Converter Pre-Charging Without Resistors for Inrush Limiting
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Solution Overview
Problem
Conventional methods to address inrush current in DC/AC, DC/DC, or AC/DC converters involve using pre-charge resistors, which introduce power loss during normal operation.
Innovation Solution
The techniques eliminate the need for pre-charge resistors by utilizing the main power path of the converter, incorporating a protection inductor that saturates at a current less than the protection diode rating to limit inrush current during startup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pre-charge resistor is placed in the current path to reduce inrush current, then the inrush current magnitude is reduced and components are protected, but power loss increases during normal operation
Solution Approach 1:
The invention extracts and removes the pre-charge resistor from the circuit entirely. By using the existing protection diode and configuring the switch circuit to control capacitor charging during startup, the patent eliminates the need for a dedicated pre-charge resistor, thereby eliminating the power loss associated with it during normal operation while still protecting components from inrush current
Solution Approach 2:
The protection diode, which normally only protects against reverse voltage, is made to serve a dual function: it protects against reverse voltage during normal operation and also limits inrush current during startup by controlling the charging path of the capacitor. This multi-functionality eliminates the need for separate pre-charge components
2Reliability
If a pre-charge resistor is used to limit inrush current, then inrush current is reduced, but the converter's current rating and impedance are reduced
Solution Approach 1:
The switch circuit is configured to control the charging of the capacitor during the startup phase before normal operation begins. By preliminarily managing the capacitor charge state through controlled switching, the patent limits inrush current without requiring a pre-charge resistor that would permanently limit the converter's current rating
Solution Approach 2:
The patent uses dynamic switching control to adapt the circuit behavior during startup versus normal operation. The electronic switches dynamically control the capacitor charging path during startup to limit inrush current, then transition to normal switching operation that allows full current rating, providing time-dependent circuit characteristics without permanent current limiting
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach increases the maximum allowable current rating and impedance of the converter, eliminating the need for resistors and reducing power consumption.
Implementation Method 1
a protection inductor coupled to the first terminal or the second terminal, wherein the protection inductor is configured to saturate at a current less than a current rating of the protection diode to limit inrush current during startup without using resistors
Data Source
AI summary
Techniques that eliminate the need for a dedicated pre-charge resistor by using the main power path of the AC/DC, DC/DC, or DC/AC converter. By eliminating the pre-charge resistor, the techniques increase the maximum allowable current rating of the converter as well as increase the impedance and inductance of the converter.