JP7450774B2 - display device - Google Patents

Description

The present disclosure relates to a display device.

As disclosed in Patent Document 1, a display device is known that includes a display device that displays an image and a power supply circuit that outputs power necessary for displaying the image to the display device. The power supply circuit converts commercial AC power into DC power and outputs the DC power obtained by the conversion to the display.

Japanese Patent Application Publication No. 2018-169461

In a display device, power is consumed not only in the display but also in the power supply circuit. Therefore, as the display device operates, the power supply circuit generates heat, and the greater the amount of heat generated by the power supply circuit, the more likely the display device is to malfunction. Therefore, a power supply circuit that suppresses heat generation is desired.

However, in conventional display devices, even if the output power of the power supply circuit decreases as the power required for displaying images decreases, it is difficult to suppress heat generation in the power supply circuit. This is because the smaller the output power of a power supply circuit, the lower the power conversion efficiency of that power supply circuit. In other words, even if the output power of the power supply circuit decreases, the power loss in the power supply circuit is difficult to reduce, and the power loss causes heat generation, so it is difficult to suppress the heat generation in the power supply circuit.

An object of the present disclosure is to provide a display device in which heat generation in a power supply circuit is suppressed more than before.

The display device according to the present disclosure includes:
It has a plurality of display units constituting a display screen on which an image is displayed, and the amount of power required to display the image on the display screen depends on the total brightness within the plane of the display screen. A time- varying indicator,
A power supply circuit having a plurality of power converters connected in parallel to a power supply unit that supplies AC power, each of the power converters converting the AC power into DC power;
A required power value representing the amount of power required to display the video on the display screen is determined, and based on the determined required power value, the smaller the required power value, the more power the plurality of power circuits constituting Determining the number of the working power converters under the condition that the number of working power converters that are the power converters to be operated among the power converters in the set is reduced, and controlling the determined number of the working power converters, The non-operating power converter, which is the power converter other than the operating power converter among the plurality of power converters constituting the power supply circuit, is brought into an operating state that outputs the DC power, and the non-operating power converter is set to an operating state in which it outputs the DC power. a control device that controls the number of units in a non-operating state, and
a repeater that distributes the DC power output by the operating power converter to the plurality of display units forming the display;
Equipped with
In the control of the number of units, the control device uses operation history data representing a cumulative operating period length of each power converter, which is a cumulative value of the period length during which the power converter was in the operating state, The operating power converter is selected from among the plurality of power converters under conditions that variation in the cumulative operating period length among the plurality of power converters is suppressed .

According to the above configuration, by controlling the number of converters, the smaller the required power value is, the smaller the number of operating power converters is. Therefore, when the required power decreases, the output power of the working power converter is less likely to decrease, so that the power conversion efficiency of the working power converter is less likely to decrease. In other words, even if the number of active power converters is reduced, power loss is unlikely to increase in the active power converters. On the other hand, the number of non-operating power converters increases as the required power value is smaller, and heat generation associated with power consumption is suppressed in non-operating power converters. As a result, heat generation in the power supply circuit is suppressed more than before.

A conceptual diagram showing the appearance of a display device according to Embodiment 1 Conceptual diagram showing the configuration of a display device according to Embodiment 1 Flowchart of heat generation suppression processing according to Embodiment 1 Conceptual diagram showing the configuration of a first power converter according to Embodiment 2 Conceptual diagram showing the configuration of a display device according to Embodiment 2 Conceptual diagram showing the configuration of a control device according to Embodiment 2 Flowchart of heat generation suppression processing according to Embodiment 2 Flowchart of heat generation suppression processing according to Embodiment 3 Conceptual diagram showing the configuration of a display device according to a comparative form

Hereinafter, a display device according to an embodiment will be described with reference to the drawings. In the figures, the same or corresponding parts are denoted by the same reference numerals.

[Embodiment 1]
As shown in FIG. 1, a display device 800 according to the present embodiment includes a display device 100 having a display screen 100a on which an image is displayed, and an equipment storage box 710 containing equipment for controlling the display device 100. Equipped with.

The display device 100 is arranged separately from the equipment storage box 710. Specifically, the display device 100 is attached to the upper end of a support 720 that is erected on the ground, and the equipment storage box 710 is placed beside the lower end of the support 720.

The display device 100 and the device housing box 710 include a power wiring 730 that transmits the power necessary for displaying images from the device housing box 710 to the display device 100, and a power wiring 730 that transmits the power necessary for displaying images from the device housing box 710 to the display device 100, and a power wiring 730 that transmits video data representing the content of the video from the device housing box 710 to the display device. 100 and a data wiring 740 for transmission.

The display device 800 is installed outdoors near a road. The display screen 100a visually provides road information in the form of images regarding road congestion, accidents, traffic regulations, weather, etc. to drivers of vehicles traveling on the road.

