onsemi NCP1207BDR2G

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 μs 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 μs 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. The NCP1207A/B implements a standard current mode architecture where the switch--off time is dictated by the peak current setpoint whereas the core reset detection triggers the turn--on event. This component represents the ideal candidate where low part--count is the key parameter, particularly in low--cost AC/DC adapters, consumer electronics, auxiliary supplies, etc. Due to its high--performance High--Voltage technology, the NCP1207A/B incorporates all the necessary components / features needed to build a rugged and reliable Switch--Mode Power Supply (SMPS):

• Transformer core reset detection: borderline / critical operation is ensured whatever the operating conditions are. As a result, there are virtually no primary switch turn--on losses and no secondary diode recovery losses. The converter also stays a first--order system and accordingly eases the feedback loop design.
• Quasi--resonant operation: by delaying the turn--on event, it is possible to re--start the MOSFET in the minimum of the drain--source wave, ensuring reduced EMI / video noise perturbations. In nominal power conditions, the NCP1207A/B operates in Borderline Conduction Mode (BCM) also called Critical Conduction Mode.
• Dynamic Self--Supply (DSS): due to its Very High Voltage Integrated Circuit (VHVIC) technology, the NCP1207A/B allows for a direct pin connection to the high--voltage DC rail. A dynamic current source charges up a capacitor and thus provides a fully independent VCC level to the NCP1207A/B. As a result, there is no need for an auxiliary winding whose management is always a problem in variable output voltage designs (e.g. battery chargers).
• Overvoltage Protection (OVP): by sampling the plateau voltage on the demagnetization winding, the NCP1207A/B goes into latched fault condition whenever an over--voltage condition is detected. The controller stays fully latched in this position until the VCC is cycled down 4.0 V, e.g. when the user un--plugs the power supply from the mains out

• 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 μs Minimum TOFF for NCP1207A, 4.5 μs 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

• 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.)