Patent Publication Number: US-2023147151-A1

Title: Charging Apparatus and Method Using Auxiliary Battery

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of Korean Patent Application No. 10-2021-0153877, filed on Nov. 10, 2021, which application is hereby incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to a charging technology. 
     BACKGROUND 
     In general, a charger (on board charger (OBC)) using a commercial alternating current (AC) power source for charging a high voltage battery is mounted in a vehicle. The charger is generally composed of a power factor correction (PFC) circuit configured to correct a power factor of the commercial AC power source and a direct current/direct current (DC/DC) converter configured to convert a voltage into a voltage required by the battery. 
     The charger is connected to a main battery, and relays are configured in the main battery to protect the battery and devices using the battery as a power source. Among them, in particular, an initial charging circuit is a circuit that is essentially applied to stably supply a voltage to peripheral components such as an inverter. 
     In particular, it is possible to prevent an excessive inrush current and minimize resonance that can occur when a high voltage is supplied by using the initial charging circuit. 
     A bidirectional low voltage DC-DC converter (LDC) is used to delete this initial charging circuit. However, to delete the initial charging circuit using the bidirectional LDC, the bidirectional LDC should be operated by changing the LDC power flow. The LDC power flow is as follows: the main battery→the auxiliary battery to the auxiliary battery→the main battery. 
     Therefore, there is a disadvantage in that the original LDC operation of charging the auxiliary battery using the main battery is impossible while the initial charging operation is performed by using the bidirectional LDC. 
     The contents described in the background are to help the understanding of the background of the present disclosure, and may include what is not previously known to those skilled in the art to which the present disclosure pertains. 
     SUMMARY 
     The present disclosure relates to a charging technology. Particular embodiments relate to an apparatus and a method for performing charging by deleting an initial charging circuit and using an auxiliary battery. 
     Embodiments of the present disclosure can solve problems in the art, and an embodiment of the present disclosure provides a charging apparatus and method, which can delete an initial charging circuit even without using a bidirectional converter. 
     In addition, another embodiment of the present disclosure provides a charging apparatus and method, which can perform an initial charging using an auxiliary battery. 
     Embodiments of the present disclosure provide a charging apparatus, which can delete an initial charging circuit even without using a bidirectional converter. 
     The charging apparatus includes a main battery, a charger configured to generate an initial charging power source by receiving a direct current (DC) power source from the auxiliary battery installed in a vehicle separately from the main battery or receiving an alternating current (AC) power source to execute an initial charging operation, and a first switch configured to block or conduct an electrical connection between the auxiliary battery and the charger to execute the initial charging operation depending upon whether the AC power source is supplied. 
     At this time, when the AC power source is not supplied, the first switch is turned on to conduct the electrical connection between the auxiliary battery and the charger. 
     In addition, the initial charging operation performs an initial charging by turning on the first switch and adjusting the duties of a boosting switch for boosting configured in a correction unit of the charger and a primary side switch configured in a conversion unit of the charger. 
     In addition, a second switch disposed between the main battery and the connection terminal is changed from OFF to ON depending upon a comparison result by comparing the initial charging power source generated on a connection terminal connected to the main battery by executing the initial charging operation with the preset reference value. 
     In addition, the preset reference value is calculated by multiplying an output power source of the main battery by a preset setting value. 
     In addition, the second switch is connected between the connection terminal and the main battery with the same polarity, and includes a first sub-switch and a second sub-switch arranged in parallel. 
     In addition, a low voltage direct current-direct current converter (LDC) among power components connected to the connection terminal is a unidirectional LDC. 
     In addition, the first switch is turned on when the vehicle travels or requires the initial charging. 
     In addition, the charger is a unidirectional charger. 
     In addition, when the AC power source is supplied, the first switch is turned off to block the electrical connection between the auxiliary battery and the charger. 
     In addition, the initial charging operation performs the initial charging by turning off the first switch and adjusting the duties of a boosting switch for boosting configured in a correction unit of the charger and a primary side switch configured in a conversion unit of the charger. 
     On the other hand, another exemplary embodiment of the present disclosure provides a charging method using an auxiliary battery including switching to block or conduct an electrical connection between the auxiliary battery and a charger using a first switch depending upon whether an alternating current (AC) power source is supplied and executing an initial charging operation by receiving a direct current (DC) power source from the auxiliary battery using the charger installed in a vehicle or receiving the AC power source to generate an initial charging power source. 
     In addition, the switching includes conducting the electrical connection between the auxiliary battery and the charger by turning on the first switch when the AC power source is not supplied. 
