NCP1560(2003) 데이터 시트보기 (PDF) - ON Semiconductor
부품명
상세내역
일치하는 목록
NCP1560 Datasheet PDF : 18 Pages
| |||
NCP1560
Typical Characteristics
80
Measured from 10% to 90% of VOH
70 VAUX = 12 V
60
TJ = 25°C
TJ = 125°C
50
40
30
20
TJ = -40°C
35
Measured from 90% to 10% of VOH
30 VAUX = 12 V
25
TJ = 125°C
20
TJ = 25°C
15
10
TJ = -40°C
10
0
0 25 50 75 100 125 150 175 200
CL, LOAD CAPACITANCE (pF)
Figure 27. Outputs Rise Time versus Load
Capacitance
5
0
0 25 50 75 100 125 150 175 200
CL, LOAD CAPACITANCE (pF)
Figure 28. Outputs Fall Time versus Load
Capacitance
DETAILED OPERATING DESCRIPTION
The NCP1560 PWM controller contains all the features
and flexibility needed for implementation of Voltage-Mode
Control in high performance DC/DC converters. This
device cost effectively reduces system part count with the
inclusion of a high voltage start-up 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/over voltage lockout, fast
line feedforward, soft start and a maximum duty cycle limit.
The Functional Block Diagram is shown in Figure 2.
The features included in the NCP1560 provide all the
advantages of Current-Mode Control, fast line feedforward,
and cycle by cycle current limit. It eliminates the
disadvantages of low power jitter, slope compensation and
noise susceptibility.
High Voltage Start-up Regulator
The NCP1560 contains an internal high voltage start-up
regulator that eliminates the need for external start-up
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.
The start- up regulator consists of a constant current source
that supplies current from the input line voltage (Vin) to the
capacitor on the VAUX pin (CAUX). The start- up current is
typically 13.8 mA. Once VAUX reaches 11 V, the start- up
regulator turns OFF and the outputs are enabled. When VAUX
reaches 7 V, the outputs are disabled and the start- up
regulator turns ON. This “7- 11” mode of operation is known
as Dynamic Self Supply (DSS). The VAUX pin can be biased
externally above 7 V once the outputs are enabled to prevent
the start-up regulator from turning ON. It is recommended
to bias the VAUX pin using an auxiliary supply generated out
of an auxiliary winding from the power transformer. An
independent voltage supply can also be used. However, if
VAUX is biased before the outputs are enabled or while a
fault is present, the One Shot Pulse Generator (Figure 2) will
not be enabled and the outputs will remain OFF.
As the DSS sources current to the VAUX pin, a diode should
be placed between CAUX and the auxiliary supply as shown
in Figure 29. This will allow the NCP1560 to charge CAUX
while preventing the start- up regulator from sourcing current
into the auxiliary supply.
ISTART
Vin 13.8 mA VAUX
Disable
IAUX
CAUX
To auxiliary supply
Isupply
Figure 29. Recommended VAUX Configuration
Power to the controller while operating in the self-bias or
DSS mode is provided by CAUX. Therefore, CAUX must be
sized such that a VAUX voltage greater than 7 V is
maintained while the outputs are switching and the
converter reaches regulation. Also, the VAUX discharge time
(from 11 V to 7 V) must be greater that the soft start charge
period to assure the converter turns ON.
The start-up circuit is rated at a maximum voltage of
150 V. If the device operates in the DSS mode, power
dissipation should be controlled to avoid exceeding the
maximum power dissipation of the controller.
http://onsemi.com
12
Share Link: 