ICE2QS03G Infineon Technologies, ICE2QS03G Datasheet - Page 7

• 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
3.1
In ICE2QS03G, a high voltage startup cell is integrated.
As shown in Figure 2, the start cell consists of a high
voltage device and a controller, whereby the high
voltage device is controlled by the controller. The
startup cell provides a pre-charging of the VCC
capacitor till VCC voltage reaches the VCC turned-on
threshold V
Once the mains input voltage is applied, a rectified
voltage shows across the capacitor C
voltage device provides a current to charge the VCC
capacitor C
certain value, the amplitude of the current through the
high voltage device is only determined by its channel
resistance and can be as high as several mA. After the
VCC voltage is high enough, the controller controls the
high voltage device so that a constant current around
1mA is provided to charge the VCC capacitor further,
until the VCC voltage exceeds the turned-on threshold
V
VCC voltage increase near linearly and the charging
speed is independent of the mains voltage level.
Figure 3
The time taking for the VCC pre-charging can then be
approximately calculated as:
where I
startup cell which is 1.05mA, typically.
Exceeds the VCC voltage the turned-on threshold
V
the IC begins to operate with a soft-start. Due to power
consumption of the IC and the fact that still no energy
from the auxiliary winding to charge the VCC capacitor
before the output voltage is built up, the VCC voltage
drops (Phase II). Once the output voltage is high
enough, the VCC capacitor receives then energy from
the auxiliary winding from the time point t
Version 2.1
VCCon
VCCon
t
1
=
V
V
V
VCCon
. As shown as the time phase I in Figure 3, the
VCCoff
of at time t
V
----------------------------------------- -
VCC
I VCCch
VCCcharge2
VCCon
VCCon
Functional Description
VCC Pre-Charging and Typical
VCC Voltage During Start-up
vcc
VCC voltage at start up
. Before the VCC voltage reaches a
arg
and the IC begins to operate.
⋅
1
C
, the startup cell is switched off, and
is the charging current from the
vcc
e2
i
t1
ii
t2
iii
2
bus
on. The VCC
. The high
t
[1]
7
then will reach a constant value depending on output
load.
3.2
At the time t
By this soft-start the switching stresses for the switch,
diode and transformer are minimised. The soft-start
implemented in ICE2QS03G is a digital time-based
function. The preset soft-start time is 12ms with 4
steps. If not limited by other functions, the peak voltage
on CS pin will increase step by step from 0.32V to 1V
finally.
Figure 4
3.3
The PWM controller during normal operation consists
of a digital signal processing circuit including an up/
down counter, a zero-crossing counter (ZC counter)
and a comparator, and an analog circuit including a
current measurement unit and a comparator. The
switch-on and -off time points are each determined by
the digital circuit and the analog circuit, respectively. As
input information for the switch-on determination, the
zero-crossing input signal and the value of the up/down
counter are needed, while the feedback signal V
the current sensing signal V
switch-off
operation of the PWM controller in normal operation
are illustrated in the following paragraphs.
3.3.1
As mentioned above, the digital signal processing
circuit consists of an up/down counter, a ZC counter
and a comparator. These three parts are key to
implement digital frequency reduction with decreasing
load. In addition, a ringing suppression time controller
is implemented to avoid mistriggering by the high
frequency oscillation, when the output voltage is very
low under conditions such as soft start or output short
circuit . Functionality of these parts is described as in
the following.
Vcs_sst
(V)
Quasi-Resonant PWM Controller
1.00
0.83
0.66
0.49
0.32
t
on
on
Soft-start
Normal Operation
Digital Frequency Reduction
determination.
, the IC begins to operate with a soft-start.
Maximum current sense voltage during
3
softstart
Functional Description
6
Details about
CS
are necessary for the
9
February 5, 2010
ICE2QS03G
12
the
Time(ms)
FB
and
full