To prevent a short-circuit in the upper and lower arms, it is necessary to set an on-off timing delay between the several arms. During this time period both devices are switched off. The dead-time needs to be set so that it is generally longer than the switching time of the IGBT (toff max.).
For details, refer to Application Manual Chapter 7.
FAQ Categories: All
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How can we determine the dead-time?
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Which parameters have an impact to IGBT’s short-circuit current?
IGBT’s short-circuit current is impacted by gate-to-emitter voltage VGE, junction temperature Tj, and switching voltage Vcc. Generally, a short-circuit current increases with a large VGE, low Tj, and large Vcc.
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How do I calculate the power cycle in cases where there are multiple temperature rise peaks?
In cases where the temperature increases n-times per device operation cycle, we assign a power cycle life expectance count as PC(k=1, 2, 3, …, n). PC(k) is the power cycle life for the k-th temperature rise. A combined power cycle life expectancy count can be expressed by the formula below.
For details, refer to Application Manual Chapter 11.
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What types of power cycle capability are available?
The types of power cycle capability include the ΔTj power cycle (ΔTj-P/C) capability curve and the ΔTc power cycle (ΔTc-P/C) capability curve. We verify device life on two models, therefore please design a product life expectancy within these power cycle capabilities. For details, refer to Application Manual Chapter 11.
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What is the diode’s I2t?
I2t is a Joule-integral for overcurrent allowed within the range that does not result in element destruction. Overcurrent is defined in one cycle at commercially restricted half-waves (50, 60 Hz).
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What is the temperature difference between Tj and NTC temperature?
Please contact Fuji Electric Corp. of America or your local sales representative or distributor to answer your question.
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Is the temperature Tj represented by the NTC temperature?
They are not the same. When incorporating it in an IGBT module, NTC is positioned far from the chip to ensure insulation. This produces a temperature gap between them although NTC’s temperature will follow that of chip’s Tj.
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What is a NTC?
NTC (Negative Temperature Coefficient Thermistor) is an electronic component whose resistance decreases while the temperature increases.
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What range is used for heat sink flatness as a reference?
Guides to flatness values for a heat sink are 50 μm or less for 100 mm between screw mounting locations, and 10 μm or less for surface roughness. An excessive convex warp will cause an insulation breakdown, leading to a critical incident. An excessive concave warp will reduce heat radiation by creating a gap between the product and heat sink, which may lead to thermal destruction.
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What thermal grease precautions should we be aware of?
While thermal grease promotes thermal conduction to a fin, it has a thermal capacity itself. Applying too much grease will obstruct the heat radiation to fins. At the same time, applying too little will increase the contact thermal resistance because thermal grease will not have good contact in some spots between the fins and module for bonding. For details, refer to Application Manual Chapter 6-3.3 “Thermal paste application” and technical documents.
