Power supply control apparatus and method thereof

[0002] This application claims the benefit of Korean No. 2001-12241, filed Mar. 9, 2001, in the Korean Industrial Property office, the disclosure of which is incorporated herein by reference.

[0003] 1. Field of the Invention

[0004] The present invention relates to a system to which power is supplied using a switching mode power supply (SMPS), and more particularly, to a power supply control apparatus, which is capable of reducing power consumption by a SMPS in the system, such as a facsimile machine, for transmitting, receiving, and outputting data, and a method thereof.

[0005] 2. Description of the Related Art

[0006] A switching mode power supply (SMPS) provides electric power to electric loads with a switching operation. A conventional SMPS, which is included in a system, such as a facsimile machine, for outputting data, is shown in FIG. 1. FIG. 1 illustrates an example in which power is supplied to a system controller (CPU) included in a system and peripherals from the SMPS included in the system.

[0007] Referring to FIG. 1, in the conventional SMPS, an alternating current (AC) voltage is changed into a direct current (DC) voltage by a rectifier circuit 101, and the DC voltage is transmitted to a driving voltage-applying portion 105 and a primary winding Np when an AC switch SW1 is turned on. In this case, a driving voltage Vcc is not applied to a pulse width modulation-integrated circuit PWM-IC 110, and thus power is induced in a primary winding Np. The driving voltage-applying portion 105 includes start up resistors R1 and R2, a capacitor C1, a resistor R3, and a diode D1 and supplies the driving voltage Vcc to the PWM-IC 110. That is, when the DC voltage is applied to the driving voltage-applying portion 105, the capacitor C1 is charged through the start up resistors R1 and R2. Due to the voltage in the capacitor C1, the driving voltage Vcc is supplied to a terminal P1 of the PWM-IC 110. As a result, the PWM-IC 110 outputs a signal for controlling a switching operation of a field-effect transistor (FET) through a terminal P3. An output switching control signal is applied to a gate terminal of the FET through a resistor R4. A resistor R5 is connected between the FET and a ground. When the FET is turned on, the primary winding Np in a transformer 115 allows the power to be induced in secondary windings Ns1 and Ns2 and in an auxiliary winding Na.

[0008] When the power is induced in the auxiliary winding Na of a transformer 115, the driving voltage Vcc is supplied to the PWM-IC 110 through the diode D1 and the resistor R3 in the driving voltage-applying portion 105. In a case where the FET is turned off and thus power is not induced in the auxiliary winding Na, the driving voltage Vcc is supplied to the PWM-IC 110 by the voltage charged in the capacitor C1.

[0009] As above, the power, which is induced in the auxiliary winding Na and the secondary windings Ns1 and Ns2, is determined in accordance with the switching operation of the FET. The switching operation of the FET is performed in accordance with a duty cycle, which is determined in the PWM-IC 110 according to a feedback signal provided from a feedback portion 120 through a terminal P4. The feedback portion 120 senses a voltage Vo1 output to the system controller (not shown) and provides a feedback signal to the terminal P4 of the PWM-IC 110 so that the output voltage Vo1 is maintained at a constant level. The PWM-IC 110 measures the peak value of current flowing into the FET through a terminal P2 and thereby prevents over-current from flowing into the FET. That is, in a case where it is recognized that the over-current flows into the FET in accordance with the measured peak value of the current, the PWM-IC 110 shuts down the FET.

[0010] Meanwhile, AC power induced in the secondary windings Ns1 and Ns2 is smoothed into a DC voltage by diodes D2 and D3 and capacitors C2, C3, C4, and C5, respectively, and thus is supplied to peripherals (not shown) and to the system controller.

[0011] However, when an AC switch SW1 is turned off, the SMPS shown in FIG. 1 stops working to supply the power to the peripherals and the system controller, as described above.

[0012] Likewise, the conventional SMPS continuously supplies power to the system controller and the peripherals in a case where the AC switch SW1 is not turned off. Thus, in order to reduce power consumption, the AC switch SW1 must be turned off when the system is not used. However, it is unknown when the output of data is required in the system, such as a fax machine, and thus the system always turns on the AC switch SW1. Thus, the power is continuously applied to the system controller and to the peripherals even when the system is not used, thereby unnecessarily consuming power.

[0013] To solve the problem, in the related art, a sleep mode has been suggested for cutting off power supplied from the SMPS to all of the peripherals of the system except the system controller in a case where it is recognized by the system controller that the system has not performed an operation for a predetermined period of time, has been suggested. However, even in a case where the sleep mode is set, the SMPS continuously supplies power to the controller, and the work for supplying power from the SMPS to the peripherals is continuously performed even though the power supply of the SMPS to the peripherals is cut off. Thus, even in a case where the sleep mode is set, power continues to be consumed in the SMPS.

