This application note provides design considerations for using the FSFR-series FPS™ in LLC resonant half-bridge converters. Topics include an explanation of LLC resonant converter operation, transformer and resonant network design, and component selection. A design example is given that walks through the design process, with each step explained in detail.
The document presents the principle of LLC resonant converters, including the roles of magnetizing inductance (Lm), resonant inductance (Lr), and resonant capacitance (Cr). It describes how the converter achieves zero‑voltage switching (ZVS) and high efficiency by reducing switching losses.
It also covers practical design topics such as integrated transformer design, operating modes for maximum gain, and a reference design example with a 400 VDC input, 24 V 8 A (192 W) output, and a 20 ms hold time. The FSFR series features a minimal component count and built‑in PFM controller for improved performance. This manual is written in Japanese.
| Input voltage (reference design) | 400 VDC |
|---|---|
| Output voltage and current (reference design) | 24 V, 8 A (192 W) |
| Hold time (reference design) | 20 ms (50 Hz) |
| PFC output current capacity | 220 A |
The reference design uses a 400 VDC input.
It provides 24 V at 8 A, which is 192 W.
The hold time is specified as 20 ms at a 50 Hz line frequency.
The PFC stage can deliver up to 220 A.