Abstract:
The present invention provides a DC-DC converter which is connected to a high voltage battery and a low voltage battery to convert a high voltage of the high voltage battery into a low voltage to charge the low voltage battery, including: a connecting unit which connects the high voltage battery and the low voltage battery; a converting unit which converts a high voltage supplied from the high voltage battery into a low voltage to charge the low voltage battery; and a protection circuit which is located between the connecting unit and the converting unit and is turned off when at least one of the high voltage battery and the low voltage battery is erroneously connected, to shut off a current path between the high voltage battery and the low voltage battery.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority under 35 U.S.C. §119 to Korean Patent Application No. 10-2014-0150192, filed on Oct. 31, 2014, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. 
       TECHNICAL FIELD 
       [0002]    The present invention relates to a DC-DC converter, and more particularly, to a DC-DC converter with a protection circuit for a connection error which may prevent a connection error of a battery. 
       BACKGROUND 
       [0003]    In order to solve the problems such as air pollution or increase of CO 2  emission, development of an electric vehicle such as a pure electric vehicle (EV) using electricity with a driving motor as a driving source without having exhaust gas or a hybrid electric vehicle (HEV) having an engine and a driving motor as a driving source has drawn attention. 
         [0004]    Generally, a power system of an electric vehicle is configured by a main battery (a high voltage battery) which supplies driving power of a driving motor, a battery management system (BMS), an auxiliary battery (a low voltage battery) which supplies driving power of other vehicle electric components and a plurality of electric devices. 
         [0005]    The electric vehicle includes an inverter and a low voltage DC-DC converter (LDC). The inverter converts a high DC voltage which is generated in the high voltage battery (a main battery) into an AC voltage to control the motor to be driven and LDC converts the high voltage generated in the high voltage battery to output a low voltage and charge the low voltage battery (an auxiliary battery). 
         [0006]    Therefore, since the high voltage battery and the low voltage battery are connected to the LDC, a high voltage (+) terminal and a high voltage (−) terminal to which the high voltage battery is connected and a low voltage (+) terminal and a low voltage (−) terminal to which the low voltage battery is connected are provided in the LDC. 
         [0007]    In this case, when an operator connects the high voltage battery and the low voltage battery to the LDC, an erroneous connection may occur due to mistake or carelessness of the operator. 
         [0008]    As examples of the erroneous connection, the (−) terminal of the high voltage battery is connected to the high voltage (+) terminal and the (+) terminal of the high voltage battery is connected to the high voltage (−) terminal, or the (−) terminal of the low voltage battery is connected to the low voltage (+) terminal and the (+) terminal of the low voltage battery is connected to the low voltage (−) terminal, or the low voltage battery is connected to the high voltage terminal, or the high voltage battery is connected to the low voltage terminal. 
         [0009]    As described above, when the battery is erroneously connected, a short-circuit may be generated through a body-diode of an FET and as a result, fatal influence may be applied to a vehicle system. 
         [0010]    Accordingly, in order to prevent an accident due to the erroneous connection, in the related art, a method which opens the circuit using a fuse in the event of over-current to stop supplying the power. 
         [0011]    According to the method of shutting off the over-current using the fuse of the related art, even though it is possible to shut off the circuit, but since the circuit is mechanically shut off, the vehicle cannot be reactivated and thus cannot be driven before exchanging the converter. 
         [0012]    The fuse which is used for the converter is an expensive component and thus lots of cost is spent for post-processing. Further, in recent years, circuit components have been diversified and thus working efficiency is lowered. 
       SUMMARY 
       [0013]    An exemplary embodiment of the present invention provides a DC-DC converter with a protection circuit for a connection error which is connected to a high voltage battery and a low voltage battery to convert a high voltage of the high voltage battery into a low voltage to charge the low voltage battery, including: a connecting unit which connects the high voltage battery and the low voltage battery; a converting unit which converts a high voltage supplied from the high voltage battery into a low voltage to charge the low voltage battery; and a protection circuit which is located between the connecting unit and the converting unit and is turned off when at least one of the high voltage battery and the low voltage battery is erroneously connected, to shut off a current path between the high voltage battery and the low voltage battery. 
