Transistor Gate Impedance Switching for Overload Withstand Time
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Solution Overview
Problem
Transistor devices face challenges in withstanding overload conditions, such as short circuits, due to delays in detection and response, which can lead to excessive energy dissipation and potential damage, as they are required to handle high currents for extended periods before being switched off.
Innovation Solution
Incorporating a variable impedance element between the control and transistor terminals, coupled with an overload detection circuit that switches the impedance from a low to a high state upon detecting an overload condition, allowing the transistor to partially or fully decouple from the control signal, thereby reducing current and prolonging the time it can withstand the overload.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the transistor device uses conventional detection and turn-off scheme, then the system can detect and respond to overload conditions, but the transistor device must withstand the overload condition during the delay time, increasing stress and potential damage
Solution Approach 1:
The variable impedance element is switched to the second state with higher impedance before the external protection circuit actually turns off the transistor device. This preliminary action reduces the current through the transistor during the delay period, preventing excessive stress accumulation while the external protection circuit is still responding.
Solution Approach 2:
The overload protection circuit switches the variable impedance element to provide beforehand cushioning against the harmful overload condition. By increasing the impedance in advance of the actual turn-off event, the circuit cushions the transistor from the full brunt of the overload stress during the necessary delay time.
2Loss of time
If the transistor device can withstand overload condition for longer time, then the detection and turn-off scheme implementation becomes easier with relaxed timing requirements, but the energy dissipation and potential damage during overload increases
Solution Approach 1:
The variable impedance element is switched to the second state with higher impedance before the external protection circuit actually turns off the transistor device. This preliminary action reduces the current through the transistor during the delay period, preventing excessive stress accumulation while the external protection circuit is still responding.
Solution Approach 2:
The overload protection circuit switches the variable impedance element to provide beforehand cushioning against the harmful overload condition. By increasing the impedance in advance of the actual turn-off event, the circuit cushions the transistor from the full brunt of the overload stress during the necessary delay time.
Data Source
Figure 1~2A
Figure 2B
Figure 3~4
AI summary
A transistor device (10) is provided including a first device load terminal (12), a second device load terminal (13) and a device control terminal (11). The device (10) includes a transistor (14). A first transistor load terminal (16) is coupled to the first device load terminal (12), a second transistor load terminal (17) is coupled to a second device load terminal (13), and a transistor control terminal (15) is coupled to the device control terminal (11) via a variable impedance element (18). An overload detection circuit (19) switches the variable impedance element (18) from a first state with lower impedance to a second state with higher impedance in response to detecting an overload condition.