Sophisticated charging and power management systems deliver performance and reliability gains

By Alix Paultre, contributing writer

Energy storage is a significant enabler for a great many
application spaces. Today’s information-based cloud-enabled society runs on
batteries. Most industrial systems and all fossil-fuel vehicles use batteries
for backup power, and next-generation methods of storing and shifting energy will
be a critical aspect of the smart grid. The growth of electric vehicles (EVs)
has also created a huge market for large-scale battery charging (Fig. 1).

Fig.
1: The growth of electric vehicles has also created a huge market for
large-scale battery charging. (Image: Alix Paultre)

These batteries come in a variety of chemistries, form factors,
and output voltages but have one common denominator (beyond the obvious one).
They all eventually stop delivering power and must be recharged or recycled.
Recharging batteries has developed into a major application space with a wide
palette of advanced solutions available.

Battery chargers fall broadly into two types: those that are
mounted inside the product and those that have separate packaging and are
deployed externally. Internal chargers are almost always DC-input devices, and
just about every external charger accepts a 110-V or 220-V AC input. The
general deployment for a portable device is an internal DC/DC battery charger
driven by an external AC/DC power adapter.

On the board
Board-level charging is a very busy space, as every portable
electronic device needs onboard power management. The IoT has created a market
for a plethora of small single-board RF-capable devices with a button battery
in an onboard clip. There are a lot of power management ICs (PMICs) available
to manage and recharge that battery, and the performance of the charging
circuit has a direct impact on the life and reliability of the battery used.

A battery charge management controller like Microchip Technology’s
MCP73830L Li-ion linear charger serves these types of low-charge current
applications (Fig. 2). Currents as low as 20 mA can be managed with a programmable
resistor, and single- and two-cell LiFePO4 batteries can be charged with the MCP738123/213
linear chargers. Most of the controllers are available with thermal regulation,
reverse discharge protection, a safety charge timer, and integrated current
sensing.

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Fig. 2: Microchip’s
MCP73830L Li-ion linear charger serves low-charge current applications. (Image: Microchip Technology)

Solutions like the MCP73830 battery charger need to offer features
supporting long life, long runtime, and fast charging, such as battery pre-conditioning,
programmable charge currents, and end-of-charge thresholds. These features
maximize battery capacity, minimize charge time, and extend battery life in the
low-component-count, small-area circuits used in portable applications.

For many portable devices, wireless charging is becoming a
cost-effective alternative to cables, which also allow device packaging to be
seamless without a charger socket. An example of this kind of solution is the
Power by Linear LTC4126 from Analog Devices Inc. The LTC4126 provides a
wireless charger for Li-ion cells with a high-efficiency multi-mode charge pump
DC/DC converter that provides a regulated 1.2-V output at up to 60 mA.

The LTC4126’s 1.2-V charge pump output offers pushbutton on/off
control and can directly power the supported product’s ASIC, greatly
simplifying the system and reducing the number of external components. The
device is suited for space-constrained low-power Li-ion–powered wearables like
hearing aids, medical smart patches, and other IoT products.

The device offers input power management circuitry to rectify AC
power from a wireless power receiver coil, managing a 2.7-V to 5.5-V input rail
to power a constant-current/constant-voltage battery charger. Features include
a pin-selectable charge voltage of 4.2 V or 4.35 V, 7.5-mA charge current,
automatic recharge, battery temperature monitoring via an NTC pin, and an
onboard 6-hour safety charge termination timer. There is also low-battery
protection that disconnects the battery from all loads when the voltage drops
below 3.0 V. In addition, the charge pump switching frequency is 50 kHz/75 kHz
to keep switching noise out of the audible range, useful in audio-related
applications such as hearing aids and wireless headsets.

Out of the box
Most products that we think of as external chargers are AC/DC
power supplies that feed an internal battery-management PMIC. One of the most
popular external power sources for DC-driven devices is the USB port. Some USB
systems take wall current and turn it into the 5-Vdc output provided, and some
are intended for internal use in a larger system with a higher-voltage internal
DC bus.

An example of a DC/DC USB power supply intended for use as an
internal subsystem in a vehicle can be found in Molex’s USB modules, which
deliver 5 V at 1.5 A and can be deployed at multiple in-vehicle locations (Fig. 3). These
modules also enable the integration of multiple I/O port connection types such
as USB, HDMI, Ethernet, SD memory cards, auxiliary jack inputs, and more to
meet end-system requirements in either active or passive designs.

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Fig. 3: Molex’s USB
modules can be deployed at multiple in-vehicle locations. (Image: Molex)

The pre-assembled active USB charger is compliant with Battery Charging
1.2 standards and is designed to fit in existing rocker-switch panels in
vehicles to facilitate drop-in design. The products are tested for electrical,
mechanical, environmental, electromagnetic interference (EMI), electrostatic
discharge (ESD), and signal integrity. These products save time and money with
full turn-key testing and product validation. Compatible with most in-vehicle
12-V power distribution architectures, the modules provide a relatively simple
way to integrate USB and other portable-device I/O and power interfaces into a
vehicle.

When it comes to EVs, there is more to the space than just cars.
There are a lot of smaller EVs used in industrial facilities and outdoor
applications. To serve applications like these, the RC1000 from Delta-Q
Technologies, as an example, is a high-frequency charging solution capable of
charging both lead-acid and Li-ion batteries (Fig. 4).
The new charger also offers controller area network (CAN bus) communications,
such as CANopen and SAE J1939, for seamless machine integration.

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Fig.
4: The RC1000 from Delta-Q is a high frequency charging solution capable of charging
both lead-acid and Li-ion batteries. (Image: Delta-Q)

Designed with original equipment manufacturers in mind, the RC1000
is suitable for use in applications such as battery-powered floor care
machines, outdoor power equipment, and utility vehicles. Similar to its family
series, the RC1000 has an IP66-rated ingress protection to seal out dirt and
fluids, while its mechanical design and component selection resist vibration,
shock, and temperature extremes.

Looking ahead

Battery-driven systems will continue to expand
and develop as a core technology enabling our digitally empowered cloud-enabled
future. These advanced batteries will always require sophisticated charging and
management systems to provide optimum value to the user. Selecting the best
charging solution for your design will pay off in major performance and
reliability gains in your products.