Patent Publication Number: US-2012043811-A1

Title: Power supply having improved system efficiency

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority of Korean Patent Application No. 10-2010-0079985 filed on Aug. 18, 2010, in the Korean Intellectual 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 power supply which is applicable to a server, and more particularly, to a power supply which can improve the system efficiency of a standby voltage supply system by supplying a standby voltage using a main voltage. 
     2. Description of the Related Art 
     In order to generate a standby voltage, a conventional power supply for a server generally uses a flyback converter having a simple structure. However, such a flyback converter has low efficiency due to high voltage stress and hard switching. 
     A conventional power supply for a server is designed so that a standby stage supplies an operating voltage and a standby voltage using a DC voltage from a power factor correction (PFC) unit, and a DC/DC stage is supplied with the operating voltage from the standby stage and generates a main voltage using the DC voltage from the PFC unit. 
     In the conventional power supply for the server, the standby stage generally uses a flyback converter, and the efficiencies of the PFC unit, the DC/DC stage, and the standby stage are about 98%, 96%, and 80%, respectively, when an input voltage of about 230 Vac is inputted thereto and a load thereof is 50%. 
     In the conventional power supply for the server, the efficiency of the standby stage is very low, even though the weight of the standby stage is low as compared to the main voltage supply unit. Consequently, the efficiency of an overall server system to which the power supply is applied will be lowered. 
     SUMMARY OF THE INVENTION 
     An aspect of the present invention provides a power supply which can improve the efficiency of a standby voltage supply system by supplying a standby voltage using a main voltage. 
     According to an aspect of the present invention, there is provided a power supply having improved system efficiency, including: a standby stage converting a DC voltage into an operating voltage and a first standby voltage, which have a preset magnitude, and supplying the first standby voltage to a standby output terminal; a DC/DC stage supplied with the operating voltage from the standby stage, converting the DC voltage into a main voltage having a preset magnitude, and supplying the main voltage to a main output terminal; and a main/standby stage converting the main voltage from the DC/DC stage into a second standby voltage having a preset magnitude, and supplying the second standby voltage to the standby output terminal. 
     According to another aspect of the present invention, there is provided a power supply having, improved system efficiency, including: a power factor correction (PFC) unit converting an AC voltage into a DC voltage having a preset magnitude; a standby stage converting the DC voltage from the PFC unit into an operating voltage and a first standby voltage, which have a preset magnitude, and supplying the first standby voltage to a standby output terminal; a DC/DC stage supplied with the operating voltage from the standby stage, converting the DC voltage into a main voltage having a preset magnitude, and supplying the main voltage to a main output terminal; and a main/standby stage converting the main voltage from the DC/DC stage into a second standby voltage having a preset magnitude, and supplying the second standby voltage to the standby output terminal. 
     According to another aspect of the present invention, there is provided a power supply having improved system efficiency, including: a standby stage converting a DC voltage into an operating voltage and a first standby voltage, which have a preset magnitude, and supplying the first standby voltage to a standby output terminal; a DC/DC stage supplied with the operating voltage from the standby stage, converting the DC voltage into a main voltage having a preset magnitude, and supplying the main voltage to a main output terminal; a main/standby stage converting the main voltage from the DC/DC stage into a second standby voltage having a preset magnitude, and supplying the second standby voltage to the standby output terminal; and a protection circuit unit connected between an output terminal of the standby stage and the standby output terminal, and opening a voltage supply line connected to the output terminal of the standby stage. 
     The power supply may further include a power factor correction (PFC) unit converting an AC voltage into the DC voltage and supplying the DC voltage to the DC/DC stage and the standby stage. 
     The main/standby stage may include a first diode having an anode connected to the main output terminal and a cathode connected to the standby output terminal, the first diode being turned on by the main voltage from the DC/DC stage and supplying the second standby voltage to the standby output terminal. 
     The protection circuit unit may include a protection diode having an anode connected to the output terminal of the standby stage and a cathode connected to the standby output terminal, the protection diode being turned off when the second standby voltage is supplied. 
