Patent Abstract:
The present invention relates to a charge status indicator and a charger. The charger comprises a charging power supply and a charge status indicator, wherein, the charge status indicator comprises a detecting chip for monitoring charge status connected between the primary winding of transformer and ground, and a display module used for displaying the charge status, wherein, said detecting chip for monitoring charge status comprising: a detecting module for detecting the charging state of the charge power supply; a comparing module for determining the current charge status based on the detected charging state. By employing the charger or the charge status indicator for a charger, a primary-side feedback control Flyback SMPS may be employed, just a simple and reliable circuit is needed, and higher efficient can be achieved.

Full Description:
FIELD OF THE INVENTION 
     The present invention relates to charge device, and, more specific, to a charger and an apparatus for differentiating between different charging states and indicating a particular charge status to a user. 
     BACKGROUND OF THE INVENTION 
     At present, a charge status indicator is always provided on an AC-DC charger for displaying charge status to a user. Traditional AC-DC charger is implemented with secondary-side feedback control Flyback switching mode power supply (SMPS). Charge status indicator used in such traditional AC-DC charger is implemented by a red and green two-color common-cathode LED  223 , a PNP transistor  222 , a silicon rectifier diode  220  and resistors  219 ,  221 ,  224  (referring to  FIG. 1 ). 
     When the product of the output current Io of VOUT and the resistance of resistors  219 , V  219  (that is the voltage drop on the resistors  219 ), is higher than the VBE (about 0.6 V) of the PNP transistor  222 , that is, Io*R  219 &gt;0.6V, the PNP transistor  222  is turned on in a saturated mode, and the red LED is lighten. Due to the saturated voltage drop VCE of PNP transistor  222  is about 0.3 V, and the turn on voltage drop of the red LED in LED  223  is about 1.6 V, and the sum of both is about 1.9 V, which is lower than the sum 2.3 V of the voltage drop 0.6V on the resistors  219  and the turn on voltage drop 1.7 V of the green LED in LED  223 , that is VCE+VR&lt;V 219 +VG, so the green LED isn&#39;t lighten. 
     When the product of the output current Io of VOUT and the resistance of resistors  219 , V  219  (that is the voltage drop on the resistors  219 ), is lower than the VBE (about 0.6 V) of the PNP transistor  222 , that is, Io*R  219 &lt;0.6V, the PNP transistor  222  is turned off, and the green LED is lighten. 
     However, the said circuit according the prior art is not a good choice for AC-DC charger implemented with primary-side feedback control Flyback SMPS because of the following reasons: 
     1. When a rated load is outputted, the voltage on capacitor  213  is higher than VOUT for 0.8V-1.0V. If primary-side feedback control Flyback SMPS is employed, which will result in that the no-load voltage of output end will higher than rated load voltage for 0.8-1V. Accordingly such circuit can&#39;t be adopted in primary-side feedback control Flyback SMPS, and only can be adopted in secondary-side feedback control Flyback SMPS. 
     2. As such circuit is used to detect the voltage drop generated when charging current is passing through the resistors  219  and diode  220 , which result in low efficiency. 
     3. Too many electronic components are employed in such circuit, which result in higher costs and lower reliability. 
     Accordingly, a simple and reliable charge status indicator circuit which can be applied in primary-side feedback control Flyback SMPS. 
     SUMMARY OF THE INVENTION 
     The primary objective of this invention is to provide a simple and reliable circuitry for displaying charge status to a user which can be applied in primary-side feedback control Flyback SMPS charger. 
     The charger according with the present invention comprises a charging power supply and a charge status indicator, the charge status indicator comprises a detecting chip for monitoring charge status connected between the primary winding of transformer and ground, and a display module used for displaying the charge status, wherein, said detecting chip for monitoring charge status comprising: 
     a detecting module for detecting the charging state of the charge power supply; 
     a comparing module for determining the current charge status based on the detected charging state. 
     Advantagely, said detecting chip for monitoring charge status further comprises a display driver for driving the display module to display the charge status based on the current charge status. 
     Advantagely, said detecting module further comprises: 
     a frequency obtaining unit for obtaining the working frequency of the detecting chip for monitoring charge status, wherein, the working frequency is proportional to the charging current; 
     a frequency-electrical signal converter for converting the working frequency to an electrical signal which is proportional to the charging current. 
