Leadtrend Unveils LD7771, The New Benchmark for LLC Efficiency

A breakthrough in LLC control, the BBCC-based half-bridge controller overcomes traditional frequency limitations. In the 120W–300W power market—covering TV power boards, laptop adapters, and high-power fast chargers—the half-bridge LLC resonant topology is favored for full-load efficiency. However, skyrocketing switching frequencies at light loads under strict energy regulations (ErP, DoE Level VII) have long been an industry pain point. Addressing this, Leadtrend has introduced the LD7771, featuring cutting-edge "Bang-Bang Charge Control" (BBCC) architecture, integrated Burst mode, and digital delay compensation. This innovation, recently published in the IEEE JESTPE journal, provides a new silicon-level control paradigm for maximizing efficiency in light-load and standby modes.

Current-Sensing-Free BBCC Control and Digital Delay Compensation. The LD7771’s core innovation lies in its departure from traditional frequency-modulation voltage regulation, optimizing dynamic response and efficiency while minimizing costs. By precisely measuring resonance capacitor voltage to infer charge transfer and output power, the chip triggers MOSFET switching without external current sensing circuits. This enables ultra-fast transient response and lower ripple with reduced BOM. Furthermore, it integrates a hardware-based digital delay compensation module to mitigate power drift and jitter in Burst mode. By defining clear entry (10W) and exit (30W) thresholds, it ensures precise burst cycles, eliminating control jitter at the hardware level.

Achieving a 6.68% Efficiency Leap and Rapid Transient Response on a 240W Platform. The LD7771 signifies a shift toward high-precision power boundary management. Validated on a 240W platform (400V input, 20V/12A output), efficiency at a 10W light load jumped from 87.26% to 93.94%—a significant 6.68% improvement. Notably, bidirectional switching time between normal and standby modes is kept within the 107µs–108µs range, preventing voltage drops during sudden load changes. Combined with Leadtrend's previous AHB-topology LD7711, the LD7771 establishes a strong competitive advantage in efficiency, speed, and system cost for high-power PD chargers and monitor power boards.