NCP1237 ONSEMI [ON Semiconductor], NCP1237 Datasheet
NCP1237
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NCP1237 Summary of contents
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... Fixed Frequency Current Mode Controller for Flyback Converters The NCP1237 is a new generation of the NCP12xx fixed−frequency current−mode controllers featuring Dynamic Self−Supply (DSS), pin−to−pin compatible with the previous generation. The DSS function greatly simplifies the design of the auxiliary supply ...
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... GND DRV 5 Figure 1. Pinout TYPICAL APPLICATION EXAMPLE HV NCP1237 VCC DRV Figure 2. Typical Application Pull the pin up or down to latch−off the controller. An internal current source allows the direct connection of an NTC for over temperature detection A pull−down optocoupler controls the output regulation. ...
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SIMPLIFIED INTERNAL BLOCK SCHEMATIC − NTC V OVP I NTC − Latch + + OTP Vclamp Brown−out FB VDD R FB(up sample + − I ...
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MAXIMUM RATINGS Supply Pin (pin 6) (Note 2) Voltage range Current range High Voltage Pin (pin 8) (Note 2) Voltage range Current range Driver Pin (pin 5) (Note 2) Voltage range Current range All other pins (Note 2) Voltage range ...
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ELECTRICAL CHARACTERISTICS (For typical values unless otherwise noted) CC Characteristics HIGH VOLTAGE CURRENT SOURCE Minimum voltage for current source operation Current flowing out of V pin @ Off−state leakage ...
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ELECTRICAL CHARACTERISTICS (For typical values unless otherwise noted) CC Characteristics CURRENT SENSE Input Bias Current Maximum internal current setpoint Threshold for immediate fault protection activation Propagation delay from V detection to DRV off ILIM Leading ...
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ELECTRICAL CHARACTERISTICS (For typical values unless otherwise noted) CC Characteristics LATCH−OFF INPUT High threshold Low threshold Current source for direct NTC connection During normal operation During soft−start Blanking duration on high latch detection Blanking duration ...
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... Introduction The NCP1237 includes all of the necessary features to build a safe and efficient power supply based on a fixed−frequency flyback converter particularly well suited for applications where low part count is a key parameter, without sacrificing safety. • Current−Mode Operation with slope compensation: ...
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... Normal operation: As long as the feedback voltage is within the regulation range, the NCP1237 runs at a fixed frequency (with jittering) in current−mode control, where the peak current (sensed on the CS pin) is set by the voltage on the FB pin. A fixed ramp compensation is applied internally to prevent sub−harmonic oscillations from occurring. The V ...
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... High−Voltage Current Source (Dynamic Self−Supply) with Built−in Brown−out Detection The NCP1237 HV pin can be connected either to the rectified bulk voltage the ac line through a rectifier. Startup HV VCC Figure 4. HV Startup Current Source Functional Schematic DETAILED DESCRIPTION Control I start ...
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At startup, the current source turns on when the voltage on the HV pin is higher than V , and turns off when V HV(min) reaches turns on again when V CC(on This sequence repeats ...
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To reduce the power dissipation in case the V shorted to GND (in case of V capacitor failure, or external CC pulldown disable the controller), the startup CC current is lowered when V is below V CC ...
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When V crosses the V threshold, the controller HV HV(start) can start immediately. When it crosses HV(start) V HV(stop) Starts at next V DRV CC(ON) Figure 7. AC Input Brown−out Timing Diagram The same scheme is ...
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Blanked voltage surge HV(OV1) V HV(OV2) OVP detected One Shot DRV Figure 8. AC Input Line Overvoltage Timing Diagram HV HV timer timer starts restarts t HV http://onsemi.com 14 time Restarts at V CC(on) time time ...
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... A OSC jitter Clamped Driver The supply voltage for the NCP1237 can be as high but most of the MOSFETs that will be connected to the DRV pin cannot tolerate a gate−to−source voltage greater than their gate. The driver pin is therefore clamped safely below 16 V ...
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... CURRENT−MODE CONTROL WITH OVERPOWER COMPENSATION AND SOFT−START Current Sensing NCP1237 is a current−mode controller, which means that the FB voltage sets the peak current flowing in the inductance and the MOSFET. This is done through a PWM comparator: the current is sensed across a resistor and the resulting voltage is applied to the CS pin ...
