Synchronous Rectifier Drive Circuit Dead Band Elimination
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Solution Overview
Problem
In power supply circuits with distributed power architecture, the dead band between drive pulses leads to power losses due to conduction through high-impedance body-drain diodes during the dead-band period, reducing conversion efficiency.
Innovation Solution
A drive circuit with time delay circuitry and buffer stages is used to provide gate drive signals to synchronous rectifiers, extending the conduction time through the dead-band period to prevent body-drain conduction, allowing current to flow through MOSFETs with lower impedance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dead band is introduced between drive pulses to prevent circuit failure, then reliability is improved, but power losses increase due to conduction through body-drain diodes
Solution Approach 1:
The drive circuit extends the gate drive signal to overlap with the dead band period, preparing the synchronous rectifier to conduct before the dead band begins and maintaining conduction through it. This preliminary action ensures the rectifier is ready to immediately handle current flow when the dead band occurs, preventing body-diode conduction and associated power losses while maintaining the protective dead band functionality.
Solution Approach 2:
The invention maintains continuous useful action by extending the gate drive signal beyond the normal pulse width to cover the dead band period. This ensures the synchronous rectifier remains in its active conduction state throughout the dead band, eliminating the interruption in current flow that would otherwise occur and the associated energy losses through the body-diode.
2Loss of energy
If the dead band duration is reduced to minimize power loss, then energy efficiency is improved, but the risk of circuit failure or malfunction increases
Solution Approach 1:
The drive circuit extends the gate drive signal to overlap with the dead band period, preparing the synchronous rectifier to conduct before the dead band begins and maintaining conduction through it. This preliminary action ensures the rectifier is ready to immediately handle current flow when the dead band occurs, preventing body-diode conduction and associated power losses while maintaining the protective dead band functionality.
Solution Approach 2:
The invention changes the temporal parameter of the gate drive signal by extending its duration to overlap with the dead band period. This parameter modification allows the synchronous rectifier to remain in active conduction state during the dead band, transforming the operation mode from body-diode conduction to MOSFET conduction, thereby reducing power loss without affecting the dead band's protective function.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach eliminates power dissipation during the dead-band by ensuring current flows through MOSFETs instead of body-diodes, enhancing conversion efficiency by preventing body-drain conduction during the dead-band.
Implementation Method 1
a transformer having a primary winding arranged to receive the input signals and a secondary winding arranged to output a first and a second intermediary signal corresponding to the inverted input signals
Data Source
AI summary
A pulsed drive signal without a dead band can be achieved by a drive circuit arranged to receive opposite pulsed input signals, having a dead band between them, a transformer arranged to receive the input signals and output intermediary signals, time delay circuitry arranged to receive the intermediary signals, and to provide buffer input signals, corresponding to the intermediary signals, but with a ramped up transition from a low to a high signal, a first and a second buffer stage arranged to receive the first and second buffer input signals, respectively, and produce the first and the second drive output signal corresponding to the first and second pulsed input signal but with the transition from a high to a low signal delayed to reduce the dead band.