Power supply device, electronic apparatus, and current supply method

Abstract

To provide a power supply device, an electronic apparatus, and a current supply method capable of improving the efficiency of power conversion.SOLUTION: A power supply device includes a power supply, a power storage device, and a supply circuit that supplies a first current from the power supply to the load, supplies a second current from the power storage device to the load by discharging the power storage device when a load current flowing through the load is larger than a set range, and supplies a third current from the power supply to the load and supplies a fourth current from the power supply to the power storage device to charge the power storage device when the load current is smaller than the set range.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a power supply device, an electronic device, and a current supply method. [Background technology]

[0002] Patent Document 1 discloses a power supply device. In this power supply device, a conversion unit converts the output of an AC power supply into a DC voltage. Furthermore, a voltage control circuit converts the output of a solar cell into a DC voltage. If it is determined that the load current flowing through an external device is in a large range, the DC voltage is output to the external device. If it is determined that the load current is in an intermediate range, the DC voltage and the DC voltage are supplied to the external device. If it is determined that the load current is in a small range, the DC voltage is supplied to the external device (paragraphs 0010, 0017, 0020, 0032, 0033, 0036, 0037, 0040, and 0041). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-220521 Summary of the Invention [Problem to be solved by the invention]

[0004] In the power supply device disclosed in Patent Document 1, when the load current is in a large range, the current output by the conversion unit increases, which may result in a decrease in conversion efficiency of the conversion unit.

[0005] In view of this problem, an aspect of the present disclosure has been made. An object of an aspect of the present disclosure is to provide, for example, a power supply device that can increase the efficiency of power conversion. [Means for solving the problem]

[0006] A power supply apparatus according to a first aspect of the present disclosure includes a power supply, an energy storage device, and a supply circuit that, when a load current flowing through a load is greater than a set range, supplies a first current from the power supply to the load, discharges the energy storage device, and supplies a second current from the energy storage device to the load, and, when the load current is smaller than the set range, supplies a third current from the power supply to the load, and supplies a fourth current from the power supply to the energy storage device to charge the energy storage device.

[0007] An electronic device according to a second aspect of the present disclosure includes the power supply device according to the first aspect of the present disclosure and the load.

[0008] A current supply method according to a third aspect of the present disclosure includes, when a load current flowing through a load is greater than a set range, supplying a first current from a power source to the load, discharging an electric storage device, and supplying a second current from the electric storage device to the load; and, when the load current is smaller than the set range, supplying a third current from the power source to the load, and supplying a fourth current from the power source to the electric storage device to charge the electric storage device. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a block diagram of a display device according to a first embodiment. [Figure 2] 4 is a graph showing an example of the relationship between the current supplied by the power supply provided in the display device of the first embodiment and the conversion efficiency of the power supply. [Figure 3A] 4 is a diagram showing a current flowing in a power supply device provided in the display device of the first embodiment when a load current flowing in a backlight provided in the display device is within a set range. FIG. [Figure 3B] 10 is a diagram showing a current flowing in a power supply device provided in the display device of the first embodiment when the load current flowing in a backlight provided in the display device is larger than a set range. FIG. [Figure 3C]5 is a diagram showing a current flowing in a power supply device provided in the display device of the first embodiment when the load current flowing in a backlight provided in the display device is smaller than a set range. FIG. [Figure 3D] 10 is a diagram showing a current flowing in a power supply device provided in the display device of the first embodiment when the amount of stored power in a secondary battery provided in the display device is greater than a first set amount of stored power. FIG. [Figure 4A] 10 is a graph showing an example of temporal changes in current supplied to a backlight provided in a display device of a reference example and current supplied by a power supply provided in the display device. [Figure 4B] 4 is a graph showing an example of temporal changes in current supplied to a backlight provided in the display device of the first embodiment and current supplied by a power supply provided in the display device. [Figure 5A] 5 is a flowchart showing a flow of control performed by a supply circuit included in the display device of the first embodiment. [Figure 5B] 5 is a flowchart showing a flow of control performed by a supply circuit included in the display device of the first embodiment. [Figure 5C] 5 is a flowchart showing a flow of control performed by a supply circuit included in the display device of the first embodiment. [Figure 6] FIG. 10 is a block diagram of a display device according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the drawings, the same or equivalent elements are designated by the same reference numerals, and redundant description will be omitted.

[0011] 1. First embodiment 1.1 Display device FIG. 1 is a block diagram of a display device according to a first embodiment.

[0012] The display device 1 of the first embodiment shown in Fig. 1 is a television receiver. Therefore, the display device 1 displays a video according to a video signal obtained from a received broadcast wave, and outputs a sound according to an audio signal obtained from the broadcast wave. The display device 1 may be a display device other than a television receiver. For example, the display device 1 may be a monitor for a personal computer (PC), a monitor-integrated PC, digital signage, etc.

