Introduction - Control of Power Inverters in Renewable Energy and Smart Grid Integration - page 27

Figure 1.27 Schematic of a typical IPM

Another option is to use power modules, within which driving circuits and protection circuits
are integrated with power switches. For example, intelligent power modules (IPM) include
short-circuit protection and fault-detecting circuits, such as over-voltage, over-current and
over-heat, in addition to driving circuits (POWEREX 2000). Due to the integrated package
of the driving circuit and the power switches, the reliability and the dynamic response are
considerably improved and the losses are reduced as well. The schematic of a typical power
module with three phase legs is shown in Figure 1.27.
It is worth noting that the energy causing high transient voltages is

1

2 Li 2 , which is pro-
portional to the line inductance L and the square of the current i . Hence, the inductance of
the DC buses should be designed as small and laminated bus structures are often adopted for
high-current applications.

1.3.2.2 Auxiliary Power Supplies

In order to drive the switches in an inverter, isolated auxiliary power supplies are often needed.
For example, for the circuit shown in Figure 1.27, the driving circuits for the three ground-
connected power switches can share one power supply but the driving circuits for the three
upper switches should be isolated and hence four isolated power supplies are needed. When
selecting auxiliary power supplies, particular attention should be paid to their capacity to
make sure that the driving current provided is enough to turn on the switches. Moreover, for
each power supply to a particular driving circuit IC, a high-frequency filter capacitor and an
electrolytic capacitor should be connected in parallel to the power supply of the IC, and as
close as possible.

1.3.2.3 Driving Circuits

For a power semiconductor device, a driving circuit is needed to provide the right voltage level
and driving current. For example, the required voltage level for IGBT is often 15 V or 20 V.
Many IC companies have developed IC products to drive IGBTs at different power levels,
which differ in terms of the switching frequency, current and voltage levels, etc.
The IR21xx series of drivers produced by International Rectifier (IR) are a typical set of
high voltage, high speed MOSFET and IGBT drivers with independent high and low side