How to protect the USB port power of the mobile phone? From the current market, most mobile phone manufacturers have adopted the micro USB interface as the charging and data interface. According to the USB specification, a USB-compliant power supply should be between 4.75V and 5.25V and provide a continuous current of at least 0.5A. But in fact, many situations can cause the USB power port to suffer from surge voltage surges that greatly exceed the USB specification.
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For a phone connected to a PC. Since the power supply output on the PC usually has a large inductance as a filter. When the external hot plug or system power switch or other internal power supply fluctuations, the output current will change rapidly. Finally, it is reflected in the USB port, there will be a spike voltage pulse, and the amplitude or width of this spike sometimes exceeds the range that the mobile phone charging IC can withstand, resulting in accidental damage of the power chip.
For some low-cost USB chargers provided by third-party manufacturers, because the design does not consider good transient suppression and voltage regulation performance, mobile phones that do not take power protection measures are connected to these third-party chargers. Damage may occur.
With the increase of mobile phone screens and the popularity of navigation software, there will be more and more cases of using mobile phones for car navigation. At this time, you need to connect the phone to the car charger to provide lasting battery life. Everyone knows that there is a serious pollution on the power bus on the car. First, the voltage range of the battery is 8V-16V, the current of the battery is very large, and the load may be disconnected at any time (through fuses or relays). In this way, the bus will generate a surge voltage that exceeds the power supply voltage several times. The battery misconnection and the battery double voltage jump activation (24V) operation will cause the charger input voltage to exceed the nominal value. Third-party power converter products have the potential to filter out some of these events, but trials have shown that these power converters have large differences in transient immunity.
The integrated circuit's OVP device can solve the overvoltage problem, but there is no surge protection function, and the TVS tube can do surge protection, but it can't overpressure for a long time. The ideal situation is to combine them, but the cost and volume will be higher.
TE's PolyZen devices integrate Zener diodes, a precision overvoltage protection component that provides synergistic protection with internal PPTC overcurrent protection components. In the event of a sustained high power state, the PPTC component in the device transitions from a low resistance state to a high resistance state, thereby limiting current and creating a voltage drop. Because of its function, it can protect the Zener diode and the electronic circuit connected behind it, effectively enhancing the power handling capability of the diode. In response to the demanding requirements on mobile phones, TE recently introduced a mini polyzen device in an ultra-small package (3.2mm x 2.5mm x 1.2mm). The occupied area is about half of TE's polyzen products. Overvoltage, surge, overcurrent, reverse connection and other protection functions can be realized at the same time. Moreover, there is no need to externally connect any other device.
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