Patent ID: 9280928
Filing Date: 2016-03-08
CPC Classification: G09G,H03L

Claim Text:
1. An apparatus for driving LED display comprising a plurality of phase locked loop circuits, each of the phase locked loop circuits comprising: a phase frequency detector configured to generate a phase difference signal according to a feedback signal and a reference signal; a charge pump configured to receive the phase difference signal and to generate an output current according to the phase difference signal to adjust phase alignment; a loop filter configured to receive the output current and to convert the output current to a voltage controlled signal; a voltage controlled oscillator configured to receive the voltage controlled signal and to generate a voltage controlled output signal; a divider configured to receive the voltage controlled output signal and a randomized number, and generate the feedback signal; a memory configured to generate a sequence of modulation profile codes; and a sigma delta block comprising at least one sigma delta modulator; and at least one gain block, wherein the sigma delta block is configured to receive the sequence of modulation profile codes and generate the sequence of randomized number to the divider, wherein each of the at least one gain block is configured to generate a value that is multiplied to at least one of the at least one sigma delta modulator so as to change a spread spectrum modulation depth, wherein the at least one sigma delta modulator and the at least one gain block are coupled in a series configuration, wherein the at least one sigma delta modulator comprises a first sigma delta modulator, and the at least one gain block has a first gain block and a second gain block, and wherein the first gain block is coupled between the memory and the first sigma delta modulator, and the second gain block is coupled between the first sigma delta modulator and the divider, and wherein the first gain block generates a fractional value, and the second gain block generates an integer value.