Power Factor Improvement Circuit Voltage Clamp for Burst Mode Stability
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Solution Overview
Problem
Switching power-supply apparatuses with power factor improvement circuits experience increased switching loss and efficiency reduction due to undershoot or overshoot of output voltage during burst operations, leading to instability and reduced power conversion efficiency.
Innovation Solution
A power factor improvement circuit that includes a first circuit outputting a voltage corresponding to the error between a reference voltage and the output voltage, a second circuit outputting a voltage that rises synchronously with the switching element being turned on, and a clamp circuit that limits the voltage during burst operations to prevent undershoot or overshoot, thereby maintaining a stable output voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If burst operation is performed to reduce switching loss during light-load conditions, then power conversion efficiency is improved, but output voltage stability deteriorates due to undershoot or overshoot
Solution Approach 1:
The patent implements feedback control by detecting the output voltage and comparing it with a reference voltage to generate an error signal. This error signal is used to adjust the switching element's operation, ensuring that output voltage stability is maintained even during burst operation at light-load conditions, thereby resolving the contradiction between reducing switching loss and maintaining voltage stability.
Solution Approach 2:
The patent applies preliminary action by pre-charging a capacitor before the switching element turns on during burst operation. This preliminary charging action prevents voltage undershoot when the switching element activates, allowing the system to reduce switching loss while maintaining output voltage stability through proactive voltage management.
2Speed
If switching frequency is increased to improve response speed, then control precision is improved, but switching loss increases
Solution Approach 1:
The patent employs periodic action by implementing burst operation mode during light-load conditions, where the switching element operates in periodic bursts rather than continuously. This approach maintains adequate response speed through timely activation while significantly reducing overall switching loss by minimizing the number of switching cycles, thus resolving the contradiction between response speed and switching loss.
3Productivity
If power factor improvement control is implemented to reduce reactive power, then power conversion efficiency is improved, but circuit complexity increases
Solution Approach 1:
The patent merges the power factor improvement function with the existing switching power supply circuit by integrating the control mechanism into the current switching element. This consolidation achieves power factor improvement and enhanced power conversion efficiency without adding separate dedicated circuits, thereby minimizing the increase in circuit complexity while maintaining productivity benefits.
Data Source
AI summary
A power factor improvement circuit that performs, on the basis of an output voltage when a switching power-supply apparatus is in a light-load state or a no-load state, a burst operation for switching between states of the switching operation of a switching element includes: a first circuit that outputs a first voltage that corresponds to the error between a reference voltage and a voltage obtained by dividing the output voltage; and a clamp circuit that, while the burst operation is performed, clamps the lower limit of the first voltage, which decreases when the switching operation of the switching element is disabled, at a lower-limit voltage higher than the ground voltage of the power factor improvement circuit and clamps the upper limit of the first voltage, which increases when the switching operation of the switching element is performed, at an upper-limit voltage.