Abstract:
Disclosed is a method for controlling charging current to a battery of a charging system, performed by a control unit of the charging system. The method includes: (a) detecting that a device is coupled to the charging system and determining what kind of the device the charging system is coupled to; (b) adjusting the charging current to a level according to the coupled device. The charging current is generated by the coupled device.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to charging systems and related methods thereof, and particularly relates to control charging current to a battery, wherein the charging current is generated by an external device. 
     A portable electronic device typically contains a battery and battery charging circuits. Various types of chargers may be employed to charge the embedded battery via the battery charging circuits. For example, the charger supporting the USB (Universal Serial Bus) specification may generate and provide current between 300 mA and 1800 mA with a voltage of 5V+−5% to charge the portable electronic device via a USB type A connector thereof. Conventional battery charging circuits limit the provided current to a fixed level, regardless of actual current that the charger provided, and types of chargers. 
     Therefore, charging systems and related methods thereof are required to dynamically adjust charging current contingent upon actual current that the charger provided, and types of chargers. 
     SUMMARY OF THE INVENTION 
     Therefore, an object of the present invention is to provide charging systems and related methods thereof, which can adjust charging current dynamically. 
     Specifically, the objective of the present invention is to provide charging systems and related methods thereof, which can adjust charging current in response to current generated by an external device, and types of various external devices. 
     An embodiment of a method for controlling charging current to a battery of a charging system, performed by a control unit of the charging system. The method comprises: (a) detecting that a device is coupled to the charging system; (b) adjusting the charging current to a level. The charging current is generated by the coupled device. 
     An embodiment of a charging system comprises a battery and a control unit. The control unit coupled to the battery detects that a device is coupled to the charging system, and adjusts charging current to the battery to a level. Wherein the charging current is generated by the coupled device. 
     An embodiment of a charging system comprises a detection unit. The detection unit generates a first voltage when the coupled device comprises a universal (USB) interface with two connected data lines, and generating a second voltage when the coupled device comprises the USB interface with two disconnected data lines 
     These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram illustrating a charging system according to an embodiment of the present invention. 
         FIG. 2  is a circuit diagram illustrating detection circuits according to an embodiment of the present invention. 
         FIG. 3  is a flowchart illustrating an adjustment method according to an embodiment of the present invention. 
         FIG. 4  is an exemplary charging timing diagram during charging current control according to an embodiment of the present invention. 
         FIG. 5  is a schematic diagram illustrating battery I-V curve during charging current control according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Certain terms are used throughout the description and following claims to refer to particular components. As one skilled in the art will appreciate, electronic equipment manufacturers may refer to a component by different names. This document does not intend to distinguish between components that differ in name but not function. In the following description and in the claims, the terms “include” and “comprise” are used in an open-ended fashion, and thus should be interpreted to mean “include, but not limited to . . . ”. Also, the term “couple” is intended to mean either an indirect or direct electrical connection. Accordingly, if one device is coupled to another device, that connection may be through a direct electrical connection, or through an indirect electrical connection via other devices and connections. 
       FIG. 1  is a charging system  100  according to an embodiment of the invention. As shown in  FIG. 1 , the charging system  100  mainly comprises a charging circuit  102 , a control unit  103 , a battery set  109 , a connector (for example, a USB connector)  111 , and a detection circuit  113 . The charging circuit  102  comprises a current control device  101  (for example, a P-MOS, an N-MOS, a BJT, and the similar), a temperature sensor  104  measuring temperature of the current control device  101 , a diode  105  and a resistor  107 . When a charger or computing apparatus such as a personal computer, a notebook, a workstation and the similar, is coupled to the charging system  100  via the connector  111 , current with a voltage V in  of 5V+−5% provided by the charger or computing apparatus flows to a battery of the battery pack  109  through the current control device  101 , the diode  105  and the resistor  107 . The resistor  107  is coupled between terminals A and B. The control unit  103  may measure current at the terminal A, and voltage at the terminal B. The diode  105  is coupled between the current control device  101  and the resistor  107 . The current control device  101  is coupled between the voltage V in  and the diode  105 . The control unit  103  controls the current control device  101  to adjust current flowed to the battery by issuing control signals CS according to the sensed voltage V in , or V ref , current at the terminal A, or temperature of the current control device  101  via the temperature sensor  104 , or any combinations thereof. The battery pack  109  further comprises a temperature sensor measuring temperature of the battery, and an identification (ID) unit providing profile information regarding the battery. Details of the detection circuits  113 , and adjustment methods performed by the control unit  103  are to be described in the following. 
