Cooling system and defrosting control method thereof

Abstract

A cooling system including an evaporator to exchange heat with air, a frost detector installed on the evaporator to detect frost, and a control unit to determine whether a current time corresponds to a frost detection point, to control the frost detector to operate when the current time corresponds to the frost detection point, and to control a defrosting operation based on a frost detection signal from the frost detector. It is possible to accurately detect the amount of frost formed on the evaporator by executing the frost detection under constant frost detection environmental conditions.

What is claimed is: 
     
         1 . A cooling system comprising:
 at least one evaporator to exchange heat with air;   a frost detector installed on the evaporator to detect frost; and   a control unit to determine whether a current time corresponds to a frost detection point, to control the frost detector to operate when the current time corresponds to the frost detection point, and to control a defrosting operation based on a frost detection signal from the frost detector.   
     
     
         2 . The cooling system according to  claim 1 , wherein the frost detection point is a point of time when a constant state of the frost is exhibited whenever the frost detector operates. 
     
     
         3 . The cooling system according to  claim 2 , wherein:
 the frost detector detects a capacitance established between the frost detector and a cooling fin provided at the evaporator, and outputs a voltage signal corresponding to the detected capacitance; and   the point of time when the constant state of the frost is exhibited is a point of time when the capacitance is constant.   
     
     
         4 . The cooling system according to  claim 1 , further comprising:
 a storage chamber to be cooled in accordance with the heat exchange of the evaporator; and   a chamber temperature detector to detect a temperature of the storage chamber,   wherein the frost detection point is a point of time when the temperature of the storage chamber reaches a predetermined temperature.   
     
     
         5 . The cooling system according to  claim 1 , further comprising:
 a storage chamber to be cooled in accordance with the heat exchange of the evaporator; and   a chamber temperature detector to detect a temperature of the storage chamber,   wherein the frost detection point is a point of time when the temperature of the storage chamber reaches a predetermined maximum temperature.   
     
     
         6 . The cooling system according to  claim 1 , further comprising:
 a storage chamber to be cooled in accordance with the heat exchange of the evaporator; and   a chamber temperature detector to detect a temperature of the storage chamber,   wherein the frost detection point is a point of time when the temperature of the storage chamber reaches a predetermined minimum temperature.   
     
     
         7 . The cooling system according to  claim 1 , further comprising:
 a compressor to supply compressed refrigerant to the evaporator,   wherein the frost detection point is a point of time when an operation state of the compressor is changed.   
     
     
         8 . The cooling system according to  claim 1 , further comprising:
 a valve to adjust flow of refrigerant to the evaporator,   wherein the frost detection point is a point of time when an operation state of the valve is changed.   
     
     
         9 . The cooling system according to  claim 1 , further comprising:
 a fan to circulate the air exchanging heat with the evaporator,   wherein the frost detection point is a point of time when an operation state of the fan is changed.   
     
     
         10 . The cooling system according to  claim 1 , further comprising:
 a ground terminal,   wherein the frost detection point is a point of time when a potential of the ground terminal reaches a predetermined potential.   
     
     
         11 . The cooling system according to  claim 1 , wherein the control unit collects a plurality of sample voltages at regular intervals for a predetermined time from the frost detection point during the operation of the frost detector. 
     
     
         12 . The cooling system according to  claim 11 , wherein the control unit calculates an average value of the sample voltages, and stores the calculated average value as a detection voltage. 
     
     
         13 . The cooling system according to  claim 12 , wherein the control unit compares the detection voltage with a reference voltage to calculate a difference between the detection voltage and the reference voltage, compares the difference with a predetermined reference variation value, and controls the defrosting operation when the difference exceeds the predetermined reference variation value. 
     
     
         14 . The cooling system according to  claim 13 , wherein the reference voltage is a detection voltage stored during an initial refrigeration cycle executed after power is initially supplied. 
     
     
         15 . The cooling system according to  claim 13 , wherein the reference voltage is a detection voltage stored during a next refrigeration cycle executed after the defrosting operation is completed. 
     
     
         16 . The cooling system according to  claim 1 , further comprising:
 an evaporator temperature detector to detect a temperature of the evaporator,   wherein the control unit controls completion of the defrosting operation based on the temperature of the evaporator detected during the defrosting operation.   
     
     
         17 . The cooling system according to  claim 1 , further comprising:
 a driving unit including a driver to output a drive signal to the frost detector in accordance with instructions from the control unit and to receive the detection signal from the frost detector, and a board temperature detector to detect a temperature of the driving unit,   wherein the control unit executes temperature compensation for the detection signal from the frost detector based on the temperature of the driving unit.   
     
