ICE3AR0680JZ Datasheet, PDF (19/34 Pages) Infineon Technologies AG – Of f -Line SMPS Cur rent Mode Cont rol ler wi th integrated 800V

CoolSET^®-F3R80
ICE3AR0680JZ
Functional Description
count will increase by 1. Then the switch S2 will turn on
again and the voltage will drop to 0.9V and rise to 4.5V
again. The count will then increase by 1 again. When
the total count reaches 256, the counter CT1 will stop
and it will release a high output signal. When both the
input signals at AND gate G5 is high, the odd skip Auto
Restart Mode is activated after the 30us spike blanking
time (Figure 30).
The total blanking time depends on the addition of the
built-in and the extended blanking time. If there is no
C_BK capacitor at BBA pin, the count will finish within
0.1ms and the equivalent blanking time is just the built-
in time of 20ms. However, if the C_BK capacitor is big
enough, it can be as long as 1s. If C_BK is 0.1uF and
I_{chg_EB} is 720uA, the extendable blanking time is around
148.6ms and the total blanking time is 168.6ms.
Since the BBA pin is a multi-function pin, it would share
with different functions. The resistor R_BO2 from
brownout feature application may however affect the
extendable blanking time (Figure 30). Thus it should
take the R_BO2 into the calculation of the extendable
blanking time. For example the extended blanking time
may be changed from 148.6ms to 201.6ms for without
and having the 12.8KW R_BO2 resistor. The list below
shows one particular C_BK, R_BO2 vs blanking time.
C_BK
R_BO2
0.1uF
0.1uF
0.1uF
-
37.5KW
12.8KW
Extended
blanking time
148.6ms
162.8ms
201.6ms
Overall blanking
time
168.6ms
182.8ms
221.6ms
Another factor to affect the extended blanking time is
the input voltage through the R_B01 and R_B02. It would, on
the contrary, reduce the extended blanking time.
release a low signal to the flip flop FF5 and the negative
output of FF5 will release a high signal to turn on the
switch S3. The constant load LD6 will start to draw
constant current I_{chg_BO} from the BBA pin. That means
the brownout mode is default “ON” during the system
starts up.
V_bulk
R_BO1
BBA
5µs
blanking
time
G21
C14
R_BO2
0.9V
30µs~60µs
blanking time
G22
Brownout
mode
S
RQ
FF5
S3
LD6
G20
UVLO
Ichg_BO
Control Unit
Figure 31 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 BBA signal
in each restart cycle (Figure 32).
V_VCC
17V
Brownout
detected
Startup and detect BBA voltage
3.7.4
Brownout Mode
When the AC input voltage is removed, the voltage at
the bulk capacitor will fall. When it reaches a point that
the system is greater than the system allowed
maximum power, the system may go into over load
protection. However, this kind of protection is not
welcome for some of the applications such as auxiliary
power for PC/server system because the output is in
hiccup mode due to over load protection (auto restart
mode). The brownout mode is to eliminate this
phenomenon. The IC will sense the input voltage
through the bulk capacitor to the BBA pin by 2 potential
divider resistors, R_BO1 and R_BO2 (Figure 31).
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 >7V, the brownout
circuit start to operate (Figure 31). 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
10.5V
V_CS
t
t
Figure 32 Brownout mode waveform
The voltage at bulk capacitor V_bulk continues to
increase and so is the voltage at BBA. When the BBA
voltage reaches 0.9V, the output of OPAMP C14 will
become low. Through the inverter gate G21, the “S”
input of the flip flop FF5 is changed to high. Then the
negative output of FF5 is low. The brownout mode is
then “OFF” and the constant current load LD6 is also
“OFF” through the turn-off of the S3. The system will
Version 2.1a
19
11 Jan 2012