The configuration of the display device 100 will be described below. The display device 100 includes a first display unit 110, a second display unit 120, a third display unit 130, and a fourth display unit 140, each of which displays an image.

The four units from the first display unit 110 to the fourth display unit 140 are combined in a matrix, specifically, in a matrix of 2 rows and 2 columns, thereby forming one display screen 100a as a whole.

Each of the first display unit 110 to the fourth display unit 140 includes a plurality of light emitting devices that emit visible light and a circuit board on which the plurality of light emitting devices are mounted. The plurality of light emitting devices are two-dimensionally distributed and arranged on the surface of the circuit board. Each light emitting device includes a red LED (Light Emitting Diode) that emits red light, a green LED that emits green light, and a blue LED that emits blue light.

Next, the internal configuration of the equipment storage box 710 will be described.

As shown in FIG. 2, the display device 800 includes a power supply section 200 configured by a distribution board that outputs commercial AC power, and a power supply circuit 300 that converts the AC power supplied from the power supply section 200 into DC power. Equipped with. The display device 100 displays an image on the display screen 100a based on the DC power converted by the power supply circuit 300.

The power supply circuit 300 includes a first power converter 310 , a second power converter 320 , a third power converter 330 , and a fourth power converter 340 connected in parallel to the power supply unit 200 . Each of the first power converter 310 to the fourth power converter 340 converts the AC power supplied from the power supply unit 200 into DC power, and outputs the DC power obtained by the conversion.

The power supply circuit 300 consumes power for power conversion from AC power to DC power. Therefore, the power supply circuit 300 generates heat, which causes the display device 800 to malfunction. Therefore, in order to reduce the probability of failure occurring in the display device 800, a configuration in which the power supply circuit 300 does not easily generate heat is desired.

Hereinafter, a comparative example will be described in order to specifically illustrate the problem to be solved by this embodiment.

As shown in FIG. 9, in the display device 900 according to the comparative embodiment, four units from the first display unit 110 to the fourth display unit 140 and four units from the first power converter 310 to the fourth power converter 340 are installed. , there is a one-to-one correspondence.

That is, the first display unit 110 receives power exclusively from the first power converter 310. The second display unit 120 receives power exclusively from the second power converter 320. The third display unit 130 receives power exclusively from the third power converter 330. The fourth display unit 140 receives power exclusively from the fourth power converter 340.

Therefore, in order to display an image on the display screen 100a, the control device 910 according to the comparative embodiment constantly operates all of the first power converter 310 to the fourth power converter 340 in parallel. Since each of the first power converter 310 to the fourth power converter 340 consumes power for power conversion during operation, heat is generated in the power supply circuit 300.

On the other hand, the amount of power required to display an image on the display screen 100a changes over time depending on the total luminance within the plane of the display screen 100a. Therefore, when the power required to display an image on the display screen 100a decreases, the total output power of the power supply circuit 300 decreases, so it is expected that the heat generation of the power supply circuit 300 will be suppressed.

However, in the display device 900, even if the total output power of the power supply circuit 300 decreases as the power required for displaying images decreases, it is difficult to suppress heat generation in the power supply circuit 300. This is because each of the first power converter 310 to the fourth power converter 340 has a characteristic that the smaller the output power, the lower the power conversion efficiency.

Here, the power conversion efficiency of a power converter refers to the value obtained by dividing the output power output by the power converter by the input power input to the power converter. When the power change efficiency of a power converter is η [%], 100−η [%] represents the power consumed by the power converter, that is, the rate of power loss in the power conversion. The greater the power loss, the greater the heat generation.

That is, even if the output power of each of the first power converter 310 to the fourth power converter 340 decreases, the power loss in each of them is difficult to decrease. Furthermore, as described above, in the comparative embodiment, all of the first power converter 310 to the fourth power converter 340 are operated at all times, so all of these four units generate heat due to power loss.

Therefore, it is difficult to suppress heat generation in the power supply circuit 300 as a whole. The heat generated by the power supply circuit 300 causes a failure of the power supply circuit 300 itself, and also causes a failure of the equipment housed together with the power supply circuit 300 in the equipment storage box 710 shown in FIG.

In order to solve the problems described above, this embodiment adopts a configuration in which the power supply circuit 300 does not easily generate heat. Hereinafter, referring back to FIG. 2, the configuration of this embodiment will be specifically described.

As shown in FIG. 2, the display device 800 according to the present embodiment has a switch group 400 connected between the power supply circuit 300 and the power supply section 200, and a switch group 400 connected between the power supply circuit 300 and the display device 100. The control device 600 further includes a repeater 500 , a display 100 , a power supply circuit 300 , a switch group 400 , and a control device 600 that controls the repeater 500 .

Note that the power supply unit 200, the power supply circuit 300, the switch group 400, the repeater 500, and the control device 600 are housed in the equipment storage box 710 shown in FIG.

