ncp1397a ON Semiconductor, ncp1397a Datasheet - Page 19

• Manufacturer Part Number: ncp1397a
• Description: High Performance Resonant Mode Controller With Integrated High-voltage Drivers
• Manufacturer: ON Semiconductor

(M
creates a hysteresis. As a result, it becomes possible to select
the turn−on and turn−off levels via a few lines of algebra:
IBO is off
IBO is on
We can now extract R
Equation 2, then solve for Rupper:
To the contrary, when the internal BO signal is high
lower
V()) + V
R
and M
upper
V()) + V
+ R
upper
) IBO
bulk2
lower
pulse), the IBO source is activated and
lower
450
350
250
150
50
bulk1
R
V
from Equation 1 and plug it into
lower
R
R
16.0
12.0
bulk1
8.0
4.0
lower
lower
Figure 41. Simulation Results for 350 / 250 ON / OFF Levels
R
R
0
VBO
lower
) R
lower
* VBO
) R
R
upper
R
20 m
) R
lower
upper
upper
Vin
upper
351 V
60 m
BO
http://onsemi.com
(eq. 1)
(eq. 2)
time in seconds
100 m
19
350 V and turn it off for V
R
R
45 mW when front−end PFC stage delivers 400 V.
Figure 41 simulation result confirms our calculations.
Latchoff Protection
fully turned−off and stay latched. This can happen in
presence of an overvoltage (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 V
disable pulses. The V
6.5 V typically to reset the controller.
upper
lower
If we decide to turn−on our converter for Vbulk1 equals
The bridge power dissipation is 400
There are some situations where the converter shall be
140 m
= 3.57 MW
= 10.64 kW
R
lowerer
250 V
+ VBO
180 m
CC
latch
bulk2
needs to be cycled down below
IBO
(4 V typical) and permanently
equals 250 V, then we obtain:
V
bulk1
V
bulk1
* V
* VBO
bulk2
2
/ 3.781 MW =