A vehicle-mounted display screen backlight brightness control system

Abstract

The application relates to the technical field of vehicle-mounted display device manufacturing, and discloses a vehicle-mounted display screen backlight brightness control system which comprises a feature extraction unit, a state solving unit and a driving control unit. The feature extraction unit avoids sampling the sampling voltage of a light-emitting diode in a pulse width modulation conduction stage to exclude parasitic voltage drops in combination with driving current and loop impedance to solve intrinsic forward voltage. The state solving unit solves real-time junction temperature according to the difference between the intrinsic forward voltage and a reference voltage and a correlation coefficient. The driving control unit outputs a compensation driving pulse according to the real-time junction temperature to query a compensation matrix, and outputs a reduced protection current when the junction temperature is over the limit. The application eliminates the interference of loop parasitic voltage drops on sampling, realizes accurate inversion of chip junction temperature and adaptive brightness compensation, effectively avoids display error reduction and stroboscopic, and guarantees full-temperature-domain display uniformity and reliability.

Description

Technical Field

[0001] This invention belongs to the field of automotive display device manufacturing technology, and particularly relates to an automotive display screen backlight brightness control system. Background Technology

[0002] Currently, most automotive display backlight modules use surface-mount LEDs as the light source. As the semiconductor junction temperature rises, the luminous flux and luminous efficiency of the LEDs will decrease non-linearly. Existing display driving methods typically use thermistors located on the edge of the printed circuit board to collect the ambient temperature and output a pulse width modulation duty cycle compensation signal to the entire backlight array based on the measured temperature.

[0003] As automotive displays become thinner and more integrated, the density of LEDs within a limited space gradually increases. Significant temperature variations within the cabin and direct sunlight cause noticeable temperature differences between the center and edge areas of the backlight module. Existing centralized temperature measurement methods typically represent the temperature of individual discrete LED units with the overall temperature, failing to reflect spatial thermal resistance and localized heat accumulation at different locations. LEDs in high-temperature areas are therefore prone to greater heat loads, leading to a faster decline in luminous efficiency and distortion of brightness and color within the display surface. Besides limitations in the layout of temperature detection hardware, existing backlight control methods also have significant shortcomings in their adjustment logic. For example, Chinese invention patent application CN113851088A discloses an adaptive backlight control system and method for automotive instruments. This system uses a light sensor and a screen temperature sensor to collect ambient illuminance and the macroscopic temperature of the display screen, and adjusts the duty cycle of the pulse width modulation signal according to a preset temperature control range. However, this control method... The current solution uses the overall macroscopic temperature of the screen as the temperature control criterion, which cannot reflect the true internal junction temperature of each light-emitting chip in the high-density array. Furthermore, the adjustment process does not consider the interference of parasitic voltage drop and transient oscillations in the circuit under high-frequency pulse drive on the sampling signal, which can easily lead to lag in luminous efficiency compensation and backlight jumps and flickering near the critical temperature. In order to obtain the temperature state of individual light-emitting devices, the existing solution also attempts to use the characteristic of the forward conduction voltage of the light-emitting diode changing with temperature to invert the junction temperature by collecting the voltage across the device. However, under the conditions of dense wiring and pulse width modulation high current drive, the copper foil of the printed circuit board trace has parasitic resistance that changes with temperature, and the power switch also has on-resistance. When the drive current flows through these parasitic impedances, it will generate additional voltage drop, which will be superimposed on the sampling voltage, causing the collected terminal voltage to deviate from the forward voltage of the PN junction of the light-emitting diode itself. At the same time, the pulse width modulation signal will also cause the charging and discharging oscillation of parasitic inductance and parasitic capacitance when the level jumps, further interfering with the sampling voltage.

[0004] Therefore, under the pulse driving conditions of automotive high-density backlight modules, how to reduce the impact of circuit parasitic voltage drop and switching transient oscillation on the sampling signal, accurately obtain the actual junction temperature of the light-emitting unit, and perform stable dynamic compensation and anti-flicker control accordingly has become the technical problem to be solved by this invention. Summary of the Invention

[0005] To address the problems in the background art, the technical solution of the present invention is as follows: A vehicle-mounted display screen backlight brightness control system, comprising: The feature extraction unit is connected to the target light-emitting diode in the backlight module of the vehicle display screen. During the conduction phase of the pulse width modulation constant current drive cycle, it delays to avoid the transient oscillation of the switch and samples the real-time sampling voltage across the target light-emitting diode during the constant plateau period to obtain the real-time drive current. The real-time drive current is multiplied by the parasitic impedance of the loop to calculate the parasitic voltage drop of the loop. The parasitic voltage drop of the loop is subtracted from the real-time sampling voltage to calculate the intrinsic real-time positive voltage. The state calculation unit, connected to the feature extraction unit, stores the calibration reference forward voltage, reference junction temperature and voltage-temperature correlation coefficient. It is used to calculate the forward voltage difference between the intrinsic real-time forward voltage and the calibration reference forward voltage, and to calculate the real-time junction temperature of the target light-emitting diode by combining the voltage-temperature correlation coefficient and the reference junction temperature. The drive control unit is connected to the state calculation unit and the target light-emitting diode, respectively. It has a built-in compensation matrix that defines the correspondence between junction temperature, target luminous flux and compensation forward current. It is used to determine the compensation forward current by querying the compensation matrix based on the real-time junction temperature. When the real-time junction temperature is lower than the junction temperature safety threshold, it outputs a drive pulse modulated with compensation forward current to the target light-emitting diode. When the real-time junction temperature reaches the junction temperature safety threshold, it outputs a derating protection current. When the real-time junction temperature falls back to below the hysteresis recovery temperature, it resumes outputting the drive pulse modulated with compensation forward current.

[0006] Preferably, the feature extraction unit includes a switching transient shielding module and a voltage correction module; the switching transient shielding module is used to delay the preset conduction stabilization time after the rising edge of the drive pulse in the pulse width modulation constant current drive cycle to avoid the charging and discharging oscillation of the parasitic inductance and capacitance of the circuit, and to sample and hold the real-time sampling voltage during the current constant plateau period; the voltage correction module is used to multiply the real-time drive current by the circuit parasitic impedance to obtain the circuit parasitic voltage drop, subtract the circuit parasitic voltage drop from the real-time sampling voltage, and output the intrinsic real-time positive voltage to the state calculation unit.

[0007] Preferably, the target light-emitting diode is a surface-mount semiconductor light-emitting device with a package structure of a plastic chip carrier with leads, a viewing angle of 120° and a size of 4.0mm × 1.4mm × 0.7mm, a rated power of 0.2W to 0.5W, and a dynamic luminous flux output range of 24lm to 75lm within an operating temperature range of -40℃ to 110℃.

[0008] Preferably, the voltage-temperature correlation coefficient stored in the state calculation unit is predetermined by the electrical parameters under calibration low temperature and calibration high temperature conditions; under calibration conditions where the calibration low temperature is set to 20℃ to 30℃ and the measured calibration low temperature forward voltage is 2.12V to 3.22V, and the calibration high temperature is set to 90℃ to 120℃ and the measured calibration high temperature forward voltage is 2.23V to 3.25V, the voltage-temperature correlation coefficient is calibrated to 480℃ / V to 510℃ / V, the calibration reference forward voltage is set to 2.15V to 3.58V, and the reference junction temperature is set to 20℃ to 30℃.

[0009] Preferably, the compensation matrix embedded in the drive control unit is pre-calibrated based on the luminous efficiency decay curve of the target light-emitting diode at different junction temperatures. When the real-time junction temperature rises within the range of 25°C to 110°C, the compensation matrix outputs a monotonically increasing compensation positive current to compensate for the luminous flux decay of the target light-emitting diode caused by the temperature rise, and maintains the constant luminous flux output of the vehicle display screen at the set level.

[0010] Preferably, the drive control unit includes a pulse width modulation (PWM) generation module and a power drive stage circuit; the PWM generation module is used to adjust the duty cycle of the output pulse based on the compensation positive current obtained by querying the compensation matrix; the power drive stage circuit is connected to the PWM generation module and is used to output a pulse drive current of corresponding intensity to the target light-emitting diode in response to the adjusted duty cycle.

[0011] Preferably, the junction temperature safety threshold is set to 100°C to 120°C; the derating protection current is less than the rated operating current of the target LED at a reference junction temperature of 20°C to 30°C; the hysteresis recovery temperature is set to a temperature threshold 10°C to 15°C lower than the junction temperature safety threshold. The drive control unit continuously outputs the derating protection current before the real-time junction temperature of the target LED drops from above 110°C to below the hysteresis recovery temperature, so as to prevent the backlight brightness from fluctuating at the critical point of the junction temperature safety threshold.

[0012] Preferably, the loop parasitic impedance includes the sum of the equivalent parasitic resistance of the copper foil of the printed circuit board trace in the backlight module of the vehicle display screen and the on-state resistance of the power switch. The calibrated resistance value of the loop parasitic impedance is between 0.30Ω and 0.80Ω, which is used to offset the millivolt-level sampling level superposition error caused by the drive current flowing through the copper foil of the trace and the internal resistance of the switch in the feature extraction unit.

[0013] Preferably, the vehicle display backlight module includes multiple light-emitting diode (LED) units arranged in a matrix. The feature extraction unit, state calculation unit, and drive control unit each form an independent closed-loop control loop with each LED unit. This loop is used to perform spatially discretized independent junction temperature calculation and differentiated brightness compensation for different LED units in the central and edge areas of the vehicle display backlight module, so as to eliminate the local brightness and color uniformity of the vehicle display under extreme temperature difference conditions.

[0014] Compared with existing technologies, the vehicle-mounted display screen backlight brightness control system of the present invention has the following advantages: 1. In the backlight brightness control of vehicle display screens, the feature extraction unit uses real-time drive current and loop parasitic impedance to correct the sampling voltage, which can reduce the influence of trace parasitic voltage drop and power switch on-resistance on the sampling results. This makes the calculated intrinsic real-time forward voltage closer to the actual conduction state of the target LED. On this basis, the state calculation unit can obtain the real-time junction temperature more accurately, avoiding the overestimation of junction temperature due to the additional voltage drop in the loop, reducing the derating protection caused by this error, and enabling the vehicle display screen backlight module to maintain a relatively stable luminous intensity and luminous flux output under conditions of large drive current and continuous operation.

[0015] 2. The feature extraction unit avoids the transient oscillation after the pulse width modulation drive signal jumps and performs sampling after the drive current enters a constant plateau period. This reduces the impact of switching interference caused by the charging and discharging of parasitic inductance and parasitic capacitance on the sampling voltage, thereby obtaining a more stable sampling signal, reducing the interference of high-frequency switching spikes on real-time junction temperature calculation, providing a reliable basis for subsequent junction temperature calculation and drive current adjustment, and improving the sampling reliability of the vehicle display under high-frequency pulse width modulation operating conditions.

[0016] 3. The state calculation unit and drive control unit determine the compensation forward current through the compensation matrix based on the real-time junction temperature of the target light-emitting diode. This allows for timely adjustment of the backlight output to address the situation where the luminous efficiency decreases with increasing temperature. This reduces the luminous flux variation caused by local temperature differences in light-emitting diodes at different locations, improves the uneven luminous intensity caused by inconsistent heat dissipation conditions inside the vehicle display screen, and reduces local brightness and color deviations. As a result, the screen maintains uniform brightness and color consistency over a wide operating temperature range. Attached Figure Description

[0017] Figure 1 This is a flowchart of the LED sampling and compensation driving closed loop of the present invention; Figure 2 This is a structural diagram of the functional units of the backlight control system of the present invention. Detailed Implementation

[0018] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0019] A vehicle-mounted display screen backlight brightness control system includes: The feature extraction unit is connected to the target light-emitting diode in the backlight module of the vehicle display screen. During the conduction phase of the pulse width modulation constant current drive cycle, it delays to avoid the transient oscillation of the switch and samples the real-time sampling voltage across the target light-emitting diode during the constant plateau period to obtain the real-time drive current. The real-time drive current is multiplied by the parasitic impedance of the loop to calculate the parasitic voltage drop of the loop. The parasitic voltage drop of the loop is subtracted from the real-time sampling voltage to calculate the intrinsic real-time positive voltage. The state calculation unit, connected to the feature extraction unit, stores the calibration reference forward voltage, reference junction temperature and voltage-temperature correlation coefficient. It is used to calculate the forward voltage difference between the intrinsic real-time forward voltage and the calibration reference forward voltage, and to calculate the real-time junction temperature of the target light-emitting diode by combining the voltage-temperature correlation coefficient and the reference junction temperature. The drive control unit is connected to the state calculation unit and the target light-emitting diode, respectively. It has a built-in compensation matrix that defines the correspondence between junction temperature, target luminous flux and compensation forward current. It is used to determine the compensation forward current by querying the compensation matrix based on the real-time junction temperature. When the real-time junction temperature is lower than the junction temperature safety threshold, it outputs a drive pulse modulated with compensation forward current to the target light-emitting diode. When the real-time junction temperature reaches the junction temperature safety threshold, it outputs a derating protection current. When the real-time junction temperature falls back to below the hysteresis recovery temperature, it resumes outputting the drive pulse modulated with compensation forward current.

[0020] Preferably, the feature extraction unit includes a switching transient shielding module and a voltage correction module; the switching transient shielding module is used to delay the preset conduction stabilization time after the rising edge of the drive pulse in the pulse width modulation constant current drive cycle to avoid the charging and discharging oscillation of the parasitic inductance and capacitance of the circuit, and to sample and hold the real-time sampling voltage during the current constant plateau period; the voltage correction module is used to multiply the real-time drive current by the circuit parasitic impedance to obtain the circuit parasitic voltage drop, subtract the circuit parasitic voltage drop from the real-time sampling voltage, and output the intrinsic real-time positive voltage to the state calculation unit.

[0021] Preferably, the target light-emitting diode is a surface-mount semiconductor light-emitting device with a package structure of a plastic chip carrier with leads, a viewing angle of 120° and a size of 4.0mm × 1.4mm × 0.7mm, a rated power of 0.2W to 0.5W, and a dynamic luminous flux output range of 24lm to 75lm within an operating temperature range of -40℃ to 110℃.

[0022] Preferably, the voltage-temperature correlation coefficient stored in the state calculation unit is predetermined by the electrical parameters under calibration low temperature and calibration high temperature conditions; under calibration conditions where the calibration low temperature is set to 20℃ to 30℃ and the measured calibration low temperature forward voltage is 2.12V to 3.22V, and the calibration high temperature is set to 90℃ to 120℃ and the measured calibration high temperature forward voltage is 2.23V to 3.25V, the voltage-temperature correlation coefficient is calibrated to 480℃ / V to 510℃ / V, the calibration reference forward voltage is set to 2.15V to 3.58V, and the reference junction temperature is set to 20℃ to 30℃.

[0023] Preferably, the compensation matrix embedded in the drive control unit is pre-calibrated based on the luminous efficiency decay curve of the target light-emitting diode at different junction temperatures. When the real-time junction temperature rises within the range of 25°C to 110°C, the compensation matrix outputs a monotonically increasing compensation positive current to compensate for the luminous flux decay of the target light-emitting diode caused by the temperature rise, and maintains the constant luminous flux output of the vehicle display screen at the set level.

[0024] Preferably, the drive control unit includes a pulse width modulation (PWM) generation module and a power drive stage circuit; the PWM generation module is used to adjust the duty cycle of the output pulse based on the compensation positive current obtained by querying the compensation matrix; the power drive stage circuit is connected to the PWM generation module and is used to output a pulse drive current of corresponding intensity to the target light-emitting diode in response to the adjusted duty cycle.

[0025] Preferably, the junction temperature safety threshold is set to 100°C to 120°C; the derating protection current is less than the rated operating current of the target LED at a reference junction temperature of 20°C to 30°C; the hysteresis recovery temperature is set to a temperature threshold 10°C to 15°C lower than the junction temperature safety threshold. The drive control unit continuously outputs the derating protection current before the real-time junction temperature of the target LED drops from above 110°C to below the hysteresis recovery temperature, so as to prevent the backlight brightness from fluctuating at the critical point of the junction temperature safety threshold.

[0026] Preferably, the loop parasitic impedance includes the sum of the equivalent parasitic resistance of the copper foil of the printed circuit board trace in the backlight module of the vehicle display screen and the on-state resistance of the power switch. The calibrated resistance value of the loop parasitic impedance is between 0.30Ω and 0.80Ω, which is used to offset the millivolt-level sampling level superposition error caused by the drive current flowing through the copper foil of the trace and the internal resistance of the switch in the feature extraction unit.

[0027] Preferably, the vehicle display backlight module includes multiple light-emitting diode (LED) units arranged in a matrix. The feature extraction unit, state calculation unit, and drive control unit each form an independent closed-loop control loop with each LED unit. This loop is used to perform spatially discretized independent junction temperature calculation and differentiated brightness compensation for different LED units in the central and edge areas of the vehicle display backlight module, so as to eliminate the local brightness and color uniformity of the vehicle display under extreme temperature difference conditions.

[0028] Example 1: The backlight module of the vehicle display screen is located in the enclosed environment of a compact cabin and an ultra-thin central control structure. The densely arranged surface-mount LED devices are subjected to the dual heat loads of direct sunlight and high internal heat accumulation. The individual devices are packaged with plastic chip carriers with leads and have a rated power in the range of 0.2W to 0.5W. The luminous flux output of the LEDs exhibits a nonlinear decay as the semiconductor junction temperature rises. When the driving system applies a high-current pulse width modulation drive signal, the parasitic resistance of the copper foil of the printed circuit board traces and the on-resistance of the power switch generate a non-negligible dynamic voltage drop in the circuit. The rising edge of the drive pulse is accompanied by the oscillation of parasitic inductance and capacitor charging and discharging. Traditional sampling to obtain the terminal voltage will lead to the level superposition and artificial increase, which will cause the calculated chip temperature to deviate from the actual state and induce unexpected derating and screen brightness distortion.

[0029] To address the aforementioned operating conditions involving high heat accumulation and intertwined circuit impedance, this system pre-calibrates and decouples the basic electrical and thermal parameters before operation; the state calculation unit incorporates a calibration reference positive voltage. 2.98V, reference junction temperature The system is set at 25℃, and the preset circuit parasitic impedance is... The impedance is 0.5Ω; the target LED has a 120° viewing angle and dimensions of 4mm × 1.4mm × 0.7mm, and is calibrated at low temperature. The calibrated low-temperature forward voltage was measured at 25℃. 2.98V, rated high temperature The calibrated high-temperature forward voltage was measured at 100℃. Under the calibration condition of 2.83V, the state calculation unit calculates the state according to the formula. Calculate the voltage-temperature correlation coefficient. It is 500℃ / V, where, This is the voltage-temperature correlation coefficient. To calibrate the high temperature, To calibrate low temperature, To calibrate the low-temperature forward voltage, To calibrate the high-temperature forward voltage, the drive control unit sets the junction temperature safety threshold to 110℃ and the hysteresis recovery temperature to the range of 95℃ to 100℃, which is 10℃ to 15℃ below the safety threshold. This establishes a full-link electrothermal physical mapping benchmark. In the physical constraints of the calibration parameters, the calibration low-temperature forward voltage range and the calibration high-temperature forward voltage range refer to the total voltage distribution range across different devices in a batch. When performing factory offline calibration on any specific target LED, under the same calibration constant injection current, due to the negative temperature characteristic of semiconductor bandgap shrinking with temperature rise, the forward voltage measured at the calibration low temperature of 20℃ to 30℃ for this single device is always higher than the forward voltage measured at the calibration high temperature of 90℃ to 120℃. The high and low temperature voltage difference of the single device is in the positive range of 0.13V to 0.18V, ensuring that the calculated voltage-temperature correlation coefficient is a constant positive slope constant of 480℃ / V to 510℃ / V.

[0030] During the steady-state dimming operation phase, the target luminous flux output of the vehicle display backlight target LED is set to 45.2 lm, and the steady-state real-time drive current supplied by the current pulse width modulation drive circuit is... The current is 120mA, or 0.12A. The transient switching shielding module within the feature extraction unit delays the transition of the pulse-width modulation drive signal from low to high for a preset conduction stabilization time to avoid the transient oscillation period caused by parasitic inductance and capacitance, completing steady-state real-time voltage sampling during the current constant plateau period. Sampling and holding, measured results The measured value is 2.91V; the voltage correction module within the feature extraction unit will drive the current in real time. With loop parasitic impedance Parasitic voltage drop in multiplication calculation loop ,Right now ,in, For the parasitic voltage drop of the loop, To drive the current in real time, The parasitic impedance of the loop is substituted into the numerical calculation to obtain... The feature extraction unit samples the voltage in real time. Parasitic voltage drop in the middle deduction loop The intrinsic real-time forward voltage across the target LED is calculated. ,Right now ,in, This is the intrinsic real-time positive voltage. To obtain the real-time sampled voltage, substitute the values ​​into the calculation. This eliminates the aliasing interference of line impedance and power switch internal resistance on the intrinsic potential of the PN junction at the signal acquisition end. In the specific hardware implementation, the feature extraction unit collects the real-time drive current through a high-precision manganese copper sampling resistor with a series resistance of 0.02Ω and an accuracy of 0.5% in the low-end circuit of the target light-emitting diode. The millivolt-level voltage drop signal across the sampling resistor is connected to an instrumentation amplifier with a gain of 20 for common-mode rejection and differential amplification. The amplified analog signal is input to an analog-to-digital converter chip with a conversion rate of 50MS / s and a resolution of 12 bits. Under the trigger of the high-level holding clock output by the transient shielding module, it is synchronously latched and quantized. The quantized digital quantity is transmitted to the register to generate the current real-time drive current value, thereby providing the voltage correction module with an accurate transient drive current hardware sampling signal.

[0031] The state calculation unit receives the intrinsic real-time positive voltage output by the feature extraction unit. Given a value of 2.85V, calculate the forward voltage difference between the intrinsic real-time forward voltage and the calibration reference forward voltage. ,Right now ,in, This is the forward voltage difference. To calibrate the reference forward voltage, substitute the values ​​and calculate... The state calculation unit is based on the junction temperature evolution relationship. Calculate the real-time junction temperature of the target LED, where, To achieve real-time junction temperature, Using the reference junction temperature, substitute the values ​​to obtain This calculation process directly reflects the internal physical state and thermal equilibrium state of the PN junction, eliminating the temperature measurement blind zone caused by the thermal lag of the external thermistor. It also avoids logical misjudgments caused by an excessively high measured voltage leading to a false increase in junction temperature to a dangerous range when voltage drop compensation is not applied. Furthermore, to eliminate the nonlinear current modulation effect on the semiconductor forward conduction voltage when the drive current is dynamically adjusted from 100mA to 152mA, the state calculation unit pre-installs a dynamic volt-ampere differential impedance curve under a 100mA reference current. When the feature extraction unit acquires the intrinsic forward voltage under non-calibrated current conditions, the state calculation unit first calculates the current-added voltage drop based on the difference between the current real-time drive current and the reference current, combined with the dynamic differential impedance. This current-added voltage drop is then subtracted from the intrinsic real-time forward voltage and normalized to the equivalent reference forward voltage corresponding to the 100mA reference current. The difference between this equivalent voltage and the calibrated reference forward voltage is then calculated and substituted into the voltage-temperature relationship to calculate the real-time junction temperature, thus decoupling the interleaved modulation effect of the injected current and chip temperature on the diode's forward voltage drop.

[0032] The drive control unit receives the real-time junction temperature value of 90℃ from the state calculation unit and performs a safety boundary judgment. It determines that 90℃ is lower than the set junction temperature safety threshold of 110℃, and the system is within the normal linear compensation range. Based on the real-time junction temperature of 90℃ and the target luminous flux of 45.2lm, the drive control unit queries the built-in compensation matrix. This compensation matrix is ​​pre-calibrated based on the luminous efficiency decay curve of the target LED at different junction temperatures. Under the 90℃ junction temperature condition, it matches and outputs the compensation forward current parameter of 138mA (0.138A) required to maintain a constant luminous flux of 45.2lm. The pulse width modulation generation module within the drive control unit adjusts based on the obtained compensation forward current. When the compensation forward current is higher than the current real-time drive current, the duty cycle of the output pulse is increased; when the compensation forward current is lower than the current real-time drive current, the duty cycle is decreased, and the power... The driver-stage circuit controls the conduction time within each pulse-width modulation constant current drive cycle according to the adjusted duty cycle. During the conduction phase, it outputs a pulse drive current to the target LED in a constant current manner, and stops outputting during the turn-off phase. This ensures that the average drive current within one drive cycle varies with the duty cycle and corresponds to the compensation positive current, thus ensuring that the device junction temperature is within the reliable range while offsetting high-temperature light decay. When encountering extreme environments that cause the calculated real-time junction temperature to reach or exceed the 110°C junction temperature safety threshold, the drive control unit outputs a derating protection current less than the rated reference operating current and maintains hysteresis control until the real-time junction temperature drops below the hysteresis recovery temperature of 95°C before resuming matrix compensation drive. This avoids high-frequency brightness jumps and visual flicker at critical temperatures, maintaining the in-plane light emission consistency and long-term operational reliability of the vehicle display screen within a wide operating temperature range.

[0033] Example 2: The current vehicle display backlight module testing system is set up inside a sealed environment test chamber. The test object includes surface-mount target light-emitting diodes arranged in a matrix. The device packaging structure is a plastic chip carrier with leads, with a 120° viewing angle and dimensions of 4mm × 1.4mm × 0.7mm. The rated power is in the range of 0.2W to 0.5W, and the dynamic luminous flux output range is in the range of 24lm to 75lm. The test chamber provides an ambient temperature range of -40℃ to 120℃, with a temperature control accuracy within ±0.2℃. The driving power supply provides a pulse width modulation driving signal with a frequency of 20kHz and an adjustable duty cycle. The sampling end is equipped with a level acquisition unit with a sampling rate of 50MS / s and a vertical resolution of 16 bits. The optical measurement end is equipped with a spectral integrating sphere measurement system with a measurement accuracy within ±0.05lm. The circuit parasitic impedance is formed by the equivalent parasitic resistance of the copper foil of the printed circuit board traces and the on-state resistance of the power switch. The oscillation is calibrated to 0.5Ω. Parasitic inductance and capacitance charging and discharging oscillation interference with a decaying oscillation frequency of 4.8MHz and a duration of 1.6μs is injected at the pulse transition edge to simulate the signal superposition state in a dense wiring environment. The state calculation unit is preset with a calibration reference positive voltage. 2.98V, reference junction temperature For 25℃, voltage-temperature correlation coefficient The test setup was 500℃ / V, with a junction temperature safety threshold of 110℃ and a hysteresis recovery temperature of 95℃. The test included the sample group of this invention using a complete control link, and also set up a control group A (without deducting loop parasitic voltage drop), a control group B (without setting a conduction delay shielding window), a control group C (using an external thermistor for temperature measurement at the edge of the printed circuit board), and a control group D (without setting a hysteresis recovery temperature). Electrothermal and optical parameters for each group were collected under different ambient temperatures and target luminous flux conditions.

[0034] In the sample group of this invention, the real-time drive current is recorded sequentially. Real-time sampling voltage parasitic voltage drop in the circuit Intrinsic real-time forward voltage Real-time junction temperature calculation The results were correlated with the actual physical junction temperature and optical measurement results. At 25℃, the real-time drive current was 100mA, and the real-time sampling voltage was 3.03V. After subtracting the 0.05V parasitic voltage drop calculated based on the circuit parasitic impedance, the intrinsic real-time forward voltage was 2.98V, and the calculated real-time junction temperature was 25℃, corresponding to the actual physical junction temperature of 25.3℃. The target luminous flux was 39.4lm, and the measured luminous flux was also 39.4lm. The optical output was linearly compensated, stable, and flicker-free. At 50℃, the real-time drive current increased to 110mA, the real-time sampling voltage was 2.985V, and the circuit parasitic voltage drop was... The intrinsic real-time forward voltage after subtracting 0.055V is 2.93V, thus the calculated real-time junction temperature is 50℃, and the actual physical junction temperature is 50.4℃. When the target luminous flux remains at 39.4lm, the measured luminous flux is 39.3lm. The optical output remains linearly compensated, stable, and flicker-free. Under 75℃ operating conditions, the real-time drive current is 122mA, the real-time sampling voltage is 2.941V, and the calculated parasitic voltage drop is 0.061V. After subtracting 0.061V, the intrinsic real-time forward voltage is 2.88V, and the calculated real-time junction temperature is 75℃, corresponding to an actual physical junction temperature of 75.5℃. The target luminous flux is 39.4lm, and the measured luminous flux is... The luminous flux is 39.4 lm, and the optical output is linearly compensated, stable, and flicker-free. Under 90℃ operating conditions, the drive control unit queries a pre-calibrated compensation matrix based on the target LED's luminous efficiency decay curve with temperature, according to the real-time junction temperature and target luminous flux. The real-time drive current is 138 mA. The real-time sampling voltage is 2.919V, and the calculated parasitic voltage drop is 0.069V. After subtracting this, the intrinsic real-time forward voltage is 2.85V, the calculated real-time junction temperature is 90℃, and the actual physical junction temperature is 90.3℃. The target luminous flux is 45.2 lm, and the measured luminous flux is 45.1 lm. The optical output is linearly compensated. Stable and flicker-free, under 105℃ operating conditions, the real-time drive current rises to 152mA, the real-time sampling voltage is 2.896V, the circuit parasitic voltage drop is 0.076V, the intrinsic real-time forward voltage after subtraction is 2.82V, the calculated real-time junction temperature is 105℃, and the actual physical junction temperature is 105.4℃; the target luminous flux is 45.2lm, and the measured luminous flux is 45lm. The optical output state maintains stable linear compensation and flicker-free operation. Under the above normal compensation conditions, the deviation between the calculated real-time junction temperature and the actual physical junction temperature remains within ±0.5℃, and the fluctuation of the measured luminous flux relative to the corresponding target value remains within ±0.3lm.

[0035] When the operating temperature rises to 110℃, the real-time drive current of the sample group of this invention drops to 60mA, the real-time sampling voltage is 2.84V, the calculated parasitic voltage drop in the loop is 0.03V, the intrinsic real-time forward voltage after deduction is 2.81V, the calculated real-time junction temperature is 110℃, corresponding to an actual physical junction temperature of 110.2℃; at this time, the junction temperature safety threshold is reached, the drive control unit outputs derating protection current, the target luminous flux is still 45.2lm, the measured luminous flux drops to 24.2lm, and the optical output status is recorded as triggering the safety threshold derating protection. When the operating temperature continues to rise to 115℃, the real-time drive current is 50mA, the real-time sampling voltage is 2.825V, the parasitic voltage drop in the loop is 0.025V, the intrinsic real-time forward voltage is 2.8V, the calculated real-time junction temperature is 115℃, and the actual physical junction temperature is 115.1℃; under the target luminous flux condition of 45.2lm, the measured luminous flux is 20. The system maintained derating protection to suppress temperature rise. During the subsequent cooling process, when the operating temperature dropped to 96℃, the real-time drive current remained at 50mA, the real-time sampling voltage was 2.863V, the parasitic voltage drop in the loop was 0.025V, the intrinsic real-time forward voltage was 2.838V, the calculated real-time junction temperature was 96℃, the actual physical junction temperature was 96.2℃, the target luminous flux was 45.2lm, and the measured luminous flux was 22.1lm. The system was still at [a certain level]. Within the hysteresis lockout range; when the operating temperature further drops to 94℃, the real-time drive current recovers to 144mA, the real-time sampling voltage is 2.914V, the parasitic voltage drop in the loop is 0.072V, the intrinsic real-time forward voltage is 2.842V, the calculated real-time junction temperature is 94℃, the actual physical junction temperature is 94.3℃, the target luminous flux is 45.2lm, and the measured luminous flux recovers to 45.1lm. The derating is lifted after the hysteresis recovery point is below 95℃.

[0036] Control group A, operating at 90℃ without deducting the parasitic voltage drop in the circuit, had a real-time drive current of 118mA, a real-time sampling voltage of 2.919V, and recorded the parasitic voltage drop as 0V. The intrinsic real-time forward voltage was directly taken as 2.919V, resulting in a calculated real-time junction temperature of 55.5℃, while the actual physical junction temperature was 91.2℃. At a target luminous flux of 45.2lm, the measured luminous flux was 37.1lm, indicating a misjudgment of the junction temperature accompanied by significant light decay. Control group B, operating at 75℃ without setting a conduction delay shielding window, had a real-time drive current of... At 122mA, affected by the high-frequency switching oscillation at the pulse leading edge, the real-time sampling voltage is 2.941V±0.115V. After deducting the 0.061V parasitic voltage drop in the circuit, the intrinsic real-time forward voltage is 2.88V±0.115V, the calculated real-time junction temperature is 75℃±57.5℃, and the actual physical junction temperature is 76.1℃. When the target luminous flux is 39.4lm, the measured luminous flux is 39.2lm±6.8lm. The optical output exhibits duty cycle jumps and flickering. Control group C uses an external thermistor on the edge of the printed circuit board under 90℃ conditions. Resistance temperature measurement, with a real-time drive current of 120mA, and without configuring real-time sampling voltage, loop parasitic voltage drop, and intrinsic real-time forward voltage, yielded a calculated real-time junction temperature of 64.5℃, while the actual physical junction temperature was 95.8℃. The target luminous flux was 45.2lm, while the measured luminous flux was 36.4lm. External temperature measurement, affected by spatial thermal resistance and heat transfer hysteresis, failed to reflect the internal heating state of the chip and resulted in luminous distortion. Control group D, operating under a critical fluctuation condition of 110℃ without setting a hysteresis recovery temperature, had an actual physical junction temperature of 110.5℃. The junction temperature fluctuated between 108.0℃ and 111.0℃ and repeatedly crossed the junction temperature safety threshold; the real-time drive current switched between 60mA and 155mA depending on the drive state, corresponding to a real-time sampling voltage of 2.840V to 2.900V, a loop parasitic voltage drop of 0.030V to 0.078V, an intrinsic real-time forward voltage of 2.810V to 2.822V, a target luminous flux of 45.2lm, and a measured luminous flux that varied between 24.2lm and 44.8lm. The critical point drive state switching produced 12Hz flicker.

[0037] As can be seen from the continuous measurement results of the above operating conditions, in the sample group of the present invention, the feature extraction unit avoids the transient oscillation of the switch and deducts the parasitic voltage drop of the circuit during the signal acquisition stage. The state calculation unit obtains the real-time junction temperature based on the corrected intrinsic real-time forward voltage. The drive control unit then completes the compensation matrix adjustment, junction temperature safety threshold determination and hysteresis recovery control based on the real-time junction temperature. The corresponding electrothermal and optical data change continuously with each processing stage. The corresponding light flux output is maintained in the normal compensation range, and derating protection and hysteresis recovery control are performed in the high temperature range to suppress thermal overload and display flicker near the critical temperature.

[0038] Example 3: Current automotive display backlight modules suffer from uneven spatial thermal resistance and electrical parasitic coupling issues in dense array arrangements. To eliminate interference from circuit parasitic impedance and switching transient oscillations on the sampling signal, offline calibration was performed on the system. The calibration equipment used was a constant temperature test chamber with a temperature control accuracy within ±0.1℃ and a high-speed oscilloscope with a time resolution of 1ns. For a target light-emitting diode with a plastic chip carrier with leads, a viewing angle of 120°, and dimensions of 4mm×1.4mm×0.7mm, a pulse with an amplitude of 100mA and a pulse width of 50μs was injected into the drive circuit under a calibration low-temperature condition of 25℃. A single reference square wave pulse was used, and a high-speed oscilloscope was used to monitor the oscillation waveform at the rising edge of the drive pulse. The duration of the damped oscillation caused by the parasitic inductance and capacitance of the circuit was measured to be 1.2 μs. Based on this, the preset turn-on stabilization time of the transient shielding module in the feature extraction unit was calibrated to 1.8 μs, so that the sampling action would be delayed by 1.8 μs after the pulse rising edge transition, avoiding transient spikes and locking at the constant plateau period of the drive current. Subsequently, the total level at both ends of the drive circuit was measured during the constant plateau period. After subtracting the intrinsic forward voltage across the target LED, the parasitic voltage drop of the circuit was obtained. Combined with the 100mA reference current, the parasitic impedance of the circuit was calculated. The impedance is calibrated to 0.48Ω, which is within the design allowable range of 0.30Ω to 0.80Ω. This impedance parameter is also stored in the non-volatile register of the feature extraction unit. In the hardware circuit design of the automotive backlight module, the printed circuit board uses a 1-ounce copper foil process with a thickness of 35μm. The drive trace width is set to 0.35mm. The physical length of the trace from the drive control terminal to the farthest light-emitting diode unit is in the range of 120mm to 320mm, corresponding to a trace parasitic resistance of 0.16Ω to 0.44Ω. In the power drive stage, a power metal-oxide-semiconductor field-effect transistor with an on-resistance in the range of 0.14Ω to 0.36Ω is selected. The two are connected in series to form a loop parasitic impedance hardware boundary of 0.30Ω to 0.80Ω.

[0039] The compensation matrix built into the drive control unit is pre-calibrated based on the luminous efficiency decay curve of the target LED at different junction temperatures. During calibration tests across a wide temperature range of -40℃ to 110℃, the decay characteristics of the target LED's internal quantum efficiency are simultaneously recorded. The junction temperature step is set to 5℃, covering the range of 25℃ to 110℃, and the target luminous flux step is set to 2lm, covering the range of 24lm to 75lm. The compensation forward current required to maintain the corresponding luminous flux at each discrete grid node is measured in a constant temperature chamber, and a two-dimensional discrete grid lookup table is constructed. During the system's steady-state dimming process, the state calculation unit calculates the current real-time junction temperature based on the sampled intrinsic real-time forward voltage. When the real-time junction temperature When the junction temperature is between two adjacent calibration junction temperature nodes, the drive control unit initiates a bilinear interpolation algorithm to calculate the compensation forward current under the current target luminous flux, using the compensation forward current of adjacent grid points as a reference. The pulse width modulation generation module adjusts the duty cycle of the output pulse based on this compensation forward current. The power drive stage circuit responds to the adjusted duty cycle and outputs a pulse drive current of corresponding intensity to the target LED. When the real-time junction temperature is output by the state calculation unit... When the junction temperature reaches or exceeds the 110℃ junction temperature safety threshold, the state machine of the drive control unit transitions from the normal matrix compensation state to the overheat protection state, forcibly reducing the drive current to the 40mA to 60mA range to suppress lattice thermal decay, while simultaneously activating the hysteresis comparator to continuously monitor the calculated real-time junction temperature; when the real-time junction temperature... When the temperature drops below the hysteresis recovery temperature of 95℃, the control state machine reverts to the matrix compensation state to eliminate repeated jump oscillations at the threshold boundary.

[0040] To prevent control loop deadlock caused by dynamic increase in drive current leading to forward voltage rise and subsequent misjudgment of junction temperature, the system implements a time-decoupling strategy during the voltage sampling phase of the pulse width modulation drive cycle. A constant reference calibration current pulse with a duration of 2μs and an amplitude of 100mA is injected at the leading edge of each drive cycle as a sampling time slot. The feature extraction unit only performs forward voltage sampling to calculate the real-time junction temperature during the stable plateau period of this reference current pulse. After the sampling time slot ends, the drive control unit determines the compensation forward current based on the calculated real-time junction temperature by querying the compensation matrix. The pulse width modulation generation module adjusts the duty cycle of the output pulse accordingly. The power drive stage circuit responds to the adjusted duty cycle by outputting a pulse drive current of corresponding intensity to the target light-emitting diode to maintain the brightness. This separates the junction temperature detection current and the brightness compensation current in time, reducing electrothermal-optical interference and oscillation in the closed-loop control.

[0041] To address the temperature gradient difference between the central and edge regions of the backlight module within the ultra-thin central control structure of the vehicle display screen, the system employs multiple independent closed-loop control loops. These loops spatially discretize and control each LED light-emitting unit in both the central and edge heat-dissipating areas. A feature extraction unit repeatedly samples the real-time voltages of the central and edge LED light-emitting units using a time-division multiplexing method. After deducting the parasitic voltage drop of the corresponding channel, it outputs the intrinsic real-time positive voltage for each. A state calculation unit independently calculates the real-time junction temperature at the center of the central LED light-emitting unit and the edge of the edge LED light-emitting unit. Under conditions of strong sunlight exposure and rising ambient temperature, the central heat-emitting area exhibits higher heat dissipation resistance. The calculated real-time junction temperature at the center is 98℃, and the calculated real-time junction temperature at the edge is 82℃. The drive control unit queries the compensation matrix according to the real-time junction temperature of different regions. The center light-emitting unit corresponds to a larger compensation positive current, and the pulse width modulation generation module increases the duty cycle of the channel accordingly. The power drive stage circuit outputs a pulse drive current of corresponding intensity to offset the high-temperature efficiency degradation. The edge light-emitting unit corresponds to a smaller compensation current adapted to the 82℃ junction temperature, and outputs a pulse drive current according to the corresponding duty cycle, so that the brightness of the center region and the edge region are compensated according to their respective real-time junction temperatures, maintaining the uniformity of in-screen light emission and color uniformity of the vehicle display under extreme temperature difference conditions.

[0042] Example 4: This example combines Figures 1 to 2 This paper describes a backlight brightness control system for an in-vehicle display screen, such as... Figure 1 As shown, the target LED provides a sampling source and receives pulse drive, transmitting real-time sampling voltage and real-time drive current to the switching transient shielding module. The switching transient shielding module delays to avoid switching transient oscillations and maintains the sampling. After sampling and holding during the constant plateau period, the data is transmitted to the voltage correction module. The voltage correction module calculates and subtracts the parasitic voltage drop of the loop, calculates the intrinsic real-time forward voltage, and transmits it to the state calculation unit. The state calculation unit calculates the real-time junction temperature based on the correlation coefficient and outputs the real-time junction temperature to the pulse width modulation generation module. The pulse width modulation generation module connects to the compensation matrix with the fixed corresponding relationship and queries the compensation forward current. Based on the query compensation current, it adjusts the conduction duty cycle and outputs the adjusted conduction duty cycle to the power drive stage circuit. The power drive stage circuit responds to the duty cycle and outputs the pulse drive current, feeding back the pulse drive or derating protection current to the target LED.

[0043] like Figure 2As shown, the vehicle-mounted display backlight brightness control system includes a feature extraction unit, a drive control unit, a state calculation unit, and an independent closed-loop control loop. The feature extraction unit includes delaying to avoid transient oscillations of the switch, deducting parasitic voltage drops in the loop, and calculating the intrinsic real-time forward voltage. The drive control unit includes querying the compensation matrix based on the real-time junction temperature, adjusting the duty cycle of the output pulse, and outputting derating protection current. The state calculation unit includes combining the voltage-temperature correlation coefficient, calculating the forward voltage difference, and calculating the real-time junction temperature. The independent closed-loop control loop includes spatially discretized independent junction temperature calculation, implementing differentiated brightness compensation, and eliminating local brightness and color non-uniformity.

[0044] Example 5: During the power-on initialization self-test phase of the current vehicle display backlight brightness control system, to eliminate baseline deviations caused by the dispersion of intrinsic parameters of different batches of devices and the assembly tolerances of printed circuit boards, the drive control unit outputs a test current pulse with a duration of 10μs and an amplitude of 10mA to the target light-emitting diode. The feature extraction unit samples the initial reference voltage across the target light-emitting diode after avoiding the transient oscillation at startup. The state calculation unit reads the current static ambient temperature output by the vehicle ambient temperature sensor as the initial reference junction temperature, compares the measured initial reference voltage with the calibration reference positive voltage at the standard temperature, and when the deviation is within the preset ±0.03V tolerance window, updates the measured initial reference voltage and writes it to the non-volatile memory as the calibration reference positive voltage for this operating cycle. When the deviation exceeds the tolerance window, the fixed calibration reference positive voltage of 2.98V is maintained and a parameter abnormality mark is generated to complete the baseline adaptive calibration of different batches of devices and initial environments. During the self-test, the state calculation unit periodically receives the ambient temperature message from the cabin temperature sensor through the vehicle controller local area network bus interface. When the vehicle is powered on, the vehicle power-off sleep timer is read first. When the power-off time exceeds 30 minutes and the cabin temperature change is less than 0.2℃ within 5 consecutive seconds, it is determined that the backlight module and the cabin environment have reached the isothermal thermal equilibrium steady state, and the received cabin static ambient temperature is confirmed as the valid initial reference junction temperature to avoid performing baseline updates when the vehicle is hot-started or has not reached the thermal equilibrium state.

[0045] During long-term operation and temperature fluctuations of the vehicle display screen, to address the impedance drift of the copper foil traces on the printed circuit board due to temperature rise and the electrical characteristic shift caused by the aging of the light-emitting chip lattice, the state calculation unit sets up periodic dynamic correction judgment logic. After continuous operation for a set working time, the drive control unit inserts a test drive gap during the backlight vertical blanking period. The feature extraction unit obtains the steady-state terminal sampling level of the target light-emitting diode under a low duty cycle pulse and combines it with the preset circuit parasitic impedance. Parasitic voltage drop in the verification circuit The linear consistency is achieved when the real-time junction temperature calculated by the state solution unit is... When the voltage remains within the critical high-temperature range of 105℃ to 110℃ and the slope of the voltage change exceeds the normal thermal equilibrium range, the drive control unit activates the look-ahead suppression logic for the rate of temperature change, based on the real-time junction temperature. Before the junction temperature reaches the safe threshold of 110℃, the pulse width modulation duty cycle is smoothly reduced according to the preset steps; real-time junction temperature. When the temperature reaches 110℃, the driving current is forcibly locked to a derating protection current that is less than the reference current until the temperature steadily drops below the hysteresis recovery temperature of 95℃. Then the lock is released and the compensation matrix modulation output is restored to suppress thermal damage to the device and maintain the light emission uniformity and operational stability of the vehicle display during long-term operation.

[0046] When the drive control unit detects the trailing edge of the field synchronization blanking of the display signal, it delays for 10μs to trigger a micro-current test pulse with a duration of 5μs and an amplitude of 10mA, and completes low duty cycle level sampling within this test pulse. When executing the look-ahead suppression logic for the rate of temperature change, the state calculation unit calculates the time differential slope of the real-time junction temperature in a calculation cycle of 100ms. When the real-time junction temperature is in the range of 105℃ to 110℃ and the calculated temperature rise slope is greater than 0.5℃ / s, the drive control unit starts look-ahead intervention. In each calculation cycle, it gradually reduces the output duty cycle by 5% of the current pulse width modulation duty cycle as a fixed step size until the temperature rise slope falls back to within 0.1℃ / s, thereby achieving smooth temperature limiting in the high-temperature critical region.

[0047] Example 6: When the backlight module of the vehicle display screen is subjected to strong sunlight with local oblique radiation and is in an asymmetrical ventilation and heat dissipation state, a spatial temperature gradient of more than 20°C is formed between the central luminous area and the edge luminous area. The system adopts a multi-channel distributed closed-loop drive architecture. The feature extraction unit, state calculation unit, and drive control unit form independent closed-loop control loops with each light-emitting diode unit. The system performs spatial discretization of independent junction temperature calculation and differentiated brightness compensation for the light-emitting diode units in the central and edge areas. The feature extraction unit integrates a multi-channel reusable level sampling switch array and a sample-and-hold circuit. The sampling action of each channel and the phase of each pulse drive signal output by the pulse width modulation generation module in the drive control unit are hardware latched. During the conduction phase of each pulse width modulation constant current drive cycle, the switch transient shielding module avoids the high-frequency charging and discharging oscillation of the parasitic inductance and parasitic capacitance of the circuit after the pulse jumps to a high level, based on the fixed 1.8μs preset conduction stabilization time. During the current constant plateau period, it synchronously captures the real-time sampling voltage of the target light-emitting diodes of each channel with a window width of 100ns. The voltage correction module is based on the real-time drive current measured in the current channel. The parasitic impedance of the channel loop is pre-calibrated and stored. Calculate the parasitic voltage drop of the loop Then from the real-time sampled voltage Parasitic voltage drop in the middle deduction loop The obtained intrinsic real-time forward voltage The output is sent to the state calculation unit to reduce the impact of crosstalk between channels and impedance voltage drop of copper foil in multi-channel dense wiring on the sampling results.

[0048] The state resolution unit is configured with a multi-channel parallel computing pipeline to receive the intrinsic real-time positive voltage transmitted from each channel. Calculate the intrinsic real-time forward voltage and the calibration reference forward voltage. Forward voltage difference between In conjunction with the preset calibration reference forward voltage of 2.98V and reference junction temperature For 25℃ and voltage-temperature correlation coefficient Calculate the real-time junction temperature of each channel's LED light-emitting unit independently at 500℃ / V. When the target LED in the center area of ​​the vehicle display screen reaches a real-time junction temperature of 102℃ due to local heat accumulation, while the LED in the edge area reaches a real-time junction temperature of 78℃, the drive control unit queries the compensation matrix based on the real-time junction temperature of each channel to determine the corresponding compensation forward current for each channel. Among them, the compensation forward current required to maintain a rated target luminous flux of 39.4lm at a junction temperature of 78℃ for the edge area channel is 124mA, and the compensation forward current required for the center area channel at a junction temperature of 102℃ is 148mA. The pulse width modulation generation module adjusts the duty cycle of the corresponding output pulse based on the compensation forward current determined for each channel. The power drive stage circuit responds to the adjusted duty cycle of each channel and outputs a pulse drive current of corresponding intensity to the corresponding LED light-emitting unit, so that the luminous flux deviation between the LED light-emitting units in the center area and the edge area is kept within ±0.2lm under the temperature difference condition.

[0049] When localized exposure causes the real-time junction temperature of the LED light-emitting unit in the central region to reach the 110°C junction temperature safety threshold, the drive control unit only performs overheat derating protection on that channel, reducing its pulse drive current to 55mA, while maintaining the compensation matrix modulation output of the other channels that have not reached the junction temperature safety threshold. After the real-time junction temperature in the central region drops below the 95°C hysteresis recovery temperature, the channel resumes the compensation matrix modulation output. Thus, each independent closed-loop control loop performs brightness compensation or derating protection according to the real-time junction temperature of the corresponding region, thereby achieving independent zoned control of the central region and the edge region under non-uniform thermal field.

[0050] The embodiments of this application have been described above with reference to the accompanying drawings. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. This application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit of this application and the scope of protection of this invention, and all of these forms are within the protection scope of this application.

Claims

1. A vehicle-mounted display screen backlight brightness control system, characterized in that, include: The feature extraction unit is connected to the target light-emitting diode in the backlight module of the vehicle display screen. During the conduction phase of the pulse width modulation constant current drive cycle, it delays to avoid the transient oscillation of the switch and samples the real-time sampling voltage across the target light-emitting diode during the constant plateau period to obtain the real-time drive current. The real-time drive current is multiplied by the parasitic impedance of the loop to calculate the parasitic voltage drop of the loop. The parasitic voltage drop of the loop is subtracted from the real-time sampling voltage to calculate the intrinsic real-time positive voltage. The state calculation unit, connected to the feature extraction unit, stores the calibration reference forward voltage, reference junction temperature and voltage-temperature correlation coefficient. It is used to calculate the forward voltage difference between the intrinsic real-time forward voltage and the calibration reference forward voltage, and to calculate the real-time junction temperature of the target light-emitting diode by combining the voltage-temperature correlation coefficient and the reference junction temperature. The drive control unit is connected to the state calculation unit and the target light-emitting diode, respectively. It has a built-in compensation matrix that defines the correspondence between junction temperature, target luminous flux and compensation forward current. It is used to determine the compensation forward current by querying the compensation matrix based on the real-time junction temperature. When the real-time junction temperature is lower than the junction temperature safety threshold, it outputs a drive pulse modulated with compensation forward current to the target light-emitting diode. When the real-time junction temperature reaches the junction temperature safety threshold, it outputs a derating protection current. When the real-time junction temperature falls back to below the hysteresis recovery temperature, it resumes outputting the drive pulse modulated with compensation forward current.

2. The vehicle-mounted display screen backlight brightness control system according to claim 1, characterized in that, The feature extraction unit includes a switching transient shielding module and a voltage correction module. The switching transient shielding module is used to delay the preset conduction stabilization time after the rising edge of the drive pulse in the pulse width modulation constant current drive cycle to avoid the charging and discharging oscillation of the parasitic inductance and capacitance of the circuit, and to sample and hold the real-time sampling voltage during the current constant plateau period. The voltage correction module is used to multiply the real-time drive current by the circuit parasitic impedance to obtain the circuit parasitic voltage drop, subtract the circuit parasitic voltage drop from the real-time sampling voltage, and output the intrinsic real-time positive voltage to the state calculation unit.

3. The vehicle-mounted display screen backlight brightness control system according to claim 1, characterized in that, The target light-emitting diode is a surface-mount semiconductor light-emitting device with a leaded plastic chip carrier in its package structure. It has a 120° viewing angle and dimensions of 4.0mm × 1.4mm × 0.7mm. Its rated power is 0.2W to 0.5W, and its dynamic luminous flux output range is 24lm to 75lm within an operating temperature range of -40℃ to 110℃.

4. The vehicle-mounted display screen backlight brightness control system according to claim 1, characterized in that, The voltage-temperature correlation coefficient stored in the state calculation unit is predetermined by the electrical parameters under calibration low temperature and calibration high temperature. Under the calibration conditions where the calibration low temperature is set to 20℃ to 30℃ and the measured calibration low temperature forward voltage is 2.12V to 3.22V, and the calibration high temperature is set to 90℃ to 120℃ and the measured calibration high temperature forward voltage is 2.23V to 3.25V, the voltage-temperature correlation coefficient is calibrated to 480℃ / V to 510℃ / V, the calibration reference forward voltage is set to 2.15V to 3.58V, and the reference junction temperature is set to 20℃ to 30℃.

5. A vehicle-mounted display screen backlight brightness control system according to claim 1, characterized in that, The compensation matrix embedded in the drive control unit is pre-calibrated based on the luminous efficiency decay curve of the target light-emitting diode at different junction temperatures. When the real-time junction temperature rises within the range of 25℃ to 110℃, the compensation matrix outputs a monotonically increasing compensation forward current to compensate for the luminous flux attenuation of the target light-emitting diode caused by the temperature rise, thus maintaining the constant luminous flux output of the vehicle display screen at the set level.

6. The vehicle-mounted display screen backlight brightness control system according to claim 1, characterized in that, The drive control unit includes a pulse width modulation generation module and a power drive stage circuit; The pulse width modulation generation module is used to adjust the duty cycle of the output pulse based on the compensation positive current obtained from the query compensation matrix; the power drive stage circuit is connected to the pulse width modulation generation module and is used to output a pulse drive current of corresponding intensity to the target light-emitting diode in response to the adjusted duty cycle.

7. A vehicle-mounted display screen backlight brightness control system according to claim 1, characterized in that, The junction temperature safety threshold is set to 100℃ to 120℃; the derating protection current is less than the rated operating current of the target LED at a reference junction temperature of 20℃ to 30℃; the hysteresis recovery temperature is set to a temperature threshold 10℃ to 15℃ lower than the junction temperature safety threshold. The drive control unit continuously outputs the derating protection current before the real-time junction temperature of the target LED drops from above 110℃ to below the hysteresis recovery temperature, in order to prevent the backlight brightness from fluctuating at the critical point of the junction temperature safety threshold.

8. A vehicle-mounted display screen backlight brightness control system according to claim 1, characterized in that, The loop parasitic impedance includes the sum of the equivalent parasitic resistance of the copper foil of the printed circuit board trace in the backlight module of the vehicle display screen and the on-state resistance of the power switch. The rated resistance of the loop parasitic impedance is between 0.30Ω and 0.80Ω, and is used to offset the millivolt-level sampling level superposition error caused by the drive current flowing through the copper foil of the trace and the internal resistance of the switch in the feature extraction unit.

9. A vehicle-mounted display screen backlight brightness control system according to claim 1, characterized in that, The vehicle display backlight module includes multiple light-emitting diode (LED) units arranged in a matrix. The feature extraction unit, state calculation unit, and drive control unit each form an independent closed-loop control loop with each LED unit. This loop is used to perform spatially discretized independent junction temperature calculation and differentiated brightness compensation for different LED units in the central and edge areas of the vehicle display backlight module, in order to eliminate local brightness and color uniformity of the vehicle display under extreme temperature difference conditions.

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