NCP1075 - ON Semiconductor L.L.C.

DN05038/D

October 2012, Rev. 0 www.onsemi.com 1

Design Note – DN05038/D

Non-Isolated, 8 Watt Dual Output, Off-line Power Supply

Device Application Input Voltage Output Power Topology I/O Isolation

NCP1075

NST45011 White Goods,

Industrial Equipment 180 to 270 Vac 8 Watts Nominal Non-Isolated

Flyback No isolation from

mains

Other Specification

Output 1 Output 2 Output 3 Output 4

Output Voltage 5.0 Vdc +/- 2% 8.5 Vdc +/- 5% N/A N/A

Ripple 200 mV p/p 200 mV p/p N/A N/A

Nominal Current 1 A 200 mA N/A N/A

Max Current 1.25 A 300 mA N/A N/A

Min Current 1% 1% N/A N/A

PFC (Yes/No) No

Efficiency 76% at 8 watts output

Inrush Limiting / Fuse Yes – limiting resistor and fuse

Operating Temp. Range 0 – 50 C

Cooling Method /

Supply Orientation Convection

No Load Standby Power 68 mW @ 230 Vac

Others Optional high regulation sense circuit using NCP431

Circuit Description

This Design Note features an 8 watt, off-line, dual output,

flyback power supply intended for powering white g oods or

industrial equipment circuitry which does not require output

isolation from the AC mains. The flyback converter is

designed around O N Semiconductor’s 1 00 kHz NCP1075

monolithic switching controller. A simple voltage sensing

and feedback scheme utilizing a current mirror transistor

pair (Q1), and zener diode (Z1) is utilized for low cost yet

effective output regulation for most typical applications.

For situations requiring mo re precise regulation on the

primary 5 volt channel (<1%), an alternate circuit using a

NCP431 programmable zener as an error amplifier is

shown within the dotted box in the sche matic.

This particular design example provides output voltages of

5V and 8.5V but these can be tailored to other voltages to

accommodate the specific requirements by appropriate

transformer turns ratio cha nges and alterations to voltage

setting zener Z1 and resistor R6.

The regulation loop is clos ed around the 5 volt main output

while the 8.5 volt output is configured using a “slave”

secondary winding on the transformer. The slave

secondary is tightly coupled to the main 5V windin g via

bifilar winding techniques which a s sures reasonable load

and cross regulation without requiring dedicated reg ulation

circuitry. Other 2nd channel voltages are possible by

changing the turns of the slave se condary winding.

Logic power (Vcc) for the control chip is derived via diode

D9 directly from the slave output. Since the control IC

needs a minimum of about 8 volts to maintain efficient

operation, Schottky D6 is provided as an optional logic Vcc

source instead of D9 in the event it is required that the

second output is somewhat less than 8 volts. At V cc

voltages less than about 8 volts, the controller will operate

in DSS mode and there will be some degradation in overall

circuit efficiency.

Although this design is for European mains voltage, a

transformer design for a universal AC input version is

available on request. A 5V/12V transformer design is also

included in the information below.

Key Features

 Schottky diodes (D6, D7) on both outputs for high

efficiency

 Dual sensing options depe nding on desired regulation

accuracy

 Input EMI filter for condu cted emission compliance

 Input fuse and inrush limiting resistor (R1)

 Good load and cross regulation on 8.5Vout due to

secondary winding technique on transformer

DN05038/D

October 2012, Rev. 0 www.onsemi.com 2

Schematic1

0.1uF

50V

0.1uF

50V

AC Input

C9A

0.1uF

"X" 0.1uF

"X"

Non-Isolated, 8 Watt, Dual Output NCP1075 PSU

with Universal AC Input (Rev 7B)

D1-D4

MRA4007

X 4 1nF

1kV

1N4937

68K

1/2W

6.8 ohms

(wire w o und)

L1A

L1B

C10

+5V

+8.5V

1 mH

C9B

1500uF, 6.3V

C11

10nF

22uF

25V

R2A

NCP1075

10uF

400V

3.3M

Primary

Ground

Plane

R2B

NOTES:

1. Crossed schematic lines are not connected.

2 . R4 value dependent on VS2 nominal output voltage.

3 . R1 is optional inrush limiting resistor.

4. U1 tab (pin 4) should have heatsinking clad pours and be

part of a ground plane area for best noise immunity.

5. Heavy lines indicate recommended ground plane areas.

6. L1A/L1B are Wurth 7447728102.

7 . Z1 sets nominal 5Vo ut. R6 can trim Vout upward.

8. Dotted area is optional sense/error amp circuit. If selected

omit Q1, Z1, R5, and R6.

