dm00133279

AN4583
Application note
Cable set-top box SMPS adaptor using VIPER27
Harjeet Singh, Alessandro Cannone
Introduction
Abstract: a set-top box (STB) is a cable box, placed in the consumer's house, that has the
ability to receive commands from the cable company. Such commands would enable the
box to decode a particular channel, such that only the customer, who subscribes to
a channel, will receive that channel. This application note describes the design for the
SMPS adaptor using the ST's innovative off-line integrated flyback controller VIPER27. The
typical power requirement is within 8 to 10W in wide range for the cable set-top application.
The VIPER27LN device has an integrated high-performance low voltage PWM controller
chip and an 800 V avalanche rugged power MOSFET in the same package. The device is
suitable for the isolated flyback converter mainly off-line power supplies.
The burst mode operation and device very low consumption help to meet the standby
energy saving regulation. Advance frequency jittering reduces the EMI filter cost. Brown-out
function protects the switch mode power supply when the rectified input voltage is below the
nominal minimum level specified for the system. The high voltage start-up circuit is
embedded in the device.
Figure 1. SMPS adaptor
Some of the common applications which can be covered with the device are listed below:
 SMPS for set-top boxes, DVD players and recorders, white goods
 Auxiliary power supply for consumer and home equipments
 ATX auxiliary power supply
 Low / medium power AC-DC adapters.
August 2015
DocID026909 Rev 1
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www.st.com
36
Contents
AN4583
Contents
1
Brief description of VIPER27 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2
Schematic and description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3
Bill of material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
4
Transformer specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
5
6
4.1
General description and characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . 14
4.2
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Performance test results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
5.1
Output regulation test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
5.2
Efficiency test results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Functional check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
6.1
Steady state waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
6.2
Transient/start-up waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
7
Burst mode operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
8
Hold-up test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
9
Soft-start test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
10
Short-circuit test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
11
Transient load test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
12
Output voltage ripple . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
13
Thermal test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
14
EMI pre-compliance test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
2/36
DocID026909 Rev 1
AN4583
Contents
15
Printed circuit board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
16
Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
17
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
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36
List of tables
AN4583
List of tables
Table 1.
Table 2.
Table 3.
Table 4.
Table 5.
Table 6.
Table 7.
Table 8.
Table 9.
Table 10.
Table 11.
Table 12.
Table 13.
Table 14.
4/36
Typical output power. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Basic specifications of adaptor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Bill of material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Winding details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Output voltage and VDD line-load regulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Energy efficiency criteria for standard models - average efficiency - Tier2 . . . . . . . . . . . . 18
Energy efficiency criteria for standard models - efficiency at 10% load - Tier2 . . . . . . . . . 18
Average efficiency at 115 VAC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Average efficiency at 230 VAC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Average efficiency at 10% of the max. output load. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Active mode efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Consumptions at no load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Temperature measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
