Abstract:
The present invention provides a charging mode control circuit and method. By utilizing such charging mode control circuit and method, a secondary battery fixed in a portable device can be quickly charged when the portable device communicate with an external computer. The method includes the steps of: a) providing a commutator, the commutator comprising an adaptor, a first interface, and a second interface, wherein the first interface is connected to the external computer and the second interface is connected to the portable device; b) filtering a charging voltage from the adaptor and obtaining a ripple voltage from the charging power supply; c) rectifying the ripple voltage; d) comparing the rectified ripple voltage with a reference voltage, thereby producing a voltage waveform signal according to a comparison result; and e) selecting a fast charging mode for the secondary battery according to the voltage waveform signal.

Description:
TECHNICAL FIELD  
       [0001]     The present invention relates to a charging mode control circuit and method, particularly to a charging mode control circuit and method used in a portable device.  
       RELATED ART  
       [0002]     Portable devices with Universal Serial Bus (USB) interfaces such as portable computers are welcomed by users for their small size and convenient usage. At present there are generally two solutions for charging a secondary battery equipped in a portable device.  
         [0003]     One of the solution is shown in  FIG. 1  where a portable device  11  is connected with a computer  12  via their USB interfaces (i.e., USB interface  113  and USB interface  121 ). According to the protocol standards of USB 1.1 and USB 2.0, the maximum power transmitted by USB interfaces is 2.5 watt (0.5 A @ 5V), in other words, the computer supplies no more than 500 mA charging current under the charging voltage of +5V. Given these circumstances, a secondary battery  111  fixed within the portable device  11  can obtain a charging current from the computer  12  while in-link with the computer, however this charging current is rather small and the charging speed is rather slow.  
         [0004]     Another solution is shown in  FIG. 2 , a portable device  21  is connected to a mains supply  24  via an alternating current to direct current converter (AC/DC) adapter  22 . The portable device  21  and the AC/DC adapter  22  both have a USB interface (i.e., USB interface  213  and USB interface  221 ) for inter-connecting to each other. A secondary battery  211  fixed within the portable device  21  obtains a charging current from a mains supply  24  after the AC/DC adapter  22  performs the voltage transformation. By using such a charging means, a secondary battery  211  fixed within the portable device  21  can obtain a fairly bigger current resulting in a quicker charging speed, however, the portable device will not be able to communicate with an external computer when the battery  211  is charging.  
         [0005]     Accordingly, it would be advantageous if the secondary battery fixed in the portable device can obtain a charging current with a fairly faster speed without terminating the data transmission between the computer and the portable device.  
       SUMMARY  
       [0006]     A charging mode control method is provided. The method is for charging a secondary battery fixed in a portable device during same time period of data communication with an external computer. The method includes the steps of: a) providing a commutator, the commutator comprising an adaptor, a first interface, and a second interface, wherein the first interface is connected to the external computer and the second interface is connected to the portable device; b) filtering a charging voltage from the adaptor and obtaining a ripple voltage from the charging power supply; d) comparing the rectified ripple voltage with a reference voltage, thereby producing a voltage waveform signal according to a comparison result; and e) selecting a fast charging mode for the secondary battery according to the voltage waveform signal.  
         [0007]     A charging mode control circuit is further provided. The charging mode control circuit is for selecting an appropriate charging mode for a secondary battery according to a voltage waveform signal. The charging mode control circuit includes: a filtering circuit for filtering a charging voltage and obtaining ripple voltages from the charging voltage; a rectification circuit for rectifying the ripple voltages from the filtering circuit; a comparing circuit having two inputs that receive the rectified ripple voltage and a reference voltage respectively, and an output which outputs a voltage waveform signal according to a comparison result of the rectified ripple voltage and the reference voltage; and a charging control circuit for selecting a corresponding charging mode for the secondary battery according to the voltage waveform signal from the comparing circuit.  
         [0008]     A commutator for connecting a portable device and an external communication device is provided. The commutator includes an adapter for obtaining a charging voltage from a mains supply, the AC/DC adapter having a VCC (power) line and a GND (Ground) line; a first interface for connecting an external communication device and transmitting data from the external communication device, the first interface having a VCC pin, a GND pin, and a plurality of data pins; and a second interface for connecting the adapter and the portable device, the second interface having a VCC pin, a GND pin, and a plurality of data pins; wherein the GND pin and the data pins of the second interface respectively connect to the GND pin and the data pins of the first interface, and the GND pin and the VCC pin of the second interface further connect to the GND line and the VCC line of the adapter respectively.  
