Tech Briefs Magazine - June 2022 - Sensor-8

TECHNOLOGY LEADERS Sensors
Protecting Electric Vehicle Charging Systems
with Advanced Current Sensing
W
hile battery range and
charging times are getting
the most attention when it
comes to electric vehicle
(EV) charging systems, safety and reliability
are a critical part of the equation. Using
the right current-sensing methodology
can go far to address these concerns.
With the expanding adoption of EVs
there is increasing pressure on the related
power infrastructure to keep up. This
pressure focuses mainly on accessibility
related to battery range and the speed of
charging. However, safety and reliability
are critical in vehicular power systems,
as human lives are involved. There are
a variety of approaches being pursued
when it comes to addressing the issue of
charging EVs. Highway and city charging
stations are currently being deployed,
but the ability to charge at home is also a
major piece of the EV charging market.
Any catastrophic failure of any aspect of
the power chain can result in a significant
fire hazard and death, especially in
a home-based system.
The power conversion system is key to
EV performance and high-quality current
sensing is a key component of that
system. However, current sensing is also
a significant contributor to safety and
reliability. Optimizing automotive power
conversion systems requires accurately
measuring current, ensuring tight power-factor
correction (PFC), and addressing
thermal issues.
In addition to impacting the performance
and efficiency of a power solution,
current measurement can also help
manage thermal performance, which
if not addressed, can be both destructive
and costly. When properly done,
the right current-sensing methodology
can significantly increase performance,
safety, and cost-effectiveness. It is used
for early fault detection and real-time
performance information. This information
can provide safety alerts, like the
indication of an overcurrent condition
or other loss of performance in order to
predict and address things like potential
thermal problems.
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Figure 2. AMR compared to the three main current sensing methods. (Image: ACEINNA)
Beyond such obvious dangers as ground
faults and short-circuits, operating at extreme
power levels and at loading conditions
beyond the system's capability to
support is also very dangerous. Charging
systems rely on feedback loops for stability
and optimum system performance - a
current sensor is a vital part of that loop.
Methods of Current Sensing
A simple device like a resistive shunt
can measure the voltage drop to determine
the current flowing through the
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circuit. Although it offers good dynamic
performance and linearity, it has limitations
especially at high currents where
the resistive power dissipation in the
shunt itself becomes a thermal issue and
is an unnecessary waste of power.
A Hall effect-based sensor is isolated,
and it doesn't affect the output in terms
of voltage drop and power dissipation as
much, but it lacks accuracy and bandwidth
capabilities compared to other solutions.
A current transformer is isolated and
can be made an accurate sensing soluSensor
Technology, June 2022
Figure 1. Good charging control is vital to protecting the charger and the battery. (Image: ACEINNA)
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5/18/22 2:19 PM

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Tech Briefs Magazine - June 2022

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