Parallel Driving Circuit Gate Voltage Control
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Solution Overview
Problem
Existing drive circuits for switching devices experience increased switching noise and loss due to rapid gate voltage rise and prolonged off-state periods when supplying output current, leading to inefficiencies and noise during turn-on operations.
Innovation Solution
A driving circuit with first and second parallel driving units, where the first unit continues to supply gate current after threshold voltage is reached and the second unit stops supply before the threshold voltage is reached, reducing switching loss and noise by controlling the gate voltage rise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the output current of the drive circuit is large at the time of turn-on of the switching device, then the gate voltage rises steeply and the switching device turns on quickly, but switching noise increases due to rapid collector current flow
Solution Approach 1:
The drive circuit is divided into two separate driving units (first and second driving units) that operate at different stages of the turn-on process. The second driving unit supplies current during the initial phase to rapidly raise the gate voltage to the threshold, while the first driving unit takes over for the subsequent phase to gradually increase the gate voltage above the threshold, thereby segmenting the turn-on process to suppress noise while maintaining speed.
Solution Approach 2:
The second driving unit performs preliminary action by supplying gate current first to quickly reach the threshold voltage, enabling the switching device to turn on. After this preliminary phase, the first driving unit continues the gate voltage increase more gradually. This preliminary fast-rise action followed by a controlled continuation suppresses switching noise while maintaining overall turn-on speed.
2Object-generated harmful factors
If the output current is limited to suppress dv/dt when gate voltage exceeds threshold voltage, then switching noise is reduced, but the period from current supply start until gate voltage exceeds threshold voltage increases, causing increased switching loss
Solution Approach 1:
The turn-on process is segmented into two phases with different current supply characteristics. The second driving unit provides high current for the initial phase to quickly reach threshold voltage, minimizing the off-state period and reducing switching loss. The first driving unit then provides controlled current for the subsequent phase to limit dv/dt and suppress switching noise. This segmentation resolves the contradiction between fast turn-on and noise suppression.
Solution Approach 2:
The second driving unit performs preliminary high-current supply to rapidly charge the gate to threshold voltage, minimizing the time the switching device remains in the off-state and thereby reducing switching loss. After this preliminary phase, the first driving unit continues with limited current to suppress noise during the voltage transition above threshold, achieving both low loss and low noise.
3Speed
If both driving units continue to supply gate current after threshold voltage is reached, then the gate voltage increases rapidly, but switching noise increases due to steep dv/dt
Solution Approach 1:
The drive circuit segments the gate current supply function between two driving units. The second driving unit supplies current during the initial phase to quickly reach threshold voltage, while the first driving unit continues supply in a controlled manner after threshold is reached. This segmentation allows rapid initial rise followed by controlled continuation, achieving fast turn-on without excessive noise.
Solution Approach 2:
The second driving unit performs preliminary high-speed charging to reach threshold voltage quickly. After this preliminary action, the first driving unit continues the gate voltage increase at a controlled rate to limit dv/dt and suppress switching noise, thereby achieving both fast response and low noise.
Data Source
AI summary
A driving circuit includes first and second driving units connected in parallel to each other, wherein both the first and second driving units start to supply a gate current to a gate of a switching device in a turn-on operation of the switching device, when a gate voltage of the switching device increases and has reached a threshold voltage of the switching device, the first driving unit continues to supply the gate current, and the second driving unit stops supply of the gate current before the gate voltage has reached the threshold voltage.