Display device for vehicle

Abstract

To provide a display device for a vehicle capable of preventing a light source from being continuously turned off due to temporary voltage fluctuation.SOLUTION: The vehicular display apparatus 10 includes a display unit 6, light sources 7 for illuminating the display unit 6, an LED driver IC2 for driving the light sources 7, and a microcomputer 5 for controlling the driving operation of the LED driver IC2. The LED driver IC2 includes an abnormality determination unit 2c that determines the presence or absence of an abnormality, and an abnormality signal output terminal Pf2 that outputs an abnormality signal Sf indicating the occurrence of an abnormality when it is determined that there is an abnormality. The microcomputer 5 has an abnormality signal input circuit Pf5 for inputting the ON of the abnormality signal Sf, performs the reset operation of the LED driver IC2 when inputting the ON of the abnormality signal Sf, and stops the drive operation of the LED driver IC2 when the reset operation reaches the preset number of times within a specified time. The cycle for performing the reset operation is set to a time in which the presence or absence of an abnormality can be determined.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] The light source abnormality determination device described in Patent Document 1 turns off the light source when it determines that there is an abnormality based on the voltage of the light source. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-101316 Summary of the Invention [Problem to be solved by the invention]

[0004] In the configuration described in Patent Document 1, a temporary voltage fluctuation such as cranking or sudden noise is deemed to be an abnormality and the light source is turned off, and there is a risk that this off state may continue.

[0005] The present disclosure has been made in consideration of the above-described circumstances, and aims to provide a vehicle display device that can prevent a light source from being kept off for a long period of time due to a temporary voltage fluctuation. [Means for solving the problem]

[0006] In order to achieve the above object, the vehicle display device according to the present disclosure includes: a display unit for displaying an image; a light source that illuminates the display unit; a driver that drives the light source; a microcomputer that controls the driving operation of the driver, The driver an abnormality determination unit that determines whether or not there is an abnormality in the vehicle display device; an abnormality signal output unit that outputs an abnormality occurrence signal indicating the occurrence of an abnormality when the abnormality determination unit determines that an abnormality has occurred; The microcomputer an abnormality signal input unit that inputs the abnormality occurrence signal; When the abnormality occurrence signal is input, a reset operation of the driver is performed, and when the reset operation reaches a predetermined number of times within a predetermined period, the driving operation of the driver is stopped; The period during which the reset operation is performed is set to a time period during which the abnormality determination unit can determine whether or not an abnormality exists. [Effects of the Invention]

[0007] According to the present disclosure, it is possible to prevent a light source from being kept off for a long time due to a temporary voltage fluctuation. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a block diagram of a vehicle display device according to an embodiment of the present disclosure. [Figure 2] 10 is a timing chart showing signals, voltages, a reset operation, and an LED lighting state of a vehicle display device in the case of a permanent failure according to an embodiment of the present disclosure. [Figure 3] 10 is a timing chart showing signals, voltages, reset operations, and LED lighting states of a vehicle display device in the case of temporary voltage fluctuation according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[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 such as an automobile, a construction vehicle, or an agricultural vehicle. As shown in FIG. 1, the vehicle display device 10 includes an LED driver IC (Integrated Circuit) 2, a boost circuit 3, a reset means 4, a microcomputer 5 (also called a microcontroller, microcomputer, or MCU (Micro Controller Unit)), a display unit 6, and a light source 7. The display unit 6 is a TFT (Thin Film Transistor) liquid crystal display panel controlled by the microcomputer 5. The light source 7 is made up of a plurality of LEDs (Light Emitting Diodes) and illuminates the display unit 6. The plurality of LEDs are connected in series and then connected in parallel to each other.

[0010] The boost circuit 3 receives a voltage (for example, 12 V) from the on-board power supply Vc, and under switching control of the LED driver IC2, boosts this voltage to the voltage required for each LED to emit light, and supplies it to the light source 7. If nine LEDs are connected in series, this required voltage is 3 V x 9 = 27 V. The boost circuit 3 is composed of resistors, coils, capacitors, FETs (Field Effect Transistors), and the like, all of which are not shown.

