Why reverse conducting IGBT can be used in high power CCM mode PFC circuit

For power factor correction (PFC), a boost converter Boost topology is usually used. It minimizes the harmonics of the input current. At the same time IGBTs are the best choice for high power PFC applications such as air conditioning, heating, ventilation and air conditioning (HVAC) and heat pumps.

Author: Jaeeul Yeon

For power factor correction (PFC), a boost converter Boost topology is usually used. It minimizes the harmonics of the input current. At the same time IGBTs are the best choice for high power PFC applications such as air conditioning, heating, ventilation and air conditioning (HVAC) and heat pumps.

In theory, in continuous conduction mode (CCM), reverse freewheeling through the IGBT never occurs. However, under light load or transient conditions, a reverse current will flow due to the resonance between the boost Inductor Lboost and the output capacitor Coss of the IGBT.

This resonant current, iQN

Why reverse conducting IGBT can be used in high power CCM mode PFC circuit

When the input voltage Vin is lower than half the output voltage (Vin


Figure 1. PFC circuit with boost converter topology

Compare different IGBT solutions for PFC applications

This phenomenon is proved by testing and comparing the operating waveforms of TRENCHSTOP™ 5 WR6 IGBT (IKWH30N65WR6) and TRENCHSTOP™ IGBT3 (IGW30N60H3) in a CCM-boost PFC circuit. The IKWH30N65WR6 contains a reverse conducting diode integrated in the IGBT chip, while the latter IGBT does not contain a reverse conducting diode. Figure 2 shows that for the IKWH30N65WR6, the reverse voltage is clamped to near zero. In the case of using the IGW30N60H3, the reverse voltage is up to -241V. Therefore, even in the CCM mode of the PFC, the reverse conducting diode is crucial to ensure the reliability of the system.

However, in this case, we do not need a high-performance freewheeling diode for the short-time soft reverse recovery current. In Figure 2, you can see that the peak value of the reverse current of the IGBT is only about 200 mA for a duration of a few microseconds.


Without reverse conducting diode


With reverse conducting diode
Figure 2. Switching waveforms of IGBTs at turn-off transition in CCM PFC at light load condition

In general, reverse conducting RC IGBTs are not suitable for applications requiring hard commutation. However, RC IGBTs are very beneficial for some hard commutation applications, such as PFC, where the reverse freewheeling diode of the IGBT does not need to have good reverse recovery performance. In this application, when high-performance diodes are redundant, they provide a more economical option.

TRENCHSTOP™ 5 WR6 IGBT for Boost PFC and Inverter Welding Applications

Infineon’s latest RC IGBT, shown in Figure 3, is based on the TRENCHSTOP™ 5 WR6 IGBT technology, where the N+ region is partially implanted into the P collector layer, forming an intrinsic PN diode. This allows reverse current to flow without the need for additional freewheeling diodes.


Figure 3. TRENCHSTOPTM 5 WR6 IGBT using a reverse-conducting (RC) IGBT concept

This TRENCHSTOP™ 5 WR6 IGBT is ideal for boost PFC and inverter welding applications. Optimizing the drift region thickness and diode rating according to the target application ensures an optimal VCE(sat) of 1.4V at rated current while maintaining a voltage rating of 650V. In addition, due to its extremely low minority carrier lifetime, no tail current occurs, which enables the TRENCHSTOP™ 5 WR6 IGBT to achieve switching frequencies of 60kHz and even higher.

When choosing TRENCHSTOP™ 5 WR6 IGBTs for PFC applications where hard commutation does not occur, there is no need to worry about diode performance issues in reverse conducting IGBTs. With this technology, it is possible to create an economical and reliable system for your next design.

References

[1] EM Findlay and F. Udrea, “Reverse-Conducting Insulated Gate Bipolar Transistor: A Review of Current Technologies,” in IEEE Transactions on Electron Devices, Vol. 66, no. 1, pp. 219-231, Jan. 2019.

[2] I. Sheikhian; N. Kaminski; S. Voss; W. Scholz; E. Herweg; “Optimization of the reverse conducting IGBT for zerovoltage switching applications such as induction cookers” Volume8, Issue3 Special Issue: Power semiconductor Devices and Integrated Circuit, May 2014 pp. 176-181

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