Page 11 - PEN eBook October2023

Cover Story — Design

The battery-charger control loop uses two transconductance amplifiers (gm , gm ) to implement
cv cc
CC and CV modes. An external compensator network (Type 2 compensator) sets the frequency
response of the CC and CV feedback loops and regulates the output voltage (V ) or output battery
BAT
current (I ) during CV or CC mode, respectively. The battery pack voltage (V ) is dictated by the
BAT BAT
reference voltage V and the configurable internal resistor divider of RU and RB. The measured
REF_CV
amplified average battery-charging current cc and reference current V dictates the battery
ctrl REF_CC
pack charging current.

Figure 4: Peak current-mode–controlled four-switch buck-boost converters with a control loop

BATTERY-CHARGING ALGORITHMS

A spectrum of charging techniques comes into play to ensure prolonged battery life and optimal
battery capacity utilization. These methods, including trickle charging, CC, CV and top-off charging,
are meticulously selected based on the battery’s state of charge (SOC) and its prevailing temperature.
In CC mode, the charging current is constant, while in CV mode, the output voltage directed toward
the battery pack is constant.

MULTISTAGE CC-MODE CHARGING ALGORITHM

In CC mode, a fixed current is used to charge the battery continuously. A high-charging current
charges the battery faster. However, it significantly affects the lifespan of the battery. While a low
charging current may provide high-capacity utilization, it takes longer to charge the battery and
is inconvenient for the users. Hence, an optimum charging strategy based on the battery capacity

OCTOBER 2023 | www.powerelectronicsnews.com 11