US20160164324A1

US20160164324A1 - Portable device capable of controlling output characteristics of adaptor, and corresponding method

Info

Publication number: US20160164324A1
Application number: US14/777,526
Authority: US
Inventors: Chih-Yuan Hsu; Chi-Ming Lee
Original assignee: MediaTek Inc
Current assignee: MediaTek Inc
Priority date: 2013-06-03
Filing date: 2014-06-03
Publication date: 2016-06-09
Also published as: CN104885328B; EP3005527B1; US20160049804A1; CN104885328A; EP3005527A1; US9929576B2; CN104335446B; EP3005527A4; WO2014194810A1; CN104335446A; WO2014194811A1

Abstract

A portable device capable of controlling output characteristics of an adaptor used for charging a battery of the portable device includes a sensing circuit and a controlling circuit. The sensing circuit senses a condition of the battery. The controlling circuit controls the adaptor to adjust its output characteristics based on the condition of the battery.

Description

TECHNICAL FIELD

The present invention relates to a charging scheme for controlling an adaptor, and more particularly to a portable device capable of controlling output characteristics of the adaptor and corresponding method.

BACKGROUND

Generally speaking, when a conventional adaptor is connected to an electronic device via a communication interface to charge a battery of the electronic device, the conventional adaptor usually employs a constant current to charge the battery in a constant current mode. However, under some conditions, considering the circuit costs and worse power dissipation, only a smaller constant current can be employed for charging the battery. The smaller current indicates that it is necessary for the conventional adaptor to consume a longer time period to charge the battery. This drawback is unacceptable by users. Accordingly, it is important to provide a novel charging scheme to overcome the shortcoming of the prior art.

SUMMARY

Therefore one of the objectives of the present invention is to provide a portable device and method capable of controlling output characteristics of an adaptor used for charging a battery of the portable device, to solve the above-mentioned problems.
According to an embodiment of the present invention, a portable device capable of controlling output characteristics of an adaptor used for charging a battery of the portable device is disclosed. The portable device comprises a sensing circuit and a controlling circuit. The sensing circuit senses a condition of the battery. The controlling circuit controls the adaptor to adjust its output characteristics based on the condition of the battery.
According to an embodiment of the present invention, a method for employing a portable device to control output characteristics of an adaptor which is used for charging a battery of the portable device comprises: sensing a condition of the battery; and controlling the adaptor to adjust its output characteristics based on the condition of the battery.
According to an embodiment of the present invention, an adaptor used for charging a battery of a portable device is disclosed. An output characteristic of the adaptor is configurable according to a condition of the battery.
According to the embodiments, the portable device can communicate with the controllable adaptor via a variety of communication interfaces and control output characteristics of the controllable adaptor, to achieve the purpose of fast charging, avoid thermal damage, enhance/improve the whole charging efficiency, and to save more power.
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 DRAWINGS

FIG. 1 is a diagram of a charging system according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a safe operating area of the conductive circuit element as shown in FIG. 1.

FIG. 3 is a diagram illustrating I-V curve of the adaptor according to the embodiments of FIG. 1.

FIG. 4 is a control flowchart of the operations of the charging system as shown in FIG. 1 according to an embodiment of fast charging in the present invention.

