Flicker-free led driver circuit with high power factor

Abstract

A flicker-free LED driver circuit with a high power factor has a rectifying unit connected with an AC power source, an LED module connected in series with the rectifying unit, a capacitor module connected in parallel with the LED module, and a constant current circuit connected in series with the LED module and the capacitor module. When the voltage output by the rectifying unit is smaller than a junction voltage of the LED module, the capacitor module discharges to the LED module so that the LED module does not go out, thereby eliminating the flickering. The input impedance of the rectifying unit can be regarded as a capacitive reactance element connected in parallel with a nonlinear resistive element. The internal resistance of the constant current source approaches infinity. Therefore, the power factor of the flicker-free LED driver circuit approximates 1, achieving a high power factor.

Description

technical field [0001] The invention relates to an AC LED driving circuit, especially to a flicker-eliminating LED driving circuit with high power factor. Background technique [0002] Light-emitting diodes (LEDs) are common lighting fixtures on the market today. Compared with traditional incandescent bulbs, they have higher luminous efficiency and energy-saving characteristics; however, because light-emitting diodes can only conduct in one direction, it is difficult to use them in traditional AC sockets For this reason, the industry has developed an AC LED drive circuit; please refer to Image 6 As shown, the existing AC LED drive circuit includes: [0003] A rectifier unit 20, whose input end is connected to an AC power supply AC / IN, and converts the AC power supply AC / IN into a pulsating DC power supply V a , and output from its output terminal; [0004] An LED unit 21 includes a plurality of LED light sources, and is electrically connected to the output end of the rect...

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Problems solved by technology

[0008] However, since the LED unit 21 must make the voltage difference V across both ends ab It can only make it glow if it is greater than its junction voltage value. If the pulsating DC power supply V a When the instantaneous voltage of the LED unit is lower than its junction voltage value, the LED unit will go out, which will cause the LED unit 21 to have a flicker phenomenon. Taking a pulsating DC power supply with a frequency of 120Hz as an example, the flicker frequency is also 120Hz

The human eye is not easy to perceive the flicker phenomenon for the 120Hz frequency light source, but for the image capture device that senses by periodic scanning, the image captured under the 120Hz frequency light source will cause the flicker phenomenon due to the difference between the scanning frequency and the light source frequency, making Multiple parallel stripes formed on the image, distorting this photo

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