JP7338636B2 - Display device - Google Patents

Description

The present invention relates to display devices.

Conventionally, as a display device, any one of three light sources that emit red, green, and blue light is selectively caused to emit light, and the light source that emits light is switched at high speed to generate illumination light of a desired color. A device that operates according to a so-called field sequential method is known. For example, the display device described in Patent Document 1 supplies a light source with current as a plurality of pulse waves (triangular waves).

Japanese Patent No. 6379490

In the configuration described in Patent Document 1, the rising slope of the pulse wave is particularly large, so that the current value may overshoot the target value, which is one of the causes of deterioration in display quality. Ta.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a display device capable of suppressing the occurrence of overshoot.

In order to achieve the above object, the display device of the present invention includes a current supply section that supplies current, a plurality of light sources that receive the current from the current supply section and emit light of different colors, and a light source that reflects light. A display element having a plurality of reflective portions for controlling angles, and supplying a current from the current supply portion to any one of the plurality of light sources as a triangular wave or a rectangular wave to cause the light source to emit light. a light source control unit that generates illumination light of a desired color from the light emitted from the plurality of light sources by a field sequential method in which the light sources are sequentially switched; a display element control unit for reflecting, a capacitor connected in parallel to the light source between the current supply unit and the ground, and a capacitor switch unit connected in series to the capacitor, wherein the light source control unit turns on the capacitor switch section when the current from the current supply section is supplied to the light source as the triangular wave , and when the current from the current supply section is supplied to the light source as the rectangular wave, The capacitor switch section is turned off.

According to the present invention, it is possible to suppress the occurrence of overshoot.

1 is a schematic diagram of a vehicle equipped with a head-up display device according to an embodiment of the present invention; FIG. 1 is a schematic diagram showing the configuration of a head-up display device according to one embodiment of the present invention; FIG. 1 is a schematic diagram showing the configuration of a lighting device according to an embodiment of the present invention; FIG. 1 is a block diagram showing an electrical configuration of a light source driving device according to one embodiment of the invention; FIG. 5 is a block diagram showing a portion of FIG. 4; FIG. 4 is a timing chart in a high luminance mode according to one embodiment of the present invention; 4 is a timing chart in medium brightness mode according to one embodiment of the present invention; 4 is a timing chart in low luminance mode according to one embodiment of the present invention; FIG. 9 is a timing chart in which a part of FIG. 8 is enlarged; FIG. It is a block diagram which shows the electrical structure of the light source drive part which concerns on the modification of this invention. It is a block diagram which shows the electrical structure of the light source drive part which concerns on the modification of this invention.

An embodiment in which a display device according to the present invention is embodied in a head-up display device (hereinafter referred to as a HUD device) will be described with reference to the drawings.

As shown in FIG. 1 , the HUD device 1 is installed on the dashboard of a vehicle 2 , generates display light L representing an image, and emits the generated display light L toward the windshield 3 . The display light L is reflected by the windshield 3 and reaches the viewer 4 (for example, the driver of the vehicle 2). Thereby, the viewer 4 can visually recognize the virtual image V representing the image formed in front of the windshield 3 . The virtual image V displays various vehicle information such as engine speed and vehicle speed.

(HUD device 1)
As shown in FIG. 2, the HUD device 1 includes an illumination device 10, a light intensity detection unit 500, a light source temperature detection unit 600, an illumination optical system 20, a display element 30, a light source driving device 5, and a projection optical system. A system 40 , a screen 50 , a plane mirror 61 , a concave mirror 62 , a concave mirror driving section 65 , a housing 70 and a translucent section 71 are provided.

The housing 70 is made of, for example, a light-shielding material and has a box shape. Each component of the HUD device 1 , such as the illumination device 10 and the illumination optical system 20 , is housed in the housing 70 . The housing 70 has an opening 70a through which the display light L passes.
The translucent part 71 is formed of a curved plate made of a translucent resin such as acrylic, and is provided so as to close the opening 70 a of the housing 70 .

The lighting device 10 generates illumination light C and emits the generated illumination light C toward the illumination optical system 20 . Specifically, as shown in FIG. 3 , the illumination device 10 includes a light source group 11 , a combining section 13 , a brightness unevenness reducing section 14 , and a transmissive film 15 .

The light source group 11 includes, for example, three light sources 11r, 11g, and 11b, each of which is an LED (Light Emitting Diode). Light source 11r emits red light R, light source 11g emits green light G, and light source 11b emits blue light B. FIG. Each of the light sources 11r, 11g, and 11b is driven by the light source driving device 5 and emits light with predetermined light intensity and timing.

The multiplexing unit 13 generates illumination light C by aligning the optical axes of the red light R, green light G, and blue light B sequentially emitted from the light sources 11r, 11g, and 11b. The light is emitted toward the unevenness reduction unit 14 . Specifically, the multiplexing unit 13 includes a reflecting mirror 13a and dichroic mirrors 13b and 13c that reflect light of a specific wavelength and transmit light of wavelengths other than the specific wavelength. . The reflecting mirror 13a reflects the incident blue light B toward the dichroic mirror 13b. The dichroic mirror 13b reflects the incident green light G toward the dichroic mirror 13c, while allowing the blue light B from the reflecting mirror 13a to pass therethrough. The dichroic mirror 13c reflects the incident red light R toward the brightness unevenness reducing unit 14, while transmitting the lights B and G from the dichroic mirror 13b as they are. As a result, the dichroic mirror 13c emits illumination light C obtained by synthesizing the red light R, the green light G, or the blue light B toward the luminance unevenness reducing section 14. FIG.

