Patent Publication Number: US-2017369340-A1

Title: Apparatus and method for controlling total dissolved solids, and water treatment apparatus including the same

Description:
PRIORITY 
     This application is a Divisional application of U.S. patent application Ser. No. 14/119,738, which was filed in the U.S. Patent and Trademark Office on Nov. 22, 2013, as a National Phase Entry of International Application No. PCT/KR2012/004123 filed May 24, 2012, and claims priority to Korean Patent Application No. 10-2012-0051100 filed with the Korean Intellectual Property Office on May 14, 2012, to Korean Patent Application No. 10-2012-0051099 filed with the Korean Intellectual Property Office on May 14, 2012, to Korean Patent Application No. 10-2011-0065149 filed with the Korean Intellectual Property Office on Jun. 30, 2011, and to Korean Patent Application No. 10-2011-0049621 filed with the Korean Intellectual Property Office on May 23, 2011, the contents of each of which is incorporated herein by reference. 
    
    
     BACKGROUND 
     1. Field of the Invention 
     The present invention relates to a water treatment apparatus such as a water purifier or a water purifier having an ionized water function, a method for controlling the water treatment apparatus, an apparatus and method for controlling total dissolved solids, and a water treatment apparatus including the apparatus for controlling total dissolved solids. More particularly, the present invention relates to a water treatment apparatus for controlling total dissolved solids contained in output water, a method for controlling the water treatment apparatus, an apparatus and method for controlling total dissolved solids, and a water treatment apparatus including the apparatus for controlling total dissolved solids. 
     2. Description of the Related Art 
     Water treatment apparatuses may be used to treat water or wastewater and produce ultra-pure water, and may be used for various purposes such as industrial purposes and home purposes (including business purposes). However, the present invention particularly relates to water treatment apparatuses that are used to produce drinking water. Since water treatment apparatuses for producing drinking water receive raw water (or water), filter the raw water, and generate purified water for drinking, they will be referred to as water purifiers in a narrow sense. Such water purifiers may be configured to receive raw water (or water), filter the raw water with a filtering unit, and supply normal-temperature purified water to users, and may also be configured to heat or cool the normal-temperature purified water and supply hot water or cold water to users. 
     Among the water treatment apparatuses for producing drinking water, there are functional water generators that supply a variety of types of functional water, such as ionized water, carbonated water, and oxygenated water, as well as purified water. In addition, there are water heaters, water coolers, ice makers and the like that primarily filter water received from a water supply unit such as a water tank, and then heat/cool/freeze the filtered water. In this specification, the term “water treatment apparatus” is used as a general term for a water purifier, a functional water generator, a water heater, a water cooler, an ice maker, and any apparatus having at least one of the functions thereof. Although typical water purifiers (including water ionizers) are exemplified for the convenience of description, such water purifiers should be understood as merely examples of water treatment apparatuses according to embodiments of the present invention. 
     In general, water purifiers are classified into ultra filtration (UF) membrane water purifiers and reverse osmosis (RO) membrane water purifiers, depending on the water purifying method carried out thereby. 
     Among them, the RO membrane water purifier has been known as being superior to other water purifying schemes in terms of removing pollutants. 
     The RO membrane water purifier may include a filtering unit including a sediment filter that receives raw water from a hydrant and removes dust particles, dregs, various suspended bodies, and the like, through 5-micron fine filters; a pre-carbon filter that removes carcinogens (e.g., trihalomethane (THM)), synthetic detergents, harmful chemicals (e.g., insecticides), residual chlorine components, and the like, by activated carbon adsorption; an RO membrane filter that includes a 0.0001-micron RO membrane, removes heavy metals (e.g., lead and arsenic), sodium, various germs, and the like, and discharges concentrated water through a drain pipe; and a post-carbon filter that removes unpleasant odors, tastes, and colors contained in water having passed through the RO membrane filter. 
     The UF membrane water purifier uses a UF membrane filter instead of an RO membrane filter. The UF membrane filter is a porous filter having tens to hundreds of nanometer (nm) pores, which removes pollutants in water through numerous fine pores that are distributed on a membrane surface. 
     However, typical RO membrane water purifiers not only remove heavy metals contained in raw water, but also various mineral components contained therein, thus failing to satisfy the desire of users to take minerals. Typical UF membrane water purifiers have lower filtration performances than typical RO membrane water purifiers, thus failing to satisfy the desire of users for pure water (ultra-pure water). 
     Furthermore, typical RO membrane water purifiers should discharge concentrated water (live water), which has failed to pass through an RO membrane, thus causing a serious waste of water. 
     Moreover, typical RO membrane water purifiers or typical UF membrane water purifiers require high maintenance costs because RO membrane filters or UF membrane filters have relatively short lifetimes and replacement periods. Particularly, in regions where raw water contains a large amount of hard minerals such as metal ions, the lifetime of RO membrane filters or UF membrane filters is further reduced. 
     There is, therefore, a need in the art for other improved water purifiers. 
     SUMMARY 
     An aspect of the present invention provides a method of controlling an amount of dissolved solids output in filtered water, with the method including applying a predetermined voltage to water flowing through a filter, measuring a current flowing through the water, determining an amount of dissolved solids in the water based on the predetermined voltage and the measured current, comparing the determined amount of dissolved solids with a target amount of dissolved solids, determining, by a controller, a target current based on the comparison, and performing pulse width modulation (PWM) to match the current flowing through the water with the target current, with the target current being an amplitude of the current flowing through the water, which makes the amount of dissolved solids in the water to be the target amount of dissolved solids. 
     Another aspect of the present invention provides an apparatus for controlling an amount of dissolved solids output in filtered water that includes a filter and a controller that is configured to apply a predetermined voltage to water flowing through the filter, measure a current flowing through the water, determine an amount of dissolved solids in the water based on the predetermined voltage and the measured current, compare the determined amount of dissolved solids with a target amount of dissolved solids, determine a target current based on the comparison, and perform pulse width modulation (PWM) to match the current flowing through the water with the target current, with the target current being an amplitude of the current flowing through the water, which matches the amount of dissolved solids in the water with the target amount of dissolved solids. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The above and other aspects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a flow passage configuration diagram illustrating a configuration of a water treatment apparatus according to an exemplary embodiment of the present invention; 
         FIG. 2  is a flow passage configuration diagram illustrating a flow passage for generating purified water in the water treatment apparatus illustrated in  FIG. 1 ; 
         FIG. 3  is a flow passage configuration diagram illustrating a flow passage for recycling a deionizing filter in the water treatment apparatus illustrated in  FIG. 1 ; 
         FIG. 4  is a flow passage configuration diagram illustrating a configuration of a water treatment apparatus according to another exemplary embodiment of the present invention; 
         FIG. 5  is a flow passage configuration diagram illustrating a flow passage for generating purified water in the water treatment apparatus illustrated in  FIG. 4 ; 
         FIG. 6  is a flow passage configuration diagram illustrating a flow passage for recycling a deionizing filter in the water treatment apparatus illustrated in  FIG. 4 ; 
         FIG. 7  is a flow passage configuration diagram illustrating a configuration of a water treatment apparatus according to another exemplary embodiment of the present invention; 
         FIG. 8  is a flow passage configuration diagram illustrating a configuration of a water treatment apparatus according to a modified example of the exemplary embodiment of the present invention illustrated in  FIG. 7 ; 
         FIG. 9  is a graph illustrating a mineral removal performance depending on a voltage; 
         FIG. 10  is a graph illustrating toxic heavy metal removal performance depending on voltage; 
         FIG. 11  is a functional block diagram illustrating a main configuration involved in controlling total dissolved solids according to an exemplary embodiment of the present invention; 
         FIG. 12  is a functional block diagram illustrating a control unit according to an exemplary embodiment of the present invention; 
         FIG. 13  is a table in which a flow rate of raw water, a voltage applied to a filtering unit, and the like are described in connection with total dissolved solids according to an exemplary embodiment of the present invention; 
         FIG. 14  is a flow chart illustrating a method for controlling a water treatment apparatus according to an exemplary embodiment of the present invention; and 
         FIG. 15  is a flow chart illustrating a deionizing filter driving process illustrated in  FIG. 14 . 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS OF THE PRESENT INVENTION 
     Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. However, in the description of the operational principles associated with the embodiments of the present invention, a detailed description of known art inventions or constructions is omitted because it may obscure the spirit of the present invention unnecessarily. 
