NCP1236 Fixed Frequency Current Mode Controller for Flyback Converters The NCP1236 is a new fixed−frequency current−mode controller featuring Dynamic Self−Supply (DSS). This device is pin−to−pin compatible with the previous NCP12xx families. The DSS function greatly simplifies the design of the auxiliary supply and the VCC capacitor by activating the internal startup current source to supply the controller during transients. Due to frequency foldback, the controller exhibits excellent efficiency in light load condition while still achieving very low standby power consumption. Internal frequency jittering, ramp compensation, and a versatile latch input make this controller an excellent candidate for converters where components cost is the key constraints. In addition, the controller includes a new high voltage circuitry that combines a start−up current source and a brown−out detector able to sense the input voltage either from the rectified ac line or the dc filtered bulk voltage. The high voltage sensing circuitry is used for the overpower protection purposes as well. Overpower protection, overload protection, and next protective features increases safety level of the final application. Finally, due to a careful design, the precision of critical parameters is well controlled over the entire temperature range (−40C to +125C). Features Fixed−Frequency Current−Mode Operation with Built−In Ramp http://onsemi.com MARKING DIAGRAM 8 SOIC−7 CASE 751U 1 36Xff ALYWX G 36Xff = Specific Device Code X = A, B, C or D ff = 65 or 100 A = Assembly Location L = Wafer Lot Y = Year W = Work Week G = Pb−Free Package PIN CONNECTIONS Latch 1 8 HV 6 VCC 5 DRV FB 2 CS 3 GND 4 Compensation (Top View) 65 kHz or 100 kHz Oscillator Frequency Frequency Foldback then Skip Mode for Maximized Performance in ORDERING INFORMATION Light Load and Standby Conditions See detailed ordering and shipping information in the package Timer−Based Overload Protection with Latched (option A) or dimensions section on page 33 of this data sheet. Auto−Recovery (option B) Operation, Shortened Overload Timer for Increased Safety (options C and D), (see all options on page 2) High−voltage Current Source with Brown−Out Internal Thermal Shutdown detection and Dynamic Self−Supply, Simplifying the Pin−to−Pin Compatible with the Existing NCP12xx Design of the VCC Capacitor Series Frequency Modulation for Softened EMI Signature, These Devices are Pb−Free, Halogen Free/BFR Free including during Frequency Foldback mode and are RoHS Compliant Adjustable Overpower Compensation Typical Applications Latch−off Input for Severe Fault Conditions, Allowing AC−DC Adapters for Notebooks, LCD, and Printers Direct Connection of an NTC for Overtemperature Offline Battery Chargers Protection (OTP) Consumer Electronic Power Supplies VCC Operation up to 28 V, with Overvoltage Detection Auxiliary/Housekeeping Power Supplies $500 mA Peak Source / Sink Current Drive Capability 4.0 ms Soft−Start Semiconductor Components Industries, LLC, 2013 April, 2013 − Rev. 3 1 Publication Order Number: NCP1236/D NCP1236 TYPICAL APPLICATION EXAMPLE VOUT VIN (dc) LATCH FB HV NCP1236 CS VCC GND DRV Figure 1. Flyback Converter Application Using the NCP1236 OPTIONS Part Frequency OCP Fault Fault Timer Autorecovery Timer A 65 kHz Latched 128 ms 1s A 100 kHz Latched 128 ms 1s B 65 kHz Autorecovery 128 ms 1s B 100 kHz Autorecovery 128 ms 1s C 65 kHz Latched 32 ms 1.5 s C 100 kHz Latched 32 ms 1.5 s D 65 kHz Autorecovery 32 ms 1.5 s D 100 kHz Autorecovery 32 ms 1.5 s Option NCP1236 PIN FUNCTION DESCRIPTION Pin No Pin Name Function 1 LATCH Latch−Off Input 2 FB Feedback 3 CS Current Sense 4 GND 5 DRV Drive output 6 VCC VCC input 8 HV High−voltage pin Pin Description 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 An optocoupler collector to ground controls the output regulation. This Input senses the Primary Current for current−mode operation, and Offers an overpower compensation adjustment. IC Ground Drives external MOSFET This supply pin accepts up to 28 Vdc, with overvoltage detection Connects to the bulk capacitor or the rectified AC line to perform the functions of Start−up Current Source, Dynamic Self−Supply and brown−out detection http://onsemi.com 2 NCP1236 SIMPLIFIED INTERNAL BLOCK SCHEMATIC + − + INTC Latch + 1 kW tLatch(OVP) HV sample HV dc VCC OVP − + HV TSD TSD blanking tLatch(OTP) Dual HV start−up current source S VOTP R Vclamp BO blanking VOVP INTC Brown−out − + VDD Q Latch TSD HV current Reset UVLO VCC VDD management Start OVP Reset UVLO VDD Soft−start end IC Start VCC OVP Brown−out Reset VCC VFB(ref) − + + Vskip 20 kW /5 slope comp. FB HV sample PWM + − V to I IOPC = 0.5m x (VHV − 125) Jitter Sawtooth Soft−start + − Stop Oscillator − + + Soft−start ramp Start t End SSTART Reset VFB(OPC) DCMAX IC Start Clamp DMAX IC Stop S Soft−start end blanking tLEB Foldback Q R CS + blanking tBCS DRV + − ILIMIT VILIM IC stop GND UVLO ILIMIT DMAX S Q R + Fault Flag Brown−out Protection Mode release + − For Autorecovery protection mode only VCS(stop) timer PWM tfault timer Fault tautorec Brown−out Reset Figure 2. Simplified Internal Block Schematic http://onsemi.com 3 Latch TSD NCP1236 MAXIMUM RATINGS Symbol Value Unit Supply Pin (pin 6) (Note 2) Voltage range Current range Rating VCCMAX ICCMAX –0.3 to 28 $30 V mA High Voltage Pin (pin 8) (Note 2) Voltage range Current range VHVMAX IHVMAX –0.3 to 500 $20 V mA Driver Pin (pin 5) (Note 2) Voltage range Current range VDRVMAX IDRVMAX –0.3 to 20 $1000 V mA VMAX IMAX –0.3 to 10 $10 V mA All other pins (Note 2) Voltage range Current range Thermal Resistance SOIC−7 Junction−to−Air, low conductivity PCB (Note 3) Junction−to−Air, medium conductivity PCB (Note 4) Junction−to−Air, high conductivity PCB (Note 5) RJ−A Temperature Range Operating Junction Temperature Storage Temperature Range TJMAX TSTRGMAX ESD Capability (Note 1) Human Body Model (All pins except HV) Machine Model 162 147 115 −40 to +150 −60 to +150 2000 200 C/W C V Stresses exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the Recommended Operating Conditions is not implied. Extended exposure to stresses above the Recommended Operating Conditions may affect device reliability. 