The brightness unevenness reduction unit 14 is composed of a mirror box, an array lens, and the like, and diffusely reflects, scatters, and refracts the illumination light C from the combining unit 13 to reduce unevenness of light.
The transmissive film 15 is made of a transmissive member having a reflectance of about 5%, for example, and transmits most of the illumination light C arriving via the brightness unevenness reducing section 14 as it is, but part of the light is transmitted by light intensity detection. It is reflected toward the part 500 .

The light intensity detection unit 500 is composed of, for example, a light receiving element having a photodiode, and is provided at a position that receives the illumination light C reflected by the transmissive film 15 . The light intensity detection unit 500 receives part of the illumination light C and detects the light intensity of each of the lights R, G, and B constituting the illumination light C in a time division manner. As shown in FIG. 4, the light intensity detector 500 outputs the detection result as a light intensity detection signal SFB to the second controller 200 of the light source driving device 5, which will be described later.
The light source temperature detection section 600 detects the temperature of each of the light sources 11r, 11g, and 11b, and outputs the detection result as a light source temperature signal ST to the second control section 200 of the light source driving device 5, which will be described later. One light source temperature detection unit 600 may be provided for the three light sources 11r, 11g, and 11b, or a total of three light source temperature detection units 600 may be provided for each of the three light sources 11r, 11g, and 11b.

As shown in FIG. 2 , the illumination optical system 20 is composed of a concave lens or the like, and adjusts the illumination light C emitted from the illumination device 10 to a size corresponding to the display element 30 .

The display element 30 is a DMD (Digital Micro-mirror Device) having a plurality of movable micromirrors 30a, which are an example of a reflecting section. The micromirror 30a has an electrode (not shown), and is turned on or off by switching the voltage applied to this electrode. When the micromirror 30a is turned on, it takes a posture inclined by +12 degrees with the hinge as a fulcrum, and at this time, the illumination light C emitted from the illumination optical system 20 is reflected toward the screen 50 via the projection optical system 40. do. When the micromirror 30a is turned off, the micromirror 30a assumes a posture inclined by, for example, -12 degrees with the hinge as a fulcrum, and reflects the illumination light C in a direction different from that of the projection optical system 40 at this time. Therefore, the display element 30 can display only the light corresponding to the image M in the illumination light C by individually driving the micromirrors 30a under the control of the second control unit 200 of the light source driving device 5, which will be described later. is projected toward the projection optical system 40 .

As shown in FIG. 2 , the projection optical system 40 is composed of a concave lens, a convex lens, or the like, and efficiently projects the display light L from the display element 30 onto the screen 50 .
The screen 50 is composed of a holographic diffuser, a microlens array, a diffusion plate, and the like. display the image M on the surface).

The plane mirror 61 reflects the display light L representing the image M displayed on the screen 50 toward the concave mirror 62 . The concave mirror 62 reflects the display light L from the plane mirror 61 toward the windshield 3 . The display light L is transmitted through the translucent portion 71 of the housing 70 and then reflected by the windshield 3 toward the viewer 4 .

The concave mirror drive unit 65 includes a motor and a gear mechanism for transmitting the driving force of the motor to the concave mirror 62, both of which are not shown. The concave mirror drive unit 65 rotates the concave mirror 62 around the rotation axis Ax extending in the direction perpendicular to the plane of FIG. By rotating the concave mirror 62 about the rotation axis Ax, the irradiation position of the display light L with respect to the viewer 4 can be adjusted in the height direction.

(Light source driving device 5)
As shown in FIG. 4, the light source driving device 5 includes a constant current supply section 300 that supplies a constant current to the light source group 11, an inductor L1, a light source driving section 43 that drives the light source group 11, a display element 30, a constant A second control unit 200 that controls the current supply unit 300 and the light source drive unit 43 and a first control unit 100 that controls the concave mirror drive unit 65 are provided. The first and second controllers 100 and 200 are examples of controllers, and the inductor L1 is an example of an energy storage unit.

The constant current supply unit 300 is composed of a constant current driver IC (Integrated Circuit) that generates a constant current based on power from an on-vehicle battery (not shown), and is controlled by the second control unit 200 .
When the constant current supply unit 300 receives an enable signal DRV_EN for turning on the constant current supply unit 300 from the second control unit 200, the constant current supply unit 300 adjusts the value according to the current value adjustment signal IADJ from the second control unit 200. A current is supplied to the light source driver 43 .
When the constant current supply unit 300 receives an enable signal DRV_EN for turning off the constant current supply unit 300 from the second control unit 200, it stops supplying the constant current.
Inductor L1 is connected between constant current supply section 300 and light source group 11 .

