EVBUM2147 - NCP1351 57 W Adapter Evaluation Board
Contents
1. Given the negative sensing technique we can use a portion of the auxiliary signal during the on time as it also swings negative However we need this compensation at high line only since standby power can be affected For this reason we have installed a small integrator made of C1g R20 To avoid charging C g during the flyback stroke Do clamps the EFFICIENCY positive excursion and offers a stronger negative voltage during the on time Finally the clamping network maintains the drain voltage below 520 V at high line 375 Vdc which provides 85 derating for the 600 V BVdss device Measurements Once assembled the board has been operated during 15 mn at full power to allow some warm up time We used a WT210A from Yokogawa to perform all power related measurements coupled to an electronic ac source Vin Pour 110 Vac 230 Vac 0 10 20 30 40 50 60 Pout W Figure 5 Switching Frequency Fey vs Pout www BD t ctom ON NCP1351ADAPGEVB Vin Pour 0 5 Output Power No load Power No load Overpower Protection Level Vin Pout Overpower Start up Time Vin lout 3 A Start up Duration On the above arrays we can see the excellent efficiency at different loading conditions The first explanation is the low leakage inductance on the tested transformer below 1 of the primary inductance Also the frequency reduction in lighter load configurations helps for the switching losses The no load standb2. TF M4 8 01 GMOS IC NCP19518 Substi Toler Manufacturer Part tution Lead Description Value ance Number Allowed Free ON Semiconductor NCP1351B Welwyn WCR12063K92 pa a pe Pre NOTE Screws nuts and washers attached to heatsinks MUST be non conductive Nylon TEST PROCEDURE FOR THE NCP1351 ADAPTER EVALUATION BOARD NOTE Be careful when manipulating the boards in operation lethal voltages up to 400 V are present on the primary side An isolation transformer is also recommended for safer manipulations Necessary Equipment e 1 Current limited 90 265 Vrms AC source current limited to avoid board destruction in case of a defective part or a 380 VDC source AGILENT 6811 e 1 AC Volt Meter able to measure up to 300 V AC KEITHLEY 2000 e 1 AC Amp Meter able to measure up to 3 A AC KEITHLEY 2000 e 1 DC Volt Meter able to measure up to 20 V DC KEITHLEY 2000 AC Source 90 265 Vac AC DC 19 V 3A adapter e 1 DC Amp Meter able to measure up to 5 A DC KEITHLEY 2000 e 1 DC Electronic Load 0 4 A AGILENT 6060B Test Procedure 1 Apply 90 230 V AC over the Vin pins Output pins Vout Ground are left floating 2 Measure the output voltage between pins Vout et Ground with a volt meter on the auto range The measurement should be between 18 8 and 19 2 V 3 Connect the electronic load between pin Vout et Ground Verify that the output voltage stays above 19 V Set curre
3. 9 yes yes N 1 capacitor 10 nF 630 V 10 radial Vishay 2222 372 61103 yes yes O de 1 electrolytic capacitor 4 7 uF 50 V 20 radial Panasonic ECA1HM4R7 yes yes C5b C5a 2 electrolytic capacitor 1000 uF 35 V 20 radial Panasonic EEUFC1V102 yes a E O O capacitor 100 nF 50 V 10 radial SR215C104KTR yes yes O N al du NO h 00 du N electrolytic capacitor 220 uF 25 V 20 radial Panasonic EEUFC1E221 yes yes SMD capacitor 220 pF 50 V 5 SMD 1206 PHYCOMP 2238 863 15471 yes yes C10 SMD capacitor 220 nF 50 V 10 SMD 1206 AVX CM316X7R224K50AT yes yes 11 X2 capacitor 220 nF 630 V 20 radial Evox Rifa PHE840MD6220M yes yes 1 electrolytic capacitor 100 uF 400 V 20 radial Panasonic ECA2GM101 yes yes 1 Y1 capacitor 2 2 nF 250 V 20 radial Ceramite 440LD22 yes yes C14 SMD capacitor 47 pF 50 V 5 SMD 1206 PHYCOMP 2238 863 15479 yes yes C15 SMD capacitor 22 pF 50 V 5 SMD 1206 PHYCOMP 2238 863 15229 es 3 yes C17 1 electrolytic capacitor 100 uF 35 V 20 radial Panasonic ECA1VM101 yes yes C18 SMD capacitor 270 pF 50 V 5 SMD 0805 PHYCOMP 2238 861 15271 yes yes 1 zener diode 15 V 225 mW 5 SOT23 ON Semiconductor BZX84C15LT1G yes yes 1 ultrafast rectifier 1 A 600 V 0 axial ON Semiconductor MUR160G Ss i y 1N4937G yes yes yes _ hight speed diode 1 A 600 V 0 axial ON Semiconductor 1 schottky diode 20 A 100 V 0 TO220 ON Semiconductor MBR20100CTG yes yes 1 hig