     The protection circuit unit may include a protection switching element connected between the output terminal of the standby stage and the standby output terminal, the protection switching element being turned off when the second standby voltage is supplied. 
     The main/standby stage may include a first switching element connected between the main output terminal and the standby output terminal, the first switching element being turned on by a first switching control signal and supplying the main voltage from the DC/Dc stage to the standby output terminal. 
     The protection circuit unit may include a protection diode having an anode connected to the output terminal of the standby stage and a cathode connected to the standby output terminal, the protection diode being turned off when the second standby voltage is supplied. 
     The protection circuit unit may include a protection switching element connected between the output terminal of the standby stage and the standby output terminal, the protection switching element being turned off when the second standby voltage is supplied. 
     The main/standby stage may include a voltage regulator converting the main voltage from the DC/DC stage into a preset voltage; and a second diode having an anode connected to an output terminal of the voltage regulator and a cathode connected to the standby output terminal, the second diode being turned on by an output voltage of the voltage regulator and supplying the second standby voltage to the standby output terminal. 
     The protection circuit unit may include a protection diode having an anode connected to the output terminal of the standby stage and a cathode connected to the standby output terminal, the protection diode being turned off when the second standby voltage is supplied. 
     The protection circuit unit may include a protection switching element connected between the output terminal of the standby stage and the standby output terminal, the protection switching element being turned off when the second standby voltage is supplied. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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: 
         FIG. 1  is a block diagram of a power supply having improved system efficiency according to an embodiment of the present invention; 
         FIG. 2  is an exemplary diagram of a main/standby stage according to a first implementation of the present invention; 
         FIG. 3  is an exemplary diagram of a main/standby stage according to a second implementation of the present invention; 
         FIG. 4  is an exemplary diagram of a main/standby stage according to a third implementation of the present invention; 
         FIG. 5  is an exemplary diagram of the power supply having improved system efficiency according to a first modification of the present invention; 
         FIG. 6  is an exemplary diagram of the power supply having improved system efficiency according to a second modification of the present invention; and 
         FIG. 7  is an operational flowchart of the power supply having improved system efficiency according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. The invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the thicknesses of layers and regions are exaggerated for clarity. Like reference numerals in the drawings denote like elements, and thus their description will be omitted. 
       FIG. 1  is a block diagram of a power supply having improved system efficiency according to an embodiment of the present invention. 
     Referring to  FIG. 1 , the power supply having improved efficiency according to the embodiment of the present invention includes a standby stage  200 , a DC/DC stage  300 , and a main/standby stage  400 . The standby stage  200  converts a DC voltage Vdc into an operating voltage Vcc and a first standby voltage Vstb 1 , which have a preset magnitude, and supplies the first standby voltage Vstb 1  to a standby output terminal OUTstb. The DC/DC stage  300  is supplied with the operating voltage Vcc from the standby stage  200 , converts the DC voltage Vdc into a main voltage Vmain having a preset magnitude, and supplies the main voltage Vmain to a main output terminal OUTmain. The main/standby stage  400  converts the main voltage Vmain from the DC/DC stage  300  into a second standby voltage Vstb 2  having a preset magnitude, and supplies the second standby voltage Vstb 2  to the standby output terminal OUTstb. 
     In addition, the power supply according to the embodiment of the present invention may further include a power factor correction (PFC) unit which converts an AC voltage into the DC voltage having a preset magnitude, and supplies the DC voltage to the DC/DC stage  300  and the standby stage  200 . 
       FIG. 2  is an exemplary diagram of the main/standby stage according to a first implementation of the present invention. 
     Referring to  FIG. 2 , the main/standby stage  400  may include a first diode D 1  having an anode connected to the main output terminal OUTmain and a cathode connected to the standby output terminal OUTstb. 
     The first diode D may be configured to be turned on by the main voltage Vmain from the DC/DC stage  300  and supply the second standby voltage Vstb 2  to the standby output terminal OUTstb. 
       FIG. 3  is an exemplary diagram of the main/standby stage according to a second implementation of the present invention. 
