Abstract:
There is provided a switching mode power supply having multiple outputs, including: a DC/DC converter converting a DC voltage level according to a change in a load and including a primary coil and a secondary coil; a boost unit boosting an output voltage of the DC/DC converter in a first mode and outputting the boosted output voltage to an output terminal; a bypass unit bypassing the output voltage of the DC/DC converter in a second mode, to output the bypassed voltage to the output terminal; and a boosting controller controlling the boost unit according to a voltage detected at a center tab of the secondary coil of the DC/DC converter.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the priority of Korean Patent Application No. 10-2010-0134517 filed on Dec. 24, 2010, in the Korean Intellectual 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 to a switching mode power supply capable of outputting multiple voltages. 
         [0004]    2. Description of the Related Art 
         [0005]    Generally, a switching mode power supply capable of satisfying a demand for miniaturization and high efficiency has been widely used as a power supply. When there is a need to supply a separate voltage, according to an operation mode of a load, a switching mode power supply capable of generating multiple outputs may be used. 
         [0006]    The switching mode power supply having multiple outputs according to the related art uses a voltage of a center tab of a transformer or a plurality of transformers to supply a standby voltage among operation modes of a load. 
         [0007]    However, even when the switching mode power supply having multiple outputs according to the related art supplies a voltage required in a standby mode using a center tab, a DC/DC converter generates a voltage higher than a voltage necessary for the standby mode, thereby increasing power consumption due to heat generation, or the like. 
         [0008]    Further, when the plurality of transformers are used, the number of components is increased. 
         [0009]    Furthermore, when the power supply having multiple outputs is applied to an external adapter, output terminals are configured in a number of three or more, thereby increasing manufacturing costs. 
       SUMMARY OF THE INVENTION 
       [0010]    An aspect of the present invention provides a power supply having multiple outputs capable of supplying multiple voltages according to operation modes while reducing power consumption due to heat generation of a DC/DC converter. 
         [0011]    According to an aspect of the present invention, there is provided a switching mode power supply having multiple outputs, including: a DC/DC converter converting a DC voltage level according to a change in a load and including a primary coil and a secondary coil; a boost unit boosting an output voltage of the DC/DC converter in a first mode and outputting the boosted output voltage to an output terminal; a bypass unit bypassing the output voltage of the DC/DC converter to the output terminal in a second mode; and a boosting controller controlling the boost unit according to a voltage detected at a center tab of a secondary coil of the DC/DC converter. 
         [0012]    The boosting controller may include: a driver generating a driving voltage according to the voltage detected from the center tab; and a control IC controlling the switch of the boost unit according to the driving voltage. 
         [0013]    The driver may include: a diode having an anode connected to the center tab to rectify the voltage detected in the center tab; and a bipolar transistor having a common collector structure including a base connected to the cathode of the diode, and a collector connected to the output terminal of the DC/DC converter, and an emitter connected to a ground and the control IC. 
         [0014]    According to another aspect of the present invention, there is provided a switching mode power supply having multiple outputs, including: a DC/DC converter converting a DC voltage level according to a change in a load; a boost unit boosting an output voltage of the DC/DC converter in a first mode and outputting the boosted output voltage to an output terminal; a bypass unit bypassing the output voltage of the DC/DC converter in a second mode and outputting the bypassed output voltage to the output terminal; and a boosting controller detecting the voltage of the output terminal to control the boost unit. 
         [0015]    The boosting controller may include: a driver generating a driving voltage according to the voltage detected from the center tab; and a control IC controlling the switch of the boost unit according to the driving voltage. 
         [0016]    The driver may include: a resistor having one end connected to the output terminal and detecting the voltage of the output terminal; and a bipolar transistor having a common collector structure including abase connected to the other end of the resistor, a collector connected to the output terminal of the DC/DC converter, and an emitter connected to a ground and the control IC. 
         [0017]    The switching mode power supply having multiple outputs may further include: a feedback circuit unit feeding back any one of the output of the bypass unit or the output of the boost unit; and a PWM controller controlling a duty ratio of the DC/DC converter according to a signal transmitted from the feedback circuit unit. 
