Abstract:
An apparatus and a method for controlling a direct-current (DC)-DC converter used in a vehicle are provided. The apparatus includes a switching control unit checking a difference between voltages of an input unit and an output unit and controlling an operation of at least one switch formed in a converter according to an operation mode of the converter according to the difference of voltages; and the converter controlling the operation of the at least one switch based on a control signal applied from the switching control unit to allow a current to flow from the input unit to the output unit.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Pursuant to 35 U.S.C. §119(a), this application claims the benefit of earlier date and right of priority to Korean Patent Application No. 10-2012-0121617, filed on Oct. 30, 2012, the contents of which is incorporated by reference herein in its entirety. 
     BACKGROUND 
     The present disclosure relates to an apparatus and a method for controlling a direct-current (DC)-DC converter used in a vehicle. 
     Due to rapid increase of oil tax, automobiles increasing fuel efficiency have been released, for example, automobiles with idle stop &amp; go (hereinafter, referred to as ISG) systems built therein. 
     ISG systems are not general starter motors of vehicles but integrated motors of starters and alternators, which operate as alternators while engines are operating. ISG systems, as described above, may be divided into an integrated type in which an alternator and a starter are formed as a single body and a separable type in which an alternator and a starter are separated from each other. However, configurations and operations thereof are similar. Accordingly, since ISG systems may be easily applied to engine automobiles, a demand thereof has increased. 
       FIGS. 1A and 1B  are configuration views illustrating general starters of vehicles including an ISG system, respectively. 
     In  FIG. 1A , the starter includes an input unit and output unit  11  and  15 , in which flows of current occur, and a plurality of switches  12  and  14  and an inductor  13  for conduction of the input unit and output unit  11  and  15 . 
     When a current flow occurs from the input unit  11  to the output unit, the input unit  11  may perform an input ripple removal function. Also, a plurality of switches  12   a  and  12   b  of a first switch unit part  12  may be driven as switches for a buck mode operation, and a plurality of switches  14   a  and  14   b  of a second switch part  14  and the inductor  13  may perform a switch function for a boost mode operation. 
     On the contrary, when a current flow occurs from the output unit  15  to the input unit  11 , the plurality of switches  14   a  and  14   b  of the second switch part  14  may be driven as switches for the buck mode operation. In the case, the plurality of switches  12   a  and  12   b  of the first switch part and the inductor  13  may perform the switch function for the boost mode operation. 
     Also, in the case of  FIG. 1B , similar to  FIG. 1A , when a current flow occurs from an input unit  21  to an output unit  25 , a plurality of switches  22   a  to  22   f  of a first switch part  22  perform a switch function for a buck mode operation. Also, a plurality of switches  23   a  to  23   f  of a second switch part  23  may perform a switch function for a boost mode operation. 
     On the contrary, when a current flow occurs from the output unit  25  to the input unit  21 , the plurality of switches  23   a  to  23   f  of the second switch part  23  may be driven as switches for the buck mode operation. Also, a plurality of inductors  24   a  to  24   c  of the inductor  24  and the plurality of switches  22   a  to  22   f  of the first switch part  22  may perform the switch function for the boost mode operation. 
     The starter of the vehicle including the ISG system as described above may have a limitation such as heat generation caused by a configuration of the pluralities of switches and inductors and high conduction losses. In the case of such converter, a converter having high capacitance is not provided and a serial structure may be used in such a way that structural complexity of a control apparatus may occur. 
     SUMMARY 
     Embodiments provide an apparatus and a method for controlling a direct-current (DC)-DC converter to simplify a structural arrangement and to reduce heating phenomenon caused by capacity, with respect to a converter formed in an idle stop &amp; go (ISG) system. 
     In one embodiment, a converter controlling apparatus includes a switching control unit checking a difference between voltages of an input unit and an output unit and controlling an operation of at least one switch formed in a converter according to an operation mode of the converter according to the difference of voltages; and the converter controlling the operation of the at least one switch based on a control signal applied from the switching control unit to allow a current to flow from the input unit to the output unit. 
     In another embodiment, a method for controlling a converter includes checking a difference between voltages of an input unit and an output unit and determining an operation mode of the converter according to the difference between voltages. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A and 1B  are configuration views illustrating general starters of vehicles including an ISG system, respectively; 
         FIG. 2  is a block configuration view illustrating a starter of a vehicle including an ISG system according an embodiment; and 
         FIG. 3  is a flowchart illustrating an operation mode of the starter according to an input output voltage state according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Terms and words used in the present disclosure and claims will not be understood being limited to general or lexical meanings. In an aspect that the inventor may properly define the concept of the terms in order to describe embodiments in the best way, the terms will be understood as meanings and concepts appropriate to the technical thoughts of the embodiments. 
     Accordingly, the embodiments disclosed in the specification and configurations illustrated in the drawings are just most exemplary embodiments, which do not represent the whole technical thoughts of the present embodiments. It should be understood various equivalents replaceable therefore and modified examples thereof may exists at the point in time of the present application. 
     Hereinafter, the embodiments will be described in detail with reference to the drawings. 
       FIG. 2  is a block configuration view illustrating a starter of a vehicle including an ISG system according an embodiment. 
     The starter may include an input unit  10 , a direct-current (DC)-DC converter  100 , an output unit  20 , and a switching control unit  200 . 
     For example, the input unit  10  may be an energy storage device for storing and outputting energy, such as an ultra capacitor UC, a lithium battery, and a lead (Pb) &amp; absorbed glass mat (AGM) battery. 
