Abstract:
A printer is connected to a host via an interface having a data wire and a power supply wire. The printer includes a power supply portion to convert an external power to a driving power and to supply the driving power to the respective electronic components of the printer, a switch portion to determine whether to supply the driving power to the respective electronic components, and a controller capable of operating from the voltage applied through the power supply wire, to control the switch portion according to a transmission of printing data through the data wire. The controller controls the switch portion to stop a supply of the driving power to the respective electronic components when the printing data is not transmitted for a predetermined time, and when the voltage is not applied through the power supply wire of the interface. Accordingly, unnecessary power consumption is reduced and convenience is improved.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of Korean Application No. 2002-4829, filed Jan. 28, 2002, in the Korean Industrial Property Office, the disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a printer, and more particularly, to a printer capable of controlling a power supply via a host. 
     2. Description of the Related Art 
     Generally, a printer is usually left in an on-state when the printer is not in use. In the on-state, the printer starts a printing operation upon receipt of a selection command from a user. In the conventional printer, the power is constantly applied to at least a part or to the entire system of the printer, even if the printer is turned off. 
     Accordingly, power is unnecessarily consumed. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a printer capable of controlling a power supply via a host. 
     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. 
     The above object is accomplished by providing a printer connected to a host via an interface having a data wire through which printing data is transmitted from the host and a power supply wire through which a voltage is applied from the host, the printer comprising a power supply portion for converting an external power to a driving power and supplying the driving power to the respective electronic components of the printer, a switch portion for determining whether to supply the driving power to the respective electronic components, and a controller capable of operating by the voltage applied through the power supply wire, for controlling the switch portion according to a transmission of the printing data through the data wire. 
     The controller controls the switch portion to stop supplying the driving power to the respective electronic components when the printing data is not transmitted for a predetermined time, when the respective electronic components do not operate for a predetermined time and when the voltage is not applied through the power supply wire. 
     Accordingly, the power supply to the printer is controlled via the host according to the transmission of the printing data from the host, and a power state of the host. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects and advantages of the invention will become apparent and more readily appreciated from the following description of the preferred embodiments, taken in conjunction with the accompanying drawings of which: 
     FIG. 1 is a block diagram showing a power supply apparatus of a printer according to an embodiment of the present invention; 
     FIG. 2 is a view showing a circuit of a power supply portion of FIG. 1; and 
     FIGS. 3A and 3B are flow charts showing a power supply control method of the printer of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     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 like elements throughout. 
     A described embodiment of the present invention includes a computer as a USB host, and a printer as a USB device of a USB system. 
     A printer  200  has a logic portion  210  to logically control an operation of the printer  200 , a printing portion  220  to perform a printing operation of the printer  200 , a power supply portion  230  to supply a power to the printer  200 , and an input portion  240  to input a selection command which is made by a user for the printing operation and other operations of the printer  200 . 
     The logic portion  210  generally has a USB interface  211 , a storing portion  212 , and a controller  217 . A logic power to operate the logic portion  210  ranges approximately from +2.5V to +3.3V. 
     The storing portion  212  has a ROM (not shown) in which a program for operations and controls of the printer  200  is stored, and a RAM (not shown) in which printing data received from a host  100  (such as a Personal Computer) is temporarily stored. 
     The USB interface  211  has a data wire (D+, D−), through which the printing data is transmitted, and a Voltage Bus (VBUS) to supply a voltage of +5V. 
     A DC/DC converter  232  converts the voltage of +5V, which is applied from the VBUS and the power supply portion  230 , to the logic voltage (+3.3V or +2.5V) to operate the logic portion  210 . 
     Accordingly, even when the power is not supplied to the printer  200 , the logic portion  210  of the printer  200  is constantly applied with the logic voltage by the DC/DC converter  232  using the voltage of +5V, which is applied from the VBUS of the USB interface  211  connected to the host  100 . 
     Using a transformer T (see FIG. 2) as a reference, the power supply portion  230  includes a first side to directly receive AC power from an AC power code, and a second side to convert the power of the first side to DC power for the printer. 
     The first side of the power supply portion  230  is provided with a switch portion  231  to determine the power supplied to the printer  200  in accordance with a control signal from the controller  217 . 
     For example, when the printing data is transmitted from the host  100 , the controller  217  recognizes the printing data as a command to supply the power to the printer  200  and accordingly, transmits a control signal to the power supply portion  230  to operate the switch portion  231 . On the other hand, when the printer  200  does not receive any printing data or does not operate for a predetermined time after completing a printing operation, the controller  210  recognizes the non-operation as a command to stop power supply to the printer  200  to save power. Accordingly, the controller  217  transmits a control signal to the power supply portion  230  to stop the operation of the switch portion  231 . 