     Advantagely, said detecting module further comprises: 
     a sample and hold circuit for sampling electrical signal from the primary auxiliary winding of the transformer; 
     an error amplifier for comparing the sample electrical signal with a reference value and outputting an electrical signal which is proportional to the charging current. 
     Advantagely, said comparing module comprises a comparator and a filter, wherein, the forward input end of the comparator is connected to the detecting module to obtain an electrical signal which is proportional to the charging current; the reverse input end of the comparator is connected to a reference electrical signal, the output end of the comparator is connected to the input end of the filter, and the output end of the filter is connected to the display driver to output the charging state. 
     Advantagely, said display driver comprises a first driver connected to the output end of the filter for driving the display module to display the first charge status, and a second driver connected to the output end of the filter for driving the display module to display the second charge status. 
     Advantagely, the display module comprises a first LED driven by the first driver, a second LED driven by the second driver, and a current-limiting resistor connected between the anodes of the first and second LEDs and the power supply. 
     Advantagely, the first and second LEDs are common-anode LED. 
     Advantagely, the display module comprises a first LED driven by the first driver, a second LED driven by the second driver, and a current-limiting resistor connected between the cathodes of the first and second LED and the ground. 
     Advantagely, the first and second LEDs are common-cathode LED. 
     Advantagely, the display driver comprises a third driver connected to the output end of the filter for driving the display module to display the first and second charge status, and the display module comprises a third LED driven by the third driver, and a current-limiting resistor connected between the anode of the third LED and the power supply. 
     The second objective of this invention is to provide a charge status indicator which comprises a detecting chip for monitoring charge status connected between the primary winding of transformer and ground, and a display module used for displaying the charge status, wherein, said detecting chip for monitoring charge status comprising: 
     a detecting module for detecting the charging state of the charge power supply; 
     a comparing module for determining the current charge status based on the detected charging state. 
     Advantagely, said detecting chip for monitoring charge status further comprises a display driver for driving the display module to display the charge status based on the current charge status. 
     Advantagely, said detecting module further comprises: 
     a frequency obtaining unit for obtaining the working frequency of the detecting chip for monitoring charge status, wherein, the working frequency is proportional to the charging current; 
     a frequency-electrical signal converter for converting the working frequency to an electrical signal which is proportional to the charging current. 
     Advantagely, said detecting module further comprises: 
     a sample and hold circuit for sampling electrical signal from the primary auxiliary winding of the transformer; 
     an error amplifier for comparing the sample electrical signal with a reference value and outputting an electrical signal which is proportional to the charging current. 
     Advantagely, said comparing module comprises a comparator and a filter, wherein, the forward input end of the comparator is connected to the detecting module to obtain an electrical signal which is proportional to the charging current; the reverse input end of the comparator is connected to a reference electrical signal, the output end of the comparator is connected to the input end of the filter, and the output end of the filter is connected to the display driver to output the charging state. 
     Advantagely, said display driver comprises a first driver connected to the output end of the filter for driving the display module to display the first charge status, and a second driver connected to the output end of the filter for driving the display module to display the second charge status. 
     Advantagely, the display module comprises a first LED driven by the first driver, a second LED driven by the second driver, and a current-limiting resistor connected between the anodes of the first and second LEDs and the power supply. 
     Advantagely, the first and second LEDs are common-anode LED. 
     Advantagely, the display module comprises a first LED driven by the first driver, a second LED driven by the second driver, and a current-limiting resistor connected between the cathodes of the first and second LED and the ground. 
     Advantagely, the first and second LEDs are common-cathode LED. 
     Advantagely, the display driver comprises a third driver connected to the output end of the filter for driving the display module to display the first and second charge status, and the display module comprises a third LED driven by the third driver, and a current-limiting resistor connected between the anode of the third LED and the power supply. 
