Zero Current Switch Circuit for Power Factor Corrector
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Solution Overview
Problem
Conventional zero current switch circuits for power-factor correctors face issues such as increased inductor magnetic loss, longer reverse recovery time of output diodes under heavy loading, and higher resistance loss due to the need for additional inductors and resistors, which affect efficiency and cost.
Innovation Solution
A zero current switch circuit with a first and second coil set, where the second coil set is wound reversely relative to the first, generating a back electromotive force for zero current switching and allowing for efficient energy storage and recovery, reducing magnetic and resistance losses by maintaining a fully saturated inductor condition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If inductor L3 with constant inductive reactance is used, then reverse energy recovery is enabled, but reverse recovery time increases under heavy loading conditions
Solution Approach 1:
The patent replaces the constant inductive reactance of a fixed inductor L3 with a dynamic saturated inductor L2 whose inductive reactance changes with current magnitude. Under heavy loading, the inductor saturates faster, dynamically adjusting its reactance to maintain optimal reverse recovery time across different loading conditions.
Solution Approach 2:
The patent changes the operating parameters of the inductor by utilizing saturation effects. The saturated inductor L2 operates in different regions (linear and saturated) depending on current magnitude, changing its effective inductive reactance to optimize performance under varying loading conditions, particularly reducing reverse recovery time under heavy loading.
2Reliability
If discharging current of resistor R1 to capacitor C3 is limited by duty cycle, then zero current switching is maintained, but saturation of inductor L2 is incomplete and resistance loss increases
Solution Approach 1:
The patent ensures continuous saturation of the inductor L2 by maintaining current flow through the second coil set N2 during the entire duty cycle. The auxiliary switch SW2 remains conductive throughout the duty cycle, continuously driving current through N2 to maintain full saturation, eliminating the discontinuity that caused incomplete saturation in the prior art.
Solution Approach 2:
The patent preliminarily saturates the inductor L2 by continuously driving current through the second coil set N2 before and during the main switching operation. This preliminary saturation ensures the inductor is fully prepared and maintains saturation throughout the duty cycle, preventing the incomplete saturation that led to increased resistance 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
The solution achieves higher efficiency and reduced losses by shortening reverse recovery time and maintaining a fully saturated inductor condition, making it suitable for higher power supplies with lower magnetic and resistance losses.
Implementation Method 1
The first coil set produces a leaking inductance to generate a back electromotive force to make the conduction switch in a zero current switching condition
Implementation Method 2
An energy conversion circuit is provided to couple with the output diode to generate a reverse recovery condition. The reverse energy is stored according to the coil ratio of the second coil set relative to the first coil set
Implementation Method 3
through input current flowing through the second coil set, the saturated inductor (first coil set) can reach a fully saturated condition. The resistance loss is lower.
Data Source
AI summary
A simple zero current switch circuit includes a first coil set and a second coil set that are wound at a selected coil ratio and bridge electrically an energy storing inductor, an output diode and a conduction switch of a power-factor corrector. The leaking inductance of the first coil set generates a back electromotive force to make the conduction switch in a zero current switching condition. An energy conversion circuit is provided to store reverse energy according to the coil ratio of the second coil set and the first coil set and reclaims the energy to an output capacitor of the power-factor corrector while the output diode generates a reverse recovery condition. Thereby reverse recovery time of the output diode can be shortened.