Torex white LED driver series: XC9106 and XC9103

White LED is widely used in mobile phone, PDA and digital camera LCD backlighting. Torex has an application control solution for this kind of LED - DC/DC converter. This article describes the use of LED backlight lighting necessary brightness control system.

Circuit 1 XC9106 boost DC/DC converter

This is a method of controlling the brightness of an LED by using a boost DC/DC converter that changes the current flowing through the LED (IF) through an external input reference voltage (Vref).

White LED forward current size:

Note: the CE side and the reference voltage (Vref) share a pin, because the CE terminal has enabled function, once the GND will stop working.

Circuit 2 XC9103 boost DC/DC converter

This system uses XC9103 series boost DC/DC converter, control the brightness can change the lighting time of white LED, using the input signal to the PWM pin of CE can control the lighting time, by raising or lowering the PWM signal dutycycle. White LED brighter or darker. Input to the CE pin the PWM signal frequency is controlled between 60HZ and 100HZ.

CE 100Hz input, Duty:20%, IF, VCE waveform

CE 100Hz input, Duty:80%, IF, VCE waveform

Source: electronic system design