     Also, when the host  100  is switched from a “turn-on” state to a “turn-off” state, the controller  217  of the printer  200  controls the switch portion  231  of the power supply portion  230  to stop the power supply to the printer  200 . 
     Also, when the host  100  is turned off or is disconnected from an interface connector (not shown) in the state that the printer  200  is supplied with the power from the power supply portion  230 , i.e., when the printer  200  is in the on-state, the controller  217  treats this situation as if the power is not supplied from the VBUS. Accordingly, the controller controls the switch portion  231  of the power supply portion  230 . 
     The printing portion  220  includes a printing head and a motor (not shown), which perform a main printing operation. A drive power to operate the printing portion  220  is approximately +30V. 
     The input portion  240  includes a manipulation button (not shown), with which the user inputs a selection command, and a selection switch S/W (see FIG. 2) to select a power on/off state. 
     That is, the power supply to the printer  200  is controlled in accordance with a transmission of the printing data from the host  100  or is controlled in accordance with a user&#39;s selection command by the selection switch S/W provided on the input portion  240 . The power supply to the printer  200 , which is disconnected from the USB interface  211 , is controlled in the same way as the power supply to a general printer. 
     Referring to FIGS. 2,  3 A and  3 B, a power supply controlling method of the printer  200  using the USB interface  211  will be described. Hereinafter, a power supply wire is referred to as a VBUS line. 
     As shown in FIG. 2, when the AC voltage is applied to the printer  200  through the AC power code, a DC voltage, which is rectified by a bridge rectifier circuit, is transmitted to the first side of the power supply portion  230 . At this point, since an operation voltage (Vcc) is not applied to a Pulse Width Modulation Integrated Circuit (PWM-IC)( 231 ), the printer  200  is not supplied with the power and thus is in the off-state. 
     Referring to FIG. 3, a process of turning the printer  200  on is described. The voltage of +5V is constantly applied from the VBUS line of the USB interface  211 , and is converted to the logic voltage (+3.3V or +2.5V) by the DC/DC converter  232 . The logic voltage operates the logic portion  210  (S  10 ). Accordingly, the logic portion  210  initializes the printer  200  (S  20 ). 
     At this point, the controller  217  determines whether the logic voltage to drive the logic portion  210  is applied from the power supply portion  230  or from the VBUS line, and reads the power state of the printer  200  (S  30 ). For example, the controller  217  reads an output terminal of +5V of the power supply portion  230 , or other available ports. If an output voltage from the port is ‘HIGH’, the controller  217  recognizes the power state of the printer  200  as being in the “power-on” state, and if the output voltage from the port is ‘LOW’, the controller recognizes the power state of the printer  200  as being in the “power-off” state. 
     If the printer  200  is in the off-state (S  40 ), the printer  200  operates in a sleep mode until the printing data, i.e., the “power-on” control signal is transmitted from the host  100 . 
     At this point, when the printing data is transmitted from the host  100  (S  50 ), the controller  217  transmits the control signal to the power supply portion  230  to operate the printing portion  220  of the printer  200 , then the process proceeds to operation S 70 , discussed below. If, however, the “power-on” signal is not received, then the process returns to S  40 . That is, the controller  217  inputs the ‘LOW’ signal into a terminal (PWR ON) of the second side of the power supply portion  230  (shown in FIG.  2 ). 
     When the ‘LOW’ signal is input into the terminal (PWR ON), a photodiode (PC 3 - 1 ) inside a photo-coupler (PC 3 - 1 , PC 3 - 2 ) operates to emit the light. By the light emitted from the photodiode (PC 3 - 1 ), a phototransistor (PC 3 - 2 ) inside the photo-coupler (PC 3 - 1 , PC 3 - 2 ) operates such that a base voltage of a transistor Q 2  becomes ‘LOW’. Therefore, according to a characteristic of a PNP type transistor, the state between a collector and an emitter becomes closed, such that the DC voltage is applied to operate a PWM-IC( 231 ). 
     A field effect transistor (FET) is switched by the operation of the PWM-IC ( 231 ) to induce the voltage of the first side to the second side. Accordingly, the power supply portion  230  supplies the logic portion  210  and the printing portion  220  of the printer  200  with their respective drive voltages +5V and +30V (S 70 ). The voltage of +5V is supplied to the logic portion  210  after being converted to a logic voltage by the DC/DC converter  232 , and the voltage +30 is directly supplied to the printing portion  220 . At this point, the controller  217  reads the output terminal(+5V or +30V) or other available ports (S  80 ), and then recognizes the power state of the printer  200  as being in the “power-on” state (S  90 ). 