DocID026909 Rev 1
AN4583
List of figures
List of figures
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Figure 7.
Figure 8.
Figure 9.
Figure 10.
Figure 11.
Figure 12.
Figure 13.
Figure 14.
Figure 15.
Figure 16.
Figure 17.
Figure 18.
Figure 19.
Figure 20.
Figure 21.
Figure 22.
Figure 23.
Figure 24.
Figure 25.
Figure 26.
Figure 27.
Figure 28.
Figure 29.
Figure 30.
Figure 31.
Figure 32.
Figure 33.
Figure 34.
Figure 35.
Figure 36.
Figure 37.
Figure 38.
Figure 39.
Figure 40.
SMPS adaptor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Typical topology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Package of VIPER27 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Picture of transformer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Line load regulation curve. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Vcc variations for line and load changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Efficiency at 115 VAC and 230 VAC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Efficiency at different line and load conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Standby power at different line inputs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Light load consumptions at different output power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Waveform at 90 VAC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Waveform at 115 VAC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Waveform at 190 VAC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Waveform at 230 VAC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Waveform at 265 VAC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Waveform at 320 VAC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Waveform of start-up at 90 VAC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Waveform of start-up at 90 VAC (zoom view 1). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Waveform of start-up at 90 VAC (zoom view 2). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Waveform of start-up at 265 VAC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Waveform of start-up at 265 VAC (zoom view 1). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Waveform of start-up at 265 VAC (zoom view 2). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Waveforms of drain-source at 320 VAC start-up condition . . . . . . . . . . . . . . . . . . . . . . . . . 25
Waveforms at no load condition, 230 VAC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Hold-up test at 230 VAC input voltage, at full load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Output soft-start at full load. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Output short-circuit behavior at 230 VAC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Output short-circuit behavior at 230 VAC (single burst). . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Output transient response at 115 VAC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Output transient response at 230 VAC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Output voltage ripple at 115 VAC, no load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Output voltage ripple at 115 VAC, full load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Output voltage ripple at 230 VAC, no load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Output voltage ripple at 230 VAC, full load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
EMI results at 115 VAC mains input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
EMI results at 230 VAC mains input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
PCB top view . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
PCB solder side bottom view . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
PCB silkscreen bottom view . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
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36
Brief description of VIPER27
1
AN4583
Brief description of VIPER27
The device is an off-line converter with an 800 V rugged power section, a PWM control, two
levels of overcurrent protection, overvoltage and overload protections, hysteretic thermal
protection, the soft-start and safe auto restart after any fault condition removal. The burst
mode operation and device’s very low consumption help to meet the standby energy saving
regulations.
Advance frequency jittering reduces the EMI filter cost. Brown-out function protects the
switch mode power supply when the rectified input voltage level is below the normal
minimum level specified for the system. The high voltage start-up circuit is embedded in the
device.
Features
6/36