The light source drive unit 43 includes switch units Swr, Swg, Swb, Swc, Swa, and Swr1, a resistor R1, a capacitor C1, and a voltage detection unit 49.
The switch units Swr, Swg, Swb, Swc, Swa, and Swr1 are composed of, for example, n-type channel FETs (Field Effect Transistors), and are turned on (closed) and off under the control of the second control unit 200. Toggles between states (open state).
The switch Swr is connected in series with the light source 11r between the light source 11r and the ground. The switch section Swg is connected in series with the light source 11g between the light source 11g and the ground. The switch section Swb is connected in series with the light source 11b between the light source 11b and the ground. The switch section Swc and the capacitor C1 are connected in series. The switch section Swr1 and the resistor R1 are connected in series.
The switch section Swr, the switch section Swg, the switch section Swb, the capacitor C1, the switch section Swc, the switch section Swa, the resistor R1, and the switch section Swc are connected in parallel with each other. Gate terminals of the switches Swr, Swg, Swb, Swc, Swa, and Swr1 are connected to the second controller 200 .

By switching to the ON state, the switches Swr, Swg, and Swb supply the current from the constant current supply unit 300 to the corresponding light sources 11r, 11g, and 11b to light the corresponding light sources 11r, 11g, and 11b. Switching to the OFF state, the switches Swr, Swg, and Swb cut off current from the constant current supply section 300 to the corresponding light sources 11r, 11g, and 11b, and turn off the corresponding light sources 11r, 11g, and 11b.
The switch section Swa has a function of controlling the inductor current Iind flowing from the constant current supply section 300 to the inductor L1 to a target value by switching to the ON state. The switch section Swr1 has a function of releasing the energy stored in the inductor L1 to the outside by switching to the ON state. The resistor R1 has the function of suppressing the flow of a large current in the switch section Swr1 when the energy stored in the inductor L1 is released to the outside, and the inductor current flowing through the inductor L1 when the switch section Swa is switched to the ON state. It has a function to adjust Iind.
The switch section Swc has a function of adjusting the slopes of rising portions of pulse waves P1, P2, P3, and P4, which will be described later, by causing a current to flow from the constant current supply section 300 to the capacitor C1 by switching to the ON state.
The voltage detection unit 49 is connected between the ground and the switches Swr, Swg, Swb, Swc, Swa, Swr1, detects the voltage detection signal SV, and outputs it to the second control unit 200 .

As shown in FIG. 4 , the first control section 100 is composed of a microcontroller including a CPU (Central Processing Unit), memory, etc., and controls the concave mirror driving section 65 . An external illuminance signal (dimming signal) SL around the vehicle 2 detected through the illuminance sensor 7 is input to the first control unit 100 . The first control unit 100 outputs the input dimming signal SL to the second control unit 200, more precisely, to the comparison unit 204, which will be described later.

The second control unit 200 is an LSI (Large Scale Integration) that realizes a desired function by hardware, and is composed of, for example, an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array).
The second control unit 200 receives a video signal SE for displaying the image M from the video signal input unit 700, a light source temperature signal ST detected by the light source temperature detection unit 600, and a voltage detection signal detected by the voltage detection unit 49. The signal SV and the light intensity detection signal SFB detected by the light intensity detector 500 are input.
The second control unit 200 temperature-corrects the relationship between the current supplied to the light sources 11r, 11g, and 11b and the brightness based on the light source temperature signal ST, and adjusts the current value supplied to the light source driving unit 43 based on the voltage detection signal SV. recognize.

The second control section 200 includes a light source control section 201 , a display element control section 202 , a current supply control section 203 and a comparison section 204 .
The display element control unit 202 controls ON/OFF of each mirror 30a in the display element 30 by a PWM (Pulse Width Modulation) method based on the video signal SE.
The comparison unit 204 determines a threshold based on the dimming signal SL, compares the determined threshold with the light intensity detection signal SFB, and outputs a comparison signal SB indicating the comparison result to the current supply control unit 203 .

A current supply control unit 203 controls a constant current supply unit 300 . Specifically, the current supply control unit 203 outputs the current value adjustment signal IADJ and the enable signal DRV_EN to the constant current supply unit 300 .
The current value adjustment signal IADJ is a signal for controlling the output current value of the constant current supply unit 300 to a target value. The enable signal DRV_EN is a signal for switching on and off of the constant current supply unit 300 .

The light source controller 201 outputs enable signals R_EN, G_EN, B_EN, S_EN1, S_EN2, and C_EN to control the switches Swr, Swg, Swb, Swc, Swa, and Swr1 in synchronization with image control by the display element controller 202. are output to the switches Swr, Swg, Swb, Swc, Swa, and Swr1.
The enable signals R_EN, G_EN, B_EN, S_EN1, S_EN2, and C_EN are Hi to turn on the switches Swr, Swg, Swb, Swc, Swa, and Swr1, and turn off the switches Swr, Swg, Swb, Swc, Swa, and Swr1. The state changes between Lo and Lo.
The light source control unit 201 outputs an enable signal R_EN corresponding to the light source 11r to the switch unit Swr, outputs an enable signal G_EN corresponding to the light source 11g to the switch unit Swg, and outputs an enable signal B_EN corresponding to the light source 11b to the switch unit Swb. output to Further, the light source control section 201 outputs an enable signal S_EN1 to the switch section Swa, outputs an enable signal S_EN2 to the switch section Swr1, and outputs an enable signal C_EN to the switch section Swc.
A control mode of the switches Swr, Swg, Swb, Swc, Swa, and Swr1 by the light source control unit 201 will be described later.