     By employing the charger or the charge status indicator for a charger, a primary-side feedback control Flyback SMPS may be employed, just a simple and reliable circuit is needed, and higher power conversion efficiency can be achieved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So as to further explain the invention, an exemplary embodiment of the present invention will be described with reference to the below drawings, wherein: 
         FIG. 1  is the circuit diagram of the charger according to the prior art; 
         FIG. 2  is the circuit diagram of the charger according to the first embodiment of the present invention; 
         FIG. 3  is the circuit diagram of the first embodiment of the status indicating part of the charge status indicator according to the present invention; 
         FIG. 4  is the circuit diagram of the second embodiment of the status indicating part of the charge status indicator according to the present invention; 
         FIG. 5  is the circuit diagram of the third embodiment of the status indicating part of the charge status indicator according to the present invention; 
         FIG. 6  is the circuit diagram of the fourth embodiment of the status indicating part of the charge status indicator according to the present invention; 
         FIG. 7  is a principle block diagram of the first embodiment of the charge status indicator which adapt to the status indicating part disclosed in  FIGS. 3 and 4 ; 
         FIG. 8  is a principle block diagram of the second embodiment of the charge status indicator which adapt to the status indicating part disclosed in  FIGS. 3 and 4 ; 
         FIG. 9  is a principle block diagram of the first embodiment of the charge status indicator which adapt to the status indicating part disclosed in  FIGS. 5 and 6 ; 
         FIG. 10  is a principle block diagram of the second embodiment of the charge status indicator which adapt to the status indicating part disclosed in  FIGS. 5 and 6 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     These and other advantage, aspect and novel features of the present invention, as well as details of an illustrated embodiment thereof, will be more fully understand from the following description and drawings. While various embodiments of the present invention has been presented by way of example only, and not limitation. 
       FIG. 2  is the circuit diagram of the charger according to the first embodiment of the present invention. Referring  FIG. 2 , the charger according with the present invention comprises a charging power supply and a charge status indicator. The charge status indicator comprises a detecting chip for monitoring charge status  100  connected between the primary winding of transformer and ground, and a display module  200  used for displaying the charge status. Wherein, said detecting chip for monitoring charge status  100  comprises a detecting module  101  for detecting the charging state of the charge power supply and a comparing module  102  for determining the current charging status based on the detected charging state. 
     In the embodiment disclosed in  FIG. 2 , the FB end of the detecting chip for monitoring charge status  100  is connected to the anode of the diode D 206  through resistor R 217 , and the cathode of the diode D 206  is grounded through capacitor C 205 . At the same time, the anode of the diode D 206  is connected to one end of the primary auxiliary winding of the transformer. The other end of the primary auxiliary winding of the transformer is grounded. The CS end of the detecting chip for monitoring charge status  100  is connected to the source of Power Switch  209 ; the gate of the Power Switch  209  is connected to the output end of the detecting chip  100  for monitoring charge status, that is, the Gate end. The drain of the Power Switch  209  is connected to one end of the primary winding of the transformer. The other end of the primary winding of the transformer is connected to the input voltage. 
     In the embodiment disclosed in  FIG. 2 , the detecting chip for monitoring charge status  100  also comprises a display driver  103  for driving the display module  200  to display the charge status based on the current charge status. As shown in  FIG. 2 , the detecting module  101  can be used to detect the output current of the charging power supply, and so as to monitor the charging state of the charging power supply, and then feedback the current charging state to the comparing module  102 . The comparing module  102  is an information processing module, which can be used to compare the current charging state feedback from detecting module  101  with a predefined charging state, so as to determine the current charging state of the charger. The predefined charging state may be preset. One skilled in the art may set this predefined charging state according to the actual situation. 
     For example, when the electrical signal obtained by detecting module  101  is the secondary output current, the comparing module  102  will compare this secondary output current with the one tenth-one eighth of the rating current. When the secondary output current is lower than the one tenth or one eighth of the predefined current, the current charge status is set to be the first charge status. The display driver  103  receiving the first charge status signal and drive the display module  200  to display the first charge status. When the secondary output current is higher than the one tenth or one eighth of the rating current, the current charge status is then set to be the second charge status. The display driver  103  receiving the second charge status signal and drive the display module  200  to display the second charge status. In another simplified embodiment according to present invention, the display module may receive and display the charge status directly, so no display driver is needed. 
       FIG. 3  is the circuit diagram of the first embodiment of the status indicating part of the charge status indicator according to the present invention. As shown in  FIG. 3 , the display module  200  comprises a red LED, a green LED, and a current-limiting resistor R 1  connected between the cathode of the red and green LEDs and ground. The anode of the red LED is connected to the LED_R pin of the display driver  103 , the anode of the green LED is connected to the LED_G pin of the display driver  103 , and the cathode of both the red LED and the green LED are grounded through the resistor R 1 . 
     In the present invention, when the comparing module  102  determine the current charge status is the second charge status, the LED_R pin of the display driver  103  output high level, and the red LED is lighten. When the comparing module  102  determine the current charge status is the first charge status, the LED_G pin of the display driver  103  output high level, and the green LED is lighten. 
