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Safe-Restart Mode
This mode is introduced to prevent the componentsfrom being destroyed during eventual
system fault conditions. Itis also used for the Burst mode. The Safe-Restart mode will be
enteredif it is triggered by one of the following functions:
z
Over voltageprotection,
z
Short winding protection,
z
Maximum ‘on time’ protection,
z
V
CC
reachingUVLO level (fold back during overload),
z
Detecting a pulse for Burst mode,
z
Over temperature protection.
When entering the Safe-Restart mode, the output driveris immediately disabled and latched.
The V
CC
winding will not chargethe V
CC
capacitoranymore and the V
CC
voltagewill drop until
UVLO is reached. To recharge the V
CC
capacitor, the internalcurrent source (I
(restart)(VCC)
)
will be switched ‘on’ to initiate a new start-upsequence as described before. This Safe-Restart
mode will persistuntil the controller detects no faults or burst triggers.
Standby
The set goes to Standby in the following cases:
z
After pressingthe ‘standby’ key on the remote control.
z
When the set is in protection mode.
In Standby, the power supply works in ‘burstmode’.
Burst mode can be used to reduce the power consumption below1 W at stand-by. During this
mode, the controller is active (generatinggate pulses) for only a short time and for a longer
time inactivewaiting for the next burst cycle.
In the active period the energy is transferred to thesecondary and stored in the buffer capacitor
C
STAB
in front of the linear stabilizer(see Figure below). During the inactive period, the load
(e.g. microprocessor)discharges this capacitor. In this mode, the controller makes useof the
Safe-Restart mode.
Pa
g
e 20 of 32SPMS
7/8/2004