The switch group 400 includes a first switch 410 interposed between the first power converter 310 and the power supply unit 200, and a second switch 420 interposed between the second power converter 320 and the power supply unit 200. , a third switch 430 interposed between the third power converter 330 and the power supply section 200 , and a fourth switch 440 interposed between the fourth power converter 340 and the power supply section 200 .

The first switch 410 can be switched between a conduction state in which the first power converter 310 is connected to the power supply unit 200 and a cutoff state in which the first power converter 310 is disconnected from the power supply unit 200. The second switch 420 can be switched between a conduction state in which the second power converter 320 is connected to the power supply unit 200 and a cutoff state in which the second power converter 320 is disconnected from the power supply unit 200. The third switch 430 can be switched between a conduction state in which the third power converter 330 is connected to the power supply unit 200 and a cutoff state in which the third power converter 330 is disconnected from the power supply unit 200. The fourth switch 440 can be switched between a conduction state in which the fourth power converter 340 is connected to the power supply unit 200 and a cutoff state in which the fourth power converter 340 is disconnected from the power supply unit 200.

As described above, while the display device 800 is in operation, the amount of power required to display an image on the display screen 100a changes. The control device 600 determines a required power value WX representing the amount of power required to display an image on the display screen 100a, and based on the determined required power value WX, the smaller the required power value WX, the first Number control is performed to reduce the number of the power converters 310 to 4th power converters 340 to be operated (hereinafter referred to as operating power converters).

Specifically, in controlling the number of units, the control device 600 controls the operating power converters to an operating state that outputs DC power, while controlling the operating power converters among the first to fourth power converters 310 to 340. (hereinafter referred to as a non-operating power converter) is controlled to be in a non-operating state by cutting off the output of DC power.

In the number control, the control device 600 controls the first switch 410 to the fourth switch 440, which are provided for the operating power converters, to be in a conductive state, while controlling the non-operating power converters to be in a conductive state. This is achieved by controlling the installed equipment to a cut-off state.

The repeater 500 distributes the DC power output by the operating power converter of the power supply circuit 300 from the first display unit 110 to the fourth display unit 140. Note that when the number of operating power converters is two or more, the repeater 500 combines the DC power output from all the operating power converters, and then transmits the combined DC power from the first display unit 110. It is distributed to the fourth display unit 140. "Composition" here means addition.

However, the number of operating power converters may be one. In that case, the repeater 500 distributes the DC power output by the operating power converter from the first display unit 110 to the fourth display unit 140.

Further, the repeater 500 includes a voltage drop section 510 that lowers the DC voltage output from the operating power converter of the power supply circuit 300 for stabilization. The magnitude of the voltage dropped by the voltage drop unit 510 may be variably adjusted under the control of the control device 600. The above-mentioned required power value is a value that takes into account the voltage drop in the voltage drop section 510. By lowering the DC voltage output from the operating power converter at the voltage drop section 510, the diameter of the power wiring 730 can be kept small.

Further, the control device 600 also controls the display device 100. This point will be explained below. Video data representing the content of the video to be displayed on the display device 100 is transmitted from an external video distribution center VD to the control device 600.

On the other hand, the control device 600 has a buffer memory 610 that temporarily stores video data sent from the video distribution center DV from time to time. Buffer memory 610 has a storage capacity in which at least two frames of video data can be written. Note that a frame refers to one still image that constitutes a moving image representing a video.

The control device 600 reads from the buffer memory 610 one frame of video data that has already been written to the buffer memory 610, and transmits the read video data to the display device 100 through the data wiring 740. Furthermore, in parallel with reading the video data from the buffer memory 610, the control device 600 writes the next frame of video data acquired from the video distribution center DV into the buffer memory 610.

In this way, the control device 600 sequentially transmits video data to the display device 100 in frame units. In the display device 100, PWM (Pulse Width Modulation) control of the light emitting devices forming each of the first display unit 110 to the fourth display unit 140 is performed based on the video data transmitted from the control device 600. Thereby, display of the video on the display screen 100a is realized.

The control device 600 performs the above-mentioned number control in parallel with the transmission of video data to the display device 100. Specifically, each time the control device 600 acquires one frame of video data from the video distribution center DV, the control device 600 uses that one frame of video data to calculate the luminance across the display screen 100a in that frame. Find the total value. Here, the "total value of brightness" means a value obtained by adding up the brightness of each pixel forming the display screen 100a for all pixels. Note that one light emitting device constitutes one pixel.

Next, the control device 600 determines a required power value WX representing the amount of power required to display an image on the display screen 100a, based on the determined total luminance value. Then, the control device 600 performs the above-mentioned number control using the obtained required power value WX.

Hereinafter, heat generation suppression processing for suppressing heat generation in the power supply circuit 300 by controlling the number of units will be described.

