DC-DC Converter Phase and Frequency Control for ZVS
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Solution Overview
Problem
Existing DC-DC converters using zero voltage switching (ZVS) face limitations in achieving efficient power transfer due to narrow operational areas and increased switching losses, as they struggle to maintain sufficient current and target output power while minimizing switching surges and noise.
Innovation Solution
A converter design incorporating a pair of full-bridge circuits, a transformer, and an inductance component, with a control circuit that adjusts phase differences and drive angular frequencies to ensure an inductor current meets a threshold, thereby expanding the ZVS operational area and reducing switching losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the duty of primary and secondary switches is controlled to minimize power difference between primary and secondary sides, then ZVS operations are accomplished, but the area where ZVS can be performed is narrowed and switching losses increase
Solution Approach 1:
The invention changes the control parameters from duty cycle to phase difference and drive angular frequency. By adjusting the phase difference between primary and secondary full-bridge circuits and modifying the drive angular frequency, the system achieves ZVS operations across a wider operating range without increasing switching losses. This parameter transformation allows the inductor current to maintain sufficient magnitude for ZVS while adapting to varying power conditions.
2Reliability
If the duty of switches is increased to pass sufficient current for ZVS, then ZVS can be accomplished, but target output power cannot be obtained
Solution Approach 1:
The invention introduces dynamic control through variable drive angular frequency and phase difference adjustment. Instead of using fixed duty cycles, the system dynamically adapts the switching frequency and phase relationship between primary and secondary sides. This dynamic approach allows the inductor current to remain sufficiently high for ZVS while the output power is precisely controlled through frequency and phase modulation, resolving the conflict between current magnitude and power output.
3Reliability
If switching frequency is changed to maintain ZVS, then ZVS operations can be performed, but heat generation and magnetic saturation increase
Solution Approach 1:
The invention transforms the control approach by using phase difference as the primary control parameter instead of relying solely on frequency changes. By adjusting the phase relationship between primary and secondary full-bridge circuits, the system achieves ZVS operations without excessive frequency modulation. This reduces the stress on magnetic components, minimizing heat generation and preventing magnetic saturation while maintaining reliable ZVS operation.
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 design enhances the ZVS operational area, suppresses heat generation and magnetic saturation, and maintains efficient power transfer by ensuring the inductor current meets the threshold, even when switching frequencies do not change, thus improving overall converter efficiency.
Implementation Method 1
a transformer including a first winding connected to the first full-bridge circuit and a second winding coupled magnetically to the first winding and connected to the second full-bridge circuit
Data Source
AI summary
A DC-DC converter has a configuration in which a first full-bridge circuit and a second full-bridge circuit are connected via a transformer and an inductor. A control circuit switches between first control for changing the phases of switching elements in the first bridge circuit and switching elements in the second bridge circuit and second control for changing the switching frequencies (drive angular frequencies) of the switching elements, in accordance with target power, so that an inductor current flowing during a dead time of the switching elements becomes larger than or equal to a threshold current. The inductor current in the first control is larger than the inductor current in the second control.