On Semi’s NCP1250 is a highly integrated PWM controller with supply voltage up to 28V, peak current mode operation, switching circuit frequency of 65kHz or 100kHz, internal adjustable over power protection (OPP) circuit, slope compensation, fixed 4ms soft start , Standby power consumption at 220VAC is less than 100mW, EPS 2.0 compatible, mainly used in AC/DC converters of TV, set-top boxes and printers, offline adapters of notebook computers and netbooks. This article introduces the main features of NCP1250, block diagram, typical application circuit diagram and 40W evaluation board NCP1250B40WGEVB circuit diagram and bill of materials.
The NCP1250 is a highly integrated PWM controller capable of delivering a rugged and high performance offline power supply in a tiny TSOP−6 package. With a supply range up to 28 V, the controller hosts a jittered 65 kHz or 100 kHz switching circuitry operated in peak current mode control. When the power on the secondary side starts to decrease, the controller automatically folds back its switching frequency down to a minimum level of 26 kHz. As the power further goes down, the part enters skip cycle while limiting the peak current .
Over Power Protection (OPP) is a difficult exercise especially when no−load standby requirements drive the converter specifications. The ON proprietary integrated OPP lets you harness the maximum delivered power without affecting your standby performance simply via two external resistors. An Over Voltage Protection input is also combined on the same pin and protects the whole circuitry in case of optocoupler failure or adverse open loop operation.
Finally, a timer−based short−circuit protection offers the best protection scheme, letting you precisely select the protection trip point irrespective of a loose coupling between the auxiliary and the power windings.
Main features of NCP1250:
Fixed−Frequency 65 or 100 kHz Current−Mode Control Operation
Internal and Adjustable Over Power Protection (OPP) Circuit
Frequency Foldback Down to 26 kHz and Skip−Cycle in Light Load Conditions
Internal Ramp Compensation
Internal Fixed 4 ms Soft−Start
100 ms Timer−Based Auto−Recovery Short−Circuit Protection
Frequency Jittering in Normal and Frequency Foldback Modes
Option for Auto−Recovery or Latched Short−Circuit Protection
OVP Input for Improved Robustness
Up to 28 V VCC Operation
+300 mA / −500 mA Source/Sink Drive Capability
Less than 100 mW Standby Power at High Line
EPS 2.0 Compliant
These are Pb−Free Devices
Typical applications of NCP1250:
ac−dc Converters for TVs, Set−top Boxes and Printers
Offline Adapters for Notebooks and Netbooks
Figure 1. NCP1250 block diagram
Figure 2. Typical application circuit diagram of NCP1250
40W Evaluation Board NCP1250B40WGEVB
The NCP1250 is a highly integrated PWM controller capable of delivering a rugged and high performance offline power supply in a tiny TSOP-6 package. With a supply range up to 28 V, the controller hosts a jittered 65 kHz or 100 kHz switching circuitry operated in peak current mode control. When the power on the secondary side starts to decrease, the controller automatically folds back its switching frequency down to a minimum level of 26 kHz. As the power further goes down, the part enters skip cycle while limiting the peak current .
Over Power Protection (OPP) is a difficult exercise especially when no-load standby requirements drive the converter specifications. The ON proprietary integrated OPP lets you harness the maximum delivered power without affecting your standby performance simply via two external resistors. An Over Voltage Protection input is also combined on the same pin and protects the whole circuitry in case of optocoupler failure or adverse open loop operation.
Evaluation Board Description
Figure 3. 40W Evaluation Board NCP1250B40WGEVB Outline Drawing
Figure 4. 40W evaluation board NCP1250B40WGEVB circuit diagram
Figure Evaluation Board NCP1250B40WGEVB Bill of Materials:
For details, see:
http://www.onsemi.cn/pub_link/Collateral/NCP1250-D.PDF
The Links: NL10276AC30-58F G220SW01-V0