POWER OUTPUT STAGE
IGBTS [insulated gate bipolar transistors] are technically similar to bipolars and MOSFETS. An IGBT is a
composite of a transistor with an N-channel MOSFET connected to the base of a PNP transistor. Like the
MOSFET, it offers high input impedance and requires low input drive current. IGBT conduction losses are low,
as with bipolar technology, and IGBT voltage drops are much lower compared with those of MOSFETs.
Consequently, the IGBT offers a high current density. With a smaller die size than the MOSFET, it can handle
the same current rating. Unlike MOSFETS, IGBTS have no intrinsic body diode. The ACT5101-1 includes 35 nsec
fast recovery rectifiers in parallel across each of the 6 IGBTS to carry the reverse current when the IGBT is
turned off.
It is important for the user to observe the Absolute Maximum ratings of the ACT5101-1 so that the voltage
and current rating is not exceeded. If over-voltage/over-current protection is desired it must be
implemented external to the ACT5101-1. Figure 3 shows the ACT5101-1 output current capability vs. case
temperature.
45
40
35
30
25
20
15
10
0
20 40 60 80 100 120 140
Case Temperature TC (°C)
FIGURE 3 - OUTPUT CURRENT VS. CASE TEMPERATURE
POWER DISSIPATION
Power dissipation in the ACT5101-1 is composed of three elements: IGBT conduction losses, IGBT switching
losses, and commutation diode conduction losses. It is important that the user calculates power dissipations
over the full range of operating conditions of the hybrid, and uses these dissipations to compute the worst
case junction temperatures both for the IGBTs and diodes. The 150° C maximum junction temperature
shown in Table 2 must not be exceeded. Additionally, program specific derating and reliability constraints
may require lower junction temperatures than the 150° C maximum.
Calculating IGBT conduction losses requires the user to determine load profiles for the hybrid both in
current and time duration. IGBT collector-emitter voltage drops are shown in Figure 4.
6
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SCD5101-1 REV D 5/14/01 Plainview NY (516) 694-6700
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