Bidirectional Resonant DC Converter Control for Wide Gain and Low Loss
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Solution Overview
Problem
Conventional bidirectional direct-current converters face challenges in achieving a wide voltage gain range with limited soft-switching capabilities, leading to increased conduction loss and heat dissipation due to reverse current flow in SiC and GaN devices, especially when the switching frequency is high.
Innovation Solution
A method and circuit for controlling a bidirectional resonant direct-current converter that reduces the modulation range of the switching frequency by setting the switching frequency above the resonant frequency and using delay time periods to control the turning off and on of switching transistors based on zero-crossing points, minimizing reverse current flow and conduction loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the switching frequency is increased to achieve a wide voltage gain range, then the voltage gain range is improved, but the conduction loss increases due to extended reverse current flow duration
Solution Approach 1:
The patent applies dynamic control of the switching frequency, allowing it to vary within a limited range above the resonant frequency based on the operating conditions. The control circuit dynamically adjusts the switching frequency to optimize the balance between voltage gain and conduction loss, rather than using a fixed frequency or excessively wide frequency modulation range.
Solution Approach 2:
The patent changes the operating parameter (switching frequency) to operate above the resonant frequency, which fundamentally alters the resonant converter's behavior. By maintaining the switching frequency above the resonant frequency and using controlled frequency modulation within a limited range, the patent achieves wide voltage gain while minimizing reverse current flow and associated conduction losses.
2Speed
If the switching frequency is increased to improve system efficiency, then the switching speed is improved, but the reverse current flow duration increases causing higher conduction loss
Solution Approach 1:
The patent implements dynamic switching frequency control that adapts to operating conditions. The switching frequency is dynamically adjusted within a controlled range above the resonant frequency, optimizing the trade-off between switching speed and reverse current duration. This dynamic approach ensures high switching speed while minimizing the time that reverse current flows through the devices.
Solution Approach 2:
The patent utilizes periodic switching action at frequencies above the resonant frequency. By establishing a periodic switching regime with controlled frequency modulation, the patent achieves high switching speeds while the periodic nature of the operation allows for predictable and minimized reverse current flow patterns, reducing overall conduction losses.
3Adaptability or versatility
If a large modulation range of switching frequency is used to achieve wide voltage gain, then the voltage gain range is improved, but the device complexity and heat dissipation difficulty increase
Solution Approach 1:
The patent employs dynamic frequency control within a limited range above the resonant frequency, which provides sufficient voltage gain adjustment capability without requiring an excessively wide frequency modulation range. This dynamic control approach simplifies the overall device complexity and reduces heat dissipation challenges compared to using a very large frequency modulation range.
Solution Approach 2:
By changing the fundamental operating parameter to switch above the resonant frequency, the patent achieves wide voltage gain range with a more moderate frequency modulation range. This parameter change simplifies the control system and reduces the thermal management complexity that would otherwise be required with conventional approaches using very wide frequency modulation.
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 enables a wide voltage gain range with reduced conduction loss and increased switching frequency, enhancing system efficiency by minimizing reverse current duration and achieving soft switching in SiC and GaN devices.
Implementation Method 1
a resonant tank arranged between the transformer and the primary circuit and/or the secondary circuit
Data Source
AI summary
A method and circuit for controlling a bidirectional resonant direct-current converter are provided. The method includes obtaining an input and/or output electrical parameter of the converter; determining respective delay time periods of bridge arms in the secondary circuit based on the input and/or output electrical parameter and a desired gain of the converter; determining a switching frequency to be greater than a resonant frequency of the resonant tank based on the input and/or output electrical parameter and a preset reference signal; and turning off, in response to a secondary resonant current of the converter reaching zero, corresponding switching transistors of the switching transistors in the secondary circuit immediately after the respective delay time periods starting from a zero-crossing point; and turning on other switching transistors complementary to the turned-off switching transistors in the secondary circuit immediately after a dead time.