Charge control program description

AN417

10/21

Doc ID 2074 Rev 2

4

Charge control program description

The microcontroller detects the inflexion point in the battery voltage versus time curve while

charging. When full charge is detected, the MCU puts the charger in trickle charge mode.

As safety protection, the MCU also terminates fast charge if -[

temperature exceeds a predetermined threshold, or a timer with programmable time

duration expires.

Figure 9 shows the simplified flowchart of the program for the complete charge control. The

overall system is reset after each new input source voltage connection. It is also reset when

a charged battery is removed, and replaced by a discharged battery.

Figure 6.

Simplified program flowchart

NEW BATTERY

INSERTED ?

START

NOISE FILTERING AND AVERAGING

CALCULATE DERIVATIVE

SMOOTH DERIVATIVE

ARE WE AT INFLEXION ?

ARE WE AT DELTA-V ?

IS TIMER EXPIRED ?

WAIT 4 SECONDS

IS TEMPERATURE ABOVE THRESHOLD ?

IS BATTERY PRESENT ?

TRICKLE MODE

MEASURE BATTERY VOLTAGE 256 TIMES

Y

Y

Y

Y

N

Y

N

N

N

N

Y

N