Active Clamp Flyback Power Converter Skip Mode Control
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Solution Overview
Problem
Power converters face challenges in achieving low power consumption at light loads due to varying primary inductance over switching frequency ranges, leading to issues with skip mode activation and potential audible noise, making it difficult to meet regulatory requirements for standby power consumption.
Innovation Solution
The active clamp flyback power converter adjusts the primary inductor current over a range of switching frequencies and associated inductances to maintain a fixed output power, ensuring efficient operation and compliance with standby power regulations by varying the primary inductor current in accordance with pre-defined tables and feedback mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the switching frequency is decreased in frequency fold-back mode to reduce switching losses, then energy efficiency is improved, but the primary inductance varies over the switching frequency range causing difficulty in achieving consistent fixed output power at light loads
Solution Approach 1:
The patent implements dynamic adjustment of the primary inductor current based on the switching frequency and associated inductance values. The controller dynamically selects from pre-defined tables of inductor current values corresponding to different switching frequencies, enabling the system to adapt to varying inductance conditions while maintaining consistent fixed output power delivery at light loads.
Solution Approach 2:
The patent changes the operating parameters by varying the primary inductor current in accordance with pre-defined tables that correlate switching frequency with appropriate inductor current values. This parameter adjustment compensates for the varying primary inductance over the switching frequency range, allowing consistent fixed output power to be maintained despite frequency changes.
2Use of energy by stationary object
If the fixed power delivery point is set too high to ensure skip mode activation, then standby power consumption is reduced, but audible noise may occur at higher loads
Solution Approach 1:
The patent dynamically adjusts the primary inductor current based on actual load conditions and switching frequency, allowing the fixed power delivery point to adapt rather than remaining static. This dynamic adjustment enables the system to achieve low standby power consumption when appropriate while avoiding audible noise at higher loads by preventing premature skip mode activation.
3Stability of the object's composition
If the primary inductor current is frozen during foldback to achieve output voltage regulation, then voltage regulation is improved, but the varying primary inductance over frequency range makes it difficult to achieve both low power consumption and fixed power delivery entry
Solution Approach 1:
The patent employs feedback mechanisms where the controller monitors the switching frequency and selects appropriate primary inductor current values from pre-defined tables. This feedback loop allows the system to maintain stable output voltage regulation while simultaneously achieving consistent fixed power delivery entry by compensating for varying primary inductance through adaptive current adjustment.
Data Source
AI summary
A power converter has a power transistor and inductor coupled in a conduction path with the power transistor. A switching frequency of the power transistor is reduced during a light load condition. A pulse width of a drive signal to the power transistor is controlled to select a current through the inductor and power transistor corresponding to the switching frequency to maintain a fixed output power of the power converter, and further to vary the current through the inductor and power transistor to maintain the fixed output power of the power converter over a range of switching frequencies. A first number of pulses of the drive signal to the power transistor during a first time period sets the fixed output power of the power converter. No pulses of the drive signal are provided during a second time period after the first time period.