Abstract:
A controller with battery recharge protective function is disclosed in this invention. The controller is used for protecting a battery module. When the battery module is in a protective state, a recharge protection circuit of the controller is activated. A charging current from a positive recharge terminal flows into one pin of the controller. Afterward, the charging current passes the recharge protection circuit, flows out through another pin of the controller, and then returns to a negative recharge terminal. Accordingly, the recharge protection circuit makes the charging current bypass the battery module, so as to prevent the battery module from being damaged.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority to China Application Serial Number 201010275197.1, filed Sep. 6, 2010, which is herein incorporated by reference. 
       BACKGROUND 
       [0002]    1. Field of Invention 
         [0003]    The present invention relates to a control circuit. More particularly, the present invention relates to a controller with battery recharge protective function. 
         [0004]    2. Description of Related Art 
         [0005]    With the progressing of electronic technology and consumer electronic products, various portable electronic devices are widespread recently. A high-quality power supply is one of the major factors of the mobility, performance and durability of the portable devices. Most portable devices right now depends on battery modules for supplying electricity. 
         [0006]    The commercially available battery modules include non-rechargeable battery, rechargeable battery and fuel battery types. The rechargeable batteries are more common in consumer electronic products, because the rechargeable batteries can be more economical and environmental friendly. The material inside the rechargeable battery can be recovered to its original state during a recharging process, such that the rechargeable battery can be repeatedly used. Lead acid battery, nickel cadmium battery, nickel hydrogen battery, lithium battery, lithium ion battery are most common examples of the rechargeable batteries. 
         [0007]    However, the safety and durability of battery is directly related to the operating habit of users. For example, when the user accidentally leaves a lithium ion battery on a recharging stand over a long time, the lithium ion battery will be over-charged, and it will boost the temperature of the battery. In this case, the over-heated battery may have problems of electrolyte decomposition, high internal pressure and lithium leakage, which may even lead to dangers of heavy metal pollution, crack and fire. On the other hand, when the lithium ion battery is over-discharged, the battery may be damaged and unable to recharge in normal procedure. 
         [0008]    To avoid the safety problems in recharging procedure and degradation of battery capacity, some controllers (e.g. control circuit or control chip) are developed for implementing into the battery or the recharging apparatus. The controller may detect the power level of the battery module and perform corresponding actions (e.g. recharge monitoring, overcharge interrupt protection, etc). Please refer to  FIG. 1 , which illustrates a controller  100  within a recharging apparatus in prior art. The controller  100  includes a voltage detection unit  101 , a control logic unit  102  and a current detection unit  103 . 
         [0009]    The voltage detection unit  101  is coupled to two terminals of a battery module  200 , for monitoring a voltage state of the battery module  200 . For example, the voltage detection unit  101  is configured to detect the voltage level difference between two terminals of the battery module  200 , and accordingly the control logic unit  102  may acknowledge the state of the battery module  200 . The battery module  200  is connected to a recharge apparatus via a positive recharge terminal  203  and a negative recharge terminal  204 . When the battery module  200  is fully charged, the control logic unit  102  may switch off a recharge switch unit  201  within the recharge apparatus, so as to interrupt the recharge loop L 1  from the battery module  200  to the negative recharge terminal  204  for avoiding some potential threats. 
         [0010]    To be noticed that, even though the external recharge loop L 1  from the battery module  200  to the negative recharge terminal  204  is interrupted, there may still exist another loop inside the controller  100 , such that a leakage current may keep on charging the battery module  200  although the protection function in prior art is activated. 
         [0011]    For example, the controller  100  in prior art may include a sampling switch unit  104  and a sampling resistor  105  for voltage adjustment (e.g. voltage pull-high or pull-low). The sampling switch unit  104  and the sampling resistor  105  provide a current sampling node  103   a  required by the current detection unit  103 , which can be used for determining whether switching the recharge switch unit  201  from off-mode back to on-mode. The sampling switch unit  104  has a parasitic diode  104   a . When the battery module is under over-charge state, even though the external recharge switch unit  201  is off to interrupt the external recharge loop L 1 , there is still a leakage current flowing through the internal loop L 2  (i.e. via the parasitic diode  104   a  of the sampling switch unit  104 , and the sampling resistor  105 ). The leakage current is existed because the level of the negative recharge terminal  204  is lower than the negative terminal of the battery module  200 , and the level of the current sampling node  103   a  is approximately equal to the level of the negative recharge terminal  204 . Therefore, the level of the current sampling node  103   a  is lower than the negative terminal of the battery module  200 . The leakage current may continuously recharge the battery module  200 , such that it may disable over-charge protection of the controller  100  in prior art and cause some potential threat. 
