Abstract:
Provided are a power supply apparatus and method for a hybrid vehicle. The power supply apparatus is integrated with a power conversion device and an energy storage device in order to reduce a size and production cost of the power supply apparatus and includes a battery unit including a plurality of battery cells configured to store different levels of power and a power control unit configured to control the battery unit to integrally or selectively output the power of the plurality of battery cells based on whether an engine of the hybrid vehicle generates power.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to and the benefit of Korean Patent Application No. 10-2014-0135878, filed on Oct. 8, 2014, the disclosure of which is incorporated herein by reference in its entirety. 
       BACKGROUND 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a power supply apparatus and method for a hybrid vehicle, and more particularly, to a power supply apparatus and method for a hybrid vehicle in which a power conversion device and an energy storage device are integrated in order to reduce a size and production cost of the power supply apparatus. 
         [0004]    2. Discussion of Related Art 
         [0005]    In general, a 48V Mild Hybrid Electric Vehicle (HEV) is a hybrid vehicle made for the purpose of improving fuel efficiency and reducing carbon dioxide emission by stopping the engine when the vehicle is stopped, performing regenerative braking when the vehicle decelerates, and performing engine torque assistance when the vehicle accelerates. 
         [0006]    Compared with an existing HEV, a 48V Mild HEV may additionally include a hybrid function by replacing an alternator and adding a 48V power device without changing a vehicle body, thus improving fuel efficiency at a low cost. 
         [0007]    Since the body of such a 48V Mild HEV cannot be changed, the size and mountability are very important factors in developing vehicle components and implementing a system. 
         [0008]    In a conventional 48V system installed in such a 48 Mild HEV, a power conversion device and an energy storage device are separated from each other. 
         [0009]    For example,  FIG. 1  is a view showing a configuration of a conventional electric system installed in a 48V Mild HEY. As shown in  FIG. 1 , the conventional electric system installed in the 48V Mild HEV includes a 48V battery  10 , a 12V battery  20 , a converter  30 , and an inverter combined with an integrated starter-generator (ISG) (ISG/inverter)  40 . 
         [0010]    When an engine is started, the 48V battery  10  supplies 48V DC power to the inverter  40 . 
         [0011]    When the engine is started, the 12V battery  20  supplies 12V DC power to the converter  30 . 
         [0012]    The converter  30  converts the 12V DC power supplied from the 12V battery  20  into 48V DC power when the engine is started, and then supplies the converted 48V DC power to the inverter  40 . 
         [0013]    The inverter  40  converts the 48V DC power supplied from the 48V battery  10  and the 48V DC power supplied from the converter  30  into 48V AC power when the engine is started, and then supplies the converted 48V AC power to the ISG 
         [0014]    In addition, when the engine generates power, the inverter  40  converts the AC power supplied from the ISG into the 48V DC power, and then supplies the converted 48V DC power to the 48V battery  10  and the converter  30 . 
         [0015]    The converter  30  converts the 48V DC power supplied from the inverter  40  into 12V DC power when the engine generates power, and then supplies the converted 12V DC power to the 12V battery  20 . 
         [0016]    The 48V battery  10  stores the 48V DC power supplied from the inverter  40  when the engine generates power. 
         [0017]    The 12V battery  20  stores the 12V DC power supplied from the converter  30  when the engine generates power. 
         [0018]    Here, the inverter  40  and the converter  30  are included in a power conversion device, and the 48V battery  10  and the 12V battery  20  are included in an energy storage device. 
         [0019]    As described above, the conventional electric system installed in the 48V Mild HEV has the power conversion device and the energy storage device, which are separated from each other, and thus has difficulties in reducing a size and production cost of the 48V Mild HEY. 
       SUMMARY OF THE INVENTION 
       [0020]    The present invention is directed to a power supply apparatus and method for a hybrid vehicle in which a power conversion device and an energy storage device are integrated in order to reduce a size and production cost of the power supply apparatus. 
         [0021]    According to an aspect of the present invention, there is provided a power supply apparatus for a hybrid vehicle, the power supply apparatus including a battery unit including a plurality of battery cells configured to store different levels of power and a power control unit configured to control the battery unit to integrally or selectively output the power of the plurality of battery cells based on whether an engine of the hybrid vehicle generates power. 