800 V avalanche rugged power section

PWM operation with frequency jittering for low EMI

Operating frequency:
–
60 kHz for L type
–
115 kHz for H type

Standby power < 50 mW at 265 VAC

Limiting current with adjustable set point

Adjustable and accurate overvoltage protection

On-board soft-start

Safe auto restart after a fault condition

Hysteretic thermal shutdown
DocID026909 Rev 1
AN4583
Brief description of VIPER27
Figure 2. Typical topology
Figure 3. Package of VIPER27
A typical output power table is shown below.
Table 1. Typical output power
Part number
VIPER27
230 VAC
85-265 VAC
Adapter(1)
Open frame(2)
Adapter(1)
Open frame(2)
13 W
16 W
10 W
12 W
1. Typical continuous power in non ventilated enclosed adapter measured at 50 °C ambient.
2. Maximum practical continuous power in an open frame design at 50 °C ambient, with adequate heat
sinking.
DocID026909 Rev 1
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36
Brief description of VIPER27
AN4583
Table 2. Basic specifications of adaptor
8/36
Parameters
Limits
Rated voltage range
90 - 265 VAC
Nominal operating voltage range
100 - 320 VAC
Input supply frequency (fL)
47 - 63 Hz
Input / output isolation
Yes, > 2.7 KV
Application
Set-top box SMPS/adaptor
Output voltage tolerance
12 V ± 0.2 V
Nominal output current
1 Amp
Total output power
12 W
Active mode efficiency
> 80%
Active mode at 10% load efficiency
> 70%
Output voltage ripple
< 50m Vp-p
Maximum ambient temperature
50 °C
Protections
Overload, short-circuit, thermal shutdown
DocID026909 Rev 1
AN4583
2
Schematic and description
Schematic and description
The schematic of the power supply is shown in Figure 4. The input section is comprised of
the fuse F1, NTC, capacitor C4 and the common mode inductor L1. L1, C4 are used to take
care of conducted emissions. The MOV1 is placed after the inductor, in this way surge
energy is also limited up to some extent by the L1 and then the MOV does its function. The
bulk capacitor C3 after bridge rectification provides also the additional path to absorb energy
and helpful in the surge immunity in addition to the filtration purpose(a).
Then the transformer T1 and the VIPer U1 are configured in typical isolated flyback
topology. The RCD clamp is made up with the R2, C1 and D2 which clamps the off-state
leakage spikes across the MOSFET device.
The integrated MOSFET of the device is 800 V avalanche rugged, which provides extra
room to take care of wide mains operating condition. Normally the power supply is intended
to use for the wide mains operation which has maximum working voltage 265 VAC, but with
800 V the device one can easily achieve the high mains line operation, provided there is
enough voltage withstanding capability of the bulk capacitor voltage after rectification. Just
an example: the power supply can even cater line to line voltage 440 VAC using the C3 as
two bulk 400 WV capacitors in series. With suitable designing of the transformer and the
turn ratio considering the 90 - 440 VAC operation, the off-state stress can be maintained
within 800 V.
There are other features of the device - by using the functionality of the BR and CONT pins
are described as below:
BR: input voltage information is provided to the BR pin by using the resistor divider network
from rectified bus voltage and can detect the brown-out threshold to turn off the device. The
resistor divider network R4, R5 and R7 is programmed to achieve brown-out protection.
If the function is not required, we can disable by grounding the BR pin using the R7 as the
0E resistor. This will also reduce the power consumption and no load losses in addition to
reduce the component counts otherwise one can easily program the values of the R4, R5
and R7 for desired mains under the voltage shutdown. The C10 helps to reduce the noise
pick-up at the BR pin (refer to the VIPER27 datasheet for more details).
CONT: with the CONT pin, one can impose a limit on the peak drain current (Idlim can be
programmed using the R9). Not using this resistor will limit the peak current to its internal
maximum Idlim value. An another feature is to have protection in case output overvoltage
(output OVP protection), which can be sensed using the auxiliary winding which is used for
VCC biasing (refer to the VIPER27 datasheet for more details).
With these features of the VIPer™ Plus family from the STMicroelectronics designer can
make the system more reliable and robust.
