DC-DC Converter Bridge Control for Soft Switching in Discontinuous Mode
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Solution Overview
Problem
Conventional control methods for phase-shifted full-bridge DC-DC converters result in high electrical losses due to hard switching of elements during discontinuous operation, which reduces the lifespan of switching elements.
Innovation Solution
A control method that switches the DC-DC converter's elements softly, utilizing a full bridge with two half-bridges on the secondary side and alternately controlling upper and lower switching elements to minimize losses and stress on the elements, allowing for active rectification and reduced electrical losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional control methods are used for phase-shifted full-bridge DC-DC converters, then the converter can operate in discontinuous conduction mode, but electrical losses increase due to hard switching of elements
Solution Approach 1:
The patent applies preliminary action by pre-charging the output capacitance of switching elements before they need to switch on. This is achieved by controlling the secondary-side full bridge to generate a current that charges the output capacitance of primary-side switching elements in advance, ensuring that when the switching elements turn on, there is no voltage across them, thus enabling soft switching and reducing electrical losses while maintaining power transfer capability
Solution Approach 2:
The patent introduces an intermediary mechanism - the secondary-side full bridge with its controlled switching elements - that acts as a mediator to prepare the electrical conditions for primary-side switching. The secondary-side circuit generates and controls the current flow that charges the output capacitance of primary switching elements, serving as an intermediary system that enables soft switching on the primary side without directly modifying the primary switching elements themselves
2Device complexity
If hard switching is used in discontinuous conduction mode, then the converter structure remains simple, but the lifespan of switching elements decreases due to high stress
Solution Approach 1:
The patent extends preliminary action to reliability by pre-charging output capacitances before switching events. This ensures that switching elements always turn on with zero voltage across them, eliminating voltage stress and hard switching conditions that degrade components over time, thereby extending service life while keeping the overall converter structure relatively simple
Solution Approach 2:
The patent applies dynamics by implementing dynamic control of switching elements on both primary and secondary sides. The control method dynamically adjusts switching timing and states based on the operational mode (continuous or discontinuous conduction), enabling the system to adaptively achieve soft switching conditions varying operating conditions, thus improving reliability without requiring a completely redesigned static structure
3Loss of energy
If soft switching is implemented to reduce electrical losses, then additional control complexity is required, but no additional hardware components are needed
Solution Approach 1:
The patent applies universality by designing the secondary-side full bridge to serve multiple functions: it performs the primary function of power transfer and rectification, and simultaneously serves as a control mechanism to charge the output capacitance of primary switching elements. This multi-functionality enables soft switching without requiring separate dedicated components, reducing hardware additions while managing control complexity through unified secondary-side control
Solution Approach 2:
The patent implements self-service by enabling the secondary-side circuit to automatically generate and control the current that charges the primary-side switching element output capacitances. The control method uses the existing secondary switching elements to create the necessary charging current, making the system self-sufficient in preparing soft switching conditions without external intervention or additional dedicated charging circuits
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 method reduces electrical losses and extends the lifespan of switching elements by enabling soft switching operations, which are less stressful and do not require additional components or increased costs.
Implementation Method 1
a transformer (30) for transferring electrical energy from the primary to the secondary side
Implementation Method 2
output capacitance (41, 42, 43, 44) of the switching elements (11, 12, 13, 14) of the primary-side full bridge (10)
Data Source
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AI summary
The present invention relates to a control method for a DC-DC converter for transferring power from a primary side to a secondary side of the DC-DC converter. A special control method which makes it possible to switch on the switching elements in the DC-DC converter essentially gently is proposed. Thus, the losses during the activation of the switching elements can be minimised.