Bidirectional DC-DC Converter Soft Switching Control
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Solution Overview
Problem
Conventional bidirectional DC-DC converters experience efficiency loss, increased noise, and switching element breakdown due to switching losses and variations in MOS transistor characteristics, especially in step-down operations and hard switching methods.
Innovation Solution
A bidirectional DC-DC converter design incorporating a controlling circuit that achieves soft switching in the high voltage-side rectifying circuit, utilizing an LC resonant circuit and a transformer with a greater number of turns in the secondary winding, and employing n-channel MOS transistors to manage switching elements, thereby reducing switching losses and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If hard switching method is used in conventional bidirectional DC-DC converter, then power transmission function is achieved, but switching loss increases and converter efficiency decreases
Solution Approach 1:
The patent changes the switching method from hard switching to soft switching by controlling the timing of switching element activation relative to current zero-crossing points. This parameter change in switching timing eliminates switching losses while maintaining power transmission functionality.
Solution Approach 2:
The patent employs periodic resonant oscillation through an LC resonant circuit to create periodic current waveforms. By synchronizing switching actions with the periodic zero-crossing points of this resonant current, the system achieves lossless switching while maintaining continuous power transmission.
2Object-affected harmful factors
If hard switching is used in bidirectional DC-DC converter, then power conversion is achieved, but noise increases and switching element breakdown occurs
Solution Approach 1:
The patent changes the switching timing parameter to occur at current zero-crossing points rather than arbitrary timing. This parameter change eliminates voltage spikes and electromagnetic noise while preventing switching element breakdown, thereby improving reliability.
Solution Approach 2:
The patent converts the naturally occurring zero-crossing points of the resonant current into beneficial switching时机. By utilizing these natural current null points for switching operations, the system transforms what would be idle moments into protective switching opportunities that prevent noise and breakdown.
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
The solution improves converter efficiency, reduces noise, and prevents switching element breakdown by enabling soft switching and appropriate partial voltage resonance in step-down operations.
Implementation Method 1
An LC resonance circuit is arranged between the transformer stage and the high voltage side switching unit for generating sine wave currents simplifying zero crossing switching.
Implementation Method 2
a transformer connected between the low voltage-side rectifying circuit and the high voltage-side rectifying circuit
Data Source
Figure 1
Figure 2
AI summary
A bidirectional DC-DC converter comprises: a first low voltage-side input/output terminal and a second low voltage-side input/output terminal; a low voltage-side rectifying circuit connected to the first low voltage-side input/output terminal and the second low voltage-side input/output terminal; a first high voltage-side input/output terminal and a second high voltage-side input/output terminal; a high voltage-side rectifying circuit connected to the first high voltage-side input/output terminal and the second high voltage-side input/output terminal; a transformer connected between the low voltage-side rectifying circuit and the high voltage-side rectifying circuit; and a controlling circuit that controls operations of switching elements in the low voltage-side rectifying circuit and the high voltage-side rectifying circuit. The controlling circuit achieves soft switching of a switching element in the high voltage-side rectifying circuit in a step-down operation.