Patent Document

CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit under 35 U.S.C. § 119 (a) from Korean Patent Application No. 2004-67715 filed on Aug. 27, 2004 in the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference in its entirety.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present general inventive concept relates generally to a method of generating a power to supply to elements in a power supply apparatus. More particularly, the present general inventive concept relates to a method of generating a power to drive elements at a primary side of a power supply apparatus.  
         [0004]     2. Description of the Related Art  
         [0005]     A liquid crystal display (LCD) applies electro-optic effects of a liquid crystal to a display device. The liquid crystal is between a liquid state and a solid state and flows having the characteristics of both a liquid and a solid. The LCD is used as a monitor, a digital television, and other display devices. Hereinafter, a power supply apparatus to drive an LCD is described with reference to  FIG. 1 .  
         [0006]      FIG. 1  illustrates a conventional power supply apparatus to drive an LCD back-light (lamp). The power supply apparatus includes an alternating current (AC) input section  100 , a rectifier  102 , a power factor correction (PFC) section  104 , a converter  110 , a main board  130 , an inverter  120 , and a lamp  132 . The PFC section  104  includes a PFC  106  and a rectifier  108 . The converter  110  includes a switch  112 , a transformer  114 , and a rectifier  116 . The inverter  120  includes a switch  122  and a transformer  124 . Operations of the elements of the power supply apparatus for driving the LCD will now be described.  
         [0007]     The AC input section  100  receives an AC power supply. An intensity of the AC power may vary depending on a user setting. The rectifier  102  rectifies the AC power received from the AC input section.  
         [0008]     The PFC section  104  improves a power factor with respect to the power received from the rectifier  102 . Typically, if the power received from the rectifier  102  is used without any power factor processing, power utilization may decrease. Accordingly, the PFC section  104  improves the power factor with respect to the power received from the rectifier  102  in order to enhance the power utilization.  
         [0009]     The power output from the PFC section  104  is transferred to the converter  110  and the inverter  120  as a primary power. The switch  112  of the converter  110  repeatedly switches between on and off states to transfer the received primary power (hot) to a secondary side (cold) of the conventional power supply apparatus. Generally, the primary side of the conventional power supply apparatus includes elements up to a primary coil of the transformer  114 , and the secondary side includes elements after a secondary coil of the transformer  114 . Thus, the secondary side includes the main board  130 , the rectifier  116 , and the secondary coil of the transformer  114 . The primary side includes the lamp  132 , the inverter  120  (including the switch  122  and the transformer  124 ), the switch  112 , and the primary coil of the transformer  114 .  
         [0010]     The transformer  114  transfers the primary power at the primary side to the secondary side depending on whether the switch  112  is in the on or off state. In particular, the transformer  114  generates an induced power in the secondary coil thereof according to whether the switch  112  is in the on or off state and transfers the power induced in the secondary coil to the secondary side. The rectifier  116  then rectifies the power received from the secondary coil of the transformer  114 .  
         [0011]     The power output from the converter  110  is a secondary power provided to the main board  130 . Elements in the main board  130  utilize the secondary power received from the converter  110  as a driving power. The number of secondary output powers received from the converter  110  may vary depending on a user setting or an amount of power required by the elements of the main board  130 . That is, the user can vary the amount of secondary power output by the transformer  114  and/or the number of secondary output powers by changing the configuration of the transformer  114 .  
         [0012]     The primary power output from the PFC section  104  is also transferred to the inverter  120 . The inverter  120  inverts the primary power received from the PFC section  104 , which is a DC power, to an AC power. The switch  122  and the transformer  124  included in the inverter  120  operate in the same manner as the switch  112  and the transformer  114  included in the converter  110 . However, the transformer  114  reduces the amount of the primary power received (i.e., step down) while the transformer  124  increases the amount of the primary power received (i.e., step up). Typically, the power output from the transformer  124  is about 1.8 kV. The power output from the inverter  120  is then provided to the lamp  132 . The lamp  132  is driven using the power provided by the inverter  120 .  
         [0013]     As mentioned above, the elements of the main board  130  are driven using the secondary power received from the converter  110 . The elements in the switch  122  of the inverter  120  are driven using the primary power supplied by the PFC section  104 . In this situation, the elements of the switch  122  cannot use the power output from the converter  110 . Specifically, the power output from the converter  110  is the secondary power, and the elements of the switch  122  are at the primary side of the conventional power supply apparatus. If the elements at the primary side of the conventional power supply apparatus use the secondary power, a short circuit is likely to occur. Accordingly, the elements at the primary side should be driven using the primary power.  