Part of the control content of the first control unit 100 may be executed by the second control unit 200, and conversely, part of the control content of the second control unit 200 may be executed by the first control unit 200. The control unit 100 may execute this. Also, the first and second controllers 100 and 200 may be configured as one controller.

Next, the second control unit 200 shifts to one of the high luminance mode, medium luminance mode, and low luminance mode based on the dimming signal SL. The second control unit 200 shifts to the low luminance mode when the dimming signal SL is equal to or less than the first threshold, and transitions to the middle luminance mode when the dimming signal SL exceeds the first threshold and is less than the second threshold. , and when the dimming signal SL is equal to or higher than the second threshold, the mode shifts to the high luminance mode. The first threshold is a threshold when the luminous intensity of the display light L is 800 candela (cd/m ² ). The second threshold is a threshold when the luminous intensity of the display light L is 4000 candela (cd/m ² ).
The operations in the high luminance mode, medium luminance mode, and low luminance mode will be described below in order.

(high brightness mode)
The operation of the light source driving device 5 in the high luminance mode will be described with reference to the timing chart of FIG. This timing chart starts when the operating power of the HUD device 1 is turned on.
In the high-luminance mode, the off period Tof→preparation period Tb→light-on period Td is followed, and thereafter, the preparation period Tb and the light-on enable period Td are repeated as long as the high-luminance mode continues. As the lightable period Td, a lightable period Td in which the light source 11r can be lit, a lightable period Td in which the light source 11g can be lit, and a lightable period Td in which the light source 11b can be lit are set in order.
Although not shown in FIG. 6, the second control unit 200 maintains the enable signal R_EN at Hi and maintains the enable signals G_EN and B_EN at Lo during the lighting-enabled period Td during which the light source 11r can be turned on. . Further, during the lighting-enabled period Td in which the light source 11g can be lit, the enable signal G_EN is maintained at Hi and the enable signals R_EN and B_EN are maintained at Lo. During the lighting-enabled period Td in which the light source 11b can be lit, the enable signal B_EN is maintained at Hi and the enable signals R_EN and G_EN are maintained at Lo.

At the start of the timing chart of FIG. 6, the switches Swr, Swg, Swb, Swc, Swa and Swr1 are in the off state. The second control unit 200 turns on the switch unit Swa by setting the enable signal S_EN1 to Hi during the off period Tof (for example, time t1). As a result, as indicated by an arrow Y1 in FIG. 5, the energy remaining in the inductor L1 flows as a current to the ground via the switch section Swa. Therefore, inductor current Iind of inductor L1 is maintained at zero.

Next, the second control unit 200 switches the enable signal DRV_EN to Hi and outputs the current value adjustment signal IADJ to the constant current supply unit 300 during the preparation period Tb (for example, time t2). A current is supplied from the supply unit 300 . At this time, as indicated by an arrow Y1 in FIG. 5, a current flows from the constant current supply section 300 to the ground via the switch section Swa. As a result, inductor current Iind of inductor L1 increases to the target value. This target value is set based on the current values supplied to the light sources 11r, 11g, and 11b in the next lighting-enabled period Td, and is set for each lighting-enabled period Td. That is, the second control unit 200 sets the target value based on the current values supplied to the light sources 11r, 11g, and 11b in the next lighting-enabled period Td, and sets the inductor current Iind to the set target value. A constant current is supplied through the constant current supply unit 300 through the value adjustment signal IADJ.
The resistor R1 can set the inductor current Iind at the start of the preparation period Tb, thereby improving the control accuracy of the inductor current Iind.

The second control unit 200 keeps the constant current supplied from the constant current supply unit 300 during the lighting-enabled period Td (for example, time t3), and sets the enable signal S_EN1 to Lo to switch the switch unit Swa. is turned off, and the switch unit Swr is turned on by setting the enable signal R_EN to Hi. Thereby, as indicated by an arrow Y4 in FIG. 5, the current from the constant current supply section 300 flows to the ground through the light source 11r and the switch section Swr. Therefore, the light source 11r lights up. At this time, the current value I supplied to the light source 11r is equivalent to the inductor current Iind at the end of the preparatory period Tb. Therefore, the light source 11r can be lit with desired luminance. Also, the current value I supplied to the light source 11r forms a rectangular wave Rw.
In the high-luminance mode, the duty ratio, which is the ratio of the period during which the current is supplied to the light source 11r, to the lighting-enabled period Td is 100%.

In the lighting-enabled period Td, the current supply control unit 203 controls the constant current supply unit 300 when the comparison unit 204 determines that the light intensity detection signal SFB is equal to or greater than the threshold value, that is, when the comparison signal SB becomes Lo. is output to the constant current supply unit 300 to turn off the enable signal DRV_EN. When the constant current supply unit 300 receives the enable signal DRV_EN for turning off the constant current supply unit 300, it stops supplying the current. As a result, the light source 11r is turned off, and the light intensity detection signal SFB becomes less than the threshold, that is, the comparison signal SB becomes Hi.
On the other hand, when the comparison unit 204 determines that the light intensity detection signal SFB is less than the threshold, that is, when the light intensity detection signal SFB becomes Hi, the current supply control unit 203 turns on the constant current supply unit 300. It outputs an enable signal DRV_EN to the constant current supply unit 300 to the effect that the Upon receiving the enable signal DRV_EN for turning on the constant current supply unit 300, the constant current supply unit 300 supplies current to the light source 11r. As a result, the light source 11r is turned on, and the light intensity detection signal SFB becomes equal to or greater than the threshold, that is, the comparison signal SB becomes Lo.
In this manner, during the lighting-enabled period Td, the enable signal DRV_EN periodically changes between Hi and Lo so that the light intensity detection signal SFB approaches the threshold, thereby forming the rectangular wave Rw.

