Switched-Mode Power Converter Control Circuit Frequency Management
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Solution Overview
Problem
Switched-mode power converters face the issue of excessive voltage across the power switch when activated, leading to potential damage due to high switch frequencies and incomplete discharge of the transformer, resulting in increased current and voltage across the power switch.
Innovation Solution
A control circuit and method that dynamically adjust the switch frequency of the power switch from a lower initial frequency to a higher frequency after a predetermined time, utilizing a multiplexer, clock generator, and pulse width modulation controller to manage the voltage across the power switch, incorporating pulse width and frequency modulation to prevent damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the control circuit quickly increases the speed of power conversion, then the power conversion efficiency is improved, but the feedback compensation signal becomes high voltage causing the power switch to have higher switch frequency which may damage the power switch
Solution Approach 1:
The control circuit performs preliminary action by initially operating at a lower first frequency to allow the transformer to discharge completely and establish stable operating conditions. After a predetermined time delay, it then transitions to the higher second frequency for normal operation, preventing voltage spikes that would occur if high frequency operation started immediately
Solution Approach 2:
The control circuit dynamically adjusts the operating frequency of the power switch based on the activation state. It transitions from a first frequency during initial activation to a second frequency after a predetermined time, allowing the system to adapt its operating characteristics to ensure safe startup conditions before achieving full performance
2Productivity
If the power switch operates at high frequency, then the power conversion efficiency is improved, but the transformer cannot discharge completely resulting in increased current and voltage across the power switch
Solution Approach 1:
The control circuit performs preliminary action by initially operating at a lower first frequency to allow the transformer to discharge completely and establish stable operating conditions. After a predetermined time delay, it then transitions to the higher second frequency for normal operation, preventing voltage spikes that would occur if high frequency operation started immediately
Solution Approach 2:
The control circuit implements periodic action by operating the power switch at different frequencies at different time periods. During the initial activation period, it uses a lower first frequency to ensure complete transformer discharge. After the predetermined time period expires, it switches to a higher second frequency for efficient continuous operation
Data Source
AI summary
A method for controlling voltage crossing a power switch of a switched-mode power converter includes the steps of: controlling a switch frequency of the power switch of the switched-mode power converter to a first frequency as activating the switched-mode power converter; and then changing the switch frequency of the power switch to a second frequency after the switched-mode power converter is activated for a predetermined time; wherein the first frequency is lower than the second frequency.