A symmetry control circuit of a trailing edge phase control dimmer circuit

Abstract

A symmetry control circuit for a trailing edge phase control dimmer circuit for controlling alternating current (AC) power to a load, the symmetry control circuit including: a bias signal generator circuit configured to monitor non-conduction periods of each half cycle of said AC power for an elapsed duration of the non-conduction periods, and generate a bias signal voltage based on the elapsed duration, whereby an amplitude of the bias signal voltage is proportional to the elapsed duration of the non-conduction periods; and a bias signal converter circuit configured to convert the bias signal voltage to a bias signal current, wherein the bias signal current is added to a reference current of a conduction period timing circuit configured to determine said conduction periods, and wherein the conduction period timing circuit is configured to alter one of the conduction periods immediately following one of the non-conduction periods based on the bias signal current when added to the reference current to compensate for a phase shift of a zero-crossing of said one of the non-conduction periods corresponding to an elapsed duration of said one of the non-conduction periods so as to restore symmetry of the non-conduction periods of each half cycle of AC power.

Description

technical field [0001] The present invention relates to a symmetrical control circuit for a trailing edge phase control dimmer circuit for controlling alternating current (AC) power to a load and for controlling each half of the alternating current (AC) power of a trailing edge phase control dimmer circuit A method of symmetry of the non-conducting period of the cycle. [0002] In particular, but not exclusively, the present invention relates to a symmetrical control circuit for controlling a capacitive load such as a 2-wire trailing edge phase-controlled dimmer circuit for a driver for an LED lamp. Background technique [0003] Dimmer circuits are commonly used to control power, particularly alternating current (AC) mains power, to loads such as light sources. In one existing approach, a light source can be dimmed using phase control dimming, whereby the control is controlled by changing the amount of time that the switch connecting the load to the mains power is on during...

AI Technical Summary

Problems solved by technology

Therefore, in this exemplary prior art dimmer circuit, AC power can be continuously applied asymmetrically to the load during the symmetrical on-period, which can lead to the above-mentioned problems, such as flicker in the lighting load

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