How Do LED light bulbs works on Mobile Phone Circuit

An LED - light emitting diode is used to illuminate keypads keys and LCD screen displays on all mobile phones handsets. It is being controlled by a voltage or current draws on its terminal leds.
a picture below is an Schematic Diagram that tells us how does the LED circuit works on cellular phone whole circuitry.

On schematic diagram  we notice that the LEDs is driven by an LED driver chip's, and an Switching Control circuit that also being packed in a chip. The LED driver is being used to stabilized the voltage and current and do take control on engaging ON and OFF status of an LEDs to light up or not.
It also drives  the amount  of  brightness or dimming status of the LEDs by applying Pulse Width Modulation signal from the Switching control circuit.

The block diagram below interpreted a component and section or parts of  an LED circuit to work during application process.
The Switching control circuit feeds and release a Pulse Width Modulation Signal (PWM) to switch and light up the LEDs light bulbs. A pulse width modulation signal is a type of digital frequency signal range up to 1khz to enable and implement to take control of  LED brightness.
Once that certain signal is being received by the LED driver, the LED driver now will engage and release the voltage or current that being feeds up from the mobile phones battery supply voltage;
The output voltage release by the LED driver is the one that draws the LED light bulbs to light up.

LED drivers is a high frequency, synchronous boost converter with constant current output to drive up to 5 white LEDs. This device circuit is designed  for maximum safety,  it integrates overvoltage  and short circuit protection when the output is being shorted to the ground. Meaning this chips circuitry will not easily  breakdown for it is designed to protect when short circuit happens.
like for example, the two LED light bulbs commits short circuit to its terminal
In mobile phones application methods; the switching control circuit that release pulse switching signal is also being synchronized programmed by the the application processor (CPU) to engaged a full control on how and which proper situation that the LED will be switch to light up or not.
like for example the LED will only switch and light up, if the handset is being in used and remain off if the handset is not in used.

The above image is an example of the LED circuit, how those particular stages and components being mounted on a phones circuits. Note that the LED driver and switching control circuits is being packed into an Integrated Circuit or ICs.


To all beginners: A bunch of simplified STEP By STEP Procedures On Troubleshooting LED Problem issues on various mobile phones  product will be Posted Here Later.. Just keep on visiting this blog more often.

Posted in: Mobile Phone Repair basics