Application Note Date: 2005-05-11 AN-Number: AN-2005-03 Page 1 SM TM Short Circuit Behaviour of IGBT³ 600 V With the development of eupec’s and Infineon’s latest 600 V IGBT³ technology the short circuit specification of this new chip generation was changed compared to the other eupec / Infineon chip generations. This is a result of extensive discussions with customers about application requirements. The short circuit withstand time of the IGBT³ 600 V is specified at 6 µs. This is the best choice between low on-state losses and short circuit withstand time in order to deliver maximum possible device efficiency to the customer. Modern short circuit detection methods are fast enough to recognise and turn-off a short circuit within 6 µs. IGBT³ Technology: For the 1200 V voltage class, the IGBT chip of the third generation is well established. With additional benefits, an IGBT³ 600 V chip is available. Both, IGBT³ 600 V and its corresponding free wheeling diode EmCon3 are qualified for a maximum junction temperature of 175 °C and a maximum operating junction temperature under switching conditions of 150 °C. This is an increase by 25 K compared to former chip generations. The IGBT chip of the third generation has a trench structure and combines the advantages of PT and NPT technologies thanks to an additional n-doped layer, known as the Field Stop (FS) layer, within the NPT structure. Punch Through Emitter Non Punch Through Gate Emitter Gate - p+ emitter (substrate) IGBT 2 n+ buffer (epi) n- basis (substrate) n- basis (substrate) Collector Collector Collector IGBT „grown“ on highly p-doped substrate wafer Gate - n- basis (epi) IGBT 1 Emitter IGBT 3 - Trench-Field-Stop Substrate is part of the IGBT structure. Backside Emitter accessible and designable Improved injection of electrons through Trench-technology & Optimisation of chip-thickness by means of a field-stop-concept Fig. 1: Evolution of IGBT chip technologies eupec GmbH Max-Planck-Straße D-59581 Warstein Tel. +49 (0) 29 02 7 64-0 Fax + 49 (0) 29 02 7 64-12 56 [email protected] www.eupec.com Author: Keggenhoff Application Note Date: 2005-05-11 Page 2 The IGBT³ technology allows both, static and dynamic losses to be minimised. In combination with higher current density and higher junction temperature of the IGBT³, an increased current range of eupec IGBT modules and higher inverter power ratings can be realised. Short Circuit Specification: The IGBT³ 600 V is specified with a short circuit robustness up to tSCmax = 6 µs at Tj = 150 °C, VGE = 15 V and VCC = 360 V and also up to tSCmax = 8 µs at Tj = 25 °C, VGE = 15 V and VCC = 360 V. Between this to temperatures a linear approximation is allowed. In comparison to the IGBT², the temperature has been increased by 25 K (according to the increased max. operation temperature) and the guaranteed short circuit withstand time has been reduced from 10 µs to 6 µs. The reduction of the short circuit withstand time is a well chosen operational point on the trade-off curve between device performance (e.g. losses under operation conditions) and short circuit withstand time. Short Circuit Destruction Modes: The following short circuit destruction modes of IGBTs are known: a) Destruction during turn-off due to a latch-up which is related to the device over-temperature. b) Destruction during the current pulse (current destruction mode) which is not related to the device temperature. c) Destruction after a successful turn-off (energy destruction) due to a thermal runaway of the device as a consequence of the dissipated energy within this pulse. This destruction mode obviously largely depends on the device temperature prior to the short circuit. Due to a latch-up free cell design the destruction mode a) is not crucial for the IGBT³ 600 V. The robust chip design also avoids destruction mode b). With the IGBT³ 600 V only destruction mode c) can be observed. eupec GmbH Max-Planck-Straße D-59581 Warstein Tel. +49 (0) 29 02 7 64-0 Fax + 49 (0) 29 02 7 64-12 56 [email protected] www.eupec.com Author: Keggenhoff Application Note Date: 2005-05-11 Page 3 IGBT³ 600 V Short Circuit Performance Trade-Off: The VCEsat value is depending, among others, on the MOS channel width. An increased MOS channel width will lead to a lower VCEsat value (lower on-state losses), but also to higher turn-off losses as well as higher short circuit currents and consequently to a decreased short circuit withstand time. MOS CHANNEL WIDTH Eoff VCEsat SC time Fig. 2: Eoff, VCEsat and SC time as a function of MOS channel width Fig. 3 shows the trade-off curves Eoff = f (VCEsat) (for a given thickness and a fixed backside emitter of the chip) and tSC = f (VCEsat) in principle. For minimised turn-off losses and also minimised on-state losses a SC time of 6 µs is the best choice to get the best performance. Eoff [µJ/A] Eoff for minimised turnoff losses IGBT³ 600 V Trade-off curve SC-time = f (Vce sat) (in principle) IGBT³ 600 V Trade-off curve Eoff = f (Vce sat) (in principle) Vce sat value for minimised on-state losses [V] SC time [µs] 6 µs Vce sat [V] Fig. 3: IGBT³ Trade-off curves in principle eupec GmbH Max-Planck-Straße D-59581 Warstein Tel. +49 (0) 29 02 7 64-0 Fax + 49 (0) 29 02 7 64-12 56 [email protected] www.eupec.com Author: Keggenhoff Application Note Date: 2005-05-11 a) Page 4 b) Fig. 4: IGBT³ - 600 V (15 A – Chip) Specified minimum short circuit capability (VCE = 360 V; VGE = 15 V; Tvj = 25 °C (a); Tvj 150 °C (b); tSC = 8 µs (a); tSC = 6 µs (b)) Red: IC; Green: VGE; Blue: VCE Fig. 4 displays the specified minimum short circuit capability @ Tvj = 25 °C as well as the short circuit capability @ Tvj = 150°C. Between these two values a linear interpolation is allowed (Fig. 5). Fig. 5 Derating of the Short Circuit time as a function of the Junction Temperature tsc = f (Tj) eupec GmbH Max-Planck-Straße D-59581 Warstein Tel. +49 (0) 29 02 7 64-0 Fax + 49 (0) 29 02 7 64-12 56 [email protected] www.eupec.com Author: Keggenhoff Application Note Date: 2005-05-11 Page 5 Conclusion: The above explanation clarifies that - once the IGBT technology is short-circuit robust - the further adjustment of a short circuit withstand time is a matter of definition. In agreement with a variety of customers it has been decided to take into account the fact that modern short circuit detection methods are fast enough to recognise and turn-off a short circuit within 6 µs. The device shows an excellent switching and short circuit robustness, with the specified short circuit time having been adjusted to 6 µs on a trade-off versus optimised device losses. eupec GmbH Max-Planck-Straße D-59581 Warstein Tel. +49 (0) 29 02 7 64-0 Fax + 49 (0) 29 02 7 64-12 56 [email protected] www.eupec.com Author: Keggenhoff