         [0022]    The power control unit may allow the power of the plurality of battery cells to be integrally output when the engine of the hybrid vehicle is started and may allow the power of the plurality of battery cells to be selectively output when the engine of the hybrid vehicle generates the power. 
         [0023]    The power control unit may include a capacitor unit configured to divide the power output from the battery unit into first power and second power that is lower than the first power and store the first power and the second power in a first capacitor and a second capacitor connected in series with each other, respectively, a converter unit configured to integrate the first power output from the first capacitor and the second power output from the second capacitor and output the integrated power as direct current (DC) power, and an inverter unit configured to convert the DC power output from the converter unit into alternating current (AC) power and supply the AC power to the engine of the hybrid vehicle. 
         [0024]    The battery unit may include a first battery cell and a second battery cell having lower output power than the first battery cell, and the power control unit may control the battery unit to supply the output power of the second battery cell to an electric field load of the hybrid vehicle. 
         [0025]    A positive electrode of the first battery cell is connected in series with a first power source, a negative electrode of the first battery cell is connected in series with a positive electrode of the second battery cell and connected in parallel with a second power source having lower power than the first power source, and the positive electrode of the second battery cell is connected in series with the second power source and a negative electrode of the second battery cell is connected in series with a ground. 
         [0026]    The first capacitor may have one end connected in series with the first power source and the other end connected in series with one end of the second capacitor and connected in parallel with one end of an inductor and the negative electrode of the first battery cell, and the second capacitor may have one end connected in parallel with the positive electrode of the second battery cell and the other end connected in parallel with the ground and the negative electrode of the second battery cell. 
         [0027]    The inverter unit may include first to sixth insulated gate field effect transistors (IGFETs), and the first and fourth IGFETs connected in series with each other, the second and fifth IGFETs connected in series with each other, and the third and sixth IGFETs connected in series with each other may be connected in parallel with one another. 
         [0028]    Drain electrodes of the first to third IGFETs may be connected in series with the first power source, source electrodes of the first to third IGFETs may be connected in series with drain electrodes of the fourth to sixth IGFETs, respectively, and source electrodes of the fourth to sixth IGFETs may be connected in series with a ground. 
         [0029]    The inverter unit may further include first to sixth diodes, and negative electrodes of the first to sixth diodes may be connected in parallel with drain electrodes of the first to sixth IGFETs, and positive electrodes of the first to sixth diodes may be connected in parallel with source electrodes of the first to sixth IGFETs. 
         [0030]    The converter unit may include seventh and eighth IGFETs connected in series with each other, and a drain electrode of the seventh IGFET may be connected to the first power source, a source electrode of the seventh IGFET may be connected in series with a drain electrode of the eighth IGFET, and a source electrode of the eighth IGFET may be connected to the ground. 
         [0031]    The converter unit may further include an inductor, and the inductor may have one end connected to the capacitor unit and the other end connected in parallel with the source electrode of the seventh IGFET and the drain electrode of the eighth IGFET. 
         [0032]    According to another aspect of the present invention, there is provided a power supply method for a hybrid vehicle including a battery unit and a power control unit, in which the battery unit includes a plurality of battery cells storing different levels of power, the power supply method including controlling, by the power control unit, the battery unit to integrally output the power of the plurality of battery cells when an engine of the hybrid vehicle is started and controlling, by the power control unit, the battery unit to selectively output the power of the plurality of battery cells when the engine of the hybrid vehicle generates power. 
         [0033]    The controlling of the battery unit to integrally output the power may include dividing the power output from the battery unit into first power and second power and store the first power and second power in a first capacitor and a second capacitor connected in series with each other, respectively. 
         [0034]    The controlling of the battery unit to integrally output the power may further include integrating the first power output from the first capacitor and the second power output from the second capacitor to output the integrated power as DC power; and converting the output DC power into AC power to supply the AC power to the engine of the hybrid vehicle. 
