the link between the minimum and maximum current for a regulator

[yanda]

hello forum, please am a little bit confused about the relationship between the current and the regulator. for instance, an LM7809 for example must hav a minimum input of its output and the max. dropout voltage which is 2.5V, hence min. input voltage of 11.5V and max of 35V. but then nothing is been mention about its minimum input current and its max current. does it mean one can operate it at any current?

also am about using LM7809 with a solar panel with max. current of appr. 7.0A and min. curent of 0.35A; will this work out or wat wil b effect of this?
the min voltage recorded from the pv module is 17.0V and the max. voltage recorded was appr. 20.0V

thanks forum ---- ------- ----- ---- in advance

 

[goodboy_pl]

Linear regulators like LM7809 do not need minimum load for proper operation. in fact the need minimum input and output capacitor (~1 to 3.3 uF).
I think the minimum current rating of the solar panel (as you say) is minimum current that it could produce, so there is no need for minimum load for the panel itself.
therefore you could use lm7809 with the panel (with very low efficiency). usually for higher efficiency and current handling switching regulators is used with solar panels.

BEST

 

[yanda]

Thanks Engr goodboy -pl but i dont seemed to get your message very clear; are u saying that even with 7A current flowing into LM7809, it can still be operated safely despite it can only provide max of 1.5A to the externally connected load.

the question to be precise is 'can i use LM7809 to regulate the output voltage from the solar pv module despite its min and max current been 0.3A and 7.0A?'

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Thanks Engr goodboy -pl but i dont seemed to get your message very clear; are u saying that even with 7A current flowing into LM7809, it can still be operated safely despite it can only provide max of 1.5A to the externally connected load.

the question to be precise is 'can i use LM7809 to regulate the output voltage from the solar pv module despite its min and max current been 0.3A and 7.0A?'

 

[nitishn5]

I think the minimum current rating of the solar panel is the minimum current required for normal operation.
If this is the case you can use a LM7809 to get 9V but you need to give a minimum load of 0.3A for the solar panel to operate.

The maximum rating of the panel is 7A and of 7809 is 1.5V, If you load either devices beyond this you might probably see smoke!
It all depends on you load. If your load consumes less than 1.5A, then you can use the panel along with 7809. If your load current is more the this, you need some other method.

BTW, with the 17V-20V input to 7809 from the solar panel to the 9V output means a drop out of atleast 8V. With the minimum current of 0.3A, this means a power loss of 2.4V just to keep the panel in normal operation. Like goodboy_pl says, it would be very inefficient.

I'd suggest that you go for Switched Mode converters (A Buck converter) to get the voltage. They need more components but are easy to make and would be highly efficient.