         [0018]    The boost unit may include: an inductor having one end connected to the output terminal of the DC/DC converter; a diode having an anode connected to the other end of the inductor and a cathode connected to the output terminal; and a switch connected between a connection node of the inductor and the diode and the ground. 
         [0019]    The bypass unit may include a bypass diode having an anode connected to the output terminal of the DC/DC converter and a cathode connected to the output terminal. 
         [0020]    The first mode may be in an operation mode in which a load connected to the output terminal is in an operating state, and the second mode may be in a standby mode in which the load is in a standby state. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    The above and other aspects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
           [0022]      FIG. 1  is a circuit diagram of a power supply having multiple outputs according to an exemplary embodiment of the present invention; 
           [0023]      FIG. 2  illustrates another exemplary embodiment of the present invention; and 
           [0024]      FIG. 3  is a circuit diagram of a boost unit of a power supply having multiple outputs according to the exemplary embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0025]    Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings so that they could be easily practiced by those skilled in the art to which the present invention pertains. However, in describing the exemplary embodiments of the present invention, detailed descriptions of well-known functions or constructions will be omitted so as not to obscure the description of the present invention with unnecessary detail. 
         [0026]    In addition, like reference numerals denote like elements throughout the drawings. 
         [0027]      FIG. 1  is a circuit diagram of a power supply having multiple outputs according to an exemplary embodiment of the present invention. 
         [0028]    Referring to  FIG. 1 , a power supply having multiple outputs according to an exemplary embodiment of the present invention may be configured to include a DC/DC converter  100 , a bypass unit  200 , a boost unit  300 , a boosting controller  400 , a feedback circuit unit  500 , and a PWM controller  600 . 
         [0029]    The DC/DC converter  100  may transfer a DC voltage having a pulse type from a primary coil to a secondary coil by using an electromagnetic induction, such that a level of DC voltage is converted according to a turn ratio of a primary coil and a secondary coil and then the level-converted DC voltage is outputted. The voltage transferred to the secondary coil is rectified and output through a diode D 1 . 
         [0030]    The DC voltage may be a DC voltage rectified by a rectifying unit that may be configured to include a bridge diode, or the like. 
         [0031]    The bypass unit  200  may bypass and output the DC voltage converted in the DC/DC converter  100  to an output terminal OUT in a standby mode. Describing in detail, the bypass unit  200  may be a bypass diode  210  having an anode connected to the output terminal of the DC/DC converter  100  and a cathode connected to the output terminal OUT. 
         [0032]    The boost unit  300  may boost the DC voltage converted in the DC/DC converter  100  to a high voltage necessary in a load and supply it to the load, in the operation mode. 
         [0033]    The boosting controller  400  may detect voltage at a center tab of the secondary coil of the DC/DC converter  100  and control the boost unit  300  according to the detected voltage. Describing in detail, the boosting controller  400  may include a driver  410  generating a driving voltage according to the voltage detected from the center tab of the secondary coil, and a control IC  420  controlling the boost unit  300  according to the generated driving voltage. 
         [0034]    In more detail, the driver  410  may include a diode  411  of which an anode is connected to the center tab of the secondary coil to rectify voltage detected at the center tab, and a bipolar transistor  413  having a common collector structure having a base connected to the cathode of the diode  411 , a collector connected to the output terminal of the DC/DC converter  100 , and an emitter connected to a ground and the control IC  420 . 
         [0035]    The feedback circuit unit  500  may feed back an output from the output terminal OUT connected to the load to the DC/DC converter  100 . That is, any one of the output of the bypass unit  200  and the output of the boost unit  300  may be fed back to the DC/DC converter  100  according to the operation modes of the load. Describing in detail, the feedback circuit unit  500  may be configured of a photo coupler in consideration of the insulating DC/DC converter  100 . 
         [0036]    The PWM controller  600  may modulate a pulse width according to the voltage of the output terminal OUT transferred from the feedback circuit unit  500  to control the switching of the DC/DC converter  100 . 
         [0037]      FIG. 2  is a circuit diagram of a power supply having multiple outputs according to another exemplary embodiment of the present invention. 
