Flyback Auxiliary Switch Control for Leakage Energy Recycling
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Solution Overview
Problem
Conventional flyback circuits face inefficiency due to leakage inductance energy being dissipated rather than recycled, leading to voltage spikes and complexity in controlling auxiliary switches to prevent mis-triggering.
Innovation Solution
A controller for an auxiliary switch is introduced, connected in series with a clamp capacitor to form an energy recycle branch, utilizing a power supply terminal, sensing terminal, ground terminal, and a turn-on control circuit to manage the switching of the auxiliary switch based on voltage logic states, thereby recycling energy and preventing mis-triggering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional RCD snubber is used to suppress voltage spikes, then voltage spikes are well suppressed, but efficiency is limited because leakage inductance energy is burned out instead of being recycled
Solution Approach 1:
The patent converts the harmful leakage inductance energy that was previously dissipated as heat in the RCD snubber into useful energy by introducing an auxiliary switch and control circuit that redirects this energy to charge the clamp capacitor, transforming waste energy into stored energy that can be reused in subsequent switching cycles
Solution Approach 2:
Instead of discarding the leakage inductance energy through the snubber resistor, the patent implements a recovery mechanism where the auxiliary switch enables the energy to be transferred to and stored in the clamp capacitor, allowing the energy to be recovered and utilized again when the primary switch turns on
2Loss of energy
If an auxiliary switch is added to recycle energy, then efficiency is improved, but device complexity increases due to additional control requirements
Solution Approach 1:
The auxiliary switch control is designed to be self-regulating, where the switch automatically turns on when the primary switch turns off (detected through voltage changes at the power supply terminal) and turns off when the primary switch turns on, eliminating the need for complex external control logic and making the system self-managing
Solution Approach 2:
The control circuit uses feedback from the power supply terminal voltage to detect the switching state of the primary switch and automatically controls the auxiliary switch accordingly, creating a closed-loop control system that simplifies the overall control architecture by using the system's own operating conditions to drive the control logic
3Reliability
If the auxiliary switch is controlled based on power supply terminal voltage logic state, then mis-triggering is prevented and control reliability is improved, but the control circuit complexity increases
Solution Approach 1:
The control circuit is designed to detect the voltage logic state at the power supply terminal in advance and prepare the auxiliary switch control signal accordingly, ensuring the auxiliary switch is ready to turn on before the energy recycling condition is fully established, preventing mis-triggering while maintaining simple control logic
Solution Approach 2:
The control circuit uses the power supply terminal voltage as a reference potential to determine when to activate the auxiliary switch, creating a stable control reference that prevents mis-triggering due to voltage fluctuations or noise, while the control logic remains relatively simple by using this inherent voltage reference
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 enhances the efficiency of the flyback circuit by recycling energy and reduces the risk of mis-triggering the auxiliary switch, simplifying the design and reducing complexity by accurately controlling the auxiliary switch operations.
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
the energy stored in the clamp capacitor Csn is consumed by the snubber resistor Rsn
Implementation Method 3
A sensing terminal of the controller is coupled to a first terminal of a current sense resistor
Data Source
AI summary
A controller for controlling auxiliary switch connected in series with a clamp capacitor to form an energy recycle branch in a flyback circuit. The controller has a power supply terminal to receive an external supply voltage, a sensing terminal connected to a first terminal of a current sense resistor which is connected in series with a primary switch, a ground terminal connected to a second terminal of the current sense resistor, a drive terminal connected to a control terminal of the auxiliary switch, and a turn on control circuit. Based on a logic state of a voltage at the power supply terminal and a voltage across the current sense resistor, the turn on control circuit provides a turn on control signal to control of the auxiliary switch.