Bi-directional Transistor Body Control Circuit for Fast Turn-off
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Solution Overview
Problem
Bi-directional switches face reliability issues during fast turn-off due to transient current causing snapback bipolar effects, leading to current focalization in a small active area, which can result in premature device destruction.
Innovation Solution
A bi-directional power transistor with a transistor body control device that includes a resistor and a transistor body switch circuit, connected between the body terminal and the drain/source terminals, to manage current distribution and prevent snapbacks by controlling the voltage and current flow, thereby reducing the risk of breakdown and improving switching speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If fast turn-off is implemented in bi-directional switch, then switching speed is improved, but transient current causes snapback bipolar effect leading to reliability degradation
Solution Approach 1:
A body terminal control circuit is introduced as an intermediary between the parasitic bipolar junction transistor and the external circuit. This control circuit actively manages the body terminal voltage to prevent snapback effect while maintaining fast switching capability, thus resolving the contradiction between switching speed and reliability
2Productivity
If fast turn-off is implemented, then productivity is improved, but current focalization in small active area causes harmful effects
Solution Approach 1:
The control circuit dynamically changes the body terminal voltage parameter during switching operations. By adjusting this voltage parameter, the circuit prevents current focalization in the active area while maintaining fast turn-off performance, thus eliminating the harmful effects associated with high-speed switching
Data Source
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AI summary
Embodiments of a transistor control device for controlling a bi-directional power transistor are disclosed. In an embodiment, a transistor control device for controlling a bi-directional power transistor 140 includes a resistor 106 connectable to a body terminal of the bi-directional power transistor and a transistor body switch circuit 108 connectable to the resistor, to a drain terminal of the bi-directional power transistor, and to a source terminal of the bi-directional power transistor. The transistor body switch circuit includes switch devices 110-1, 110-2 and alternating current (AC) capacitive voltage dividers 112-1, 112-2 connected to control terminals of the switch devices. The AC capacitive voltage dividers are configured to control the switch devices to switch a voltage of the body terminal of the bi-directional power transistor as a function of a voltage between the drain terminal of the bi-directional power transistor and the source terminal of the bi-directional power transistor.