8 W DVD Power Supply with NCP1027

AND8262/D
8 W DVD Power Supply with
NCP1027
Prepared by: Christophe Basso
ON Semiconductor
http://onsemi.com
APPLICATION NOTE
Overview
Digital Video Disks players require a few different
voltages to power the logic circuitry but also all
servo−mechanisms linked to the tray and optical head
actuators. The NCP1027 lends itself very well to this kind of
applications where simple architectures lead to the lowest
assembly cost. Despite the variety of low−end DVD players
on the market, there is a common trend on the power supply
requirements:
• Universal input voltage: 85 to 265 Vac, 2 wire power
cord
• 5 different dc voltages, 1 non−filtered bias level:
1. 5 V / 1 A
2. 3.3 V / 1 A
3. – 12 V / 20 mA
4. + 12 V / 20 mA
5. – 23 V / 10 mA
6. Floating display bias
• Low standby power in no−load and partial load
conditions
These specifications can fluctuate depending on a
particular type of player but the basic power supply
architecture remains the same. We will use a current−mode
flyback regulator built around the integrated power
switcher, the NCP1027. This DIP 8 package hosts a high
performance controller together with a low RDS(on) 700 V
BVdss MOSFET. On top of the standby needs, we have
packed other interesting goodies in this circuit. They are
summarized below:
• Brown−out Detection: the controller will not allow
operation in low mains conditions. You can adjust the
level at which the circuit starts or stops operation.
• Ramp Compensation: designing in Continuous
Conduction Mode helps to reduce conduction losses.
However, at low input voltage (85 Vac), the duty−cycle
might exceed 50% and the risk exists to enter a
subharmonic mode. A simple resistor to ground injects
the right compensation level.
• Over Power Protection: a resistive network to the bulk
reduces the peak current capability and accordingly
harnesses the maximum power at high line. As this is
© Semiconductor Components Industries, LLC, 2006
August, 2006 − Rev. 0
•
•
done independently from the auxiliary VCC, the design
gains in simplicity and execution speed.
Latch−off Input: some manufacturers require a complete
latch−off in presence of an external event, e.g. over
temperature or a severe over−voltage protection. The
controller offers this possibility via a dedicated input.
Frequency Dithering: the switching frequency (here
65 kHz) is modulated during operation. This naturally
spreads the harmonic content and reduces the peak
value when analyzing the signature.
Design Description
Figure 2 shows the electrical schematic used for this
application. The NCP1027 directly connects to the power
transformer and a classical RCD clamping network prevents
any BVdss runaways. A string of resistors (R14 , R15 and R9 )
set the minimum operating voltage to increase safety in case
of a low input level: the circuit does not switch until enough
voltage appears on the mains connector. During this time,
VCC goes up and down via the activated high−voltage
current source and self−supplies the controller. When the
mains reaches the adequate level (70 Vac here), the power
supply automatically resumes operation and performs its
duty. Please note that bringing pin 3 above a certain level
(3.5 V) permanently latches off the switcher. It can be useful
in case safety specifications impose a complete shutdown in
presence of a stringent event: Over Temperature Protection
(OTP), latched OverVoltage Protection (OVP)…
As this design enters the Continuous Conduction Mode
(CCM) at low line, we have added some ramp compensation
via a single resistor connected from pin 2 to ground: no
sub−harmonic oscillations can be detected at low line input
and full load.
Thanks to the NCP1027, the power supply is inherently
protected against short−circuits, whatever the VCC pin level
is. An internal circuitry permanently monitors the feedback
pin and starts a timer when pin 4 goes high (open−loop
conditions in startup sequence or in a short−circuit
condition). If the timer reaches completion before the fault
has gone, the switcher stops all pulses and enters an
auto−recovery protective mode. When the fault disappears,
1
Publication Order Number:
AND8262/D
AND8262/D
the switcher resumes operation. However, the point at which
the controller detects the fault can move in relationship to the
input rail: the power delivered at high line is slightly greater
than at low line. The guilty is the total propagation delay
from the current sense comparator to the output latch.