         [0014]    In this case, the protection circuit may include a first protection element which is connected between a high voltage input line to which a positive electrode of the high voltage battery is connected and a low voltage output line to which a positive electrode of the low voltage battery is connected and is turned on when a turn on voltage or higher is applied to the high voltage input line; and a second protection element which is connected between the low voltage line and the low voltage output line to which a negative electrode of the high voltage battery and a negative electrode of the low voltage battery are commonly connected and is turned on when the turn on voltage or higher is applied to the low voltage output line. Here, the first and second protection elements may be formed of MOS-FETs. 
         [0015]    In this case, when the first protection element is turned on, a current path may be formed in the low voltage output line and when the first protection element is turned off, the current path of the low voltage output line may be shut off. 
         [0016]    When the first protection element is turned on, the second protection element may be turned on or turned off in accordance with a voltage on the low voltage output line. 
         [0017]    In the meantime, a gate of the first protection element may be connected between the converting unit and the connecting unit on the high voltage input line; a source of the first protection element may be connected to the converting unit along the low voltage output line; and a drain of the first protection element may be connected to the connecting unit along the low voltage output line. 
         [0018]    On the other hand, a gate of the second protection element may be connected between the first protection element and the converting unit on the low voltage output line; a source of the second protection element may be connected to the converting unit along the low voltage line; and a drain of the second protection element may be connected to the connecting unit along the low voltage line. 
         [0019]    The converting unit may include: a first switching element which is connected between the high voltage input line and the low voltage output line; a second switching element which is connected between the low voltage output line and the low voltage line; and an inductor which is connected between a contact of the first and second switching elements and the first protection element. 
         [0020]    The connecting unit may include: a high voltage battery positive connection terminal which is located on the high voltage input line and is connected with a positive electrode of the high voltage battery; a low voltage battery positive connection terminal which is located on the low voltage output line and is connected with a positive electrode of the low voltage battery; and a negative connection terminal which is located on the low voltage line and commonly connected with a negative electrode of the high voltage battery and a negative electrode of the low voltage battery. 
         [0021]    A case when at least one of the high voltage battery and the low voltage battery is erroneously connected may include at least one of a case when the high voltage battery is normally connected but the low voltage battery is erroneously connected, a case when the high voltage battery is reversely connected and the low voltage battery is erroneously connected, a case when the low voltage battery is normally connected but the high voltage battery is erroneously connected, and a case when the high voltage battery is erroneously connected and the low voltage battery is reversely connected. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]      FIG. 1  is a circuit diagram of a DC-DC converter with a protection circuit for a connection error according to an exemplary embodiment of the present invention. 
           [0023]      FIGS. 2A to 2C  are circuit diagrams illustrating a case when a high voltage battery is normally connected but a low voltage battery is erroneously connected. 
           [0024]      FIGS. 3A to 3C  are circuit diagrams illustrating a case when a high voltage battery is reversely connected and a low voltage battery is erroneously connected. 
           [0025]      FIGS. 4A to 4C  are circuit diagrams illustrating a case when a low voltage battery is normally connected but a high voltage battery is erroneously connected. 
           [0026]      FIGS. 5A to 5C  are circuit diagrams illustrating a case when a high voltage battery is erroneously connected and a low voltage battery is reversely connected. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0027]    Hereinafter, exemplary embodiments will be described in detail with reference to the accompanying drawings. Throughout the drawings and the detailed description, unless otherwise described, the same drawing reference numerals will be understood to refer to the same elements, features, and structures. The relative size and depiction of these elements may be exaggerated for clarity, illustration, and convenience. The following detailed description is provided to assist the reader in gaining a comprehensive understanding of the methods, apparatuses, and/or systems described herein. Accordingly, various changes, modifications, and equivalents of the methods, apparatuses, and/or systems described herein will be suggested to those of ordinary skill in the art. Also, descriptions of well-known functions and constructions may be omitted for increased clarity and conciseness. 
