EMI reduction for a flat-panel display controller using horizontal-line based spread spectrum

摘要: A graphics controller uses spread-spectrum techniques to modulate the pixel clock over a range of frequencies, reducing maximum intensity EMI emissions. When input is replaced with modulated clock, image on CRT distorted. Distortion avoided by only modulating flat-panel LCD interface. The vertical and horizontal timing signals for both are generated from un-modulated clock. Using these critical ensures that each line displayed same period time. Brighter dimmer lines thus avoided. second embodiment modulates clocks LCD, emissions interfaces. Even use frequency sweep reset at end every line. Thus all period, although transfer pixels within modulated. though while written displays, sequence modulations repeated different aligned zig-zag wiggle distortions seen when simple asynchronous modulation applied