     In addition, after the executing of the initial charging operation, the charging method includes comparing, by the control unit, a charging power source generated on a connection terminal connected to a main battery by executing the initial charging operation with a preset reference value and changing, by the control unit, a second switch disposed between the main battery and the connection terminal from OFF to ON depending upon the comparison result. 
     In addition, the switching includes blocking the electrical connection between the auxiliary battery and the charger by turning off the first switch when the AC power source is supplied. 
     According to embodiments of the present disclosure, it is possible to delete the initial charging circuit between the main battery and the connection terminal by adding the switching element between the input terminal of the charger and the auxiliary battery. 
     In addition, as another embodiment of the present disclosure, the added switching element, as the relay, can be cheaper and smaller than the initial charging circuit of the connection terminal, thereby reducing the cost and/or the size. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a block diagram showing a configuration of a charging apparatus using an auxiliary battery according to an exemplary embodiment of the present disclosure and a concept diagram of a circuit operation in a traveling situation. 
         FIG.  2    is a block diagram showing the configuration of the charging apparatus using the auxiliary battery according to an exemplary embodiment of the present disclosure and a concept diagram of a circuit operation in a charging situation. 
         FIG.  3    is a concept diagram showing an initial charging operation of a connection terminal connected to a main battery in a slow charging situation as an example of the circuit diagram of the charging apparatus shown in  FIG.  2   . 
         FIG.  4    is a result graph according to the setting of input values based on  FIG.  3   . 
         FIG.  5    is a result graph according to another setting of the input values based on  FIG.  3   . 
         FIG.  6    is a concept diagram showing the initial charging operation of the connection terminal connected to the main battery in a traveling situation as an example of the circuit diagram of the charging apparatus shown in  FIG.  1   . 
         FIG.  7    is a result graph according to the setting of input values based on  FIG.  6   . 
         FIG.  8    is a flowchart showing a process of performing the initial charging without an initial charging circuit using the auxiliary battery according to an exemplary embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
     The aforementioned objects, features, and advantages will be described later in detail with reference to the accompanying drawings, and therefore, those skilled in the art to which the present disclosure pertains can easily practice the technical spirit of the present disclosure. In describing embodiments of the present disclosure, if it is determined that a detailed description of a known technology related to the present disclosure can unnecessarily obscure the gist of the present disclosure, the detailed description thereof will be omitted. Hereinafter, preferred exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals are used to indicate the same or similar components. 
     Hereinafter, a charging apparatus and method using an auxiliary battery according to an exemplary embodiment of the present disclosure will be described in detail with reference to the accompanying drawings. 
       FIG.  1    is a block diagram showing a configuration of a charging apparatus  100  using an auxiliary battery  120  according to an exemplary embodiment of the present disclosure and a concept diagram of a circuit operation in a traveling situation. Referring to  FIG.  1   , the charging apparatus  100  can be configured to include an alternating current (AC) power source unit  110 , an auxiliary battery  120 , a first switch  130 , a charger  140 , a connection terminal  150 , a second switch  160 , a main battery  170 , and a control unit  180 . 
     The AC power source unit no serves to receive an AC system power source. In general, a rectifying circuit is configured in the charger  140 . Therefore, the AC power source unit no serves to supply the AC power source to the charger  140 . 
     Of course, the rectifying circuit can be configured in the AC power source unit  110 . In this case, the AC power source unit no can convert the AC power source into a DC power source to supply the DC power source. In this case, the rectifying circuit cannot be configured in the charger  140 . 
     The AC power source unit  110  can receive a commercial AC power source. Each country has a different commercial AC power source. Representatively, the commercial AC power source is 230 VAC/50 Hz in EU, 240 VAC/60 Hz in North America, and 220 VAC/60 Hz in Korea. 
     The auxiliary battery  120  serves to supply the direct current (DC) power source as a low-voltage battery. The auxiliary battery  120  is a low-voltage power source battery for driving an electric part load (not shown) and generally uses a 12V-level voltage. The auxiliary battery  120  can include a chargeable battery cell, a super capacitor, etc. 
     The first switch  130  serves to block or allow the DC power source to flow into the charger  140  from the auxiliary battery  120 . In other words, the first switch  130  is turned off to become a blocking state and is turned on to become a conduction state. To this end, as the first switch  130 , a relay switch is mainly used but the present disclosure is not limited thereto, and a semiconductor switching element such as a field effect transistor (FET) or a metal oxide semiconductor FET (MOSFET) can also be used. 
