Abstract:
A battery module for a portable electronic device is disclosed. The battery module is connected with the portable electronic device with at least three contacts. The battery module includes a battery, a recognition circuit, and a thermal sensing circuit. The recognition circuit has an energy storage element and a current limiting element, and the thermal sensing circuit has a switch and a thermal sensing element. The thermal sensing element varies its electric parameter in accordance with the temperature of the battery module. With the charging curve of charging the energy storage element by way of the current limiting element, the portable electronic device can determine a battery type, and the thermal sensing circuit is then initiated to acquire the thermal information of the battery module.

Description:
RELATED APPLICATIONS 
     The present application is a Continuation Application of U.S. application Ser. No. 12/346,792, filed on Dec. 30, 2008 which claims priority to Taiwan Application Serial Number 96151488, filed Dec. 31, 2007, which is herein incorporated by reference. 
    
    
     BACKGROUND 
     1. Field of Invention 
     The invention is related to a battery module and a method for determining battery module ID and temperature thereof, more particularly, to a battery module for a portable electronic device. 
     2. Description of Related Art 
     A battery module can provide energy for operating portable electronic devices (such as mobile phone, person digital assistant, etc.). Every battery module needs to be charged when the power within it is almost run out. However, before a charging operation, a battery type of the battery module should be determined so as to provide an appropriate charging current and voltage according to the specification of the battery module. Temperature is also an important criterion for determining the charging current and voltage. For example, if the temperature of the battery module is too high, the charging current should be reduced or turned off to ensure the battery used in a safe environment. 
     For acquiring signals related to battery types and temperatures of different battery modules and determining charging states, three or four electrodes positioned on the battery modules are implemented. However, comparing with the four electrodes, battery modules with the three electrodes have an advantage of lowering cost and size. 
       FIG. 1  is a schematic graph of a conventional battery module. The battery module  10  includes a battery  11 , a negative temperature coefficient thermistor NTC 1 , resistors R 1  and R 2 , and electrodes  12 ,  13  and  14 . The anode of the battery is connected to the electrode  14 , and the cathode is connected to the electrode  12 . The resistor R 1  is serially connected to the resistor R 2 , and the resistors R 1  and R 2  are separately connected to the electrodes  12  and  13 . Also, the thermistor NTC 1  is parallelly connected to the resistor R 2 . A voltage or current is applied to the electrode  13 , and a signal is measured on the electrode  13 . The signal is determined with an equivalent resistance of the thermistor NTC 1 , the resistors R 1  and R 2 . With the signal, the battery type and temperature of the battery module  10  are determined. 
       FIG. 2   a  is schematic graph showing resistance ranges of different conventional battery modules. In a first battery module type, the resistances of the resistors R 1  and R 2  are respectively selected as R 1 ′ and R 2 ′, and the equivalent resistance of the thermistor NTC 1 , and the resistors R 1  and R 2  fall in the range between R 1 ′ and R 1 ′+R 2 ′. Also, in a second type of battery module, the resistances of the resistors R 1  and R 2  are respectively selected as R 1 ″ and R 2 ″, and the equivalent resistance falls in a range of R 1 ″˜R 1 ″+R 2 ″. 
     Accordingly, when the equivalent resistance is in the range of R 1 ′˜R 1 ′+R 2 ′, the battery module will be classified as the first type and the temperature of which is also acquired, thus the battery is charged according to the charging specification of the first type of battery module. Similarly, when the equivalent resistance is in the range of R 1 ″˜R 1 ″+R 2 ″, the corresponding battery will be classified as the second type and the temperature of which is also acquired, thus the battery is charged according to the charging specification of the second type of battery module. 
       FIG. 2   b  is another schematic graph showing resistance ranges of different conventional battery modules. Please refer to  FIG. 1  and  FIG. 2   b . If the equivalent resistances of two types of battery module partially overlap with each other, as illustrated in the range between R 1 ′ and R 1 ″+R 2 ″, and the equivalent resistance measured falls in the range between R 1 ′ and R 1 ″+R 2 ″(such as the shadow in the  FIG. 2   b ), it is hard to determine the battery type and temperature of the battery module. Thus, charging the battery module with an appropriate current and voltage is also impossible. To prevent such overlaps, ranges of equivalent resistances of different battery types of battery modules must be shortened, but the shortened ranges reduce the accuracy for determining the temperature of the battery. 
     Therefore, a new battery module and charging device should be provided to solve aforesaid problem and would have the ability to modulate the charging current and voltage in accordance with the battery type and temperature of the battery module. 
     SUMMARY 
     One aspect of the disclosure is to provide a battery module, which is integrated into a portable electronic device, which can precisely determine the battery type and temperature of a battery module so as to provide the battery with an appropriate charging current and voltage at lower costs. 
     Another aspect of the disclosure is to provide a method for determining the charging state of the battery module. The charging state determining method is used to determine the battery type and temperature of a battery so as to provide the battery with an appropriate charging current and voltage at lower costs. 
     According to one of aforesaid aspects, the disclosure provides a battery module. An interface of the battery module, which is connected to a portable electronic device, has at least a first terminal, a second terminal, and a third terminal. The battery module comprises: a battery, a recognition circuit and a thermal sensing circuit. The anode and cathode of the battery are respectively connected with the second terminal and first terminal. The recognition circuit includes an energy storage element and a current limiting element, and the thermal sensing circuit includes a switch and a thermal sensing element. Connections between different elements will be described as follow: one end of the energy storage element is connected to the first terminal, a current limiting element is serially connected between the energy storage element and the third terminal, one end of the switch is connected to the first terminal, and the thermal sensing element is serially connecting between the switch and the third terminal. Besides, the resistance of the thermal sensing element varies with the temperature of the battery module. 
     With the charging curve of charging the energy storage element by way of the current limiting element, the portable electronic device can recognize a battery type, and the switch is turned on to initiate the thermal sensing circuit so as to acquire the thermal information of the battery module. 
     According to another one of aforesaid aspects, the disclosure provides an electronic device. The electronic device includes a reference power source, a battery module and a charging state controlling device. The battery module comprises: a battery, a recognition circuit and a thermal sensing circuit. The recognition circuit includes an energy storage element and a current limiting element, and the thermal sensing circuit includes a switch and a thermal sensing element. Besides, an interface of the battery module, which is connected to a portable electronic device, has at least a first terminal, a second terminal, and a third terminal. The anode and cathode of the battery are respectively connected with the second terminal and first terminal. One end of the energy storage element is connected to the first terminal, and a current limiting element is serially connected between the energy storage element and the third terminal. One end of the switch is connected to the first terminal, and the thermal sensing element is serially connected between the switch and the third terminal. Furthermore, the resistance of the thermal sensing element varies with the temperature of the battery module. 
     Also, with the charging curve of charging the energy storage element by way of the current limiting element, the portable electronic device can recognize a battery type, and the switch is then turned on to initiate the thermal sensing circuit so as to acquire the thermal information of the battery module. According to an embodiment of the disclosure, the operation of the switch can directly be under the control of the voltage of energy storage element being charged. 
     According to the aforesaid aspects, the disclosure provides a method for determining a charging state of a battery module to charge the battery module in accordance with a battery type of and a temperature of the battery module. The method includes steps of providing a current by way of a current limiting element to charge an energy storage element; determining a type of the battery module in accordance with a terminal voltage of the energy storage element at a first time; providing the current flowing through a thermal sensing element; and determining a temperature of the battery module by measuring a terminal voltage of the thermal sensing element at a second time. 
     By the above description, with the battery module and the method for determining the charging state of the battery module, a charging state can be adjusted in accordance with battery types and temperatures of different battery modules. On the other hand, it is not necessary to implement additional terminals, thus an advantage of lowering cost is achieved. 
     Another advantage of this method is that temperature measurement has higher accuracy. This is because compare to prior art, the resistance range need to be separate into two range but this method can use the complete range for temperature measurement. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing aspects and many of the attendant advantages of this disclosure will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1  illustrates a conventional battery module. 
         FIG. 2   a  illustrates resistance ranges of different conventional battery modules. 
         FIG. 2   b  illustrates resistance ranges of different conventional battery modules. 
         FIG. 3   a  illustrates a battery module in accordance with an embodiment of the disclosure. 
         FIG. 3   b  illustrates a battery module in accordance with another embodiment of the disclosure. 
         FIG. 4  illustrates an exemplary circuit of a battery module and a charging device in accordance with a preferred embodiment of the disclosure. 