1. This device series contains ESD protection and exceeds the following tests: Human Body Model 2000 V per JEDEC standard JESD22, Method A114E Machine Model Method 200 V per JEDEC standard JESD22, Method A115A 2. This device contains latch−up protection and exceeds 100 mA per JEDEC Standard JESD78 3. As mounted on a 80 x 100 x 1.5 mm FR4 substrate with a single layer of 50 mm2 of 2 oz copper traces and heat spreading area. As specified for a JEDEC 51−1 conductivity test PCB. Test conditions were under natural convection or zero air flow. 4. As mounted on a 80 x 100 x 1.5 mm FR4 substrate with a single layer of 100 mm2 of 2 oz copper traces and heat spreading area. As specified for a JEDEC 51−2 conductivity test PCB. Test conditions were under natural convection or zero air flow. 5. As mounted on a 80 x 100 x 1.5 mm FR4 substrate with a single layer of 650 mm2 of 2 oz copper traces and heat spreading area. As specified for a JEDEC 51−3 conductivity test PCB. Test conditions were under natural convection or zero air flow. http://onsemi.com 4 NCP1236 ELECTRICAL CHARACTERISTICS (For typical values TJ = 25C, for min/max values TJ = −40C to +125C, VHV = 125 V, VCC = 11 V unless otherwise noted) Characteristics Test Condition Symbol Min Typ Max Unit VHV(min) − 30 60 V Istart1 Istart2 0.2 3 0.5 6 0.8 9 mA Istart(off) − 25 50 mA Turn−on threshold level, VCC going up HV current source stop threshold VCC(on) 11.0 12.0 13.0 V HV current source restart threshold VCC(min) 9.5 10.5 11.5 V Turn−off threshold VCC(off) 8.5 9.5 10.5 V HIGH VOLTAGE CURRENT SOURCE Minimum voltage for current source operation Current flowing out of VCC pin VCC = 0 V VCC = VCC(on) − 0.5 V Off−state leakage current VHV = 500 V SUPPLY Overvoltage threshold VCC(ovp) 25 26.5 28 V Blanking duration on VCC(off) and VCC(ovp) detection (Note 7) tVCC(blank) 7 10 13 ms VCC decreasing level at which the internal logic resets VCC(reset) 3.6 5.0 6.0 V VCC level for ISTART1 to ISTART2 transition VCC(inhibit) 0.4 1.0 1.6 V ICC1 ICC1 ICC2 ICC2 ICC3 ICC4 1.2 1.2 1.9 2.2 0.67 0.4 1.8 1.9 2.5 2.9 0.9 0.7 2.2 2.3 3.2 3.6 1.13 1.0 mA VHV(start) VHV(stop) 92 79 107 92 122 105 V tHV 47 68 90 ms Oscillator frequency fOSC 60 92 65 100 70 108 kHz Maximum duty cycle DMAX 75 80 85 % Frequency jittering amplitude, in percentage of FOSC Ajitter $4 $6 $8 % Frequency jittering modulation frequency Fjitter 85 125 165 Hz Internal current consumption (Note 6) DRV open, VFB = 3 V, 65 kHz DRV open, VFB = 3 V, 100 kHz Cdrv = 1 nF, VFB = 3 V, 65 kHz Cdrv = 1 nF, VFB = 3 V, 100 kHz Off mode (skip or before start−up) Fault mode (fault or latch) BROWN−OUT Brown−Out thresholds VHV going up VHV going down Timer duration for line cycle drop−out OSCILLATOR OUTPUT DRIVER Rise time, 10% to 90 % of VCC VCC = VCC(min) + 0.2 V, CDRV = 1 nF trise − 40 70 ns Fall time, 90% to 10 % of VCC VCC = VCC(min) + 0.2 V, CDRV = 1 nF tfall − 40 70 ns Current capability VCC = VCC(min) + 0.2 V, CDRV = 1 nF DRV high, VDRV = 0 V DRV low, VDRV = VCC IDRV(source) IDRV(sink) − − 500 500 − − mA Clamping voltage (maximum gate voltage) VCC = VCCmax – 0.2 V, DRV high, RDRV = 33 kW, Cload = 220 pF VDRV(clamp) 11 13.5 16 V 6. Internal supply current only, current in FB pin not included (current flowing in GND pin only). 7. Guaranteed by design. http://onsemi.com 5 NCP1236 ELECTRICAL CHARACTERISTICS (continued) (For typical values TJ = 25C, for min/max values TJ = −40C to +125C, VHV = 125 V, VCC = 11 V unless otherwise noted) Characteristics Test Condition Symbol Min Typ Max Unit VCC = VCC(min) + 0.2 V, RDRV = 33 kW, DRV high VDRV(drop) − − 1 V OUTPUT DRIVER High−state voltage drop CURRENT SENSE Input Bias Current VCS = 0.7 V Ibias − 0.02 − mA Maximum internal current setpoint VFB > 3.5 V VILIM 0.66 0.7 0.74 V Propagation delay from VIlimit detection to DRV off VCS = VILIM tdelay − 80 110 ns tLEB 190 250 310 ns VCS(stop) 0.95 1.05 1.15 V Leading Edge Blanking Duration for VCS(stop) tBCS 90 120 150 ns Slope of the compensation ramp Scomp(65kHz) Scomp(100kHz) − − −32.5 −50 − − mV / ms tSSTART 2.8 4.0 5.2 ms KOPC − 0.54 − mA / V Leading Edge Blanking Duration for VILIM Threshold for immediate fault protection activation Soft−start duration From 1st pulse to VCS = VILIM OVERPOWER COMPENSATION VHV to IOPC conversion ratio Current flowing out of CS pin VHV = 125 V VHV = 162 V VHV = 325 V VHV = 365 V IOPC(125) IOPC(162) IOPC(325) IOPC(365) − − − 105 0 20 110 130 − − − 150 mA FB voltage above which IOPC is applied VHV = 365 V VFB(OPCF) 2.12 2.35 2.58 V FB voltage below which is no IOPC applied VHV = 365 V VFB(OPCE) − 2.15 − V tWD(OPC) − 32 − ms RFB(up) 15 20 25 kW VFB to internal current setpoint division ratio KFB 4.7 5 5.3 − Internal pull−up voltage on the FB pin VFB(ref) 4.3 5 5.7 V Watchdog timer for dc operation FEEDBACK Internal pull−up resistor TJ = 25C OVERCURRENT PROTECTION Fault timer duration From CS reaching VILIMIT to DRV stop tfault 98 128 168 ms Fault timer duration (for the C version only) From CS reaching VILIMIT to DRV stop tfault 16 32 48 ms Autorecovery mode latch−off time duration tautorec 0.85 1.00 1.35 s Autorecovery mode latch−off time duration (for the C version only) tautorec 1.0 1.5 2.0 s 6. Internal supply current only, current in FB pin not included (current flowing in GND pin only). 