As shown in FIG. 3, first, the control device 600 calculates the required power value WX using the video data acquired from the video distribution center DV as described above (step S11).

Then, if the required power value WX is less than or equal to the first threshold value W1 predetermined as the upper limit of the power that can be output by the first power converter 310 (step S12; YES), the control device 600 1 power converter 310 is operated as a working power converter (step S13).

Moreover, the control device 600 stops the second power converter 320 to the fourth power converter 340 as non-operating power converters. Specifically, the control device 600 controls the first switch 410 to be in a conductive state, and controls the second switch 420 to the fourth switch 440 to be in a disconnected state.

In this case, the repeater 500 appropriately reduces the output voltage of the first power converter 310 in the voltage drop section 510, and then distributes the output voltage equally from the first display unit 110 to the fourth display unit 140.

On the other hand, the control device 600 determines that the required power value WX is larger than the first threshold value W1 (step S12; NO) and that the total power of the first power converter 310 and the second power converter 320 can output. If it is less than or equal to the second threshold value W2 predetermined as the upper limit of the power (step S14; YES), the first power converter 310 and the second power converter 320 are operated as working power converters (step S15). ).

Moreover, the control device 600 stops the third power converter 330 and the fourth power converter 340 as non-operating power converters. Specifically, the control device 600 controls the first switch 410 and the second switch 420 to be in the conductive state, and controls the third switch 430 and the fourth switch 440 to be in the disconnected state.

In this case, the repeater 500 combines the output voltages of the first power converter 310 and the second power converter 320, lowers the voltage appropriately in the voltage drop section 510, and then displays the output voltage from the first display unit 110 to the fourth display. Evenly distributed among units 140.

On the other hand, the control device 600 determines that the required power value WX is larger than the second threshold value W2 (step S14; NO), and that the total power output from the three power converters 310 to 330 is possible. If it is below the third threshold W3 predetermined as the upper limit of the power (step S16; YES), the first power converter 310 to the third power converter 330 are operated as working power converters (step S17). ).

Further, the control device 600 stops the fourth power converter 340 as a non-operating power converter. Specifically, the control device 600 controls the first switch 410 to the third switch 430 to be in a conductive state, and controls the fourth switch 440 to be in a disconnected state.

In this case, the repeater 500 combines the output voltages from the first power converter 310 to the third power converter 330, lowers the output voltage appropriately in the voltage drop section 510, and then displays the output voltages from the first display unit 110 to the fourth display. Evenly distributed among units 140.

On the other hand, if the required power value WX is larger than the third threshold value W3 (step S16; NO), the control device 600 converts all of the first power converter 310 to the fourth power converter 340 into operating power converters. (Step S18). Specifically, the control device 600 controls the first switch 410 to the fourth switch 440 to be in a conductive state.

In this case, the repeater 500 combines the output voltages of the first power converter 310 to the fourth power converter 340, lowers them appropriately in the voltage drop section 510, and then displays the output voltages from the first display unit 110 to the fourth display. Evenly distributed among units 140.

The processes from steps S11 to S18 described above represent number control in which the smaller the required power value WX, the smaller the number of operating power converters.

Next, when the control device 600 ends displaying the video on the display device 100 (step S19; YES), the control device 600 ends the heat generation suppression process. On the other hand, when the control device 600 continues displaying the video on the display device 100 (step S19; NO), the control device 600 returns to step S11 again and repeats the number control.

The repetition frequency of the number control, that is, the repetition frequency of steps S11 to S18 is equal to the frame rate of the video on the display screen 100a. Here, the frame rate refers to the number of still images displayed per second, that is, the number of frames per second. In this embodiment, the frame rate is 0.5 Hz or more and 5 Hz or less, specifically, 1 Hz or more and 2 Hz or less.

Hereinafter, specific values of the power consumed in the power supply circuit 300 shown in FIG. 2, that is, the power loss in the power supply circuit 300, will be illustrated.

As a premise, each of the first power converter 310 to the fourth power converter 340 exhibits a power conversion efficiency of 95% when the output power is 100W, and a power conversion efficiency of 90% when the output power is 50W. shall be shown. Further, it is assumed that the first threshold value W1 mentioned above is 150 [W], the second threshold value W2 is 250 [W], and the required power value WX is 200 [W].

In this case, according to the number control shown in FIG. 3, the first power converter 310 and the second power converter 320 are operated as operating power converters in step S15. The first power converter 310 and the second power converter 320 equally share the required power value WX of 200 [W], so each unit requires an output power of 100 [W]. be.

As mentioned above, the power conversion efficiency is 95% when the output power is 100W, so the power loss in each of the first power converter 310 and the second power converter 320 is (100/0.95)× 0.05≒5.3 [W]. That is, to obtain an output power of 100 W, approximately 105.3 [W] of input power is required, of which 5.3 [W] is consumed.

