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DC Filament Circuit for Fluorescent Lamp

IP.com Disclosure Number: IPCOM000119283D
Original Publication Date: 1991-Jan-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Nakano, M: AUTHOR

Abstract

This article describes a DC filament circuit for a hot cathode fluorescent lamp without using an inverter for a filament.

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This is the abbreviated version, containing approximately 100% of the total text.

DC Filament Circuit for Fluorescent Lamp

      This article describes a DC filament circuit for a hot
cathode fluorescent lamp without using an inverter for a filament.

      Fig. 1 shows a sample circuit to heat filaments by directly
supplied DC voltage.  F.L. is a hot cathode fluorescent lamp.  L is a
common mode winding coil which is necessary to have large enough
impedance at the main inverter frequency.

      Filament current flows along the solid arrows in Fig. 1. Two
filaments are connected in serial circuit.  L is never saturated by
DC current because DC current flows differentially each winding.  C1
cuts DC current flowing into transformer T.  Discharge current flows
through along the dotted arrows in Fig. 1.  C1 is working as a
discharge current limit capacitor.  This current does not flow into
L. The filament current does not interfere with the discharge
current.  Fig. 2 shows another example.  Filaments are connected in a
parallel circuit.