Abstract:
An apparatus for charging and discharging an electrical device in vehicle is provided. The apparatus comprises a switch, first and second power sources, and first and second contactors. The first power source is configured to provide a low voltage. The switch is configured to enable/disable the first power source. The second power source is configured to provide a high voltage for charging the electrical device. The first contactor is operably coupled to the first power source and to the second power source, the first contactor being configured to enable the second power source to provide the high voltage for charging the electrical device in response to the switch enabling the first power source. The second contactor is operably coupled to the first power source and to the second power source, the second contactor being in an open state in response to the switch enabling the first power supply.

Description:
TECHNICAL FIELD 
       [0001]    Embodiments of the present invention generally relate to a method and apparatus for charging or discharging an electrical device in a vehicle. 
       BACKGROUND 
       [0002]    Electrical energy is used as a mechanism to drive a hybrid and/or electric vehicle. To provide enough power to drive the vehicle, high voltage power may be utilized to drive one or more motors in such vehicles. It is known that the high voltage energy stored in various capacitors may need to be discharged when the vehicle shuts down or in other situations. Conventional discharge methods include an active discharge and a passive discharge to remove stored HV energy. In the active discharge, windings within the motor of the vehicle are used to discharge the energy. In the passive discharge, a resistor (i.e., bleeding resistor) is used to discharge the energy. 
         [0003]    To reduce energy loss while the vehicle is an operational mode, it may be desirable to select a resistance of the resistor to be large. However, in order to quickly discharge energy in a passive discharge, it may be desirable for the resistance of the resistor to be small. By selecting a small resistance for the resistor to satisfy a quick passive discharge, this condition may negatively affect vehicle fuel economy. 
       SUMMARY 
       [0004]    In one embodiment, an apparatus for charging and discharging an electrical device in vehicle is provided. The apparatus comprises a switch, first and second power sources, and first and second contactors. The first power source is configured to provide a low voltage. The switch is configured to enable/disable the first power source. The second power source is configured to provide a high voltage for charging the electrical device. The first contactor is operably coupled to the first power source and to the second power source, the first contactor being configured to enable the second power source to provide the high voltage for charging the electrical device in response to the switch enabling the first power source. The second contactor is operably coupled to the first power source and to the second power source, the second contactor being in an open state in response to the switch enabling the first power supply. 
         [0005]    In another embodiment, an apparatus comprising a first contactor, a second contactor, a controller, and a capacitor is provided. The first contactor receives a low voltage from a first power source and a high voltage from a second power source. The second contactor receives the low voltage and the high voltage. The controller enables/disables a transmission of the low voltage. The capacitor receives the high voltage to store energy in response to the controller enabling the transmission of the low voltage. 
         [0006]    In another embodiment, a method for charging an electrical device in vehicle is provided. The method comprises providing a first contactor and a second contactor and controlling the first contactor to close and the second contactor to open in response to a low voltage. The method further comprises charging the electrical device with energy from a high voltage in response to controlling the first contactor to close and the second contactor to open. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The embodiments of the present invention are pointed out with particularity in the appended claims. However, other features of the various embodiments that are within the scope of the invention as claimed will become more apparent and will be best understood by referring to the following detailed description in conjunction with the accompany drawings in which: 
           [0008]      FIG. 1  depicts an apparatus in an operation mode; 
           [0009]      FIG. 2  depicts the apparatus in a discharge mode; and 
           [0010]      FIG. 3  depicts an apparatus in accordance to one embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. 
         [0012]      FIG. 1  depicts an apparatus  10  in an operation mode. The apparatus  10  may be implemented in a hybrid or electric vehicle. It is recognized that various adaptations of the apparatus and/or methods as described herein may be used in connection with any type of vehicle that utilizes a discharge function for discharging various electrical components in any system. The apparatus  10  includes a high voltage power source  12 , a contactor  14 , a discharge circuit  16 , a charge element  18 , a bi-directional inverter/rectifier  20  (hereafter “bi-directional circuit  20 ”), and a motor  22 . In general, the power source  12  may include any number of batteries or battery cells and is configured to generate high voltage (HV) DC energy. When the contactor  14  is closed, the HV DC energy may be transferred between the power source  12  and the motor through the bi-directional circuit  20 . The bi-directional circuit  20  inverts the HV DC energy into AC energy for transfer to windings  24   a - 24   n  (“ 24 ”) of the motor  22 . The bi-directional circuit  20  includes a plurality of switches  26   a - 26   n  (e.g., each switch may be an insulated gate bi-polar transistor (IGBT), a field effect transistor (FET) or other suitable electronic device) that enable the DC energy to be inverted into AC energy. The motor  22  is an AC motor that may provide additional power to the vehicle, in addition to an internal combustion engine (not shown) or that may produce electrical energy in a generator mode. The apparatus  10  also enables the flow of energy back from the motor  22  back to the power source  12  to charge the power source  12 . 
