How does Charging Circuit Works from a Battery Charger to charge a Mobile phone Battery

This lesson is also important for charging problem troubleshooting for knowing which parts or components has being used to make a charging circuit. Many mobile phone technicians had been asking me, how does mobile phone charging circuit works? How does a battery charger can charge a mobile phone battery?
To tell the truth many of them has never heard of this even they already fix thousands of mobile phones in their years of cellphone repair careers." and I am one of them.
I don't know but I know how fix it, its so easy"  that's what we've oftenly  said.
Well, we all know that all  mobile phones  are all battery operated handsets that needs to charge the battery so that it will continue working,  failure to charge it will result to unable to power up the mobile phone handsets.

Here's a brief explanation of how charging circuit works,
 I prepare this simple idea and diminished some electronics technical terms so that everyone without adequate knowledge on electronics technical terms might can catch up with this.

A  charging circuit is composed of the following stages or sections. 

1. Battery Charger Circuits - Although this is not found on mobile phones PC board circuit and have separate circuit but definitely  this is also part of charging circuit; without this, the charging circuit is not complete and will not work completely.  
This circuit is all parts and components  that being mounted on any mobile phone charger, this is the one that converts AC (Alternating Current)voltage to DC  (Direct Current)voltage.
What is AC Voltage? This voltage is a power source that we used in our household appliances to work  and operate, this voltage can cause risk of electric shock and very dangerous to humans when being touch.This kind of voltage has an alternate polarity.
What is DC voltage? This voltage is a low level voltage which typically found on any kind of  batteries.
This kind of voltage have two polarities, the negative and the positive.

Here's how the battery charger works, the 110 or 220 AC volts  coming from the electrical outlet at home or etc. will be converted to a desired DC voltage like 4.5 to 6 volt DC because the phone only accepts and can be operated into small amount of DC voltage.

A DC voltage output of a charger is only an artificial DC voltage, why is that? because only a battery cell can produce a 100% pure DC voltage.

2. Protection Circuit- this circuit is composed of a Fuse, Inductor coil Diode and Capacitors,  before the DC voltage reach to the charging voltage control circuits the protection circuit is the one that control and check if that  voltage is in exact amount. Let say the desired amount of DC voltage is only 5.6 volts above that point the fuse will be blown out to stop the voltage to flow so that it prevents damaging to another corresponding circuits.
In a protection circuit below of Nokia BB5 mobile phones a diode is the one that measure the amount of voltage from the battery charger, this diode has a reaching point of desired voltage to measure of how much amount of voltage will be allowed to flow within that line, when exceed to that desired point of voltage the diode will then cut it off.

 like for example if that diode is being designed that only allows only 7 volts from the battery charger to flow on that line. Now, above that desired voltage let say that the voltage becomes 8 or higher the diode will then be reacts and destruct itself, this is what then so-called shorted component; so that the current will flow directly to ground and will not reach to the following or corresponding circuit. If the diode will cut off or shorted the fuse will tends to blow and totally cut the voltage line. The inductor coil's role is to filter unwanted voltage saturation, it rejects abnormal voltage modulation caused by electrostatic interference.

3. Charger Voltage Control Circuit - This is the stage where the charger voltage and current is being stabilized, amplified, rectified, regulated and other voltage purification process is being held in this area before it feeds to the battery. This kind of circuit commonly being pack in a chips together with another circuits. 

A failure of this certain area will result on charging problem status. This area mostly called by most technician as a Charging IC it is because this circuit is inside in a particular IC chips, but eventually  this circuit also accompanied by many other circuit types and not exclusive to a certain charging area.

This pictures shows is the next corresponding circuit from the protection circuit area. The voltage from charger is now then feeds into  three  terminal inputs of the charger voltage control circuits.

in this figure shows  after the voltage stabilization and purification process the voltage is now then feeds to the battery terminal.

4. Charging Control Circuit - this is the area where the charging process is being monitored, this is the one that sends information to  the application processor to start or stop  the charging process. This area is part of  Power management circuit, so-called POWER IC by many technicians.

In this picture  that there are two terminal signal from the voltage  control  that sends data to the Charging control circuit, this two data signals  will inform to the charging control circuit that a charger voltage is being  entered or plug-in. After this charging control circuits receives the data it will then analyze and convert that data into digital signal then sends it to the Application processor.

The application processor which is the brain of all the circuits now then decide if all the data's are in correct or in right information to begin the process,
It always relies on the data that sends by the charging control circuit, then  decide all data and completely process it.


Okay now lets take an example and apply this particular method on a mobile phone circuitry component layout, I have here a Nokia N95 board, which is a good way to start with, while we still working on advance training.  Now, try to analyze and compare all of those previous picture above and combined them into each corresponding stages or section, in this manner you can build an step by step tracing procedure on how to deal charging problem issues.

In the picture above shows, how and where the voltage flow from a charger voltage source through the entire  PC board circuit. This is the the method where you can start and manage how to locate and trace each and every component to find possible problems regarding charging problem issues.

Posted in: Mobile Phone Repair basics