Functional Description
3.5 Protection Functions
The IC provides full protection functions. The following
table summarizes these protection functions.
Table 2 Protection features
During operation, the VCC voltage is continuously
monitored. In case of an under- or an over-voltage, the
IC is reset and the main power switch is then kept off.
After the VCC voltage falls below the threshold
V
VCCUVP
, the power cell is activated. The VCC capacitor
is then charged up. Once the voltage exceeds the
threshold V
VCCon
, the IC begins to operate with a new
soft-start.
In case of open control loop or output over load, the
regulation voltage will be pulled up . After a blanking
time of 24ms, the IC enters auto-restart mode. The
blanking time here enables the converter to provide a
high power in case the increase in V
REG
is due to a
sudden load increase. During off-time of the power
switch, the voltage at the zero-crossing pin is
monitored for output over-voltage detection. If the
voltage is higher than the preset threshold v
OPOVP
, the
IC is latched off after the preset blanking time.
If the voltage at the current sensing pin is higher than
the preset threshold v
csSW
during on-time of the power
switch, the IC is latched off. This is short-winding
protection.
During latch-off protection mode, the power cell is
activated and it keeps the VCC voltage at the level of
V
VCCBL.
VCC Overvoltage Auto Restart Mode
VCC Undervoltage Auto Restart Mode
Overload/Open Loop Auto Restart Mode
Output Overvoltage Latched Off Mode
Short Winding Latched Off Mode
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