         [0014]      FIG. 2  illustrates an apparatus to generate the primary power to be supplied to the elements at the primary side of the conventional power supply apparatus. The primary power to be supplied to the elements at the primary side is derived from the power output from the PFC section  104 . The power output from the PFC section  104  is input to a regulator  200 . The regulator  200  reduces the input power to a predetermined level and outputs the reduced power. Typically, the power input to the regulator  200  is between 300V and 400V, and the power output from the regulator  200  is about 5V. The power output from the regulator  200  is then supplied to the elements of the switch  122  at the primary side. The elements of the switch  122  at the primary side are driven using the power supplied by the regulator  200 .  
         [0015]     The difference between the power input to the regulator  200  and the power output from the regulator  200  determines a power loss at the regulator  200 . The greater the difference between the input and output power in the regulator  200 , the greater the power loss that occurs in the regulator  200 . Moreover, since the 300V to 400V power from the PFC section  104  is reduced to 5V by the regulator  200  and is then input to the inverter  120 , the transformer  124  is now required to provide a larger increase in power from 5V to about 1.8 kV used to power the lamp  132  (as opposed to between 300V and 400V to about 1.8 kV). Therefore, it would be desirable to reduce the power loss that occurs in the regulator  200  by adjusting the amount of the power input to the regulator  200 .  
       SUMMARY OF THE INVENTION  
       [0016]     The present general inventive concept provides an apparatus and method of reducing a power loss at a regulator in a power supply apparatus used to provide power to an LCD device.  
         [0017]     The present general inventive concept also provides an apparatus and method of adjusting an amount of a power input to a regulator to reduce a power loss at the regulator in a power supply apparatus used to provide power to an LCD device.  
         [0018]     Additional aspects of the present general inventive concept will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the general inventive concept.  
         [0019]     The foregoing and/or other aspects of the present general inventive concept are achieved by providing a power supply apparatus including an input unit to receive an alternating current (AC) power, a power factor improvement unit to improve a power factor of the received AC power, a transformer to receive the AC power having the improved power factor on a primary coil and to generate an induced power on a secondary coil, and a predetermined element located on a primary side of the power supply apparatus to be driven, in part, by the AC power received from the primary coil.  
         [0020]     The power supply apparatus may further include a switch to alternate between an on and off switching state at predetermined time intervals with respect to the AC power input to the primary coil to generate the induced power at the secondary coil, and a rectifier to convert the AC power received from the primary coil to a direct current (DC) power.  
         [0021]     The power supply apparatus may further include a regulator to receive the DC power and to reduce the DC power to a predetermined level when the DC power from the rectifier exceeds the predetermined level. The predetermined level comprises an amount of power appropriate to drive the predetermined element located at the primary side.  
         [0022]     The foregoing and/or other aspects of the present general inventive concept are also achieved by providing a power supply method of supplying power to a predetermined element on a primary side of a power supply apparatus including receiving an alternating current (AC) power, improving a power factor of the received AC power, providing the AC power having the improved power factor to a primary coil of a transformer and generating an induced power at a secondary coil of the transformer, and driving the predetermined element on the primary side of the power supply apparatus using, in part, the AC power received from the primary coil.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]     These and/or other aspects and advantages of the present general inventive concept will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:  
         [0024]      FIG. 1  illustrates a conventional power supply apparatus;  
         [0025]      FIG. 2  illustrates an apparatus to generate a power to be supplied to a primary side of the conventional power supply apparatus;  
         [0026]      FIG. 3  illustrates a power supply apparatus to drive a liquid crystal display (LCD) according to an embodiment of the present general inventive concept; and  
         [0027]      FIG. 4  illustrates an operation of the power supply apparatus of  FIG. 3  according to an embodiment of the present general inventive concept. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0028]     Reference will now be made in detail to the embodiment of the present general inventive concept, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiment is described below in order to explain the present general inventive concept by referring to the drawings.  
         [0029]     The present general inventive concept provides an apparatus and a method to transfer a power from a primary coil of a transformer directly to a regulator. Therefore, it is possible to reduce a power loss at the regulator.  
         [0030]      FIG. 3  is a block diagram illustrating a power supply apparatus to drive a liquid crystal display (LCD) according to an embodiment of the present general inventive concept, which is described below. The power supply apparatus of  FIG. 3  has some of the same elements as the conventional power supply apparatus of  FIG. 1 ; therefore, the same reference numerals are used to refer to the elements that are the same in both figures. The power supply apparatus to drive the LCD includes an AC input section  100 , a rectifier  102 , a power factor correction (PFC) section  104 , a converter  110 , a main board  130 , an inverter  120 , and a lamp  132 .  
