Bidirectional DC-to-DC Converter Inrush Current Suppression
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Solution Overview
Problem
Conventional DC-to-DC converters experience inrush current issues during activation, especially when there is a voltage difference between the input and output, which can damage devices and is exacerbated by the connection of high-capacity capacitors.
Innovation Solution
A DC-to-DC converter design incorporating a first and second switching leg, full-bridge circuits, transformers, reactors, and a control unit that adjusts phase differences and duty ratios to manage power transmission and suppress inrush current by limiting the switching devices' on periods and using complementary signals to control the flow of current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high-capacity capacitors are connected to the direct current bus, then the energy storage capability is improved, but inrush current increases during activation
Solution Approach 1:
The control unit performs preliminary action by detecting voltage differences between input and output terminals before full activation, and pre-charges the output capacitor through controlled switching at reduced duty ratios, preventing inrush current during full power transmission
Solution Approach 2:
The system dynamically adjusts the duty ratio of switching devices during activation. The control unit varies the duty ratio from a lower initial value to a higher operating value, enabling smooth capacitor charging while preventing excessive inrush current
2Adaptability or versatility
If there is a voltage difference between input and output terminals, then the converter can operate with asymmetric voltage levels, but inrush current flows through body diodes and freewheeling diodes
Solution Approach 1:
The control unit acts as an intermediary by detecting voltage differences and mediating the activation process through controlled switching sequences. It uses complementary signals and duty ratio control to prevent direct connection of voltage sources with different levels, eliminating inrush current through body diodes
Solution Approach 2:
The control unit applies preliminary anti-action by detecting voltage differences before activation and implementing preventive switching control. It ensures that switching devices are activated in a sequence that prevents reverse current flow through body diodes and freewheeling diodes
3Productivity
If the converter is activated with full duty ratio, then power transmission efficiency is maximized, but device damage may occur due to inrush current
Solution Approach 1:
The control unit implements periodic action by using pulse-width modulation with varying duty ratios during activation. It transitions from lower duty ratio pulses to higher duty ratio pulses, enabling gradual power transmission that prevents device damage while achieving full power efficiency
Solution Approach 2:
The control unit changes the duty ratio parameter from a lower initial value to a higher operating value during activation. This parameter change enables the system to balance between preventing inrush current and achieving full power transmission efficiency
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
Effectively suppresses inrush current during activation and maintains stable power transmission by controlling phase differences and duty ratios, preventing device damage and ensuring efficient operation even with high-capacity capacitors.
Implementation Method 1
a transformer (3), wherein one end of a primary winding of the transformer is connected to the other end of the first reactor and the other end of the primary winding of the transformer is connected to the fourth reactor
Implementation Method 2
a first reactor (16), wherein one end of the first reactor is connected to a node between the first switching device and the second switching device and the other end of the first reactor is connected to one end of the primary winding of the transformer
Data Source
AI summary
A first full-bridge circuit, a transformer, a first reactor, a second full-bridge circuit, a second reactor, a capacitor, and a control unit are included. When activated, the control unit switches one or more of a combination of a first switching leg and a second switching leg and a combination of a third switching leg and a fourth switching leg with a certain second phase difference and drives first, third, fifth, and seventh switching devices or second, fourth, sixth, and eighth switching devices with a first duty ratio, which is lower than a duty ratio during normal operation.