Patent Publication Number: US-2012032513-A1

Title: Battery management circuit, battery module and battery management method

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates an electric power management circuit, and more particularly, to a cell level battery management circuit, an array battery management circuit and a battery module. 
     2. Description of Related Art 
     In general, a battery, also called a cell, is consisted of a plurality of cells connected in series or in parallel, with lead-acid batteries being the most common used ones. Batteries can be divided into general battery (primary battery) and rechargeable battery (or called secondary battery). The general battery generally can not be recharged after the general battery is run out of power. While the rechargeable battery, such as Lithium-ion batteries, nickel-iron batteries, lead acid batteries, nickel cadmium batteries, nickel metal hydride battery, can be recharged after the battery is run out of power. 
     Since the rechargeable battery has memory effect, with the nickel-cadmium battery being the worst, the battery would be damaged if overcharging or over-discharging occurs. One battery set usually includes a plurality of cells; each cell has slightly different charging and discharging characteristics. Some cells may be damaged if using the same voltage to charge all the cells. In contrast, during discharging, some cells of the battery set may be damaged due to over-discharging. 
     In related arts, the power management is very important to the rechargeable battery. However, in most current management techniques, the cells are managed as a set rather than being managed individually, which result in lower charging/discharging efficiency, and during charging or discharging, the cells may be easily damaged due to overcharging or over-discharging. 
     SUMMARY OF THE INVENTION 
     The present disclosure provides a battery management circuit which is capable of monitoring the states of charge of a plurality of cells (rechargeable battery) and preventing each rechargeable battery from being overcharged or over-discharged, and therefore increasing the power efficiency and extending the lifetime of the rechargeable battery. 
     The present disclosure further provides a battery module which monitors the individual rechargeable battery through an array controller. The battery module may adjust the charging/discharge paths to skip the problematic rechargeable battery and prevents the individual rechargeable battery from being overcharged or over-discharged, therefore increasing the power efficiency and lifetime of the battery sets. 
     The present disclosure also provides a battery management method which is capable of directly monitoring the states of charge of all the rechargeable batteries and protecting the rechargeable batteries from damage by controlling the charging/discharging paths of the rechargeable batteries. Additionally, the method may also collect the states of charge of the individual rechargeable battery, such as charging/discharging efficiency or remaining electric power thereof. 
     The present disclosure further provides a battery module. There is a backup battery set added in the battery module, thereby extending the lifetime of battery module and preventing a single battery set form the damage and avoiding affecting the overall power output of the battery module. 
     The present disclosure is directed to a battery management circuit suitable for a rechargeable battery, comprising: a conduction circuit coupled to the rechargeable battery, the conduction circuit having a first conduction path passing through the rechargeable battery and a second conduction path without passing through the rechargeable battery; and a control circuit coupled to the rechargeable battery and the conduction circuit for selectively conducting the first conduction path or the second conduction path of the conduction circuit according to a battery voltage of the rechargeable battery. 
     According to one embodiment of the disclosure, when the battery voltage of the rechargeable battery is greater than a first threshold value, the conduction circuit conducts the second conduction path and turns off the first conduction path. When the battery voltage of the rechargeable battery is less than a second threshold value, the conduction circuit conducts the second conduction path and turns off the first conduction path. When the battery voltage of the rechargeable battery is less than the first threshold value and greater than the second threshold value, the conduction circuit conducts the first conduction path and turns off the second conduction path, wherein the first threshold value is greater than the second threshold value. 
     According to one embodiment of the disclosure, the conduction circuit comprises: a first switch coupled to a positive electrode of the rechargeable battery and a first terminal; a second switch coupled to a negative electrode of the rechargeable battery and a second terminal; and a third switch coupled to the first terminal and the second terminal; wherein when the battery voltage of the rechargeable battery is greater than a first threshold value, the conduction circuit conducts the third switch but turns off the first switch and the second switch; when the battery voltage of the rechargeable battery is less than a second threshold value, the conduction circuit conducts the third switch and turns off the first switch and the second switch; when the battery voltage of the rechargeable battery is less than the first threshold value and greater than the second threshold value, the conduction circuit conducts the first switch and the second switch and turns off the third switch. 
