LED color lamp control scheme based on NXP STARplug series chips

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

1. Point light source: The principle of LED color screen display is used to enlarge its pixels to reduce the overall cost. Each module is a color pixel. Application environment: bar, KTV, stage, shopping mall, exhibition hall, as music melody display, background wall decoration, curtain wall advertising, etc.

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

System hardware design:

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

1. Drive module design

How to achieve the LED module to display different colors, mainly rely on the principle of human visual intermittent inertia, using the duty cycle of the three primary colors of R, G, B LED to achieve color mixing. The LED color display of this design scheme 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) output 256 gray scale Color to achieve color display. The controller only needs to transmit the gray value of the RGB color of the module to realize the color display.

1. Four LED drivers, each driver can be programmed into four states through software, namely: on, off, programmable PWM flash control output, programmable gray level for each channel, and supports four PWMs for overall brightness adjustment Mixed light output.

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

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

4. The overall brightness of the four PWM outputs can be adjusted by 256 levels through the 190Hz PWM output.

5. The four-bit output can be programmed as a push-pull output (at 5V, the sink current is 25mA and the sink 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 I2C bus.

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

10. Support hot insertion, low standby current, support voltage range: 2.3 ~ 5.5V.

The following figure shows the design of the drive unit. The number of red, green and blue LEDs can be multiple. According to your design requirements, you can choose parallel or series connection, and then choose the appropriate according to the LED connection method and voltage / current requirements. The switch can be used, and 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 it is connected to the I2C bus output by the control module. Each I2C bus can be connected to 126 dimming driver modules.

2. Control module design

The control module is shown in the following figure. The 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. 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 device, other operations can also be added, such as display image processing, communication with the PC, expansion of storage space, etc.