|
|
PDF NCP1205 Data sheet ( Hoja de datos )
| Número de pieza | NCP1205 | |
| Descripción | Single Ended PWM Controller Featuring QR Operation and Soft Frequency Foldback | |
| Fabricantes | ON | |
| Logotipo |  |
|
Hay una vista previa y un enlace de descarga de NCP1205 (archivo pdf) en la parte inferior de esta página. Total 20 Páginas | ||
|
No Preview Available !
NCP1205
Single Ended PWM
Controller Featuring QR
Operation and Soft
Frequency Foldback
The NCP1205 combines a true Current Mode Control modulator
and a demagnetization detector to ensure full Discontinuous
Conduction Mode in any load/line conditions and minimum drain
voltage switching (Quasi–Resonant operation, also called critical
conduction operation). With its inherent Variable Frequency Mode
(VFM), the controller decreases its operating frequency at constant
peak current whenever the output power demand diminishes.
Associated with automatic multiple valley switching, this unique
architecture guarantees minimum switching losses and the lowest
power drawn from the mains when operating at no–load conditions.
Thus, the NCP1205 is optimal for applications targeting the newest
International Energy Agency (IEA) recommendations for standby
power.
The internal High–Voltage current source provides a reliable
charging path for the VCC capacitor and ensures a clean and short
start–up sequence without deteriorating the efficiency once off.
The continuous feedback signal monitoring implemented with an
Over–Current fault Protection circuitry (OCP) makes the final design
rugged and reliable. An internal Over Voltage Protection (OVP) circuit
continuously monitors the VCC pin and stops the IC whenever its level
exceeds 36 V. The DIP14 offers an adjustable version of the OVP
threshold via an external resistive network.
Features
• Natural Drain Valley Switching for Lower EMI and Quasi–Resonant
Operation (QR)
• Smooth Frequency Foldback for Low Standby and Minimum Ripple
at Light–Load
• Adjustable Maximum Switching Frequency
• Internal 200 ns Leading Edge Blanking on Current Sense
• 250 mA Sink and Source Driver
• Wide Operating Voltages: 8.0 to 36 V
• Wide UVLO Levels: 7.2 to 15 V Typical
• Auto–Recovery Internal Short–Circuit Protection (OCP)
• Integrated 3.0 mA Typ. Start–Up Source
• Current Mode Control
• Adjustable Over–Voltage Level
• Available in DIP8 and DIP14 Package
Applications
• High Power AC/DC Adapters for Notebooks, etc.
• Offline Battery Chargers
• Power Supplies for DVD, CD Players, TVs, Set–Top Boxes, etc.
• Auxiliary Power Supplies (USB, Appliances, etc.)
8
1
http://onsemi.com
PDIP–8
N SUFFIX
CASE 626
MARKING
DIAGRAMS
8
NCP1205P
AWL
YYWW
1
14
1
14
PDIP–14
P SUFFIX
CASE 646
NCP1205P2
AWLYYWW
1
A = Assembly Location
WL = Wafer Lot
YY = Year
WW = Work Week
ORDERING INFORMATION
Device
Package
Shipping
NCP1205P
PDIP–8
50 Units/Rail
NCP1205P2
PDIP–14
25 Units/Rail
© Semiconductor Components Industries, LLC, 2002
April, 2002 – Rev. 2
1
Publication Order Number:
NCP1205/D
1 page  
NCP1205
VCC Pin 13
Startup
HV 1
NC 2
Over Voltage
Protection (VCC > 40 V)
Last Pulse of Demag
after 4 µs
Internal VCC
Internal Regulator
UVLOH = 15 V
UVLOL = 7.2 V
14
13 VCC
Demag 3
FB 4
Ct 5
OVP 6
NC 7
DEMAG ?
Rf
Internal Clamp
Verr Max = 3 V
Ri
– Verr Min = 10 mV
+ OVP
1/3
Clock
R Flip–Flop Q
+
–
2.5 V
D
Current Comparator
Driver
200 ns L.E.B
12 DRV
11 Isense
10 Gnd
Over Current
Protection (OCP)
V(–) < 1.5 V
+
–
1V
Verr
VCO Feedback
Toff = f (Verr)
Max Toff = f (Ct)
VCC Pin 13
35 V Zener
9 NC
8 NC
Lasts more than 128 ms?
