1. Implementation principle of dimming function
The dimming function of high beam driver plus light source is usually based on two main principles: current regulation and pulse width modulation (PWM). In the current regulation mode, the driver controls the brightness of the light by changing the current output to the light source. For example, for LED light sources, as the current decreases, the luminous intensity of the LED will decrease accordingly. This method is relatively simple, but problems such as color shift may occur at low currents. PWM dimming, on the other hand, adjusts the average light output with different duty cycles by quickly switching the light source on and off. For example, in one cycle, the longer the high level time is, the longer the light source will emit light, and the higher the average brightness will be; otherwise, it will be lower. The advantage of PWM dimming is that it can maintain the color stability of the light source within a wide brightness range and has high dimming accuracy. The control circuit inside the driver accurately adjusts the parameters of the current or PWM signal according to the set dimming signal, such as the dimming command from the vehicle control system, so as to adjust the brightness of the light source.
2. Factors affecting dimming accuracy
There are several factors that affect dimming accuracy. The first is the accuracy of the circuit components of the driver, such as the current detection resistor and the clock frequency stability of the PWM generator. If the accuracy of the current detection resistor is not high, the current size cannot be accurately fed back, which in turn affects the dimming accuracy adjusted according to the current. The second is the characteristics of the light source itself. Different batches of light sources may have differences in luminous efficiency and voltage-current characteristics, which will also lead to different brightness under the same driving conditions. In addition, electromagnetic interference is also an important factor. External electromagnetic interference may affect the control signal of the driver and cause dimming deviations. For example, near strong electromagnetic interference sources such as vehicle engines, the dimming signal may be interfered with and produce incorrect dimming actions.
3. Measures to improve dimming accuracy
To improve dimming accuracy, we can start from many aspects. In circuit design, high-precision circuit components, such as high-precision current detection chips and stable PWM generators, are selected, and key components are temperature compensated to reduce component parameter drift caused by temperature changes. For the differences in light sources, the light sources can be graded and screened during the production process, light sources with similar characteristics can be combined together, and corresponding compensation parameters can be set in the driver to perform personalized driving according to different grades of the light source. For electromagnetic interference, good shielding measures are adopted, such as adding shielding layers to the driver housing and PCB layout, filtering the input and output lines, removing interference signals, and ensuring stable transmission of dimming signals.
4. Testing and calibration of dimming accuracy
To ensure dimming accuracy, testing and calibration are essential. During the production process, professional light measuring instruments, such as photometers, are used to accurately measure the brightness of light sources at different dimming levels. The measurement results are compared with the set target brightness. If there is a deviation, the control parameters of the driver are adjusted for calibration. For example, if the brightness is found to be high at a certain dimming level, the current can be appropriately reduced or the duty cycle of the PWM can be adjusted. After the vehicle is assembled, the dimming function of the high beam should also be tested regularly to ensure that the dimming accuracy still meets the requirements during long-term use to ensure driving safety and comfort.
