Patent Publication Number: US-2013229060-A1

Title: Multi power supply system

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a power system, and particularly to a multi power supply system. 
     2. Description of Related Art 
     A multi power supply system uses surge protectors, such as electromagnetic relays, to switch between power sources. If a solar cell module is one of the power sources, the solar cell module can supply power when an amount of light absorption is large enough for the solar cell module. However, light absorption on the solar cell module is unstable so that an output voltage of the solar call module is also unstable. Therefore, the surge protectors of the multi power supply system switch frequently in a high operating voltage between the solar cell module and the other power sources, which easily induces oxidation of contacts in the surge protectors. Since the oxidation of the contacts will influence the switches between the power sources, stability of the multi-power supply system will be decreased. 
     Therefore, there is need for improvement in the art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the present disclosure can be better understood with reference to the following drawing(s). The components in the drawing(s) are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawing(s), like reference numerals designate corresponding parts throughout the several views. 
         FIG. 1  is a block diagram of an embodiment of a power system of the present disclosure. 
         FIG. 2  is a part circuit diagram of the power system in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates an embodiment of a power system  100  of the present disclosure. The power system  100  is a multi power supply system and supplies power to a power supply unit (PSU)  20  of a server. The power system  100  includes a power supply  40 , a power source  30 , a power distribution unit (PDU)  10 , a second protection unit  70 , a first conversion unit  116 , a direct current (DC) power module  80 , a battery module  90 , a second conversion unit  85 , a control unit  105 , a power circuit  95 , a rectifying unit  65 , a first protection unit  45 , a first switch element D 1 , and a second switch element D 2 . The PDU  10  further includes a first breaker unit  60  and a second breaker unit  50 . In the embodiment, the first and the second protection units  45  and  70  are surge protectors, the first conversion unit  116  is a boost converter, the rectifying unit  65  is a rectifier, a power circuit  95  is a power factor correction (PFC) circuit, the second conversion unit  85  is a buck converter, and the first and the second breaker unit  60  and  50  are breakers. 
     The power supply  40  is connected to a first terminal of the first switch element D 1  through the first breaker unit  60 , the first protection unit  45 , the rectifying unit  65 , and the power circuit  95 . A second terminal of the first switch element D 1  is connected to a first input terminal of the PDU  10  through the second conversion unit  85 . The power source  30  is connected to a first terminal of the second switch element D 2  through the second breaker unit  50 , the second protection unit  70 , and the first conversion unit  116 . A second terminal of the second switch element D 2  is connected to the second terminal of the first switch element D 1 . The battery module  90  is connected to a second input terminal of the PDU  10 , and the DC power module  80  is connected to a third input terminal of the PDU  10 . An output terminal of the PDU  10  is connected to an input terminal of the PSU  20 . 
     In the embodiment, the first and the second protection units  45  and  70  are electromagnetic relays. The first and the second protection units  45  and  70  are turned off on condition that there is a surge current or an overvoltage in a circuit of the power system  100 . If there is no surge current and overvoltage in the power system  100 , the first and the second protection units  45  and  70  are turned on. In addition, the first and the second breaker units  60  and  50  protect the power system  100  from an overcurrent. Thus, the first and the second breaker units  60  and  50  and the first and the second protection units  45  and  70  are installed in the power system  100  for protection, if necessary. 
     The power supply  40  is an alternating current (AC) power supply. In the embodiment, the power supply  40  is connected to a mains supply. The AC power supply can be a single phase AC power supply or a multi phase AC power supply, such as a three phase AC power supply. The rectifying unit  65  converts an AC voltage of the power supply  40  to a DC voltage, and the power circuit  95  increases a power factor of the DC voltage transmitted from the rectifying unit  65  to provide a first voltage to the first terminal of the first switch element D 1 . 
     The second conversion unit  85  converts the first voltage transmitted from the power circuit  95  into a converted voltage. The converted voltage is provided to the first input terminal of the PDU  10 . 
