AN3032 datasheet(13/26 Pages) STMICROELECTRONICS

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AN3032

Ballast design

Doc ID 16165 Rev 2

13/26

3.2.4

Power MOSFET

The choice of MOSFET relates mainly to its RDS(on), which depends on the output power

and its breakdown voltage, the latter being fixed by the output voltage Vbuspfc = 420 V only,

plus the overvoltage

ΔV

OVPpfc = 60 V allowed, and a safety margin.

The MOSFET's power dissipation depends on the conduction and switching losses.

Assuming maximum total power losses PlossesAdm = 1%, PoutTOT = 1.16 W, it is easy to

verify that with the MDmeshTM V Power MOSFET STP16N65M5, the estimated total

MOSFET power losses PlossesEst are about = 0.7 W (worst case) and that this was the

correct choice. To better dissipate the power losses, we have added a small heatsink.

3.2.5

Boost diode

The boost freewheeling diode is a fast recovery one. The breakdown voltage is fixed with the

same criterion as the MOSFET. The value of its DC and RMS current, needed to choose the

current rating of the diode, are reported.

Equation 17

Since the PFC works in transition mode, we have used the Turbo 2 ultrafast high-voltage

rectifier STTH3L06.

3.3

Design of the half bridge inverter

According to the criteria described in AN993 chapter 5 (design tips) with regard to the

design of the resonant circuit, the following values have been selected.

●

For Lres = L1 = L2 = 1.8 mH, we have used the inductor 1646-0006 manufactured by

MAGNETICA.

A second-generation MDmeshTM power MOSFET STD10NM60N has been inserted in the

half-bridge section to reduce the power losses.

276

BUSpfc

outTOT

BUSpfc

inrmsMin

INrmsMax

rms

⋅

res

1.8 mH

res

10 nF 1600 V

block

100 nF 400 V

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