Abstract:
An apparatus for and a method of controlling standby power to minimize energy consumption in a standby mode. The standby power control apparatus includes a control unit, a power supply unit, a constant voltage unit, and a standby power generation unit. The control unit controls an overall operation of the system. The power supply unit converts an alternating current (AC) power into a direct current (DC) voltage and outputs the DC voltage to a load. The constant voltage unit drops the output DC voltage of the power supply unit and provides the control unit with the dropped output voltage. The standby power generation unit drops the output voltage of the power supply unit from a first value to a second value lower than the first value if the system is switched to a standby mode.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims the benefit of Korean Application No. 2002-26688 filed May 15, 2002, in the Korean Industrial Property Office, the disclosure of which is incorporated herein by reference. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates generally to power consumption control of a system, and more particularly to power consumption control of a system having a standby mode for saving power.  
           [0004]    2. Description of the Related Art  
           [0005]    [0005]FIG. 1 is a schematic block diagram illustrating a conventional power control apparatus. An overall system  100  of FIG. 1 includes a conventional power control apparatus which supplies power to a load  104  through a power supply unit  102 . As shown in FIG. 1, in the overall system  100 , the power supply unit  102  converts Alternating Current (AC) power into Direct Current (DC) power and provides the load  104  of the conventional system  100  with the DC power.  
           [0006]    The power supply unit  102  is a Switching Mode Power Supply (SMPS) and normal AC power is input to the power supply unit  102 . An output voltage level of the power supply unit  102  is controlled to 12 volts DC by operations of a zener diode  114 , whose rated voltage is 12 volts, and a feedback control unit  110 . Since the rated voltage of the zener diode  114  is 12 volts, a voltage is fed back to the control unit  110  if a voltage across the zener exceeds 12 volts. The feedback control unit  110  stops the operation of the power supply unit  102  if the output voltage of the power supply unit  102  is found to exceed 12 volts by observing the output voltage level.  
           [0007]    A constant voltage unit  106  drops the 12 volts DC output from the power supply unit  102  to 5 volts DC, and provides a control unit  108  with the 5 volts DC. The 5 volts DC output from the constant voltage unit  106  is the operational voltage of the control unit  108 . The constant voltage unit  106  is a kind of voltage regulator, and serves to obtain output voltage of a desired level by dissipating heat corresponding to a difference between an input voltage and a target output voltage, thus consuming the difference.  
           [0008]    An AC power detection unit  112  observes whether normal AC power is input to the power supply unit  102 , and provides the control unit  108  with observation results. The AC power detection unit  112  determines whether input AC power is normal by zero point detection of the AC power. Additionally, since the period of the AC power is constant, the motor rotation velocity and motor driving member of the load  104  and the like are precisely controllable by the zero point detection.  
           [0009]    [0009]FIGS. 2A through 2D are waveform diagrams illustrating electrical characteristics of portions of the conventional system  100 , that is, the voltage of nodes N 1  through N 4  as shown in FIG. 1. At node N 1 , the output voltage of the power supply unit  102  is always maintained at 12 volts as shown in FIG. 2A. At node N 2 , the output voltage of the constant voltage unit  106  is always maintained at 5 volts as shown in FIG. 2B. At node N 3 , AC power is input to the AC power detection unit  112  in a form of a wave as shown in FIG. 2C. At node N 4 , a pulse signal, as shown in FIG. 2D, generated within the power supply unit  102  determines a value of the output voltage at node N 1 .  
           [0010]    In FIGS. 2A  2 D, t a  and t b  indicate a beginning of an operation stopping period and a beginning of an operation restarting period, respectively, of the system  100 . The operation stopping period t a  to t b  of the system  100  designates an idle state in which the load  104  is not required to operate. In such an operation stopping period, the control unit  108  observes whether an external input occurs and whether the external input possesses data required for the operation of the system  100 , so the control unit  108  must be activated. Upon receipt of the required data, the system  100  is restarted at time t b .  
           [0011]    However, in accordance with the prior art, while the system  100  is not in operation, the voltage of 12 volts is continuously provided to the constant voltage unit  106  and AC power is continuously provided to the AC power detection unit  112 . Accordingly, in the constant voltage unit  106 , unnecessary power consumption occurs in the process of dropping the 12 volts to the 5 volts and a large amount of heat is generated, so the performance of the conventional system  100  is deteriorated. Additionally, unnecessary power consumpton occurs in the AC power detection unit  112 , further contributing to system inefficiency.  