7. Guaranteed by design. http://onsemi.com 6 NCP1236 ELECTRICAL CHARACTERISTICS (continued) (For typical values TJ = 25C, for min/max values TJ = −40C to +125C, VHV = 125 V, VCC = 11 V unless otherwise noted) Characteristics Test Condition Symbol Min Typ Max Unit Feedback voltage threshold below which frequency foldback starts VFB(foldS) 1.8 2.0 2.2 V Feedback voltage threshold below which frequency foldback is complete VFB(foldE) 1.22 1.35 1.48 V VFB = Vskip(in) + 0.2 fOSC(min) 22 27 32 kHz VFB going down VFB going up Vskip(in) Vskip(out) 0.63 0.72 0.7 0.80 0.77 0.88 V High threshold VLatch going up VOVP 2.35 2.5 2.65 V Low threshold VLatch going down VOTP 0.76 0.8 0.84 V Current source for direct NTC connection During normal operation During soft−start VLatch = 0 V Blanking duration on high latch detection 65 kHz version 100 kHz version FREQUENCY FOLDBACK Minimum switching frequency SKIP−CYCLE MODE Feedback voltage thresholds for skip mode LATCH−OFF INPUT mA Blanking duration on low latch detection Clamping voltage ILatch = 0 mA ILatch = 1 mA INTC INTC(SSTART) 65 130 95 190 105 210 tLatch(OVP) 35 25 50 35 70 45 ms tLatch(OTP) − 350 − ms Vclamp0(Latch) Vclamp1(Latch) 1.0 2.0 1.2 2.4 1.4 3.0 V TTSD 135 150 165 C TTSD(HYS) 20 30 40 C TEMPERATURE SHUTDOWN Temperature shutdown (Note 7) TJ going up Temperature shutdown hysteresis (Note 7) TJ going down 6. Internal supply current only, current in FB pin not included (current flowing in GND pin only). 7. Guaranteed by design. http://onsemi.com 7 NCP1236 TYPICAL PERFORMANCE CHARACTERISTICS 40.00 35 38.00 30 36.00 25 32.00 Istart(off) (V) VHV(min) (V) 34.00 30.00 28.00 26.00 20 15 10 24.00 5 22.00 20.00 −50 −25 0 25 50 75 TEMPERATURE (C) 100 0 −50 125 120 105 115 100 110 95 105 100 95 25 50 75 TEMPERATURE (C) 100 125 90 85 80 90 −50 −25 0 25 50 75 100 125 75 −50 0 25 50 75 100 TEMPERATURE (C) TEMPERATURE (C) Figure 6. Brown−Out Device Stop Threshold VHV(stop) 0.75 1.15 0.74 1.13 0.73 1.11 0.72 1.09 0.71 0.70 0.69 1.05 1.03 1.01 0.67 0.99 0.66 0.97 −25 0 25 50 75 100 125 0.95 −50 −25 0 25 50 75 100 TEMPERATURE (C) TEMPERATURE (C) Figure 7. Maximum Internal Current Setpoint VILIM Figure 8. Threshold for Immediate Fault Protection Activation VCS(stop) http://onsemi.com 8 125 1.07 0.68 0.65 −50 −25 Figure 5. Brown−out Device Start Threshold VHV(start) VCS(stop) (V) VILIM (V) 0 Figure 4. Off−State Leakage Current Istart(off) VHV(stop) (V) VHV(start) (V) Figure 3. Minimum Current Source Operation VHV(min) −25 125 NCP1236 TYPICAL PERFORMANCE CHARACTERISTICS 300 110 290 100 280 270 80 260 tLEB (ns) tdelay (ns) 90 70 250 240 230 60 220 50 40 210 −50 −25 0 25 50 75 100 200 −50 125 −25 0 TEMPERATURE (C) Figure 9. Propagation Delay tdelay 100 125 5.20 22 5.10 21 VFB(ref) (V) RFB(up) (kW) 75 5.30 23 20 19 18 5.00 4.90 4.80 17 4.70 16 −50 −25 0 25 50 75 TEMPERATURE (C) 100 4.60 −50 125 Figure 11. FB Pin Internal Pull−up Resistor RFB(up) 70 105 69 104 68 103 67 102 66 101 65 64 62 97 61 96 0 25 50 75 TEMPERATURE (C) 100 25 50 75 TEMPERATURE (C) 100 125 99 98 −25 0 100 63 60 −50 −25 Figure 12. FB Pin Open Voltage VFB(ref) fOSC (kHz) fOSC (kHz) 50 Figure 10. Leading Edge Blanking Duration tLEB 24 15 25 TEMPERATURE (C) 95 −50 125 Figure 13. Oscillator Frequency fOSC for the 65 kHz version −25 0 25 50 75 TEMPERATURE (C) 100 Figure 14. Oscillator Frequency fOSC for the 100 kHz version http://onsemi.com 9 125 NCP1236 TYPICAL PERFORMANCE CHARACTERISTICS 85 2.20 84 2.15 83 2.10 VFB(foldS) (V) DMAX (%) 82 81 80 79 78 2.00 1.95 1.90 77 1.85 76 75 −50 2.05 −25 0 25 50 75 TEMPERATURE (C) 100 125 1.80 −50 1.45 0.75 50 75 100 125 0.73 1.40 Vskip(in) (V) VFB(foldE) (V) 0.77 1.35 1.30 0.71 0.69 0.67 1.25 0.65 −25 0 25 50 75 100 125 0.63 −50 −25 0 25 50 75 100 TEMPERATURE (C) TEMPERATURE (C) Figure 17. FB Pin Voltage Below Which Frequency Foldback is Complete VFB(foldE) Figure 18. FB Pin Skip−in Level Vskip(in) 0.88 30 0.86 29 125 28 fOSC(min) (kHz) 0.84 Vskip(out) (V) 25 Figure 16. FB Pin Voltage Below Which Frequency Foldback Starts VFB(foldS) 1.50 0.82 0.80 0.78 0.76 27 26 25 24 23 22 0.74 0.72 −50 0 TEMPERATURE (C) Figure 15. Maximum Duty Cycle DMAX 1.20 −50 −25 21 −25 0 25 50 75 100 125 20 −50 TEMPERATURE (C) −25 0 25 50 75 100 TEMPERATURE (C) Figure 20. Minimum Switching Frequency fOSC(min) Figure 19. FB Pin Skip−Out Level Vskip(out) http://onsemi.com 10 125 NCP1236 TYPICAL PERFORMANCE CHARACTERISTICS 2.60 150 2.55 145 2.50 2.45 VFB(OPCF) (V) IOPC(365) (mA) 140 135 130 125 120 2.40 2.35 2.30 2.25 2.20 115 2.15 110 −50 −25 0 25 50 75 100 125 2.10 −50 −25 0 TEMPERATURE (C) 100 125 Figure 22. FB Pin Level VFB(OPCF) Above Which is the Overpower Compensation Applied Figure 21. Maximum Overpower Compensating Current IOPC(365) Flowing Out of CS Pin 2.65 2.40 2.35 2.60 2.30 2.25 2.55 2.20 VOVP (V) VFB(OPCE) (V) 25 50 75 TEMPERATURE (C) 2.15 2.10 2.50 2.45 2.05 2.00 2.40 1.95 1.90 −50 −25 0 25 50 75 TEMPERATURE (C) 100 125 2.35 −50 Figure 23. FB Pin Level VFB(OPCE) Below Which is No Overpower Compensation Applied 1.34 0.84 1.32 0.83 25 50 75 TEMPERATURE (C) 100 125 1.30 0.82 0.81 Vclamp0 (V) VOTP (V) 0 Figure 24. Latch Pin High Threshold VOVP 0.85 0.80 0.79 0.78 1.28 1.26 1.24 1.22 0.77 1.20 0.76 0.75 −25 −50 −25 0 25 50 75 TEMPERATURE (C) 100 125 1.18 −50 −25 0 25 50 75 TEMPERATURE (C) 100 Figure 26. Latch Pin Open Voltage Vclamp0 Figure 25. Latch Pin Low Threshold VOTP http://onsemi.com 11 125 NCP1236 110 2.70 105 2.60 100 2.50 95 INTC (mA) 2.80 2.40 2.30 90 85 2.20 80 2.10 75 2.00 −50 −25 0 25 50 75 TEMPERATURE (C) 100 125 70 −50 −25 0 25 210 200 190 180 170 160 150 −25 75 100 Figure 28. Current INTC Sourced from the Latch Pin, Allowing Direct NTC Connection 220 140 −50 50 TEMPERATURE (C) Figure 27. Latch Pin Voltage