DETAILED DESCRIPTION

Please refer to FIG. 1, which is a diagram of a charging system 100 according to an embodiment of the present invention. The charging system 100 comprises an adaptor 105 such as an AC-to-DC traveler adaptor (but not limited) and a portable device 110 such as a mobile device (e.g. a smart phone device, a tablet). The portable device 110 comprises a conductive circuit element 1101, a resistor 1102, a battery 1103, a sensing circuit 1104, and a controlling circuit 1105. The sensing circuit 1104 and the controlling circuit 1105 can be regarded as a battery charger device which can be implemented by using an integrated circuit chip. The adaptor 105 is used for converting an AC source into DC charging voltage Vchg and charging current Ichr and providing the charging voltage Vchg and charging current Ichr for charging the battery 1103 of portable device 110. In addition, the adaptor 105 is capable of providing a variety of different charging voltages and charging currents for the battery 1103 based on different conditions of the battery 1103. The output characteristic of the adaptor 105 is configurable according to a condition of the battery 1103. The portable device 110 can inform the adaptor 105 of the condition of the battery 1103 such as a battery voltage, and control the adaptor 105 to dynamically output different charging voltages and charging currents under different conditions. Preferably, this can achieve rapidly charging the battery 1103 of the portable device 110 and avoid that power dissipation exceeds a power dissipation threshold. The conductive circuit element 1101 in this embodiment is implemented with (but not limited) a bipolar junction transistor or a MOS transistor. The battery 1103 includes at least one cell. The sensing circuit 1104 is coupled to the battery 1103 and used for sensing a condition of the battery 1103. For example, the sensing circuit 1104 senses the battery voltage Vbat of the battery 1103 to generate a sensing result of the battery voltage Vbat. The controlling circuit 1105 is coupled to the sensing circuit 1104 and used for controlling the adaptor 105 to adjust its out characteristics based on the condition of the battery 1103. The controlling circuit 1105 can determine the desired charging voltage and/or charging current that are supplied from the adaptor 105 based on the sensing result of battery voltage Vbat. The controlling circuit 1105 informs the adaptor 105 of the determined charging voltage and charging current by sending control signals to the adaptor 105 via a specific communication interface such as via the VBUS line of USB communication interface, via a dedicated communication line of USB communication interface, or via any communication interface between the adaptor 105 and the portable device 110. The adaptor 105 can provide the charging voltage and charging current determined by the portable device 110 for charging the battery 1103 according to the control signals. Specifically, in order to achieve fast charging and thermal protection simultaneously, the portable device 110 controls the adaptor 105 to supply a maximum charging current to the battery 1103 as far as possible. The maximum charging current that can be provided by the adaptor 105 depends on a condition of the battery 1103 and a power dissipation threshold associated with the thermal protection. In this embodiment, the condition indicates the battery voltage Vbat, and the power dissipation threshold Pdmax of the conductive circuit element is considered as the power dissipation threshold associated with the thermal protection. However, this is not intended to be a limitation. In other embodiments, the power dissipation threshold associated with the thermal protection may be a threshold of another different circuit element included within the portable device 110. In order to achieve fast charging and avoid the power dissipation of the conductive circuit element 1101 exceed above a power dissipation threshold Pdmax, the controlling circuit 1105 controls the adaptor 105 to adjust and then provide the charging voltage Vchg after determining the maximum charging current that can be provided by the adaptor 105 as far as possible so that the provided charging current and charging voltage would not result in a power dissipation exceeding above the power dissipation threshold Pdmax. The relation of power dissipation resulted from the conductive circuit element 1103 can be calculated according to the following equation:
Pd=(Vchg−Vbat)×Ichr
