Boost Converters Drive OLEDs and White LEDs

May 10, 2006 1:39 PM

Two high-efficiency, dual-output dc-dc boost converters from Texas Instruments (TI), the TPS61140 and TPS61150, each manage two sets of six white LEDs. Each device requires a single inductor. The devices feature an input voltage of 3 V to 6 V and can deliver up to 0.7 A of output current, making them well suited to drive organic LED (OLED) subsdisplays and white LED backlights.

The boost converters incorporate a power MOSFET and power diode, eliminating the need for any external active power components. The chips supply up to 27 V and operate with up to 82% efficiency.

TI’s TPS61140 allows each individual voltage and current level to be programmed through external resistors. If its voltage output is enabled, the boost converter is controlled by pulse-frequency modulation (PFM) to achieve high efficiency over a wide load range. If the current output is selected, the device adopts a 1.2-MHz pulse width modulation (PWM) control method to maximize output current. Applying an external PWM signal to the select pin reduces the output current, thereby allowing white LED dimming.

TI’s TPS61150 high-frequency boost converter with two regulated current outputs drives white LEDs in LCD backlights. As with the TPS61140, this device allows output current reduction or PWM dimming of the white LEDs. The regulator’s 1.2-MHz fixed switching frequency reduces output ripple and avoids audible noises.

The TPS61140 and TPS61150 are available in volume production in a 10-pin, 3-mm x 3-mm QFN package. They are priced at $1.85 for the TPS61140 and $1.65 for the TPS61150 in quantities of 1,000 units.