DER-50

Set Top Box Design using TOP245R

April 20, 2005

Page 2 of 31

Power Integrations

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Table Of Contents

1

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

2

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

3

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

4

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

5

PCB Layout ................................................................................................................ 8

6

Bill Of Materials .......................................................................................................... 9

7

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

7.1

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

7.2

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

7.3

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

7.4

Transformer Build Diagram ............................................................................... 13

7.5

Transformer Construction.................................................................................. 14

8

Transformer Spreadsheets....................................................................................... 15

9

Performance Data .................................................................................................... 18

9.1

Efficiency........................................................................................................... 18

9.2

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

9.3

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

9.3.1

Line Regulation (Transformer Outputs only) .............................................. 19

9.3.2

Cross Regulation (18V Output) .................................................................. 20

9.3.3

Cross Regulation (23V Output) .................................................................. 20

10

Waveforms............................................................................................................ 22

10.1

Drain Voltage and Current, Normal Operation .................................................. 22

10.2

Output Voltage Start-up Profile (from Transformer Outputs only) ..................... 22

10.3

Drain Voltage and Current Start-up Profile........................................................ 23

10.4

Load Transient Response ................................................................................. 23

Output Ripple Measurements ...................................................................................... 25

10.4.1

Ripple Measurement Technique ................................................................ 25

10.4.2

Measurement Results (Transformer Outputs only) .................................... 26

11

Conducted EMI ..................................................................................................... 28

12

Revision History .................................................................................................... 30

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.

Design Reports contain a power supply design specification, schematic, bill of materials,

and transformer documentation. Performance data and typical operation characteristics

are included. Typically only a single prototype has been built.