wherein Pd indicates the power dissipation, Vchg indicates the output charging voltage outputted by the adaptor 105 for charging the battery 1103, Vbat indicates the battery voltage, and Ichr indicates the charging current. The battery voltage Vbat can be sensed by the sensing circuit 1104, and accordingly the controlling circuit 1105 can adjust the charging current Ichr and output charging voltage Vchg in order to maximize the charging current Ichr and avoid the power dissipation Pd exceed the power dissipation threshold Pdmax. That is, in order to increase the charging current Ichr as far as possible, the portable device 110 is arranged to decrease the voltage difference between the output charging voltage Vchg and the battery voltage Vbat. Thus, by maximizing the charging current Ichr that can be supplied from the adaptor 105, the battery 1103 can be charged rapidly, and this significantly reduces the whole charging time. In this situation, the controlling circuit 1105 may set the output charging voltage Vchg as a voltage level that is lower than a level calculated based on the maximized charging current Ichr, so that the corresponding power dissipation Pd is slightly smaller than the power dissipation threshold Pdmax and the conductive circuit element 1101 is not damaged. That is, after determining and configuring the charging current Ichr provided by the adaptor 105, the portable device 110 can control the adaptor 105 to selectively output or supply different output charging voltage levels. For example, a first level may be determined based on the above-mentioned equation and the maximized charging current, and a second level may be a level which is slightly lower than the first level. The selection of supplying different output charging voltage levels according to the same charging current provides a flexibility of outputting different powers. The portable device 110 controls the adaptor 105 to select one of multiple charging levels corresponding to different powers and provide the selected voltage for the battery 1103 under different conditions.
As mentioned above, the portable device 110 (or the controlling circuit 1105) can be used for configuring the charging current Ichr supplied by the adaptor 105 based on the battery voltage Vbat, determining the output charging voltage Vchg provided by the adaptor 105 according to the configured charging current Ichr, and controlling the adaptor 105 to output the determined output charging voltage Vchg and the configured charging current Ichr. Accordingly, the portable device 110 including the sensing circuit 1104 and controlling circuit 1105 is capable of controlling output characteristics of the adaptor 105. The output characteristics may indicate (but not limited to) the charging current Ichr or the output charging voltage Vchg. In other examples, the output characteristics may include AC-to-DC switching frequency, AC-to-DC bias current, the precision of output voltage, voltage ripple, and the dynamic loading, etc. The portable device 110 can also be used to control the output characteristics of the adaptor 105 by adjusting at least one characteristic of AC-to-DC switching frequency, AC-to-DC bias current, the precision of output voltage, voltage ripple, and the dynamic loading, etc., so as to adjust the charging current Ichr.
It should be noted that the controlling circuit 1105 can adjust the output charging voltage Vchg after determining/configuring the charging current Ichr in a first embodiment or can adjust the charging current Ichr after determining/configuring the output charging voltage Vchg in a second embodiment according to the equation of power dissipation of conductive circuit element 1101.
In the embodiments, the conductive circuit element 1101 can be implemented with a bipolar junction transistor. The bipolar junction transistor is turned on and becomes saturated when the adaptor 105 is charging the battery 1103. The voltage drop between the collector and emitter of the bipolar junction transistor is marked as VCE which in some examples may be equivalent to 0.25 Volts-0.4 Volts. The voltage different between the output charging voltage Vchg and battery voltage Vbat can be represented by VCE+Ichr*R wherein R indicates the resistance value of the resistor 1102 disposed between the bipolar junction transistor and the battery 1103. The resistance value is very small and can be ignored. The voltage different between the output voltage Vchg and battery voltage Vbat is almost equivalent to VCE. Accordingly, the maximum of charging current Ichr can be calculated or estimated by the following equation:
$I \max = \frac{Pd \max}{V_{CE}}$
Imax indicates the maximum of charging current Ichr. For example, if the power dissipation threshold Pdmax is designed as 0.7 W, then the maximum charging current Imax can be configured as 2.8 A−1.75 A that is dependent upon the voltage drop VCE between the collector and emitter of the bipolar junction transistor. If the voltage drop VCE is equal to 0.25 Volts, the maximum charging current Imax can be configured as 2.8 A. If the voltage drop VCE is equal to 0.4 Volts, the maximum charging current Imax can be configured as 1.75 A. The controlling circuit 1105 of portable device 110 is arranged to control the adaptor 105 to output the maximum charging current Imax as the charging current Ichr for the battery 1103 and output the output charging voltage Vchg that is equal to the sum of the voltage drop VCE and battery voltage Vbat. The output charging voltage Vchg supplied by the adaptor 105 can be dynamically adjusted according to the change of the battery voltage Vbat since the battery voltage Vbat can be sensed by the sensing circuit 1104 and the voltage drop VCE can be determined. That is, the portable device 110 can control the adaptor 105 to output the stable maximum current Imax and different charging voltage levels based on the different levels of the battery voltage Vbat. Thus, the battery 1103 can be rapidly charged with the maximum charging current Imax in a constant current mode.
