LLC Resonant Converter Feedforward Control for Input Disturbances
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Solution Overview
Problem
LLC resonant converters have a poor transient response to input disturbances due to their reliance on variable frequency methods for output voltage regulation, which is exacerbated by the need for large output capacitors to improve transient immunity, posing challenges in applications like aerospace where size and weight are critical.
Innovation Solution
The implementation of a feed-forward compensation technique in LLC resonant converters, where a controller connected to the input line and switch array uses pulse frequency modulation (PFM) to regulate output voltage, improves transient response by varying the switching frequency in response to input voltage changes, thereby reducing the need for large output capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If variable frequency method is used to regulate output voltage in LLC resonant converters, then output voltage control is achieved, but transient response to input disturbance deteriorates
Solution Approach 1:
The feed-forward controller predicts future input voltage disturbances and preemptively adjusts the switching frequency to compensate for upcoming variations. By acting in advance rather than reacting after disturbances occur, the system maintains output voltage stability during transitions, resolving the contradiction between voltage control and transient response.
2Reliability
If larger output capacitors are used to improve transient response, then transient immunity improves, but size and weight increase
Solution Approach 1:
The patent replaces the passive mechanical approach of using large capacitors with an active electronic control system. The feed-forward controller uses sensing and computation to dynamically adjust switching parameters, substituting the need for bulky energy-storing capacitors with a lightweight control algorithm that achieves the same transient immunity function.
Solution Approach 2:
Instead of changing the physical parameter of capacitor size to improve transient response, the system changes the operational parameter of switching frequency dynamically. The feed-forward controller modulates switching frequency in response to predicted input disturbances, achieving transient immunity through parameter modulation rather than physical component scaling.
3Reliability
If larger output capacitors are used to improve transient response, then transient immunity improves, but device complexity and cost increase
Solution Approach 1:
The patent replaces the passive mechanical approach of using large capacitors with an active electronic control system. The feed-forward controller uses sensing and computation to dynamically adjust switching parameters, substituting the need for bulky energy-storing capacitors with a lightweight control algorithm that achieves the same transient immunity function.
Data Source
AI summary
An LLC resonant converter comprises, an LLC resonant converter circuit with an output line and an input line. The LLC resonant converter circuit includes a switch array operatively connecting between the input line and the output line. A controller is connected to the input line by a feed forward line and connected to a respective gate of each switch in the switch array. The controller includes machine readable instructions configured to cause the controller to receive feed forward input from the input line and control switching of the switch array with a pulse frequency modulation (PFM) switching pattern to regulate voltage of the output line.