Flyback Circuit Energy Recycling via Auxiliary Switch
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Solution Overview
Problem
Flyback circuits in AC/DC converters face inefficiency due to the burning of leakage inductance energy, which is not recycled, leading to limited suppression of voltage spikes.
Innovation Solution
An energy recycle circuit is introduced, featuring an auxiliary switch and a recycle control circuit that monitors and controls the charging and discharging of a clamp capacitor, allowing the leakage inductance energy to be recycled by turning the auxiliary switch on during charging and off at the end of discharging, based on voltage and current signals, with timing controlled by a timer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a conventional RCD snubber circuit is used to suppress voltage spikes, then voltage spike suppression is improved, but energy efficiency deteriorates because leakage inductance energy is burned out instead of being recycled
Solution Approach 1:
The patent applies the discarding and recovering principle by capturing the leakage inductance energy that would otherwise be wasted through the snubber resistor, storing it in the clamp capacitor during the charging phase, and then recovering it by transferring the stored energy back to the primary winding through the auxiliary switch during the discharging phase. This transforms the harmful energy dissipation into a useful energy recycling process, simultaneously maintaining voltage spike suppression and improving energy efficiency
Solution Approach 2:
The patent converts the harmful effect of leakage inductance energy (which causes voltage spikes and efficiency loss) into a beneficial resource. By using the clamp capacitor to store this energy and the auxiliary switch to redirect it back to the primary winding, the circuit transforms what was previously wasted energy into useful energy that can be reused, thereby improving overall circuit efficiency while maintaining voltage spike suppression capability
2Loss of energy
If an energy recycle circuit with auxiliary switch and timing control is implemented, then energy efficiency is improved through leakage inductance energy recycling, but device complexity increases
Solution Approach 1:
The clamp capacitor serves multiple functions: it acts as a voltage spike suppression element during the charging phase when the auxiliary switch is off, and simultaneously serves as an energy storage element for recycling during the discharging phase when the auxiliary switch is on. This multi-functionality allows the circuit to achieve energy recycling without adding excessive complexity, as existing components are utilized for multiple purposes
Solution Approach 2:
The timing control circuit uses feedback signals from the auxiliary switch current and voltage to automatically control the timing of the auxiliary switch. The control circuit monitors the charging completion of the clamp capacitor and triggers the auxiliary switch at the appropriate moment to initiate energy transfer, eliminating the need for complex external control circuits while ensuring precise timing for energy recycling
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 solution effectively recycles the leakage inductance energy, enhancing the efficiency of flyback circuits by preventing energy wastage and improving voltage spike suppression.
Implementation Method 1
a leakage inductance Lk of a transformer T1 transfer its leakage inductance energy to charge the clamp capacitor Csn via the diode Dsn
Implementation Method 2
the auxiliary switch is turned on during a charging process of the clamp capacitor, and is turned off at an end of an immediate subsequent discharging process of the clamp capacitor
Data Source
AI summary
An energy recycle circuit for a flyback circuit and method thereof. The energy recycle circuit has an auxiliary switch coupled in series to a clamp capacitor to form a branch, and the branch is coupled in parallel with the primary winding, or with the primary switch. The energy recycle circuit further has a recycle control circuit to generate an auxiliary switching signal. The auxiliary switch is turned on during a charging process of the clamp capacitor, and is turned off at an end of an immediate subsequent discharging process of the clamp capacitor. The charging process of the clamp capacitor is timed at a first length of time, and the immediate subsequent discharging process of the clamp capacitor is timed at a second length of time, based on an auxiliary switch current signal. The second length of time is adjustable to have an equal time length with the first length of time, or have a unequal time length with the first length of time.