PFC Stage Voltage Control for Switching Power Supply Start-Up

The PFC stage target level is made dynamic rather than fixed. During start-up, the target level is temporarily increased to allow operation with higher AC input voltages. Once the power supply reaches steady-state operation, the target level returns to the normal steady-state level. This dynamic adjustment resolves the contradiction by adapting the target level to the operational phase, ensuring reliable start-up without permanently increasing control complexity.

The PFC stage target level is adjusted periodically based on the operational phase. During the transient start-up phase, the target level is increased to prevent shutdown from high AC input voltage. During steady-state operation, the target level returns to the optimal steady-state level for maximum efficiency. This periodic adjustment between different target levels resolves the contradiction by applying the appropriate target level at the appropriate time.

Different target levels are applied to different operational phases and loading conditions. The system implements a first target level for start-up conditions, a second target level for steady-state full loading conditions, and a third target level for light loading conditions. This local optimization of target levels for specific operating conditions resolves the contradiction by improving efficiency where needed without requiring complete system redesign.