––> Protection Circuitry
2.0 k
OVP
2.8 V
+
–
18 k
Figure 4. Internal Circuit Architecture for DIP14 Version
http://onsemi.com
5
5 Page 
NCP1205
If we now enter this formula into a spreadsheet, we can easily plot the switching frequency versus the output power demand:
250000
200000
150000
Fmax
100000
Transition
BCM to VFM
Fmax
50000
0
0
VCO Action
5 10 15
OUTPUT POWER (W)
20
Figure 12. A Typical Behavior of Free Running Systems
with a Smooth Frequency Foldback with the NCP1205
The typical above diagram shows how the frequency
moves with the output power demand. The components used
for the simulation were: Vin = 300 V, Lp = 6.5 mH,
Vout = 10 V, Np/Ns = 12.
The red line indicates where the maximum frequency is
clamped. At this time, the VCO takes over and decreases the
switching frequency to the minimum value.
VCO Operation
The VCO is controlled from the Verr voltage. For Verr
levels above 1.0 V, the VCO frequency remains unchanged
at 125 kHz. As soon as Verr starts to decrease below 1.0 V,
the VCO frequency decreases with a typical small–signal
slope of –175 kHz/mV @ Verr = 500 mV down to
zero (typically at FB ≈ 3.3 V). The demagnetization
synchronization is however kept when the Toff expands.
The maximum switching frequency can be altered by
adjusting the Ct capacitor on pin 5. The 125 kHz maximum
operation ensures that the fundamental component stays
external from the international EMI CISPR–22
specification beginning.
The following drawing explains the philosophy behind
the idea:
Internal Verr
VCO Frequency
is Fixed at 130 kHz
VCO Frequency
can Decrease
BCM Mode
Peak current
can change
Peak Current is Fixed
3V
1V
0.75 V
Figure 13. When the Power Demand goes Low, the Peak Current is Frozen and the Frequency Decreases
Zero Crossing Detector
To detect the zero primary current, we make use of an
auxiliary winding. By coupling this winding to the primary,
we have a voltage image of the flux activity in the core.
Figure 13 details the shape of the signal in BCM.
The auxiliary winding for demagnetization needs to
be wired in Forward mode. However, the application
note describes an alternative solution showing how to wire
the winding in Flyback as well. As Figure 13 depicts, when
the MOSFET closes, the auxiliary winding delivers
(Naux/Np . Vin). At the switch opening, we couple the
auxiliary winding to the main output power winding and
thus deliver: (–Naux/Ns . Vout). When DCM occurs, the
ringing also takes place on the auxiliary winding. As soon
as the level crosses–up the internal reference level
(65 mV), a signal is internally sent to re–start the MOSFET.
Three different conditions can occur:
http://onsemi.com
11
11 Page | ||
| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet NCP1205.PDF ] | |
Hoja de datos destacado
| Número de pieza | Descripción | Fabricantes |
| NCP120 | Very Low Dropout Bias Rail CMOS Voltage Regulator |  ON Semiconductor |
| NCP1200 | PWM Current-Mode Controller for Low-Power Universal Off-Line Supplies | ON Semiconductor |
| NCP1200A | PWM Current-Mode Controller for Universal Off-Line Supplies Featuring Low Standby Power | ON |
| NCP1200AP100 | PWM Current-Mode Controller for Universal Off-Line Supplies Featuring Low Standby Power | ON Semiconductor |
| Número de pieza | Descripción | Fabricantes |
| SLA6805M | High Voltage 3 phase Motor Driver IC. |
 Sanken |
| SDC1742 | 12- and 14-Bit Hybrid Synchro / Resolver-to-Digital Converters. |
 Analog Devices |
|
DataSheet.es es una pagina web que funciona como un repositorio de manuales o hoja de datos de muchos de los productos más populares, |
| DataSheet.es | 2020 | Privacy Policy | Contacto | Buscar |