Vclamp1 (Latch−off Pin is Sinking 1 mA) INTC(SSTART) (mA) Vclamp1 (V) TYPICAL PERFORMANCE CHARACTERISTICS 0 25 50 75 100 TEMPERATURE (C) Figure 29. Current INTC(SSTART) Sourced from the Latch Pin, During Soft−Start http://onsemi.com 12 125 125 NCP1236 APPLICATION INFORMATION Introduction The NCP1236 includes all necessary features to build a safe and efficient power supply based on a fixed−frequency flyback converter. It is particularly well suited for applications where low part count is a key parameter, without sacrificing safety. Current−Mode Operation with slope compensation: The primary peak current is permanently controlled by the FB voltage, ensuring maximum safety: the DRV turn−off event is dictated by the peak current setpoint. It also ensures that the frequency response of the system stays a first order if in DCM, which eases the design of the FB loop. The controller can be also used in CCM applications with a wide input voltage range thanks to its fixed ramp compensation that prevents the appearance of sub−harmonic oscillations. Fixed−Frequency Oscillator with Jittering: The NCP1236 is available in different frequency options to fit any application. The internal oscillator features a low−frequency jittering that helps passing the EMI limits by spreading out the energy content of frequency peaks in quasi−peak and average mode of measurement. Latched / Autorecovery Timer−Based Overload Protection: The overload protection depends only on the FB signal, making it able to work with any transformer, even with very poor coupling or high leakage inductance. When the fault timer elapses the device can be permanently latched in version A or the latch can be reset by an autorecovery restart of the device in version B. The power supply has to be stopped then restarted in order to resume operation, even if the overload condition disapears, in case of usage the A version of the NCP1236. The fault timer duration is internally fixed. The controller also latches off if the voltage on the CS pin reaches 1.5 times the maximum internal setpoint (allowing to detect winding short−circuits), with the same modes of releasing the latch in A or B version. High Voltage Start−Up Current Source with Brown−Out Detection: Due to ON Semiconductor’s Very High Voltage technology, the NCP1236 can be directly connected to the high input voltage. The start−up current source ensures a clean start−up and the Dynamic Self−Supply (DSS) restarting the start−up current source to supply the controller if the VCC voltage transiently drops. The high voltage pin also features a high−voltage sensing circuitry, which is able to turn the controller off if the input voltage is too low (brown−out condition). This protection works either with a DC input voltage or a rectified AC input voltage, and is independent of the high voltage ripple. Adjustable Overpower Compensation: The high input voltage sensed on the HV pin is converted into a current to build on the current sense voltage an offset proportional to the input voltage. By choosing the value of the resistor in series with the CS pin, the amount of compensation can be adjusted to the application. Frequency foldback then skip mode for light load operation: In order to ensure a high efficiency under all load conditions, the NCP1236 implements a frequency foldback for light load condition and a skip mode for extremely low load condition. The switching frequency is decreased down to 27 kHz to reduce switching losses. Extended VCC range: The NCP1236 accepts a supply voltage as high as 28 V, with an overvoltage threshold VCC(ovp) (typically 26.5 V) that latches the controller off. Clamped Driver Stage: Despite the high maximum supply voltage, the voltage on DRV pin is safely clamped below 16 V, allowing the use of any standard MOSFET, and reducing the current consumption of the controller. Dual Latch−off Input: The NCP1236 can be latched off by 2 ways: The voltage increase applied to its Latch pin (typically an overvoltage) or by a decrease this voltage. Thanks to the internal precise pull−up current source a NTC can be directly connected to the latch pin. This NTC will provide an overtemperature protection by decreasing its resistance and consequently the voltage at Latch pin, Soft−Start: At every start−up the peak current is gradually increased during 4.0 ms to minimize the stress on power components. Temperature Shutdown: The NCP1236 is internally protected against self−overheating: if the die temperature is too high, the controller shuts all circuitries down (including the HV start−up current source), allowing the silicon to cool down before attempting to restart. This ensures a safe behavior in case of failure. http://onsemi.com 13 NCP1236 Typical Operation Start−up: The HV start−up current source ensures the charging of the VCC capacitor up to the start−up threshold VCC(on), until the input voltage is high enough (above VHV(start)) to allow the switching to start. The controller then delivers pulses, starting with a soft−start period tSSTART during which the peak current linearly increases before the current−mode control takes over. During the soft−start period, the low level latch is ignored, and the latch current is double, to ensure a fast pre−charge of the Latch pin decoupling capacitor. Normal operation: As long as the feedback voltage is within the regulation range and VCC is maintained above VCC(min), the NCP1236 runs at a fixed frequency (with jittering) in current−mode control. The peak current (sensed on the CS pin) is set by the voltage on the FB pin. Fixed ramp compensation is applied internally to prevent sub−harmonic oscillations from occurring. Light load operation: When the FB voltage decreases below