Abstract:
An apparatus and method for reducing the level of power consumption in an electronic device when the electronic device is operating in a standby mode or low-power mode. The level of power consumption is reduced by alternately shutting off standby power and turning on standby power to the electronic device. A standby cycle timer circuit is provided for automatically controlling the supply of standby power to the electronic device during standby mode. The standby cycle timer circuit becomes inactive when the electronic device resumes normal operation.

Description:
TECHNICAL FIELD OF THE INVENTION 
     The present invention is directed, in general, to electronic devices and, more specifically, to an apparatus and method for reducing the level of power consumption in an electronic device when the electronic device is operating in a standby mode or low-power mode. 
     BACKGROUND OF THE INVENTION 
     In electronic devices it is sometimes desirable to operate the device in a standby mode (also called a low-power mode) rather than to turn off all power to the device when the device is not in use. For example, in a television set it is customary to continually supply power to the heating elements of the electronic circuitry even when the set is otherwise turned off. This permits the electronic circuitry that operates the various components of the television set (e.g., circuitry that operates the cathode ray tube of the television screen) to very quickly achieve the proper level of operation when the set is turned on. If one did not keep the set minimally powered in a standby mode it would be necessary to wait for the heating elements of the set to warm up when the set was turned on. 
     Therefore, it is desirable and useful to use the standby mode in electronic devices such as radio sets, television sets, stereo sets, and other similar types of electronic devices. The amount of energy that is consumed when an electronic device is in standby mode is small in comparison to the amount of power that the electronic device uses when the set is turned on. However, because the use of standby mode in electronic devices is so widespread and because the use of standby mode does consume electric power, the power that is consumed by standby mode in the aggregate is quite large. To realize the magnitude of the aggregate power consumption due to use of the standby mode, one may multiply the small amount of power consumed in one television set that is operating in standby mode by the millions of television sets that exist in the world today. 
     Certain improvements in electronic design within the last few years have reduced the amount of power consumption that is due to the operation of standby mode circuitry. Because the aggregate amount of standby mode power consumption is still quite large, however, there still remains a need to find additional ways to further reduce the level of standby mode power consumption in electronic devices. 
     SUMMARY OF THE INVENTION 
     To address this problem, it is a primary object of the present invention to provide an apparatus and method for reducing the level of power consumption in an electronic device that is operating in standby mode. 
     It is a further object of the present invention to provide a means for reducing the amount of power consumption in an electronic device that is operating in standby mode by at least fifty percent. 
     The apparatus and method of the present invention will be described as an apparatus and method for reducing the level of power consumption in a television set that is operating in a standby power mode. It is important to realize that the apparatus and method of the present invention is not limited to only a television set. Those skilled in the art will readily understand that the principles of the present invention may also be successfully applied to other types of electronic devices. However, in the descriptions that follow, a television set is employed for illustration purposes 
     In the preferred embodiment of the invention, the invention comprises a standby cycle timer circuit coupled within a television power supply circuit capable of operating in a standby mode. The standby cycle timer causes the power supply circuit to alternate between its standard standby mode and a shutdown power mode. In a shutdown power mode, all power from the power supply circuit to other circuit elements is turned off. After a predetermined period of time has elapsed, the shutdown power mode is terminated and the standby power mode is resumed. After another predetermined period of time has elapsed, the standby power mode is terminated and the shutdown power mode is resumed. The alternation of the standby power mode and the shutdown power mode continues until the television receives an “on” signal to power up the television for normal operation. 
     If the time that the shutdown power mode is in operation is equal to the time that the standby power mode is in operation, then the power consumption of the combination is half of the power consumption required to otherwise operate in only the standby power mode. If the time that the shutdown power mode is in operation is greater than the time that the standby power mode is in operation, then the power consumption of the combination will be less than half of the power consumption required to otherwise operate in only the standby power mode. Therefore, the invention provides a significant reduction in the amount of power needed to operate a television in a standby power mode. 