         FIG. 5  illustrates charging curves for different battery modules showing voltages varying with the time in accordance with a preferred embodiment of the disclosure. 
         FIG. 6  illustrates a charging curve for a battery module showing a voltage varying with the time in accordance with a preferred embodiment of the disclosure. 
         FIG. 7  is a flow chart of a method for determining a charging state of the battery module in accordance with a preferred embodiment of the disclosure. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Charging and discharging curves of energy storage elements vary with electric parameters of the energy storage elements and current limiting element connected thereto. Different parameters result in different charging and discharging curves. With such characteristics, the following embodiments are configured to precisely select an appropriate charging state for a battery module in accordance with battery type and temperature. 
     The battery module and the charging device of the following embodiments are configured to be connected to or within a portable electronic device, such as a mobile phone, a personal digital assistant, and a notebook etc. The following embodiments implement the mobile phone for the sake of clarity. 
       FIG. 3   a  illustrates a battery module in accordance with an embodiment of the disclosure. Please refer to  FIG. 3   a , a battery module  30  includes a battery  31 , a battery recognition circuit  32 , a thermal sensing circuit  33 , and terminals  1 ,  2  and  3  to connect to the mobile phone. The anode and cathode of the battery are respectively connected with the terminal  3  and  1 , and the battery recognition circuit  32  and the thermal sensing circuit  33  is positioned between the terminal  1  and  2 . With the battery recognition circuit  32  and the thermal sensing circuit  33 , the battery type and temperature can be respectively acquired. 
       FIG. 3   b  illustrates a battery module in accordance with another embodiment of the disclosure. A battery module  30  includes a battery  31 , a battery recognition circuit  32 , a thermal sensing circuit  33 . The recognition circuit  32  has an energy storage element  321 , a current limiting element  322 , and the thermal sensing circuit  33  has a switch  331  and a thermal sensing element  332 . The energy storage element  321  is serially connected to the current limiting element  322 , and the switch  331  is serially connected to the thermal sensing element  332  between a terminal  1  and  2 . In such configuration, when the switch  331  is turned on, the thermal sensing element  332  is connected to a terminal  1  via the switch  331 . Preferably, the operation of the switch  331  may be controlled by the charging state of the energy storage element  321 . Beside, the resistance of the thermal sensing element  332  varies with the temperature of the battery module  30 . 
     A reference power source provides a current to the battery recognition circuit  32  via the terminal  2 , and the current charges the energy storage element  321  via the current limiting element  322 . Voltages V 1  and V 2  can be received at terminal  2  respectively at a first and second time t 1  and t 2 , and the voltage V 1  is meant to determine the battery type of the battery module  30 , and the voltage V 2  is meant to determine the temperature of the battery module  30 . Generally, the voltage V 1  is measured before the energy storage element  321  is fully charged, and the voltage V 2  is measured after the energy storage element  321  is fully charged. 
     Note that the voltages V 1  and V 2  are only exemplary, according to characteristics of the energy storage element  321  and the current limiting element  322 , currents I 1  and I 2  can also be measured at the terminal  2  respectively at the first and second times t 1  and t 2 . 
     At the first time t 1 , the switch  331  is turned off, and a current flowing through the current limiting element  322  charges the energy storage element  321 , and the voltage V 1  is determined by the electric parameters of the energy storage element  321  and the current limiting element  322 . At the second time t 2 , the energy storage element  321  is in a steady state, the switch  331  is turned on, and the current flows through the thermal sensing element  332 , thus the voltage V 2  is determined by the electric parameters of the thermal sensing element  332 . 
     To upgrade the accuracy of the voltages V 1  and V 2 , ensuring the charging state of the energy storage element  321  is essential. Therefore, before the current is provided to the energy storage element  321 , terminal  2  is connected to ground by turning on a switch SW so as to discharge the energy storage element  321 . By discharging the energy storage element  321 , the accuracy of the voltages V 1  and V 2  can be ensured. Later, the voltages V 1  and V 2  are analyzed to determine the battery type and temperature of the battery module  30 . 
       FIG. 4  illustrates an exemplary circuit of a battery module and a charging device in accordance with a preferred embodiment of the disclosure. The charging device could be configured in a portable electronic device, such as a mobile phone, to charge the aforesaid battery module. Please refer to  FIG. 4 , a charging device  400  for charging a battery module  410  includes a connector  420 , a reference power source  430  and a microcontroller (MCU)  440 . 