         [0009]     Based on the present invention, the secondary battery can be charged in a fast-charging mode by inserting the commutator which include the AC/DC adaptor therein between the communication device and the portable device. The AC/DC adaptor provides a relative large current for the charging mode control circuit, which make it feasible to charge the secondary battery fixed within the portable device quickly during data transmission with an external communication device.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1  is a block diagram of an exemplary application of prior charging means;  
         [0011]      FIG. 2  is a block diagram of another exemplary application of prior charging means;  
         [0012]      FIG. 3  is a block diagram of an exemplary application of a charging mode control circuit and method in accordance with a preferred embodiment of the present invention; and  
         [0013]      FIG. 4  depicts details of an exemplary charging mode control circuit of  FIG. 3 . 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0014]      FIG. 3  is a block diagram of an exemplary application of a charging mode control circuit and method in accordance with a preferred embodiment of the present invention. Shown here are a portable device  31 , a commutator  32 , and a computer  33 . The portable device  31  has a charging mode control circuit  312  incorporated therein and a secondary battery  311  fixed therein. The charging mode control circuit  312  is used to select a selective charging mode on the secondary battery  311  according to a peculiar charging power supply available.  
         [0015]     The commutator  32  includes an adapter  323  and two USB interfaces  321  and  322 . The USB interface  321  is connected directly to the USB interface  313  of the portable device  31  and the USB interface  322  is connected directly to the USB interface  322  of the computer  33 . Each of the USB interfaces  321  and  322  has a VCC (power) pin, a GND (ground) pin, and a plurality of DATA pins. The AC/DC adapter  323  has a VCC line and a GND line. The VCC pin and the GND pin of the USB interface  321  are respectively connected to the VCC line and the GND line of the AC/DC adapter  323 , thereby obtaining a charging power supply from an external power supply (not shown) via the AC/DC adapter  323 . Furthermore, the GND pin and DATA pins of the USB interface  321  are respectively connected to the GND pin and DATA pins of the USB interface  322 , thereby communicating with the computer  33  when the USB interface  322  is connected to a USB interface  331  of the computer  33 . The VCC pin of the USB interface  322  is kept idle.  
         [0016]     Thus, by utilizing such connections, the portable device  30  not only can quickly obtain the charging power supply with a fairly great current (larger than 500 mA) from the external mains supply, but can also perform data communications with the computer  33 . During this charging process, the charging mode control circuit  312  chooses a rapid charging mode on the secondary battery  311 .  
         [0017]      FIG. 3  shows the charging mode of the secondary battery  311  obtaining a large charging current (referred to as “a fast-charging mode”). If the portable device  11  is associated with the computer  12  via their own USB interfaces (i.e., USB interface  313  and USB interface  331 ) similar to  FIG. 1 , the secondary battery  311  obtains a small charging current (referred to as “a slow-charging mode”). The two charging modes both support data communication between the portable device  31  and the computer  33  while the secondary battery  311  is charging.  
         [0018]      FIG. 4  depicts details of an exemplary charging mode control circuit. Shown here are a charging mode control circuit  312  and a secondary battery  311 . The charging mode control circuit  312  mainly includes a filtering circuit  41 , a protecting circuit  42 , a comparing circuit  43 , an integral circuit  44 , and a charging control circuit  45 .  
         [0019]     The filtering circuit  41  includes two resistances R 1  and R 2 , and two capacitors C 1  and C 2 . The resistance R 1  and the capacitor C 1  have a serialized combination therebetween (referred to as a “serial R 1 C 1 ”), and the resistance R 2  and the capacitor C 2  have a parallelized combination therebetween (referred to as a “parallel R 2 C 2 ”). A resistance end of the serial R 1 C 1  is connected to a cathode of a diode D 4 , and a capacitance end of the serial R 1 C 1  is connected to an end of the parallel R 2 C 2  (namely, node “a”). The node “a” further connects to an anode of a diode D 1  of the protecting circuit  42  and a positive input of the comparing circuit  43 . In addition, the other end of the parallel R 2 C 2  is connected to an analog ground (GND).  
         [0020]     The protecting circuit  42  includes two diodes D 1  and D 2 , a resistance R 3 , and a capacitor C 3 . The diodes D 1  and D 2  have a serialized combination therebetween (referred to as a “serial D 1 D 2 ”). The resistance R 3  and the capacitor C 3  have a serialized combination therebetween (referred to as a “serial R 3 C 3 ”). A cathode of diode D 2  is connected to a resistance end of the serial R 3 C 3  (namely, node “d”). The node “d” further connects to a cathode of a diode D 3 , an end of a capacitor C 4 , and a resistance R 4  of the comparing circuit  43 . In addition, the other end of the serial R 3 C 3  is connected to the analog ground (GND). The diode D 1  and diode D 2  have a node “c” therebetween, as well as the resistance R 3  and capacitance C 3  have a node “b” therebetween. The node “b” is further directly connected to the node “c”.  
         [0021]     The comparing circuit  43  includes a comparator CP, a reference voltage generating circuit, and a feedback circuit. The comparator CP has a positive input and an inverse input. The reference voltage generating circuit has two serialized resistances R 4  and R 5  (referred to as a “serial R 4 R 5 ”). The feedback circuit has a resistance R 6 . The comparing circuit  43  associates with the filtering circuit  41  by a resistance R 4  connecting to the node “d” and associates with the protecting circuit  42  by the positive input of the comparator CP. The serial R 4 R 5  has a node “e” therebetween. The node “e” is connected to the inverse input of the comparator CP and the resistance R 6 . One end of the serial R 4 R 5  is connected to the cathode of the diode D 3  for receiving a reference voltage Vcc 2  that is filtered by a filtering circuit component of the diode D 3  and the capacitance C 4 . The other end of the serial R 4 R 5  is connected to the analog ground (GND). As to the feedback circuit, two end of the resistance R 6  are respectively connected to the output of the comparator CP and the inverse input of the comparator CP.  
