Direct Control of LED Current Boost Converter

To control the current of white  LED  white LED current detection, detection of white LED current is the easiest and most convenient way is to use a sense resistor in series with the white LED, the total output voltage of such a converter is white LED forward voltage and current-sense resistor and pressure drop. To simplify the circuit and reduce costs, designed to make the best sense resistor feedback voltage of the voltage drop across resistor selected converter. Galvanometer voltage drop across the resistor should be as small as possible, so as to minimize power consumption, too high a voltage will only increase the power consumption. White LED forward voltage and current-sense resistor voltage drop of usually higher than the mobile phone battery voltage, therefore, must use a boost converter to provide power. Assume that the converter's feedback voltage is 500mV, the total output voltage must be between 4.1 ~ 4.3V. Direct control of the white LED current boost converter shown in Fig.