VFB(foldS), typically corresponding to a load of 33 % of the maximum load (for a DCM design), the switching frequency starts to decrease down to fOSC(min). By lowering the switching losses, this feature helps to improve the efficiency in light load conditions. The frequency jittering is enabled in light load operation as well. No load operation: When the FB voltage decreases below Vskip(in), typically corresponding to a load of 2 % of the maximum load, the controller enters skip mode. By completely stopping the switching while the feedback voltage is below Vskip(out), the losses are further reduced. This allows minimizing the power dissipation under extremely low load conditions. As the skip mode is entered at very light loads, for which the peak current is very small, there is no risk of audible noise. VCC can be maintained between VCC(on) and VCC(min) by the DSS, if the auxiliary winding does not provide sufficient level of VCC voltage under this condition. Overload: The NCP1236 features timer−based overload detection, solely dependent on the feedback information: as soon as the internal peak current setpoint hits the VILIM clamp, an internal timer starts to count. When the timer elapses, the controller stops and enter the protection mode, autorecovery for the B version (the controller initiates a new start−up after tautorec elapses), or latched for the A version (the latch is released if a brown−out event occurs or VCC is reset). Brown−out: The NCP1236 features a true AC line monitoring circuitry. It includes a minimum start−up threshold and an autorecovery brown−out protection; both of them independent of the ripple on the input voltage. It can even work with an unfiltered, rectified AC input. The thresholds are fixed, but they are designed to fit most of the standard AC−DC conversion applications. Latch−off: When the Latch input is pulled up (typically by an over−voltage condition), or pulled down (typically by an over−temperature condition, using the provided current source with an NTC), the controller latches off. A voltage higher than VCC(ovp) on the VCC pin has the same effect. The latch is released when a brown−out condition occurs, or when the VCC is reset. http://onsemi.com 14 NCP1236 DETAILED DESCRIPTION High−Voltage Current Source with Built−in Brown−out Detection The NCP1236 HV pin can be connected either to the rectified bulk voltage, or to the ac line through a rectifier. Start−up HV Istart TSD Control IC Start VCC + − + VCC(on) R Q S − + + VCC(min) blanking − + + UVLO tUVLO(blank) VCC(off ) − + + Reset VCC(reset) Figure 30. HV Start−up Current Source Functional Schematic condition, otherwise the power dissipation on the die would be too much. As a result, an auxiliary voltage source is needed to supply VCC during normal operation. The DSS is useful to keep the controller alive when no switching pulses are delivered, e.g. in brown−out condition, or to prevent the controller from stopping during load transients when the VCC might drop. If the voltage increases above the overvoltage protection threshold VCC(ovp), the controller is latched off. At start−up, the current source turns on when the voltage on the HV pin is higher than VHV(min), and turns off when VCC reaches VCC(on), then turns on again when VCC reaches VCC(min), until the input voltage is high enough to ensure a proper start−up, i.e. when VHV reaches VHV(start). The controller actually starts the next time VCC reaches VCC(on). Even though the DSS is able to maintain the VCC voltage between VCC(on) and VCC(min) by turning the HV start−up current source on and off, it can only be used in light load http://onsemi.com 15 NCP1236 VHV VHV(start) Waits next VCC(on) before starting VHV(min) time VCC VCC(on) VCC(min) HV current source = Istart1 HV current source = Istart2 VCC(inhibit) time DRV Figure 31. Start−up Timing Diagram time the HV current source will always turn on and off to maintain VCC between VCC(min) and VCC(on). For safety reasons, the start−up current is lowered when VCC is below VCC(inhibit), to reduce the power dissipation in case the VCC pin is shorted to GND (in case of VCC capacitor failure, or external pull−down on VCC to disable the controller). There are only two conditions for which the current source doesn’t turn on when VCC reaches VCC(min): the voltage on HV pin is too low (below VHV(min)), or a thermal shutdown condition (TSD) has been detected. In all other conditions, Brown−out protection When the input voltage goes below VHV(stop), a brown−out condition is detected, and the controller stops. The HV current source alternatively turns on and off to maintain VCC between VCC(on) and VCC(min) until the input voltage is back above VHV(start). http://onsemi.com 16 NCP1236 HV stop Brown-out or AC OVP detected Waits next VCC(on) before starting VCC time VCC(on) VCC(min) time DRV time Figure 32. Brown−out Timing Diagram When VHV crosses the VHV(start) threshold, the controller can start immediately. When it crosses VHV(stop), it triggers a timer of duration tHV: this ensures that the controller doesn’t stop in case of line cycle drop−out. http://onsemi.com 17 NCP1236 VHV Brown-out VHV(start) VHV(stop) time Starts at next VCC(ON) DRV t HV time Figure 33. AC Input Brown−out Timing Diagram Clamped Driver Oscillator with Maximum Duty Cycle and Frequency Jittering The supply voltage for the NCP1236 can be as high as 28 V, but most of the MOSFETs that will be connected to the DRV pin cannot accept more than 20 V on their gate. The driver pin is therefore clamped safely below 16 V. This driver has a typical current capability of $500 mA. The NCP1236 includes an oscillator that sets the switching frequency with an accuracy of $7%. Two frequency options can be