         [0031]     The AC input section  100  receives an AC power supply. An amount of the AC power may vary depending on a user setting or an amount of the power supplied from the power supply apparatus. The rectifier  102  rectifies the received AC power. Generally, the rectifier  102  may include a rectifier diode and a capacitance. The rectifier diode passes only a portion of the AC power having a value that is greater than a predetermined level, and the capacitance smoothes the portion of the AC power passed by the rectifier diode. Accordingly, the AC power is converted to approximate a direct current (DC) power. It should be understood that the rectifier  102  may include other elements instead of (or in addition to) the rectifier diode and the capacitance.  
         [0032]     A PFC  106  of the PFC section  104  improves a power factor of the received power. Generally, if the power received from the rectifier  102  is used without any processing thereof, a power utilization may decrease. For example, without the power factor improvement performed by the PFC  106 , the power factor ranges from 0.5 to 0.6. In contrast, the power factor improvement performed by the PFC  106  increases the power factor to almost 1. Thus, by using the PFC  106 , the power supply apparatus can improve the power factor of the received power, thereby enhancing the utilization of the power. The power having the improved power factor is then rectified by a rectifier  108 .  
         [0033]     The rectified power is then input to the converter  110  as a primary power. A switch  112  of the converter  110  repeatedly switches between an on and off state to transfer the received primary power to a secondary side.  
         [0034]     The transformer  114  transfers the primary power to the secondary side according to whether the switch  112  is in the on or off state. The transformer  114  generates an induced power in a secondary coil (i.e., a secondary power) of the transformer  114  according to whether the switch  112  is in the on or off state, and transfers the secondary power induced in the secondary coil to the secondary side of the power supply apparatus. A rectifier  116  rectifies the received secondary power and outputs the rectified secondary power from the converter  110 . The secondary power output from the converter  110  is then input to the main board  130 .  
         [0035]     Elements of the main board  130  are driven by the secondary power received from the converter  110 . According to an amount of the secondary power used by the elements of the main board  130 , the main board  130  may receive at least two secondary power supplies from the converter  110 . In general, the main board  130  may receive secondary power of about 5V.  
         [0036]     The primary power output from the PFC section  104  is also transferred to the inverter  120 . The inverter  120  inverts the primary power received from the RFC section  104 , which is a DC power, to an AC power. A switch  122  and a transformer  124  included in the inverter  120  operate in the same manner as the switch  112  and the transformer  114  of the converter  110 . Yet, while the transformer  114  reduces the amount of the primary power received (i.e., step down), the transformer  124  increases the amount of the primary power received (i.e., step up). Typically, the power output from the transformer  124  is about 1.8 kV. The transformer  124  provides the output power from the inverter  120  to the lamp  132 . The lamp  132  can be driven using the power received from the inverter  120 .  
         [0037]     The following describes a method of generating the primary power to drive elements (i.e., the switch  122  of the inverter  120 ) at the primary side. As mentioned above, the power at the primary side of the transformer  114  ranges between 300V and 400V. The power supply apparatus induces the required power using, in part, a primary coil of the transformer  114 . By using the power at the primary side, it is possible to prevent a short-circuit, which may occur when using the power at the secondary side. Referring to  FIG. 3 , a power level of 20V is induced from the primary coil of the transformer  114 . The power induced from the primary coil of the transformer  114 , which is an AC power, is then input to the rectifier  300 . The rectifier  300  converts the received AC power to DC power. The power output from the rectifier  300  is input to a regulator  302 . The regulator  302  steps down (i.e., reduces) the received power to a power level that is suitable to drive the elements at the primary side.  
         [0038]     The power level output from the regulator  302  is about 5V, as described above. The power output from the regulator  302  is then transferred to the elements at the primary side. For instance, in  FIG. 3 , the power output from the regulator  302  is provided to the switch  112  of the converter  110  and the switch  122  of the inverter  120 .  FIG. 3  illustrates that the power is induced from the primary coil of the transformer  114  in the converter  110 , but not limited to this coil. It should be understood that the user can set the power supply apparatus to induce the power from a primary coil of the transformer  124  in the inverter  120 . Since the power level input to the regulator  302  depends on a number of coils at the primary side of the transformer  114 , the user can vary the number of coils to obtain a desired amount of the power.  
