Isolated DC-DC Converter with Synchronized Buck-Boost Regulation
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Solution Overview
Problem
Existing multiple output DC to DC converters face challenges in providing independent regulation of isolated output voltages due to cost and size constraints, particularly when feedback across an isolation barrier is impractical, leading to inadequate line and load regulation.
Innovation Solution
A multiple output DC to DC converter design incorporating a buck converter with a half-bridge switching circuit and a boost converter, where the boost converter is magnetically coupled with the buck converter's transformer primary winding, using a PWM controller to synchronize switching with the low side switch based on sensed secondary winding voltage, thereby achieving independent regulation of both output voltages without additional feedback components across the isolation barrier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If feedback is provided across the isolation barrier to regulate the isolated output voltage, then the line and load regulation of the isolated output is improved, but the cost and size of the converter increases
Solution Approach 1:
The patent uses the transformer as an intermediary to transfer not only power but also timing synchronization signals from the primary to secondary side. The transformer's magnetic coupling enables the secondary controller to synchronize its switching with the primary controller without requiring direct feedback communication across the isolation barrier, thus maintaining regulation while avoiding complex feedback circuitry.
Solution Approach 2:
The patent implements feedback on the secondary side by sensing the isolated output voltage and using it to regulate the secondary converter's operation. The secondary controller monitors its own output and adjusts its duty cycle accordingly, creating a closed-loop regulation system that does not depend on feedback from the primary side across the isolation barrier.
2Device complexity
If a single converter provides multiple isolated outputs, then the device integration is improved, but the ability to independently regulate each output voltage deteriorates
Solution Approach 1:
The patent divides the multiple output converter into separate primary and secondary converter modules, each with its own controller. The primary converter regulates the first output voltage while the secondary converter independently regulates the isolated second output voltage. This segmentation allows each converter to be optimized and regulated independently while maintaining overall system integration.
Solution Approach 2:
The patent uses periodic PWM switching in both primary and secondary converters, synchronized through the transformer. Each converter operates in periodic cycles with controlled duty cycles, allowing independent voltage regulation while maintaining synchronized operation. The periodic nature of the switching enables precise control of energy transfer and output voltage for each converter.
3Adaptability or versatility
If the converter operates with wide input voltage variations, then the adaptability is improved, but the line regulation becomes more difficult to maintain
Solution Approach 1:
The patent employs dynamic PWM duty cycle control in both primary and secondary converters. The controllers continuously adjust the duty cycles in response to input voltage variations and load changes, enabling the converters to maintain stable output voltages across a wide input voltage range. This dynamic adjustment allows the system to adapt to line variations while maintaining regulation.
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 design enables effective line and load regulation for both output voltages, accommodating wide input voltage variations and load changes without additional circuitry, while maintaining efficiency and reducing costs by eliminating the need for feedback across the isolation barrier.
Implementation Method 1
a transformer secondary winding magnetically coupled with the primary winding to provide a boost converter inductor
Data Source
AI summary
Disclosed examples include multiple output DC to DC converters with a buck converter including a half bridge switching circuit and transformer primary winding to provide a first output voltage signal, as well as a boost converter to provide an isolated second output voltage signal. The boost converter includes a transformer secondary winding magnetically coupled with the primary winding to provide a boost converter inductor, a switching circuit, an output diode providing the second output voltage signal, and a PWM controller that synchronizes the boost converter switching with the low side switch of the buck converter based on a sensed voltage of the transformer secondary winding.