Abstract:
A power adapter for an electronic device selectively works in different modes according to a working state signal of the electronic device. When the electronic device is powered off or on with a battery in a determined charge state, the power adapter controls a relay to turn off the relay to disconnect power to the electronic device.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present disclosure relates to power adapters and power supply methods, and particularly to a power adapter of a electronic device and a power supply method of the power adapter. 
         [0003]    2. Description of Related Art 
         [0004]    As long as a power adapter is connected to an electronic device, such as a notebook computer, the power adapter will continue to supply a working voltage to the electronic device, even if the electronic device is powered off or working off the battery. Therefore, power is wasted. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  is a block diagram of an exemplary embodiment of a power adapter connected to an electronic device. 
           [0006]      FIG. 2  is one embodiment of a circuit diagram of the power adapter and the electronic device of  FIG. 1 . 
           [0007]      FIG. 3  is a flowchart of an exemplary embodiment of a power supply method of the power adapter of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0008]    Referring to  FIG. 1 , an exemplary embodiment of a power adapter  100  is applied to an electronic device  200 . The power adapter  100  includes a power input interface  10 , a power output interface  20 , an alternating current/direct current (AC/DC) converter  30 , a first switch  40 , a relay  50 , a relay drive circuit  60 , a microprocessor  70 , and a power converting circuit  80 . The electronic device  200  includes a power input port  210 , a universal serial bus (USB) connector  220 , and a battery  230 . In one embodiment, the electronic device may be a notebook computer, for example. 
         [0009]    Referring to  FIG. 2 , the power input interface  10  is connected to an alternating current (AC) power supply P 1 , such as a 120V, to receive an AC voltage signal, and transmit the AC voltage signal to the power converting circuit  80  via the first switch  40 , the relay  50 , and the power output port  20 . 
         [0010]    The AC/DC converter  30  receives the AC voltage signal from the AC power supply P 1  via the power input interface  10 , and converts the AC voltage signal into a 5V first direct current (DC) voltage signal, for the relay  50  and the microprocessor  70 . 
         [0011]    The first switch  40  is a single-pole-double-throw (SPDT) switch including a pole  1 , a first throw  2 , and a second throw  3 . The pole  1  is connected to the power input interface  10  to receive the AC voltage signal. The first throw  2  is connected to the power output interface  20 . The second throw  3  is connected to the power output interface  20  via the relay  50 . The power adapter  100  works in a common mode when the pole  1  is connected to the first throw  2 , in which the AC voltage signal from the AC power supply P 1  is provided for the power converting circuit  80  directly via the power output port  20 . The power adapter  100  works in an energy saving mode when the pole  1  is connected to the second throw  3 , in which the AC voltage signal from the AC power supply P 1  is provided for the power converting circuit  80  via the relay  50  and the power output port  20 . 
         [0012]    The relay  50  includes a second switch K and a coil J. The second switch K is connected between the second throw  3  of the first switch  40  and the power output interface  20 . A first end of the coil J is connected to the AC/DC converter  30 , to receive the 5V first DC voltage signal via two resistors R 1  and R 2  in series, and is also grounded via a capacitor C 1 . A second end of the coil J is connected to the relay drive circuit  60 , to receive a first or a second drive signal from the relay drive circuit to drive the second switch K of the relay  50 . 
         [0013]    The relay drive circuit  60  includes a transistor Q 1 . The collector of the transistor Q 1  is connected to the second coil J of the relay  50 , to output the first or the second drive signal to the relay  50 . In this embodiment, the first drive signal is a low level signal of about 0 volts and the second drive signal is a high level signal of about 5 volts. The emitter of the transistor Q 1  is grounded. The base of the transistor Q 1  is connected to the microprocessor  70 , to receive a first or a second control signal from the microprocessor  70 . In this embodiment the first control signal is a high level signal of about 3.3 volts and the second control signal is a low level signal of about 0 volts. In another exemplary embodiment, the relay drive circuit  60  can be replaced by another kind of drive circuit, such as a metallic oxide semiconductor field effect transistor (MOSFET), a transistor combination circuit, a MOSFET combination circuit, a transistor-MOSFET combination circuit, and so on. 
         [0014]    In one exemplary embedment, the microprocessor  70  may be a EM78612A type chip. A pin P 63  of the microprocessor  70  is connected to a pin VSS of the USB connector  220  of the electronic device  200 , and also connected to a pin V3.3V of the microprocessor  70 . A pin P 72  of the microprocessor  70  is connected to the base of the transistor Q 1  via a resistor R 4 . A pin VSS of the microprocessor  70  is grounded, and connected to the pin V3.3V of the microprocessor  70  via a capacitor C 2 . The pin V3.3V is to output a 3.3V signal. Pins OSCI and OSCO of the microprocessor  70  are interconnected via a crystal Y 1 , and both grounded respectively via capacitors C 3  and C 4 . A pin VDD of the microprocessor  70  is grounded via parallel capacitors C 5  and C 6 , and connected to the AC/DC converter  30  to receive the first DC voltage signal. Pins P 50  and P 51  are correspondingly connected to pins D+ and D− of the USB connector  220  of the electronic device  220 . Other pins P 61 , P 62 , P 70 , P 71 , P 65 , P 64 , and P 60  are all null, in one embodiment. 
