LED Open-circuit Protective Circuit

Published:2011/5/3 8:34:00 Author:Joyce | Keyword: LED, Open-circuit, Protective, CP2126 | From:SeekIC

As you can see,italmost has no impact on the receiving sensitivity of mobile phones that whether CP2126 works or not .But if the chip X is at work,the receiving sensitivity would decrease because of the interference caused by EMI . Meanwhile, under the typical condition that CP2126 with a voltage input of 3.6 V drives three white light LED, the conversion efficiency can reach 83% . The design of PCB will also have a great influence on the performance of the circuit. Generally, routings on the part of high frequency should be as short and thick as possible,vias to the ground should be as lagre and abundant aspossible to meet the requirements claimed in the relevant information of CP2126 . In application, LED may happen to have some open fault.In this case, because the feedback voltage of pin CS will keep at 0, so if there is no protective circuit, this kind of boost circuit will boost till the switching tube within gets punctured and breaks down.Therefore, chips without the protection of built-in protective circuit need to add a Zener diode to protect the internal switching tube. The LED open-circuit protection circuit is shown in the graph.It is obvious that such protective circuit will increase the cost of the system and the acreage of PCB . Another method to protect the circuit is to add a pin, use capsulation like SOT23-6L,and sample and detect the voltage of UOUT. Because CP2126 has a built-in output open-circuit protective circuit, it can ensure that the chip would not be damaged in the circumstance that no change has to be done to the peripheral application circuit and LED is open.When malfunction is removed, thechipcan again work properly.



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