At present, emerging vehicles represented by new energy vehicles are rapidly 
replacing traditional fuel vehicles. Although new energy vehicles are becoming 
the choice of more people, there is no doubt that they still have pain points 
in consumer experience. One is inconvenient charging experience or slow 
charging speed, and the other is range anxiety.

To expand the future market of new energy vehicles, it is necessary to start 
from the perspective of electrification efficiency, and the current important 
trend is to use 800V electrical architecture + SiC power devices, in which 
isolation and driver technology is indispensable.

New trend of vehicle electrification

The trend of vehicle electrification is first to develop high-voltage 
architecture, increasing charging power under the condition of increasing 
charging voltage and constant charging current, so as to achieve the goal of 
driving for 200 kilometers by charging for 5 minutes. At present, some domestic 
and foreign vehicle models have been using super charging pile, and 800V bus 
voltage has also been applied and mass produced for many models. Market 
research shows that by 2025, it is expected that the sales volume of new energy 
vehicles with 800V high-voltage architecture will reach about 1 million units, 
and the three-year CAGR (compound annual growth rate) will reach 270%; in 2025, 
global sales of new energy vehicles equipped with 800V architecture are 
expected to reach 2 million units.

The second trend is the use of high-voltage SiC power devices; its advantage is 
that the third-generation semiconductor devices features high voltage, low 
on-off loss, small size and other advantages, helping to improve the electric 
drive efficiency, optimize the electric drive weight, and increase the range by 
10%-15%.

The above two trends put forward new and higher requirements for isolation IC 
and driver IC. Firstly, the voltage level of the battery, motor and electric 
control systems (including OBC, DC-DC and BMS) of 800V high-voltage platform, 
as well as the air compressor, PTC and electric driver will be increased 
accordingly.

Isolation and driver technology in new energy vehicles

Firstly, the isolation of new energy vehicles is based on safety certification 
requirements to protect personal and equipment safety at the 400V-800V battery 
voltage, and processors and other weak current devices also require isolation 
chip for electrical isolation from the high voltage side; the second is the 
common ground requirement, which needs to use the isolation device to realize 
the level conversion function; the third is high noise resistance requirements 
to achieve higher CMTI (common mode transient immunity), and avoid large noise 
interference, resulting in power tube mis-opening; in particular, the 
application of SiC can make the switching frequency rise, causing relatively 
large dv/dt noise.

Creepage is also one of the requirements of the safety compliance, which 
represents the distance of the chip packaging surface to produce flashover or 
breakdown (marking). The common creepage distance in the high-voltage battery, 
motor and electric control system of new energy vehicles is the isolation 
device of 8mm. With the upgrading of the battery, motor and electric control 
system to 800V voltage, the creepage distance will also increase.

In addition, the large peak output current requires to turn on the switch tube 
with larger current to meet the requirement of quick opening and closing the 
power tube. New energy vehicles rely on electric air compressors to drive, and 
main motor driver and PTC also require high voltage electrical isolation.

At present, there are several mainstream isolation technologies in the 
industry, and NOVOSENSE adopts the capacitive isolation technology based on 
capacitance coupler. In a capacitor isolation chip, the isolation capacitors 
are located on two separate bare chips. Since it adopts superior enhanced 
isolation technology for electrical isolation, two capacitive plates are 
connected in series to achieve isolation in an enhanced architecture. The 
isolation medium between them is silicon dioxide, which is a kind of isolation 
medium with higher isolation strength. The withstand voltage of each micron 
isolation can reach more than 400V, which is 5-6 times of the isolation medium 
(epoxy resin) used by the optical coupler. Theoretically, the isolation grid 
with thickness of 30 microns can reach isolation voltage of more than 10kV. The 
measured 60-second withstand voltage can also reach the level of 12kV. In 
addition, capacitance-isolated differential transmission architecture per 
channel also helps to improve common-mode noise suppression.

For common-mode suppression, modulation is needed, that is, an input signal is 
transmitted in a capacitor or other medium through modulation. The prevailing 
approach is usually to use OOK encoding, which modulates an input signal to 
more than 400 megabytes of carrier and then transmits it between capacitors. 
The patented Adaptive OOK coding scheme is optimized by NOVOSENSE, which 
further improves the capability of the isolator to resist common-mode noise. 
Compared with the other two approaches, OOK coding modulation has the advantage 
of strong resistance to common-mode suppression.

NOVOSENSE products feature withstand voltage isolation capability of 12kVrms, 
EMC performance and surge of > 12kV and both-side capability of ESD > 10kV. 
These products have obtained UL/CUL/VDE/CQC and other mainstream safety 
compliance certification in the industry.

NOVOSENSE provides digital isolation chips and isolation power supply, 
including isolation sampler, isolation driver, as well as some interface 
related products and automotive grade isolation devices, which are now in full 
mass production.

The third-generation semiconductor has higher requirements for isolation 
devices. The switching frequency has been increased from 10kHz of silicon base 
to 100kHz of SiC, and the isolation voltage has been increased to more than 
1000V.

In addition, requirements of SiC devices on digital isolators are higher 
switching frequency and higher transmission rate with common mode inhibition 
ability of not less than 100kV/microsecond. NOVOSENSE isolation devices can 
reach 150kV or even 200kV.

In the new-generation electric drive development platform, CMTI, wide grid 
voltage swing, large peak output current, fast rise and fall time, fast short 
circuit protection and soft shutdown ability are the key indicators to be 
considered when selecting suitable SiC power tube driver chips.

NOVOSENSE system and product solutions

In the application of NEV electric driver main motor driver, NOVOSENSE has 
mass-produced isolation drivers, including NSi6611 and NSi6651 intelligent 
protection enhanced isolation driver, as well as enhanced digital isolator and 
enhanced isolation sampler.

In addition to the driver, it provides bus voltage or current isolation 
samplers NSi1311 and NSi1300 for the battery, motor and electric control system 
with relatively high market shares.

NSi82xx is the earliest automotive grade digital isolation product launched by 
NOVOSENSE. It covers 1-6 channel schemes and adopts different packages, such as 
narrow body 8, wide body 8 and wide body 16, including ultra-wide body 
isolation devices that match 800V applications with a creepage distance of 
15mm. In addition, there are some interface products such as the 1042, 1051, 
1043 for CAN and the 1145 with sample to be ready soon.

The main advantage of the enhanced isolation is the isolation of the operating 
voltage, with withstand voltage of 5,000V AC per minute. NSi82xx enhanced 
digital isolator is a hero product with nominal isolation voltage of 5000Vrms, 
measured withstand voltage of 12kV in the insulation oil, sufficient margin and 
relatively high reliability.

Since the isolation operating voltage is applied to both ends of the isolation 
grid for a long period of 20 years or more, it is necessary to ensure that the 
failure rate of the isolator is less than 1 ppm. If it is basic isolation, this 
requirement is much looser, requiring failure rate of less than 1000 ppm, a 
difference of 1000 times.

Meet the demand of auto manufacturers

NOVOSENSE isolation and driver products are mainly used in OBC, DC-DC, main 
motor driver, BMS and thermal management system. The performance of its 
products are competitive in isolation and drive technology industry, with safe 
and reliable production supply chain in China. Mature product experience and 
sound intelligent production system are reflected in the AEC-Q100 
qualification, and it has strictly followed the automotive grade process and 
control concept from product definition and development to the back-end wafer 
packaging.

SOURCE: NOVOSENSE Microelectronics

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