     The charger  140  can be a unidirectional on board charger (OBC) mounted in a vehicle. Therefore, the charger  140  can be configured to include a correction unit  141  configured to correct a power factor of the power source, and a conversion unit  142  configured to convert the DC power source into a smaller DC power source. Of course, the correction unit  141  can be configured to include the rectifying circuit. In this case, the correction unit  141  can serve to convert the AC power source directly introduced from the AC power source unit no into the DC power source and to improve the power factor. Therefore, the correction unit  141  can be provided with a power factor correction (PFC) circuit. 
     The conversion unit  142  can be configured to include a DC-DC converter to convert the DC power source into the smaller DC power source. 
     The connection terminal  150  is connected to the main battery  170  to become a passage that delivers an output power source of the charger  140  to the main battery  170 . Of course, the connection terminal  150  can be an input terminal of a low-voltage direct current (LDC) (not shown) or an input terminal of an inverter (not shown). 
     The LDC is a DC-DC converter configured to charge the auxiliary battery  120  through the main battery  170  to drive the electric part load (not shown). In addition, the inverter serves to convert the DC power source from the main battery  170  into the AC power source to supply the AC power source to a driving motor (not shown). 
     The second switch  160  is a main switch and conducts or blocks the DC power source to flow into the main battery  170 . In addition, the second switch  160  conducts or blocks the DC power source output from the main battery  170 . The second switch  160  can include a first sub-switch  161  and a second sub-switch  162 . In general, an initial charging circuit has a structure in which a power relay (not shown) and a resistor (not shown) are configured in series and connected to the first sub-switch  161  in parallel. Of course, a positive temperature coefficient (PTC) element instead of the resistor is used. According to an exemplary embodiment of the present disclosure, it is possible to stably supply the power source to peripheral power components such as an inverter even while deleting this initial charging circuit. 
     As the second switch  160 , the power relay is mainly used but the present disclosure is not limited thereto, and a semiconductor switching element such as a field effect transistor (FET), a metal oxide semiconductor FET (MOSFET), an insulated gate bipolar mode transistor (IGBT), a power rectifying diode, a thyristor, a gate turn-off (GTO) thyristor, a triode for alternating current (TRIAC), a silicon controlled rectifier (SCR), an integrated circuit (IC), etc. can be used. 
     In particular, for the semiconductor element, a bipolar transistor, a power metal oxide silicon field effect transistor (MOSFET) element, etc. can be used. The power MOSFET element performs a high-voltage and high-current operation and has a structure of a double-diffused metal oxide semiconductor (DMOS) unlike the general MOSFET. 
     The main battery  170  serves to supply the power source to the driving motor (not shown), the auxiliary battery  120 , etc. In general, the power source of the main battery  170  is about 160 to 250 V for a hybrid electric vehicle (HEV) and about 400 to 800 V for a battery electric vehicle (BEV). Some cost-saving type electric vehicle systems can also share and use the grounds of the auxiliary battery and the main battery by designing the power source of the main battery as about 48 V level. 
     The main battery  170  can have the battery cells (not shown) configured in series and/or in parallel, and this battery cell can be a high-voltage battery cell for an electric vehicle such as a nickel metal battery cell, a lithium ion battery cell, a lithium polymer battery cell, a lithium-sulfur battery cell, a sodium-sulfur battery cell, or an all-solid-state battery cell. In general, the high-voltage battery refers to a battery with a high voltage of 100 V or more as the battery used as the power source that moves the electric vehicle. 
     The control unit  180  serves to control the ON/OFF of the first switch  130 , the charger  140 , and the second switch  160 . In addition, the control unit  180  performs an algorithm that executes the initial charging operation when the vehicle travels or requires the initial charging. To this end, the control unit  180  can be configured to include a microprocessor, a microcomputer, a memory, etc. 
     The memory can be a memory provided in the control unit, and a separate memory. Therefore, the memory can be configured by combining a non-volatile memory such as a flash memory disk (solid state disk (SSD)), a flash memory, an electrically erasable programmable read-only memory (EEPROM), a static RAM (SRAM), a ferro-electric RAM (FRAM), a phase-change RAM (PRAM), a magnetic RAM (MRAM) and/or a volatile memory such as a dynamic random access memory (DRAM), a synchronous dynamic random access memory (SDRAM), or a double data rate-SDRAM (DDR-SDRAM). 
     In addition, the control unit  180  can be connected to a sensor (not shown) to measure a power generated by or input from each power component. The sensor can be installed inside or outside each power component. In particular, according to an exemplary embodiment of the present disclosure, the sensor can be installed on the AC power source unit no, the charger  140 , the connection terminal  150 , or the main battery  170 . The sensor can be a current sensor, a voltage sensor, etc. 