ordered: 65 kHz and 100 kHz. The maximum duty cycle of the DRV pin is 80%, with an accuracy of $7%. In order to improve the EMI signature, the switching frequency jitters $6% around its nominal value, with a triangle−wave shape and at a frequency of 125 Hz. This frequency jittering is active even when the frequency is decreased to improve the EMI in light load condition. VCC Clamp DRV signal fOSC fOSC + 6 Nominal fOSC fOSC − 6 Figure 35. Clamped Driver Time 8% (125 Hz) Figure 34. Frequency Jittering http://onsemi.com 18 DRV NCP1236 CURRENT−MODE CONTROL WITH OVERPOWER COMPENSATION AND SOFT−START Current sensing input of the PWM comparator through a 250 ns LEB block. On the other input the FB voltage divided by 5 sets the threshold: when the voltage ramp reaches this threshold, the output driver is turned off. The maximum value for the current sense is 0.7 V, and it is set by a dedicated comparator. NCP1236 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. It is applied to one VFB(ref) KFB + − RFB(up) PWM Jitter Soft−start + − Oscillator Soft−start ramp Start tSSTART Reset FB DCMAX IC Start IC Stop S Q R blanking tLEB CS DRV Stage + − + VILIM IC stop UVLO blanking tBCS + − + Protection Mode VCS(stop) HV stop Latch TSD Fault Figure 36. Current Sense Block Schematic Each time the controller is starting, i.e. the controller was off and starts – or restarts – when VCC reaches VCC(on), a soft−start is applied: the current sense setpoint is linearly increased from 0 (the minimum level can be higher than 0 because of the LEB and propagation delay) until it reaches VILIM (after a duration of tSSTART), or until the FB loop imposes a setpoint lower than the one imposed by the soft−start (the 2 comparators outputs are OR’ed). The soft−start ramp signal is generated by the D/A converter in the NCP1236, that’s why there are observable 15 discrete steps instead the truly linearly increasing current setpoint ramp. http://onsemi.com 19 NCP1236 VFB VFB(fault) Time Soft-start ramp VFB takes over soft-start VILIM Time tSSTART CS Setpoint VILIMI Time Figure 37. Soft−Start Overpower compensation Under some conditions, like a winding short−circuit for instance, not all the energy stored during the on time is transferred to the output during the off time, even if the on time duration is at its minimum (imposed by the propagation delay of the detector added to the LEB duration). As a result, the current sense voltage keeps on increasing above VILIM, because the controller is blind during the LEB blanking time. Dangerously high current can grow in the system if nothing is done to stop the controller. That’s what the additional comparator, that senses when the current sense voltage on CS pin reaches VCS(stop) (= 1.5 x VILIM), does: as soon as this comparator toggles, the controller immediately enters the protection mode (latched or autorecovery according to the chosen option). The power delivered by a flyback power supply is proportional to the square of the peak current in the discontinuous conduction mode: P OUT + 1 @ h @ L p @ F SW @ I p 2 2 (eq. 1) Unfortunately, due to the inherent propagation delay of the logic, the actual peak current is higher at high input voltage than at low input voltage, leading to a significant difference in the maximum output power delivered by the power supply. http://onsemi.com 20 NCP1236 IP IP to be compensated ILIMIT High Line Low Line time tdelay tdelay Figure 38. Line Compensation for True Overpower Protection would be in the same order of magnitude. Therefore the compensation current is only added when the FB voltage is higher than VFB(OPCE). However, because the HV pin can be connected to an ac voltage, there is needed an additional circuitry to read or at least closely estimate the actual voltage on the bulk capacitor. To compensate this and have an accurate overpower protection, an offset proportional to the input voltage is added on the CS signal by turning on an internal current source: by adding an external resistor in series between the sense resistor and the CS pin, a voltage offset is created across it by the current. The compensation can be adjusted by changing the value of the resistor. But this offset is unwanted to appear when the current sense signal is small, i.e. in light load conditions, where it (68 ms) S Q R Q Brown Out HV Timer HV thv (32 ms) Watch Dog VHVstop A/D 3 bit Converter + Peak Detector 3 bit Register I Generator I ctrl FB To CS Block Tblanking LEB CS VFB (OPC) Figure 39. Schematic Overpower Compensation Circuit input. If only the DC high voltage input is used, no reset signal is generated by the VHV(stop) condition and the 32 ms watch dog is used to generate the sampling events for sampling the DC input high voltage line. A 3 bit A/D converter with the peak detector senses the ac input, and its output is periodically sampled and reset, in order to follow closely the input voltage variations. The sample and reset events are given by the VHV(stop) comparator used for sampling detection for the AC line http://onsemi.com 21 NCP1236 IOPC VHV VFB(OPCE) VFB VFB(OPCF) Figure 40. Overpower Compensation Current Relation to Feedback Voltage and Input Voltage VHV VHV(stop) time Sample/reset signal time HV timer starts One shot HV timer restarts HV timer restarts HV timer restarts t HV time Peak detector Reset Reset Reset Reset Reset time IOPC Sample Sample Sample Sample Reset time Figure 41. Overpower Compensation http://onsemi.com 22 NCP1236 VHV VHV(stop) time twd twd twd Peak detector Reset time IOPC Sample Sample Reset Sample tHV time Figure 42. Overpower Compensation Feedback with Slope Compensation 3.5 V. There is a pull−up resistor of 20 kW from FB pin to an internal reference. The ratio from the