Select Page

Cell Phone Charger Circuit

Mobile phones usually charge with 5v regulated DC offer, therefore primarily we have a tendency to are about to build a 5v regulated DC offer from 220 AC. This DC offer may be wont to charge mobiles further because of the power supply for digital circuits, breadboard circuits, ICs, microcontrollers, etc.

You can additionally build 6V DC, 9V, 12V, 15V, etc by victimization correct electrical device, electrical condenser, and transformer. the essential construct remains identical, you only ought to prepare a conductor for higher voltage and current.

This circuit chiefly consists of a step down the electrical device, a Full wave bridge rectifier and a 5V transformer IC (7805). we will divide this circuit into four parts: (1) Step down AC voltage (2) Rectification (3) Filtration (4) Voltage Regulation.

1.Step down AC voltage

As we have a tendency to square measure changing 220V AC into a 5V DC, 1st we’d like a transformer to cut back such high voltage. Here we’ve used 9-0-9 1A transformer, that converts 220V AC to 9V AC. In electrical device their square measure primary and secondary coils that boost up or step down the voltage in step with the no of flip within the coils.

Selection of correct electrical device is extremely vital. The current rating depends upon this demand of Load circuit (circuit which is able to use the generate DC). The voltage rating ought to be over the specified voltage. means that if we’d like 5V DC, the electrical device ought to a minimum of having a rating of 7V, as a result of transformer IC 7805 a minimum of would like 2V a lot of i.e. 7V to produce a 5V voltage.


2. Rectification

Rectification is that the method of removing the negative a part of the Alternate Current (AC), thus manufacturing the partial DC. this will be achieved by exploitation of four diodes. Diodes solely permit current to flow in one direction. In half cycle of AC diode D2 & D3 are forward biased and D1 and D4 are reversed biased, and within the half cycle (negative half) Diode D1 and D4 are forward biased and D2 and D3 are reversed biased. this mix converts the negative [*fr1] cycle into positive.

A full wave bridge rectifier element is obtainable within the market, that consist that combination of four diodes internally. Here we’ve used this element.

3. Filtration

The output when the Rectification isn’t a correct DC, it’s oscillation output and contains a terribly high ripple issue. we have a tendency to don’t want that rhythmical output, for this, we have a tendency to use capacitance. capacitance charge until the wave goes to its peak and discharge into Load circuit once wave goes low. therefore once output goes low, capacitance maintains the right voltage provide into the Load circuit, therefore making the DC. currently, however, the worth of this filter capacitance ought to be calculated. Here is that the formulae:

 C = I * t / V

 C= capacitance to be calculated

 I= goop output current (let’s say 500mA)

 t= 10ms,


We will get a wave of 100Hz frequency when changing 50Hz AC into DC, through full wave bridge rectifier. because the negative a part of the heartbeat is regenerate into positive, one pulse is counted 2. that the fundamental measure is 1/100= .01 Second= 10ms


V = Peak voltage – voltage given to transformer IC (+2 overrated suggests that 5+2=7)

9-0-9 is that the RMS worth of transforms, therefore, the peak voltage is Vrms * one.414= 9* 1.414= 12.73v


Now, 1.4v is born on two diodes (0.7 per diode) as two are forward biased for 0.5 waves.

So 12.73 – 1.4 = 11.33v

When capacitance discharges into the load circuit, it should offer 7v to 7805 IC to figure therefore finally V is:

V = 11.33 – 7= 4.33v

So currently C = I * t / V

C = 500mA * 10ms / four.33 = .5 * .01 / 4.33 = 1154uF ~ 1000uF

4. Voltage Regulation

A transformer IC 7805 is employed to produce a regulated 5v DC. Input voltage ought to be 2volts over the rated output voltage for correct operating of IC, means that a minimum of 7v is required, though it will operate in input voltage vary of 7-20V. Voltage regulators have all the electronic equipment within it to produce a correct regulated DC. condenser of zero.01uF ought to be connected to the output of the 7805 to eliminate the noise, created by transient changes in voltage.

Here is that the complete circuit diagram for cellular phone charger circuit: