Download VIPower: low cost universal input DVD supply with VIPer22A

AN1897
- APPLICATION NOTE
®
VIPower: LOW COST UNIVERSAL INPUT
DVD SUPPLY WITH VIPer22A
Jun-feng Zhang
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INTRODUCTION
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In the past few years, many consumer products have been provided to the end user, such as DVD or
VCD players. Generally their power supply require multiple outputs to supply a variety of control circuits:
MCU, Motor, Amplifier, VFD.
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ST VIPer series of off-line switch mode power supply regulators combines an optimized, high voltage,
avalanche rugged Vertical Power MOSFET with current mode control PWM circuitry. The result is truly
innovative AC to DC conversion that is simpler, quicker and - with component count halved - less
expensive.
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The VIPer family also represents the easiest solution to comply with the "Blue Angel" and "Energy Star"
Eco norms, with extremely low total power consumption at stand-by mode, thanks to the burst operation.
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This document would present the application on DVD player power supply with VIPer22A satisfying the
specification See table 1 below.
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Table 1: Output Specification
INPUT
OUTPUT 1
OUTPUT 2
OUTPUT 3
OUTPUT 4
OUTPUT 5
OUTPUT 6
Universal
mains line
5 V +/- 5% +12 V +/- 5% -12 V +/- 5% -26 V +/- 5%
(See note 1) (See note 1) (See note 1) (See note 1)
3.3 V +/- 5%
(See note 1)
5Vstb +/- 5%
Min: 85Vac
Max:
265Vac
Imin: 20mA
Imax: 1.5 A
Imax: 150mA
Imax: 100mA
Imax: 30 mA Imax: 30 mA Imax: 50mA
(See note 1)
Note 1: The accuracy of +/-5% is reached only for a certain range of loads combination. See paragraph 3.2 for cross regulation results.
March 2004
1/11
AN1897 - APPLICATION NOTE
1. APPLICATION DESCRIPTION AND DESIGN
1.1 Schematics
The overall schematic is shown in figure 2.
1.1.1 Start-up Phase
As any member of the VIPer family, VIPer22A has an integrated high voltage current source linked to
Drain pin. At the startup converter, it will charge the V DD capacitor until it reaches VIPer startup level
(14.5V), and then the VIPer22A starts switching.
1.1.2 Auxiliary Supply
VIPer22A has a wide operating voltage range from 8V to 42V, respectively minimum and maximum
values for under-voltage and over-voltage protections.
This function is very useful for achieving low stand-by total power consumption. During normal working,
the feedback loop is connected to 5V output by D12 to regulate 5V output. At the mean time, +5Vstb
output is blocked by Q3, so +5Vstb regulation is neglected. When the stand-by signal is present, the Vce
of Q3 can not provide enough voltage to maintain D12 conducted, so the 5V output is blocked, and the
+5Vstb output is connected to the feedback loop. In this condition the +5Vstb is regulated. Thanks to the
transformer structure, all the other secondary outputs and the auxiliary voltages are pulled down to a very
low level, also pulling down the total power consumption.
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All these contents can be summarized by the following list:
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• in normal full load, the VDD voltage of the device must be lower than the over-voltage protection;
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• in short circuit, the V DD voltage must be lower than the shutdown voltage. Actually, this condition leads
to the well known hiccup mode in practice;
• in no load condition, the VDD voltage must be higher than the shutdown voltage.
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1.1.3 Burst Mode
The Viper22A integrates a current mode PWM with a Power MOSFET and includes the leading edge
blanking function. The burst mode is a feature which allows VIPer22A to skip some switching cycles
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when the energy drained by the output load goes below E=(Tb*Vin)2 * fsw/2Lp (Tb=blanking time, Vin=DC
input voltage, f sw=Switching frequency, Lp=Primary Inductance).
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It has the consequence to reduce the switching losses when working in low load condition by reducing
the switching frequency.
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1.1.4 Feedback Loop
The 5V output voltage is regulated with a TL-431 (U3) via an optocoupler (U2) to the feedback pin. If the
output voltage is high, the TL-431 will draw more current through its cathode to the anode and the current
increases in the optocoupler diode. The current in optocoupler NPN increases accordingly and the
current into the VIPer22A FB pin increases. When the FB current increases, the VIPer22A will skip some
cycles to decrease turn on time and lower the output voltage to the proper level (see figure 1).
The 5V output voltage is regulated thanks to the reference voltage of TL-431 and the resistive divider R8
and R9.
2/11
AN1897 - APPLICATION NOTE
Figure 1: VIPer22A FB pin internal structure
DRAIN
60kHz
OSCILLATOR
+Vdd
S
PWM
LATCH
R
Id
Q
Secondary
feedback
Is
0.23V
IFB
1 kΩ
FB
R1
C
230 Ω
R2
SOURCE
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1.1.5 Primary Driver
In a fly-back power supply, the transformer is used as an energy tank fuelled during the ON time of the
MOSFET. When the MOSFET turns off, its drain voltage rises from a low value to the input voltage plus
the reflected voltage while the secondary diode conducts, transferring on the secondary side the
magnetic energy stored in the transformer. Because primary and secondary windings are not perfectly
magnetically coupled, there is a serial leakage inductance that behaves like an open inductor charged at
Ipk that causes the voltage spikes on the MOSFET drain. These voltage spikes must be clamped to keep
the VIPer22A Drain voltage below the BVdss (730Vmin) rating. If the peak voltage is higher than this
value, the device will be destroyed. The most used solution is the RCD clamp (see figure 3). This is a
very simple and cheap solution, but it impacts on the efficiency and even on the power dissipation in
stand-by condition. Also the clamping voltage varies with load current. RCD clamp circuits may allow the
drain voltage to exceed the data sheet breakdown rating of VIPer22A during overload operation or during
turn on with high line AC input voltage. So, a zener clamp is recommended (see figure 4). However such
a solution gives higher power dissipation at full load, even if the clamp voltage is exactly defined.
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1.2 Transformer Consideration
On the electrical specification of a multiple output transformer (cross regulation, leakage inductance), the
main efforts focused on the proper coupling between the windings. A lower leakage inductance
transformer will allow a lower power clamp to reduce the input power. It will lead to lower power
dissipation on the primary side.
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Auxiliary and secondary windings are swapped in order to decrease the coupling to the primary one. The
secondary windings act as a shielding layer to reduce the capacitive coupling. Fewer spikes are
generated on the auxiliary windings, the primary and secondary windings have better coupling.
Designing transformers for low leakage inductance involves several considerations:
•Minimize number of turns
•Keep winding build (ratio of winding height to width) small
•Increase width of windings
•Minimize insulation between windings
•Increase coupling between windings
3/11
AN1897 - APPLICATION NOTE
Figure 2: Application schematic
J3
J5
J4
9
8
7
6
5
4
3
2
1
4
3
2
1
CON4
5
4
3
2
1
CON5
CON9
STB
3.3V
Vout
3
+5Vstb / 0.1A
F+ (3.3Vac)
F- (3.3Vac) / 0.15A
C15
100uF/10V
GND 2
R9
R8
5.1K
5.1K
LD33V
U4
Vin
1
+5V / 1.5A
--26V / 0.05A
--12V / 0.03A
+12V / 0.03A
R6
1K
C10
D12
1N5818
R11
680 ohm
U1A
47pF
U3
C13
817
C25
TL431
470uF16V
100uF/10V
Q3
8550
1K
220uF/50V
220uF/50V
BYW 100/200BYW 100/200
1000uF/16V
D8
STPS5L60
D9
D7
BYW 100/200
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BYW 100/200
9
8
13
10
12
7
11
14
15
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TX1
TFO EC28---VER3
2
1
D6
1N4937
47pF/1KV
FR157
1
2
J2
CON2
Auxiliary Volt 10 Vmin
3.3Vac
0.15A
- 26V
0.05A
+ 12V
0.03A
- 12V
0.03A
+ 5Vstb 0.1A
+ 5V
1.5A
0.1uF X2
4/11
CON2
1nF / 1KV
C3
1
2
250V 1A
F1
J1
C8
2
1
C6
47nF
817
2
VIPER22A
1
2.2mH
CH1
3
U1B
SOURCE
C1
2200pF Y1
C2
2200pF Y1
NTC5D-9
RT1
4
VDD
1N4007
D1
1N4007
D2
1N4007
D3
D4
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1N4007
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R3
9.1K
CONTROL
100k/1W
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47uF/50V
U2
R3
C4
C7
DRAIN
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D5
JP1
JUMPER
C5
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1K
C9
C12
D11
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9014
R4
D10
47uF/400V
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Q1
C20
C19
470uF/25V
470uF/25V
C17
D13
1N5818
R5
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AN1897 - APPLICATION NOTE
Figure 3: RCD clamp topology
Figure 4: Zener clamp topology
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For a transformer meeting international insulation and safety requirements, a practical value for leakage
inductance is about 1-3% of the open circuit primary inductance.
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A high efficiency transformer should have low inter-winding capacitance to decrease the switching
losses. Energy stored in the parasitic capacitance of the transformer is absorbed by VIPer cycle by cycle
during the turn-on transition. Excess capacitance will also ring with stray inductance during switch
transitions, causing noise problems. Capacitance effects are usually the most important in the primary
winding, where the operating voltage (and consequent energy storage) is high. The primary winding
should be the first winding on the transformer. This allows the primary winding to have a low mean length
per turn, reducing the internal capacitance. The driven end of the primary winding (the end connected to
the Drain pin) should be the beginning of the winding rather than the end.
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This takes advantage of the shielding effect of the second half of the primary winding and reduces
capacitive coupling to adjacent windings. A layer of insulation between adjacent primary windings can cut
the internal capacitance of the primary winding by as much as a factor of four, with consequent reduction
of losses. A common technique for winding multiple secondaries with the same polarity sharing a
common return, is to stack the secondaries (see figure 5). This arrangement will improve the load
regulation, and reduce the total number of secondary turns.
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Commonly a clamper based on an RCD network or a diode with a zener to clamp the rise of the drain
voltage is used.
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Figure 5: Multiple output winding
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AN1897 - APPLICATION NOTE
2. LAYOUT RECOMMENDATION
Since EMI issues are strongly related to layout, a basic rule has to be taken into account in high current
path routing, i.e. the current loop area has to be minimized. If a heat-sink is used it has to be connected
to ground too, in order to reduce common mode emissions, since it is close to the floating drain tab.
One more consideration has to be made regarding the control ground connection: in fact in order to avoid
any noise interference on VIPer logic pin the control ground has to be separated from power ground.
3. EXPERIMENTAL RESULT
3.1 Efficiency
Figure 6: Efficiency at 230Vac (Load on 5V)
Figure 7: Efficiency at 260Vac (Load on 5V)
+12V/30mA, -12V/30mA, -26V/50mA,
3.3V/0.15A
+12V/30mA, -12V/30mA, -26V/50mA,
3.3V/0.15A
80.00%
80.00%
70.00%
70.00%
60.00%
Efficiency
Efficiency
60.00%
50.00%
40.00%
30.00%
50.00%
40.00%
20.00%
20.00%
10.00%
10.00%
0.1A
0.1A
0.5A
1A
1.5A
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0.1A
0.5A
1.0A
1.5A
2A
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Figure 9: Load Regulation (load on +5V)
5.20
5.15
5.10
Voltage
+12V/30mA, -12V/30mA, -26V/50mA,
3.3V/0.15A
du
1A
Efficiency at 260Vac Input
Figure 8: Efficiency at 85Vac (Load on 5V)
76.00%
74.00%
72.00%
70.00%
68.00%
66.00%
64.00%
62.00%
60.00%
0.5A
2A
Efficiency at 230Vac Mains Input
Efficiency
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0.00%
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30.00%
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5.05
5.00
4.95
4.90
4.85
4.80
1.5A
2.0A
0A
0.1A
0.5A
1A
1.5A
2A
Load (A)
Efficiency at 85Vac Input
+5V Load Regualtion
3.2 Regulation
Table 2: Line regulation
5V/ 0.1A
5Vstb/ 0A
12V/ 0A
-12V/ 0A
-26V/ 0A
3.3V/ 0A
6/11
Output
85Vac
5.15V
5.15V
12.08V
-11.98V
-25.82V
3.87V
230Vac
5.15V
5.15V
12.11V
-11.99V
-25.85V
3.87V
260Vac
5.15V
5.15V
12.12V
-12.00V
-25.86V
3.88V
AN1897 - APPLICATION NOTE
Figure 10: Cross regulation
+5V/0.5A
15.00
10.00
5.00
Voltage
0.00
0mA
-5.00
10mA
30mA
50mA 100mA 150mA
-10.00
-15.00
-20.00
-25.00
-30.00
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Load (mA)
+12V
-12V
-26V
3.3V
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Table 3: Stand by model
Output
85Vac
5V
2.05V
5Vstb (100mA)
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-12V
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-26V
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3.3V
Pdis
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230Vac
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260Vac
2.05V
2.07V
5.11V
5.14V
4.00V
3.99V
3.98V
3.99V
3.99V
3.98V
9.12V
9.10V
9.08V
1.70V
1.50V
1.51V
0.8W
1W
1.1W
5.08V
12V
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Table 4: Full Load Regulation
bs
85Vac
230Vac
260Vac
5V/ 1.5A
Output
5.02V
5.09V
5.08V
5Vstb/ 0A
5.02V
5.09V
5.08V
12V/30mA
12.03V
12.06V
12.05V
-12V/30mA
-12.01V
-12.05V
-12.05V
-26V/50mA
-26.06V
-26.16V
-26.15V
3.3V/0.15A
3.77V
3.80V
3.78V
VIPer Temp
53°C
47°C
45°C
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7/11
AN1897 - APPLICATION NOTE
4. TRANSFORMER SPECIFICATION
Figure 11: Transformer Structure
Primary inductance: Lp = 2.8 mH 1KHz, 0.3V
Leakage inductance: Lk < 28uH at Secondary
and auxiliary winding short (1KHz, 0.3V)
Core: EER28L
Bobbin: ER28 (6 + 9 Pin)
Vendor: YuanDongDa electronics Co., Ltd
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Table 5: Winding Parameters
Layers description
Symbol
Start Pin
Primary
Wp
Pin2
Out1 (5V/1.5A)
W5
Pin7
Out2 (12V/0.03A)
W12
Pin11
Out3 (-12V/0.03A)
W-12
Out4 (-26V/0.05A)
W-26
(s)
Wstb
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Number of Layer Turns
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Pin1
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Out5 (5Vstb/0.1A)
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End Pin
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Wire Size
(mm)
2
65
0.3
Pin12
1
4
2*0.6
Pin7
1
5
0.3
Pin12
Pin10
1
9
0.45
Pin10
Pin13
1
10
0.3
Pin9
Pin8
1
12
0.3
Out6 (3.3V/0.15A)
W3v3
Pin14
Pin15
1
3
0.3
Auxiliary
Waux
Pin6
Pin5
1
24
0.3
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O
B
B
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12
7
10
13
15
8
5
Wp
W5
W12
W-12
W-26
W3v3
Wstb
Waux
7
11
12
14
9
6
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Barrier (3mm)
1
10
Barrier (3mm)
8/11
AN1897 - APPLICATION NOTE
5. PCB LAYOUT
Figure 12: Bottom view of the demo board (not in scale)
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Figure 13: PCB Art Work (not in scale)
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9/11
AN1897 - APPLICATION NOTE
5. BILL OF MATERIALS
Ref.
Description
Note
U1
Photocoupler PC817
SHARP
U2
VIPer22A DIP
STMicroelectronics
U3
TL431 ACZ
STMicroelectronics
U4
L4931 ABV33
STMicroelectronics
Q1
SS9014
Q3
SS8550
D1, D2, D3, D4
1N4007
D5
FR157
D6, D7, D9, D10, D13 STTH102
D8
D11, D12
STMicroelectronics
X2 Capacitor 0.1uF
C4
Electrolytic Capacitor 100uF/400V
C6
Ceramic Capacitor 47nF/50V
C7
Electrolytic Capacitor 47uF/50V
C9
Electrolytic Capacitor 220uF/50V
Ceramic Capacitor 47pF/50V
C12
Electrolytic Capacitor 1000uF/16V
C13
Electrolytic Capacitor 470uF/16V
C15
Electrolytic Capacitor 100uF/10V
C17
Electrolytic Capacitor 470uF/25V
C19
Electrolytic Capacitor 470uF/25V
C20
Electrolytic Capacitor 220uF/50V
C25
Electrolytic Capacitor 220uF/16V
)
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R3
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R4, R5, R6
Not fit
9.1KΩ ¼ W
100KΩ 1W
1KΩ ¼ W
R8, R9
5.1KΩ ¼ W
R11
680Ω ¼ W
CH1
2.2mH Common choke
TX1
EER28 transformer
F1
Fuse 1A
J1, J2
2pin connector
J3
5pin connector
J4
4pin connector
J5
9pin connector
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C10
R2
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1nF/1KV
RT1
10/11
1N5818
C3
C5, C8
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STMicroelectronics
Y1 Capacitor 2200pF
C1, C2
bs
STMicroelectronics
STPS5L60
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AN1897 - APPLICATION NOTE
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Information furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibility for the consequences
of use of such information nor for any infringement of patents or other rights of third parties which may results from its use. No license is
granted by implication or otherwise under any patent or patent rights of STMicroelectronics. Specifications mentioned in this publication are
subject to change without notice. This publication supersedes and replaces all information previously supplied. STMicroelectronics products
are not authorized for use as critical components in life support devices or systems without express written approval of STMicroelectronics.
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