SMPS AC Power Loss Detection via Frequency Shift
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Solution Overview
Problem
Switched-mode power supply systems face challenges in maintaining power to critical circuits during AC input voltage loss, leading to inefficient shutdown sequences and potential data loss in applications like LED television sets.
Innovation Solution
A power supply system with a primary-side controller that detects AC input power loss by monitoring rectified signals and increasing the switching frequency of the resonant DC/DC converter, allowing for a controlled shutdown sequence while maintaining power to load circuits, including CPU operations, using a combination of PFC and LLC converter stages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the power supply immediately shuts down upon AC input loss, then power consumption is reduced, but data loss occurs and shutdown sequences are inefficient
Solution Approach 1:
The system performs preliminary action by detecting AC input power loss and maintaining power to critical circuits (CPU, memory) for a predetermined time period before shutdown. This allows the system to complete shutdown sequences and preserve data without continuous power consumption, resolving the contradiction between energy savings and data preservation.
2Reliability
If the switching frequency is increased upon AC power loss detection, then power is maintained to critical circuits, but the system complexity increases
Solution Approach 1:
The system uses feedback by monitoring the rectified AC input signal at the primary side and automatically adjusting the switching frequency of the resonant converter based on the detected power loss condition. This feedback mechanism enables reliable power maintenance during shutdown without requiring complex additional control circuits, as the existing control circuit adapts its behavior based on real-time conditions.
3Loss of information
If the power supply maintains power during AC input loss, then shutdown sequences are controlled and data is preserved, but power consumption increases
Solution Approach 1:
The system performs preliminary action by maintaining power only for a predetermined, limited time period after AC input loss detection. This temporary power maintenance enables complete shutdown sequences and data preservation, after which the system shuts down to minimize energy consumption, thus resolving the contradiction between data preservation and energy savings.
4Measurement precision
If a primary-side controller monitors rectified signals, then AC power loss is detected accurately, but the measurement precision requirements increase
Solution Approach 1:
The system uses self-service by utilizing the existing rectified signal from the power conversion circuitry for AC power loss detection, rather than requiring separate sensing circuits. The primary-side controller monitors the already-present rectified signal, enabling accurate detection without adding measurement complexity or requiring additional sensing infrastructure.
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
Enables a controlled shutdown sequence that preserves data and maintains regulated voltage during AC power loss, reducing power consumption and ensuring seamless restarts when AC input is reinstated.
Implementation Method 1
detecting a loss of at least one of an AC input voltage an AC input power at an input of the power supply
Implementation Method 2
switched-mode power supply system includes a resonant DC/DC converter
Data Source
AI summary
In accordance with an embodiment, a method of operating a power supply includes detecting a loss of at least one of an AC input voltage an AC input power at an input of the power supply, and increasing a switching frequency of the power supply upon detection of the loss of the AC input voltage or AC input power.