Cypress CY3274 Catatan Aplikasi - Halaman 7
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Halaman Cetak2.4
Power Supply
This section describes the power supply design for the high voltage boards. The schematic of the power supply is
shown in
Figure
5. The BOM of the power supply is listed in
The offline switch mode power supply on the high voltage boards is a standard isolated flyback converter. Bridge
rectifier D7 produces a rectified input from the AC line, which is used to drive the primary side of the converter.
Capacitors C30 and C31 provide charge storage to guarantee a sufficiently high input voltage to operate the
converter throughout the entire AC line cycle. C30 and C31, in combination with T3, minimize the conduction of
power supply switching transients onto the AC line. R41 provides in-rush current limiting.
Inductor L3 and capacitor C29 provide isolation to prevent the 133 kHz transmitter signal from riding the AC line
voltage into the rectifier, creating harmonic energy on the AC lines. The inductor also presents a high impedance to
the powerline so that the power supply does not load the PLC signal. These components provide an additional
measure of protection for both conducted immunity and conducted radiation.
An iWatt iW1690 power controller manages the power conversion. Startup current for the device is provided on its Vin
pin via resistors R32 and R34. When it starts operating, power and regulation voltage sensing is provided to the
controller by the auxiliary secondary winding of T2.
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Figure 5. Cypress High Voltage PLC Board Power Supply Circuit
Document No. 001-55427 Rev. *E
Cypress Powerline Communication Board Design Analysis
Table
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