     Referring to  FIG. 3 , the main/standby stage  400  may include a first switching element SW 1  connected between the main output terminal OUTmain and the standby output terminal OUTstb. 
     The first switching element SW 1  may be configured to be turned on by a first switching control signal and supply the main voltage Vmain from the DC/DC stage  300  to the standby output OUTstb. 
       FIG. 4  is an exemplary diagram of the main/standby stage according to a third implementation of the present invention. 
     Referring to  FIG. 4 , the main/standby stage  400  may include a voltage regulator  410  and a second diode D 2 . The voltage regulator  410  converts the main voltage Vmain from the DC/DC stage into a preset voltage. The second diode D 2  has an anode connected to an output terminal of the voltage regulator  410  and a cathode connected to the standby output terminal OUTstb. 
     The second diode D 2  may be configured to be turned on by the output voltage of the voltage regulator  410  and supply the second standby voltage Vstb 2  to the standby output terminal OUTstb. 
       FIG. 5  is an exemplary diagram of the power supply having improved system efficiency according to a first modification of the present invention. 
     Referring to  FIG. 5 , the power supply according to the first modification of the present invention may include a protection circuit unit  500  which is connected between the output terminal of the standby stage  200  and the standby output terminal OUTstb and opens a voltage supply line connected to the output terminal of the standby stage  200  when the second standby voltage Vstb 2  is supplied. 
     The protection circuit unit  500  may include a protection diode D 5  having an anode connected to the output terminal of the standby stage  200  and a cathode connected to the standby output terminal OUTstb. 
     The protection diode D 5  may be configured to be turned off when the second standby voltage Vstb 2  is supplied. 
       FIG. 6  is an exemplary diagram of the power supply having improved system efficiency according to a second modification of the present invention. 
     Referring to  FIG. 6 , the protection circuit unit  500  may include a protection switching element SW 2  connected between the output terminal of the standby stage  200  and the standby output terminal OUTstb. 
     The protection switching element SW 2  may be configured to be turned off when the second standby voltage Vstb 2  is supplied. 
       FIG. 7  is an operational flowchart of the power supply having improved system efficiency according to an embodiment of the present invention. In  FIG. 7 , S 100  is a process in which the PFC unit  100  performs a PFC operation, and S 200  is a process in which the standby stage  200  generates and supplies the first standby voltage Vstb 1  and the operating voltage Vcc. S 300  is a process in which the DC/DC stage  300  performs the DC/DC conversion operation, and S 400  is a process in which the main/standby stage  400  operates to supply the second standby voltage Vstb 2  using the main voltage Vmain. 
     Hereinafter, the operation and effect of the present invention will be described with reference to the accompanying drawings. 
     The power supply having improved system efficiency according to the embodiment of the present invention will be described below with reference to  FIGS. 1 through 7 . First, in the power supply illustrated in  FIG. 1 , the PFC unit  100  may convert the AC voltage of 90-266 Vac into the preset DC voltage (e.g., 380 Vdc), and supply the DC voltage to the DC/DC stage  300  and the standby stage  200  (S 100  of  FIG. 7 ). 
     The standby stage  200  may convert the DC voltage Vdc from the PFC unit  100  into the operating voltage Vcc (e.g., 10 Vdc) and the first standby voltage Vstb 1  (e.g., 10 Vdc), and supply the first standby voltage Vstb 1  to the standby output terminal OUTstb (S 200  of  FIG. 7 ). In this case, the first standby voltage Vstb 1  becomes the standby voltage Vstb. 
     In addition, the DC/DC stage  300  may be supplied with the operating voltage. Vcc from the standby stage  200  to operate the internal circuit thereof. Accordingly, the DC/DC stage  300  may convert the DC voltage Vdc into the preset main voltage Vmain (e.g., 12 Vdc), and supply the main voltage Vmain (e.g., 12 Vdc) to the main output terminal OUTmain (S 300  of  FIG. 7 ). 