     According to one embodiment of the disclosure, the control circuit comprises: a voltage sensing unit coupled to a positive electrode and a negative electrode of the rechargeable battery for sensing the battery voltage of the rechargeable battery; a control unit coupled to the voltage sensing unit and the conduction circuit for controlling the conduction circuit to conduct the first conduction path or the second conduction path according to the battery voltage of the rechargeable battery, wherein the control circuit further comprises a current sensing unit coupled to the rechargeable battery and the control unit for sensing a current value flowing through the rechargeable battery; wherein the control unit calculates a state of charge of the rechargeable battery according to the battery voltage and the current value flowing through the rechargeable battery. 
     The present disclosure further provides a battery module which includes a plurality of power units and an array controller. Each power unit has a rechargeable battery. The array controller has a plurality of channels coupled to the power units respectively. The array controller respectively detects the states of charge of the rechargeable batteries through the channels and respectively controls the charge/discharge paths of the rechargeable battery according to the states of charge of the rechargeable batteries. 
     The present disclosure further provides a battery module which comprises a plurality of battery sets, each battery set having a plurality of rechargeable batteries; a backup battery set having a plurality of rechargeable batteries; a power path circuit coupled to the battery sets and the backup battery set for switching conduction paths of the battery sets and the backup battery set; a voltage sensing unit coupled to the power path circuit for sensing whether or not the battery voltages of the battery sets are normal; and a controller coupled to the voltage sensing unit and the power path circuit. Wherein the controller determines whether or not the battery sets are damaged according to a sense result from the voltage sensing unit, when one of the battery sets is damaged, the controller adjusts the conduction paths of the battery sets and the backup battery set through the power path circuit to replace the damaged battery set with the backup battery set. 
     The present disclosure further provides a battery management method including the following steps: (a) providing a plurality of channels respectively coupled to a plurality of power units having a rechargeable battery respectively; (b) respectively detecting states of charge of the rechargeable batteries through the channels; and (c) respectively controlling the charge/discharge paths of the rechargeable batteries according to the states of charge of the rechargeable batteries. 
     In summary, by the battery management circuit in the present disclosure, the problems resulting in damage of the individual cell due to overcharging or over-discharging the cell are solved. The present disclosure also has the following benefits: (1) monitoring the states of charge of the individual cell to prevent the cell from being overcharged or over-discharged; (2) the array controller is able to monitor the states of charge of all the cells, and thus providing the most accurate power consumption statuses; (3) the backup battery set is able to replace the damaged battery set and thus increase the lifetime of the battery module and prevent the electric power output of the battery module from being affected due to the damage of a single cell. 
     In order to have further understanding of the present invention, the following embodiments are provided along with illustrations to facilitate the disclosure of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows schematic diagram of a battery management according to the first embodiment of the present disclosure; 
         FIG. 2  shows a schematic diagram of a battery module according to the first embodiment of the present disclosure; 
         FIG. 3  shows a schematic diagram of a battery module according to a second embodiment of the present disclosure; and 
         FIG. 4 , which shows a flow chart of battery management method according to a third embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the paragraphs below, figures will be referenced to explain different embodiments of the instant disclosure in details. For identical parts, same numbers are used in different figures for illustrations. 
     First Embodiment 
       FIG. 1  shows schematic diagram of a battery management according to the first embodiment of the present disclosure. The battery management circuit  100  is suitable for managing the charge/discharge procedures of a rechargeable battery  102 . The battery management circuit  100  includes a control circuit  110  and a conduction circuit  120 . The control circuit  110  is coupled to the conduction circuit  120  and a rechargeable battery  102 . The conduction circuit  120  is coupled to a positive electrode and a negative electrode of the rechargeable battery  102 . The control circuit  110  includes a current sensing unit  112 , a voltage sensing unit  114  and a control unit  116 , wherein the current sensing unit  112  is coupled to the positive electrode of the rechargeable battery  102  for sensing a current value flowing through the rechargeable battery  102 , and the voltage sensing unit  114  is coupled to the positive and negative electrodes of the rechargeable battery  102  for sensing the battery voltage of the rechargeable battery  102 . The control unit  116  is coupled to the current sensing unit  112 , the voltage sensing unit  114  and the conduction circuit  120 . The control unit  116  may control the conduction circuit  120  to form a corresponding conduction path according to the sense result form the voltage sensing unit  114 , and calculates the states of charge of the rechargeable battery  102 , such as battery level or power consumption, according to the sense results from the current sensing unit  112  and the voltage sensing unit  114 . 
