Title
Reference Design Report for 1.6 W,
Linear Replacement Adapter with 10 kV
surge withstand
Specification
85–265 VAC Input, 7.7 V, 210 mA Output
Application
Author
Document
Number
Date
Revision
Cordless Phone Adapter
Power Integrations Applications Department
RDR-83
Sept 29, 2006
1.0
Summary and Features
•
Highly efficient, low cost switching solution
•
Replacement for existing AC line transformer based design
•
Designed to withstand 10 kV common-mode surges
•
Ideal for applications connected to telephone network
•
EcoSmart
®
– meets all existing and proposed harmonized energy efficiency
standards including: CECP (China), CEC, EPA, AGO, European Commission
•
No-load power consumption <220 mW at 265 VAC
•
61.3% active-mode efficiency (exceeds requirement of 53.2%)
•
Integrated
LinkSwitch
safety/reliability features:
•
Accurate (± 5%), auto-recovering, hysteretic thermal shutdown function
maintains safe PCB temperatures under all conditions
•
Auto-restart protects against output short circuits and open feedback loops
•
Meets EN55022 and CISPR-22 Class B conducted EMI with >15 dBµV margin
•
Meets IEC61000-4-5 Class 4 AC line surge
The products and applications illustrated herein (including circuits external to the products and transformer
construction) may be covered by one or more U.S. and foreign patents or potentially by pending U.S. and foreign
patent applications assigned to Power Integrations. A complete list of Power Integrations’ patents may be found at
www.powerint.com.
RDR-83 7.7 V, 210 mA Adapter with 10 kV surge withstand
29-Sept-06
Table Of Contents
Introduction.................................................................................................................3
Power Supply Specification ........................................................................................4
2.1
Typical Output Characteristic and limits ..............................................................5
3 Schematic...................................................................................................................6
4 Circuit Description ......................................................................................................7
4.1
Input Stage ..........................................................................................................7
4.2
LinkSwitch-LP......................................................................................................7
4.3
Feedback.............................................................................................................8
4.4
Output Rectification .............................................................................................9
5 PCB Layout ..............................................................................................................10
6 Bill Of Materials ........................................................................................................11
7 Transformer Specification.........................................................................................12
7.1
Electrical Diagram .............................................................................................12
7.2
Electrical Specifications.....................................................................................12
7.3
Materials............................................................................................................12
7.4
Transformer Build Diagram ...............................................................................13
7.5
Transformer Construction..................................................................................13
8 Design Spreadsheets ...............................................................................................14
9 Performance Data ....................................................................................................19
9.1
Efficiency ...........................................................................................................19
9.1.1
Active Mode ENERGY STAR / CEC Efficiency Measurement Data...........20
9.2
No-load Input Power..........................................................................................21
9.3
Available Standby Output Power.......................................................................21
9.4
Regulation .........................................................................................................22
9.4.1
VI Curve vs. Input Voltage..........................................................................22
10
Thermal Performance ...........................................................................................23
10.1 LNK562 Temperature Rise................................................................................23
10.2 Thermal Image ..................................................................................................23
11
Waveforms............................................................................................................24
11.1 Drain Voltage and Current, Normal Operation...................................................24
11.2 Output Voltage Start-up Profile..........................................................................24
11.3 Drain Voltage and Current Start-up Profile ........................................................25
11.4 Load Transient Response (50% to 100% Load Step) .......................................26
11.5 Output Ripple Measurements............................................................................27
11.5.1 Ripple Measurement Technique ................................................................27
11.5.2 Measurement Results ................................................................................28
12
Line Surge.............................................................................................................29
13
Conducted EMI .....................................................................................................30
14
Revision History ....................................................................................................32
Important Note:
Although this board is designed to satisfy safety isolation requirements, the engineering prototype
has not been agency approved. Therefore, all testing should be performed using an isolation
transformer to provide the AC input to the prototype board.
1
2
Power Integrations
Tel: +1 408 414 9200 Fax: +1 408 414 9201
www.powerint.com
Page 2 of 36
29-Sept-06
RDR-83 7.7 V, 210 mA Adapter with 10 kV surge withstand
1 Introduction
This reference design report describes a switched-mode power supply that was designed
to replace line frequency transformer based solutions. The supply uses a member of the
LinkSwitch-LP
family of devices, and is capable of withstanding common-mode line
surges of up to 10 kV. That is often a requirement for applications that connect to a
telephone line, such as modems, cordless phones and answering machines.
The report includes the power supply specification, a circuit diagram, a bill of materials,
transformer documentation, a printed circuit layout board, and performance data.
Figure 1 –
Populated Circuit Board Photograph.
Page 3 of 36
Power Integrations
Tel: +1 408 414 9200 Fax: +1 408 414 9201
www.powerint.com
RDR-83 7.7 V, 210 mA Adapter with 10 kV surge withstand
29-Sept-06
2 Power Supply Specification
Description
Input
Voltage
Frequency
No-load Input Power (230 VAC)
Output
Output Voltage 1
Output Ripple Voltage 1
Output Current 1
Total Output Power
Continuous Output Power
No Load Output Voltage
Efficiency
Full Load
Required average efficiency at
25, 50, 75 and 100 % of P
OUT
Environmental
Conducted EMI
Safety
Surge
Differential Mode
Common Mode
Surge
Ambient Temperature
T
AMB
Meets CISPR22B / EN55022B
Designed to meet IEC950, UL1950
Class II
Symbol
V
IN
f
LINE
Min
85
47
Typ
Max
265
64
0.3
8.7
400
Units
VAC
Hz
W
V
mV
A
W
V
%
%
Comment
2 Wire – no P.E.
50/60
V
OUT1
V
RIPPLE1
I
OUT1
P
OUT
6.7
0.21
1.4
7.7
0.21
1.6
20 MHz bandwidth
11
η
η
CEC
60
53
Measured at P
OUT
25 C
Per ENERGY STAR / CEC
requirements
o
2
6
2
0
10
50
kV
kV
KV
o
1.2/50
µs
surge, IEC 1000-4-5,
Series Impedance:
Differential Mode: 2
Ω
Common Mode: 12
Ω
100 kHz ring wave, 500 A short
circuit current, differential
Free convection, sea level
C
Power Integrations
Tel: +1 408 414 9200 Fax: +1 408 414 9201
www.powerint.com
Page 4 of 36
29-Sept-06
RDR-83 7.7 V, 210 mA Adapter with 10 kV surge withstand
2.1 Typical Output Characteristic and Limits
The following diagram shows the output characteristic of the
LinkSwitch-LP
solution and
that of the linear transformer solution it was designed to replace. As can be seen, the
LinkSwitch-LP
solution provides a more controlled output characteristic.
18
115 VAC
16
14
12
UPPER LIMIT
LOWER LIMIT
Linear Adapter
RD-83 115 VAC
Volts
10
8
6
4
2
0
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Amps
Figure 2 –
Output Characteristic Comparison and Limits.
Page 5 of 36
Power Integrations
Tel: +1 408 414 9200 Fax: +1 408 414 9201
www.powerint.com
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