The NCP1207A/B combines a true current mode modulator and ademagnetization detector to ensure full borderline/critical ConductionMode 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 fallsbelow a predetermined level. As this happens at low peak current, noaudible noise can be heard. For the NCP1207A, an internal 8.0 s timerprevents the free−run frequency to exceed 125 kHz (therefore below the150 kHz CISPR−22 EMI starting limit), while the skip adjustmentcapability lets the user select the frequency at which the burst foldbacktakes place. For the NCP1207B, the internal timer duration is reduced to4.5 s to allow operation at higher frequencies (up to 200 kHz).The Dynamic Self−Supply (DSS) drastically simplifies thetransformer design in avoiding the use of an auxiliary winding tosupply the NCP1207A/B. This feature is particularly useful inapplications where the output voltage varies during operation (e.g.battery chargers). Due to its high−voltage technology, the IC isdirectly connected to the high−voltage DC rail. As a result, theshort−circuit trip point is not dependent upon any VCC auxiliary level.The transformer core reset detection is done through an auxiliarywinding which, brought via a dedicated pin, also enables fastOvervoltage Protection (OVP). Once an OVP has been detected, theIC permanently latches off.Finally, the continuous feedback signal monitoring implementedwith an overcurrent fault protection circuitry (OCP) makes the finaldesign 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 s Minimum TOFF for NCP1207A,4.5 s 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
The product is in the warehouse and can be shipped immediately
***************************************************************
FOR MORE DETAILS , PLEASE CONTACT US, THANK YOU.
Email:
[email protected]
