Abstract:
A method and apparatus for reducing power consumption of a digital set-top box (STB) during a standby mode are provided. The method includes the steps of receiving a multimedia signal, the multimedia signal having an audio signal and a video signal, demultiplexing the multimedia signal into the audio signal and the video signal and decoding the audio and video signals, and selectively amplifying at least one of the decoded audio signal and the decoded video signal depending on a power mode of the digital STB and outputting the resulting audio and video signals, wherein the power mode comprises a standby mode and an on mode.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the benefit under 35 U.S.C. §119(a) of Korean Patent Application No. 10-2004-0048292 filed on Jun. 25, 2004 in the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a method and apparatus for reducing the power consumption of a digital set-top box in standby.  
         [0004]     2. Description of the Related Art  
         [0005]     Recent developments in digital technologies have allowed satellite, cable, and terrestrial wave broadcasters to provide digital broadcasts. Satellite broadcasting enables networks to be relatively easily constructed and provides consumers with a choice of several hundred digital broadcast channels. The development and advancement of satellite broadcasting has promoted the digitalization of cable broadcasting.  
         [0006]     Cable broadcasting has more advantages than satellite broadcasting regarding the provision of bi-directional services, even though cable broadcasting requires a considerable amount of time and money to establish new networks. In addition, the digitalization of terrestrial broadcasting is under way as major investments have been made therein. However, it is expected to take more time to digitalize terrestrial broadcasting than to digitalize satellite and cable broadcasting.  
         [0007]     With the advent of digital broadcasting, customer demand for a large variety of services has dramatically grown worldwide. In order to fulfill this demand, many digital broadcast receivers have been developed. Currently, domestic broadcasters are also promoting digitalization. However, in order to produce and transmit digital broadcast programs, capital investments are necessary, which has hindered many broadcasters from meeting customer demand.  
         [0008]     By taking advantage of a wider variety of broadcast programs, early cable broadcasters opened new broadcasting stations with a smaller amount of investment than the amount spent by terrestrial broadcasters to open their broadcasting stations. In order for users to watch cable broadcast programs, the users are required to have a special device called a set-top box (STB). Analog STBs, which are classified as the first generation of STBs, were only capable of unidirectionally receiving cable broadcast programs from cable broadcasting stations.  
         [0009]     In order to receive digital broadcast programs, which are characterized by higher audio and video qualities and hundreds of television (TV) channels, digital STBs are necessary. Digital STBs, which are classified as the second generation of STBs, provide a set of well-defined functions and additional services so that they can be successfully redefined as home appliances.  
         [0010]     A digital STB is both a digital broadcast receiver that receives various types of digital broadcast programs such as satellite, cable, or terrestrial broadcast programs, and a digital multimedia device that transmits a digital broadcast (video/audio) signal compressed in MPEG-2 format to a display device, such as a TV set. In order words, a digital STB is a type of signal converter for receiving digital broadcast programs.  
         [0011]     MPEG-2 is an image compression standard for digital storage mediums, networks, communication, and broadcasting. In addition, MPEG-2 is also a moving image compression standard for DVDs, digital TVs, satellite broadcasting, and digital cable broadcasting.  
         [0012]     In most cases, digital broadcast programs can be viewed by connecting a digital STB to a conventional TV set. Even though STBs have initially been designed to simply receive digital satellite, cable, and terrestrial broadcast programs, they are expected to be further developed to provide high-functionality broadcasting, interactive, bi-directional broadcasting, facilitate access to the Internet, and serve as personal storage mediums.  
