NCP1396B ON Semiconductor, NCP1396B Datasheet - Page 19

• Manufacturer Part Number: NCP1396B
• Description: High Performance Resonant Mode Controller featuring High-voltage Drivers
• Manufacturer: ON Semiconductor

Figure 43. The internal brown-out configuration with
an offset current source
To the contrary, when the internal BO signal is high
(Mlower and Mupper pulse), the IBO source is activated
and creates a hysteresis. As a result, it becomes possible
IBO is off
IBO is on
We can now extract Rlower from equation 1 and plug it into equation 2, then solve for Rupper:
If we decide to turn-on our converter for Vbulk1 equals
350V and turn it off for Vbulk2 equals 250V, then we
obtain:
Rupper = 1MΩ
Rlower = 2.86kΩ
The bridge power dissipation is 400² / 1.00286MΩ =
160mW when front-end PFC stage delivers 400V.
Figure 44 simulation result confirms our calculations.
V
V
Rupper
Rlower VBO
( )
( )
Rupper
Rlow er
+ =
+ =
Vbulk
Vbulk
Vbulk
=
=
Rlower
IBO
1
2
BO
×
×
×
Vdd
Rlower Rupper
Rlower Rupper
IBO
×
Vbulk
Vbulk
Rlower
×
Rlower
VBO
(
ON/OFF
VBO
Vbulk
+
+
-
+
1
1
−
−
VBO
Vbulk
1
−
VBO
2
+
IBO
BO
)
NCP1396A, NCP1396B
× ⎜
⎛
⎝
http://onsemi.com
Rlower Rupper
Rlower Rupper
50.0
450
350
250
150
16.0
12.0
8.00
4.00
0
19
×
+
Figure 44. Simulation results for 350 / 250 ON / OFF levels
Vin
20.0u
to select the turn-on and turn-off levels via a few lines of
algebra:
Latch-off protection
shall be fully turned-off and stay latched. This can happen
in presence of an over-voltage (the feedback loop is
drifting) or when an over temperature is detected. Thanks
to the addition of a comparator on the BO pin, a simple
external circuit can lift up this pin above VLATCH (4 V
typical) and permanently disable pulses. The Vcc needs to
be cycled down below 6.5 V typically to reset the
controller.
351 volts
⎞
⎟
⎠
There are some situations where the converter
60.0u
BO
eq. 1
eq. 2
100u
140u
250 volts
180u
2
1