Feedback current depended ramp generator for switched mode power supply

A Switched-Mode Power Supply (SMPS), comprising:

• an energy storage device;
• a current sense circuit configured to produce a feedback current according to a current flowing through the energy storage device;
• and
• a ramp generator circuit configured to produce a ramp signal according to the feedback current,
• wherein the SMPS is configured to control a duty cycle of the current flowing through the energy storage device using the ramp signal,
• wherein an increase in a magnitude of the feedback current causes a decrease in the duty cycle,
• wherein a decrease in the magnitude of the feedback current causes an increase in the duty cycle, and
• wherein the ramp generator circuit comprises:
• a current-to-voltage converter configured to produce a feedback voltage according to the feedback current;
• a reference current source producing a reference current;
• a ramp capacitor configured to be charged according to the reference current;
• and
• a discharge circuit coupled across the ramp capacitor and receiving the feedback voltage, the discharge circuit configured to discharge the ramp capacitor in response to the ramp signal being greater than the feedback voltage;
• wherein the ramp signal is produced at an output node coupled between the reference current source and the capacitor.

A method of controlling a Switched-Mode Power Supply (SMPS), the method comprising:

• producing a feedback current corresponding to a current flowing through an energy storage device of the SMPS;
• producing a ramp signal having an amplitude corresponding to the feedback current, the amplitude being a difference between the highest value and lowest value of the ramp signal during a cycle;
• and
• controlling a duty cycle of a power switch using the ramp signal,
• wherein a power source of the SMPS provides a current to the energy storage device and to a load connected to an output of the SMPS when the power switch is on, and
• wherein the energy storage device provides the current to the load when the power switch is off,
• wherein an increase in a magnitude of the feedback current causes a decrease in the duty cycle,
• wherein a decrease in the magnitude of the feedback current causes an increase in the duty cycle, and
• wherein producing the ramp signal comprises:
• producing a reference current having a predetermined value;
• producing a charging current having a magnitude corresponding to subtracting the magnitude of the feedback current from the reference current;
• and
• producing the ramp signal by charging a ramp capacitor using the charging current and discharging the ramp capacitor at the beginning of each cycle of a clock signal of the SMPS.