Head-up display device

Abstract

To provide a head-up display device that can correctly achieve the light source luminance with a simple structure.SOLUTION: An HUD 100 includes: a display unit 10; a light source 18a that lights to emit light to the display unit 10; a light source driver IC 72 that lights the light source 18a; and a microcomputer 71 that outputs a lighting signal (first PWM signal Spwm1 and ADIM signal Sadim) commanding light source current Iled to the light source driver IC 72, thereby supplying the light source current Iled commanded by the lighting signal to the light source 18a. The light source driver IC 72 has an upper limit current setting port Piset that outputs constant current which is an upper limit current setting signal Siset. An upper limit value of current flowing as the light source current Iled is set according to terminal voltage generated at the upper limit current setting port Piset, and the upper limit current setting port Piset is connected to the ground through a resistor 72r.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a head-up display device. [Background technology]

[0002] For example, a head-up display device described in Patent Document 1 includes an LED (Light Emitting Diode) and a microcomputer that outputs a first PWM signal and acquires a cathode voltage of the LED. This microcomputer detects a luminance abnormality fault when it determines that a specific point specified by the cathode voltage and the duty ratio of the first PWM signal is within a high luminance abnormality range. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2020 / 235683 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a head-up display device that has a simple configuration but can emit light source luminance more accurately. [Means for solving the problem]

[0005] In order to achieve the above object, a head-up display device according to an aspect of the present invention comprises: A display device; A light source that is turned on to emit light to the display; A driver for turning on the light source; a microcomputer that outputs a lighting signal instructing a light source current to the driver, thereby supplying the light source current instructed by the lighting signal to the light source; The driver includes: Depending on the terminal voltage generated by outputting a constant current, Set the upper limit of the current flowing as the light source current An upper limit current setting port; Depending on the duty ratio of the input pulse wave, Set the current value of the current that actually flows as the light source current. A current setting port; having The current setting port is connected to ground through a resistor; The microcomputer outputs the pulse wave as the lighting signal to the current setting port. Effect of the Invention

[0006] According to the present invention, in a head-up display device, it is possible to more accurately emit light source luminance while having a simple configuration. [Brief description of the drawings]

[0007] [Figure 1] 1 is a schematic diagram of a vehicle equipped with a head-up display device according to an embodiment of the present invention. [Diagram 2] 1 is a schematic diagram of a head-up display device according to an embodiment of the present invention. [Diagram 3] 1 is a block diagram of a head-up display device according to an embodiment of the present invention. [Figure 4] FIG. 1 is a circuit diagram of a head-up display device according to a conventional example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] An embodiment of a head-up display device according to the present invention will be described with reference to the drawings. 1, the head-up display device 100 is installed in the dashboard of a vehicle 200. The head-up display device 100 emits display light L that displays an image toward a windshield 201, which is an example of a projection target member of the vehicle 200. The display light L is reflected by the windshield 201 and reaches a viewer 1 (mainly the driver of the vehicle 200). As a result, a virtual image V is displayed so as to be visible to the viewer 1.

[0009] As shown in FIG. 2, the head-up display device 100 includes a display unit 10, a plane mirror 20, a concave mirror 30, a housing 60, and a control unit .

[0010] The display unit 10 emits display light L that represents an image under the control of the control unit 70. The display unit 10 includes a display device 14 and an illumination device 18.

[0011] The plane mirror 20 reflects the display light L emitted by the display unit 10 toward the concave mirror 30. The concave mirror 30 reflects the display light L reflected by the plane mirror 20 toward a windshield 201 (see FIG. 1) while magnifying it. The plane mirror 20 may be a concave mirror.

[0012] The housing 60 is made of a non-translucent resin or metal and has a hollow, substantially rectangular parallelepiped shape. Within the housing 60, each component of the head-up display device 100 is housed. An opening 61 is formed in the housing 60 at a position facing the windshield 201. The housing 60 includes a curved plate-like window portion 50 that closes the opening 61. The window portion 50 is made of a translucent resin such as acrylic that transmits the display light L.

[0013] The display 14 is a TFT (Thin Film Transistor) type liquid crystal display panel controlled by the control unit 70. The display 14 receives light from the illumination device 18 and emits display light L.