     The conduction circuit  120  includes a first switch SW 1 , a second switch SW 2  and a third switch SW 3 , wherein the first switch SW 1  is coupled to the positive electrode of the rechargeable battery  102  and the first terminal T 1  through the current sensing unit  112 . The second switch SW 2  is coupled to the negative electrode of the rechargeable battery  102  and the second terminal T 2 . The third switch SW 3  is coupled to the first terminal T 1  and the second terminal T 2 . The first terminal T 1  and the second terminal T 2  may replace the original positive and negative electrodes of the rechargeable battery to connect with external circuitries or other rechargeable batteries. In other words, the external circuitries can only connect to the rechargeable battery through the conduction circuit  120 . 
     The conduction circuit  120  may be configured to form a first conduction path P 1  and a second conduction path P 2 , wherein the first conduction path P 1  is configured to pass through the first switch SW 1 , the rechargeable battery  102  and the second switch SW 2 , and the second conduction path P 2  is configured to pass through the third switch SW 3  but not the rechargeable battery  102 . When the first switch SW 1  and the second switch SW 2  are turned on, the first conduction path P 1  is conducted. When the third switch SW 3  is turned on, the second conduction path P 2  is conducted. The control unit  116  may selectively conduct the first conduction path P 1  or the second conduction path P 2  by controlling the first switch SW 1 , the second switch SW 2  and the third switch SW 3 . 
     The control unit  116  may be configured with a first threshold value and a second threshold value which are used to compare with the battery voltage of the rechargeable battery  102 , and whether or not the rechargeable battery  102  is overcharged or over-discharged is determined accordingly, wherein the first threshold value is greater than the second threshold value. The rechargeable battery  102  is overcharged when the battery voltage of the rechargeable battery  102  is greater than the first threshold value. The rechargeable battery  102  is over-discharged when the battery voltage of the rechargeable battery  102  is less than the second threshold value. When the battery voltage of the rechargeable battery  102  exceeds (is not in) the range from the first threshold value to the second threshold value (namely, greater than first threshold value or less than the threshold value), the control unit  116  conducts the second conduction path P 2  and turns off the first conduction path P 1 , thereby avoiding to continue charge or discharge the rechargeable battery  102 . In contrast, when the battery voltage of the rechargeable battery  102  is less than the first threshold value and greater than the second threshold value, the control unit  116  conducts the first conduction path P 1  and does not conduct the second conduction path P 2  so that the rechargeable battery  102  may continue to be charged or discharged normally. 
     Take the first switch SW 1 , the second switch SW 2  and the third switch SW 3  as an example, the control unit  120  may turn on the third switch SW 3  and turn off the first switch SW 1  and the second switch SW 2  when the battery voltage of the rechargeable battery  102  is greater than the first threshold value or less than the second threshold value. The control unit  120  may turn on the first switch SW 1  and the second switch SW 2  and turn off the third switch SW 3  when the battery voltage of the rechargeable battery  102  is less than the first threshold value and greater than the second threshold value. 