         [0013]     High-functionality broadcasting is partly bi-directional and provides, for example, program guides, games, and weather forecasts. Bi-directional broadcasting has gradually broadened its applicability to pay-per-view programs, remote shopping, remote games, remote banking services, quizzes, and bidirectional advertisements. Currently, web browsing and e-mail services are realized in digital TVs. Given that integration of broadcasting technology with communication technology is being aggressively promoted and implemented, digital STBs are expected to become one of the most common devices enabling access to the Internet. Recently, STBs have been manufactured to have a hard disk drive (HDD) installed therein, which has dramatically changed users&#39; ways of watching TV. Thus, the users can store broadcast programs of interest in the HDD and watch the stored broadcast programs whenever they want. In addition, the STBs equipped with an HDD can provide a time shifting function so that a user who has stopped watching the TV program can resume watching an unwatched portion of the TV program at a later time. In the near future, home electronic appliances are expected to be connected to a home network, and digital STBs are expected to be further developed to play a significant role in such a home network.  
         [0014]     One of the most important factors to be considered when designing digital STBs with a variety of functions is power consumption. Digital STBs receive not only broadcast programs but also data and other broadcast-related audio or video signals. Therefore, when not outputting video or audio signals, digital STBs may consume a considerable amount of power to execute a variety of functions. In a standby mode, conventional STBs unnecessarily consume power to output a black video signal, even though they are not outputting any images. According to the Energy Star criteria, STBs are required to consume only 7 watts or less of power in standby mode.  
         [0015]     Therefore, in order to meet the Energy Star criteria, it is necessary to develop a method and apparatus to reduce the power consumption of STBs in the standby mode.  
       SUMMARY OF THE INVENTION  
       [0016]     The present invention provides a method and apparatus that reduce the power consumption of a set-top box (STB) in the standby mode.  
         [0017]     The present invention also provides a method and apparatus that reduce the number of signals unnecessarily output in the standby mode.  
         [0018]     The above stated object as well as other objects, features and advantages, of the present invention will become clear to those skilled in the art upon review of the following description, the attached drawings and appended claims.  
         [0019]     In accordance with an aspect of the present invention, there is provided a method of reducing power consumption of a digital set-top box (STB), the method comprising receiving a multimedia signal, the multimedia signal comprising an audio signal and a video signal, demultiplexing the multimedia signal into the audio signal and the video signal and decoding the audio and video signals, and selectively amplifying at least one of the decoded audio signal and the decoded video signal depending on a power mode of the digital STB and outputting the resulting audio and video signals, wherein the power mode comprises a standby mode and an on mode.  
         [0020]     In accordance with another aspect of the present invention, there is provided a digital STB comprising a broadcast signal receipt module, which receives a multimedia signal comprising an audio signal and a video signal, a demultiplexer, which demultiplexes the multimedia signal into the audio signal and the video signal, a decoder, which decodes the audio and video signals, and an amplification module, which selectively amplifies at least one of the decoded audio and video signals depending on a power mode of the digital STB, wherein the power mode comprises a standby mode and an on mode. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]     The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:  
         [0022]      FIG. 1  is a diagram illustrating power modes of a set-top box (STB) according to an exemplary embodiment of the present invention;  
         [0023]      FIG. 2  is a block diagram of an STB according to an exemplary embodiment of the present invention;  
         [0024]      FIG. 3  is a circuit diagram of a transistor of the video amplification module of  FIG. 2 ;  
         [0025]      FIG. 4  is a detailed block diagram of the video amplification module of  FIG. 2 ;  
         [0026]      FIG. 5  is a detailed block diagram of a power control portion of the STB according to an embodiment of the present invention shown in  FIG. 2 , which can cut off the power supplied to a video amplification module of the STB;  
         [0027]      FIG. 6  is a flowchart of a method for reducing power supplied to a video amplification module in standby mode according to an exemplary embodiment of the present invention;  
         [0028]      FIG. 7  is a flowchart of a method for reducing the power supplied to a video amplification module in standby mode, which is performed in the STB of  FIG. 2 ; and  
         [0029]      FIG. 8  is a flowchart of a method for reducing the power supplied to a video amplification module in standby mode, which is performed in the STB of  FIG. 5 . 
     
    
       [0030]     Throughout the drawings, it should be understood that like reference numbers refer to like features, structures and elements.  
       DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS  
       [0031]     In embodiments of the present invention, the term “module”, as used herein, means, but is not limited to, a software or hardware component such as a Field Programmable Gate Array (FPGA) or an Application Specific Integrated Circuit (ASIC), which performs certain tasks. The module may advantageously be configured to reside on an addressable storage medium and configured to execute on one or more processors. Thus, a module may include, by way of example, components such as software components, object-oriented software components, class components, task components, processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays, and variables. The functionality provided for in the components and modules may be combined into fewer components and modules or further separated into additional components and modules. Terms frequently used in this disclosure will now be described in more detail.  
         [0032]     Standby Mode  
         [0033]     There are three power modes of an STB: off, on, and standby. In the off mode, the power supplied to modules of the STB is cut off. In the on mode, a user can respectively view or listen to video or audio data provided via the STB. Standby mode is an intermediate mode between on and off. In the standby mode, the STB performs its operations with the exception of an operation of outputting a broadcast program. The user sees a black screen as if the STB is not outputting anything to the screen. However, in the standby mode the STB transmits a black video signal that makes the screen turn black. In the standby mode, the STB is standing by ready to output a broadcast program.  
         [0034]     Amplifier  
         [0035]     An amplifier is a module for amplifying a signal input thereto. A signal input via a wire or wireless manner may be attenuated, or it may contain noise, it is undesirable to output the input signal without appropriately processing. Thus, it is necessary to appropriately amplify the input signal to be suitably used. An amplifier amplifies a signal using a voltage or current. That is, the voltage or current is applied to the input and the output ports of the amplifier such that the voltage applied to the output port is greater than that applied to the input port, thereby amplifying the input signal in order to output an amplified signal. In a video/audio device, the amplifier amplifies a video/audio signal. An STB includes a video amplifier, which amplifies a video signal in a broadcast signal, and an audio amplifier, which amplifies an audio signal in the broadcast signal. Embodiments of the present invention will be described later in further detail using a video amplifier as an example of the amplifier. However, the amplifier is not restricted to a video amplifier and other types of amplifiers, such as an audio amplifier, can be used.  
         [0036]     Manipulation Signal and Control Signal  
         [0037]     A manipulation signal is input to an STB via a remote controller or a timer, and then the STB operates in response to the manipulation signal. A control signal is transmitted between modules of the STB in order to control the modules of the STB. When the STB receives the manipulation signal via the remote controller, a controller of the STB, which controls the rest of the STB, transmits the control signal to one of the modules of the STB that needs to be controlled. Depending on the type of the STB, the manipulation signal may be converted into the control signal or may be transmitted as the control signal between the modules of the STB.  
         [0038]      FIG. 1  is a diagram illustrating power modes of a set-top box (STB) according to an exemplary embodiment of the present invention. An STB may have three power modes: off mode  11 , standby mode  21 , and on mode  31 . In the off mode  11 , power is not supplied to most of the modules of the STB. In the off mode  11 , some of the modules of the STB, such as an inner scheduler or timer, and a manipulation signal receiver are still powered. The modules of the STB operate in the off mode  11  may be determined depending on the type of the STB. Immediately after the STB is switched to the standby mode  21  from the off mode  11 , the STB supplies power to the modules that need to be powered on and checks the state of the corresponding modules. In addition, in the standby mode  21  the STB performs operations for receiving audio/video signals and receives an electronic program guide (EPG). Once all the modules are powered and a monitoring operation of the corresponding modules states is completed, and the STB is switched to the on mode  31 . Depending on the type of the STB, a manipulation signal may be needed to switch the STB from the standby mode  21  to the on mode  31 . While listening/watching a reproduction of audio/video data, a user may switch the STB from the on mode  31  to the standby mode  21  and then stop listening/watching the reproduced audio/video data. In the standby mode  21 , the STB does not provide any video/audio data to the user but performs operations such as receiving the EPG. Therefore, the STB sends a black video signal, rather than a typical audio/video signal, to the screen and the screen turns black.  
