Flicker refers to rapid, repeated changes over time in light intensity. According to whether the flicker is consciously perceivable by a human eyes or not, there are visible and invisible flickers. Most of visible flickers are kind of defectiveness; however invisible flicker depends on different mechanism. There’re multiple reasons that can lead to flicker.
Reason #1: Because electricity is delivered through alternating current (AC) at a power line frequency of 60 hertz in many countries, the voltage delivered to a source bounces between on and off as it rides the sine wave between the positive and negative poles. As a result, the potential flicker frequency is twice the power line frequency, or 120 Hz, however 60-70Hz is normally deemed as the threshold of flicker visibility to human eyes. Without the proper electronic circuitry—such as a ballast, driver, or capacitor—a light source willflicker.
Reason #2: bad contact between bonding wire and electrode. Due to poor encapsulation process (e.g. insufficient welding strength ). the interval time of this kind of flicker is often few seconds to 10 minutes even longer but seldom rapidly alternates. When bonding wire is heated up by electric current, contact-break appears due to thermal stress therefore, the light go off; and when the bonding wire is cooled down it contact to the electrode again and the light on,and such cycle repeats.
Reason #3: unusual service condition of LED driver due to its self-protection design. Many constant current drivers are designed with self-protection mechanism, when there’s over-heat, over-current or over-load circumstance the intelligent chip of LED driver will suspend it’s working condition until the abnormal situation disappear. For example in case the LED light is working under excessive high temperature due to heat dissipation disablement, the driver will stop working until the temperature is cooled down, and when the light restart the temperature will rise again which lead to another cycle. This is often described figuratively as “hiccup phenomenon”.