This application note presents a solution for designing a 400W fixed-off-time controlled PFC preregulator using the L6563S and L6563H. The solution utilizes peak current-mode control with fixed-off-time, combining the simplicity and affordability of TM operation with the high-current capability of FF-CCM operation.
This document introduces fixed-off-time (FOT) control as a cost-effective alternative for Power Factor Correction (PFC) preregulators, combining the simplicity of transition mode with high-current capabilities. It details the operation of FOT-controlled circuits and presents the specific implementation using the L6563S controller.
The guide provides a step-by-step design procedure for a 400W board, covering component selection for the bridge rectifier, input/output capacitors, boost inductor, and power MOSFET. It also includes a design example utilizing an Excel spreadsheet and compares the L6563S with the L6563H variant.
| Power rating | 400 W |
|---|---|
| Control method | Peak current-mode control with fixed-off-time |
| Controller models | L6563S, L6563H |
| Topology | Boost |
FOT control couples the simplicity and affordability of transition mode operation with the high-current capability of continuous conduction mode operation.
No, it does not need a specialized control IC, only a simple modification of a standard TM PFC controller with a few additional passive parts.