculator to calculate the power based on the output current and the DC terminal voltage; a power controller to output a speed command value based on the calculated power and a power command value; and a speed controller to output the voltage command value based on the speed command value and the speed calculated by the speed calculator. 
     In the laundry treatment machine according to an embodiment of the present disclosure, the motor to drive the drain pump may include a brushless DC motor. 
     The laundry treatment machine according to an embodiment of the present disclosure may further include a DC terminal capacitor storing a DC power, and the output current detector may be disposed between the DC terminal capacitor and the inverter. 
     According to another embodiment of the present disclosure, a laundry treatment machine includes a controller to change a dewatering entry time point based on a level of a lift, when drainage is completed, wherein the lift is a difference between a water level of a water introduction part through which water flows into a drain pump and a water level of a water discharge part through which the water is discharged out of the drain pump. 
     In the laundry treatment machine according to an embodiment of the present disclosure, when a level of the lift is a first level, the controller may control the dewatering to be started at a first time point, and when the level of the lift is a second level greater than the first level, the controller may control the dewatering to be started at a second time point after the first time point. 
     In the laundry treatment machine according to an embodiment of the present disclosure, the controller may control power supplied to the motor, during the drainage, to be constant without decreasing over time. 
     In the laundry treatment machine according to an embodiment of the present disclosure, the controller may perform power control with respect to the motor when the drainage is started, and the controller may terminate the power control when a residual water level is reached. 
     Advantageous Effects 
     A laundry treatment machine according to an embodiment of the present disclosure includes a controller configured to start dewatering after a first period from completion of drainage when a lift is at a first level, and to start the dewatering after a second period from the completion of the drainage when the lift is at a second level greater than the first level, wherein the second period is longer than the first period, wherein the lift is a difference between a water level of the water introduction part through which water flows into the drain pump and a water level of a water discharge part through which the water is discharged out of the drain pump. In this way, it is possible to change the dewatering entry period after drainage is completed, based on the lift. In particular, it is possible to shorten the dewatering entry period after drainage is completed. 
     In the laundry treatment machine according to an embodiment of the present disclosure, the controller may be configured to perform the dewatering after the first period when the water level in the washing tub is equal to or less than a first water level and the lift is at the first level, during the drainage before the dewatering, and thus it is possible to shorten the dewatering entry period after the completion of the drainage. 
     In the laundry treatment machine according to an embodiment of the present disclosure, the controller may be configured to perform the dewatering after the first period when a level of the output current is equal to or less than a reference level, the water level in the washing tub is equal to or less than a first water level, and the lift is at the first level. Accordingly, the dewatering is performed based on the output current, and thus the dewatering entry period after the completion of the drainage can be shortened. 
     In the laundry treatment machine according to an embodiment of the present disclosure, the controller may be configured to drive the motor with a first power when the lift is at the first level during the drainage, and the controller may be configured to perform the dewatering after the first period when a power supplied to the motor is out of a first allowable range based on the first power. Accordingly, the dewatering is performed based on the power supplied to the motor, and thus the dewatering entry period after the completion of the drainage can be shortened. 
     In the laundry treatment machine according to an embodiment of the present disclosure, the controller may be configured to drive the motor with the first power when the lift is at the second level during the drainage, and the controller may be configured to perform the dewatering after the second period when the power supplied to the motor is out of the first allowable range based on the first power. In this way, it is possible to change the dewatering entry period after drainage is completed, based on the lift. 
     In the laundry treatment machine according to an embodiment of the present disclosure, when the lift is at the first level during the drainage, the controller may be configured to drive the motor with a power within the first allowable range based on the first power, without decreasing over time, from a first time point after the drainage is started until the completion of the drainage, and when the lift is at the second level, the controller may be configured to drive the motor with a power within the first allowable range based on the first power, without decreasing over time, from the first time point until the completion of the drainage. Accordingly, water pumping can be performed smoothly even if the lift is changed during the drainage. 
     In particular, since power control is performed to drive the motor with a constant power, the converter merely needs to supply the constant power. Thus, the stability of the converter can be improved. 
     In the laundry treatment machine according to an embodiment of the present disclosure, when the power supplied to the motor reaches the first power, the controller may control a speed of the motor to be constant. Since the power control is performed as described above, it is possible to minimize a decrease in drainage performance according to installation conditions. 
     In the laundry treatment machine according to an embodiment of the present disclosure, when the speed of the motor is increased, the controller may control the output current to be constant. Accordingly, the motor can be operated with a constant power. 
     In the laundry treatment machine according to an embodiment of the present disclosure, the controller may control the decrease in the amount of water pumped by the operation of the drain pump according to the increase in the level of the lift to be smaller when the power control is performed with respect to the motor than when speed control is performed with respect to the motor. Accordingly, when compared to the speed control, the power control makes it possible to set a greater range of lift levels, thereby increasing a freedom of installation. 
     In the laundry treatment machine according to an embodiment of the present disclosure, the controller may control the power supplied to the motor, during the drainage, to be constant without decreasing over time. Accordingly, a drainage time can be shortened. 
     In the laundry treatment machine according to an embodiment of the present disclosure, the controller may be configured to perform the power control when the drainage is started and to terminate the power control when a residual water level is reached. Accordingly, the drainage operation can be efficiently performed. 
     In the laundry treatment machine according to an embodiment of the present disclosure, the controller may calculate a power based on the output current and the DC terminal voltage and output a voltage command value based on the calculated power, and a second controller may output a switching control signal to the inverter based on the voltage command value. 
     In the laundry treatment machine according to an embodiment of the present disclosure, the controller may be configured to increase the voltage command value and a duty of the switching control signal as level of the output current decreases. Accordingly, the motor can be driven with a constant power. 
     In the laundry treatment machine according to an embodiment of the present disclosure, the controller may include: a speed calculator to calculate a speed of the motor based on voltage information of the motor; a power calculator to calculate the power based on the output current and the DC terminal voltage; a power controller to output a speed command value based on the calculated power and a power command value; and a speed controller to output the voltage command value based on the speed command value and the speed calculated by the speed calculator. Accordingly, the power control can be performed stably. 
     In the laundry treatment machine according to an embodiment of the present disclosure, the motor to drive the drain pump may include a brushless DC motor. Accordingly, the power control, rather than constant-speed control, can be implemented in a simple manner. 
     The laundry treatment machine according to an embodiment of the present disclosure may further include a DC terminal capacitor storing a DC power, and the output current detector may be disposed between the DC terminal capacitor and the inverter. Accordingly, the output current flowing in the motor can be detected through the output current detector in a simple manner. 
     A laundry treatment machine according to another embodiment of the present disclosure includes a controller to change a dewatering entry time point based on a level of a lift, when drainage is completed, wherein the lift is a difference between a water level of a water introduction part through which water flows into a drain pump and a water level of a water discharge part through which the water is discharged out of the drain pump. In this way, it is possible to change the dewatering entry period after drainage is completed, based on the lift. In particular, it is possible to shorten the dewatering entry period after drainage is completed. 