     It is noted that the first switch SW 1 , the second switch SW 2  and the third switch SW 3  may be implemented with NMOS transistor (N channel metal-oxide-semiconductor field-effect transistor), PMOS transistor (P channel metal-oxide-semiconductor field-effect transistor) or other switch elements, and the present invention is not limited thereto. Further, the conduction circuit  120  may be implemented with multiplexers or other switch elements, and the present invention is not limited thereto. The current sensing unit  112  is mainly used to sense the current value flowing through the rechargeable battery  102 , which may be arranged at the positive electrode or the negative electrode of the rechargeable battery  102 , and the present disclosure is not limited thereto, provided that the current sensing unit  112  can be arranged on the current conduction path through the rechargeable battery  102 . By using the voltage sensing unit  114  and the current sensing unit  112 , the control unit  116  may obtain the battery voltage of the rechargeable battery  102  and current value flowing through the rechargeable battery  102 , therefore the remaining power, the output power and the charge efficiency may be calculated. The current sensing unit  112  may be deleted to reduce the cost if the above calculations are not necessary. 
     Additionally, the battery management circuit  100  may protect the rechargeable battery  102  from overcharging or over-discharging during charging or discharging procedures. However, after the charging or discharging procedure is complete, the control unit  120  conducts the first conduction path P 1  and turns off the second conduction path P 2  to return the external connection relations of the rechargeable battery  102  and functions thereof for the system or battery sets. The control unit  120  may determine whether the charging or discharging procedure is complete by sensing the current value and current direction on the second conduction path P 2  or receiving a acknowledge signal from an external circuit. 
     The battery management circuit  100  may be applied on rechargeable battery of battery sets to achieve the benefits of monitoring the cells individually and prevent the battery set from being damaged due to single cell damage. Refer to  FIG. 1  and  FIG. 2  which shows a schematic diagram of a battery module according to the first embodiment of the present disclosure. The battery module  200  is able to manage a plurality of rechargeable battery, such as one battery set or several battery sets. The battery module  200  includes a plurality of power unit  210  and an array controller  230 . Each power unit  210  has a rechargeable battery  102  and a battery management circuit  100  including a control circuit  110  and a conduction circuit  120 , as shown in  FIG. 1 . The control circuit  110  and the conduction circuit  120  are coupled to the rechargeable battery  102  for controlling the conduction paths between the rechargeable battery  102  and the external circuits. The detail circuits and operation manners with respect to the control circuit  110  and the conduction circuit  120  are described on the above-mentioned descriptions of the first exemplary embodiment, and the descriptions are omitted. 
     In  FIG. 2 , the array controller  230  may connect to the power unit  210  through a plurality of channels CH 1 ˜CH 13  respectively. The channels CH 1 ˜CH 13  and the power unit  210  are arranged one by one rather than hierarchical arrangement. Hence, the array controller  230  is directly coupled to each power unit  210  and may obtain the states of charge thereof to manage the charge/discharge paths of each power unit  210 . The array controller  230  and all the management circuits  100  may form an array control circuit which is able to monitor the states of charge (including voltage and current) of all the rechargeable batteries  102  and control each conduction circuit  120  to selectively conduct the first conduction path P 1  or the second conduction path P 2 , as shown in  FIG. 1 . The array controller  230  may receive the battery voltage and current value of each rechargeable battery  102  through the control circuit  110 , so as to achieve the benefits of monitoring each rechargeable battery  102  individually. According to the battery voltage status of each rechargeable battery  102 , the array controller  230  may determine whether or not the current conduction path of the battery module skips the rechargeable battery  102 , so as to prevent any rechargeable battery  102  from being damaged due to overcharging or over-discharging. In other words, the second conduction path P 2  of the conduction circuit  120  is conducted and the first conduction path P 1  is not conducted, so that the charging current or the discharging current flowing through the problematic rechargeable battery  102  is avoided. The electrical information or internal configuration values obtained by the array controller  230  or the control circuit  110  may be stored in built-in or external memories, such as EEPROM (Electrically-Erasable Programmable Read-Only Memory) or flash memory, and the present disclosure is not limited thereto. 
     Additionally, the battery module  200  may enable the control circuit  110  to return the current conduction path between the given rechargeable battery  102  and other rechargeable batteries  102  (namely, conducting the first conduction path P 1  and turning off the second conduction path P 2 ). In another embodiment of the present disclosure, the array controller  230 , the control circuit  110  and the conduction circuit  120  may be integrated in the same integrated circuit or implemented with discrete components, and the present disclosure is not limited. In  FIG. 2 , the array controller  230  is mainly used to integrate the electrical information of all the rechargeable batteries  102  and control the conduction circuit  120  through the control circuit  110 , so as to achieve the benefits of monitoring individually. 
