Active Clamp Power Converter Controller for Leakage Energy Recovery
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Solution Overview
Problem
Conventional flyback converters face efficiency losses due to energy wastage in leakage inductance and complexity in optimizing burst mode operation for wide output voltage ranges, particularly in light load conditions, where achieving zero voltage switching (ZVS) is challenging without resorting to complex LC output winding networks.
Innovation Solution
A power converter controller that controls an active clamp and flyback converter, enabling continuous variable frequency ZVS operation without burst mode, allowing for optimal loop response and line rejection, and determining conduction modes based on input line voltage, thereby reducing conduction and switching losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional passive clamps (RCD clamp) are used to handle leakage energy, then the device voltage is protected from exceeding ratings, but energy is wasted and efficiency is reduced
Solution Approach 1:
The patent converts the harmful leakage energy that was previously wasted in resistors into useful energy by recycling it through the active clamp circuit. The clamp capacitor stores the leakage energy and the controller transfers it back to the primary side, transforming the waste energy into a beneficial resource that improves overall system efficiency while maintaining voltage protection.
Solution Approach 2:
Instead of discarding the leakage energy through resistive dissipation, the patent implements a recovery mechanism where the clamp circuit captures the energy in the clamp capacitor and the controller actively transfers it back to the primary side. This recovery process eliminates the energy waste while maintaining the protective function.
2Loss of energy
If active clamp with resonant LC secondary output winding is used to achieve ZVS, then efficiency is improved, but controller complexity increases due to burst mode operation requirements
Solution Approach 1:
The patent implements dynamic control of the clamp switch timing based on real-time detection of the primary switch current. The controller adjusts the clamp switch turn-on timing dynamically to achieve zero voltage switching without requiring burst mode operation. This dynamic adaptation simplifies the controller while maintaining high efficiency across varying load conditions.
Solution Approach 2:
The system uses feedback from the primary switch current detection to control the clamp switch timing. The controller monitors the current and uses this information to determine the optimal moment to activate the clamp switch, ensuring ZVS is achieved without complex burst mode control strategies. This feedback mechanism simplifies the overall control architecture.
3Reliability
If burst mode operation is used for active clamp ZVS, then ZVS is achieved, but loop speed and stability optimization becomes challenging for wide output voltage ranges
Solution Approach 1:
The patent replaces the static burst mode operation with dynamic continuous conduction mode operation. The clamp switch timing is dynamically adjusted based on real-time current detection, allowing ZVS to be maintained across wide output voltage ranges without the complexity of optimizing burst mode parameters. This dynamic approach eliminates the need for complex loop speed and stability optimization.
Solution Approach 2:
Instead of using discontinuous burst mode operation, the patent implements continuous conduction mode where the active clamp circuit operates continuously. This continuous operation simplifies the control strategy by eliminating the need to optimize burst mode parameters while maintaining ZVS across varying conditions, reducing controller complexity for wide output voltage ranges.
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 enhances efficiency by reducing RMS currents and eliminating the need for burst mode complexity, achieving high efficiency across varying load conditions and output voltage ranges through continuous conduction mode operation.
Implementation Method 1
a clamp capacitor coupled across the primary winding and the power switch and configured to store energy from the leakage inductance
Implementation Method 2
the controller detecting when the stored energy in the clamp capacitor reaches a threshold level
Implementation Method 3
the controller transferring the stored energy from the clamp capacitor back to the primary side of the energy transfer element
Data Source
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AI summary
A controller for a power converter (100). The controller comprising a control circuit coupled to receive an input line voltage sense signal (149) representative of an input voltage (VIN) of the power converter. The control circuit configured to generate a control signal in response to a request signal (135) representative of an output of the power converter. The control signal represents a delay time to turn on a power switch (SI) after a turn on of a clamp switch (108) in response to the input line voltage sense signal (149). The control circuit can further generate a clamp drive signal to control a clamp driver and a drive circuit configured to generate a drive signal to control the power switch to transfer energy from an input of the power converter to the output of the power converter.