ICE2QS03G Infineon Technologies, ICE2QS03G Datasheet - Page 10

• Manufacturer Part Number: ICE2QS03G
• Description: IC CTRLR PWM QUASI-RESON DSO8
• Manufacturer: Infineon Technologies

Specifications of ICE2QS03G

• Output Isolation: Isolated
• Frequency Range: 52kHz
• Voltage - Input: 11.2 V ~ 27 V
• Operating Temperature: -25°C ~ 130°C
• Package / Case: 8-SOIC (0.154", 3.90mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

3.4.1
When the main bus voltage increases, the switch on
time becomes shorter and therefore the operating
frequency is also increased. As a result, for a constant
primary current limit, the maximum possible output
power is increased, which the converter may have not
been designed to support.
To avoid such a situation, the internal foldback point
correction circuit varies the V
to the bus voltage. This means the V
decreased when the bus voltage increases. To keep a
constant maximum input power of the converter, the
required maximum V
voltage can be calculated, which is shown in
Figure 7
According to the typical application circuit, when
MOSFET is turned on, a negative voltage proportional
to bus voltage will be coupled to auxiliary winding.
Inside ICE2QS03G, an internal circuit will clamp the
voltage on ZC pin to nearly 0V. As a result, the current
flowing out from ZC pin can be calculated as
When this current is higher than I
current exceeding this threshold is used to generate an
offset to decrease the maximum limit on V
ideal curve shown in
digital block in ICE2QS03G is implemented to get a
better control of maximum output power. Additional
advantage to use digital circuit is the production
tolerance is smaller compared to analog solutions. The
Version 2.1
I ZC
0.9
0.8
0.7
0.6
1
80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400
=
V
------------------------
R ZC1 N P
BUS
to the IZC current
Variation of the VCS limit voltage according
Foldback Point Correction
N
a
Figure 7
CS
versus various input bus
Vin(V)
CS
voltage limit according
is a nonlinear one, a
ZC_1
, the amount of
CS
CS
. Since the
Figure
will be
[5]
7.
10
typical maximum limit on V
shown in
Figure 8
3.5
At light load condition, the IC enters Active Burst Mode
operation to minimize the power consumption. Details
about Active Burst Mode operation are explained in the
following paragraphs.
3.5.1
For determination of entering
operation, three conditions apply:
•
•
•
Once all of these conditions are fulfilled, the Active
Burst Mode flip-flop is set and the controller enters
Active Burst Mode operation. This multi-condition
determination for entering Active Burst Mode operation
prevents mistriggering of entering Active Burst Mode
operation, so that the controller enters Active Burst
Mode operation only when the output power is really
low during the preset blanking time.
3.5.2
After entering the Active Burst Mode the feedback
voltage rises as V
inactive PWM section. One comparator observes the
feedback signal if the voltage level V
exceeded. In that case the internal circuit is again
activated by the internal bias to start with swtiching.
Turn-on of the power MOSFET is triggered by the
timer. The PWM generator for Active Burst Mode
operation composes of a timer with a fixed frequency of
52kHz, typically, and an analog comparator. Turn-off is
resulted by comparison of the voltage signal v
internal threshold, by which the voltage across the
shunt resistor V
also be triggered by the maximal duty ratio controller
which sets the maximal duty ratio to 50%. In operation,
the feedback voltage is lower than the threshold of
V
voltage across the shunt resistor is 0.17;
the up/down counter is 7; and
a certain blanking time (t
Quasi-Resonant PWM Controller
0.9
0.8
0.7
0.6
FBEB
1
300
(1.25V). Accordingly, the peak current sense
Figure
500
Active Burst Mode Operation
Entering Active Burst Mode Operation
During Active Burst Mode Operation
V
CS-max
csB
700
8.
is 0.34V, accordingly. A turn-off can
OUT
900
versus I
Functional Description
starts to decrease due to the
1100
CS
Izc(uA)
BEB
ZC
versus the ZC current is
1300
).
Active Burst Mode
February 5, 2010
1500
ICE2QS03G
1700
BH
(3.6V) is
1900
1
with an
2100