Toshiba mini NB250 series, Maintenance Manual

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1.3 Power Supply 1 Hardware Overview
NB250/NB255 Maintenance Manual 1-9
1.3 Power Supply
The power supply unit provides constant voltage (19V) for the system board and performs the
following functions:
1. Power input monitor

Checks whether the AC adapter (DC power supply) is connected to the computer.

Checks whether the battery pack is connected to the computer.

Monitors the DC power supply input voltage (AC Adapter output voltage).
2. Power supply's internal control

Turns on and off the battery pack charging power supply.

Issues a charging current instruction to the PWM control IC of the battery pack charging
power supply.

Controls the supply of DC power supply input (AC Adapter output) to the power supply
unit.

Controls the supply of power to the system block (load/logic circuit side).

Controls forced shutdown if the power supply malfunctions.
3. Logic circuit control

Instructs the gate array to enable/disable tuning the power on.

Controls power-on/off operation.
4. Status display

Turns on the Power LED (in Green).

Battery indicator (in Green or Amber).

DC-IN indicator (in Green)
5. External interface

Performs communication through the I2C bus (via the internal EC/KBC).

Transfers the power supply operation mode.