LEADTREND LD7792: Deep Dive into Transition-Mode PFC + Quasi-Resonant PWM Integrated Controller
The LD7792 is an enhanced version of the LD7790, targeting cost-sensitive medium-power applications (40W~150W LED drivers, adapters, monitor power supplies). It integrates a Transition-Mode (TM/BCM) PFC controller and a QR current-mode PWM controller, greatly reducing external component count.
Key Technical Highlights: • PFC section uses Boundary Conduction Mode (TM) with a high-precision multiplier for high power factor (PF >0.92) and low THDi. • QR PWM section supports valley switching, reducing switching losses, improving light-load efficiency, and lowering audible noise (significant improvement in startup and light-load noise). • Supports 3-in-1 dimming (resistive, 0-10V, PWM) with high constant-current accuracy and excellent current ripple control. • Comprehensive protections: OTP, OCP, OVP, Brown-in/out, etc. • SOP-16 package with simple peripheral circuitry, suitable for single-stage or two-stage architectures.
Compared to the previous generation, THDi is lower, startup noise is reduced, and overall efficiency improves by 1~2 percentage points, offering better BOM cost competitiveness.
Typical Applications: - Smart lighting (panel lights, downlights, track lights) - Medium-power AC-DC adapters - TV / monitor power supplies
Design Considerations: - Set PFC output voltage around 380~400V for optimal efficiency when paired with the QR stage. - Flexible dimming interface; choose the appropriate mode based on requirements. - Green Mode automatically engages at light load, easily meeting the latest standby power regulations.
Engineers working on LED drivers or PFC projects — the reference designs for this chip are worth downloading. Have you encountered any dimming compatibility issues in practice? Feel free to share circuit diagrams or PCB layout experience in the comments!
