Series-Resonant DC-DC Converter Phase Control for Loss Reduction
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Solution Overview
Problem
DC-to-DC converters with dual active bridge topology and series resonant circuits face efficiency losses due to deviations in the ratio of DC output voltage to DC input voltage from the transformer ratio, leading to increased conductive and switching losses.
Innovation Solution
Controlling the phase shift between the primary or secondary AC voltage and the series resonant circuit current to zero by adjusting the clock frequency, depending on the voltage ratio, reduces reactive power flow and switching losses, thereby optimizing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the ratio of DC output voltage to DC input voltage deviates from the transformer ratio, then the converter can operate at different voltage levels, but efficiency decreases due to increased conductive and switching losses
Solution Approach 1:
The patent applies dynamics by making the clock frequency variable rather than fixed. The control unit dynamically adjusts the clock frequency based on the detected voltage ratio between DC input and DC output. This dynamic adaptation allows the converter to maintain optimal efficiency across different operating conditions while preserving voltage ratio adaptability, directly resolving the technical contradiction.
Solution Approach 2:
The patent changes the parameter of clock frequency based on the voltage ratio condition. When the voltage ratio deviates from the transformer ratio, the system modifies the clock frequency to compensate and maintain efficiency. This parameter change approach enables the converter to operate efficiently across different voltage levels without suffering excessive losses, resolving the contradiction between adaptability and energy loss.
2Power
If phase shift between AC voltage and series resonant circuit current is non-zero, then power transfer can be controlled, but reactive power flow increases causing efficiency loss
Solution Approach 1:
The patent implements feedback by having the control unit continuously detect the voltage ratio and adjust the clock frequency accordingly. This closed-loop feedback mechanism ensures that the phase shift is optimized to minimize reactive power flow while maintaining the required power transfer, thereby resolving the contradiction between power control capability and reactive power loss.
Solution Approach 2:
The system dynamically adjusts the clock frequency in response to changing operating conditions to maintain optimal phase shift. This dynamic control allows the converter to minimize reactive power flow and associated losses while preserving the ability to control power transfer, directly addressing the technical contradiction.
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 approach minimizes conductive and switching losses, enhancing the overall efficiency of the DC-to-DC converter by ensuring zero current switching and compensating for measurement inaccuracies and phase shift fluctuations.
Implementation Method 1
a series resonant circuit for each AC voltage phase... controlling to zero a phase shift between the primary or secondary AC voltage and a series resonant circuit current corresponding thereto
Data Source
AI summary
A DC-to-DC converter converts a DC input voltage to a DC output voltage by generating a primary AC voltage and transforming the primary AC voltage into a secondary AC voltage with a transformation ratio. The DC-to-DC converter has series resonance circuit for each AC voltage phase. When the ratio of the DC output voltage to the DC input direct voltage is greater than the transformation ratio, a phase shift between the primary alternating voltage and a series resonance circuit current corresponding to the primary alternating voltage is controlled to zero by changing a clocking frequency clocking the AC voltages. Conversely, when the ratio of the DC output voltage to the DC input voltage is less than the transformation ratio, the phase shift between the secondary AC voltage and a series resonance circuit current corresponding to the secondary AC voltage is controlled to zero by changing a clocking frequency.