Primary-Side Resonant Converter Control for Current Regulation
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Solution Overview
Problem
Conventional flyback converters face challenges in accurately regulating current and power due to bidirectional current flow and high frequency oscillations caused by resonant waveforms, which affect the precision of current regulation and introduce errors, while maintaining galvanic isolation between the primary and secondary sides.
Innovation Solution
The implementation of nested control loops and an active clamp flyback controller that accounts for bidirectional current flow and high frequency oscillations, using a magnetizing inductor and a resonant circuit to dampen oscillations and accurately calculate output current and power, while maintaining galvanic isolation through an auxiliary winding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional current regulation methods are used in resonant converters, then the converter can operate with resonant topology, but current regulation precision deteriorates due to bidirectional current flow and high frequency oscillations
Solution Approach 1:
The patent extracts and removes the harmful bidirectional current component and high frequency oscillations from the primary current signal by using synchronous rectification control and selective current sampling only during the forward conduction period, thereby eliminating the source of regulation errors while preserving the resonant topology benefits
Solution Approach 2:
The patent implements primary-side feedback control that senses the primary current and uses it to regulate the converter operation. By incorporating feedback control with selective current sampling and synchronous rectification, the system achieves accurate current regulation despite the resonant waveform characteristics
2Reliability
If primary current amplitude is used to estimate secondary current, then galvanic isolation is maintained, but regulation accuracy deteriorates due to resonant waveform errors
Solution Approach 1:
The patent implements primary-side feedback control that directly senses and regulates the primary current waveform. By using feedback control on the primary side, the system achieves accurate regulation without requiring secondary side information, thereby maintaining galvanic isolation while improving regulation accuracy through active compensation of resonant effects
Solution Approach 2:
The patent changes the approach from estimating secondary current based on simple primary current amplitude to using sophisticated primary current waveform analysis that accounts for resonant characteristics. By analyzing the shaped primary current waveform and using synchronous rectification timing, the system accurately determines power transfer while maintaining galvanic isolation
3Device complexity
If conventional regulation methods are used, then device complexity is reduced, but power and current regulation capability deteriorates
Solution Approach 1:
The patent enables primary-side control where the converter regulates itself using only primary side components. The control circuit uses primary current sensing and synchronous rectification control to automatically regulate both current and power output without requiring secondary side feedback, thereby reducing device complexity while maintaining comprehensive regulation capability
Solution Approach 2:
The patent implements a unified primary-side control mechanism that simultaneously provides both current regulation and power regulation capabilities. The same primary current sensing and synchronous rectification control circuitry enables the converter to operate in different modes (current mode, power mode, voltage mode) depending on control parameters, providing multi-functionality without increasing device complexity
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 eliminates errors caused by bidirectional current flow and high frequency oscillations, enabling precise regulation of output current, power, and voltage in flyback converters, ensuring accurate power conversion while maintaining galvanic isolation.
Implementation Method 1
current flows in the primary, thus inducing a magnetic flux in the core of the transformer
Implementation Method 2
an oscillating resonant waveform will be presented to the switch on the primary side due to a leakage inductance of the transformer and a capacitance of the switch
Implementation Method 3
using a magnetizing inductor and a resonant circuit to dampen oscillations
Data Source
AI summary
A method for controlling a resonant converter includes maintaining an output current equal to an output power of the converter divided by an output voltage of the converter in response to a secondary current of a transformer being greater than or equal to a maximum output current. The output power is maintained at a constant output power in response to the output power being greater than or equal to a maximum output power, and the secondary current being less than the maximum output current. Maintaining the output current ratio and the constant output power each comprises changing the duty cycle of a primary-side switch configured to gate a primary current of the transformer. The output voltage is limited to a maximum output voltage in response to the secondary current being less than the maximum output current, and the output power being less than the maximum output power.