Therefore the linear driver powered LED lamps are more likely to flicker if the circuit design does not have features to smooth out the large output current ripple that causes the flickers.įlickering in LED lamps can occur in the use of a Triac circuit for analog LED dimming or phase angle dimming. The main shortcoming of this circuit is the high current ripples of the output current as it uses only MOSFET transistors and integrated circuits to control both stage and does not use electrolytic capacitors to decrease current ripple in the LEDs as the manufacturers think electrolytic capacitors are too large and expensive, and may degrade circuit reliability due to their temperature-sensitive property.
LED LIGHT FLICKER DRIVERS
However, there's an increasing trend to use linear driver or AC direct drivers in LED lamps because of their simple design, low cost, compact size, and immunity to electromagnetic interference (EMI). The ripple current in the LED load may be reduced by utilizing an electrolytic capacitor across the diode bridge in the driver circuitry. The driver circuitry is designed to convert the AC mains voltage into the constant load voltage and constant load current to ensure that flicker is not visible to the human eye. An LED driver is a self-contained power supply which includes outputs matched to the electrical characteristics of the LEDs. A flicker of the LED takes place when a current waveform of the power provided to the LED is imbalanced. Line voltage sources are AC waveforms and the voltage at the line source varies with time. LEDs are current driven rather than voltage driven devices. The ripple current is often twice the input AC line frequency, as an illustration, if the AC sinusoidal frequency is 60 Hz, the rectified sinusoidal frequency will double as 120 Hz. The LEDs can't be forward-biased to illuminate and the flicker phenomenon takes place during the dead time (near the beginning and end of each DC pulse cycle in which the input voltage is less than the combined forward voltage drop of the LEDs) at a repetition rate of twice the AC sinusoidal frequency. The AC sinusoidal input voltage would typically be rectified by a full-wave or a half-wave rectifier into a rectified sinusoidal input voltage before being delivered to power the LEDs.
A residual of the alternating current (AC) input may come up on the output as a variation or ripple which may correspond to the AC frequency, like for example 120 or 100 Hz. Flicker and visual fluctuation can be noticed when there are sufficiently large ripples in the direct current (DC) delivered to the LED lamp.
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