AN3276 datasheet(14/22 Pages) STMICROELECTRONICS

14 / 22 page

The new ST solution - BC2: energy recovery circuit

AN3276

14/22

Doc ID 17975 Rev 1

2.5

Calculation of L

There are several ways to rate the inductance L. For instance, its turn-on dI/dt can be rated

at 50 A/µs. Then, m2 and m1 are calculated taking into account the corresponding IRM of

diode DB. However, the reverse voltage across the DB, VRDB_reverse, must not exceed 75%

of VRRM to meet the system design rule, 75% x 650 = 487 V. If VRDB_reverse is higher than

487 V, the L value should be reduced. Therefore, the dI/dt of L and the IRM diode of DB

increase as well. Thus, m1 and m2 should be recalculated to get VRDB_reverse below 487 V.

But this calculation method does not optimize the inductance L and its size. Ultimately, a

good rating should minimize L size. ST has developed a software tool using all the

parameters: the IRM diode of DB versus the dI/dt and junction TJ, the L inductance

tolerances, and the switch-on power losses. This tool is proposed to help designers to

choose the best L inductance for its application. Table 2 shows two PFC examples using the

BC2 concept.

2.6

Range of products

ST offers the BC2 technology in a range of products:

●

STTH8BC065DI, STTH8BC060D, STTH5BCF060 for applications from 800 W to 2 kW

●

STTH16BC065CT, STTH5BCF060 for applications from 400 W to 1 kW

●

STTH10BC065CT + STTH3BCF060U for applications from 280 W to 600 W

Table 2.

Inductor and size versus the PFC types

Case 1

Case 2

Input power

100 W < Pin < 1.1 kW

50 W < Pin < 450 W

VmainsRMS

90V < Vmainsrms < 264 V

90 V <Vmainsrms< 264 V

VOUT

400 V

95 kHz

Inductor and size

3 µH

5 µH

Core reference

Core DR78381

(Datatronics Limited)

Core DR79124

(Datatronics Limited)

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