Fortunately, it can easily be compensated via current
injection in pin 7, as shown in AND8241/D. Again, if your
design specifications impose a precise output over current
protection, implementing this solution can represent a viable
option.
The output feedback implements a so−called weighted
control where two outputs are observed. Depending on the
required precision, a weight is imposed on each control loop,
let us select 30% for the 5 V and 70% for the 3.3 V.
Calculation is as follows:
1. select a bridge current. We will use 250 mA with
our TL431.
2. evaluate the lower side resistor given the
considered output voltage:
Rupper * 5 V + 10 k + 33.3 kW
0.3
Rupper * 3.3 V + 3.2 k + 4570 W
0.7
These two resistors are respectively made of R4 – R6 and
R3 – R7 on the final schematic. A simple 100 nF introduces
a pole−zero combination together with C16 .
Finally, various inductors are placed on the outputs to
reduce the switching ripple down to an acceptable level.
Transformer
The transformer is made by Pulse Engineering and has the
reference 2472.0003A (please BOM details). The device
exhibits the following turn ratios and inductance, its pinout
appears on Figure 1:
Lp = 2.2 mH
Lleak < 40 mH @ 100 kHz
W1:W2 (aux. winding) = 74:14
W1:W4 (5 V) = 74:1
W1:W3 (3.3 V) = 74:2
W1:W5 (12 V) = 74:4
W1:W6 (– 22 V) = 74:12
W1:W7 (FL1 and FL2) = 74:3
Rupper * 5 V + 5 * 2.5 + 10 kW
250 m
Rupper * 3.3 V + 3.3 * 2.5 + 3.2 kW
250 m
3. now apply the selected weighting factor to each
resistor:
7
+12 V
11
+Vin
W5
+5 V
10
W1
W4
8
+3.3 V
W3
Drain
3
9
W6
+VCC
1
12
−22 V
13
+F
W7
W2
2
14
−F
Figure 1. The Transformer Pinout Showing an AC Stacked Winding Configuration
Given the selected core, the transformer can deliver an
output power up to 12 W. Thanks to pin 7, you can precisely
alter the peak current limit and thus, the maximum output to
the level of your choice: a wide range of DVD players
applications can then be covered.
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2
AND8262/D
D3
1N4934
1
C1
10 mF
63 V
+
233 m
2
7
R14
2.2 M
F1
LCM
1
3
TR1
R8
47
R15
2.7 M
PT1
DF08
R27
47 k
C7
10 n
+
IN
−
C55
47 mF
Type = 400 V
+
R13
5.6 k
D1
1N4007
C18
220 nF _X2
7
6
5
IC1
NCP1027
1
C4
10 nF
C8
22 mF
10 V
2
3
C16
1n
+
IC3
R16 R9
75 k 27 k
Figure 2. The Complete Application Schematic, Primary Side
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3
4
AND8262/D
C20
470 p
R2
150
13
D12
1N4148
14
R12
1k
GND
R5
820
D8
1N4934
L8
10 mH
FL2
12
FL1
+
200 m
D4
1N963
C9
47 mF _35 V
9
C2
100 n
+
C19
47 mF _16 V
−22 V
−12 V
L2
10 m
D14
1N5822
3.3 V
8
5.0 V
+
36 m
C5
100 m
C14
470 mF _10 V
9
12 V
L3
10 m
D13
1N5822
10
+
56 m
C6
100 mF 10 V
C15
470 mF _10 V
9
D15
1N4934
11
C21
470 mF _16 V
142 m
+
9
R4
330
R3
270
R6
33 k
R7
4.3 k
C13
2.2 nF
Type = Y1
IC3
R11
1.0 k
R10
1.0 k
C12
100 nF
IC2
TL431
R1
10 k
Figure 3. The Complete Application Schematic, Secondary Side
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4
AND8262/D
Operating Waveforms and Test Results
To perform some tests, we have loaded the prototype converter with a DVD player and artificially loaded some of its outputs,
mainly the +3.3 V and the +5 V. The static board load is the following:
3.3 V = 700 mA
5 V = 500 mA
12 V = 20 mA
–12 V = 25 mA
– 23 V = 2 mA
A 520 mA peak current was then added on top of the 5 V or the 3.3 V output. Results are displayed below:
520 mA
3.3 V
5V
Figure 4. Both Input Levels Give the Same Performance when the 5 V is
Loaded by 520 mA Peaks.