     The terms used in this specification are used for describing specific embodiments and do not limit the scope of the present invention. A singular expression may include a plural expression, as long as they are obviously different from each other in context. 
     It will be understood that when an element is referred to as being “connected” to another element, it may be directly connected to the other element or may be indirectly connected to the other element with element(s) interposed therebetween. Unless explicitly described to the contrary, the terms “include” and “have” will be understood to imply the inclusion of stated elements but not the exclusion of any other elements. 
     Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. The invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In describing the present invention, if detailed descriptions of related known functions or configurations are considered to unnecessarily divert the gist of the present invention, such descriptions will be omitted. Like reference numerals will be used to denote like elements throughout the specification. In the drawings, the shapes and sizes of elements and the distance between elements may be exaggerated for clarity of illustration. 
     First, a water treatment apparatus  100  according to exemplary embodiments of the present invention will be described with referenced to  FIGS. 1 through 6 . 
     As illustrated in  FIGS. 1 through 6 , a water treatment apparatus  100  according to an exemplary embodiment of the present invention may include a filtering unit  110  including a deionizing filter  130 , a water output unit  170  outputting water filtered by the filtering unit  110 , and a control unit  200  controlling power applied to the deionizing filter  130 . The water treatment apparatus  100  may further include a cooling unit  150  and a heating unit  160  changing the temperature of water extracted, and a display unit (not illustrated) displaying an operation status of the water treatment apparatus  100  by light or sound. In addition, as illustrated in  FIGS. 4 through 6 , a water treatment apparatus  100  according to an exemplary embodiment of the present invention may further include an ionized water generating unit  140  generating ionized water by using water filtered by the filtering unit  110 . 
     The filtering unit  110  may sequentially filter and purify raw water. The filtering unit  110  may include a sediment filter, a pre-carbon filter, a deionizing filter  130 , and a post-carbon filter  112 . If the filtering unit  110  includes a deionizing filter  130 , the types, the number and the order of filters may vary depending on the filtering performance of a water treatment apparatus (water purifier). In addition, as illustrated in  FIGS. 1 through 6 , a hybrid filter  111  composed of a sediment filter and a pre-carbon filter may be included, and a variety of types of functional filters may be added or substituted. 
     The sediment filter may receive raw water from a raw water supply unit, and adsorb and remove relatively large suspended particles and solids (e.g., sand particles) contained in the raw water. The pre-carbon filter may receive water filtered by the sediment filter, and remove harmful chemicals (e.g., volatile organic compounds, carcinogens, synthetic detergents, and insecticides) and residual chlorine components contained in the water, by activated carbon adsorption. Although  FIGS. 1 through 6  illustrate that the sediment filter and the pre-carbon filter are included in the hybrid filter  111 , the sediment filter and the pre-carbon filter may be installed separately from each other. 
     Meanwhile, a raw water feed valve V 2  for selectively shutting off raw water supplied from a raw water supply unit may be installed at a rear end of the hybrid filter  111 . However, the installation position of the raw water feed valve V 2  is not limited thereto as long as the raw water feed valve V 2  can shut off the supply of the raw water. For example, the raw water feed valve V 2  may also be installed at a front end of the hybrid filter  111 . In addition, as illustrated in  FIGS. 1 through 6 , a pressure reducing valve V 1  may be installed to maintain the pressure of raw water, which flows in from the filtering unit  110 , at a predetermined level. 
     In addition, the post-carbon filter  112  may adsorb and remove an unpleasant taste, odor or color from water filtered by the deionizing filter  130 . Purified water filtered by the post-carbon filter  112  may be supplied through the water output unit  170  to a user. In this case, other complex functions may be added to the post-carbon filter  112 , or other additional filters may be added to the post-carbon filter  112 . 
     In addition, the deionizing filter  130  provided to remove (including the meanings of filtering off, adsorption, and separation from water) dissolved solids may be provided between the hybrid filter  111  and the post-carbon filter  112 ; however, the present invention is not limited thereto. For example, the deionizing filter  130  may be used together with other filters, or the deionizing filter  130  may be solely provided in the filtering unit  110 . 
     The deionizing filter  130  may reduce total dissolved solids (TDS), which is contained in water flowed therein, by an application of power thereto. That is, the deionizing filter  30  may be configured to remove (separation from water) dissolved solids (ionized materials), which are contained in water, by electricity. The term total dissolved solids (TDS) is also used to imply the amount of solids that are dissolved in water and contain mineral components such as calcium, sodium, magnesium, and iron, which is expressed in units of mg/l or ppm. In this manner, the total dissolved solids imply the total amount of dissolved solids, which exist as ionized materials in general. 
     For example, the deionizing filter  130  may be configured to remove dissolved solids (ionized materials), which are contained in water, by any one of electrodialysis (ED), electrodeionization (EDI), and capacitive deionization (CDI). However, the deionizing filter  130  is not limited thereto as long as the deionizing filter  130  can remove dissolved solids (ionized materials) by power that is applied to a positive electrode and a negative electrode thereof. For example, the deionizing filter  130  may be configured such that an ion exchange resin is adhered or applied to a membrane and electricity is applied to the membrane. In this case, the dissolved solids removed by the deionizing filter  130  are generally ionized materials. Therefore, in the specification including the claims of the present invention, the meaning of removing dissolved solids includes the meaning of removing ionized materials. 
     Meanwhile, EDI performs deionization (desalination) by direct current (DC) electricity, which is also referred to as membrane deionization (MDI) or continuous electrodeionization (CEDI). In this specification, EDI is described as including MDI and CEDI. 
