Shanghai ZhongYing VFD Co.Ltd.

	CAR
	AUDIO
	ECR/POS BALANCE
	HOME
	MASSAGE CHAIR
	MONEY COUNTER
	DVD/VCD
	OTHERS

VFD Module

CCFL

Online Order

		VFD - Custom Panel Design
		VFD - Custom Module Design

Email:

zycfhf@188.com

jiafengz@gmail.com

zhanghai7936@126.com

Tel:

+86 21 57617857

Fax:

+86 21 57617859

VFD Operation

The VFD is composed of three basic electrodes; the Cathode (Filaments), Anodes (Phosphor) and Grids under a high vacuum condition in a glass envelope.
The Cathode consists of fine tungsten wires which are coated by alkaline earth metal oxides which emit electrons.
The Grids are a thin metal mesh which control and diffuse electrons emitted from the Cathode.
The Anodes are conductive electrodes on which the phosphor is printed to indicate characters, icons or symbols.
Electrons emitted from the Cathode are accelerated with positive potential applied to both Grid and Anode, which upon collision with the Anode excites the phosphor to emit light. The desired illuminated patterns can be achieved by controlling the positive or negative potentials on each Grid and Anode. This voltage can be as low as 10VDC

1.	Glass Substrate (Anode Plate)	10.	Getter
2.	Conductive Layer	11.	Face Glass (Cover Glass)
3.	Anode (Base)	12.	Spacer Glass
4.	Insulation Layer	13.	Evacuation Tube
5.	phosphor (Display Pattern)	14.	NESA (or ITO) coating
6.	Conductive Paste	15.	Lead Pin
7.	Grid Mesh	16.	Mold Resin
8.	Conductive Frit Glass	17.	Solder
9.	Filament (cathode)	18.	Frit Glass

Disassembled VFD

The VFD is composed of a vacuum envelope with a front glass and the base plate, in which cathode (filament), grid and anode are formed as the basic electrodes

Cross section of VFD

Filament consists of tungsten coated with the oxidized Ba, Sr and Ca. Powered filament generates heat and emits thermal electrons which are dispersed and selected by the grid electrode and reach the anode electrode. On the anode electrode, display pattern is formed with phosphor which emit light.

This display is robbed from a VCR. The two large connection at each side is the connection to the filament. The voltage over the filament should be about 2-3V the current consumption is about 100mA. The display has 11 grids. Each of them has a connection out from the glass substrate. The 9 rest pins are connection to the segments in the display.

The controlling electronic will do like this:

First it will put the first grid to +14V and the rest to 0V and apply +14V to the segment you want to be lighted in the first grid. Then it will put the first grid to 0V and got to the next grid and apply +14V. This scann will continue untill the last grid was activated and the process will start all over again. The scanntime is fast so you will not see that only one grid is activated at one time. You will see them all shining.

If you want to test a VFD just connect 3V over the filament. Then you apply +14V to one grid. the minus should be connected to the filament. Now take a wire from the +14V and touch the segment pins from the display except the filament, then you will burn it upp!
You will now see that the segment in the active grid will shine. If you touch another grid nothing will happen, so don't worry.

How to drive the filament

AC Drive
Most popular method for the audio system and large-size VFDs.
[Connection of AC Drive]	[Potential of AC Drive]
DC Drive
Mainly used for small-size VFDs driven by the car batteries. In this case, there are differences in the grid and anode voltages at the ends of the display pattern in the value of filament voltage, which requires correction of the filament structure. Therefore, DC drive is not available for large-size VFDs.
[Connection of DC Drive]	[Potential of DC Drive]
Pulse Drive
If battery or DC supply is used, a pulse wave form is available for the filaments from the DC to AC converter. The idea of pulse voltage supply to the filament operates under the same principle as an AC filament drive. However; using a DC to AC converter with center-tap is recommended.