         [0035]    The battery unit may include a first battery cell and a second battery cell having lower output power than the first batter cell, and the controlling of the battery unit to selectively output the power may include controlling the battery unit to supply the output power of the second battery cell to an electric field load of the hybrid vehicle. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0036]    The above and other objects, features and advantages of the present invention will become more apparent to those of ordinary skill in the art by describing in detail exemplary embodiments thereof with reference to the accompanying drawings, in which: 
           [0037]      FIG. 1  is a view showing a configuration of a conventional 48V system installed in a 48V Mild HEY; 
           [0038]      FIG. 2  is a view showing a power supply apparatus for a hybrid vehicle according to an embodiment of the present invention; and 
           [0039]      FIGS. 3 and 4  are circuit diagrams showing a power supply apparatus for a hybrid vehicle according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0040]    Advantages and features of the present invention, and implementation methods thereof will be clarified through the following embodiments described with reference to the accompanying drawings. The present invention may, however, be embodied in different forms and should not be construed as 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 present invention to those skilled in the art. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
         [0041]    A power supply apparatus for a hybrid vehicle according to an embodiment of the present invention will be described below with reference to  FIGS. 2 to 4 . 
         [0042]      FIG. 2  is a view showing the power supply apparatus for the hybrid vehicle according to an embodiment of the present invention, and  FIGS. 3 and 4  are circuit diagrams showing the power supply apparatus for the hybrid vehicle according to an embodiment of the present invention. 
         [0043]    As shown in  FIG. 2 , the power supply apparatus for the hybrid vehicle according to an embodiment of the present invention includes an integrated power system (IPS)  100  and an integrated starter-generator (ISG)  200 . 
         [0044]    As shown in  FIGS. 3 and 4 , the integrated power system  100  supplies predetermined power (e.g., 48V power) to the ISG  200  and includes a power control unit (PCU)  110  and a battery unit  120 . 
         [0045]    The PCU  110  includes an inverter unit  111 , a converter unit  112 , and a capacitor unit  113 . 
         [0046]    The inverter unit  111  converts DC power into AC power and includes six n-channel type insulated gate field effect transistors (IGFETs) Q 1 , Q 2 , Q 3 , Q 4 , Q 5 , and Q 6  and six diodes D 1 , D 2 , D 3 , D 4 , D 5 , and D 6 . 
         [0047]    A circuit configuration of the inverter unit  111  will be described below in more detail. 
         [0048]    The inverter unit  111  includes a first IGFET Q 1 , a second IGFET Q 2 , a third IGFET Q 3 , a fourth IGFET Q 4 , a fifth IGFET Q 5 , and a sixth IGFET Q 6 . 
         [0049]    First, the first IGFET Q 1  and the fourth IGFET Q 4  are connected in series with each other. 
         [0050]    For example, the first IGFET Q 1  has a drain electrode connected in series with a first power source (e.g., a 48V power source) and a source electrode connected in series with a drain electrode of the fourth IGFET Q 4 . The fourth IGFET Q 4  has a drain electrode connected in series with a source electrode of the first IGFET Q 1  and a source electrode connected in series with the ground. 
         [0051]    In addition, the first IGFET Q 1  is connected in parallel with the first diode D 1 , and the fourth IGFET Q 4  is connected in series with the fourth diode D 4 . 
         [0052]    For example, the first IGFET Q 1  has a drain electrode connected in parallel with a negative electrode of the first diode D 1  and a source electrode connected in parallel with a positive electrode of the first diode D 1 . The fourth IGFET Q 4  has a drain electrode connected in parallel with a negative electrode of the fourth diode D 4  and a source electrode connected in parallel with a positive electrode of the fourth diode D 4 . 
         [0053]    The second IGFET Q 2  and the fifth IGFET Q 5  are connected in series with each other. 
         [0054]    For example, the second IGFET Q 2  has a drain electrode connected in series with a 48V power source and a source electrode connected in series with a drain electrode of the fifth IGFET Q 5 . The fifth IGFET Q 5  has a drain electrode connected in series with a source electrode of the second IGFET Q 2  and a source electrode connected in series with the ground. 
         [0055]    In addition, the second IGFET Q 2  is connected in parallel with the second diode D 2 , and the fifth IGFET Q 5  is connected in parallel with the fifth diode D 5 . 
         [0056]    For example, the second IGFET Q 2  has a drain electrode connected in parallel with a negative electrode of the second diode D 2  and a source electrode connected in parallel with a positive electrode of the second diode D 2 . The fifth IGFET Q 5  has a drain electrode connected in parallel with a negative electrode of the fifth diode D 5  and a source electrode connected in parallel with a positive electrode of the fifth diode D 5 . 