     Second Embodiment 
     The present disclosure further provides a battery module, as depicted in  FIG. 3 .  FIG. 3  shows a schematic diagram of a battery module according to a second embodiment of the present disclosure. The battery module  300  includes a plurality of battery sets  310 , a backup battery set  320 , a power path circuit  330 , a controller  340  and a voltage sensing unit  350 . Each of the battery sets  310  and the backup battery set  320  has a plurality of rechargeable batteries which may be connected in series or in parallel. The power path circuit  330  is coupled to all the battery sets  310  and the backup battery set  320  for switching the conduction paths of the battery sets  310  and the backup battery set  320 . The voltage sensing unit  350  is coupled to the power path circuit  330  for sensing whether the voltage of the individual battery set  310  is normal. The controller  340  is coupled to the voltage sensing unit  350  and the power path circuit  330 . 
     The controller  340  is able to determine whether or not the battery set  310  is damaged. When one of the battery sets  310  is damaged, the controller  340  may switch the conduction path between the battery sets  310  and the backup battery set  320  through the power path circuit  330  to replace the damaged battery set  310  with the backup battery set  320 . The power path circuit  330  includes a circuitry for selectively coupling the battery set  310  and the backup battery set  320 , which circuitry may be implemented with switches or multiplexers. 
     Third Embodiment 
     A battery management method can be derived based on preceding embodiments. Please refer to  FIG. 4 , which shows a flow chart of battery management method according to a third embodiment of the present disclosure. First, the method provides a plurality of channels which are coupled to a plurality of power units respectively, where each power unit has a rechargeable battery (step S 410 ), and then the states of charge of the rechargeable batteries are detected through the channels respectively (S 420 ). Next, the charge/discharge paths of the rechargeable batteries are respectively controlled according to the states of charge of the rechargeable batteries (S 430 ). 
     In step S 430 , a first conduction path and a second conduction path are further provided to each rechargeable battery, wherein the first conduction path passes through the corresponding rechargeable battery and the second conduction path does not passes through the corresponding rechargeable battery. The first conduction path or the second conduction path is respectively conducted according to the battery voltage of each rechargeable battery to protect the corresponding rechargeable battery from the damage. In step S 430 , when the battery voltage of a first rechargeable battery of the rechargeable batteries is in a predetermined interval, the first conduction path corresponding to the first rechargeable battery is conducted and the second conduction path corresponding to the first rechargeable battery is turned off. When the battery voltage of the first rechargeable battery of the rechargeable batteries is not in (exceeds) the predetermined interval, the second conduction path corresponding to the first rechargeable battery is conducted and the first conduction path corresponding to the first rechargeable battery is turned off, wherein the predetermined interval is less than a first threshold value and greater than the second threshold value. 
     Those skilled in the art should be able to deduce the other details of the battery management method in the present disclosure through the above embodiments, and the detail descriptions are omitted. 
     Furthermore, it is noteworthy that the coupling relation between above-mentioned components includes direct or indirect electrical connections as long as electrical signal transmission may be achieved, and the present disclosure is not limited thereto. The techniques described in the above-mentioned embodiments may be combined or used independently, further the associated components may add, delete, modify or replace according to the requirements of both functional and designed, and the present invention are not limited thereto. 
     In summary, the current conduction paths of the battery module may be adjusted according to the state of charge (power status) of each rechargeable battery in the present invention, thereby preventing the rechargeable batteries from being overcharged or over-discharged, and causing the damage. The present invention has benefits of extending the lifetime of the battery sets and providing the battery information for the user. 
     The descriptions illustrated supra set forth presenting the preferred embodiments of the instant disclosure; however, the characteristics of the instant disclosure are by no means restricted thereto. All changes, alternations, or modifications conveniently considered by those skills in the art are deemed to be encompassed within the scope of the instant disclosure delineated by the following claims.