[0014] To solve the above problems, it is a first object of the present invention to provide a power supply control apparatus, which controls the operation of a switching mode power supply (SMPS) so that power consumption in a system including the SMPS is reduced, and a method thereof.

[0015] It is a second object of the present invention to provide a power supply control apparatus, which controls to operate a SMPS only when power to a system is required, without a need for an alternating current (AC) switch, and a method thereof.

[0016] It is a third object of the present invention to provide a power supply control apparatus so that a system, such as a fax machine, is automatically turned on only when the output of data is required, and a method thereof.

[0017] Additional objects and advantageous 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.

[0018] Accordingly, to achieve the above and other objects, according to the present invention, there is provided an apparatus for controlling power supply to each part in a system including a system controller and a data output device. The apparatus includes a switch that is set to an ON state by a user's contact, a detection portion which is connected in parallel with the switch and for detecting whether a signal for requiring a predetermined operation is applied to the system from outside, and a power supply portion for supplying power to each part of the system when the switch is temporarily set to the ON state or a second signal for indicating the detection of the signal is input from the detection portion, and for terminating the power supply to each part in the system including the system controller when a power off signal is applied from the system controller when the switch is set to an OFF state or when the second signal for indicating the detection of the signal is not input from the detection portion.

[0019] In order to achieve the above and other objects, according to the present invention, there is provided an apparatus for controlling power supply to a system having a system controller and peripherals requiring the power supply. The apparatus includes a switch that is controlled to turn on/off by a user, a first switching unit, a pulse width modulation (PWM) portion that supplies a pulse signal for controlling the switching operation of the first switching unit when a driving voltage is applied, a transformer that supplies power in accordance with the operation of the first switching unit, a driving voltage-applying portion which applies the driving voltage to the PWM portion when the switch is turned on, and a power-off signal detection portion which stops the operation of the PWM portion when a power off signal is detected. The system controller generates the power off signal when a predetermined period of time passes after power output from the transformer is applied, and then, a sleep mode is set.

[0020] The apparatus further includes a detection portion for detecting whether a signal for requiring a predetermined operation is applied to the system from outside, and the driving voltage-applying portion is connected to the detection portion so that the driving voltage is applied to the PWM portion when a second signal for indicating the detection of the signal from the detection portion is applied.

[0021] In order to achieve the above and other objects, according to the present invention, there is provided a method of controlling power supply in a system which supplies power output from a power supply function portion to a system controller and peripherals. The method includes controlling the power that is supplied to the peripherals and the system controller from the power supply function portion either when a switch that is set to an ON state if a user is in contact with the switch, or when a signal for requiring a predetermined operation is applied from outside the system, and controlling the power supply function portion to terminate the power supply to the peripherals and the system controller when a power off signal is generated from the system controller in the state where power is supplied to the peripherals and the system controller.

[0022] These and other objects and advantages of the present invention will become more apparent and more readily appreciated from the following description of the preferred embodiment, taken in conjunction with the accompanying drawings of which:

[0023] FIG. 1 is a circuit diagram of a conventional switching mode power supply (SMPS);

[0024] FIG. 2 is a detailed circuit diagram of a power supply control apparatus according to an embodiment of the present invention; and

[0025] FIGS. 3A through 3E are timing diagrams of the power supply control apparatus shown in FIG. 2.

[0026] Reference will now be made in detail to the present preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described in order to explain the present invention by referring to the figures.

[0027] FIG. 2 is a detailed circuit diagram of a system including a power supply control apparatus according to an embodiment of the present invention and illustrates an example of the system, such as a facsimile machine or a printer, having a function of transmitting and receiving data through a telephone line or a network communication line.

[0028] Referring to FIG. 2, the system including a power supply control apparatus includes a switching mode power supply (SMPS) function portion 200, a switch SW2, peripherals 225, and a system controller 230. The SMPS function portion 200 includes a rectifier circuit 201, a driving voltage-applying portion 205, a transformer 215, a pulse width modulation-integrated circuit PWM-IC 210, a field-effect transistor (FET) corresponding to a switching unit, a feedback portion 220, a power-off signal detection and over-voltage prevention portion 240, a ring signal detection portion 250 connected to an external telephone line or a network system, resistors R4 and R9, and capacitors C7 and C8.

[0029] The ON/OFF state of the switch SW2 is controlled by a user. The switch SW2 has the same structure as that of a tact switch. Thus, the switch SW2 is set to the ON-state only when the user contacts the switch SW2 by pressing the switch SW2, and the switch SW2 is set to the OFF state in a case where the user does not contact the switch SW2 by releasing the switch SW2.

