Date: 13/02/2012

New conntroller IC from ST for LLC resonant voltage converters

STMicroelectronics has unveiled new controller IC for LLC resonant voltage converters. ST says the L6699D, is the first of its type to combine anti-capacitive protection, auto-adaptive dead-time and enhanced safe-start operation.

By reducing stress on the power MOSFETs of the converter half-bridge, the L6699D's anti-capacitive protection and safe start-up allow designers to specify smaller, lower-cost MOSFETs.

ST's patented auto-adaptive dead-time adjusts the duration when both power switches in the half-bridge are turned off. This enables optimized zero-voltage switching over the complete load range from light load to full load using a smaller transformer and resonant components, thereby minimizing both solution size and energy loses in the resonant components, explains ST. By increasing efficiency at light loads, the L6699D can also save the need for a separate standby power supply in equipment such as televisions pr all-in-one PCs thereby further reducing cost and form factor, suggests ST.

The L6699D is used with two companion chips, the L6563H Power-Factor Correction (PFC) controller and SRK2000 synchronous rectifier driver, to create a complete control solution for medium to high-power applications. Compared to other approaches that combine resonant control, PFC control and sometimes also power MOSFETs in the same package, ST's discrete devices enhance functionality and flexibility for designers, claims ST.

Major features of L6699D:
Anti capacitive mode detection
Adaptive dead time
Reduced audible noise with enhanced burst mode
Reduced stress on power mosfets with enhanced safe start feature
Direct interface with PFC stage
Two-level Over-Current Protection (OCP): frequency shift and immediate shutdown

The L6699D is sampling now in the SO16N package, priced at $1.50 for orders over 1000 pieces. Mass production will begin within Q1 2012.