Display divice

Abstract

To provide a display unit capable of suppressing variations in luminance of each light source.SOLUTION: A display divider 10 for a vehicle includes a display panel 80 that receives illumination light and emits display light, a plurality of light sources 41a to 41n that emits illumination light and is arranged on a rear side of the display panel 80, a power supply unit 30 that supplies power to the plurality of light sources 41a to 41n, and voltage divider circuits 60a to 60n that apply an output voltage Vd from the power supply unit 30 to the light sources 41a to 41n after lowering the output voltage Vd by an amount of voltage drop corresponding to a luminance difference ΔB such that the luminance difference ΔB due to individual differences among the plurality of light sources 41a to 41n is reduced.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a display device. [Background technology]

[0002] The vehicle display device described in Patent Document 1 includes a liquid crystal display panel and a plurality of light sources disposed directly below the liquid crystal display panel. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-8296 A Summary of the Invention [Problem to be solved by the invention]

[0004] Each light source has a brightness rank that arises during manufacturing due to individual differences in brightness characteristics, and when light sources of multiple brightness ranks are used in a single display device, there will be variations in the brightness of the light sources for each brightness rank, even if a constant current is passed through each light source.

[0005] The present disclosure has been made in consideration of the above-described circumstances, and has an object to provide a display device capable of suppressing variations in the emission luminance of each light source. [Means for solving the problem]

[0006] In order to achieve the above object, the display device according to the present disclosure comprises: a display panel that receives illumination light and emits display light; a plurality of light sources that emit the illumination light and are disposed on the rear side of the display panel; a power supply unit for supplying power to the plurality of light sources; and a voltage dividing unit that divides the voltage from the power supply unit to reduce a voltage drop amount corresponding to the brightness difference and applies the voltage to the light sources so that a brightness difference due to individual differences among the plurality of light sources is reduced. Effect of the Invention

[0007] According to the present disclosure, it is possible to suppress variation in the emission luminance of each light source. [Brief description of the drawings]

[0008] [Figure 1] 1 is a block diagram of a vehicle display device according to an embodiment of the present disclosure. [Diagram 2] FIG. 2 is a circuit diagram of a voltage divider circuit according to an embodiment of the present disclosure. [Diagram 3] FIG. 2 is a partial plan view of a mounting surface of a light source substrate according to an embodiment of the present disclosure. [Figure 4] 11 is a graph showing a luminance difference between a first and second rank light source according to a comparative example having no voltage divider circuit. [Diagram 5] 11 is a graph showing a voltage drop amount of a voltage applied to a second rank light source according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] A vehicle display device according to an embodiment of the present disclosure will be described with reference to the drawings. The vehicle display device is mounted on a vehicle, for example, a motorcycle. The vehicle display device is a digital meter that displays an image.

[0010] As shown in Fig. 1, the vehicle display device 10 includes a microcomputer (microcontroller) 20, a power supply unit 30, a light source board 40 on which a plurality of light sources 41a to 41n (n is any natural number) and voltage division circuits 60a to 60n (n is any natural number) are mounted, light source drivers 50a to 50n (n is any natural number), and a display panel 80. Note that, as for the types of lines connecting the components in Fig. 1, solid lines are power supply lines, and dashed lines and dashed dotted lines are communication signal lines.

[0011] The power supply unit 30 converts a battery voltage Vc from an in-vehicle battery (not shown) into a constant voltage (e.g., 8 V) and applies the converted constant voltage as an output voltage Vd to an output line Lo. Voltage dividing circuits 60a-60n (described later) divide the applied output voltage Vd and apply the divided voltage to the light sources 41a-41n as a forward voltage Vf.

[0012] The power supply unit 30 includes a main power supply 31 and multiple sub-power supplies 32a, 32b. The main power supply 31 and the multiple sub-power supplies 32a, 32b are each configured with a power supply element made up of a DC-DC converter. The main power supply 31 and the multiple sub-power supplies 32a, 32b are connected in parallel with each other, and the output terminals of the main power supply 31 and the multiple sub-power supplies 32a, 32b are connected to one output line Lo. The main power supply 31 and the multiple sub-power supplies 32a, 32b supply power to the output line Lo in cooperation with each other.