     Meanwhile, when the user inputs a selection command using the selection switch (S/W), i.e., when the selection switch is pressed (S  51 ), the transistor Q 2  of the power supply portion  230  is turned on, such that the PWM-IC( 231 ) operates normally, and the printer  200  is applied with the power (S  80 ). 
     At this time, a photo coupler (PC 4 - 1 , PC 4 - 2 ) is operated, and the controller  217  recognizes the power state of the printer  200  by checking an output voltage of the phototransistor (PC 4 - 2 ) in a polling method. That is, if the output voltage of the phototransistor (PC  4 - 2 ) is ‘LOW’ (S 80 ), the controller  217  recognizes the power state of the printer  200  as being “power-on” (S 90 ). 
     Next, the printer  200  is supplied with the power from the power supply portion  230  and is placed on standby for the printing operation (S  100 ), and performs the printing operation based on the printing data transmitted from the host  100 . 
     Next, referring to FIGS. 2 and 3B, a process of turning the printer  200  off is described. After completing the printing operation as described above, if the printer  200  is continuously kept in a standby mode (S  100 ) for a predetermined time (S  110 ), i.e., if the printing data and the control signal are not transmitted for a predetermined time, the controller  217  transmits the control signal to the terminal (PWR OFF) of the second side, as shown in FIG. 2, to stop the power supply to the power supply portion  230 . 
     That is, if a ‘HIGH’ signal is input into the terminal (PWR OFF), the ‘HIGH’ signal is supplied to the base of the transistor Q 36  such that the collector and the emitter close. By the operation of the photo-coupler (PC 2 - 1  and PC 2 - 2 ), the operation voltage (Vcc) of the PWM-IC( 231 ) is bypassed to the PWM enable terminal and is stopped. Switching of the FET is stopped such that the voltage applied to the second side is stopped. Accordingly, the printer  200  is not applied with power (S  120 ). 
     Also, if the selection switch (S/W) is pressed within a predetermined time to stop the power (S  130 ), the controller  217  confirms that the selection switch (S/W) is pressed, and then transmits the control signal to the terminal (PWR OFF) of the second side of the power supply portion  230  to stop the power supply to the printer  200 . At this point, the controller  217  determines the power supply state of the printer  200  (S  140 ) by reading the terminal (PWR_STATUS), and re-determines the power supply state of the printer  200  before stopping the power supply to the printer  200 . 
     Accordingly, if the power supply state of the printer  200  is determined as the “power-off” state by operation S  140 , there is an error in the operation of the printer  200 . On the other hand, if the power supply state of the printer  200  is determined as the “power-on” state, the controller  217  transmits the control signal to the terminal (PWR OFF), to stop the power supply to the printer  200 . 
     The operation S  120 , in which the controller  217  inputs the ‘HIGH’ signal into the terminal (PWR OFF) to turn the printer  200  off, is identical to the operation as described above, and accordingly a description at this point is omitted. 
     Meanwhile, if the power for the host  100  is turned off, the host  100  transmits a power-off command to the controller  217  of the printer  200  through the data wire of the interface (S  150 ). The controller  217  inputs the ‘HIGH’ signal into the terminal (PWR OFF) of the second side of the power supply portion  230 , such that the printer  200  is turned off. After that, the operation to turn the printer  200  off continues in the same way as described above (S  120 ). 
     Since the voltage of +5V is stopped from being supplied from the VBUS line to the logic portion  210  of the printer  200  when the host  100  is turned off. Also, the controller  217  transmits the control signal to the terminal (PWR OFF) of the second side of the power supply portion  230  to stop the power supply to the printer  200  (S  150 ). As described above, the operation of the switch portion  230  is stopped by the control signal such that the printer is turned off (S  120 ). Accordingly, when the printer  200  does not perform the printing operation, the power is not applied to the printer  200 . 
     As described above, the voltage of +5V, which is supplied from the host  100  through the VBUS line, is used as the drive voltage to drive the logic portion  210  such that the logic operation of the printer  200  is controlled when the printer  200  is in the off-state. Accordingly, the power supply to the printer  200  is controlled according to the transmission of the printing data from the host  100 . 
     According to the present invention, since the printer  200  is capable of remote control of the power state via the host  100 , the printer  200  is set in a power on/off state according to the transmission of the printing data from the host  100 . This differs from the conventional design, in which a user controls the state through the input portion. 
     Therefore, the present invention reduces unnecessary power consumption, and is also more convenient for the user. 
     Although a few preferred embodiments of the present invention have been shown and described, it will 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.