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Mobile phone data cable overheating protection

OneProblems in smart phone data cable   

 Smartphones currently on the market increasing battery capacity, so as not to degrade the user experience, mobile phone charger the charging current has changed from 0.5mA~0.7mA until 2A~8.0A. Charging current increases, the requirements for charging data cable is also put forward higher requirements, not just power and grounding cables in the cable line diameter thick and contact reliability for small Micro USB port also demand higher.If Micro USB port in using process in the has contact bad, and or has foreign body off into (similar sweat, and iron like things), situation occurred, so in big current charging of process in the, in Mirco USB port at on will has is big of power (I2R of relationship), if this power greatly of over phone Micro USB port can bear of range, port on will fever, then burn black, serious situation Xia will burned phone, occurred fire.In actual use in smartphones, cell phone burned even the explosion of cases, heard, this poses a significant risk to consumer safety, so the smart cell phone Micro USB port security has become the focus of many cell phone manufacturers are paying more attention.

                    

                                     USB fever burning black (picture from the Internet)

TwoSolutions

Noir stars provide a cable Micro USB Vbus line PTC thermal protection scheme this scheme in MicroUSB port for adding a PCB, reflow soldering on the PCB SMD PTC (as shown in the following figure), the programme has produced a simple technology, high reliability.

  

This plan works as a result of the presence of foreign bodies in port, Micro USB ports form a low impedance circuit, mobile phone charger current low resistance via Micro USB port loop back to the charger circuit, where current will not flow inside the device, (as shown in the following figure).Port at this time the temperature rose sharply, passed through heat conduction of heat to the PTC, the PTC temperature when the PTC temperature the operating temperature is reached, PTC, cut off the charging circuit, temperature decreases the charge port, avoid extreme situations.  PTC action has a slight leakage current, PTC maintain the status until the charger from the socket pull out or foreign bodies are removed, PTC would be restored to its initial state, do not affect the normal use of the cable.

 

ThreeMeasured results

1, pencil port temperature curve

Charging port is seen from above the surface temperatures of up to 120 ℃, within the surface temperature was 65 c   
2, appearance   

       

Pencil lead Shell to complete a circuit and the ports are in good condition, the invisible

To sum up, Pinot star data line thermal protection scheme can be a good port charging temperature is 120 ℃, surface temperature is less than 65 ℃, to avoid the occurrence of extreme situations.

4、Concluding remarks

About smart cell phone Micro USB port protection, Pinot star the PTC program, and integrated circuit than, high reliability, low cost, easy to use features. Integrated circuit using temperature temperature sensor port, needs to chip, NTC temperature sensor for temperature detection and control circuits, components, complex and costly.PTC Pinot stars passed UL certification is a kind of high reliability components,Only need one element can achieve effective protection.   Noir star can be the product and installation design simplifies the Micro USB port to minimize Visual Basic does not change the shape of the original Micro USB data cable.