Patent Publication Number: US-2023156142-A1

Title: Composite Display Apparatus And Controlling Method Therefor

Description:
TECHNICAL FIELD 
     The present technology relates to a composite display apparatus and a controlling method therefor, and particularly to a composite display apparatus that includes multiple display devices each including a power supply and that makes it possible to achieve reduction in size and reduction in cost of the power supplies and a controlling method for the composite display apparatus. 
     BACKGROUND ART 
     A multi-display apparatus is known in which a large screen formed by arranging multiple display devices contiguously to each other is used as a single display apparatus to display one video (for example, refer to PTL 1). 
     CITATION LIST 
     Patent Literature 
     [PTL 1] 
     
         
         Japanese Patent Laid-Open No. 2001-188524 
       
    
     SUMMARY 
     Technical Problem 
     In the multi-display apparatus described above, power consumptions of the individual display devices arranged contiguously may not necessarily be same as each other. Even in a case where it is obvious that the individual display devices do not operate simultaneously with maximum loads that are consumable by the individual display devices, it is necessary for the multi-display apparatus to include power supply devices that are ready for the maximum loads. Therefore, when the aggregation of the multiple display devices is regarded as a single apparatus, the apparatus has power supplies that are redundant with respect to the maximum load that can be consumed by the apparatus. 
     The present technology has been made in view of such a situation as described above and enables achievement of reduction in size and reduction in cost of power supplies in a composite display apparatus that includes multiple display devices each including a power supply. 
     Solution to Problem 
     A composite display apparatus according to one aspect of the present technology is an apparatus including multiple display devices each including a power supply having predetermined supply power and a power supply connection unit that connects the power supplies of the respective display devices to each other in parallel. In a case where at least one display device among the multiple display devices requires electric power exceeding the predetermined supply power of the power supply of the display device, electric power is supplied to the display device from the power supply of the other display device or devices. 
     A controlling method for a composite display apparatus according to one aspect of the present technology is a controlling method for a composite display apparatus that includes multiple display devices each including a power supply having predetermined supply power and a power supply connection unit that connects the power supplies of the respective display devices to each other in parallel. The controlling method includes causing, in a case where a first display device among the multiple display devices requires electric power exceeding the predetermined supply power of the power supply of the first display device, a second display device among the multiple display devices to supply electric power to the first display device. 
     In one aspect of the present technology, in the composite display apparatus that includes multiple display devices each including a power supply having predetermined supply power and a power supply connection unit that connects the power supplies of the respective display devices to each other in parallel, in a case where a first display device among the multiple display devices requires electric power exceeding the predetermined supply power of the power supply of the first display device, electric power is supplied from a second display device among the multiple display devices to the first display device. 
     The composite display apparatus may be an independent apparatus or may be an internal block included in one equipment. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a view depicting an example of video displaying by a multi-display apparatus. 
         FIG.  2    is a block diagram depicting an example of a configuration of a general multi-display apparatus as a comparative example. 
         FIG.  3    is a view depicting a relation between a light emission luminance and a power consumption of a single display device. 
         FIG.  4    is a view depicting a relation between the light emission luminance and the power consumption of an entire multi-display apparatus. 
         FIG.  5    is a view depicting an example of video displaying that appears on the multi-display apparatus of the comparative example. 
         FIG.  6    is a view depicting examples of video displaying by a multi-display apparatus to which the present technology is applied. 
         FIG.  7    is a block diagram depicting an example of a configuration of the multi-display apparatus to which the present technology is applied. 
         FIG.  8    is a view depicting details of a first configuration example of the multi-display apparatus of  FIG.  7   . 
         FIG.  9    is a view depicting a relation between a differential voltage that is an output of a voltage error amplifier and a value of a current flowing through a MOS-FET. 
         FIG.  10    is a view depicting details of a second configuration example of the multi-display apparatus of  FIG.  7   . 
         FIG.  11    is a block diagram depicting an example of a configuration of a composite apparatus including two devices. 
         FIG.  12    is a block diagram depicting an example of a configuration of a composite apparatus including four devices. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     In the following, modes for carrying out the present technology (hereinafter referred to as embodiments) are described with reference to the accompanying drawings. It is to be noted that, in the present specification and the drawings, components having substantially the same functional configurations are denoted by the same reference signs, and overlapping description of them is omitted. The description is given in the following order. 
     1. Functions Implemented by Multi-display Apparatus to Which Present Technology Is Applied 
     2. Block Diagram of Multi-display Apparatus to Which Present Technology Is Applied 
     3. First Configuration Example of Multi-display Apparatus 
     4. Second Configuration Example of Multi-display Apparatus 
     5. Example of Configuration of Composite Apparatus to Which Present Technology Is Applied 
     1. Functions Implemented by Multi-Display Apparatus to which Present Technology is Applied 
     The present technology can be applied, for example, to a multi-display apparatus (composite display apparatus) in which multiple display devices cooperate with each other to display a predetermined video. 
     Now, functions implemented by a multi-display apparatus to which the present technology is applied are described with reference to  FIGS.  1  to  6   . 
     First, as a comparative example, a general multi-display apparatus is described, and thereafter, functions that are implemented by the multi-display apparatus to which the present technology is applied are described. 
     A multi-display apparatus includes multiple display devices arranged contiguously to each other in at least one of a vertical direction or a horizontal direction, and a large screen formed by a combination of the multiple display devices is used as a single display apparatus to display one video. 
     For example, in a case where the multi-display apparatus includes four display devices arranged in 2×2, the multi-display apparatus displays a video  11  depicted in A of  FIG.  1    by causing the four display devices to individually display videos  11 RA,  11 LA,  11 RB, and  11 LB depicted in B of  FIG.  1   . 
       FIG.  2    is a block diagram depicting an example of a configuration of a multi-display apparatus that can display the video  11  depicted in  FIG.  1    and that is a general multi-display apparatus. 
     A multi-display apparatus  21  of  FIG.  2    includes four display devices  22 RA,  22 LA,  22 RB, and  22 LB. 
     The four display devices  22 RA,  22 LA,  22 RB, and  22 LB are identical display devices  22  each including a power supply  23  and a display unit  24 . The power supplies  23  and the display units  24  of the display devices  22 RA,  22 LA,  22 RB, and  22 LB are denoted by similar reference signs in such a manner that they are referred to as a power supply  23 RA and a display unit  24 RA, a power supply  23 LA and a display unit  24 LA, a power supply  23 RB and a display unit  24 RB, and a power supply  23 LB and a display unit  24 LB. 
     The display unit  24 RA of the display device  22 RA arranged in the upper right displays the video  11 RA, and the display unit  24 LA of the display device  22 LA arranged in the upper left displays the video  11 LA. The display unit  24 RB of the display device  22 RB arranged in the lower right displays the video  11 RB, and the display unit  24 LB of the display device  22 LB arranged in the lower left displays the video  11 LB. 
     The display devices  22  making up the multi-display apparatus  21  each include the power supply  23  that supplies electric power necessary for driving the display unit  24 . Here, it is assumed that the maximum power the power supply  23  of each display device  22  can supply is 100 W and the maximum luminance B when the display unit  24  is driven to emit light from an overall area thereof is 100 (B=100). 
       FIG.  3    is a view depicting a relation between the light emission luminance and the power consumption of a single display device  22 . 
     In a case where the display unit  24  does not emit light, the luminance B of the display unit  24  is B=0 and the power consumption is 0 W as depicted in A of  FIG.  3   . 
     In a case where one half area on one side of the display unit  24  is caused to emit light with its maximum luminance B=100 while the remaining half area thereof does not emit light (luminance B=0) as depicted in B of  FIG.  3   , the power consumption is 50 W. 
     Further, also in a case where the overall area of the display unit  24  is caused to emit light with one half luminance B=50 as depicted in C of  FIG.  3   , the power consumption is 50 W. 
     In a case where the overall area of the display unit  24  is caused to emit light with the maximum luminance B=100 as depicted in D of  FIG.  3   , the power consumption is 100 W. 
     Further, if the display area of the display unit  24  is limited to ¼ and the maximum power of 100 W is used as depicted in E of  FIG.  3   , then the display unit  24  can emit light with the luminance B=400 that is four times the luminance at the time of light emission from the overall area. 
       FIG.  4    is a view depicting a relation between the light emission luminance and the power consumption of the entire multi-display apparatus  21  including the four display devices  22 . 
     The multi-display apparatus  21  includes the display devices  22  of the same configuration arrayed in 2×2, and therefore, each of the four display devices  22  can display a video with the display capability of a single device described hereinabove with reference to  FIG.  3   . 
     For example, it is possible to cause each of the four display devices  22  to emit light with the maximum luminance B=100 from the overall area of the display unit  24  as depicted in A of  FIG.  4   . 
     Further, for example, it is possible to cause three of the display devices  22  to emit light with the maximum luminance B=100 from the overall area of the display unit  24  and cause the remaining one display device  22  to emit light with the luminance B=400, which is four times the luminance upon light emission from the overall area, from ¼ of the display area of the display unit  24 , as depicted in B of  FIG.  4   . 
     Further, for example, it is possible to cause all of the four display devices  22  to emit light with the luminance B=400, which is four times the luminance upon light emission from the overall area, from ¼ of the display area of the display unit  24  in such a manner that light emission is performed with the high luminance B=400 from a central display area corresponding to ¼ of the large screen, as depicted in C of  FIG.  4   . 
     In this manner, even if the four display devices  22  are combined to display a video, the relation between the light emission luminance and the power consumption of the single display device  22  is decided originally as described hereinabove with reference to  FIG.  3   . 
     Accordingly, for example, in a case where such displaying is performed in such a manner as to move a video, in which light is emitted with the high luminance B=400 from ¼ of the display area of the large screen as depicted in A of  FIG.  5   , to the display unit  24 LA side of the display device  22 LA as depicted in B of  FIG.  5   , since the display area for which the display unit  24 LA is responsible exceeds ¼, light emission with the high luminance B=400 cannot be maintained, so that the luminance drops to a luminance B of light that can be emitted with the maximum power of 100 W by one display device  22  as depicted in C of  FIG.  5   . For example, the luminance B of the display area of the display unit  24 LA drops to 200 (B=200). On the other hand, the display units  24 RA,  24 RB, and  24 LB in which display areas for which they are responsible are smaller than ¼ can emit light within a range of the maximum power of 100 W, and the luminance B of light that can be emitted increases to 500 (B=500), 1000 (B=1000), and 500 (B=500), respectively. 
     In this manner, in the general multi-display apparatus  21 , since the light emission capability of one display device  22  is decided originally, even if multiple display devices  22  are combined, failure of the display luminance occurs depending upon the balance of display videos of the display devices  22 . In displaying of a moving image, it is highly possible that a display target that requires a high luminance moves not only in the central region of the large screen of  FIG.  5    but also within the large screen as depicted in C of  FIG.  5   . In a case where the display area of a video becomes one-sided as depicted in C of  FIG.  5   , the multi-display apparatus  21  prevents failure of the display luminance, for example, by adjusting the luminances of the display units  24 RA,  24 RB, and  24 LB to the maximum luminance B=200 of the display unit  24 LA. 
     In contrast,  FIG.  6    depicts examples of video displaying on the large screen of a multi-display apparatus  41  that is a multi-display apparatus to which the present technology is applied and that is hereinafter described with reference to  FIG.  7   . It is to be noted that reference signs of the display units of  FIG.  6    coincide with the reference signs of the multi-display apparatus  21 . 
     A of  FIG.  6    depicts an example of displaying in a case where a video same as that in C of  FIG.  5    is displayed on the multi-display apparatus  41  hereinafter described. 
     The multi-display apparatus  41  can cause the display unit  24 LA to perform, even in a case where the display area for which the display unit  24 LA is responsible exceeds ¼ as depicted in C of  FIG.  5   , emission of light with the high luminance B=400 as depicted in A of  FIG.  6    by receiving supply of power from the other display units  24 RA,  24 RB, and  24 LB that have smaller display areas. Also in each of the display units  24 RA,  24 RB, and  24 LB, the display area is narrower than ¼, and thus, emission of light with the high luminance B=400 is possible. As a result, the entire four screens can perform displaying in such a manner as to cause the display area corresponding to ¼ of the large screen to emit light with the high luminance B=400. 
     It is also possible for the multi-display apparatus  41 , for example, to perform displaying in such a manner as to cause the overall area of the display unit  24 LA to emit light with the four-time luminance B=400 by causing the three display units  24 RA,  24 RB, and  24 LB to emit no light and supplying electric power for them to the remaining one display unit  24 LA, as depicted in B of  FIG.  6   . 
     Further, in a case where displaying is limited to ¼ of the display area of the one display unit  24 LA as depicted in C of  FIG.  6   , it is also possible for the multi-display apparatus  41  to cause the ¼ display area of the display unit  24 LA to emit light with a luminance B=1600, which is 16 times the luminance upon light emission from the overall area of the display unit  24 LA. 
     In this manner, by incorporating a power sharing function for regarding electric power of the respective power supplies of the multiple display devices that operate in a cooperative manner as a totaling one power supply and distributing the electric power to the individual display devices as occasion demands, the multi-display apparatus  41  hereinafter described can perform high-luminance displaying that cannot be implemented by the multi-display apparatus  21  described hereinabove. 
     It is to be noted that, although the example in  FIG.  6    is an example in which the number of display devices making up the multi-display apparatus  41  is four, the number of display devices is not limited to four. For example, in a case where the number of display devices making up the multi-display apparatus  41  is N (N&gt;1) and light emission is concentrated on the overall area of one display unit as depicted in B of  FIG.  6   , displaying with a light emission luminance equal to N times the luminance in the case of using only one display device is possible. Further, in a case where the number of display devices making up the multi-display apparatus  41  is N (N&gt;1) and light emission is concentrated on a display area corresponding to 1/M (M&gt;1) of only one of the display devices, displaying with a light emission luminance equal to N×M times the luminance in the case of using only one display device is possible. 
     In the following, a particular configuration of a multi-display apparatus having the power sharing function depicted in  FIG.  6    is described. 
     2. Block Diagram of Multi-Display Apparatus to which Present Technology is Applied 
       FIG.  7    is a block diagram depicting an example of a configuration of a multi-display apparatus to which the present technology is applied. 
     It is to be noted that, while an example in which a multi-display apparatus includes two display devices is depicted in  FIG.  7    in order to simplify the description, the present technology can also be applied similarly in a case where the number of display devices is three or more. 
     The multi-display apparatus  41  of  FIG.  7    includes two display devices  42  arranged contiguously in the vertical direction or the horizontal direction. In order to distinguish the two display devices  42  from each other, one of the display devices  42  is referred to as a display device  42 A while the other display device  42  is referred to as a display device  42 B. 
     The display devices  42  each include a power supply  51 , a power supply controlling circuit  52 , and a display unit  53 . Accordingly, the display device  42 A includes a power supply  51 A, a power supply controlling circuit  52 A, and a display unit  53 A, and the display device  42 B includes a power supply  51 B, a power supply controlling circuit  52 B, and a display unit  53 B. 
     The power supply  51  ( 51 A,  51 B) has a capability of supplying predetermined electric power and supplies predetermined required electric power to the display unit  53  as a load through a power supply line  54  ( 54 A,  54 B). 
     The power supply controlling circuit  52  ( 52 A,  52 B) controls supply of electric power from the power supply  51  to the display unit  53 . 
     The display unit  53  ( 53 A,  53 B) receives supply of electric power from the power supply  51  and displays a predetermined video on the basis of a video signal inputted thereto through a signal line not depicted. In the present embodiment, it is assumed that the display unit  53 A and the display unit  53 B have screen sizes equal to each other. 
     The power supply line  54 A that connects the power supply  51 A and the display unit  53 A to each other in the display device  42 A and the power supply line  54 B that connects the power supply  51 B and the display unit  53 B to each other in the display device  42 B are connected to each other by a power supply connection line  55 . The power supply connection line  55  is a power supply connection unit that connects the power supply  51 A of the display device  42 A and the power supply  51 B of the display device  42 B in parallel. 
     In the multi-display apparatus  41  configured in such a manner as described above, outputs of the power supplies  51  of the two display devices  42  are controlled in such a manner that supply of electric power of the power supplies  51  is balanced. 
     The power supply  51  provided in each of the display devices  42  is a power supply having a supply capability lower than the maximum power that is consumed by the own display device  42 . For example, although a video of a four-time luminance B=400 or a 16-time luminance B=160 can be displayed using the electric power of 400 W, for example, like the display device  42  in the upper left in B and C of  FIG.  6   , the power supply  51  provided in the display device  42  is a power supply having a supply capability of 100 W lower than 400 W. 
     In a case where the display device  42 A requires electric power exceeding the supply capability of the power supply  51 A of the display device  42 A, that is, in a case where a video is to be displayed with a luminance higher than the luminance corresponding to the maximum value (100 W) of the supply power of the power supply  51 A, electric power is supplied from the power supply  51 B of the other display device  42 B. 
     Although a load A of the display unit  53 A and a load B of the display unit  53 B each vary depending upon the video to be displayed thereon, the electric power supplied from each of the power supplies  51 A and  51 B is an average value (A+B)/2 of the load A and the load B. 
     3. First Configuration Example of Multi-Display Apparatus 
       FIG.  8    depicts details of a first configuration example of the multi-display apparatus  41  of  FIG.  7   . 
     The display device  42 A includes the power supply  51 A, the power supply controlling circuit  52 A, and the display unit  53 A as described hereinabove. 
     The power supply controlling circuit  52 A includes a voltage error amplifier  71 A, a bidirectional switch  72 A, a current mode PWM controller  73 A, a converter  74 A, resistors  75 A and  76 A, and a target voltage generation unit  77 A. 
     The converter  74 A is a DC-DC converter that converts a first voltage V E _A (power supply voltage V E _A) supplied from the power supply  51 A into a second voltage V O _A on the basis of a PWM (Pulse Width Modulation) signal from the current mode PWM controller  73 A and outputs the second voltage V O _A. More specifically, the converter  74 A is configured as a boost chopper circuit that includes an inductor  81 A, a MOS-FET  82 A, a resistor  83 A, a diode  84 A, and a capacitor  85 A and boosts a first voltage V E  to a second voltage V O  by turning on and off the MOS-FET  82 A of the N-channel type that serves as a switching element. Here, an inductance of the inductor  81 A is La, a stored charge of a parasitic capacitance of the MOS-FET  82 A is Qa, and a resistance value of the resistor  83 A is Ra. 
     The display device  42 B is also configured in a manner similar to the display device  42 A, and therefore, description thereof is omitted. Here, the converter  74 B converts a first voltage V E _B (power supply voltage V E _B) supplied from the power supply  51 B into a second voltage V O _B and outputs the second voltage V O _B. It is to be noted that the inductance of the inductor  81 B is Lb, the stored charge of the parasitic capacitance of the MOS-FET  82 B is Qb, and the resistance value of the resister  83 B is Rb. 
     In a case where the screen sizes of the display unit  53 A and the display unit  53 B are equal to each other, the inductances La and Lb of the inductors  81 A and  81 B are set to values equal to each other (La=Lb), and also the resistance values Ra and Rb of the resistors  83 A and  83 B are set to values equal to each other (Ra=Rb). 
     In the multi-display apparatus  41  according to the first configuration example depicted in  FIG.  7   , one of the two display devices  42 A and  42 B operates as a master that controls supply of electric power of all power supplies  51  of the multi-display apparatus  41  while the other operates as a slave that is controlled by the master. It is to be noted that, in a case where the multi-display apparatus  41  includes three or more display devices  42 , a predetermined one of the display devices  42  operates as a master while the remaining display devices  42  operate as slaves. 
     The multi-display apparatus  41  includes at least one master/slave signal generation unit  91  and at least one supply power controlling unit  92 . The master/slave signal generation unit  91  and the supply power controlling unit  92  may be provided separately from the multiple display devices  42  or may be configured in such a manner that, for example, they are provided in each display device  42  and the master/slave signal generation unit  91  and the supply power controlling unit  92  of the display device  42  that operates as a master are set to a valid state to operate. It is assumed that, in the present embodiment, the master/slave signal generation unit  91  and the supply power controlling unit  92  of the display device  42 A are set to the valid state to operate. 
     The master/slave signal generation unit  91  generates a master/slave signal for controlling whether the power supply controlling circuit  52  of each display device  42  is to operate as a master or operate as a slave, and supplies the master/slave signal to the power supply controlling circuit  52  of each display device  42 . 
     In the present embodiment, since the display device  42 A operates as a master and the display device  42 B operates as a slave, a master signal is supplied to the power supply controlling circuit  52 A of the display device  42 A while a slave signal is supplied to the power supply controlling circuit  52 B of the display device  42 B. 
     The supply power controlling unit  92  calculates a target voltage Vref necessary for a video to be displayed on all the display units  53  of the multi-display apparatus  41  and supplies the target voltage Vref to the target voltage generation unit  77 A. For example, in a case where a video to be displayed on all the display units  53  is a dark image, in order to cause all the display units  53  to emit light with a low light emission luminance, the target voltage Vref is low. On the other hand, in a case where a video to be displayed on all the display units  53  is a bright image, in order to cause all the display units  53  to emit light with a high light emission luminance, the target voltage Vref is high. 
     The master/slave signal outputted from the master/slave signal generation unit  91  is supplied to the bidirectional switch  72  of the power supply controlling circuit  52  in each display device  42 . The bidirectional switch  72  includes two N-channel MOS-FETs connected in what is generally called back-to-back connection to each other, and the master/slave signal is supplied to the gate of the N-channel MOS-FETs. The master signal indicating that the power supply controlling circuit  52  is to operate as a master is a High signal that turns on the bidirectional switch  72 , and is supplied to the bidirectional switch  72 A. The slave signal indicating that the power supply controlling circuit  52  is to operate as a slave is a Low signal that turns off the bidirectional switch  72 , and is supplied to the bidirectional switch  72 B. 
     In the power supply controlling circuit  52 A of the display device  42 A in which the bidirectional switch  72 A is turned on, an output of the voltage error amplifier  71 A is validated. On the other hand, in the power supply controlling circuit  52 B of the display device  42 B in which the bidirectional switch  72 B is turned off, an output of the voltage error amplifier  71 B is invalidated. Consequently, the outputs of the voltage error amplifiers  71 A and  71 B are prevented from interfering with each other. 
     It is to be noted that the bidirectional switches  72  are not limited to those having a configuration of two MOS-FETs connected back-to-back to each other and may have any configuration only if the output thereof can be bidirectionally turned on and off. 
     To a first input of the voltage error amplifier  71 A, a value obtained by dividing the second voltage V O _A, which is an output voltage of the converter  74 A, between the resistor  75 A and the resistor  76 A is inputted as a first input voltage V′(A). Meanwhile, to a second input of the voltage error amplifier  71 A, a target voltage Vref generated by the target voltage generation unit  77 A is inputted as a second input voltage Vref. The target voltage generation unit  77 A generates the target voltage Vref set from the supply power controlling unit  92  and supplies the generated target voltage Vref to the voltage error amplifier  71 A. 
     The voltage error amplifier  71 A calculates a differential voltage Vfb between the first input voltage V′(A) and the second input voltage Vref and outputs the calculated differential voltage Vfb to the bidirectional switch  72 A. For example, if the target voltage Vref is 2 V, the output voltage of the converter  74 A is 100 V, and the voltage division ratio between the resistor  75 A and the resistor  76 A is 1/40, then the first input voltage V′(A) becomes 2.5 V, and the difference 0.5 V between 2 V and 2.5 V is outputted as the differential voltage Vfb of an analog value. 
     The differential voltage Vfb that is the output of the voltage error amplifier  71 A is supplied to the current mode PWM controller  73 A via the bidirectional switch  72 A that is in an on state, and is supplied also to the current mode PWM controller  73 B of the power supply controlling circuit  52 B of the display device  42 B that is a slave through a connection line  93 . 
     The current mode PWM controller  73 A supplies a PWM signal generated on the basis of the differential voltage Vfb from the voltage error amplifier  71 A to the gate of the MOS-FET  82 A of the converter  74 A, to thereby turn the MOS-FET  82 A on or off. 
     Where the value of a current flowing through the MOS-FET  82 A is IRa, when the MOS-FET  82 A is turned on, the relation between the differential voltage Vfb that is the output of the voltage error amplifier  71 A and the current value IRa flowing through the MOS-FET  82 A is such as depicted in  FIG.  9   . 
     The current mode PWM controller  73 A turns on and off the MOS-FET  82 A by using, as a target value, a value that varies in proportion to the differential voltage Vfb that is the output of the voltage error amplifier  71 A. The current mode PWM controller  73 A controls the MOS-FET  82 A between on and off in such a manner that, when the differential voltage Vfb is large, the current value IRa flowing through the MOS-FET  82 A that is a switching element is high, but when the differential voltage Vfb is small, the current value IRa flowing through the MOS-FET  82 A that is a switching element is low, as depicted in  FIG.  9   . If the current value IRa flowing through the MOS-FET  82 A increases until it reaches the output of the voltage error amplifier  71 A, then the current mode PWM controller  73 A controls the MOS-FET  82 A to be turned off. 
     That is, the converter  74 A is a current mode-controlled power supply circuit that switching-controls the current flowing through the MOS-FET  82 A to thereby convert the first voltage V E _A into the second voltage V O _A to be outputted. 
     In this manner, the power supply controlling circuit  52 A controls the current value IRa flowing through the MOS-FET  82 A on the basis of the output from the voltage error amplifier  71 A that outputs the differential voltage Vfb between the division voltage V′(A) of an actual output voltage (second voltage V O _A) of the converter  74 A and the target voltage Vref. 
     Further, the output of the voltage error amplifier  71 A is supplied also to the current mode PWM controller  73 B of the power supply controlling circuit  52 B of the display device  42 B, which is a slave, through the connection line  93 . Accordingly, also in the power supply controlling circuit  52 B, the current value IRb flowing through the MOS-FET  82 B is controlled on the basis of the output from the voltage error amplifier  71 A in a similar manner. 
     In both of the power supply controlling circuits  52 A and  52 B, the current value IRa flowing through the MOS-FET  82 A and the current value IRb flowing through the MOS-FET  82 B are controlled on the basis of the output from the one voltage error amplifier  71 A. In the power supply controlling circuits  52 A and  52 B, since the inductances La and Lb of the inductors  81 A and  81 B are equal to each other (La=Lb) and the resistance values Ra and Rb of the resistors  83 A and  83 B are equal to each other (Ra=Rb), the current value IRa and the current value IRb become equal to each other. Consequently, supply of electric power from the power supply  51 A (second voltage V O _A) and supply of electric power from the power supply  51 B (second voltage V O _B) are controlled to be balanced. 
     According to the first configuration example of the multi-display apparatus  41  described above, each of the power supply controlling circuits  52  ( 52 A and  52 B) of the multiple display devices  42  ( 42 A and  42 B) acquires a control signal indicating whether the display device is to operate as a master or a slave. Then, the power supply controlling circuit  52 A that acquires the master signal indicating that the display device is to operate as a master controls also the power supply controlling circuit  52 B of the other display device  42 B. 
     The power supply controlling circuit  52 A, as the master, controls the output of the own power supply  51 A and the output of the other power supply  51 B in such a manner that supplies of electric power of the power supplies  51 A and  51 B of the two display devices  42 A and  42 B are balanced. 
     It is to be noted that, while the present embodiment described above is directed to a case in which the display unit  53 A and the display unit  53 B have screen sizes equal to each other, for example, in a case where the screen sizes of the display unit  53 A and the display unit  53 B are different from each other, similar control can be performed by setting the ratio between the inductances La and Lb and the ratio between the resistance values Ra and Rb to values according to the ratio between the power supplies  51  corresponding to the screen sizes. For example, by setting La=2Lb and Ra=2Rb, the ratio between the outputs of the power supply  51 A and the power supply  51 B can be set to 1:2. 
     4. Second Configuration Example of Multi-Display Apparatus 
       FIG.  10    depicts details of a second configuration example of the multi-display apparatus  41  of  FIG.  7   . 