         SUMMARY OF THE INVENTION  
         [0012]    Accordingly, the present invention has been made keeping in mind the above and other problems occurring in the prior art, and an object of the present invention is to provide a system for and a method of controlling standby power, which, where the system is switched to a standby mode, drops the output voltage of a power supply unit to a minimum operational voltage level of a control unit and cuts off AC power provided to a AC power detection unit.  
           [0013]    Additional objects and advantages of the invention will be set forth in part in the description which follows, and, in part, will be obvious from the description, or may be learned by practice of the invention.  
           [0014]    In order to accomplish the above and other objects, the present invention provides an apparatus for controlling standby power comprising a control unit which controls an overall operation of a system; a power supply unit which converts an AC voltage into a DC voltage and outputs the DC voltage to a load; a constant voltage unit which drops the DC output voltage of the power supply unit and provides the control unit with the dropped output voltage; and a standby power generation unit which drops the DC output voltage of the power supply unit from a first value to a second value lower than the first value if the system is switched to a standby mode.  
           [0015]    In order to accomplish the above and other objects, the present invention provides a method of controlling standby power in a system, the system having a control unit which controls an overall operation of the system, a power supply unit which converts an AC voltage into a first DC voltage, and a constant voltage unit which drops the first DC voltage to a second DC voltage, wherein the method comprises: counting an operation stopping time of the system if the operation of the system is stopped; and if the operation stopping time of the system exceeds a preset reference time, converting an operation mode of the system into a standby mode and dropping a value of the first DC voltage to a value of the second DC voltage. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:  
         [0017]    [0017]FIG. 1 is a schematic block diagram illustrating a conventional power control apparatus;  
         [0018]    FIGS.  2 A, through  2 D are waveform diagrams of voltages at nodes N 1  through N 4 , respectively, shown in FIG. 1;  
         [0019]    [0019]FIG. 3 is a schematic block diagram illustrating an apparatus for controlling standby power in accordance with an embodiment the present invention;  
         [0020]    [0020]FIG. 4A is a circuit diagram illustrating a standby power generation unit of the standby power control apparatus shown in FIG. 3;  
         [0021]    [0021]FIG. 4B is a circuit diagram illustrating a power cutoff unit of the standby power control apparatus shown in FIG. 3;  
         [0022]    [0022]FIGS. 5A through 5F are waveform diagrams of voltages at nodes N 5  through N 10 , respectively, shown in FIG. 3; and  
         [0023]    [0023]FIG. 6 is a flowchart illustrating an operation of the standby power control apparatus shown in FIG. 3. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0024]    Reference will now be made in detail to the present embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout.  
         [0025]    With reference to FIGS. 3 through 6, an apparatus and method for controlling standby power in accordance with a preferred embodiment of the present invention is described below.  
         [0026]    [0026]FIG. 3 is a schematic block diagram illustrating the apparatus for controlling standby power in accordance with the present invention. As shown in FIG. 3, in an overall system  300  including the standby power control apparatus of the present invention, unnecessary power consumption is reduced in a constant voltage unit  306  by dropping output voltage N 7  of the power supply unit  302  using a standby power generation unit  316  while the system  300  is in a standby mode, and in a AC power detection unit  312  by cutting off the power supplied to the AC power detection unit  312  by using a power cutoff unit  318 .  
         [0027]    The system  300  of the present invention is switched to the standby mode if an operation stopping time of the system  300 , for which a load  304  is not operated, exceeds a preset reference time while power is on. In this standby mode, all the component elements of the system  300  except a control unit  308 , the standby power generation unit  316  and the power cutoff unit  318  are not activated. If, in the standby mode, external input occurs, the activated control unit  308  generates a control signal to drive the load  304 .  
         [0028]    The power supply unit  302  of the system  300  converts AC power into a DC voltage and provides the load  304  with the DC voltage. A Switched mode power supply (SMPS) is employed as the power supply unit  302  and normal AC power is input to the power supply unit  302 . In the normal operation mode of the system  300 , the output voltage of the power supply unit  302  is restricted to 12 volts DC by the operation of a zener diode  314 , whose rated zener voltage is 12 volts, and a feedback control unit  310 . Since the rated voltage of the zener diode  314  is 12 volts, a voltage is input to the feedback control unit  310  if the output voltage at node N 7  exceeds 12 volts. The feedback control unit  310  stops the operation of the power supply unit  302  if the output voltage level of the power supply unit  302  is found to exceed 12 volts by observing the output voltage level. Unlike the normal operation mode, in the standby mode of the system  300 , the control unit  308  controls the standby power generation unit  316  so that the output voltage of the power supply unit  302  is restricted to 5 volts, that is, the operation voltage of the control unit  308 .  
