AN2454 Datasheet, PDF (1/24 Pages) STMicroelectronics – Universal input voltage power supply for ESBT based breaker and metering applications

AN2454
Application note
Universal input voltage power supply for ESBT based
breaker and metering applications
Introduction
This document describes how to design a 3-phase power supply with the UC3845B PWM
driver and the new STC04IE170 ESBT as main switch. It is associated with the release of
the STEVAL-IPB001V1 demo board (see figure below). The design is a complete solution
for the 2 W single output SMPS, which is widely used as a power supply in breaker
applications. However, the design method can also be applied to an SMPS suitable for 3-
phase power metering applications, as it can easily be upgraded for higher output power.
In this report particular attention has been paid to the ESBT base driving circuit, where
some useful methods have been investigated to better optimize power dissipation (see
Section 6: Base driving circuit design).
The influence of the parasitic capacitances of the transformer on the ESBT is also explained
in detail (see Section 3: Parasitic capacitances and related issues). In addition, an active
start-up circuit has been implemented on the demo board to optimize the converter
efficiency, is also described (see Section 7: Active start-up circuit). A dedicated active
component (the Darlington Q3) has been developed to support the very high voltage
required (see Figure 1).
Finally, the most important waveforms and thermal results are given in Section 8:
Experimental results: waveforms and Section 9: Experimental results: efficiency and special
considerations. They demonstrate the benefits of using this solution with the start-up circuit.
Refer to AN1889 for the overall design of an auxiliary power supply using an ESBT.
STEVAL-IPB001V1 demo board
December 2006
Rev 1
1/24
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