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Simple, Higher Integration DC-DC Converter for Coaxial Ethernet Transceivers

IP.com Disclosure Number: IPCOM000109364D
Original Publication Date: 1992-Aug-01
Included in the Prior Art Database: 2005-Mar-24
Document File: 2 page(s) / 90K

Publishing Venue

IBM

Related People

Mussenden, GA: AUTHOR

Abstract

This article describes a circuit arrangement which eliminates the need for an external voltage post-regulator on the secondary side of DC-DC converters used for powering the coaxial media transceiver on devices attached to local area networks (LANs) which operate according to ANSI-IEEE 802.3/ISO 8802-3 (Ethernet/Cheapernet) access methodology.

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This is the abbreviated version, containing approximately 52% of the total text.

Simple, Higher Integration DC-DC Converter for Coaxial Ethernet Transceivers

       This article describes a circuit arrangement which
eliminates the need for an external voltage post-regulator on the
secondary side of DC-DC converters used for powering the coaxial
media transceiver on devices attached to local area networks (LANs)
which operate according to ANSI-IEEE 802.3/ISO 8802-3
(Ethernet/Cheapernet) access methodology.

      Fig. 1 shows a circuit that is typically used in the Ethernet
industry for the DC-DC converter.  It utilizes a series (three
terminals) post-regulator on the secondary (output) side of the
converter.  Also, it requires a relatively complex transformer.

      Fig. 2 shows the flyback DC-DC power converter of this
disclosure.  TL1 is the power-transferring transformer/inductor and
Q1 is the switching power transistor, with an optional current
sensing resistor Rc attached to its emitter.  D2 is the output
rectifier and Co the output filter capacitor.  R1 is a handy
representation of the load - transceiver.  Rs and Cs form a snubber
network, attached to rectifier Ds, used to dissipate the energy
contained in the primary (transistor) side leakage inductance of TL1.
Further, Cs also serves as a storage for the feedback voltage
necessary for the pulse width modulator (PWM).

      R1 and R2 form a divider network to obtain the appropriate
scaled feedback voltage for the PWM which controls the duty cycle of
Q1 so as to obtain the desired output voltage, Vo.  The PWM is a
conventional controller, which outputs a train of turn-on pulses
whose duty cycle is adjusted by it such that the feedback voltage it
receives, Vf2, is identical...