Power Converter Switch Input Circuit for Inrush Current Control
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Solution Overview
Problem
Power converters, such as AC-DC converters, face challenges in efficiently charging the output capacitor while avoiding high inrush currents during startup.
Innovation Solution
The method involves a power converter with a control circuit that detects its operating state and operates in a switched-mode by alternately switching on and off first and second electronic switches, regulating the input current to charge the output capacitor efficiently and prevent high inrush currents. This includes using bidirectionally blocking switches, like MOSFETs in series, and controlling their operation to manage the input current effectively during startup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the output capacitor is charged directly during startup, then the capacitor charges quickly, but high inrush currents occur
Solution Approach 1:
The patent applies preliminary action by pre-charging the output capacitor through a dedicated charging circuit before the main power converter operation begins. The charging circuit is activated first to charge the capacitor to a predetermined voltage level, and only after this preliminary charging is complete does the main converter start operating. This sequence prevents inrush currents by ensuring the capacitor is already charged when the main power path is engaged.
Solution Approach 2:
The patent uses an intermediary charging circuit as a mediator between the power source and the output capacitor during startup. This intermediate charging path, controlled by a separate switch, provides a controlled route for charging the capacitor without subjecting the main converter components to high inrush currents. The intermediary circuit handles the charging function while the main converter remains protected.
2Loss of energy
If switched-mode operation is used to regulate input current, then power conversion efficiency improves, but circuit complexity increases
Solution Approach 1:
The patent applies universality by designing the switched-mode circuit to perform multiple functions: it regulates input current during normal operation, charges the output capacitor during startup through the same switching mechanism, and provides soft-start functionality. By making the switching circuit multi-functional, the patent achieves efficient power conversion without adding separate dedicated circuits for each function, thereby limiting the increase in overall system complexity.
Solution Approach 2:
The patent uses dynamics by implementing a dynamic control scheme where the switching frequency and duty cycle are adjusted based on the operating state. During startup, the switching parameters are controlled to charge the capacitor gradually; during normal operation, they are adjusted for optimal power conversion efficiency. This dynamic adaptation allows a single circuit design to handle multiple operating conditions efficiently.
Data Source
AI summary
A method for operating a power converter and a control circuit are disclosed. The method includes, in a power converter including an input, a converter stage, a first switch connected between the input and the converter stage, a second switch connected between input nodes of the converter stage, and an output capacitor connected between output nodes of the converter stage: detecting an operating state of the power converter; and operating the power converter in a first operating mode when the power converter is in a first operating state. Operating the power converter in the first operating mode includes regulating an input current received at the input by a switched-mode operation of the first and second electronic switches.