Can USB charger get supply voltage from USB itself ??

[milvapp]

I have no idea what a PV panel is.

PV panel is a photovoltaic cell.
So my charger needs to be outdoors that why I am seeking a supply from the device it is going to charge.

From what I know devices that have a USB plug have internal charging circuit so what is the external charger you describe, did you make it?

I think the internal charging circuit you mention is the circuit used for charging the battery of the device
No I have not made it yet , and there is no reason to give the details of the design .
The overall idea is that it harvests solar energy ,storing it to supercapacitors and then charging a usb device.
In this system there are opamps which need supply voltage.

You insist on the charger getting supply from the device it is intended to charge, I don't know why you insist on that.

I insist because as I explained above the charging circuit will be for outdoor use so it will not be ''appropriate'' to have an extra power supply for that

 

[sky_123]

It doesn't seem a well-thought out idea, to somehow rely on charge from a device that could potentially be totally discharged, in order to charge that device(!?!) Maybe I'm wrong..

You can see from the answers how people are interpreting your question - if this is incorrect, I think the "lost in translation" issue is at your end, and you need to find an alternate way to describe your problem (hint: a diagram may be better since in so many posts your requirement is still as clear as mud : (

 

[alexan_e]

I was under the impression that the discussion was related to a mobile charge, apparently this is not the case.
So do you just want to get power from the mobile to power your circuit?
Why to you want to use the mobile as a power source instead of using an external rechargable battery?

 

[D.A.(Tony)Stewart]

@milvap I believe the answer you are looking for is that YES you can use multiple sources for charging a battery and YES you can use the USB port for a bidirectional power port. The spec indicates 100mA until host senses that the peripheral demands more power power 500mA for USB2 and 900mA for USB3.

I have not used this new chip from Linear Tech. for managing USB power bi-directionally.

Intuitively for your needs , I would use a step down temp compensated CV source to charge the battery which is wired OR if possible from the USB port. As the previously linked**broken link removed** indicates there is a critical voltage for charging Li-Ion batteries , there is also a critical voltage for drawing power from the PV solar panels to obtain optimal power from these leaky current sources. Naturally high efficiency losses of your buck regulator needs to be better than the ESR losses of the PV panel.

But yes you may charge your battery from the ac powered devicebe's USB port or the PV panel and then return power from the battery to the device's same USB port when the ac charger is no longer connected. I am not certain what factors need to be done to satisfy your device hosts needs to allow this.

The LTI chip..."The part can directly detect the impedance on the ID pin of a micro-AB receptacle to automatically tell the internal bidirectional switching regulator to provide a 5V output on VBUS for USB On-The-Go."

Considerations to voltage and current limits need to further addressed for your application.

 

[tpetar]

What is voltage and current of that photovoltaic panel ? (characteristics of panel)

 

[milvapp]

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Why to you want to use the mobile as a power source instead of using an external rechargable battery?

That could be one solution ,would take more space ,but definitely less complicated one.

- - - Updated - - -

It doesn't seem a well-thought out idea, to somehow rely on charge from a device that could potentially be totally discharged, in order to charge that device(!?!) Maybe I'm wrong..

You can see from the answers how people are interpreting your question - if this is incorrect, I think the "lost in translation" issue is at your end, and you need to find an alternate way to describe your problem (hint: a diagram may be better since in so many posts your requirement is still as clear as mud : (

No, you got the point.

 

[tpetar]

You can take solar cells from cheap garden solar lamp, they have about 20mA some have 50mA. Use several in serie to get needed voltage, and in parallel to get higher current, and use bypass shottky diode for each cell.

**broken link removed**

or

this cheap device solar cells with few Ah Li-Ion battery inside and 5V on output:

 

[milvapp]

@SunnySkyguy Thank you.You substantially helped me

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@tpetar thank you for the recommendation.
I know that the 5mA getting from my PV panel is an issue,
however it should fit along with mobile or wearable devices.
That was a factor for choosing a PV panel like this SANYO - AM-5913CAR-SCE.

 

[tpetar]

@SunnySkyguy Thank you.You substantially helped me

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@tpetar thank you for the recommendation.
I know that the 5mA getting from my PV panel is an issue,
however it should fit along with mobile or wearable devices.
That was a factor for choosing a PV panel like this SANYO - AM-5913CAR-SCE.

I whant to tell this earlier but You didnt give me a chance.

:wink:

This portable solar cell with builtin Li-Ion 4,5Ah is about 13eur new.


I use this a lots for SMS/GSM alarm/remote control systems, they are cheap and do the job. Just 12V 7,2Ah lead acid is 18eur-20eur in my country.

 

[D.A.(Tony)Stewart]

I find the PV LED garden lights do not hold a candle up to telephone wire and an external source of power. I can make my LEDs just as bright with 1.5mA, but I tend to run then around 150mA using laptop chargers to run strings of 6x1W then 13 to 20 strings all in parallel. ! but I run the well below max power levels. so there is plenty of stability margin and they run cool.

 

[tpetar]

I find the PV LED garden lights do not hold a candle up to telephone wire and an external source of power. I can make my LEDs just as bright with 1.5mA, but I tend to run then around 150mA using laptop chargers to run strings of 6x1W then 13 to 20 strings all in parallel. ! but I run the well below max power levels. so there is plenty of stability margin and they run cool.

Did you point some gun in that little leds and let them that they must light like sun or ..... ?

:grin:

 

[D.A.(Tony)Stewart]

As you see in my avatar, I use them indoors too but here I have 19V and about 60 LEDS rated at 1W but operated at around 75%.
I never let the source shine direct in your eyes. Yes the bay window is about 2~3x as bright as direct sunlight from 2m above.
Solar power is not cost effective for me. Although it is possible to use the LEDs as photo sensors when off.

 

[tpetar]

Although it is possible to use the LEDs as photo sensors when off.

How do You mean that ?

I must admit I didnt think in that way earlier.

**broken link removed**

Something new for me today, thanks.

 

[D.A.(Tony)Stewart]

sorry I dont use the LEDs as reversible light engines like milvapp wants to the USB port as a bidirection power port... and they are bbi-directional but not very efficient.

My point was I prefer to be hardwired than use PV panels.