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Controller IC tailored for single-ended switching power converters

Posted: 15 Dec 2005 ?? ?Print Version ?Bookmark and Share

Keywords:STMicroelectronics? controller IC? L6668?

current-mode primary controller IC

STMicroelectronics (ST) announced a current-mode primary controller IC designed to build single-ended switching power converters. The new L6668 is targeted for use in high-end AC/DC adapters and chargers for laptop PCs. According to ST, the versatility of the L6668's current-mode PWM controller makes it suitable for power supplies of STBs, DVD players, low-end LCD TVs and other digital consumer equipment.

The company added that one of the innovative functions of its new chip is the interface with the PFC controller that enables pre-regulator turn off when the load level falls below a threshold, saving typically 0.5W to 1W of no-load power consumption. This interface can be easily connected to the RUN or PFC_OK pins of ST's L6563 power factor corrector IC.

In addition, the chip's high-voltage (HV) technology, when combined with a multi-chip approach, makes it possible to integrate a HV start-up system that is connected directly to the rectified mains voltage. The HV generator is physically located on a separate chip, made with Bipolar-CMOS-DMOS off-line technology able to withstand 700V, controlled by a low-voltage chip, where all of the control functions reside. This feature helps it to be compliant with energy saving recommendations with minimum usage of external components without compromising the performance, said ST.

Additional features of the L6668 include programmable soft-start, slope compensation for stable operation at duty cycles greater then 50 percent, a disable function, current sense leading edge blanking to improve noise immunity, latched disable for over-voltage or over-temperature shutdown, and protective output current limiting in case the secondary diode fails to short circuit.

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