Flyback Transformer Communication via ZVS Pulse Modulation
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Solution Overview
Problem
Existing isolated power converters face challenges in communicating digital information from the secondary side to the primary side without requiring additional components or separate communication channels, especially when supporting zero voltage switching (ZVS) and constant frequency modes.
Innovation Solution
Modulating the period between zero voltage switching (ZVS) pulses initiated by a synchronous rectification (SR) transistor on the secondary side to encode and transmit digital information, which is then detected and decoded on the primary side using stable and accurate ZVS pulse detection techniques, without the need for additional communication devices or channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separate communication channel with isolation (such as an optoisolator) is used to communicate between secondary and primary sides, then communication reliability is improved, but device complexity and cost increase
Solution Approach 1:
The patent makes the existing power transformer serve dual functions: power conversion and signal communication. By modulating the ZVS pulse timing on the secondary side and detecting these timing variations on the primary side, the transformer becomes a multi-functional device that eliminates the need for separate communication channels like optoisolators, thereby reducing device complexity while maintaining communication capability
Solution Approach 2:
The system uses its own operational signals (ZVS pulses generated during normal power conversion) as the communication carrier. The secondary side controller modulates the timing of these self-generated ZVS pulses to encode digital information, which is then detected by the primary side controller. This self-service approach eliminates external communication components while utilizing the system's inherent operational characteristics
2Adaptability or versatility
If additional components are added to modulate existing signals for communication, then communication capability is improved, but device complexity increases
Solution Approach 1:
The system uses its own operational signals (ZVS pulses generated during normal power conversion) as the communication carrier. The secondary side controller modulates the timing of these self-generated ZVS pulses to encode digital information, which is then detected by the primary side controller. This self-service approach eliminates external communication components while utilizing the system's inherent operational characteristics
Solution Approach 2:
The patent communicates digital information by modulating the timing parameter of the ZVS pulses. The secondary side controller varies the time interval between consecutive ZVS pulses to encode binary information (e.g., shorter interval for one bit value, longer interval for another). This parameter modulation approach enables communication capability without adding modulating components, as it simply reuses the existing ZVS pulse timing mechanism
3Productivity
If ZVS pulse timing is modulated to encode digital information, then communication efficiency is improved, but detection precision requirements increase
Solution Approach 1:
The primary side controller detects the timing of ZVS pulses and uses this timing information to decode the digital information transmitted from the secondary side. The system establishes a feedback loop where the primary controller adjusts its operation based on the detected pulse timing variations, enabling reliable communication through precise timing measurement and responsive control adjustment
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 method allows reliable and efficient communication of digital information across the power transformer while maintaining galvanic isolation, supporting both discontinuous and continuous conduction modes, and compatible with ZVS and constant frequency control systems, without increasing complexity or cost.
Implementation Method 1
initiate zero voltage switching (ZVS) by controlling a switching time of the SR switch
Implementation Method 2
communicate digital information across the power transformer
Implementation Method 3
detect the switching time of the SR switch based on a reflected voltage sensed on a primary winding
Data Source
AI summary
The disclosure describes techniques to send digital information from the secondary side to the primary side of a power converter, such as a flyback power converter. By modulating the amount of time between zero voltage switching (ZVS) pulses initiated by a synchronous rectification (SR) transistor on the secondary side, a power converter circuit of this disclosure may communicate digital information to the primary side from the secondary side. The power converter circuit of this disclosure may include stable, accurate and reliable ZVS pulse detection techniques on the primary side to determine slight changes in the period between ZVS pulses from the secondary side. A controller circuit on the secondary side may encode digital information by modulating the ZVS period, e.g. increased period, decreased period or no change to the period.