[0030] The rectifier circuit 201 rectifies an alternating current (AC) voltage when the AC voltage is applied to the rectifier circuit 201, and outputs a direct current (DC) voltage, as explained with regard to the rectifier circuit 101 shown in FIG. 1. The output DC voltage is transmitted to the driving voltage-applying portion 205 and the transformer 215. However, in this case, a driving voltage Vcc is not applied to the PWM-IC 210, and thus the FET is in an OFF state, and power is not induced in the transformer 215. Thus, even though the AC voltage is applied to the SMPS function portion 200, the SMPS function portion 200 doesn't supply power to the system controller 230 and the peripherals 225. The peripherals 225 are elements in the system other than the system controller 230 and require the power supply to drive a motor.

[0031] The driving voltage-applying portion 205 comprises start up resistors R1, R2, R3, R6, R7, and R8, capacitors C1 and C6, and a NPN-type transistor Q1, and supplies the driving voltage (Vcc) to the PWM-IC 210. However, unlike the conventional SMPS of FIG. 1, when the switch SW2 is not turned on during start up, the driving voltage Vcc cannot be supplied to the PWM-IC 210. This is the reason the transistor Q1 is maintained in an OFF state when the switch SW2 is not turned on. As a result, the SMPS function portion 200 is in a power off mode.

[0032] In this way, in a case where the user presses the switch SW2 in the power off mode, the transistor Q1 is in a conductive state such that the DC voltage applied through the start up resistors R1 and R2 is supplied to a terminal P1 of the PWM-IC 210 through a contact point A between the transistor Q1 and the capacitor C6. As a result, the PWM-IC 210 outputs a switching control signal having a duty cycle to the FET through a terminal P3 in response to the driving voltage.

[0033] In a case where the FET is switched, power is induced in the secondary windings Ns1 and Ns2 and the auxiliary winding Na by current flowing through the primary winding Np of the transformer 215. As a result, the power induced through capacitors C2, C3, C4, and C5, and diodes D2 and D3, each coupled to the secondary windings Ns1 and Ns2, is smoothed and transmitted to the peripherals 225 and the system controller 230.

[0034] After that, even though the switch SW2 is not pressed by the user, as shown in FIG. 2, the driving voltage (Vcc) is supplied to the terminal P1 of the PWM-IC 210 by the power induced in the auxiliary winding Na and the voltage charged in the capacitor C1, and thus switching of the FET is controlled. In addition, as shown in FIG. 2, the PWM-IC 210 adjusts the duty cycle of the FET according to a feedback signal, which is transmitted from the feedback portion 220 to a terminal P4 of the PWM-IC 210.

[0035] In this manner, in a case where the power to the SMPS function portion 200 is turned on, and thus the power is applied to the system controller 230 and the peripherals 225, the system controller 230 checks whether the peripherals 225 of the system operate or not. As a result of checking, when a non-operating period during which the peripherals 225 don't operate exceeds a predetermined reference period of time, the system can be set to a sleep mode, and the system controller 230 outputs a power off signal with an active state. In an embodiment of the present invention, the active state means a high level.

[0036] As a result, the power-off signal detection and over-voltage prevention portion 240 detects the power off signal. The power-off signal detection and over-voltage prevention portion 240 includes a photocoupler having a photodiode PhD2 and a phototransistor PhQ2, a transistor Q2, resistors R10, R11, R13, and R14, and a Zener diode ZD. Thus, the power off signal with the high level is applied from the system controller 230, the transistor Q2 is in a conductive state, and thus the photodiode PhD2 emits light. As a result, the phototransistor PhQ2 becomes conductive, and thus the driving voltage Vcc applied to the terminal P1 is supplied to an ON/OFF control terminal P5 of the PWM-IC 210. In such a case, a certain level of an FET off signal, which is applied to the ON/OFF control terminal P5 of the PWM-IC 210 by the capacitor C7, becomes high. As a result, the PWM-IC 210 is turned off to be in the off state in response to the high level of the FET off signal, and thus the outputting of the switching control signal of the FET stops. Thus, the SMPS function portion 200 is in a power off state.

[0037] Likewise, the operation in which the SMPS function portion 200 is set to the power off mode after being set to a power on state will be more easily understood from intervals from “power on” to “power off” of the timing diagrams shown in FIGS. 3A through 3E.

[0038] That is, in a case where the switch SW2 is controlled to be in the ON state, as shown in FIG. 3D, in the state where AC power is applied to the SMPS function portion 200, as shown in FIG. 3A, the level of output voltages Vo1 and Vo2 transmitted from the SMPS function portion 200 to the peripherals 225 and the system controller 230 is changed from a low state into a high state, as shown in FIG. 3C. This means that the power is supplied to the peripherals 225 and the system controller 230. In this way, the system doesn't perform any operations after the power is supplied to the peripherals 225 and the system controller 230, and thus the system is set to the sleep mode, and when the duration of the sleep mode exceeds the predetermined reference period of time, the power off signal output from the system controller 230 is changed from a low level to the high level, as shown in FIG. 3B. As a result, as described above, the SMPS function portion 200 is in the power off mode, and thus the output voltages Vo1 and Vo2 output to the peripherals 225 and the system controller 230 are changed from the high level to the low level, as shown in FIG. 3C.