         [0013]    The charge circuit  18  may be implemented as a capacitor. The capacitor  18  is arranged to buffer the HV energy between the power source  12  and the motor  22 . The discharge circuit  16  includes a switch  30  and a discharge resistor  32 . The operational mode is generally defined as a mode in which the motor  22  receives AC power from the bi-directional circuit  20  or a mode in which the power source  12  receives energy from the motor  22 . In the operational mode, the vehicle is in a state in which it is being driven or has been started. When it is desired to transfer energy to the motor  22 , a controller (not shown) controls the contactor  14  to close and the switch  30  to open such that energy flows to the motor  22 . It is recognized that the switch  30  may be a transistor, IGBT, MOSFET or other suitable device that is configured to open/close to enable energy transfer therethrough when desired. The switch  30  remains open in the operational mode to prevent energy loss through the resistor  32 . In the operational mode, the capacitor  18  stores at least portion of the HV energy that is generated from the power source  12 . The capacitor  18  provides a transient current to the bi-directional circuit  20  to reduce voltage spikes on a HV bus and to stabilize the HV bus voltage. When it is desired to transfer energy from the motor  22  back to the power source  12 , the controller controls the contactor  14  to close again and controls the switch  30  to open. 
         [0014]      FIG. 2  depicts the apparatus  10  in the discharge mode. The discharge mode is generally defined as a mode in which the transfer of energy to and from the motor  22  is disabled (e.g., the vehicle may be shut down). In the discharge mode, the controller controls the contactor  14  to open for preventing the flow of HV energy to and from the motor  22 . In addition, the controller controls the switch  30  to close and the stored energy across the capacitor  18  is discharged across the resistor  32 . It is desirable in the discharge mode to discharge the energy stored on the capacitor  18  and on the motor windings  24   a - 24   n  to ensure operator safety in the event an operator services the vehicle. The resistance of the resistor  32  may be small so that energy from the capacitor  18  can be discharged in a rapid manner. The placement of the discharge circuit  16  with respect to the position of the contactor  14  may allow for a small resistance value to be selected for the resistor  32 . Due to the placement of the discharge circuit  16  and the small resistance for the resistor  32 , power loss in the apparatus  10  may be minimized when the apparatus  10  is in the operation mode. 
         [0015]      FIG. 3  depicts an apparatus  50  in accordance to one embodiment of the present invention. The apparatus  50  includes a HV power source  52 , a contactor  54 , a LV circuit  56 , a discharge circuit  58 , a capacitor  60 , and a bidirectional inverter/rectifier  62  (hereafter “bi-directional circuit  62 ”), a motor  64  and a controller  65 . In a similar manner to that described with the apparatus  10  of  FIG. 1 , the power source  52  generally includes any number of batteries or battery cells and is configured to provide electrical energy to the motor  64  or to store energy generated by the motor  64 . The bi-directional circuit  62  includes a plurality of switches  68   a - 68   n  (“ 68 ”) (such as, but not limited to, IGBTs and FETs). The plurality of switches  68  enable the DC energy to be inverted into AC energy for delivery to the motor  64 . The plurality of switches  68  also enable the AC energy to be rectified into DC energy for storage on the power source  52 . 
         [0016]    The capacitor  60  buffers the HV energy between the power source  52  and the motor  64 . The discharge circuit  58  includes a contactor  70  and a resistor  72 . The contactor  54  and the contactor  70  may each be in the form of a mechanical relay. The contactor  54  includes a winding  74  and a switch  76  that forms the relay. The contactor  54  may be implemented as a normally open relay. The normally open relay is generally defined as the switch  76  being opened when the winding  74  is not energized. The contactor  70  includes a winding  78  and a switch  80  that forms the relay. The contactor  70  may be implemented as a normally closed relay. The normally closed relay is generally defined as the switch  80  being closed when the winding  78  is not energized. The windings  74 ,  78  are positioned on the LV circuit  56 . The LV circuit  56  further includes a power supply  82 , a switch  84 , a diode  86 , and a zener diode  88 . 
