ICE3AR4780CJZ Datasheet, PDF (19/33 Pages) Infineon Technologies AG – Off-Line SMPS Current Mode Controller with integrated 800V

CoolSET^®-F3R80
ICE3AR4780CJZ
Functional Description
input AC voltage to the BRL pin by an AC hold up circuit
and 2 potential divider resistors.
In some applications, it needs the IC to continue to
work for certain time when AC voltage is disconnected.
After that, the IC will stop working. If the brownout
connection is taping from the bulk capacitor, the delay
time is too short. Therefore, it needs the brown out
detetction at the AC input (Figure 30). The C_BR0 is
charged up by AC line voltage through R_BO0, which is
then fed to BRL pin through a voltage divider. When the
AC voltage drops, if the BRL pin voltage is lower than
1V for 270μs, the ICE3ARxx80CJZ will go into
brownout mode. If, however, the AC line goes up again,
the BRL voltage will be larger than 1.25V and the
ICE3ARxx80CJZ will leave brown out mode and
recover to normal operation.
The brownout mode is default “ON” during the system
starts up. When the system is powered up, the bulk
capacitor and the Vcc capacitor are charged up at the
same time. When the Vcc voltage is charged to >8V,
the brownout circuit starts to operate (Figure 30). Since
the UVLO is still at low level as the Vcc voltage does
not reach the 17V UVLO “ON” voltage. The NAND gate
G20 will release a low signal to the flip flop FF2 and the
negative output of FF2 will release a high signal. Hence
it is in brownout mode during the system starts up.
Vac
RBO0
CBR0
RBO1
1.25V
C1a
Brownout
mode
SQ
VVCC
17V
Brownout
detected
Startup and detect BBL voltage
10.5V
VCS
t
t
Figure 31 Brownout mode waveform
If the brownout feature is not needed, it needs to tie the
BRL pin to the Vcc pin through a current limiting
resistor, 5MΩ~10MΩ. The BRL pin cannot be in
floating condition.
3.7.4
Fast AC reset
During normal operation, the ICE3ARxx80CJZ can be
latched by pulling down the BRL voltage below 0.4V for
210μs. There are 2 condtions to reset the latch feature.
The first one is to pull down the Vcc voltage to below
8V. However, the Vcc drop would take quite a long time
if it is by normal AC power down. The second one is to
have a slow rise time of the BRL voltage from 0.4V to
1V for at least 450μs after the BRL pin is pulled down.
This timing can be achieved by the AC recycle. And it
is also called the fast AC reset (Figure 32).
BRL
C1b
RQ
FF2
RBO2
1V
G21
Blanking Time
270µs
G20
UVLO
Control Unit
Figure 30 Brownout detection circuit
Once the system enters the brownout mode, there will
be no switching pulse and the IC enters into another
type auto-restart mode which is similar to the protection
auto-restart mode but the IC will monitor the BRL signal
in each restart cycle (Figure 31).
Vac
RBO0
CBR0
RBO1
TLE
BRL
RBO2
Latch
Enable
Signal
C3
0.4V
Blanking time
210us
Latch
Mode
0.4V
&
C2a
Blanking time
450µs
G2
C2b
1V
Vcc
C11
8V
Latch
Reset
G3
Control Unit
Figure 32 Latch and fast AC reset
Figure 33 shows different latch and reset cases.
Case a : not latched (solid line); the timing below 0.4V
is 150μs and is less than 210μs.
Version 2.0
19
19 Apr 2013