Method for improving LED light modulation performance via variable frequency PWM

Abstract

A method for improving LED light modulation performance via variable frequency PWM is disclosed. In an LED lamp, lamp brightness can be controlled via PWM and a constant current driving chip through use of a one-chip microcomputer and embedded software. PWM frequency multiplied by light modulation precision must be less than or equal to main frequency of the one-chip microcomputer. A conventional method which adopts fixed PWM frequency and light modulation precision has deficiencies. Stroboflash which can be perceived by naked eyes is caused in a high brightness condition, and obvious light and dark interlaced strips are left on a digital image device; perceivable brightness fluctuation can be generated due to insufficient precision in a low brightness condition. According to the method for improving the LED light modulation performance via the variable frequency PWM, the above deficiencies are overcome via PWM frequency and light modulation precision change according to lamp brightness in light modulation processes. In the high brightness condition, high frequency PWM and low light modulation precision are adopted; in the low brightness condition, low frequency PWM and high light modulation precision are adopted. PWM frequency and light modulation precision can be changed in a smooth manner. LED illumination requirements for zero stroboflash in the high brightness condition, smooth modulation in the low brightness condition and zero brightness jitter can be met.

Description

technical field [0001] The invention relates to the lighting field, in particular to a system for controlling LED lamps by using single-chip microcomputer technology and embedded software technology. Background technique [0002] With the decline of LED prices and the improvement of performance, the application of LED lamps is becoming more and more common. The method of using single-chip microcomputer and embedded software to control the brightness of LED lamps through PWM and constant current drive chips has also been gradually promoted. However, since the operating frequency of the single-chip microcomputer is generally limited, the PWM frequency and dimming accuracy used are limited by the operating frequency of the single-chip microcomputer, that is, the PWM frequency multiplied by the dimming accuracy must be less than or equal to the operating frequency of the single-chip microcomputer. Therefore, the existing systems that use single-chip microcomputers to control th...

AI Technical Summary

Problems solved by technology

One is to use 500hz PWM frequency, combined with 32K level dimming accuracy, under this combination, the LED brightness changes smoothly at low brightness, and there is no perceivable brightness fluctuation, but there will be visible frequency at high brightness. flicker phenomenon, and will leave light and dark stripes on the photo when taking pictures with a digital camera

Or use 4Khz PWM frequency and 4k-level dimming accuracy. Under this combination, there is no perceptible stroboscopic flicker when the brightness is high, and there will be no bright and dark interlaced stripes when taking pictures with a digital camera. At low brightness, the brightness change is not smooth, there will be perceivable brightness fluctuations

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