CCM Boost Converter with Flyback Transformer for Soft Switching
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Solution Overview
Problem
Continuous Conduction Mode (CCM) boost converters face challenges such as reverse recovery issues of the boost diode and Right Half Plane Zero stability problems, especially at high frequencies and higher output voltages, leading to significant switching losses and potential thermal runaway in the boost switch.
Innovation Solution
Incorporating a flyback transformer in series with the normal boost inductor operating in CCM and adopting Boundary Control Mode (BCM) to achieve complete soft switching of all switching elements without additional auxiliary switches, utilizing a BCM controller to manage zero current and zero voltage switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If CCM control is used in boost converter, then lower input peak currents and associated lower losses are achieved, but reverse recovery problem of the boost diode and Right Half plane Zero stability issue occur
Solution Approach 1:
The patent segments the single inductor into two separate inductors (L1 and L2) connected in series, where L1 is the boost inductor and L2 is the resonant inductor. This segmentation allows the boost diode to operate without reverse recovery issues while maintaining CCM operation, as the resonant inductor L2 provides the necessary current continuity independently.
Solution Approach 2:
The resonant inductor L2 acts as an intermediary element between the boost diode and the load, providing current continuity during the switching transitions. This intermediary inductor prevents the boost diode from experiencing reverse recovery problems while enabling soft switching operation.
2Reliability
If BCM control is used in boost converter, then reverse recovery issue with boost diode is eliminated, but peak currents become much larger (up to 6 times the average current)
Solution Approach 1:
By segmenting the inductor into two separate inductors L1 and L2, the patent enables CCM operation while eliminating reverse recovery issues. The segmented structure allows the boost diode to conduct continuously without reverse recovery, avoiding the high peak currents characteristic of BCM operation.
Solution Approach 2:
The patent changes the operating parameters by introducing a resonant inductor L2 with specific inductance value that enables soft switching. This parameter change allows the system to operate in CCM with reduced peak currents while maintaining the benefits of eliminated reverse recovery effects.
3Loss of energy
If soft switching is achieved with active snubbers or auxiliary switches, then switching losses are reduced, but device complexity and number of power components increase
Solution Approach 1:
The resonant inductor L2 serves multiple functions: it enables soft switching for the boost switch, provides current continuity to eliminate reverse recovery issues, and maintains CCM operation. This multi-functional element achieves soft switching without requiring additional auxiliary switches or complex active snubber circuits.
Solution Approach 2:
The resonant inductor L2 and capacitor Co form a natural resonant circuit that automatically provides soft switching conditions. The system self-regulates the switching transitions through the resonant interaction between L2 and Co, eliminating the need for external control circuits or additional power components.
4Productivity
If switching frequency is increased to improve power density, then converter size is reduced, but switching losses and thermal runaway risk increase
Solution Approach 1:
The patent introduces dynamic soft switching operation where the switching transitions occur at optimal moments determined by the resonant circuit dynamics. The resonant inductor L2 and capacitor Co create dynamic conditions that enable lossless switching at high frequencies, allowing the converter to operate at higher frequencies without proportionally increasing switching 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 stress, achieves zero current and zero voltage switching for all switching elements, improves efficiency, and reduces Electro-Magnetic Interference (EMI), enabling effective power factor correction at high power levels without additional power components or control burdens.
Implementation Method 1
inserting a fly back transformer in series with a normal boost inductor operating in a continuous conduction mode
Implementation Method 2
achieve complete soft switching of all switching elements
Data Source
AI summary
Realizing ZVS and ZCS in a CCM Boost Converter with BCM control with a single switch. Embodiments disclosed herein relate to continuous conduction mode (CCM) boost converters and more particularly to continuous conduction mode (CCM) boost converters with boundary control mode. The embodiments herein achieve a scheme to achieve complete soft switching of all the switching elements of a boost converter, without incorporating any additional auxiliary switch, wherein total soft switching is achieved by inserting a fly back transformer in series with a normal boost converter operating in a continuous conduction mode, and adopting boundary control mode.