EPR-84 – Single Output, Universal Input, Cell Phone Charger

23-May-05

Page 2 of 28

Power Integrations

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Table Of Contents

1

Introduction............................................................................................................. 3

2

Power Supply Specification .................................................................................... 4

3

Schematic............................................................................................................... 5

4

Circuit Description .................................................................................................. 6

4.1

Input Rectification, Bulk Capacitance and EMI Filtering...................................... 6

4.2

Primary DRAIN Voltage Clamp Circuit................................................................ 6

4.3

Auxiliary Bias Supply .......................................................................................... 6

4.4

Output Rectification and Filtering ........................................................................ 7

4.5

Output Voltage Sensing, Feedback and Constant Current Control..................... 7

4.6

Transformer: Conducted EMI Noise Cancellation and Suppression Windings.... 8

5

PCB Layout ............................................................................................................ 9

6

Bill Of Materials .................................................................................................... 10

7

Transformer Specification..................................................................................... 11

7.1

Electrical Diagram............................................................................................. 11

7.2

Electrical Specifications .................................................................................... 11

7.3

Materials ........................................................................................................... 12

7.4

Transformer Build Diagram ............................................................................... 12

7.5

Transformer Construction ................................................................................. 13

8

Transformer Spreadsheets ................................................................................... 14

9

Performance Data ................................................................................................ 17

9.1

Efficiency........................................................................................................... 17

9.2

No-load Input Power ......................................................................................... 18

9.3

Regulation......................................................................................................... 19

9.3.1

Load........................................................................................................... 19

9.3.2

Line ............................................................................................................ 19

10

Thermal Performance........................................................................................... 20

11

Waveforms ........................................................................................................... 21

11.1

Drain Voltage and Current, Normal Operation .................................................. 21

11.2

Output Voltage Start-up Profile ......................................................................... 21

11.3

Drain Voltage and Current Start-up Profile ....................................................... 22

11.4

Load Transient Response (75% to 100% Load Step) ....................................... 22

11.5

Output Ripple Measurements ........................................................................... 23

11.5.1

Ripple Measurement Technique ................................................................ 23

11.5.2

Measurement Results ................................................................................ 24

12

Conducted EMI..................................................................................................... 25

13

Revision History.................................................................................................... 27

Important Note:

Although this circuit board has been designed to meet 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.