     The deionizing filter  130  removes dissolved solids (ionized materials) from water by an application of power. Accordingly, total dissolved solids are reduced in water that has passed through the deionizing filter  130 . The control of total dissolved solids by the deionizing filter  130  may be performed by the control unit  200 . That is, the control unit  200  may control power applied to the deionizing filter  130 , so that total dissolved solids in water filtered by the deionizing filter  130 , or a reduction rate of total dissolved solids by the deionizing filter  130  may be controlled. 
     In this case, the control unit  200  may control power applied to the deionizing filter  130 , so that the type of water depending on total dissolved solids in water filtered by the deionizing filter  130 , or the type of water depending on a reduction rate of total dissolved solids by the deionizing filter  130  may be divided in at least two stages prior to output. 
     For example, the control unit  200  may control power applied to the deionizing filter  130 , so that mineral water generated by removing total dissolved solids from raw water at a predetermined level, and ultra-pure water containing less total dissolved solids than the mineral water may be output. However, the division of water depending on total dissolved solids or a reduction rate of total dissolved solids may be subdivided in addition to mineral water and ultra-pure water. 
     For example, the mineral water may correspond to water whose reduction rate of total dissolved solids by the deionizing filter  130  is equal to or greater than about 30% and less than about 80%, in comparison with water (or raw water) that has not flowed into the deionizing filter  130 , and the ultra-pure water may correspond to water whose reduction rate of total dissolved solids by the deionizing filter  130  is equal to or greater than about 80%. In this manner, the reduction rate of total dissolved solids corresponding to the mineral water or the ultra-pure water may be selected directly by a user. However, the reduction rate of total dissolved solids corresponding to the mineral water or the ultra-pure water may also be preset to a predetermined range or a predetermined value prior to prior to product launch. For example, the reduction rate of total dissolved solids (dissolved solid reduction rate) by the deionizing filter  130  in the case of the ultra-pure water may be set to about 90%, and the reduction rate of total dissolved solids by the deionizing filter  130  in the case of the mineral water may be set to about 50%. 
     Meanwhile, in a case in which the ionized water generating unit  140  is included as illustrated in  FIGS. 4 through 6 , mineral water containing a large amount of minerals (total dissolved solids) may be supplied to the ionized water generating unit  140  so that the ionized water generating unit  140  can efficiently generate alkali water or acid water having a desired pH even by low-power (low-current) driving. To this end, when ionized water (alkali water) is selected, the control unit  200  may control power applied to the deionizing filter  130 , so that total dissolved solids of an amount corresponding to mineral water are contained in water. 
     In addition, opposite-polarity power may be applied to the deionizing filter  130  to perform a recycling process. 
     To this end, a recycling flow passage L 2  separated from a purified water flow passage L 1  may be installed in the filtering unit  110  of the water treatment apparatus  100 . 
     The recycling flow passage L 2  may supply inflow raw water to an output side of the deionizing filter  130 . Specifically, the recycling flow passage L 2  may be branched from a recycling flow passage switch valve  113  and connected to a connection unit F that is located at an output side of the deionizing filter  130 . In addition, recycling water flowing through the deionizing filter  130  in a reverse direction may be drained through a drain pipe D. In this case, a recycling feed valve V 6  may be installed in the drain pipe D. The recycling feed valve V 6  may be closed in a water purifying mode and opened in a recycling mode so that water having passed through the hybrid filter  111  is not drained through the drain pipe D in a purified water generating mode. 
     In addition, a flow rate sensor  120  may be installed at a front end of the deionizing filter  130  so that a flow rate of water flowing into the deionizing filter  130  may be measured to control total dissolved solids removed by the deionizing filter  1230 , or a reduction rate of the total dissolved solids. 
     The flow rate sensor  120  may be installed at a front end of the connecting unit F that connects the purified water flow passage L 1  and the drain pipe D. That is, the drain pipe D may be connected to the purified water flow passage L 1  between the flow rate sensor  120  and the deionizing filter  130 , so that no water passes through the flow rate sensor  120  in a recycling mode. Accordingly, when a flow through the flow rate sensor  120  is detected in a recycling mode of the deionizing filter  130 , it may be determined that there is a problem in switching a flow passage by the recycling flow passage switch valve  113 . When it is determined by the flow rate sensor  120  that there is a problem in performing a recycling mode, the control unit  200  may display a malfunction of the recycling mode by light or sound through a display unit (not illustrated). Accordingly, the installation position of the flow rate sensor  120  may be controlled such that the deionizing filter  130  can be prevented from malfunctioning due to a recycling failure. 
     In the recycling mode, a flow passage is formed along arrows illustrated in  FIGS. 3 and 6 . That is, when the recycling flow passage switch valve  113  switches a flow passage such that the purified water flow passage L 1  and the recycling flow passage L 2  communicate with each other, raw water flows through the recycling flow passage switch valve  113  into the recycling flow passage L 2 . The raw water having flowed into the recycling flow passage L 2  flows into an output side of the deionizing filter  130 , passes the deionizing filter  130  in the reverse direction, and drains through the connection unit F connected to the drain pipe D, through the recycling feed valve V 6 , and through the drain pipe D. In the recycling mode, opposite-polarity power is applied to the deionizing filter  130 . 
     Then, when a purified water extracting valve V 3  is opened by a purified water extracting selection of a user, water having total dissolved solids controlled by a filtering operation of the filtering unit  110  is discharged through a normal-temperature water flow passage L 3  to the water output unit  170 . 
     Meanwhile, a water treatment apparatus  100  according to an exemplary embodiment of the present invention may include at least one of the cooling unit  150  and the heating unit  160  in order to change the temperature of water filtered by the filtering unit  110 . 
     In order to supply water through the cooling unit  150  or the heating unit  160 , the cooling unit  150  may be installed at a cold water flow passage L 4 , and the heating unit  160  may be installed at a hot water flow passage L 5 . Water may be extracted from the cooling unit  150  when a cold water extracting valve V 4  is opened; and water may be extracted from the heating unit  160  when a hot water extracting valve V 5  is opened. 
     The drawings of the specification illustrate electronic valves that are automatically opened by user selection to extract water through the water output unit  170 . However, mechanical valves may be used instead of such electronic valves. 
     Meanwhile,  FIGS. 1 through 3  illustrate that the normal-temperature water flow passage L 3 , the cold water flow passage L 4 , and the hot water flow passage L 5  are merged together such that water is discharged through one extracting port  171  provided in the water output unit  170 . However, the number of extracting ports  171 , the flow passage configuration at a front side of the water output unit  170 , and the flow passage configuration in the water output unit  170  may vary according to various embodiments. 
     For example, the cooling unit  150  may include a cold water tank, and the heating unit  160  may include a heating tank. As another example, the cooling unit  150  may include an instant cooling device that cools water supplied by the water pressure of raw water, and the heating unit  160  may include an instant heating device that heats water supplied by the water pressure of raw water. When a direct water cooling unit  150  and/or a direct water heating unit  160  using the water pressure of a raw water is used as above, the propagation of bacteria or microorganisms in water stored in a relevant tank can be prevented, and the size and manufacturing costs of a water treatment apparatus  100  can be reduced because it is not necessary to install a relevant tank. 
