Stable 5v supply from 4 to 6 volts - how?

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whitecollar

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Hi,

I cannot find a decent LCD that runs from 3.3v, so I am forced to use 5v for my system.

The power source is 4 x AA cells (6v) and I need to get a stable 5v supply from it. I can't just use a LDO linear regulator because the batteries will quickly discharge to a point where they are below the LDO limit (say 4.5 - 5v).

So basically I need a way to get stable 5v from a 4 - 6v supply?

Any suggestions?

Thanks.
 

This is buck/boost converter territory but you might also be
able to use a boost converter or charge pump doubler, followed
by a linear regulator (since LCD current is quite small, at least
excluding backlight).
 

Instead working on the said requirement, you may directly use a 6 volt source with a single diode in forward direction whcih will naturally drop 0.6 volts and 5.4 will be available to your circuitry which is quite acceptabel at the top end. It will be still safer when the 6 volt drops down. But the batteries may need relacement when they reach 4.5 volts as the output will be at 3.9 volts. But it has to be monitored about at what low volatge your circuitry shuts down.
Cheers
 

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