CLLC Converter Synchronous Rectification On-Time Without Extra Sensors
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Solution Overview
Problem
Bidirectional CLLC converters face challenges in determining synchronous rectification on-time due to conflicts with MOSFET gate drive, requiring additional hardware like high-speed current sensors and zero-crossing comparators, or laborious measurement processes for lookup tables.
Innovation Solution
A method that determines synchronous rectification on-time by calculating coefficients using simulation datasets of peak and output currents, resonant frequency, and transformer turns ratio, allowing for interpolation to calculate diode on-time without additional hardware, such as high-bandwidth current sensors or zero-crossing detection circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional hardware (current sensor and zero-crossing comparator) is added to determine synchronous rectification on-time, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent extracts the on-time determination function from complex hardware circuits and relocates it to a lookup table stored in memory. The controller reads pre-calculated on-time values from the lookup table based on operating conditions, eliminating the need for additional current sensors and zero-crossing comparators while maintaining measurement precision.
Solution Approach 2:
The patent performs preliminary calculations of diode on-time under various operating conditions during the design phase and stores these results in a lookup table. During operation, the controller simply retrieves the pre-calculated values based on current operating parameters, avoiding real-time complex measurements and calculations.
2Measurement precision
If additional hardware (current sensor and zero-crossing comparator) is added to determine synchronous rectification on-time, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The patent removes the need for expensive high-speed current sensors and zero-crossing comparators by extracting the measurement function and implementing it through software-based lookup table methodology, thereby reducing component count and manufacturing cost.
Solution Approach 2:
The patent replaces expensive hardware components with a cost-effective software solution stored in memory. The lookup table approach uses inexpensive memory storage and simple controller logic to achieve the same functional result, significantly reducing overall system cost.
3Device complexity
If lookup table method is used to determine synchronous rectification on-time, then device complexity is reduced, but labor intensity increases due to required measurements
Solution Approach 1:
The patent performs the labor-intensive measurement and calculation work during the design phase to create the lookup table. Once created, the table can be reused across multiple production units without requiring repeated measurements, converting one-time labor intensity into long-term manufacturing efficiency.
Data Source
AI summary
An example method may include: determining a transformer turns ratio and resonant frequency of a converter; determining datasets of peak current and output current of a secondary side diode, an excitation current of a primary excitation inductor when the secondary side diode is off, and an excitation current of the primary excitation inductor when a primary side driving signal is off; measuring a operating frequency and output current of the converter; determining coefficients equal to a ratio of the output current to the peak current multiplied byπ2,and a ratio of an excitation current of the primary excitation inductor when the secondary side diode is off to an excitation current of the primary excitation inductor when the primary side driving signal is off; measuring a resonant current initial value of a primary resonant inductor; and based on all these, calculating a diode on-time.