AN2946 datasheet(7/38 Pages) STMICROELECTRONICS

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AN2946

General description

Doc ID 15473 Rev 2

7/38

The sunlight delivers rays of photons (solar energy) which hit the solar panel

(Photovoltaic or PV module). The photons (energy) are absorbed by the PV and

electrons are released.

The electrons flow along the metal contact of the PV and form electricity.

Energy is stored in the battery during daytime and consumed at night.

The LED lamp (LED streetlight) is driven to operate by the LED lamp driver. This

controller monitors the system and manages the light-on and light-off in day and night

time.

When the battery goes low, the controller sends an enable signal to the 'Mains switch'

which enables the AC offline power supply.

The AC offline power supply (not included in this application note) works as a backup

source to power the LED streetlight.

2.3

Scope of the solar-LED streetlight controller

The block diagram of the solar-LED streetlight controller is shown in Figure 3. The controller

consists of the following blocks:

●

Auxiliary power supply - supplied from the battery, regulated to 12VDC for driving every

MOSFET and then 3.3 VDC for the MCU and its peripherals.

●

Battery charger - a DC/DC converter using buck topology. It converts solar energy to

electricity and stores the electricity in the battery.

●

LED lamp driver - a DC/DC converter using flyback topology in order to drive the LED

lamp and provide even illumination.

●

Driver - generates gate voltage in order to drive every MOSFET properly in the battery

charger and the LED lamp driver including KCHG.

●

Protection circuits - OVP, UVP, OCP, OTP (through the temperature sense block) and

reverse-connection protection for the battery and the LED lamp.

●

MCU - the microcontroller includes the human machine interfaces (HMI), the DIP

switch for the selection of the operating time schedule and the indicators of the

debugging status. The software routines for OVP, UVP, OCP and OTP are implemented

in the MCU.

Figure 3.

System block diagram

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