     The battery module  410  illustrates more details compared with the battery module  30  shown in  FIG. 3   b . The battery module  410  includes a battery  411 , a capacitor  412  (i.e. an energy storage element), a resistor  413  (i.e. a current limiting element), an NMOS transistor  414  (i.e. a switch), a negative temperature coefficient thermistor  415  (i.e. a thermal sensing element), and electrodes  416 ,  417  and  418 . The anode of the battery  411  is connected to the electrode  418 , and the cathode is connected to the electrode  416 . The capacitor  412  is serially connected to the resistor  413  between the electrodes  416  and  417 . Besides, the transistor  414  is positioned between the electrode  416  and the thermistor  415 , and the gate of the transistor  414  is connected to a node N 1  between the capacitor  412  and resistor  413 , thus a terminal voltage of the capacitor  412  controls the operation of the transistor  414 . When the transistor  414  is turned on, the thermistor  415  is connected with the electrode  416  via the transistor  414 . On the other hand, the thermistor  415  is also connected to the electrode  417 . The resistance of the thermistor  415  varies with a temperature of the battery module  410 . 
     The reference power source  430  provides a current flowing through the resistor to charge the capacitor  412  via the electrode  417 , at a first time t 1  and a second time t 2 , the microcontroller  440  respectively receives the voltages V 1  and V 2  and analyzes them to determine the battery type and temperature of the battery module  410 . Generally, the voltage V 1  is received before the energy storage element  412  is fully charged, and the voltage V 2  is received after the energy storage element  412  is fully charged. 
     The connector  420  includes electrodes  421 ,  422  and  423  respectively connected to the electrodes  416 ,  417  and  418 . The electrode  421  is connected to ground, the electrode  422  is connected to the microcontroller  440  and the electrode  423  is connected to the reference power source  430 . The connector  420  is fixed within the mobile phone to transmit energy and signals to the mobile phone so as to provide energy for the mobile phone. 
     The reference power source  430  may include a reference voltage source  431  and a resistor  433 . Alternatively, the reference voltage source  431  is connected to the electrode  423  to receive energy from the battery  411 . The energy would be transformed into a constant voltage, and the constant voltage would charge the capacitor  412  through the resistor  413  via the electrode  417 . 
     Also, in an embodiment in accordance with the preferred embodiment, a reference current source is implemented to replace the reference voltage source  431 , and an inductor is implemented to replace the capacitor  412 , and a current-controlled switch is implemented to replace the NMOS transistor  414 . In a similar way as described above, the battery type and temperature of a battery module would be determined with accuracy in the embodiment. 
     The microcontroller  440  has an analog-digital converter (ADC)  441  and a control signal generator  443 . The analog-digital converter  441  transforms the voltages V 1  and V 2  into digital signals S 1  and S 2 , the control signal generator  443  generates signals to charger that charges the battery module  410  in accordance with the digital signals S 1  and S 2 . 
     To ensure the accuracy of the voltages V 1  and V 2  is essential to ensure the charge on the capacitor  412  is zero. Therefore, a NMOS transistor  450  is implemented in the preferred embodiment as a switch to connect the capacitor to ground. The gate of the transistor  450  is connected to the microcontroller  440 , the drain of the transistor  450  is connected to the electrode  422 . Before the reference power source charging the capacitor, the electrode  417  is connected to ground via the transistor  450  to discharge the capacitor  412 . Microcontroller would output a control signal Sg to the gate of the transistor to controller the switching operation between the drain and the gate of the transistor  450 . 
     After the energy stored in the capacitor is discharged, the accuracy of the voltages V 1  and V 2  could be ensured. Later, the voltages V 1  and V 2  would be analyzed to determine the battery type and temperature of the battery module  410 . 
     The operation of the transistor  414  is controlled with a charging voltage of the capacitor  412 . Originally, there is no charge existing in the capacitor  412 , and the transistor  414  is turned off. After the capacitor  412  starts to be charged, a terminal voltage of the capacitor  412 , i.e., the voltage on the node N 1 , is lower than a threshold voltage of the transistor  414 , thus the transistor is still turned off. After a period of time of charging (e.g. the capacitor is fully charged and reaches a steady state), the voltage on the node N 1  is higher than the threshold voltage, and the transistor is then turned on. 