         [0022]     The integral circuit  44  includes a resistance R 7  and a capacitance C 5 . One end of the resistance R 7  is connected to the output of the comparator CP, and the other end of the resistance R 7  is serially connected to one end of the capacitance C 5  by a node “f”. The other end of the capacitance C 5  is connected to the analog ground (GND). The node “f” is also connected to the charging control circuit  45 .  
         [0023]     The charging control circuit  45  includes two input ports “Cn” and “Pin”, and an output port “Out”. The input port “Cn” is connected to the node “f”, and the input port “Pin” is connected to the charging voltage Vin 1  (Vcc 1 ). The output port “Out” is connected to the secondary battery  311 .  
         [0024]     The filtering circuit  41  receives a charging voltage Vin 1  (VCC 1 ), (including direct voltage and alternating voltages with various amplitudes) from an external power supply (e.g., a computer or a mains supply), and filters out the direct voltage therein, thereby obtaining the alternating voltages (referred to as “ripple voltage Vout 1 ”). Further, the ripple voltage Vout 1  is a resultant voltage from a plural of voltages with various amplitudes. The amplitudes of the plural of voltages are different due to different external power supplies. Therefore, the ripple voltage Vout 1  has different amplitudes in regards to the different external power supplies. For example, if the external power supply is the mains supply, the amplitude of the maximum voltage Vm 1  of the ripple voltage Vout 1  is equal to or more than 100 mV; alternatively, if the external power supply is the computer  33 , the amplitude of the maximum voltage Vm 2  of the ripple voltage Vout 1  is less than 100 mV.  
         [0025]     The voltage comparing circuit  43  receives the ripple voltage Vout 1  via the positive input of the comparator CP and the reference voltage Vref via the inverse input of the comparator CP. The comparator CP produces a selective voltage waveform Vout 2  after comparing the ripple voltage Vout 1  with the reference voltage Vref. The reference voltage Vref can be set according to the ripple voltage Vout 1 , that is, the reference voltage Vref is in a range from Vm 1  to Vm 2 . For example, supposing Vm 1  is 500 mV and Vm 2  is 100 mV, for simplicity, the reference voltage Vref is set to 300 mV. Given these circumstances, if the ripple voltage Vout 1  is filtered from the mains supply, the voltage waveform Vout 2  is a rectangular-wave; if the Vout 1  is filtered from the computer, the voltage waveform Vout 2  is a continuous low voltage level waveform.  
         [0026]     The integral circuit  44  integrates the selective voltage waveform Vout 2  and produces a corresponding control waveform single Vout 3 . If the voltage waveform Vout 2  is a rectangular-wave, the waveform of the control waveform single Vout 3  is a saw-tooth waveform or a triangle waveform; if the voltage waveform Vout 2  is a continuous low voltage level waveform, the waveform of the control waveform single Vout 3  is also a continuous low voltage level waveform.  
         [0027]     The charging control circuit  45  identifies the charging power supply according to the control waveform single Vout 3  from the integral circuit  44 , and selects a selective charging mode on charging the secondary battery  311 . The input port “Pin” receives the voltage Vin 1  (Vcc 1 ) from the VCC pin of the USB interface  313 , and the input port “Cn” receives the charging control waveform Vout 3  from the output of the integral circuit  44 . The output port “Out” outputs a selective charging current for the secondary battery  311 .  
         [0028]     For example, if the voltage waveform signal Vout 3  is a triangle wave, the charging control circuit  45  selects the fast-charging mode on the secondary battery  311  with a relative large charging current between 0 mA and 1000 mA; if the voltage waveform Vout 3  is the continuous low voltage level waveform, the charging control circuit  45  selects the slow-charging mode on the secondary battery  311  with a relative small charging current between 0 mA and 500 mA.  
         [0029]     The protecting circuit  42  here is used to prohibit an impairment caused by a large instantaneous charging current Vin 1 . As described, a voltage of the node “a” is equal to the ripple voltage Vout 1 , and a voltage of the node “d” is supplied from the reference voltage supply Vcc 2 . Therefore, under normal conditions, the diode D 1  maintains a cut-off state because the amplitude of the ripple voltage Vout 1  held on the node “a” is far less than the amplitude of the voltage held on the node “d” supplied from the reference voltage supply Vcc 2 . When a very large instantaneous voltage surges in the charging voltage Vcc 1 , the amplitude of the ripple voltage Vout 1  held on the node “a” is larger than the amplitude of the voltage held on the node “d” that is supplied by the reference voltage supply Vcc 2 , thereupon the protecting circuit  42  initiates to work and the capacitance C 3  eliminates the very large instantaneous charging voltage for prohibiting the impairment to the charging mode control circuit  312 .  
         [0030]     It is believed that the present embodiments and their advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments of the invention.