520 mA
3.3 V
5V
Figure 5. Here, the 3 V is Loaded by 520 mA Peaks on Top of
its Current Consumption
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5
AND8262/D
I(5V5)
I(5V)
5V5
5V
Figure 6. Opening the Tray Gives Birth to a Current Train of Pulses
As these plots reveal, the voltage variations stay well within 5% of the nominal output. When left operated at 230 Vac in
no−load conditions, the input standby power is 0.5 W.
Figure 7. EMI plot of a DVD player powered by the power supply – the dark blue curve
corresponds to the Quasi−Peak sweep whereas the light blue describes the Average sweep.
The efficiency lies around 75% from 90 Vac up to 265 Vac.
The NCP1027 case temperature moves between 60°C (low
line) and 54°C (high line). In both cases, the ambient was
25°C. The Brown−Out protection imposes an operating
window above 82 Vac (start−up) and stops operations below
56 Vac. These numbers can of course be altered by playing
on R14 , R15 and R9 (for calculation details, please the
NCP1027 data−sheet).
The front−end filter includes a simple 2 x 6.8 mH common
mode inductor whose leakage inductance forms a
differential mode filter together with C18. The EMI plot in
both Quasi−Peak (QP) and Average modes looks good as
testified by Figure 7. Both sweeps were obtained with the
DVD chassis operating and connected to the earth via a wire.
Figure 8 and 9 show the pcb silkscreen and the copper
traces.
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6
AND8262/D
Figure 8. The Demoboard Silkscreen
Figure 9. PCB Copper Layout
As we stated, the transformer is available from Pulse
Engineering at the following address:
Pulse Italy s.r.l con s.u.
Via Ticino, 2C
I−22070 Senna Comasco (CO) − ITALY
Tel: +39031463071
Fax:+390314630790
e−mail: consumerdivision@pulseeng.com
website: www.pulseeng.com
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7
AND8262/D
Bill of Materials − NCP1027
Designator
C1
Qty
1
20%
Footprint
radial
Manufacturer
Panasonic
Manufacturer Part
Number
ECA1JM100
100nF/50V
10nF/100V
10nF/630V
100uF/16V
10%
10%
10%
20%
radial
radial
radial
radial
Murata
Murata
Vishay
Panasonic
22uF/16V
20%
radial
47uF/35V
20%
2.2nF/250V
470uF/16V
yes
rper71h104k2m1a05u
rper72a103k2m1b05a
mkt1822310635
eca1cm101
yes
yes
yes
yes
no
no
no
no
Panasonic
ECA1CM220
yes
no
radial
Panasonic
ECA1VM470
yes
no
20%
20%
radial
radial
Ceramite
BC Comp.
