NCP1560_06 ONSEMI [ON Semiconductor], NCP1560_06 Datasheet - Page 12

• Manufacturer Part Number: NCP1560_06
• Description: Full Featured Voltage Mode PWM Controller
• Manufacturer: ONSEMI [ON Semiconductor]

and
Voltage−Mode Control in high performance DC−DC
converters. This device cost effectively reduces system part
count with the inclusion of a high voltage startup regulator.
The NCP1560 provides two control outputs. Output 1
controls the main switch of a forward or flyback topology.
Output 2 has an adjustable overlap delay, which can be used
to control an active clamp/reset switch, a synchronous
rectifier switch, or both. Other distinctive features include:
two mode overcurrent protection, line under/overvoltage
lockout, fast line feedforward, soft−start and a maximum
duty cycle limit. The Functional Block Diagram is shown in
Figure 2.
advantages
feedforward, and cycle−by−cycle current limit. It eliminates
the disadvantages of low power jitter, slope compensation
and noise susceptibility.
High Voltage Startup Regulator
regulator that eliminates the need for external startup
components. In addition, this regulator increases the
efficiency of the supply as it uses no power when in the
normal mode of operation, but instead uses power supplied
by an auxiliary winding.
that supplies current from the input line voltage (V
capacitor on the V
typically 13.8 mA. Once V
regulator turns OFF and the outputs are enabled. When V
reaches 7.0 V, the outputs are disabled and the startup
regulator turns ON. This “7 − 11” mode of operation is known
The NCP1560 PWM controller contains all the features
The features included in the NCP1560 provide all the
The NCP1560 contains an internal high voltage startup
The startup regulator consists of a constant current source
80
70
60
50
40
30
20
10
0
0
flexibility
Measured from 10% to 90% of V
V
AUX
Figure 27. Outputs Rise Time versus Load
25
= 12 V
of
AUX
50
C
Current−Mode
L
needed
, LOAD CAPACITANCE (pF)
pin (C
75
Capacitance
AUX
T
J
AUX
for
= 25°C
100
reaches 11 V, the startup
). The startup current is
Control,
OH
implementation
125
DETAILED OPERATING DESCRIPTION
T
J
T
= −40°C
TYPICAL CHARACTERISTICS
J
150
= 125°C
fast
in
175
) to the
http://onsemi.com
AUX
line
of
200
12
as Dynamic Self Supply (DSS). The V
externally above 7 V once the outputs are enabled to prevent
the startup regulator from turning ON. It is recommended to
bias the V
an auxiliary winding from the power transformer. An
independent voltage supply can also be used. However, if
V
fault is present, the One Shot Pulse Generator (Figure 2) will
not be enabled and the outputs will remain OFF.
be placed between C
in Figure 29. This will allow the NCP1560 to charge C
while preventing the startup regulator from sourcing current
into the auxiliary supply.
DSS mode is provided by C
sized such that a V
maintained while the outputs are switching and the
converter reaches regulation. Also, the V
(from 11 V to 7 V) must be greater that the soft−start charge
period to assure the converter turns ON.
If the device operates in the DSS mode, power dissipation
should be controlled to avoid exceeding the maximum
power dissipation of the controller.
AUX
V
35
30
25
20
15
10
As the DSS sources current to the V
Power to the controller while operating in the self−bias or
The startup circuit is rated at a maximum voltage of 150 V.
in
5
0
Figure 29. Recommended V
0
Measured from 90% to 10% of V
V
is biased before the outputs are enabled or while a
AUX
Disable
I
START
Figure 28. Outputs Fall Time versus Load
AUX
25
= 12 V
pin using an auxiliary supply generated out of
V
C
50
AUX
L
I
AUX
, LOAD CAPACITANCE (pF)
AUX
AUX
I
START
75
Capacitance
and the auxiliary supply as shown
AUX
voltage greater than 7 V is
100
C
T
AUX
. Therefore, C
J
= 125°C
T
AUX
OH
J
125
AUX
= 25°C
AUX
Configuration
I
AUX
supply
To auxiliary supply
pin, a diode should
pin can be biased
150
discharge time
T
J
AUX
= −40°C
175
must be
AUX
200