On the other hand, since the third power converter 330 and the fourth power converter 340 are non-operating power converters, the power loss therein is substantially zero. Therefore, the power loss as a whole of the power supply circuit 300 is 5.3×2=10.6 [W]. In this case, the power supply circuit 300 generates heat of 10.6 [W].

On the other hand, according to the comparison mode described above, since the required power value WX of 200 [W] is equally shared between the four units from the first power converter 310 to the fourth power converter 340, the output per unit is Power is suppressed to 50 [W]. As mentioned above, the power conversion efficiency is 90% when the output power is 50W, so the power loss in each of the first power converter 310 to the fourth power converter 340 is (50/0.9)×0 .1≒5.6 [W].

Therefore, in the comparative example, the power loss as a whole of the power supply circuit 300 reaches 5.6×4=22.4 [W]. As described above, according to the number control of the present embodiment, the power loss of the power supply circuit 300 as a whole can be suppressed to less than half that of the comparative embodiment. Therefore, heat generation in the power supply circuit 300 is suppressed more than in the case of the comparative embodiment.

As explained above, according to the present embodiment, the number of operating power converters is reduced as the required power value WX is smaller, through the number control performed by the control device 600. Therefore, when the required power value WX decreases, the output power of the working power converter is unlikely to decrease.

Each of the first power converter 310 to the fourth power converter 340 has a characteristic that the smaller the output power is, the lower the power conversion efficiency is. This means that the power conversion efficiency of the converter is less likely to decrease. In other words, even if the number of active power converters is reduced as the required power value WX decreases, power loss is unlikely to increase in the active power converters.

On the other hand, the number of non-operating power converters increases as the required power value WX is smaller, and heat generation due to power consumption is suppressed in the non-operating power converters. As a result, heat generation in power supply circuit 300 is suppressed more than in the comparative embodiment.

Moreover, according to the number control according to the present embodiment, the second to fourth power converters 320 to 340 are not always operated but are selectively operated. Therefore, compared to a comparative example in which four power converters from the first power converter 310 to the fourth power converter 340 are operated at all times, the period during which each of the second power converter 320 to the fourth power converter 340 is operated is reduced. be done. As a result, the life of the power supply circuit 300 and, in turn, the life of the display device 800 can be extended.

Note that in this embodiment, the power conversion characteristics of the first power converter 310 to the fourth power converter 340 may be equal to each other. That is, the dependence of the power conversion efficiency on the output power in each of the first power converter 310 to the fourth power converter 340 may be substantially equal. Since the first power converter 310 to the fourth power converter 340 having substantially the same power conversion characteristics can be used, manufacturing of the power supply circuit 300 and production management are facilitated.

[Embodiment 2]
In the first embodiment described above, switching between the operating state and the non-operating state of each of the first power converter 310 to the fourth power converter 340 is realized using the switch group 400. The operating state and the non-operating state may be switched by controlling each of the first power converter 310 to the fourth power converter 340 without using the switch group 400. A specific example will be described below.

FIG. 4 illustrates the configuration of the first power converter 310. The first power converter 310 includes a primary circuit 351 to which AC power is input from the power supply unit 200 shown in FIG. 2, a secondary circuit 352 to output DC power to the repeater 500 shown in FIG. This is a switched-mode power supply having a transformer 353 interposed between a secondary circuit 351 and a secondary circuit 352 and a switching element 354 connected to the transformer 353. Note that the primary circuit 351 includes a smoothing capacitor 351a for smoothing the voltage.

When the primary circuit 351 rectifies AC power and the switching element 354 performs a switching operation in which it repeatedly switches ON and OFF alternately, a rectangular waveform is transmitted from the primary circuit 351 to the secondary circuit 352 through the transformer 353. It is permissible to apply a voltage of The secondary circuit 352 smoothes the applied square wave voltage into a DC voltage. As a result, conversion from AC power to DC power in the first power converter 310 is realized. In other words, the first power converter 310 is in operation.

On the other hand, when the switching element 354 stops its switching operation, specifically, when the switching element 354 is kept in a cut-off state or a conductive state, application of voltage from the primary circuit 351 to the secondary circuit 352 is blocked. . Therefore, the first power converter 310 becomes inactive.

Further, like the first power converter 310, the second power converter 320 to the fourth power converter 340 shown in FIG. 2 are switching power supplies having the same configuration as that shown in FIG. 4.

FIG. 5 shows the configuration of a display device 800 according to this embodiment. As shown in FIG. 5, the display device 800 according to this embodiment does not include the switch group 400 shown in FIG. 2. In this embodiment, the control device 600 brings the non-operating power converters into a non-operating state by causing the switching elements 354 of the non-operating power converters to stop the switching operation in the number control. On the other hand, the control device 600 causes the switching element 354 of the working power converter to perform a switching operation, thereby bringing the working power converter into an operating state.

