With an Aging Industrial Infrastructure, Reliable IGBT Drivers Are More Important Than EverMarch 09, 2020 by Gary Elinoff
High voltage and high reliability is king in IGBT drivers. Power Integrations is rising to the call.
When it comes to an aging US infrastructure, especially for industrial and power transmission applications, high voltage and high reliability are paramount.
Despite this, not many companies offer some of the specific hardware needed to drive these loads. One company that does offer hardware solutions for these applications is Power Integrations, which announced its newest driver for high-voltage press-pack IGBT (PPI) modules.
The 1SP0351. Image used courtesy of Power Integrations
The 1SP0351 is designed to drive 4500 V press-pack IGBT (PPI) modules, which designers can find through ABB, Toshiba, and Westcode. Power Integrations specifically calls out these three companies as target partners for their new gate driver. This product, therefore, represents a situation wherein a semiconductor company is striving to accommodate the needs of industrial applications.
The 1SP0351 is designed to be plug-and play compatible with press-pack IGBT (PPI) modules from these major manufacturers.
The Purpose of IGBT Drivers
Insulated gate bipolar transistors (IGBT) play critical roles in modern electrical power technology, and we’ll get to them later. But, for now, why do they need to be “driven”?
As Texas Instruments describes it, a gate driver is a "power amplifier that accepts a low-power input from a controller IC and produces the appropriate high-current gate drive for a power MOSFET."
As Robert Keim describes in his article on an isolated IGBT gate driver from Analog Devices, a designer can turn an IGBT on and off through its gate, which, as described earlier, appears as a capacitor to the circuity that drives it. But switching the IGBT on and off requires charging and discharging that capacitive structure.
As high-power devices, IGBTs are structurally large, as is the gate’s capacitance. To turn the IGBT on and off at the high speeds required calls for much more current than a typical digital output stage can deliver. Thus, an IGBT driver is required to serve as a power-boosting intermediary between the powerful IGBT and the very low-power digital signal that controls it.
The Critical Role of the IGBT
Insulated gate power transistors (IGBT) today play a central role in high-voltage power applications. Here, they are employed as switching devices, operating in the range of kilovolts and hundreds or even thousands of amps.
They have applications in a broad range of industrial applications, railway operations, and EVs—which seems to be the industries Power Integrations is targeting with their new IGBT drivers.
IGBTs play a major role in the ever-expanding power grid. They are particularly instrumental in static synchronous compensators (STATCOM). STATCOMs are part of a flexible AC transmission system (FACTS), which serves to maintain the reliability of AC grids. When you see power transfer capability increase, you can expect controllability to improve as well.
Because high-power IGBTs are also reliable, these semiconductors are considered a critical component in the reconstruction of the aging electrical infrastructure of the US power grid. The future is even more exciting with the increasing role of renewables in the power generation system.
Renewable sources are by nature variable and somewhat unpredictable. They lend themselves to high-voltage DC transmissions based on voltage source converters (VSC-HVDC), which are in turn based on IGBTs switched on and off many thousands of times per second via pulsed-width modulation (PWM) techniques.
What Are Press Pack IGBTs?
Press pack IGBTs (or PPIs) utilize pressure contacts as opposed to wire bonds. Press pack IGBTs are a great advantage with power applications that require series connectivity because they can readily be connected electrically and mechanically in series.
A few examples on the market include StakPak from ABB, a dominant industrial company, press-pack IGBTs from IXYS Westcode (now owned by Littelfuse), and IEGT PPIs from Toshiba.
ABB explains that StakPak is "a family of high power insulated gate bipolar transistor (IGBT) press-packs and diodes in an advanced modular housing that guarantees uniform chip pressure in multiple-device stacks."
ABB’s 5SNA family of press-pack IGBT modules. Image used courtesy of ABB
IXYS offers its own press-pack IGBTs. These units are free of wire and solder bonds, which renders them immune from mechanical fatigue issues associated with conventional modules.
Internal structure of a Toshiba PPI. Image used courtesy of Toshiba
In this structure, multiple IEGT chips are pressed in place by a molybdenum plate. As illustrated above, this arrangement puts the collector and emitter electrodes of each IEGT chip in contact with the external copper electrodes. It also establishes solid electrical connections while facilitating heat dissipation.
IXYS Westcode offers the CO44BG400 series of gate driver boards specifically for use with the company’s press-pack IGBTs.
A C044BG400 family gate driver with its associated press-pack IGBT. Image used courtesy of IXYS
Members of this family of gate driver boards can deliver up to 44 A of gate driving current. A gate driver board and its associated IGBT work together as illustrated below.
Block diagram of gate driver board and its IGBT. Image used courtesy of IXYS
The left side of the above diagram is the gate driver board. Note that the IXYS device’s use of magnetically-based coupling, too. The right side is the IGBT assembly. Notice the clear indication of the capacitance coupling of the gate to the rest of the semiconductor.
As the newest member of the Power Integrations' SCALE-iDriver IC family, the 1SP0351 eschews troublesome optoelectronic coupling in favor of its magnetically-based FluxLink technology.
Have you experienced the fallout of an IGBT driver (or any other component for that matter) that wasn't as reliable as you expected? How did you course correct? Share your experience in the comments below.