     In the laundry treatment machine according to an embodiment of the present disclosure, when a level of the lift is a first level, the controller may control the dewatering to be started at a first time point, and when the level of the lift is a second level greater than the first level, the controller may control the dewatering to be started at a second time point after the first time point. In this way, it is possible to change the dewatering entry period after drainage is completed, based on the lift. In particular, it is possible to shorten the dewatering entry period after drainage is completed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and other advantages of the present disclosure will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a perspective view illustrating a laundry treatment machine according to an embodiment of the present disclosure; 
         FIG. 2  is a side cross-sectional view of the laundry treatment machine of  FIG. 1 ; 
         FIG. 3  is an internal block diagram of the laundry treatment machine of  FIG. 1 ; 
         FIG. 4  illustrates an example of an internal block diagram of a drain pump driving apparatus of  FIG. 1 ; 
         FIG. 5  illustrates an example of an internal circuit diagram of the drain pump driving apparatus of  FIG. 4 ; 
         FIG. 6  is an internal block diagram of the main controller of  FIG. 5 ; 
         FIGS. 7A and 7B  are views illustrating various examples of a drain pipe connected to the drain pump of the laundry treatment machine of  FIG. 1 ; 
         FIGS. 8A to 8C  are graphs illustrating a relationship of the lift with the water-pumped amount, the output power, or the input power; 
         FIG. 9  is a flowchart showing an operation method of a drain pump driving apparatus according to an embodiment of the present disclosure; 
         FIGS. 10 to 17  are reference views for explaining the operation method of  FIG. 9 ; and 
         FIG. 18  is a perspective view illustrating a laundry treatment machine according to another embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made in detail to the preferred embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
     As used herein, the suffixes “module” and “unit” are added or used interchangeably to facilitate preparation of this specification and are not intended to suggest distinct meanings or functions. Accordingly, the terms “module” and “unit” may be used interchangeably. 
       FIG. 1  is a perspective view illustrating a laundry treatment machine according to an embodiment of the present disclosure, and  FIG. 2  is a side cross-sectional view illustrating the laundry treatment machine of  FIG. 1 . 
     Referring to  FIGS. 1 and 2 , the laundry treatment machine  100  according to an embodiment of the present disclosure conceptually includes a washing machine having fabric inserted therein for performing washing, rinsing and dewatering, or a dryer having wet fabric inserted therein. The washing machine will be mainly described below. 
     The washing machine  100  includes a casing  110  forming an outer appearance, operation keys for receiving various control commands from a user, and a control panel  115  equipped with a display for displaying information on the operating state of the washing machine  100  to provide a user interface, and a door  113  rotatably installed in the casing  110  to open and close an entrance hole through which the laundry enters and exits. 
     The casing  110  includes a body  111  for defining a space in which various components of the washing machine  100  can be accommodated and a top cover  112  provided at an upper side of the body  111  and forming a fabric entrance hole to allow the laundry to be introduced into an inner tub  122  therethrough. 
     The casing  110  is described as including the body  111  and the top cover  112 , but the casing  110  is not limited thereto as long as it forms the appearance of the washing machine  100 . 
     A support rod  135  is coupled to the top cover  112  which is one of the constituent elements of the casing  110 . However, the support rod  135  is not limited thereto and may be coupled to any part of the fixed portion of the casing  110 . 
     The control panel  115  includes operation keys  117  for controlling an operation state of the laundry treatment machine  100  and a display  118  disposed on one side of the operation keys  117  to display the operation state of the laundry treatment machine  100 . 
     The door  113  opens and closes a fabric entrance hole (not shown) formed in the top cover  112  and may include a transparent member such as reinforced glass to allow the inside of the body  111  to be seen. 
     The washing machine  100  may include a washing tub  120 . The washing tub  120  may include an outer tub  124  containing wash water and an inner tub  122  rotatably installed in the outer tub  124  to accommodate laundry. A balancer  134  may be provided at the upper portion of the washing tub  120  to compensate for unbalance amount generated when the washing tub  120  rotates. 
     Meanwhile, the washing machine  100  may include a pulsator  133  rotatably provided at a lower portion of the washing tub  120 . 
     The driving apparatus  138  serves to provide a driving force for rotating the inner tub  122  and/or the pulsator  133 . A clutch (not shown) for selectively transmitting the driving force of the driving apparatus  138  may be provided such that only the inner tub  122  is rotated, only the pulsator  133  is rotated, or the inner tub  122  and the pulsator  133  are rotated at the same time. 
     The driving apparatus  138  is operated by a driver  220  of  FIG. 3 , that is, a driving circuit. This will be described later with reference to  FIG. 3  and other drawings. 
     A detergent box  114  for accommodating various additives such as a laundry detergent, a fabric softener, and/or a bleaching agent is retrievably provided to the top cover  112 , and the wash water supplied through a water supply channel  123  flows into the inner tub  122  via the detergent box ( 114 ). 
     A plurality of holes (not shown) is formed in the inner tub  122 . Thereby, the wash water supplied to the inner tub  122  flows to the outer tub  124  through the plurality of holes. A water supply valve  125  for regulating the water supply channel  123  may be provided. 
     The wash water is drained from the outer tub  124  through a drain channel  143 . A drain valve  145  for regulating the drain channel  143  and a drain pump  141  for pumping the wash water may be provided. 
     The support rod  135  is provided to hang the outer tub  124  in the casing  110 . One end of the support rod  135  is connected to the casing  110  and the other end of the support rod  135  is connected to the outer tub  124  by a suspension  150 . 
     The suspension  150  attenuates vibration of the outer tub  124  during the operation of the washing machine  100 . For example, the outer tub  124  may be vibrated by vibration generated as the inner tub  122  rotates. While the inner tub  122  rotates, the vibration caused by various factors such as unbalance laundry amount of laundry in the inner tub  122 , the rotational speed of the inner tub  122  or the resonance characteristics of the inner tub  122  can be attenuated. 
       FIG. 3  is an internal block diagram of the laundry treatment machine of  FIG. 1 . 
     Referring to  FIG. 3 , in the laundry treatment machine  100 , the driver  220  is controlled by the main controller  210 , and the driver  220  drives the motor  230 . Thereby, the washing tub  120  is rotated by the motor  230 . 
     Meanwhile, the laundry treatment machine  100  may include a motor  630  for driving the drain pump  141  and a drain pump driving apparatus  620  for driving the motor  630 . The drain pump driving apparatus  620  may be controlled by the main controller  210 . 
     In this specification, the drain pump driving apparatus  620  may be referred to as a drain pump driver. 
     The main controller  210  operates by receiving an operation signal from an operation key  117 . Accordingly, washing, rinsing, and dewatering processes may be performed. 
     In addition, the main controller  210  may control the display  118  to display a washing course, a washing time, a dewatering time, a rinsing time, a current operation state, or the like. 
     Meanwhile, the main controller  210  controls the driver  220  to operate the motor  230 . For example, the main controller  210  may control the driver  220  to rotate the motor  230 , based on a current detector  225  for detecting an output current flowing in the motor  230  and a position sensor  235  for sensing a position of the motor  230 . While it is illustrated in  FIG. 3  that the detected current and the sensed position signal are input to the driver  220 , embodiments of the present disclosure are not limited thereto. The detected current and the sensed position signal may be input to the main controller  210  or to both the main controller  210  and the driver  220 . 
     The driver  220 , which serves to drive the motor  230 , may include an inverter (not shown) and an inverter controller (not shown). In addition, the driver  220  may further include a converter or the like for supplying a direct current (DC) power input to the inverter (not shown). 
     For example, when the inverter controller (not shown) outputs a switching control signal in a pulse width modulation (PWM) scheme to the inverter (not shown), the inverter (not shown) may perform a high-speed switching operation to supply an alternating current (AC) power at a predetermined frequency to the motor  230 . 
     The main controller  210  may sense a laundry amount based on a current io detected by the current detector  225  or a position signal H sensed by the position sensor  235 . For example, while the washing tub  120  rotates, the laundry amount may be sensed based on the current value io of the motor  230 . 