       FIG. 4  is the circuit diagram of the second embodiment of the status indicating part of the charge status indicator according to the present invention. Referring to  FIG. 4 , when the comparing module  102  inside the chip output the second charge status, the LED_R pin output low level, and the LED_G pin output high level, so red LED is lighten, and the green LED isn&#39;t lighten or only slightly lighten. When the comparing module  102  inside the chip output the first charge status, the LED_G pin output low level, and the LED_R pin output high level, so green LED is lighten, and the red LED isn&#39;t lighten or only slightly lighten. Resistor R 1  is the current-limiting resistor for LED, and the red and green LEDs are common-anode LEDs. As shown in  FIG. 4 , the detecting chip for monitoring charge status  100  also comprises a high voltage starting module for providing high starting voltage to the common-anode LEDs. 
       FIG. 5  is the circuit diagram of the third embodiment of the status indicating part of the charge status indicator according to the present invention. Referring to  FIG. 5 , when the comparing module  102  determine the current charge status is the second charge status, the LED_R pin of the display driver  103  output low level, as a result the red and green LED is lighten together. When the comparing module  102  determines the current charge status is the first charge status, the LED_R pin of the display driver  103  output high level, as a result the green LED is lighten, and the red LED isn&#39;t lighten or only slightly lighten. As shown in  FIG. 5 , the detecting chip for monitoring charge status  100  also comprises a high voltage starting module for providing high starting voltage to the common-anode LEDs. 
       FIG. 6  is the circuit diagram of the fourth embodiment of the status indicating part of the charge status indicator according to the present invention. As shown in  FIG. 6 , the display module  200  comprises a LED, a resistor R 1 , the anode of the LED is connected to the power supply Vcc through the resistor R 1 , the cathode of the LED is connected to the LED pin of the display driver  103 . When the comparing module  102  determines the current charge status is the second charge status, the LED pin of the display driver  103  output low level, as a result the LED is lighten. When the comparing module  102  determines the current charge status is the first charge status, the LED pin of the display driver  103  output high level, as a result the green LED isn&#39;t lighten. In another embodiment, vice versa. 
     In the other embodiment of the present invention, the red LED may indicate large charging output current (that is the second charge status), and the green LED may indicate small charging output current (that is the first charge status). Alternatively, a monochrome LED may be used to indicate the large and small charging output current separately by flashing or not. 
       FIG. 7  is a principle block diagram of the first embodiment of the charge status indicator which adapt to the status indicating part disclosed in  FIGS. 3 and 4 . In such embodiment, this charge status indicator is applied in a PWM control charging system. As shown in  FIG. 7 , the detecting module  101  comprises a sample and hold circuit  203  and an error amplifier  204 . The comparing module  102  comprises a comparator  207  and a filter  208 . The display driver  102  comprises a first driver  209  and a second driver  210 . The first driver  209  is connected to the LED_G pin of the detecting chip  100  for monitoring charge status, and the second driver  210  is connected to the LED_R pin of the detecting chip  100  for monitoring charge status. 
     The sample and hold circuit  203  is used to obtain sampling voltage from the FB end of the detecting chip  100  for monitoring charge status. 
     The error amplifier  204  is used for comparing the sample voltage with a preset reference value and output a voltage which is proportional to the charging current. As it is in the PWM control system, the work frequency of the chip is constant, so the charging current of the charging power supply is proportional to the output voltage of the error amplifier  204 . 
     The comparator  207  is a voltage comparator, the forward input end of which is connected to the output end of the error amplifier  204 , and the reverse input end is connected to a reference voltage, so as to compare the output voltage of error amplifier  204  with the preset reference voltage. Once the reference voltage is determined, the output results of comparator  207  represent the current charging state. In order to make sure the accuracy of the output results of comparator  207 , filter  208  is used to low pass filter the output results. 
     In another embodiment according to the present invention, the sample and hold circuit  203  may simple a current signal or a power signal, and then the error amplifier  204  is used to convert it into a voltage which is proportional to the charging current. One skilled in the art knows that different device can be employed to convert different signal to voltage, current or power signal which is proportional to the charging current, and then deliver such signal to comparator  207  for comparing. Accordingly, an appropriate voltage, current or other electrical signal comparator also may be adopted. 
