Flyback Power Supply Dynamic Load Control
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Solution Overview
Problem
Flyback switching power supplies face challenges in achieving rapid dynamic response and short voltage recovery time, especially when switching from full load to extremely light load, with existing control methods resulting in slow response, long recovery times, and significant overshoot voltage.
Innovation Solution
A control system for flyback switching power supplies that includes a sampling module, multi-modes judgment module, dynamic control module, load point judgment module, and PWM drive module, which turns off the primary-side switching transistor and controls the secondary-side synchronous rectification transistor with a fixed cycle and duty cycle during heavy-to-light load switching, rapidly reducing output voltage and determining the load point based on the voltage slope to stabilize the system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If digital multi-modes control algorithm is used to improve dynamic response, then switching speed is improved, but response time increases and overshoot voltage increases when loads are switched in large range
Solution Approach 1:
The patent introduces a dynamic process detection module that proactively identifies load switching events before the system fully transitions to a new steady state. By detecting the dynamic process early and predicting the target load range, the system can prepare and switch control modes in advance, rather than sequentially transitioning through each mode boundary. This preliminary detection and prediction mechanism significantly reduces the overall response time when loads are switched in large ranges.
2Speed
If PI parameters are increased to speed up compensation, then dynamic performance is improved, but system stability may be compromised and improvement is limited for multi-modes control
Solution Approach 1:
The patent implements dynamic adjustment of PI parameters based on the detected load switching state. During normal operation, standard PI parameters are used to maintain system stability. When a load switching event is detected and the system enters dynamic mode, the PI parameters are dynamically adjusted to accelerate compensation. This dynamic parameter adjustment allows the system to achieve fast response during transients while maintaining stability during steady-state operation, resolving the contradiction between speed and reliability.
Data Source
AI summary
Provided is a dynamic control method that turns off a primary-side switching transistor when an output voltage exceeds an upper limit, and control the switching of a secondary-side synchronous rectification transistor with a fixed cycle and a fixed duty cycle. During the time that the synchronous rectification transistor is turned on, the energy of a load capacitor at the output end is extracted to the primary side, which causes the output voltage to drop rapidly and the overshoot voltage to decrease greatly.