         [0029]    The constant voltage unit  306  drops the 12 volts DC output from the power supply unit  302  to 5 volts DC, and provides the control unit  308  with the 5 volts DC. The 5 volts DC output from the control unit  308  is the operation voltage of the control unit  308 . The constant voltage unit  306  is a kind of voltage regulator, and serves to obtain the output voltage of a desired level by dissipating heat corresponding to a difference between input voltage and target output voltage, thus consuming the difference. In the standby mode of the system  300  of the present invention, the input voltage of the constant voltage unit  306  is 5 volts, so there is no surplus voltage that is consumed as heat in the constant voltage unit  306 . Accordingly, there is no heat generation caused by the operation of the constant voltage unit  306  in the standby mode of the present invention.  
         [0030]    The AC power detection unit  312  observes whether normal AC power is inputted to the power supply unit  302 , and provides the control unit  308  with the observed results. The AC power detection unit  312  determines whether the AC power signal is not normal using zero point detection of the AC power signal. Additionally, since the period of the AC power is constant, the motor rotation velocity and motor driving member of the load  304  and the like are precisely controllable by the zero point detection. Where the system  300  is switched to the standby mode, the control unit  308  drives the power cutoff unit  318  so that power provided to the AC power detection unit  312  is cut off.  
         [0031]    [0031]FIG. 4A is a circuit diagram illustrating a standby power generation unit  316  of the standby power control apparatus of FIG. 3. As shown in FIG. 4A, a transistor  404  is turned on/off by a standby power control signal at node N 5 , which is output from the control unit  308 . Where the system  300  is in the normal operation mode, the standby power control signal at node N 5  is low, so the transistor  404  is turned off. When the transistor  404  is turned off, a zener diode  402  is not electrically conducting, so the output voltage of the power supply unit  302  at node N 7  is maintained at 12 volts DC. On the contrary, where the system  300  is in the standby mode, the standby power control signal at node N 5  is high, so the transistor  404  is turned on. Where the transistor  404  is turned on, the zener diode  402  whose rated voltage is 5 volts is electrically conducting, so the output voltage at node N 7  of the power supply unit  302  is restricted to 5 volts DC. The 5 volts DC are provided to the feedback control unit  310 . The feedback control unit  310  observes the output voltage of the power supply unit  302 , and stops the operation of the power supply unit  302  if the output voltage exceeds 5 volts. Capacitor  410  filters the power control signal at node N 5 . Resistors  406  and  408  limit a base current of the transistor  404  and establish a minimum voltage at the node N 5  necessary to turn on the transistor  404 .  
         [0032]    [0032]FIG. 4B is a circuit diagram illustrating a power cutoff unit  318  of the standby power control apparatus of FIG. 3. As shown in FIG. 4B, a photosensitive bi-directional three-terminal thyristor  462  is installed on an AC power transmission line  320  connecting the AC power detection unit  312  and the source of AC power. A light emitting diode  452  is employed as a light emitting device to drive the thyristor  462 . Where the system  300  is in the normal operation mode, a power cutoff control signal at node N 2  is high, so a transistor  454  is turned on. Where the transistor  454  is turned on, the light emitting diode  452  electrically conducts and emits light, which is transmitted into the thyristor  462 , thereby turning the thyristor  462  on. Where the thyristor  462  is turned on, the AC power is provided to the AC power detection unit  312 . On the contrary, where the system  300  is in the standby mode, the power cutoff control signal at node N 6  is low, so the transistor  454  is turned off. Where the transistor  454  is turned off, the light emitting diode  452  does not electrically conduct and does not emit light, thereby turning the thyristor  462  off. Where the thyristor  462  is turned off, the AC power is not provided to the AC power detection unit  312 . Capacitor  460  filters the power cutoff control signal at node N 6 . Resistors  456  and  458  limit a base current of the transistor  454  and establish a minimum voltage at the node N 6  necessary to turn on the transistor  454 . Resistor  453  connected between the light emitting diode  452  and a voltage source V CC  limits a current flow through the light emitting diode  452 .  
