Flyback Converter Input Side Clamp Circuit Leakage Energy Recovery
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Solution Overview
Problem
Coupled-inductance converters, such as flyback and forward converters, face efficiency limitations due to high switching frequencies required for small size and high output, which increase the impact of leakage inductance, especially in AC-DC conversion applications, and existing active clamp solutions provide only modest efficiency enhancements with complex and expensive components.
Innovation Solution
A converter circuit with an input side clamp circuit that includes an energy store and a switch arrangement to discharge leakage inductance energy to the input side of the input coil, enhancing energy utilization and efficiency, using simple and low-cost components like capacitors and MOSFETs or GaN switches, allowing operation without a magnetic core structure for higher switching frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the switching frequency is increased to reduce converter size and increase output, then the converter size is reduced and output is increased, but the efficiency deteriorates due to significant leakage inductance effects
Solution Approach 1:
The patent recycles the leakage inductance energy that was previously lost as heat by capturing it in a capacitor during the switch-off period and then discharging it back to the input coil during the switch-on period. This converts the harmful leakage inductance effect into a beneficial energy recovery mechanism, improving overall converter efficiency while maintaining high switching frequencies
Solution Approach 2:
The patent implements an energy recovery scheme where leakage inductance energy is temporarily stored in a capacitor and then recovered and reused in the next switching cycle. This discards the traditional approach of dissipating leakage energy as heat and instead recycles it back into the system, improving efficiency without requiring magnetic core structures
2Loss of energy
If traditional active clamp arrangements are used to recover leakage inductance energy, then some efficiency enhancement is achieved, but the device complexity and cost increase significantly
Solution Approach 1:
The patent extracts the essential function of leakage energy recovery from the complex traditional active clamp circuit and implements it using a simple capacitor connected across the input coil with basic switching control. This removes unnecessary complexity while retaining the core energy recovery benefit
Solution Approach 2:
The patent replaces expensive and complex active clamp components with inexpensive passive components (capacitor and basic switch) that perform the same energy recovery function. The simple capacitor-based approach achieves efficiency enhancement without the high cost and complexity of traditional active clamp arrangements
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 enhanced efficiency in converters by effectively utilizing leakage inductance energy, reducing heat generation and packaging constraints, and enabling smaller, more cost-effective designs, particularly suitable for high-frequency operations without the need for magnetic cores.
Implementation Method 1
When the switch is closed the input coil, which is directly connected to the associated voltage source, experiences an increase in the current and magnetic flux associated therewith, and energy is stored therein
Implementation Method 2
the input coil being arranged to allow it to be magnetically coupled with an output coil
Implementation Method 3
the input side clamp circuit comprising an energy store and a switch arrangement controlled such that the leakage inductance energy stored, in use, in the energy store, can be discharged to the input side of the input coil
Data Source
AI summary
A flyback converter and forward converter is described that include an input coil, a primary switch connected in series with the input coil, and an output coil magnetically coupled to the input coil. The input coil has an input side connected to an input of the circuit and a switch side connected to the primary switch. The converter further includes an input side clamp circuit, the input side clamp circuit including an energy store and a switch arrangement controlled such that the leakage inductance energy stored, in use, in the energy store, can be discharged to the input side of the input coil.