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PWM Current-Mode Controller for Free Running Quasi-Resonant Operation
NCP1207A, NCP1207B
The NCP1207A/B combines a true current mode modulator and a demagnetization detector to ensure full borderline/critical Conduction Mode in any load/line conditions and minimum drain voltage switching (Quasi−Resonant operation). Due to its inherent skip cycle capability, the controller enters burst mode as soon as the power demand falls below a predetermined level. As this happens at low peak current, no audible noise can be heard. For the NCP1207A, an internal 8.0 ms timer prevents the free−run frequency to exceed 125 kHz (therefore below the 150 kHz CISPR−22 EMI starting limit), while the skip adjustment capability lets the user select the frequency at which the burst foldback takes place. For the NCP1207B, the internal timer duration is reduced to 4.5 ms to allow operation at higher frequencies (up to 200 kHz).
The Dynamic Self−Supply (DSS) drastically simplifies the transformer design in avoiding the use of an auxiliary winding to supply the NCP1207A/B. This feature is particularly useful in applications where the output voltage varies during operation (e.g. battery chargers). Due to its high−voltage technology, the IC is directly connected to the high−voltage DC rail. As a result, the short−circuit trip point is not dependent upon any VCC auxiliary level.
The transformer core reset detection is done through an auxiliary winding which, brought via a dedicated pin, also enables fast Overvoltage Protection (OVP). Once an OVP has been detected, the IC permanently latches off.
Finally, the continuous feedback signal monitoring implemented with an overcurrent fault protection circuitry (OCP) makes the final design rugged and reliable.
Features
• Free−Running Borderline/Critical Mode Quasi−Resonant Operation • Current−Mode with Adjustable Skip−Cycle Capability • No Auxiliary Winding VCC Operation • Auto−Recovery Overcurrent Protection • Latching Overvoltage Protection • External Latch Triggering, e.g. Via Overtemperature Signal • 500 mA Peak Current Source/Sink Capability • Undervoltage Lockout for VCC Below 10 V • Internal 1.0 ms Soft−Start • Internal 8.0 ms Minimum TOFF for NCP1207A,
4.5 ms Minimum TOFF for NCP1207B
• Adjustable Skip Level • Internal Temperature Shutdown • Direct Optocoupler Connection • SPICE Models Available for TRANsient Analysis • These are Pb−Free and Halide−Free Devices
8 1
8 1
SOIC−8 D SUFFIX CASE 751
SOIC−7 D SUFFIX CASE 751U
MARKING DIAGRAM 8
1207A ALYW
G
1
8
1207B ALYW
G 1
8
8 1
PDIP−8 P SUFFIX CASE 626
1207AP AWL
YYWWG
1
1207A/B/AP = Device Code
A
= Assembly Location
L, WL
= Wafer Lot
Y, YY
= Year
W, WW G or G
= Work Week = Pb−Free Package
PIN CONNECTIONS
Dmg 1 FB 2 CS 3
GND 4
8 HV 7 NC 6 VCC 5 Drv
ORDERING INFORMATION
Device
Package
Shipping†
NCP1207ADR2G SOIC−8 (Pb−Free)
2500/Tape & Reel
NCP1207APG
PDIP−8 50 Units / Tube (Pb−Free)
NCP1207BDR2G SOIC−7 (Pb−Free)
2500/Tape & Reel
†For information on tape and reel specifications, including part orientation and tape sizes, please refer to our Tape and Reel Packaging Specifications Brochure, BRD8011/D.
Typical Applications
• AC−DC Adapters for Notebooks, etc. • Offline Battery Chargers • Consumer Electronics
(DVD Players, Set−Top Boxes, TVs, etc.)
• Auxiliary Power Supplies
(USB, Appliances, TVs, etc.)
© Semiconductor Components Industries, LLC, 2016
1
September, 2022 − Rev. 15
Publication Order Number: NCP1207A/D
Universal Network
NCP1207A, NCP1207B
*
+ OVP and NCP1207A/B
Demag
1
8
2
7
3
6
4
5
+
Vout +
GND
*Please refer to the application information section Figure 1. Typical Application
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ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Pin PinName
Function
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ 1
Demag Core reset detection and OVP
Description The auxiliary FLYBACK signal ensures discontinuous operation and offers a fixed
overvoltage detection level of 7.2 V.
2
FB
Sets the peak current setpoint By connecting an Optocoupler to this pin, the peak current setpoint is adjusted
accordingly to the output power demand. By bringing this pin below the internal
skip level, device shuts off.
3
CS
Current sense input and skip This pin senses the primary current and routes it to the internal comparator via an
cycle level selection
L.E.B. By inserting a resistor in series with the pin, you control the level at which
the skip operation takes place.
4
GND
The IC ground
−
5
Drv
Driving pulses
The driver’s output to an external MOSFET.
6
VCC
Supplies the IC
7
NC
−
This pin is connected to an external bulk capacitor of typically 10 mF.
This unconnected p.