# Boost or buck regulator?

Can't decide what Converter to use. In theory, I want to buy three solar panels (5V, 250mA) and connect them in parallel. Then the stabilizer, which will feed either poverbank, or telephone. What is confusing is that everywhere we use step-down dc-dc, but we have only 5 volts, it is logical to assume that we need on the contrary increases. Help to understand, please.
July 8th 19 at 16:04
4 answers
July 8th 19 at 16:06
Considering that the phone and poverbank already have an inverter, you can do without the fuss. Voltage 4...7 V, which give the batteries they will survive.
July 8th 19 at 16:08
To begin with, you need to plug the phone's power to apply a certain voltage, usually is a stable 5V on the USB input. If panel 5V it does not mean that they will always give 5V. On this panel, it is better to include consistently you will get a voltage of 5,5-15V so the voltage can infect lithium battery through a special charge controller and from the battery via the boost Converter to apply 5V to the phone. Ie you have a Powerbank solar charger.
Wouldn't I lose power, if the first increase, and then decrease the voltage, because the controller is not 100% efficiency? - kaylee.Breitenberg commented on July 8th 19 at 16:11
when output current is 3A and input voltage 6V efficiency of 75% at a voltage of 15 V efficiency 80%
while the 7805 does not work at 6V (7.5 V minimum), and at a voltage of 15% efficiency 30% - Luisa_Lueilwi commented on July 8th 19 at 16:14
it would lose but little when using a switching regulator, for example, the LM2596. My great-grandfather 7805 it is time to forget
when output current is 3A and input voltage 6V efficiency of 75% at a voltage of 15 V efficiency 80%
while the 7805 does not work at 6V (7.5 V minimum), and at a voltage of 15% efficiency 30% - Luisa_Lueilwi commented on July 8th 19 at 16:17
Last question then: what's wrong boost regulator, when connected in a parallel way? - kaylee.Breitenberg commented on July 8th 19 at 16:20
What are you going to increase if the battery is 4.2 V full charge - Luisa_Lueilwi commented on July 8th 19 at 16:23
July 8th 19 at 16:10
lm7805 will help you
Will not help. On it drops a couple of volts that the solar panels will be critical. We need something better. - kaylee.Breitenberg commented on July 8th 19 at 16:13
July 8th 19 at 16:12
That is, get in sume a maximum current of 0.75 mA, consider the voltage sometimes drops, you need to be consistently 5 to see such a plan Converter robo4ip.com.ua/povyshayuschie/37-preobrazovatel-na... , he was just max and give 0,7 mA for a charge. But definitely not buck!

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