Fixed Frequency CurrentMode Controller for Flyback Converter NCP1239 The NCP1239 is a fixed-frequency current-mode controller www.onsemi.com featuring a high-voltage start-up current source to provide a quick and lossless power-on sequence. This function greatly simplifies the design of the auxiliary supply and the V capacitor by activating the CC internal start-up current source to supply the controller during start-up, transients, latch, stand-by etc. With a supply range up to 35 V, the controller hosts a jittered 65 or SOIC7 100-kHz switching circuitry operated in peak current mode control. CASE 751U When the power on the secondary side starts to decrease, the controller automatically folds back its switching frequency down to minimum PIN CONNECTIONS level of 26 kHz. As the power further goes down, the part enters skip cycle while limiting the peak current that insures excellent efficiency Fault 1 8 HV in light load condition. NCP1239 features a timer-based fault detection circuitry that FB 2 ensures a quasi-flat overload detection, independent of the input voltage. 6 CS 3 VCC Features 4 5 GND DRV Fixed-Frequency 65-kHz or 100-kHz Current-Mode Control Operation Frequency Foldback Down to 26 kHz and Skip Mode to Maximize MARKING DIAGRAM Performance in Light Load Conditions Adjustable Over Power Protection (OPP) Circuit 8 High-Voltage Current Source with Brown-Out (BO) Detection 1239xfff Internal Slope Compensation ALYWX Internal Fixed Soft-Start Frequency Jittering in Normal and Frequency Foldback Modes 1 64-ms Timer-Based Short-Circuit Protection with Auto-Recovery or Latched Operation 1239xfff = Specific Device Code x = A, B, C, D, E, F, G, H, I, Pre-Short Ready for Latched OCP Versions J, K, L, M, N, P, Q or R Latched OVP on VCC Autorecovery for C and E Versions fff = 065 or 100 A = Assembly Location Latched OVP/OTP Input for Improved Robustness L = Wafer Lot 35-V V Operation CC Y = Year 500 mA Peak Source/Sink Drive Capability W = Work Week = PbFree Package Internal Thermal Shutdown Extremely Low No-Load Standby Power Pin-to-Pin Compatible with the Existing NCP1236/1247 Series ORDERING INFORMATION These Devices are Pb-Free and are RoHS Compliant See detailed ordering and shipping information on page 26 of this data sheet. Typical Applications AC-DC Converters for TVs, Set-Top Boxes and Printers Offline Adapters for Notebooks and Netbooks Semiconductor Components Industries, LLC, 2016 1 Publication Order Number October, 2020 Rev. 25 NCP1239/D. NCP1239 Vbulk Vout OVP NCP1239 1 8 2 3 6 45 OPP NTC adjsut. Figure 1. Application Schematic (OPP Adjustment) Table 1. PIN FUNCTION DESCRIPTION Pin No. Pin Name Description 1 Fault The controller enters fault mode if the voltage of this pin is pulled above or below the fault thresholds. A precise pull up current source allows direct interface with an NTC thermistor. Fault detection triggers a latch. 2 FB Hooking an optocoupler collector to this pin will allow regulation. 3 CS This pin monitors the primary peak current but also offers an overpower compensation adjustment. When the CS pin is brought above 1.2 V, the part is permanently latched off. 4 GND The controller ground. 5 DRV The drivers output to an external MOSFET gate. 6 VCC This pin is connected to an external auxiliary voltage. An OVP comparator monitors this pin and offers a means to latch the converter in fault conditions. 7 NC Non-connected for improved creepage distance. 8 HV Connected to the bulk capacitor or rectified ac line, this pin powers the internal current source to deliver a start- up current. It is also used to provide the brown-out detection and the HV sensing for the Overpower protection. www.onsemi.com 2