[0013] The main power supply 31 transmits its own drive frequency as a synchronization clock to the secondary power supplies 32a, 32b. The secondary power supplies 32a, 32b receive the synchronization clock and operate in synchronization with the main power supply 31. The main power supply 31 and the two sub-power supplies 32a and 32b are activated when the voltage value of the battery voltage Vc from the vehicle battery exceeds a threshold value. The main power supply 31 and the multiple sub-power supplies 32a and 32b gradually increase the output current supplied to the output line Lo to a target current value while transmitting and receiving current tuning signals to each other. The main power supply 31 and the two sub-power supplies 32a and 32b each output an output current of a target current value (1960 mA), and supply an output current of a current value (5880 mA) obtained by multiplying the target current value by the number of power supplies (three) to the output line Lo. In this way, the main power supply 31 and the sub-power supplies 32a and 32b can share the output current and supply it to the output line Lo. The main power supply 31 and the two sub-power supplies 32a and 32b monitor a feedback signal from the light source driver 50n and control the output voltages to be the same.

[0014] The light sources 41a to 41n are LEDs and connected in parallel to one another. The light sources 41a to 41n are disposed on the rear surface of the display panel 80, and are arranged in a matrix on the mounting surface of the light source substrate 40, as shown in Fig. 3. The light sources 41a to 41n illuminate the display panel 80 by lighting up.

[0015] As shown in Fig. 1, the light source drivers 50a to 50n are connected to the cathode terminals (negative electrodes) of the light sources 41a to 41n, respectively. The light source drivers 50a to 50n are made of switching circuits. The light source drivers 50a to 50n are turned on and off by a PWM (Pulse Width Modulation) signal from the microcomputer 20 to control the lighting and non-lighting and lighting brightness of the light sources 41a to 41n.

[0016] The display panel 80 is a TFT (Thin Film Transistor) liquid crystal panel. The display panel 80 receives illumination light from the light sources 41a to 41n and displays vehicle information as an image.

[0017] The microcomputer 20 includes an image control unit 21 that displays an image on the display panel 80, and a light source control unit 22 that controls the lighting of the light sources 41a to 41n via the light source drivers 50a to 50n. The light source control unit 22 has a local dimming function capable of adjusting the brightness of the light sources 41a to 41n in units of multiple areas. The light source control unit 22 controls the lighting and non-lighting and lighting brightness of the light sources 41a to 41n by outputting a PWM signal to each of the light source drivers 50a to 50n.

[0018] The voltage dividing circuits 60a to 60n are connected to the anode terminals of the light sources 41a to 41n, respectively. The voltage dividing circuits 60a to 60n have resistance values ​​determined according to the luminance ranks of the light sources 41a to 41n, and are light source voltage adjusting means that adjust the forward voltages Vf of the light sources 41a to 41n by dropping the output voltage Vd by an amount of voltage drop determined according to the resistance value so as to reduce luminance variations between the light sources.

[0019] As shown in FIG. 2, the voltage dividing circuit 60a includes resistors R1 and R2. The resistor R1 is connected between the output line Lo and the anode terminals of the light sources 41a to 41n. One end of the resistor R2 is connected between the resistor R1 and the anode terminal of the light source 41a, and the other end of the resistor R2 is connected to the ground. The output voltage Vd is divided by the resistors R1 and R2, and a voltage value equal to the voltage value applied to the resistor R2 is applied to the light source 41a as a forward voltage Vf. The forward voltage Vf applied to the light source 41a is set by the following formula. In the following formula, R1 and R2 are the resistance values ​​(Ω) of the resistors R1 and R2. Vf = [R2 / (R1+R2)] × Vd The difference between the output voltage Vd and the forward voltage Vf is the voltage drop. The greater the resistance of R1 relative to the resistance of R2, the greater this voltage drop will be. For example, when an output voltage Vd of 8V is dropped by 1V through resistor R1 and then dropped by 7V through resistor R2, the forward voltage Vf applied to the light source 41a becomes 7V. The voltage dividing circuits 60b to 60n have the same configuration as the voltage dividing circuit 60a. The resistance values ​​of the resistors R1 and R2 of each of the voltage dividing circuits 60a to 60n will be described later.

[0020] Here, the light sources 41a to 41n have brightness ranks that arise due to individual differences in brightness characteristics, and these brightness ranks are defined by the relationship between the light source current supplied to the light source and the light emission brightness of the light source. In this embodiment, the light sources 41a to 41n are either a first brightness rank or a second brightness rank. As shown in FIG. 3, the first rank light sources 411 of the first brightness rank are arranged in the regions A1, A3, A5, and A7 of the mounting surface of the light source board 40. The second rank light sources 412 of the second brightness rank are arranged in the regions A2, A4, A6, and A8 of the mounting surface of the light source board 40. The regions A1 to A8 are each set in a range including light sources arranged in a row in the Y direction. The regions A1, A3, A5, and A7 in which the first rank light sources 411 are arranged and the regions A2, A4, A6, and A8 in which the second rank light sources 412 are arranged are arranged so as to be alternately arranged in the X direction. The X and Y directions are set in directions perpendicular to each other on the mounting surface of the light source board 40. The X direction is the same as the longitudinal direction of the rectangular plate-shaped light source board 40, and the Y direction is the same as the lateral direction of the light source board 40.