The device is biased using the auxiliary winding and using the D3, R3 and C9. The C2 helps
for noise reduction and enhances also the ESD immunity.
a. The inrush is also reduced by the common mode inductor L1. So one can also remove the NTC as it consumes
some power and reduces the efficiency of converter.
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36
Schematic and description
AN4583
The C11, C12 and R12 comprise of the type - II compensation network for feedback loop
stability (for more details, refer to the VIPER27 datasheet). The device is configured with the
secondary side regulation using the U2, U3: the optocoupler and the TS431 standard
secondary side feedback network. The R11 and R14 are programmed for 12 V output by
fixing 1.25 V reference to the TS431.
There is also the option to make the loop regulated by using the simple Zener diode, Z1 and
eliminating all other parts: U3, R11, R13, R14 and C13 to bring the system solution cost
down. In the board, the option to place the Zener diode is also provided in case one doesn't
want to use TS431 based feedback design. This simple scheme is also fine as long as there
is no stringent requirement of transient specifications. The power supply is tested in both
condition with or without the TS431, however the performance is shown with standard
TS431 configuration.
The used transformer is the EE19 profile, which is suitable to provide the power
requirements for cable set box requirements. Of course the board is tested in a fully
enclosed frame with an output of 12 W power. This is explained further and shown the
thermal performance. In the board, there is also kept the option to mount the EE20 profile
core and the board can easily accommodate the EE20 transformer as well if the EE19 is not
the customer's choice.
Output rectification is achieved using the ST Schottky rectifier STPS3150U in the SMD
package along with the low ESR capacitor C5 for filtering function. The L2 and C6 comprise
the post LC filter to reduce the switching noise to a very low level as desired in set-top box
requirements.
10/36
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Schematic and description
Figure 4. Schematic
11/36
36
Bill of material
3
AN4583
Bill of material
Table 3. Bill of material
Part value and
S.
no.
Reference
1
BR1
Bridge rectifier, MB6S
2
C1
3
Manufacturer
Manufacturer part no.
Package
Qty.
Vishay Semiconductor
MB6S-E3/45
SMD
1
Capacitor disc type, 220
pF/400 V
TH
1
C2, C13,
C7
Capacitor, 100 nF/50 V
SMD, 0805
3
4
C3
Capacitor electrolytic,
22 F/450 V
TH
1
5
C4
Capacitor 100 nF/
320 V, X2 type
TH(1)
1
6
C5
Capacitor electrolytic,
1000 F/25 V, low ESR,
105 °C
Rubycon
25ZL1000MEFC12.5X20
TH
1
7
C6
Capacitor electrolytic,
220 F/25 V
Rubycon
25YXH220MEFC8X11.5
TH
1
8
C8
Capacitor, 2.2 nF/
250 V X1/Y1 type
Murata
DE2E3KY222MA2BM01
TH
1
9
C9
Capacitor electrolytic,
22 F/35V
Panasonic
EEUFC1V220
TH
1
10
C11
Capacitor, 56 nF/25 V
SMD, 0805
1
11
C12
Capacitor, 1 nF/25 V
SMD, 0805
1
12
D1
Schottky diode,
STPS3150U
STMicroelectronics
SMA
1
13
D2
Ultrafast diode,
STTH1R06A
STMicroelectronics
SMD
1
14
D3
Schottky diode, 1N4148
STMicroelectronics
SMD
1
15
LD1A
LED red, 3 mm
TH
1
16
L1
Common mode line
inductor, 35 mH
TH
1
17
L2
Filter inductor, 4.7 H
TH, drum
type
1
18
MOV1
MOV, S10K320E2
10 mm
1
19
R1, R15
Resistor, 2.2 K
SMD 1206
2
20
R2
Resistor CFR 330 K
1 W CFR
TH
1
21
R3
Resistor, 22E
SMD, 0805
1
22
R6, R8
Resistor, 1.5 K
SMD, 0805
2
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description
Panasonic
DocID026909 Rev 1
EEUEE2W220S
AN4583
Bill of material
Table 3. Bill of material (continued)
S.
no.
Reference
23
R7
24
Part value and
Package
Qty.
Resistor, 0E
SMD, 0805
1
R10
Resistor, 100 K
SMD, 0805
1
25
R11
Resistor, 130 K, 1%
SMD, 0805
1
26
R12
Resistor, 22 K
SMD, 0805
1
27
R13
Resistor, 200 K
SMD, 0805
1
28
R14
Resistor, 15 K, 1%
SMD, 0805
1
29
T1
Transformer, EE19
TH, 7 pins
1
30
U1
VIPer27LN
DIP-7
1
31
U2
Optocoupler, PC817A/B
DIP4
1
32
U3
TS431
TO-92
1
33
NTC
34
F1
Manufacturer
description
Manufacturer part no.
STMicroelectronics
STMicroelectronics
(2)
1
NTC 10-16E at 25 °C
Fuse 2.5 A/250 VAC
Cooper Bussmann
SS-5H-2-5A-BK
TH
1
1. “TH” stands for a through hole package.
2. Optional, not mounted on board.
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36
Transformer specification
AN4583
4
Transformer specification
4.1
General description and characteristics
4.2