     In a typical television power supply circuit, a pulse width modulator circuit controls the operation of the power supply circuit by alternately turning the power on and off in the primary side of a flyback transformer circuit. The pulse width modulator circuit puts the power supply circuit into standby mode turning off the power for longer periods of time. 
     The standby cycle timer of the present invention is coupled to the pulse width modulator circuit. The standby cycle timer alternately sends “on” and “off” signals to said pulse width modulator circuit. When the standby cycle timer sends an “on” signal, the pulse width modulator circuit causes the power supply circuit to operate in a standby mode. When the standby cycle timer sends an “off” signal, the pulse width modulator circuit causes the power supply circuit to operate in a shutdown mode. The standby cycle timer causes the “on” and “off” signals to be sent to the pulse width modulator circuit at specific time intervals. The time intervals are predetermined by the choice of particular values for certain circuit elements in the standby cycle timer. 
     The standby cycle timer automatically alternates between sending the required “on” and “off” signals to the pulse width modulator circuit. The alternate “on” and “off” signals control the pulse width modulator so that it causes the power supply circuit to automatically alternate between the standby mode and the shutdown mode. When the television receives an external signal to resume normal operation, the standby cycle timer automatically ceases sending the alternate “on” and “off” signals, and sends only an “on” signal to the pulse width modulator circuit so that the power supply circuit can provide continuous operating power to the television. 
     When the television receives an external signal to cease normal operation, the standby cycle timer automatically resumes sending the alternate “on” and “off” signals to the pulse width modulator circuit to resume alternating between the standby mode and the shutdown mode. 
     The foregoing has outlined rather broadly the features and technical advantages of the present invention so that those skilled in the art may better understand the Detailed Description of the invention that follows. Additional features and advantages of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they may readily use the conception and the specific embodiment disclosed as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the invention in its broadest form. 
     Before undertaking the Detailed Description, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document: the terms “include” and “comprise” and derivatives thereof, mean inclusion without limitation; the term “or,” is inclusive, meaning and/or; the phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like; and the term “controller,” “processor,” or “apparatus” means any device, system or part thereof that controls at least one operation, such a device may be implemented in hardware, firmware or software, or some combination of at least two of the same. It should be noted that the functionality, associated with any particular controller may be centralized or distributed, whether locally or remotely. Definitions for certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior, as well as future uses of such defined words and phrases. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, wherein like numbers designate like objects, and in which: 
     FIG. 1 is a simplified circuit diagram of a typical power supply circuit with multiple outputs for powering a television set showing the connection of the standby cycle timer of the present invention within said power supply circuit; 
     FIG. 2 is a circuit diagram of a standby cycle timer of the present invention; and 
     FIG. 3 is a timing diagram of the electronic signals that are utilized in the present invention; and 
     FIG. 4 is a flow diagram illustrating the logic of the operation of the alternating standby mode apparatus of the present invention. 
    
    
     DETAILED DESCRIPTION 
     FIGS. 1 through 4, discussed below, and the various embodiments used to describe the principles of the present invention in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the invention. Those skilled in the art will understand that the principles of the present invention may be implemented in any suitably arranged electronic device capable of operating in a standby or low power mode. 
     FIG. 1 shows a simplified circuit diagram of a typical power supply circuit  100  for powering a television set comprising a flyback transformer circuit with multiple outputs. The primary side of the transformer of the power supply circuit  100  comprises a power source  102  coupled to an electromagnetic interference (EMI) filter  104  coupled to a bridge rectifier circuit  106  coupled to the primary coil  108  of the transformer. The power supply circuit  100  is controlled by a standby controller  110 . In the preferred embodiment of the invention the standby controller  110  is a pulse width modulator (PWM) control integrated circuit (IC)  110 . For convenience, the pulse width modulator control integrated circuit  110  will be referred to as the PWM circuit  110 . PWM circuit  110  controls the operation of power supply circuit  100  through transistor  112 . 
     A feedback signal is fed back from one of the secondary side outputs through feedback loop  120  and is used to provide closed loop regulation of the PWM circuit  110 . The feedback signal at the primary side is isolated from the secondary side by an isolator circuit  130  that may employ, for example, an opto-isolator device of a type well known in the prior art. 