         [0038]    Referring to  FIG. 2 , a power supply having multiple outputs according to an exemplary embodiment of the present invention may include the DC/DC converter  150 , the bypass unit  200 , the boost unit  300 , the boosting controller  400 , the feedback circuit unit  500 , and the PWM controller  600 . In this configuration, the configuration in the DC/DC converter  150 , the feedback circuit unit  500 , the bypass unit  200 , and the boost unit  300  is in a similar manner to that of the power supply having multiple outputs according to the one exemplary embodiment of the present invention and therefore, the detailed description thereof will be omitted. 
         [0039]    The boosting controller  400  may detect the voltage of the output terminal OUT and may control the boost unit  300  according to the detected voltage. In detail, the boosting controller  400  may include the driver  410  generating a driving voltage according to the voltage detected at the output terminal OUT connected to the load, and the control IC  420  controlling the boost unit  300  according to the generated driving voltage. 
         [0040]    In more detail, the driver  410  may include a resistor  415  sensing the voltage of the output terminal OUT, and the bipolar transistor  413  having the common collector structure having a base connected to the resistor  415 , a collector connected to the output terminal of the DC/DC converter  100 , and an emitter connected to the ground and the control IC  420 . 
         [0041]    The output terminal OUT connected to the load may be configured of two terminals only, that is, an output terminal OUT from which multiple voltages are output, and a ground potential (GND), when the power supply having multiple outputs according to the exemplary embodiment of the present invention is applied to an adaptor. 
         [0042]      FIG. 3  is a circuit diagram of a boost unit of the power supply having multiple outputs according to the exemplary embodiment of the present invention. 
         [0043]    Referring to  FIG. 3 , the boost unit  300  may be a boost converter that includes an inductor  310  of which one end is connected to an output node N 1  of the DC/DC converter, a diode  320  having an anode connected to the other end of the inductor  310  and a cathode connected to an output terminal node N 2 , and a switch  330  connected between a connection node of the inductor  310  and the diode  320  and the ground. The switch may be controlled by the control IC through a connection node (NC) with the control IC. 
         [0044]    In this configuration, the boost unit  300  is not limited thereto and may include all types of circuits boosting the level of DC voltage, such as a Buck-boost converter, or the like. 
         [0045]    Hereinafter, the operations and effects according to embodiments of the present invention will be described in detail with reference to the accompanying drawings. 
         [0046]    Referring to  FIG. 1 , the switching mode power supply with multi outputs according to the exemplary embodiment of the present invention will be described with reference to  FIG. 1 . 
         [0047]    In  FIG. 1 , the DC/DC converter  100  according to the exemplary embodiment of the present invention may transfer the DC voltage having a pulse type input to the primary coil to the secondary coil by using the electromagnetic induction. In this case, the voltage level output to the secondary coil is determined according to the turn ratio of the primary coil and the secondary coil. The voltage transferred to the secondary coil is an AC voltage, which is rectified in a diode D 1  and is output. The DC/DC converter  100  can control a switching duty by the PWM controller  600  to which the voltage of the output terminal OUT connected to the load is fed back. 
         [0048]    The DC voltage output from the DC/DC converter  100  is a relatively low voltage necessary for a standby mode among operation modes of the load. 
         [0049]    Meanwhile, the bypass unit  200  according to the exemplary embodiment of the present invention may transfer the output voltage of the DC/DC converter  100  intact, which is necessarily required to be of a low voltage when the load is in a second mode, the standby mode, to the load. The bypass unit  200  may be the bypass diode  210  having an anode connected to the output terminal of the DC/DC converter  100  and a cathode connected to the output terminal OUT. 
         [0050]    The boost unit  300  may supply a voltage required when the load is in a first mode, the operation mode. That is, the boost unit  300  may serve to generate a relatively higher voltage than a voltage required when the load is in the standby mode according to the control of the boosting controller  400  and supply the generated voltage to the load. 
