# IGBTs: Loss calculation and junction temperature estimation for an SPWM voltage source converter – KBA236566

## IGBTs: Loss calculation and junction temperature estimation for an SPWM voltage source converter – KBA236566

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Community Translation: IGBTs: SPWM (正弦波パルス幅変調)電圧電源コンバータにおける損失計算と接合温度見積 – KBA236566

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Insulated Gate Bipolar Transistors (IGBTs) are dominantly used in high-current and medium-voltage power converter applications. IGBTs are designed to operate at high power and medium switching frequency. Because of the high power associated with IGBTs, losses would also be of large magnitude. It is important to precisely calculate the device losses to carry out the thermal design and efficiency estimation in the design stage. Otherwise, it can hamper the system’s performance later on.

Loss components of an IGBT

• Conduction loss: Figure 1 shows a typical IGBT’s collector-emitter voltage, VCE versus collector current, and IC characteristics of an IGBT. The relationship between IGBT on-state voltage and current is written as:

A typical value of on-state resistance, RT, and threshold voltage VCE0 can be derived from the device datasheet and are related to junction temperature.

IGBT conduction loss is the function of collector current and junction temperature. Conduction loss for IGBT calculated as:

Figure  1   Typical VCE versus IC characteristics of an IGBT

• Switching loss: Figure 2 shows the analytical switching waveforms of IGBT’s collector-emitter voltage and current.

Figure  2   Typical switching waveforms of an IGBT

The turn-on energy loss, EOn, and diode reverse recovery energy, Erec calculated as:

Similarly, turn-off energy, EOff loss calculated as:

Invariably, EOn, EOff, and Erec can be deduced from the device datasheet and applied to calculate the switching losses at a particular voltage and current. The average and RMS current flowing through IGBT and blocking voltage depends upon the power converter topology and various converter parameters.

In conjunction with this article, see the following articles for the details of IGBT loss calculation and junction temperature estimation for an SPWM voltage source converter.

1. KBA236568: Describes a simplified method for calculating IGBT losses for an SPWM voltage source converter.
2. KBA236569: Demonstrates a loss calculation considering Infineon IGBT FF1200R12IE5P in an SPWM voltage source converter topology.
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