LLC Resonant Converter Hysteric Control for Smaller Output Capacitors
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Solution Overview
Problem
LLC power converters face efficiency reduction due to the series resistance of output capacitors, and using smaller capacitors increases output impedance, leading to voltage undershoot and overshoot during load changes.
Innovation Solution
A resonant converter controller with a hybrid hysteric controller (HHC) is employed, which includes a current feedforward circuit to improve bandwidth and regulate output voltage by generating switching signals based on voltage and current sensing signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a larger output capacitor is used, then the ESR is reduced and operating efficiency is improved, but the size and footprint of the power converter increases
Solution Approach 1:
The patent implements a control loop that senses output voltage and current, and adjusts switching signals to maintain stable output voltage. This feedback mechanism allows the system to compensate for the higher ESR of smaller capacitors, enabling the use of reduced-size capacitors without sacrificing efficiency or stability.
Solution Approach 2:
The patent changes the control parameters by implementing a hybrid hysteric controller that dynamically adjusts switching based on voltage and current sensing. This parameter adjustment allows the system to optimize performance with smaller capacitors by actively managing the electrical characteristics rather than relying solely on passive capacitor properties.
2Area of stationary object
If a smaller output capacitor is used, then the footprint of the power converter is reduced, but the output impedance increases causing voltage undershoot and overshoot
Solution Approach 1:
The current feedforward circuit anticipates load changes by sensing current variations and preemptively adjusting the switching signals. This preliminary action compensates for the higher output impedance of smaller capacitors before voltage undershoot or overshoot can occur, maintaining stability during transient load conditions.
Solution Approach 2:
The control loop continuously monitors output voltage and current, and rapidly adjusts switching signals in response to detected deviations. This feedback mechanism compensates for the higher ESR and output impedance of smaller capacitors, maintaining voltage stability during load transitions that would otherwise cause significant undershoot or overshoot.
Data Source
AI summary
An apparatus includes a resonant converter controller having a converter voltage sensing terminal, a reference voltage terminal, a converter current sensing terminal, first and second converter capacitor terminals, and first and second control outputs. The resonant converter controller is configured to: receive a current sensing signal at the converter current sensing terminal; generate a first signal based on the current sensing signal; generate a second signal representing a difference between a first voltage at the converter voltage sensing terminal and a reference voltage at the reference voltage terminal; and generate first and second switching signals at, respectively, the first and second control outputs responsive to the first signal, the second signal, and a capacitor voltage between the first and second converter capacitor terminals to regulate the first voltage based on the reference voltage.