Power Transistor Gate Driver Circuit for Faster Turn-Off
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Solution Overview
Problem
Existing power transistors used in Lidar applications require longer times to turn off compared to turning on, which affects the precision and speed of light pulse generation, and is influenced by parasitic common source inductance that can vary with packaging.
Innovation Solution
A control driver circuit is designed to quickly turn a power transistor off by using a switching transistor and an inductive element, where turning on the switching transistor induces current in the inductive element to turn the power transistor on, and turning off the switching transistor draws the induced current to turn the power transistor off.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a conventional driver circuit is used to control the power transistor, then the circuit structure is simple, but the turn-off time is longer than the turn-on time
Solution Approach 1:
The driver circuit uses different impedance paths for turn-on and turn-off operations. The first driver circuit provides a low-impedance path for charging the gate (fast turn-on), while the second driver circuit provides a low-impedance path for discharging the gate (fast turn-off). This dynamic switching of driver configurations enables asymmetric speed control optimized for each transition direction.
Solution Approach 2:
The driver circuit is divided into two separate driver circuits: a first driver circuit for turn-on control and a second driver circuit for turn-off control. Each driver circuit is independently optimized for its specific function, allowing the turn-on and turn-off processes to be controlled separately with different timing characteristics.
2Speed
If the parasitic common source inductance is reduced for faster turn-off, then the turn-off speed improves, but the packaging complexity increases
Solution Approach 1:
The patent introduces a compensation capacitor as an intermediary element that counteracts the effects of parasitic inductance. The capacitor is connected in parallel with the power transistor and is sized to compensate for the parasitic common source inductance, thereby enabling fast turn-off without requiring complex packaging modifications.
Solution Approach 2:
The patent modifies the electrical parameters of the driver circuit by using different drive strengths and impedance levels for turn-on and turn-off operations. The second driver circuit uses a lower impedance path and appropriate timing control to achieve faster turn-off, effectively changing the operational parameters to overcome parasitic inductance effects.
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
The solution allows for rapid turning off of the power transistor with reduced dependence on parasitic common source inductance, enabling precise and high-intensity light pulses for improved Lidar performance.
Implementation Method 1
in response to the switching transistor being turned on, a current is induced within the inductive element and a voltage from the first voltage supply is provided to a control node of the power transistor
Implementation Method 2
in response to the switching transistor being turned off, the induced current is drawn from the output node to thereby turn the power transistor off
Data Source
AI summary
A control driver circuit that includes a switching transistor coupled between a first voltage supply node and an output node of the gate, the output node coupled or couplable to a control node of the power transistor. A circuit includes an inductive element coupled between the control transistor and a second voltage supply node. The circuit is configured such that if the output node is coupled to the power transistor, and in response to the switching transistor being turned on, a current is induced within the inductive element and a voltage from the first voltage supply is provided to a control node of the power transistor to thereby turn on the power transistor. On the other hand, in response to the switching transistor being turned off, the induced current is drawn from the output node to thereby turn the power transistor off.