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Performance Comparison of1200 V SiC MOSFET and Si
IGBT Used in Power
Integrated Module for1100 V Solar Boost Stage
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AND90082/D

APPLICATION NOTE
Introduction

It is important to evaluate the highest junction temperature(Tj) of the semiconductor device under all conditions, andguarantee they do not exceed the rated value in the datasheet.
Users also prefer to operate as close as possible to the Tj limit(after allowing for a safety margin) to lower the overall
cost/Watt. Loss and Tj simulation is a useful method toanswer above questions. High temperature (for example
125°C) characteristic is more important than room
temperature because designers must consider worst
conditions while solar inverters work at full load and highenvironment temperature. In this paper, only hightemperature data is considered.
Key performance comparison of Si IGBT and SiC
MOSFET is shown in Table 1.
Until 2019, a common output current of a solar string wasaround 12 A. These two PIMs were designed for connecting
two strings in parallel for a MPPT (maximum power point
tracking) of 26 A. Table 1 shows current of 30 A which isa typical operating point. SiC has faster switching speed
because of unipolar device nature (no turn off tail current)
and smaller Qg. Due to lower switching losses (Eon andEoff), PIM−SIC has a significantly lower total loss comparedwith PIM−IGBT under the same operating conditions.
Figure 1 shows a comparison of conduction loss andswitching loss for the switches used in the two PIMs.

This application note compares the performance of twopower integrated modules (PIMs) in the boost stage of an1100 V solar inverter. One PIM used state−of−the−artsilicon 1200 V IGBT (part number NXH100B120H3Q0[1]) defined as PIM−IGBT and the other PIM used a new1200 V SiC MOSFET (part number NXH40B120MNQ0[2]) defined as PIM−SIC. These two PIMs utilized the same
Q0 package technology and SiC Schottky boost diode. They
are pin−to−pin compatible allowing customers to upgradefrom Si IGBT to the SiC MOSFET version. Due to fasterswitching characteristics of the SiC device, this paper
explains gate driver and PCB layout topics which must be
considered when using fast switching devices like SiC
MOSFETs.
Performance Comparison

For the design of a solar inverter, the critical operating
conditions include:• maximum solar panel input current• inverter dc bus voltage• dc inductor ripple• budget of cooling system (forced air or convectioncooling)

Table 1. KEY PERFORMANCE COMPARISON OF SI IGBT AND SIC MOSFETPIM−IGBTPIM−SIC

Rated Current

Parameter

50 A

38 A

Voltage Drop (30 A)

1.55 V

1.85 VEon (30 A)

400 (mJ)

240 (mJ)

Eoff (30 A)

1730 (mJ)

140 (mJ)

Qg (0 to 15 V)

410 (nC)

80 (nC)

Gate Voltage+15 V/−9 V+20 V/−4 VRthjc (°C/W)

0.51

0.81

Cost

100%

180%

© Semiconductor Components Industries, LLC, 2020

December, 2020 − Rev. 01Publication Order Number:AND90082/D

AND90082/D
more expensive than IGBTs due to a more complex
manufacturing process. It is reasonable to design SiC
MOSFET with a smaller die size. This smaller die area
results in higher thermal resistance, which is not favorable
for reducing Tj. Table 3 shows the power loss and Tj
simulation results for a circuit using PIM−IGBT andPIM−SIC operating under the same conditions. The Si IGBThas significantly higher Eoff due to slower dv/dt di/dt and tailcurrent. For conduction loss, the SiC MOSFET has lower
Vds when current is below cross point of 25 A due tounipolar nature.
Assumed the dc inductor has fix inductance value (nosaturation), the switch current waveform is shown as the redline in Figure 2. PIM−IGBT and PIM−SIC have similar
conducting loss and turn on loss in conditions given in
Table 3. PIM−IGBT has much higher turn off losses thanPIM−SIC. Gate driver parameters, such as gate resistance(Rg), also have strong impact on Eon and Eoff. Only Rg = 5 W
is discussed in this paper for simplifying the comparison.
Table 3. COMPARISON OF LOSS SIMULATION
Parameter

PIM−IGBTPIM−SIC

Conducting Loss

13.33 W

12.17 W

Switching Frequency

16 kHz

16 kHzTurn On Loss Eon

3.8 W

3.17 W

Turn Off Loss Eoff

34.66 W

3.06 W

Total Loss

51.79 W

18.39 W

Tj (Tc = 95°C)

137.9°C

109.9°C

Figure 1. Comparison of Conduction Lossand Switching Loss

Figure 2. IGBT Current Waveform

System cost is one of the most critical considerations fora solar application. If a SiC solution is used, the PIM is moreexpensive. This is justified only if using a SiC solution
reduces the cost of other parts of the inverter such as a lower
cost inductor and a cheaper and lighter cooling system.
An optimal design of PIM−SIC increases switchingfrequency (fsw) to 40 kHz, so the inductor size is reduced to1/3 as 200 mH. Heatsink size is also reduced. Alternatively
the heatsink size can be kept the same and the cooling ischanged from forced air cooling to natural cooling. Asa result of the reduction of heatsink size, the PIM casetemperature is assumed to rise to 110°C whereas it was 95°C
in the previous configuration.

Table 2. SYSTEM PARAMETERS OF A TYPICALSOLAR BOOST CONVERTER
ParameterValuePV Input Voltage/Current

500 V/25 A

Output DC Bus Voltage

800 V

Switching Frequency

16 kHzInductor

600 mH

Module Case Temperature

95°C

System parameters of a typical solar boost converter using
an IGBT solution are shown in Table 2. SiC MOSFETs arewww.onsemi.com
2AND90082/D
Place a low parasitic inductance film capacitor as close as
possible to the module to make the following commuting
loop as small as possible:• film capacitor − SiC MOSFET − SiC diode

Loss simulation results under these new conditions areshown in Table 4 and compared with the PIM−IGBT losses
from the previous table. Even when operating at a higher
frequency, the PIM−SIC solution has lower losses than thePIM−IGBT solution, indicating a higher system efficiencyof SiC solution.

This reduces the inductance of that loop, and reduces theradiated EMI generated from that loop.
Figure 4 gave an example of the film capacitors (Wurthpart# 890493427007CS) that were placed closely to pins ofDC+ and DC−.
The gate driver positive bias voltage of SiC MOSFET isselected as +20 V. Higher voltage reduces conducting loss.
This gives a 5 V margin to the maximum positive Vgs valueis +25 V. Negative bias voltage of −4 V is selected which
provides sufficient margin to maximum negative Vgs valueof −15 V. The negative bias increases the cost of the gate
driver but gave smaller Eoff and less Vgs ringing during turnoff. 2 W isolated dc−dc power supplies from Mornsun(QA01C +20 V/−4 V and QA151 +15 V/−8 V) were used
here. Optocoupler FOD3120 [3] from ON Semiconductor
provides galvanic isolation between control signal andpower circuit. It has maximum 2.5 A peak output current.
Because gate current goes as high as 5 A, BJT pairs of2SA2016 and 2SC5569 [4] were used to buffer gate current
up to 7 A.

Table 4. COMPARISON OF LOSS SIMULATION
Parameter

Si IGBTSiC MOSFETConduction Loss

13.33 W

13.6 W

Switching Frequency

16 kHz40 kHzTurn On Loss Eon

3.8 W7.22 W

Turn Off Loss Eoff

34.66 W

8.34 W

Total Loss

51.79 W

29.16 W

Tj

137.9°C(Tc = 95°C)

133.6°C(Tc = 110°C)

Design Consideration

Users have to pay attention at circuit design and layout
while adopting SiC PIMs, because of their faster switching
characteristics. A comparison of the switching speed ofPIM−IGBT and PIM−SIC at maximum dv/dt and maximum
di/dt is shown in Figure 3.

Figure 3. Comparison of Switching Speed

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3

AND90082/DFigure 4. PCB Layout Example

comparison purpose, the same SiC MOSFET switchingcurrent was measured by both Rogowski coil and co−axial
current shunt as shown in Figure 4. A comparison waveform
is shown in Figure 5, the Rogowski coil filtered out somefast portion and induced a certain offset. Shunt resistor isable to precisely capture turn on current overshoot due tohigh dv/dt capacitance charge current of the commuting pair
SiC schottky diode. When comparing IGBT current
waveforms, there is no significant difference between shunt
resistor and Rogowski coil due to IGBT’s lower di/dt anddv/dt.

Measuring voltage and current of SiC application
becomes more challenging due to faster rising and falling
time [5]. High bandwidth equipment and probing techniques
are necessary as shown in Figure 4. The equipment used isshown in Table 5.
As shown in Figure 5, the rise time of SiC MOSFET is inrange of ns. Based on Tr = 0.35/BW [6], bandwidth of all
equipment must be over 300 MHz.
Long grounding loop of voltage probe should be avoided,
otherwise unwanted loop inductance brings overshoot andringing noise to scope waveform. Short ground leads weresoldered here as an example. Differential voltage probe is
not recommended here due to limited bandwidth (usually up
to 200 MHz) and long grounding loop.
Rogowski coil (part# Iwatsu SS−665, 30 MHz bandwidth)
is a preferred tool of measuring IGBT switching current,
because it is very easy to assemble and disassemble into atarget circuit. However, the fast speed of SiC device goesbeyond bandwidth of normal Rogowski coil. For

Table 5.
Vgs Gate Voltage

Tek TPP1000 (1 GHz Bandwidth)

Vds Voltage

Tek P5100A (500 MHz Bandwidth)Id Switching Current

T&M Research SDN−414−10(0.1 W, 2 GHz Bandwidth)

Figure 5. CH1: Current Measured by Rogowski Coil; CH2: Vgs by Passive Probe TPP1000;
CH3: Vds by Passive Probe P5100A; CH4: Current Measured by Co−axial Shuntwww.onsemi.com
4

AND90082/D
In order to reduce ringing of gate voltage Vgs duringswitching, it is recommend to keep the gate driver loop
parasitic inductance Lg as small as possible. Actions shownin Figure 4 include: place gate driver IC closer to PIM, usewider copper trace on PCB, place return trace close to active
trace so magnetic cancelation reduces common inductance.
A comparison of Vgs turn off waveform with optimized Lg
is shown in Figure 6.

Figure 6. Optimized Lg at Left Figure (CH2: Vgs) which has less Ringing, Compared with Right Figure
Summary[3] ON Semiconductor datasheet FOD3120
https://www.onsemi.com/pub/Collateral/FOD3120−D.pdf[4] ON Semiconductor datasheet 2SA2016/2SC5569
https://www.onsemi.com/pub/Collateral/EN6309−D.
PDF[5] Z. Zhang, B. Guo, F. F. Wang, E. A. Jones,L. M. Tolbert and B. J. Blalock, ”Methodology for
Wide Band−Gap Device Dynamic Characterization,”in IEEE Transactions on Power Electronics, vol. 32,
no. 12, pp. 9307−9318, Dec. 2017, doi:
10.1109/TPEL.2017.2655491.
[6] Application Note (No. EA 60W−6053−14),
Tektronix, January, 2016

After comparing the performance of a boost module using
IGBTs and a boost module using SiC MOSFETs, thisapplication note showed the efficiency benefits of using
a SiC MOSFET module even at a much higher switchingfrequency than with an IGBT module. Careful attention
must be made to the circuit layout and measurement
methods because of the fast switching speeds of the SiC
component.
References[1] ON Semiconductor datasheet
NXH100B120H3Q0SG.
https://www.onsemi.com/pub/Collateral/NXH100B120H3Q0−D.PDF[2] ON Semiconductor datasheet
NXH40B120MNQ0SNG.
https://www.onsemi.com/pub/Collateral/NXH40B120
MNQ0−D.PDF

ON Semiconductor andare trademarks of Semiconductor Components Industries, LLC dba ON Semiconductor or its subsidiaries in the United States and/or other countries.
ON Semiconductor owns the rights to a number of patents, trademarks, copyrights, trade secrets, and other intellectual property. A listing of ON Semiconductor’s product/patent
coverage may be accessed at www.onsemi.com/site/pdf/Patent−Marking.pdf. ON Semiconductor reserves the right to make changes without further notice to any products herein.
ON Semiconductor makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does ON Semiconductor assume any liability
arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation special, consequential or incidental damages.
Buyer is responsible for its products and applications using ON Semiconductor products, including compliance with all laws, regulations and safety requirements or standards,
regardless of any support or applications information provided by ON Semiconductor. “Typical” parameters which may be provided in ON Semiconductor data sheets and/orspecifications can and do vary in different applications and actual performance may vary over time. All operating parameters, including “Typicals” must be validated for each customer
application by customer’s technical experts. ON Semiconductor does not convey any license under its patent rights nor the rights of others. ON Semiconductor products are notdesigned, intended, or authorized for use as a critical component in life support systems or any FDA Class 3 medical devices or medical devices with a same or similar classification
in a foreign jurisdiction or any devices intended for implantation in the human body. Should Buyer purchase or use ON Semiconductor products for any such unintended or unauthorized
application, Buyer shall indemnify and hold ON Semiconductor and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, andexpenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if suchclaim alleges that ON Semiconductor was negligent regarding the design or manufacture of the part. ON Semiconductor is an Equal Opportunity/Affirmative Action Employer. Thisliterature is subject to all applicable copyright laws and is not for resale in any manner.

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