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VFD/4DIGITS-7SEGMENTS CONTROLED BY A VFD IC

IP.com Disclosure Number: IPCOM000145750D
Publication Date: 2007-Jan-25
Document File: 3 page(s) / 235K

Publishing Venue

The IP.com Prior Art Database

Related People

LAURENT GLAIS: INVENTOR [+2]

Abstract

It is possible that a Set Top Box implements a KDB (Key Display Board) for driving a display VFD (Vacuum Fluorescent Display). A VFD provides a nice blue light with, typically, digits having 14 segments. Many other STBs, however, use LED technology for the display. When the STB is in a standby mode, the display shows 4 digits : the hours and the minutes, with two points between the digits : " 1 4 : 3 0 ". In certain cases, the set top box has two versions : a VFD display and an LED display. The printed board of the two versions is the same. It is typically equipped with a driver circuit that drives only the VFD component. The VFD component manages specific voltages between -26 volts and 3 volts for driving the VFD display. Many problems have been encountered by the engineers : - the same circuit must drive a VFD display (14 segments – 8 digits) or a LED display (7 segments) , - the low level software layers are the same in the two versions, - when the STB is switched on, the software knows the versions, but in a standby mode, the run software is the same and it does not know if it is a Led display or a VFD display. But this software updates the hours and minutes. - the voltages are very different between a VFD display and a LED display.

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Title

VFD/4DIGITS-7SEGMENTS CONTROLED BY A VFD IC

Background

      It is possible that a Set Top Box implements a KDB (Key Display Board) for driving a display VFD (Vacuum Fluorescent Display). A VFD provides a nice blue light with, typically, digits having 14 segments. Many other STBs, however, use LED technology for the display. When the STB is in a standby mode, the display shows 4 digits : the hours and the minutes, with two points between the digits : “ 1 4 : 3 0 “.

      In certain cases, the set top box has two versions : a VFD display and an LED display. The printed board of the two versions is the same.  It is typically equipped with a driver circuit that drives only the VFD component. The VFD component manages specific voltages between -26 volts and 3 volts for driving the VFD display.

      Many problems have been encountered by the engineers :

- the same circuit must drive a VFD display (14 segments – 8 digits) or a LED display (7 segments) ,

- the low level software layers are the same in the two versions,

- when the STB is switched on, the software knows the versions, but in a standby mode, the run software is the same and it does not know if it is a Led display or a VFD display. But this software updates the hours and minutes.

- the voltages are very different between a VFD display and a LED display.

Solution

      The adopted solution consists in that :

      1st version (VFD) : the driver circuit STFPC 320 is directly connected to the VFD display. The high level software (e.g., version VFD) manages the displayed information.  For example, a text can be displayed.

      2nd version (LED) : the components for a conversion voltage circuit are added on the printed board. The driver circuit is powered with GND and 3.3 volts. In one embodiment, the logic inverse for t...