     The main controller  210  may sense an amount of eccentricity of the washing tub  120 , that is, an unbalance (UB) of the washing tub  120 . The sensing of the amount of eccentricity may be performed based on a ripple component of the current io detected by the current detector  225  or an amount of change in rotational speed of the washing tub  120 . 
     Meanwhile, a water level sensor  121  may measure a water level in the washing tub  120 . 
     For example, a water level frequency at a zero water level with no water in the washing tub  120  may be 28 KHz, and a frequency at a full water level at which water reaches an allowable water level in the washing tub  120  may be 23 KHz. 
     That is, the frequency of the water level detected by the water level sensor  121  may be inversely proportional to the water level in the washing tub. 
     The water level Shg in the washing tub output from the water level sensor  121  may be a water level frequency or a water level that is inversely proportional to the water level frequency. 
     Meanwhile, the main controller  210  may determine whether the washing tub  120  is at a full water level, a zero water level, or a reset water level, based on the water level Shg in the washing tub detected by the water level sensor  121 . 
       FIG. 4  illustrates an example of an internal block diagram of the drain pump driving apparatus of  FIG. 1 , and  FIG. 5  illustrates an example of an internal circuit diagram of the drain pump driving apparatus of  FIG. 4 . 
     Referring to  FIGS. 4 and 5 , the drain pump driving apparatus  620  according to an embodiment of the present disclosure serves to drive the motor  630  in a sensorless manner, and may include an inverter  420 , an inverter controller  430 , and a main controller  210 . 
     The main controller  210  and the inverter controller  430  may correspond to a controller and a second controller described in this specification, respectively. 
     The drain pump driving apparatus  620  according to an embodiment of the present disclosure may include a converter  410 , a DC terminal voltage detector B, a DC terminal capacitor C, and an output current detector E. In addition, the drain pump driving apparatus  620  may further include an input current detector A and a reactor L. 
     Hereinafter, an operation of each constituent unit in the drain pump driving apparatus  620  of  FIGS. 4 and 5  will be described. 
     The reactor L is disposed between a commercial AC power source  405  (Vs) and the converter  410 , and performs a power factor correction operation or a boost operation. In addition, the reactor L may also function to limit a harmonic current resulting from high-speed switching of the converter  410 . 
     The input current detector A may detect an input current is input from the commercial AC power source  405 . To this end, a current transformer (CT), a shunt resistor, or the like may be used as the input current detector A. The detected input current is may be input to the inverter controller  430  or the main controller  210  as a discrete signal in the form of a pulse. In  FIG. 5 , it is illustrated that the detected output current idc is input to the main controller  210 . 
     The converter  410  converts the commercial AC power source  405  having passed through the reactor L into a DC power and outputs the DC power. Although the commercial AC power source  405  is shown as a single-phase AC power source in  FIG. 5 , it may be a 3-phase AC power source. The converter  410  has an internal structure that varies based on the type of commercial AC power source  405 . 
     Meanwhile, the converter  410  may be configured with diodes or the like without a switching device, and may perform a rectification operation without a separate switching operation. 
     For example, in case of the single-phase AC power source, four diodes may be used in the form of a bridge. In case of the 3-phase AC power source, six diodes may be used in the form of a bridge. 
     As the converter  410 , for example, a half-bridge type converter having two switching devices and four diodes connected to each other may be used. In case of the 3-phase AC power source, six switching devices and six diodes may be used for the converter. 
     When the converter  410  has a switching device, a boost operation, a power factor correction, and a DC power conversion may be performed by the switching operation of the switching device. 
     Meanwhile, the converter  410  may include a switched mode power supply (SMPS) having a switching device and a transformer. 
     The converter  410  may convert a level of an input DC power and output the converted DC power. 
     The DC terminal capacitor C smooths the input power and stores the smoothed power. In  FIG. 5 , one element is exemplified as the DC terminal capacitor C, but a plurality of elements may be provided to secure element stability. 
     While it is illustrated in  FIG. 5  that the DC terminal capacitor C is connected to an output terminal of the converter  410 , embodiments of the present disclosure are not limited thereto. The DC power may be input directly to the DC terminal capacitor C. 
     For example, a DC power from a solar cell may be input directly to the DC terminal capacitor C or may be DC-to-DC converted and input to the DC terminal capacitor C. Hereinafter, what is illustrated in  FIG. 5  will be mainly described. 
     Both ends of the DC terminal capacitor C may be referred to as DC terminals or DC link terminals because the DC power is stored therein. 
     The DC terminal voltage detector B may detect a voltage Vdc between the DC terminals, which are both ends of the DC terminal capacitor C. To this end, the DC terminal voltage detector B may include a resistance element and an amplifier. The detected DC terminal voltage Vdc may be input to the inverter controller  430  or the main controller  210  as a discrete signal in the form of a pulse. In  FIG. 5 , it is illustrated that the detected output current idc is input to the main controller  210 . 
     The inverter  420  may include a plurality of inverter switching devices. The inverter  420  may convert the smoothed DC power Vdc into an AC power by an on/off operation of the switching device, and output the AC power to the synchronous motor  630 . 
     For example, when the synchronous motor  630  is in a 3-phase type, the inverter  420  may convert the DC power Vdc into 3-phase AC powers va, vb and vc and output the 3-phase AC powers to the three-phase synchronous motor  630  as shown in  FIG. 5 . 
     As another example, when the synchronous motor  630  is in a single-phase type, the inverter  420  may convert the DC power Vdc into a single-phase AC power and output the single-phase AC power to a single-phase synchronous motor  630 . 
     The inverter  420  includes upper switching devices Sa, Sb and Sc and lower switching devices S′a, S′b and S′c. Each of the upper switching devices Sa, Sb and Sc that are connected to one another in series and a respective one of the lower switching devices S′a, S′b and S′c that are connected to one another in series form a pair. Three pairs of upper and lower switching devices Sa and S′a, Sb and S′b, and Sc and S′c are connected to each other in parallel. Each of the switching devices Sa, S′a, Sb, S′b, Sc and S′c is connected with a diode in anti-parallel. 
     Each of the switching devices in the inverter  420  is turned on/off based on an inverter switching control signal Sic from the inverter controller  430 . Thereby, an AC power having a predetermined frequency is output to the synchronous motor  630 . 
     The inverter controller  430  may output the switching control signal Sic to the inverter  420 . 
     In particular, the inverter controller  430  may output the switching control signal Sic to the inverter  420 , based on a voltage command value Sn input from the main controller  210 . 
     The inverter controller  430  may output voltage information Sm of the motor  630  to the main controller  210 , based on the voltage command value Sn or the switching control signal Sic. 
     The inverter  420  and the inverter controller  430  may be configured as one inverter module IM, as shown in  FIG. 4 or 5 . 
     The main controller  210  may control the switching operation of the inverter  420  in a sensorless manner. 
     To this end, the main controller  210  may receive an output current idc detected by the output current detector E and a DC terminal voltage Vdc detected by the DC terminal voltage detector B. 
     The main controller  210  may calculate a power based on the output current idc and the DC terminal voltage Vdc, and output a voltage command value Sn based on the calculated power. 
     In particular, the main controller  210  may perform power control to stably operate the drain motor  630  and output a voltage command value Sn based on the power control. Accordingly, the inverter controller  430  may output a switching control signal Sic corresponding to the voltage command value Sn based on the power control. 
     The output current detector E may detect an output current idc flowing in the 3-phase motor  630 . 
     The output current detector E may be disposed between the DC terminal capacitor C and the inverter  420  to detect an output current idc flowing in the motor. 
     In particular, the output current detector E may include one shunt resistance element Rs. 
