This application note provides simple approach designing driver utiliz

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AND8136/D Offline Driver
This application note provides simple approach designing driver utilizing Semiconductor NCP1014 self-supplied monolithic switcher. easy-to-follow step-by-step procedure guides user into designing different blocks that constitute power supply, mainly input block, power stage, magnetics, snubber, output block, feedback loop. circuit diagram, bill material, layout also included application note. This power supply specifically designed drive three LED's. meets requirements. minimal achievable efficiency greater possible. NCP1014 integrates fixed-frequency current mode controller MOSFET. This device housed PDIP-7 package features soft-start, frequency jittering, short-circuit protection, skip-cycle, dynamic self-supply need auxiliary winding). Design Parameters first step designing power supply define predetermine input output parameters. Universal Input Voltage Range:
Vac(min) Vac, Vac(max)
Input Peak Current:
Ipeak Iin(avg)
Circuit Description
Input Block
input block power supply consists fuse, filter, diode bridge rectifier, input bulk capacitor.
Fuse
fuse protecting circuit from current surges occurring turn this application, rated Vac.
Filter
Output Specifications:
Vout 11.75 Iout
filter suppresses common mode differential mode noise very dependent upon board layout, component selection, etc. capacitor common mode choke placed across lines attenuate differential mode noise, Figure inductor slowing down transient voltage surge reduce high frequency noise. Both capacitor choke should placed before diode bridge close line input possible minimize RFI.
Diode Bridge Rectifier
Input Power:
where estimated efficiency Pout Vout Iout 11.75 0.350 NPin 5.25 0.78
order choose right diode bridge rectifier, values forward surge currents blocking voltage must considered. surge current reach values five times that average input current. therefore necessary select rectifier capable handling such large currents. Blocking Voltage calculated high line:
Vdc(max)
Rail Voltages Line High Line:
Vdc(min) Vac(min) Vdc(max) Vac(max)
Forward Current:
Iin(avg) 0.044
Average Input Current:
Iin(avg) 5.25 dc(min)
Surge Current:
IFSM 0.066
Semiconductor Components Industries, LLC, 2005
March, 2005 Rev.
Publication Order Number: AND8136/D
AND8136/D
Input Bulk Capacitor
purpose input bulk capacitor hold rectified line voltage also filter common mode noise. placed between bridge rectifier output ground. size bulk capacitor depends peak rectified input voltage ripple voltage magnitude. larger capacitor will lower ripple voltage input line, will induce larger surge current when supply powered Assuming ripple magnitude about peak rectified voltage line, Cbulk then calculated using:
Cbulk (Vpeak(min)2 Vin(min)2) (1202 962)
calculated will cause power supply output fall regulation.
(operating frequency) (maximum duty cycle) Vin(min) Vdc(min) (minimum input voltage) Pout (output power) (estimated efficiency) Ipeak +220 (input peak current) Vin(min) Ipeak 0.48 2.09mH 0.220
Lpri
Primary secondary turns ratio:
Npri Vin(min) Vout max) 0.48 turns 11.75 0.875 (1-0.48)
this case, chose aluminum electrolytic availability. Power Stage heart power stage Semiconductor NCP1014. NCP1014 current-mode controller with high voltage power MOSFET monolithic structure. NCP1014 features soft-start, frequency jittering, short circuit protection, maximum peak current point, dynamic self-supply. operates skip-cycle mode below maximum peak current limit, thus acoustic noise present. more information this device, please www.onsemi.com. Magnetics Calculations next step design flyback transformer. design magnetics block most important delicate part whole design process because will determine well power supply will perform. flyback-mode transformer functions first conducting current primary winding, thus storing energy core transformer. core energy then transferred secondary winding when primary side turned off. core bobbin standard EFD20 sizes. order regulator operate discontinuous mode under worse case conditions maximize power, maximum time full period, therefore maximum primary inductance calculated based maximum duty cycle 48%. Using larger inductance than
easy check power capability transformer large enough supply output with following equation:
Pin(core) Pin(core) Lpri Ipeak2 Pout 2.09 0.2202 5.05
Input Snubber Because high dv/dt characteristic power transistor drain voltage transformer leakage inductance, voltage spikes ringing occur drain when power switch turned off. Resistor compromise snubber. parallel primary winding which compromise ringing damper which slows down dv/dt reduces peak voltage therefore decreasing ringing high frequency noise. Since increasing
capacitance will also reduce magnitude voltage ripple. snubber ringing damper together protect from voltage transients greater than reduce radiated noise.
