Opto-Electronics


Buck-boost LED driver

18 April 2012 Opto-Electronics

Linear Technology’s LT3791 is a synchronous buck-boost DC/DC LED driver and voltage controller which can deliver over 100 W of LED power. Its 4,7 V to 60 V input voltage range makes it ideal for a wide variety of applications, including automotive, industrial and architectural lighting.

Similarly, its output voltage can be set from 0 V to 60 V, enabling it to drive a wide range of LEDs in a single string.

The internal four-switch buck-boost controller operates from input voltages above, below or equal to the output voltage, ideal for applications such as automotive, where the input voltage can vary dramatically during stop/start, cold crank and load dump scenarios.

Transitions between buck, pass-through and boost operating modes are seamless, offering a well-regulated output even with wide variations of supply voltage. The LT3791’s design utilises three control loops to monitor input current, LED current and output voltage to deliver optimal performance and reliability.

The IC uses four external switching MOSFETs and delivers from 5 W to over 100 W of continuous LED power with efficiencies up to 98,5%. LED current accuracy of ±6% ensures constant lighting while ±2% output voltage accuracy enables the converter to operate as a constant voltage source.

The LT3791 utilises either analog or PWM dimming as required by the application. Furthermore, its switching frequency can be programmed between 200 kHz and 700 kHz or synchronised to an external clock. Additional features include output disconnect, input and output current monitors, open and shorted LED detection and integrated fault protection.



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