     In  FIG.  10   , elements corresponding to those of the first configuration example depicted in  FIG.  8    are denoted by the same reference signs, and description of them is omitted suitably. 
     In the second configuration example, the two display devices  42 A and  42 B have no such a master-slave relation as in the first configuration example, and the two display devices  42 A and  42 B have the same configuration. Therefore, in the following description, the display device  42 A is described, and description of the display device  42 B is suitably complemented. 
     The power supply controlling circuit  52 A of the display device  42 A includes a voltage error amplifier  71 A that compares a first input voltage V′(A) obtained by voltage division between the resistor  75 A and the resistor  76 A and a second input voltage Vref generated by the target voltage generation unit  77 A with each other and outputs a resulting differential voltage Vfb, as in the first configuration example. The display device  42 A includes a supply power controlling unit  92 A that calculates a target voltage Vref on the basis of a video to be displayed on the display unit  53 A and supplies the target voltage Vref to the target voltage generation unit  77 A. 
     Further, the power supply controlling circuit  52 A includes a converter  101 A that converts a first voltage V E _A (power supply voltage V E _A) from the power supply  51 A into a second voltage V O _A on the basis of the output of the voltage error amplifier  71  and outputs the second voltage V O _A. The converter  101 A may be a current mode-controlled converter as in the first configuration example or may be a different control type converter. In other words, in the second configuration example, the controlling method of the converter may be freely determined. 
     Further, the power supply controlling circuit  52 A includes, on an output path of the converter  101 A, a resistor  102 A as a current detection element that detects a value of a current flowing through the display unit  53 A as a load and converts the current value into a voltage and an amplifier  103 A that amplifies the voltage obtained by the conversion. Here, the resistance value of the resistor  102 A is r a , and the amplification rate of the amplifier  103 A is A a . 
     Further, the power supply controlling circuit  52 A includes a comparator  104 A, which has a first input to which a voltage Va that is an output of the amplifier  103 A is inputted and a second input to which an end point on the opposite side (the other end) of a resistor  105 A connected at one end thereof to the output of the amplifier  103 A is inputted. 
     The resistor  105 A of the power supply controlling circuit  52 A is connected to a resistor  105 B of the power supply controlling circuit  52 B of the display device  42 B through a connection line  106 , and a connection point between the resistor  105 A and the resistor  105 B is set as the second input of the comparator  104 A of the power supply controlling circuit  52 A. Therefore, to the second input, an average value Vave of the output voltage Va of the amplifier  103 A of the power supply controlling circuit  52 A and the output voltage Vb of the amplifier  103 B of the power supply controlling circuit  52 B is inputted. 
     The comparator  104 A compares the output voltage Va of the amplifier  103 A that is the first input and the average value Vave of the output voltages Va and Vb that is the second input with each other and outputs (a voltage of) a result of the comparison to a connection point between the target voltage generation unit  77 A and a resistor  106 A. 
     The power supply controlling circuit  52 A of the display device  42 A is configured in such a manner as described above, and also the power supply controlling circuit  52 B of the display device  42 B is configured in a manner similar to the power supply controlling circuit  52 A. It is to be noted that, where the resistance value of the resistor  102 B in the power supply controlling circuit  52 B is represented by r b  and the amplification rate of the amplifier  103 B is represented by A b , the resistance values and the amplification rates have respective relations of r a =r b  and A a =A b . 
     Operation of the power supply controlling circuit  52 A described above is described. The comparator  104 A compares the output voltage Va of the amplifier  103 A, which is equivalent to a value of a current flowing through the output path of the converter  101 A, and the average value Vave that is equivalent to an average value of current values flowing through the output paths of the converters  101 A and  101 B. Further, the supply of electric power (second voltage V O _B) from the power supply  51 A is controlled on the basis of the comparison result of the comparator  104 A. More specifically, in a case where the current value of the converter  101 A is smaller than the average current value, the comparator  104 A outputs (a voltage of) such a comparison result that raises the second input voltage Vref that is the target voltage of the voltage error amplifier  71 , but in a case where the current value of the converter  101 A is larger than the average current value, the comparator  104 A outputs (a voltage of) such a comparison result that lowers the second input voltage Vref that is the target voltage of the voltage error amplifier  71 . 
     Also the power supply controlling circuit  52 B performs similar operation to perform such control as to make, in each of the power supply controlling circuits  52 A and  52 B, current values to be outputted from the converters  101 A and  101 B equal to each other. In short, the power supply controlling circuits  52 A and  52 B perform control of the current values in such a manner that the supply of electric power of the power supplies  51 A and  51 B in the respective display devices  42 A and  42 B is balanced. 
     It is to be noted that the resistance values and the amplification rates have respective relations of r a =r b  and A a =A b  in a case where the screen sizes of the display unit  53 A and the display unit  53 B are equal to each other. In a case where the screen sizes of the display unit  53 A and the display unit  53 B are different from each other, the ratio between the resistance values r a  and r b  and the ratio between the amplification rates A a  and A b  are changed according to the screen sizes (power supplies). 
     While it is described that, in the above-described embodiment, the power supply controlling circuit  52  is configured in such a manner as to control the power supplies  51  incorporated in the individual display devices  42  of the multi-display apparatus  41  in which the multiple display devices  42  operate cooperatively, the power supply controlling circuit  52  of the present technology can be applied to other apparatuses in addition to such a display apparatus. In particular, the power supply controlling circuit  52  described above can be applied to a power supply controlling apparatus that controls power supplies of multiple devices in a case where the multiple devices cooperatively making up the entire apparatus. For example, in a case where the power supply controlling circuit  52  is used in a charger, charging can be accelerated when the number of batteries connected is small. 
