LED BACKLIGHT CONTROLLERGenera l D igital ™ Corporatio n 8 Nutm e g R oa d So ut h Sout h W indsor , CT 0 6 0 7 4 To l l - F r e ePhone : 800.952.2535 : . : . . Specification s subjec t t o chan g e withou t notic e or obligation . Trademark sare th e pro pe rt y o f the i r respectiv e o w n e r s . Februar y 2010 L E D B A C K L I G H T C O N T R O L L E R Over viewP a g e 1 o f 6General Digital’s™ micr opro cesso r-base d LED Backlight Controllerhas been designed to support LCD Monitor ap pl ic at io ns th at requ ir e su nl ig ht re ad ab ili t y, as well as night time vision (NVIS) performance. This con tro lle r is opti ma lly des igne d to drive up to four (4) LED rails (up to two sun ligh t rea dab le rails and up to two NVIS rails). The controllerwill operate from + 1 2 Vdc to + 3 4 Vdc an d drives LEDs up to 10 amps in sun ligh t rea dab le mode, an d 3 amps in NVIS mode. The maximum and minimum brightness for each mode ofope rat ion (su nlig ht rea dab le/ NVIS) is programmable. The controllerallows brightness control from full off to full brightness in both modes ofope rat ion, prov idin g 256 steps and more than 1000:1 dim- ming. It accepts both push bu tto n br ig htn ess contr ol via a mem bra ne swi tch orme cha nical butt ons (Fig. 4) or a 10Kanalog potentiometer (Fig. 5). In sunlight mode, the max- imum curren t is monitored and controlled to prevent “ther ma l runaway ” under extre me tem perat ure condi- tions, assur ing long life for the LEDs. Operators may select bet wee n sun lig ht mode and NVIS mode via a two-pin input from a me cha nic al swi tch or TTL signal. OVER TE M PE R ATU RE A LG OR ITH M Ourmi cro pro ces so r-dr iv e n LED contro lle ris con figu re d to co mmu ni cat e wi t h a pair ofte mper at ur e sensors (t h e rmis- tors). This ab il it y enables ourco ntr ol le rto m on it o rth e te m pe ra tu r e of our LED Backlight rails. The LED control- ler ’s firmwar e can be pr og ra mm e d to re sp on d to “overtem pe ra tur e ” c on di tio n s th a t can re su l t from failure ofth e mo nito r’s ele ctr oni c s (e.g., fans), op er at o rerror(e.g., blocked fan airflow), oren vi ro nmen ta l co nd it io n s (e.g., airco ndi ti on in g failure, solarra di at io n orext re m e heat) that can th re at e n the he a lt h of the LCD and /o r othe r monitorele ctr oni cs . When the rail te mp er at ur e exceeds apr ed et e r- mined “overte mp er at ur e ” limit, the co nt ro ll erautomati- cally reduces the ba ck lig h t br ig ht ne s s (e.g. 80%) to reduce p ow e r consu mpt io n , whi c h in turn, will reduce the amount of heat ge nerate d . If the te m pe ratu r e co nt inu e s to rise an d reaches a s uccessive limit th re sh o ld , then the back light bright nes s is fu rt he r r ed uc ed . In the event th a t the rail te mpe ra tu r e r ep or te d exceeds a final l imit, the bac kli gh t is turned offcom ple tel y. The ba ck li gh t br igh tne s s will be Serial Layout Figure 1 Serial-Parallel Layout Figure 2
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G e n e r al D i g i t a l™ C o r p o r a t i on 8 N u t m eg R o ad S o u th S o u th W i n d s o r , CT 0 6 0 74 To l l - F r ee P h o n e:8 0 0 . 9 5 2 . 2 5 3 5 : . : . .S p e c i f i c a t i o ns s u b j e ct to c h a n ge w i t h o ut n o t i ce o r o b l i g a t i o n. Tr a d e m a r ks a re t he p r o p e r ty of the ir r e s p e c t i ve o w n e r s . F e b r u a r y 2 0 1
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General Digital’s™ microprocesso r-based LED Backlight
Controller has been designed to support LCD Monitor
applications that require sunlight readabilit y, as well as
night time vision (NVIS) performance. This controller is
optimally designed to drive up to four (4) LED rails (up to
two sunlight readable rails and up to two NVIS rails). Thecontroller will operate from +12 Vdc to +34 Vdc and
drives LEDs up to 10 amps in sunlight readable mode, and
3 amps in NVIS mode. The maximum and minimum
brightness for each mode of operation (sunlight readable/
NVIS) is programmable. The controller allows brightness
control from full off to full brightness in both modes of
operation, providing 256 steps and more than 1000:1 dim-
ming. It accepts both push button brightness control via a
membrane switch or mechanical buttons (Fig. 4) or a 10K
analog potentiometer (Fig. 5). In sunlight mode, the max-
imum current is monitored and controlled to prevent“thermal runaway ” under extreme temperature condi-
tions, assuring long life for the LEDs. Operators may select
between sunlight mode and NVIS mode via a two-pin
input from a mechanical switch or TTL signal.
OVER TEMPER ATURE ALGORITHM
Our microprocesso r-drive n LED controlle r is configure d to
communicat e wit h a pair of temperatur e sensors (the r mis-
tors). This abilit y enables our controlle r to monito r the
temperatur e of our LED Backlight rails. The LED control-
ler ’s firmwar e can be programme d to respon d to “over temperature ” condition s that can resul t from failure of the
monito r ’s electronic s (e.g., fans), operato r error (e.g.,
blocked fan airflow), or environmenta l condition s (e.g., air
conditionin g failure, solar radiatio n or extrem e heat) that
can threate n the healt h of the LCD and/o r other monitor
electronics . When the rail temperatur e exceeds a predete r
mined “over temperature ” limit, the controlle r automati-cally reduces the backligh t brightnes s (e.g. 80%) to reduce
powe r consumption , whic h in turn, will reduce th
amount of heat generated . If the temperatur e continue s t
rise and reaches a successive limit threshold , then th
backlight brightnes sis furthe r reduced . In the event tha
the rail temperatur e reporte d exceeds a final limit, th
backligh t is turned off completel y. The backligh
S p e c i f i c a t i o ns s u b j e ct t o ch an ge w i t h o ut n o t i ce o r o b l i g a t i o n. Tr a d e m a r ks a re t he p r o p e r ty o f their r e s p e c t i ve o w n e r s. F e b r u a r y 2 0 1 0