ICE2QS03G View Datasheet(PDF) - Infineon Technologies
Part Name
Description
MFG CO.
'ICE2QS03G' PDF : 19 Pages View PDF
Quasi-Resonant PWM Controller
ICE2QS03G
Functional Description
the output flip-flop will be reset by one of these signals
which come first.
If the output load is still low, the feedback signal
decreases as the PWM section is operating. When
feedback signal reaches the low threshold VBL(3.0V),
the internal bias is reset again and the PWM section is
disabled until next time regultaion siganl increases
beyond the VBH threshold. If working in Active Burst
Mode the feedback signal is changing like a saw tooth
between 3.0V and 3.6V shown in Figure 9.
3.5.3
Leaving Active Burst Mode Operation
The feedback voltage immediately increases if there is
a high load jump. This is observed by one comparator.
As the current limit is 34% during Active Burst Mode a
certain load is needed so that feedback voltage can
exceed VLB (4.5V). After leaving active busrt mode,
maximum current can now be provided to stabilize VO.
In addition, the up/down counter will be set to 1
immediately after leaving Active Burst Mode. This is
helpful to decrease the output voltage undershoot.
VFB
VFBLB
VFBBOn
VFBBOff
Entering
Active Burst
Mode
Leaving
Active Burst
Mode
VFBEB
Blanking Window (tBEB)
t
VCS
1.0V
VCSB
Current limit level
during Active Burst
Mode
VVCC
t
VVCCoff
VO
t
Max. Ripple < 1%
3.6
Protection Functions
The IC provides full protection functions. The following
table summarizes these protection functions.
Table 2 Protection features
VCC Overvoltage
Auto Restart Mode
VCC Undervoltage
Auto Restart Mode
Overload/Open Loop
Auto Restart Mode
Over temperature
Auto Restart Mode
Output Overvoltage
Latched Off Mode
Short Winding
Latched Off Mode
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 VVCCoff,
the startup 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
feedback 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 VFB 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 vZCOVP, the
IC is latched off after the preset blanking time.
If the junction temperature of IC exceeds 140 0C, the IC
enter into autorestart mode.
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, when the VCC
voltage drops to 10.5V,the startup cell is activated and
the VCC voltage is charged to 18V then the startup cell
is shut down again and repeats the previous procedure.
There is also a maximum on time limitation inside
ICE2QS03G. Once the gate voltage is high longer than
tOnMAx, it is turned off immediately.
t
Figure 9 Signals in Active Burst Mode
Version 2.1
11
February 5, 2010
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