LD-14115-10 6-2. Back light driving

The back light system is an edge-lighting type with six CCFTs (Cold Cathode Fluorescent Tube). The characteristics of the lamp are shown in the following table.

The value mentioned below is at the case of one CCFT.

CCFT Model Name：KTBE26MSTF‐A424NE209‐Z‐3（STANLEY.ELECTRIC.CO.,LTD）

Parameter

Symbol

Min.

Typ.

Max.

Unit

Remark

Lamp current range

IL

3.0

6.0

6.5

mArms

【Note1】

Lamp voltage

VL

－

790

－

Vrms

Ta=25℃

Lamp power consumption

PL

－

4.7

－

W

【Note2】

Lamp frequency

FL

30

60

70

KHz

【Note3】

Kick-off voltage

Vs

－

－

1,500

Vrms

Ta=25℃【Note4】

 

 

－

－

2,000

Vrms

Ta=0℃【Note4】

 

 

 

 

 

 

 

Lamp life time

TL

50,000

－

－

Hour

【Note5】

【Note1】 A lamp can be light in the range of lamp current shown above.

Maximum rating for current is measured by high frequency current measurement equipment connected to VLOW at circuit showed below.

(Note : To keep enough kick-off voltage and necessary steady voltage for CCFT.) Lamp frequency : 30～70kHz

Ambient temperature : 0～50℃

Module

CN1:1,2,3,4,5,6: 1pin(Vhigh)

CN1:1,2,3,4,5,6: 2pin(Vlow)

Inverter

Ａ

～

【Note2】 Referential data per one CCFT by calculation ( IL × VL ) . The data doesn’t include loss at inverter .

【Note3】 Lamp frequency of inverter may produce interference with horizontal synchronous frequency, and this may cause horizontal beat on the display. Therefore, adjust lamp frequency, and keep inverter as far as from module or use electronic shielding between inverter and module to avoid interference.

【Note4】Kick-off voltage value is described as the index in the state of lamp only.

The kick-off voltage is estimated to be risen up as approx. +200V in the state of module only, and the further rise up can be seen according to the assembling status of user cabinet. Please set the kick-off voltage of inverter to avoid the lighting failures in the state of operation. Please design the inverter so that its open output voltage can be connected for more than 1 second to startup. Otherwise, the lamp may not be turned on. But, please set as 100ms when the ambient luminance around the lamp is more than 1lux.

【Note5】 Lamp life time is defined as the time when either ① or ② occurs in the continuous operation under the condition of Ta=25℃ and IL=6.0 mArms .

①Brightness becomes 50% of the original value under standard condition.

② Kick-off voltage at Ta=0℃ exceeds maximum value,2000Vrms .

《Note》

The performance of the backlight, for example lifetime or brightness, is much influenced by the characteristics of the DC-AC inverter for the lamp. When you design or order the inverter, please make sure that a poor lighting caused by the mismatch of the backlight and the inverter (miss-lighting, flicker, etc.) never occurs. When you confirm it, the module should be operated in the same condition as it is installed in your instrument.

Use the lamp inverter power source incorporating such safeguard as overvoltage / overcurrent protective circuit or lamp voltage waveform detection circuit, which should have individual control of each lamp.

In case one circuit without such individual control is connected to more than two lamps, excessive current may flow into one lamp when the other one is not in operation.

Synchronize frequency and phase of two CCFT in the same connector. Otherwise it may exceed rated voltage of connector.