       FIG. 2  is a diagram illustrating detection circuits (e.g.  113  of  FIG. 1 ) according to an embodiment of the invention. Of course, it is not meant to limit the scope of the present invention; detection circuits with different but similar structures that perform the same function should also fall in the scope of the present invention. In this embodiment, the detection circuit comprises resistors  605 ,  609 ,  611 ,  613  and  615 , and a diode  607 . When a charger or a computing apparatus is coupled to a charging system (e,g,  100  of  FIG. 1 ), two data lines are coupled between a control unit (e.g.  103  of  FIG. 1 ) and the charger or the computing apparatus through resistors  613  and  615  for matching of the characteristic impedance. Terminals D+ and D− are coupled to the connected charger or computing apparatus. Those skilled in the art may realize that the terminals USB_DP(BB) and USB_DM(BB) are coupled to the control unit for data transmission. A voltage V ref  on a node between the resistor  605  and the diode  607  is provided to the control unit. The resistor  611  is coupled between a power voltage V usb  and the terminal USB_DP(BB). The power voltage V usb  may be 3.3V in order to conform to the universal serial bus (USB) standard. The resistor  605  is coupled between the diode  607  and a power voltage V DD . The power voltage V DD , such as 2.8V, is lower than the power voltage V usb . The diode  607  is coupled between resistors  605  and  609 . The resistor  609  is coupled between the terminal D−, the diode  607  and ground. The voltage V ref  varies with statuses of two data lines coupled to terminals D+ and D−. It is to be understood that the USB interface further comprises a power line. 
     Types of the coupled charger or computing apparatus can be determined with reference to the voltage V ref . For an example, a computing apparatus may comprise two data lines, one is grounded and coupled to the terminal D−, and the other is coupled to the terminal D+ via a connector (e.g.  111  of  FIG. 1 ). Thereafter, the voltage V ref  is substantially on a ground level. Therefore, when detecting that the voltage V ref  is lower than a first threshold (e.g. 1V), the control unit determines that a computing apparatus is coupled to the charging system. It is to be understood that the first threshold can be configured to a value lower than a half of the power voltage V DD . For another example, a first type of charger may comprise two data lines been respectively coupled to terminals D− and D+, and these two data lines are connected. Thereafter, the output voltage V ref  substantially equals the power voltage V DD  because V usb  is higher than V DD , and current can not flow through the diode  607 . Therefore, when detecting that the voltage V ref  exceeds a second threshold (e.g. 2V), the control unit determines that a first type of charger is coupled to the charging system. It is to be understood that the second threshold can be configured to a value higher than a half of the power voltage V DD . For still another example, a second type of charger may comprise two data lines been respectively coupled to terminals D− and D+, and these two data lines are disconnected. Thereafter, the output voltage V ref  substantially equals a half of the power voltage V DD  because currents can separately flow to the resistors  609  and  615  through the diode  607 . Therefore, when detecting the voltage V ref  between the first and second thresholds, the control unit determines that a second type of charger is coupled to the charging system. In some embodiments, the voltage V ref  may be further input to an analog to digital converter (ADC) of the control unit as reference signals for adjustment methods. 
       FIG. 3  is a flowchart illustrating an adjustment method according to an embodiment of the present invention. 
     As shown in  FIG. 3 , the control method comprises: 
     Step  200   
     Detect that a device such as a computing apparatus or charger is coupled to a charging system (e.g.  FIG. 1 ). 
     Step  201   
     Determine whether the coupled device is the described first type of the charger. If the coupled device is the described first type of charger, go to step  205 ; if not, go to step  203 . The determination may be achieved by detecting a voltage outputted from detection circuits (e.g. V ref  of  FIG. 2 ). 