         [0028]    Advantages and characteristics of the present invention and a method of achieving the advantages and characteristics will be clear by referring to exemplary embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the exemplary embodiment disclosed herein but will be implemented in various forms. The exemplary embodiments are provided to enable the present invention to be completely disclosed and the scope of the present invention to be easily understood by those skilled in the art. Therefore, the present invention will be defined only by the scope of the appended claims. Like reference numerals indicate like elements throughout the specification. 
         [0029]    In the following description of the exemplary embodiments of the present invention, a detailed description of known configurations or functions incorporated herein will be omitted when it is determined that the detailed description may unnecessarily make the subject matter of the present invention unclear. Further, the terms used in the description are defined considering the functions of the exemplary embodiment of the present invention and may vary depending on the intention or usual practice of a user or operator. Accordingly, the terms need to be defined based on details throughout this specification. 
         [0030]    Hereinafter, a DC-DC converter with a protection circuit for a connection error according to an exemplary embodiment of the present invention will be described in detail with reference to accompanying drawings. 
         [0031]      FIG. 1  is a diagram illustrating a DC-DC converter with a protection circuit for a connection error according to an exemplary embodiment of the present invention. 
         [0032]    Referring to  FIG. 1 , a power supply  200  is connected to a DC-DC converter  100  and the DC-DC converter  100  converts a high voltage supplied from a high voltage battery  210  of the power supply  200  into a low voltage and supplies the converted low voltage to a low voltage battery  220  of the power supply  200  to charge the low voltage battery  220 . 
         [0033]    Therefore, the DC-DC converter  100  includes a high voltage input line L 1  to which the high voltage from the high voltage battery  210  is input, a low voltage output line L 2  from which a low voltage is output to the low voltage battery  220 , and a low voltage line L 3  to which a negative electrode of the high voltage battery  210  and a negative electrode of the low voltage battery  220  are connected. 
         [0034]    In this case, the DC-DC converter  100  includes a converting unit  110 , a connecting unit  120 , and a protection circuit  130 . The protection circuit  130  is located between the converting unit  110  and the connecting unit  120  and the power supply  200  is connected to the connecting unit  120 . 
         [0035]    The converting unit  110  converts the high voltage which is supplied from the high voltage battery  210  through the high voltage input line L 1  into a low voltage and supplies the converted low voltage to the low voltage battery  220  through the low voltage output line L 2  to charge the low voltage battery  220 . 
         [0036]    The connecting unit  120  is configured by terminals to which the power supply  200  is connected and is configured by a high voltage battery positive connection terminal T 1 +, a low voltage battery positive connection terminal T 2 + and a negative connection terminal T−. 
         [0037]    The high voltage battery positive connection terminal T 1 + is located on the high voltage input line L 1  and the positive electrode of the high voltage battery  210  is connected to the high voltage battery positive connection terminal T 1 +. 
         [0038]    The low voltage battery positive connection terminal T 2 + is located on the low voltage output line L 2  and the positive electrode of the low voltage battery  220  is connected to the low voltage battery positive connection terminal T 2 +. 
         [0039]    The negative connection terminal T− is located on the low voltage line L 3  and the negative electrode of the high voltage battery  210  and the negative electrode of the low voltage battery  220  are commonly connected to the negative connection terminal T−. 
         [0040]    The protection circuit  130  is located between the converting unit  110  and the connecting unit  120  to prevent the shot circuit which is generated when the power supply  200  is erroneously connected to the DC-DC converter  100 , by a circuit. In this case, the connection error refers to a case when the circuits are erroneously connected such as reverse connection or erroneous connection. 
         [0041]    A configuration of the converting unit  110  will be described in detail. The converting unit  110  may be configured by a first switching element  111 , a second switching element  112 , and an inductor  113 . 
         [0042]    The first switching element  111  is connected between the high voltage input line L 1  and the low voltage output line L 2 . That is, the first switching element  111  is located between the high voltage battery positive connection terminal T 1 + and the low voltage battery positive connection terminal T 2 +. 