Next, the second control unit 200 switches the enable signal DRV_EN to Lo during the first half of the preparatory period Tb (for example, time t4) after the lighting-enabled period Td elapses, so that the constant current supply unit 300 By stopping the current supply and setting the enable signal S_EN2 to Hi, the switch section Swr1 is turned on. As a result, the energy stored in the inductor L1 during the previous lighting-enabled period Td flows as a current to the ground through the resistor R1 and the switch section Swr1, as indicated by an arrow Y3 in FIG. Therefore, inductor current Iind of inductor L1 decreases. At this time, the resistor R1 can adjust the rate of decrease of the inductor current Iind, that is, the slope of the decrease. As the resistance value of the resistor R1 becomes smaller, the decreasing speed of the inductor current Iind and the slope at the time of decreasing become larger. Further, the resistance value of the resistor R1 is such that it suppresses a large current from flowing through the switch section Swr1 when the energy stored in the inductor L1 is released to the outside, thereby suppressing the heat generation of the switch section Swr1, and , so that the energy stored in the inductor L1 can be prevented from flowing back to the constant current supply unit 300 as a current.

Next, the second control unit 200 performs the same process as at time t2 during the latter half of the preparation period Tb (for example, time t5). As a result, inductor current Iind of inductor L1 increases to the target value.
Thereafter, similarly to the above, the light-onable period Td and the preparatory period Tb are alternately repeated. The high brightness mode ends when the HUD device 1 is turned off or switched to another mode.
This is the end of the description of the high brightness mode.

(medium brightness mode)
The operation of the light source driving device 5 in the middle luminance mode will be described with reference to the timing chart of FIG.
In the middle luminance mode, the duty ratio, which is the ratio of the period during which the light sources 11r, 11g, and 11b are supplied with current to the lighting-enabled period Td, is less than 100%, for example, 20% to 40%. The following description focuses on the differences from the high luminance mode.

As shown in FIG. 7, in the on-duty period Ton (for example, time t3) during which current is supplied to the light sources 11r, 11g, and 11b during the lighting-enabled period Td, the second control unit 200 controls the , the switch unit Swr is turned on by maintaining the constant current supply state from the constant current supply unit 300 and turning on the enable signal R_EN. As a result, the light source 11r is supplied with the current of the rectangular wave Rw, and the light source 11r is turned on.
After that, the second control unit 200 maintains the enable signal DRV_EN at Hi during the off-duty period Tod (for example, time t3a) during which no current is supplied to the light sources 11r, 11g, and 11b in the lighting-enabled period Td. By setting S_EN1 to Hi, the switch section Swa is turned on. As a result, as indicated by an arrow Y1 in FIG. 5, the current from the constant current supply unit 300 flows to the ground via the switch unit Swa. Therefore, the inductor current Iind is maintained at the target value even during the off-duty period Tod.
Then, in the next preparatory period Tb (for example, time t4), the second control unit 200 switches the switch unit Swr1 to the ON state in the same manner as in the above-described high luminance mode, so that the energy stored in the inductor L1 is The energy is discharged as a current to the ground through the resistor R1 and the switch section Swr1. By maintaining the inductor current Iind at the target value during the off-duty period Tod of the lighting-enabled period Td, the inductor L1 can release the stored energy in a short period of time during the preparation period Tb.
This is the end of the description of the medium luminance mode.

(low brightness mode)
The operation of the light source driving device 5 in the low luminance mode will be described with reference to the timing chart of FIG. This timing chart starts when the operating power of the HUD device 1 is turned on.
In the low-brightness mode, the order of the off period Tof→the illuminable period Tdr during which the light source 11r can be illuminated→the illuminable period Tdg during which the light source 11g can be illuminated→the off period Tof→the illuminable period Tdb during which the light source 11b can be illuminated is repeated. be

During the OFF period Tof (for example, time ta), the second control unit 200 sets the enable signal S_EN1 to Hi in the same manner as in the OFF period Tof of the high brightness mode, that is, turns the switch unit Swa into the ON state. By doing so, the energy remaining in the inductor L1 is released.

Then, the second control unit 200 supplies currents to the light source 11r as pulse waves P1, P2, and P3, which are triangular waves, during the lighting-enabled period Tdr.
Specifically, the second control unit 200 turns on the switch unit Swc by setting the enable signal C_EN to Hi in the lightable period Tdr (for example, time tb), switches the enable signal DRV_EN to Hi, In addition, current is supplied from the constant current supply section 300 by outputting the current value adjustment signal IADJ to the constant current supply section 300 . At this time, even if the switch Swc is switched to the ON state, the switch Swa is maintained in the ON state. Therefore, as indicated by an arrow Y1 in FIG. 5, the current from the constant current supply section 300 flows to the ground through the switch section Swa, and no current flows through the capacitor C1. At this time, the inductor current Iind is adjusted to the target value, and the light sources 11r, 11g, and 11b are turned off.

