ICE2A180 Infineon Technologies Corporation, ICE2A180 Datasheet - Page 8

• Manufacturer Part Number: ICE2A180
• Manufacturer: Infineon Technologies Corporation

The primary current is sensed by the external series
resistor R
CoolMOS™. By means of Current Mode the regulation
of the secondary voltage is insensitive on line
variations. Line variation causes varition of the
increasing current slope which controls the duty cycle.
The external R
the maximum source current of the integrated
CoolMOS™.
Figure 6
To improve the Current Mode during light load
conditions the amplified current ramp of the PWM-OP
is superimposed on a voltage ramp, which is built by
the switch T
low pass filter composed of R
Figure 7). Every time the oscillator shuts down for max.
duty cycle limitation the switch T2 is closed by V
When the oscillator triggers the Gate Driver T2 is
opened so that the voltage ramp can start.
In case of light load the amplified current ramp is to
small to ensure a stable regulation. In that case the
Voltage Ramp is a well defined signal for the
comparison with the FB-signal. The duty cycle is then
controlled by the slope of the Voltage Ramp.
By means of the C5 Comparator the Gate Driver is
switched-off until the voltage ramp exceeds 0.3V. It
allows the duty cycle to be reduced continously till 0%
by decreasing V
Datasheet
Preliminary Data
O s cilla to r
F B
V oltage Ram p
S oft-S tart C o m p ara to r
V
O S C
Sense
Improved Current Mode
2
T
, the voltage source V
2
inserted in the source of the integrated
Sense
C
FB
1
0.3V
below that threshold.
allows an individual adjustment of
1 0 k
R
2 0p F
1
P W M C o m pa ra to r
C 5
Preliminary Specification
1
0.8V
and C
V
1
P W M -La tch
G a te D rive r
1
and the 1st order
1
(see Figure 6,
P W M O P
x3 .6 5
OSC
.
8
Figure 7
3.2.1
The input of the PWM-OP is applied over the internal
leading edge blanking to the external sense resistor
R
source current into a sense voltage. The sense voltage
is amplified with a gain of 3.65 by PWM OP. The output
of the PWM-OP is connected to the voltage source V1.
The voltage ramp with the superimposed amplified
current singal is fed into the positive inputs of the PWM-
Comparator, C5 and the Soft-Start-Comparator.
3.2.2
The PWM-Comparator compares the sensed current
signal of the integrated CoolMOS
signal V
optocoupler or external transistor in combination with
the internal pullup resistor R
information of the feedback circuitry. When the
amplified current signal of the integrated CoolMOS™
exceeds the signal V
off the Gate Driver.
Sense
0 .8 V
0 .3 V
V olta ge R a m p
F B
V
G a te D rive r
connected to pin ISense. R
FB
O S C
(see Figure 8). V
PWM-OP
PWM-Comparator
Light Load Conditions
D u ty C yc le
m a x.
FB
Functional Description
the PWM-Comparator switches
ICE2A165/265/365
FB
FB
is created by an external
and provides the load
ICE2A180/280
TM
CoolSET™-II
Sense
with the feedback
February 2001
converts the
t
t
t