Abstract:
A method of operating a Real Time Clock (RTC) in a terminal is provided. The method includes detecting a clock signal transmitted to an RTC block when the main power supply is switched off, and supplying a power to the RTC block for its operation by charging and discharging the power periodically supplied from the backup battery according to the detected clock signal. A DC/DC converter connected to a backup battery is periodically switched on and off, and a capacitor is charged and discharged using the power of the backup battery, thereby avoiding supplying power from a backup battery continuously to an RTC block. Therefore, power consumption is reduced and a duration of time for maintaining RTC data is extended.

Description:
PRIORITY 
       [0001]    This application claims the benefit under 35 U.S.C. §119(a) of a Korean patent application filed in the Korean Intellectual Property Office on Oct. 31, 2007 and assigned Serial No. 2007-0109996, the entire disclosure of which is hereby incorporated by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a terminal having a Real Time Clock (hereafter, RTC) operator and a method of RTC operation using the same. More particularly, the present invention relates to a terminal having an RTC operator, enabling a reduction of power consumption from a backup battery by periodically switching on/off a DC/DC converter, and charging/discharging a capacitor with the power from the backup battery when the power supplied from a main power source is switched off, and a method of RTC operation using the same. 
         [0004]    2. Description of the Related Art 
         [0005]    Unlike a synchronous Code Division Multiple Access (CDMA) terminal, in an asynchronous mobile communication system, such as a Global System for Communications (GSM) terminal and a General Packet Radio Service (GPRS) terminal, a user must input a time so that an internal clock of the terminal operates correctly. 
         [0006]    In the case of a synchronous terminal, the time of an internal clock of the terminal is automatically set during a setting operation using time information received from a network system, and thereby the internal clock always maintains a correct time without requiring a user&#39;s input. 
         [0007]    However, in the case of an asynchronous terminal, a network system does not send time information to the terminal, and therefore a user of the terminal must input a time. Therefore, each terminal may have a different time setting, and the user may be inconvenienced by having to input the time whenever the terminal is switched on. 
         [0008]    In order to solve this problem, the asynchronous terminal uses a backup battery to protect the time information from being erased when the power from a main power source is discontinued. The asynchronous terminal has an internal RTC to manage and display the time information. 
         [0009]    However, for the operation of the RTC, the backup battery supplies power to the RTC continuously, which may result in discontinuation of RTC operation when the backup battery is completely discharged. At this moment, the RTC is reset to an initial time setting (generally, “0”), and thereby display of the correct time is not possible. 
       SUMMARY OF THE INVENTION 
       [0010]    An aspect of the present invention is to address at least the above-mentioned problems, and/or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of the present invention is to provide a terminal having an RTC operator that reduces consumption of a backup battery power, and a method of RTC operation using the same. 
         [0011]    Another aspect of the present invention is to provide a terminal having an RTC operator that charges and discharges a capacitor to supply an operating power to an RTC block by periodically switching on/off a DC/DC converter connected to a backup battery, and a method of RTC operation using the same. 
         [0012]    In accordance with an aspect of the present invention, a method of operating an RTC in a terminal having an RTC block, a main power supply and a backup battery is provided. The method includes activating the backup battery when the main power supply is switched off, and detecting a clock signal transmitted to the RTC block, supplying and discontinuing a supply of power from the backup battery according to the detected clock signal, and supplying an operating power to the RTC block for its operation by charging and discharging a capacitor with the power of the backup battery. 
         [0013]    In accordance with another aspect of the present invention, a terminal having an RTC block, a main power supply and a backup battery is provided. The terminal includes a control unit for generating a power-off signal when the main power supply is switched off, a switch for generating an activation signal of the backup battery by a switching function according to the power-off signal, a detector for detecting a clock signal generated by an activation of the backup battery, a DC/DC converter connected to the backup battery for periodically switching on and off according to the switching function and the detected clock signal, a capacitor for generating an operating power by charging and discharging using a power of the backup battery according to periodic switching on and off of the DC/DC converter, and an RTC block for generating time information using the operating power. 
         [0014]    In accordance with still another aspect of the present invention, a DC/DC converter connected to a backup battery is periodically switched on and off, and a capacitor is charged and discharged with the power of the backup battery, thereby avoiding supplying a power of the backup battery continuously to an RTC block. Therefore, power consumption is reduced and a duration of time for maintaining RTC data is extended. 
         [0015]    Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    The above and other aspects, features and advantages of certain exemplary embodiments of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings, in which: 
           [0017]      FIG. 1  is a block diagram illustrating a configuration of a terminal having an RTC operator according to an exemplary embodiment of the present invention; 
           [0018]      FIG. 2  is a block diagram illustrating a configuration of an RTC operator according to an exemplary embodiment of the present invention; and 
           [0019]      FIG. 3  is a flowchart showing a method of RTC operation in a terminal having an RTC operator according to an exemplary embodiment of the present invention. 