         [0051]    As described above, due to the bypass unit  200  and the boost unit  300 , the switching mode power supply having multiple outputs according to the exemplary embodiment of the present invention may supply the voltage of the DC/DC converter  100  to the load by using the bypass unit  200  when the load is in the standby mode and supply a boosted voltage higher than the voltage of the DC/DC converter  100  by using the boost unit  300  when the load is in the operation mode. 
         [0052]    Therefore, the DC/DC converter  100  does not need to continually supply a relatively high voltage necessary in the operation mode, thereby reducing power consumption due to the heat generation, or the like. 
         [0053]    The boosting controller  400  may include the driver  410  including the diode  411  and the bipolar transistor  413 , and the control IC  420  controlling the boost unit  300 . 
         [0054]    The driver  410  may include the diode  411  rectifying the voltage detected at the center tab of the secondary coil of the DC/DC converter  100 , and the bipolar transistor  413  using the rectified voltage as the base voltage. 
         [0055]    Describing in more detail, the voltage detected at the center tab of the secondary coil of the DC/DC converter  100  may be rectified in the diode  411  and transferred to the base of the bipolar transistor  413 . In this case, when the load is in the standby mode, the voltage is lower than a threshold voltage of the bipolar transistor  413 , such that the bipolar transistor  413  is not conducted and does not supply the voltage to the control IC  420 . Therefore, the boost unit  300  is not operated. 
         [0056]    When the load is in the operation mode, the output of the DC/DC converter  100  may be slightly increased through the feedback circuit unit  500  and the PWM controller  600 , and the voltage detected at the center tab may be also increased. In this case, the bipolar transistor  413  is turned-on, such that the control IC  420  is driven and the boosted voltage is supplied to the output terminal OUT. In this configuration, the bipolar transistor  413  has a common collector structure and the voltage output to the control IC  420  has a level lower than the base voltage rectified in the diode  411  and becomes a voltage level necessary in the control IC. 
         [0057]    Referring to  FIG. 2 , the switching mode power supply having multiple outputs according to another exemplary embodiment of the present invention will be described. 
         [0058]    As shown in  FIG. 2 , the switching mode power supply having multiple outputs according to another exemplary embodiment of the present invention has a different configuration only in the driver  410  of the boosting controller  400 , and thus the repeated description of operations and effects thereof will be omitted. 
         [0059]    The driver  410  may include a resistor  415  sensing the voltage of the output terminal OUT and the bipolar transistor  413  having the common collector structure having a base connected to the resistor  415 , a collector connected to the output terminal of the DC/DC converter  150 , and an emitter connected to the ground and the control IC  420 . 
         [0060]    When the load is in the standby mode, the resistor  415  may be preset not to turn the bipolar transistor  413  on, such that the control IC  420  cannot be driven. When the load is in the operation mode, the voltage of the output terminal OUT may be raised to be higher than a threshold voltage of the bipolar transistor  413  so as to drive the control IC  420 . 
         [0061]    Therefore, the switching mode power supply having multiple outputs according to another exemplary embodiment of the present invention may supply the voltage of the DC/DC converter  150  to the load by using the bypass unit  200  when the load is in the standby mode, and may supply a boosted voltage higher than the output voltage of the DC/DC converter  150 , to the load by using the boost unit  300 , when the load is in the operation mode, in a similar manner to the exemplary embodiment of  FIG. 1 . 
         [0062]    In  FIG. 3 , the boost unit  300  is shown as the boost converter including the inductor  310 , the diode  320 , and the switch  330  as the exemplary embodiment of the present invention. The boost unit  300  may control the turn-on/off of the switch  330  to control a current conduction period of the inductor  310  according to the control of the control IC connected to the connection node NC, thereby boosting the input voltage. 
         [0063]    As set forth above, according to the exemplary embodiment of the present invention, the DC/DC converter may generate a relatively low voltage, thereby reducing power consumption due to the heating generation, or the like, and removing the need for a separate transformer. In addition, two output terminals only are sufficient when the power supply having multiple outputs is applied to the external adaptor, thereby reducing the manufacturing costs thereof. 
         [0064]    While the present invention has been shown and described in connection with the exemplary embodiments, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the spirit and scope of the invention as defined by the appended claims.