[0039] The above-mentioned power-off signal detection and over-voltage prevention portion 240 may be driven so as to prevent the over-voltage from being supplied to the peripherals 225 when the SMPS function portion 200 is in the power on mode. That is, in a case where the output voltage Vo2 is higher than a threshold voltage of the Zener diode ZD, the transistor Q2 becomes conductive, and thus the photodiode PhD2 emits the light. As a result, the phototransistor PhQ2 becomes conductive, and the PWM-IC 210 stops operation, as described above. Thus, the SMPS function portion 200 is set to the power off mode, and thus power supply to the peripherals 225 and the system controller 230 is cut off.

[0040] As described above, in a case where the user presses the switch SW2 so as to transmit arbitrary data in the state where the SMPS function portion 200 is set to the power off mode, like during start up, the SMPS function portion 200 drives and supplies the output voltages Vo1 and Vo2 to the peripherals 225 and the system controller 230, respectively.

[0041] That is, as shown from the intervals from “power on” to “power off” of the timing diagrams shown in FIGS. 3A through 3E, in a case where the switch SW2 is pressed by the user at a time shown in FIG. 3D, the output voltages Vo1 and Vo2 output from the SMPS function portion 200 are changed from the low level into the high level, as shown in FIG. 3C.

[0042] In a case where a predetermined period of time for setting the sleep mode passes after a related data receiving or outputting operation is completed and the system is set to the sleep mode, as shown in FIG. 3B, the power off signal is generated, and thus the SMPS function portion 200 is set to the power off mode, and the output voltages Vo1 and Vo2 output from the SMPS function portion 200 are changed into the low level, as shown in FIG. 3C.

[0043] In this manner, in a case where a ring signal is detected by a ring signal detection portion 250 in the state where the SMPS function portion 200 is set to the power off mode, the transistor Q1 of the driving voltage-applying portion 205 is in a conductive state, and thus, like during start up, the driving voltage (Vcc) is supplied to the PWM-IC 210. Thus, the SMPS function portion 200 is set to the power on mode and supplies power to the peripherals 225 and the system controller 230, and thereby performs the the data receiving operation.

[0044] The ring signal detection portion 250 includes a photocoupler having a photodiode PhD3 and a phototransistor PhQ3. The photodiode PhD3 may be included outside the SMPS function portion 200. For example, in a case where a line interface unit (LIU) (not shown) is included in the system, the photodiode PhD3 may be included in the LIU. The ring signal detection portion 250 connects the photodiode PhD3 to a ring signal-receiving portion (not shown) so that the ring signal transmitted through a tip/ring line is detected. The ring signal has characteristics of being transmitted by inducing voltage, and thus the ring signal may be received even when the power of the system is off.

[0045] As described above, as the ring signal is detected in the state where the SMPS function portion 200 is set to the power off mode, the process in which the SMPS function portion 200 is set to the power on mode will be more easily understood by referring to the interval from “power on according to the generation of the ring signal” to “power off” as shown in the timing diagrams of FIGS. 3A through 3E. That is, in a case where the ring signal is detected as show in FIG. 3E in the state where the SMPS function portion 200 is set to the power off mode after a predetermined period of time after being set to the sleep mode, the SMPS function portion 200 is set to the power on mode, and thus the output voltages Vo1 and Vo2 are changed from the low level to the high level.

[0046] The operation performed in a case where the ring signal is externally applied is explained in the above-mentioned embodiment; however, a signal (an arbitrary operation-requiring signal of a system externally applied) which can be detected using the same structure as that of the ring signal detection portion 250 in the state where the power of the system is off, may be applied to the embodiment. In addition, the transistors Q1, Q2, and Q3 mentioned in the embodiment are used as a switching unit.

[0047] According to the present invention, the power supply state of the SMPS in the system to which the power is supplied using the SMPS is adaptively controlled to be changed according to an operation state of the system, thereby reducing unnecessary power consumption and performing the power on/off of the SMPS without a need for an extra AC switch. There is no need to include an extra auxiliary power so as to detect a ring signal in the state where the power of the system is turned off.

[0048] In particular, in a case where data is not transmitted in a system, such as a fax machine, the essential power supply from the SMPS to the system controller and the peripherals stops, thereby reducing power consumption in the system.

[0049] While this invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

[0050] Although a few preferred 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 this embodiment without departing from the principles and sprit of the invention, the scope of which is defined in the claims and their equivalents.