Bidirectional PSFB Converter Cold Start Voltage Overshoot
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Solution Overview
Problem
Bidirectional phase-shifted full-bridge (PSFB) converters experience voltage overshoots during cold start-up, leading to increased electromagnetic interference and the need for auxiliary circuitry, which complicates the converter design and reduces efficiency.
Innovation Solution
A novel modulation scheme that allows the PSFB converter to operate without auxiliary circuitry by controlling the inductor current and using synchronous rectification to manage energy transfer from the secondary to the primary side, eliminating voltage overshoots and simplifying the startup process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If auxiliary circuitry is added to reduce voltage overshoots during cold start-up, then voltage overshoots are reduced, but device complexity increases
Solution Approach 1:
The converter uses its own output capacitor to provide the startup current needed during cold start-up, eliminating the need for external auxiliary circuitry. The output capacitor naturally discharges through the synchronous rectifier transistors to charge the input capacitor, making the system self-sufficient for startup.
Solution Approach 2:
The auxiliary circuitry traditionally used for cold start-up is completely removed from the system. The patent extracts this unnecessary component and replaces it with a control method that uses existing components (output capacitor and synchronous rectifier) to perform the startup function.
2Reliability
If auxiliary circuitry is added to manage cold start-up, then startup reliability is improved, but manufacturing cost increases
Solution Approach 1:
The converter system uses its own existing components (output capacitor and synchronous rectifier transistors) to perform the startup function, eliminating the need for separate auxiliary circuitry and reducing manufacturing complexity while maintaining reliability.
3Loss of energy
If synchronous rectification is used to manage energy transfer, then efficiency is improved, but control complexity increases
Solution Approach 1:
The synchronous rectifier transistors are controlled to automatically conduct during the startup phase when the input capacitor voltage is below the output capacitor voltage, enabling efficient energy transfer without requiring complex external control circuitry. The control is integrated into the existing synchronous rectification control mechanism.
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
The solution effectively eliminates voltage overshoots and reduces complexity by enabling a cold start without auxiliary circuitry, improving reliability and efficiency in bidirectional PSFB converters.
Implementation Method 1
a transformer having a primary winding and a secondary winding
Implementation Method 2
an input capacitor coupled to the primary winding
Implementation Method 3
an output inductor coupled to the secondary winding
Data Source
AI summary
A phase-shifted full bridge (PSFB) switching converter includes a transformer having a primary winding and a secondary winding; an input capacitor coupled to the primary winding via a first transistor full bridge; an output inductor coupled to the secondary winding via a synchronous rectifier circuit including at least one first transistor and at least one second transistor; and a controller circuit for generating switching signals for the rectifier circuit to operate the PSFB switching converter in reverse direction. During a startup phase, at the beginning of which the input capacitor is substantially discharged, the at least one first transistor is switched on in each switching cycle to allow an inductor current to pass from an output node, via the output inductor and the secondary winding, to a ground node, the at least one first transistor is again switched off when the inductor current reaches a threshold value.