Resonant Isolated PFC Rectifier Reducing Switching Losses
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Solution Overview
Problem
Existing isolated power converters experience significant switching losses and primary transformer power losses due to switching losses caused by the main switch drain capacitance and leakage inductance of the primary transformer.
Innovation Solution
The method involves using a resonant capacitor across a bi-directional switch to create a resonant tank circuit with a resonant inductor, allowing for zero-voltage switching (ZVS) and reducing power losses, and employing a full bridge rectifier on the output side to maximize transformer usage, with additional bi-directional switches and resonant capacitors to distribute voltage evenly across switches, enabling scalable high-voltage operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional switching is used in isolated power converters, then the circuit structure is simple, but switching losses and primary transformer power losses are significant
Solution Approach 1:
The patent applies resonant oscillation (analogous to mechanical vibration principles) by creating a resonant tank circuit with the transformer leakage inductance and a parallel capacitor. This resonant operation allows the main switch to turn on and off at zero voltage, eliminating switching losses while maintaining a relatively simple circuit structure consisting of the resonant capacitor and existing transformer components
Solution Approach 2:
The patent changes the operating parameters of the switch by ensuring it operates at zero voltage switching conditions through the resonant tank circuit. This parameter change (from conventional voltage-mode switching to zero-voltage switching) dramatically reduces switching losses without requiring complex additional circuitry
2Power
If higher voltage operation is required, then power conversion capability increases, but switching losses and transformer losses increase
Solution Approach 1:
By operating the transformer in resonance with the parallel capacitor, the patent enables higher voltage operation while maintaining low losses. The resonant operation ensures that the transformer leakage inductance and capacitance work together to achieve zero-voltage switching, allowing higher power capability without proportionally increasing losses
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 primary transformer power losses, achieving efficient AC-DC or DC-DC power conversion while allowing for higher voltage operation using lower voltage switches, thereby improving overall power savings and efficiency.
Implementation Method 1
a resonant tank circuit (defined by a combination of Cr1, Cr2, and Lr) used during an ON-time portion of the circuit cycle to achieve zero current switching
Implementation Method 2
inducing current to flow through a transformer
Implementation Method 3
rectifying alternating current (AC) output from the transformer to create direct current (DC)
Data Source
AI summary
A method of driving an isolated converter includes opening a first bi-directional switch on an input side of a transformer, accepting current into a resonant capacitor connected across the first bi-directional switch to reduce voltage across the first bi-directional switch in response to said opening the first bi-directional switch, reversing current out of the resonant capacitor, and closing the first bi-directional switch as voltage across the first bi-directional switch is approximately zero volts.