FB voltage to the current sense setpoint is 5, meaning that the FB voltage corresponding to VILIM is VFB(ref) 20 kW FB K FB slope comp. + PWM − CS Oscillator blanking tLEB Figure 43. FB Circuitry In order to allow the NCP1236 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 comparator is −32.5 mV/ms typical for the 65 kHz version, and −50 mV/ms for the 100 kHz version. http://onsemi.com 23 NCP1236 Overcurrent protection with Fault timer latched off (latched protection, version A), or it enters an autorecovery mode (version B). The timer is reset when the CS setpoint goes back below VILIM before the timer elapses. The fault timer is also started if the driver signal is reset by the max duty cycle. When an overcurrent occurs on the output of the power supply, the FB loop asks for more power than the controller can deliver, and the CS setpoint reaches VILIMIT. When this event occurs, an internal tfault timer is started: once the timer elapsed, DRV pulses are stopped and the controller is either FB + − /5 Fault Flag PWM R Q S timer tfault Protection Mode Autorecovery protection mode only blanking CS Reset DRV release timer tLEB + + − Brown−out Reset VILIM DC MAX DRV Figure 44. Timer−Based Overcurrent Protection In autorecovery mode, the controller tries to restart after tautorec. If the fault has gone, the supply resumes operation; if not, the system starts a new burst cycle. http://onsemi.com 24 t autorec NCP1236 Fault disappears Output Load Overcurrent applied Max Load Fault Flag time Fault timer starts VCC time VCC(on) VCC(min) Restart At VCC(on) (new burst cycle if Fault still present) DRV time Controller stops Fault timer time tfault tfault tautorec time Figure 45. Autorecovery Timer−Based Protection Mode In the latched version, the controller can restart only if a brown−out or a VCC reset occurs, which in a real application can only happen if the power supply is unplugged from the mains line. http://onsemi.com 25 NCP1236 Output Load No restart when fault disappears Overcurrent applied Max Load Fault Flag time Fault timer starts VCC time VCC(on) VCC(min) DRV time Controller latches off Fault timer time tfault tfault Figure 46. Latched Timer−Based Overcurrent Protection http://onsemi.com 26 time NCP1236 LOW LOAD OPERATION Frequency Foldback VFB(foldS), and is complete before VFB reaches Vskip(in), whatever the nominal switching frequency option is. The current−mode control is still active while the oscillator frequency decreases. Note that the frequency foldback is disabled if the controller runs at its maximum duty cycle. 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 fOSC(min). This frequency foldback starts when the voltage on FB pin goes below fOSC Nominal fOSC Skip fOSC(min) Vskip(in) FB VFB(foldS) VFB(foldE) Figure 47. Frequency Foldback when the FB Voltage Decreases Skip Cycle Mode − + + Vskip S Q FB KFB CS blanking tLEB DRV stage R + − Figure 48. Skip Cycle Schematic When the FB voltage reaches Vskip(in) while decreasing, skip mode is activated: the driver stops, and the internal consumption of the controller is decreased. While VFB is below Vskip(out), the controller remains in this state; but as soon as VFB crosses the skip out threshold, the DRV pin starts to pulse again. http://onsemi.com 27 NCP1236 VFB VFB(fold) Vskip(out) Vskip(in) Exits Exits skip Enters Enters skip skip Time skip DRV Time Figure 49. Skip Cycle Timing Diagram Latch−off Input VDD + − + INTC blanking tLatch(OVP) VOVP INTC Latch + 1 kW − + blanking tLatch(OTP) VOTP Vclamp S Q R Latch Brown−out Reset Soft−start end Figure 50. Latch Detection Schematic To avoid any false triggering, spikes shorter than 50 ms (for the high latch) or 350 ms (for the low latch) are blanked and only longer signals can actually latch the controller. Reset occurs when a brown−out condition is detected or the VCC is cycled down to a reset voltage, which in a real application can only happen if the power supply is unplugged from the AC line. Upon start−up, the internal references take some time before being at their nominal values; so one of the comparators could toggle even if it should not. Therefore the internal logic does not take the latch signal into account before the controller is ready to start: once VCC reaches VCC(on), the latch pin High latch state is taken into account The Latch pin is dedicated to the latch−off function: it includes two levels of detection that define a working window, between a high latch and a low latch: within these two thresholds, the controller is allowed to run; but as soon as either the low or the high threshold is crossed, the controller is latched off. The lower threshold is intended to be used with an NTC thermistor, thanks to an internal current source INTC. An active clamp prevents the voltage from reaching the high threshold if it is only pulled up by the INTC current. To reach the high threshold, the pull−up current has to be higher than the pull−down capability of the clamp (typically 1.5 mA at VOVP). http://onsemi.com 28 NCP1236 and the DRV switching starts only if it is allowed; whereas the Low latch (typically sensing an overtemperature) is taken into account only after the soft−start is finished. In addition, the NTC current is doubled to INTC(SSTART) during the soft−start period, to speed up the charging of the Latch pin capacitor. The maximum value of Latch pin capacitor is given by the following formula (The standard start−up condition is considered and the NTC current is neglected) : C LATCHmax + t SSTARTmin @ I NTC(SSTART)min V clamp0min (eq. 2) 2.8 @ 10 −3 @ 130 @ 10 −6 + F + 364 nF 1.0 VCC VCC(on) VCC(min) Start-up initiated by VCC(on) Internal Latch Signal Noise spike ignored (tLatch blanking) Latch signal high