AND8136/D
Output Block output block secondary side Figure consists main diodes, (forward diode) (flyback diode), optocoupler, resistors, zener diodes storage capacitors. Diode operates forward mode conducts while internal switch turned Resistor limits forward current diode limits voltage This also acts auxiliary supply secondary side provides power optocoupler TLV431 labeled IC3. During flyback mode, energy stored transformer released secondary load capacitor D10. Capacitor smoothes current pulses establishes effectively constant voltage LEDs. current controlled limited using feedback. current converted voltage using resistor control reference IC3. There fault conditions that occur; open circuit short circuit. open circuit fault condition occurs when there LEDs connected there current flowing. order limit secondary voltage during this fault condition, over-voltage zener diode, added. secondary flyback voltage rises above starts conducting causes optocoupler conduct current well, which then informs NCP1014 primary side reduce energy transferred through transformer. During this time, there which totals secondary side. Under short circuit fault conditon, LEDs shorted. This occur only shorted LEDs supplied with current through cable. wires cable either twisted together shorted together. secondary current limited resistor which develops 1.25 voltage drop. When voltage across greater than 1.25 conducts causes NCP1014 reduce energy transferred secondary side. This identical open circuit fault condition previously discussed.
Fuse
MUR160
220p
NCP1014 MUR120 1.0k 1N5338B Midcom SFH615A-4 MMSD914 100p
2.2k
Connector
0.001 TLV431 1N5917 LED1
2.2k
100p
1N5941B
*1N4006
1N5917
LED2
NCP1014P100
LED3
Photo Transistor
MUR120
1N5917
Figure Circuit Diagram
AND8136/D
Table Bill Materials
Ref. D1-4 D6,D10 D11,12,13 C13* R10* LED1-3 Connector Component Value kHz, PDIP-7 Opto Coupler, 1.25 Shunt Reg., TO-92 Purp Ultrafast Ultrafast Zener Switching diode Zener Zener Flyback Transformer Choke, Common Mode, film, radial radial 10%, disc 10%, disc uF,radial uF,radial 0.001mF, ceramic 20%, radial radial 10%, disc 100,1/4,5% 1/4W, 3.6,1W,5% Luxeon Star axial Part Number NCP1014AP100 SFH615A-4 TLV431ALP 1N4006 MUR160 MUR120 1N5338B MMSD914 1N5941B 1N5917 31842 40479 R46104M275BIS KME400VB33RM16X31LL NCD221K1KVY5F NCD470K1KVSL ECA-1HHG220 ECA-1HHG101 SR155C102KAA SME16VB10RM5X11LL SR215E105MAA NCD101K1KVY5F RS-1W-91K-5 CF-1/2W-2.2K-5 CF-1/4W-1k-5 CF-1/4W-2.2K-5 CF-1/4W-2K-5 RN-1/4W-T1-100-5 RS-1-R5-5TR RS-1-1R2-5TR CF-1/4W-22R-5 CF-1/4W-221-5 CF-1W-3.6-5 LXHL-MW1C 251002TR1 1715035 Manufacturer Semiconductor Isocom Semiconductor Semiconductor Semiconductor Semiconductor Semiconductor Semiconductor Semiconductor Semiconductor Midcom Midcom Nissei United Chem-Con Components Components Panasonic Panasonic United Chem-Con Components Luxeon LittleFuse Phoenix Contact
AND8136/D
Figure Metal Layer (front)
Figure Metal Layer (back)
AND8136/D
Figure Silk Screen
References Brown, Marty, Power Supply Cookbook, Butterworth-Heinemann, 1994. Pressman, Abraham Switching Power Supply Design, Second Edition, McGraw-Hill, 1998. Motorola, Inc., Handling Switch Mode Power Supply Design, AN-SMPS-EMI, Motorola, Inc., 1998. NCP1014 Datasheet, Semiconductor, www.onsemi.com Spangler, Hayes, AND8024 Application Note, Semiconductor, www.onsemi.com
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AND8136/D

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