[0013] As shown in FIG. 1, the display device 1 includes a power supply device 11, a backlight 12, and a liquid crystal display panel 13.

[0014] The power supply device 11 generates DC power P4 from supplied AC power P1 and supplies the generated DC power P4 to the backlight 12. The power supply device 11 can convert the AC power P1 into DC power P2 and include all or part of the DC power P2 in the DC power P4, or can store electrical energy using all or part of the DC power P2, or can generate DC power P3 from the stored electrical energy and include it in the DC power P4. The AC power P1 is supplied from a commercial power source. The AC power P1 may also be supplied from a power source other than a commercial power source. The power supply device 11 may convert the supplied DC power into DC power P2.

[0015] The backlight 12 emits light according to the supplied DC power P4.

[0016] The liquid crystal display panel 13 modulates the emitted light in accordance with the video signal, thereby displaying an image according to the video signal.

[0017] The backlight 12 is an example of a load, and the display device 1 is an example of an electronic device. Therefore, the power supply device 11 may supply DC power P4 to a load other than the backlight 12, and an electronic device other than the display device 1 may include the power supply device 11.

[0018] 1.2 Power supply As shown in FIG. 1, the power supply device 11 includes a power source 21, a secondary battery 22, and a supply circuit .

[0019] The power supply 21 is a switching-type alternating current-direct current (AC-DC) converter. Therefore, the power supply 21 converts AC to DC, converting AC power P1 into DC power P2. When the power supply device 11 converts supplied DC power into DC power P2, the power supply 21 is a switching-type direct current-direct current (DC-DC) converter. The power supply 21, which is a DC-DC converter, converts DC to DC, converting the DC power into DC power P2. In this conversion, voltage is increased or decreased.

[0020] The secondary battery 22 is charged by a part or all of the DC power P2 and discharges the DC power P3. The secondary battery 22 is a lithium ion battery, a lithium ion polymer battery, a nickel-metal hydride battery, a nickel-cadmium battery, a lead-acid battery, or the like. The secondary battery 22 is an example of an electricity storage device. The secondary battery 22 may be replaced with another type of electricity storage device. For example, the secondary battery 22 may be replaced with an electric double layer capacitor.

[0021] The supply circuit 23 can supply all or part of the DC power P2 from the power source 21 to the backlight 12, can supply all or part of the DC power P2 to the secondary battery 22 to charge the secondary battery 22, or can discharge the secondary battery 22 and supply DC power P3 from the secondary battery 22 to the backlight 12. The supply circuit 23 controls the supply of all or part of the DC power P2 from the power source 21 to the backlight 12, the supply of all or part of the DC power P2 from the power source 21 to the secondary battery 22, and the supply of DC power P3 from the secondary battery 22 to the backlight 12, according to the magnitude of the DC power P4 to be supplied to the backlight 12.

[0022] 1.3 Supply circuit As shown in FIG. 1, the supply circuit 23 includes a first current path 31, a first switch 32, a second current path 33, a second switch 34, a third current path 35, a fourth current path 36, a charging circuit 37, a first detection unit 41, a second detection unit 42, and a control unit 51.

[0023] The first current path 31 conducts a current from the power supply 21 to the backlight 12. As a result, the first current path 31 includes all or part of the DC power P2 in the DC power P4.

[0024] The first switch 32 is inserted in the first current path 31. The first switch 32 opens and closes the first current path 31 in accordance with a first control C1 performed by the control unit 51. When the first switch 32 closes the first current path 31, the first current path 31 can conduct current from the power source 21 to the backlight 12, and all or part of the DC power P2 can be included in the DC power P4. When the first switch 32 opens the first current path 31, the first current path 31 cannot conduct current from the power source 21 to the backlight 12, and all or part of the DC power P2 cannot be included in the DC power P4.

[0025] The second current path 33 conducts a current from the secondary battery 22 to the backlight 12. As a result, the second current path 33 includes the DC power P3 in the DC power P4.

[0026] The second switch 34 is inserted into the second current path 33. The second switch 34 opens and closes the second current path 33 in accordance with the second control C2 performed by the control unit 51. When the second switch 34 closes the second current path 33, the second current path 33 can conduct a current from the secondary battery 22 to the backlight 12, and the DC power P3 can be included in the DC power P4. When the second switch 34 opens the second current path 33, the second current path 33 cannot conduct a current from the secondary battery 22 to the backlight 12, and the DC power P3 cannot be included in the DC power P4.

[0027] The third current path 35 conducts a current from the power supply 21 to the charging circuit 37. As a result, the third current path 35 supplies the charging circuit 37 with all or part of the DC power P2.