       SUMMARY 
       [0012]    In order to solve the aforesaid problem of leakage current and continuing over-charge, the goal of the invention is to provide a controller which may utilize a current-guiding mean to make sure that the leakage current bypasses the battery module, or utilize a voltage-clamping mean to prevent the unwanted current leakage. Therefore, the safety in battery recharge procedure can be ensured. 
         [0013]    An aspect of the invention is to provide a controller with battery recharge protective function, which includes a first pin, a second pin, a third pin and a recharge protection circuit. The first pin is coupled to a positive recharge terminal. The second pin is coupled to a positive terminal of a battery module. The third pin is coupled to a negative terminal of the battery module. The recharge protection circuit is coupled to the first pin and the third pin. When the battery module is in a protective state, the recharge protection circuit is activated, such that an in-flowing current at the first pin goes through the recharge protection circuit and out-flows via the third pin. 
         [0014]    According to an embodiment of the invention, the recharge protection circuit includes a voltage-clamping unit. When the recharge protection circuit is activated, the voltage-clamping unit clamps a level of the first pin to be equal to or lower than a sum of a level of the second pin and a predetermined level difference, wherein the predetermined level difference is positive. 
         [0015]    According to another embodiment of the invention, the controller with battery recharge protective function further includes an electrostatic discharge protection circuit coupled between the first pin and the second pin. 
         [0016]    Another aspect of the invention is to provide a controller with battery recharge protective function. The controller includes a first pin, a second pin, a third pin and a recharge protection circuit. The first pin is coupled to a negative recharge terminal. The second pin is coupled to a positive terminal of a battery module. The third pin is coupled to a negative terminal of the battery module. The recharge protection circuit is coupled to the first pin and the second pin. When the battery module is in a protective state, the recharge protection circuit is activated, such that an out-flowing current at the first pin in-flows from the second pin and goes through the recharge protection circuit, so as to out-flow via the first pin. 
         [0017]    According to an embodiment of the invention, the recharge protection circuit includes a voltage-clamping unit. When the recharge protection circuit is activated, the voltage-clamping unit clamps a level of the first pin to be equal to or higher than a level of the third pin minus a predetermined level difference, wherein the predetermined level difference is positive. 
         [0018]    According to another embodiment of the invention, the controller further includes an electrostatic discharge protection circuit coupled between the first pin and the third pin. 
         [0019]    Another aspect of the invention is to provide a controller with battery recharge protective function. The controller includes a first pin, a second pin, a third pin and a voltage-clamping circuit. The first pin is coupled to a positive recharge terminal. The second pin is coupled to a positive terminal of a battery module. The third pin is coupled to a negative terminal of the battery module. The voltage-clamping circuit is coupled to the first pin and the third pin. The voltage-clamping circuit is configured to maintain a level of the first pin to be equal to or lower than a sum of a level of the second pin and a predetermined level difference, wherein the predetermined level difference is positive. 
         [0020]    According to an embodiment of the invention, the voltage-clamping circuit includes a voltage-clamping unit and a switch unit. The switch unit is switched-on when the level of the first pin is higher than the level of the second pin plus the predetermined level difference. 
         [0021]    According to another embodiment of the invention, an in-flowing current at the first pin goes through the voltage-clamping circuit and out-flows via the third pin when the switch unit is switched-on. 
         [0022]    Another aspect of the invention is to provide a controller with battery recharge protective function. The controller includes a first pin, a second pin, a third pin and a voltage-clamping circuit. The first pin is coupled to a positive recharge terminal. The second pin is coupled to a positive terminal of a battery module. The third pin is coupled to a negative terminal of the battery module. The voltage-clamping circuit is coupled to the first pin and the second pin. The voltage-clamping circuit is configured to maintain a level of the first pin to be equal to or higher than a level of the third pin minus a predetermined level difference, wherein the predetermined level difference is positive. 
         [0023]    According to an embodiment of the invention, the voltage-clamping circuit includes a voltage-clamping unit and a switch unit. The switch unit is switched-on when the level of the first pin is lower than the level of the third pin minus the predetermined level difference. 
         [0024]    According to an embodiment of the invention, when the switch unit is switched-on, an out-flowing current at the first pin in-flows from the second pin and goes through the recharge protection circuit, so as to out-flow via the first pin. 