     In the first configuration example of the power supply controlling circuit  52  depicted in  FIG.  8   , since currents flowing through the respective converters  74  coincide with each other pulse by pulse, even in the case of a load whose variation is great and whose peak is great, it is possible to cause the peak load to be shared. Therefore, the first configuration example is suitable for the multi-display apparatus described above and so forth. 
     On the other hand, since the second configuration example of the power supply controlling circuit  52  of  FIG.  10    is free from restriction in regard to the type of the converters  101 , it can be applied to such an apparatus as a charger whose output variation is small, and the range choices for the converters  101  can be extended. 
     5. Configuration Example of Composite Apparatus to which Present Technology is Applied 
       FIG.  11    is a block diagram depicting an example of a configuration of a composite apparatus in a case where the power supply control of the present technology described above is applied to a composite apparatus whose use is not limited. 
     A composite apparatus  141  of  FIG.  11    includes two devices  142 A and  142 B. 
     The device  142 A and the device  142 B have the same configuration, and therefore, description is given of the device  142 A while description of the device  142 B is omitted. 
     The device  142 A includes a power supply  151 A, a power supply controlling circuit  152 A, and a load  153 A. The power supply  151 A supplies electric power V(A)×I(A) required for operation of the load  153 A to the load  153 A. The power supply controlling circuit  152 A controls supply of electric power from the power supply  151 A. More specifically, the power supply controlling circuit  152 A performs control in such a manner that electric power to be supplied from the power supply  151 A to the load  153 A becomes equal to a target value. The load  153 A receives supply of electric power (consumes electric power) from the power supply  151 A and performs predetermined operation. 
     The power supply controlling circuit  152 A includes a computation unit  171 A, a Ref voltage generation unit  172 A, a voltage detection unit  173 A, a differential outputting unit  174 A, and a control unit  175 A. 
     The computation unit  171 A calculates a current value required for the load  153 A and supplies the calculated current value to the Ref voltage generation unit  172 A. The Ref voltage generation unit  172 A calculates a target voltage Vref(A) on the basis of the current value supplied from the computation unit  171 A and supplies the calculated target voltage Vref(A) to the differential outputting unit  174 A. The target voltage Vref(A) is a value obtained from a voltage value corresponding to the required current value supplied from the computation unit  171 A while taking a proportional coefficient M similar to that in the voltage detection unit  173  into consideration. 
     In the example of the multi-display apparatus  41  described hereinabove, the load  153 A corresponds to the display unit  53 , and the computation unit  171 A calculates a current value required for a video to be displayed on the display unit  53 . 
     The voltage detection unit  173 A detects an actual output voltage V(A) from the power supply  151 A to the load  153 A and supplies a conversion voltage V′(A) converted in proportion to the output voltage V(A) to the differential outputting unit  174 A. For example, the conversion voltage V′(A) is a voltage that satisfies V′(A)=V(A)/M (M&gt;0). 
     The differential outputting unit  174 A compares the target voltage Vref(A) supplied from the Ref voltage generation unit  172 A and the conversion voltage V′(A) supplied from the voltage detection unit  173 A with each other, generates a differential voltage Vfb(A) for feedback on the basis of a result of the comparison, and supplies the generated differential voltage Vfb(A) to the control unit  175 A. 
     The control unit  175 A controls supply of electric power of the power supply  151 A on the basis of the differential voltage Vfb(A) from the differential outputting unit  174 A. More specifically, the control unit  175 A performs, in a case where the conversion voltage V′(A) is lower than the target voltage Vref(A), control to raise the voltage V(A) of the power supply  151 A, but performs, in a case where the conversion voltage V′(A) is higher than the target voltage Vref(A), control to lower the voltage V(A) of the power supply  151 A. 
     Also the device  142 B has a configuration similar to that of the device  142 A and performs similar operation. 
     A voltage supply line  181 A of the power supply  151 A of the device  142 A and a voltage supply line  181 B of the power supply  151 B of the device  142 B are shared through a connection line  182 . Consequently, the voltage V(A) of the power supply  151 A and the voltage V(B) of the power supply  151 B become equal to each other (V(A)=V(B)), and to the load  153 A and the load  153 B, electric power is supplied from the two power supplies  151 A and  151 B. 
     For example, in a case where the maximum power consumption of the load  153 A of the single device  142 A is 100 W (load  153 A≤100 W), the maximum power consumption of the load  153 B of the single device  142 B is 100 W (load  153 B≤100 W), and the maximum power consumption of the overall composite apparatus  141  is 150 W ({(load  153 A)+(load  153 B)}≤150 W), it is sufficient if each of the power supplies  151  of the devices  142 A and  142 B has the supply capability of 75 W. Since, in the power supply control of the conventional method, it is necessary for each of the devices  142 A and  142 B to include the power supply  151  having the supply capability of 100 W, the power supply control of the present technology can implement reduction in size and reduction in cost of the power supply  151 . 
     Further, in a case where the power supplies  151  of the devices  142 A and  142 B have the supply capability of 100 W as in the conventional method, the overall composite apparatus  141  has the supply capability of 200 W ({(load  153 A)+(load  153 B)}≤200 W), and it is also possible, for example, to supply 200 W to the load  153 A and supply 0 W to the load  153 B. 
       FIG.  12    is a block diagram depicting an example of a configuration of the composite apparatus  141  in a case where the composite apparatus  141  includes four devices  142 A to  142 D. 
     Although detailed description of each of the four devices  142 A to  142 D is omitted because it is similar to that in  FIG.  11   , a voltage supply line  181 A of the power supply  151 A of the device  142 A, a voltage supply line  181 B of the power supply  151 B of the device  142 B, a voltage supply line  181 C of the power supply  151 C of the device  142 C, and a power supply line  181 D of the power supply  151 D of the device  142 D are shared through the connection line  182 . Consequently, the loads  153 A to  153 D become equal in magnitude and the voltages of them satisfy V(A)=V(B)=V(C)=V(D), and therefore, the values of electric power to be supplied from the power supplies  151 A to  151 D become equal to each other. 
