Design of LED color light control solution using NXP STARplug series chips-EEWORLD

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LED is a display device with excellent performance, with the advantages of long life, power saving, high brightness, multiple luminous colors, fast response speed and low driving voltage. While saving energy, it can also adjust the LED luminous intensity through PWM devices, adjust various colors based on the principle of mixing the three primary colors of R, G, and B, and then realize various display effects through MCU intelligent control. It is now widely used in urban lighting, architectural landscape lighting, stage lighting design and other fields.

Main chips: PCA9633/34/35: NXP I2 bus RGB/RGBA LED flashing/mixed light chip; TEA152x: NXP power chip; LPC92x: NXP 900 series MCU; P82B96/PCA9600: NXP I2C bus driver chip.

1. Point light source: Apply the principle of LED color screen display, enlarge its pixels, reduce the overall cost, and each module is a color pixel. Application environment: bars, KTV, stages, shopping malls, exhibition halls, as music melody display, background wall decoration, curtain wall advertising, etc.

2. LED rainbow tube: Each light tube is composed of multiple color pixels (RGB), and each monochrome pixel can produce 256 grayscale changes. Application environment: decorative lighting in different places such as overpasses, river guardrails, and building exterior walls.

System hardware design:

The LED color light control system mainly includes three parts: drive module, control module, and LED power supply.

1. Drive module design

How to make the LED module present different colors mainly depends on the principle of human visual intermittent inertia, and the duty cycle of the three primary colors of R, G, and B is used to achieve color mixing. The LED color display of this design mainly relies on NXP's I2C interface LED flashing/mixed light driver chip PCA9633 (PCA9633-4-bit PWM output, PCA9634-8-bit PWM output, PCA9635-16-bit PWM output) to output 256 grayscale levels to achieve color display. The controller only needs to transmit the grayscale value of the RGB color of the module to achieve color display.

1. 4-way LED driver, each driver can be programmed into four states through software, namely: on, off, programmable PWM flicker control output, programmable gray level for each channel, and support PWM mixed light output with overall brightness adjustment of four channels.

2. Dimming control, PWM output frequency 97kHz, 256 gray levels for each channel.

3. Flicker control, PWM programmable frequency range 24Hz~10.73s, duty cycle programmable range 0%~99.6%.

4. The overall brightness of the four-way PWM output can be adjusted in 256 levels through 190Hz PWM output.

5. The four-bit output can be programmably set to push-pull output (at 5V, the sink current is 25mA and the pull current is 10mA).

6. 7 hardware address setting pins, the same I2C bus can connect up to 126 pieces.

7. Each PCA9633 has four programmable software addresses: one full response address and three sub-addresses.

8. Built-in 25MHz crystal oscillator and power-on reset circuit, software reset can also be achieved through the I2C bus.

9. SDA/SCL has built-in noise filter and supports 1MHz I2C fast mode.

10. Supports hot insertion, low standby current, and supports voltage range: 2.3~5.5V. The

figure below shows the design of the driver unit, in which the number of red, green and blue LEDs can be multiple. You can choose parallel or series connection according to your own design requirements, and then choose the appropriate switch tube according to the connection method of the LED and voltage/current requirements. A small number of LEDs can also be directly driven by PCA9633. For specific parameters, see PCA9633 data. The driver module sets the access address through the A6~A0 pins of PCA9633, and it can work normally when connected to the I2C bus output by the control module. Each I2C bus can connect 126 dimming driver modules.

2. Control module design

The control module is shown in the figure below. Its main function is to control all dimming modules on the I2C bus through the MCU to achieve various display effects. P82B96 is an I2C bus driver chip used to improve the bus driving capability. When the transmission rate is 20~50kbps, the transmission distance can reach 1km. The MCU can be selected according to the actual system requirements. While controlling the dimming of the bus devices, other operations can also be added, such as display image processing, communication with PC, expansion of storage space, etc.

3. Power supply

The specific parameters of the power supply should be determined according to factors such as the specific number of LEDs and the connection method. The figure below shows an LED power supply solution using the NXP STARplug series chip. This solution has the advantages of simple design, small size, wide voltage input, low cost, low loss, etc., and is widely used in the LED field.

Keywords：STARplug Reference address：Design of LED color light control solution using NXP STARplug series chips

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