Series-Parallel Mode Active Clamp Flyback Converter Leakage Energy Recovery
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Solution Overview
Problem
Flyback converters face efficiency challenges due to parasitic leakage inductances that cause energy losses, and the need for miniaturization often results in higher switching frequencies, which further degrade efficiency.
Innovation Solution
The implementation of series-parallel mode active clamps that absorb and retain leakage energy in snubber capacitors, allowing it to be returned to the input power source, while minimizing switching losses by selectively turning on the clamp switch near peak voltages and delaying its turn-off for zero-voltage switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If miniaturization is pursued to reduce converter size, then volume is reduced, but switching frequency increases which degrades efficiency
Solution Approach 1:
The patent converts the harmful leakage energy that would normally be lost into a beneficial resource by capturing it in snubber capacitors and returning it to the input power source. This allows the converter to achieve high efficiency without requiring high switching frequencies, thus avoiding the efficiency degradation that typically accompanies miniaturization.
Solution Approach 2:
The patent changes the operating parameters by implementing series-parallel mode operation with active clamps, allowing the converter to operate at lower switching frequencies while maintaining compact size. The series-parallel topology enables flexible control of energy transfer and allows optimization of switching frequency independent of size constraints.
2Loss of energy
If leakage energy recovery is implemented, then efficiency is improved, but device complexity increases
Solution Approach 1:
The snubber capacitors serve multiple functions: they capture leakage energy during the switch-off period, hold this energy during the working energy transfer, and then discharge it back to the input power source. This multi-functionality reduces the need for separate dedicated leakage energy recovery circuitry, thereby limiting the increase in device complexity.
Solution Approach 2:
The patent merges the leakage energy recovery function with the existing snubber circuitry and power transfer pathways. By integrating these functions into the existing converter architecture rather than adding completely separate systems, the increase in device complexity is minimized while still achieving efficient leakage energy recovery.
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 enhances efficiency by recovering leakage energy and reducing switching losses, allowing for smaller, more efficient power converters without the need for high switching frequencies.
Implementation Method 1
the converters may transfer the leakage energy from the leakage inductance to snubber capacitors by charging the snubber capacitors in series
Implementation Method 2
two coils that are electromagnetically coupled with each other, like primary and secondary windings of a transformer
Implementation Method 3
the converter embodiments described herein may then start a resonance between the primary coil (and leakage inductance) and a parasitic capacitance of the primary switch. The resonance may create a sinusoidal voltage across the primary switch
Implementation Method 4
the converter embodiments described herein may turn off the clamp switch adaptively, and after a delay, at zero-voltage switching (ZVS) or a minimum non-zero voltage turn on the main primary switch
Data Source
AI summary
This disclosure describes a flyback converter with a series-parallel mode (SPM) active clamp. The active clamp, coupled in parallel with the primary coil, may include a clamp switch, two or more snubber capacitors, and associated diodes. The active clamp may be configured to absorb and retain the leakage energy from the leakage inductance of the flyback converter. The clamp switch may be turned on selectively as the primary switch approaches one of a plurality peak values to adjust frequencies of the switching devices. With the active clamp circuit, the flyback converter may first re-capture the leakage energy in the active clamp circuit and then recover it back to the power source.