US 2015/0318786 A1 · SYSTEM AND METHOD FOR MAINTAINING A CONSTANT OUTPUT VOLTAGE RIPPLE IN A BUCK CONVERTER IN DISCONTINUOUS CONDUCTION MODE

Abstract

The system and method creates a substantially constant output voltage ripple in a buck converter in discontinuous conduction mode by varying the on-time of a pulse width modulator (PWM) signal driving the buck converter when the buck converter is operating in discontinuous conduction mode. A first signal is generated that is a function of the switching frequency of the buck converter. This signal is low-pass filtered and compared with a second signal that is a function of the switching frequency of the buck converter when operating in continuous conduction mode and with constant PWM on-time. The output signal generated by the comparator is a signal that is equal to the ratio of said first signal and said second signal. The on-time of a voltage controlled oscillator is controlled by said output signal, the oscillator signal causing the on-time of said PWM signal to vary in a controlled fashion.

Claims12

Dependent claims

A method for varying the on-time of a pulse width modulator (PWM) signal driving a buck converter when the buck converter is operating in discontinuous conduction mode, comprising:

generating a first signal that is a function of the switching frequency of the buck converter;
low-pass filtering said first signal;
generating a second signal that is a function of the switching frequency of the buck converter when it is operating in continuous conduction mode and the on-time of the PWM signal is constant;
generating an output signal equal to the ratio of said first signal and said second signal;
varying the on-time of an oscillator signal as a function of said output signal, the oscillator signal causing the on-time of said PWM signal to vary;
and
causing said output signal to vary said first signal so as to create a control loop that regulates said output signal.

4 more elements

A system for varying the on-time of pulse width modulator (PWM) signal driving a buck converter when said buck converter is operating in a discontinuous conduction mode, comprising:

a first circuit for converting the switching frequency of the buck converter into a first signal;
a low-pass filter to filter said first signal;
a second circuit for generating a second signal that is a function of the switching frequency of the buck converter when it is operating in continuous conduction mode
a comparator for generating an output signal that is a function of the ratio of the filtered first signal and said second signal;
a feedback loop for coupling the output signal to said first circuit;
and
an oscillator for varying the on-time of said PWM signal as a function of said output signal.

4 more elements

Dependencies are inferred from the claim text.

System and method for maintaining a constant output voltage ripple in a buck converter in discontinuous conduction mode

Life of this patent

System and method for maintaining a constant output voltage ripple in a buck converter in discontinuous conduction mode

Life of this patent

Abstract

Claims12