ICE2AS01_06 INFINEON [Infineon Technologies AG], ICE2AS01_06 Datasheet - Page 10

• Manufacturer Part Number: ICE2AS01_06
• Description: Off-Line SMPS Current Mode Controller
• Manufacturer: INFINEON [Infineon Technologies AG]

Figure 11
3.4
3.4.1
The oscillator generates a frequency f
resistor, a capacitor and a current source and current
sink which determine the frequency are integrated. The
charging and discharging current of the implemented
oscillator capacitor are internally trimmed, in order to
achieve a very accurate switching frequency. The ratio
of controlled charge to discharge current is adjusted to
reach a max. duty cycle limitation of D
3.4.2
The frequency of the oscillator is depending on the
voltage at pin FB. The dependence is shown in Figure
12. This feature allows a power supply to operate at
lower frequency at light loads thus lowering the
switching losses while maintaining good cross
regulation performance and low output ripple. In case
of low power the power consumption of the whole
SMPS can now be reduced very effective. The minimal
reachable frequency is limited to 20kHz / 21.5 kHz to
avoid audible noise in any case.
Datasheet
Preliminary Data
5.3V
4.8V
V
OUT
V
V
V
FB
SoftS
OUT
Oscillator and Frequency
Reduction
Oscillator
Frequency Reduction
Start Up Phase
T
T
Start-Up
Soft-Start
switch
max
=0.72.
= 100kHz. A
t
t
t
10
Figure 12
3.5
There is a cycle by cycle current limiting realised by the
Current-Limit Comparator to provide an overcurrent
detection. The source current of the external Power
Switch is sensed via an external sense resistor R
By means of R
a sense voltage V
exceeds the internal threshold voltage V
Current-Limit-Comparator immediately turns off the
gate drive. To prevent the Current Limiting from
distortions caused by leading edge spikes a Leading
Edge Blanking is integrated at the Current Sense.
Furthermore a Propagation Delay Compensation is
added to support the immediate shut down of the
Power Switch in case of overcurrent.
3.5.1
Figure 13
Each time when the external Power Switch is switched
on a leading spike is generated due to the primary-side
capacitances and secondary-side rectifier reverse
V
csth
f
standby
kHz
f
V
norm
Sense
1,0
f
f
norm
standby
Current Limiting
Leading Edge Blanking
:
1,1
Frequency Dependence
Leading Edge Blanking
:
Sense
1,2
ICE2BS01(G)
67kHz
20kHz
1,3
the source current is transformed to
Sense
Functional Description
t
1,4
LEB
. When the voltage V
V
1,5
= 220ns
FB
ICE2AS01/S01G
ICE2BS01/S01G
1,6
ICE2AS01(G)
100kHz
21.5kHz
1,7
1,8
30 Jun 2006
1,9
csth
2
t
Sense
Sense
V
the
.