[0028] The fourth current path 36 conducts a current from the charging circuit 37 to the secondary battery 22. As a result, the fourth current path 36 supplies the secondary battery 22 with all or part of the DC power P2.

[0029] The charging circuit 37 switches between a state in which all or part of the supplied DC power P2 is supplied to the secondary battery 22 and a state in which no power is supplied to the secondary battery 22, in accordance with the third control C3 performed by the control unit 51. As a result, the charging circuit 37 switches between a state in which the secondary battery 22 is being charged and a state in which charging of the secondary battery 22 is stopped, in accordance with the third control C3.

[0030] The first detector 41 detects the load current flowing through the backlight 12 and inputs load current information F1 indicating the detected load current to the controller 51. When local dimming is performed to independently control the brightness of multiple regions of the backlight 12, the detected load current is the average of the load currents flowing through the multiple regions.

[0031] The second detection unit 42 detects the amount of stored power in the secondary battery 22 and inputs stored power information F2 indicating the detected amount of stored power to the control unit 51. The amount of stored power is also called the remaining charge amount, state of charge (SOC), etc.

[0032] Based on the load current indicated by the input load current information F1 and the amount of stored power indicated by the input stored power information F2, the control unit 51 performs a first control C1 on the first switch 32, a second control C2 on the second switch 34, and a third control C3 on the charging circuit 37. The control unit 51 performs the first control C1, the second control C2, and the third control C3 so as to increase the efficiency of conversion performed by the power supply 21.

[0033] The first current path 31, the second current path 33, the third current path 35, and the fourth current path 36 are formed by patterns, vias, through holes, lead wires, lead plates, connector terminals, etc. provided on a printed circuit board (PCB), a flexible printed circuit board (FPC), etc. The first switch 32 and the second switch 34 are formed by semiconductor switching elements such as metal oxide semiconductor field effect transistors (MOSFETs) and bipolar transistors, relays, etc. The first detection unit 41 is part of a system-on-chip (SoC) that integrates multiple functions required for the display device 1, an LED driver that drives light-emitting diodes (LEDs) provided in the backlight 12, etc. The second detection unit 42 is part of the SoC, charging circuit 37, etc. The control unit 51 is part of the SoC, etc. The SoC has a built-in processor and memory. The processor executes programs stored in the memory to perform various processes.

[0034] A portion of one current path included in the first current path 31, the second current path 33, the third current path 35, and the fourth current path 36 may overlap with a portion of another current path included in the first current path 31, the second current path 33, the third current path 35, and the fourth current path 36.

[0035] 1.4 Power Conversion Efficiency FIG. 2 is a graph showing an example of the relationship between the current supplied by the power supply provided in the display device of the first embodiment and the conversion efficiency of the power supply.

[0036] In the graph of Fig. 2, the horizontal axis represents current and the vertical axis represents conversion efficiency. The graph of Fig. 2 shows an example of the relationship when the current supplied by power supply 21 is 9.2 A and the conversion efficiency of power supply 21 reaches a maximum efficiency of 86%. The maximum efficiency may be different from 86%, and the current supplied by power supply 21 when the conversion efficiency of power supply 21 reaches its maximum efficiency may be different from 9.2 A.

[0037] 2, the conversion efficiency of power supply 21 reaches a maximum efficiency of 86% when the current supplied by power supply 21 is a specific current of 9.2 A. Therefore, the conversion efficiency decreases as the current decreases when the current is smaller than the specific current of 9.2 A. Furthermore, the conversion efficiency decreases as the current increases when the current is larger than the specific current of 9.2 A.

[0038] Therefore, when the current supplied by power supply 21 is within a high efficiency range R1 around a specific current of 9.2 A, the conversion efficiency of power supply 21 is a specific efficiency of 82% or more. Also, when the current is within a low efficiency range R2 smaller than high efficiency range R1 or within a low efficiency range R3 larger than high efficiency range R1, the conversion efficiency is less than the specific efficiency of 82%. The specific efficiency may be different from 82%.

[0039] 1.5 Contents of the first, second and third controls As shown in FIG. 1, the control unit 51 sets a set range SR to be compared with the load current indicated by the load current information F1. The set set range SR coincides with the high-efficiency range R1 described above. The control unit 51 also sets a first set storage amount ST1 and a second set storage amount ST2 to be compared with the storage amount indicated by the storage amount information F2. The first set storage amount ST1 is a storage amount sufficient to allow the secondary battery 22 to discharge the power required to operate the backlight 12. The second set storage amount ST2 is a storage amount close to empty, just before the secondary battery 22 becomes over-discharged. Therefore, the second set storage amount ST2 is less than the first set storage amount ST1.

[0040] FIG. 3A is a diagram showing a current flowing in a power supply device provided in the display device of the first embodiment when a load current flowing in a backlight provided in the display device is within a set range.