4. NCP1351ADAPGEVB NCP1351 57 W Adapter Evaluation Board User s Manual The NCP1351 at a Glance Fixed ton variable tore current mode control implementing a fixed peak current mode control hence the more appropriate term quasi fixed ton the NCP1351 modulates the off time duration according to the output power demand In high power conditions the switching frequency increases until a maximum is hit This upper limit depends on an external capacitor selected by the designer In light load conditions the off time expands and the NCP1351 operates at a lower frequency As the frequency reduces the contribution of all frequency dependent losses accordingly goes down driver current drain capacitive losses switching losses naturally improving the efficiency at various load levels Peak Current Compression at Light Loads Reducing the frequency will certainly force the converter to operate into the audible region To prevent the transformer mechanical resonance the NCP1351 gradually reduces compresses the peak current setpoint as the load becomes lighter When the current reaches 30 of the nominal value the compression stops and the off duration keeps expanding towards low frequencies Low Standby power the frequency reduction technique offers an excellent solution for designers looking for low standby power converters Also compared to the skip cycle method the smooth off time expansion does not bring additional r
5. ade the power supply output impedance and regulation will suffer A 1 5 kQ has proven to do just well without degrading the standby power D2 MUR160 MBR20100 1N4937 11 D5 86H 6232 4 A 600 V M1 SPPO4N60C3 27 kQ oe R10 39 kQ C5 0 1 uF R18 opto e U1 SFH6156 2 Figure 3 The 57 W Adapter Board Featuring the NCP1351 Controller www BD PT tom ON NCP1351ADAPGEVB The overvoltage protection uses a 15 V zener diode D1 connected to the auxiliary Voc When the voltage on this rail exceeds 15 V plus the NCP1351 5 V latch trip point total is thus 20 V the circuit latches off and immediately pulls the Vcc pin down to 6 V The reset occurs when the injected current into the Vcc pin passes below a few uA that is to say when the power supply is deconnected from the mains Vbulk Ist outlet To speed up this reset phase a connection via a diode to the half wave point will reset the circuit faster Figure 4 Please note that the half wave resistor equals the original bulk start up resistor divided by 3 14 This provides the Same startup current despite the half wave signal The power dissipation is also slightly reduced by 30 roughly Rstartup 3 14 Figure 4 Connecting the startup resistor to the mains before the diode bridge helps to speed up the NCP1351 reset time when latched To satisfy the maximum power limit we can install an Over Power Protection OPP circuit
6. ht speed diode 0 2 A 75 V 0 axial Philips Semiconductor 1N4148 yes yes D8 D9 1 0 2 A 100 V 6 2 C W 2 5 36 V 1 100 mA hight speed diode 0 SOD 123 ON Semiconductor MMSD4148G yes yes HS1 HS2 2 heatsink 0 radial Seifert KL195 25 4 SWI yes yes IC2 1 shunt regulator 2 TO92 ON Semiconductor TL431ILPG yes yes C gt diode bridge 4 A 800 V 0 radial Multicomp KBU4K e es lt 0 fi qc connector 230 Vac 0 radial Schurter 0721 PP yes yes connector 2 0 rad5 08mm Weidmuller PM5 08 2 90 yes yes mb Common mode 2 27 mH 0 8 A 0 radial Schaffner RN114 0 8 02 yes yes m Inductor 2 2 uH 10 A 0 radial Wurth Elektronik 744772022 yes yes power MOSFET N Channel 4 A 600 V 0 TO220 Infineon SPPO4N60C3 yes yes PNP transistor 100 mA 45 V 0 TO92 ON Semiconductor BC857 e lt 0 yes SMD resistor 2 2 kQ 0 25 W 1 SOT23 Welwyn WCR12062K22 yes yes R2 R7 2 resistor 1 MQ 0 33 W 5 Vishay SFR2500001004JR50 yes yes J al S lt AREF SMD resistor 2 5 kQ 0 25 W 2 SMD 1206 Welwyn WCR12062K52 yes yes R6b R6a 2 SMD resistor 1 Q 1 W 5 SMD 2512 PHYCOMP 232276260108 yes yes mb resistor 1 k0 0 4 W 5 Vishay SFR2500001001JR50 yes yes mb SMD resistor 10 k02 0 25 W 2 SMD 1206 Welwyn WCR120610K2 yes es yes www BD tl7ctom ON NCP1351ADAPGEVB BILL OF MATERIALS FOR THE NCP1351ADAPGEVB SMD resistor 1 MEA 18 9 0 a a FIX 4H LCBS
