I have started to tear down my lcd to try feeding the ccfl, Im down to these pins :
- SMB_CLK SMBUS interface for sending brightness & contrast information to the inverter/panel
- SMB_DAT SMBUS interface for sending brightness & contrast information to the inverter/panel
- INV_PWM System side PWM input signal for brightness control
Ok, if i have understand this correctly DAT & CLK provides a ratio and i will not try to modify that, atleast not for the moment, instead:
There are two control signals that come form system to control lamp brightness. One signal is
named DAC_BRIG, which limits current to meet LCD lamp current specification. Another one is
named PWM, which adjusts lamp brightness. This inverter brightness is adjusted by PWM burst
mode. The PWM burst mode is that turning on and off the lamp at rate of 150Hz. The effective
brightness is a function of the duty cycle
INV_PWM 142 150 158 Hz PWM signal frequency
3.0 3.3 3.6 V PWM signal amplitude
This is for a acer ccfl, but i have compared with some others and it seems to be almost the same.
I feel like i am having a monologue, however if my meassuring is correct the inv_pwm is pin number 13. I will use the USB as my power source, but i saw someone earlier in this thread mentioning that it was a bad choice of source and I am curious why, if i understand it right it provides 5v and 0,5mA which is more than I need.
Ok, to be honest i got my 7800 to work so i have been using it as reference, i meassured the inv_pwm to 0.7 and according to some data sheets i found it is :
Input voltage Low VPWM_H NV_PWM
V5VALW =4.75～5.2V 0 － 0.7 V
Input voltage High VPWM_L 2.1 － － V
BUT!, when i cut the cable and restarted the computer, the CCFL was still working, this means the IC-controller is set to SMBus mode(atleast i think so.)
Next step is to either reroute the inverter board to bypass the IC-controller or modify the SMB_DAT & SMB_CLK.
Edited by englund33 - 8/6/11 at 3:34am