Brightness adjustment methods, devices, head-up display equipment and media

Abstract

This disclosure provides a brightness adjustment method, apparatus, head-up display device, and medium. The brightness adjustment apparatus is applied to an image display unit including a light source and includes a temperature sensor, a light source driver, a display driver, and a controller. The light source driver includes a first control terminal and a second control terminal. The first control terminal receives a first control signal transmitted by the controller, and the second control terminal receives a second control signal output by the display driver. The controller acquires a temperature signal corresponding to the light source temperature; when the temperature is greater than a first threshold, it transmits the first control signal to the light source driver via the first control terminal to reduce the light source power; when the first control signal reaches a preset lower limit and the temperature is greater than a second threshold, it controls the display driver to output a second control signal via the second control terminal to continue reducing the light source power while the first control signal remains at the preset lower limit.

Description

Technical Field

[0001] This disclosure relates to the field of display control technology, and in particular to a brightness adjustment method, apparatus, head-up display device and medium. Background Technology

[0002] Head-up displays (HUDs) operate at high temperatures in automotive environments. In HUDs employing Liquid Crystal on Silicon (LCOS) display technology, the light source used to illuminate the LCOS display panel is typically one of the main heat sources in the image display unit. When the temperature of the light source or the thermally coupled lamp panel rises, the physical properties of the liquid crystal material within the LCOS display panel may change, causing color shift, decreased contrast, and motion blur. If the temperature continues to rise beyond the device's tolerance limit, it may trigger the LCOS display panel to enter protective shutdown, resulting in display interruption.

[0003] Therefore, for image display units or head-up display devices using LCOS technology, it is necessary to perform graded control on the power output from the light source driver to the light source after detecting the temperature signal corresponding to the light source temperature. Summary of the Invention

[0004] In a first aspect, this disclosure provides a brightness adjustment device applied to an image display unit, the image display unit including a light source. The brightness adjustment device includes a temperature sensor, a light source driver, a display driver, and a controller. The temperature sensor is configured to output a temperature signal corresponding to the temperature of the light source. The light source driver is connected to the light source and configured to control the power of the light source, the light source driver including a first control terminal and a second control terminal. The display driver is connected to the second control terminal of the light source driver. The controller is connected to the temperature sensor, the first control terminal of the light source driver, and the display driver respectively; the controller is configured to: acquire the temperature signal; when the temperature indicated by the temperature signal is greater than a first threshold, transmit a first control signal to the light source driver via the first control terminal to cause the light source driver to reduce the power of the light source; and when the first control signal reaches a preset lower limit and the temperature indicated by the temperature signal is greater than a second threshold, control the display driver to output a second control signal to the light source driver via the second control terminal to cause the light source driver to continue to reduce the power of the light source while the first control signal remains at the preset lower limit.

[0005] Secondly, this disclosure provides a brightness adjustment method executed by a controller of a brightness adjustment device. The method includes: acquiring a temperature signal corresponding to the temperature of a light source; when the temperature indicated by the temperature signal is greater than a first threshold, transmitting a first control signal to the light source driver via a first control terminal of the light source driver to cause the light source driver to reduce the power of the light source; and when the first control signal reaches a preset lower limit and the temperature indicated by the temperature signal is greater than a second threshold, controlling a display driver to output a second control signal to the light source driver via a second control terminal of the light source driver to cause the light source driver to continue reducing the power of the light source while the first control signal remains at the preset lower limit.

[0006] Thirdly, this disclosure provides an image display unit, comprising: a light source; an image generation unit that receives light emitted by the light source and generates an image; and the brightness adjustment device described in the first aspect, used to adjust the brightness of the light source.

[0007] Fourthly, this disclosure provides a head-up display device, including the image display unit described in the third aspect; and an optical projection component that projects the image generated by the image display unit onto a projection medium to form a virtual image.

[0008] Fifthly, this disclosure provides a computer-readable storage medium storing at least one instruction that is executed by a processor to implement the brightness adjustment method as described in the second aspect. Attached Figure Description

[0009] Figure 1 This is a schematic diagram of the structure of the head-up display device provided in this disclosure.

[0010] Figure 2 This is a schematic diagram of the structure of the image display unit provided in this disclosure.

[0011] Figure 3 This is a schematic diagram showing the correspondence between the duty cycle of the PWM signal and the power of the light source provided in this disclosure.

[0012] Figure 4 This is a schematic diagram of the structure of the display driver provided in this disclosure.

[0013] Figure 5 This is a schematic diagram illustrating the relationship between the temperature and power of the light source provided in this disclosure.

[0014] Figure 6 This is a flowchart illustrating a brightness adjustment method provided in this disclosure.

[0015] Figure 7 This is a flowchart illustrating another brightness adjustment method provided in this disclosure. Detailed Implementation

[0016] The technical solutions in this disclosure will now be clearly and completely described with reference to the accompanying drawings.

[0017] Figure 1 This is a schematic diagram of the structure of a head-up display device provided in this disclosure. Figure 1 In this configuration, the Head-Up Display (HUD) 100 is located within the vehicle's cockpit, specifically integrated into the instrument panel or the recessed space in front of the instrument panel. The HUD 100 presents instrument information, navigation guidance, and driving assistance information to the driver in the form of virtual images, reducing the driver's need to switch between looking at the road ahead and the in-vehicle instruments.

[0018] See Figure 1 The head-up display device 100 includes an image display unit 110 and an optical projection assembly 120. The image display unit 110 is used to generate a display image. The optical projection assembly 120 is optically coupled to the image display unit 110, projecting the display image generated by the image display unit 110 onto a projection medium 200, and forming a virtual image 300 in front of the projection medium 200.

[0019] exist Figure 1 In this configuration, the image display unit 110 includes a light source 111 and an image generation unit (PGU) 112. Light emitted from the light source 111 enters the image generation unit 112, and the image generation unit 112 generates a display image accordingly.

[0020] In some embodiments of this disclosure, the light source 111 may include a red light-emitting diode (LED), a green light-emitting diode, and a blue light-emitting diode disposed on a lamp panel. Furthermore, the light source 111 may be a combination light source including red LEDs, green LEDs, and blue LEDs, or it may be a monochromatic LED emitting white light.

[0021] The light source driver 132 outputs multiple driving signals corresponding to the red, green and blue light sources to the light source 111 to control the output brightness of the image generation unit 112.

[0022] In this disclosure, the image generation unit 112 employs a liquid crystal on silicon (LCOS) display panel. A reflective liquid crystal layer is integrated on the silicon substrate of the LCOS display panel, and the orientation of the liquid crystal molecules is changed by the image signal, thereby modulating the polarization state of the reflected light to form a display image.

[0023] exist Figure 1In this configuration, the optical projection assembly 120 includes at least one reflector and at least one lens. The reflector is used to change the optical path direction of the image generated by the image generation unit 112. The lens is used to magnify or correct distortion of the image.

[0024] In some examples, the optical projection assembly 120 may consist of a freeform mirror and a collimating lens. In other examples, the optical projection assembly 120 may consist of two plane mirrors and two freeform mirrors forming a multi-reflection structure. The output of the optical projection assembly 120 is reflected or partially reflected by the projection medium 200 and enters the driver's eye (E), appearing as a virtual image 300 suspended at a preset distance in front of the vehicle in the driver's viewing direction.

[0025] exist Figure 1 In this system, the projection medium 200 is used to reflect or partially reflect light from the optical projection component 120. In an in-vehicle head-up display, the projection medium 200 can be the windshield of the vehicle. Specifically, the projection medium 200 is a semi-reflective screen disposed in front of or integrated with the windshield.

[0026] In HUD 100, when light source 111 is an LED light source and PGU 112 is an LCOS display panel, the temperature rise of the LED light source used to illuminate the LCOS display panel can cause changes in the physical properties of the liquid crystal material within the LCOS display panel, potentially leading to color shift, decreased contrast, and motion blur. If the temperature continues to rise above the device's tolerance limit, it may also trigger the LCOS display panel to enter protective shutdown, resulting in display interruption.

[0027] In this disclosure, Figure 2 This is a schematic diagram of the image display unit 110. Figure 2 As shown, the image display unit 110 includes a brightness adjustment device 113, which, together with the light source 111 and the image generation unit 112, constitutes the three components of the image display unit 110. (See also...) Figure 2 The brightness adjustment device 113 may include a temperature sensor 131, an LED driver 132, an LCOS driver 133, and a controller 134.

[0028] In some brightness control schemes, the controller 134 can output control signals such as pulse width modulation signals directly to the control terminal of the light source driver 132, causing the light source driver 132 to reduce the average power of the light source. However, such control signals directly output by the controller 134 to the light source driver 132 are constrained by the controller clock resolution, the minimum recognizable pulse width of the light source driver, the risk of low duty cycle flicker, and the minimum visible brightness of the image display unit. When the control signal is reduced to a preset lower limit, further reduction may lead to light source driver instability, visible flicker, or sudden changes in display brightness. If the temperature of the light source 111 continues to rise at this time, the system usually has to enter shutdown protection, resulting in the interruption of the display output of the head-up display device.

[0029] For an image display unit 110 including a display driver 133 and a light source driver 132, there is usually a control link between the display driver 133 and the light source driver 132 for light source control or display timing coordination. However, existing brightness control schemes do not fully utilize this control link to continue reducing the light source power after the control signal directly applied by the controller 134 to the light source driver 132 reaches a preset lower limit; nor do they modify the registers related to light source control inside the display driver 133 to allow the display driver 133 to output another control signal through another control terminal of the light source driver 132, so that the light source driver 132 continues to reduce the light source power, while the control signal remains at the preset lower limit.

[0030] Therefore, this disclosure provides a brightness adjustment scheme in which the controller, when the temperature indicated by the temperature signal is greater than a first threshold, transmits a first control signal through the first control terminal of the light source driver to reduce the light source power; and when the first control signal reaches a preset lower limit and the temperature indicated by the temperature signal is greater than a second threshold, the controller modifies the registers related to light source control inside the display driver to control the display driver to output a second control signal through the second control terminal of the light source driver, so as to continue to reduce the light source power while the first control signal remains at the preset lower limit. The second threshold is greater than the first threshold.

[0031] In some embodiments, the controller 134 can be a microcontroller, the light source driver 132 can be a light-emitting diode driver, and the display driver 133 can be a silicon-based liquid crystal driver. The first control signal may include a pulse width modulation signal RGB_PWM and / or an enable signal LED_EN, and the second control signal may include a light source control signal LED_RGB output by the display driver 133 via a light source control link with the light source driver 132. The controller 134 can directly control the first control terminal 1321 of the light source driver 132 via the first control signal, and can configure the registers related to light source control inside the display driver 133 via a serial peripheral interface, so that the display driver 133 provides a second control signal to the light source driver 132 via the second control terminal 1322. Thus, the brightness adjustment device 113 forms a two-level control structure: coarse adjustment directly by the controller and fine adjustment on the display driver side.

[0032] exist Figure 2 In this embodiment, temperature sensor 131 can be positioned close to light source 111, outputting a temperature signal corresponding to the temperature of light source 111. Specifically, temperature sensor 131 may include a negative temperature coefficient (NTC) thermistor. The resistance value of this NTC thermistor decreases as the temperature increases. In this disclosure, the temperature signal corresponding to the temperature of light source 111 may include a signal directly characterizing the temperature of light source 111, or it may include a signal characterizing the temperature of the lamp board, light source substrate, heat sink, heat sink, or location thermally coupled to light source 111.

[0033] In some embodiments, a negative temperature coefficient thermistor can be placed on the lamp board where the light source 111 is located or at a position thermally coupled to the lamp board. The analog temperature signal output by the negative temperature coefficient thermistor can be input to the controller 134 via the analog-to-digital converter interface. The controller 134 calculates the lamp board temperature based on the analog-to-digital conversion sample value. The lamp board temperature can reflect the change in the heat load of the light source inside the image display unit 110 more directly than the ambient temperature of the vehicle compartment.

[0034] In some embodiments, a negative temperature coefficient thermistor can be disposed on the light source substrate of the light source 111. Figure 1 (Not shown in the image) A low thermal resistance channel is formed between the light source 111 and the light source 111, so that the temperature change of the light source 111 can be quickly reflected to the resistance value change of the negative temperature coefficient thermistor.

[0035] In other embodiments, the negative temperature coefficient thermistor can also be soldered to the back of the light source substrate at the position corresponding to the light source 111.

[0036] In other embodiments, the negative temperature coefficient thermistor can also be mounted on the side of the light source 111 package or on the surface of the light source heat dissipation substrate.

[0037] In other embodiments, a negative temperature coefficient thermistor is also embedded inside the metal heat sink of the light source 111.

[0038] exist Figure 2 In this configuration, the light source driver 132 is connected to the light source 111 and controls the power of the light source 111. The display driver 133 is connected to the light source driver 132. The display driver 133 is also connected to the image generation unit 112 and outputs an image signal to the image generation unit 112 to drive the image generation unit 112 to generate a display image based on the light from the light source 111. The controller 134 is connected to the temperature sensor 131, the light source driver 132, and the display driver 133, respectively.

[0039] See Figure 2 The controller 134 may include a temperature sampling interface 1341, a first brightness control output terminal 1342, and a second brightness control output terminal 1343. Specifically, the controller 134 is connected to the temperature sensor 131 via the temperature sampling interface 1341, to the light source driver 132 via the first brightness control output terminal 1342, and to the display driver 133 via the second brightness control output terminal 1343.

[0040] The temperature sampling interface 1341 may include an analog-to-digital converter interface for receiving the analog temperature signal output by the temperature sensor 131. The first brightness control output terminal 1342 may output a pulse width modulation signal and an enable signal, and the second brightness control output terminal 1343 may communicate with the display driver 133 through a serial peripheral interface.

[0041] See Figure 2 The light source driver 132 may include a first control terminal 1321 and a second control terminal 1322.

[0042] Specifically, the first control terminal 1321 is connected to the first brightness control output terminal 1342 of the controller 134. The second control terminal 1322 is connected to the output terminal of the display driver 133.

[0043] The light source driver 132 may also include a drive logic module 1323. The drive logic module 1323 can determine the drive current or conduction timing output by the light source driver 132 to the light source 111, and thus determine the power of the light source 111.

[0044] In some embodiments, the driving logic module 1323 jointly determines the effective driving energy output to the light source 111 based on a first control signal received from the first control terminal 1321 and a second control signal received from the second control terminal 1322. The first control signal can be used to determine the conduction ratio of the light source driving signal during the switching cycle; the second control signal can be used to determine the target current amplitude of the light source driving signal, the intra-frame conduction window, or the brightness ratio of the color channel. Thus, even when the first control signal has reached a preset lower limit and remains unchanged, the driving logic module 1323 can still reduce the average power of the light source 111 according to the second control signal.

[0045] In detail, the light source driver 132 can be implemented by a separate LED driver chip or integrated into a power management chip containing multiple functional modules, and this disclosure does not limit it in this way.

[0046] In this disclosure, the controller 134 receives the temperature signal output by the temperature sensor 131 and adjusts the power of the light source 111 in stages according to the temperature signal output by the temperature sensor 131. Specifically, the controller 134 in the head-up display device 100 can be implemented by a microcontroller unit (MCU). Alternatively, the controller 134 can also be implemented by an application-specific integrated circuit (ASIC) or a programmable logic device (PLC).

[0047] Specifically, the process by which controller 134 adjusts the power of light source 111 may include: When the temperature indicated by the temperature signal is lower than the first threshold, the controller 134 maintains the current control state, and the light source driver 132 drives the light source 111 according to the normal working configuration, and the light source 111 is at normal working power.

[0048] When the temperature indicated by the temperature signal exceeds the first threshold, the controller 134 transmits a first control signal to the first control terminal 1321 of the light source driver 132 via the first brightness control output terminal 1342. The first control signal causes the light source driver 132 to reduce the drive current or conduction time output to the light source 111, thereby reducing the power of the light source 111.

[0049] Specifically, the controller 134 can also continue to adjust the first control signal according to the continuous rise in temperature, so that the power of the light source 111 continues to decrease, thereby avoiding color drift, contrast reduction and motion blur caused by high temperature on the LCOS display panel.

[0050] In this disclosure, the first control signal is constrained by a preset lower limit during the aforementioned adjustment process. That is, after the first control signal reaches the preset lower limit, the controller 134 can no longer reduce the power of the light source 111 through the first control signal.

[0051] The preset lower limit can be determined by at least one of the following: the clock resolution of the controller 134, the minimum identifiable pulse width of the light source driver 132 for the first control signal, the flicker limitation of the light source 111 at a low duty cycle, and the minimum visible brightness of the image display unit 110. When the first control signal reaches the preset lower limit, the controller 134 keeps the first control signal at the preset lower limit state and does not continue to reduce the power of the light source 111 by reducing the first control signal.

[0052] When the first control signal reaches a preset lower limit and the temperature indicated by the temperature signal is greater than the second threshold, the controller 134 can control the display driver 133 via the second brightness control output terminal 1343, causing the display driver 133 to output a second control signal to the second control terminal 1322 of the light source driver 132 or change the already output second control signal. While the first control signal remains at the preset lower limit, the second control signal can further reduce the driving current, conduction timing, or effective light-emitting window within the display frame of the light source 111 in another control dimension, causing the power of the light source 111 to continue to decrease.

[0053] In detail, the second control signal is transmitted via an electrical connection between the display driver 133 and the second control terminal 1322 of the light source driver 132. This transmission path differs from the transmission path of the first control signal between the controller 134 and the first control terminal 1321 of the light source driver 132. The two transmission paths are physically independent and act on two different control terminals of the light source driver 132.

[0054] In this disclosure, the brightness adjustment device 113 acts relay-wise on the light source driver 132 via two independent transmission paths. The first brightness control path, i.e., the transmission path directly connected from the controller to the light source driver, can reduce the power of the light source 111 in the initial stage of temperature rise. The second brightness control path, i.e., the transmission path connecting the controller to the light source driver 132 via the display driver 133, can continue to reduce the power of the light source 111 after the first control path reaches the lower control limit. The relay operation of the two paths allows the power of the light source 111 to be continuously reduced without entering the shutdown protection state, thereby extending the available time for the image generation unit 112 to maintain display output in high-temperature environments.

[0055] In this disclosure, when the temperature rise cannot be prevented by the second control signal, the controller 134 enters the over-temperature protection stage, and can shut down the light source 111 or stop the image generation unit 112 from displaying by performing a protection operation.

[0056] In some embodiments, the above control structure may correspond to four control links. The first control link is a temperature acquisition link, whereby the temperature sensor 131 provides the lamp board temperature to the controller 134 via the temperature sampling interface 1341 or the analog-to-digital converter interface. The second control link is a first brightness control link, whereby the controller 134 directly controls the light source driver 132 through a first control signal and an enable signal, and the light source driver 132 reduces the drive output of the light source 111. In a specific embodiment, this link may correspond to a coarse adjustment link where the controller 134 transmits the pulse width modulation signal RGB_PWM or the enable signal LED_EN to the light source driver 132, and the light source driver 132 controls the brightness of the light source 111 through the multiple drive signal LED_R_G_B. The third control link is the second brightness control link, where the controller 134 modifies the internal registers of the display driver 133 through the serial peripheral interface, causing the display driver 133 to further influence the output of the light source driver 132 via the second control terminal 1322. In a specific embodiment, this link can correspond to the controller 134 modifying the internal registers of the display driver 133 through the Serial Peripheral Interface (SPI), the display driver 133 generating a light source control signal LED_RGB based on the register value and transmitting it to the light source driver 132, and the light source driver 132 controlling the fine-tuning of the brightness of the light source 111 through the multiplexed drive signal LED_R_G_B. The fourth control link is the over-temperature protection link, which shuts down the light source 111 or stops the image generation unit 112 from displaying when the temperature reaches the third threshold.

[0057] In some embodiments of this disclosure, the first control signal may be implemented using a pulse width modulation (PWM) signal. That is, the first control signal output by the controller 134 to the first control terminal 1321 of the light source driver 132 via the first brightness control output terminal 1342 may include a pulse width modulation signal. Figure 3 This is a schematic diagram illustrating the relationship between the duty cycle of a PWM signal and the power of a light source, as provided in this disclosure.

[0058] Figure 3 The upper part is a schematic diagram of the duty cycle change of the PWM signal waveform. Figure 3 In the diagram, the horizontal axis represents time t, and the vertical axis represents the PWM signal level. The waveform consists of three adjacent stages. The first stage has a duty cycle of D1, corresponding to a relatively high duty cycle level. The second stage has a duty cycle of D2, corresponding to a middle duty cycle level, and D2 is less than D1. The third stage has a duty cycle of Dmin, corresponding to a preset lower limit, and Dmin is less than D2.

[0059] Figure 3The lower half of the diagram illustrates the relationship between the light source power and the duty cycle of the pulse width modulation signal. The horizontal axis represents time t, and... Figure 3 The upper half of the graph is aligned. The vertical axis represents the light source power P. The light source power is P1 in the first stage, P2 in the second stage, and P1-min in the third stage. P1 is greater than P2, and P2 is greater than P1-min. P1-min is the light source power corresponding to the preset lower limit.

[0060] Combination Figure 3 The process by which the light source driver 132 controls the operation of the light source 111 according to the pulse width modulation signal received from the first control terminal 1321 may include: When the pulse width modulation signal is at a high level, the light source driver 132 provides driving current to the light source 111, causing the light source 111 to emit light. When the pulse width modulation signal is at a low level, the light source driver 132 stops providing driving current to the light source 111 or reduces the driving current to near zero, and the light source 111 does not emit light or is in a low brightness state.

[0061] Thus, when the frequency of the pulse width modulation signal is sufficiently high, such as 10kHz to 20kHz, the emission of light source 111 is equivalent to continuous emission rather than flickering on the response time scale of the human eye and optical components. The average power of light source 111 is proportional to the duty cycle of the pulse width modulation signal. A decrease in the duty cycle reduces the average emission time of light source 111 in each cycle, resulting in lower brightness and consequently lower average power.

[0062] In this disclosure, the light source driver 132 includes a sampling and response circuit (not shown) for identifying the edge of a pulse width modulation signal and controlling the on / off state of the drive current of the light source 111 accordingly. This sampling and response circuit has a minimum identifiable pulse width; that is, when the duty cycle of the pulse width modulation signal is lower than the lower limit corresponding to this minimum identifiable pulse width, the light source driver 132 cannot stably provide drive current to the light source 111. The light source 111 will exhibit visible low-frequency flicker at extremely low duty cycles, affecting display stability. Therefore, the preset lower limit of the first control signal can be constrained by the lower limit of the duty cycle corresponding to the minimum identifiable pulse width of the sampling and response circuit. Furthermore, the preset lower limit of the first control signal can also be constrained by the clock frequency of the controller.

[0063] In this disclosure, controller 134 may output a pulse width modulation signal to a light source driver via the following example.

[0064] For example, the controller 134 can look up the target duty cycle value corresponding to the current temperature according to the preset temperature-duty cycle lookup table, and output the pulse width modulation signal accordingly.

[0065] For example, the controller 134 can also use linear interpolation to map the current temperature to the corresponding value on a linear curve of the duty cycle from the initial duty cycle to the preset lower limit.

[0066] For example, the controller 134 uses a proportional-integral-derivative control method to dynamically adjust the duty cycle based on the difference between the current temperature and the first threshold.

[0067] In addition, when the light source 111 consists of a red light source, a green light source, and a blue light source, the controller 134 can output three pulse width modulation signals corresponding to the red, green, and blue channels to the light source driver 132. The light source driver 132 controls the power of the red, green, and blue light sources respectively according to the duty cycles of the three pulse width modulation signals. When the duty cycles of the three pulse width modulation signals decrease in response to temperature changes, they can be reduced synchronously in the same proportion, so that the overall white balance of the light source 111 remains stable during brightness adjustment.

[0068] In some embodiments, the three pulse width modulation signals corresponding to the red, green, and blue channels can be the pulse width modulation signal RGB_PWM output by the controller 134 to the light source driver 132. The controller 134 can also output an enable signal LED_EN to the light source driver 132. During the first stage of brightness adjustment, the enable signal LED_EN remains active, and the duty cycle of the pulse width modulation signal RGB_PWM decreases as the temperature increases; during the over-temperature protection stage, the controller 134 can set the enable signal LED_EN to inactive to turn off the light source driver 132's drive of the light source 111.

[0069] In this embodiment, the controller 134 transmits a pulse width modulation signal as the first control signal to the first control terminal 1321 of the light source driver 132. The light source driver 132 controls the power of the light source 111 according to the duty cycle of the pulse width modulation signal. The reduction of the duty cycle of the pulse width modulation signal reduces the average power of the light source 111, thereby effectively suppressing the heat generation power of the light source 111 in the early stage of temperature rise.

[0070] In this disclosure, the duty cycle of the pulse width modulation signal is constrained by a preset lower limit. When the duty cycle of the pulse width modulation signal reaches the preset lower limit, the controller 134 cannot continue to reduce the power of the light source by reducing the duty cycle of the pulse width modulation signal output to the light source driver 132. In this case, if the temperature continues to rise and reaches a second threshold, the controller 134 can control the display driver 133 to output a second control signal to the light source driver 132, so that the light source driver 132 continues to reduce the power of the light source 111.

[0071] In some embodiments of this disclosure, the display driver 133 may include a register, and the controller 134 modifies the value of the register so that the display driver 133 outputs a second control signal corresponding to the value of the register to the light source driver 132.

[0072] Figure 4 This is a schematic diagram of the structure of the display driver provided in this disclosure. Figure 4 In this design, the display driver 133 includes a serial peripheral interface 1331 and a register 1332. The controller 134 is bidirectionally connected to the SPI 1331 of the display driver 133 via a second brightness control output terminal 1343. The controller 134 writes control data to the display driver 133 through the serial peripheral interface 1331. The written control data is used to modify the value of the register 1332 inside the display driver 133.

[0073] The display driver 133 determines the second control signal to be output to the second control terminal 1322 of the light source driver 133 based on the value of the register 1332. When the value of the register 1332 changes, the second control signal output by the display driver 133 changes accordingly.

[0074] In some embodiments, the internal register 1332 of the display driver 133 may include a register related to the control of the light source control signal LED_RGB. After the controller 134 modifies the register through the serial peripheral interface 1331, the display driver 133 changes the second control signal through the LED_RGB control link between itself and the light source driver 132, so that the light source driver 132 further reduces the driving state of the output to the red light source, green light source and blue light source.

[0075] Specifically, the serial peripheral interface 1331 can be implemented using a master-slave synchronous serial communication interface, including a serial clock line, master output / slave input data lines, master input / slave output data lines, and a chip select line. More specifically, the controller 134 acts as the master device, and the display driver 133 acts as the slave device. When the controller 134 writes control data to the display driver 133 through this interface, it first pulls the chip select line low to put the display driver 133 into a receiving state, and then sends the control data bit by bit through the master output / slave input data lines under the synchronization of the serial clock line. The control data includes a register address and the value to be written. After receiving the complete control data, the display driver 133 stores the value to be written into the register location at the corresponding address. Alternatively, the controller 134 and the display driver 133 can also be connected using an Inter-Integrated Circuit (I2C) bus or other general-purpose digital serial communication interfaces.

[0076] like Figure 4As shown, register 1332 may include at least one of the following: duty cycle register 1332-1, conduction window register 1332-2, color channel brightness ratio register 1332-3, and current control parameter register 1332-4. In this disclosure, register 1332 may contain only one of the above four types of registers, or it may contain two, three, or all four types simultaneously.

[0077] The following sections describe the implementation methods for brightness adjustment corresponding to various registers.

[0078] In some implementations, the duty cycle register 1332-1 is used to store a value representing the duty cycle of the second control signal. The controller 134 writes control data to the duty cycle register 1332-1 through the serial peripheral interface 1331, causing the value of the duty cycle register 1332-1 to change.

[0079] The display driver 133 generates a second control signal with a corresponding duty cycle based on the current value of the duty cycle register 1332-1, and outputs it to the light source driver 132 via the second control terminal 1322. The light source driver 132 adjusts the on-time ratio of the light source drive signal generated internally accordingly.

[0080] In detail, the duty cycle value stored in the duty cycle register 1332-1 is proportional to the duty cycle of the second control signal output by the display driver 133. A decrease in the value of the duty cycle register 1332-1 reduces the duty cycle of the second control signal, thereby reducing the power of the light source 111.

[0081] In this embodiment, the duty cycle of the first control signal is constrained by the clock frequency of the controller and the minimum identifiable pulse width input to the light source driver 132, forming a preset lower limit. The second control signal is input to the light source driver 132 via the second control terminal 1322, and its duty cycle is determined by the value of the duty cycle register 1332-1. The resolvable minimum step size is only limited by the register bit width and is not limited by the clock resolution of the controller 134. This allows the numerical resolution supported by the duty cycle of the second control signal to be higher than the resolution supported by the duty cycle of the first control signal directly generated by the controller 134.

[0082] In other embodiments, the conduction window register 1332-2 is used to store the value representing the conduction window of the light source 111 within a display frame. The conduction window refers to the start time and duration of the light source 111 emitting light within each display frame cycle. The controller 134 writes control data to the conduction window register 1332-2 through the serial peripheral interface 1331, causing the value of the conduction window register 1332-2 to change.

[0083] The display driver 133 generates a second control signal corresponding to the conduction window based on the current value of the conduction window register 1332-2, and outputs it to the light source driver 132 via the second control terminal 1322. The light source driver 132 then adjusts the effective output period of its internally generated light source drive signal within each display frame accordingly.

[0084] In detail, when light source 111 consists of red, green, and blue light sources, the red, green, and blue light sources are turned on sequentially within each display frame, with each color corresponding to a specific conduction window. When the value stored in the conduction window register 1332-2 changes, the timing or duration of the corresponding color light source's activation changes accordingly, reducing the cumulative light-emitting time of light source 111 within each display frame and lowering the average power. Compared to the duty cycle register 1332-1, which adjusts the ratio of high to low levels within a single switching cycle, the conduction window register 1332-2 adjusts the position and width of the light source's on-time within a single display frame.

[0085] In other embodiments, when the light source 111 consists of a red light source, a green light source, and a blue light source, the color channel brightness ratio register 1332-3 is used to store values ​​representing the relative brightness ratios between the three color channels: red, green, and blue. The color channel brightness ratio register 1332-3 may include sub-registers corresponding to the red, green, and blue channels respectively, with each sub-register storing the brightness ratio value for one channel. The controller 134 writes control data to the color channel brightness ratio register 1332-3 via the serial peripheral interface 1331, causing the brightness ratio values ​​of the three channels to change synchronously.

[0086] The display driver 133 generates second control signal components corresponding to the three channels based on the current value of the color channel brightness ratio register 1332-3, and outputs them to the light source driver 132 via the second control terminal 1322. The light source driver 132 adjusts its drive signals to the red, green, and blue light sources accordingly.

[0087] In detail, when the brightness ratios of the three channels are reduced synchronously at the same ratio, the overall white balance and color temperature of the light source 111 remain unchanged during the brightness adjustment process, avoiding color drift during the brightness reduction. In another embodiment, the brightness ratios of the three channels are adjusted asynchronously at different ratios, so that the white balance of the light source 111 changes according to a preset rule during the brightness adjustment process, in order to compensate for the influence of temperature on the color response characteristics of the silicon-based liquid crystal display panel.

[0088] In some other embodiments, the current control parameter register 1332-4 is used to store a value characterizing the target value of the operating current of the light source 111. The controller 134 writes control data to the current control parameter register 1332-4 through the serial peripheral interface 1331, causing the value of the current control parameter register 1332-4 to change.

[0089] The display driver 133 generates a corresponding second control signal based on the current value of the current control parameter register 1332-4, and outputs it to the light source driver 132 via the second control terminal 1322.

[0090] For example, the second control signal may include an analog voltage signal characterizing the target current. The light source driver 132 adjusts the amplitude of the drive current output to the light source 111 via its internal current regulation circuitry accordingly.

[0091] In other examples, the second control signal may include a target current value in digital code form; the digital-to-analog converter circuit inside the light source driver 132 converts the digital code into a corresponding current regulation voltage, thereby adjusting the amplitude of the drive current.

[0092] Specifically, reducing the value of the current control parameter register 1332-4 reduces the operating current amplitude of the light source 111, and consequently reduces the luminous power of the light source 111.

[0093] In this embodiment, the controller 134 uses the serial peripheral interface 1331 as a communication channel and controls the second control signal output by the display driver 133 to the light source driver 132 by modifying the value of the internal register 1332 of the display driver 133. The specific physical dimensions set in the register 1332 may include any one or more of the following: duty cycle, conduction window, color channel brightness ratio, or current control parameters. The display driver 133 can change the second control signal according to multiple configurable values ​​of the register 1332, so that the light source driver 132 can perform multi-level adjustments to the driving current amplitude, intra-frame conduction window, or color channel brightness ratio output to the light source 111 after the first control signal reaches a preset lower limit.

[0094] Compared with the coarse adjustment stage where the controller 134 directly outputs the first control signal, the internal register 1332 of the display driver 133 can set the duty cycle, conduction window, color channel brightness ratio or current control parameters of the second control signal in the form of multi-level values, so that the second stage adjustment has finer adjustment steps in the low brightness range, thereby reducing brightness abrupt changes and delaying or avoiding the image display unit 110 from directly entering the shutdown protection.

[0095] In some embodiments of this disclosure, combined with Figure 5 The protection operation is described. Figure 5This is a schematic diagram illustrating the relationship between light source temperature and power. Figure 5 In the diagram, the horizontal axis represents the temperature T of the light source 111, and three threshold points are marked on the horizontal axis: the first threshold T1, the second threshold T2, and the third threshold T3. The vertical axis represents the power P of the light source 111.

[0096] The relationship between light source temperature and power is as follows: Figure 5 As shown in the curve, this curve can be divided into four stages based on three threshold points. The first stage corresponds to the temperature range below the first threshold T1, where the power of light source 111 maintains the normal operating power Pnormal. The second stage corresponds to the temperature range between the first threshold T1 and the second threshold T2, where the power of light source 111 decreases based on the first control signal, and the curve ends at the preset lower limit corresponding to power P1-min. The third stage corresponds to the temperature range between the second threshold T2 and the third threshold T3, where the power of light source 111 continues to decrease based on the second control signal, and the curve continues to extend downwards. When the power of light source 111 drops to P2-min and the temperature reaches or exceeds the third threshold, it enters the fourth stage. The fourth stage corresponds to the temperature range reaching or exceeding the third threshold T3, where the power of light source 111 drops to zero or near zero based on protection operation.

[0097] It should be noted that, Figure 5 The boundary between the second and third stages does not mean that the controller automatically switches to the second control signal simply because the temperature reaches the second threshold T2. For the controller 134 to enter the adjustment stage based on the second control signal, both the first control signal must reach a preset lower limit and the temperature indicated by the temperature signal must be greater than the second threshold T2. If only one of these conditions is met, the controller 134 can maintain the current control stage or continue to adjust based on the first control signal.

[0098] In this disclosure, the first threshold T1, the second threshold T2, and the third threshold T3 satisfy the relationship that T1 is less than T2 and T2 is less than T3. The first threshold T1 can be set to 85°C as a warning temperature for starting to reduce the power of the light source 111 via the first control signal. The second threshold T2 can be set to 95°C as the temperature condition for entering the second control stage after the first control signal reaches a preset lower limit. The third threshold T3 can be set to 100°C as the temperature for performing protection operations.

[0099] When the temperature indicated by the temperature signal reaches the third threshold T3, the controller 134 performs a protection operation to turn off the light source 111 or stop the image generation unit 112 from displaying. Specific implementations of the protection operation may include at least one of the following embodiments.

[0100] In some embodiments, the controller 134 sets a first control signal via a first brightness control output terminal 1342 to a state that causes the light source driver 132 to stop providing drive current to the light source 111. Specifically, the controller 134 reduces the duty cycle of the pulse width modulation signal, which serves as the first control signal, to zero or sets the pulse width modulation signal to a continuous low level. Accordingly, the light source driver 132 stops outputting drive current to the light source 111, and the light source 111 stops emitting light.

[0101] In other embodiments, the controller 134 outputs an independent enable control signal to the light source driver 132 via the first brightness control output terminal 1342. This enable control signal is used to switch the enable state of the light source driver 132. The controller 134 sets the enable control signal to an invalid state, causing the light source driver 132 to enter a disabled state and stop providing any drive current to the light source 111. Compared with the embodiment that directly sets the pulse width modulation signal to zero, this embodiment can also put some circuits inside the light source driver 132 into a low-power state, further reducing the overall power consumption during protection operation.

[0102] In some other embodiments, the controller 134 writes protection control data to the display driver 133 via the second brightness control output terminal 1343. This protection control data causes the register 1332 of the display driver 133 to enter a preset protection state. Accordingly, the display driver 133 stops outputting a valid second control signal to the second control terminal 1322 of the light source driver 132, or sets the second control signal to a state that causes the light source driver 132 to stop outputting drive current. Accordingly, the light source driver 132 stops providing drive current to the light source 111, and the light source 111 stops emitting light.

[0103] In some other embodiments, while performing protection operations, the controller 134 may also output a command signal or control signal to the image generation unit 112 to turn off the display. This command signal or control signal causes the image generation unit 112 to enter a stopped display state, preventing the image generation unit 112 from incurring additional heat load due to the continuous operation of the liquid crystal cell after the light source 111 has been turned off.

[0104] After performing the protection operation, the controller 134 can continue to monitor the temperature signal output by the temperature sensor 131. When the temperature indicated by the temperature signal decreases from the third threshold T3 to below the preset recovery temperature, the controller 134 restores the driving state of the light source 111 according to a preset strategy. The preset recovery temperature can be lower than the second threshold T2 or lower than the first threshold T1 to form a temperature hysteresis range between turning off protection and restoring display, reducing the risk of repeated switching.

[0105] In this embodiment, when the temperature reaches the third threshold T3, the controller 134 performs a protection operation to shut down the light source 111. Shutting down the light source 111 stops it from generating heat as the main heat source for the image generation unit 112, and the temperature of the light source 111 drops rapidly, preventing aging or damage to the silicon-based liquid crystal display panel device caused by continuous temperature increases.

[0106] Please see Figure 6 The diagram illustrates a flow chart of the brightness adjustment method provided in this disclosure. This method is applied to the brightness adjustment device 113 disclosed in the foregoing embodiments, and is executed collaboratively by the controller 134 in the brightness adjustment device 113 in conjunction with the temperature sensor 131, the light source driver 132, and the display driver 133.

[0107] See Figure 6 In step S610, a temperature signal corresponding to the temperature of the light source is received.

[0108] Specifically, the controller 134 can receive the temperature signal output by the temperature sensor 131, which corresponds to the temperature of the light source 111, through the temperature sampling interface 1341.

[0109] See Figure 6 In step S620, it is determined whether the temperature indicated by the temperature signal is greater than the first threshold. If the temperature indicated by the temperature signal is not greater than the first threshold, the controller 134 maintains the current control state and returns to step S610 to continue monitoring the temperature signal.

[0110] If the temperature indicated by the temperature signal is greater than the first threshold, the controller 134 enters step S630: transmits a first control signal to the light source driver to cause the light source driver to reduce the power of the light source.

[0111] Specifically, the controller 134 can transmit a first control signal to the first control terminal 1321 of the light source driver 132 via the first brightness control output terminal 1342, causing the light source driver 132 to reduce the power of the light source 111. The first control signal may include a pulse width modulation signal.

[0112] See Figure 6 In step S640, the controller 134 determines whether the current state of the first control signal is at a preset lower limit and whether the temperature indicated by the temperature signal is greater than the second threshold.

[0113] If the first control signal has not yet reached the preset lower limit, or the temperature indicated by the temperature signal is not greater than the second threshold, the controller 134 returns to step S630 to continue adjusting the first control signal according to the temperature signal.

[0114] If the first control signal reaches the preset lower limit and the temperature indicated by the temperature signal is greater than the second threshold, the controller 134 enters step S650: controlling the display driver to output the second control signal so that the light source driver continues to reduce the power of the light source.

[0115] Specifically, the controller 134 controls the display driver 133 via the second brightness control output terminal 1343. It can also modify the values ​​of registers related to light source control within the display driver 133 to cause the display driver 133 to output a second control signal to the second control terminal 1322 of the light source driver 132, or to change the already output second control signal, thereby causing the light source driver 132 to further reduce the power of the light source 111. A specific implementation of controlling the display driver 133 includes modifying the values ​​of the internal register 1332 of the display driver 133 via the serial peripheral interface 1331, as described in the previous embodiments, and will not be repeated here.

[0116] In step S650, the display driver 133 can output a second control signal to the light source driver 132 via the second control terminal 1322 based on the modified value of the register 1332. The drive logic module 1323 of the light source driver 132, while the first control signal remains at a preset lower limit, adjusts the drive current amplitude, the brightness ratio of the intra-frame conduction window, or the color channel according to the second control signal, thereby further reducing the average power of the light source 111.

[0117] After the above steps, if the temperature of light source 111 continues to rise, see [link to relevant documentation]. Figure 7 After steps S610 to S650 above, the controller 134 will enter step S660: determine whether the temperature has reached the third threshold.

[0118] Specifically, controller 134 can compare the temperature indicated by the temperature signal with the magnitude of a third threshold. If the temperature indicated by the temperature signal does not reach the third threshold, controller 134 returns to step S650 to continue adjusting the control of the display driver 133 according to the temperature signal.

[0119] If the temperature indicated by the temperature signal reaches the third threshold, the controller 134 enters step S670: performing a protection operation to turn off the light source 111 or to stop the image generation unit 112 from displaying.

[0120] Specifically, the specific implementation methods for the protection operation are the same as those described in the foregoing embodiments, and will not be repeated here.

[0121] This disclosure also provides a computer-readable storage medium storing at least one instruction that is executed by a processor to implement the brightness adjustment method described in the above embodiments.

[0122] This disclosure also provides a computer program product including computer instructions stored in a computer-readable storage medium; a processor of a computing device reads the computer instructions from the computer-readable storage medium and executes the computer instructions, causing the computing device to perform the brightness adjustment method described in the above embodiments.

[0123] Those skilled in the art will recognize that the functions described in this disclosure in one or more of the examples above can be implemented using hardware, software, firmware, or any combination thereof. When implemented in software, these functions can be stored in a computer-readable medium or transmitted as one or more instructions or code on a computer-readable medium. Computer-readable media include computer storage media and communication media, wherein communication media include any medium that facilitates the transfer of a computer program from one place to another. Storage media can be any available medium accessible to a general-purpose or special-purpose computer.

[0124] It should be noted that the technical solutions described in this disclosure can be combined arbitrarily as long as they do not conflict.

[0125] The above description is merely a specific embodiment of this disclosure, but the scope of protection of this disclosure is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this disclosure should be included within the scope of protection of this disclosure.

Claims

1. A luminance adjusting device, characterized by comprising: The brightness adjustment device is applied to the image display unit, the image display unit includes a light source, and the brightness adjustment device includes: A temperature sensor configured to output a temperature signal corresponding to the temperature of the light source; A light source driver, connected to the light source and configured to control the power of the light source, the light source driver including a first control terminal and a second control terminal; The display driver is connected to the second control terminal of the light source driver; and The controller is connected to the temperature sensor, the first control terminal of the light source driver, and the display driver, respectively. The controller is configured to: acquire the temperature signal; when the temperature indicated by the temperature signal is greater than a first threshold, transmit a first control signal to the light source driver via the first control terminal to cause the light source driver to reduce the power of the light source; and when the first control signal reaches a preset lower limit and the temperature indicated by the temperature signal is greater than a second threshold, control the display driver to output a second control signal to the light source driver via the second control terminal to cause the light source driver to continue to reduce the power of the light source while the first control signal remains at the preset lower limit, wherein the second threshold is greater than the first threshold.

2. The brightness adjustment device according to claim 1, characterized in that, The temperature sensor includes a negative temperature coefficient thermistor disposed on the lamp board of the light source or at a position thermally coupled to the lamp board, and the controller acquires the temperature signal output by the negative temperature coefficient thermistor via an analog-to-digital conversion interface.

3. The brightness adjustment device according to claim 1, characterized in that, The first control signal includes a pulse width modulation signal, and the light source driver reduces the power of the light source according to the duty cycle of the pulse width modulation signal; the preset lower limit is the lower limit of the duty cycle of the pulse width modulation signal.

4. The brightness adjustment device according to claim 3, characterized in that, The light source includes a red light source, a green light source, and a blue light source, and the pulse width modulation signal includes multiple pulse width modulation signals corresponding to the red light source, the green light source, and the blue light source, respectively.

5. The brightness adjustment device according to claim 3, characterized in that, The duty cycle lower limit is determined based on at least one of the following: the minimum recognizable pulse width of the light source driver, the clock resolution of the controller, the flicker limitation of the light source, and the minimum visible brightness of the image display unit.

6. The brightness adjustment device according to claim 1, characterized in that, The display driver includes registers related to light source control, and the controller is configured to modify the value of the registers so that the display driver outputs a second control signal corresponding to the value of the registers.

7. The brightness adjustment device according to claim 6, characterized in that, The controller is connected to the display driver via a serial peripheral interface, and the controller writes control data to the display driver via the serial peripheral interface to modify the value of the register.

8. The brightness adjustment device according to claim 1, characterized in that, The second control signal is used to perform multi-level adjustment on at least one of the following: the amplitude of the driving current output by the light source driver to the light source, the brightness ratio of the intra-frame conduction window, or the color channel after the first control signal reaches the preset lower limit.

9. The brightness adjustment device according to claim 1, characterized in that, The controller is further configured to perform a protection operation to shut down the light source or stop the image generation unit of the image display unit from displaying when the temperature indicated by the temperature signal reaches a third threshold; wherein the protection operation includes at least one of the following: setting the enable signal output to the light source driver to an invalid state, setting the first control signal to a closed state, writing protection control data to the display driver, or controlling the image generation unit to stop displaying; wherein the third threshold is greater than the second threshold.

10. A brightness adjustment method, characterized in that, The method is executed by a controller of a brightness adjustment device, the brightness adjustment device including a temperature sensor, a light source driver, and a display driver, the light source driver including a first control terminal and a second control terminal, and the method includes: Acquire the temperature signal corresponding to the temperature of the light source; When the temperature indicated by the temperature signal is greater than a first threshold, a first control signal is transmitted to the light source driver via the first control terminal to cause the light source driver to reduce the power of the light source; and, When the first control signal reaches a preset lower limit and the temperature indicated by the temperature signal is greater than a second threshold, the display driver is controlled to output a second control signal to the light source driver via the second control terminal, so that the light source driver continues to reduce the power of the light source while the first control signal is kept at the preset lower limit; wherein, the second threshold is greater than the first threshold.

11. A head-up display device, characterized in that, The head-up display device includes: an image display unit and an optical projection component; The image display unit includes: a light source; an image generation unit that receives light emitted by the light source and generates an image; and a brightness adjustment device according to any one of claims 1 to 9, for adjusting the brightness of the light source. The optical projection component projects the image generated by the image display unit onto the projection medium to form a virtual image.

12. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores at least one instruction, which is executed by a processor to implement the brightness adjustment method as described in claim 10.

Images