         [0025]    The advantages of the embodiment in the invention is to ensure that the battery module and the controller are free from unexpected current or voltage signal by utilizing a current-guiding mean to make sure the leakage current bypass the battery module, or utilizing a voltage-clamping mean to prevent the unwanted current leakage. Therefore, the safety and durability in battery recharge procedure can be ensured. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]    The invention can be more fully understood by reading the following detailed description of the embodiment, with reference made to the accompanying drawings as follows: 
           [0027]      FIG. 1  is a block diagram illustrating a controller within a recharging apparatus in prior art; 
           [0028]      FIG. 2A  is a block diagram illustrating a controller for protecting a battery module according to an embodiment of the invention; 
           [0029]      FIG. 2B  is a block diagram illustrating a controller according to a second embodiment of the invention; 
           [0030]      FIG. 3A  is a block diagram illustrating a controller for protecting a battery module according to a third embodiment of the invention; and 
           [0031]      FIG. 3B  is a block diagram illustrating a controller for protecting a battery module according to a fourth embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0032]    To achieve aforesaid advantages and solve aforesaid problems in prior art, the controller in the embodiments of the invention implements a current-guiding and/or voltage-clamping circuit for preventing the negative effects caused by unexpected current or voltage signals. The detail descriptions of implementation are demonstrated in following paragraphs. 
         [0033]    Please refer to  FIG. 2A , which is a block diagram illustrating a controller  300  for protecting a battery module  400  according to an embodiment of the invention. When the battery module  400  is connected to a household power outlet or a specific recharge apparatus for recharging, the controller is used for protecting the battery module  400 . In practical applications, the controller  300  can be a control chip or a control unit, which can be integrated with the specific recharge apparatus, the household power outlet or the battery module  400 . However, the invention is not limited to this. In some other cases, the controller  300  may also be an independent apparatus. 
         [0034]    As shown in  FIG. 2A , a positive terminal of the battery module  400  is coupled to a positive recharge terminal  403  of the household power outlet or the specific recharge apparatus, and a negative terminal of the battery module  400  is coupled to a negative recharge terminal  404  of the household power outlet or the specific recharge apparatus, so as to form a recharge loop (i.e. the external recharge loop L 1  in  FIG. 2A ). A recharge switch unit  401  can be disposed on the recharge loop. The recharge switch unit  401  is used for switching on/off the external recharge loop L 1  from the battery module  400  to the negative recharge terminal  404 . 
         [0035]    In the embodiment, the controller  300  has an outward connection interface including a first pin P 1 , a second pin P 2 , a third pin P 3  and a fourth pin P 4 . The first pin P 1  is coupled to the negative recharge terminal  404 . The second pin P 2  is coupled between a positive terminal of the battery module  400  and the positive recharge terminal  403 . The third pin P 3  is coupled between the negative terminal of the battery module  400  and the recharge switch unit  401 . The fourth pin P 4  is used for controlling the recharge switch unit  401 . 
         [0036]    Besides, the controller  300  may includes a voltage detection unit  301 , a control logic unit  302 , a current detection unit  303  and a recharge protection circuit  306 . 
         [0037]    The voltage detection unit  301  is coupled to two terminals of a battery module  400  via the second pin P 2  and the third pin P 3 , for monitoring a voltage state of the battery module  400  and judging if a protective action is needed. For example, the voltage detection unit  301  is configured to detect the voltage level difference between two terminals of the battery module  400 , and accordingly the control logic unit  302  may acknowledge the state of the battery module  400  (e.g. the battery module  400  is fully charged, or the battery module  400  is over-discharged). When the battery module  400  is fully charged or over-discharged, the control logic unit  302  may switch off a recharge switch unit  401  via the fourth pin P 4 , so as to interrupt the recharge loop L 1  from the battery module  400  to the negative recharge terminal  404 , and accordingly to prevent from recharging the battery module  400  which has been fully charged or over-discharged already. 
         [0038]    In the embodiment, the controller  300  may further include other internal operational circuits. To be noticed that, part of the internal operational circuits (e.g. a sampling switch unit  304  and a sampling resistor  305  in  FIG. 2A ) may be coupled between the first pin P 1  and the third pin P 3 . 
         [0039]    In this case, even though the external recharge loop L 1  is interrupted, the operational circuits between the first pin P 1  and the third pin P 3  inside the controller  300  forms another loop (e.g. through a parasitic diode  304   a  of the sampling switch unit  304  and the sampling resistor  305 ), which causes over-charging issue to the battery module  400 . 
         [0040]    To be noticed that, the recharge protection circuit  306  of the controller  300  in the embodiment can be utilized to solve aforesaid issue. The recharge protection circuit  306  is coupled to the first pin P 1  and the second pin P 2   [H1] . When the battery module  400  is in a protective state, the recharge protection circuit  306  is activated to correspondingly protect the battery module  400 . In this embodiment, the so-called protective state is existed when the voltage detection unit  301  detects that the voltage level difference between the second pin P 2  and the third pin P 3  exceeds a specific first voltage value (e.g. the nominal voltage of the battery module  400 , representing the battery module  400  is fully charged), or the voltage level difference between the second pin P 2  and the third pin P 3  is lower than a second voltage value (representing the battery module  400  is over-discharged). 