Transformer type: closed

Coil former: vertical type, 4 + 3 pins, two slots

Max. temperature rise: 45 °C

Max. operating ambient temperature: 60 °C

Mains insulation: in accordance with EN60950
Electrical characteristics

Converter topology: fixed frequency flyback

Core type: EE19-N67 or equivalent

Min. operating frequency: 60 kHz

Typical operating frequency: 60 kHz

Primary inductance: 1400 H ± 10% at 10 kHz - 0.25 V (measured between pins 2 - 1)

Auxiliary inductance: 43 H ± 15% at 10 kHz - 0.25 V (measured between pins 3 - 4)

Secondary inductance: 28 H ± 20% at 10 kHz - 0.25 V (measured between pins 7 - 5)

Leakage inductance : 17 H ± 10% at 50 kHz - 0.25 V (measured between pins 2 - 1
with secondary winding 7 - 5 shorted)

Primary (2 - 1) - secondary (8 - 5) turn ratio: 6.3:1

Primary (2 - 1) - auxiliary turn ratio: 8:1

Dielectric strength between primary (2 - 1) - secondary (7 - 5): 2.5 KV, 5 mA, 1 min.
Figure 5. Picture of transformer
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AN4583
Transformer specification
Table 4. Winding details
Winding name
Pins (start - stop)
Wire
Method
Np
2-1
1UEW 0.30 mm x 1
Solenoid (split halves)
Naux
3-4
1UEW 0.12 m x 1
Spread
Ns
7-5
1UEW 0.60 mm x 1
Solenoid
Transformer part number: RDTS - 1907.
Manufacturer: GSP Electronics Pvt. Ltd., Noida, India.
E-mail: [email protected]; [email protected]
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36
Performance test results
AN4583
5
Performance test results
5.1
Output regulation test
The output voltage of the board is measured in different line and load conditions (see
Table 5). The output voltage is practically not affected by the line condition. The Vcc voltage
is also measured to verify that it is inside the operating range of the device.
Table 5. Output voltage and VDD line-load regulation
Vinac
(Vrms)
No load
25% load
Vout (V) Vcc (V) Vout (V)
50% load
75% load
Vcc (V)
Vout (V)
Vcc (V)
Vout (V)
Vcc (V)
100% load
Vout (V) Vcc (V)
90
11.99
11.45
11.98
14.90
11.98
15.30
11.98
16.60
11.98
17.70
115
11.99
11.50
11.98
14.90
11.98
15.30
11.97
16.72
11.97
17.60
230
11.98
11.30
11.98
14.90
11.95
15.30
11.95
17.02
11.95
17.60
265
11.98
11.30
11.95
14.80
11.94
15.10
11.94
17.01
11.94
17.60
Figure 6. Line load regulation curve
Lineloadregulation
12.50
Vout([V]
12.00
11.50
AtNoLoad
At25%Load
11.00
At50%Load
At75%Load
10.50
AtFullLoad
10.00
70
90
110
130
150
170
190
210
230
250
270
Vinac[Vrms]
Looking to Figure 6, the output voltage is tightly regulated for wide mains variation at
different load conditions.
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AN4583
Performance test results
Figure 7. Vcc variations for line and load changes
20
18
16
Vcc [V]
14
12
10
8
6
4
2
0
70
90
110
130
150
170
190
210
230
250
270
Vinac[Vrms]
At25%Load
At50%Load
At75%Load
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AtFullLoad
AtNoLoad
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36
Performance test results
5.2
AN4583
Efficiency test results
The efficiency of the converter is measured in different load and line voltage conditions. The
measurements are taken at 25%, 50%, 75% and the full load for different input voltages and
the efficiency at the 10% load and the measurement falls under limits of the “EC CoC
version 5 Tier2” requirements as shown in Table 8, Table 9 and Table 10.
Table 6. Energy efficiency criteria for standard models - average efficiency - Tier2
Nameplate output power (Pno)
Minimum average efficiency (expressed as a decimal)
0 to ≤ 1 watt
≥ 0.5 * Pno + 0.169
> 1 to ≤ 49 watts
≥ [0.071 * In (Pno)] - 0.00115 * Pno + 0.67
> 49 watts
≥ 0.890
Table 7. Energy efficiency criteria for standard models - efficiency at 10% load - Tier2
Nameplate output power (Pno)
Minimum average efficiency (expressed as a decimal)
0 to ≤ 1 watt
≥ 0.5 * Pno + 0.06
> 1 to ≤ 49 watts
≥ [0.071 * In (Pno)] - 0.00115 * Pno + 0.57
> 49 watts
≥ 0.790
Table 8. Average efficiency at 115 VAC
% load
IOUT (A)
VOUT (V)
PIN (W)
POUT (W)
Efficiency (%)
25%
0.25
11.98
3.612
2.995
82.92
50%
0.50
11.98
7.140
5.990
83.89
75%
0.75
11.97
10.750
8.978
83.51
100%
1.00
11.97
14.430
11.970
82.95
