Gate Driver Current Switching for Reverse Recovery Suppression
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Solution Overview
Problem
Bridge circuits experience unstable output voltage due to through current caused by reverse recovery current in flywheel diodes, leading to unwanted ringing and radiation.
Innovation Solution
A gate driver circuit with a turn-on circuit and turn-off circuit that dynamically control the current supplied to the power transistor, switching between different current amounts to manage the reverse recovery current, thereby suppressing through current and ringing, and optimizing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the high-side transistor is turned on immediately after switching from high-impedance state, then the switching speed is improved, but reverse recovery current causes through current and ringing
Solution Approach 1:
The gate driver circuit performs preliminary action by pre-charging the gate capacitor with a first current before the main turn-on switching. This preliminary charging prepares the gate voltage to rise gradually, preventing the abrupt turn-on that causes reverse recovery current and ringing in the flywheel diode.
Solution Approach 2:
The gate driver circuit segments the turn-on process into multiple phases: a first period with first current for preliminary charging, and a second period with second current for complete turn-on. This segmentation allows the transistor to turn on gradually rather than abruptly, eliminating the harmful reverse recovery current effect.
2Productivity
If a large current is supplied to the gate to shorten turn-on time, then productivity is improved, but power consumption increases
Solution Approach 1:
The gate driver circuit uses periodic action by supplying current in two distinct periods: first current during a first period for preliminary charging, and second current during a second period for complete turn-on. This periodic current supply achieves fast switching while controlling peak current and reducing overall power consumption compared to continuous high current supply.
Solution Approach 2:
The gate driver circuit implements dynamic current control by switching between first current and second current based on the switching phase. The control circuit dynamically adjusts the gate current magnitude, providing high current when needed for fast switching and lower current during preliminary phases to minimize power consumption.
Data Source
AI summary
A turn-on circuit is configured to supply a current as a source to the gate of a high-side transistor. A first current source supplies an output current that is switchable between a first current amount and a second current amount that is smaller than the first current amount. A first switch is coupled between a first output node of a first current mirror circuit and the gate of the high-side transistor. A second current source generates a second current. A second switch is coupled between a first output node of a second current mirror circuit and the gate of the high-side transistor.