Circuit diagram shows a typical simple low cost solution with a ZXSC310 driving a 1W LED with a typical forward voltage of 3.4V at 300mA from a dual cell battery. A dual cell supply will have a voltage range of 1.8V to 2.5V for NiCd and NiMH type batteries and up to 3V for alkaline type batteries. Low cost, small and simple solutions are important in applications such as flashlight, signage and illuminations where 1W high power LED is powered from a low voltage supply as in single and dual cell batteries.

Typical dual cell battery powered 1W LED drive circuit. Source: Zetex

Dimming and shutdown In circuit diagram, the shutdown pin, Stdn, can be tied to VCC pin for normal operation. If the shutdown pin is taken to ground, the ZXSC310 enters standby mode with a low quiescent current of 5microA. The shutdown pin can also be used for PWM dimming by connecting a PWM signal. The LED current is then dependent on PWM duty ratio.