[0021] The voltage dividing circuits 60a to 60n include a first voltage dividing circuit 601 connected to each of the first rank light sources 411, and a second voltage dividing circuit 602 connected to each of the second rank light sources 412. The voltage drop amount of the second voltage dividing circuit 602 is set to be larger than the voltage drop amount of the first voltage dividing circuit 601.

[0022] In a configuration according to a comparative example that does not include the voltage dividing circuits 60a to 60n, the second rank light source 412 has a higher emission luminance relative to a light source current than the first rank light source 411. That is, when a light source current of the same current value is supplied to the first rank light source 411 and the second rank light source 412, the emission luminance of the second rank light source 412 is higher than the emission luminance of the first rank light source 411 by a luminance difference ΔB, as shown in FIG.

[0023] On the other hand, in this embodiment, the voltage drop amount of the second voltage dividing circuit 602 is set to be larger than the voltage drop amount of the first voltage dividing circuit 601. As a result, the forward voltage Vf of the second rank light source 412 becomes smaller, and the emission luminance of the second rank light source 412 approaches the emission luminance of the first rank light source 411. For example, the voltage drop amount of the first voltage dividing circuit 601 is set to zero (the resistance values ​​of the resistors R1 and R2 are set to 0Ω), and the voltage drop amount ΔV of the second voltage dividing circuit 602 is set to a value corresponding to the luminance difference ΔB, as shown in Fig. 5. This reduces the emission luminance of the second rank light source 412, as shown by the arrow Ar in Fig. 4, and the luminance difference ΔB between the first rank light source 411 and the second rank light source 412 becomes smaller, and ideally the luminance difference ΔB becomes zero. Therefore, the emission luminance of each of the light sources 41a to 41n can be made uniform, and the display quality of the display panel 80 can be improved.

[0024] (effect) According to the embodiment described above, the following effects are achieved. (1) A vehicle display device 10, which is an example of a display device, includes a display panel 80 that receives illumination light and emits display light, a plurality of light sources 41a to 41n that emit illumination light and are arranged on the rear side of the display panel 80, a power supply unit 30 that supplies power to the plurality of light sources 41a to 41n, and voltage divider circuits 60a to 60n, which are an example of a voltage divider unit, that drop the output voltage Vd from the power supply unit 30 by an amount of voltage drop corresponding to the luminance difference ΔB so that the luminance difference ΔB due to individual differences among the plurality of light sources 41a to 41n is reduced, and then apply the output voltage Vd to the light sources 41a to 41n. According to this configuration, it is possible to suppress variations in the emission luminance of each of the light sources 41a to 41n. Furthermore, it becomes possible to use light sources of a plurality of brightness ranks, eliminating the need to carefully select the brightness rank of the light source. Furthermore, adjusting the light source current according to the brightness rank of all light sources using software control would increase the number of parameters and become complicated, but with the above configuration, it is simple to add only voltage division circuits 60a to 60n consisting of two resistors R1 and R2.

[0025] (2) The light sources 41a to 41n are arranged on the rear surface of the display panel 80, and are assigned luminance ranks defined by the relationship between light source current and light emission luminance. Among the light sources 41a to 41n, the first rank light sources 411, which are assigned the first luminance rank, are arranged in the areas A1, A3, A5, and A7, which are an example of the first area. Among the light sources 41a to 41n, the second rank light sources 412, which are assigned the second luminance rank, which has a higher light emission luminance relative to the light source current than the first luminance rank, are arranged in the areas A2, A4, A6, and A8, which are an example of the second area. The voltage drop amount in the second voltage divider circuit 602 corresponding to the second rank light source 412 is set to be larger than the voltage drop amount in the first voltage divider circuit 601 corresponding to the first rank light source 411. According to this configuration, small variations in luminance are less noticeable than in a configuration in which the first rank light sources 411 and the second rank light sources 412 are randomly arranged, and the luminance of the display panel 80 can be made more uniform.

