Download High Speed IGBT

TRENCHSTOP™5 boosts efficiency in Home Appliance, Solar and
Welding Applications
Davide Chiola - Senior Mgr IGBT Application Engineering
Mark Thomas – Product Marketing Mgr Discrete IGBT
Infineon Technologies Austria AG, Siemensstr. 2, 9500 Villach, Austria
Abstract
Modern trends in power electronics require higher efficiency power semiconductors at
competitive cost. The new 650V TRENCHSTOP™5 IGBT technology cuts the switching
losses of previous generations by half, still maintaining low conduction losses. It sets a new
benchmark in power density, allowing significant benefit for the end application. This paper
presents the fast switching version of this technology platform and highlights the benefits in
the target applications by extensive application tests.
1. Introduction
Energy efficiency requirements set by Regulatory Agencies in different regions are steering
the adoption of very efficient power semiconductors and enabling smart system solutions in
order to meet the efficiency standard. In Photovoltaic applications for example, any fraction
of % efficiency gained in the Solar inverter will translate in lower energy bill or shorter time to
get to a grid parity. At the same time the inverter cost must cope with declining PV panel
costs. In consumer applications like Motor Drives for Home Appliance, the solution cost must
be kept within the limits set by a very competitive marketplace. In modern split Air
conditioning above 1kW for example, a Power Factor Correction circuit is required to reduce
the energy wasted by the system. In this case high efficiency of the PFC conversion along
with very low solution cost must be guaranteed to win these high volumes, cost-driven
consumer markets.
Also in the industrial segment new regulations are coming up: PFC is being introduced in
portable welders in the Chinese market to improve the grid quality. In these applications high
switching frequency of the AC/DC stage allows to reduce the size of the output filters and
hence the weight of the machine. Reducing switching losses for the IGBT allows to lower the
operating temperature of the device, translating in longer lifetime for these system operating
in harsh environments.
The above general trends call for new switch technologies offering an overall reduction of
power losses (W / mm2), still keeping the same or lower chip cost / mm2. At the same time
different flavors of the technology are required to address specific requirements of each
application.
2. TRENCHSTOPTM 5 and High Speed 5 IGBT
To address these needs a new technology platform called TRENCHSTOPTM 5 has been
developed: a special cell design and ultrathin wfr technology allow to achieve simultaneously
low conduction and switching losses. The architecture of the new technology is shown in
figure 1:
Figure 1: TRENCHSTOP™5 technology platform and its derivatives
The fast switching version “High Speed 5”is currently being released and will be discussed in
this paper. It addresses fast switching applications like PFC or boost stages as well as
inverter stages in Solar and UPS, DCDC converters in Welding.
A comparison with previous IGBT generations is provided in Figure 2:
Figure 2: High Speed 5 vs previous Infineon IGBT generations.
Additional technology variants are currently in development and will be released in 2013 and
2014: an “R” version for resonant topologies to be found in Inductive Cooking and a low
Vcesat “L” version to be used mainly as polarity switch in Solar inverters.
The high Speed 5 is offered in 2 versions to offer additional flexibility to the end-user:

High Speed 5 – H: “plug&play” replacement of previous generation High Speed 3. It
results in a drastic performance improvement and doesn’t require any special
precaution in design-in.

High Speed 5 – F: it provides additional loss reduction, however needs a split Rg,on
and Rg,off driving stage. It is a best fit for design with low stray inductance in the
commutation loop and in combination with SiC Schottly diode, for example as boost
Diode in active PFC.
The different switching behavior of H and F version is illustrated in Figure 3, capturing the
turn-off event during application test on an internally developed 2 kW H4 Bridge topology:
Figure 3: Current and Voltage waveforms during turn-off: H5 and F5 vs previous
generation H3.
The H5 provides a faster voltage rise than H3, resulting in lower turn-off losses. The current
waveform is however very similar to the H3. The apparent oscillation of the tail current are
amplified by the time scale used (20ns / div). The F5 on the other hand provides shorter tf
and faster current fall dI/dt. This translates in additional loss reduction, but also in additional
voltage overshoot Ls dI/dt beyond the DC link voltage. In this case 900A/us provides almost
100V of voltage overshoot, meaning approx 110 nH of stray inductance. In order to keep the
voltage spike within a more reasonable ~50V, stray inductance of the PCB tracks should be
limited to 30~50 nH. A multilayer PCB is preferred, as well as Surface Mounted SMD discrete
packages or modules with low lead inductance. The voltage spike increases as load current
is increased, therefore it can be mitigated by slightly over-rating the device or paralleling
multiple devices. The Voltage spike can be finally reduced by increasing Rg,off, hence a split
Rg,on-Rg,off driver stage is preferred for the F version, keeping the Rg,on as low as possible
to meet the required EMI specs and increasing Rg,off the meet de-rating specification of
normally 80% Vbrces.
The High Speed 5 provides drastically improved performance compared to High Speed 3
across the whole range of electrical parameters: lower conduction losses, higher blocking
voltage, lower switching and capacitive losses, lower gate charge (Figure 4, left). This results
in a drastically improved Vcesat-Eoff trade-off compared to previous 600V IGBT generations
(Figure 4, right):
Figure 4: Electrical parameter comparison (left) andTrade-off Vcesat / Eoff (right) of the
HighSpeed5 in comparison to previous technologies HighSpeed3 and TrenchStopTM
3. Application test.
3.1 Power Factor Correction (PFC)
We verified the improvement of the new technology by extensive characterization and
application test. In Figure 5 we show an efficiency test in a 1 kW CCM mode PFC test board,
where the High Speed 5 (H5) is compared to previous generation High Speed 3 (H3) and
competitor’s IGBTs commonly found in these applications. Switching frequency is 60 kHz in
this case.
Figure 5: Efficiency and case temperature (at max power) comparison in a 1kW PFC
test board
The High Speed 5 shows an efficiency improvement of 0.5% to the High Speed 3 and 1% to
the best competitor.
The PFC circuit is normally the AC/DC conversion stage of motor drives to be found in
modern Air conditioning split systems above 1 kW.
Assuming that the Airc conditioning is running on average at 50% load and an efficiency of
95% for the inverter stage, this would translate in 5 W average power saving for each Air
conditioning unit sold with a High Speed 5 IGBT on it. Considering that only the top 4 Aircon
suppliers in China produce approximately 25 Million inverterized Aircon units / years, this
would result in a power saving of 100 MW in China only, equivalent to 430 Million of kWh
saving in one year, assuming a utilization rate of 50%.
The device can work at relatively high switching frequency of 60 kHz, where normally 20 kHz
are used by conventional IGBTs. This translates in the possibility to reduce the size of the
PFC choke still keeping the same ripple current, and hence reduce system cost.
Even more interesting are the thermal results: thanks to the reduce power dissipation, the Hi
gh Speed 5 in TO220 package can reduce the case temperature compared to previous IGBT
s housed in the much bigger TO247 package (up to 30°C compared to the best competitors
at 800W). This allows to save board spacing due to the smaller footprint, reduce the cooling r
equirement and finally reduce the solution cost, very important in this demanding consumer
market.
3.2 Solar inverter
Before looking into the real application of solar inverter, let’s firstly get a direct feeling of the
power loss improvement of H5 against previous generation HighSpeed3. Based on a very
simple condition of a 20A square wave with 50% duty cycle, junction temperature 100°C, the
total power loss per IGBT vs switching frequency is shown in Figure 6 below:
Figure 6: Power dissipation as a function of switching frequency
At 20KHz, which is commonly used in state-of-the-art inverter design, the total power loss
per IGBT dropped from 32.80 W by HighSpeed 3 to 25.04 W by using the H5, that means
approximately 24% reduction. Moreover, if we replace the anti-parallel diode with Infineon
2nd Gen SiC Schottky diode, another 11% power loss reduction could be achieved. This
allows to either increase the system output power by keeping the same device temperature,
or increase the switching frequency, as explained below.
In the application field, with specific thermal design of the power system, the allowable total
maximum loss is defined according to heatsink size, ventilation as well as the configuration
of power devices, magnetic components etc. At the same time the junction temperature of all
the power devices must fulfill the de-rating requirement of e.g. 80% of the Tjmax. That
means also that the maximum allowable power loss per device is defined as well.
Take a practical value e.g. 40W for standard TO247, and the same load condition mentioned
above (20A square wave, 50% duty cycle) for a 40A device. The maximum operation
frequency of HighSpeed3, with respect to max junction temperature 100°C, is around 28
KHz. As a comparison, the new IGBT H5 it could be driven up to 50 KHz. At this frequency
the cost and reliability benefit brought by the frequency increase, like smaller and light-weight
magnetic components, as well as possibility of reduction or even elimination of electrolytic
capacitors in some cases, would definitely overcome the additional design complexity
(thermal, layout optimization etc). This is extremely important for applications like Solar and
UPS, where the cost of the passive components dominate the bill of material.
To validate the above considerations, an application test was carried out on a Solar inverter
at Fraunhofer Institute ISE. The HERIC topology consists of 6 duo-pak IGBTs and 2 discrete
diodes. By replacing the High Speed 3 IGBT with High Speed 5 - H5 at 16 kHz, the peak
efficiency is increased by 0.2 % to reach 98.3%. In a separate test, the H5 allows to triple the
switching frequency (from 16 to 48 kHz) by keeping the same or higher efficiency as previous
generation High Speed 3 over the entire load range, confirming the simulated results.
Figure 7: Efficiency measurement on Solar inverter with HERIC topology.
Courtesy of Fraunhofer ISE.
4. Conclusions
In summary, we presented in this paper the newly developed High Speed 5 IGBT, fast
version of the TRENCHSTOPTM 5 technology platform. Thanks to advanced thin wafers
technology, it provides drastically improved performance compared to previous generation
and competitor’s IGBT. After highlighting the major electrical parameters and switching
behavior, the benefit of the new technology are verified in real application test circuits,
resulting in drastically improved efficiency and thermal behavior. This translates in higher
system reliability, and possibility to meet higher efficiency targets not increasing the BOM
cost.