Synchronous Rectifier Gate Drive Circuit for Chattering Suppression
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Solution Overview
Problem
Autonomous type synchronous rectification MOSFETs experience chattering and through-current malfunctions due to noise-induced erroneous on/off state determinations, particularly at low switching speeds and varying temperature and frequency conditions, which existing solutions fail to adequately address.
Innovation Solution
A rectifier configuration with a determination circuit that inputs voltage between the MOSFET's main terminals to determine the on/off state and a gate drive circuit that extends the time for boosting the gate voltage during turn-on and shortens it for turn-off, ensuring stable operation and preventing chattering and through-current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If autonomous type synchronous rectification MOSFET is used, then power loss is reduced and rectification efficiency is improved, but chattering and through-current malfunctions occur due to noise-induced erroneous on/off state determinations
Solution Approach 1:
The determination circuit performs preliminary assessment of the on/off state by evaluating voltage between main terminals before actual switching occurs. This preliminary determination prevents erroneous switching by verifying the actual electrical state matches the control signal intent, thereby suppressing chattering and through-current while maintaining the low power loss benefits of synchronous rectification
Solution Approach 2:
The determination circuit continuously monitors the voltage between main terminals and provides feedback to verify correct on/off state. This feedback mechanism detects and corrects noise-induced erroneous determinations, ensuring reliable operation while preserving the energy efficiency of the autonomous synchronous rectification MOSFET
2Speed
If MOSFET switching speed is increased, then rectification response is improved, but chattering and noise susceptibility increase
Solution Approach 1:
The determination circuit performs preliminary verification of switching conditions by measuring voltage between main terminals before executing the switch transition. This preliminary action ensures that switching occurs only when electrically appropriate, preventing noise-induced chattering even at high switching speeds while maintaining fast response capability
3Ease of manufacture
If simple control circuit is used to reduce cost, then manufacturing cost is reduced, but ability to suppress chattering and noise effects is insufficient
Solution Approach 1:
The determination circuit utilizes the existing voltage between main terminals of the autonomous synchronous rectification MOSFET to self-determine the correct on/off state without requiring external sensors or complex control logic. This self-service approach achieves reliable noise immunity while keeping the control circuit simple and cost-effective
Solution Approach 2:
The invention replaces complex sensor-based control systems (mechanical/electrical measurement systems) with an electronic determination circuit that directly evaluates voltage conditions. This substitution achieves equivalent or superior noise immunity with simpler, more cost-effective electronics
Data Source
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AI summary
A rectifier including an autonomous type synchronous-rectification MOSFET is provided, which prevents chattering and through-current caused by a malfunction when a noise is applied. The rectifier (132) includes: a rectification MOSFET (101) for performing synchronous rectification; a determination circuit (103) configured to input a voltage between a pair of main terminals (TH, TL) of the rectification MOSFET (101), and to determine whether the rectification MOSFET (101) is in on or off state on the basis of the inputted voltage; and a gate drive circuit (105) configured such that a gate of the rectification MOSFET (101) is turned on and off by a comparison signal (Vcomp) from the determination circuit (103), and such that a time required to boost a gate voltage (Vgs) when the rectification MOSFET (101) is turned on is longer than a time required to lower the gate voltage (Vgs) when the rectification MOSFET (101) is turned off.