Please refer to FIG. 2, which is a diagram illustrating a safe operating area of the conductive circuit element 1101 such as the bipolar junction transistor as shown in FIG. 1. As shown in FIG. 2, in addition to configuring the charging current Ichr as the maximum charging current Imax, the controlling circuit 1105 can also configure the charging current Ichr as any currents that are smaller than the maximum charging current Imax, and can control the adaptor 105 to adjust the output charging voltage Vchg or not to adjust the output charging voltage Vchg. The dotted line area of FIG. 2 indicates that the conductive circuit element 1101 is not damaged due to thermal damage caused by the power dissipation when the conductive circuit element 1101 is turned on and becomes saturated. That is, the dotted line area represents the safe operating area of the conductive circuit element 1101. For example, the charging current Ichr may be configured by the portable device 110 as a current (e.g. 368 mA, 500 mA, or 777 mA) that is smaller than the maximum current Imax such as 1.75 A. The portable device 110 (or controlling circuit 1105) correspondingly. sets the output charging voltage Vchg as 5.5 Volts, 5 Volts, or 4.5 Volts when the level of battery voltage Vbat is equal to 3.6 Volts. The combination of 500 mA and 5 Volts (or the other combinations of voltages and currents) indicates that the adaptor 105 can output more or maximum power. In addition, when the portable device 110 configures the charging current Ichr as a current smaller than the maximum current Imax, the portable device 110 can control the adaptor 105 to output different voltage levels for charging. For example, when the portable device 110 configures the charging current Ichr as a current of 777 mA smaller than 1.75 A, the portable device 110 can control the adaptor 105 to output different voltage levels 4 Volts-4.5 Volts for charging. Similarly, when the portable device 110 configures the charging current Ichr as a current of 500 mA, the portable device 110 can control the adaptor 105 to output different voltage levels 4 Volts-5 Volts for charging. The charging current Ichr becomes smaller, and the range of output charging voltage level becomes wider. It should be noted that the example shown in FIG. 2 is merely used for illustrative purposes and is not intended to be a limitation of the present invention; in other examples, the battery voltage Vbat may be changed with time when the adaptor 105 continuously charges the battery 1103, and the safe operating area of the conductive circuit element 1101 becomes different correspondingly. In addition, the maximum power dissipation (i.e. power dissipation threshold) of the conductive circuit element, 0.7 W, is merely used for illustrative purposes and is not intended to be a limitation of the present invention.
Please refer to FIG. 3, which is a diagram illustrating I-V curve of the adaptor 105 according to the embodiments of FIG. 1. The controlling circuit 1105 is arranged to adjust the charging current Ichr after determining/configuring the output charging voltage Vchg. As shown in FIG. 3, for example, the controlling circuit 1105 or the portable device 110 can control the adaptor 105 to supply a current of 1 A (i.e. the charging current Ichr) and 5 Volts (i.e. the output charging voltage Vchg) for charging the battery 1103. The adaptor 105 is capable of providing the power of 5 W. Alternatively, the controlling circuit 1105 or portable device 110 can control the adaptor 105 to decrease and configure the output charging voltage Vchg as 4.6 Volts that is lower than 5 Volts, and then control the adaptor 105 to select one current value from a range of 1000 mA-1086 mA as the charging current Ichr for charging the battery 1103. If the charging current Ichr is configured as 1086 mA, then this indicates that the adaptor 105 is still providing the output power of 5 W almost. The adaptor 105 substantially keeps its output power at 5 W. Also, the charging current Ichr can be still configured as 1 A. Alternatively, the controlling circuit 1105 or portable device 110 can control the adaptor 105 to decease and configure the output charging voltage Vchg as 3.8 Volts lower than 4.6 Volts, and then control the adaptor 105 to select one current value from a range of 1000 