     The embodiment of the present technology is not limited to the embodiments described above and can be altered in various manners without departing from the scope of the present technology. 
     For example, it is possible to adopt modes in which all or part of the embodiments described above are combined. 
     It is to be noted that the advantages described in the present specification are exemplary to the last and are not restrictive, and advantages other than those described in the present specification may be obtained. 
     It is to be noted that the present technology can adopt the following configurations. 
     (1) 
     A composite display apparatus including: 
     multiple display devices each including a power supply having predetermined supply power; and 
     a power supply connection unit that connects the power supplies of the respective display devices to each other in parallel, in which, 
     in a case where at least one display device among the multiple display devices requires electric power exceeding the predetermined supply power of the power supply of the display device, electric power is supplied to the display device from the power supply of the other display device or devices. 
     (2) 
     The composite display apparatus according to (1) above, in which, 
     in a case where the display device performs displaying with a luminance higher than a luminance corresponding to a maximum value of the supply power of the display device, it is determined that electric power exceeding the predetermined supply power of the power supply of the display device is required, and electric power is supplied to the display device from the power supply of the other display device or devices. 
     (3) 
     The composite display apparatus according to (1) or (2) above, in which 
     each of the display devices includes a power supply controlling circuit that controls supply of electric power from the power supply of the own display device, and 
     a first power supply controlling circuit that is the power supply controlling circuit in a predetermined one of the multiple display devices also controls the power supply controlling circuit of the other display device or devices in such a manner that supply of electric power of the power supplies of the respective display devices is balanced. 
     (4) 
     The composite display apparatus according to (3) above, in which 
     the power supply controlling circuit of each of the multiple display devices acquires a control signal for controlling whether or not the power supply controlling circuit is to operate as the first power supply controlling circuit that also controls the power supply controlling circuit of the other display device or devices, and 
     a predetermined one of the power supply controlling circuits that has acquired the control signal indicating that the power supply controlling circuit is to operate as the first power supply controlling circuit operates as the first power supply controlling circuit. 
     (5) 
     The composite display apparatus according to (3) or (4) above, in which 
     the power supply controlling circuit controls supply of electric power of the power supply on the basis of an output from a differential outputting unit that outputs a difference between an actual output voltage from the power supply and a target voltage. 
     (6) 
     The composite display apparatus according to any one of (3) to (5) above, in which 
     the power supply controlling circuit includes a current mode-controlled power supply circuit and controls supply of electric power from the power supply by switching-controlling a current. 
     (7) 
     The composite display apparatus according to (4) above, further including: 
     a signal generation unit that generates and outputs the control signal. 
     (8) 
     The composite display apparatus according to (5) above, further including: 
     a supply power controlling unit that sets the target voltage. 
     (9) 
     The composite display apparatus according to (1) or (2) above, in which 
     each of the display devices includes a power supply controlling circuit that controls supply of electric power from the power supply of the own display device, and 
     the power supply controlling circuit controls the own power supply in such a manner that supply of electric power of the power supplies of the respective display devices is balanced. 
     (10) 
     The composite display apparatus according to (9) above, in which 
     the power supply controlling circuit includes a current detection element that detects a value of a current flowing through a load of the own display device and converts the current value into a voltage, and compares a first voltage obtained by the conversion by the current detection element and a second voltage that corresponds to an average value of values of currents flowing through loads of the respective display devices, to thereby control supply of electric power of the power supply on the basis of a result of the comparison. 
     (11) 
     A controlling method for a composite display apparatus that includes 
     multiple display devices each including a power supply having predetermined supply power, and 
     a power supply connection unit that connects the power supplies of the respective display devices to each other in parallel, 
     the controlling method including: 
     causing, in a case where a first display device among the multiple display devices requires electric power exceeding the predetermined supply power of the power supply of the first display device, a second display device among the multiple display devices to supply electric power to the first display device. 
     REFERENCE SIGNS LIST 
     
         
         
           
               41 : Multi-display apparatus 
               42 A,  42 B: Display device 
               51 A,  51 B: Power supply 
               52 A,  52 B: Power supply controlling circuit 
               53 A,  53 B: Display unit 
               54 A,  54 B: Power supply line 
               55 : Power supply connection line 
               71 A,  71 B: Voltage error amplifier 
               72 A,  72 B: Bidirectional switch 
               73 A,  73 B: Current mode PWM controller 
               74 A,  74 B: Converter 
               75 A,  75 B,  76 A,  76 B: Resistor 
               77 A,  77 B: Target voltage generation unit 
               81 A,  81 B: Inductor 
               82 A,  82 B: MOS-FET 
               83 A,  83 B: Resistor 
               84 A,  84 B: Diode 
               85 A,  85 B: Capacitor 
               91 : Master/slave signal generation unit 
               92 : Supply power controlling unit 
               93 : Connection line 
               101 A,  101 B: Converter 
               102 A,  102 B: Resistor 
               103 A,  103 B: Amplifier 
               104 A,  104 B: Comparator 
               105 A,  105 B: Resistor 
               141 : Composite apparatus 
               142 A to  142 D: Device 
               151 A to  151 D: Power supply 
               152 A to  152 D: Power supply controlling circuit 
               153 A to  153 D: Load 
               171 A to  171 D: Computation unit 
               172 A to  172 D: Ref voltage generation unit 
               173 A to  173 D: Voltage detection unit 
               174 A to  174 D: Differential outputting unit 
               175 A to  175 D: Control unit 
               181 A to  181 D: Voltage supply line