     The output current detector E may detect a phase current ia, ib or is which is the output current idc flowing in the motor  630 , in a time-division manner, when the lower switching device of the inverter  420  is turned on, using the one shunt resistor element Rs. 
     The detected output current idc may be input to the inverter controller  430  or the main controller  210  as a discrete signal in the form of a pulse. In  FIG. 5 , it is illustrated that the detected output current idc is input to the main controller  210 . 
     The 3-phase motor  630  includes a stator and a rotor. The rotor rotates when the AC power at a predetermined frequency for each phase is applied to a coil of the stator for each phase (phase a, b or c). 
     Such a motor  630  may include a brushless DC (BLDC) motor. 
     The motor  630  may include, for example, a surface-mounted permanent-magnet synchronous motor (SMPMSM), an interior permanent magnet synchronous motor (IPMSM), and a synchronous reluctance motor (SynRM). The SMPMSM and the IPMSM are permanent magnet synchronous motors (PMSM) employing permanent magnets, while the SynRM has no permanent magnet. 
       FIG. 6  is an internal block diagram of the main controller of  FIG. 5 . 
     Referring to  FIG. 6 , the main controller  210  may include a speed calculator  520 , a power calculator  521 , a power controller  523 , and a speed controller  540 . 
     The speed calculator  520  may calculate a speed of the drain motor  630 , based on the voltage information Sm of the motor  630  received from the inverter controller  430 . 
     Specifically, the speed calculator  520  may calculate a zero crossing for the voltage information Sm of the motor  630  received from the inverter controller  430 , and calculate a speed of the drain motor  630  based on the zero crossing. 
     The power calculator  521  may calculate a power P supplied to the motor  630 , based on the output current idc detected by the output current detector E and the DC terminal voltage Vdc detected by the DC terminal voltage detector B. 
     The power controller  523  may generate a speed command value ω*r based on the power P calculated by the power calculator  521  and a preset power command value P*r. 
     For example, the power controller  523  may generate the speed command value ω*r, while a PI controller  525  performs PI control, based on a difference between the calculated power P and the power command value P*r. 
     Meanwhile, the speed controller  540  may generate a voltage command value Sn, based on the speed calculated by the speed calculator  520  and the speed command value ω*r generated by the power controller  523 . 
     Specifically, the speed controller  540  may generate the voltage command value Sn, while a PI controller  544  performs PI control, based on a difference between the calculated speed and the speed command value ω*r. 
     The generated voltage command value Sn may be output to the inverter controller  430 . 
     The inverter controller  430  may receive the voltage command value Sn from the main controller  210 , and generate and output an inverter switching control signal Sic in the PWM scheme. 
     The output inverter switching control signal Sic may be converted into a gate drive signal in a gate driver (not shown), and the converted gate drive signal may be input to a gate of each switching device in the inverter  420 . Thus, each of the switching devices Sa, S′a, Sb, S′b, Sc and S′c in the inverter  420  performs a switching operation. Accordingly, the power control can be performed stably. 
     Meanwhile, the main controller  210  according to an embodiment of the present disclosure may be configured to drive the motor  630 , during drainage, based on the output current idc and the DC terminal voltage Vdc with a first power when a lift is at a first level and to drive with the first power when the lift is at a second level greater than the first level, wherein the lift is a difference between a water level of a water introduction part through which water flows into the drain pump  141  and a water level of a water discharge part through which the water is discharged out of the drain pump  141 . Accordingly, water pumping can be performed smoothly even if the lift is changed during the drainage. 
     In particular, since the power control is performed to drive the motor  630  with a constant power, the converter  410  merely needs to supply the constant power. Thus, the stability of the converter can be improved. 
     When the power supplied to the motor  630  reaches the first power, the main controller  210  according to an embodiment of the present disclosure may control a speed of the motor  630  to be constant. Since the power control is performed as described above, it is possible to minimize a decrease in drainage performance according to installation conditions. 
     When the main controller  210  according to an embodiment of the present disclosure controls the speed of the motor  630  to be increased, a period during which the speed of the motor  630  is increased may include an initial rise section and a second rise section where the increase in the speed of the motor is less than the increase in the speed of the motor in the initial rise section. Particularly, the main controller  210  may control the output current idc to be constant in the second rise section. Accordingly, the motor  630  can be operated with a constant power. 
     The main controller  210  according to an embodiment of the present disclosure may configured to increase the speed of the motor  630 , during the drainage as a level of the lift increases. 
     The main controller  210  according to an embodiment of the present disclosure may control an amount of water pumped by an operation of the drain pump  141 , during the drainage, to be decreased as the level of the lift increases. 
     The main controller  210  according to an embodiment of the present disclosure may configured to increase the speed of the motor  630 , during the drainage as the water level in the washing tub  120  decreases. 
     The main controller  210  according to an embodiment of the present disclosure may control the decrease in the amount of water pumped by the operation of the drain pump  141  according to the increase in the level of the lift to be smaller when the power control is performed with respect to the motor  630  than when speed control is performed with respect to the motor  630 . Accordingly, when compared to the speed control, the power control makes it possible to set a greater range of lift levels, thereby increasing a freedom of installation. 
     The main controller  210  according to an embodiment of the present disclosure may control the power supplied to the motor  630 , during the drainage, to be constant, without decreasing over time. Accordingly, a drainage time can be shortened. 
     The main controller  210  according to an embodiment of the present disclosure may configured to perform the power control when the drainage is started and to terminate the power control when a residual water level is reached. Accordingly, the drainage operation can be efficiently performed. 
     The main controller  210  according to an embodiment of the present disclosure may control the voltage command value Sn and a duty of the switching control signal Sic to be greater as the output current idc is at a smaller level. Accordingly, the motor  630  can be driven with a constant power. 
     The drain motor  630  according to an embodiment of the present disclosure may be implemented as a brushless DC motor  630 . Accordingly, the power control, rather than constant-speed control, can be implemented in a simple manner. 
     Meanwhile, the main controller  210  according to another embodiment of the present disclosure may configured to increase the speed of the motor  630 , during the drainage when the power supplied to the motor  630  does not reach the first power and to be decreased when the power supplied to the motor  630  exceeds the first power. Accordingly, since the power control is performed to drive the motor  630  with a constant power, the converter  410  merely needs to supply the constant power. Thus, the stability of the converter can be improved. In addition, since the power control is performed, it is possible to minimize a decrease in drainage performance according to installation conditions. 
     The main controller  210  according to further another embodiment of the present disclosure may control the speed of the motor  630  to be constant, when the power supplied to the motor  630  reaches the first power. Since the power control is performed as described above, it is possible to minimize a decrease in drainage performance according to installation conditions. 
     The main controller  210  according to further another embodiment of the present disclosure may control the speed of the motor  630 , during drainage, to be increased as the level of the lift increases, wherein the lift is a difference between a water level of the water introduction part through which water flows into the drain pump  141  and a water level of the water discharge part through which the water is discharged out of the drain pump  141 . Accordingly, water pumping can be performed smoothly even if the lift is changed during the drainage. In particular, since the power control is performed, it is possible to minimize a decrease in drainage performance according to installation conditions. 
     The main controller  210  according to further another embodiment of the present disclosure may configured to increase the speed of the motor  630 , during the drainage as the water level in the washing tub  120  decreases. Accordingly, water pumping can be smoothly performed even if the water level in the washing tub  120  decreases during the drainage. 
       FIGS. 7A and 7B  are views illustrating various examples of a drain pipe connected to the drain pump of the laundry treatment machine of  FIG. 1 . 
