Battery life is critical in portable applications. If the LED driver is practical, it must be efficient. The efficiency measurement of the LED driver differs from that of the typical power supply. The typical power efficiency measurement is defined as the output power divided by the input power. And for the LED driver, the output power is not the relevant parameters. It is important to produce the desired input power value for the expected led brightness.
This can be determined simply by dividing the LED power by the input power. Please note that if this definition is efficient, the power dissipation in the current-detection resistor will result in a loss of supply power. By using the formula shown in Figure 3, we can see that the smaller current sensing voltage produces a more efficient LED driver. Figure 4 illustrates the efficiency improvement of the power supply using the 0.25V reference voltage compared to the 1V reference voltage. Low current sensing voltage power supply is more effective, regardless of input voltage or led current, as long as other conditions are the same, lower reference voltage can improve efficiency and prolong battery life.