Page 13 - PEN eBook October2023

Cover Story — Design

current goes below the cutoff threshold. CC mode helps accelerate the charging time, and CV mode
influences the capacity utilization of the battery.

Mixed CC-CV charging mode provides longer battery life and greater safety. CC mode prevents
overcurrent charging, and CV mode prevents overvoltage. If the battery voltage goes below a
specified threshold, the charging can be resumed automatically (Figure 6).

INDIVIDUAL CELL MONITORING & BATTERY PROTECTION

Lithium-ion battery cell voltage cannot exceed 4.20 V for the safety and longevity of the battery
pack. In addition to monitoring the total battery pack voltage while charging, it is also critical
to monitor individual cells’ voltages and ensure the cell voltage doesn’t exceed 4.20 V. EZ-PD™
PMG1-B1’s 12-bit SAR ADC along with GPIOs enable individual cell monitoring of the battery pack.

The EZ-PD™ PMG1-B1’s battery-charging algorithm can cut off charging to the battery pack if any
individual cell voltages exceed 4.20 V and protect the battery pack.

The multi-purpose high-side CSA block supports CC mode for implementing the battery-charging
algorithm. In addition, the CSA block monitors the battery-charging current and offers
hardware-based protection against overcurrent issues on the battery pack. The CSA block can cut
off the battery charging without firmware intervention in the event of detecting an overcurrent. The

overcurrent threshold can be configured through EZ-PD™ PMG1-B1 firmware.

Similarly, the EZ-PD™ PMG1-B1’s UVOV block can detect any undervoltage (UV) and overvoltage
(OV) conditions on the battery voltage (V ) and can cut off the battery charging without firmware
BAT
intervention. The threshold levels for OV and UV detection can be set independently.

POWER
THROTTLING BASED
ON TEMPERATURE

At lower temperatures, the
internal resistances of the
battery increase and the battery
capacity decreases. At colder
temperatures, charging the
battery using reduced current
is recommended to prevent

the batteries from getting
Figure 7: Battery-charge current control based on battery temperature damaged. Similarly, charging a
variation
hot battery at full current can
result in the battery catching fire. So measuring the battery temperature and modulating or terminating
the battery-charging process is critical for safety as well as for the increased life of the battery.

OCTOBER 2023 | www.powerelectronicsnews.com 13