         [0017]    The vehicle is generally configured to operate at two voltage levels, a HV power level (e.g., approximately 150V or greater) and a LV power level (e.g., approximately 12 V or greater). The HV power source  52 , the capacitor  60 , the bi-directional circuit  62 , the motor  64 , the switch  76  of the contactor  54 , the switch  80  of the contactor  70 , and the resistor  72  are generally configured to operate in the high power voltage level domain. The power supply  52  may generate a voltage at 150V or greater. In general, when the controller  65  controls the switch  84  to close, the contactor  54  closes and the contactor  70  opens. In response thereto, the bi-directional circuit  62  inverts the HV energy into an AC voltage for driving the motor  64  or rectifies the AC energy into HV DC energy. 
         [0018]    The power supply  82 , the switch  84 , the winding  74  of the contactor  54 , the winding  78  of the contactor  70 , the diode  86 , and the zener diode  88  are generally configured to operate in the low power voltage level domain. The LV energy generated by the power supply  82  may generate a voltage at approximately 12 V. Various functions such as, but not limited to, vehicle heating/cooling, entertainment, locking, lights (exterior/interior) are generally driven from the power supply  82 . 
         [0019]    When the vehicle is in the operational mode, the controller  65  controls the switch  84  to close thereby causing the LV energy to be transferred to the winding  74  and the winding  78 . The winding  74  generates an electromagnetic field in response to the LV energy which causes the switch  76  of the contactor  54  to close. In a similar manner, the winding  78  generates an electromagnetic field in response to the LV energy which causes the switch  80  of the contactor  70  to open (e.g., the contactor  70  is a normally open state and will close when induced by the electromagnetic field). This condition enables the HV energy to pass through the bi-directional circuit  62 . The bi-directional circuit  62 , in turn, inverts the DC energy into AC energy for delivery to the motor  64  or rectifies the AC energy from the motor  64  to the power source  52 . 
         [0020]    By implementing the contactor  54  and the contactor  70  as mechanical relays, this condition may physically isolate such devices and may minimize or prevent leakage current that may affect the ability for the capacitor  60  to reach a fully charged state. For example, while the contactor  70  is opened (e.g., the switch  80  is opened), leakage current generated as a result of the contactor  54  being closed may be generally prevented from passing to the resistor  72  thereby increasing the amount of energy that is capable of being transferred to the capacitor  60 . 
         [0021]    In the event the contactor  54  and the contactor  70  are implemented as solid state based switches, such devices may enable an unacceptable amount of leakage current to pass therethrough, even if the contactor  54  or the contactor were in an open state. In particular, by implementing the contactor  70  as a solid state switch, the contactor  70  may allow an undesirable amount of leakage current to flow therethrough even if in an open state. Such leakage current may increase power loss and may adversely affect fuel economy. 
         [0022]    In the discharge mode (e.g. vehicle is shut down), the controller  65  may control the switch  84  to open thereby preventing the flow of LV energy to the winding  74  and  78 . The switch  76  opens in response thereto, and the flow of energy is prevented from reaching the motor  64  (or flow of energy is prevented from being transferred from the motor  64  to the power source  52 ). In addition, the winding  78  is de-energized causing the switch  80  to close. As a result, energy stored across the capacitor  60  is discharged through the switch  80  of the discharge switch  58 . The resistor  72  may be implemented with a small resistance to ensure rapid discharge of the energy from the capacitor  60 . In addition, it is recognized that the zener diode  88  may assist in dissipating all of the energy from the windings  74  and  78 . For example, the zener diode  88  may add a higher voltage drop (in addition to that added with the diode  86 ), which may cause the energy to dissipate faster (e.g., P=V*I, where V is the total voltage drop across the diode  86  and the zener diode  88 ). In the event the zener diode  88  is not implemented, the diode  86  may provide for a voltage drop of roughly 0.7 V after the switch  84  opens. Power consumption of the diode  86  alone may be small in this case. This may create the condition in which a longer time is needed to consume all of the energy of the windings  74  and  78  and cause a delay of the switching action of the contactor  54  and the contactor  70  when the switch  84  is opened. 
         [0023]    It is recognized that the contactor  54 , while implemented as a mechanical relay, may not allow leakage current (or may significantly reduce the potential) for leakage current to pass through capacitor  60 . Such a condition may also ensure that the energy stored on capacitor  60  is discharged from the apparatus  50  within a rapid amount of time. 
         [0024]    While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.