2unit of lm7805 input connected in series

[circuit_freak]

Hi all,

As shown in diagram below, possible to get 5V output with above configuration

**broken link removed**

Thanks in advance.

 

[sijukrishnan]

Couldn't view the diagram.

 

[nandhu015]

No...

First Read and try to understand datasheet of 7805

 

[circuit_freak]

This idea come to me in a sudden.
As i know 12V input to 5V will have 7V heat losses.
So just wondering if series as in attached diagram make it two unit with 6V input to 5V will be ok or not.

please advise which consideration i have missout.

Thanks

 

[umesh49]

Why the second input is grounded. Are you trying two achieve two stage conversion? What is your output current requirment?

 

[circuit_freak]

because i am trying to connect both lm7805 in series so that the input voltage is 6V per unit hence less heat will be generated.
assume 800mA will be used for my circuit.

 

[IanP]

If your idea is to spread loses between two 7805s then you have to connect [input-output]==>[input-output] in series ..
Pin[2] is the reference for the 7805's output, which is fixed at 5V level, and can not be used in any other role ..
Have a look at the attached picture and see how you can "shift" the output voltage of the 7805 so it produces more than 5V - in this example it is roughly 8V ..

Also keep in mind that a standard 7805 regulator needs at least 3V difference between input and output ..

:wink:
IanP

 

[circuit_freak]

Hi IanP,

can you please help to provide a rough drawing/circuit "connect [input-output]==>[input-output] in series"?
i cant get the picture.
Btw i think you have miss out the attachment previously.

thanks for help.