         [0033]    [0033]FIGS. 5A through 5F are waveform diagrams illustrating the electrical characteristics of portions of the standby power control apparatus of FIG. 3, that is, voltage variations between the normal operation mode and standby mode at nodes N 5  through N 10  shown in FIG. 3. As shown in FIGS. 5A through 5F, where the system  300  is in the normal operation mode, the standby power control signal at node N 5  and the power cutoff control signal at node N 6 , which are output from the control unit  308 , are low (L) and high (H), respectively, prior to time t 1 ). In the normal operation mode, if a preset time Δt elapses after the operation of the system  300  is stopped, i.e., (interval t 1  to t 2 ), the system  300  is switched to the standby mode at time t 2 .  
         [0034]    Where the system  300  is switched to the standby mode (time t 2 ), the standby power control signal at node N 5  and the power cutoff control signal at node N 6 , which are output from the control unit  308 , are changed into a low level (L) and a high level (H), respectively. As the standby power control signal at node N 5  is changed into a high level, the output voltage of the power supply unit  302  at node N 7  is dropped to 5 volts DC from 12 volts DC by the driving of the standby power generation unit  316 . Voltage at node N 8  provided to the control unit  308  by the constant voltage unit  306  is always maintained at 5 volts regardless of the operation mode (normal operation or standby mode) of the system  300 .  
         [0035]    AC power at node N 9  is supplied from the power cutoff unit  318  to the AC power detection unit  312 . Where the system  300  is in the normal operation mode, normal AC power is provided to the AC power detection unit  312  by the power cutoff unit  318 . However, where the system  300  is switched to the standby mode, the AC power is no longer provided to the AC power detection unit  312  by the cutoff operation of the power cutoff unit  318 . Where the system  300  is again switched from the standby mode to the normal operation mode (time t 3 ), the AC power is provided to the AC power detection unit  312 .  
         [0036]    A pulse signal at a node N 1  is generated within the power supply unit  302 . Where the system  300  is switched to the standby mode, the pulse width of the pulse signal becomes narrow, so the output voltage at node N 7  is maintained at 5 volts DC. Thereafter, where the system  300  is again switched from the standby mode to the normal operation mode, the pulse width of the pulse signal at the node N 10  becomes wide, so the size of the output voltage N 7  is again maintained at 12 volts DC.  
         [0037]    As shown in FIG. 5, where the system  300  is switched to the standby mode, the output voltage of the power supply unit  302  at node N 7  is dropped to 5 volts DC from 12 volts DC and the AC power provided to the AC power detection unit  312  via transmission line  320  is electrically cut off, so the AC power is not provided to the AC power detection unit  312 . Accordingly, there is no power consumption in the constant voltage unit  306  and the AC power detection unit  312 .  
         [0038]    [0038]FIG. 6 is a flowchart illustrating an operation of the standby power control apparatus of FIG. 3. As shown in FIG. 6, where the operation of the system  300  is stopped at operation S 604  while the system  300  is in operation at operation S 602 , the operation stopping time of the system  300  is counted at operation S 606 .  
         [0039]    Thereafter, it is determined whether the operation stopping time of the system  300  exceeds a preset reference time Δt at [step] operation S 608 . As the result of the determination at [step] operation S 608 , if the operation stopping time of the system  300  exceeds the preset reference time Δt, the output voltage of the power supply unit  302  at node N 7  is dropped from 12 volts to 5 volts by the operation of the standby power generation unit  316  at operation S 610 . Accordingly, power provided to the constant voltage unit  306  is reduced. Additionally, unnecessary power consumption is also reduced by driving the power cutoff unit  318  at operation S 612  to cut off power provided to the AC power detection unit  312 . At the same time, where the system  300  is switched to the standby mode, the standby mode starts at operation S 614 . In this case, all component elements of the system  300  except the control unit  308 , the standby power generation unit  316  and the power cutoff unit  318  are inactivated.  
         [0040]    Thereafter, it is determined whether the system  300  is restarted at operation S 616 . As the result of the determination at operation S 616 , where external input occurs in the standby mode, the system  300  is switched to the normal operation mode at operation S 618  and all the component elements of the system  300  are activated. Thereafter, the system  300  resets data relating to the standby mode at operation S 620 , and then a corresponding operation according to the external input is carried out at operation S 620 .  
         [0041]    Accordingly, the standby power control apparatus and method of the present invention reduces unnecessary power consumption and heat generation in the constant voltage unit  306  by dropping the output voltage of the power supply unit  302  to the operation voltage of the control unit  308  where the system  300  is switched to the standby mode to save power.  
         [0042]    Additionally, the standby power control apparatus and method of the present invention suppress unnecessary power consumption in the standby mode by cutting off AC power provided to the AC power detection unit so as to observe whether the AC power is normal.  
         [0043]    Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.