         [0039]     In the conventional standby mode, an STB outputs a unique video signal, which is different from other regular video signals, so that the screen turns black. This unique video signal is called a black video signal. Thus, a user sees a black screen and believes the display module is not displaying any signals. But, in the conventional standby mode the display module displays black images. In order to output video signals, the STB amplifies the video signals using an amplifier, regardless of whether or not the video signals are black video signals. Therefore, in the conventional standby mode, the STB unnecessarily consumes power by amplifying black video signals even though the black video signals do not have any data to be processed.  
         [0040]     In the present embodiment, in the standby mode  21 , the STB does not output any video signal to a video output module, and the output of a video amplification module is greatly reduced. In other words, the STB does not send a video signal to the video output module or the STB outputs a video signal to the video output module, but the signal is too weak to make the video output module operate normally. As a result, it prevents the STB from unnecessarily consuming power by amplifying the video signal, and a user views the same black screen as in the conventional standby mode.  
         [0041]      FIG. 2  is a block diagram of an STB according to an exemplary embodiment of the present invention.  
         [0042]     Referring to  FIG. 2 , a manipulation signal receipt module  900  issues a command to turn on or off the STB  1000  and receives a signal input via a remote controller or an external panel equipped with buttons.  
         [0043]     A tuner  101  receives a video signal, an audio signal, or data from a satellite, terrestrial, or cable broadcasting station, and transmits the video signal, the audio signal, or the data to a demodulator  103 .  
         [0044]     The demodulator  103  converts an analog signal input thereto into a digital signal by sampling the analog signal, and then transmits the digital signal either directly to a demultiplexer  107  or via a descrambler  105 .  
         [0045]     The descrambler  105  descrambles a signal, which has been previously scrambled, by using key information obtained from an integrated circuit (IC) card (not shown). Scrambling, which is usually performed on pay-per-view broadcast programs, for example, is a process of converting signals or mixing the signals together. Therefore, a user cannot watch scrambled signals without the help of a descrambler.  
         [0046]     The demultiplexer  107 , which is a kind of filter, extracts signals corresponding to a channel selected by the user from among a number of signals corresponding to various channels input via the tuner  101 , and then transmits the extracted signals to both a video decoder  131  and an audio decoder  111 .  
         [0047]     The video decoder  131  decodes video signals from among the extracted signals. The video decoder  131  decodes the video signals by using a memory  141  because decoding the video signals requires a large amount of computation and a large amount of memory capacity. The memory  141  may be a random access memory (RAM), which is readable and writable. The video signals decoded by the video decoder  131  may be converted into analog signals by a digital-to-analog converter (DAC)  135  and then output. Alternatively, the decoded video signals may be processed to be compatible with the National Television Systems Committee (NTSC) standard or the Phase Alternating Line (PAL) standard, converted into analog signals by the DAC  135 , and then output.  
         [0048]     The audio decoder  111  decodes audio signals from among the extracted signals. The audio decoder  111 , like the video decoder  131 , needs the memory  141  to decode the audio signals. The decoded audio signals are converted to signals in a predetermined output format by an audio information processing module  113  and then output via an audio output module  117 .  
         [0049]     Since the video signals, which are converted into analog signals by the DAC  135 , are weak, they need to be amplified by a video amplification module  300  before being output.  
         [0050]     A video output module  137  and the audio output module  117 , which respectively output final video signals and final audio signals, are connected to an input terminal of an external display module (not shown) and an input terminal of an external audio device (not shown), respectively.  
         [0051]     A central processing module (CPU)  200  both controls other modules of the STB  1000  so that they can exchange information with one another, and processes this exchanged information.  
         [0052]     In the present embodiment, when the CPU  200  informs the video amplification module  300  that the STB  1000  has entered the standby mode, the video amplification module  300  does not amplify any signals input thereto.  
         [0053]      FIG. 3  is a circuit diagram of a transistor of the video amplification module  300  of  FIG. 2 .  
