Universal Backlight Inverter?

[alexanna]

Well I thought I open this for some discussion, and maybe get some ideas.
I have a really nice 24” monitor that the Separate inverter is beyond repair. My thoughts are to use a universal 6 CCFL inverter. My question is that the monitor supplies 28v to the inverter when it's not under any load. Playing around with it I tried a 4 lamp inverter I had sitting around. The inverter I used was rated at 19v the voltage under a load dropped to right at 25v and everything seems to work except a really dark screen. If I install a 100 ohm resistor in the supply line the voltage drops well below 12v, and the inverter doesn't like the lower voltage [noisy and flickering ect.]
I have found a universal 6 lamp inverter but it's rated at 12v with a 5 amp fuse protecting the circuit. The BL on and Dim pins should work
If the capacitors on the inverter are rated at or above 25v is this something I need to worry about, or would there be an easy to figure what resistor I should use to drop the supply voltage down closer to 12V?
There is not going to be a great deal of money involved for the inverter, so I would be willing to experiment, and share the information within this forum.

[PlainBill]

Re: Universal Backlight Inverter?

I doubt the inverter would survive with 25 volts applied. A fair amount of engineering went into designing that inverter to operate off 12 Volts. In particular, the transformers and driver transistors are likely to be damaged.

Using a conservative estimate of 3A for the current required, the resistor would have to be a 50 watt resistor. I'd say it would be time to design a DC-DC bucking converter.

PlainBill

[Timorad]

Re: Universal Backlight Inverter?

A few days ago I was wondering the same thing about using a universal inverter (See another thread). The inverter input voltage is 20 volt, so I will need to downregulate it.

I found a linear regulator 78S12 that does what I want (and is cheap), but it is designed for 2 amps max. According to what the powerboard reads (see photo below), 2A will be enough. Or am I misinterpreting this?

It reads:
12V/2.4A
20/1.8A (Not clear from the picture)

A second option is to hook the inverter directly to the 12v line. However, I don't think it is a good idea to have both the load of the inverter and logic boards on one line.

Edit: It seems there is a 78T12 too, designed for 3A. Not really efficient though..

[alexanna]

Re: Universal Backlight Inverter?

^
I haven't decided exactly what I'm going to do, One option I am thinking is to use a 12V power brick that's rated at the correct amperage to power the 12V circuit,Space is really limited, and I would feel more comfortable to be able to have all the shields/covers installed.
The back light on and dim pins would be powered by the regular monitors power supply.
I am lucky; I have various bricks sitting around.
Like I say I am unsure exactly I am going to do that's just on option.

[Timorad]

Re: Universal Backlight Inverter?

That it ofcourse another option, but requires making a hole in the back of my screen. Not the most elegant solution I was kinda hoping to find a simple buck converter or any other simple/cheap device that does what I want.

Back to my situation: unfortunately I do not have the schematics for the powerboard to determine whether the 12V line is enough to power both the logic and inverter board. This would ofcourse be the most optimal solution in my case. Perhaps there is an expert here that can shed more light on this matter?

[Timorad]

Re: Universal Backlight Inverter?

I am looking for step down converters on ebay, and found the following links:

http://cgi.ebay.com/High-Efficiency-...-/270675796876 (Up to 4A with heatsink)
http://cgi.ebay.com/ULTRA-HIGH-Effic...-/270702265079 (up to 8A)

[avr]

Re: Universal Backlight Inverter?

Hi,

I also have a small question regarding this matter.

I have a monitor without inverter (Dell 2007fpb). Luckily I have one inverter sitting around from another monitor (Viewsonic vp201b).
Now Dell supplies around 19.3V to the inverter, and Viewsonic had 18V line. Would it be safe to use this Viewsonic inverter, or should I somehow try to drop the 19V to near 18V?

[PlainBill]

Re: Universal Backlight Inverter?

Hi,

I also have a small question regarding this matter.

I have a monitor without inverter (Dell 2007fpb). Luckily I have one inverter sitting around from another monitor (Viewsonic vp201b).
Now Dell supplies around 19.3V to the inverter, and Viewsonic had 18V line. Would it be safe to use this Viewsonic inverter, or should I somehow try to drop the 19V to near 18V?

I'd give it a try as-is. The inverter supply is usually not well regulated, and can change by more than 10%.

PlainBill