[0041] In FIG. 3A, current paths through which current flows are depicted by solid lines, and current paths through which no current flows are depicted by dashed lines.

[0042] When the load current indicated by the load current information F1 is within the set range SR, the control unit 51 executes a first control C1 on the first switch 32 to cause the first switch 32 to close the first current path 31. The control unit 51 also executes a second control C2 on the second switch 34 to cause the second current path 33 to open. The control unit 51 also executes a third control C3 on the charging circuit 37 to cause the charging circuit 37 to stop charging the secondary battery 22. As a result, as shown in FIG. 3A , the supply circuit 23 supplies a current i from the power source 21 to the backlight 12. The supplied current i is a direct current obtained by the conversion performed by the power source 21. The supply circuit 23 also does not charge or discharge the secondary battery 22. As a result, the current supplied by the power source 21 becomes the same as the load current within the set range SR, and falls within the set range SR. This allows the conversion efficiency of the power source 21 to be a specific efficiency of 82% or higher.

[0043] FIG. 3B is a diagram showing a current flowing in a power supply device provided in the display device of the first embodiment when the load current flowing in the backlight provided in the display device is larger than a set range.

[0044] In FIG. 3B, current paths through which current flows are depicted by solid lines, and current paths through which no current flows are depicted by dashed lines.

[0045] When the load current indicated by the load current information F1 is greater than the set range SR, the control unit 51 executes a first control C1 on the first switch 32 to cause the first switch 32 to close the first current path 31. The control unit 51 also executes a second control C2 on the second switch 34 to close the second current path 33. The control unit 51 also executes a third control C3 on the charging circuit 37 to cause the charging circuit 37 to stop charging the secondary battery 22. As a result, as shown in FIG. 3B , the supply circuit 23 supplies a first current i1 from the power source 21 to the backlight 12. The supplied first current i1 is a direct current obtained by conversion performed by the power source 21. The supply circuit 23 also discharges the secondary battery 22 to supply a second current i2 from the secondary battery 22 to the backlight 12. As a result, the first current i1 supplied by the power source 21 becomes smaller than the load current by the amount of the second current i2 and approaches the set range SR. This allows the conversion efficiency of the power supply 21 to approach the maximum efficiency of 86%. The control unit 51 performs second control C2 on the second switch 34 to adjust the second current i2 so that the first current i1 falls within the set range SR. This allows the conversion efficiency of the power supply 21 to be increased to a specific efficiency of 82% or higher.

[0046] FIG. 3C is a diagram showing a current flowing in a power supply device provided in the display device of the first embodiment when the load current flowing in a backlight provided in the display device is smaller than a set range.

[0047] In FIG. 3C, current paths through which current flows are depicted by solid lines, and current paths through which no current flows are depicted by dashed lines.

[0048] When the load current indicated by the load current information F1 is smaller than the set range SR, the control unit 51 performs a first control C1 on the first switch 32, causing the first switch 32 to close the first current path 31. The control unit 51 also performs a second control C2 on the second switch 34, causing the second switch 34 to open the second current path 33. The control unit 51 also performs a third control C3 on the charging circuit 37, causing the charging circuit 37 to charge the secondary battery 22. As a result, as shown in FIG. 3C , the supply circuit 23 supplies a third current i3 from the power source 21 to the backlight 12 and a fourth current i4 from the power source 21 to the secondary battery 22, thereby charging the secondary battery 22. The supplied third current i3 and fourth current i4 are direct currents obtained by conversion performed by the power source 21. As a result, the sum of the third current i3 and the fourth current i4 supplied by the power supply 21 becomes larger than the load current by the amount of the fourth current i4 and approaches the set range SR. This allows the conversion efficiency of the power supply 21 to approach the maximum efficiency of 86%. The control unit 51 performs third control C3 on the charging circuit 37 to adjust the fourth current i4 so that the sum of the third current i3 and the fourth current i4 is within the set range SR. This allows the conversion efficiency of the power supply 21 to be a specific efficiency of 82% or higher.

[0049] FIG. 3D is a diagram showing a current flowing in a power supply device provided in the display device of the first embodiment when the amount of stored power in the secondary battery provided in the display device is greater than a first set amount of stored power.

[0050] In FIG. 3D, current paths through which current flows are depicted by solid lines, and current paths through which no current flows are depicted by dashed lines.