     In addition, a drain flow passage switch valve VD may be installed in the water output unit  170  or at the front end of the water output unit  170  so that water output from the heating unit  160  may be discharged through the drain pipe D or through the extracting port  171  of the water output unit  170 . To this end, the drain flow passage switch valve VD may be installed to switch a flow passage such that the output side of the heating unit  160  communicates with the drain pipe D or the extracting port  171 . As with the driving of other valves, the driving of the drain flow passage switch valve VD may be controlled by the control unit  200 . 
     In this case, the control unit  200  may switch a flow passage of the drain flow passage switch valve VD such that the output side of the heating unit  160  may be connected through a drain flow passage V 7  to the drain pipe D during a predetermined period of time to drain water remaining in the instant heating unit  160 . That is, when the valves connected to the heating unit  160 , such as the raw water feed valve V 2 , are opened, water filtered by the filtering unit  110  flows into the heating unit  160  to discharge water remaining in the heating unit  160 , so that air in the heating unit  160  can be removed. In this manner, by removal of residual water in the heating unit  160 , the damage of the heating unit  160  caused by bubbles can be prevented. In this case, a check valve V 9  may be installed in the drain flow passage V 7  such that water flowing through the drain flow passage V 7  does not flow backward. 
     Meanwhile, the heating unit  160  may be driven after removal of residual water in the heating unit  160  during a predetermined period of time (for example, 1 to 2 seconds), so that the temperature of water output from the heating unit  160  can be increased, and the flow passage in the water output unit  170  and the flow passage connected to the water output unit  170  may be sterilized using such hot water. That is, the heating unit  160  may be driven under the control of the control unit  200  during at least a portion (for example, a period to the end of drainage after the lapse of about 1 to 1.5 seconds) of a period of time (for example, about 2 to 3 seconds) when water remaining in the heating unit  160  is drained through the drain pipe P, so that a flow passage provided in the water output unit  170  may be sterilized. 
     For example, the sterilization of the water output unit  170  by the heating unit  160  may be performed at the time of outputting hot water. As another example, the sterilization of the water output unit  170  by the heating unit  160  may be performed by user selection or may be automatically performed at predetermined periods. Meanwhile, a heating amount (power supply amount) of the heating unit  160  may be controlled based on a flow rate measured by a flow rate sensor FS provided in a front end of the heating unit  160 , so that the temperature of water heated and output by the heating unit  160  may be effectively controlled. 
     Meanwhile, as illustrated in  FIGS. 4 through 6 , a water treatment apparatus  100  according to an exemplary embodiment of the present invention may further include an ionized water generating unit  140 . 
     The ionized water generating unit  140  may generate acid water or alkali water when power is applied to electrodes provided therein. 
     As with a typical ice maker or an ice water purifier, the ice making unit  195  may generate ice. A detailed method and configuration of the ice making unit  195  for generating ice is not specifically limited as long as the ice making unit  195  can receive water and generate ice. In addition, ice generated by the ice making unit  195  may be stored in an ice storage space (not illustrated) prior to being supplied to a user. 
     The sterilized water generating unit  192  may generate sterilized water containing sterilizing materials when power is applied to electrodes thereof. 
     For example, the sterilized water generating unit  192  may be configured to electrolyze (in this specification, “electrolysis” will be described as including “redox reaction”) inflow water and generate sterilized water containing a material having a sterilizing function, such as a mixed oxidant (MO). 
     The sterilized water generating unit  192  may sterilize or extinguish microorganisms or bacteria remaining in water by passing water between electrodes of different polarities. In general, sterilization of purified water by electrolysis may be performed by a combination of a direct redox reaction that directly oxidizes microorganisms at a positive electrode, and an indirect redox reaction that oxidizes microorganisms by a variety of types of mixed oxidants (for example, residual chorine, ozone, OH radical, and oxygen radicals) that may be generated at a positive electrode. 
     In this manner, water having flowed into the sterilized water generating unit  192  may move to the ice making unit  195  while containing mixed oxidants. In this case, since water having flowed into the ice making unit  195  is used to generate ice, it may be necessary to control power applied to the electrodes of the sterilized water generating unit  192 , so that sterilized drinking water containing mixed oxidants with a concentration, which is drinkable by a user, may be supplied to the ice making unit  195 . 
     Therefore, according to an exemplary embodiment of the present invention, sterilized drinking water containing mixed oxidants is generated by the sterilized water generating unit  192 , and the sterilized drinking water is used to generate ice in the ice making unit  195 . Accordingly, unpolluted ice can be supplied to a user, and the pollution of ice by bacteria can be minimized even when the ice is stored in an ice storage space (not illustrated) for a long period of time. 
     In addition, as illustrated in  FIG. 7 , a water treatment apparatus  100  according to an exemplary embodiment of the present invention may further include a storage tank for storing water filtered by the filtering unit  110 . In this case, mixed oxidants generated by the sterilized water generating unit  192  (specifically, sterilized water containing mixed oxidants) may be supplied to the storage tank  193 , and the ice making unit  195  may be configured to receive sterilized drinking water containing the mixed oxidants stored in the storage tank  193  and generate ice. 
     For example, the storage tank  193  may include a normal-temperature storage tank. As another example, the storage tank  193  may include a cold water tank so that the ice making unit  195  can rapidly perform an ice making operation. 
     When the storage tank  193  is provided as above, the concentration (amount) of mixed oxidants generated by the sterilized water generating unit  192  may be controlled such that the mixed oxidants generated by the sterilized water generating unit  192  may be diluted with the water stored in the storage tank  193 , to generate sterilized drinking water having a predetermined concentration. 
     When the storage tank  193  is provided as above, water supplied to the ice making unit  195  is prestored. Therefore, in this case, the time taken to supply water to the ice making unit  195  can be reduced as compared to a case in which water having passed through the filtering unit  110  is directly supplied to the ice making unit  195 . 
     Meanwhile, a water treatment apparatus  100  according to an exemplary embodiment of the present invention includes a normal-temperature water tank at the normal-temperature flow passage L 3  or includes a cold water tank at the cooling unit  150  as illustrated in  FIG. 8 . In this case, the storage tank  193  may include a normal-temperature water tank or a cold water tank. In addition, the sterilized water generating unit  192  may be provided on an inflow side of the cold water tank and configured to supply mixed oxidants to the normal-temperature water tank or the cold water tank. 
     When the storage tank  193  is provided as above, sterilized drinking water containing mixed oxidants can be supplied through the sterilized water generating unit  192  to the storage tank  193 . Accordingly, the propagation of bacteria or microorganisms in water stored in the storage tank  193  can be prevented. Therefore, ice can be generated using unpolluted, clean water. In addition, sine the ice making unit  195  generates ice by using sterilized drinking water containing a small amount of mixed oxidants, the propagation of bacteria or microorganisms in the ice can be prevented even when the ice is stored in an ice storage space for a long period of time. 
