Application circuit diagram of NCP5602 and NCP5612

Progressive brightness changes are mainly used in portable electronic devices to create theater-like lighting effects when starting up or shutting down. When starting up, the backlight current will gradually amplify to 20mA in a stepwise manner at preset time intervals. It is also used when shutting down. The opposite action gradually decreases. To achieve this effect, PWM signals with different frequencies can be sent to the enable end of the LED drive circuit through the microprocessor, and the LED current can be increased in multiple steps at specific time intervals or reduce. The disadvantage of this method is that it consumes real-time processor resources. This function is available on LED driver chip products such as NCP 5602 and NCP5612.

The application circuit using NCP5602 and NCP5612 to drive two LEDs is shown in the figure. Figure (a) is an LED drive circuit using a PC control interface; Figure (b) is an LED drive circuit using a single-wire S-Wire control interface.

ck="window.open(this.src)" alt="Click to see larger image"/>

Figure NCP5602 and NCP5612 application circuit

These driver chips require two clamping capacitors, one at the output and one at the input, and a resistor (R1) to control the maximum output current. The progressive brightness change control instruction is sent from the processor to the driver chip through the I2C or I/O port. The instruction itself should include the starting and final current values, as well as the time interval of the brightness change.

If these driver chips are applied to RGB LEDs, this function can be used to produce situational lighting effects. Each RGB LED has 32 levels of brightness. LED driver chips like NCP 5623 can reach 32,768 colors. Variety. Due to its fine brightness gradient and shallow embedded logarithmic algorithm, the color changes can be linearized and quite smooth. The RGB LED driver circuit includes independently controlled PWM current sources 9 for adjusting the output currents of the three LEDs to produce the desired color output.

Since the timing and current size of each current output can be independently controlled and adjusted, white light or colored LEDs can be used, and different lighting modes can be used to achieve colorful decorations or instructions. Some circuits with individual audio inputs also enable colored LEDs to be synchronized to different frequency bands of embedded MP3 or polyphonic ringtones embedded inside.