       FIG. 2  illustrates a part circuit of the power system  100  of the present disclosure. The first conversion unit  116  includes a first input terminal M, a second input terminal N, an inductive element L, a third switch element D 3 , a fourth switch element Q, and a capacitive element C. The first and the second input terminals M and N of the first conversion unit  116  connect to the second protection unit  70  to receive a second voltage from the power source  30 . In the embodiment, the first input terminal M receives an input voltage and the second input terminal N receives a ground voltage. Thus, the second voltage of the first conversion unit  116  received from the power protection unit  70  is a voltage between the input voltage of the first input terminal M and the ground voltage of the second input terminal N. A first terminal of the fourth switch element Q is connected to the control unit  105 , a second terminal of the fourth switch element Q is connected to the first input terminal M through the inductive element L, and a third terminal of the fourth switch element Q is grounded through the second input terminal N. A first terminal of the third switch element D 3  is connected to the second terminal of the fourth switch element Q, and a second terminal of the third switch element D 3  is connected to the first terminal of the second switch element D 2  and grounded through the capacitive element C. In the embodiment, the inductive element L is an inductor, the first, the second and the third switch elements D 1 -D 3  are diodes, the first terminals of the diodes are anodes, the second terminals of the diodes are cathodes, the fourth switch element Q is a field effect transistor (FET), the first terminal of the FET is a gate, the second terminal of the FET is a drain, the third terminal of the FET is a source, and the capacitive element is a capacitor. In addition, the power source  30  is a solar cell module and converts solar energy to provide the second voltage. 
     The control unit  105  transmits a timing signal to the first conversion unit  116  to adjust a third voltage of the first conversion unit  116  according to the timing signal. The timing signal includes information about a duty cycle. The duty cycle can be preset in the range of 0 to 1 by a user according to electrical properties of the power source  30  to fully utilize solar energy. In the embodiment, the duty cycle is not larger than 50%. The duty cycle is pre-set according to a relation equation between the second voltage and the third voltage, Vout/Vin=1/(1−D), wherein Vout is an output voltage of the first conversion unit  116 , i.e. the third voltage, Vin is an input voltage of the first conversion unit  116 , i.e. the second voltage, and D is the duty cycle received by the first conversion unit  116 . The first conversion unit  116  provides the third voltage to the first terminal of the second switch element D 2 . In the embodiment, the third voltage is larger than or equal to the second voltage according to the relation equation. 
     If the first voltage provided by the power circuit  95  is a first voltage value, such as 390 volts, and the duty cycle provided by the control unit  105  is 50%, the second voltage of the power source  30  can be one-half of the first voltage, such as 195 volts, according to the relation equation when the third voltage is equal to the first voltage. When the second voltage provided by the power source  30  is larger than one-half of the first voltage, the third voltage converted from the second voltage by the first conversion unit  116  is larger than the first voltage. For example, the third voltage can be 400 volts. Therefore, the second switch element D 2  is turned on and the first switch element D 1  is turned off, since the third voltage of the first conversion unit  116  is larger than the first voltage of the power circuit  95 . Thus, the third voltage is received by the second conversion unit  85  while the first voltage is not received by the second conversion unit  85 . On the contrary, the third voltage converted from the second voltage is smaller than the first voltage when the second voltage provided by the power source  30  is smaller than one-half of the first voltage. Therefore, the second switch element D 2  is turned off and the first switch element D 1  is turned on. The first voltage is received by the second conversion unit  85  but not the third voltage. In addition, the third voltage is equal to the first voltage when the second voltage is equal to one-half of the first voltage. Therefore, both of the first and second switch elements D 1  and D 2  are turned on so that the first voltage and the third voltage are received by the second conversion unit  85  to supply power at the same time. 
     In the embodiment, the power source  30  is a solar cell module. Thus, the power source  30  has an open-circuit voltage when there is no external load connected to the power source  30 . Since the open-circuit voltage of the solar cell module is a maximum voltage of the solar cell module, the open-circuit voltage must be larger than the second voltage. If the third voltage converted from the second voltage is smaller than the first voltage, there is still possibility that a fifth voltage converted from the open-circuit voltage by the first conversion unit  116  may be larger than the first voltage. 