     The main/standby stage  400  may convert the main voltage Vmain from the DC/DC stage  300  into the preset second standby voltage Vstb 2  (e.g., 10 V), and supply the second standby voltage Vstb 2  to the standby output terminal OUTstb (S 400  of  FIG. 7 ). In this case, the second standby voltage Vstb 2  becomes the standby voltage Vstb. 
     Referring to  FIG. 2 , in a case in which the main voltage Vmain is equal to the standby voltage Vstb, the main/standby stage  400  may include the first diode D 1  as the first implementation. The first diode D 1  may be turned on by the main voltage Vmain from the DC/DC stage  300  and supply the second standby voltage Vstb 2  to the standby output terminal OUTstb. 
     Referring to  FIG. 3 , in a case in which the main voltage Vmain is equal to the standby voltage Vstb, the main/standby stage  400  may include the first switching element SW 1  as the second implementation. The first switching element SW 1  may be turned on by the first switching control signal and supply the main voltage Vmain from the DC/DC stage  300  to the standby output terminal OUTstb. 
     For example, in a case in which the main voltage Vmain is supplied from the DC/DC stage  300 , the power supply may be configured to provide the first switching control signal. In this case, the first switching element SW 1  may be turned off by the first switching control signal. 
     Referring to  FIG. 4 , in a case in which the main voltage Vmain is not equal to the standby voltage Vstb, the main/standby stage  400  may include the voltage regulator  410  and the second diode D 2  as the third implementation. 
     The voltage regulator  410  may convert the main voltage Vmain from the DC/DC stage  300  into the preset voltage. 
     The second diode D 2  may be turned on by the output voltage of the voltage regulator  410  and supply the second standby voltage Vstb 2  to the standby output terminal OUTstb. 
     As illustrated in  FIG. 5 , the power supply having improved system efficiency according to the first modification may include the protection circuit unit  500 . 
     The protection circuit unit  500  is connected between the output terminal of the standby stage  200  and the standby output terminal OUTstb and opens the voltage supply line connected to the output terminal of the standby stage  200  when the second standby voltage Vstb 2  is supplied. Therefore, it is possible to prevent the second standby voltage Vstb 2  from being introduced to the standby stage  200 , thereby protecting the standby stage  200 . 
     As an example, in a case in which the protection circuit unit  500  includes the protection diode D 5 , the protection diode D 5  may be turned off when the second standby voltage Vstb 2  is supplied. 
     For example, when the first and second standby voltages Vstb 1  and Vstb 2  are 10 Vdc, an offset state is initiated in the protection diode D 5 . 
     As illustrated in  FIG. 6 , the protection circuit unit  500  of the power supply having improved system efficiency according to the second modification may include the protection switching element SW 2 . The protection switching element SW 2  may be turned off when the second standby voltage Vstb 2  is supplied. 
     For example, when the second standby voltage Vstb 2  is supplied, the power supply may be configured to provide a protection switching control signal. In this case, the protection switching element SW 2  may be turned off by the protection switching control signal. 
     As described above, when the DC/DC stage  300  does not operate, the output voltage can be obtained from the output voltage of the PFC unit  100  through the standby stage  200 . When the DC/DC stage  300  operates, the output voltage can be obtained through the DC/DC stage  300  and the main/standby stage  400 . 
     In addition, when the AC input voltage is about 230 Vac and the load thereof is 50%, the efficiencies of the PFC unit  100 , the DC/DC stage  300 , and the standby stage  200  are about 98%, 96%; and 80%, respectively, and the efficiency of the voltage regulator  410  of the main/standby stage  400  is about 92%. 
     Accordingly, the efficiency of the DC/DC stage  300  and the voltage regulator  410  is 88%, which is improved by about 8%, as compared to a case in which the standby stage is obtained through the standby stage. 
     In particular, when the standby voltage is equal to the main voltage, the voltage regulator of the main/standby stage can be removed. In this case, the efficiency of the power supply can be improved by about 16%. 
     As set forth above, according to exemplary embodiments of the invention, the efficiency of the standby voltage supply system can be improved by supplying the standby voltage using the main voltage. 
     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.