Soft Switching Circuit With Auxiliary Inductor for Zero-Voltage Turn-On
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Solution Overview
Problem
Traditional switch power supplies face increased switching loss and reduced efficiency as switching frequency increases, limiting the potential for smaller volume and higher power density due to the parasitic capacitor charging and discharging in switch devices.
Innovation Solution
A soft switch circuit design that includes a power supply, switch transistors, inductors, and a control unit, where an auxiliary inductor and main inductor are connected in parallel to form an equivalent inductor with a smaller inductance value, allowing for zero-voltage turn-on of switch transistors, thereby reducing switching loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the switching frequency of switch devices is continuously increased to reduce the volume of switch power supply, then the power density is improved, but the switching loss increases due to parasitic capacitor charging and discharging
Solution Approach 1:
The auxiliary switch transistor is turned on before the main switch transistor to pre-charge or pre-discharge the parasitic capacitor of the main switch transistor. This preliminary action ensures that when the main switch transistor turns on, the voltage across it is already at the desired level (zero or target voltage), eliminating the voltage transition process and reducing switching loss while enabling higher switching frequencies for compact power supply design
2Productivity
If the switching frequency is increased to improve conversion efficiency, then the power conversion efficiency is improved, but the switching loss becomes a main factor preventing further frequency increase
Solution Approach 1:
The auxiliary switch transistor acts as an intermediary device that controls the voltage across the main switch transistor's parasitic capacitor independently. By using this intermediary to pre-establish the voltage condition, the main switch transistor can turn on without undergoing voltage transition, thereby eliminating switching loss and enabling high-frequency operation for improved conversion efficiency
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
The soft switch circuit effectively reduces switching loss, enabling higher switching frequencies and smaller volumes in switch power supplies by ensuring zero-voltage turn-on of switch transistors, thus enhancing efficiency and power density.
Implementation Method 1
an auxiliary inductor and main inductor are connected in parallel to form an equivalent inductor with a smaller inductance value
Data Source
AI summary
The present disclosure relates to the field of circuit design. The embodiments of the present disclosure provide a soft switch circuit, a circuit board assembly, and a switch power supply. The soft switch circuit includes a power supply, a first switch transistor, a second switch transistor, a third switch transistor, a fourth switch transistor, a capacitor, a main inductor, an auxiliary switch transistor, an auxiliary inductor, and a control unit, wherein the control unit is configured to: if the current of the main inductor is positive, turn on the auxiliary switch transistor before the first switch transistor and the fourth switch transistor are turned on; and if the current of the main inductor is negative, turn on the auxiliary switch transistor before the second switch transistor and the third switch transistor are turned on.