       FIG.  2    is a block diagram showing the configuration of the charging apparatus  100  using the auxiliary battery  120  according to an exemplary embodiment of the present disclosure and a concept diagram of a circuit operation in a charging situation.  FIG.  2    has the same configuration as the configuration of the charging apparatus shown in  FIG.  1   , but there is a difference in that the charger  140  receives the power source. 
     In other words, this is the operation of the charging apparatus  100  when the vehicle is in the charging state other than in the traveling state. Therefore, during charging, before charging, or for the initial charging on the connection terminal  150  connected to the main battery, the charger  140  is connected to the AC power source unit no to receive the power source (i.e., AC system power source). Of course, if the charger  140  is connected to the AC power source unit  10 , the first switch  130  is turned off. The first switch  130  is turned on when the vehicle travels or requires the initial charging. In particular, the first switch  130  can use the relay element. In this case, since the first switch  130  uses the low voltage, the price is very cheap. The low voltage can be about 12 V to 48 V or less. 
     Continuously referring to  FIG.  2   , if the charger  140  is used for slow charging, the auxiliary battery  120  and the input terminal of the charger  140  cannot be connected. However, the charger  140  itself serves to deliver the power from the AC system power source to the main battery  170 . Therefore, the charger  140  can replace the role of the initial charging circuit of the main battery  170  because it performs the original charging operation. 
       FIG.  3    is a concept diagram showing an initial charging operation of the connection terminal  150  connected to the main battery  170  in the slow charging situation as an example of the circuit diagram of the charging apparatus  100  shown in  FIG.  2   . Referring to  FIG.  3   , the initial charging of the connection terminal  150  connected to the main battery  170  in the slow charging operation is performed by turning off the first switch  130  connected to the charger  140  and adjusting the duties of a boosting switch  301  and a primary side switch  351 - 1  configured in a direct current-alternating current (DC-AC) converter  351 . The AC system power source  311  is converted by the alternating current-direct current (AC-DC) converter  312 , and the boosting switch  301  is turned on or off when the boosting of a link voltage  341  is required. 
     A front end of the direct current-alternating current (DC-AC) converter  351  is connected to a capacitor  302  for smoothing the link voltage in parallel. The output power source of the connection terminal  150  connected to the main battery  170  is adjusted by adjusting the duty of the primary side switch  351 - 1  configured in the DC-AC converter  351 . In other words, the output voltage output by adjusting the duty of the primary side switch  351 - 1  is changed in size through an inductor  352  and a transformer  353  and converted back into the DC power source through a rectifier  354 . The primary side switch  351 - 1  is formed of an FET and controls ON/OFF through a pulse width modulation (PWM) waveform. The primary side switches  351 - 1  are turned on when the input voltages are larger than reference voltages (Vsw 1 , Vsw 2 ). 
     The rectifier  354  is a bridge circuit connecting four diodes  354 - 1 . 
     The converted DC power source becomes the charging power source input to the main battery  170  by the capacitor  357  through a resistor  355  and an inductor  356 . In other words, the charging power source is generated on the connection terminal  150 . 
     When the power source of the connection terminal connected to the main battery and a reference power source are similar, the initial charging operation is terminated and the main switch ( 160  in  FIG.  1   ) is turned on to connect the connection terminal with the main battery. For example, if the power source of the connection terminal is larger than the power source of the main battery×0.9, the initial charging operation is terminated, and the connection terminal and the main battery are electrically connected. 
     When the initial charging operation is terminated, the main battery  170  is charged by using the charger  140 . 
       FIG.  4    is a result graph according to the setting of input values based on  FIG.  3   . Referring to  FIG.  4   , the setting of the input values is as follows. 
     AC input power source=220 Vrms (“rms” stands for root mean square) 
     PFC duty=0 (“PFC” stands for Power Factor Correction) 
     DC-DC duty=0.47 
     Link voltage (Vlink)=308 V 
     Main battery power source (VHVB)=778 V 
     Continuously referring to  FIG.  4   , for the top graph, as a charger input voltage  410  is input within a range of about +300 to −300 V, a charger link voltage  420  initially increases rapidly but becomes almost flat as it approaches 0.1 seconds, and becomes a flat state after 0.2 seconds. 
     For the bottom graph, a main battery power source  430  shows a pattern similar to the charger link voltage  420 . 
       FIG.  5    is a result graph according to another setting of the input values based on  FIG.  3   . Referring to  FIG.  5   , the setting of the input values is as follows. 
     AC input power source=110 Vrms 
     PFC duty=0.5 
     DC-DC duty=0.47 
     Link voltage (Vlink)=313 V 
     Main battery power source (VHVB)=781 V 
     Continuously referring to  FIG.  5   , for the top graph, as a charger input voltage  510  is input within a range of about +150 to −150 V, a charger link voltage  520  initially increases rapidly but becomes almost flat as it approaches 50 msec, and becomes a flat state after 0.15 seconds. 