(100 kHz)

(4.3V)

120

1000uF

16V

Com

MBRS240

NST45011

0.1uF

BAT54

100

Vtrim

MMSZ

5229B

NCP431

R7 R8

R10

R11

C12

0.1

10K 10K

10K

4.7K

Optional Sense Amp

MMSZ

5223B

(2.7V)

MMSD

4148A

VS1

VS2

DN05038/D

October 2012, Rev. 0 www.onsemi.com 3

MAGNETICS DESIGN DATA SHEET

Part Description: 8 watt flyback transforme r, 100k Hz, 5V/9V outputs (Rev 5 - Euro version)

Project / Custom er: ON Sem iconductor - NCP1014/1075, 8W dual output PSU

Schematic ID: T1 Wurth Electronics Part # 750313309 Rev 02

Core Type: EF16 (E16/8/5); 3C90 material or similar

Core Gap: Gap for 5.5 mH +/- 5% inductance across primary (pins 1 - 4)

Inductance: 5 to 6 mH when m e asuring from pin 1 to pin 4

Bobbin Type : 8 pin horizontal m ount for EF16

Windings (in order):

Winding # / type Turns / Material / Gauge / Insula tion Data

Hipot:

Schematic Lead Breakou t / Pinout

Primary A (4 - 2) 78 turns of #38 m ag wire wound over 1 layer.

Insulate with Mylar tape for at least 1kV breakdown.

5V/8.5V Secondaries (8,5 - 7,6) 7 turns of two pieces of #26 magnet wire (different

colors) spiral wound bifilar over one layer. Remove two

turns so winding terminating to pins 7/6 has only

5 turns. Triple Insulated wire can also be used if

desired. Self-leads to pins.

Primary B (2 - 1) Same as primary A.

1 kV from primary to secondary - no agency primary/secondary insulation requirem ents

(Bottom View - facing pins)

Varnish assembly

Pri A

Pri B

7 turns

(5Vout)

5 turns

(8Vstack)

DN05038/D

October 2012, Rev. 0 www.onsemi.com 4

MAGNETICS DESIGN DATA SHEET

Part Description: 8 watt flyback transformer, 100k Hz, 5V/12V outputs (Rev 1 - Euro version)

Project / Custom er: ON Semiconductor - NCP1014/1075, 8W dual output PSU

Schemat ic ID: T1

Core Type: EF16 (E16/8/5); 3C90 m aterial or similar

Core Gap: Gap for 5.5 mH +/- 5% inductance across primary (pins 1 - 4)

Inductance: 5 to 6 mH when measuring from pin 1 to pin 4

Bobbin Type: 8 pin horizontal m o unt for EF16

Windings (in order):

Winding # / type Turns / Material / Gauge / Insulation Data

Hipot:

Schematic Lead Breakout / Pinout

Primary A (4 - 2) 78 turns of #38 mag wire wound over 1 layer.

Insulate with Mylar tape for at least 1kV breakdown.

5V/12V Secondaries (8,5 - 7,6) 7 turns of two pieces of #26 magnet wire (different

colors) spiral wound bifilar over one layer. Add two

m ore tu rns so the winding te rminating to pins 7/6 ha s

9 turns total (12V stack). Triple Insulated wire c an also

be used if desired. Self-leads to pins.

Prim a ry B (2 - 1) Same as primary A.

1 kV from primary to secondary - no agency primary/secondary insulation requirements

(Bottom View - facing pins)

Varnish assembly

Pri A

Pri B

7 turns

(5Vout)

9 turns

(12Vstack)

DN05038/D

October 2012, Rev. 0 www.onsemi.com 5

Efficiency versus Pout (5V:8.5V = 2:1 Loading Ratio Respectively)

8.5 Vout Load Regulation (5 Vout set to 1A Load)

DN05038/D

October 2012, Rev. 0 www.onsemi.com 6

Cross Regulation (8.5Vout loaded at 100mA)

Output Ripple – 5 Vout at 1 Amp

Output Ripple – 8.5 Vout at 350 mA

DN05038/D

October 2012, Rev. 0 www.onsemi.com 7

Mosfet Drain Voltage at 150 Vac Input and 8 Watt Load

Mosfet Drain Voltage at 265 Vac Input and 8 Watt Load

Mosfet Drain Voltage at 260 Vac Input and 1 Watt Load

DN05038/D

October 2012, Rev. 0 www.onsemi.com 8

Conducted EMI Scan with 8 Watt Load (EN55022, Level B; Average)

Average

EN 55022; Class B Conducted, Average

-20

-10

1 10

dBuV 1075 Dual

240Vac 60Hz Input

10/15/2012 11:24:00 AM (Start = 0.15, Stop = 30.00) MHz

PC Board Layout / Photo

DN05038/D

October 2012, Rev. 0 www.onsemi.com 9

Designator Qty Description Value Tolerance Footprint Manufacturer Manufacturer Part Number Substitution