Then, the second control unit 200 turns off the switch unit Swa by setting the enable signal S_EN1 to Lo before supplying the current of the pulse wave P1 in the lightable period Tdr (for example, time tc). At this time, the current indicated by the arrow Y1 in FIG. 5 is cut off, and the current flows from the constant current supply section 300 to the ground via the capacitor C1 and the switch section Swc as indicated by the arrow Y5 in FIG. As a result, the capacitor C1 is charged with energy.

As the capacitor C1 approaches a fully charged state, the current value flowing through the capacitor C1 decreases and the current value I supplied to the light source 11r increases. As a result, the waveform of the rising portion of the pulse wave P1 is formed. The slope of the increase in the forward voltage of the light source 11r and the slope of the rising portion of the pulse wave P1 can be adjusted by the capacitor C1.

Then, as shown in FIG. 9, the comparison signal SB becomes Lo when the current value I reaches the target value Tgt. The second control unit 200 turns on the switch unit Swa by setting the enable signal S_EN1 to Hi at time td when the comparison signal SB becomes Lo. At this time, as indicated by an arrow Y1 in FIG. 5, the current from the constant current supply section 300 flows to the ground via the switch section Swa, and the current value I supplied to the light source 11r decreases. As a result, the waveform of the falling portion of the pulse wave P1 is formed.
After generating the pulse wave P1 as described above, the second control unit 200 generates pulse waves P2 and P3 in the same manner as the pulse wave P1.

Then, the second control unit 200 generates a pulse wave P4 with the current value I supplied to the light source 11g during the lightable period Tdg after the lightable period Tdr. The target value Tgt for the pulse wave P4 is smaller than the target value Tgt for the pulse wave P1 described above. Except for this point, the pulse wave P4 is generated by the same method as the pulse wave P1.
Next, the second control unit 200 does not generate a pulse wave during the lighting-enabled period Tdb after the off period Tof, which is the same as the off period Tof described above, in this example. However, the current may be supplied as a pulse wave to the light source 11b even during the lightable period Tdb.
This completes the description of the low luminance mode.

(effect)
According to the embodiment described above, the following effects are obtained.

(1-1) The HUD device 1, which is an example of a display device, includes a constant current supply unit 300, which is an example of a current supply unit that supplies current, and receives current from the constant current supply unit 300, and produces different colors. a plurality of light sources 11r, 11g, and 11b that emit lights R, G, and B; an inductor L1 that is an example of an energy storage unit that stores energy when current is supplied to each of the light sources 11r, 11g, and 11b; A current from a constant current supply unit 300 is supplied to a display element 30 having a micromirror 30a, which is an example of a plurality of reflection units that control the angle of reflection, and one of the plurality of light sources 11r, 11g, and 11b. Light R, G, and B emitted from a plurality of light sources 11r, 11g, and 11b by a field sequential method in which any one of the light sources 11r, 11g, and 11b is caused to emit light, and the light sources 11r, 11g, and 11b are sequentially switched. A light source control unit 201 that generates illumination light C of a desired color from the light source control unit 201, a display element control unit 202 that reflects the display light L corresponding to the image M from the illumination light C through the micromirror 30a, and an inductor L1. A resistor R1 and a switch Swr1, which are an example of an energy release section that releases energy, and a switch section Swa, which is an example of a current setting section that controls the inductor current Iind flowing through the inductor L1 based on the current from the constant current supply section 300. , provided. Before the light sources 11r, 11g, and 11b are turned on, the light source control unit 201 releases the energy stored in the inductor L1 through the resistor R1 and the switch unit Swr1, and then the constant current supply unit 201 through the switch unit Swa. Based on the current from 300, the inductor current Iind is controlled to a target value. This target value is set based on the current value supplied when lighting the light sources 11r, 11g, and 11b.
According to this configuration, the inductor current Iind is controlled to the target value before lighting the light sources 11r, 11g, and 11b. can be done. As a result, it is possible to prevent the brightness of the image M from lowering and the gradation of the image M from deteriorating, thereby improving the display quality.

(1-2) The current setting section is connected in parallel to the light sources 11r, 11g, and 11b, and under the control of the light source control section 201, the ON state in which the inductor L1 is connected to the ground and the OFF state in which the inductor L1 is not connected to the ground. It comprises a switch part Swa, which is an example of an energy release switch part that switches between states. The energy release section is connected in parallel to the switch section Swa, and under the control of the light source control section 201, the switch section Swr1 switches between an ON state in which the inductor L1 is connected to the ground and an OFF state in which the inductor L1 is not connected to the ground. and a resistor R1 connected in series to the switch section Swr1. Before the light sources 11r, 11g, and 11b are turned on, the light source control unit 201 switches the switch unit Swr1 to the ON state to release the energy stored in the inductor L1, and then switches the switch unit Swr1 to the OFF state. The inductor current Iind is controlled to the target value by switching the switch section Swa to the ON state while the current is supplied from the constant current supply section 300 .
According to this configuration, the inductor current Iind can be controlled to the target value after the energy of the inductor L1 is released with a simple configuration and control.
Further, by selectively using the switch Swr1 for releasing the energy of the inductor L1 and the switch Swa for controlling the inductor current Iind to a target value, it is possible to suppress heat generation due to the currents of the switches Swa and Swr1. .