440ld22
2222−13555471
yes
yes
no
no
1nF/100V
220nF/630V
47uF/16V
10%
20%
20%
radial
radial
radial
Murata
Evox Rifa
Panasonic
rper72a102k
phe840md6220m
ECA1CM470
yes
yes
yes
no
no
no
470pF/100V
100nF/630V
47uF/400V
5%
20%
20%
radial
radial
radial
AVX
Evox Rifa
Panasonic
sr211a471jtr
phe840mx6100m
ECA2GM470
yes
yes
yes
yes
no
yes
1A/1000V
1A/100V
0%
0%
axial
axial
ON Semiconductor
ON Semiconductor
1n4007g
1n4934g
yes
yes
yes
yes
12V/0.5W
0.2A/75V
0%
0%
axial
axial
1n963b
1n4148
yes
yes
yes
no
3A/40V
500mA/temp
NCP1027
0%
0%
2.5−36V/1−100mA
sfh6156/
2p/250V
2/
2%
0%
0%
0%
Fairchild
Philips Semiconductor
ON Semiconductor
Schurter
ON Semiconductor
ON Semiconductor
Vishay
Multicomp
Weidmuller
1n5822g
0034.6612
NCP1027
tl431ilpg
sfh6156−2t
jr−201s
pm5.08/2/90
yes
yes
yes
yes
yes
yes
yes
yes
no
yes
yes
yes
no
no
Schaffner
Wurth Elektronik
Schaffner
General Semiconductor
Neohm
Neohm
Neohm
Neohm
Neohm
Neohm
Phoenix Passive
Components
Neohm
Neohm
Neohm
rn112−1.2/02
744772100
rn114−0.8/02
DB106G
yes
yes
yes
yes
no
yes
no
no
cfr25j10k
cfr25j150R
cfr25j270R
cfr25j330R
cfr25j820R
cfr25j33k
mrs25−4k3−1%
yes
yes
yes
yes
yes
yes
yes
no
no
no
no
no
no
yes
cfr25j47R
cfr25j27k
cfr25j1k0
yes
yes
yes
no
no
no
cfr25j15k
cfr25j2M2
sfr25−2m7−5%
yes
yes
yes
no
no
yes
mrs25−75k−1%
yes
yes
cfr200j47k
yes
no
Value
10uF/63V
C2,C12
C4
C7
C5,C6
2
1
1
2
C8
1
C9
1
C13
C14,C15,
C21
C16
C18
C19
1
3
C20
C22
C55
1
1
1
D1
D3,D8,
D15
D4
D12
1
3
D13,D14
F1
IC1
IC2
IC3
J1
J2,J3,J4,
J5
LCM
L2,L3,L8
L9
PT1
2
1
1
1
1
1
4
zener diode
hight−speed
diode
schottky diode
fuse
CMOS IC
shunt regulator
optocoupler
connector
connector
1
3
1
1
inductor
inductor
inductor
diode bridge
2*6.8mH/1.2A
10uH/2.6A
2*27mH/0.8A
800V/1A
0%
20%
0%
0%
axial
radial
dip8
to92
SMD
radial
rad5.0
8mm
radial
radial
radial
dil
R1
R2
R3
R4
R5
R6
R7
1
1
1
1
1
1
1
resistor
resistor
resistor
resistor
resistor
resistor
resistor
10kR/0.33W
150R/0.33W
270R/0.33W
330R/0.33W
820R/0.33W
33kR/0.33W
4.3kR/0.6W
5%
5%
5%
5%
5%
5%
1%
axial
axial
axial
axial
axial
axial
axial
R8
R9
R10,R11,
R12
R13
R14
R15
1
1
3
resistor
resistor
resistor
47R/0.33W
27kR/0.33W
1kR/0.33W
5%
5%
5%
axial
axial
axial
1
1
1
resistor
resistor
resistor
5.6kR/0.33W
2.2MR/0.33W
2.7MR/0.4W
5%
5%
5%
axial
axial
axial
R16
1
R27
TR1
1
1
1
1
1
1
1
Substitution
Allowed
Lead
Free
no
Description
electrolytic capacitor
capacitor
capacitor
capacitor
electrolytic capacitor
electrolytic capacitor
electrolytic capacitor
y1 capacitor
electrolytic capacitor
capacitor
x2 capacitor
electrolytic capacitor
capacitor
x2 capacitor
electrolytic capacitor
rectifier diode
rectifier diode
Tolerance
Neohm
Neohm
Phoenix Passive
Components
resistor
75kR/0.6W
1%
axial
Phoenix Passive
Components
resistor
47kR/2W
5%
axial
Neohm
2472.0003A − multi−output transformer from Pulse Engineering
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8
AND8262/D
Figure 10. Demo Board
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AND8262/D