December 9, 2022

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Why Reliable IGBT Drivers Are Important Amidst Aging Digital Infrastructure

High voltage and high reliability are critical in an aging US infrastructure, particularly for industrial and power transmission applications. Despite this, only a few companies supply some of the specialized hardware required to power these loads. 

One company that does provide hardware solutions for these applications is Power Integrations, which recently announced a new driver for high-voltage press-pack IGBT (PPI) modules.

1SP0351
The 1SP0351. Image used courtesy of Power Integrations.

The 1SP0351 is designed to supply power to 4500 V press-pack IGBT (PPI) modules from ABB, Toshiba, and Westcode. These three companies are specifically mentioned by Power Integrations as potential gate driver partners. As a result, this product is an example of a semiconductor company attempting to meet the requirements of industrial applications.

The 1SP0351 is intended to work with the press-pack IGBT (PPI) modules from these major manufacturers.

The Purpose of IGBT Drivers

Insulated gate bipolar transistors (IGBTs) play critical roles in modern electrical power technology, as we will see later. But, for the time being, why do they need to be “driven”?

A gate driver is a “power amplifier that accepts a low-power input from a controller IC and generates the appropriate high-current gate drive for a power MOSFET.”

An IGBT can be turned on and off by a designer using its gate, which, as previously described, appears as a capacitor to the circuitry that drives it. However, turning on and off the IGBT inverter necessitates charging and discharging that capacitive structure.

As high-power devices, IGBTs have a large structural size, as does the gate capacitance. Much more current is required to turn the IGBT on and off at the required high speeds than a typical digital output stage can provide. As a result, an  IGBT driver must serve as a power-supply intermediary between the powerful IGBT and the very low-power digital signal that controls it.

The Critical Role of the IGBT

Today, insulated gate power transistors (IGBTs) are widely used in high-voltage power applications. In this application, they serve as switching devices with voltages ranging from kilovolts to hundreds to thousands of amps.

They are used in a wide range of industrial applications, railway operations, and EVs, which appears to be the industry Power Integrations is aiming for with their new  IGBT drivers.

IGBTs are critical components of the ever-expanding power grid. They are essential components of static synchronous compensators (STATCOM). STATCOMs are a component of the flexible AC transmission system (FACTS), which aids in the smooth operation of AC grids. As power transfer capability improves, so should controllability.

Because they are also reliable, high-power IGBTs are regarded as an essential component in the reconstruction of the aging electrical infrastructure of the US power grid. The future looks even brighter with renewables playing an increasing role in the power generation system.

Renewable energy sources are, by definition, variable and unpredictable. They are well-suited for high-voltage direct current transmissions based on voltage source converters (VSC-HVDC), which are based on IGBTs that are switched on and off thousands of times per second using pulse-width modulation (PWM) techniques.

What Are Press Pack IGBTs?

Pressure contacts are used instead of wire bonds in press pack IGBTs (or PPIs). Press pack IGBTs have a significant advantage in power applications that require series connectivity because they can be easily connected electrically and mechanically in series.

ABB’s StakPak, a dominant industrial company, press-pack IGBTs from IXYS Westcode (now owned by Littelfuse), and Toshiba’s IEGT PPIs are a few market examples.

StakPak is a family of high power insulated gate bipolar transistor (IGBT) press-packs and diodes in an advanced modular housing that ensures uniform chip pressure in multiple-device stacks.

ABB’s 5SNA family of press-pack IGBT modules

Press-pack IGBT modules from ABB’s 5SNA family. Image courtesy of ABB.

IXYS manufactures its own press-package IGBTs. Because these units lack wire and solder bonds, they are immune to mechanical fatigue issues that plague conventional modules.

Toshiba’s PPIs are built on IEGT chips. These are similar to IGBT drivers, but have deeper and wider trenches, which gives them an advantage in some applications.

Internal structure of a Toshiba PPI
ABB 5SNA press-pack IGBT modules ABB supplied the image. Image used courtesy of Toshiba.

In this structure, a molybdenum plate presses multiple IEGT chips into place. The collector and emitter electrodes of each IEGT chip are brought into contact with the external copper electrodes by this arrangement, as shown above. It also helps to dissipate heat and makes solid electrical connections.

IXYS Westcode’s CO44BG400 series of gate driver boards is specifically designed for use with the company’s press-pack IGBTs.

A C044BG400 family gate driver with its associated press-pack IGBT
A gate driver from the C044BG400 family, along with a press-pack IGBT. Image used courtesy of IXYS.

This gate driver board family’s members can deliver up to 44 A of gate driving current. A gate driver board and its associated IGBT work in tandem, as shown below.

Block diagram of gate driver board and its IGBT.
The gate driver board and its IGBT. Image used courtesy of IXYS.