Battery life is critical in portable applications. If the LED driver is practical, it must be highly efficient. The efficiency measurement of LED driver is different from that of typical power supply. Typical power efficiency measurements are defined by the output power divided by the input power. For the LED driver, the output power is not the relevant parameter. What is important is the input power value required to produce the expected brightness of the LED. This can be determined simply by dividing the LED power by the input power. Please note: If this definition of efficiency, the current detection resistor in the power consumption will cause power dissipation. With the formula shown in Figure 3, we can see that a smaller current sensing voltage produces a more efficient LED driver. Figure 4 illustrates the selection of 0.25V reference voltage power supply compared with the 1V reference voltage power supply, the efficiency of the two is improved. Low current sensing voltage is more efficient, regardless of the input voltage or led current, as long as the other conditions are the same, the lower reference voltage can increase efficiency and prolong battery life.