     When the third voltage is smaller than the first voltage, the second switch element D 2  is turned off and the first switch element D 1  is turned on. The power circuit  95  provides the first voltage to the second conversion unit  85  through the first switch element D 1 , and the solar cell module loses its external load and provides the open-circuit voltage. If the fifth voltage is larger than the first voltage, the first switch element D 1  will be turned off and the second switch element D 2  will be turned on. The first conversion unit  116  provides the fifth voltage to the second conversion unit  85  through the second switch element D 2 , and the solar cell module reconnects to its external load and provides the second voltage. Since the third voltage converted from the second voltage is smaller than the first voltage, the second element D 2  will be turned off and the first element D 1  will be turned on again. The power circuit  95  provides the first voltage to the second conversion unit  85  again through the first switch element D 1 . Thus, the first and the second switch elements D 1  and D 2  can be alternately and periodically turned on since the power source  30  alternately provides the second voltage and the open-circuit voltage. In the embodiment, a time interval between the second voltage and the open-circuit voltage is controlled by a capacitance of the capacitive element. 
     When the light intensity is too little for the solar cell module to provide a voltage larger than the first voltage, the third voltage will be smaller than the first voltage. However, the power source  30  of the power system  100  can still supply power when the power source  30  provides the open-circuit voltage. Accordingly, the power source  30  can supply power to the PSU  20  even if the light intensity is too little for the solar cell module. In addition, the power supply  40  of the power system  100  can supply power when the light intensity is too little, so the power supply  40  can compensate for insufficient power of the power source  30 . 
     The second conversion unit  85  is connected to the second terminals of the first and the second switch elements D 1  and D 2 . The second conversion unit  85  transmits a fourth voltage to the PDU  10  for supplying power according to a received voltage of the second conversion unit  85 . When the first voltage is larger than the third voltage, the second conversion unit  85  receives the first voltage to convert to the fourth voltage. When the first voltage is smaller than the third voltage, the second conversion unit  85  receives the third voltage to convert to the fourth voltage. Therefore, the fourth voltage is determined by comparing the first voltage with the third voltage. 
     The battery module  90  and the DC power module  80  are standby power sources for the power system  100 . When the power supply  40  and the power source  30  are broken down and stop supplying power, the battery module  90  and the DC power module  80  can replace the power supply  40 and the power source  30  to supply power to the PDU  10 . Therefore, the power system  100  can be an uninterruptible power supply (UPS) system. In the embodiment, the DC power module  80  can be a power system of another server, which is the same as the power system  100  of the present disclosure. The battery module  90  and the DC power module  80  can directly provide a standby DC voltage to the PDU  10  to supply power to the PSU  20 . 
     The power system  100  can preset the duty cycle of the first conversion unit  116  and automatically adjust the output voltage of the first conversion unit  116  according to the duty cycle and the output voltage of the power source  30 . Therefore, the first and the second switch units D 1  and D 2  can be turned off or turned on so that the power supply  40  and the power source  30  can alternately supply power to the PDU  10 . Thus, it is unnecessary the power supply  40  and the power source  30  are turned on or off by the first and the second protection units  45  and  70 . The first and the second protection units  45  and  70  can be turned on continuously to prevent oxidation of contacts of the first and the second protection units  45  and  70 . Moreover, the power supply  40  can supply power to the PDU  10  without switching off the first conversion unit  116  so the stability of the power system  100  is increased. In addition, utilization rate of the solar energy is increased since the power supply  40  and the power source  30  can alternately or simultaneously supply power to the PDU  10 . 
     While the disclosure has been described by way of example and in terms of preferred embodiment, it is to be understood that the disclosure is not limited thereto. To the contrary, it is intended to cover various modifications and similar arrangements as would be apparent to those skilled in the art. Therefore, the range of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.