[0011] The LED driver IC2 receives a PWM control signal Sp from the microcomputer 5 and drives the light source 7 via the boost circuit 3 so that the LED brightness corresponds to the duty ratio of the PWM control signal Sp. The LED driver IC2 has a PWM input terminal Pi2 for inputting a PWM control signal Sp, a power supply input terminal Pv2 for inputting the operating power of the LED driver IC2, a plurality of LED current input terminals Pd2, an LED voltage detection terminal Pe2, a switching signal output terminal Pg2, and an abnormality signal output terminal Pf2. The LED current input terminal Pd2 is connected to the cathode terminals of the LED group and receives the LED current. The LED voltage detection terminal Pe2 receives a voltage detection signal Vs corresponding to the LED voltage output from the boost circuit 3. The switching signal output terminal Pg2 outputs a switching control signal Ss to the boost circuit 3.

[0012] The LED driver IC2 includes an LED current detector 2a, an LED voltage detector 2b, and an abnormality detector 2c. The LED current detector 2a detects the LED current IL input via the LED current input terminal Pd2. The LED voltage detector 2b detects the LED voltage VL based on the voltage detection signal Vs input via the LED voltage detection terminal Pe2.

[0013] The abnormality determination unit 2c determines whether or not there is an open circuit abnormality, an overcurrent abnormality, an overvoltage abnormality, or an undervoltage abnormality, and if there is one or more of these abnormalities, it turns on the abnormality signal Sf output via the abnormality signal output terminal Pf2, and if there is no abnormality, it turns off the abnormality signal Sf output via the abnormality signal output terminal Pf2. When the abnormality determination unit 2c switches the abnormality signal Sf it outputs from OFF to ON, the abnormality determination unit 2c keeps the abnormality signal Sf ON unless the LED driver IC2 is reset.

[0014] The abnormality determination unit 2c determines that an open circuit abnormality has occurred when the LED current IL detected by the LED current detection unit 2a is equal to or less than the open circuit abnormality threshold, and determines that an open circuit abnormality has not occurred when the LED current IL exceeds the open circuit abnormality threshold. The open circuit abnormality threshold is set based on the value of the LED current when the LED wiring is broken. The abnormality determination unit 2c determines that an overcurrent abnormality has occurred when the detected LED current IL is equal to or greater than an overcurrent threshold, and determines that an overcurrent abnormality has not occurred when the detected LED current IL is less than the overcurrent abnormality threshold, which is set to a current value greater than the rated current of the LED. The abnormality determination unit 2c determines that an overvoltage abnormality has occurred when the LED voltage VL detected by the LED voltage detection unit 2b is equal to or greater than an overvoltage abnormality threshold, and determines that an overvoltage abnormality has not occurred when the detected LED voltage VL is less than the overvoltage abnormality threshold, which is set to a voltage value greater than the rated voltage of the LED. The abnormality determination unit 2c determines that a low voltage abnormality exists when the detected LED voltage VL is equal to or less than the low voltage abnormality threshold, and determines that a low voltage abnormality does not exist when the detected LED voltage VL exceeds the low voltage abnormality threshold. Regarding the low voltage abnormality, since the boost circuit 3 is used, the lower the input voltage, the higher the input voltage becomes, making it more likely that an overcurrent will occur. The low voltage abnormality threshold is set to a voltage value low enough to cause an overcurrent.

[0015] The reset means 4 is connected between the power supply input terminal Pv2 of the LED driver IC2 and the reset signal output terminal Pr5 of the microcomputer 5, and turns on and off the power supply to the power supply input terminal Pv2 depending on the state of a reset signal Sr from the power supply input terminal Pv2. When the input reset signal Sr is at L (low) level, the reset means 4 supplies power from the power supply Vd (3.3 V in this example) to the power supply input terminal Pv2, and when the input reset signal Sr is at H (high) level, the reset means 4 stops the power supply from the power supply Vd to the power supply input terminal Pv2. After the power supply to the power supply input terminal Pv2 is stopped, the power supply to the power supply input terminal Pv2 is resumed, thereby resetting the LED driver IC2.

