STMicroelectronics boosts resonant converter efficiency

STMicroelectronics has introduced the STNRG599A and STNRG599B resonant-converter controllers featuring an advanced phase-shift control (PSC) technique designed to increase efficiency, particularly under no-load conditions, while supporting deep, flicker-free dimming in lighting systems.

The STNRG599A targets power conversion applications and integrates X-capacitor discharge circuitry for enhanced safety in adapters, chargers, TV power supplies, and industrial SMPS. The STNRG599B, without the discharge function, is optimized for lighting-driver designs. Both devices operate at switching frequencies up to 750 kHz and support a wide input-voltage range suitable for applications from 90 W to several hundred watts.

Each IC provides two complementary outputs driving external high- and low-side switches 180° out of phase, enabling zero-voltage switching (ZVS) across the entire operating range. ST’s PSC method directly controls the phase shift between the half-bridge voltage and resonant-tank current, reducing sensitivity to LLC/LCC component tolerances. This approach stabilizes burst-mode transitions, improves dynamic response, and enhances input-voltage ripple rejection.

Integrated protections include hard-switching prevention, anti-capacitive protection, programmable overcurrent management with delayed shutdown and automatic restart, and non-latched brown-out/brown-in protection with adjustable thresholds. These features increase system robustness in short-circuit and overload conditions.

To support rapid development, ST offers the EVLG599-250WLLC evaluation board, combining the STNRG599A with the SRK2001A synchronous rectifier and MasterGaN1L power SiP. The compact, heatsink-free converter achieves sub-1 µA standby current and delivers up to 10 A continuous output current.

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