[0014] The lighting device 18 is located behind the display 14 and illuminates the display 14 with illumination light. The lighting device 18 includes a plurality of light sources 18a that emit light to the display 14 under the control of the control unit 70. Each light source 18a is made of an LED.

[0015] Next, the electrical configuration of the display unit 10 and the control unit 70 will be described. 3, the display unit 10 includes a plurality of light sources 18a, a display 14, and a signal adjustment circuit 73. The control unit 70 includes a microcomputer 71, a light source driver IC 72, and an input voltage switching circuit 78.

[0016] The input voltage switching circuit 78 is provided between the power supply voltage Vc and the light source driver IC 72, and switches between an on state and an off state in response to a control signal Sc from the microcomputer 71. When the input voltage switching circuit 78 is in the on state, a voltage from the power supply voltage Vc is applied to the light source driver IC 72. When the input voltage switching circuit 78 is in the off state, application of the voltage from the power supply voltage Vc to the light source driver IC 72 is stopped.

[0017] The light source driver IC72 is a switch circuit that receives a power supply voltage Vc and generates a second PWM signal Spwm2 by boosting a first PWM (Pulse Width Modulation) signal Spwm1 (to be described later) from the microcomputer 71. The second PWM signal Spwm2 is a signal synchronized with the first PWM signal Spwm1. The light source driver IC72 supplies a light source current Iled to the multiple light sources 18a via the second PWM signal Spwm2. An anode terminal of the light source 18a is connected to the light source driver IC72. A cathode terminal of the light source 18a is connected to the microcomputer 71 via a signal adjustment circuit 73.

[0018] The light source driver IC72 has an upper limit current setting port Piset connected to the ground via a resistor 72r. The upper limit current setting port Piset outputs a constant current as an upper limit current setting signal Siset. The upper limit current setting port Piset outputs the upper limit current setting signal Siset, which is a constant current, to the resistor 72r connected to the ground, and generates a terminal voltage. The voltage value of this terminal voltage is specifically a value obtained by multiplying the resistance value of the resistor 72r and the current value of the upper limit current setting signal Siset. The light source driver IC72 determines the upper limit value of the current value that can flow as the light source current Iled according to the magnitude of the terminal voltage of the upper limit current setting port Piset. Therefore, the higher the resistance value of the resistor 72r, the higher the upper limit value of the light source current Iled.

[0019] The upper limit current setting port Piset is configured without using elements with sensitive temperature characteristics such as capacitors, so as to be less susceptible to the effects of temperature. Specifically, as explained above, the upper limit current setting port Piset is connected to ground only via resistor 72r. This configuration makes it less susceptible to the effects of environmental temperature, and allows the light source luminance to be emitted more accurately despite the simple configuration.

[0020] Here, a conventional example shown in Fig. 4 will be described. Fig. 4 shows a head-up display device 101 and a display unit 11 provided therein. Among the configurations of the head-up display device 101 and the display unit 11, the description of configurations that overlap with the configurations in Fig. 3 is omitted.

[0021] In the conventional configuration, the light source driver IC 72 is connected to the microcomputer 71 via a DA conversion circuit C. Specifically, the DA conversion circuit C is connected between the digital output port of the microcomputer 71 and an upper limit current setting port Piset. The microcomputer 71 outputs a PWM control signal from the digital output port. The DA conversion circuit C outputs a predetermined analog voltage value to the upper limit current setting port Piset according to the duty ratio of the input PWM control signal. The light source driver IC 72 sets an upper limit value of the light source current Iled according to the analog voltage value applied to the upper limit current setting port Piset.

[0022] Originally, the upper limit current setting port Piset was generally configured in this way so that the upper limit of the current could be appropriately set in response to a control signal from a microcomputer. This was done to control the brightness difference caused by individual differences in the light source driver IC and the light source 18a so as to offset the difference in brightness. However, since such analog electronic circuits contain capacitors, their behavior (output characteristics, conversion characteristics) changes depending on the operating temperature.

[0023] Therefore, the configuration disclosed herein in which the upper limit current setting port Piset is connected to ground without a capacitor is less susceptible to the effects of temperature and can achieve more accurate light emission brightness. In the configuration of the present disclosure, the brightness difference caused by the individual difference of the light source driver IC or the light source may be offset by adjustment using other lighting signals such as the ADIM signal Sadim. For example, when the head-up display device is manufactured, a setting may be made to select one table to be used in the actual lighting operation from among a plurality of ADIM signal tables stored in the storage unit of the dimming unit 71a.

[0024] The explanation returns to the content of FIG. The signal adjustment circuit 73 receives the voltages (anode voltage and cathode voltage Vct) across the light source 18a, generates a PWM feedback signal Sfp that is a feedback signal of the second PWM signal Spwm2, and outputs the generated PWM feedback signal Sfp to the microcomputer 71. The signal adjustment circuit 73 generates the binarized PWM feedback signal Sfp by comparing the cathode voltage of the light source 18a with a threshold value. The signal adjustment circuit 73 has a capacitor, a resistor, and a switching element.

[0025] The microcomputer 71 includes a processing unit such as a CPU (Central Processing Unit) that executes an operating program, a ROM (Read Only Memory) in which the operating program of this processing unit is stored, and a RAM (Random Access Memory) used as a work area for this processing unit. The microcomputer 71 includes, as functional blocks, a dimming unit 71a, a luminance abnormality determination unit 71b, and a display control unit 71c that controls the display device 14.

[0026] The light control unit 71a controls the lighting of the light source 18a via the light source driver IC 72. The light control unit 71a receives a requested luminance signal Sa from the outside and lights up the light source 18a at the requested luminance included in the requested luminance signal Sa. The requested luminance signal Sa increases in proportion to an external light intensity detection value indicating the surrounding brightness included in vehicle information from an ECU (Electronic Control Unit) mounted on the vehicle, for example. When the power supply of the display unit 10 is turned on, the light control unit 71a outputs an enable signal Sen to the light source driver IC 72 to permit operation of the light source driver IC 72. After determining that a luminance abnormality has occurred, the light control unit 71a stops outputting the enable signal Sen to disable operation of the light source driver IC 72.

[0027] The dimming unit 71a adjusts the duty ratio of the first PWM signal Spwm1 and the duty ratio of the ADIM (analog dimming input) signal Sadim to adjust the brightness of the light source 18a. The higher the on-duty ratio of the first PWM signal Spwm1, the longer the time that the light source current Iled is supplied to the light source 18a, and the higher the brightness of the light source 18a. The lower the on-duty ratio of the ADIM signal Sadim, the higher the peak current value of the light source current Iled.

[0028] When the on-duty ratio of the ADIM signal Sadim is 0, the peak current value of the light source current Iled becomes the upper limit value set by the upper limit current setting port Piset. That is, the peak current value of the light source current Iled is adjusted by the light source driver IC 72 within the range of 0 or more and the upper limit value or less according to the on-duty ratio of the ADIM signal Sadim.

[0029] The frequency of the first PWM signal Spwm1 is set to, for example, 1 kHz to several hundreds of kHz. The frequency of the ADIM signal Sadim is set to, for example, several tens of kHz, preferably 50 kHz.

[0030] When the required luminance is within the normal luminance range, the dimming unit 71a generates the first PWM signal Spwm1 having a duty ratio according to the required luminance while fixing the duty ratio of the ADIM signal Sadim to a specified value. In the normal luminance range, the higher the required luminance is, the higher the on-duty ratio of the first PWM signal Spwm1 is set.

[0031] When the required luminance is within a low luminance range set to a range lower than the normal luminance range, the dimming unit 71a generates an ADIM signal Sadim with a duty ratio according to the required luminance while fixing the duty ratio of the first PWM signal Spwm1 to a lower limit value. In the low luminance range, the higher the required luminance is, the higher the on-duty ratio of the ADIM signal Sadim is set. The lower limit value of the duty ratio of the first PWM signal Spwm1 is set to, for example, 0.2%. The light control unit 71a may output the ADIM signal Sadim based on a table that does not set the duty ratio to 100% depending on the individual differences of the light source driver IC 72 and the light source 18a. In other words, when the light source driver IC 72 and the light source 18a have high light emission luminance due to individual differences, the light control unit 71a adjusts the on-duty ratio of the ADIM signal Sadim so that it is always greater than 0.

[0032] The luminance abnormality determination unit 71b determines whether or not there is an abnormality in the luminance of the light source 18a, based on the ADIM signal Sadim output from the microcomputer 71 and an ADIM feedback signal Sfb that is a feedback signal of this ADIM signal Sadim.

[0033] (effect) According to the embodiment described above, the following effects are achieved. (1) The head-up display device 100 is A display unit 10; A light source 18a that is turned on to emit light to the display unit 10; a light source driver IC 72 for turning on the light source 18a; a microcomputer 71 that outputs a lighting signal (a first PWM signal Spwm1 and an ADIM signal Sadim) that commands a light source current Iled to a light source driver IC 72, thereby supplying the light source current Iled commanded by the lighting signal to the light source 18a; The light source driver IC72 is The upper limit current setting port Piset outputs a constant current that is an upper limit current setting signal Siset. The upper limit of the light source current Iled is set according to the terminal voltage generated at the upper limit current setting port Piset. The upper limit current setting port Piset is connected to ground via a resistor 72r. According to this configuration, the desired light source luminance can be more accurately emitted despite the simple configuration.

[0034] The present invention is not limited to the above-described embodiment and drawings. Modifications (including the deletion of components) can be made as appropriate within the scope of the present invention. An example of a modification will be described below.

[0035] [Variations] In the above embodiment, the upper limit current setting port Piset sets the upper limit of the light source current Iled according to the terminal voltage generated by outputting a constant current to the resistor 72r. However, the upper limit current setting port does not have to output a current. For example, the upper limit current setting port may be a high impedance analog input terminal, and the upper limit of the current value may be set according to a post-voltage division voltage input via a voltage divider circuit. It is preferable that at least the upper limit current setting port is configured in a manner that does not include an element such as a capacitor whose impedance varies according to the operating temperature. However, it is preferable that the upper limit current setting port, which is a port for setting a current value, sets the current according to the terminal voltage generated by the current, like the upper limit current setting port Piset.

[0036] In the above embodiment, when the luminance abnormality determination unit 71b determines that the light source 18a has a luminance abnormality, the display control unit 71c may switch the display 14 to a non-transmitting state (black display state). This prevents the viewer 1 viewing the virtual image V from being dazzled.

[0037] In the above embodiment, the lighting signal is the ADIM signal Sadim, and the feedback lighting signal is the ADIM feedback signal Sfb, but this is not limited thereto, and the lighting signal may be the first PWM signal Spwm1, and the feedback lighting signal may be the detection signal Son.

[0038] In the above embodiment, the display 14 is a liquid crystal display panel, but is not limited to this and may be a reflective display such as a DMD (Digital Micro Mirror Device) element.

[0039] In the above embodiment, the head-up display device 100 is mounted on the vehicle 200, but may be mounted on a vehicle other than the vehicle 200, such as an airplane or a ship. In addition, the projection member is not limited to the windshield 201, and may be a dedicated combiner. [Explanation of symbols]

[0040] 1. Viewer 10 Display 14 Display 18 Lighting Equipment 18a light source 20 plane mirror 30 concave mirror 50 Window 60 Case 61 Opening 70 Control section 71 Microcomputer 71a Dimming section 71b Judgment part 71c Display control unit 72 Light source driver IC 73 Signal conditioning circuit 78 Input voltage switching circuit 100 Head-up display device 200 vehicles 201 Windshield L display light V Virtual Image Sa Required luminance signal Sc control signal Vc power supply voltage Sfb ADIM feedback signal Sen Enable signal Iled Light source current Spwm1 1st PWM signal Spwm2 2nd PWM signal Sadim ADIM signal Siset Upper limit current setting signal Piset upper limit current setting port C DA conversion circuit

Claims

[Claim 1] A display device; A light source that is turned on to emit light to the display; A driver for turning on the light source; a microcomputer that outputs a lighting signal instructing a light source current to the driver, thereby supplying the light source current instructed by the lighting signal to the light source; The driver includes: It has an upper limit current setting port that outputs a constant current, an upper limit value of a current flowing as the light source current is set according to a terminal voltage generated at the upper limit current setting port; The upper limit current setting port is connected to ground via a resistor. Head-up display device.

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