Switching Power Supply Frequency Reduction for Light Load Efficiency
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Solution Overview
Problem
Switching power supplies face inefficiencies due to high switching frequency and increased energy losses in both power factor correction and DC-DC converters, especially in light load conditions, where precise load condition detection is challenging and affected by input AC voltage phase angles.
Innovation Solution
Implementing a switching power supply design with independent load condition detection and frequency reduction control in both power factor correction and DC-DC converters, utilizing bottom skip control to adjust switching frequencies based on load conditions, allowing for precise load detection and minimizing energy losses by stabilizing the input voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If switching frequency is increased in light load condition, then power factor correction performance is improved, but switching loss increases and efficiency deteriorates
Solution Approach 1:
The patent implements dynamic switching frequency adjustment where the PFC converter operates at high frequency during heavy load to maintain power factor correction performance, and automatically reduces switching frequency during light load conditions to minimize switching losses. This dynamic adaptation resolves the contradiction by optimizing operating parameters according to actual load demands.
Solution Approach 2:
The system changes the switching frequency parameter based on load detection results. When light load is detected, the control circuit reduces the switching frequency of the PFC converter, directly changing this critical parameter to reduce switching losses while maintaining adequate power factor correction through the DC-DC converter's regulation capability.
2Measurement precision
If independent load condition detection is implemented in both PFC and DC-DC converters, then frequency reduction control precision is improved, but device complexity increases
Solution Approach 1:
The patent introduces a shared detection circuit as an intermediary that both the PFC converter and DC-DC converter utilize for load condition detection. This intermediary component provides accurate load information to both controllers without requiring separate complete detection systems, thereby improving detection precision while limiting the increase in device complexity through resource sharing.
3Loss of energy
If switching frequency is reduced in light load condition, then switching loss is reduced and efficiency is improved, but power factor correction capability deteriorates
Solution Approach 1:
The patent segments the power factor correction function across two independent converters: the PFC converter handles power factor improvement primarily during heavy load conditions, while the DC-DC converter provides continuous output voltage regulation and contributes to power factor correction during light load conditions. This segmentation allows frequency reduction in PFC during light load without compromising overall power factor correction capability.
Solution Approach 2:
The system employs feedback control where the DC-DC converter continuously monitors output voltage and load conditions, adjusting its operation to compensate for the reduced PFC activity during light load. This feedback mechanism ensures that power factor correction capability is maintained even when PFC switching frequency is reduced, as the DC-DC converter adapts to maintain overall system performance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach optimizes efficiency by reducing switching losses and improving power factor correction, maintaining high precision in load detection and frequency control, thereby enhancing overall conversion efficiency without relying on input AC voltage variations.
Implementation Method 1
A resonance capacitor C4 in parallel with the switching element Q2 and an output capacitor C5 connected through a rectifying diode D2 to the secondary winding S1 of the isolation transformer. A control circuit IC2 ON/OFF-drives the switching element Q2 to generate a quasi-resonant oscillation in a resonance circuit composed of a leakage inductance of the isolation transformer T and the resonance capacitor C4
Data Source
AI summary
Aspects of the invention provide a switching power supply in which frequency reduction control in a light load condition both in a power factor correction converter and a DC-DC converter restrains energy loss and achieves optimum efficiency. A switching power supply can include a power factor correction converter and a DC-DC converter. The DC-DC converter can include a load condition detecting means for detecting a condition of the load, and a frequency reducing means for reducing a switching frequency in the DC-DC converter when a light load condition is detected by the load condition detecting means. The power factor correction converter can include a frequency reducing means for reducing a switching frequency in the power factor correction converter corresponding to the load condition detected by the load condition detecting means of the DC-DC converter.