         [0057]    The third IGFET Q 3  and the sixth IGFET Q 6  are connected in series with each other. 
         [0058]    For example, the third IGFET Q 3  has a drain electrode connected in series with a 48V power source and a source electrode connected in series with a drain electrode of the sixth IGFET Q 6 . The sixth IGFET Q 6  has a drain electrode connected in series with a source electrode of the third IGFET Q 3  and a source electrode connected in series with the ground. 
         [0059]    In addition, the third IGFET Q 3  is connected in parallel with the third diode D 3 , and the sixth IGFET Q 6  is connected in parallel with the sixth diode D 6 . 
         [0060]    For example, the third IGFET Q 3  has a drain electrode connected in parallel with a negative electrode of the third diode D 3  and a source electrode connected in parallel with a positive electrode of the third diode D 3 . The sixth IGFET Q 6  has a drain electrode connected in parallel with a negative electrode of the sixth diode D 6  and a source electrode connected in parallel with a positive electrode of the sixth diode D 6 . 
         [0061]    As described above, the inverter unit  111  has the first IGFET Q 1  and the fourth IGFET Q 4  connected in series with each other, the second IGFET Q 2  and the fifth IGFET Q 5  connected in series with each other, and the third IGFET Q 3  and the sixth IGFET Q 6  connected in series with each other. Moreover, the first IGFET Q 1  and fourth IGFET Q 4  connected in series with each other, the second IGFET Q 2  and fifth IGFET Q 5  connected in series with each other, and the third IGFET Q 3  and sixth IGFET Q 6  connected in series with each other are connected in parallel with one another. 
         [0062]    The converter unit  112  receives first power (e.g., 36V power) and second power (e.g., 12V power) from the capacitor unit  113  and transfers predetermined power (e.g., 48V power), which is a sum of the first power and the second power, to the inverter unit  111 . The converter unit  112  includes two N-channel type IGFETs Q 7  and Q 8  and one inductor L 1 . 
         [0063]    A circuit configuration of the converter unit  112  will be described below in more detail. 
         [0064]    The converter unit  112  includes the seventh IGFET Q 7  and the eighth IGFET Q 8 , and the seventh IGFET Q 7  and the eighth IGFET Q 8  are connected in series with each other. 
         [0065]    For example, the seventh IGFET Q 7  has a drain electrode connected in series with a 48V power source and a source electrode connected in series with a drain electrode of the eighth IGFET Q 8 . The eighth IGFET Q 8  has a drain electrode connected in series with a source electrode of the seventh IGFET Q 7  and a source electrode connected in series with the ground. 
         [0066]    In addition, the seventh IGFET Q 7  is connected in parallel with the seventh diode D 7 , and the eighth IGFET Q 8  is connected in parallel with the eighth diode D 8 . 
         [0067]    For example, the seventh IGFET Q 7  has a drain electrode connected in parallel with a negative electrode of the seventh diode D 7  and a source electrode connected in parallel with a positive electrode of the seventh diode D 7 . The eighth IGFET Q 8  has a drain electrode connected in parallel with a negative electrode of the eighth diode D 8  and a source electrode connected in parallel with a positive electrode of the eighth diode D 8 . 
         [0068]    The first inductor L 1  has one end connected to the capacitor unit  113 . The first inductor L 1  has the other end connected in parallel with a source electrode of the seventh IGFET Q 7  and connected in parallel with a drain electrode of the eighth IGFET Q 8 . 
         [0069]    As described above, the converter unit  112  is connected in parallel with the inverter unit  111 , and connected with the capacitor unit  113  through the first inductor L 1 . 
         [0070]    The capacitor unit  113  receives and stores the first power (e.g., 36V power) and the second power (e.g., 12V power) from the battery unit  120 . The capacitor unit  113  includes a first capacitor C 1  and a second capacitor C 2 . Here, the first capacitor C 1  may be a 36V capacitor that receives and stores the 36V power from the battery unit  120 , and the second capacitor C 2  may be a 12V capacitor that receives and stores the 12V power from the battery unit  120 . The following description assumes that the first capacitor C 1  and the second capacitor C 2  are a 36V capacitor and a 12V capacitor, respectively. 
