Driving Device for Synchronous Rectification Dead Time Control
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Solution Overview
Problem
In synchronous rectification systems, the dead time between switching elements leads to output voltage drops and losses, necessitating a reduction in dead time while preventing short-circuits and diode deterioration.
Innovation Solution
A driving device that includes a determination unit to detect free wheeling current and a drive control unit to reduce switching speed and adjust gate resistor resistance, allowing the main switching element to remain on-state during dead time when free wheeling current is detected, thereby shortening actual dead time and preventing short-circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dead time is provided between switching elements to prevent short-circuit, then reliability is improved, but output voltage drops and losses increase
Solution Approach 1:
The patent changes the switching speed parameter dynamically based on the state of the free-wheeling diode. When the free-wheeling diode is conducting, the switching element turns off more slowly, allowing the diode to continue conducting and maintain output voltage, thereby reducing energy loss during the dead time period while still preventing short-circuits
2Reliability
If dead time is extended to ensure safe switching, then reliability is improved, but productivity decreases
Solution Approach 1:
The patent implements dynamic control of the switching element's turn-off process by adjusting the gate voltage discharge rate based on free-wheeling diode conduction state. This dynamic approach allows the system to maintain reliability while reducing the effective dead time, thereby enabling higher switching frequencies and improved productivity
3Productivity
If switching speed is increased to improve productivity, then switching frequency is improved, but risk of short-circuit increases
Solution Approach 1:
The patent uses feedback from the free-wheeling diode's conduction state to control the switching element's turn-off process. By detecting whether the free-wheeling diode is conducting and adjusting the switching speed accordingly, the system can operate at high frequencies while maintaining safety margins against short-circuits
Data Source
AI summary
In recent years, it has been desired to further shorten the dead time. Provided is a driving device that drives on/off a main switching element to which a free wheeling diode is anti-parallel connected, wherein the driving device includes a determination unit configured to output a determination signal indicating whether free wheeling current is flowing from a source terminal to a drain terminal of the main switching element; and a drive control unit configured to reduce a switching speed when the main switching element is driven from an on-state to an off-state on condition that the determination signal indicating that the free wheeling current is flowing is output.