Pulse width modulation controller and pulse waveform control method

Abstract

A pulse width modulation (PWM) controller includes a first counter for counting a reference clock signal, and thus outputting a first count value, a leading edge control signal generator for outputting a leading edge control signal on a basis of the first count value, an adjustment clock generator for generating an adjustment clock signal, a second counter controller for instructing the adjustment clock generator to start to output the adjustment clock signal, a second counter for outputting a second count value, a trailing edge control signal generator for outputting a trailing edge control signal on a basis of the second count value, and a PWM pulse generator for synthesizing the leading edge control signal and the trailing edge control signal, and thus generating a pulse width modulation signal.

1 . A pulse width modulation (PWM) controller, comprising:
 a first counter counting a first count value;   a leading edge control signal generator detecting that the first count value reaches a first prescribed value, and outputting a leading edge control signal to specify a leading edge on the PWM signal;   a second counter counting a second count value in response to the first count value, the second counter has an operation cycle different from that of the first counter;   a trailing edge control signal generator detecting that the second count value reaches a second prescribed value, and outputting a trailing edge control signal to specify a trailing edge on the PWM signal; and   a PWM pulse generator generating a pair of edges of the PWM signal, wherein one of the pair of edges is based on the leading edge control signal and the other of the pair of edges is based on the trailing edge control signal.   
     
     
         2 . A pulse width modulation (PWM) generating circuit, comprising:
 a leading edge comparator for receiving an output signal of a first counting circuit, said leading edge comparator outputting a leading edge control signal that specifies a leading edge on a PWM signal when it detects that the output of said first counting circuit reaches a first prescribed value;   a second counting circuit for receiving said output signal from said first counting circuit, said second counter having an operation cycle different from that of said first counter;   a trailing edge comparator detecting that an output signal from said second counting circuit reaches a second prescribed value, said trailing edge comparator outputting a trailing edge control signal that specifies a trailing edge on the PWM signal; and   a PWM pulse generator generating a pair of edges for the PWM signal, wherein a first edge of the pair of edges is based on the leading edge control signal and a second edge of the pair of edges is based on the trailing edge control signal.   
     
     
         3 . A pulse width modulation (PWM) generating circuit, comprising:
 a leading edge comparator for receiving an output signal of a first counting operation based on a first timing cycle, said leading edge comparator outputting a leading edge control signal specifying a leading edge for a PWM signal when said leading edge comparator detects that the output signal of said first counting operation indicates a first prescribed value;   a second counting circuit based on a second timing cycle different from said first timing cycle, said second counting circuit beginning an execution of a second counting operation within said second counting circuit based upon a detection that said first counting operation has reached a second prescribed value;   a trailing edge comparator detecting that an output signal from said second counting circuit reaches a third prescribed value, said trailing edge comparator outputting a trailing edge control signal that specifies a trailing edge on the PWM signal; and   a PWM pulse generator receiving said leading edge control signal and said trailing edge control signal and generating edges for the PWM signal, wherein a first edge of the PWM signal is based on the leading edge control signal and a second edge of the PWM signal is based on the trailing edge control signal.