mA-1315 mA as the charging current Ichr for charging the battery 1103. If the charging current Ichr is configured as 1315 mA, then this indicates that the adaptor 105 is still providing the output power of 5 W almost. The adaptor 105 substantially keeps its output power at 5 W. Also, the charging current Ichr can be still configured as 1 A or 1.086 A. That is, when the controlling circuit 1105 (or portable device 110) configures the charging voltage Vchg as a lower level, the charging current Ichr that can be supplied by the adaptor 105 to the battery 1103 can be increased for rapidly charging the battery 1103 especially in a constant current charging mode, and the adaptor 105 is capable of substantially keeping its output power at a rated maximum output power such as 5 W.
In order to make readers easily understand the spirit of the present invention, FIG. 4 is provided to show a control flowchart of the operations of the charging system 100 as shown in FIG. 1 according to an embodiment of fast charging in the present invention. Provided that substantially the same result is achieved, the steps of the flowchart shown in FIG. 4 need not be in the exact order shown and need not be contiguous, that is, other steps can be intermediate. The steps are detailed in the following:
Step 405: The controlling circuit 1105 of portable device 110 (i.e. a charging host) communicates with the adaptor 105 via a specific communication interface such as a USB communication interface;
Step 410: The controlling circuit 1105 of portable device 110 checks whether the adaptor 105 is a controllable adaptor or not. If the adaptor 105 is controllable, the flow proceeds to Step 415, otherwise, the flow proceeds to Step 450;
Step 415: The controlling circuit 1105 of portable device 110 determines or calculates the maximum charging current Imax according to the power dissipation threshold Pdmax and the voltage drop VCE across the conductive circuit element 1101, and configures the charging current Ichr as the maximum charging current Imax;
Step 420: The sensing circuit 1104 senses the battery voltage Vbat, and the controlling circuit 1105 gradually raise up the charging voltage Vchg provided by the adaptor 105 according to the sensed battery voltage Vbat and the voltage drop VCE;
Step 425: The sensing circuit 1104 is arranged to sense the charging current Ichr and check whether the charging current Ichr reaches the maximum charging current Imax that has been configured. If the charging current Ichr reaches the maximum charging current Imax, the flow proceeds to Step 430, otherwise, the flow proceeds back to Step 420.
Step 430: The sensing circuit 1104 is arranged to sense and check whether the actual power dissipation of the conductive circuit element 1101 exceed above the power dissipation threshold Pdmax or not by using a temperature sensor to detect the operating temperature of conductive circuit element 1101. If the detected temperature is lower than a temperature threshold, this may indicate that the actual power dissipation of conductive circuit element 1101 does not exceed above the power dissipation threshold Pdmax and the flow proceeds to Step 435; otherwise, the flow proceeds to Step 450;
Step 435: The controlling circuit 1105 of portable device 110 sets/configures the adjusted output charging voltage Vchg provided by the adaptor 105;
Step 440: The sensing circuit 1104 is arranged to sense the battery voltage Vbat, and the controlling circuit 1105 is arranged to estimate whether the sensed battery voltage Vbat is changed or not. If the sensed battery voltage Vbat is changed, the flow proceeds to Step 420; otherwise, the flow proceeds to Step 445.
Step 445: The controlling circuit 1105 controls and keeps the adaptor 105 to output the output charging voltage Vchg that has been set/configured in Step 435; and
Step 450: End.
In Step 405, the portable device 110 is arranged to communicate with the adaptor 105 via the specific communication interface such as USB communication interface.
In practice, the USB communication interface may be implemented by using a USB cable, and the portable device 110 can send information or commands to the adaptor 105 via data line (i.e. D+ or D−) and/or power supply line (i.e. VBUS) of the USB cable so as to control/adjust the output characteristics of the adaptor 105. It should be noted that the above-mentioned example is not meant to a limitation of the present invention. Other examples of using different communication interfaces or using different communication protocols to control/adjust the output characteristics of the adaptor 105 should fall within the scope of the present invention.
