Feedback current depended ramp generator for switched mode power supply

Patent metadata

Field	Value
Publication number	US-12451805-B2
Application number	US-202318351059-A
Country	US
Kind code	B2
Filing date	Jul 12, 2023
Priority date	Jul 12, 2023
Publication date	Oct 21, 2025
Grant date	Oct 21, 2025

Abstract

To reduce sub-harmonic oscillations in a Switched-Mode Power Supply (SMPS). a ramp generator circuit of the SMPS produces a ramp signal having an amplitude corresponding to a sensed current through an energy storage device, such as an inductor, of the SMPS. The ramp signal is used to control a duty cycle of the SMPS. The ramp generator circuit may include a reference current circuit, a ramp capacitor, and a discharge circuit to periodically discharge the ramp capacitor. The ramp capacitor may be charged using a charging current produced by combining a feedback current corresponding to the sensed current with a reference current produced by the reference current circuit and may be periodically discharged at a fixed frequency, or may be charged using the reference current and discharged at a time determined according to the feedback current.

First claim

The invention claimed is:

1 . 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 reference current source;
an output node configured to:
receive an output of the reference current source and the feedback current, and
produce a charging current according to a sum of the output of the reference current source and the feedback current;

a ramp capacitor coupled to the output node; and
a discharge circuit coupled across the ramp capacitor and receiving a clock signal, the discharge circuit configured to discharge the ramp capacitor in response to the clock signal,
wherein the ramp capacitor is charged according to the charging current, and wherein the ramp signal is produced at the output node.

2 . The SMPS of claim 1 ,
wherein the generator circuit is configured to control an amplitude of the ramp signal according to the feedback current, the amplitude being a difference between the highest value and lowest value of the ramp signal during a cycle.

3 . The SMPS of claim 1 , wherein a rate of increase of the ramp signal varies according to the magnitude of the feedback current.

4 . The SMPS of claim 1 , wherein the discharge circuit comprises:
a discharge switch coupled across the ramp capacitor; and a one-shot circuit controlling the discharge switch according to the clock signal, wherein the one-shot circuit turns the switch on for a preset interval in response to an edge of the clock signal.

5 . The SMPS of claim 1 , wherein the discharge circuit comprises:
a discharge switch coupled across the ramp capacitor; and a comparator circuit to output a comparison signal according to a comparison of s voltage of the ramp signal to a ramp low voltage; and a control circuit configured to: turn the discharge switch on in response to an edge of the clock signal, and turn the discharge switch off in response to the comparator signal indicating that the voltage of the ramp signal is less than or equal to the ramp low voltage.

6 . The SMPS of claim 1 , wherein the ramp generator is configured to control a cycle time of the ramp signal according to a magnitude of the feedback current.

7 . 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.

8 . The SMPS of claim 7 , wherein the discharge circuit comprises:
a discharge switch coupled across the ramp capacitor; a control circuit configured to: turn the discharge switch on in response to the ramp signal being less than or equal to a predetermined ramp low voltage, and turn the discharge switch off in response to the ramp signal being greater than or equal to the feedback voltage.

9 . The SMPS of claim 1 , wherein the energy storage device is an inductor.

10 . 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.

11 . The method of claim 10 , wherein producing the ramp signal comprises:
decreasing the slope of the ramp signal when the feedback current increases, and increasing the slope of the ramp signal when the feedback current decreases.

12 . The method of claim 10 , wherein discharging the ramp capacitor at the beginning of each cycle of the clock signal comprises turning on a discharge switch coupled across the ramp capacitor for a preset interval in response to an edge of the clock signal.

13 . The method of claim 10 , wherein discharging the ramp capacitor at the beginning of each cycle of the clock signal comprises:
turning on a discharge switch coupled across the ramp capacitor in response to an edge of the clock signal, and turning off the discharge switch in response to the ramp signal being less than or equal to a preset ramp low voltage.

14 . The method of claim 10 , wherein producing the ramp signal comprises controlling a cycle time of the ramp signal according to the feedback current.

15 . The method of claim 10 , wherein controlling the duty cycle of the power switch using the ramp signal comprises:
determining an error signal having a voltage corresponding to a difference between an output voltage provided by the SMPS to the load and a reference voltage; comparing the error signal to the ramp signal to produce a phase control signal; controlling the duty cycle of the power switch using the phase control signal.

Assignees

• Globalfoundries Us Inc

Inventors

• Hoffmann Matthias

Classifications

• H02M1/0009

  Devices or circuits for detecting current in a converter · CPC title

• H03K4/502

  the capacitor being charged from a constant-current source · CPC title

• H03K4/50

  in which a sawtooth voltage is produced across a capacitor · CPC title

• H02M1/0003

  Details of control, feedback or regulation circuits · CPC title

• H02M3/158 Primary

  including plural semiconductor devices as final control devices for a single load · CPC title