Inrush Current Reduction via Dynamic Overcurrent Gain Control
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Solution Overview
Problem
Inrush current during the initial transient state of power conversion devices can negatively impact their reliability and peripheral circuits due to the large difference between internally generated band-gap voltage and output capacitor voltage, making it challenging to control gain and bandwidth effectively.
Innovation Solution
A method and apparatus that generate a first signal based on internal voltage, linearly increasing or decreasing it to compare with a reference voltage, allowing for dynamic adjustment of overcurrent sensing gain to control the overcurrent prevention function, thereby reducing inrush current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the reference voltage is linearly increased to reduce the voltage difference between band-gap voltage and output capacitor voltage, then inrush current is reduced, but the gain and bandwidth of the controller are lowered due to the relatively low voltage level in the initial state
Solution Approach 1:
The patent applies dynamics by making the overcurrent sensing gain variable rather than fixed. The gain is dynamically adjusted based on the comparison between the first signal (linearly increasing from zero) and the reference voltage. During the initial transient state when the first signal is lower than the reference voltage, the overcurrent sensing gain is increased to prevent inrush current. As the first signal exceeds the reference voltage, the gain is decreased to恢复正常 controller performance. This dynamic adjustment resolves the contradiction between reducing inrush current and maintaining controller reliability.
Solution Approach 2:
The patent changes the parameter of overcurrent sensing gain based on the operating state. By comparing the first signal with the reference voltage, the system determines whether to use a higher gain (when first signal < reference voltage) or a lower gain (when first signal > reference voltage). This parameter change allows the system to optimize performance for different operating conditions, reducing inrush current during startup while maintaining normal controller functionality during steady-state operation.
2Device complexity
If a fixed overcurrent sensing gain is used, then the control circuit is simple, but it cannot effectively control inrush current during the initial transient state while maintaining proper operation during steady state
Solution Approach 1:
The patent implements dynamics by introducing a variable overcurrent sensing gain that changes based on the comparison between the first signal and reference voltage. The gain control unit adjusts the gain dynamically: increased during the initial transient state to prevent inrush current, and decreased during steady state to maintain normal operation. This dynamic approach effectively controls inrush current while keeping the circuit structure relatively simple, avoiding the need for complex multiple gain stages or switches.
Data Source
AI summary
This disclosure provides a method and apparatus for reducing an inrush current inflowing from an external power source during an initial transient state. The method may include generating a first signal based on a level of internal voltage. The first signal may linearly increase or decrease, wherein the slope of the first signal may be fixed. The method may further include comparing the first signal with the reference voltage, and controlling an overcurrent prevention function based on the comparison results. An inrush current reducing device may include a reference voltage generating unit configured to compare a first signal and the reference voltage to control an overcurrent sensing gain, a gain unit configured to compare a first signal and the reference voltage to control an overcurrent sensing gain, and an overcurrent prevention signal generating unit configured to control an overcurrent prevention function based on the comparison results.