       
    
    
       [0020]    Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features and structures. 
       DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0021]    The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention. Also, descriptions of well-known functions and constructions are omitted for clarity and conciseness. 
         [0022]    Although a Global System for Communications (GSM) terminal is illustrated as an example in the description of the present invention, the present invention is not limited thereto. That is, the terminal according to exemplary embodiments of the present invention may be any terminal, such as a General Packet Radio Service (GPRS) terminal, a Universal Mobile Telecommunications System (UMTS) terminal, a Wideband Code Division Multiple Access (WCDMA) terminal and the like. 
         [0023]      FIG. 1  is a block diagram illustrating a configuration of a terminal having an RTC operator according to an exemplary embodiment of the present invention. 
         [0024]    Referring to  FIG. 1 , the terminal includes a key input unit  103 , a memory unit  105 , a display unit  107 , a control unit  109 , and a Real Time Clock (RTC) operator  200 . 
         [0025]    The key input unit  103  receives a key input for controlling the operation of the terminal. The key input unit  103  may be used for an operation such as a time setting when the main power of the terminal is switched on after having been switched off and RTC information is reset due to a complete discharge of a backup battery  201  (shown in  FIG. 2 ). While the supply of power and discontinuation of the supply power are described herein as being switch on and switched off, respectively, the present invention is not limited thereto. Exemplary embodiments of the present invention are equally applicable to any manner in which power is supplied or discontinued. 
         [0026]    The memory unit  105  stores programs and information required for the operation of the terminal, and stores time setting information input by a user. The time setting information is deleted when the main power is switched off. 
         [0027]    The display unit  107  displays an operational state and information related to the operation of the terminal. The display unit  107  displays the time setting information, and a screen for requesting time setting when the RTC information is reset. 
         [0028]    The display unit  107  may be provided as a Liquid Crystal Display (LCD). In this case, the display unit  107  may include a controller for controlling the LCD, a video memory in which image data is stored and an LCD element. If the LCD is provided as a touch screen, the display unit  107  may perform a part or all of the functions of the key input unit  103 . 
         [0029]    The control unit  109  controls the general operations of individual components of the terminal. The control unit  109  controls the operational function of the RTC operator  200 . The control unit  109  generates a power-off signal when the main power is switched off, and outputs the generated power-off signal to the RTC operator  200 . The main power may be determined to be switched off in any one of various ways. For example, the main power may be determined to be switched off when a main power-off key is depressed, when a main power-off menu item is selected, if the main power is determined to be close to being exhausted, or if it removal of battery supplying the main power is detected. Additionally, the control unit  109  activates the RTC operator  200  when the main power is switched off. Such a function is later described in more detail referring to  FIG. 2 . Further, the control unit  109  deletes the RTC information upon switching off the main power and controls for a complete discharge of the backup battery  201 . 
         [0030]    The terminal may further include a Radio Frequency (RF) unit for performing wireless communications. The RF unit includes an RF transmitter that up-converts the frequency of a signal to be transmitted and amplifies the signal, and an RF receiver that low-noise amplifies a received signal and down-converts its frequency. 
         [0031]    Hereinafter, the RTC operator of the terminal according to the present invention is described. 
         [0032]      FIG. 2  is a block diagram illustrating a configuration of an RTC operator according to an exemplary embodiment of the present invention. 
         [0033]    Referring to  FIG. 2 , the RTC operator  200  includes a backup battery  201 , a DC/DC converter  203 , a switch  205 , a crystal oscillator  207 , a detector  209 , a capacitor  211 , and an RTC block  213 . 
         [0034]    As described above, the control unit  109  generates a power-off signal when a main power is switched off, and outputs the power-off signal to the switch  205 . Because the switch  205  is an NPN type transistor, a low signal is inputted to base of the transistor. Subsequently, the switch  205  is disconnected to the DC/DC converter  203  and the detector  209  by switching off. In the present exemplary embodiment, the switch is an NPN type transistor. However, the present invention is not limited thereto. That is, the switch may be a PNP type transistor. 
         [0035]    The crystal oscillator  207  having a slip mode is connected to the RTC block  213 , and generates a clock signal by using the power supply from the backup battery  201 . Here, the clock signal may be generated with a frequency of 32.768 KHz, and may have a voltage value in the range of 0-1 V. 
         [0036]    The detector  209 , which is connected to an enable pin EN of the DC/DC converter  203 , detects the clock signal generated by the crystal oscillator  207 . The detector  209  may have a comparator for comparing a setting voltage with the clock signal generated by the crystal oscillator  207 , and may generate a square wave signal having a specific period by using a compared value. 
