Power supply apparatus and power supply method

Abstract

A power supply apparatus is provided that has a plurality of secondary batteries connected in series, outputs a composite voltage of all of the secondary batteries, and outputs an output of a part of the secondary batteries as a partial voltage. The power supply apparatus includes a detecting unit that detects states of the secondary batteries, a changing unit that changes an order of series connection of the plurality of secondary batteries based on a detection result of the detecting unit in such a manner that the partial voltage is outputted from a secondary battery that is in a relatively good state.

What is claimed is: 
     
         1 . A power supply apparatus that has a plurality of secondary batteries connected in series, outputs a composite voltage of all of the secondary batteries, and outputs an output of a part of the secondary batteries as a partial voltage, the power supply apparatus comprising:
 a detecting unit that detects states of the secondary batteries; and   a changing unit that changes an order of series connection of the plurality of secondary batteries based on a detection result of the detecting unit in such a manner that the partial voltage is outputted from a secondary battery that is in a relatively good state.   
     
     
         2 . The power supply apparatus according to  claim 1 , wherein
 the power supply apparatus has two secondary batteries;   the power supply apparatus outputs a composite voltage of terminal voltages of the two secondary batteries and a terminal voltage of a secondary battery connected to a ground side as a partial voltage;   the detecting unit detects states of the two secondary batteries; and   the changing unit changes an order of the series connection in such a manner that a secondary battery that is in a relatively good state, which has been detected by the detecting unit, is connected to a ground side.   
     
     
         3 . The power supply apparatus according to  claim 2 , wherein
 the changing unit has four switches each having a single common terminal, a first selective terminal and a second selective terminal;   a positive pole and a negative pole of each of the two secondary batteries are connected to the respective common terminals of the four switches;   respective first selective terminals of the four switches are connected with one another, the respective first selective terminals being a terminal that outputs the partial voltage;   respective second selective terminals of two switches connected to the positive pole through the respective common terminals are connected with each other, the respective second selective terminals being a terminal that outputs the composite voltage;   respective second selective terminals of the two switches connected to the negative pole through the respective common terminals are connected with each other, the respective second selective terminals being a terminal that is connected to a ground; and   the order of series connection is changed by controlling a connecting state of the four switches.   
     
     
         4 . The power supply apparatus according to  claim 3 , wherein the detecting unit is connected between a terminal connected to the ground and the ground. 
     
     
         5 . The power supply apparatus according to  claim 3 , wherein a discharge unit that makes the secondary battery discharge when detecting the states of the secondary batteries is connected between the terminal that outputs the partial voltage and the ground. 
     
     
         6 . The power supply apparatus according to  claim 3 , wherein the two secondary batteries are connected in parallel by the four switches and the partial voltage is supplied to a load. 
     
     
         7 . The power supply apparatus according to  claim 1 , wherein, in detecting the states of the secondary battery by the detecting unit, the state of one of the secondary batteries is detected by the detecting unit and a terminal voltage of the other secondary battery is supplied to the load as a partial voltage. 
     
     
         8 . The power supply apparatus according to  claim 1 , wherein the power supply apparatus has three secondary batteries;
 the power supply apparatus outputs a composite voltage of terminal voltages of the three secondary batteries and a terminal voltage of one of the secondary batteries connected to a ground side as a partial voltage;   the detecting unit detects the states of the three secondary batteries; and   the changing unit changes an order of series connection in such a manner that a secondary battery having a relatively good state, which has been detected by the detecting unit, is connected to a ground side.   
     
     
         9 . The power supply apparatus according to  claim 1 , wherein
 the power supply apparatus has four secondary batteries;   the power supply apparatus outputs a composite voltage of terminal voltages of the four secondary batteries and outputs a terminal voltage of one or two of the secondary batteries, which is connected to the ground side, as a partial voltage;   the detecting unit detects the states of the four secondary batteries; and   the changing unit changes an order of the series connection in such a manner that a secondary battery having a relatively good state, which has been detected by the detecting unit, is connected to a ground side.   
     
     
         10 . The power supply apparatus according to  claim 1 , wherein, in the power supply apparatus, a single detecting unit that detects the states of the secondary batteries is provided. 
     
     
         11 . A power supplying method that has a plurality of secondary batteries connected in series, outputs a composite voltage of all of the secondary batteries, and outputs an output of a part of the secondary batteries as a partial voltage, the power supply method comprising:
 detecting states of the secondary batteries; and   changing an order of series connection of the plurality of secondary batteries in such a manner that the partial voltage is outputted from a secondary battery in a relatively good state, based on a detection result of the detecting unit.   
     
     
         12 . The power supplying method according to  claim 11 , wherein,
 in the power supplying method, a changing switch is switched only when a current detected in the detecting is less than or equal to a predetermined current.