     The secondary side consists of multiple outputs that are used to generate the different voltage levels required in a typical television. For example, the television may have a voltage output level connected to the high voltage gain (HVG) circuit  140  that has a value of several hundred volts. The HVG circuit  140  signal is fed to a voltage multiplier that ultimately delivers the several kilovolts needed by the cathode ray tube (CRT) (not shown). This signal may be tightly regulated by feedback loop  120 . 
     A second output voltage having a value in the range of approximately one hundred volts to two hundred volts (100V 200V) is used to operate the video amplifiers  150  that modulate the CRT. A third output supply of approximately six volts (6V) is used to operate the heater  160  to heat the filament in the CRT. A fourth output voltage of twelve volts (12V) is used to drive the audio amplifiers  170 . The fifth output voltage provides five volts (5V) for the logic circuits  180 . 
     The output voltage for the video amplifiers  150  is regulated by providing a linear regulator (LR)  200  at the transformer output. The output voltage for the audio amplifiers  170  is regulated by a linear regulator (LR)  210  at the output. The output voltage for the logic circuits  180  is regulated by providing linear regulator (LR)  220  at the output. Only the output voltage for the HVG circuit  140  is well regulated by the primary side PWM circuit  110  through feedback loop  120 . The other output voltages would usually suffer from poorer performance if they were not regulated with the linear regulators  200 ,  210 , and  220 . 
     In addition to delivering power during normal operation, the power supply circuit for the television must be capable of going into a standby mode. The standby mode dissipates as little power as possible but still provides some minimum functions. In the standby mode it is desirable to keep the CRT heaters  160  warm so that the television picture comes on nearly instantly when the television is turned back on. Also the power to the logic circuits  180  must be maintained in standby mode so that television&#39;s logic circuits  180  and the television&#39;s main microprocessor (not shown) can quickly power up when the television is turned back on. 
     The power to the logic circuits  180  in standby mode is also used to operate the infrared (IR) remote receiver  230  via power supply line  240 . The IR receiver  230  receives a signal from the infrared (IR) detector  250  in response to a transmitted infrared on/off signal from an infrared transmitter  260  located in a typical hand-held television remote control unit. The IR receiver  230  also contains a memory circuit  232  for storing signal values during the times when IR receiver  230  is without power during the shutdown mode. 
     The output voltage circuit that supplies power to the HVG circuit  140  has a switch  270  in series with the load so that during standby mode the switch  270  is opened to turn off power to the HVG circuit  140 . Similarly, the output voltage circuit that supplies power to the video amplifiers  150  has a switch  280  in series with the load so that during standby mode the switch  280  is opened to turn off power to the video amplifiers  150 . Similarly, the output voltage circuit that supplies power to the audio amplifiers  170  has a switch  290  in series with the load so that during standby mode the switch  290  is opened to turn off power to the audio amplifiers  170 . 
     When the standby mode is operating, switch  270 , switch  280 , and switch  290  are opened by the IR receiver  230  to turn off power to the respective circuit branches controlled by these switches. Alternatively, switch  270 , switch  280 , and switch  290  may be opened by the television&#39;s main microprocessor (not shown) during standby mode. As a result of switch  270 , switch  280 , and switch  290  being opened during standby mode, the power that is consumed by the television is substantially lower in standby mode than it is in normal operating mode. 
     Even so, there are significant inefficiencies involved in operating the television power supply circuit in a standby mode. Most power supplies run most efficiently at high output power levels. Power supply operating efficiency drops off significantly when the power supply is operated at low output power levels. This inefficiency contributes to additional unnecessary power consumption. Therefore, it is desirable to reduce the level of power consumption in the standby mode as much as possible. 
     To further reduce the level of power consumption during standby mode, the present invention provides an apparatus and method for operating the power supply circuit with an alternating standby mode. That is, the present invention causes the power supply circuit to alternate between a standby mode of operation and a shutdown mode. 