       FIG. 7A  illustrates that a difference in height between the drain pump  141  and the drain pipe  199   a  is ha.  FIG. 7B  illustrates that a difference in height between the drain pump  141  and the drain pipe  199   a  is hb greater than ha. 
     That is,  FIG. 7A  illustrates that the level of the lift is ha, wherein the lift is a difference between a water level of the water introduction part through which water flows into the drain pump  141  and a water level of the water discharge part through which the water is discharged out of the drain pump  141 , and  FIG. 7B  illustrates that the level of the lift is hb that is much greater than ha. 
     For example, ha may be about 0.5 m and hb may be about 3 m. 
     When the laundry treatment machine  100  is installed in a basement, the drain pipe  199   a  should extend to the ground for drainage. Therefore, as shown in  FIGS. 7A and 7B , the drain pipe  199   a  should extend to a position that is higher than that of the drain pump  141 . 
     In this case, if the drain pump is implemented in a solenoid type, the drainage will not be performed smoothly due to the low pumping power. 
     Accordingly, a motor is preferably used to drive the drain pump. Conventionally, an AC motor has been employed and driven at a constant speed of about 3000 rpm or 3600 rpm using an AC power of 50 Hz or 60 Hz. 
     In this case, since the motor is driven at a constant speed irrespective of the height of the drain pump, noise is generated by movement of residual water remaining in the drain pipe  199   a.    
     In order to solve this problem, the motor  630  capable of changing its speed is used in the present disclosure. 
     In particular, the brushless DC (BLDC) motor  630  is used as the motor  630  for driving the drain pump  141  according to an embodiment of the present disclosure. 
     Meanwhile, when using the BLDC motor  630 , there is an advantage that the speed can be changed. 
     The present disclosure proposes a way to change the dewatering entry period after drainage is completed, based on the lift. 
     In addition, the present disclosure proposes a way to shorten a dewatering entry period after drainage is completed. 
     In addition, the present disclosure proposes a way to perform pumping smoothly even if the lift is changed during drainage. 
     Further, the present disclosure proposes a way to stably drive the converter even if the lift is changed during drainage. 
     In addition, the present disclosure proposes a way to minimize a decrease in drainage performance according to installation conditions. This will be described with reference to  FIG. 9  and other drawings. 
       FIG. 8  is a graph illustrating a relationship of the lift with the water-pumped amount, the output power, or the input power. 
     Referring to (a) of  FIG. 8 , as the level of the lift increases, that is, from ha in  FIG. 7A  toward hb in  FIG. 7B , the water-pumped amount Q may decrease. 
     Alternatively, as the level of the lift decreases, that is, from hb in  FIG. 7B  toward ha in  FIG. 7A , the water-pumped amount Q may increase. 
     For example, when the drain motor  630  is controlled to be driven at a constant speed of 3600 rpm, the water-pumped amount is larger as the level of the lift is from hb toward ha, and accordingly, the output power consumed by the pump motor  630  increases. 
     Accordingly, the power supplied to the pump motor  630  also needs to increase as the level of the lift is from hb toward ha. 
     That is, as shown in (b) of  FIG. 8 , as the level of the lift increases, that is, from ha in  FIG. 7A  toward hb in  FIG. 7B , the output power MPo decreases, and as the level of the lift decreases, that is, from hb in  FIG. 7B  toward ha in  FIG. 7A , the output power MPo increases. 
     In addition, as shown in (c) of  FIG. 8 , as the level of the lift increases, that is, from ha in  FIG. 7A  toward hb in  FIG. 7B , the power MPi supplied to the pump motor  630  decreases, and as the level of the lift decreases, that is, from hb in  FIG. 7B  toward ha in  FIG. 7A , the power MPi supplied to the pump motor  630  increases. 
     In a case where the output power MPo or the power MPi supplied to the pump motor  630  varies according to the change in the level of the lift, it is required that the converter  410  supplying a DC power be of high performance. In particular, it is required that the smaller the level of the lift, the greater the power supplied. 
     However, in order to design the converter  410  having a power that is variable based on the level of the lift, high expenses are incurred or complicated control is required. 
     Thus, the present disclosure proposes a way of driving the motor  630  based on the power control for making the power supplied to the pump motor  630  or the output power based on the level of the lift constant. Based thereon, the converter merely needs to supply the constant power, thereby improving the stability of the converter. This will be described with reference to  FIG. 11  and other drawings. 
       FIG. 9  is a flowchart showing an example of a method of operating the drain pump driving apparatus according to an embodiment of the present disclosure, and  FIGS. 10 to 17  are reference views for explaining the operation method of  FIG. 9 . 
     The main controller  210  of the drain pump driving apparatus may control each of the washing process, the rinsing process, and the dewatering process to be performed. 
     Meanwhile, the washing process may consist of washing, draining, and dewatering stages, the rinsing process may consist of rinsing, draining, and dewatering stages, and the dewatering process may consist of draining and dewatering stages. 
       FIG. 9  may illustrate washing (S 810 ), draining (S 820 ), and dewatering (S 830 ) in the washing process. The draining (S 820 ) and the dewatering (S 830 ) at this time may correspond to what are performed within the washing process, the rinsing process, and the dewatering process. For example, the draining (S 820 ) may be performed before the end of the washing process, before the end of the rinsing process, and at the end of initial dewatering in the dewatering process. 
     Alternatively,  FIG. 9  may illustrate the washing process (S 810 ), the draining (S 820 ), and the dewatering process (S 830 ). The draining (S 820 ) and the dewatering (S 830 ) at this time may correspond to the draining and the dewatering after the washing process and the rinsing process are completed. 
     Meanwhile, after the draining (S 820 ), in order to shorten the dewatering (S 830 ) entry period, a way to perform power control is proposed. This will be described with reference to  FIG. 10 . 
       FIG. 10  is a flowchart showing steps from drainage to the start of dewatering. 
     Referring to the drawing, the main controller  210  may perform power control during the drainage (S 910 ). 
     Specifically, the main controller  210  may be configured to drive the motor  630  with a constant power despite a change in the level of the lift during the drainage. 
     That is, the main controller  210  may be configured to drive the motor  630  with a first power P 1  when the lift is at the first level (ha), and may be configured to drive the motor  630  with the same first power P 1  even when the lift is greater than the second level hb greater than the first level ha. 
     Meanwhile, the power control will be described with reference to  FIG. 11 . 
     Next, the main controller  210  may determine whether or not the water level in the washing tub  120  reaches the first water level during power control during the drainage (S 920 ). 
     Here, the first water level may be a zero water level. The zero water level may correspond to (c) of  FIG. 13A . 
     The main controller  210  may receive water level information Shg detected by the water level sensor  121 . Here, the water level information Shg may be a water level frequency that is inversely proportional to the water level in the washing tub. Alternatively, the water level information Shg may be an inverse value of the water level frequency. 
     (a) of  FIG. 13A  illustrates a full water level fss indicating that an inner tub  122  and outer tub  124  of the washing tub  120  are filled with water to a upper limit level, (b) of  FIG. 13A  illustrates a reset water level ress indicating that the inner tub  122  of the washing tub  120  is slightly filled with water, and (c) of  FIG. 13A  illustrates a zero water level indicating that there is no water in the inner tub  122  and the outer tub  124  of the washing tub  120 . 
     The main controller  210  may determine whether or not the water level in the washing tub  120  is the zero water level as shown in (c) of  FIG. 13A , based on the water level information Shg detected by the water level sensor  121  during the power control during drainage. 
     Next, the main controller  210  may determine whether or not the level of the output current idc is less than or equal to the reference level or the output power supplied to the motor  630  is less than or equal to the reference level, in the state of reaching the zero water level (S 925 ). 