(1-3) The light source control unit 201 supplies the current to the light sources 11r, 11g, and 11b during the on-duty period Ton (for example, time t3 in FIG. 7) of the lighting-enabled period Td. In the off-duty period Tod (for example, time t3a in FIG. 7) after the duty period Ton, the switch section Swa is switched to the ON state, thereby causing current to flow from the constant current supply section 300 to the switch section Swa through the inductor L1, thereby reducing the off-duty period. After the period Tod, the energy stored in the inductor L1 is released by switching the switch section Swr1 to the ON state.
According to this configuration, the inductor current Iind is maintained at the target value during the off-duty period Tod. Therefore, in the preparatory period Tb after the off-duty period Tod, the energy stored in the inductor L1 can be released in a short period of time.

(2-1) The HUD device 1, which is an example of a display device, includes a constant current supply unit 300 that supplies current, and upon receiving the current from the constant current supply unit 300, emits lights R, G, and B of different colors. a display element 30 having a plurality of light sources 11r, 11g, and 11b that emit light, a plurality of micromirrors 30a that control the angle of reflection of light, and a constant current supply unit to any one of the plurality of light sources 11r, 11g, and 11b. A field sequential system in which any one of the light sources 11r, 11g, and 11b is caused to emit light by supplying current from 300 as pulse waves P1, P2, P3, and P4 or a rectangular wave Rw, and the light sources 11r, 11g, and 11b that emit light are sequentially switched. A light source control unit 201 that generates illumination light C of a desired color from lights R, G, and B emitted from a plurality of light sources 11r, 11g, and 11b, and a micromirror 30a, which emits illumination light C to an image M. The slopes of the rising portions of the pulse waves P1, P2, P3, and P4 connected in parallel to the light source between the display element control section 202 that reflects the corresponding display light L and the constant current supply section 300 and the ground are reduced. and a switch section Swc, which is an example of a capacitor switch section connected in series with the capacitor C1. The light source control unit 201 turns on the switch unit Swc when supplying the currents from the constant current supply unit 300 as pulse waves P1, P2, P3, and P4 to the light sources 11r, 11g, and 11b. The switch Swc is turned off when supplying the current from the rectangular wave Rw to the light sources 11r, 11g, and 11b.
According to this configuration, by turning on the switch Swc, the capacitor C1 can reduce the inclination of the rising portions of the pulse waves P1, P2, P3, and P4. As a result, it is possible to prevent the current value I supplied to the light sources 11r, 11g, and 11b from overshooting the target value Tgt. Therefore, it is possible to prevent the brightness of the image M from lowering and the gradation of the image M from deteriorating, thereby improving the display quality.
In addition, since the current does not flow through the capacitor C1 by turning off the switch Swc, the delay in the rise of the rectangular wave Rw due to the capacitor C1 is suppressed.
As described above, the switch section Swc can enable or disable the capacitor C1. Therefore, the light sources 11r, 11g, and 11b can be lit with desired brightness.

(2-2) In the high brightness mode, the light source control unit 201 supplies the current from the constant current supply unit 300 as a rectangular wave Rw to the light sources 11r, 11g, and 11b while maintaining the switch unit Swc in the OFF state. In the luminance mode, the current from the constant current supply unit 300 is supplied as pulse waves P1, P2, P3, and P4 to the light source 11r while maintaining the ON state of the switch Swc over the lighting-enabled period Td during which the light sources 11r, 11g, and 11b can be turned on. , 11g and 11b.
According to this configuration, the switch section Swc is turned off in the high brightness mode, so the capacitor C1 does not function. Therefore, in the high brightness mode, delay in rising of the current value I supplied to the light sources 11r, 11g, and 11b by the capacitor C1 can be suppressed, and high brightness can be realized. On the other hand, in the low-luminance mode, the switch Swc is turned on, so the capacitor C1 reduces the gradients of the rising portions of the pulse waves P1, P2, P3, and P4. Therefore, overshoot is suppressed in the low luminance mode.

(2-3) The HUD device 1 includes a switch section Swa, which is an example of an energy release switch section connected in parallel to the capacitor C1 and the switch section Swc. In the low-brightness mode, the light source control unit 201 controls the switching unit Swa when the current value I supplied to the light sources 11r, 11g, and 11b reaches the target value Tgt due to the rising portions of the pulse waves P1, P2, P3, and P4. is turned on, the current from the constant current supply unit 300 is caused to flow to the ground through the switch unit Swa.
According to this configuration, when the current value I reaches the target value Tgt, by turning on the switch section Swa, the current from the constant current supply section 300 flows into the ground via the switch section Swa. Therefore, the pulse waves P1, P2, P3, and P4 can be lowered quickly, and overshoot can be suppressed.

In addition, this invention is not limited by the above embodiment and drawing. Modifications (including deletion of components) can be made as appropriate without changing the gist of the present invention. An example of modification will be described below.

