Flyback Energy Recycle Circuit for Leakage Inductance Recovery
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Solution Overview
Problem
Flyback circuits face inefficiency due to the burning of leakage inductance energy, which is not recycled, leading to limited suppression of voltage spikes and increased voltage stress.
Innovation Solution
An energy recycle circuit is introduced, featuring an auxiliary switch and a clamp capacitor in series, controlled by an integrated circuit with pins for external supply voltage, power ground, current sensing, and maximum ON-time threshold setting, allowing the energy recycle branch to be coupled in parallel with the primary winding to recycle leakage inductance energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an RCD snubber circuit is used to suppress voltage spikes, then voltage spike suppression is improved, but energy is lost because the leakage inductance energy is burned out instead of being recycled
Solution Approach 1:
The patent recovers the leakage inductance energy that would otherwise be dissipated as heat in the snubber resistor. By introducing an auxiliary switch and clamp capacitor, the energy stored in the leakage inductance is redirected to charge the clamp capacitor during the switch-off transient, and then this recovered energy is transferred to the output during the switch-on period, effectively recovering what would have been lost energy while maintaining voltage spike suppression.
2Reliability
If a snubber resistor is used to consume the energy stored in the clamp capacitor, then voltage stress is reduced, but efficiency is limited due to energy being burned out
Solution Approach 1:
The patent converts the harmful effect of the snubber resistor burning energy into a beneficial energy recovery mechanism. Instead of dissipating energy as heat, the circuit uses the clamp capacitor to store energy temporarily and then transfers it to the output through the auxiliary switch, transforming the previously harmful energy loss into a useful energy transfer that improves efficiency while maintaining voltage stress protection.
3Loss of energy
If an energy recycle circuit with auxiliary switch and clamp capacitor is introduced, then leakage inductance energy is recycled improving efficiency, but device complexity increases
Solution Approach 1:
The auxiliary switch serves multiple functions: it controls the energy transfer from the leakage inductance to the clamp capacitor during the off-transient, controls the discharge of the clamp capacitor to the output during the on-period, and works with the integrated circuit to provide maximum ON-time control and over-current protection. This multi-functionality reduces the need for separate dedicated components for each function, thereby limiting the increase in overall circuit complexity.
Solution Approach 2:
The clamp capacitor acts as an intermediary energy storage element between the leakage inductance and the output. It temporarily stores the recovered energy from the leakage inductance and then transfers it to the output through the auxiliary switch, mediating the energy transfer process and enabling efficient energy recycling without requiring direct coupling between the leakage inductance and output, thus simplifying the overall energy management architecture.
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 effectively recycles leakage inductance energy, enhancing the efficiency of flyback circuits by preventing energy wastage and improving voltage spike suppression without increasing complexity or cost.
Implementation Method 1
a leakage inductance Lk of a transformer T transfer its leakage inductance energy to charge the clamp capacitor Csn
Implementation Method 2
an auxiliary switch and a clamp capacitor connected in series to form an energy recycle branch
Implementation Method 3
A third pin is configured to sense a branch current flowing through the energy recycle branch
Data Source
AI summary
An energy recycle circuit for a flyback circuit, the flyback circuit has a primary winding of a transformer a primary switch. The energy recycle circuit has an energy recycle branch coupled in parallel with the primary winding, and an integrated circuit having a plurality of pins. The energy recycle branch has an auxiliary switch and a clamp capacitor connected in series. Among the plurality of pins, a first pin receives an external supply voltage. A second pin is used as a power ground that is different from a primary power ground. A third pin is used to sense a branch current flowing through the energy recycle branch. A fourth pin is used to control an operation of the auxiliary switch. A fifth pin that is connected to an external resistor for setting a maximum ON-time threshold of the auxiliary switch.