     In the shutdown mode all power to the secondary side of the power supply is turned off completely. This means that during the time interval of the shutdown mode the heater circuit  160  is turned off, and the logic circuits  180  are turned off, and the IR receiver  230  is turned off. If the duty ratio between the standby mode and the shutdown mode is designed to be fifty percent, then the standby mode is on half of the time and the shutdown mode is on half of the time. Then the standby power consumed using the alternating mode method of the present invention is half of the standby power consumed when one uses the standard standby mode method. Because the heater current in heater  160  will also be reduced by half, the time to start up the television will be slightly increased compared to the time to start up the television using the standard standby mode method. 
     If the duty ratio between the standby mode and the shutdown mode is designed to be less than fifty percent, then the standby mode is on less than half of the time and the shutdown mode is on more than half of the time. Then the standby power consumed using the alternating mode method of the present invention is less than half of the standby power consumed when one uses the standard standby mode method. 
     To implement the alternating standby mode of the present invention, a new control circuit is added to the primary side of the power supply circuit. The new control circuit is the standby cycle timer  300 . The standby cycle timer  300  controls the PMW circuit  110  through the PMW circuit&#39;s “on/off” input as shown in FIG.  1 . The standby cycle timer  300  is controlled by the ON/STANDBY signal from the IR receiver  230  on the secondary side of the power supply circuit. IR receiver  230  sends either an ON signal or a STANDBY signal to the standby cycle timer  300 . The signal at the standby cycle timer  300  is isolated from the secondary side of the power supply circuit by an isolator circuit  320  that may employ, for example, an opto-isolator device of a type well known in the prior art. 
     When the ON/STANDBY signal is not active (when normal operation of the television is in progress), the standby cycle timer  300  generates a continuous “on” signal to the PWM circuit  110 . When the ON/STANDBY signal is activated, then the standby cycle timer  300  generates an alternating signal with a preset duty ratio and frequency to alternately turn the PWM circuit  110  on and off. 
     A preferred embodiment of the standby cycle timer  300  of the present invention is shown in FIG.  2 . When the ON/STANDBY signal is high (the ON state) then the output of inverter  400  is low and the output of AND gate  402  is also low. The low output state from AND gate  402  turns off transistor Q 1   404 . When transistor Q 1   404  is off, capacitor C  406  begins to charge from the V supply  voltage  408 . The voltage on capacitor C  406  begins to rise toward the voltage level of the V supply  voltage  408 . 
     As the voltage on capacitor C  406  increases toward the value of the V supply  voltage  408 , the output of Comparator COMP  2  ( 410 ) is forced to go high as well because its threshold on its negative input is only one third (⅓) of the V supply  voltage  408 . This is due to the fact that the value of resistor  412  is chosen to be twice the value of resistor  414  and the negative input of Comparator Two  410  is connected to the circuit node that connects resistor  412  and resistor  414 . As a result the output of Comparator Two  410  is high and the input to the PWM circuit  110  is always “on”. 
     When the ON/STANDBY signal goes low (when the television is in the standby mode) then the output of inverter  400  is high and the output of AND gate  402  is also high because the V a  signal from Comparator One  416  is high. The high output state from AND gate  402  turns on transistor Q 1   404 . Turning on transistor Q 1   404  forces capacitor C  406  to discharge and bring V c  quickly down to a value of zero volts. 
     The threshold to the negative input of Comparator One  416  is two thirds (⅔) the value of the V supply  voltage  408 . This is due to the fact that the value of resistor  418  is chosen to be twice the value of resistor  420  and the negative input of Comparator One  416  is connected to the circuit that connects resistor  418  and resistor  420 . Because the threshold to the negative input of Comparator One  416  is two thirds (⅔) the value of the V supply  voltage  408 , the output of Comparator One  416  will go low when V c  drops to zero volts. At the same time, the output of Comparator Two  410  will also go low, and thereby send an “off” signal to the PWM circuit  110 . The PWM circuit  110  then will turn itself off. 