         [0054]     Referring to  FIG. 3 , a video signal, which is input to the transistor as soon as the transistor is turned on, is amplified by the transistor and then output. The input video signal may be prevented from being amplified by the transistor by applying a shutdown signal to the transistor. When the shutdown signal, which is a type of a power supply signal, is applied to the transistor, the transistor is prevented from consuming power because it is disconnected from the video amplification module  300 . Therefore, it is possible to reduce the power consumption of the STB during the standby mode by applying the shutdown signal to each transistor of the video amplification module  300 .  
         [0055]      FIG. 4  is a detailed block diagram of the video amplification module  300  of  FIG. 2 . Referring to  FIG. 4 , the video amplification module  300  receives a video signal, such as a composite video burst sync (CVBS) signal or a super video home system (SVHS) signal, amplifies the received video signal by using transistors thereof (such as the transistor of  FIG. 3 ), and outputs the amplified signal. The inner structure of the video amplification module  300  may vary depending on the type of the video amplification module  300 . The video amplification module  300  may include various circuit elements other than the transistors.  
         [0056]     When receiving a standby signal, the video amplification module  300  does not amplify video signals input thereto. In the standby mode, the video amplification module  300  does not output any signals, instead of amplifying and outputting a black video signal. However, there is no difference or very little difference between outputting nothing and outputting a black signal to display device, such as a TV set which is connected to the video output module  137 , during the standby mode.  
         [0057]      FIG. 5  is a detailed block diagram of a power control portion of the STB shown in  FIG. 2  according to an embodiment of the present invention, which can cut off the power supplied to a video amplification module in the STB.  
         [0058]     The STB shown in  FIG. 5  is similar to the STB shown in  FIG. 2 . A power supply module  800  illustrated in  FIG. 5  is not illustrated in  FIG. 2 . An encoded video signal, which has been processed by a demultiplexer, is decoded by a video decoder  131 . The decoded video signal is converted into an analog signal by a DAC  135  and then output. Since the video signal output from the DAC  135  is weak, it needs to be amplified by a video amplification module  300 .  
         [0059]     The power supply module  800  supplies power to various modules of the STB  1000 ′ and is controlled by a CPU  200 . When a manipulation signal receiving module  900  receives a command to turn off the respective modules of the STB  1000 ′, the CPU  200  sends a command to the power supply module  800  to cut off the power supplied to the respective modules of the STB. Accordingly, the power supplied to each module of the STB  1000 ′ is cut off, and each module of the STB  1000 ′ stops operating. Thereafter, when the manipulation signal receiving module  900  receives a signal requesting a standby mode or when the STB  1000 ′ is switched to the standby mode by an internal timer, the CPU  200  controls a power supply control module  700  to cut off the power supplied to the video amplification module  300 .  
         [0060]     In the illustrative embodiment, unlike in the previous embodiment, the power supplied to each module of the STB  1000 ′ is controlled by an external module, thus reducing the power consumption of the STB  1000 ′ during the standby mode.  
         [0061]      FIG. 6  is a flowchart of a method for reducing power supplied to a video amplification module according to an exemplary embodiment of the present invention.  
         [0062]     Referring to  FIG. 6 , in operation S 201 , a manipulation signal is input by a remote controller or an external panel equipped with buttons or is input by an internal scheduler in operation S 201 .  
         [0063]     In operation S 203 , a control module, such as a CPU, determines whether the manipulation signal is a standby signal.  
         [0064]     In operation S 205 , power supplied to a video amplification module is cut off if the manipulation signal is a standby signal. The power supplied to the video amplification module may also be cut off by a power supply control module disposed outside the video amplification module or by the video amplification module by applying a shutdown signal to its transistors, as illustrated in  FIG. 3 .  
         [0065]     In operation S 207 , when the power supplied to the video amplification module is cut off, the video amplification module stops amplifying signals input thereto, and no video signal is output to a video output module.  