7. ipple in no load conditions the output voltage remains quiet Natural Frequency Dithering the quasi fixed tp mode of operation improves the EMI signature since the switching frequency varies with the natural bulk ripple voltage Extremely Low Start up Current built on a proprietary circuitry the NCP1351 startup section does not consume more than 10 uA during the startup sequence The designer can thus easily combine startup time and standby consumption Overload Protection Based on Fault Timer every designer knows the pain of building converters where a precise over current limit must be obtained When the fault detection relies on the auxiliary Vcc the pain even increases Here the NCP1351 observes the lack of feedback current starts a timer to countdown At the end of its charge the timer either triggers an auto recovery sequence auto restart B version or permanently latches off A Latch Fault Input a dedicated input lets the designer externally trigger the latch to build additional protections such as over voltage OVP or over temperature OTP ON Semiconductor http onsemi com EVAL BOARD USER S MANUAL Figure 1 Evaluation Board Photo The Schematic The design must fulfil the following specifications Input voltage 90 265 Vac Output voltage 19 V 3 A Over voltage protection Over power protection Auto recovery short circuit protection Offering a good EMI signature the 65 kHz maximum
8. kVoutn 2NPout Where Ipeak is the selected peak current in the inductor Vout the output voltage n the converter efficiency Pout the delivered power N the transformer turn ratio Np Ns 1 N Since we are limited to 265 Vac we can see that the converter will always be in CCM at full power To the opposite we can also predict the power level at which the converter leaves CCM at low and high line conditions NlbeakVinVout Pout crit Vout NVin eq 2 For an input voltage of 120 Vdc the converter enters DCM for an output power below 42 W When the voltage increases to 330 Vdc the power level at which CCM is excited is 55 W Two 1 MQ resistors ensure a clean start up sequence with the 4 7 uF capacitor C3 directly from the bulk capacitor Despite a small value for C3 the Vcc still maintains in no load conditions thanks to the split configuration NCP1351 220 pF 47 pF 2x 19 x 0 9 2 x 0 25 x 57 35 V D1 1N4148 a EN CU La o a n De 5 2x57 x 19 380 Vdc eq 1 bulk Figure 2 The split Vcc configuration helps to start up in a small period of time CVcc to charge alone but the addition of a second larger capacitor Cres ensures enough Vcc in standby The primary side feedback current is fixed to roughly 300 uA via Rs and an additional bias is provided for the TL431 1 mA at least must flow in the TL431 in worse case conditions full load Failure to respect this will degr
9. nder 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 ofthe 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 N American Technical Support 800 282 9855 Toll Free ON Semiconductor Website www onsemi com Literature Distribution Center for ON Semiconductor USA Canada P O Box 5163 Denver Colorado 80217 USA Europe Middle East and Africa Technical Support Order Literature http www onsemi com orderlit Phone 303 675 2175 or 800 344 3860 Toll Free USA Canada Ph
10. nt 3 A 4 If every step is going well the board 1s considered to be ok DC LOAD 19VW 0 3A Figure 15 Test Setup www BD PT tom ON NCP1351ADAPGEVB PCB layout NCP1351ZADIG D TLS 0406 SIG VZ TSETIDN JOJ3MPUOITUSS NO Figure 17 Copper Traces at jaz cll wan man TM fle ca A El TE lr Figure 18 SMD components ON Semiconductor and f 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 u