         [0039]     In various embodiments, the transformer  114  may include an auxiliary coil adjacent to the secondary coil on the secondary side of the power supply apparatus. Thus, while about 5V used to drive the rectifier  116  (and the main board  130 ) is induced on the secondary coil, about 20V can be induced on the auxiliary coil to drive the rectifier  300  and the regulator  302 . For example, if the voltage on the primary coil of the transformer  114  is 300V, a first coil ratio from the primary coil to the secondary coil could be used to induce the 5V on the secondary coil. Additionally, a second coil ratio from the primary coil to the auxiliary coil could be used to induce the 20V on the auxiliary coil. The regulator  302  then reduces the 20V to 5V used to drive the switch  122  of the inverter  120  and the switch  112  of the converter  110 . Thus, since the regulator  302  reduces the voltage from 20V to 5V, a power loss that occurs in the regulator  302  can be reduced. Additionally, since the 5V is not provided from the secondary coil on the secondary side to the primary side, the possibility of a short circuit is reduced. It should be understood that other voltages can be induced by the secondary and auxiliary coils to drive the primary and secondary sides, respectively, and the coil ratios can be modified accordingly to induce the other voltages on the secondary and auxiliary coils of the transformer  114 .  
         [0040]     In various embodiments, 20V is induced on the secondary coil of the transformer  114  and is provided to the rectifier  300  and the regulator  302 . The regulator  302  reduces the 20V to 5V and provides the 5V to drive the switch  122  in the inverter  120  and the switch  112  of the converter  110  on the primary side.  
         [0041]      FIG. 3  illustrates that the power level of about 20V is induced from the primary coil of the transformer  114 . Alternatively, the power used to drive the elements at the primary side may be induced directly from the primary coil of the transformer  114 . For example, the power of 5V may be induced directly from the primary coil of the transformer  114  to the auxiliary coil. The power induced on the auxiliary coil is then rectified to the DC power by the rectifier  300  and is supplied to the elements at the primary side. Thus, the regulator  302  would be unnecessary.  
         [0042]     Although the description of  FIG. 3  refers to the main board  130  as typically being driven at 5V, the main board  130  may alternatively be driven at a different voltage level. For example, the main board  130  may be driven at 3.3V. For this reason, a voltage used to drive the switches  112  and  122  is isolated from the voltage used to drive the main board  130 .  
         [0043]      FIG. 4  is a flowchart illustrating operations of the power supply apparatus of  FIG. 3  according to an embodiment of the present general inventive concept. In particular,  FIG. 4  illustrates a method of generating the power to be supplied to the elements at the primary side.  
         [0044]     The rectifier  102  of the power supply apparatus rectifies an AC power received at the AC input section  100  at operation S 400 . The rectifier converts the received AC power into a DC power. The PFC  106  of the power supply apparatus improves a power factor of the received power at operation S 402 . It should be understood that the operation S 402  may be omitted according to a user setting.  
         [0045]     The rectifier  108  of the power supply apparatus then re-rectifies the power having the improved power factor at operation S 404 . As a result of the re-rectification operation S 404 , the received power can be rectified to more closely approximate a DC power.  
         [0046]     The power supply apparatus transfers the received power to the secondary side and generates the power to drive the elements at the primary side at operation S 406 . As described above, the power to drive the elements at the primary side is induced from the primary coil of the transformer  114  in order to prevent a short circuit from occurring. The amount of the power induced from the primary coil of the transformer  114  may differ according to the user setting. The power induced from the transformer  114  is then rectified by the rectifier  300 . When the amount of the rectified power is equal to the power level required by the elements at the primary side (e.g., the switch  122  of the inverter  120  and the switch  112  of the converter  110 ), the power supply apparatus proceeds to operation S 408 . When the amount of the rectified power exceeds the power level required by the elements at the primary side, the regulator  302  of the power supply apparatus reduces the voltage and proceeds to operation S 408 .  
         [0047]     The power supply apparatus then transfers the induced power to the elements at the primary side at operation S 408 . The elements at the primary side are driven by the power received by the rectifier  300  and/or the regulator  302 .  
         [0048]     In light of the foregoing embodiments, the power used to drive the elements at the primary side of the power supply apparatus is generated from the primary coil of the transformer  114 , not from the PFC section  104 . Accordingly, it is possible to prevent waste of unnecessary power. As the power consumption depends on the amount of the power provided to the regulator  302 , the power consumed at the regulator  302  can be reduced by decreasing the amount of the power provided to the regulator  302 . Furthermore, the regulator  302  may not be necessary, because the power used to drive the elements at the primary side can be generated directly from the primary coil of the transformer  114 .  
         [0049]     Although a few embodiments of the present general inventive concept have been shown and described, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the general inventive concept, the scope of which is defined in the appended claims and their equivalents.

Technology Category: 4