IGBT Gate Drive with Desaturation Step for Lower Turn-Off Loss
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Solution Overview
Problem
Bipolar switchable power semiconductor components, such as IGBTs, experience high turn-off losses due to high electric field strengths when switching off, limiting switching speed and efficiency.
Innovation Solution
A control device that reduces the electrical voltage from a first voltage value to a desaturation value greater than the pinch-off voltage, and then to a second voltage value, to efficiently switch off the power semiconductor component by initially discharging the gate to a desaturation pulse before the actual turn-off, reducing charge carrier concentration and turn-off losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the gate is discharged directly from the first voltage value to the second voltage value to switch off the power semiconductor device, then the switching speed is improved, but the turn-off losses increase due to high electric field strengths and high charge carrier concentration
Solution Approach 1:
The patent applies preliminary action by first reducing the gate voltage to a desaturation value (intermediate voltage level) before the final switch-off to the second voltage value. This intermediate step reduces the charge carrier concentration in the power semiconductor device before complete turn-off, thereby reducing turn-off losses while maintaining acceptable switching speed. The desaturation phase prepares the device for more efficient switching by partially removing charge carriers in advance.
2Speed
If the gate discharge current is increased to achieve faster switching, then the switching speed is improved, but the electric field strength increases causing higher turn-off losses
Solution Approach 1:
The patent segments the gate discharge process into two distinct phases: first, discharge to a desaturation voltage level, and second, discharge to the final second voltage level. This segmentation allows the switching process to be divided into manageable stages, where the first phase reduces charge carrier concentration and the second phase completes the turn-off. This prevents the need for excessively high discharge currents in a single step, thereby reducing harmful electric field strengths while achieving fast switching.
3Loss of energy
If the charge carrier concentration is reduced to minimize turn-off losses, then the turn-off losses are improved, but the switching speed is limited by the required safe operating range
Solution Approach 1:
The patent applies preliminary action by reducing the gate voltage to a desaturation value before complete turn-off. This intermediate desaturation phase partially removes charge carriers in advance, reducing the burden on the final switch-off phase. As a result, turn-off losses are reduced because fewer charge carriers need to be removed during the critical switch-off moment, while the overall switching speed remains within the safe operating range because the discharge is spread over two controlled phases rather than one aggressive phase.
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
This method reduces turn-off losses and enhances the efficiency of the switching process by minimizing the charge removal during the shutdown of the power semiconductor component, allowing for faster and more efficient switching.
Implementation Method 1
The control device (2) is designed to apply an electrical voltage to a gate terminal of the power semiconductor device (1)
Implementation Method 2
When the power semiconductor device is switched off, the gate is discharged via a resistor to an electrical voltage with a second voltage value. This removal of charge carriers generates high electric field strengths.
Implementation Method 3
During the switch-off of conventional and reverse-conducting IGBTs, this removal of charge carriers generates high electric field strengths. This field strength prevents the power semiconductor device from being switched off arbitrarily quickly.
Data Source
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AI summary
The invention relates to a control device (2) for driving a bipolar switchable power semiconductor component (1), wherein the control device (2) is designed to apply an electrical voltage (U) to a gate terminal of the power semiconductor component (1) and to reduce the electrical voltage (U) for turning off the power semiconductor component (U) from a first voltage value (UB+) to a second voltage value (UB-), wherein the control device (2) is designed, for turning off the power semiconductor component (1), firstly to reduce the electrical voltage (U) from the first voltage value (UB+) to a desaturation value (Usat) and then to reduce the electrical voltage (U) from the desaturation value (Usat) to the second voltage value (UB-), wherein the desaturation value (Usat) is greater than a pinch-off voltage (UP) of the power semiconductor component (1).