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Switching regulator efficiently drives HB-LEDs

Posted: 09 Oct 2007 ?? ?Print Version ?Bookmark and Share

Keywords:HB-LEDs? switching regulator? LED driver?


ON Semiconductor has introduced the NCP3065 switching regulator designed to efficiently drive high-brightness LEDs (HB-LEDs) typically used in low-voltage lighting, landscape path and solar lighting, halogen bulb replacements and automotive and marine lighting. Several reference designs are available to drive the latest HB-LEDs in various buck, boost and SEPIC applications.

The NCP3065 is a 1.5A monolithic switching regulator that features a very low feedback voltage of 235mV. The feedback voltage is used to regulate the average current through the LED string in a constant current regulator configuration. The low feedback voltage also allows the use of a smaller and more cost-competitive sense resistor. The power dissipation in the sense resistor is reduced by 80 percent compared to competitive devices which utilize a standard 1.25V feedback voltage. This can result in up to 2 percent savings on the overall system efficiency. The internal reference voltage is trimmed to 2 percent to provide very accurate current regulation even with wide variations in input voltage, LED forward voltage and inductor tolerance.

The device has a wide input voltage that range from 3V to 40 V to allow operation from 12Vac and 12Vdc supplies commonly used for lighting applications and unregulated power supplies such as lead acid batteries. The devices can be configured in a controller topology with the addition of an external transistor to support higher LED currents beyond the 1.5 A rated switch current of the internal transistor. In a boost configuration, the external switch also enables the capability of higher output voltages.

"The NCP3065 offers our customers a versatile and easy-to-implement regulator for HB-LED applications," said Tim Kaske, product line marketing manager for ON Semiconductor's power regulation product group. "We had a customer recently looking to utilize HB-LED in a handheld lighting application. It needed to fit into the existing area and thermal solution of an incandescent bulb. The NCP3065 in the small 4mm x 4mm DFN package was the only solution available that could meet the efficiency, thermal, size and voltage requirements. We are already seeing that with the flexibility and performance of the NCP3065, it is becoming the standard for DC/DC conversion in HB-LED applications at our customers."

The NCP3065 is also available in automotive grade as the NCV3065. The NCP3065 and NCV3065 are offered in a 4mm x 4mm DFN-8 package and priced at 32 cents per unit in 10,000-unit quantities. The devices are also offered in an SOIC-8 and a PDIP-8 package priced at 30 cents per unit in 10,000-unit quantities.

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