Dual-Active-Bridge DC/DC Converter With Variable Switching Frequency
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Solution Overview
Problem
In DC/DC converters with dual active bridge circuits, the power transmission efficiency is reduced due to increased power loss in transformers at higher current levels, particularly in step-down operation modes, where the ratio of switching loss to total power loss is significant, especially at lower power transmission amounts.
Innovation Solution
A DC/DC converter design with a transformer and full bridge circuits on both sides, where the control circuit adjusts the switching frequency of switching elements based on the power transmission amount, keeping the switching elements on the power-receiving side in an off state and reducing the switching frequency when the power transmission is below a reference value to minimize switching losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the switching frequency is increased to improve power transmission capability, then the power transmission amount increases, but the switching loss increases and power conversion efficiency deteriorates
Solution Approach 1:
The patent applies dynamics by making the switching frequency variable rather than fixed. The control circuit dynamically adjusts the switching frequency based on the detected power transmission amount, switching between a first frequency (higher) and a second frequency (lower). This dynamic adjustment resolves the contradiction by allowing high frequency when high power transmission is needed and low frequency when power transmission is low, thus optimizing both productivity and energy loss at different operating conditions.
Solution Approach 2:
The patent changes the parameter of switching frequency based on the power transmission amount. When the power transmission amount is below a reference value, the switching frequency is lowered from the first frequency to the second frequency. This parameter change directly addresses the contradiction by reducing switching loss (energy loss) when high power transmission capability is not required, while maintaining the ability to operate at higher frequencies when maximum power transmission is needed.
2Power
If the switching frequency is maintained at a high level to ensure sufficient power transmission capability, then the power transmission capability is adequate, but the power conversion efficiency deteriorates in low power transmission regions
Solution Approach 1:
The system dynamically adjusts switching frequency based on actual power transmission demands. When power transmission amount is low (below reference value), the switching frequency is reduced to the second frequency, improving power conversion efficiency. When power transmission amount is high (at or above reference value), the switching frequency increases to the first frequency, ensuring sufficient power transmission capability. This dynamic adaptation resolves the contradiction between maintaining power capability and improving efficiency.
Solution Approach 2:
The switching frequency parameter is changed based on the power transmission amount threshold. The control circuit detects whether the power transmission amount is below the reference value and adjusts the switching frequency accordingly. This parameter change ensures that the system operates at optimal efficiency points when power demands are low, while maintaining adequate power transmission capability when demands are high.
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 reduces switching losses and improves power conversion efficiency by effectively utilizing the transformer's voltage-time product margin, especially in regions with low power transmission amounts, thereby enhancing overall efficiency.
Implementation Method 1
The transformer has a first winding and a second winding magnetically coupled
Data Source
AI summary
In a DC/DC converter, in first power transmission in which power is transmitted from a first DC power source to a second DC power source, on/off drive of a positive electrode-side switching element and a negative electrode-side switching element is stopped in a third bridge circuit on the power-receiving side. When a power transmission amount by the first power transmission is smaller than a first reference value, a control circuit lowers the switching frequency of the switching elements of a first bridge circuit and a second bridge circuit on the power-transmitting side and a fourth bridge circuit on the power-receiving side, compared with when the power transmission amount is equal to or greater than the first reference value.