NGTB20N60L2TF1G High speed SW Application of the IGBT Application Note http://onsemi.com ABSTRACT Generally, Ic tailing phenomenon occurs to Power IGBT at the time of cutoff of switching operation. Therefore, when IGBT is used in the application of SMPS or INVERTER, the operating frequency is restricted and only a narrow-range applications can addressed. To respond to this situation, FS2-IGBT is developed that Ic tailing hardly occurs at the time of switching, so it can be used in interleave PFC circuit. It is the optimal device for PFC circuit of the air-conditioners with an output higher than 1kW. IGBT’s SW performance evaluation Characteristics of IGBT that are critical to the circuit efficiency are VCE(sat) characteristic and SW characteristic, but when the frequency exceeds 15~20kHz, SW characteristic becomes dominating. We compared the switching characteristic between NPT type that is used as Power IGBT and FS-2 type newly developed. When considering application in interleave PFC circuit, the circuit becomes discontinuous mode or critical mode when the load is light. Also because the value of Inductor is less than 1mH, Ic waveform inclines. Concerning the switching loss, Eoff(fall) is more dominant than Eon(rise). VGE L-load switching operation test & comparison VGE 90% First compare the two in L-load switching circuit. VGE 10% Ic With regard to switching time(tf, ton & etc) and Ic 90% switching loss(Eon, Eoff), the observed points Ic 10% VCE VCE 10% Ic 10% are shown in fig.1. We changed Ic and observed that, for NPT type (WP.1), Eof f Eon Ic tailing prominently occurred at the time of cut-off. fig.1 SW time parameters But Ic taling hardly occurred for FS-2 (WP.2). This shows that Ic tailing can be seen prominently at a comparatively low current in NPT. By contrast, FS-2 shows a good fall characteristic in a wide current range. From the aspect of current-dependency of Eoff, difference was seen in the current region like shown in fig.2, but in the other current regions, there was almost no difference. Here are the calculation for switching loss using frequency and Eoff. Take Operating Frequency as f[Hz], then P(Eoff）=f × Eoff [W] 1/5 NGTB20N60L2TF1G Application Note In case of continuous mode operation, Eon is further added. But because the actual waveform is with slope, Eon＜Eoff. Therefore, influenced of Eoff on switching loss becomes large. Ic-1A/div VCE-100V/div Ic-1A/div Ic tailing VCE-100V/div WP.1 NPT IGBT SW(5A) WP.2 FS2 IGBT SW(5A) fig.2 Eoff VS Ic Adaptability of IGBT to Interleave PFC circuit Interleave PFC circuit is one of the active PFC circuits, which as shown in fig.3 becomes the circuit configuration to let two switching element have ON/OFF in turn. 。 fig.3 Active PFC circuit 2/5 NGTB20N60L2TF1G Application Note Flowing current into two paths allows reduction in IGBT’s peak current and inductor’s peak current as well as reduction in current ripple. It is a method that is positively adopted in room air-conditioners driving by large current. IGBT behavior in Interleave PFC circuit – (1) We operated NPT and FS-2 in interleave operation circuit and compared their characteristics. (Table.1 ) Interleave circuit controls its output current so that it is resembled to the input voltage, so IGBT’s Ic constantly changes. WP.3 is the waveform of single-side IGBT at peak current of PFC operation. In NPT, prominent Ic tailing is observed from Ic waveform. Table.1 Test result Comparison between FS-2 and NPT @ Inter leave PFC circuit (par each) VAC=100V Iout=1.5A Vout 388V f=34kHz FS-2 NPT η[%] toff[nS] Eoff[μJ] tf[nS] Pin[W] VCEp[V] IDp[A] 94.4 92.2 313 461 161 309 93 253 619 631 444 440 8.9 9.0 Ic-2A/div VCE-100V/div Ic tailing WP.3 NPT IGBT SW @PFC WP.4 FS-2 IGBT SW @PFC The operating efficiency at this time: η（NPT）=92.2%. On the other hand, η(FS-2)=94.4％(2.2% up) when operating the same with FS-2. The operation waveform is WP.4, where you can confirm little tailing to Ic, which contributes much to low loss. 3/5 NGTB20N60L2TF1G Application Note IGBT behavior of interleave PFC circuit -(2) Next we compared the characteristic when changing frequency in this circuit. (See fig.4) NPT: efficiency is low, efficiency decreases abruptly when raising frequency. Whereas FS-2: efficiency changes little with frequency. It can be operated up to 50kHz, which is assumed high-freq. operation. fig.4 Efficiency VS Frequency Structure of NPT and FS-2 NPT(Non punch through) requires a certain wafer thickness of wafer to secure depletion layer of N-layer in order to ensure collector-emitter withstand voltage at the time of Ic cutoff. FS-2 is thin-form IGBT that adopts 2nd generation Field Stop structure. A comparatively high-concentrated N-layer forms between N-layer and the backside P-layer. So compared with NPT, wafer can be made thinner. This enables better switching characteristic, especially high-quality current at the time of cutoff. Switching speeding-up and VCE(sat) lowering is in trade-off relation, FS-2 contributes to improve the trade-off relation, and meanwhile helps reduce VCE(sat). (See fig.5, fig.6). Gate Emitter Gate Emitter FS-2: N-layer (drift layer) becomes thinner N- drift layer N+ buffer layer P+ layer N- drift layer Collector P+ layer Collector fig.6 FS-2 IGBT structure fig.5 NPT IGBT structure 4/5 NGTB20N60L2TF1G Application Note Actual product of FS-2 As product, we have NGTB20N60L2TF1G (600V/20A), NGTB30N60L2WG (600V/30A). Table.2 shows FS-2 IGBT Lineup. Absolute maximum ratings Type No. IC IC PD @Tc= 25ºC @Tc= 100ºC @Tc= 25ºC [V] [A] [A] [W] Package VCES FRD Electrical Characteristics / Ta=25ºC Electrical characteristics /Ta=25ºC/VGE=15V VCE(sat) typ @IC [V] VF trr(typ) max @IC 100A/µs Cies [A] [pF] [V] [ns] NGTB20N60L2TF1G TO-3PF-3L 600 40 20 64 1.45 20 2000 1.5 20 70 NGTB30N60L2WG TO-247-3L 600 60 30 130 1.4 4130 1.7 25 70 30 ** IF=10A,VR=50V,di/dt=100A/us ON Semiconductor and the ON logo are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). 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