[0051] When the amount of stored power indicated by the stored power amount information F2 is greater than the first set amount of stored power ST1, the control unit 51 executes a first control C1 on the first switch 32 to cause the first switch 32 to open the first current path 31. The control unit 51 also executes a second control C2 on the second switch 34 to cause the second switch 34 to close the second current path 33. The control unit 51 also executes a third control C3 on the charging circuit 37 to cause the charging circuit 37 to stop charging the secondary battery 22. As a result, as shown in FIG. 3D , the supply circuit 23 does not supply current from the power source 21 to the backlight 12, but discharges the secondary battery 22 and supplies a fifth current i5 from the secondary battery 22 to the backlight 12. This causes the power source 21 to stop supplying current. This makes it possible to suppress losses due to conversion performed by the power source 21.

[0052] 1.6 Relationship between display screen brightness and current flowing through the display The control unit 51 increases the load current flowing through the backlight 12 as the screen brightness of the display device 1 increases.

[0053] Therefore, when the screen brightness of the display device 1 is the set brightness, the supply circuit 23 supplies a current i from the power source 21 to the backlight 12, and does not charge or discharge the secondary battery 22. Furthermore, when the screen brightness of the display device 1 is higher than the set brightness, the supply circuit 23 supplies a first current i1 from the power source 21 to the backlight 12, discharges the secondary battery 22, and supplies a second current i2 from the secondary battery 22 to the backlight 12. Furthermore, when the screen brightness of the display device 1 is lower than the set brightness, the supply circuit 23 supplies a third current i3 from the power source 21 to the backlight 12 and supplies a fourth current i4 from the power source 21 to the secondary battery 22, thereby charging the secondary battery 22. Here, the set brightness is the screen brightness of the display device 1 when the load current flowing through the backlight 12 is within the set range SR.

[0054] 1.7 Time variation of the current supplied by a power source 4A and 4B are graphs showing an example of temporal changes in current supplied by a power supply included in the display device of the reference example and the first embodiment, respectively.

[0055] In the graphs of FIGS. 4A and 4B, time is plotted on the horizontal axis and current is plotted on the vertical axis.

[0056] In the display device of the reference example, the power supply device does not include a secondary battery, and the power supply 21 exclusively supplies DC power to the backlight 12.

[0057] In the display device of the reference example, the current supplied by the power supply 21 is the same as the current supplied to the backlight 12. Therefore, as shown in FIG. 4A , when the current supplied to the backlight 12 falls within the low efficiency range R3, the current supplied by the power supply 21 also falls within the low efficiency range R3. When the current supplied to the backlight 12 falls within the low efficiency range R2, the current supplied by the power supply 21 also falls within the low efficiency range R2. Therefore, the current supplied by the power supply 21 cannot be maintained within the high efficiency range R1.

[0058] In contrast, in the display device 1 of the first embodiment, the current supplied by the power supply 21 is smaller than the current supplied to the backlight 12 when the current supplied to the backlight 12 is too large, and is larger than the current supplied to the backlight 12 when the current supplied to the backlight 12 is too small. Therefore, as shown in FIG. 4B , even when the current supplied to the backlight 12 falls within the low-efficiency range R3, the current supplied by the power supply 21 falls within the high-efficiency range R1. Even when the current supplied to the backlight 12 falls within the low-efficiency range R2, the current supplied by the power supply 21 falls within the high-efficiency range R1. Therefore, the current supplied by the power supply 21 can be maintained within the high-efficiency range R1.

[0059] 1.8 Control Flow 5A, 5B, and 5C are flowcharts showing the flow of control performed by the supply circuit provided in the display device of the first embodiment.

[0060] In response to the load current information F1 being input to the control unit 51, the supply circuit 23 executes steps S101 to S115 shown in FIGS. 5A, 5B, and 5C.

[0061] In step S101, the control unit 51 determines whether the load current indicated by the load current information F1 is smaller than the set range SR. If it is determined that the load current is smaller than the set range SR, step S103 is executed. If it is determined that the load current is not smaller than the set range SR, step S102 is executed.

[0062] In step S102, the control unit 51 determines whether the load current indicated by the load current information F1 is greater than the set range SR. If it is determined that the load current is greater than the set range SR, step S108 is executed. If it is determined that the load current is not greater than the set range SR, step S115 is executed.

[0063] If steps S101 and S102 determine that the load current indicated by the load current information F1 is smaller than the set range SR, steps S103 to S107 are executed. If the load current is larger than the set range SR, steps S108 to S114 are executed. If the load current is within the set range SR, step S115 is executed. Steps S103 to S107 are executed when the screen brightness of the display device 1 is lower than the set brightness. Steps S108 to S114 are executed when the screen brightness of the display device 1 is higher than the set brightness. Step S115 is executed when the screen brightness of the display device 1 is the set brightness.

[0064] In step S103, the control unit 51 determines whether the amount of stored power indicated by the stored power amount information F2 is greater than the first set amount of stored power ST1. If it is determined that the amount of stored power is greater than the first set amount of stored power ST1, step S104 is executed. If it is determined that the amount of stored power is smaller than the first set amount of stored power ST1, step S106 is executed.