Average efficiency
83.32
EC Coc version 5 Tier2 - minimum average efficiency
83.26
Table 9. Average efficiency at 230 VAC
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% load
IOUT (A)
VOUT (V)
PIN (W)
POUT (W)
Efficiency (%)
25%
0.25
11.96
3.696
2.990
80.90
50%
0.50
11.95
7.148
5.975
83.59
75%
0.75
11.95
10.630
8.963
84.31
100%
1.00
11.95
14.130
11.950
84.57
Average efficiency
83.34
EC Coc version 5 Tier2 - minimum average efficiency
83.26
DocID026909 Rev 1
AN4583
Performance test results
Table 10. Average efficiency at 10% of the max. output load
VIN [VAC]
IOUT (A)
VOUT (V)
PIN (W)
POUT (W)
Efficiency [%]
115
0.10
11.99
1.517
1.199
79.04
230
0.10
11.98
1.633
1.198
73.36
EC Coc version 5 Tier2 - minimum efficiency at 10% load
73.26
Figure 8. Efficiency at 115 VAC and 230 VAC
7BD
&GGJDJFODZ <>
7BD
"WFSBHFBU7BD
"WFSBHFBU7BD
.JOJNVNBWFSBHFFGGJDJFODZ
0VUQVU DVSSFOU MPBE <">
".
Table 11. Active mode efficiency
Efficiency [%]
VIN [VAC]
Average
efficiency
0.25 A
0.50 A
0.75 A
1A
90
82.83
83.01
82.28
80.73
82.21
115
82.92
83.89
83.51
82.95
83.32
150
83.03
84.13
84.38
84.18
83.93
180
82.46
84.07
84.46
84.57
83.89
230
80.90
83.59
84.31
84.57
83.34
265
79.69
82.97
83.93
84.32
82.73
DocID026909 Rev 1
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36
Performance test results
AN4583
Figure 9. Efficiency at different line and load conditions
&GGJDJFODZ <>
DVSSFOU MPBE
DVSSFOU MPBE
DVSSFOU MPBE
DVSSFOU MPBE
7*/ <7"$ >
".
Table 12. Consumptions at no load
PIN [mW]
20/36
90
39.91
115
37.90
150
37.96
180
37.07
230
40.09
265
43.38
DocID026909 Rev 1
POUT [mW]
0
AN4583
Performance test results
Figure 10. Standby power at different line inputs
1*/ <N8>
7*/ <7"$>
".
To be complying with the EuP Lot 6, the EPS requires efficiency higher than 50% when the
output load is 250 mW.
Figure 11. Light
at different
H load consumptions
Q
Q Qoutput power
N8
N8
1*/ <N8>
N8
N8
7*/ <7"$>
".
From efficiency analysis, the results are very close to the limits as per Tier2 although the
power supply satisfies the requirement of cable Set top box applications and is targeted
mainly for cable set top box application in India.
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36
Functional check
6
AN4583
Functional check
The converter is operated at different mains conditions (refer from Figure 12 to Figure 17),
starting from 90 to 320 VAC and the drain switching waveform and drain current waveforms
are captured at each line voltage at full load conditions.
6.1
Steady state waveforms
The typical operating waveforms are captured for wide mains variation input at full loaded
conditions.
22/36
Figure 12. Waveform at 90 VAC
Figure 13. Waveform at 115 VAC
CH1: drain current; CH2: Vcc voltage;
CH3: FB signal; CH4: drain-source voltage
CH1: drain current; CH2: Vcc voltage;
CH3: FB signal; CH4: drain-source voltage
Figure 14. Waveform at 190 VAC
Figure 15. Waveform at 230 VAC
CH1: drain current; CH2: Vcc voltage;
CH3: FB signal; CH4: drain-source voltage
CH1: drain current; CH2: Vcc voltage;
CH3: FB signal; CH4: drain-source voltage
DocID026909 Rev 1
AN4583
6.2
Functional check
Figure 16. Waveform at 265 VAC
Figure 17. Waveform at 320 VAC
CH1: drain current; CH2: Vcc voltage;
CH3: FB signal; CH4: drain-source voltage
CH1: drain current; CH2: Vcc voltage;
CH3: FB signal; CH4: drain-source voltage
Transient/start-up waveforms
In this section, both the primary current as well as voltage stress on the MOSFET are
captured at extreme mains conditions 90 VAC and 265 VAC at full loaded conditions.
Following waveforms are analyzed from Figure 18 to Figure 24.
Figure 18. Waveform of start-up at 90 VAC
Figure 19. Waveform of start-up at 90 VAC
(zoom view 1)
CH1: drain current; CH2: Vcc voltage;
CH3: FB signal; CH4: drain-source voltage
CH1: drain current; CH2: Vcc voltage;
CH3: FB signal; CH4: drain-source voltage
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36
Functional check
AN4583
Figure 20. Waveform of start-up at 90 VAC
(zoom view 2)
Figure 21. Waveform of start-up at 265 VAC
CH1: drain current; CH2: Vcc voltage;
CH3: FB signal; CH4: drain-source voltage
CH1: drain current; CH2: Vcc voltage;
