Adaptive Soft Start for Switching Power Converters
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Solution Overview
Problem
Conventional primary-only feedback switching power converters are slow to reach the regulated target voltage during start-up and are susceptible to false fault detection due to inaccurate voltage sensing, especially when coupled with high capacitance output filters, leading to potential damage or failure.
Innovation Solution
The switching power converter employs adaptive control by operating in Continuous Conduction Mode at initial startup for rapid voltage rise, transitioning to open loop Discontinuous Conduction Mode once the output voltage reaches a threshold, and then to closed loop Discontinuous Conduction Mode to minimize overshoot and ringing, using sensed voltage thresholds to accurately monitor and regulate the output voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional primary-only feedback converters use fixed reference voltage comparison during start-up, then the control scheme is simple, but the output voltage rises slowly and may cause damage to connected devices
Solution Approach 1:
The patent applies dynamics by transitioning the converter between different conduction modes (CCM and DCM) based on the output voltage level. During start-up, the converter operates in CCM to achieve rapid voltage rise, then switches to DCM when the voltage reaches a threshold, providing adaptive control that resolves the contradiction between speed and safety
Solution Approach 2:
The patent changes the conduction mode parameter based on operating conditions. By detecting the output voltage level and switching between CCM and DCM, the system dynamically adjusts its behavior to achieve both fast start-up and safe operation, preventing damage to connected devices
2Speed
If the converter operates in continuous conduction mode during start-up, then the output voltage rises rapidly, but the sensed voltage provides inaccurate representation leading to false fault detection
Solution Approach 1:
The patent dynamically switches between CCM and DCM based on the output voltage threshold. When the voltage is low during start-up, CCM provides rapid rise. When the voltage reaches the threshold, the system transitions to DCM where voltage sensing becomes accurate, eliminating false fault detection while maintaining fast response
3Stability of the object's composition
If the converter uses high capacitance electrolytic capacitors in the output filter, then the output filtering is improved, but the start-up time is significantly extended
Solution Approach 1:
The patent uses dynamic mode switching to overcome the time constant limitation of high capacitance filters. By operating in CCM during start-up, the converter delivers maximum power to charge the output capacitors rapidly, then transitions to DCM for stable regulation, achieving both fast start-up and stable output
Data Source
AI summary
A switching power converter provides regulated voltage to a load according to a desired regulation voltage. The switching power converter includes a transformer coupled to a switch and a switch controller for generating a control signal to control switching. The switch controller monitors a sensed voltage representing the output voltage of the switching power converter. The switch controller controls switching of the switch to operate the switching power converter in a continuous conduction mode while the sensed output voltage indicates that the output voltage is less than a first threshold voltage. The switch controller controls switching of the switch to operate the switching power converter in a discontinuous conduction mode while the sensed output voltage is above the first threshold voltage.