DC-DC Converter Phase Shift Control for ZVS Loss Reduction
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Solution Overview
Problem
Existing DC-DC converters face challenges in achieving zero voltage switching (ZVS) efficiently, as short on-duty times may not allow sufficient current passage, while longer times can lead to excessive current flow, increasing losses and reducing power transmission efficiency.
Innovation Solution
A DC-DC converter design incorporating a first and second full-bridge circuit, a transformer, and an inductance component, with a control circuit that manages inductor current to ensure it meets a threshold, thereby preventing excessive current flow and optimizing ZVS by adjusting voltage output periods and inductor current levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the on-duty time of switching elements is increased to pass sufficient current for ZVS, then the current magnitude increases, but this causes excessive current flow leading to increased losses and decreased power transmission efficiency
Solution Approach 1:
The patent changes the control parameter from duty cycle to phase difference between primary and secondary full-bridge circuits. By adjusting the phase difference θ while maintaining fixed duty cycles at 50%, the system achieves ZVS through resonant current control without excessive current magnitude, resolving the contradiction between reliable ZVS and energy loss
Solution Approach 2:
The patent introduces dynamic phase shift control where the phase difference θ between primary and secondary switching waves is continuously adjusted based on load conditions. This dynamic adjustment enables the system to maintain optimal current levels for ZVS while preventing excessive current flow, thereby reducing losses
2Loss of energy
If the on-duty time of switching elements is decreased to reduce current flow and losses, then power transmission efficiency improves, but insufficient current passage prevents achievement of ZVS
Solution Approach 1:
The patent merges the control of primary and secondary full-bridge circuits into a unified phase-shift control system. By coordinating the switching phases of both bridges with a fixed 50% duty cycle, the system generates resonant current that simultaneously achieves ZVS and limits excessive current flow, resolving the contradiction between low losses and reliable ZVS
3Ease of operation
If different output voltages are produced by the two full-bridge circuits, then voltage regulation is achieved, but inductor current inconsistency during polarity inversion increases losses
Solution Approach 1:
The patent implements feedback control where the control circuit monitors the output voltages of both full-bridge circuits and adjusts the phase difference θ accordingly. This feedback mechanism ensures that inductor current remains consistent during polarity inversion while maintaining the required voltage regulation, resolving the contradiction between voltage control and loss reduction
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 effectively maintains inductor current consistency across polarity inversion periods, preventing excessive current flow and reducing losses, thus enhancing power transmission efficiency by ensuring ZVS operations in DC-DC converters.
Implementation Method 1
a transformer (T) including a first winding (n1) and a second winding (n2), the first winding being connected to the first full-bridge circuit, and the second winding being connected to the second full-bridge circuit and magnetically coupled to the first winding
Implementation Method 2
four switching elements that include a capacitor serving as a parasitic capacitance or an external parallel-connected capacitor
Implementation Method 3
an inductance component connected in series with the first winding or the second winding
Data Source
AI summary
The DC-DC converter has a configuration in which a first full-bridge circuit and a second full-bridge circuit are connected via a transformer. A control circuit controls soft switching of each switching element. An inductor current flowing through the transformer or an equivalent inductor equivalent to the transformer at a time of switching of turning on or off each switching element is greater than or equal to a threshold current. When the first full-bridge circuit and the second full-bridge circuit have different output voltages V1 and V2, the control circuit causes the inductor current at start times t4 and t8 of a polarity inversion period to approach the inductor current at end times t5 and t9, the polarity inversion period being a period in which V1 and V2 have reverse polarities. This suppresses an increase in loss resulting from a flow of large current and enables ZVS control.