     For the bottom graph, a main battery power source  530  shows a pattern similar to the charger link voltage  520 . 
       FIG.  6    is a concept diagram showing the initial charging operation of the connection terminal connected to the main battery in a traveling situation as an example of the circuit diagram of the charging apparatus shown in  FIG.  1   .  FIG.  6    is a circuit diagram that is the same as in  FIG.  3   , but there is no AC system power source, and the auxiliary battery  120  is in a state of being electrically connected to the charger  140  by the ON operation of the first switch  130 . 
     The initial charging on the connection terminal  150  connected to the main battery  170  in the situation where the AC system power source is not applied is performed by turning on the first switch  130  connected to the charger  140  and adjusting the duties of the boosting switch  301  and the primary side switch  351 - 1 . In other words, the boosting switch  301  is turned on when the input voltage is larger than a reference value (Vpfc). In addition, the primary side switches  351 - 1  are also turned on when the input voltages are larger than reference values (Vdcdc 1 , Vdcdc 1 _). 
     Then, power components such as the inverter and the LDC using the main battery  170  are driven. 
       FIGS.  3  and  6    show that the charger is the unidirectional charger, but all kinds of chargers can perform the corresponding initial charging operation regardless of the unidirectionality/bidirectionality, the type of PFC circuit, and the type of DC-DC circuit of the charger. 
       FIG.  7    is the result graph according to the setting of input values based on  FIG.  6   . Referring to  FIG.  7   , the setting of the input values is as follows. 
     Charger input power source=12 Vdc 
     PFC duty=0.965 
     DC-DC duty=0.488 
     Link voltage (Vlink)=314 V 
     Main battery power source (VHVB)=784 V 
     Continuously referring to  FIG.  7   , for the top graph, as a charger input voltage  710  is input at about 12 V, a charger link voltage  720  initially increases rapidly but smoothly increases after 0.1 seconds, and becomes almost flat after 0.4 seconds. 
     For the bottom graph, a main battery power source  730  shows a pattern similar to the charger link voltage  720 . 
       FIG.  8    is a flowchart showing a process of performing the initial charging without the initial charging circuit using the auxiliary battery according to an exemplary embodiment of the present disclosure. Referring to  FIG.  8   , first, when there are power components such as the inverter and the LDC using the main battery  170 , the control unit  180  confirms whether the AC system power source is detected on the input of the charger  140  (steps S 810 , S 820 ). 
     In step S 820 , as the confirmation result, when the AC system power source is detected, the initial charging operation is performed by using the AC system power source (step S 831 ). 
     In contrast, in the step S 820 , as the confirmation result, when the AC system power source is not detected, the initial charging operation is performed by using the auxiliary battery as the input of the charger (step S 832 ). 
     When the initial charging operation is completely performed, the initial charging power generated on the connection terminal and a pre-computed reference value are compared (step S 840 ). In other words, for example, the reference value can be the main battery power source×0.9. 
     In the step S 840 , as the comparison result, when the initial charging power on the connection terminal is smaller than the reference value, it proceeds to the step S 820  and the steps S 820 , S 831 , S 832 , and S 840  are executed again. 
     In contrast, in the step S 840 , as the comparison result, when the initial charging power on the connection terminal is larger than the reference value, the main switch (i.e., the second switch  160 ) is turned on to electrically connect the connection terminal  150  with the main battery  170  (step S 850 ). 
     In addition, some of the steps of the method or algorithm described in connection with the exemplary embodiments disclosed herein can be implemented in the form of program instructions that can be performed through various computer means such as a microprocessor, a processor, and a central processing unit (CPU) and recorded on a computer-readable medium. The computer-readable medium can include program (instruction) codes, data files, data structures, etc. alone or in combination. 
     The program (instruction) code recorded on the medium can be ones specially designed and configured for the present disclosure, or can also be ones known and available to those skilled in the art of computer software. Examples of computer-readable recording media can include magnetic media such as a hard disk, a floppy disk, and a magnetic tape, optical media such as a CD-ROM, a DVD, and a Blu-ray, and semiconductor memory elements specially configured to store and execute the program (instruction) code such as a ROM, a RAM, and a flash memory. 
     Here, examples of the program (instruction) code include high-level language codes that can be executed by a computer using an interpreter, etc. as well as machine language codes such as those generated by a compiler. The aforementioned hardware devices can be configured to operate as one or more software modules to perform the operations of the present disclosure, and vice versa.