According to the present embodiment, the switch group 400 shown in FIG. 2 is not required, so the number of parts constituting the display device 800 can be reduced.

In addition, when using the switch group 400 shown in FIG. 2, when switching from a non-operating power converter to an operating power converter, after the smoothing capacitor 351a of the primary circuit 351 shown in FIG. Otherwise, output of DC power from the secondary circuit 352 will not start.

In contrast, in this embodiment, the smoothing capacitor of the primary circuit 351 is maintained in a charged state during the period when the switching element 354 shown in FIG. 2 is made to stop its switching operation and the switching element 354 is kept OFF. Ru. Therefore, when the non-operating power converter is switched to the operating power converter, there is no need to wait for charging of the smoothing capacitor 351a, and output of DC power from the secondary circuit 352 immediately starts. Therefore, according to this embodiment, even when the video frame rate is high, the supply of DC power from the operating power converter switched from the non-operating state to the operating state is unlikely to be interrupted.

[Embodiment 3]
In the heat generation suppression process shown in FIG. 3, the frequency of operation of the fourth power converter 340 is lower than the frequency of operation of the first power converter 310. Therefore, a configuration is desired in which variations in the frequency of operation of the first power converter 310 to the fourth power converter 340 are less likely to occur. A specific example of the configuration will be described below.

As shown in FIG. 6, the control device 600 according to the present embodiment has a memory in which operation history data 620 for managing the frequency of operation of each of the first power converter 310 to the fourth power converter 340 is stored. 630. The operation history data 620 represents the cumulative operating period length of each of the first power converter 310 to the fourth power converter 340, which is the cumulative value of the period length during which the power converter was in the operating state.

FIG. 7 shows a flowchart of heat generation suppression processing according to this embodiment. Hereinafter, only the differences between the heat generation suppression process shown in FIG. 7 and the heat generation suppression process shown in FIG. 3 will be described.

The control device 600 according to the present embodiment, when the required power value WX is less than or equal to the first threshold value W1 predetermined as the upper limit of the power that can be output by one operating power converter (step S12; YES) , First, using the operation history data 620, select among the four power converters from the first power converter 310 to the fourth power converter 340 under the condition that the change in the variance of the operating period length among the four power converters is minimized. Select one unit as the operating power converter. Specifically, the one with the shortest cumulative operating period length among the four converters is selected as the operating power converter. Then, the selected working power converter is controlled to be in the working state, and the remaining three non-working power converters are controlled to be in the non-working state (step S21).

In addition, the control device 600 according to the present embodiment sets the required power value WX to be larger than the first threshold value W1 (step S12; NO) and sets the upper limit value of the power that can be output by the two operating power converters in advance. If it is less than or equal to the predetermined second threshold W2 (step S14; YES), first, using the operation history data 620, calculate the operation period length between the four power converters 310 to 340. Two of these four converters are selected as operating power converters under the condition that the change in the variance of is minimized. Then, the two selected operating power converters are controlled to be in the operating state, and the remaining two non-operating power converters are controlled to be in the non-operating state (step S22).

Further, the control device 600 according to the present embodiment sets the required power value WX larger than the second threshold value W2 (step S14; NO) and sets it as the upper limit value of the power that can be output by the three operating power converters. If it is less than or equal to the predetermined third threshold value W3 (step S16; YES), first, using the operation history data 620, the length of operation period among the four power converters from the first power converter 310 to the fourth power converter 340 is calculated. Three of these four converters are selected as operating power converters under the condition that the change in variance of is minimized. Then, the three selected operating power converters are controlled to be in the operating state, and the remaining one non-operating power converter is controlled to be in the non-operating state (step S23).

As described above, in this embodiment, the operating power converters are selected under the condition that the change in the dispersion of the operating period length among the four power converters from the first power converter 310 to the fourth power converter 340 is minimized. Ru. Therefore, variations in the frequency of operation of the first power converter 310 to the fourth power converter 340 are less likely to occur. This contributes to extending the life of the power supply circuit 300.

Further, the control device 600 according to the present embodiment updates the operation history data 620 after the previously described step S21, S22, S23, or S18 (step S24). In other words, the control device 600 according to this embodiment updates the operation history data 620 every time it performs number control. Therefore, the latest operation history data 620 can be used in the next number control.

Further, in step S24, the control device 600 according to the present embodiment refers to the updated operation history data 620, and determines whether the operation period length of at least one of the first power converter 310 to the fourth power converter 340 is Check whether the predetermined reference period length is exceeded. Then, if there is a power conversion device whose operating period length exceeds the reference period length, the control device 600 issues a warning to that effect to the outside.

