Asymmetric DC-DC Converter Control for Biasing Current Reduction
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Solution Overview
Problem
Asymmetric DC-DC converters face issues with increased biasing and ripple currents due to direct current biasing, which affects conversion efficiency and reliability, especially under varying load conditions.
Innovation Solution
A control method and module that samples the output signal to generate control signals for power switches with specific duty cycles, adjusting the turn ratio of coils to minimize biasing and ripple currents through pulse-width modulation, ensuring the sum of duty cycles is one.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If asymmetric complementary control is adopted to reduce switching voltage stress and simplify structure, then device complexity is reduced, but biasing current increases which worsens conversion efficiency
Solution Approach 1:
The patent implements dynamic control of the first and second duty cycles based on real-time detection of biasing current and ripple current. The controller adjusts duty cycles D1 and D2 dynamically so that their sum equals one, adapting to varying load conditions to minimize both biasing current and ripple current, thereby resolving the contradiction between simplified asymmetric structure and energy loss.
Solution Approach 2:
The patent changes the control parameters by introducing duty cycle constraints where D1 + D2 = 1, and dynamically adjusting the individual duty cycle values based on load conditions. This parameter optimization allows the converter to maintain low biasing current and ripple current across different operating points, improving conversion efficiency without complicating the basic asymmetric structure.
2Object-generated harmful factors
If inductance of inductor Lm is reduced or larger magnetic cores are used to reduce biasing current impact, then biasing current effect is reduced, but conversion efficiency deteriorates and output power density is reduced
Solution Approach 1:
The patent employs feedback control by detecting the biasing current and ripple current in real-time, then using this information to dynamically adjust the duty cycles D1 and D2. This closed-loop control eliminates the need to physically reduce inductance or increase magnetic core size, as the control system actively compensates for biasing current effects, maintaining high conversion efficiency and power density.
3Ease of operation
If conventional asymmetric control is used under light loading, then converter operates simply, but reverse direction inductor current causes voltage peak of synchronous rectifier to increase reducing reliability
Solution Approach 1:
The patent uses feedback control to detect when inductor current attempts to flow in reverse direction under light loading conditions. The controller responds by adjusting the duty cycles to prevent reverse current flow, thereby avoiding voltage peaks at the synchronous rectifier that would compromise reliability, while maintaining simple operation through automated control.
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
The solution reduces biasing and ripple currents, enhancing the efficiency and reliability of asymmetric DC-DC converters by optimizing power density and reducing switching voltage stress, suitable for various load conditions.
Implementation Method 1
a voltage-converting circuit that cooperates with the first and second power switches for generating the output signal. The voltage-converting circuit includes a primary coil unit and a secondary coil unit that is operatively associated with the primary coil unit for voltage conversion
Data Source
AI summary
A control method is provided for controlling an asymmetric DC-DC converter including first and second power switches that are driven respectively by first and second control signals, and a voltage-converting circuit that is operatively associated with the first and second power switches for generating an output signal. The voltage-converting circuit includes a primary coil unit and a secondary coil unit operatively associated therewith for voltage conversion, and including first and second coils that have a turn ratio not equal to one. The control method includes: sampling the output signal to obtain a sample signal corresponding thereto; and generating the first and second control signals, which correspond respectively to first and second duty cycles having a sum of one, based on a comparison between the sample signal and a reference signal such that the first and second power switches are driven in an alternating manner.