       FIG. 5  illustrates charging curves for different battery modules showing voltages varying with the time in accordance with a preferred embodiment of the disclosure. Please refer to  FIG. 4  and  FIG. 5 , before t=0, the microcontroller  440  outputs a control signal Sg with a high voltage level to turn on the transistor  450  so as to connect the capacitor  412  to ground and thus discharge the capacitor  412 . Later, microcontroller  440  switches control signal Sg to a low voltage level to turn off the transistor. 
     After transistor  450  turned off, the reference power source  430  provides the current to start charging the capacitor  412  via the electrode  422 . Since the terminal voltage of the capacitor is still lower than the threshold voltage of the transistor  414 , the transistor  414  is still turned off, and the current flows through the resistor  413  and the capacitor  412 . The analog-digital converter  441  receives the voltage V 1  on the electrode  417  via a node N 2  at the first time t 1  and transforms the voltage V 1  into digital signals S 1  to facilitate the following analysis. In the embodiment, the voltage V 1  varies with a product RC of the capacitance C of the capacitor  412  and the resistance R of the resistor  413 . Therefore, with different capacitances C and resistances R in different battery modules, the battery types of the battery modules can be determined. That is, different battery modules have different RC products, the higher the RC product, the lower the voltage V 1  received. For example, if two different battery modules have the same resistance R, and the capacitances of which are respectively C 1  and C 3 , and C 1 &gt;C 3 , then V 1 &lt;V 3 . By measuring the voltage at the first time t 1 , the type of the battery module can be determined with accuracy. 
       FIG. 6  illustrates a charging curve for a battery module showing voltage varying with the time in accordance with a preferred embodiment of the disclosure. Please refer to  FIG. 4  and  FIG. 6 . After the capacitor  412  has been charging for a period of time, the voltage on the node N 1  is higher than the threshold voltage of the transistor  414 , then the transistor is turned on, and the current flows through the thermistor  415 . Furthermore, the analog-digital converter  441  receives the voltage V 2  on the electrode  417  via the node N 2  at the second time, and converts the voltage V 2  into the digital signal S 2  for the following analysis. In the embodiment, since the voltage varies with the resistance of the thermistor  415  determined by the temperature of the battery module  410 , the voltage V 2  would differ in different temperatures. Thus, the battery type of the battery module  410  can be determined with accuracy by analyzing the voltage V 2  at the second time t 2 . 
     As shown in  FIG. 6 , the analog-digital converter  441  sequentially receives the voltage V 1  and V 2  on the electrode  417  at the time t 1  and the second time t 2 . The voltage V 1  is meant to determine the battery type of the battery module  410 , and the voltage V 2  is meant to determine the temperature of the battery module  410 . 
     It should be noted that the thermistor  415  and the resistor  413  are not necessarily both connected to the electrode  417 , for those skilled in the art, a plurality of electrodes are implemented to respectively connect the thermistor  415  and the resistor  413  without departing from the sprit and range of the disclosure. 
       FIG. 7  is a flow chart of a method for determining the charging state of the battery module in accordance with a preferred embodiment of the disclosure. Please refer to  FIG. 7 . First, in the step S 71 , an energy storage element is discharged before starting to charge the energy storage element. Later, a current flowing through a current limiting element is provided to charge an energy storage element, and a battery type of the battery module is determined in accordance with a terminal voltage of the energy storage element at a first time (in the step S 73  and S 75 ). Furthermore, in the step S 77 , the current flowing through a thermal sensing element is provided. Finally, a temperature of the battery module is determined in accordance with a terminal voltage of the thermal sensing element at a second time in the step S 79 . 
     As described above, the battery type and the temperature of the battery module of the disclosure can be efficiently and precisely determined without implementing additional electrodes, so as to determine a charging state of the battery module. Therefore, the battery module implemented by a portable electronic device can solve the problem of the conventional art, and has advantages of upgrading the accuracy for determining the charging state and lowering cost. 
     While the present disclosure has been described with respect to preferred embodiments thereof, it will be apparent to those skilled in the art that the disclosed disclosure may be modified in numerous ways and may assume many embodiments other than those specifically described above. Accordingly, it is intended by the appended claims to cover all modifications of the disclosure that fall within the true spirit and scope of the disclosure.