Soft start techniques for control loops that regulate DC/DC converters

摘要

Improved soft start techniques for control loops that regulate DC/DC converter circuits are provided. An improved soft start circuit provides a varying voltage at the output of an error amplifier in the control loop during the start-up phase of the DC/DC converter. The varying voltage generated by an improved soft start circuit is related to the amplitude of the saw-tooth ramp signal that controls the switching duty cycle. The varying voltage generated by an improved soft start circuit is also related to the switching frequency of the DC/DC converter. These features allow the duty cycle of the DC/DC converter to gradually increase from zero during power-on. An effective soft start function is provided for DC/DC converters that have a variable switching frequency or a variable saw-tooth ramp signal.