     Meanwhile, as illustrated in  FIG. 7 , a water treatment apparatus  100  according to an exemplary embodiment of the present invention may further include a chlorine removing filter  194  that is provided at a rear end of the storage tank  193  to remove chlorine components contained in the sterilized drinking water. 
     When the chlorine removing filter  194  is provided as above, chlorine components contained in the sterilized drinking water stored in the storage tank  193  can be removed. Accordingly, odors or tastes caused by chlorine components can be removed, thus eliminating an unpleasant sensation that may be experienced by a user. Meanwhile, in a case in which water filtered the chlorine removing filter  194  is supplied to the ice making unit  195 , the effect of preventing the propagation of bacteria or microorganisms in ice may be low, as compared to a case in which water is not filtered by the chlorine removing filter  194 . However, since water, which has few bacteria or microorganisms due to the mixed oxidants present in the storage tank  193 , is supplied to the ice making unit  195 , an ice storage space time can be increased as compared to the case of ice generated by a typical ice maker. 
     Meanwhile, as illustrated in  FIG. 8 , a water treatment apparatus  100  according to an aspect of the present invention may be configured such that mixed oxidants generated by the sterilized water generating unit  192  may pass through the cooling unit  150  and cooled water may be supplied to the ice making unit  195 . In this case, a current/voltage applied to the sterilized water generating unit  192  may be controlled such that sterilized water containing mixed oxidants generated by the sterilized water generating unit  192  can be used as sterilized drinking water. 
     In  FIGS. 7 and 8 , reference numerals  191  and  191 ′ denotes a flow passage switch valve that is configured to switch a flow passage such that water filtered by the filtering unit  110  can be supplied to the ice making unit  195 . In  FIG. 3 , V 4  denotes a flow passage switch valve that is configured to switch a flow passage between a flow passage for extraction of cold water and a flow passage connected to the ice making unit  195 . 
     Meanwhile, in a typical water purifying mode of the water treatment apparatus  100 , purified water is extracted along arrows in  FIGS. 2 and 5 . That is, water having passed through the purified water flow passage L 1  may be discharged at a normal temperature through the normal-temperature water flow passage L 3 , may be cooled and discharged through the cold water flow passage L 4 , and may be heated and discharged through the hot water flow passage L 5 . In addition, as described above, when hot water is extracted, water remaining in the heating unit  160  may be initially drained as represented by a dotted arrow. 
     In this case, water extraction after the passage of the hot water flow passage L 5  may be performed according to user selection. In this manner, extracted water may have a plurality of types depending on total dissolved solids (or reduction rate). For example, water may be extracted as mineral water or ultra-pure water, and mineral water may be subdivided into a high-concentration type and a low-concentration type. 
     If a user selects mineral water or ultra-pure water, water having total dissolved solids of an amount corresponding to mineral water or ultra-pure water, or water having a reduction rate of total dissolved solids corresponding to mineral water or ultra-pure water may be output. In this case, mineral water or ultra-pure water may be discharged through the normal-temperature water flow passage L 3 , the cold water flow passage L 4  or the hot water flow passage L 5  and through the water extracting port  171  of the water output unit  170 . In this case, the water output unit  170  may have a plurality of water output ports having different functions, and may have one water output port as illustrated in  FIG. 1 , which are all included in the scoped of the present invention. 
     In this manner, a water treatment apparatus  100  according to an exemplary embodiment of the present invention can output various types of extracted water with different total dissolved solids (or reduction rate), and can extract various types of water in various temperatures, thus satisfying various desires of users. 
     Meanwhile, when the ionized water generating unit  140  is provided as illustrated in  FIGS. 4 and 5 , purified water having passed through the filtering unit  110  may be supplied through the flow passage switch valve V 7  and an inflow passage L 7  to the ionized water generating unit  140 . The water supplied to the ionized water generating unit  140  may be divided into alkali water and acid water. The alkali water may be extracted as normal-temperature alkali water through a normal-temperature alkali water flow passage L 8  and the water output unit  170 , or may be extracted as cold alkali water through a cold alkali water flow passage L 9  and the water output unit  170 . The acid water may be drained through an acid water flow passage L 10  to the outside. In this case, the acid water flow passage L 10  may be connected to the drain pipe D. However, the acid water flow passage L 10  may be extracted through a separate extraction unit and used for other purposes such as cleaning. In this case, in order to implement a desired pH of ionized water, water supplied to the ionized water generating unit  140  may have a sufficient amount of total dissolved solids. Accordingly, when the extraction of ionized water is selected, the control unit  200  may control the power (current or voltage) applied to the deionizing filter  130 , such that total dissolved solids (or a reduction rate thereof) corresponding to mineral water is implemented in the deionizing filter  130  and mineral water is supplied to the ionized water generating unit  140 . 
     Hereinafter, an operation of controlling total dissolved solids removed by the deionizing filter  130  will be described in detail. 
       FIG. 9  is a graph illustrating an ion removal performance depending on a voltage, and  FIG. 10  is a graph illustrating toxic heavy metal removal performance depending on voltage. Specifically,  FIG. 9  is a graph illustrating the performance of removing ions in raw water by electrodeionization, depending on an applied voltage, and  FIG. 10  is a graph illustrating the performance of removing toxic heavy metals in raw water by electrodeionization, depending on an applied voltage. Experiments of  FIGS. 9 and 10  were performed after the deionizing filter  130  is recycled. On the condition that a TDS concentration of raw water was 320 ppm and a flow rate was 1 LPM (liter/min), measurements were performed while changing a voltage condition from 50 V to 260 V. 
     It can be seen from  FIG. 10  that while an applied voltage changes from 50 V to 260 V, almost all of the toxic heavy metals are removed (a toxic heavy metal removal performance is a rate of 90% to 100%). In addition, it can be seen that the toxic heavy metal removal performance is not greatly affected by the amplitude of an applied voltage, and almost all of the heavy metals contained in raw water are removed. 
     On the other hand, it can be seen from  FIG. 9  that while an applied voltage changes from 50 V to 260 V, the removal performance with respect to ions except the toxic heavy metals (i.e., useful mineral ions) rapidly increases with an increase in the applied voltage. In addition, it can be seen that while an applied voltage changes from 50 V to 260 V, a reduction rate of total dissolved solids (TDS) gradually increases from 35% to 85%. 
     Accordingly, by controlling the amplitude of a voltage or a current applied to the deionizing filter  130 , ultra-pure water (for example, a TDS (mineral) reduction rate is equal to or greater than 80%) or mineral water (for example, a TDS (mineral) reduction rate is equal to or greater than 30% and less than 80%) can be generated, and general purified water (for example, a TDS (mineral) reduction rate is less than 30%) can be generated. 
     In particular, as illustrated in  FIG. 9 , it can be seen that calcium ions are removed by more than 80% even when a low voltage is applied. Accordingly, as described above, when the ionized water generating unit (electrolyzer)  140  is installed at the rear end of the deionizing filter  130 , a scale generation in electrodes provided in the ionized water generating unit  140  can be significantly reduced and the lifetime of the electrodes provided in the ionized water generating unit  140  can be greatly increased. 