[0065] In step S104, the control unit 51 performs a first control C1 on the first switch 32 to cause the first switch 32 to open the first current path 31. The control unit 51 also performs a second control C2 on the second switch 34 to cause the second switch 34 to close the second current path 33. The control unit 51 also performs a third control C3 on the charging circuit 37 to cause the charging circuit 37 to stop charging the secondary battery 22. This causes the supply circuit 23 to stop supplying current from the power source 21 to the backlight 12, discharge the secondary battery 22, and supply a fifth current i5 from the secondary battery 22 to the backlight 12. As a result, when the amount of charge stored in the secondary battery 22 is sufficient, the secondary battery 22 exclusively supplies current, and the power source 21 stops supplying current. This makes it possible to suppress losses due to conversion performed by the power source 21.

[0066] In the following step S105, the control unit 51 determines whether the amount of stored power indicated by the stored power amount information F2 is greater than the first set stored power amount ST1. If it is determined that the amount of stored power is greater than the first set stored power amount ST1, step S104 is executed. If it is determined that the amount of stored power is less than the first set stored power amount ST1, step S106 is executed.

[0067] By steps S104 and S105, while the amount of stored power in the secondary battery 22 is sufficient, it is possible to maintain a state in which the secondary battery 22 supplies current exclusively and the power supply 21 stops supplying current. Also, when the amount of stored power in the secondary battery 22 becomes insufficient due to the secondary battery 22 supplying current, this state can be released.

[0068] In step S106, the control unit 51 performs a first control C1 on the first switch 32, causing the first switch 32 to close the first current path 31. The control unit 51 also performs a second control C2 on the second switch 34, causing the second switch 34 to open the second current path 33. The control unit 51 also performs a third control C3 on the charging circuit 37, causing the charging circuit 37 to charge the secondary battery 22. As a result, the supply circuit 23 supplies a third current i3 from the power source 21 to the backlight 12 and a fourth current i4 from the power source 21 to the secondary battery 22, thereby charging the secondary battery 22. As a result, when the amount of charge stored in the secondary battery 22 is insufficient, the power source 21 exclusively supplies current, and the charging circuit 37 charges the secondary battery 22. As a result, the current supplied by the power source 21 can be made larger than the load current within the low efficiency range R2, bringing the current closer to the high efficiency range R1.

[0069] In the following step S107, the control unit 51 determines whether the amount of stored power indicated by the stored power amount information F2 is greater than the first set stored power amount ST1. If it is determined that the amount of stored power is greater than the first set stored power amount ST1, step S104 is executed. If it is determined that the amount of stored power is less than the first set stored power amount ST1, step S106 is executed.

[0070] By steps S106 and S107, while the amount of stored power in the secondary battery 22 is insufficient, it is possible to maintain a state in which the power source 21 supplies current exclusively and the charging circuit 37 charges the secondary battery 22. Furthermore, by the charging circuit 37 charging the secondary battery 22, this state can be released in conjunction with the amount of stored power in the secondary battery 22 becoming sufficient.

[0071] In step S108, the control unit 51 determines whether the amount of stored power indicated by the stored power amount information F2 is greater than the first set stored power amount ST1. If it is determined that the amount of stored power is greater than the first set stored power amount ST1, step S109 is executed. If it is determined that the amount of stored power is less than the first set stored power amount ST1, step S111 is executed.

[0072] In step S109, the control unit 51 performs a first control C1 on the first switch 32 to cause the first switch 32 to open the first current path 31. The control unit 51 also performs a second control C2 on the second switch 34 to cause the second switch 34 to close the second current path 33. The control unit 51 also performs a third control C3 on the charging circuit 37 to cause the charging circuit 37 to stop charging the secondary battery 22. This causes the supply circuit 23 to stop supplying current from the power source 21 to the backlight 12, discharge the secondary battery 22, and supply a fifth current i5 from the secondary battery 22 to the backlight 12. As a result, when the amount of charge stored in the secondary battery 22 is sufficient, the secondary battery 22 exclusively supplies current, and the power source 21 stops supplying current. This makes it possible to suppress losses due to conversion performed by the power source 21.

[0073] In the following step S110, the control unit 51 determines whether the amount of stored power indicated by the stored power amount information F2 is greater than the first set stored power amount ST1. If it is determined that the amount of stored power is greater than the first set stored power amount ST1, step S109 is executed. If it is determined that the amount of stored power is less than the first set stored power amount ST1, step S112 is executed.

[0074] By steps S109 and S110, while the amount of stored power in the secondary battery 22 is sufficient, it is possible to maintain a state in which the secondary battery 22 supplies current exclusively and the power supply 21 stops supplying current. Also, when the amount of stored power in the secondary battery 22 becomes insufficient due to the secondary battery 22 supplying current, this state can be released.

[0075] In step S111, the control unit 51 determines whether the amount of stored power indicated by the stored power amount information F2 is greater than the second set stored power amount ST2. If it is determined that the amount of stored power is greater than the second set stored power amount ST2, step S112 is executed. If it is determined that the amount of stored power is less than the second set stored power amount ST2, step S114 is executed.

[0076] In step S112, the control unit 51 performs a first control C1 on the first switch 32, causing the first switch 32 to close the first current path 31. The control unit 51 also performs a second control C2 on the second switch 34, causing the second switch 34 to close the second current path 33. The control unit 51 also performs a third control C3 on the charging circuit 37, causing the charging circuit 37 to stop charging the secondary battery 22. This causes the supply circuit 23 to supply a first current i1 from the power source 21 to the backlight 12, discharge the secondary battery 22, and supply a second current i2 from the secondary battery 22 to the backlight 12. This allows the power source 21 and the secondary battery 22 to supply current when the amount of charge in the secondary battery 22 is insufficient but not close to empty. This allows the current supplied by the power source 21 to be smaller than the load current in the low efficiency range R3, and to approach the high efficiency range R1.

[0077] In the following step S113, the control unit 51 determines whether the amount of stored power indicated by the stored power amount information F2 is greater than the second set stored power amount ST2. If it is determined that the amount of stored power is greater than the second set stored power amount ST2, step S112 is executed. If it is determined that the amount of stored power is less than the second set stored power amount ST2, step S114 is executed.

[0078] Steps S112 and S113 enable the power source 21 and the secondary battery 22 to maintain a state in which they supply current while the amount of charge stored in the secondary battery 22 is insufficient but not nearly empty. Furthermore, as the secondary battery 22 supplies current, this state can be released in conjunction with the amount of charge stored in the secondary battery 22 approaching empty.

[0079] In step S114, the control unit 51 executes a first control C1 on the first switch 32 to cause the first switch 32 to close the first current path 31. The control unit 51 also executes a second control C2 on the second switch 34 to cause the second switch 34 to open the second current path 33. The control unit 51 also executes a third control C3 on the charging circuit 37 to cause the charging circuit 37 to stop charging the secondary battery 22. As a result, the supply circuit 23 supplies the first current i1 from the power source 21 to the backlight 12, does not discharge the secondary battery 22, does not charge the secondary battery 22, and does not supply the second current i2 from the secondary battery 22 to the backlight 12. As a result, when the amount of charge stored in the secondary battery 22 is nearly empty, the power source 21 exclusively supplies current, but the charging circuit 37 does not charge the secondary battery 22. This prevents the current supplied by the power source 21 from becoming even larger than the load current within the low efficiency range R3, and prevents the secondary battery 22, which has a nearly empty storage capacity, from being further discharged and over-discharged.

[0080] In step S115, the control unit 51 performs a first control C1 on the first switch 32 to cause the first switch 32 to close the first current path 31. The control unit 51 also performs a second control C2 on the second switch 34 to cause the second switch 34 to open the second current path 33. The control unit 51 also performs a third control C3 on the charging circuit 37 to cause the charging circuit 37 to stop charging the secondary battery 22. This causes the supply circuit 23 to supply current from the power source 21 to the backlight 12, but not charge the secondary battery 22, and not discharge the secondary battery 22. This allows the current supplied by the power source 21 to be the same as the load current in the high efficiency range R1, and to fall within the high efficiency range R1.

[0081] 2. Second embodiment The following describes the differences between the second embodiment and the first embodiment. For points that are not described, the second embodiment also employs the same configuration as that employed in the first embodiment.

[0082] FIG. 6 is a block diagram of a display device according to the second embodiment.

[0083] In the display device 2 of the second embodiment, the supply circuit 23 includes a brightness sensor 43, as shown in FIG.

[0084] The brightness sensor 43 detects the brightness of the environment in which the display device 1 is installed, and inputs brightness information F3 indicating the detected brightness to the control unit 51. The detected brightness is luminance or the like.

[0085] The control unit 51 increases the load current flowing through the backlight 12 as the brightness indicated by the input brightness information F3 increases. As a result, the control unit 51 increases the screen brightness of the display device 1 as the brightness increases. If the brightness is darker than the set brightness, the control unit 51 makes the screen brightness of the display device 1 darker than the standard screen brightness, and if the brightness is brighter than the set brightness, the control unit 51 makes the screen brightness of the display device 1 brighter than the standard screen brightness.

[0086] The set brightness is set so that the load current flowing through the backlight 12 falls within the set range SR when the brightness of the environment in which the display device 1 is installed is the set brightness.

