A LED drive circuit and a dimming control method thereof

Abstract

The invention discloses an LED driving circuit and a dimming control method thereof. The LED driving circuit comprises a rectifier bridge for converting an AC input voltage into a DC bus voltage having a half power frequency period; A main circuit connected between the first output terminal and the second output terminal of the rectifier bridge for supplying the load current required by the LED and adjusting the duration of the load current in the half power frequency period according to the DC bus voltage so as to realize dimming; And a drain circuit connected between the first output terminal and the second output terminal of the rectifier bridge for supplying a drain current, wherein the drain circuit controls on and off of the drain current according to the DC bus voltage and the loadcurrent, and the drain current is used for supplying a sustain current of the dimmer. The LED driving circuit adopts different modes to compensate the discharge current according to different conduction angles of the thyristor in the dimmer, thereby suppressing the flicker of the LED lamp, improving the compatibility of the LED driving circuit and the thyristor dimmer, and expanding the dimming range.

Description

technical field [0001] This article relates to related fields of power electronics, in particular, relates to an LED driving circuit and a dimming control method thereof. Background technique [0002] Thyristor dimming technology is a very mature dimming application scheme. Utilizing the characteristics of the thyristor itself, it can be well applied to the dimming of traditional incandescent lamps. It works in two phases, turn-on and turn-off. The working principle is to use the variable resistor R inside the dimmer (that is, the knob or slider) to charge the internal capacitor C. When the voltage on the capacitor C reaches the conduction voltage of the internal thyristor device, the controllable Silicon conduction, at this time, the voltage across the dimmer is almost zero, and all the AC voltage is added to the output of the lamp. Therefore, by adjusting the resistance of the variable resistor R, the RC charging time of the turn-on voltage of the thyristor can be adjus...

AI Technical Summary

Problems solved by technology

LED lighting drive power is difficult to be compatible with different types of thyristor dimmers

[0004] The common problem of LED lighting products adopting thyristor dimming is: at small conduction angle, the conduction time of thyristor is too short, resulting in slight flickering of LED lights; at medium conduction angle, thyristor is conducting Instantaneous voltage oscillation causes the holding current to be too small to disconnect the thyristor, resulting in LED light flickering. At a large conduction angle, if the chopping edge voltage is greater than the load voltage, the holding current is too small to cause the thyristor to be disconnected, resulting in LED lights flashing

Also, during chopping, the SCR doesn't work due to the LED's linear circuit not being able to charge the dimmer, resulting in a narrow dimming range

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