     The input unit  10  and the output unit  20  may be movable according to a direction of a current flow. 
     The DC-DC converter  100  may include an inductor part  110  including one or more inductors  111 ,  112 , and  113  and a switch part  120  including one or more switches  121 ,  122 ,  123 ,  124 ,  125 , and  126 . 
     The switches  121 ,  122 ,  123 ,  124 ,  125 , and  126  of the switch part  120  may be configured as a shape in which one arm is connected in parallel and the number of the arms connected in parallel is not limited. In the present embodiment, a structure in which three arms including two switches are connected in parallel will be described. 
     The switch may be an insulated gat bipolar transistor (IGBT) or a metal-oxide semiconductor field-effect-transistor (MOSFET). Power supplied through the inductor  110  that is a three phase inductor may be connected to central points of the switches  121  and  122 ,  123  and  124 , and  125  and  126  forming one arm, respectively. 
     Also, one or more arms  121  and  122 ,  123  and  124 , and  125  and  126  of the switch part  120 , formed of two switches, respectively, may be connected in parallel. 
     The converter  100  may measure input and output voltages of the input unit  10  and the output unit  20  and may operate in one of a buck mode, a bypass mode, and a boost mode according to an input and output voltage value. According to a control signal of the switching control unit  200 , the respective switches  121 ,  122 ,  123 ,  124 ,  125 , and  126  operate as switching devices when a switching control signal is inputted, that is, turned on and operate as diodes when a switching signal is turned off. 
     The inductor part  110  including the one or more inductors  111 ,  112 , and  113  and the switch part  120  including the one or more switches  121 ,  122 ,  123 ,  124 ,  125 ,  126  perform switching operations to allow the converter  100  to operate as a certain mode according to a difference between voltages of the input unit  10  and the output unit  20 , thereby increasing or decreasing an input voltage. 
     The switch control unit  200  may check the difference between voltages of the input unit  10  and the output unit  20  and may control respective switching signals of the switch part  120 . The switching signal may determine an operation mode of the converter  100  according to the difference between voltages of the input unit  10  and the output unit  20 . 
     Referring to  FIGS. 2 and 3 , the operation of the converter  100  according to the difference between input and output voltages will be described in detail. 
       FIG. 3  is a flowchart illustrating an operation mode of the starter according to an input output voltage state according to an embodiment. 
     Referring to  FIGS. 2 and 3 , the switching control unit  200  checks voltage values of the input unit  10  and the output unit  20  (S 310 ). 
     The switch control unit  200  may determine an operation mode S 230  of the converter  100  according to a difference between voltages of the input unit  10  and the output unit  20 . The operation mode S 230  of the converter  100  may be one of a buck mode S 231 , a bypass mode S 322 , and a boost mode S 323 . 
     The switching control unit  200  checks voltage values of the input unit  10  and the output unit  20 . 
     The switching control unit  200 , when the voltage value of the input unit  10  is greater than the voltage value of the output unit  20 , that is, when the difference between voltages is +, turns off the respective switches  121 ,  122 ,  123 ,  124 ,  125 , and  126  forming the switch part  120  to perform a drop of an input voltage value by using inner diodes. 
     The inner diodes of the switches  121 ,  122 ,  123 ,  124 ,  125 , and  126 , when the switches  121 ,  122 ,  123 ,  124 ,  125 , and  126  are turned off, may drop a voltage about 1.3 V. Considering inner resistances and conduction losses of the inductor part  110 , about 1.5 V may be dropped with respect to the input voltage value. 
     Accordingly, when the difference between voltages of the input unit  10  and the output unit  20  is +, in order to perform a drop of voltage with respect to the input voltage value in the converter  100 , the switching control unit  200  turns off the switches  121 ,  122 ,  123 ,  124 ,  125 , and  126  of the switch part  120  and performs the buck mode in which a current is conducted through inner diodes in a first switch  121 , a third switch  123 , and a fifth switch  125  (S 321 ). 
     Accordingly, the voltage value of the input unit  10  may be outputted to the output unit  20  while being dropped by about 1.5 V according to a voltage drop mode of the converter  100 . 
     Alternatively, as a result of checking the voltage values of the input unit  10  and the output unit  20  by the switching control unit  200 , when the voltage values of the input unit  10  and the output unit  20  are identical, that is, when the difference between voltages of the input unit  10  and the output unit  20  is ‘0’, to output the input voltage value toward the output unit  20 , the converter  100  performs a bypass mode S 322 . 
     The switching control unit  200 , in the bypass mode, turns on the first switch  121 , the third switch  123 , and the fifth switch  125  among a plurality of switches forming the switch part  120  and turns off a second switch  122 , a fourth switch  124 , and a sixth switch  126 . 
     Accordingly, the converter  100  operates in the bypass mode of outputting input power to the output unit  20  as it is (S 330 ). 
     As described above, according to the difference between voltages of the input unit  10  and the output unit  20 , the converter  100  may operate one of the buck mode, the bypass mode, and the boots mode, thereby maintaining the difference between voltages of the input unit  10  and the output unit  20  as ‘0’. 
     On the contrary, the first switch  121 , the second switch  122 , the third switch  123 , the fourth switch  124 , the fifth switch  125 , and the sixth switch  126  of the switches of the switch part  120 , in which a current flow occurs from the output unit  20  to the input unit  10  may be turned off to operate in the buck mode that is a voltage drop mode. In this case, the inductors  111 ,  112 , and  113  of the inductor part  110  performs an operation for reducing ripples as an output LC filter together with the input unit  10 . 
     Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.