Quasi-Resonant Power Supply Control for Over-Voltage Protection
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Solution Overview
Problem
Traditional power supply devices for household appliances face inefficiencies in over-voltage protection, leading to potential damage and increased complexity and costs due to the need for complex protection circuits.
Innovation Solution
A power supply device utilizing a Quasi-Resonant switching converter with a control loop that monitors bus voltage and switch voltage to detect over-voltage events, adjusting the switching device's commutation state to prevent excessive voltage at the terminals, and employing burst state commutations to manage over-voltage situations without dedicated protection circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional protection circuits are incorporated to limit voltage at switching device terminals, then over-voltage protection is provided, but circuit complexity and manufacturing costs increase
Solution Approach 1:
The controller performs dual function: it both controls the switching device operation and detects over-voltage conditions. By using the existing control circuitry to monitor voltage levels and trigger protective actions, the invention eliminates the need for separate protection circuits, thereby maintaining reliability while reducing complexity and costs
Solution Approach 2:
The controller is designed to perform multiple functions: normal switching control, input current regulation via PWM, and over-voltage detection and protection. This multi-functionality consolidates what would traditionally require separate circuits into a single integrated control unit, resolving the contradiction between protection capability and circuit complexity
2Reliability
If switch operations are immediately stopped upon over-voltage detection, then switching device protection is achieved, but operational continuity is disrupted
Solution Approach 1:
Instead of immediate permanent shutdown, the controller implements periodic switching actions during over-voltage conditions. It alternates between blocking and enabling the switching device at reduced frequency, allowing the system to ride through transient over-voltage events while maintaining eventual operational continuity, thus balancing protection with productivity
Solution Approach 2:
The protective response is made dynamic rather than static. The controller adjusts switching behavior based on real-time voltage conditions, transitioning between different operational states (normal operation, reduced frequency switching, blocked state) as over-voltage conditions develop and resolve, thereby maintaining both protection and operational continuity
3Reliability
If complex protection circuits are used to ensure effective over-voltage protection, then device reliability improves, but manufacturing costs increase
Solution Approach 1:
The controller utilizes its own existing resources (voltage sensing capabilities, processing unit, output control) to perform over-voltage protection functions. This self-service approach eliminates the need for additional protection circuit components, directly reducing material costs and assembly complexity while maintaining effective protection
Solution Approach 2:
The protection function is extracted from the domain of hardware protection circuits and implemented through software/control logic within the existing controller. This extraction eliminates physical protection components while preserving the protective function, thereby reducing manufacturing costs without sacrificing reliability
Data Source
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AI summary
The present invention relates to a power supply device (100) for a household appliance. The power supply device comprises switching converter (110)comprising an input filtering stage (LD, CD) and a rectifying stage (12) that are electrically connected with the mains (10). The switching converter comprises a bus capacitor (13), electrically connected in parallel with output terminals of said rectifying stage, and a resonant tank (200), electrically connected with said bus capacitor. The switching converter further comprises a switching device (130) electrically connected with said resonant tank and control means (132, 161, 162) for operating said switching device. Said control means operate said switching device with a switching cycle that comprises a first switching period, in which said switching device allows the flow of a first current between said bus capacitor and said resonant tank, and a second switching period, in which said switching device blocks the flow of said first current. Said control means are configured to determine the occurrence of an over-voltage event, on the base of detection data or signals indicative the behaviour of a bus voltage across the terminals of said bus capacitor (13). Said control means operate said switching device, so as to bring or maintain a switch voltage, across output terminals of said switching device, within predefined safety limits, when the occurrence of an over-voltage event is determined. In a further aspect, the present invention relates to a method for operating a power supply device for a household appliance.