[SOLVED] Weird problem of usb charger circuit. Urgent !

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Sunny55

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Testing of the usb charger circuit was conducted using a small solar panel and a car battery. The results are as follows.

For small solar panel, the phone charges normally without any problem.

When connected to car battery, phone keeps on changing from charging to discharging mode very often and does not charge at all.

What could cause such problem when connected to car battery? Can it be the current? What can i do to fix the problem?

Please help !

Thanks
Sunny55.
 

This totally depends on how your circuit is designed. The possible causes are- Over voltage (>5V), over current, under voltage or current. This is for sure that it gets some energy from the car battery, but it may be either excess or under valued. Your phone is rejecting to accept the input. I guess, because of the over voltage. Can you post your circuit diagram???
 

It should be overcurrent as the circuits input voltage is regulated using a 12v to 5v regulator. The circuit is a mix of two circuits.

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TL2575 gives 5Vdc supply to run TPS2511.
 

It seems your regulator TL2575 is maybe not configured properly. Have you checked the output of the regulator with a multimeter, when it is connected with load??? Try using LM7805. It requires no voltage configurations...
 

Genovator said:
It seems your regulator TL2575 is maybe not configured properly. Have you checked the output of the regulator with a multimeter, when it is connected with load??? Try using LM7805. It requires no voltage configurations...
Click to expand...

Yes, TL2575 gives Vout of 5.03V and is working well.

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Vout of 5.03V is fed into TPS2511(As Vin) and TPS2511 gives 5V for charging phone(Standard usb 5v)
 

Is the CS, EN & ILIM_SET pins are configured accordingly????

What is the value of R(ILIM) you are using??? and for what device???

This was written in the datasheet...

Thermal Sense
The TPS2511 provides thermal protection from two independent thermal sensing circuits that monitor the operating temperature of the power distribution switch and turn off for 12 seconds (typ) if the temperature exceeds recommended operating conditions. The device operates in constant-current mode during an overcurrent condition and OUT pin voltage is above 3.8 V (typ), which has a relatively large voltage drop across power switch. The power dissipation in the package is proportional to the voltage drop across the power switch, so the junction temperature rises during the over-current condition. The first thermal sensor turns off the power switch when the die temperature exceeds 135°C and the device is within the current limit. The second thermal sensor turns off the power switch when the die temperature exceeds 155°C regardless of whether the power switch is in current limit. Hysteresis is built into both thermal sensors, and the switch turns on after the device has cooled approximately 10°C. The switch continues to cycle off and on until the fault is removed.

See if it is getting hot or not...
 


I was told by TI engineers to follow circuit in figure 5 of TPS2511 datasheet and i did the same. Yes, CS, EN & ILIM_SET pins are same as the figure given. Rilim used is around 60Kohm for 1A if i am not wrong. Regarding the ic heating, only the TL2575 12v to 5v ic heats up when connected to car battery.
 

only the TL2575 12v to 5v ic heats up when connected to car battery.
Click to expand...

Yes, This is obvious. If possible, try to keep it cool.

With 60K ohm, you will get around 0.854A of current.
Your circuit seems good. Can't say what is the fault unless I see it. You have to do some experiments...

Try changing TL2575 with LM7805. If it is not possible for you, change C(out) to around 4700uF from 330uF. Remove L1 and connect directly.

Connect a heat sink with TL2575 to avoid thermal shutdown factor, if possible.

Use a multimeter to measure the current flow through the regulator.

Increase the value of R(ilim) in TPS2511 to few more k ohm.
 

The problem is solved. I tried using LM7805 with heatsink and no more charging problems . Thanks to all who gave solutions to solve this problem. Cheers.
 

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