         [0015]    The power converting circuit  80  is connected between the power output interface  20  and the power input port  210  of the electronic device  200 , to convert the AC voltage signal output from the power output interface  20  into a second DC voltage signal for the electronic device  200 . The second DC voltage signal may be 19V, in one example. 
         [0016]    When the power input interface  10  is connected to the AC power supply P 1 , and at the same time, the pole  1  of the first switch  40  is connected to the second throw  3  to make the electronic device  200  work in the energy saving mode. In the energy saving mode, the AC/DC converter  30  converts the AC voltage signal into the 5V first DC voltage signal for powering the microprocessor  70 . The pin P 72  of the microprocessor  70  outputs the first control signal to turn on the transistor Q 1 . The transistor Q 1  outputs the first drive signal to close the second switch K, thereby the AC power supply P 1  is connected to the power converting circuit  80  via the first switch  40 , the relay  50 , and the power output interface  20 , and the AC voltage signal is converted into the 19V second DC voltage signal for the electronic device  200 . 
         [0017]    If the electronic device is powered off or on but using the battery  230  and the battery  230  is more than 80% charged, the electronic device  200  outputs a first computer state signal via the USB connector  220  to the microprocessor  70 . The pin P 72  of the microprocessor  70  outputs the second control signal to turn off the transistor Q 1 . The transistor Q 1  outputs the second drive signal to open the second switch K of the relay  50 . Therefore, the AC power supply P 1  is disconnected from the power converting circuit  80 . The power adapter  100  will not provide the 19V second DC voltage signal to the electronic device  200  anymore. 
         [0018]    In one exemplary embodiment, when the electronic device is on and using the battery  230  more than 80% charged, the microcomputer  70  is set to alternately output the first control signal for 5 minutes and the second control signal for 55 minutes, repeatedly. Therefore, the battery  230  can be charged for 5 minutes every hour to avoid discharging the battery  230  completely. It may be understood that these times are exemplary and may vary depending on the embodiment. 
         [0019]    However, if the electronic device  100  is on without using the battery  230  or on but using the battery  230  which is not more than 80% charged, the electronic device  200  outputs a second computer state signal for the microprocessor  70  via the USB connector  220 . The pin P 72  of the microprocessor  70  still outputs the first control signal to turn on the transistor Q 1 . The transistor Q 1  still outputs the first drive signal to close the second switch K of the relay  50 . Therefore, the AC voltage signal from the AC power supply P 1  is still provided for the power converting circuit  80 , to be converted into the 19V second DC voltage signal for the electronic device  200 . 
         [0020]    In an other exemplary embodiment, the electronic device  200  may output the first or second computer state signal according to the battery  230  with another determined charge state, such as 60% charged and 90% charged, not limited with 80% charged. 
         [0021]    Referring to  FIG. 3 , a power supply method of the power adapter  100  of the electronic device  200  includes the following steps. 
         [0022]    In step S 1 , the power input interface  10  receives an AC voltage signal from the AC power supply P 1 . 
         [0023]    In step S 2 , the AC/DC converter  30  converts the AC voltage signal into the 5V first DC voltage signal supplied for the microprocessor  70  and the relay  50 . 
         [0024]    In step S 3 , the microprocessor  70  outputs the first control signal to turn on the relay drive circuit  60 , and the relay drive circuit  60  outputs the first drive signal to close the relay  50 , thereby the power converting circuit  80  converts the AC voltage signal into the 19V second DC voltage signal for the electronic device  200 . 
         [0025]    In step S 4 , a determination is made whether the electronic device  200  is powered off. If the electronic device  200  is powered off, the flow goes to step S 5 . If the electronic device is not powered off, the flow goes to step S 6 . 
         [0026]    In step S 5 , the electronic device  200  outputs the first computer state signal for the microprocessor  70 , and the microprocessor  70  outputs the second control signal to make the relay drive circuit  60  output the second drive control signal to open the second switch K of the relay  50 . 
         [0027]    In step S 6 , a determination is made whether the electronic device  200  is installed with the battery  230  or not. If the electronic device  200  is not installed with the battery  230 , the flow goes to step  7 . If the electronic device  200  is installed with the battery  230 , the flow goes to step S 8 . 
         [0028]    In step S 7 , the electronic device  200  outputs the second computer state signal for the microprocessor  70 , and the microprocessor  70  still outputs the first control signal to make the relay drive circuit  60  still output the first drive control signal to close the second switch K of the relay  50 . 
         [0029]    In step S 8 , a determination is made whether the battery  230  is more than 80% charged or not. If the battery  230  is not more than 80%, the flow returns to step S 7 . If the battery  230  is more than 80%, the flow returns to step S 5 . 
         [0030]    It is to be understood, however, that even though numerous characteristics and advantages of the present disclosure have been set forth in the foregoing description, together with details of the structure and function of the disclosure, the disclosure is illustrative only, and changes may be made in details, especially in matters of shape, size, and arrangement of parts within the principles of the disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.