     As can be seen from  FIGS. 9 and 10 , by controlling a voltage applied to the deionizing filter  130 , most of the toxic heavy metals can be removed, and the amount of mineral ions can be determined according to user preferences, so that mineral water or ultra-pure water can be extracted. 
     Accordingly, a total dissolved solid (mineral ion, ion materials) controlling apparatus ( 100 ′ of  FIG. 11 ) and a total dissolved solid controlling method (S 100 ′ of  FIG. 15 ), which can determine the amount of mineral ions according to user preferences while removing most of the toxic heavy metals, may be considered based on the experiment examples of  FIGS. 9 and 10 . That is, when a voltage applied to raw water is controlled between 50 V and 260 V, about 90% to 100% toxic heavy metals can be removed without being affected by a change in the amplitude of the voltage, as illustrated in  FIG. 10 , and the amount of mineral ions in the raw water can be determined as illustrated in  FIG. 9 . 
     Since a power supply unit (not illustrated) can have a voltage between 50 V and 260 V, the control of total dissolved solid removal by a voltage requires a voltage controlling device that can implement a change in the voltage. However, a voltage controlling device supporting a voltage control having a relatively large variation width of 50 V to 260 V is complex in configuration and requires an expensive circuit configuration cost. 
     Accordingly, as will later be described, an aspect of the present invention provides a total dissolved solid controlling apparatus ( 100 ′ of  FIG. 11 ) and a total dissolved solid controlling method (S 100 ′ of  FIG. 15 ), which can easily control the removal of total dissolved solids while removing almost all of the toxic heavy metals. 
     Referring to  FIG. 11 , a total dissolved solid controlling apparatus  100 ′ according to an aspect of the present invention may include a deionizing filter  130 , a flow rate sensor  120 , and a control unit  200 . 
     As described above, the deionizing filter  130  may remove total dissolved solids (ionized materials), which are contained in raw water, by at least one of electrodialysis (ED), electrodeionization (EDI), and capacitive deionization (CDI). Herein, total dissolved solids removed by the deionizing filter  130  or a reduction rate of the total dissolved solids may be determined according to an input current applied to the deionizing filter  130 . For the convenience of description,  FIG. 11  illustrates that a total dissolved solid controlling apparatus  100 ′ according to an aspect of the present invention includes only the deionizing filter  130 . However, the total dissolved solid controlling apparatus  100 ′ may further include other filters than the deionizing filter  130 , such as a sediment filter, a pre-carbon filter, and a post-carbon filter. 
     Meanwhile, when electrodialysis is used to remove ions contained in raw water, the deionizing filter  130  may include an electrode and an ion exchange membrane. 
     Specifically, when the deionizing filter  130  applies an input current to raw water through an electrode, total dissolved solids (ionized materials) contained in raw water is moved by an electrical attraction force to a positive electrode or a negative electrode according to their polarity. Herein, since the positive electrode and the negative electrode are provided with an ion exchange membrane, only the total dissolved solids moved by the electrical attraction force may be connected/adsorbed to the ion exchange membrane. Accordingly, as described above, the deionizing filter  130  may remove ions from inflow raw water. 
     Unlike this, when electrodeionization is used to remove dissolved solids (ionized materials) contained in raw water, the deionizing filter  130  may include an electrode, an ion exchange membrane, and an ion exchange resin. 
     Specifically, an ion exchange resin filling a space between a positive ion exchange membrane and a negative ion exchange membrane may be used to collect/adsorb positive ions and negative ions in raw water that has flowed into the deionizing filter  130 . Herein, when an input current is applied to the ion exchange membrane, the collection/adsorption of dissolved solids in raw water may be accelerated by an electrical attraction force. Since the dissolved solids in raw water are collected/adsorbed by the ion exchange membrane as above, dissolved solids contained in inflow raw water can be removed by the deionizing filter  120 . 
     In addition, unlike the electrodialysis and the electrodeionization, when capacitive deionization is used to remove ions contained in raw water, the deionizing filter  130  may not include an ion exchange membrane or an ion exchange resin. That is, the capacitive deionization may directly adsorb dissolved solids (ionized materials) and remove ions from raw water having flowed in the deionizing filter  130 . Accordingly, the electrode of the deionizing filter  130  may be a porous carbon electrode that has small reactivity while having a wide surface area. The porous carbon electrode may be implemented by activated carbon. As compared to a variety of types of other porous carbon materials, the activated carbon has a good work capacity, a high specific surface area, and a high desorption/adsorption performance. Therefore, it may be more preferable to use the activated carbon as the electrode of the deionizing filter  130 . 
     According to an exemplary embodiment of the capacitive deionization, when a voltage is applied to two porous carbon electrodes and raw water is flowed therebetween, the positive ions contained in the raw water may be adsorbed to the negative electrode, and the negative ions may be adsorbed to the positive electrode. In this case, the amount of ions adsorbed to the electrodes may be increased, so that the electrodes may be saturated. When the electrodes are saturated, opposite-polarity voltages may be applied to the respective electrodes. Then, the ions adsorbed to the electrodes may be desorbed by an electrical repulsion force. That is, opposite-polarity voltages may be applied to the electrodes to recycle the electrodes. 
     When the capacitive deionization is used as above, since separate configurations such as an ion exchange membrane and an ion exchange resin are not necessary, the configuration of the deionizing filter  130  is simplified. Also, since ions are adsorbed to the electrodes, the amplitude of a voltage for attracting the ions can be reduced as compared to the cases of electrodialysis and electrodeionization. That is, according to the capacitive deionization, the deionizing filter  130  can remove ions even with a low voltage. Therefore, the configuration of a power supply unit supplying power to the deionizing filter  130  can be simplified, and the price of the power supply unit can be reduced. In addition, since the deionizing filter  130  is driven with a low voltage, the energy consumption in a deionizing operation can be reduced. 
     However, the deionizing filter  130  is not limited to an electrodialysis filter, an electrodeionization filter, and a capacitive deionization filter. The structure of the deionizing filter  130  may vary as long as the deionizing filter  130  can remove dissolved solids by an application of power. 
     As described above, the deionizing filter  130  may use electrodialysis, electrodeionization, and/or capacitive deionization to remove dissolved solids (ionized materials) contained in raw water. Herein, the amount of dissolved solids removed by the deionizing filter  130  or a reduction rate of the dissolved solids may be determined according to an input current applied to the deionizing filter  130 . 
     Also, the control unit  200  may control an input current applied to the deionizing filter  130 , such that water discharged through the deionizing filter  130  has target total dissolved solids (TDS). 
     The control unit  200  may apply a predetermined fixed voltage to the deionizing filter  130  and may control an input current by pulse width modulation (PWM). The predetermined fixed voltage may vary according to a reduction rate of total dissolved solids inputted by the user (or total dissolved solids contained in extracted water). 
     The target total dissolved solids may be predetermined, or may be inputted by the user. The target total dissolved solids may vary according to a reduction rate of total dissolved solids inputted by the user (or total dissolved solids contained in extracted water). 
