Series Resonant Converter Fixed-Frequency Duty Cycle Control
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Solution Overview
Problem
Conventional series resonant converters face difficulties in maintaining desired output voltage and current due to frequency variations and input/output fluctuations, which complicates the design of magnetic components and filters, and fails to achieve stable power regulation.
Innovation Solution
A series resonant converter with a converter controller that uses a fixed frequency control algorithm, incorporating a phase delay between switching signals and two control loops (average trajectory radius loop and voltage loop) to maintain constant switching frequency and regulate output voltage, along with optional over-voltage and over-current protection mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If frequency control is employed to control operation of the series resonant converter, then output voltage regulation can be achieved, but design of magnetic components and filters becomes difficult
Solution Approach 1:
The patent changes the control parameter from frequency variation to duty cycle modulation at a fixed frequency. The controller maintains a constant switching frequency and regulates output voltage by adjusting the duty cycle of the switching signals, which simplifies the design of magnetic components and filters while achieving precise output voltage regulation.
2Power
If frequency is varied with respect to resonant frequency to achieve desired output voltage, then power regulation can be performed, but magnetic component design becomes complicated
Solution Approach 1:
The patent transitions from frequency-based power regulation to duty cycle-based power regulation at a fixed switching frequency. This allows the resonant circuit parameters (inductors and capacitors) to be designed for a specific frequency, simplifying magnetic component design while maintaining effective power regulation capability through duty cycle modulation.
3Productivity
If conventional frequency control techniques are used, then basic power conversion is achieved, but desired output voltage cannot be achieved when input power or output load varies
Solution Approach 1:
The patent implements a feedback control system where the controller monitors the output voltage and adjusts the duty cycle of the switching signals accordingly. This closed-loop feedback mechanism ensures that the desired output voltage is maintained even when input power or output load conditions vary, overcoming the limitations of conventional open-loop frequency control.
4Manufacturing precision
If switching frequency is varied for power regulation, then output voltage control is possible, but system response to load transients becomes slow
Solution Approach 1:
The patent changes the controlled parameter from frequency to duty cycle at fixed frequency, which enables faster response to load transients. Duty cycle modulation can be adjusted more rapidly and precisely than frequency changes, allowing the system to quickly respond to and correct output voltage deviations caused by load variations.
Data Source
AI summary
A resonant power supply is disclosed. The resonant power supply includes a series resonant configured to convert an input DC voltage to an output DC voltage. The resonant power supply further comprises a converter controller coupled to the series resonant converter and configured to receive a DC voltage feedback signal measured at the output of the series resonant converter, or a resonant current feedback signal representing a resonant current flowing through the series resonant converter. The converter controller is further configured to generate control signals to be applied to the series resonant converter to limit the output DC voltage of the series resonant converter according to the DC voltage feedback signal and a predetermined voltage threshold signal, or to limit the resonant current of the series resonant converter according to the resonant current feedback signal and a predetermined current threshold signal.