     Now because the output of Comparator One  416  is low, the output of the AND gate  402  also goes low and turns off transistor Q 1   404 . After transistor Q 1   404  is turned off, the voltage on capacitor C  406  will slowly increase with a time constant RC. The time constant RC. is the product of the resistance of resistor R  422  and the capacitance of the capacitor C  406 . When the voltage at V c  reaches a value of one third (⅓) of the value of the V supply  voltage  408 , the output of Comparator Two  410  goes high. A high output from Comparator Two  410  sends an “on” signal to PWM circuit  110 . The “on” signal turns on the PWM circuit  110  and causes the power supply circuit  100  to resume the standby mode. 
     When the voltage at V c  reaches two thirds (⅔) of the V supply voltage  408 , the output of Comparator One  416  goes high and the cycle repeats itself as shown in FIG.  3 . By setting appropriate values for the capacitor C  406  and for the resistors  412 ,  414 ,  418 ,  420 , and  422 , the frequency and the duty ratio of the alternating standby mode signal may be easily adjusted to any desired values. 
     The operation of the power supply circuit utilizing the present invention that has been described above is illustrated in the timing diagram shown in FIG.  3 . Following the reception of an “off” signal from the IR transmitter  260 , the ON/STANDBY output signal from the IR receiver  230  goes low. At the same time the signals V c , V a , and PWM on/off all go low, and the power supply circuit  100  is put into the shutdown mode. The switching signal from the PWM circuit  110  is completely turned off. After a period of time determined by the component values of resistor R  422  and capacitor C  406 , the standby mode is activated. Now the PWM circuit  110  enters its standby mode (low power mode) of operation which is usually a form of burst mode in which the PWM circuit  110  cycles between “high frequency switching” and “off” at a rate of a few kilohertz. 
     The alternation of the shutdown modes and the standby modes continues until the IR transmitter  260  sends an “on” signal that is received by the IR receiver  230 . Since the IR receiver  230  is only active during the standby mode, the transmission must be sent several times to ensure that it overlaps with the time during which the IR receiver  230  is on. In FIG. 3 the first “on” transmission from the IR transmitter  260  arrives during a shutdown period and is not received. The second “on” transmission from the IR transmitter  260  arrives during a standby period and is received. 
     IR receiver  230  stores signal information in memory  232  so that IR receiver  230  can remain in the standby mode when it is powered up during alternating standby cycles. That is, memory  232  stores signal information for IR receiver  230  during the times when IR receiver  230  is without power during the shutdown mode. 
     The duration of the standby mode and the duration of the shutdown mode can be on the order of one fourth (¼) of a second. Because the time required to push the “power on” button in a television is likely be more than one fourth (¼) of a second, it is likely that the television will be in at least a portion of one standby mode cycle when the “power on” button is pushed and the corresponding “on code” is received. Therefore television viewers in most instances will be able to turn on the television with a single push of the “power on” button. If the television does not turn on after the first push of the “power on” button, the viewer can simply push the “power on” button again. 
     FIG. 4 is a flow diagram illustrating the logic of the operation of an exemplary alternating standby mode apparatus of the present invention. In decision step  500  a determination is made whether the electronic device is on. If the electronic device is on, then the normal operating power is used as shown in operation step  560 . If the electronic device is not on, then the standby power is turned on as shown in operation step  510 . 
     Then the electronic device is operated in the shutdown mode for one cycle as shown in operation step  520 . Then the electronic device is operated in the standby mode for one cycle as shown in operation step  530 . Then in decision step  540  a determination is again made whether the electronic device is on. If the electronic device is on, then the standby power is turned off as shown in operation step  550  and the normal operating power is used as shown in operation step  560 . 
     If the electronic device is not on, then the electronic device is again operated in the shutdown mode for one cycle as shown in operation step  520  and the cycle repeats. The alternation between the standby mode and the shutdown mode continues indefinitely until the electronic device is turned back on. 
     Although the present invention has been described in detail with respect to a television power supply, those skilled in the art should understand that they can make various changes, substitutions and alterations herein without departing from the spirit and scope of the invention in its broadest form.