Flyback Converter Valley Switching Control for High Frequency Efficiency
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Solution Overview
Problem
Conventional QR control mode of flyback converters is not suitable for miniaturization and high switching frequency applications due to increased switching loss, which hinders the development trend of miniaturization and high efficiency in switching power supplies.
Innovation Solution
A converter system with a transformer, primary and secondary side switches, load detection, state detection, and control circuits that set a blanking time based on load state signals to optimize the switching of the primary side switch at the valley of resonance, reducing switching loss across various load states and switching frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional QR control mode is used in flyback converter, then circuit structure is simple and switching loss is low at low frequency, but switching loss increases rapidly with high switching frequency
Solution Approach 1:
The patent applies dynamic control by adjusting the blanking time parameter based on different working conditions. The control circuit dynamically modifies the blanking time to optimize switching timing, enabling the converter to achieve low switching loss across a wide frequency range while maintaining simple circuit structure. This dynamic parameter adjustment resolves the contradiction between structural simplicity and energy efficiency at high frequencies.
2Volume of moving object
If switching frequency is increased to achieve miniaturization, then power supply size is reduced, but switching loss increases
Solution Approach 1:
The patent changes the timing parameter (blanking time) to optimize switching operation. By adjusting the blanking time based on detected working conditions, the control circuit enables efficient switching at high frequencies, allowing miniaturization without proportionally increasing switching losses. This parameter optimization resolves the contradiction between size reduction and energy efficiency.
3Device complexity
If fixed blanking time is used, then control is simple, but switching loss cannot be optimized across various load states
Solution Approach 1:
The patent implements feedback control by detecting working conditions and using this information to adjust the blanking time. The control circuit receives feedback about the operating state and dynamically modifies the blanking time parameter to optimize switching timing, thereby reducing switching losses across different load conditions while maintaining relatively simple control structure.
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 effectively reduces switching loss and supports miniaturization and high-frequency applications by optimizing the switching timing of the primary side switch, ensuring compatibility with various switching frequencies and load states, thereby enhancing the efficiency and compatibility of flyback converters.
Implementation Method 1
The transformer includes a primary winding and a secondary winding
Implementation Method 2
the primary side switch is turned on when a drain-source voltage of the primary side switch is at a valley of the resonance
Data Source
AI summary
A converter includes a transformer, a primary side switch, a load detection circuit, a state detection circuit and a control circuit. The transformer is configured to output a voltage to a load. The primary side switch is coupled to a primary winding and a primary ground terminal. The load detection circuit is configured to detect a load state of the load and output a load state signal. The state detection circuit is configured to detect a reference time point. The control circuit is configured to output a control signal to turn on or off the primary side switch. The control circuit further sets a blanking time according to the load state signal, such that the primary side switch is turned on when a drain-source voltage of the primary side switch is at a valley of the resonance after the blanking time starting from the reference time point.