     Then, when the level of the output current idc is equal to or less than the reference level or the output power supplied to the motor  630  is equal to or less than the reference level in the state in which the air water level is reached, the main controller  210 , may determine that the washing tub  120  is in the no-load state and may control the dewatering to be started immediately after the pause state of a first period Pm (S 930 ). 
     Meanwhile, unlike  FIG. 10 , in order to start dewatering after the end of drainage, the main controller  210  may control the dewatering of step S 930  to be immediately started when it is determined that the water level is the zero water level based on the water level information Shg detected by the water level sensor of step S 920 . That is, step S 925  may be omitted. 
     Meanwhile, unlike  FIG. 10 , in order to start dewatering after the end of drainage, the main controller  210  may control the dewatering of step S 930  to be immediately started when it is determined that the level of the output current idc detected by the output current detector E in step S 925  is equal to or less than the reference level. That is, step S 920  may be omitted. 
     Meanwhile, unlike  FIG. 10 , in order to start dewatering after the end of drainage, the main controller  210  may control the dewatering of step S 930  to be immediately started when it is determined that the level of power calculated based on the level of the output current idc in step S 925  is equal to or less than the reference level. That is, step S 920  may be omitted. 
     Meanwhile, in the present disclosure, since the speed of the motor  630  for the drain pump is changed by power control, heat generation of the motor  630  is considerably low compared with the motor driving by constant speed operation. Accordingly, after the pause state period of the first period Pm, which is considerably short compared with a pause period when the motor  630  is driven by constant speed operation, the dewatering may be started immediately. This will be described with reference to  FIGS. 14A and 14B . 
       FIG. 14A  is a reference view for explaining drainage and dewatering according to the power control of the present disclosure. 
     Referring to the drawing, (a) of  FIG. 14A  illustrates a power waveform Wva supplied to the drain motor  630  during drainage and dewatering. 
     Specifically, during the drainage, the substantially constant first power P 1  is supplied to the motor  630  by power control as shown in (a) of  FIG. 14A . In particular, during draining, power within a first allowable range based on the first power P 1  may be supplied to the motor  630 . 
     On the other hand, since there is no water supplied from the washing tub  120  when the completion of the drainage, the power supplied to the motor  630  rapidly falls even if power control is performed. 
     That is, from the time point Tff of (a) of  FIG. 14A , the power supplied to the motor  630  rapidly falls. 
     Meanwhile, the main controller  210  may determine that the completion of the drainage when the power supplied to the motor  630  is out of the first allowable range Prag based on the first power P 1 , and may be configured to perform the dewatering after the first period Pm from the time point out of the first allowable range Prag. 
     (a) of  FIG. 14A  illustrates the rotational speed waveform Wvb of the washing tub  120  during drainage and dewatering. 
     When the power supplied to the motor  630  is out of the first allowable range Prag based on the first power P 1  at the time point Tff, The main controller  210  may rotate the washing tub  120  at a speed V 1  from the time point Tst after the first period Pm. In this way, dewatering is started. 
     During the dewatering, the main controller  210  may control the washing tub  120  to rotate at a V 1  speed, stop, rotate at a V 3  speed faster than V 1  speed, rotate at a V 2  speed slower than V 3  speed and faster than V 1 , stop, rotate at the V 2  speed, and rotate at a V 4  speed slower than V 3  and faster than V 2 . 
       FIG. 14B  is a reference view for explaining drainage and dewatering according to constant speed control. 
     Referring to the drawing, (a) of  FIG. 14B  illustrates a power waveform Wvc supplied to the drain motor  630  during drainage and dewatering. 
     Specifically, during the drainage, the power P 1  sequentially decreasing by constant speed control is supplied to the motor  630  as shown in (a) of  FIG. 14B . 
     When the drainage is complete, the motor  630  stops at the time point Tfx. 
     Meanwhile, when driving the motor for the drain pump by constant speed control as described above, in order to reduce heat generation, dewatering is to be performed after securing a fairly long pause period such as the Px period in the drawing. 
     (b) of  FIG. 14B  illustrates the rotational speed waveform Wvd of the washing tub  120  during drainage and dewatering. 
     Accordingly, after time point Tff point, from the time point Tsx where the Px period has elapsed, the washing tub  120  may rotate at the V 1  speed, stop, rotate at a V 5  speed faster than the V 1  speed, rotate at the V 2  speed slower than the V 5  speed and faster than the V 1  speed, stop, rotate at the V 2  speed and rotate at the V 5  speed. 
     Comparing  FIG. 14A  and  FIG. 14B , the drainage completion time point are at the time point Tff and the time point Tfx, respectively, which are similar to each other, but the pause periods are Pm and Px, respectively, which are significantly different from each other. 
     For example, Pm may be approximately 4 seconds or less, and the Px period may be approximately 30 seconds or more. Accordingly, according to the method of  FIG. 14A , the dewatering entry time can be shortened by at least 25 seconds. 
     Meanwhile, the maximum speed during the dewatering is V 3  of  FIG. 14A  and V 5  of  FIG. 14B , and at this time, V 3  of  FIG. 14A  may be set to a larger value. That is, according to  FIG. 14A , after rapid dewatering entry, high-speed dewatering can be performed at a faster maximum dewatering speed. 
     Meanwhile, the present disclosure proposes a way to change the pause period based on the lift when the lift is changed when entering from the drainage to the dewatering. This will be described with reference to  FIG. 12 . 
     Referring to  FIG. 12 , the main controller  210  may determine whether or not the level of the output current idc is less than or equal to the reference level or the output power supplied to the motor  630  is less than or equal to the reference level (S 1110 ). 
     Then, the main controller  210  may determine whether or not the lift is at the first level ha to start the dewatering when the level of the output current idc is less than or equal to the reference level or the output power supplied to the motor  630  is less than or equal to the reference level (S 1115 ). 
     The main controller  210  may control the dewatering to be started after the first period Pma from the completion of the drainage, when the lift is at the first level (ha) (S 1120 ). 
     Meanwhile, the main controller  210  may control the dewatering to be started after the second period Pmb longer than the first period Pma from the completion of the drainage, when the lift is at the second level (hb) (S 1120 ). 
     For example, the main controller  210  may change the dewatering entry time point, based on the level of the lift. 
     Specifically, the main controller  210  may control the dewatering to be started at the first time point when the level of the lift is the first level ha, and may control the dewatering to be started at the second time point after the first time point when the level of the lift is the second level hb greater than the first level ha. 
       FIG. 13B  is a diagram illustrating the relationship between the lift and the pause period. 
     During dewatering after the completion of the drainage, the greater the level of the lift, the longer the pause period becomes. 
       FIG. 13B  illustrates that the pause period of the motor  630  is a first period Pma when the level of the lift is the first level ha as in  FIG. 7A , and the pause period of the motor  630  is a second period Pmb when the level of the lift is the second level hb as in  FIG. 7B . 
     In this way, it is possible to change the dewatering entry period after drainage is completed, based on the lift. In particular, it is possible to shorten the dewatering entry period after drainage is completed. 
     Meanwhile, the main controller  210  may be configured to drive the motor  630  with the first power P 1  during the drainage when the lift is at the first level ha, and may be configured to perform the dewatering after the first period Pma when the power supplied to the motor  630  is out of the first allowable range Prag based on the first power P 1 . 
     In addition, the main controller  210  may be configured to drive the motor  630  with the first power P 1  during the drainage when the lift is at the second level hb, and may be configured to perform the dewatering after the second period Pmb when the power supplied to the motor  630  is out of the first allowable range Prag based on the first power P 1 . 
