4: Theory of Operation
PRC-PS-MS
4-3
whatever current (up to 1.1A) is necessary to maintain this voltage. The
BB-LA6 is now fully charged and can be left on the charger in this state for
extended periods of time.
If for some reason the BB-LA6 voltage drops below 12 Vdc, the PRC-PS
returns to the bulk charge state and repeats the charge cycle.
The following chart shows the charge levels in the three charging states.
4.3
Status LEDs
The front panel LEDs provide charge level status. The charger IC provides
two signals to control the status LEDs: the enable comparator output at pin 11
and the state level output at pin 10.
4.3.1
Fault LED
The enable comparator output (pin 11) goes directly to the display board
where it drives the FAULT LED through current limiting resistor R2. It also
drives the base of Q1 that shunts voltage away from diodes D1 and D2 when it
is conducting, preventing the CHARGING and READY LEDs from lighting.
4.3.2
Charge LED
The state level output (pin 10) drives the inverting input to operational
amplifier U2. The non-inverting input is fixed at 1.3 Vdc. Pin 10 is at ground
potential during the bulk charge and overcharge states keeping the output of
U2B high. When U2B is high (near B+ voltage but always greater than
12 Vdc), the CHARGING LED conducts through R4; it also reverse-biases
the READY LED so that it cannot light up.
Figure 4-1. Charge States
0
5
10
15
BULK
CHARGE
STATE
13.3
OVER
CHARGE
STATE
FLOAT
CHARGE
STATE
DC
VOLTAGE
FAULT
STATE
CHARGE
LED
(
YELLOW
)
READY
LED
(
GREEN
)
14.0
FLOAT
CHARGE
STATE
OVER
CHARGE
STATE
FAULT
STATE
BULK
CHARGE
STATE