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Each time the controller is starting (i.e. the controller was off and starts, or restarts, when V CC soft−start is applied: the current sense setpoint is linearly increased from 0 (the minimum level can be higher than ...
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Compensation for Overpower Detection The power delivered by a flyback power supply is proportional to the square of the peak current OUT (in discontinuous conduction mode ...
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... The ratio from the FB voltage to the current sense setpoint is typically 5. This means that the FB voltage corresponding order to allow the NCP1237 to operate in CCM with a duty cycle above 50%, a fixed slope compensation is internally applied to the current−mode control. The slope appearing on the internal voltage setpoint for the PWM ...
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OVERCURRENT PROTECTION WITH FAULT TIMER Classical Overcurrent Protection When an overcurrent occurs on the output of the power supply, the feedback loop asks for more power than the controller can deliver, and the CS setpoint reaches V When this event ...
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Overcurrent Output Load applied Max Load Fault Flag Fault timer starts CC(on) V CC(min) DRV Fault timer t fault t fault Figure 18. Autorecovery Timer−Based Protection Mode Fault disappears Restart V At CC(on) (new burst cycle if ...
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In the latched version (Figure 19), the controller can restart only if a brown−out Output Load Overcurrent applied Max Load Fault Flag Fault timer starts CC(on) V CC(min) DRV Fault timer t fault ...
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Dual−Level Overcurrent Protection For some applications (e.g. printer adapters necessary that the controller maintains regulation while it has detected a first level of overload. This is to authorize a transient peak power higher than the maximum continuous output ...
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The typical level at which this transient peak timer starts 0.5 V, which gives half the maximum output CS(tran) power in DCM. Output Load Max transient Load Max continuous Load DRV Timer duration t tran t fault ...
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Output Load Max transient Load Max continuous Load Transient peak timer DRV Timer duration t tran t fault Figure 22. Too Long Transient Peak Power Delivery Transient peak power starts http://onsemi.com 25 time Controller enters Protection mode time time ...
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Frequency Foldback In order to improve the efficiency in light load conditions, the frequency of the internal oscillator is linearly reduced from its nominal value down to f OSC(min) foldback starts when the voltage on FB pin ...
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FB(fold) V skip(out) V skip(in) Enters skip DRV CS setpoint Figure 25. Skip Cycle with Soft−Skip Timing Diagram If during the Soft−Skip duration the FB voltage goes above V , the Soft−Skip ends instantaneously, and the FB(fold) ...
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Latch−off Input VDD I NTC Latch clamp Soft−start The Latch pin is dedicated to the latch−off function. It includes two thresholds that define a working window, between a high latch and a low latch. Within these 2 ...
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CC(on) V CC(min) Internal Latch Signal Latch signal pre-start phase DRV Switching allowed (no latch event) Figure 27. Latch−off Function Timing Diagram Temperature shutdown The die includes a temperature shutdown protection with a turn−off threshold guaranteed between ...
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HV Startup Current Source No TSD TSD Stop Figure 28. HV Startup Current Source State Diagram STATE DIAGRAMS start1 V < CC(inhibit) TSD TSD V < CC(min) TSD http://onsemi.com 30 > V CC(inhibit) ...
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Controller Operation (Latched Version: A Option) S Brown-out S HV OVP S TSD Stopped S Brown-out S VCC reset S High Latch S Low Latch Latch S High Latch S Low Latch Figure 29. Controller Operation State Diagram (Latched Overload ...
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... Figure 30. Controller Operation State Diagram (Autorecovery Overload Protection) Table 1. ORDERING INFORMATION Part No. Overload Protection NCP1237AD65R2G Latched NCP1237BD65R2G Autorecovery †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. High Latch V > ...
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... The product described herein (NCP1237) may be covered by one or more of the following U.S. patents: 5,073,850, 6,271,735, 6,362,067, 6,385,060, 6,597,221, 6,633,193, 6,587,351, 6,940,320, 7,638,405. There may be other patents pending. Soft−Skip is a trademark of Semiconductor Components Industries, LLC (SCILLC). ON Semiconductor and are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC reserves the right to make changes without further notice to any products herein ...
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