during pre-start phase time time DRV Latch-off Switching allowed (no latch event) time Figure 51. Latch−off Function Timing Diagram Temperature Shutdown instantaneously, and the HV current source is turned off. Internal logic state is reset. When the temperature falls below the low threshold, the HV start−up current source is enabled, and a regular start−up sequence takes place. The die includes a temperature shutdown protection with a trip point guaranteed above 135C and below 165C, and a typical hysteresis of 30C. When the temperature rises above the high threshold, the controller stops switching http://onsemi.com 29 NCP1236 STATE DIAGRAMS HV Start−up Current Source VCC > VCC(inhibit) Istart1 No TSD Istart2 VCC < VCC(inhibit) TSD TSD Stop TSD VCC < VCC(min) VCC > VCC(on) TSD Off Figure 52. HV Start−up Current Source State Diagram http://onsemi.com 30 NCP1236 Controller Operation (Latched Version: A Option) High Latch VCC > VCC(ovp) VCC > VCC(on) Soft−start Brown−out TSD Soft−start ends Brown−out TSD Stopped Brown−out TSD Brown−out TSD Skip Brown−out VCC reset Skip in Latch High Latch Low Latch VCC > VCC(ovp) Skip out Running Fault High Latch Low Latch VCC > VCC(ovp) With Fault= tfault expires VCS > VCS(stop) VCC < VCC(off) Figure 53. Controller Operation State Diagram (Latched Protection) http://onsemi.com 31 NCP1236 Controller Operation (Autorecovery Version: B Option) High Latch VCC > VCC(ovp) VCC > VCC(on) Soft−start Brown−out TSD tautorec counting Brown−out TSD Soft−start ends Stopped Brown−out TSD Fault Brown−out TSD Skip Brown−out VCC reset Skip in Latch High Latch Low Latch VCC > VCC(ovp) Skip out Running High Latch Low Latch VCC > VCC(ovp) With Fault= tfault expires VCS > VCS(stop) VCC < VCC(off) Figure 54. Controller Operation State Diagram (Autorecovery Protection) http://onsemi.com 32 NCP1236 Table 1. ORDERING INFORMATION Switching Frequency Overload Protection Fault Timer NCP1236AD65R2G 65 kHz Latched 128 ms NCP1236AD100R2G 100 kHz Latched 128 ms NCP1236BD65R2G 65 kHz Autorecovery 128 ms NCP1236BD100R2G 100 kHz Autorecovery 128 ms NCP1236CD65R2G (Note 8) 65 kHz Latched 32 ms NCP1236CD100R2G (Note 8) 100 kHz Latched 32 ms NCP1236DD65R2G 65 kHz Autorecovery 32 ms NCP1236DD100R2G (Note 8) 100 kHz Autorecovery 32 ms Part No. Package Shipping† SOIC−7 (Pb−Free) 2500 / Tape & Reel †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. 8. Contact your ON Semiconductor Sales Representative. These parts will be released upon customer request. http://onsemi.com 33 NCP1236 PACKAGE DIMENSIONS SOIC−7 CASE 751U ISSUE E −A− 8 NOTES: 1. DIMENSIONING AND TOLERANCING PER ANSI Y14.5M, 1982. 2. CONTROLLING DIMENSION: MILLIMETER. 3. DIMENSION A AND B ARE DATUMS AND T IS A DATUM SURFACE. 4. DIMENSION A AND B DO NOT INCLUDE MOLD PROTRUSION. 5. MAXIMUM MOLD PROTRUSION 0.15 (0.006) PER SIDE. 5 −B− S 0.25 (0.010) B M M 1 4 DIM A B C D G H J K M N S G C R X 45 _ J −T− SEATING PLANE H 0.25 (0.010) K M D 7 PL M T B S A S MILLIMETERS MIN MAX 4.80 5.00 3.80 4.00 1.35 1.75 0.33 0.51 1.27 BSC 0.10 0.25 0.19 0.25 0.40 1.27 0_ 8_ 0.25 0.50 5.80 6.20 INCHES MIN MAX 0.189 0.197 0.150 0.157 0.053 0.069 0.013 0.020 0.050 BSC 0.004 0.010 0.007 0.010 0.016 0.050 0_ 8_ 0.010 0.020 0.228 0.244 SOLDERING FOOTPRINT* 1.52 0.060 7.0 0.275 4.0 0.155 0.6 0.024 1.270 0.050 SCALE 6:1 mm Ǔ ǒinches *For additional information on our Pb−Free strategy and soldering details, please download the ON Semiconductor Soldering and Mounting Techniques Reference Manual, SOLDERRM/D. ON Semiconductor and are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC owns the rights to a number of patents, trademarks, copyrights, trade secrets, and other intellectual property. A listing of SCILLC’s product/patent coverage may be accessed at www.onsemi.com/site/pdf/Patent−Marking.pdf. SCILLC reserves the right to make changes without further notice to any products herein. SCILLC makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does SCILLC assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation special, consequential or incidental damages. “Typical” parameters which may be provided in SCILLC data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. All operating parameters, including “Typicals” must be validated for each customer application by customer’s technical experts. SCILLC does not convey any license under its patent rights nor the rights of others. SCILLC products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applications intended to support or sustain life, or for any other application in which the failure of the SCILLC product could create a situation where personal injury or death may occur. Should Buyer purchase or use SCILLC products for any such unintended or unauthorized application, Buyer shall indemnify and hold SCILLC and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that SCILLC was negligent regarding the design or manufacture of the part. SCILLC is an Equal Opportunity/Affirmative Action Employer. This literature is subject to all applicable copyright laws and is not for resale in any manner. PUBLICATION ORDERING INFORMATION LITERATURE FULFILLMENT: Literature Distribution Center for ON Semiconductor P.O. Box 5163, Denver, Colorado 80217 USA Phone: 303−675−2175 or 800−344−3860 Toll Free USA/Canada Fax: 303−675−2176 or 800−344−3867 Toll Free USA/Canada Email: [email protected] N. American Technical Support: 800−282−9855 Toll Free USA/Canada Europe, Middle East and Africa Technical Support: Phone: 421 33 790 2910 Japan Customer Focus Center Phone: 81−3−5817−1050 http://onsemi.com 34 ON Semiconductor Website: www.onsemi.com Order Literature: http://www.onsemi.com/orderlit For additional information, please contact your local Sales Representative NCP1236/D