Synchronous Rectification Circuit Power-Down Protection
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Solution Overview
Problem
In switching power supplies for display devices, the synchronous rectification circuit faces issues with back-flowing currents during power interruptions, leading to potential damage to MOS transistors and reduced conversion efficiency due to the inability to turn off the MOS transistors quickly enough.
Innovation Solution
A synchronous rectification circuit is designed with a protection circuit that detects power-down signals and immediately turns off the MOS transistors, preventing back-flowing currents and ensuring the MOS transistors in the synchronous rectification circuit are turned off before those in the main circuit, thereby reducing damage and improving efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If MOS transistors are used for synchronous rectification to reduce rectification loss, then conversion efficiency is improved, but the risk of damage from back-flowing currents during power interruptions increases
Solution Approach 1:
The protection circuit detects power interruption signals in advance and activates before back-flowing currents can damage the MOS transistors. By performing the turn-off action preliminarily upon detecting the power interruption, the system prevents the harmful back-flowing currents from occurring in the first place, thus resolving the contradiction between using MOS transistors for efficiency and protecting them from damage risk.
2Reliability
If MOS transistors are turned off quickly to prevent back-flowing currents, then reliability is improved, but the complexity of the control circuit increases
Solution Approach 1:
A dedicated protection circuit is introduced as an intermediary component between the power supply and the MOS transistors. This separate protection circuit simplifies the main control circuit's burden by handling the emergency turn-off function independently, thus achieving quick response for reliability while keeping the overall system architecture clean and manageable.
3Reliability
If the protection circuit immediately turns off MOS transistors upon detecting power interruption, then damage prevention is improved, but conversion efficiency during normal operation may be affected
Solution Approach 1:
The system dynamically adjusts its behavior based on operating conditions. During normal operation, the MOS transistors remain in synchronous rectification mode for high efficiency. Upon detecting power interruption, the protection circuit dynamically switches to a protective state by turning off the transistors. This dynamic adaptation allows the system to optimize for efficiency during normal operation while providing rapid protection when needed.
Data Source
AI summary
A synchronous rectifier circuit and a display device are provided. In some implementations, the circuit includes a controller, a first MOSFET and a protection circuit. A first detection terminal of the controller is connected with a first end of the first MOSFET, an input of the controller is connected with a second end of the first MOSFET and configured to input a driving voltage to the first MOSFET, and a ground terminal of the controller is connected with a third end of the first MOSFET. An output of the protection circuit is connected with the control end of the controller. The protection circuit is configured to send a control signal to the controller when receiving a shutdown signal and/or a power-down signal of an alternating current power supply. The control signal is configured for the controller to stop sending the driving voltage to the first MOSFET or supplying power to the controller.