     In order to control a removal amount of total dissolved solids of the deionizing filter  130  by current control, the control unit  200  may apply a predetermined fixed voltage to the deionizing filter  130 . When the fixed voltage is applied to the deionizing filter  130 , a current may flow in the deionizing filter  130  by positive ions and negative ions that are present in raw water. That is, since a redox action, in which negative ions in the raw water supply electrons to the positive electrode and the negative electrode supplies electrons to positive ions in the raw water, is generated, a current may flow in the deionizing filter  130 . 
     When other conditions are the same, the current flowing in the deionizing filter  130  may be proportional to the amount of dissolved solids (ionized materials) removed by the deionizing filter  130 . Therefore, the current flowing in the deionizing filter  130  may be controlled to control a reduction rate of total dissolved solids in raw water (a removal rate of dissolved solids). 
     More specifically, a total dissolved solid controlling apparatus  100 ′ according to an aspect of the present invention may control an input current by pulse width modulation. The pulse width modulation may change an input period of a fixed voltage inputted to the deionizing filter  130  and control an input current while maintaining a voltage at a constant level. In order to implement the pulse width modulation, the control unit  200  may include a switching element. The control unit  200  may control an input current applied to the deionizing filter  130  based on a period of time when the switching element is closed, and dissolved solids (ionized materials) removed from raw water may be determined accordingly. 
     Also, the flow rate sensor  120  may measure a flow rate of raw water flowing into the deionizing filter  130 . 
     The flow rate sensor  120  may provide information about the measured flow rate to the control unit  200 . The total dissolved solid removal performance of the deionizing filter  130  may be affected not only by total dissolved solids in raw water, but also by a flow rate of raw water flowing into the deionizing filter  130 . Accordingly, when the flow rate sensor  120  provides information about the measured flow rate to the control unit  200 , the control unit  200  may control the deionizing filter  130  more accurately. 
       FIG. 12  is a functional block diagram illustrating a control unit  200  according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 12 , the control unit  200  may include a determiner  210 , an input current determiner  220 , and an input current supplier  230 , and may further include a data table  240 . 
     The determiner  210  may use an input current to determine total dissolved solids in raw water having flowed into the deionizing filter  130 . More specifically, the determiner  210  may use the data table  240  to determine total dissolved solids in raw water having flowed into the deionizing filter  130 . In the data table  240 , the flow rate of raw water, and the voltage and current applied to the deionizing filter  130  may be described in connection with the total dissolved solids. 
     Specifically, the magnitude of a load resistance may be determined by the amplitude of a fixed voltage applied to the deionizing filter  130  and the amplitude of a current flowing in the deionizing filter  130 . Herein, the magnitude of a load resistance may include information about the amount of ions in raw water, that is, total dissolved solids. Thus, total dissolved solids (ionized materials) in raw water may be determined from the magnitude of a load resistance. However, as another embodiment, a total dissolved solid measurer (for example TDS meter) may be used, and the present invention does not preclude the use of a total dissolved solid measurer. 
     In addition, total dissolved solids contained in raw water may be experimentally determined based on the flow rate of raw water and the voltage and current applied to the deionizing filter  130 , and the results may be described in a data table. Thus, the control unit  200  may use the data table  240  to determine the total dissolved solids in inflow raw water. 
     The input current determiner  220  may compare the determined total dissolved solids with the target total dissolved solids, and determine an input current applied to the deionizing filter  130 , based on the comparison results. The input current determiner  220  may determine the input current applied to the deionizing filter  130 , based on the comparison results of the determined total dissolved solids and the target total dissolved solids, or may determine the input current applied to the deionizing filter  130 , based on the data table  240 . In the data table  240 , the flow rate of raw water, and the voltage and current applied to the deionizing filter  130  may be described in connection with the total dissolved solids. 
     If the determined total dissolved solids are greater than the target total dissolved solids, the input current determiner  220  may set an input current such that more current may flow in the deionizing filter  130  in order to increase the reduction rate of total dissolved solids in raw water (the removal rate of ionized materials). If the determined total dissolved solids are less than the target total dissolved solids, the input current determiner  220  may set an input current such that less current may flow in the deionizing filter  130  in order to reduce the reduction rate of total dissolved solids in raw water (the removal rate of ionized materials). 
     More specifically, the data table  240  may be used to set the input current. Since the amplitudes of current and voltage corresponding to the respective total dissolved solids are described in the data table  240 , an input current to be applied to the deionizing filter  130  may be set according to this in order to obtain the target dissolved solids. 
     When current control is performed using pulse width modulation, an input current applied to the deionizing filter  130  may be set by setting a period of time when a current is applied to the deionizing filter  130 . 
     Then, the input current supplier  230  may apply a predetermined fixed voltage to the deionizing filter  130  and supply the input current to the deionizing filter  130  by pulse width modulation. 
     The pulse width modulation may change an input period of a fixed voltage inputted to the deionizing filter  130  and control an input current while maintaining a voltage at a constant level. In order to implement the pulse width modulation, the control unit  230  may include a switching element. The control unit  200  may control a current applied to the deionizing filter  130  based on a period of time when the switching element is closed, and dissolved solids (ionized materials) removed from raw water may be determined accordingly. 
     In the data table  240 , the flow rate of raw water, and the voltage and current applied to the deionizing filter  130  may be described in connection with the total dissolved solids, as described above. A simple example of the data table  240  is illustrated in  FIG. 13 . 
     The measurement of a current flowing in the deionizing filter  130  may be compared with the data table  240  to determine total dissolved solids contained in raw water, and it may be determined which amount of current is to be applied to the deionizing filter  130  in order to obtain target total dissolved solids. 
     As described above, the control unit  200  may apply a predetermined fixed voltage to the deionizing filter  130  and may use pulse width modulation (PWM) to control an input current applied to the deionizing filter  130 . 
     Hereinafter, a water treatment apparatus controlling method S 100  according to another aspect of the present invention will be described with reference to  FIGS. 1 through 6, 14 and 15 . 
     A water treatment apparatus controlling method S 100  according to another aspect of the present invention relates to a method for controlling a water treatment apparatus  100  including a deionizing filter  130  that removes total dissolved solids (TDS) contained in inflow water by an application of power. The water treatment apparatus controlling method S 100  may include a user selection operation S 110  for receiving an extraction of mineral water generated by removing total dissolved solids from raw water to a predetermined level, or an extraction of ultra-pure water having less total dissolved solids than the mineral water, a deionizing filter driving operation S 120  for applying power to the deionizing filter  130  to control total dissolved solids contained in water filtered by the deionizing filter  130  according to a type of water inputted in the user selection operation S 110 , or a reduction rate of total dissolved solids removed by the deionizing filter  130 , and a water outputting operation S 140  for extracting mineral water or ultra-pure water filtered by the deionizing filter  130 . The water treatment apparatus controlling method S 100  may further include a output water flow passage changing operation S 130  for controlling a temperature of water filtered by a filtering unit  110  before the water outputting operation S 140 . 
