Flyback Converter Clamp Control for Lower Switch Voltage Stress
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Solution Overview
Problem
Existing flyback power converters face high voltage stress on the switch element due to leakage inductance, leading to energy loss and efficiency issues, with RCD clamping circuits consuming leakage inductance energy and active clamp methods being complex and risky for isolation failure.
Innovation Solution
A flyback power converter design replaces the diode in the RCD clamping circuit with a clamping switch element, controlled by a control circuit based on capacitor voltage and current, eliminating reverse recovery loss and simplifying the control method.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If an RCD clamping circuit with diode is used to suppress voltage stress, then voltage stress on switch element is reduced, but reverse recovery loss increases and efficiency decreases
Solution Approach 1:
The patent changes the fundamental parameter of the clamping circuit by replacing the diode with a controllable switch element (MOSFET or IGBT). This allows active control of the clamping action timing and duration, enabling the circuit to suppress voltage stress while avoiding the reverse recovery loss inherent in passive diode-based RCD clamping circuits.
Solution Approach 2:
The clamping switch element is controlled to turn on automatically when voltage stress exceeds a threshold level and turn off when the stress is relieved, creating a self-regulating protection mechanism that recovers leakage inductance energy without requiring complex external control circuits.
2Loss of energy
If active clamp flyback (ACF) control method is used to recover leakage inductance energy, then efficiency is improved and voltage stress is reduced, but control complexity increases and isolation failure risk appears
Solution Approach 1:
The patent incorporates a feedback mechanism where the control circuit monitors the voltage across the switch element and automatically activates the clamping switch when voltage stress exceeds a predetermined threshold. This feedback-based automatic control simplifies the overall system by eliminating complex timing circuits and multiple switches required in traditional ACF methods.
Solution Approach 2:
The clamping switch element serves multiple functions: it acts as a protection element during switching transitions, a energy recovery element during the off-period, and a voltage clamping element. This multi-functionality reduces the need for separate dedicated components for each function, thereby simplifying the overall control mechanism.
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 reduces reverse recovery loss, enhances efficiency, and avoids isolation failure while maintaining lower voltage stress, offering a more cost-effective and simplified control mechanism compared to active clamp flyback methods.
Implementation Method 1
A first terminal of the first capacitor is electrically connected with a first terminal of a primary winding of the transformer
Implementation Method 2
The transformer includes a primary winding and a secondary winding
Data Source
AI summary
A flyback power converter includes a transformer, a voltage clamping circuit, a main switch element and a control circuit. The voltage clamping circuit includes a first capacitor and a clamping switch element. The first capacitor is electrically connected with a primary winding of the transformer. The clamping switch element is electrically connected between the capacitor and the primary winding. The control circuit detects a capacitor voltage of the first capacitor and a current flowing through the clamping switch element. If the capacitor voltage is greater than a reference voltage, the clamping switch element is turned on. If the capacitor voltage is not greater than the reference voltage and the current flowing through the clamping switch element is lower than a reference current value, the clamping switch element is turned off.