CH3: FB signal; CH4: drain-source voltage
Figure 22. Waveform of start-up at 265 VAC
(zoom view 1)
Figure 23. Waveform of start-up at 265 VAC
(zoom view 2)
CH1: drain current; CH2: Vcc voltage;
CH3: FB signal; CH4: drain-source voltage
CH1: drain current; CH2: Vcc voltage;
CH3: FB signal; CH4: drain-source voltage
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AN4583
Functional check
Figure 24. Waveforms of drain-source at 320 VAC start-up condition
CH1: drain current; CH2: Vcc voltage; CH3: FB signal; CH4: drain-source voltage
Looking into above waveforms, the duty cycle is progressively increased which is the
inherent property of VIPer Plus devices to maintain the soft-start feature and to protect the
converter from excessive stress and avoiding the saturation in magnetic (if any) that may
arise due to uncontrolled duties at the start-up. In any case, no abnormal behavior in terms
of saturation effect observed in the transformer at various peak detections.
Referring to Figure 24, the drain source start-up instants are captured at 320 VAC at full
loaded condition. It is found that the maximum off-state stress on the MOSFET is 618 V,
means at worst start-up condition, the device has enough margin of around 800 - 618 = 182
Volts. This indicates that the converter could be even operated at higher line voltages,
provided the bulk capacitor and other rectifiers are rated accordingly. In addition, since the
VIPer Plus has an avalanche rugged MOSFET which gives extra protections against spikes,
that may happen due to improper transformer leakages and other abnormal conditions if the
stress voltage exceeds 800 V.
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36
Burst mode operation
7
AN4583
Burst mode operation
During no load condition, the device enters into the burst mode and the input power
consumption drops to minimum level. The corresponding switching waveforms are
displayed in Figure 25.
Figure 25. Waveforms at no load condition, 230 VAC
CH1: drain current; CH2: Vcc voltage;
CH3: FB signal; CH4: drain-source voltage
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8
Hold-up test
Hold-up test
The mains input is interrupted at loaded conditions to see the hold-up capability of the
SMPS. Referring to the waveform in Figure 26, the converter is able to deliver the load in
case there is missing of about 4 cycles of the 50 Hz mains supply at 230 VAC.
Figure 26. Hold-up test at 230 VAC input voltage, at full load
CH1: load current; CH4: mains input voltage
9
Soft-start test
The output voltage start-up behavior is captured at full load condition as shown in Figure 27.
Figure 27. Output soft-start at full load
CH1: load current; CH2:ouput voltage
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36
Short-circuit test
10
AN4583
Short-circuit test
The VIPerX7 family has several protections, one of them prevents converter damage in
case of the overload or output short-circuit. If the load power demand increases, the output
voltage decreases and the feedback loop reacts by increasing the voltage on the feedback
pin. The increase of the feedback pin voltage leads to the PWM current set point increase
which increases the power delivered to the output until this power equals the load power. If
the load power demand exceeds the converter's power capability (which can be adjusted
using RLIM), the voltage on the feedback pin continuously rises, but the power delivered no
longer increases. When the feedback pin voltage exceeds VFBlin (3.5 V typ.), VIPER27L
logic assumes that it is a warning for an overload event. Before shutting down the system,
the device waits for a period of time set by the capacitor present on the feedback pin. In fact
if the voltage on the feedback pin exceeds VFBlin, the internal pull-up is disconnected and
the pin starts sourcing a 3 A typ current that charges the capacitor connected to it. As the
voltage on the feedback pin reaches the VFBOLP threshold (4.8 V typ.), the VIPER27L stops
switching and is not allowed to switch again until the VDD voltage goes below VDD(RESTART)
(4.5 V typ.) and rises again up to VDDON (14 V typ.).
