NCP1308, LM2575: Universal Input, 50 W, 5 Output Quasi-Resonant Flyback Converter

DN06029/D
Design Note – DN06029/D
Universal Input, 50W, 5 Output PSU
Device
NCP1308,
LM2575
Application
Input Voltage
Medical Equipment
85 to 265 Vac
Output Power
Topology
I/O Isolation
40 W average,
50 W peak
QuasiResonant
Mode Flyback
Yes – 3kV
Other Specifications
Output Voltage
Ripple
Nominal Current
Max Current
Min Current
Output 1
Output 2
Output 3
Output 4
12 VDC
+/- 20mV
2.5 A
3A
10 mA
-12 VDC
+/- 20mV
150 mA
300 mA
10 mA
5 VDC
2% - 5%
900 mA
1.2 A
10 mA
3.3 VDC
2% - 5%
150 mA
300 mA
10 mA
PFC (Yes/No)
No
Minimum Efficiency
75 % at nominal load
Inrush Limiting / Fuse
Yes - both
Operating Temp. Range
Cooling Method/Supply
Orientation
0 to +60°C
Others
Convection
5th Output with 350 Vdc @ +/- 20 V at 50 mA max.
Circuit Description
Key Features
This Design Note features a universal AC input, 50
watt peak output flyback power supply with 5 separate
output voltages. The 3.3 volt and 5 volt outputs are
derived from the +12 volt output using identical
LM2575 monolithic buck regulators. The 350 volt
output is derived from a “slave” secondary flyback
winding
on
the
main
transformer.
ON
Semiconductor’s NCP1308 controller provides for
quasi-resonant Mosfet switching and current mode
control of the flyback topology for high conversion
efficiency and low noise generation. Voltage sensing
and regulation for the main +12 volt output is
achieved utilizing the conventional TL431A error amp
and optocoupler feedback scheme. The negative 12
volt output achieves satisfactory regulation via a
tightly coupled secondary winding with the main +12
V output’s secondary winding (bifilar wound). The 3.3
V and 5 V outputs require minimal components
utilizing the LM2575 buck regulators and off-the-shelf
ferrite inductors.
y
July 2007, Rev. 1
Over-current, over-voltage, and over-temperature
protection.
y Input common and differential mode EMI filter for
agency EMI compliance.
y NTC thermistor for inrush current limiting at initial
supply turn-on.
y Pi-network ripple filters (L2, L3) on the +/-12 V
outputs for low output noise and ripple.
y Main flyback transformer designed with common
industry standard ETD29 ferrite core.
www.onsemi.com
1
DN06029/D
Schematic
2A
F1 250Vac
AC Input
C2
TH1
C5 180uF
400V
C3 C4
10 ohm
2.0A
2.2nF
1kV
1N4007
Q1
R5
2.2
R6
10K
0.5W
1nF x 2
"Y2"
6
R4
10K
R3
0.4 ohms
0.5W
D9
8
D6
6
2
4
3
C7
1nF
R8 1N4148
68K
R9
470
C8
C9
22uF 100pF
16V
100
12
8
2
5
3
3
5
L4A & B
390uH
D11A, B
1N5817
L3
+12V
0.1
Com
C20
220uF
25V
C22
C21
0.1
-12V
0.1uF
50V
U2
1
2
750
R13
1K
C10 R14
0.1
R15
9.1K
10K
R16
2.4K
NOTES:
Out
C24A, B
470uF
6.3V
Gnd
Buck Regulator Notes:
1. U4B requires small heatsink (TO-220).
2. C23 should be multilayer ceramic cap
and located next to U4.
3. L4 is Coilcraft PCV-0-394-03L or equivalent
(390 uH, 3A).
July 2007, Rev. 1
R11
5.1K
3.3V
C14
0.1
C17 C18
4.7uH
U3
TL431A
4
LM2575 -3.3 2
or LM2575 -5
L2
4.7uH
470uF
16V
C19
D10 470uF
25V
5V
R12
3.3V and 5V Buck Regulator Blocks (A & B)
In
Gnd
MBR1100
4
U4A & B
Buck Reg
Out
C13
0.1
C15 C16
MBR10100
1000uF
4
16V x 2
R7
C12
1nF
1kV
3.3V Regulator Out
Block (A)
In
NCP1308
U1
1
C23
A, B
2.2uF,
16V
5V Regulator
Block (B)
In
13
D5
9
5
1
350V
R10
1M
0.5W
C11
10uF,
400V
MUR160 x 2
Gnd
1Meg
0.5W
Chassis
Gnd
7
1
R2
47
1W
R1
T
Gnd
C6
D1 thru
D4
1N4007
x4
L1
C1
0.22uF
"X2"
D7 D8
T1
0.22uF
"X2"
1. Crossed lines on schematic are not connected.
2. Heavy lines indicate recommended ground plane area.
3. L1 is Coilcraft BU15-2721R6BL or similar EMI inductor.
4. L2 & L3 are Coilcraft PCV-0-472-05L or equivalent.
5. U2 is Vishay H11A817A or equivalent optocoupler.
6. Q1 is 6A, 650V Mosfet (TO-220).
7. Q1 and D9 will need small stamped heatsinks.
50 Watt, 5 Output Universal Input Power Supply
www.onsemi.com
2
DN06029/D
1
MAGNETICS DESIGN DATA SHEET
50W, 5 output
power
Project : Schneider
Electric,
50W,supply
5 Output Power Supply
Part Description: Quasi-resonant flyback transformer, 50W, +/-12Vout/350Vout
Schematic ID: T1
Core Type: ETD29 (Ferroxcube 3C95 material or equivalent)
Core Gap: Gap for 400 uH +/- 5% acros pins 13 to 1
Inductance: 380 to 420 uH nominal across primary (pins 13 to 1)
Bobbin Type: ETD 13 pin horizontal pc mount (Ferroxcube PC1-29H)
Windings (in order):
Winding # / type/pins
Turns / Material / Gauge / Insulation Data
Aux winding (12 - 2)
5 turns of # 26HN spiral wound evenly over bobbin.
Self-leads to pins. Insulate for 1 kV to next winding.
Primary (13 - 1)
42 turns of #26HN over one full bobbin layer;
Self-leads to pins; insulate for 3 kV to next layer.
+/-12V secondary (9,8, - 4,5)
5 turns of 5 strands #25HN; one strand should be
green for -12V winding; flat-wind over 1 layer with
3.5 mm approximate end margins. Winding ends
should be cuffed with tape. Self-leads to pins
with 4 wires per pin on +12 strands. Insulate with
tape for 3 kV to next winding.
350V secondary (7 - 6)
135 turns of #38HN over 1 layer; self-leads to
pins. Final tape insulation to 3kV.
Hipot: 3 kV primary/aux to all secondaries. Vacuum varnish.
Schematic
Lead Breakout / Pinout
7
1
Pri
13
Aux
12
Bottom (pin side) view
350V
6
9
4
8
2
5
1 2 3
+12V, 4 strands
#25
4 5 6
Multifilar
Wound
-12V, 1 strand
#25 green
13 12 11 10 9 8 7
1
© 2007 ON Semiconductor.
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 license to its or any third party’s intellectual property rights. This document is provided 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-mail: [email protected]
July 2007, Rev. 1
www.onsemi.com
3