User`s guide

SMPS AC/DC REFERENCE

DESIGN USER’S GUIDE

Chapter 1. Introduction

This chapter provides an introduction to the SMPS AC/DC Reference Design and

includes the following major topics:

• System Specifications

•Block Diagram

• Multi-Phase Synchronous Buck Converter

• Listing of I/O Signals for Each Block, Type of Signal and Expected Signal Levels

1.1 SYSTEM SPECIFICATIONS

This reference design describes the design of an off-line Switch Mode Power Supply

(SMPS) design using an SMPS dsPIC

DSC (dsPIC33FJ16GS504).

The SMPS AC/DC Reference Design works with universal input voltage range and

produces three output voltages (12V, 3.3V and 5V). The continuous output rating of the

reference design is 300 Watts. This reference design is based on a modular structure

having three major block sets as shown in Figure 1-1. Figure 1-2 shows a more

detailed block diagram with all functional blocks as implemented on the SMPS AC/DC

Reference Design.

The Power Factor Circuit (PFC) converts the universal AC input voltage to constant

high-voltage DC, and maintains the sinusoidal input current at high power factor. The

Phase-Shift Zero Voltage Transition circuit converts high-voltage DC to intermediate

low-voltage DC with isolation from the input AC mains, at high efficiency. The

Multi-Phase Synchronous and Single-Phase Synchronous Buck circuit converts

intermediate low-voltage DC to very low-voltage DC at high current at high efficiency.

The input and output specifications are as follows:

• Input:

- Input voltage: 85 V

AC-265 VAC

- Input frequency: 45 Hz-65 Hz

• Outputs (individually loaded):

- Output voltage 1 (Vo 1 ) = 12V

- Output load 1 (Io1) = 0A-30A

- Output voltage 2 (Vo 2 ) = 3.3V

- Output load 2 (Io2) = 0A-69A

- Output voltage 3 (Vo 3 ) = 5V

- Output load 3 (Io3) = 0A-23A

• Outputs (simultaneously loaded):

- Output voltage 2 (Vo 2 ) = 3.3V

- Output load 2 (Io2) = 0A-56A

- Output voltage 3 (Vo 3 ) = 5V

- Output load 3 (Io3) = 0A-23A