Quasi-Resonant PWM Controller
ICE2QS01
Functional Description
3.5
Protection Functions
The IC provides full protection functions. The following
table summarizes these protection functions.
Table 2
Protection features
VCC Overvoltage
Auto Restart Mode
Auto Restart Mode
Auto Restart Mode
Latched Off Mode
Latched Off Mode
VCC Undervoltage
Overload/Open Loop
Output Overvoltage
Short Winding
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 VVCCon, 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 VREG 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 vOPOVP, the
IC is latched off after the preset blanking time.
If the voltage at the current sensing pin is higher than
the preset threshold vcsSW 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
VVCCBL.
Version 2.1
11
October 2007
INFINEON [ Infineon ]
