NCP1336 ONSEMI [ON Semiconductor], NCP1336 Datasheet - Page 10

• Manufacturer Part Number: NCP1336
• Description: Quasi-Resonant Current Mode Controller for High Power Universal Off-Line Supplies
• Manufacturer: ONSEMI [ON Semiconductor]

operation and VCO operation.
The operating mode is fixed by the FB voltage:
•
•
occur between V
= 370 Vdc) the current delivered by the startup device will
seriously increase the junction temperature. For instance,
since IC2 equals 3 mA (the min corresponds to the highest
T
avoid this situation, the controller includes a novel circuitry
made of two startup levels, IC1 and IC2. At power−up, as
long as V
delivers IC1 (around 300 mA typical), then, when V
reaches 0.7 V, the source smoothly transitions to IC2 and
delivers its nominal value. As a result, in case of
short−circuit between V
will drop to 370 V x 300 mA = 111 mW. Figure 4 portrays
this particular behavior:
J
The NCP1336 has two operating modes: quasi resonant
In some fault situations, a short−circuit can purposely
), the device would dissipate 370 V x 3 mA = 1.11 W. To
Quasi−resonant operation occurs for FB voltage higher
than 0.8 V (FB decreasing) or higher than 1.6 V (FB
increasing) which correspond to high output power and
medium output power.
During quasi−resonant operation, the operating valley
(1
compared internally to several voltage references
corresponding to the different valleys. There is a wide
hysteresis on each valley, allowing the controller to
adjust the output power by the current−mode control
without jumping between valleys. The peak current is
variable and is set by the FB voltage divided by 4.
VCO operation occurs for FB voltage lower than 0.8 V
(FB decreasing) or lower than 1.6 V (FB increasing).
This corresponds to low output power.
During VCO operation, the peak current is fixed to 25%
st
, 2
nd
CC
, 3
is below a certain level (0.7 V typ.), the source
rd
or 4
Figure 3. Startup Circuitry: The Current Source Brings V
CC
th
and GND. In high line conditions (V
) is fixed by the FB voltage which is
CC
and GND, the power dissipation
+
VCC
VCC
on
min
+
-
APPLICATION INFORMATION
IC1 or IC2
http://onsemi.com
VCC
GND
HV
HV
CC
10
Startup
derives current from the bulk line to charge the V
capacitor. When the power supply is first connected to the
mains outlet, the internal current source is biased and
charges up the V
capacitor reaches the VCC
off, reducing the amount of power being dissipated. At this
time, the controller is only supplied by the V
and the auxiliary supply should take over before V
collapses below VCC
arrangement of this structure:
NCP1336 includes a high voltage startup circuitry that
of its maximum value and the frequency is variable.
The frequency is set by the end of charge of Ct
capacitor. This capacitor is charged with a constant
current source and the capacitor voltage is compared to
an internal threshold fixed by FB voltage. When this
capacitor voltage reaches the threshold the capacitor is
rapidly discharged down to 0 V and a new period start.
Figure 4. The Dual Level Startup Current Source
+
CC
HV
Above 15 V and Turns Off
CC
capacitor. When the voltage on this V
min
. Figure 3 shows the internal
on
level, the current source turns
V
CC
CC
capacitor,
CC
CC
CC