     Step  203   
     Set the charging current to a first predetermined value by controlling a current control device (e.g.  101  of  FIG. 1 ). 
     Step  205   
     Set the charging current to a second predetermined value by controlling a current control device (e.g.  101  of  FIG. 1 ). 
     For example, when the coupled device is the described first type of charger, the charging current from the coupled device to a battery may be limited between 300-1800 mA. When the coupled device is not the described first type of charger, the charging current from the coupled device to a battery may be limited to 500 mA. Therefore, the first predetermined value is lower than 500 mA, and the second predetermined value is between 300 mA and 1800 mA. 
     Step  207   
     Increase the charging current by controlling a current control device (e.g.  101  of  FIG. 1 ). 
     Step  209   
     Determine whether the charging current exceeds the maximum value. If so, go to step  211 ; if not, go to step  213 . 
     Step  211   
     Decrease the charging current by controlling a current control device (e.g.  101  of  FIG. 1 ). 
     Step  213   
     Determine whether the temperature of the current control device is higher than a predetermined value. If so, go to step  211  to decrease the charging current, resulting in the temperature of the current control device decreases. If not, go to step  215 . 
     A temperature sensor can be utilized to detect the temperature of the current control device, for example,  104  of  FIG. 1 . 
     Step  215   
     Determine whether a voltage of input current from the coupled device (e.g. V in  of  FIG. 1 ) is decreased exceeding a predetermined level such as 0.5V. If not, go back to the step  207  to increase the charging current. If yes, go to step  217  to maintain the charging current. Specifically, in step  217 , the control unit does not adjust the charging current. 
     Via the steps  207 - 217 , the flowed current can be dynamically increased, thereby decreasing charging time. Also, it should be noted that the flowchart shown in  FIG. 3  is just an example and is not meant to limit the scope of the present invention. For example, the order of the steps  209 ,  213  and  215  may be changed with relevant modification of process flow, and part or all of the steps  207 - 217  may be removed from the adjustment method shown in  FIG. 3 . 
     Additionally, as known by persons skilled in the art, a current control device such as a P-MOS, N-MOS, BJT and the similar, has a saturation region; that is, a region in which the current control device can provide the maximum current. Also, the conductive device has a smaller resistance value in the saturation region. Therefore, the adjustment method according to an embodiment of the present invention can further control the current control device to operate in the saturation region such that the controllable conductive device provides the maximum current. 
       FIG. 4  is an exemplary charging timing diagram during charging current control by an embodiment of adjustment methods shown in  FIG. 3 . As shown in  FIG. 4 , the charging current can be increased step by step, or linearly, illustrated by a step-wise and solid line, or a straight and dashed line. There are two limits for the charging current: one is the “charger maximum output current”, and the other is the “maximum charging current limit”. The “charger maximum output current” indicates the maximum current that the charger can support, and the “maximum charging current limit” indicates the maximum value in step  209 . The maximum charging current limit may be decided according to the ID information of a battery. As shown in  FIG. 4 , when detecting that a input voltage (e.g. V in  of  FIG. 1 ) is dropped by a predetermined level (e.g. 0.5V), it is determined that the charging current reaches the “charger maximum output current”, as a result, the charging current should be decreased. It is to be understood that the voltage drop is generated by the first type of charger when detecting that charging circuits consume excessive current than the “charger maximum output current”. 
       FIG. 5  is a schematic diagram illustrating battery I-V curve during charging current control by an embodiment of adjustment methods. Referring to above-mentioned methods, the charging current is increased until the battery almost reaches a predetermined voltage level (that is, the battery is fully charged), as shown in a bold line. However, a traditional charging system would keep a constant charging current, as shown in a dashed line. Therefore, a charging system utilizing the control mechanism according to an embodiment of the present invention can reduce charging time than that of a traditional charger. 
     According to the above-mentioned method and circuits, the charging current of a charger can be adjusted according to its charger type. The charging current can further be adjusted according to other characteristics sensed by a control unit during charging. Therefore, the charging system not only adjusts charging current for different types of chargers, but adjusts charging current as higher as possible to reduce charging time without damages caused by excessive charging current. Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention.