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Aeroflex Circuit Technology

SCD5101-1 REV D 5/14/01 Plainview NY (516) 694-6700

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.

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

shown in Table 2 must not be exceeded. Additionally, program specific derating and reliability constraints

may require lower junction temperatures than the 150

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.

0

20

40

60

80

100 120 140

10

15

20

25

30

35

40

45

°C)