Isolated Power Converter Data Link via Transformer Reset
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Solution Overview
Problem
Isolated switching power converters face challenges in efficient secondary-side to primary-side communication, particularly during both discontinuous and continuous conduction modes of operation, due to limitations in existing optocoupler-based methods which are costly, unreliable, and low-speed, and valley-mode switching is not applicable in continuous conduction mode.
Innovation Solution
A secondary-side controller that uses a comparator and logic circuit to assert output signals based on the voltage across a synchronous rectifier switch transistor, allowing the gate driver to switch the synchronous rectifier switch transistor on or off during transformer reset periods to transmit data, enabling efficient communication across the transformer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If optocoupler-based feedback is used to transmit output voltage data from secondary side to primary side, then galvanic isolation is maintained, but communication speed is low, cost increases, and reliability decreases
Solution Approach 1:
The patent extracts the data transmission function from the traditional optocoupler-based feedback system and implements it through the existing transformer structure. By utilizing the transformer's magnetic coupling to transmit data during reset periods, the system eliminates the need for separate optocoupler components while maintaining galvanic isolation, thereby reducing device complexity and cost without compromising communication reliability
Solution Approach 2:
The transformer is made multi-functional by enabling it to perform both power transfer and data transmission functions. During the reset period when the primary switch is off, the transformer's magnetic core resets and this period is utilized to encode and transmit data bits from the secondary side to the primary side, allowing a single component to serve dual purposes and eliminating the need for dedicated optocouplers
2Adaptability or versatility
If valley-mode switching is used for data transmission, then communication during discontinuous conduction mode is achieved, but it is not applicable during continuous conduction mode
Solution Approach 1:
The patent implements a dynamic data transmission scheme that automatically adapts to the converter's operating mode. The system detects whether the converter is operating in discontinuous or continuous conduction mode and adjusts the data encoding strategy accordingly - using valley-mode detection for DCM and alternative encoding methods for CCM, ensuring reliable data transmission across all operating conditions without requiring separate circuits for each mode
Solution Approach 2:
The system changes operational parameters based on conduction mode detection. By monitoring the timing and characteristics of the reset period and switch cycling behavior, the system identifies the conduction mode and modifies the data transmission protocol accordingly, allowing the same hardware to reliably transmit data in both discontinuous and continuous conduction modes through parameter adaptation rather than structural modification
3Loss of energy
If synchronous rectification is used instead of output diode, then efficiency is improved, but control complexity increases requiring secondary-side controller
Solution Approach 1:
The patent implements a feedback mechanism where the secondary-side controller monitors the output voltage and encodes this information into data bits that are transmitted back to the primary side during transformer reset periods. This feedback loop enables the primary-side controller to adjust its operation based on actual output conditions, achieving precise voltage regulation and optimal efficiency while maintaining a manageable control architecture through coordinated control between primary and secondary sides
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 allows for reliable and efficient data transmission between the secondary-side and primary-side controllers in both discontinuous and continuous conduction modes, improving communication speed and reducing costs by eliminating the need for optocouplers, while maintaining high efficiency.
Implementation Method 1
a secondary-side controller that uses a comparator and logic circuit to assert output signals based on the voltage across a synchronous rectifier switch transistor, allowing the gate driver to switch the synchronous rectifier switch transistor on or off during transformer reset periods to transmit data, enabling efficient communication across the transformer
Data Source
AI summary
An isolated switching power converter having a primary-side and secondary-side in signal communication with an input and an output is disclosed. The isolated switching power converter comprises a transformer, primary-side switch, secondary-side switch, primary-side controller, and secondary-side controller. The transformer includes a primary-winding and a secondary-winding in signal communication with the input and output. The primary-side switch is in signal communication with the primary-winding and the secondary-side switch is in signal communication with the secondary-winding. The primary-side controller is on the primary-side and the secondary-side controller is on the secondary-side. The primary-side controller is configured to output a control signal for operating the primary-side switch and the secondary-side controller configured to monitor a voltage across the secondary-side switch, output a control signal for switching the secondary-side switch, and turn-off the secondary-side switch at an off-time of the primary-side switch to transmit a data signal to the primary-side controller.