Resonant Converter Frequency Control via Input Voltage Sensing
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Solution Overview
Problem
Resonant converters with open-loop control exhibit poor line regulation performance, which is inadequate for applications requiring high power quality, and the use of optical couplers in closed-loop systems increases costs.
Innovation Solution
A control method and circuit for a resonant converter that adjusts the switching frequency based on the comparison of the input voltage with a reference threshold voltage, using a clock generator and frequency adjusting circuit to sense the input voltage and adjust the clock signal, thereby maintaining a constant output voltage without the need for closed-loop feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If open-loop control is used in resonant converter, then cost is reduced by eliminating optical couplers, but line regulation performance deteriorates
Solution Approach 1:
The patent applies preliminary action by detecting the input voltage before it causes output voltage variation, and proactively adjusting the switching frequency in advance to compensate for the expected change. The frequency adjusting circuit senses input voltage changes and modifies the clock signal frequency before the output voltage deviates significantly, thereby achieving good line regulation performance in open-loop control without requiring feedback components like optical couplers.
2Reliability
If switching frequency is adjusted to compensate for input voltage changes, then line regulation performance is improved, but control circuit complexity increases
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the switching frequency parameter in response to input voltage changes. The frequency adjusting circuit modifies the clock signal frequency based on the detected input voltage level, creating a simple yet effective control mechanism that improves line regulation performance without introducing complex control circuits. The solution changes the operating frequency parameter to compensate for input variations.
Solution Approach 2:
The patent replaces complex mechanical or electronic feedback mechanisms (such as optical couplers in closed-loop systems) with a simpler frequency adjustment mechanism. By substituting the need for isolated feedback hardware with a direct frequency modulation approach based on input voltage sensing, the circuit achieves comparable or superior line regulation with reduced complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides good line regulation performance and maintains a stable output voltage, addressing the limitations of open-loop resonant converters while reducing costs by eliminating the need for optical couplers.
Implementation Method 1
a resonant tank with a characteristic resonant frequency
Implementation Method 2
a transformer having a primary winding and a secondary winding
Data Source
AI summary
A control method for regulating the switching frequency of a resonant converter having an input terminal to receive an input voltage and an output terminal to output an output voltage. The control method is sensing the input voltage and adjusting the switching frequency based on the comparison of the input voltage with a reference threshold voltage. When the input voltage is less than the reference threshold voltage, the switching frequency is adjusted to decrease, and when the input voltage is higher than the reference threshold voltage, the switching frequency is adjusted to increase.