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A common reason and treatment method of LED lights flashing

2014.06.18

 Usually the human eye can perceive light flashing frequency of 70 hz, above this frequency is not felt. So in LED lighting applications, if the pulse signal frequency is lower than 70 hz low frequency component, the eye will feel the shine. In the specific application, of course, there are many factors could lead to LED lights flashing. For example, in an off-line low power LED lighting applications, a common power supply topology type is to isolate the flyback topology. In compliance with "energy star" semiconductor solid-state lighting standard from line 8 w LED driver in GreenPoint? Reference design as an example, as a result of the flyback voltage regulator of sine square wave power conversion did not provide primary offset constant energy, dynamic self-supply (DSS) circuit may be activated and trigger light flashing. To avoid this problem, must enable primary bias to partial discharge in each half cycle, accordingly, need to choose appropriate constitute the bias circuit of capacitance and resistance value.

 
In addition, even if it is in use to provide excellent support power factor correction, TRIAC dimmable LED driver applications, the electromagnetic interference (EMI) filter. Caused by a TRIAC step (step) transient current inspire EMI filter inductance and capacitance in the resonant nature. If the resonant characteristics lead to input current fell below the TRIAC to maintain current, TRIAC will be closed. After a short delay, the TRIAC and often conduction, inspire the same resonance. In the input power source waveform of one and a half cycle, this series of events may be repeated many times, to form a visible LED flashing. In order to deal with this problem, a key demand of TRIAC dimmer is EMI filter input capacitance is extremely low, and the capacity to be able to pass the TRIAC and winding impedance of decoupling. According to the formula, the dimmer module capacitance decreases, can increase the resonance circuit resistance, inhibiting oscillation principle, circuit restore want work.


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