LLC Phase-Shift Control for Lagging Bridge Hard-Switching Avoidance
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Solution Overview
Problem
LLC resonant converters face issues with excessive phase-shift angles leading to capacitive operation, causing hard switching and reverse recovery losses, increased stress on switch transistors, and reduced service life due to body diode reverse recovery losses.
Innovation Solution
A phase-shift control circuit and method that includes a sampling module, logical operation module, and control module to adjust the phase-shift angle of lagging bridge switch transistors based on real-time voltage and current phase differences, ensuring operation within an inductive region to avoid hard switching and reduce stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If phase-shift technology is used to increase gain range, then the gain range of LLC circuit is improved, but the phase-shift angle becomes excessively large causing the circuit to work in capacitive region
Solution Approach 1:
The patent employs feedback control by detecting the phase difference between resonant current and voltage of the lagging bridge switch transistor, then adjusting the phase-shift angle based on this detected phase difference to maintain proper operating region
Solution Approach 2:
The patent dynamically adjusts the phase-shift angle parameter based on the detected phase difference, changing this critical parameter to prevent excessive phase-shift angles and avoid capacitive region operation
2Adaptability or versatility
If phase-shift angle is increased to extend gain range, then the LLC circuit can operate at higher gains, but hard switching occurs causing reverse recovery loss
Solution Approach 1:
The control module detects phase difference and uses this feedback to adjust the phase-shift angle, preventing excessive angles that would cause hard switching and reverse recovery losses in the body diode
Solution Approach 2:
The system proactively adjusts the phase-shift angle before the circuit enters capacitive region, preventing hard switching and reverse recovery loss before they occur
3Adaptability or versatility
If phase-shift angle is increased to extend gain range, then the LLC circuit achieves higher gain capability, but stress on switch transistor increases
Solution Approach 1:
The system continuously monitors phase difference and adjusts phase-shift angle accordingly, preventing excessive stress on switch transistors by avoiding operation in capacitive region where stress would be highest
4Adaptability or versatility
If phase-shift angle is increased to extend gain range, then the LLC circuit can achieve broader operating range, but service life of LLC circuit decreases
Solution Approach 1:
The feedback control mechanism prevents operation conditions that would degrade components, thereby extending service life while maintaining broad gain range capability through intelligent phase-shift adjustment
Solution Approach 2:
The system proactively prevents harmful operating conditions by adjusting phase-shift angle before the circuit enters regions that would cause damage, cushioning against potential harm to extend service life
Data Source
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AI summary
A phase-shift control circuit and a phase-shift control method for an LLC circuit are provided. The phase-shift control circuit includes: a sampling module, configured to obtain a voltage of a switch transistor of the LLC circuit and a resonant current; a logical operation module, configured to obtain a phase difference between the voltage of the switch transistor and the resonant current; and a control module, configured to: transmit a control signal to control terminals of the switch transistors of the LLC circuit, and control phase shift to be performed on a lagging bridge switch transistor of the LLC circuit; and adjust, in response to that a time value corresponding to the phase difference is less than a first target value, a phase-shift angle of the lagging bridge switch transistor until the time value corresponding to the phase difference is greater than or equal to the first target value, where the first target value is a difference between a sampling delay of the resonant current and a sampling delay of the voltage of the switch transistor. In the present application, hard switching of the lagging bridge switch transistor in the LLC circuit can be avoided, to avoid generation of a reverse recovery loss of a body diode, thereby improving working efficiency of the LLC circuit, reducing stress of the switch transistor, reducing a loss of the switch transistor, and improving a service life of the LLC circuit.