portable battery charger

[div850]

i am currently working on a project of making a portable battery charger for mobile phones.
firstly, i started with lm7805 regulator but it consumes a lot of power, then,
there is a solution with linear technology lt1302 ic but i don't have this type of ic in my area.
so i used a simple step up converter from 3.7 to 5v ic mc34063 for providing 5v and 1.5A current , i wanted to know if the calculations i made for the components required are feasible and economical.
i am attaching a photo with this to show the circuit with calculated values.

thanks in advance.

 

[jiripolivka]

The values look correct. Use standard values, like 160 pF and 470 uF for the capacitors. Check the real circuit for lower than 3.7 V input, to see the regulation range at output.

The 7805 regulators require 7-8 V input to regulate, and a good heat sink as they behave as a controlled resistor. Your switching regulator has an advantage over it. Make sure it is built in a metal case to avoid interference to nearby mobile phone or other circuits.

 

[div850]

The values look correct. Use standard values, like 160 pF and 470 uF for the capacitors. Check the real circuit for lower than 3.7 V input, to see the regulation range at output.

The 7805 regulators require 7-8 V input to regulate, and a good heat sink as they behave as a controlled resistor. Your switching regulator has an advantage over it. Make sure it is built in a metal case to avoid interference to nearby mobile phone or other circuits.

thankyou for replying ...i also wanted to know which one is good in terms of efficiency linear or switching regulator...less power usage?
thanks in advance..

 

[jiripolivka]

thankyou for replying ...i also wanted to know which one is good in terms of efficiency linear or switching regulator...less power usage?
thanks in advance..

Switchers are much more efficient as they transfer power in pulses. LInear regulators are simply variable resistors that dissipate power. The problem with switchers is that the pulse spectrum is wide and causes interference in sensitive circuits.

 

[div850]

Why don't you try voltage doubler. This will increase to 7.4V. After that apply a regulator to drop it down to the 5v.

yes we could do that but the problem it involves it that voltage regulator absorbs power too much thereby reducing efficiency almost half of what is given by switching one...
so not a good one while on the go.
thankyou for your reply...

 

[ZASto]

You must consider that the 1.5A current is PEAK current that 34063A can deliver. Usable continuous current is in 1A ballpark.
Second, why don't you use 2S Li batteries (double input voltage) and then LM2576-5?
When travelling I'm using, as a safety backup 3S2P pack rated 2200 mAh LM2576-5 as regulator (I designed it that the regulator can be used with the battery or in a car) and can deliver up to 3A on a double female USB-A output.