Here, "external" specifically refers to a terminal located at a remote management center that manages the operation of display device 800, a warning light attached to display device 800, and a terminal that notifies maintenance personnel of other warnings. Means means of notification.

By issuing a warning to the outside in this way, maintenance and inspection of the power supply circuit 300 can be performed before the power supply circuit 300 breaks down. In other words, failures can be prevented. On the other hand, if there is no power conversion device whose operating period length exceeds the reference period length, the control device 600 proceeds to step S19 described above.

[Embodiment 4]
In the configuration according to Embodiment 1-3 above, the upper limit value of the brightness of the display screen 100a may be changed depending on the time of day. A specific example will be described below.

As shown in FIG. 8, the control device 600 according to the present embodiment first determines whether a brightness change time predetermined as a time to change the brightness of the display screen 100a has arrived (step S31). . In this embodiment, the brightness change times are 5:00 a.m., 10:00 a.m., 3:00 p.m., and 7:00 p.m.

In the following description, "early morning" refers to the period from 5 a.m. to 10 a.m. “Daytime” refers to the period from 10 a.m. to 3 p.m. "Evening" refers to the period from 3:00 pm to 7:00 pm. “Nighttime” refers to the period from 7:00 pm to 5:00 am.

In the outdoors where the display device 800 is installed, the illuminance due to sunlight is lower at night than during the day, so the contrast of the display screen 100a is increased and the display screen 100a becomes easier to see. Therefore, there is no problem in reducing the brightness of the display screen 100a at night.

Therefore, when night has arrived, that is, when 7:00 pm has arrived as the brightness change time in step S31 (step S31; YES), the control device 600 sets the upper limit value of brightness for all pixels of the display screen 100a. , the upper limit value is changed to a value 60% lower than the upper limit value in the daytime (step S32).

In addition, at night, even if the same video data is displayed on the display screen 100a, the control device 600 controls the arbitrary brightness value represented by the video data under the condition that the instantaneous value of the brightness of each pixel is reduced by 60% compared to the daytime value. is corrected to a value that is 60% lower than during the day.

Similarly, in the early morning and in the evening, the display screen 100a is easier to see than during the day, so the brightness of the display screen 100a can be suppressed.

Therefore, when early morning or evening arrives, that is, when 5 am or 7 pm arrives as the brightness change time in step S31 (step S31; YES), the control device 600 controls all pixels of the display screen 100a. The upper limit value of the brightness is changed to a value that is 40% lower than the upper limit value in the daytime (step S32).

In addition, in the early morning and evening, even when displaying the same video data on the display screen 100a, the control device 600 controls the arbitrary value represented by the video data under the condition that the instantaneous value of the luminance of each pixel is reduced by 40% compared to the daytime value. The brightness value is corrected to a value that is 40% lower than the daytime value.

On the other hand, if the brightness change time has not yet arrived (step S31; NO), or after changing the brightness upper limit value in step S32, the control device 600 performs the above-mentioned number control (step S33). Specifically, step S33 refers to the process from step S11 to step S18 in FIG. 3, or the process from step S11 to step S24 in FIG.

Next, when the control device 600 ends displaying the video on the display device 100 (step S19; YES), the control device 600 ends the heat generation suppression process. On the other hand, if the control device 600 continues displaying the video on the display device 100 (step S19; NO), the control device 600 returns to step S31 again and repeats the same process.

As described above, in this embodiment, the control device 600 changes the upper limit value of the brightness of the display screen 100a depending on the time of day. As a result, power consumption in the display device 100 can be reduced, and heat generation in the power supply circuit 300 can be further suppressed.

Embodiments 1-4 have been described above. The following variations are also possible.

In Embodiment 1, the display device 800 is installed near a road and displays road information. , advertisements, etc. may be displayed. Further, although FIG. 1 illustrates a configuration in which the display 100 and the equipment storage box 710 are separated, the display 100, the power supply section 200, the power supply circuit 300, the switch group 400, the repeater 500, and the control device 600 may be housed within a common frame.

Further, in the first embodiment, the frame rate of the moving image displayed on the display screen 100a is exemplified as a value of 0.5 Hz or more and 5 Hz or less, but the frame rate is not limited to this value. The frame rate may be 24 Hz or higher, specifically 24 Hz, 30 Hz, 50 Hz, or 60 Hz.

Further, in the first embodiment, the case where the repetition frequency of the number of devices control is equal to the frame rate of the moving image is illustrated, but the repetition frequency of the number of devices control and the frame rate do not necessarily have to be equal. Generally, when the frame rate of a moving image is f and the natural number is n, the number of devices may be controlled repeatedly at a repetition frequency expressed as f/n.