[0026] (3) The power supply unit 30 includes a main power supply 31 and a plurality of auxiliary power supplies 32a, 32b connected in parallel between an on-board battery and the plurality of light sources 41a to 41n. The main power supply 31 and the plurality of auxiliary power supplies 32a, 32b cooperate with each other to supply power to a common output line Lo connected to the anodes of the plurality of light sources 41a to 41n. According to this configuration, an increase in required current caused by connecting the multiple light sources 41a to 41n in parallel can be shared by the main power supply 31 and the multiple sub-power supplies 32a and 32b. Furthermore, by distributing the power sources using the main power source 31 and the multiple sub-power sources 32a, 32b, it is possible to cope with a case where a large power source cannot be used due to height restrictions or operating temperature conditions.

[0027] The present disclosure is not limited to the above-described embodiments and drawings. Modifications (including deletion of components) can be made as appropriate within the scope of the present disclosure. An example of a modification will be described below.

[0028] (Modification) In the above embodiment, the vehicle display device 10 is mounted on a motorcycle, but may be mounted on vehicles other than motorcycles (including construction machines). The vehicle display device 10 may also be combined with an analog gauge having a pointer. The vehicle display device 10 may be a head-up display device.

[0029] In the above embodiment, the light sources 41a to 41n have two luminance ranks, the first luminance rank and the second luminance rank, but may have three or more ranks.

[0030] In the above embodiment, the voltage divider circuits 60a-60n are provided in a one-to-one correspondence with all the light sources 41a-41n, but one voltage divider circuit may be provided for a plurality of light sources. Also, the voltage divider circuit may be omitted for light sources of a low luminance rank having a low light emission luminance relative to the light source current among the light sources 41a-41n.

[0031] In the above embodiment, the power supply unit 30 includes the multiple sub-power sources 32a, 32b, but the multiple sub-power sources 32a, 32b may be omitted.

[0032] In the above embodiment, the main power supply 31 may cooperate with the multiple sub-power supplies 32a, 32b to supply power to the light sources 41a-41n when the light sources 41a-41n are turned on at high brightness, and may supply power to the light sources 41a-41n alone by putting the multiple sub-power supplies 32a, 32b into a sleep state when the light sources 41a-41n are turned on at low brightness. This makes it possible to suppress deterioration in efficiency of output current caused by the main power supply 31 and the multiple sub-power supplies 32a, 32b working together when the required supply current is small.

[0033] In the above embodiment, the microcomputer 20 may independently control the on / off of the light sources 41a to 41n via the light source drivers 50a to 50n. In this case, the light sources may be used to turn on warning lights. In addition, the light sources may be densely arranged in the area where the warning lights are turned on. [Explanation of symbols]

[0034] 10 Vehicle display device 20 Microcomputer 21 Image control section 22 Light source control unit 30 Power supply section 31 Main power supply 32a,32b Sub-power supply 40 Light source board 41a~41n Light source 50a~50n Light source driver 60a~60n voltage divider circuit 80 Display Panel 411 First-Rank Light Source 412 Second-Rank Light Source 601 1st voltage divider circuit 602 Second voltage divider circuit A1~A8 area ΔB Brightness difference R1,R2 resistance ΔV Voltage drop Vc Battery voltage Vd Output voltage Lo Output Line Vf forward voltage

Claims

1. a display panel that receives illumination light and emits display light; a plurality of light sources that emit the illumination light and are disposed on the rear side of the display panel; a power supply unit for supplying power to the plurality of light sources; a voltage dividing unit that divides the voltage from the power supply unit to reduce a luminance difference due to an individual difference between the plurality of light sources, and applies the voltage to the light sources after reducing the voltage drop amount according to the luminance difference. Display device.

2. the plurality of light sources are disposed on the rear side of the display panel, and are assigned a luminance rank defined by a relationship between a light source current and a light emission luminance; A plurality of first light sources having a first luminance rank among the plurality of light sources are arranged in a first region, Among the plurality of light sources, a plurality of second light sources having a second luminance rank in which the luminance relative to a light source current is higher than that of the first luminance rank are disposed in a second region, the voltage drop amount in the second voltage dividing unit corresponding to the second light source is set to be larger than the voltage drop amount in the first voltage dividing unit corresponding to the first light source; The display device according to claim 1 .

3. The power supply unit includes: a main power source and a sub-power source connected in parallel between a battery and the plurality of light sources; the main power supply and the sub-power supply cooperate with each other to supply power to a common output line connected to an anode of each of the plurality of light sources; The display device according to claim 1 .

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