Synchronous Rectifier Gate Precharge for Reverse Current Control
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Solution Overview
Problem
Conventional synchronous rectifiers face efficiency issues due to improper timing of switching ON and OFF, leading to reverse current or current flow through body diodes, which reduces power supply efficiency.
Innovation Solution
A synchronous rectification controller that precharges the control signal at a sub-threshold voltage based on detection signals, ensuring timely and efficient switching of the synchronous rectifier by identifying conditions for turning it on quickly and minimizing impedance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the synchronous rectifier turns on quickly to improve efficiency, then conduction losses are reduced, but reverse current may occur
Solution Approach 1:
The control signal is precharged to a sub-threshold voltage level before the switching event. This preliminary anti-action prepares the gate in a state that enables rapid turn-on while preventing premature conduction that would cause reverse current, thus achieving fast switching without the harmful effects.
2Device complexity
If conventional diodes are used for rectification, then device simplicity is maintained, but voltage drop reduces power supply efficiency
Solution Approach 1:
The patent changes the operating parameter of the synchronous rectifier by precharging the control signal to a sub-threshold voltage. This parameter change enables the actively controlled switch to operate with very low on-resistance, achieving voltage drop characteristics comparable to or better than conventional diodes while maintaining the efficiency benefits of synchronous rectification.
Data Source
AI summary
A control method is disclosed to generate a control signal in a power supply with a synchronous rectifier. The control signal turns ON the synchronous rectifier to provide a channel approximately short-circuited if the control signal is greater than a threshold voltage, and turns OFF the synchronous rectifier to turn the channel into an open circuit if the control signal is between the threshold voltage and a ground reference voltage. A detection signal is generated based on one end of the channel, and compared with a predetermined level higher than the ground reference voltage. An excitation time is a period when the detection signal exceeds the predetermined level. When the excitation time exceeds a preset time, the control signal is precharged to a sub-threshold voltage between the threshold voltage and the ground reference voltage.