     Meanwhile, the power control  910  during the drainage of  FIG. 10  will be described in detail with reference to  FIG. 11 . 
       FIG. 11  is a reference view for explaining detailed operations in step S 910  of  FIG. 10 . 
     For the power control, the main controller  210  may determine, during the drainage, whether the first power, which is a target power, has been reached (S 1010 ). 
     In particular, the main controller  210  may calculate a power supplied to the motor  630 , based on the output current idc detected by the output current detector E and the DC terminal voltage Vdc detected by the DC terminal voltage detector B. 
     When the power supplied to the motor  630  does not reach the first power, the main controller  210  may control a speed of the motor  630  to be increased (S 1015 ). 
     On the other hand, when the power supplied to the motor  630  has reached the first power, the main controller  210  may control the speed of the motor  630  to be maintained (S 1020 ). 
     When the power supplied to the motor  630  exceeds the first power (S 1025 ), the main controller  210  may control the speed of the motor  630  to be decreased (S 1030 ). 
     Since the power control is performed as described above, it is possible to minimize a decrease in drainage performance according to installation conditions. 
       FIG. 15  is a reference view for explaining  FIG. 11 . 
     (a) of  FIG. 15  illustrates a waveform gda of the speed of the drain motor  630 , (b) of  FIG. 15  illustrates a waveform gdb of the water level frequency detected by the water level sensor  121  in the washing tub  120 , and (c) of  FIG. 15  illustrates a waveform gdc of the output current flowing in the drain motor  630 . 
     Initially, the washing tub  120  is at a zero water level and may have a water level frequency of Lvb. 
     At time point Tin, water may be introduced into the washing tub  120 , and the water level frequency may be gradually lowered. At time point Tst, the washing tub  120  may have the lowest water level frequency of Lva. 
     When drainage is started at time point Tst, power control is performed with respect to the drain motor  630 , and accordingly, the speed of the drain motor  630  may be increased as shown in (a) of  FIG. 15 . 
     As described above, when the power supplied to the drain motor  630  does not reach the first power, the speed of the drain motor  630  may be continuously increased. 
     Meanwhile, the main controller  210  may control a period Prsto during which the speed of the motor is increased to include an initial rise section Pr 1  and a second rise section Pr 2  where the increase in the speed of the motor is less than the increase in the speed of the motor in the initial rise section Pr 1 . 
     The initial rise section Pr 1  is a section in which the speed of the motor  630  is sharply rises, and accordingly, the output current idc flowing in the drain motor  630  also sharply increases as shown in (c) of  FIG. 15 . 
     The initial rise section Pr 1  may correspond to an section for open loop control, rather than closed loop feedback control, of the drain motor  630 . 
     When the speed of the motor  630  reaches Vm 1 , the main controller  210  may perform the closed loop feedback control, particularly performing the power control such that the power supplied to the drain motor  630  reaches the first power P 1 . 
     Accordingly, as shown in (a) of  FIG. 15 , the speed of the drain motor  630  may rise slowly in the second rise section Pr 2 , when compared to that in the initial rise section Pr 1 . 
     At this time, as shown in (c) of  FIG. 15 , the output current idc flowing in the drain motor  630  may be constant, based on the power control. Accordingly, the motor  630  can be operated with a constant power. 
     When the power supplied to the drain motor  630  reaches the first power P 1 , the main controller  210  may control the speed of the drain motor to be maintained as it is at that time. 
     (a) of  FIG. 15  illustrates that the power supplied to the drain motor  630  has reached the first power P 1  at time point Tff, and the speed of the drain motor  630  at that time is Vm 2 . 
     Thereafter, when the power supplied to the drain motor  630  is maintained as the first power, the speed of the drain motor  630  is maintained as Vm 2 . 
     In particular, the speed of the drain motor  630  may be maintained as Vm 2  until time point Tfa when the power control is terminated. 
     When the drainage is started at time point Tst, the water level frequency may rise from Lva, up to time point Tfa, to Lvb, which corresponds to the zero water level. 
     Referring to (c) of  FIG. 15 , the output current idc flowing in the drain motor  630  may be at a constant level Lm after time point Tstx when the power control is started until time point Tfa when the power control is terminated. 
     In this way, the main controller  210  may control the output current idc to be constant when the speed of the motor  630  is increased, particularly in the second rise section Pr 2 . Accordingly, the motor  630  can be operated with a constant power. 
     Meanwhile, the constant output current idc in (c) of  FIG. 15  may mean that the current is within an allowable range based on level Lm. For example, when the current is pulsating within about 10% based on level Lm, the current may be regarded as constant. 
       FIG. 16  is a view showing a power supplied to the motor when the power control or the speed control is performed. 
     When the power control is performed as in the embodiments of the present disclosure, a time-dependent waveform of the power supplied to the motor  630  may be exemplified as Pwa. 
       FIG. 16  illustrates that the power is maintained in a substantially constant manner until time point Tm 1  by performing the power control, and the power control is terminated at time point Tm 1 . 
     By performing the power control, the main controller  210  may control the power supplied to the motor  630 , during the drainage, to be constant without decreasing over time, although the water level in the washing tub  120  decreases. 
     By performing the power control, the main controller  210  may control the power supplied to the motor  630 , during the drainage, to be the first power P 1 . 
     In particular, even if the lift is changed, the main controller  210  may control the power supplied to the motor  630 , during the drainage, to be the constant first power P 1 , by performing the power control. 
     At this time, the constant first power P 1  may mean that the motor  630  is driven with a power within a first allowable range Prag based on the first power P 1 . For example, the power within the first allowable range Prag may be a power pulsating within about 10% based on the first power P 1 . 
     In  FIG. 16 , it is illustrated that when the power control is performed, the motor  630  is driven with a power within the first allowable range Prag based on the first power P 1  from time point Tseta until time point Tm 1  when the completion of the drainage, excluding an overshooting period Pov. Accordingly, water pumping can be performed smoothly even if the lift is changed during the drainage. In addition, the stability of the converter  410  can be improved. 
     Here, the first allowable range Prag may be greater as the first power P 1  is at a higher level. In addition, the first allowable range Prag may be greater as a drainage completion period Pbs is longer. 
     That is, when the lift is at the first level, the main controller  210  may be configured to drive the motor  630  with a power within the first allowable range Prag based on the first power P 1 , without decreasing over time, from first time point Tseta after the drainage is started until time point Tm 1  when the completion of the drainage, and when the lift is at the second level, the main controller  210  may be configured to drive the motor  630  with a power within the first allowable range Prag based on the first power P 1 , without decreasing over time, from first time point Tseta until time point Tm 1  when the completion of the drainage. 
     To this end, when the power control is performed during the drainage, the main controller  210  may calculate a power based on the output current idc and the DC terminal voltage Vdc and output a voltage command value Sn based on the calculated power, and the inverter controller  430  may output a switching control signal Sic to the motor  630  based on the voltage command value Sn. 
     Meanwhile, the main controller  210  may control the voltage command value Sn and a duty of the switching control signal Sic to be greater as the output current idc is at a smaller level. Accordingly, the motor  630  can be driven with a constant power. 
     Meanwhile, the main controller  210  may control the speed of the motor  630  to be increased as the level of the lift increases. Accordingly, water pumping can be performed smoothly even if the lift is changed during the drainage. In particular, since the power control is performed, it is possible to minimize a decrease in drainage performance according to installation conditions. 
     Meanwhile, the main controller  210  may configured to increase the speed of the motor  630 , during the drainage as the water level in the washing tub  120  decreases. Accordingly, water pumping can be smoothly performed even if the water level in the washing tub  120  decreases during the drainage. 
