Multi-color-temperature light board circuits achieve color temperature adjustment by mixing red, green, and blue primary color LEDs. The core of this system lies in the precise and independent control of each color LED by the driving circuit. Traditional driving methods often employ a dual-power supply scheme, separately driving high and low color-temperature LED arrays, and achieving color temperature mixing by adjusting the current ratio. However, this design has significant drawbacks: low power supply reliability, mutual interference between dimming and color-temperature adjustment functions, and difficulty in achieving independent adjustment of brightness and color temperature. To overcome these technical bottlenecks, modern driving circuits adopt a single-power-supply architecture, combining PWM dimming technology and power switching devices to achieve precise and independent control of each color temperature.
In the single-power-supply driving scheme, the circuit design needs to focus on the integration of the color-temperature adjustment circuit. This circuit uses a PWM signal as its core, controlling the conduction timing of the high and low color-temperature LED arrays through power switching transistors (such as MOSFETs). Specifically, the PWM signal is directly connected to the gate of the switching transistor of the cool white LED array, and simultaneously processed by an inverter before being connected to the gate of the switching transistor of the warm white LED array. When the PWM signal is high, the cool white LED array is turned on, and the warm white LED array is turned off; conversely, the opposite is also true. By adjusting the duty cycle of the PWM signal, the conduction time ratio of the two LEDs per unit time can be precisely controlled, utilizing the persistence of vision in the human eye to achieve a smooth color temperature transition.
The key to independent control lies in the decoupling design of the drive circuit. In traditional solutions, the dimming pin of the dual power supply is occupied by the color temperature adjustment function, causing brightness and color temperature adjustment to interfere with each other. The single power supply solution, by introducing an independent PWM dimming channel, separates the power supply's output current regulation from the color temperature adjustment circuit. The power supply's dimming terminal is controlled by a single PWM signal, achieving linear adjustment of the overall brightness; the color temperature adjustment circuit independently controls the conduction ratio of the two LEDs through another PWM signal. This decoupling design ensures that brightness and color temperature adjustment do not interfere with each other, allowing users to freely combine different brightness and color temperature parameters to meet diverse lighting needs.
The selection of power switching devices directly affects the accuracy of color temperature control. MOSFETs, due to their low on-resistance and high switching speed, are the ideal choice for color temperature adjustment circuits. In circuit design, MOSFETs with appropriate parameters must be matched according to the on-state voltage drop and current requirements of the LED array. For example, cool and warm white LED arrays with similar on-state voltage drops can be connected in parallel to the power output, each controlled by an N-channel MOSFET. By optimizing the MOSFET's gate drive circuit, switching losses can be reduced, improving the response speed and stability of color temperature adjustment.
Constant current drive technology is another core element of multi-color temperature light board circuit board design. The brightness and color temperature stability of LEDs are highly dependent on the accuracy of current control. Traditional current-limiting resistor solutions are significantly affected by voltage fluctuations and temperature, and have been gradually replaced by integrated constant current drive chips. Modern drive circuits mostly use switch-mode constant current control (SMPS), dynamically adjusting the output current through a feedback loop to ensure that each color LED maintains constant brightness over a wide voltage range. Some high-end solutions also integrate overcurrent protection and temperature compensation functions, further improving system reliability and lifespan.
Heat dissipation design is equally important in multi-color temperature light board circuit boards. Prolonged operation of high-density LED arrays can easily lead to localized overheating, causing color temperature shift and light decay. The circuit board layout needs to optimize heat conduction paths by distributing high-heat-generating components (such as power switches and constant-current driver chips) and increasing the copper foil area to improve heat dissipation efficiency. Furthermore, using substrate materials with high thermal conductivity (such as aluminum substrates) can effectively reduce LED junction temperature and ensure long-term stability of color temperature control.
From an application perspective, independent control technology for multi-color-temperature light board circuit boards has been widely used in smart lighting, film and television lighting, and other fields. Through deep integration with microcontrollers or DSPs, the driver circuit can realize complex dimming algorithms and scene mode switching. For example, combined with an ambient light sensor, the light board can automatically adjust color temperature and brightness to simulate changes in natural light; in film and television shooting, precise color temperature control can meet the stringent requirements of different shots for lighting atmosphere. With technological evolution, multi-color-temperature light board circuit boards are developing towards higher integration and lower power consumption, providing key technological support for the intelligent upgrading of the lighting industry.