         [0043]    In this case, a drain D of the first switching element  111  is connected to the high voltage battery positive connection terminal T 1 + through the high voltage input line L 1  and a source S of the first switching element  112  is located between the low voltage battery positive connection terminal T 2 + via the low voltage output line L 2 . 
         [0044]    The second switching element  112  is connected between the low voltage output line L 2  and the low voltage line L 3 . That is, the second switching element  112  is located between the low voltage battery positive connection terminal T 2 + and the negative connection terminal T−. 
         [0045]    In this case, a drain D of the second switching element  112  is connected to a source S of the first switching element  111  through the low voltage output line L 2  and the source S of the second switching element  112  is connected to the negative connection terminal T−. 
         [0046]    The inductor  113  is connected between a contact n 1  of the first switching element  111  and the second switching element  112  and a first protection element  131  of the protection circuit  130 . 
         [0047]    The first and second switching elements  111  and  112  may be N-MOS FETs like the exemplary embodiment, but may be P-MOS FETs. A structure of the converting unit  110  is a known technology and detailed description thereof will be omitted. 
         [0048]    A configuration of the protection circuit  130  will be described in detail. The protection circuit  130  may be configured by a first protection element  131  and a second protection element  132 . 
         [0049]    In this case, the first and second protection elements  131  and  132  may be P-MOS FETs or N-MOS FETs and in the exemplary embodiment, an example in which the first and second protection elements  131  and  132  are N-MOS FETs will be described. 
         [0050]    The first protection element  131  is connected between the high voltage input line L 1  to which the positive electrode of the high voltage battery  210  is connected and the low voltage output line L 2  to which the positive electrode of the low voltage battery  220  is connected and is turned on when a turn-on voltage or higher is applied to the high voltage input line L 1 . 
         [0051]    A gate G 1  of the first protection element  131  is connected between the converting unit  110  and the connecting unit  120  on the high voltage input line L 1  and specifically, located between the drain D of the first switching element  111  an the high voltage battery positive connection terminal T 1 +. 
         [0052]    A source S 1  of the first protection element  131  is connected to the converting unit  110  along the low voltage output line L 2  and specifically, connected to the inductor  113 . 
         [0053]    A drain D 1  of the first protection element  121  is connected to the connecting unit  120  along the low voltage output line L 2  and specifically, connected to the low voltage battery positive connection terminal T 2 +. 
         [0054]    The second protection element  132  is connected between the low voltage line L 3  to which a negative electrode of the high voltage battery  210  and a negative electrode of the low voltage battery  220  are commonly connected and the low voltage output line L 2  and is turned on when a turn-on voltage or higher is applied to the low voltage output line L 2 . 
         [0055]    A gate G 2  of the second protection element  132  is located on the low voltage output line L 2  to be connected between the first protection element  131  and the converting unit  110  and specifically, connected between the inductor  113  and the source S 1  of the first protection element  131 . 
         [0056]    A source S 2  of the second protection element  132  is connected to the converting unit  110  along the low voltage line L 3  and specifically, connected to the source S of the second switching element  112 . 
         [0057]    A drain D 2  of the second protection element  132  is connected to the connecting unit  120  along the low voltage line L 3  and specifically, connected to the negative connection terminal T−. 
         [0058]    When a turn on voltage or higher of the first protection element  131  is applied through the high voltage input line L 1 , the first protection element  131  is turned on and thus a current path is formed in the low voltage output line L 2 . 
         [0059]    In contrast, when a voltage which is lower than the turn on voltage of the first protection element  131  is applied through the high voltage input line L 2 , the first protection element  131  is turned off and thus a current path of the low voltage output line L 2  is shut off. 
         [0060]    In the meantime, even though the first protection element  131  is turned on to form the current path in the low voltage output line L 2 , when a voltage which is lower than the turn on voltage of the second protection element  131  is applied through the low voltage output line L 2 , the second protection element  132  is not turned on, but is maintained in a turned-off state. 
         [0061]    Accordingly, when the first protection element  131  is turned on, the second protection element  132  is turned on or turned off in accordance with the voltage on the low voltage output line L 2 . 