         [0066]     In operation S 203 , if the manipulation signal is an on signal, which enables a user to watch video data in operation S 203 , power is supplied to the video amplification module in operation S 211 .  
         [0067]     In operation S 213 , video signals are output.  
         [0068]      FIG. 7  is a flowchart of a method for reducing power supplied to a video amplification module, which is performed by the STB of  FIG. 2 .  
         [0069]     Referring to  FIG. 7 , in operation S 290 , if a current power mode of the STB is not a standby mode but an on mode, the video amplification module amplifies a video signal and then transmits the amplified video signal to the video output module  137 .  
         [0070]     In operation S 301 , the manipulation signal receiving module  900  transmits a standby signal, which it has received from an external or internal scheduler or a timer, to the CPU  200 .  
         [0071]     In operation S 303 , the CPU  200  transmits the standby signal to the video amplification module  300 . The video amplification module  300  transmits a shutdown signal to transistors thereof so that they can be shut down.  
         [0072]     In operation S 307 , due to the shutdown signal, the video amplification module  300  stops both amplifying signals input thereto and transmitting the amplified signals to the video output module  137 . As a result, the power consumption of the transistors of the video amplification module  300  can be reduced.  
         [0073]     In operation S 311 , the manipulation signal receiving module  900  transmits an on signal to the CPU  200 .  
         [0074]     In operation S 313 , the CPU  200  transmits the on signal to the video amplification module  300 .  
         [0075]     In operation S 317 , the video amplification module  300  supplies power to the transistors thereof, which had been shut down, so that it can resume both amplifying video signals input thereto and outputting the amplified video signals to the video output module  137 .  
         [0076]      FIG. 8  is a flowchart of a method for reducing the power supplied to a video amplification module, which is performed by the STB of  FIG. 5 .  
         [0077]     The method of  FIG. 8  is similar to the method of  FIG. 7 . In the on mode, the video amplification module  300  amplifies a video signal and transmits the amplified video signal to the video output module  137  in operation S 390 .  
         [0078]     In operation S 401 , the manipulation signal receiving module  900  transmits a standby signal, among various signals that it has received from an external or internal scheduler or a timer, to the CPU  200 .  
         [0079]     In operation S 403 , the CPU  200  transmits the standby signal to the power supply control module  700 .  
         [0080]     In operation S 405 , the power supply control module  700  cuts off power supplied to the video amplification module.  
         [0081]     In operation S 407 , the video amplification module  300  stops outputting video signals.  
         [0082]     In operation S 411 , the manipulation signal receiving module  900  transmits an on signal to the CPU  200  during the standby mode.  
         [0083]     In operation S 413 , the CPU  200  transmits a control signal to the power supply control module  700  indicating that the STB has switched from the standby mode to the on mode.  
         [0084]     In operation S 417 , the power supply control module  700  supplies power to the video amplification module  300  so that the video amplification module  300  can resume amplifying video signals input thereto and transmitting the amplified video signals to the video output module  137 .  
         [0085]     According to an embodiment of the present invention, a voltage of 5 V is supplied to the video amplification module of the STB, and only an insignificant amount of current remains in the video amplification module when the current supplied to the video amplification module is cut off during the standby mode. Accordingly, during the standby mode, the STB consumes approximately 5 V×several mA of power, which is insignificant. Therefore, it is possible to reduce the power consumption of the STB during the standby mode.  
         [0086]     In concluding the detailed description, those skilled in the art will appreciate that many variations and modifications can be made to the preferred embodiments without substantially departing from the principles of the present invention. Embodiments of the present invention provide a method and apparatus for cutting off power supplied to a module for amplifying video or audio signals (for example, a video amplification module). However, the present invention should not be considered restricted to the embodiments thereof set forth herein. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.  
         [0087]     According to embodiments of the present invention, it is possible to reduce the power consumption of an STB during a standby mode.  
         [0088]     In addition, the STB incorporating embodiments of the present invention can meet international standards regarding power consumption.