In Step 410, before controlling the output characteristics of the adaptor 105, the portable device 110 is arranged to check whether the adaptor 105 is a controllable adaptor capable of supporting this controllable scheme. In this embodiment, the adaptor 105 is a controllable adaptor, and the flow proceeds to Step 415 so that the portable device 110 begins to control the output characteristics of the adaptor 105. However, if another adaptor not supporting this controllable scheme is connected to the portable device 110, the flow proceeds to Step 450 and the portable device 100 is not arranged to control the output characteristics of this adaptor.
In Step 415, the controlling circuit 1105 is arranged to configure the charging current Ichr as the maximum charging current Imax so as to achieve the purpose of fast charging. However, in other embodiments, the controlling circuit 1105 can configure the charging current Ichr as a current that is slightly smaller than the maximum charging current Imax, to achieve the purpose of fast charging. This modification can also reduce the whole charging time effectively.
The above-mentioned temperature sensor employed by the sensing circuit 1104 may be implemented by using a negative temperature coefficient (NTC) thermistor or a positive temperature coefficient (PTC) thermistor. The modifications of implementation of the temperature sensor should fall within the scope of the present invention.
Additionally, the portable device 110 can inform the adaptor 105 of the condition of the battery 1103, and control the adaptor 105 to dynamically provide/supply different output characteristics corresponding to different operation modes. According to a third embodiment of the present invention, the adaptor 105 comprises a normal mode and a green mode (or called sleep mode). Under the normal mode, the controlling circuit 1105 of portable device 110 controls the adaptor 105 to provide normal output characteristics such as a normal output power. The normal output characteristics may include AC-to-DC switching frequency, AC-to-DC bias current, the precision of output voltage, voltage ripple, and/or the dynamic loading, etc. The controlling circuit 1105 can control the sensing circuit 1104 to sense the condition of the battery 1103 (i.e. the loading condition), and control the adaptor 105 to decrease the output characteristics of the adaptor 105 if it has been not required for the adaptor 105 to charge the battery 1103. In this situation, the controlling circuit 1105 is arranged to control the adaptor 105 to exit from the normal mode and enter the green mode or sleep mode. That is, the portable device 110 can sense the loading condition and control the adaptor 105 exit from the normal mode and enter the green mode or sleep mode according to the sensing result. In addition, the controlling circuit 1105 can also control the adaptor 105 to decrease the output characteristics and control the adaptor 105 to enter the green mode or sleep mode if the controlling circuit 1105 estimates that the portable device 110 switches from a heavy loading condition to a light loading condition.
Additionally, in other embodiments, the adaptor 105 may be designed as an adaptor device operating under the green mode or sleep mode according to the default setting. Under the green mode or sleep mode, the controlling circuit 1105 of portable device 110 controls the adaptor 105 to provide the decreased/reduced output characteristics such as a lower output power. The controlling circuit 1105 can check whether the adaptor 105 is connected to portable device 110 to charge the battery 1103, and can control the adaptor 105 to increase the output characteristics of the adaptor 105 and control the adaptor 105 to exit from the green mode or sleep mode to enter the normal mode if it is required for the adaptor 105 to charge the battery 1103. That is, the portable device 110 can sense the loading condition and control the adaptor 105 exit from the green mode or sleep mode and enter the normal mode according to the sensing result. In addition, the controlling circuit 1105 can also control the adaptor 105 to increase the output characteristics of the adaptor 105 so as to control the adaptor 105 to enter the normal mode if the controlling circuit 1105 estimates that the portable device 110 switches from a light loading condition to a heavy loading condition.
In addition, the portable device 110 as shown in FIG. 1 employs the linear charger structure; however, this is not intended to be a limitation of the present invention. Other types of charger structure can be also applied into the portable device 110. For example, the portable device 110 can also employ the switching mode charger structure. This also falls within the scope of the present invention.
According to the above-mentioned embodiments, the portable device 110 can communicate with the controllable adaptor 105 via a variety of communication interfaces and control output characteristics of the controllable adaptor 105, to achieve the purpose of fast charging, avoid thermal damage, enhance/improve the whole charging efficiency, and to save more power.
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. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.

