Parallel Bidirectional Flyback Control for Stable Valley Switching
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Solution Overview
Problem
High-power bidirectional flyback converters face challenges in maintaining stable interleaved operation and reducing electromagnetic noise due to variable switching frequency, especially under changing load conditions.
Innovation Solution
Implementing a master-slave configuration where the master controller feedback-controls the overall current output and slave controllers adjust their ON times to maintain phase delays, ensuring stable interleaved operation and reducing ripple voltages by locking switching frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If valley switching is implemented to minimize switching losses, then switching efficiency is improved, but switching frequency becomes variable which makes interleaved operation difficult to coordinate
Solution Approach 1:
The patent implements a master-slave control architecture where the master controller generates a reference switching signal and slave controllers use feedback mechanisms to synchronize their switching operations. The slave controllers detect the master's switching events and adjust their phase delays accordingly, ensuring stable interleaved operation despite variable switching frequency caused by valley switching.
Solution Approach 2:
The master controller acts as an intermediary between the variable frequency valley switching operation and the slave controllers. It generates timing reference signals that mediate the synchronization between parallel converter units, allowing each slave to maintain proper phase relationship without directly sensing the variable frequency oscillations.
2Power
If multiple converters are operated in parallel to achieve high-power applications, then power output capability is improved, but coordination difficulty increases making it challenging to maintain constant time shift and meet EMC requirements
Solution Approach 1:
The patent merges the control functions of multiple parallel converters into a unified master-slave architecture. The master controller consolidates the timing reference generation for all slave units, simplifying the coordination complexity that would otherwise arise from managing multiple independent controllers in parallel high-power conversion systems.
Solution Approach 2:
The control system is segmented into hierarchical levels: a master controller that handles overall synchronization and timing reference generation, and slave controllers that handle individual unit switching execution. This segmentation divides the complex coordination task into manageable portions, reducing overall system complexity while enabling high-power parallel operation.
3Object-generated harmful factors
If valley switching is used to achieve zero voltage switching, then electromagnetic noise is reduced, but maintaining stable phase relationships becomes challenging under variable load conditions
Solution Approach 1:
The master controller preliminarily establishes the switching phase relationships by generating reference timing signals before the actual switching events occur. This preliminary timing framework allows slave controllers to maintain stable phase relationships even when valley switching causes variable frequency operation under changing load conditions.
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 approach allows for efficient, scalable, and cost-effective high-power operation with reduced electromagnetic noise and stable power conversion rates across converter units, even under varying load conditions.
Implementation Method 1
During the ON time, the switch in the primary circuit is closed so that the primary current may ramp up in the primary winding, with the result that magnetic energy is stored in the transformer
Implementation Method 2
Then, during the OFF time, the switch in the primary circuit may be turned OFF while the switch (or a parallel diode thereof) on the secondary side are conductive, so that the energy that has been accumulated during the ON time may be delivered to an output terminal on the secondary side
Implementation Method 3
Valley switching means that the primary side switch is closed at a time when the oscillating voltage across that switch has a minimum, so that the energy stored in the output capacitance of the switch at the time when the switch is closed is relatively small
Implementation Method 4
Under certain conditions, the voltage drop across the primary side switch may even reach zero at the deepest point of the 'valley', so that a zero voltage switching (ZVS) operation may be achieved which is particularly efficient in terms of switching losses (soft switching)
Data Source
AI summary
A bidirectional power converter includes flyback converter units connected in parallel, each having a controller and adapted to accumulate power from a primary side during an ON time and to deliver the accumulated power to a secondary side during an OFF time, the primary and secondary sides being interchangeable as to the direction of power conversion, the controller operating at a boundary between discontinuous and continuous conduction modes and performing valley switching when switching from OFF to ON, one converter unit operating as a master wherein the controller is adapted to control the length of ON time in order to feedback-control an overall current output of the converter, and each other converter unit operating as a slave wherein the controller controls the length of ON time in order to feedback-control a phase delay of ON time of the slave relative to ON time of another converter unit.