AN4068 datasheet(27/63 Pages) STMICROELECTRONICS

номер детали	AN4068

подробное описание детали	ST7580 power line communication system-on-chip design guide

PDF	63 Pages

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производитель	STMICROELECTRONICS [STMicroelectronics]

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27 / 63 page

AN4068

ST7580 reference design description

Doc ID 022923 Rev 2

27/63

Figure 13.

Montecarlo simulation of the transmission line coupling response loaded

with the EN50065-1 LISN impedance

7.1.4

Zero crossing coupling

The zero crossing coupling circuit is aimed at providing a bipolar (AC) signal synchronous

with the mains network voltage to the ZC_IN pin. This signal must be centered on VSS and

limited to ± 5 V peak [1].

The isolated zero crossing circuit is realized through an optocoupler in an inverting

configuration. Neutral and phase lines are brought to the optocoupler through four 56 k

Ω, 1

W size SMD resistors in series, as represented in Figure 14. The LL4148 acts as a free-

wheeling diode during negative half-wave. The series resistors limit the photodiode input

current to nearly 1 mA rms at 230 VAC, leading to less than 250 mW of total consumption of

the solution. Having two resistors per line helps to prevent short-circuits in the case of

resistor degradation.

Figure 14.

Isolated zero crossing coupling circuit

AN4068 датащи(PDF) 27 Page - STMicroelectronics