Allowed Lead

Free Comments

D7, D8 2 Schottky diode 3A, 40V SMB ON Semi MBRS240L (or MBRS2040L) No

D1, 2, 3, 4 4 Diode - 60 Hz, 1A, 800V SMA ON Semi MRA4007 No

D5 1 Diode - fast recov 1A, 600V axial lead ON Semi 1N4937 No

D6 1 Schottky diode 200mA, 30V SOD-123 ON Semi BAT54 No

D9 1 Signal diode 100mA, 100V SOD-123 ON Semi MMSD4148A No For 12Vout and higher

Z1 1 Z ener diode 4.3V, 500 mA SOD-123 ON Semi MMSZ5229B No

Z2 1 Z ener diode 2.7V, 500 mA SOD-123 ON Semi MMSZ5223B No

Q1 1 Dual NPN matched xstr 45V, 100 mA SOT-363 ON Semi NST45011 No

U2 1 Programmable zener 2.5V SOIC8 / SOT23 ON Semi NCP431A No

U1 1 Switcher IC - NCP1075 100 kHz SOT223 ON Sem i NCP1075ST100 No

C1, C2 2 "X" cap, box type 100nF, X2 LS = 15 mm Rifa, Wima TBD Yes

C4 1 Ceramic c ap, disc 1 nF, 1kV 5% LS = 7.5 mm Rifa, Wima T BD Yes

C6 1 Ceramic cap, monoly thic 1 nF, 50V 10% 1206 AVX, Murata TBD Yes

C7, 8, 11 3 Ceramic cap, monolythic 100nF, 50V 10% 1206 AVX, Murata TBD Yes

C12 1 Cera mic cap, monolythic 100nF, 50V 10% 1206 AVX, Murata TBD

C3 1 Electrolytic cap 10uF, 400/450V 10% LS=7.5mm, D=16mm UCC, Panasonic TBD Yes

C10 1 Electrolytic cap 1000uF, 16V 10% LS= 5 mm, D=12.5mm UCC, Panasonic TBD Yes

C5 1 Electrolytic cap 22uF, 25V 10% LS= 2 .5mm, D=6.3mm UCC, Panasonic TBD

C9A, C9B 2 Electroly t ic cap 1,500uF, 6.3V 10% LS=5mm, D=12.5mm UCC, Panasonic TBD Yes 12V version

R1 1 Resistor, 2W, Wire wound 6.8 ohm, 2W 10% LS=7.5mm, D=7mm Ohmite, Dale TBD Yes

R3 1 Resistor, 0.5W, metal film 68K, 0.5W 10% A xial lead; LS= 12.5mm Ohmite, Dale TBD Yes

R2A,R2B 2 Resistor, 1/4W SMD 3.3 Meg 5% SMD 1206 AVX, Vishay, Dale TBD Yes

R5 1 Resistor, 1/4W SMD 120 ohms 1% SMD 1206 AVX, Vishay, Dale TBD Yes

R4 1 Resistor, 1/4W SMD 2.0K 1% SMD 1206 AVX, Vishay, Dale TBD

R9, R10 2 Resistor, 1/4W SMD 10K 1% SMD 1206 AVX, Vishay, Dale TBD Yes

R7 1 Resistor, 1/4W SMD 10K 1% SMD 1206 AVX, Vishay, Dale TBD Yes

R6 1 Resistor, 1/4W SMD 100 ohms 1% SMD 1206 AVX, Vishay, Dale TBD Yes

R8 1 Resistor, 1/4W SMD 1 Meg 1% SMD 1206 AVX, Vishay, Dale TBD Yes

R11 1 Resistor, 1/4W SMD 4.7K 1% SMD 1206 AVX, Vishay, Dale TBD Yes

F1 1 Fuse, TR-5 style 1A TR-5, LS=5mm Minifuse Yes

L1A/B 1 Inductor (EMI c hoke) 1 mH, 500 mA See Wurth Drawing LS=5mm, D=8mm 7447728102 Yes

T1 (5/8.5Vou

1 Transform er E20/10/6 core See Mag Drawing Wurth Magnetics 750313309 Rev 02 Yes

J1 1 Sc r ew Term inal LS = 0.2" DigiKey # 281-1435-ND Yes

Yellow indicates parts for standard Vout sense scheme

Green indicates parts for alternate Vout sense scheme.

DN05038/D

October 2012, Rev. 0 www.onsemi.com 10

References:

NCP1075 data sheet: http://www.onsemi.com/pub_link/Collateral/NCP1072-D.PDF

NCP1075 Design Note: http://www.onsemi.com/pub_link/Collateral/DN05018-D.PDF

NCP1072 EVAL Board Documents:

http://www.onsemi.com/PowerSolutions/supportDoc.do?type=boards&rpn=NCP1072

Disclaimer: ON Semiconductor is providing this design note “AS IS” and does not assume any liability arising from its use; nor

does ON Semiconductor convey any licens e to its or any third party’s intellectual pro perty rights. This document is provi ded only to

assist customers in evaluation of the referenced circuit implementation and the recipient assumes all liability and risk associated

with its use, including, but not limited to, compliance with all regulatory standards. ON Semiconductor may change any of its

products at any time, without notice.

Design note created by Frank Cathell, e-m ail: f.cathell@onsemi.com