The configuration of voltage drop section 510 shown in FIG. 2 is not particularly limited. The voltage drop section 510 can be configured by a voltage drop circuit including one or more DC (direct current)/DC converters (DC to DC converter) or other transformers. When the voltage drop section 510 is configured by a plurality of voltage drop circuits connected in parallel, each voltage drop circuit can be configured to be lighter in weight, compared to when the voltage drop section 510 is configured from a single voltage drop circuit. Moreover, a plurality of voltage drop circuits can be arranged separately. Therefore, it is possible to prevent the load of the voltage drop section 510 from being concentrated in a narrow area. Therefore, there is no need to form the member that supports the voltage drop section 510 with high rigidity, so that the weight of the member that supports the voltage drop section 510 can be reduced.

However, the repeater 500 does not need to include the voltage drop section 510. That is, the repeater 500 may supply the direct current voltage output from the power supply circuit 300 to the display 100 as it is.
When the repeater 500 does not include the voltage drop section 510, the weight of the repeater 500 can be reduced.

In the embodiment described above, the light emitting device included in the display 100 is a light emitting diode, but the light emitting device may be one that emits visible light using an element that generates organic electroluminescence.

This disclosure is capable of various embodiments and modifications without departing from the broad spirit and scope of this disclosure. Further, the embodiments described above are for explaining the present disclosure, and do not limit the scope of the present disclosure. The scope of the disclosure is indicated by the claims, rather than the embodiments. Various modifications that come within the scope of the claims and the meaning of equivalent disclosures are deemed to be within the scope of the present disclosure.

DESCRIPTION OF SYMBOLS 100... Display device, 100a... Display screen, 110... First display unit, 120... Second display unit, 130... Third display unit, 140... Fourth display unit, 200... Power supply unit, 300... Power supply circuit, 310... First power converter, 320... Second power converter, 330... Third power converter, 340... Fourth power converter, 351... Primary circuit, 351a... Smoothing capacitor, 352... Secondary circuit, 353 ...Transformer, 354...Switching element, 400...Switch group, 410...First switch, 420...Second switch, 430...Third switch, 440...Fourth switch, 500...Relayer, 510... Voltage drop unit, 600... Control device, 610... Buffer memory, 620... Operation history data, 630... Memory, 710... Equipment storage box, 720... Support column, 730... Power wiring, 740... Data wiring, 800... Display device, 900 ...Display device, 910...Control device, VD...Video distribution center.

Claims (7)

It has a plurality of display units constituting a display screen on which an image is displayed, and the amount of power required to display the image on the display screen depends on the total brightness within the plane of the display screen. A time- varying indicator,
A power supply circuit having a plurality of power converters connected in parallel to a power supply unit that supplies AC power, each of the power converters converting the AC power to DC power;
A required power value representing the amount of power required to display the video on the display screen is determined, and based on the determined required power value, the smaller the required power value, the more power the plurality of power circuits constituting Determining the number of the working power converters under the condition that the number of working power converters that are the power converters to be operated among the power converters in the set is reduced, and controlling the determined number of the working power converters, The non-operating power converter, which is the power converter other than the operating power converter among the plurality of power converters constituting the power supply circuit, is brought into an operating state that outputs the DC power, and the non-operating power converter is set to an operating state in which it outputs the DC power. a control device that controls the number of units in a non-operating state, and
a repeater that distributes the DC power output by the operating power converter to the plurality of display units forming the display;
Equipped with
In the control of the number of units, the control device uses operation history data representing a cumulative operating period length of each power converter, which is a cumulative value of the period length during which the power converter was in the operating state, selecting the operating power converter from among the plurality of power converters under conditions that suppress variations in the cumulative operating period length among the plurality of power converters;
Display device. When the cumulative operating period length of at least one of the plurality of power converters exceeds a predetermined reference period length, the control device issues a warning to that effect.
The display device according to claim 1 . A switch is provided for each of the power converters, and each switch is in a conductive state in which the power converter provided with the switch is electrically connected to the power supply unit, and the switch is provided with a conductive state. a group of switches capable of switching to a cutoff state in which the power converter is disconnected from the power supply unit;
Furthermore,
In the number control, the control device brings the switch provided for the operating power converter into the conductive state, while the switch provided for the non-operating power converter puts the switch in the disconnection state. state,
The display device according to claim 1 or 2 . Each of the power converters has a switching element that performs a switching operation to convert the AC power to the DC power,
In the number control, the control device causes the switching elements of the operating power converters to perform the switching operation, while causing the switching elements of the non-operating power converters to stop the switching operation.
The display device according to claim 1 or 2 . the video is a video;
The control device repeatedly performs the number control at a repetition frequency expressed by f/n, where f is the frame rate of the video and n is a natural number.
A display device according to any one of claims 1 to 4 . the control device changes the upper limit value of the brightness of the display screen according to the time of day;
The display device according to any one of claims 1 to 5 . The repeater is
a voltage drop unit that stabilizes the DC power output by the operating power converter;
The display device according to any one of claims 1 to 6 , comprising: