AN2946 datasheet(9/38 Pages) STMICROELECTRONICS

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AN2946

General description

Doc ID 15473 Rev 2

9/38

discharged. In order to prolong battery operating life, the charging current is

constrained at Imax = 0.5 A.

●

Stage 2 (high-current bulk charging): 11 V

≤ U

BAT < 14.3 V. In this stage, the battery is

charged with the maximum power of the PV module. The charging current (Imp) may

not be constant.

●

Stage 3 (floating charging): UBAT ≥ 14.3 V. In this stage, battery is charged at constant

voltage (14.3 V).

The voltage values 11 V and 14.3 V define the boundaries of the stages that are based on

the characteristics of a typical 12 V lead acid battery. The voltage needed depends on the

type of battery.

2.4.2

LED lamp driving management

During nighttime, normally the ambient light is weak, the LED lamp lights for N hours. The

determined light-on duration (N hours) can be set by selecting a switch, DIP1~4. The

controller turns on/off the LED lamp to automatically correspond to the ambient light.

Figure 5 illustrates how the controller turns on the LED lamp. The DIP switch also provides a

test mode to test the LED lamp.

Figure 5.

LED lamp driving scheme

2.4.3

System monitoring circuit

The microcontroller (MCU) provides a real-time system monitoring for the controller,

including:

●

Error detection/protection for solar module output voltage (USC), battery voltage(UBAT),

LED lamp voltage(ULED), battery charging current (IBAT) and LED lamp current(ILED)

●

Temperature detection for the operating temperature of the battery, MOSFET and LED

lamp

●

System self-recovery

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