LLC resonant controller cuts energy loss, BOM and size

STMicroelectronics is starting to sample a controller that it says can make power units such as laptop adapters, PC power supplies and LED lighting ballasts more efficient, cost effective, reliable and quiet.

Dubbed the L6699D, ST says its latest controller for LLC resonant voltage converters is the first of its type to combine anti-capacitive protection, auto-adaptive dead-time and enhanced safe-start operation. These features are implemented using patented techniques, and effectively reduce stress on associated power semiconductors while enabling optimized zero-voltage switching for greater energy efficiency across the power supply's full load range.

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. There is also a patented method for improving burst-mode operation, which reduces audible noise from the converter without requiring a large or expensive filter.

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. By increasing efficiency at light loads, the L6699D can also save the need for a separate standby power supply in equipment.

Key features:

• 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

Pricing: $1.50 for orders over 1000 pieces.

Availability: Sampling now in the SO16N package; mass production will begin within Q1 2012.