Two-Transistor Flyback Converter Soft Switching With Auxiliary Winding
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Solution Overview
Problem
Current two-transistor flyback converters suffer from high energy loss due to hard switching, especially at high frequencies, limiting conversion efficiency and imposing high voltage withstand requirements on power switching transistors.
Innovation Solution
Incorporating an auxiliary circuit with an auxiliary winding and capacitor to store and discharge energy, adjusting the potential at the primary-side winding ends, enabling soft switching of the switching transistors by reducing the voltage between their electrodes to zero before turning them on.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If hard switching is used for the switching transistors, then the structure remains simple, but energy loss increases and conversion efficiency decreases
Solution Approach 1:
The auxiliary winding performs preliminary action by charging before the primary-side winding charging begins. This pre-charging action prepares the voltage conditions needed for soft switching, reducing energy loss when the main switching transistors are turned on.
Solution Approach 2:
The auxiliary winding acts as an intermediary element between the input voltage source and the primary-side winding. It mediates the voltage conditions to enable soft switching of the main transistors, reducing energy loss without complicating the overall structure significantly.
2Productivity
If switching frequency is increased to improve productivity, then output per unit time increases, but energy loss per switching event accumulates and reduces overall efficiency
Solution Approach 1:
The auxiliary winding performs preliminary voltage preparation before each main switching event. This allows the system to operate at higher frequencies while maintaining low energy loss per switching event, as the soft switching condition is pre-established by the auxiliary winding's prior charging action.
3Adaptability or versatility
If the voltage withstand requirement for switching transistors is reduced, then easier transistor selection is possible, but hard switching causes high energy loss during switching
Solution Approach 1:
The auxiliary winding performs preliminary voltage preparation to create the potential difference needed for soft switching. This allows transistors with lower voltage withstand ratings to be used while avoiding the high energy loss associated with hard switching, as the voltage is gradually reduced before switching occurs.
Solution Approach 2:
The auxiliary winding serves as an intermediary that enables the use of transistors with lower voltage ratings. By mediating the voltage transition and enabling soft switching, it allows flexible transistor selection without incurring the penalties of hard switching energy loss.
4Loss of energy
If an auxiliary circuit is added to enable soft switching, then energy loss is reduced and efficiency improves, but device complexity increases
Solution Approach 1:
The auxiliary winding performs preliminary voltage preparation using a simple charging-discharging mechanism. This approach reduces energy loss through soft switching while adding minimal complexity, as the auxiliary circuit only needs to charge before the main switching event and then naturally discharge through the transistor.
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
Reduces energy loss and improves conversion efficiency by implementing soft switching, thereby lowering the voltage withstand requirements on power switching transistors.
Implementation Method 1
the auxiliary circuit may charge the auxiliary winding, so that the auxiliary winding stores electric energy
Implementation Method 2
switching-on and switching-off of the switching transistor Q1 and the switching transistor Q2 are controlled to control charging and discharging of the primary-side winding, so that the primary-side winding can cooperate with a secondary-side circuit to complete voltage conversion
Data Source
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AI summary
This application provides a two-transistor flyback conversion circuit, a power module, an electric vehicle, and a control method. The two-transistor flyback converter includes an auxiliary circuit. Before charging of a primary-side winding starts, the auxiliary circuit may increase a potential at a first end of the primary-side winding, and decrease a potential at a second end of the primary-side winding. By adding the auxiliary circuit, soft switching can be implemented for switching transistors at both ends of the primary-side winding, thereby helping reduce loss of the two-transistor flyback converter and improve conversion efficiency of the two-transistor flyback converter.