     Unlike the embodiments of the present disclosure, when the speed control is performed, that is, when the speed of the drain motor  630  is controlled to be maintained constantly, a time-dependent waveform of the power supplied to the motor  630  may be exemplified as Pwb. 
     In  FIG. 16 , it is illustrated that the speed control is performed until time point Tm 2 , and the speed control is terminated at time point Tm 2 . 
     The waveform Pwb of the power based on the speed control indicates that the power supplied to the motor  630  may be gradually reduced, while the speed of the motor  630  is constant, as the water level in the washing tub decreases during the drainage. 
     In  FIG. 16 , it is illustrated that, during a speed control period Pbsx, the power supplied to the motor  630  is gradually reduced up to approximately Px at time point Tm 2  when the completion of the drainage. 
     Accordingly, the time when the operation of the motor  630  is terminated in a case where the speed control is performed is Tm 2 , which is delayed by approximately period Tx, when compared to that in a case where the power control is performed. 
     Consequently, according to the embodiments of the present disclosure, since the power control is performed during the drainage, the drainage time can be shortened by approximately period Tx, when compared to that in the case where the speed control is performed. In addition, the power supplied from the converter  410  can be kept constant, thereby improving the operation stability of the converter  410 . 
       FIG. 17  is a view illustrating a relationship between the lift and the water-pumped amount. 
     Referring to  FIG. 17 , waveform LNa and waveform LNc are waveforms indicating the water-pumped amount with respect to the lift when the power control is performed, and waveform LNb is a waveform indicating the water-pumped amount with respect to the lift when the speed control is performed. 
     In particular, waveform LNa indicates that the power control is performed with a constant power greater than that indicated by waveform LNc. 
     According to  FIG. 17 , the main controller  210  may control a decrease in the amount of water pumped by the operation of the drain pump  141  as the level of the lift increases to be smaller when the power control is performed with respect to the motor  630  than when speed control is performed with respect to the motor  630 . 
     Waveforms LNa to LNc commonly indicate that the water-pumped amount decreases from minimum level Hmin of the lift toward maximum level Hmax of the lift, that is, as the level of the lift increases. 
     However, the decrease in the amount of water pumped by the operation of the drain pump  141  as the level of the lift increases is smaller when the power control is performed than when the speed control is performed. That is, as shown in  FIG. 17 , the level of the lift at which the water-pumped amount becomes zero (0) is lowest in waveform LNb. 
     The level of the lift at which the water-pumped amount becomes zero (0) is higher in waveform LNc than waveform LNb, and the level of the lift at which the water-pumped amount becomes zero (0) is highest in waveform LNa. 
     That is, the decrease in the amount of water pumped by the operation of the drain pump  141  according to the increase in the level of the lift is smaller when the power control is performed with respect to the motor  630  than when the speed control is performed with respect to the motor  630 . 
     Therefore, the drainage can be made within a greater range of lift when the power control is performed, as compared to that when the speed control is performed. That is, when compared to the speed control, the power control makes it possible to set a greater range of lift levels, thereby increasing a freedom of installation. 
     In  FIG. 17 , it is illustrated that a water-pumped amount at time point Pmin is identical between waveform LNa representing the power control and wave form LNb representing the speed control, but a water-pumped amount at time point Pmax is much greater in waveform LNa representing the power control than wave form LNb representing the speed control. 
     That is, the amount of water pumped by the operation of the drain pump  141  is greater when the power control is performed with respect to the motor  630  than when the speed control is performed with respect to the motor  630 . Therefore, the drainage time can be further shortened when the power control is performed. 
     Meanwhile,  FIG. 1  illustrates a top loading type machine as a laundry treatment machine, but the drain pump driving apparatus  620  according to an embodiment of the present disclosure may also be applied to a front loading type machine, that is, a drum type machine. This will be described with reference to  FIG. 18 . 
       FIG. 18  is a perspective view illustrating a laundry treatment machine according to another embodiment of the present disclosure. 
     Referring to  FIG. 18 , the laundry treatment machine  100   b  according to an embodiment of the present disclosure is a laundry treatment machine in a front loading type in which fabric is inserted into a washing tub through the front of the machine. 
     Referring to  FIG. 18 , the laundry treatment machine  100   b  is a drum-type laundry treatment machine, and includes a casing  110   b  forming an outer appearance of the laundry treatment machine  100   b , a washing tub  120   b  disposed inside the casing  110   b  and supported by the casing  110   b , a drum  122   b  that is a washing tub disposed inside the washing tub  120   b  to wash fabric, a motor  130   b  for driving the drum  122   b , a wash water supply apparatus (not shown) disposed outside a cabinet body  111   b  to supply wash water into the casing  110   b , and a drainage apparatus (not shown) formed under the washing tub  120   b  to discharge the wash water to the outside. 
     A plurality of through holes  122 Ab are formed in the drum  122   b  to allow the wash water to pass therethrough, and a lifter  124   b  may be disposed on an inner surface of the drum  122   b  such that laundry is lifted to a predetermined height and then falls by gravity when the drum  122   b  rotates. 
     The casing  110   b  includes a cabinet body  111   b , a cabinet cover  112   b  disposed on the front of the cabinet body  111   b  and coupled to the cabinet body  111   b , a control panel  115   b  disposed on the cabinet cover  112   b  and coupled to the cabinet body  111   b , and a top plate  116   b  disposed on the control panel  115   b  and coupled to the cabinet body  111   b.    
     The cabinet cover  112   b  includes a fabric entrance hole  114   b  formed to allow fabric to enter and exit therethrough, and a door  113   b  disposed in such a manner as to be rotatable in a horizontal direction to open or close the fabric entrance hole  114   b.    
     The control panel  115   b  includes operation keys  117   b  for controlling an operation state of the laundry treatment machine  100   b , and a display  118   b  disposed on one side of the operation keys  117   b  to display the operation state of the laundry treatment machine  100   b.    
     The operation keys  117   b  and the display  118   b  in the control panel  115   b  are electrically connected to a controller (not shown), and the controller (not shown) electrically controls each component of the laundry treatment machine  100   b . A description about an operation of the controller (not shown) is omitted because the operation of the controller  210   b  illustrated in  FIG. 3  can be referred to. 
     Meanwhile, an automatic balancer (not shown) may be provided in the drum  122   b . The automatic balancer (not shown), which is provided to reduce vibrations generated based on an eccentric amount of laundry accommodated in the drum  122   b , may be implemented as a liquid balancer, a ball balancer, or the like. 
     Meanwhile, the drain pump driving apparatus  620  according to an embodiment of the present disclosure may be applied to various machines such as dishwashers and air conditioners, in addition to the laundry treatment machines  100  and  100   b.    
     The drain pump driving apparatus and the laundry treatment machine including the same according to embodiments of the present disclosure are not limited to the configurations and methods of the above-described embodiments, and various modifications to the embodiments may be made by selectively combining all or some of the embodiments. 
     Meanwhile, a method for operating the drain pump driving apparatus and the laundry treatment machine according to the present disclosure can be implemented with processor-readable codes in a processor-readable recording medium provided for each of the drain pump driving apparatus and the laundry treatment machine. The processor-readable recording medium includes all kinds of recording devices for storing data that is readable by a processor. 
     It will be apparent that, although the preferred embodiments of the present disclosure have been illustrated and described above, the present disclosure is not limited to the above-described specific embodiments, and various modifications can be made by those skilled in the art without departing from the gist of the present disclosure as claimed in the appended claims. The modifications should not be understood separately from the technical spirit or prospect of the present disclosure.