Why Do PWM Circuit Need Slope compensation?
PWM duty cycles above 50% require a compensating ramp, called slope-compensation, to avoid instability. Higher duty cycles require even greater slope compensation. That is, if the PWM switch is turned on for more than 50% of the switching period, slope compensation must be used to keep the system stable. With traditional slope compensation, the switching converter may become unstable for duty cycles approaching 100%, so a special slope compensation must be employed. Figure 3 shows a PWM controller that employs slope compensation.