         [0041]    When the battery module  400  is in the protective state, the control logic unit  302  activates the recharge protection circuit  306 , such that an in-flowing current at the second pin P 2  (which is coupled to the positive terminal of the battery module  400 ) goes through a switch unit  306   a  and a resistor  306   b  of the recharge protection circuit  306 , and then the current flows out via the first pin P 1  back to the negative recharge terminal  404  (shown as the current-guiding loop L 3  in  FIG. 2A ). In this way, the recharging current from the positive recharge terminal  403  skips the battery module  400  and is guided through the second pin P 2 , the recharge protection circuit  306 , the first pin P 1  and back to the negative recharge terminal  404 . Accordingly, the recharge protection circuit  306  forms the current-guiding loop L 3 , inside the controller  300 , to protect the battery module  400  against an unexpected current when the battery module  400  is in the protective state. 
         [0042]    The aforesaid paragraph discloses a current-guiding way for ensuring the safety of the battery module; however, the invention is not limited to the current-guiding way. In another embodiment, the invention utilizes a way of clamping the voltage level difference between the first pin P 1  and the third pin P 3  within a predetermined level difference, in order to protect the battery module  400  and prevent unwanted recharge problems. 
         [0043]    Please refer to  FIG. 2B , which is a block diagram illustrating a controller  300 ′ according to a second embodiment of the invention. The main difference between the controller  300 ′ in the second embodiment and the controller  300  in the first embodiment is that the controller  300 ′ in  FIG. 2B  includes a voltage-clamping circuit  306 ′, which is coupled to the first pin P 1  and the second pin P 2 . The voltage-clamping circuit  306 ′ is configured to force a level of the first pin P 1  to be equal to or higher than a level of the third pin minus a predetermined level difference, i.e. Vp 1 ≧Vp 3 −Vset, wherein Vp 1  is the level of the first pin P 1 , Vp 3  is the level of the third pin P 3 , and Vset is the predetermined level difference, which is positive. In practical applications, Vset can be set based on the threshold voltage of the parasitic diode  304   a  of the sampling switch unit  304 . 
         [0044]    The voltage-clamping circuit  306 ′ is utilized to limit the voltage level difference between the first pin P 1  and the third pin P 3 , so as to avoid the leakage current loop based on the operational circuits (e.g. the parasitic diode  304   a  of the sampling switch unit  304  and the sampling resistor  305 ) inside the controller  300 . 
         [0045]    In this embodiment, the voltage-clamping circuit  306 ′ may further include a voltage-clamping unit  306   b ′ and a switch unit  306   a ′. The voltage-clamping unit  306   b ′ detects levels of the first pin P 1  and the third pin P 3 . When the level of the first pin P 1  is lower than the level of the third pin P 3  minus the predetermined level difference, the voltage-clamping unit  306   b ′ switches on the switch unit  306   a ′ and adjusts equivalent resistance of the switch unit  306   a ′. Accordingly, the level of the first pin P 1  is elevated, such that the level of the first pin P 1  will not be far below the level of the third pin P 3 . 
         [0046]    In aforesaid embodiments, the invention utilizes a way of current-guiding or voltage-clamping for protecting the battery module. In aforesaid embodiments, the switch units (such as the sampling switch unit  304 , the switch unit  306   a , and the switch unit  306   a ′, etc) take N-channel Metal Oxide Semiconductors (NMOS) for example. In aforesaid demonstration example, the recharge switch unit  401  is coupled between the negative terminal of the battery module  400  and the negative recharge terminal  404 , and the first pin P 1  is coupled to the negative recharge terminal  404 . However, the invention is not limited to this. 
         [0047]    In another embodiment, aforesaid switch units utilize P-channel Metal Oxide Semiconductors (PMOS) instead. Besides, the recharge switch unit is coupled between the positive terminal of the battery module and the positive recharge terminal. In this case, the controller in the invention can achieve similar effect by adjusting positive/negative connection logic. The corresponding logical adjustment is known by people in art. 
         [0048]    Please refer to  FIG. 3A  and  FIG. 3B .  FIG. 3A  is a block diagram illustrating a controller  500  for protecting a battery module  600  according to a third embodiment of the invention.  FIG. 3B  is a block diagram illustrating a controller  500 ′ for protecting a battery module  600  according to a fourth embodiment of the invention. 