(Modification)
In the above embodiment, the light source driving section 43 includes the switch section Swr1 corresponding to the resistor R1, but instead of the switch section Swr1, it may include a Zener diode ZD1 as shown in FIG. The cathode terminal of Zener diode ZD1 is connected to inductor L1, and the anode terminal of Zener diode ZD1 is connected to resistor R1.
When the reverse voltage applied to the Zener diode ZD1 exceeds the breakdown voltage of the Zener diode ZD1 due to energy accumulated in the inductor L1, the avalanche breakdown phenomenon causes the energy stored in the inductor L1 to exceed the breakdown voltage of the Zener diode ZD1. The energy is released as a current to ground through Zener diode ZD1 and resistor R1. The reverse voltage of the Zener diode ZD1 is set to exceed the breakdown voltage of the Zener diode ZD1 at the timing when the enable signal S_EN2 of the above embodiment is set to Hi.
As a result, it is possible to obtain the same functions and effects as those of the above-described embodiment in a simple manner in terms of control and configuration.

Further, as shown in FIG. 11, the light source driving section 43 further includes a switch section Swz that switches between an ON state and an OFF state by a Zener diode ZD1. The switch section Swz is composed of an n-channel FET. The gate terminal of the switch Swz is connected between the Zener diode ZD1 and the resistor R1, the drain terminal of the switch Swz is connected to the inductor L1, and the source terminal of the switch Swz is grounded. In this configuration, when the reverse voltage applied to the Zener diode ZD1 exceeds the breakdown voltage of the Zener diode ZD1 due to the accumulation of energy in the inductor L1, the gate voltage of the switch Swz rises, causing the switch Swz to Switch to ON state. When the switch section Swz is switched to the ON state, the energy stored in the inductor L1 is released as current to the ground through the switch section Swz, as indicated by the arrow Yg in FIG. By providing the switch section Swz, the energy of the inductor L1 can be released to the outside in a short period of time.

In the above-described embodiments, the display device according to the present invention is applied to a vehicle-mounted head-up display device. . Moreover, although the display light L from the HUD device 1 is projected onto the windshield 3, it may be projected onto a dedicated combiner. Also, the display device according to the present invention may be applied to a display device such as a projector used indoors or outdoors, instead of a head-up display device.

In the above-described embodiment, the second control unit 200 shifts to any one of the high-luminance mode, the medium-luminance mode, and the low-luminance mode based on the value of the dimming signal SL. Alternatively, the viewer 4 may operate an operation unit (not shown) provided on the vehicle 2 to shift between the above modes. Further, the modes may be changed according to the operation of a switch for turning on/off the lights of the vehicle 2 .

An inductor L1, which is an example of an energy storage unit, may be provided for each of the light sources 11r, 11g, and 11b. The energy storage unit is not limited to the inductor L1, and may be, for example, the parasitic capacitances of the light sources 11r, 11g, and 11b.

In the above embodiment, the second control section 200 turns on the switch section Swa during the off period Tof, but the switch section Swr1 may be turned on. This also allows the energy remaining in the inductor L1 to be released.

1 HUD device 2 vehicle 3 windshield 5 light source driving device 7 illuminance sensor 10 lighting devices 11, 11b, 11g, 11r light source 30 display element 30a micromirror 43 light source driving unit 61 plane mirror 62 concave mirror 65 concave mirror driving unit 100 first control unit 200 second control unit 201 light source control unit 202 display element control unit 203 current supply control unit 204 comparison unit 300 constant current supply unit 500 light intensity detection unit C1 capacitor L1 inductor P1, P2, P3, P4 pulse wave R1 resistor ZD1 zener Diodes Swr, Swg, Swb, Swr1, Swa, Swc, Swz Switch section Ton On-duty period Tod Off-duty period Iind Inductor current

Claims (3)

a current supply unit that supplies current;
a plurality of light sources that receive current from the current supply unit and emit light of different colors;
a display element having a plurality of reflecting portions that control the angle of reflection of light;
The current from the current supply unit is supplied as a triangular wave or a rectangular wave to any one of the plurality of light sources to cause the light source to emit light, and the plurality of light sources are sequentially switched by a field sequential method. a light source controller that generates illumination light of a desired color from light emitted from the light source;
a display element control unit that reflects light corresponding to an image out of the illumination light through the reflection unit;
a capacitor connected in parallel to the light source between the current supply and ground;
a capacitor switch unit connected in series with the capacitor,
The light source control unit turns on the capacitor switch unit when supplying the current from the current supply unit to the light source as the triangular wave , and supplies the current from the current supply unit to the light source as the square wave. When doing so, the capacitor switch section is turned off,
display device. The light source control unit can supply the current from the current supply unit to the light source as the square wave while maintaining the capacitor switch unit in an off state in a high luminance mode, and turn on the light source in a low luminance mode. supplying the current from the current supply unit as the triangular wave to the light source while maintaining the capacitor switch unit in an ON state for a lighting-enabled period;
The display device according to claim 1. The display device comprises an energy release switch unit connected in parallel to the capacitor and the capacitor switch unit,
In the low luminance mode, the light source control section turns on the energy release switch section when the current value supplied to the light source reaches a target value due to the rising portion of the triangular wave. current from the section to ground through the energy release switch section;
3. The display device according to claim 2.

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