Claims

1. A portable device capable of controlling output characteristics of an adaptor which is used for charging a battery of the portable device, comprising:

a sensing circuit, for sensing a condition of the battery; and

a controlling circuit, coupled to the sensing circuit, for controlling the adaptor to adjust its output characteristics based on the condition of the battery.

2. The portable device of claim 1, wherein the output characteristics comprises a charging current, a charging voltage, a switching frequency, a bias current, a precision of output voltage, a voltage ripple, and a dynamic loading.

3. The portable device of claim 1, wherein the sensing circuit is arranged to sense a battery voltage of the battery, and the controlling circuit is arranged to control the adaptor according to the sensed battery voltage.

4. The portable device of claim 3, wherein the controlling circuit is arranged to configure a charging current and then to adjust a charging voltage according to the sensed battery voltage.

5. The portable device of claim 3, wherein the controlling circuit is arranged to configure a charging current as a maximum charging current which can be supplied by the adaptor based on the sensed battery voltage.

6. The portable device of claim 5, wherein the controlling circuit is arranged to determine the charging voltage provided by the adaptor according to the maximum charging current and a power dissipation threshold, and to control the adaptor to output the determined output voltage and the maximum charging current.

7. The portable device of claim 6, further comprising:

a conductive circuit element, coupled between the battery and an input of the portable device;

wherein the sensing circuit is arranged to sense a voltage drop across the conductive circuit element and the controlling circuit is arranged to estimate the maximum charging current according to the power dissipation threshold and the voltage drop.

8. The portable device of claim 3, wherein the charging current determined by the controlling circuit is inversely proportional to a voltage difference between the charging voltage and the sensed battery voltage.

9. The portable device of claim 3, wherein the controlling circuit is arranged to configure a charging voltage and then to adjust a charging current according to the sensed battery voltage.

10. The portable device of claim 9, wherein the controlling circuit is arranged to configure the charging voltage and then to adjust the charging current according to the sensed battery voltage, to keep the adaptor supply/provide a rated output power substantially.

11. The portable device of claim 1, wherein the sensing circuit is arranged to sense a loading of the battery, and the controlling circuit is arranged to control the adaptor to decrease the output characteristics of the adaptor and control the adaptor to enter a green mode or a sleep mode when the loading switches from a heavy loading condition to a light loading condition.

12. The portable device of claim 1, wherein the sensing circuit is arranged to sense a loading of the battery, and the controlling circuit is arranged to control the adaptor to raise up the output characteristics of the adaptor and control the adaptor to exit from a green mode or a sleep mode when the loading switches from a light loading condition to a heavy loading condition.

13. A method for employing a portable device to control output characteristics of an adaptor which is used for charging a battery of the portable device, comprising:

sensing a condition of the battery; and

controlling the adaptor to adjust its output characteristics based on the condition of the battery.

14. The method of claim 13, wherein the output characteristics comprises a charging current, a charging voltage, a switching frequency, a bias current, a precision of output voltage, a voltage ripple, and a dynamic loading.

15. The method of claim 13, wherein the step of sensing the condition of the battery comprises:

sensing a battery voltage of the battery; and

the step of controlling the adaptor to adjust its output characteristics based on the condition of the battery comprises:

controlling the adaptor according to the sensed battery voltage.

16. The method of claim 15, wherein the step of controlling the adaptor according to the sensed battery voltage comprises:

configuring a charging current; and

adjusting a charging voltage according to the sensed battery voltage.

17. The method of claim 15, wherein the step of controlling the adaptor according to the sensed battery voltage comprises:

configuring a charging current as a maximum charging current which can be supplied by the adaptor based on the sensed battery voltage.

18. The method of claim 17, wherein the step of controlling the adaptor according to the sensed battery voltage further comprises:

determining the charging voltage provided by the adaptor according to the maximum charging current and a power dissipation threshold; and

controlling the adaptor to output the determined output voltage and the maximum charging current.

19. The method of claim 18, further comprising:

sensing a voltage drop across a conductive circuit element coupled between the battery and an input of the portable device; and

estimating the maximum charging current according to the power dissipation threshold and the voltage drop.

20. The method of claim 15, wherein the charging current is inversely proportional to a voltage difference between the charging voltage and the sensed battery voltage.

21. The method of claim 15, wherein the step of controlling the adaptor according to the sensed battery voltage comprises:

configuring a charging voltage; and

adjusting a charging current according to the sensed battery voltage.

22. The method of claim 21, wherein the step of controlling the adaptor according to the sensed battery voltage further comprises:

keeping the adaptor supply/provide a rated output power substantially.

23. The method of claim 13, wherein the step of sensing the condition of the battery comprises:

sensing a loading of the battery; and

the method further comprises:

controlling the adaptor to decrease the output characteristics of the adaptor and controlling the adaptor to enter a green mode or a sleep mode when the loading switches from a heavy loading condition to a light loading condition.

24. The method of claim 13, wherein the step of sensing the condition of the battery comprises:

sensing a loading of the battery; and

the method further comprises:

controlling the adaptor to raise up the output characteristics of the adaptor and controlling the adaptor to exit from a green mode or a sleep mode when the loading switches from a light loading condition to a heavy loading condition.

25. An adaptor used for charging a battery of a portable device, wherein an output characteristic of the adaptor is configurable according to a condition of the battery.