         [0062]    According to the configuration of the protection circuit  130  of the present invention as described above, since the first and second protection circuits  131  and  132  are implemented by MOS FETs, the first and second protection circuits  131  and  132  are turned on only when the voltages of the gates G 1  and G 2  are applied, due to characteristic of the MOS FET. Accordingly, in the event of reverse connection, since (−) voltage is applied to the gates G 1  and G 2  of the first and second protection elements  131  and  132 , the first and second protection elements  131  and  132  are maintained in a turned-off state and a loop through which the current flows does not exist, so that the short circuit caused by the reverse connection may be prevented by a circuit. 
         [0063]    In the above description, the configuration of the DC-DC converter with a protection circuit for a connector error according to the exemplary embodiment of the present invention has been described with reference to  FIG. 1 . Hereinafter, with a case when the power supply  200  is erroneously connected to the DC-DC converter as an example, an operation of a protection circuit according to an exemplary embodiment of the present invention will be described. 
         [0064]      FIGS. 2 to 5  are circuit diagrams illustrating an example in which a power supply is erroneously connected to the DC-DC converter, in which  FIGS. 2A to 2C  illustrate a case when a high voltage battery is normally connected but a low voltage battery is erroneously connected,  FIGS. 3A to 3C  illustrate a case when a high voltage battery is reversely connected and a low voltage battery is erroneously connected,  FIGS. 4A to 4C  illustrate a case when a low voltage battery is normally connected but a high voltage battery is erroneously connected, and  FIGS. 5A to 5C  illustrate a case when a high voltage battery is erroneously connected and a low voltage battery is reversely connected. 
         [0065]    Since the operations of the protection circuit in the exemplary embodiments are the same, only one case in each exemplary embodiment will be described. 
         [0066]    Referring to  FIG. 2A , since a high voltage is normally connected, the first protection element  131  is turned on. However, as the first protection element  131  is turned on, the negative electrode of the low voltage battery  220  is connected to the gate G 2  of the second protection element  132  so that the second protection element  132  is turned off. Therefore, a current path is not formed. 
         [0067]    As illustrated in  FIG. 3A , when the high voltage battery  210  and the low voltage battery  220  are erroneously connected, since both the first and second protection elements  131  and  132  are turned off, the current path is not formed. 
         [0068]    As illustrated in  FIG. 4A , even though the low voltage battery  220  is normally connected, the high voltage battery  210  is reversely connected, so that the first protection element  131  is turned off and the current path is not formed. 
         [0069]    As illustrated in  FIG. 5A , when the negative electrode of the high voltage battery  210  is connected to the low voltage battery positive connection terminal to form erroneous connection and the low voltage battery  220  is reversely connected, even though the first protection element  131  is turned on, the second protection element  132  is turned off, so that the current path is not formed. 
         [0070]    Even though the DC-DC converter with a protection circuit for a connection error according to the present invention has been described with reference to the exemplary embodiment, the scope of the present invention is not limited to a specific exemplary embodiment and various substitutions, modifications, and changes may be made within a scope which is obvious to those skilled in the art. 
         [0071]    When a protection circuit for a connection error of the present invention is applied to a DC-DC converter, even though a high voltage battery and a low voltage battery are erroneously connected to the DC-DC converter, a protection element of the protection circuit is maintained to be turned off, so that no current path is formed, which may prevent a short circuit caused by an erroneous connection. 
         [0072]    Therefore, different from the related art which uses a fuse to prevent the overcurrent due to an erroneous connection, since the current path is shut off by a circuit, an expensive fuse is not used, thereby saving cost. Further, a size of an MOS FET is smaller than a size of the fuse, thereby reducing a size of the circuit. 
         [0073]    A number of exemplary embodiments have been described above. Nevertheless, it will be understood that various modifications may be made. For example, suitable results may be achieved if the described techniques are performed in a different order and/or if components in a described system, architecture, device, or circuit are combined in a different manner and/or replaced or supplemented by other components or their equivalents. Accordingly, other implementations are within the scope of the following claims.