The following waveforms show the behavior of the converter when the output is shorted.
The converter is powered up at 230 VAC and output terminals are short-circuited. The device
enters into the hiccup mode, reducing the input power throughput from the mains. Refer to
short-circuit behavior as shown in Figure 28 and Figure 29.
Figure 28. Output short-circuit behavior at
230 VAC
Figure 29. Output short-circuit behavior
at 230 VAC (single burst)
CH1: drain current; CH2: Vcc voltage;
CH3: FB signal; CH4: drain-source voltage
CH1: drain current; CH2: Vcc voltage;
CH3: FB signal; CH4: drain-source voltage
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11
Transient load test
Transient load test
The converter is powered at 115 and 230 VAC at step load condition, i.e.: a sudden full load
is applied at output of the converter and removed to observe the undershoot and overshoot
in output voltage of the converter. The dynamic performance of the converter is analyzed as
shown in Figure 30 and Figure 31 at 115 VAC and 230 VAC respectively. There is the
negligible overshoot and undershoot observed in output and it shows good stable design of
the converter feedback loop.
Figure 30. Output transient response at 115 VAC Figure 31. Output transient response at 230 VAC
CH1: output voltage; CH4: load current
CH1: output voltage; CH4: load current
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36
Output voltage ripple
12
AN4583
Output voltage ripple
The peak-to-peak high frequency switching output voltage ripples are measured at output
terminals at no load as well as full load conditions. The ripple waveforms are captured at
different line conditions - 115 VAC and 230 VAC, as displayed from Figure 32 to Figure 35.
The peak-to-peak ripple voltage is approximately 25 - 35 mV at full load condition.
Figure 32. Output voltage ripple at 115 VAC, no
load
Figure 33. Output voltage ripple at 115 VAC, full
load
CH1: load current; CH2: output voltage ripple
CH1: load current; CH2: output voltage ripple
Figure 34. Output voltage ripple at 230 VAC, no
load
Figure 35. Output voltage ripple at 230 VAC, full
load
CH1: load current; CH2: output voltage ripple
CH1: load current; CH2: output voltage ripple
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13
Thermal test
Thermal test
The converter is kept on at the full load in a fully enclosed form at 90 VAC and 230 VAC and
at an ambient of 40 °C, following are the temperature readings for critical components noted
in stabilized condition:
Table 13. Temperature measurements
Sr. no.
Part and location of sensor
Temperature at 90 VAC
Temperature at 230 VAC
1
U1, VIPER27 case temperature
101.5 °C
72.8 °C
2
T1, transformer coil temperature
91.4 °C
82.1 °C
3
T1, transformer core temperature
87.0 °C
81.5 °C
4
C3, bulk capacitor body
59.2 °C
44.5 °C
5
D1, output Schottky rectifier
107.8 °C
100.2 °C
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36
EMI pre-compliance test
14
AN4583
EMI pre-compliance test
A pre-compliance test for EN55022 (Class B) European normative(b) was also performed
and the results are shown in Figure 36 and Figure 37.
Figure 36. EMI results at 115 VAC mains input
Figure 37. EMI results at 230 VAC mains input
b. Using an average measurement method.
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15
Printed circuit board
Printed circuit board
Figure 38. PCB top view
Figure 39. PCB solder side bottom view
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36
Printed circuit board
AN4583
Figure 40. PCB silkscreen bottom view
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16
Reference
Reference
VIPER27L datasheet (VIPER27 - “Off-line high voltage converters”).
17
Revision history
Table 14. Document revision history
Date
Revision
25-Aug-2015
1
Changes
Initial release.
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36
AN4583
IMPORTANT NOTICE – PLEASE READ CAREFULLY
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improvements to ST products and/or to this document at any time without notice. Purchasers should obtain the latest relevant information on
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