     In addition, when an ionized water generating unit  140  is provided as illustrated in  FIGS. 4 through 6 , a water treatment apparatus controlling method S 100  according to an exemplary embodiment of the present invention may further include an operation for receiving an extraction of ionized water in the user selection operation S 110 , and may further include an ionized water generating operation for generating ionized water by using the water filtered by the deionizing filter  130 , in the output water flow passage changing operation S 130 , when an extraction of ionized water is inputted. In addition, the water outputting operation S 140  may include an operation for extracting normal-temperature ionized water or cold ionized water. 
     In particular, when an extraction of ionized water is selected in the user selection operation S 110 , the deionizing filter driving operation S 120  may include an operation for controlling the power applied to the deionizing filter  130  to generate mineral water in the deionizing filter  130  and supply the mineral water to the ionized water generating unit  140 . For example, the mineral water may correspond to water whose reduction rate of total dissolved solids by the deionizing filter  130  is equal to or greater than about 30% and less than about 80%, in comparison with water (or raw water) that has not flowed into the deionizing filter  130 , and the ultra-pure water may correspond to water whose reduction rate of total dissolved solids by the deionizing filter  130  is equal to or greater than about 80%; however, the present invention is not limited thereto. 
     In addition, as described above, the deionizing filter  130  may be configured to remove dissolved solids (ionized materials) contained in water, by any one of electrodialysis (ED), electrodeionization (EDI), and capacitive deionization (CDI). 
     Hereinafter, the deionizing filter driving operation S 120  will be described in detail with reference to  FIG. 15 . The deionizing filter driving operation S 120  may be included in a total dissolved solid controlling method S 100 ′ according to another aspect of the present invention. 
     A deionizing filter driving operation S 120  included in a water treatment apparatus controlling method S 100  according to an aspect of the present invention and a total dissolved solid controlling method S 100 ′ according to an aspect of the present invention may include a fixed voltage applying operation S 121 , a dissolved solid removing operation S 122 , a current measuring and flow rate measuring operation S 123 , a total dissolved solid determining operation S 124 , a total dissolved solid comparing operation S 125 , an input current determining operation S 126 , and an input current applying operation S 127 . 
     The fixed voltage applying operation S 121  may be configured to apply a predetermined fixed voltage to a deionizing filter  130 . Herein, the fixed voltage applied to the deionizing filter  130  may vary according to a reduction rate of total dissolved solids inputted by a user. According to an exemplary embodiment of the present invention, since a predetermined fixed voltage is applied, a load resistance can be easily detected from a current flowing in the deionizing filter  130 , and total dissolved solids (TDS) in raw water can be determined (measured) accordingly. Also, unlike a voltage-controlled method, since a fixed voltage is applied, a complex configuration for voltage control may not be included. The fixed voltage may be applied by the control unit  200  to the deionizing filter  130 . 
     The dissolved solid removing operation S 122  may be configured to use the fixed voltage to remove dissolved solids (ionized materials) contained in raw water flowing into the deionizing filter  130 . The deionizing filter  130  may use electrodialysis, electrodeionization, and/or capacitive deionization to remove dissolved solids contained in raw water. 
     The current measuring and flow rate measuring operation S 123  may measure the amplitude of a current flowing in the deionizing filter  130  by the fixed voltage and may measure a flow rate of raw water flowing into the deionizing filter  130 . Information about the measured current and flow rate may be transmitted to the control unit  200 . 
     The total dissolved solid determining operation S 124  may be configured to determine total dissolved solids in raw water by using the measured amplitude of the current. The total dissolved solids may be determined using a table in which the flow rate of raw water and the voltage and current applied to the deionizing filter  130  are described in connection with the total dissolved solids. Specifically, the magnitude of a load resistance may be determined by the amplitude of a fixed voltage applied to the deionizing filter  130  and the amplitude of a current flowing in the deionizing filter  130 . Herein, since the magnitude of a load resistance includes information about the amount of total dissolved solids (ionized materials) in raw water (that is, total dissolved solids) the amount of ions in raw water (that is, total dissolved solids) may be determined from the magnitude of a load resistance. 
     In addition, total dissolved solids contained in raw water may be experimentally determined based on the flow rate of raw water and the voltage and current applied to the deionizing filter  130 , and the results may be described in a table (see  FIG. 13 ). The total dissolved solids in the inflow raw water may be determined using a table in which the flow rate of raw water and the voltage and current applied to the deionizing filter  130  are described in connection with the total dissolved solids. 
     The total dissolved solid comparing operation S 125  may be configured to compare the determined (measured) total dissolved solids of raw water with the target total dissolved solids. It is determined whether the determined total dissolved solids are equal to the target total dissolved solids. If the determined total dissolved solids are equal to the target total dissolved solids, a feedback method controlling an input current applied to the deionizing filter  130  may be used. 
     The input current determining operation S 126  may be configured to determine the amplitude of a current to be applied to the deionizing filter  130 , based on the comparison results of the determined (measured) total dissolved solids of raw water and the target total dissolved solids. In addition, the current applied to the deionizing filter  130  may be determined based on the measured flow rate of raw water and the comparison results of the determined (measured) total dissolved solids of raw water and the target total dissolved solids, or may be determined using a table in which the flow rate of raw water and the voltage and current applied to the deionizing filter  130  are described in connection with the total dissolved solids. 
     If the determined total dissolved solids is greater than the target total dissolved solids, an input current may be set such that more current may flow in the deionizing filter  130  in order to increase the reduction rate of total dissolved solids in raw water (the removal rate of total dissolved solids (ionized materials)). If the determined total dissolved solids is less than the target total dissolved solids, an input current may be set such that less current may flow in the deionizing filter  130  in order to reduce the reduction rate of total dissolved solids in raw water (the removal rate of total dissolved solids (ionized materials)). 
     More specifically, the input current may be set based on a table in which the flow rate of raw water and the voltage and current applied to the deionizing filter  130  are described in connection with the total dissolved solids. 
     The input current applying operation S 127  may be configured to apply the determined current to the deionizing filter  130  by pulse width modulation. The pulse width modulation may change an input period of a fixed voltage inputted to the deionizing filter  130  and control an input current while maintaining a voltage at a constant level. In order to implement the pulse width modulation, the control unit  200  may include a switching element (not illustrated). The control unit  200  may control a current applied to the deionizing filter  130  based on a period of time when the switching element is closed, and dissolved solids (ionized materials) removed from raw water may be determined accordingly. 
     In this manner, the deionizing filter driving operation S 120  may be configured to apply a predetermined fixed voltage to the deionizing filter  130  and control an input current applied to the deionizing filter  130 , by pulse width modulation. 
     Meanwhile, a water treatment apparatus including a total dissolved solid controlling apparatus according to an aspect of the present invention may include the above-described total dissolved solid controlling apparatus ( 100 ′ of  FIG. 11 ). 
     While the present invention has been shown and described in connection with the exemplary embodiments, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the spirit and scope of the invention as defined by the appended claims.