[0087] 5A, 5B, and 5C are also flowcharts showing the flow of control performed by the supply circuit provided in the display device of the second embodiment.

[0088] As described above, in the second embodiment, when the brightness of the environment in which the display device 1 is installed is the set brightness, the load current flowing through the backlight 12 falls within the set range SR. Therefore, steps S103 to S107 are executed when the brightness is darker than the set brightness. Steps S108 to S114 are executed when the brightness is brighter than the set brightness. Step S115 is executed when the brightness is the set brightness.

[0089] The present disclosure is not limited to the above-described embodiments, and may be replaced with a configuration that is substantially the same as the configuration shown in the above-described embodiments, a configuration that has the same effect, or a configuration that can achieve the same purpose. [Explanation of symbols]

[0090] 1,2 Display device 11 Power supply 12 Backlight 13 LCD display panel 21 Power supply 22 Secondary battery 23 Supply circuit 31 First current path 32 First Switch 33 Second current path 34 Second Switch 35 Third current path 36 Fourth current path 37 charging circuit 41 First detection unit 42 Second detection unit 43 Brightness sensor 51 Control section C1 First control C2 Second control C3 Third Control F1 Load current information F2 Energy storage information F3 Brightness Information R1 High Efficiency Range R2,R3 Low efficiency range SR setting range ST1 First set charge amount ST2 Second set charge amount

Claims

1. Power supply and an electricity storage device; a supply circuit that, when a load current flowing through a load is larger than a set range, supplies a first current from the power supply to the load, discharges the power storage device, and supplies a second current from the power storage device to the load, and, when the load current is smaller than the set range, supplies a third current from the power supply to the load, and supplies a fourth current from the power supply to the power storage device to charge the power storage device; A power supply device comprising:

2. the first current is within the set range; The sum of the third current and the fourth current is within the set range. The power supply device of claim 1 .

3. The power supply converts AC to DC, the first current, the third current, and the fourth current are direct currents; The efficiency of the conversion is equal to or greater than a specified efficiency when the current supplied by the power supply is within the set range of currents. The power supply device of claim 1 .

4. When the amount of power stored in the power storage device is greater than a set amount of power stored, the supply circuit does not supply a current from the power source to the load, but discharges the power storage device and supplies a fifth current from the power storage device to the load. The power supply device of claim 1 .

5. the set amount of stored power is a first set amount of stored power, The second set amount of stored power is less than the first set amount of stored power, When the load current is greater than the set range and the amount of stored power is less than the first set amount of stored power and greater than the second set amount of stored power, the supply circuit supplies the first current from the power source to the load, discharges the power storage device, and supplies the second current from the power storage device to the load.

5. The power supply device according to claim 4.

6. the set amount of stored power is a first set amount of stored power, The second set amount of stored power is less than the first set amount of stored power, When the load current is greater than the set range and the stored power amount is less than the second set stored power amount, the supply circuit supplies the first current from the power source to the load and does not supply the second current from the power storage device to the load.

6. The power supply device according to claim 4 or 5.

7. When the load current is smaller than the set range and the stored power amount is smaller than the set stored power amount, the supply circuit supplies the third current from the power source to the load and supplies the fourth current from the power source to the power storage device to charge the power storage device.

5. The power supply device according to claim 4.

8. the load is a backlight of a display device, The supply circuit includes a detection unit that detects the load current.

6. The power supply device according to claim 1.

9. the load is a backlight of a display device, the display device increases the load current as the screen brightness of the display device increases, When the screen brightness is higher than a set brightness, the supply circuit supplies the first current from the power supply to the load, discharges the power storage device, and supplies the second current from the power storage device to the load; when the screen brightness is lower than the set brightness, the supply circuit supplies the third current from the power supply to the load, and supplies the fourth current from the power supply to the power storage device to charge the power storage device.

6. The power supply device according to claim 1.

10. the load is a backlight of a display device, the display device increases the load current as the brightness of the environment in which the display device is installed increases, When the brightness is brighter than a set brightness, the supply circuit supplies the first current from the power supply to the load, discharges the power storage device, and supplies the second current from the power storage device to the load; when the brightness is darker than the set brightness, the supply circuit supplies the third current from the power supply to the load, and supplies the fourth current from the power supply to the power storage device to charge the power storage device.

6. The power supply device according to claim 1.

11. A power supply device according to any one of claims 1 to 5; The load; An electronic device comprising:

12. the electronic device is a display device, The load is a backlight The electronic device according to claim 11.

13. When a load current flowing through a load is larger than a set range, a first current is supplied from a power source to the load, and a power storage device is discharged to supply a second current from the power storage device to the load; When the load current is smaller than the set range, supplying a third current from the power source to the load and supplying a fourth current from the power source to the power storage device to charge the power storage device; A current supply method including:

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