Synchronous Rectifier Driving Circuit with Clamping for False Turn-On Prevention
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Solution Overview
Problem
Synchronous rectifier devices in isolated converters face startup failures and potential damage due to abrupt voltage drops and noise coupling at the control terminal, especially when the power supply has not reached a sufficient voltage level to power the driving circuit.
Innovation Solution
A driving circuit with a controllable clamping circuit that connects and disconnects the control terminal of the synchronous rectifier device to a reference ground based on a supply indication signal, using a controllable voltage regulation module and clamping switch to manage voltage levels and prevent false turn-ons during startup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the synchronous rectifier device is used at the secondary side of isolated converters, then rectification efficiency is improved, but false turn on may occur during startup due to noise coupling at the control terminal
Solution Approach 1:
A clamping circuit is introduced as an intermediary component between the control terminal and the noise source. The clamping circuit includes a clamping switch and voltage regulation module that actively clamp the control terminal voltage to a safe level during startup, preventing noise from falsely turning on the synchronous rectifier device while allowing normal operation when the supply voltage is established
2Use of energy by moving object
If the control terminal resistance is very large during startup, then the driving circuit cannot be powered properly, but the control terminal becomes vulnerable to noise coupling
Solution Approach 1:
The clamping circuit is activated in advance during the startup phase when supply voltage is not yet established. It proactively clamps the control terminal voltage to prevent noise coupling before harmful effects can occur. The circuit automatically deactivates once the supply voltage reaches the established level, transitioning from protective clamping to normal operation
3Productivity
If an abrupt increase in voltage drop occurs on the synchronous rectifier device at startup, then current flows through the primary winding, but the control terminal voltage becomes unstable
Solution Approach 1:
The clamping circuit is designed to activate automatically at startup before normal operation begins. It establishes a stable voltage reference at the control terminal in advance, preventing voltage instability caused by abrupt current flow. The voltage regulation module ensures the control terminal maintains a predetermined safe voltage level throughout the startup transient
Data Source
AI summary
A driving circuit for driving a synchronous rectifier device. The driving circuit may include a controllable clamping circuit having a first terminal coupled to a sensing terminal of the driving circuit, a second terminal coupled to a reference ground terminal of the driving circuit, a third terminal coupled to a driving terminal of the driving circuit, and a control terminal configured to receive a supply indication signal indicative of a voltage potential at a supply terminal of the driving circuit. The third terminal of the controllable clamping circuit may be connected to the second terminal of the controllable clamping circuit when the supply indication signal indicates that the voltage potential at the supply terminal has not been established to maintain the synchronous rectifier device off.