Flyback Converter Adaptive Frequency Control for Phase Margin Stability
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Solution Overview
Problem
Prior art output-programmable flyback power converters experience a decrease in operation frequency and equivalent output impedance when switching to a lower output voltage, leading to a reduced phase margin and system instability.
Innovation Solution
A flyback power converter with a transformer circuit, power switch circuit, current sense circuit, opto-coupler circuit, and control circuit that adaptively adjusts operation frequency, current gain, feedback attenuation, and slope compensation to maintain a same or higher operation frequency and output current when switching to a lower output voltage, ensuring a stable phase margin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the output voltage is switched to a relatively lower level, then the output power decreases, but the operation frequency decreases and phase margin becomes unstable
Solution Approach 1:
The control circuit dynamically adjusts the operation frequency based on the detected output voltage level. When switching to a lower output voltage, the control circuit adaptively increases the operation frequency to compensate for the decreased output power, thereby maintaining stable phase margin and preventing system instability.
Solution Approach 2:
The patent changes the operation frequency parameter in response to output voltage switching. Specifically, when the output voltage switches to a lower level, the operation frequency is increased to maintain adequate phase margin, representing a dynamic parameter adjustment to resolve the stability issue.
2Productivity
If the operation frequency is reduced to match lower output power, then the bandwidth increases, but the equivalent output impedance decreases and system stability deteriorates
Solution Approach 1:
The control circuit employs feedback mechanisms to monitor the output voltage and phase margin conditions. Based on this feedback, the control circuit adjusts the operation frequency to maintain system stability, preventing the deterioration that would result from simple frequency reduction approaches.
3Adaptability or versatility
If the output voltage is programmed to switch between different levels, then the adaptability improves, but the phase margin becomes lower than 45 degrees at lower voltage levels
Solution Approach 1:
The system dynamically adjusts the operation frequency based on the programmed output voltage level. When operating at lower voltage levels, the frequency is increased to maintain adequate phase margin, allowing the system to maintain both adaptability and stability 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
The solution maintains a stable phase margin and output current when switching to a lower output voltage, preventing system instability and ensuring efficient power conversion.
Implementation Method 1
a transformer circuit, which includes: a primary winding, for receiving an input voltage; a secondary winding, for generating the output voltage at an output node
Implementation Method 2
an opto-coupler circuit, which is coupled to the secondary winding, for generating a feedback signal according to an output power and the setting signal
Data Source
AI summary
The present invention provides a flyback power converter with a programmable output and a control circuit and a control method thereof. The flyback power converter converts an input voltage to a programmable output voltage according to a setting signal, wherein the programmable output voltage switches between different levels. The flyback power converter includes: a transformer circuit, a power switch circuit, a current sense circuit, an opto-coupler circuit, and a control circuit. The control circuit adaptively adjusts an operation signal according to a level of the programmable output voltage, to maintain a same or relatively higher operation frequency of the operation signal when the programmable output voltage switches to a relatively lower level, so as to maintain a phase margin while supplying the same output current.