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12. switching frequency has become an industry standard for the vast majority of power supplies connected on the mains With the NCP1351 selecting a C capacitor of 270 pF fixes the upper limit to 65 kHz As a result when the controller detects a need for a higher frequency implying an overload condition it will start to charge the timer capacitor if the overload disappears the timer capacitor goes back to zero If the fault remains the timer capacitor voltage reaches 5 V and starts the auto recovery process The transformer has been derived using the design recommendations described in the NCP1351 data sheet We came up to the following values Lp 770 uH Np Ns 1 0 25 Np Naux 1 0 18 It is also possible to use the Excel spreadsheet available from the ON Semiconductor website which also gives transformer parameters The core is a PQ26x25 made of a 3F3 material and has been manufactured by Delta Electronics reference 86H 6232 The leakage inductance is kept around 1 leading to a good efficiency and reduced losses in no load conditions The schematic appears on Figure 3 The converter operates in CCM with a 40 duty cycle at low mains and stays CCM at high line Despite Semiconductor Compon i 1 bl cation Order Number October 2012 Rev RA WAY W com EVBUM2147 D NCP1351ADAPGEVB the frequency variation it is possible to evaluate the input voltage point at which the converter leaves CCM Vina 2PoutVout meen lbea
13. the drain thanks to the low leakage term www BD t ctom ON NCP1351ADAPGEVB Figure 11 The Drain source Waveform at Different Output Currents 3 A 2 A and 1 A The Input Voltage is 230 Vac ojec TB PREM lt gt A Figure 12 Short circuit on the Optocoupler LED The output voltage increases to 28 V and then the controller latches off Different levels can be obtained by changing D1 www BD PT tom ON NCP1351ADAPGEVB Conclusion The adapter built with the NCP1351 exhibits an excellent performance on several parameters like the efficiency and the no load standby The OPP is made in a simple non dissipative way and does not hamper the standby power The limited number of surrounding components around the controller associated to useful features timer based protection latch input makes the NCP1351 an excellent choice for cost sensitive adapter designs Goos RS gt CEE lt ol gt i lt Figure 13 Load Step from 0 5 A to 3 A with a1 A us Slew rate from a 90 Vac o e 3 20 0 ms div Figure 14 Load Step from 0 5 Ato 3 A witha 1 A us Slew rate from a 230 Vac source www BD PT tom ON NCP1351ADAPGEVB BILL OF MATERIALS FOR THE NCP1351ADAPGEVB Substi Toler Manufacturer Part tution ance Desig nator Qty Description Free Number Allowed Value r D oa C1 C4 C5 C9 3 SMD capacitor 100 nF 50 V 5 SMD 1206 PHYCOMP 2238 581 1564
14. y power stays below 150 mW at high line a good performance for a 60 W adapter Please note that the high voltage probe observing the drain was removed and the load totally disconnected to avoid leakage The OPP proves to work ok Perhaps an improved margin would help 110 Vac 0 5 W 833 mW 112 mW 230 Vac 865 mW 139 mW 265 Vac 230 Vac at 90 Vac which could be obtained by slightly increasing R 9 or if necessary by increasing R15 Despite operation in the audible range we did not notice any noise problems coming from either the transformer or the RCD clamp capacitor Scope shots Below are some oscilloscope shots gathered on the demoboard ofe a a cae o gt gt Figure 6 Startup time V 90 Vac It ojea sl 500 ms diw DR E Figure 7 Startup time Vin 230 Vac www BD PT tom ON NCP1351ADAPGEVB 0 Rim OEM O HEN or margin ole agl uaa t t eje alal 100 ms div aja t Oos ajoj mee 4 T Figure 8 Startup Sequence to Test the Margin on Figure 9 Short circuit Vin 265 Vac the 100 ms Timer Vin 90 Vac lout 3 A On the above picture a short circuit has been made at the highest line voltage During the burst operation the input power was maintained to 6 3 W at 275 Vac It dropped to 5 2 W at 230 Vac Control Setup Measure Analyze Utilities Help 13 34 100 Mav s o e2 3 1 00 us div ala Figure 10 Maximum Output Power V 265 Vac Note the good margin on
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