China made mobile phone battery chargers used to be produced mostly in China as did mobile phones. But this becomes a history now. I recently opened some old (no more use) simple AC Adapters used for charging mobile phone battery.
Nokia Model AC-3C
I remember that Switching type very light weight battery chargers (as compared with the conventional heavy Transformer type) were called as "travel charger" including this Nokia model as a heavy Transformer type charger was much heavier to carry than a mobile phone, which seems ridiculous and should have been solved by not paying so much.
Surprisingly simple and light weight.
Switching is made by Transistor 13001 connected to a small and light Transformer. Actually I did this (opening power supplies) because I wanted to know more about Switching Transistors and Switching Transformers and Analog Switches.
Input: 100-240V, 50-60Hz, 35mA
Output: 5V 350mA (DC Plug)
The major function of Transformer is to change Voltage (eventually Current also changed) by winding number differences. But Voltage should not be constant DC but AC or AC like. Here C is for Current but AC (Alternate Current) can be used for Voltage, and can be called as AC Voltage.
<Switching is made by Transistor> means Transistor has a switch(ing) function by supplying or not supplying enough current to Base (by controlling the Base current) to change Collector current (Ic), which changes the output voltage.
Collector current (Ic) is high (Transistor works as a conductor) - Output voltage is low
Collector current (Ic) is low (Transistor works as a resistor) - Output voltage is high
This sounds like strange but
V = IR
where I is Collector current (Ic) and R is Transistor's R value controlled by Base current). V is not a supply Voltage but "Voltage drop" made by Transistor's R value. Please note that if Ic is very large it may damage or destroy Transistor you must put a resistor between Voltage source and Transistor to limit Ic. This resistor and Transistor's 'Variable Resistor' make 'Voltage Divide'. See below (Wiki: Transistor)
Amplifier circuit, common-emitter configuration with a voltage-divider bias circuit.
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The above explanation can be found in Transistor Basic Textbooks or Internet Sites in more professional ways. Every part in this schematic has its function but Wiki shows only <voltage-divider bias>. Two Capacitors have their functions too. Two Transistors while two Capacitors and four Resistors are used. This is why so large demands of Capacitors and Resistors in Electronic products.
Back to Nokia Model AC-3C Spec
Components
T1: Switching Transformer - still the largest
C1: Input Aluminum Electric Capacitor 3.3uF 400V
C2: Output Aluminum Electric Capacitor 10uF 100V
C3: Ceramic Disc Capacitor
C4: Output Aluminum Electric Capacitor 220uF (Voltage cannot seen)
Q1: Switching Transistor 13001
Q2: Transistor C945 (for feedback circuit, connected to Base of Transistor)
ZD1; Zener Diode
D2 1N4007 (1000V 1A) for Input
D3, D4: not found
D5: Glass case Diode
D6: 1N58 (Schottky Diode)
Resistors: R1 - R6
There are no parts on the other side of PCB. No SMT parts and no ICs used. The production cost is supposed to be very low in Shenzhen 15-20 years ago. The label says in Chinese.: Made for Nokia.
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Actually I opened the following Charger first and was surprised how simple it was and wanted to know how it works. This is very similar to the above Nokia model except only one (1) Transistor instead of two (2) while one red indicator LED is used.
Name: TL(brand) Courier Charger, Model TL-888-<IC>
Input: 100-250VAC 50/60 Hz 150mA
Output: 5.0V 1000mA +/-50mA (USB Connector)
Components
Switching Transformer
C1: Input Aluminum Electric Capacitor 2.2uF 400V
C2: 22uF 25V
C3: 220uF 10V (output)
Ceramic Disc Capacitor (no marking)
Q1: Switching Transistor 13001
D1:Input
ZD1
D2
Resistors: Four
LED (Red)
USB Connector - big
The component count is less than that of the Nokia model.
How it works ?
I found some good articles or videos for this (How it works.? ) on the net - usually titled "Cheap (China made) battery charger".
Mobile charger circuit diagram, 100-220V AC
https://www.circuitsdiy.com/mobile-charger-circuit-diagram/
The components and their arrangement are very similar to the above <Courier Charger>. To summarize this article:
Rectifier 1 - AC input side
Oscillator - including Tr 13001, Switching Trans. Primary and Auxiliary Winding with feedback (to Base of Tr 13001) circuit
Rectifier 2 - DC output side
Oscillator part is called "Oscillating (Ringing Choke Converter, RCC) flyback Oscillator" and the author estimates Switching 10K -50K cycles/sec - remarkable.
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Another remarkable thing is that this uses only one Tr 13001, further cost down while it uses a LED for charging indicator.
One more article
DIY RCC SMPS Circuits
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I opened some more and they are more complicated, more parts are used so may not be very Cheap though Made in China.
sptt
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