Semiconductor Drive Circuit With Temperature-Adaptive Switching Speed
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Solution Overview
Problem
Conventional semiconductor switching element drive circuits fix the switching speed timing regardless of temperature, leading to increased switching loss at high junction temperatures and reduced withstand voltage at low temperatures, which can result in surge voltage exceeding the element's withstand voltage.
Innovation Solution
A semiconductor switching element drive circuit that adjusts the switching speed based on temperature through an output voltage detection unit, generating different switching signals for varying temperatures to optimize switching speed timing and reduce both switching loss and surge voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the switching speed is increased to reduce switching loss, then the switching loss decreases, but the surge voltage increases
Solution Approach 1:
The gate resistance value is dynamically switched between a first value and a second value during the turn-off operation based on the output voltage level. When the output voltage reaches a predetermined level, the gate resistance switches from the first value to the second value, enabling adaptive control of switching speed to optimize both switching loss and surge voltage
Solution Approach 2:
The gate resistance parameter is changed during the switching operation. By switching the gate resistance value between two different values, the invention changes the electrical parameters to simultaneously reduce switching loss and control surge voltage, resolving the trade-off between these two parameters
2Device complexity
If the switching timing is fixed regardless of temperature, then the device complexity is reduced, but the switching loss deteriorates at high junction temperatures
Solution Approach 1:
The switching timing is controlled based on feedback from the output voltage level. The gate resistance value switches when the output voltage reaches a predetermined level, creating a feedback mechanism that adapts the switching timing to temperature conditions without requiring direct temperature sensing, thus maintaining low device complexity while reducing switching loss at high temperatures
3Device complexity
If the drive conditions are kept constant regardless of junction temperature, then the device complexity is reduced, but the surge voltage may exceed the withstand voltage at low temperatures
Solution Approach 1:
The gate resistance switching is triggered by feedback from the output voltage level, which indirectly reflects temperature conditions. At low temperatures, the output voltage reaches the predetermined level at a different timing, automatically adjusting the switching timing to ensure surge voltage remains within safe margins without requiring direct temperature measurement or complex compensation circuits
Data Source
AI summary
An object is to provide a technique that makes it possible to change a switching speed depending on a temperature. The semiconductor switching element drive circuit includes an output voltage detection unit that generates a switching signal based on a temperature related to a semiconductor switching element and an output voltage of the semiconductor switching element. The output voltage for generating the switching signal by the output voltage detection unit in a case where the temperature is a first temperature is larger than the output voltage for generating the switching signal by the output voltage detection unit in a case where the temperature is a second temperature lower than the first temperature.