         [0071]    The 36V capacitor C 1  has one end connected in series with a 48V power source and the other end connected in series with one end of the 12V capacitor C 2 . 
         [0072]    The 12V capacitor C 2  has one end connected in series with the other end of the 36V capacitor C 1  and the other end connected in series with the ground. 
         [0073]    In addition, the 36V capacitor C 1  has the other end connected in parallel with one end of the first inductor L 1 , and the 12V capacitor C 2  has one end connected in parallel with one end of the first inductor L 1 . 
         [0074]    The battery unit  120  includes a first battery cell  121  and a second battery cell  122 . Here, the first battery cell  121  may be a 36V battery cell, and the second battery cell  122  may be a 12V battery cell. The following description assumes that the first battery cell  121  is a 36V battery cell and the second battery cell  122  is a 12V battery cell. 
         [0075]    The 36V battery cell  121  and the 12V battery cell  122  are connected in series with each other. 
         [0076]    For example, the 36V battery cell  121  has a positive electrode connected in series with the 48V power source. The 36V battery cell  121  has a negative electrode connected in series with a positive electrode of the 12V battery cell  122  and connected in parallel with a second power source (e.g., a 12V power source). Here, the second power source may have lower power than the first power source. 
         [0077]    The 12V battery cell  122  has a positive electrode connected in series with a negative electrode of the 36V battery cell  121  and connected in series with the 12V power source. The 12V battery cell  122  has a negative electrode connected in series with the ground. 
         [0078]    As described above, according to an embodiment of the present invention, it is possible to improve assemblability and simplify a process by integrating the power conversion device, in which the converter and the inverter are included, and the energy storage device. It is also possible to reduce a capacity of the converter according to a 36V/12V cell voltage balancing function to decrease the number of components and save the production cost by using one integrated 48V battery instead of a 48V battery and a 12V battery, which are separated from each other. 
         [0079]      FIGS. 3 and 4  are circuit diagrams showing the power supply apparatus for the hybrid vehicle according to an embodiment of the present invention. In detail,  FIG. 3  is a circuit diagram showing the flow of power as a direction of an arrow when an engine of a hybrid vehicle is started, and  FIG. 4  is a circuit diagram showing the flow of power as a direction of an arrow when the engine of the hybrid vehicle generates power. 
         [0080]    As shown in  FIG. 3 , the flow of power when engine is started is in the direction of the arrow. 
         [0081]    For example, when a vehicle stops and then goes, the engine is stopped and then restarted, and the battery unit  120  is discharged to transfer 48V power to the power control unit  110 . 
         [0082]    The power control unit  110  transfers the 48V transferred by the battery unit  120  to a 48V ISG Finally, the 48V ISG supplies the 48V power transferred by the battery unit  120  to the engine. 
         [0083]    In addition, as shown in  FIG. 4 , the flow of power when the engine generates power is in the direction of the arrow. 
         [0084]    For example, when a vehicle is running, the engine is operated to transfer the power to the 48V ISG, and the 48V ISG transfers the power of the engine to the power control unit  110 . 
         [0085]    The power control unit  110  supplies the power transferred from the 48V ISG to the battery unit  120 . The battery unit  120  charges the power supplied from the power control unit  110 . 
         [0086]    According to an embodiment of the present invention, it is possible to improve assemblability and simplify a process by integrating the power conversion device, in which the converter and the inverter are included, and the energy storage device. 
         [0087]    It is also possible to reduce a capacity of the converter according to a 36V/12V cell voltage balancing function to decrease the number of components and save the production cost by using one integrated 48V battery instead of a 48V battery and a 12V battery, which are separated from each other. 
         [0088]    It is also possible to improve performance of the ISG by forming the ISG as an independent structure rather than a structure integrated with an inverter to increase the capacity of the ISG 
         [0089]    It should be understood that although the present invention has been described above in detail with reference to the accompanying drawings and exemplary embodiments, this is illustrative only and various modifications may be made without departing from the spirit or scope of the invention. Thus, the scope of the present invention is to be determined by the following claims and their equivalents, and shall not be restricted or limited by the foregoing detailed description.