         [0037]    The DC/DC converter  203  is connected to the backup battery  201 . When the main power is switched off, the DC/DC converter  203  receives power from the backup battery  201  and supplies the power to the RTC block  213 . The DC/DC converter  203  is connected to the detector  209  through the enable pin EN, and performs a periodic switching on/off operation according to the signal generated by the detector  209 . That is, the DC/DC converter  203  is periodically switched on/off according to the activation through the switch  205  and the signal generated by the detector  209 . The power supplied from the backup battery  201  is thereby switched on and off accordingly. 
         [0038]    The capacitor  211  is connected between the DC/DC converter  203  and the RTC block  213 . The capacitor  211  is charged according to the periodical switching on/off operation of the DC/DC converter  203  and discharges when power is not supplied from the backup battery  201 . That is, when the DC/DC converter  203  is switched on, the capacitor  211  transmits the power supplied from the backup battery  201  to the RTC block  213 , and simultaneously is charged to a preset power level. When the DC/DC converter  203  is switched off, the supply of power from the backup battery  201  is discontinued. The capacitor  211  then supplies the charged power to the RTC block  213  for the operation of the RTC block  213 . The capacitor  211  is selected by considering a time constant of charge/discharge, such that the power supplied to RTC block  213  maintains substantially constant. 
         [0039]    The RTC block  213  generates time information (hour, minute, and second) by counting the clock signal generated by the crystal oscillator  207 . The RTC block  213  maintains RTC information, namely time setting information, by using the power supplied through the charge/discharge of the capacitor  211 . 
         [0040]    In the present exemplary embodiment referring to  FIG. 2 , the RTC operator does not include a switch for switching on/off of backup battery. However, the present invention is not limited thereto. That is, the RTC operator may also include a switch for switching on/off of backup battery for example, backup battery is switched off when main power is switched on and backup battery is switched on when main power is switched off. 
         [0041]    Hereinafter, a method of RTC operation in a terminal having an RTC operator according to an exemplary embodiment of the present invention is described referring to  FIGS. 1 to 3 . 
         [0042]      FIG. 3  is a flowchart illustrating a method of RTC operation in a terminal having an RTC operator according to an exemplary embodiment of the present invention. 
         [0043]    Referring to  FIG. 3 , the control unit  109  first detects that a main power is switched off in step S 301 . A user of the terminal may switch off the power when not using the terminal or when battery replacement is necessary. In addition, the main battery may switch off due to a complete discharge of the battery. 
         [0044]    The detector  209  detects a clock signal generated by the crystal oscillator  207  in step S 305 . The crystal oscillator  207  operating by the power supply from the backup battery  201  generates the clock signal to be transferred to the RTC block  213 . The detector  209  connected to the crystal oscillator  207  generates a square wave signal having a preset period by comparing a setting voltage with the clock signal of the crystal oscillator  207 . 
         [0045]    The DC/DC converter  203  is periodically switched on and off in step S 307 . That is, the enable pin EN of the DC/DC converter  203  is connected to the detector  209 , and the DC/DC converter  203  is periodically switched on and off according to the square wave signal having a preset period generated by the detector  209  in step S 305 . 
         [0046]    The capacitor  211  is charged or discharged according to the power supplied from the backup battery  201  in step S 309 . As the DC/DC converter  203  is periodically switched on and off in step S 307 , the power supplied from the backup battery  201  to the DC/DC converter  203  is thereby periodically discontinued. At this time, the power supply from the DC/DC converter  203  to the RTC block  213  is interrupted by switching off the power. In order not to interrupt the supply of power required by the RTC block  213 , the capacitor  211  is installed between the DC/DC converter  203  and the RTC block  213  to charge and discharge according to the power supplied from the backup battery  201 . While the DC/DC converter  203  is switched on, the DC/DC converter  203  converts the power supplied from the backup battery  201  into a power having a constant direct current and supplies the power to the capacitor  211 . 
         [0047]    Lastly, the power charged in the capacitor  211  in step S 309  is supplied to the RTC block  213  in step S 3   11 . That is, when the DC/DC converter  203  is switched on, the capacitor  211  transmits the power supplied from backup battery  201  to the RTC block  213  and is simultaneously charged by the power of the backup battery. When the DC/DC converter  203  is switched off, the capacitor  211  supplies the charged power to the RTC block  213  while the supply of power from the backup battery  201  is discontinued. 
         [0048]    Although exemplary embodiments of the present invention have been described in detail hereinabove, it should be understood that many variations and modifications of the basic inventive concept herein described, which may appear to those skilled in the art, will still fall within the spirit and scope of the exemplary embodiments of the present invention as defined in the appended claims their equivalents.