AN1889 STMicroelectronics, AN1889 Datasheet

Manufacturer Part Number

AN1889

Description

ESBT STC03DE170 IN 3-PHASE AUXILIARY POWER SUPPLY

Manufacturer

STMicroelectronics

Datasheet

1.AN1889.pdf (25 pages)

1. INTRODUCTION

The need to choose a high value of the fly-back voltage is well known to power supply designers when

efficiency and high duty cycle become important requirements. Three-phase auxiliary power supplies,

starting from a bulk voltage of 750V, require theoretically power transistors with a block voltage capability

higher than 1200V. Practical considerations linked to better efficiency and safe margin may impose to

choose devices with even higher breakdown voltage (i.e. 1500V, 1700V). Looking at the power switches

currently available, while power bipolar transistors are strongly limited in switching frequency operation,

power MOSFETs show a much lower current capability, which may limit their use to low power

applications. Recently available in the market, the ESBTs (Emitter Switched Bipolar Transistors)

represent a valuable and cost effective alternative for all those applications where high voltage and high

switching frequencies are a must.

This application note describes the realization of a 50W 3-phase auxiliary power supply by using the

STC03DE170 as main switch for the fly-back converter. Particular attention has been given to the

transformer design as well as to the ESBT driving circuit requirements.

2. ESBT: THEORY AND EVOLUTION

The "emitter switching" concept was widely investigated a few decades ago with the aim of improving the

trade-off between switching and conduction losses mainly in high voltage applications.

Figure 1: ESBT Symbol and Equivalent Circuit

AN1889/0905

STC03DE170 IN 3-PHASE AUXILIARY POWER SUPPLY

APPLICATION NOTE

AN1889

ESBT

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