         [0049]    As shown in  FIG. 3A , the controller  500  includes a first pin P 1 , a second pin P 2 , a third pin P 3 , a fourth pin P 4 , a fifth pin P 5 , a voltage detection unit  501 , a control logic unit  502 , a current detection  503  and a recharge protection circuit  506 . Besides, the controller  500  further includes internal operational circuits coupled between the first pin P 1  and the second pin P 2 , e.g. a sampling switch unit  504  and a sampling resistor  505 . In this embodiment, the battery module  600  includes two battery cells. The voltage detection unit  501  is coupled to two battery cells battery of the battery module  600  via the second pin P 2 , the third pin P 3  and the fifth pin P 5 , for monitoring voltage states of each battery cell of the battery module  600  and judging if a protective action is needed. 
         [0050]    In the embodiment, a recharge switch unit  601  is coupled between a positive terminal of the battery module  600  and the positive recharge terminal  603 . The first pin P 1  is coupled to the positive recharge terminal  603 . The second pin P 2  is coupled between a positive terminal of the battery module  600  and the positive recharge terminal  603 . The third pin P 3  is coupled between the negative terminal of the battery module  600  and the negative recharge terminal  604 . 
         [0051]    The recharge protection circuit  506  is coupled to the first pin P 1  and the third pin P 3 . When the battery module  600  is in a protective state, the recharge protection circuit  506  is activated, such that an in-flowing current at the first pin P 1  goes through a switch unit  506   a  and a resistor  506   b  of the recharge protection circuit  506 , and then the current flows out via the third pin P 3  back to the negative recharge terminal  604  (shown as the current-guiding loop L 3  in  FIG. 3A ). In this way, the recharging current from the positive recharge terminal  603  skips the battery module  600  and is guided through the first pin P 1 , the recharge protection circuit  506 , the third P 3  and back to the negative recharge terminal  604 . Accordingly, the recharge protection circuit  506  forms the current-guiding loop L 3 , inside the controller  500 , to protect the battery module  600  against an unexpected current when the battery module  600  is in the protective state. 
         [0052]    The operation and detail structure of the controller  500  in the third embodiment substantially has a corresponding and logic-opposite relationship to the controller  300  in the first embodiment. It can be easily understood by a person in the art. 
         [0053]    On the other hand, the controller  500 ′ in the fourth embodiment shown in  FIG. 3B  implements a voltage-clamping circuit  506 ′. The voltage-clamping circuit  506 ′, which is coupled to the first pin P 1  and the third pin P 3 . The voltage-clamping circuit  506 ′ is configured to force a level of the first pin P 1  to be equal to or lower than a level of the second pin P 2  plus a predetermined level difference, i.e. Vp 1 ≦Vp 2 +Vset, wherein Vp 1  is the level of the first pin P 1 , Vp 2  is the level of the second pin P 2 , and Vset is the predetermined level difference, which is positive. In practical applications, Vset can be set based on the threshold voltage of the parasitic diode  504   a  of the sampling switch unit  504 . 
         [0054]    The detail structure and operation of the controller  500 ′ in the fourth embodiment is similar to the controller  300 ′ in the second embodiment, so not to be repeated here. Please refer to the paragraphs about the detail description of the controller  300 ′ in the second embodiment. 
         [0055]    Aforesaid embodiments has demonstrates the recharge protection of the controller in the invention. To be emphasized that, some common operational circuits in the integrated circuit applied to the recharging apparatus may occur an unexpected current, and it may cause the unwanted recharge effect. For example, an electrostatic discharge (ESD) protection circuit is disposed in the integrated circuit (IC) for preventing that an ESD pulse (e.g. high voltage pulse signal) caused by ESD effect from damaging the internal circuits of the controller. The ESD protection circuit is active during the battery recharging procedure. If the positive recharge terminal level exceeds the positive terminal level of the battery module plus a predetermined level difference, or if the negative recharge terminal level is below the negative terminal level of the battery module minus a predetermined level difference, there may an unexpected leakage current, which flows through the ESD protection circuit and keeps on recharging the battery module. The current-guiding/voltage-clamping function of the recharge protection circuit disclosed in aforesaid embodiments can be used to solve the unexpected leakage current and the unwanted recharging problem as well. 
         [0056]    According to the embodiments of the invention, the battery module and the controller are free from unexpected current or voltage signal (over-charging issue or ESD issue) by utilizing a current-guiding mean to make sure the leakage current bypass the battery module, or utilizing a voltage-clamping mean to prevent the unwanted current leakage. Therefore, the safety and durability in battery recharge procedure can be ensured. 
         [0057]    It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims.