DLP brightness constant control system and method based on piecewise linear voltage inverse compensation

Abstract

This invention discloses a constant brightness control system and method for a DLP (Digital Lighting System) based on piecewise linear voltage inverse compensation, belonging to the field of automotive lighting control technology. The method includes: S1, receiving and parsing a brightness demand command sent by the host; S2, acquiring the actual power supply voltage of the LED driver module and preprocessing the actual power supply voltage; S3, using the LED driver module power supply voltage corresponding to the LED's rated operating condition as a reference, setting a voltage sampling interval, selecting multiple test voltage points within the voltage sampling interval, calculating the brightness linearity error of each test voltage point, and determining the boundary of the nonlinear interval; S4, determining the piecewise linear compensation interval; S5, performing voltage inverse compensation based on the target brightness value and the piecewise linear compensation interval to obtain the actual brightness setting value; S6, outputting a PWM control signal based on the actual brightness setting value. This invention eliminates the influence of LED driver module power supply voltage fluctuations on LED light source brightness, achieving brightness consistency under different voltage conditions.

Description

Technical Field

[0001] This invention relates to the field of vehicle lighting control technology, and in particular to a DLP constant brightness control system and method based on piecewise linear voltage inverse ratio compensation. Background Technology

[0002] With the rapid development of automotive intelligence, intelligent headlight systems have become an important component of modern automotive safety lighting. DLP (Digital Light Processing) technology, as an advanced micromirror array control technology, is gradually being applied to high-end intelligent automotive headlights. The core of DLP technology is the digital micromirror device, which contains millions of independently controllable micromirrors, each approximately 5.4 μm in size. Through precise deflection control of these micromirrors, DLP headlights can achieve over one million addressable pixels, thereby enabling high-resolution dynamic light pattern adjustment.

[0003] In intelligent headlight systems, brightness adjustment is a core function, and existing technologies involve three LED brightness control schemes. First, a constant current driver chip is used to stabilize the LED current. However, the feedback adjustment speed of the constant current driver chip is limited, making it unable to track rapid voltage fluctuations and compensate for changes in the LED's luminous efficiency with voltage. Second, LED brightness is controlled through pulse width modulation (PWM). This scheme simply maps the brightness requirement directly to the PWM duty cycle, without considering the impact of power supply voltage fluctuations on the actual LED brightness. Third, the temperature of the LED or driver circuit is monitored by a temperature sensor, and compensation is performed using a temperature-brightness mapping table. When the temperature changes, a compensation coefficient is obtained by looking up the table, and the PWM duty cycle or drive current is adjusted. However, temperature compensation addresses the LED's thermal decay problem, not the power supply voltage fluctuation problem; the temperature change rate is relatively slow and cannot meet the compensation requirements for rapid voltage fluctuations. Summary of the Invention

[0004] The technical problem to be solved by the present invention is: in order to solve the problem that the brightness of DLP cannot be adaptively adjusted with the fluctuation of power supply voltage and is greatly affected by the fluctuation of power supply voltage in the prior art, the present invention provides a constant brightness control system and method for DLP based on piecewise linear voltage inverse compensation.

[0005] The technical solution adopted by this invention to solve its technical problem is: On one hand, the present invention provides a DLP brightness constant control method based on piecewise linear voltage inverse compensation, comprising: S1. Receive and parse the brightness requirement command sent by the host to obtain the target brightness value; S2. Collect the actual power supply voltage of the LED driver module and preprocess the actual power supply voltage; S3. Using the LED driver module power supply voltage corresponding to the rated operating condition of the LED as a reference, set the voltage sampling interval, select multiple test voltage points within the voltage sampling interval, calculate the brightness linearity error of each test voltage point, and determine the boundary of the nonlinear interval based on the brightness linearity error. S4. Determine the piecewise linear compensation interval based on the preprocessed actual power supply voltage and the boundary of the nonlinear interval; S5. Perform voltage inverse compensation based on the target brightness value and the piecewise linear compensation interval to obtain the actual brightness setting value; S6. Output PWM control signal based on actual brightness setting value.

[0006] It achieves precise and constant control of DLP brightness across the entire voltage fluctuation range of the LED driver module, significantly suppressing brightness drift caused by power supply voltage changes and improving brightness stability and compensation accuracy.

[0007] Furthermore, the formula for calculating the brightness linearity error at each test voltage point is as follows: ; In the formula, This refers to the brightness linearity error. The actual brightness value corresponding to each test voltage point; These are the theoretical brightness values ​​corresponding to each test voltage point.

[0008] Furthermore, the determination of the nonlinear interval boundary based on the brightness linearity error includes: Within the voltage sampling range, starting from the LED driver module power supply voltage corresponding to the LED's rated operating condition, each test voltage point is traversed sequentially from near to far towards the low-voltage side and the high-voltage side. The brightness linearity error of each test voltage point is compared point by point towards the low voltage side. The test voltage point that first exceeds the preset error threshold is set as the low boundary of the nonlinear interval. ; The brightness linearity error of each test voltage point is compared point by point towards the high voltage side. The test voltage point that first exceeds the preset error threshold is set as the high boundary of the nonlinear interval. .

[0009] A detailed process for determining the boundaries of nonlinear intervals is presented, enabling the method to automatically recalibrate across different LED batches or after LED aging. This avoids the inaccuracies of manually setting fixed voltage boundary points and enhances adaptability. By traversing from the rated operating point outwards and prioritizing the detection of the most common operating voltage regions, the method can quickly locate the boundaries of nonlinear intervals and reduce computational overhead.

[0010] Furthermore, the piecewise linear compensation interval includes: Low voltage range: The actual supply voltage of the LED driver module < ; Normal voltage range: ≤Actual power supply voltage of LED driver module≤ ; High voltage range: The actual supply voltage of the LED driver module > .

[0011] The entire voltage range is divided into three intervals with different characteristics. The normal voltage range can be simplified or even eliminated for compensation, thereby reducing computational complexity and improving system real-time performance while ensuring accuracy.

[0012] Furthermore, the formula for calculating the actual brightness setting value is as follows: ; In the formula, Set the value for the actual brightness; The target brightness value; This refers to the rated operating voltage of the LED light source; This refers to the actual power supply voltage of the LED driver module. Piecewise linear compensation interval Brightness compensation coefficient; Piecewise linear compensation interval The brightness offset.

[0013] It can correct brightness drift in different segmented linear compensation intervals to achieve accurate fitting.

[0014] Furthermore, it also includes: After LED brightness compensation based on the PWM control signal, the compensated brightness deviation data is calculated, and the boundary of the nonlinear interval is adaptively adjusted based on the compensated brightness deviation data. This forms a closed-loop adaptive mechanism that dynamically corrects the boundary of the nonlinear interval using the compensated brightness deviation data, overcoming long-term variations such as LED aging and maintaining constant brightness performance over the long term.

[0015] Furthermore, the calculation formula for adaptively adjusting the boundaries of the nonlinear interval is as follows: ; ; In the formula, , The adjusted nonlinear interval boundary; , This represents the initial nonlinear interval boundary; The learning rate; The data represents the compensated brightness deviation within the low voltage range. The data represents the compensated brightness deviation within the high-voltage range. The brightness deviation threshold is used. A learning rate update rule with a brightness deviation threshold is adopted to avoid frequent boundary jitter caused by minor fluctuations.

[0016] Furthermore, it also includes: undervoltage shutdown and overvoltage protection for the actual power supply voltage of the LED driver module, and rated upper limit protection for the actual brightness setting value. This prevents LEDs from being damaged under extreme voltages or exhibiting unsafe ultra-high brightness, improving the safety and reliability of the system and meeting engineering application specifications.

[0017] Furthermore, the undervoltage shutdown and overvoltage protection process includes: When the actual supply voltage of the LED driver module is less than or equal to the voltage drop of the LED driver module, the actual brightness setting value of the LED light source is 0; when the actual supply voltage of the LED driver module is greater than the maximum operating voltage of the LED driver module, the actual brightness setting value of the LED light source is the maximum brightness value of the LED light source. This avoids LED flickering or overdriving caused by incorrect calculations in the compensation algorithm within the invalid voltage range, thus extending the LED's lifespan.

[0018] On the other hand, the present invention provides a DLP constant brightness control system, comprising: The host computer is used to issue brightness requirement commands. The brightness requirement parsing unit is used to parse the brightness requirement command sent by the host to obtain the target brightness value; The ADC sampling circuit is used to acquire the actual power supply voltage of the LED driver module. The compensation calculation unit is used to calculate the actual brightness setting value after piecewise linear voltage inverse compensation based on the target brightness value and the actual power supply voltage of the LED driver module. The PWM generator is used to convert the actual brightness setting value into a PWM control signal and send it to the LED driver module. The LED driver module is used to drive the LED light source to light up according to the PWM control signal.

[0019] Through a closed-loop control architecture, rapid, accurate, and stable constant control of LED light source brightness is achieved, effectively resisting the impact of LED driver module power supply voltage fluctuations on output brightness. Attached Figure Description

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0021] Figure 1 This is a flowchart of the DLP brightness constant control method based on piecewise linear voltage inverse compensation of the present invention; Figure 2 This is the brightness curve of the compensated LED light source; Figure 3 This is a block diagram of the principle of the DLP constant brightness control system based on piecewise linear voltage inverse compensation of the present invention. Detailed Implementation

[0022] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, illustrating only the basic structure of the invention, and therefore only show the components relevant to the invention.

[0023] Example 1: like Figure 1 As shown, this embodiment provides a DLP brightness constant control method based on piecewise linear voltage inverse ratio compensation, including: S1. Receive and parse the brightness requirement command sent by the host to obtain the target brightness value. .

[0024] S2. The actual power supply voltage of the LED driver module is acquired through the ADC sampling circuit, and the actual power supply voltage is preprocessed. First-order low-pass filtering is used for preprocessing to improve anti-interference capability. By adjusting the sampling accuracy and sampling frequency of the ADC sampling circuit, the brightness compensation accuracy can be flexibly controlled.

[0025] S3, the power supply voltage of the LED driver module corresponding to the rated operating conditions of the LED ( Based on ), at a level lower than The low-pressure side and higher Multiple test voltage points are selected on the high-voltage side. Specifically, a voltage sampling range is first set (preferably between the lowest and highest supply voltages allowed for LED operation), and multiple test voltage points are selected within the voltage sampling range with a preset step size (preferably 0.5V).

[0026] The brightness linearity error at each test voltage point is calculated, and the boundary of the nonlinear interval is determined based on this error. Specifically, the formula for calculating the brightness linearity error is: ; In the formula, This refers to the brightness linearity error. The actual brightness values ​​corresponding to each test voltage point are obtained through actual measurement. These are the theoretical brightness values ​​corresponding to each test voltage point.

[0027] Within the voltage sampling range, starting from the LED driver module power supply voltage corresponding to the LED's rated operating condition, each test voltage point is traversed sequentially from near to far towards the low-voltage side and the high-voltage side. The brightness linearity error of each test voltage point is compared point by point towards the low voltage side. The test voltage point that first exceeds the preset error threshold (preferably 5%) is set as the low boundary of the nonlinear interval. The brightness linearity error of each test voltage point is compared point by point towards the high-voltage side. The test voltage point that first exceeds the preset error threshold (preferably 5%) is set as the high boundary of the nonlinear interval. If the brightness linearity error at all test voltage points does not exceed the preset error threshold, the LED brightness is determined to be approximately linear throughout the entire voltage sampling interval, and no segmented compensation is required.

[0028] S4. Based on the preprocessed actual supply voltage and the boundaries of the nonlinear interval, determine the piecewise linear compensation interval, which specifically includes: Low voltage range: The actual supply voltage of the LED driver module < ; Normal voltage range: ≤ Actual power supply voltage of LED driver module ≤ ; High voltage range: The actual supply voltage of the LED driver module > .

[0029] S5, Based on target brightness value The actual brightness setting value is obtained by performing inverse voltage compensation on the piecewise linear compensation interval. For example... Figure 2 As shown, the compensated brightness curve is close to the target brightness curve. The specific formula for calculating the actual brightness setting value is: ; In the formula, This is the actual brightness setting value, i.e., the brightness setting value after compensation. The target brightness value; This refers to the rated operating voltage of the LED light source; This refers to the actual power supply voltage of the LED driver module. Piecewise linear compensation interval Brightness compensation coefficient; Piecewise linear compensation interval The algorithm compensates for the brightness offset. After compensation, regardless of fluctuations in the power supply voltage of the LED driver module, the brightness output of the LED light source always remains consistent with the target brightness. Furthermore, this compensation algorithm has low computational complexity, making it suitable for embedded real-time processing. Voltage sampling and compensation calculations can be completed within 10ms of each sampling cycle, demonstrating fast response. It also eliminates the need for additional constant voltage circuits or complex driver chips, utilizing only existing hardware resources.

[0030] It should be noted that different piecewise linear compensation intervals employ different methods. and The voltage was obtained through actual measurement and calibration. Two or more voltage sampling points were selected within different piecewise linear compensation intervals. At each voltage sampling point The actual brightness value corresponding to the measurement below. , obtain measurement data pairs ( According to the compensation calculation formula ,make (Normalized brightness) (The reciprocal of the normalized voltage ratio), its equation is transformed into a standard linear form to obtain: ,in, These are measured values. These are known values. Based on multiple sets of measurement data, ( ),structure( , The data pairs were then used. Finally, the least squares method was employed to fit the straight line. Solve for the unique value within each piecewise linear compensation interval. and The value. The equivalent voltage drop of the drive circuit has already been... and Implicit compensation is provided. Within the normal voltage range, no compensation is required. =1, It is 0. and The principle of segmented value selection is described in Table 1.

[0031] Table 1: Segmented Compensation Parameter Table

[0032] S6. Output a PWM control signal based on the actual brightness setting value, and output the PWM control signal to the LED driver module to adjust the LED brightness so that the LED light source can maintain a constant brightness output under different voltage conditions.

[0033] The system records the compensated brightness deviation data in real time under different voltages during actual LED operation, specifically monitoring the compensation error in both low-voltage and high-voltage ranges. When the compensation error in a certain range exceeds a brightness deviation threshold... At that time, the boundary values ​​of the corresponding interval are dynamically updated according to the following formula: ; ; In the formula, , The adjusted nonlinear interval boundary; , This represents the initial nonlinear interval boundary; The learning rate, with a value ranging from 0.01 to 0.1; The data represents the compensated brightness deviation within the low voltage range. The data represents the compensated brightness deviation within the high-voltage range. The brightness deviation threshold is preferably 0.3. A closed-loop adaptive mechanism is formed, which dynamically corrects the nonlinear interval boundary using the compensated brightness deviation data, thus overcoming long-term variation factors such as LED aging and maintaining constant brightness performance over a long period of time.

[0034] Example 2 Unlike Embodiment 1, this embodiment also includes: undervoltage shutdown and overvoltage protection processing for the actual power supply voltage of the LED driver module, and rated upper limit protection processing for the actual brightness setting value.

[0035] Specifically, when the actual supply voltage of the LED driver module is less than or equal to the voltage drop of the LED driver module, the actual brightness setting value of the LED light source is 0; when the actual supply voltage of the LED driver module is greater than the maximum operating voltage of the LED driver module, the actual brightness setting value of the LED light source is the maximum brightness value of the LED light source; when the actual brightness setting value of the LED light source is greater than the maximum brightness value of the LED light source, the actual brightness setting value of the LED light source is set to the maximum brightness value of the LED light source to prevent exceeding the rated operating range of the LED. This prevents the LED light source from being damaged under extreme voltage or exhibiting unsafe ultra-high brightness, improving the safety and reliability of the system and conforming to engineering application specifications.

[0036] Example 3 Unlike Embodiment 1, this embodiment uses a lookup table method instead of the compensation algorithm in step S5. A voltage-compensation coefficient lookup table is pre-calculated ( (6~18V, step: 0.5V) to further reduce the computational burden on the chip.

[0037] Table 2 Voltage-Compensation Coefficient Comparison Table

[0038] Actual brightness setting value , .in, It refers to according to The voltage compensation coefficient obtained from the table, It is based on The calculated lookup index value. When hour, Take the 0th coefficient in the table ( K= 2) When hour, Take the first coefficient in the table ( K= 1.85).

[0039] Example 4: like Figure 3 As shown, this embodiment provides a control system for the DLP constant brightness control method as described in the above embodiments, including: The host is used to issue brightness requirement commands.

[0040] The brightness requirement parsing unit is used to parse the brightness requirement command sent by the host and obtain the target brightness value.

[0041] The ADC sampling circuit is used to acquire the actual power supply voltage of the LED driver module.

[0042] The compensation calculation unit is used to calculate the actual brightness setting value after piecewise linear voltage inverse compensation based on the target brightness value and the actual power supply voltage of the LED driver module.

[0043] The PWM generator is used to convert the actual brightness setting value into a PWM control signal and send it to the LED driver module.

[0044] The LED driver module is used to drive the LED light source to light up according to the PWM control signal.

[0045] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A DLP brightness constant control method based on piecewise linear voltage inverse ratio compensation, characterized in that, include: S1. Receive and parse the brightness requirement command sent by the host to obtain the target brightness value; S2. Collect the actual power supply voltage of the LED driver module and preprocess the actual power supply voltage; S3. Using the LED driver module power supply voltage corresponding to the rated operating condition of the LED as a reference, set the voltage sampling interval, select multiple test voltage points within the voltage sampling interval, calculate the brightness linearity error of each test voltage point, and determine the boundary of the nonlinear interval based on the brightness linearity error. S4. Determine the piecewise linear compensation interval based on the preprocessed actual power supply voltage and the boundary of the nonlinear interval; S5. Perform voltage inverse compensation based on the target brightness value and the piecewise linear compensation interval to obtain the actual brightness setting value; S6. Output PWM control signal based on actual brightness setting value.

2. The DLP brightness constant control method based on piecewise linear voltage inverse compensation according to claim 1, characterized in that, The formula for calculating the brightness linearity error at each test voltage point is as follows: ； In the formula, This refers to the brightness linearity error. The actual brightness value corresponding to each test voltage point; These are the theoretical brightness values ​​corresponding to each test voltage point.

3. The DLP brightness constant control method based on piecewise linear voltage inverse ratio compensation according to claim 1, characterized in that, The determination of the nonlinear interval boundary based on the brightness linearity error includes: Within the voltage sampling range, starting from the LED driver module power supply voltage corresponding to the LED's rated operating condition, each test voltage point is traversed sequentially from near to far towards the low-voltage side and the high-voltage side. The brightness linearity error of each test voltage point is compared point by point towards the low voltage side. The test voltage point that first exceeds the preset error threshold is set as the low boundary of the nonlinear interval. ; The brightness linearity error of each test voltage point is compared point by point towards the high voltage side. The test voltage point that first exceeds the preset error threshold is set as the high boundary of the nonlinear interval. .

4. The DLP brightness constant control method based on piecewise linear voltage inverse ratio compensation according to claim 3, characterized in that, The piecewise linear compensation interval includes: Low voltage range: The actual supply voltage of the LED driver module < ; Normal voltage range: ≤Actual power supply voltage of LED driver module≤ ; High voltage range: The actual supply voltage of the LED driver module > .

5. The DLP brightness constant control method based on piecewise linear voltage inverse ratio compensation according to claim 1, characterized in that, The formula for calculating the actual brightness setting value is: ； In the formula, Set the value for the actual brightness; The target brightness value; This refers to the rated operating voltage of the LED light source; This refers to the actual power supply voltage of the LED driver module. Piecewise linear compensation interval Brightness compensation coefficient; Piecewise linear compensation interval The brightness offset.

6. The DLP brightness constant control method based on piecewise linear voltage inverse ratio compensation according to claim 1, characterized in that, Also includes: After LED brightness compensation is performed based on the PWM control signal, the compensated brightness deviation data is calculated, and the boundary of the nonlinear interval is adaptively adjusted based on the compensated brightness deviation data.

7. The DLP brightness constant control method based on piecewise linear voltage inverse ratio compensation according to claim 6, characterized in that, The calculation formula for adaptively adjusting the boundaries of the nonlinear interval is as follows: ； ； In the formula, , The adjusted nonlinear interval boundary; , This represents the initial nonlinear interval boundary; The learning rate; The data represents the compensated brightness deviation within the low voltage range. The data represents the compensated brightness deviation within the high-voltage range. This is the brightness deviation threshold.

8. The DLP brightness constant control method based on piecewise linear voltage inverse ratio compensation according to claim 1, characterized in that, It also includes: undervoltage shutdown and overvoltage protection for the actual power supply voltage of the LED driver module, and rated upper limit protection for the actual brightness setting value.

9. The DLP brightness constant control method based on piecewise linear voltage inverse ratio compensation according to claim 8, characterized in that, The undervoltage shutdown and overvoltage protection process includes: When the actual power supply voltage of the LED driver module is less than or equal to the voltage drop of the LED driver module, the actual brightness setting value of the LED light source is 0; when the actual power supply voltage of the LED driver module is greater than or equal to the maximum operating voltage of the LED driver module, the actual brightness setting value of the LED light source is the maximum brightness value of the LED light source.

10. A DLP constant brightness control system applying the DLP constant brightness control method based on piecewise linear voltage inverse compensation as described in any one of claims 1 to 9, comprising: The host computer is used to issue brightness requirement commands. The brightness requirement parsing unit is used to parse the brightness requirement command sent by the host to obtain the target brightness value; The ADC sampling circuit is used to acquire the actual power supply voltage of the LED driver module. The compensation calculation unit is used to calculate the actual brightness setting value after piecewise linear voltage inverse compensation based on the target brightness value and the actual power supply voltage of the LED driver module. The PWM generator is used to convert the actual brightness setting value into a PWM control signal and send it to the LED driver module. The LED driver module is used to drive the LED light source to light up according to the PWM control signal.

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