     When the filter  208  output the first charge status, the first driver  209  receive the first charge status signal and drive the green LED to emit green light, and when the filter  208  output the second charge status, the second driver  210  receive the second charge status signal and drive the red LED to emit red light. 
     In such embodiment, the detecting chip for monitoring charge status  100  further comprises a PWM control unit, which comprises a PWM comparator  205  and a PWM output driver  206 . The output end of the PWM output driver  206  is connected to the gate of the power switch to control the working state of the power switch. 
       FIG. 8  is a principle block diagram of the second embodiment of the charge status indicator which adapt to the status indicating part disclosed in  FIGS. 3 and 4 . In such embodiment, the charge status indicator is adopted in a PFM control charging system. Wherein, the detecting module  101  comprises a frequency obtaining unit  213  and a frequency-voltage converter  201 . The frequency obtaining unit  213  is used for obtaining the working frequency of the detecting chip  100  for monitoring charge status, wherein, the working frequency is proportional to the charging current. One skilled in the art knows various methods for obtaining the working frequency of a PFM control system, and each of them can be used in present invention. The frequency-voltage converter  201  is used for converting the working frequency to a voltage which is proportional to the working frequency, and such voltage is proportional to the charging current, that is, the smaller the output voltage of the frequency-voltage converter  201  is, the lower the working frequency is, that is, the smaller the charging current is. 
     The comparator  202  is a voltage comparator, the forward input end of which is connected to the output end of the frequency-voltage converter  201 , and the reverse input end is connected to a reference voltage, so as to compare the output voltage of frequency-voltage converter  201  with the preset reference voltage. In order to make sure the accuracy of the output results of comparator  202 , filter  208  is used to low pass filter the output results. 
     When the filter  208  output the first charge status, the first driver  204  receive the first charge status signal and drive the green LED to emit green light, and when the filter  208  output the second charge status, the second driver  205  receive the second charge status signal and drive the red LED to emit red light. 
     Although in such embodiment, the red LED may indicate large charging output current (that is the second charge status), and the green LED may indicate small charging output current (that is the first charge status). In the other embodiment of the present invention, a monochrome LED may be used to indicate the large and small charging output current separately by flashing or not. Moreover, a monochrome LED may be used to indicate the large and small charging output current separately by lighting for a long time or flashing. Based on the teaching of the present invention, other method may be employed to distinguish different charging states; all of these are included by the present invention. 
     In another embodiment of the present invention, the detecting module  101  is a frequency-current converter, which can be used to convert the working frequency of the detecting chip for monitoring charge status  100  which is proportional to the charging current to a current which is proportional to the charging current. Meanwhile, the comparator  202  is a current comparator, the forward input end of which is connected to the output end of the frequency current converter  201 , and the reverse input end is connected to a reference current, so as to compare the output current of frequency-current converter  201  with the preset reference current. In order to make sure the accuracy of the output results of comparator  202 , filter  208  is used to low pass filter the output results. In one embodiment according to present invention, the reference current may be 1/10-⅛ of the rated current. 
     Although the frequency-electrical signal converter is explained as a frequency-voltage converter and frequency-current converter. However, based on the teach of the present invention, one skilled in the art may find out that, other electrical signals, such as average power, instant power and other electrical signal which is proportional to the charging current can be adopted, and corresponding reference signal may be employed for determining. 
       FIG. 9  is a principle block diagram of the first embodiment of the charge status indicator which adapt to the status indicating part disclosed in  FIGS. 5 and 6 .  FIG. 10  is a principle block diagram of the second embodiment of the charge status indicator which adapt to the status indicating part disclosed in  FIGS. 5 and 6 . It can be seen from the Figures that,  FIG. 9  is basically the same as  FIG. 8  only with the difference that, in the display driver of  FIG. 9 , only driver  214  is provided, so it is applicable in  FIGS. 5 and 6 , in which, a display module with one LED is disclosed. Similarly,  FIG. 10  is basically the same as  FIG. 7  only with the difference that, in the display driver of  FIG. 10 , only driver  219  is provided, so it is applicable in  FIGS. 5 and 6  in which, a display module with one LED is disclosed. 
     The foregoing description is just the preferred embodiment of the invention. It is not intended to exhaustive or to limit the invention. Any modifications, variations, and amelioration without departing from the spirit and scope of the present invention should be included in the scope of the prevent invention.

Technology Classification (CPC): 7