[0016] The reset means 4 includes a transistor TR1 and resistors R1 to R3. The base terminal of transistor TR1 is connected to reset signal output terminal Pr5 via resistor R2. The emitter terminal of transistor TR1 is connected to power supply Vd, and the collector terminal of transistor TR1 is connected to power supply input terminal Pv2. One end of resistor R1 is connected to the base terminal, and the other end of resistor R1 is connected to the emitter terminal. One end of resistor R3 is connected to the collector terminal, and the other end of resistor R3 is connected to ground. When a reset signal Sr at an L level is input to the base terminal of the transistor TR1, the transistor TR1 is turned on, and power from the power supply Vd is supplied to the power supply input terminal Pv2. On the other hand, when a high-level reset signal Sr is input to the base terminal of the transistor TR1, the transistor TR1 is turned off, and power from the power supply Vd is not supplied to the power supply input terminal Pv2.

[0017] The microcomputer 5 includes a CPU (Central Processing Unit), a GDC (Graphic Display Controller), and the like, and controls the driving of the light source 7 via an LED driver IC 2, and also controls the display of an image on the display unit 6. The microcomputer 5 includes a PWM output terminal Pp5 for outputting a PWM control signal Sp, an abnormality signal input terminal Pf5 for inputting an abnormality signal Sf, and a reset signal output terminal Pr5 for outputting a reset signal Sr. The microcomputer 5 determines the LED brightness in response to an illuminance sensor (not shown), generates a PWM control signal Sp with a duty ratio corresponding to the determined LED brightness, and outputs the generated PWM control signal Sp from the PWM output terminal Pp5 to the LED driver IC 2. When the LED brightness is at maximum, the duty ratio is 100%, and when the light source 7 is turned off, the duty ratio is 0%.

[0018] When the microcomputer 5 determines that the abnormality signal Sf input via the abnormality signal input terminal Pf5 has switched from OFF to ON, it determines that an abnormality has occurred in the vehicle display device 10, and sets the duty ratio of the PWM control signal Sp to 0% to turn off the light source 7. This puts the vehicle display device 10 into a protection mode in which no current flows through the light source 7 when an abnormality occurs.

[0019] Here, when the abnormality determination unit 2c determines that an abnormality has occurred, it may be a temporary voltage fluctuation due to cranking, noise, etc., or a permanent malfunction. If the protection mode is immediately entered despite the voltage fluctuation being temporary, the light source 7 cannot be turned on even after the temporary voltage fluctuation has been resolved, which is inconvenient. In this embodiment, when the abnormality determination unit 2c determines that an abnormality has occurred, the microcomputer 5 temporarily turns off the light source 7, and as long as the abnormality determination continues, causes the reset means 4 to repeatedly execute the reset operation of the LED driver IC2 a specified number of times (X times, described below) within a specified time Ta, and then transitions to protection mode. Therefore, if the malfunction is permanent, the protection mode is transitioned to after X reset operations. On the other hand, if the malfunction is temporary voltage fluctuation, the abnormality determination is no longer made after a specified number of reset operations, and the light source 7 is turned on in normal operation mode. Therefore, the light source 7 can be turned on after the temporary voltage fluctuation is resolved. The microcomputer 5 measures the time from the first reset operation using a timer (not shown), counts the number of reset operations until this measured time reaches a specified time Ta, and executes an abnormality determination process (described later) when the count reaches X. On the other hand, if an abnormality is no longer determined before this measured time reaches the specified time Ta, the time measured by the timer is reset. This is explained in detail below.

[0020] The operation of the vehicle display device 10 in the case of a permanent failure will be described with reference to the timing chart of FIG. When the abnormality determination unit 2c determines that the light source 7 is turned on, the abnormality signal Sf switches from OFF to ON (time t1). Accordingly, the microcomputer 5 sets the duty ratio of the PWM control signal Sp to 0%, thereby turning off the light source 7.

[0021] Then, in order to reset the LED driver IC2, the microcomputer 5 switches the reset signal Sr from L level to H level once, and then switches it back from H level to L level (time t2). This causes the LED driver IC2 to perform a first reset operation. This first reset operation returns the LED driver IC2 to its initial state. As a result, the output of the abnormality signal Sf is temporarily stopped, and the abnormality determination unit 2c performs an abnormality determination again. In this example, since the failure is permanent, the abnormality determination unit 2c determines that there is an abnormality, as at time t1 above, and the abnormality signal Sf is switched from OFF to ON (time t3).

[0022] Then, the microcomputer 5 temporarily switches the reset signal Sr from L level to H level, causing the LED driver IC2 to perform a reset operation again. This causes the LED driver IC2 to perform a second reset operation (time t4). Thereafter, the reset operation is similarly performed X times, which is a preset number of times.

[0023] After the Xth reset operation, when the abnormality determination unit 2c determines an abnormality again (time t5), the microcomputer 5 executes an abnormality determination process. In this abnormality determination process, the duty ratio of the PWM control signal Sp is fixed to 0% and the light source 7 is fixed to an off state. At this time, the reset signal Sr is maintained at H level and the supply of power to the power input terminal Pv2 is maintained in a stopped state. No reset operation is performed after time t5.

[0024] The first to Xth reset operations are executed within a specified time Ta. X times is a preset number of times or more, and is set to, for example, 10 to 30 times, and preferably 20 times. The reset period is set to a time period during which the LED driver IC2 restarts after a predetermined number of reset operations, allowing the abnormality determination unit 2c to determine whether an abnormality has occurred. The reset period is, for example, 100 ms to 500 ms, and preferably 300 ms. If the reset period is too short, it may cause an overcurrent in the light source circuit, which may then generate heat. If the reset period is too long, it may take a long time for the light source 7 to light up again after a temporary voltage fluctuation has ended. From this perspective, the reset period is set to the above value. As an example, if the reset operation cycle is 300 mS (milliseconds) and X times is 20 times, it takes about 6S (seconds) to perform the reset operation from the first to the Xth time. The specified time Ta is set to a time of at least about 6S (seconds). The specified time Ta is set to be longer than the time during which the voltage temporarily fluctuates, and X times is set to be within the number of times that the circuit elements of the display device 10 for vehicles will not be damaged.

[0025] The operation of the vehicle display device 10 in the case of a temporary voltage fluctuation will be described with reference to the timing chart of FIG. When the abnormality determination unit 2c determines that an abnormality has occurred due to a temporary voltage fluctuation, the abnormality signal Sf switches from OFF to ON (time t1). Accordingly, the microcomputer 5 sets the duty ratio of the PWM control signal Sp to 0%, thereby turning off the light source 7. In this example, the temporary voltage fluctuation that occurred at time t1 is resolved before and after the first reset operation. In this case, the abnormality determination unit 2c determines that there is no abnormality after the first reset operation, and the abnormality signal Sf is turned off. As a result, at time 6, the reset signal Sr is set to L level, power is supplied to the power input terminal Pv2, and the light source 7 is turned on again. In this example, the voltage abnormality was resolved after the first reset, but this is not limited to this. A temporary voltage fluctuation may continue after the first reset, and the voltage abnormality may be resolved after X resets from the second reset.

[0026] (effect) According to the embodiment described above, the following effects are achieved. (1) The vehicle display device 10 includes a display unit 6 that displays an image, a light source 7 that illuminates the display unit 6, an LED driver IC2 that is an example of a driver that drives the light source 7, and a microcomputer 5 that controls the driving operation of the LED driver IC2. The LED driver IC2 includes an abnormality determination unit 2c that determines whether or not there is an abnormality in the vehicle display device 10, and an abnormality signal output terminal Pf2 that is an example of an abnormality signal output unit that outputs an abnormality occurrence signal (an abnormality signal Sf is ON) indicating the occurrence of an abnormality when it is determined that there is an abnormality. The microcomputer 5 includes an abnormality signal input terminal Pf5 that is an example of an abnormality signal input unit that receives the ON abnormality signal Sf. When the ON abnormality signal Sf is input, the microcomputer 5 resets the LED driver IC2. When the reset operation reaches a predetermined number of times (X times) within a predetermined period (a specified time Ta), the microcomputer 5 stops the driving operation of the LED driver IC2 to maintain the light source 7 in an off state. The reset operation is performed at a period that allows the abnormality determination unit 2c to determine whether or not there is an abnormality. According to this configuration, after a temporary voltage fluctuation occurs, if the abnormality determination unit 2c determines again after the reset operation that there is no abnormality, the light source 7 can be turned on. Therefore, it is possible to prevent the light source 7 from being kept off due to a temporary voltage fluctuation. In the case of a permanent failure, the number of resets within the specified time Ta reaches X times, and the driving operation of the LED driver IC2 is stopped. This prevents the reset operation from being repeated endlessly while maintaining the safety of the vehicle display device 10.

[0027] (2) When it is determined that an abnormality exists, the abnormality signal output terminal Pf2 continues to output the ON abnormality signal Sf until a reset operation is performed. According to this configuration, the reset operation stops the output of the abnormality signal Sf, and the abnormality determination unit 2c re-determines the abnormality. Therefore, by repeating the reset operation X times, it becomes possible to re-determine the abnormality each time. Therefore, when the temporary voltage fluctuation disappears, the abnormality determination is no longer made, and the light source 7 can be turned on.

[0028] The present disclosure is not limited to the above-described embodiments and drawings. Modifications (including deletion of components) may be made as appropriate within the scope of the present disclosure. An example of such a modification is described below.

[0029] (Variation) In the above embodiment, when it is determined that an abnormality exists, the abnormality signal output terminal Pf2 continues to output the abnormality signal Sf in an ON state until a reset operation is performed. However, the ON time of this abnormality signal Sf may be limited to a certain period of time, and the abnormality signal Sf may be turned off after the certain period of time has elapsed. In the above embodiment, the vehicle display device 10 is a type equipped with a liquid crystal panel and a light source 7, but it may be of any type as long as it is equipped with a light source 7, for example, it may be a type equipped with a DMD (Digital Micro mirror Device) and a light source 7. In the above embodiment, the vehicle display device 10 was a direct-view type display device, but it is not limited to a direct-view type display device and may be a head-up display device that displays a projected image by projecting display light onto a projected member (windshield or combiner). The type of abnormality determined by the abnormality determination unit 2c is not limited to the above embodiment, and may be any type, such as an abnormality in LED brightness. [Explanation of symbols]

[0030] 2...LED driver IC, 2a...LED current detection section, 2b...LED voltage detection section, 2c...abnormality judgment section, Pd2...LED current input terminal, Pe2...LED voltage detection terminal, Pg2...switching signal output terminal, Pf2...abnormality signal output terminal, Pi2...PWM input terminal, Pv2...power supply input terminal 3...Boost circuit 4...Reset means, R1 to R3...Resistors, TR1...Transistor, Vd...Power supply 5...Microcomputer, Pf5...Fault signal input terminal, Pr5...Reset signal output terminal, Pp5...PWM output terminal 6…Display section 7…Light source 10...Vehicle display device Vc...Automotive power supply, Sf...Fault signal, Sp...PWM control signal, Sr...Reset signal, Ss...Switching control signal, Vs...Voltage detection signal, IL...LED current, VL...LED voltage, t1 to t5...Time, Ta...Specified time

Claims

1. A vehicle display device, a display unit for displaying an image; a light source that illuminates the display unit; a driver that drives the light source; a microcomputer that controls the driving operation of the driver, The driver an abnormality determination unit that determines whether or not there is an abnormality in the vehicle display device; an abnormality signal output unit that outputs an abnormality occurrence signal indicating the occurrence of an abnormality when the abnormality determination unit determines that an abnormality has occurred; The microcomputer an abnormality signal input unit that inputs the abnormality occurrence signal; When the abnormality occurrence signal is input, a reset operation of the driver is performed, and when the reset operation reaches a predetermined number of times within a predetermined period, the driving operation of the driver is stopped; The period during which the reset operation is performed is set to a time period during which the abnormality determination unit can determine whether or not an abnormality exists. Vehicle display device.

2. the abnormality signal output unit continues to output the abnormality occurrence signal when the abnormality determination unit determines that an abnormality has occurred until the next reset operation is performed; The vehicle display device according to claim 1 .

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