     
         18 . The cooling system according to  claim 17 , wherein:
 the driving unit receives the detection signal from the frost detector through a connection terminal, to which the frost detector is connected, while receiving a noise signal through a non-connection terminal, to which the frost detector is not connected; and   the control unit deducts the noise signal from the detection signal.   
     
     
         19 . The cooling system according to  claim 17 , wherein the driving unit further includes a filter to filter the detection signal from the frost detector such that low frequency components of the detection signal pass through the filter. 
     
     
         20 . The cooling system according to  claim 1 , wherein the control unit further has a function to convert the detection signal from the frost detector into a digital signal. 
     
     
         21 . The cooling system according to  claim 1 , wherein the at least one evaporator comprises at least one of a refrigerating compartment evaporator, a freezing compartment evaporator, and an ice making compartment evaporator. 
     
     
         22 . A control method of a cooling system including a frost detector to detect frost formed on an evaporator, comprising:
 determining whether a current time corresponds to a predetermined frost detection point;   operating the frost detector when the current time corresponds to the predetermined frost detection point, thereby detecting the frost; and   controlling a defrosting operation based on a detection signal generated through the frost detector.   
     
     
         23 . The control method according to  claim 22 , wherein the frost detection point is a point of time when a temperature of a storage chamber cooled by air exchanging heat with the evaporator reaches one of a predetermined temperature, a predetermined maximum temperature and a predetermined minimum temperature. 
     
     
         24 . The control method according to  claim 22 , wherein the frost detection point is a point of time when an operation state of one of a compressor to supply compressed refrigerant to the evaporator, a valve to adjust flow of the refrigerant supplied to the evaporator and a fan to circulate the air exchanging heat with the evaporator is changed. 
     
     
         25 . The control method according to  claim 22 , wherein the frost detection point is a point of time when a potential of a ground terminal provided at the cooling system reaches a predetermined potential. 
     
     
         26 . The control method according to  claim 22 , further comprising:
 collecting a plurality of sample voltages from the detection signal generated during the operation of the frost detector.   
     
     
         27 . The control method according to  claim 26 , further comprising:
 calculating an average value of the sample voltages; and   storing the calculated average value as a detection voltage.   
     
     
         28 . The control method according to  claim 27 , wherein the storing the calculated average value as the detection voltage comprises setting the detection voltage to a reference voltage if the detection voltage is a detection voltage stored during a refrigeration cycle initially executed after power is initially supplied. 
     
     
         29 . The control method according to  claim 28 , wherein the storing the calculated average value as the detection voltage comprises again setting the detection voltage to the reference voltage if the detection voltage is a detection voltage stored during a refrigeration cycle initially executed after completion of the defrosting operation. 
     
     
         30 . The control method according to  claim 22 , wherein the controlling the defrosting operation based on the detection signal comprises:
 calculating a difference between the detection voltage and a predetermined reference voltage;   comparing the difference with a reference variation value;   executing the defrosting operation when the difference exceeds the reference variation value; and   executing a next refrigeration cycle when the difference does not exceed the reference variation value.   
     
     
         31 . The control method according to  claim 22 , wherein the controlling the defrosting operation comprises:
 detecting a temperature of the evaporator during the defrosting operation; and   completing the defrosting operation when the temperature of the evaporator is equal to or higher than a predetermined defrosting completion temperature.   
     
     
         32 . The control method according to  claim 22 , further comprising:
 detecting a temperature of a driving unit to operate the frost detector; and   executing temperature compensation for the detection signal based on the temperature of the driving unit.   
     
     
         33 . The control method according to  claim 22 , wherein the operating the frost detector comprises:
 outputting a drive signal through a connection terminal to which the frost detector is connected;   receiving the detection signal from the frost detector through the connection terminal;   outputting a drive signal through a non-connection terminal to which the frost detector is not connected;   receiving a noise signal from the non-connection terminal; and   removing a component corresponding to the noise signal from the detection signal.   
     
     
         34 . The control method according to  claim 22 , wherein the detecting the frost comprises:
 detecting a capacitance established between the frost detector and a cooling fin provided at the evaporator and arranged adjacent to the frost detector; and   outputting a voltage signal corresponding to the detected capacitance.   
     
     
         35 . The cooling system according to  claim 1 , wherein the frost detector includes a first electrode to detect frost formed between the first electrode and the cooling fin provided at the evaporator, a first insulator arranged in contact with the first electrode, a second electrode arranged in contact with the first insulator, and a second insulator arranged in contact with the second electrode. 
     
     
         36 . The cooling system according to  claim 35 , wherein the first insulator includes an exposed portion around the first electrode, the second electrode extends around the exposed portion of the first insulator to surround the exposed portion of the first insulator so that an insulation gap is formed between the second electrode and the first electrode to insulate the second electrode from the first electrode.