Switching Power Supply Dynamic Frequency Control for Light Load Efficiency
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Solution Overview
Problem
Conventional DC/DC converters experience efficiency degradation and increased noise levels when operating at light load conditions due to insufficient energy accumulation in resonance coils, preventing soft switching operations.
Innovation Solution
A switching power supply apparatus is designed with a DC/AC converter unit, transformer, resonance circuit, AC/DC converter circuit, output detector, duty ratio controller, energy detector, and controller, which adjusts the switching frequency to maintain energy accumulation in resonance coils, ensuring efficient operation even at light loads by controlling the duty ratio and switching frequency based on detected output currents and voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the switching frequency is lowered to reduce switching loss and enable soft switching, then switching loss is reduced, but at light load conditions the resonance circuit cannot accumulate enough energy to complete capacitor charging and discharging, causing soft switching to fail
Solution Approach 1:
The patent applies dynamics by making the switching frequency adjustable rather than fixed. The control unit dynamically changes the switching frequency based on load conditions: at light loads, it lowers the frequency to allow sufficient energy accumulation in the resonance circuit for soft switching, while at heavy loads, it increases the frequency to maintain efficient power conversion. This dynamic adaptation resolves the contradiction between maintaining soft switching reliability and reducing switching loss across varying load conditions.
Solution Approach 2:
The patent changes the switching frequency parameter according to load conditions. By detecting the load state and adjusting the switching frequency accordingly, the system optimizes energy accumulation in the resonance circuit at light loads while maintaining efficient operation at heavy loads. This parameter change enables the system to achieve both soft switching reliability and reduced switching loss in different operating conditions.
2Object-generated harmful factors
If the switching frequency is lowered to reduce noise, then noise level is reduced, but the resonance circuit current decreases and insufficient energy prevents soft switching operation
Solution Approach 1:
The system dynamically adjusts the switching frequency based on load detection. At light load conditions, it lowers the frequency to reduce noise and enable sufficient energy accumulation for soft switching. At heavy load conditions, it increases the frequency to maintain proper resonance current and soft switching operation. This dynamic control resolves the contradiction between noise reduction and soft switching reliability.
3Loss of energy
If the conventional phase shift PWM control method is used to achieve soft switching, then switching loss is reduced, but at light load the resonance circuit cannot accumulate enough energy to charge and discharge the capacitors, causing soft switching to fail
Solution Approach 1:
The patent enhances adaptability by implementing dynamic switching frequency control that responds to load conditions. The control unit detects load state and adjusts the switching frequency accordingly: lowering it at light loads to enable energy accumulation and soft switching, and raising it at heavy loads to maintain efficient power conversion. This dynamic adaptation allows the system to maintain soft switching across the full load range, significantly improving load condition adaptability while preserving switching loss benefits.
Solution Approach 2:
The system changes the switching frequency parameter based on detected load conditions, enabling the conventional phase shift PWM control to achieve soft switching at both light and heavy loads. This parameter adaptation resolves the limitation of fixed-frequency control and improves versatility across different operating conditions.
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 solution effectively suppresses efficiency reduction and noise increase at light loads, enabling continuous soft switching operations and maintaining high efficiency and low noise levels across varying load conditions.
Implementation Method 1
a resonance circuit, provided between the DC/AC converter unit and the transformer
Implementation Method 2
the transformer is configured to convert the AC voltage to an AC voltage having a predetermined voltage value
Data Source
AI summary
A switching power supply apparatus includes: an DC/AC converter unit for converting a DC voltage to an AC voltage based on switching operation of switching devices; a transformer for converting the AC voltage to an AC voltage having a voltage value; a resonance circuit provided between the DC/AC converter unit and the transformer; an AC/DC converter circuit for converting an AC voltage from the transformer to a DC; an output detector unit for detecting an output voltage or an output current of the apparatus; a duty ratio controller unit for controlling a duty ratio of switching of the apparatus such that a detected output voltage or current becomes a target value; an energy detector unit for detecting an energy accumulated in the resonance circuit; and a controller unit for controlling a switching frequency such that a detected energy becomes a threshold value.