Output voltage control in overcurrent conditions for switching converters

Patent metadata

Field	Value
Publication number	US-9973085-B2
Application number	US-201615218794-A
Country	US
Kind code	B2
Filing date	Jul 25, 2016
Priority date	Jul 25, 2016
Publication date	May 15, 2018
Grant date	May 15, 2018

Abstract

A method and apparatus for controlling a converter are provided. In the method and apparatus, a converter is operated in accordance with a duty cycle and based on a difference between a feedback signal representing an output voltage of the converter and a reference signal. An overcurrent condition is detected in the converter. In response to detecting the overcurrent condition, the duty cycle used to operate the converter is limited and the reference signal is made to track the feedback signal to mitigate an output voltage overshoot at an end of the overcurrent condition.

First claim

The invention claimed is:

1. A device comprising:
a voltage converter having an input and an output and being configured to receive, at the input, a control signal for operating the voltage converter in accordance with a duty cycle and provide, at the output, an output voltage;
a voltage control stage having a first input coupled to the output of the voltage converter, a second input, a third input and an output coupled to the input of the voltage converter and configured to:
receive, at the first input, a feedback voltage signal representative of the output voltage,
receive, at the second input, a reference voltage signal,
receive, at the third input, an overcurrent protection signal,
generate the control signal based on a difference between the feedback voltage signal and the reference voltage signal,
limit the duty cycle of the control signal in response to the overcurrent protection signal being asserted, and
output the control signal at the output of the voltage control stage; and

an overcurrent control stage having an input coupled to the output of the voltage converter and an output coupled to the third input of the voltage control stage and configured to detect an overcurrent condition in the voltage converter, assert the overcurrent protection signal in response to detecting the overcurrent condition and output the overcurrent protection signal at the output of the overcurrent control stage; and
a reference voltage control stage having an input coupled to the output of the overcurrent control stage and an output coupled to the second input of the voltage control stage and configured to receive the overcurrent protection signal, in response to the overcurrent protection signal being asserted, enable a reference voltage control phase that causes the reference voltage signal to track the feedback voltage signal and the control signal to be limited during the overcurrent condition, and output the reference voltage signal at the output of the reference voltage control stage.

2. The device of claim 1 , wherein the overcurrent control stage is configured to detect the overcurrent condition when an output current of the voltage converter exceeds a threshold for the output current.

3. The device of claim 1 , wherein the reference voltage control stage is configured to cause the reference voltage signal to track the feedback voltage signal by selecting, from a plurality of reference voltage levels, a reference voltage level that is closest to a voltage level of the feedback voltage signal and setting a voltage level of the reference voltage signal to the reference voltage level of the plurality of reference voltage levels.

4. The device of claim 1 , wherein the reference voltage control stage is configured to:
determine that a voltage level of the reference voltage signal that tracks the feedback voltage signal has returned to its voltage level prior to enablement of the reference voltage control phase; and
disable the reference voltage control phase in response to determining that the voltage level of the reference voltage signal that tracks the feedback voltage signal has returned to its voltage level prior to the enablement of the reference voltage control phase.

5. The device of claim 4 , wherein the reference voltage control stage is configured to set the voltage level of the reference voltage signal to a static reference voltage level when the reference voltage control phase is disabled.

6. The device of claim 1 , wherein the reference voltage control stage includes:
a comparator having an inverting input for receiving the reference voltage signal, a non-inverting input for receiving the feedback voltage signal and an output for providing a comparison signal;
control logic having an input coupled to the output of the comparator and an output for providing a counter signal, the control logic being configured to determine a logical value for the counter signal based on whether the comparison signal is asserted or not asserted;
a digital-to-analog converter having a control input coupled to the output of the control logic, a plurality of reference voltage inputs for receiving a plurality of reference voltage levels, respectively, and an output, the digital-to-analog converter being configured to select a reference voltage level of the plurality of reference voltage levels based on the counter signal and provide, at the output of the digital-to-analog converter, the selected reference voltage level; and
voltage setting circuitry coupled to the output of the digital-to-analog converter and configured to set a voltage level of the reference voltage signal to the selected reference voltage level when the reference voltage control phase is enabled.

7. A device comprising:
a voltage control stage configured to receive a reference voltage signal and a feedback voltage signal representative of an output voltage of a converter and output, based on a difference between the feedback voltage signal and the reference voltage signal, a control signal for operating the converter in accordance with a duty cycle, the voltage control stage being configured to receive an overcurrent protection signal and limit the duty cycle when the overcurrent protection signal is asserted;
an overcurrent control stage configured to detect an overcurrent condition in the converter, and assert the overcurrent protection signal in response to detecting the overcurrent condition; and
a reference voltage control stage configured to enable a reference voltage control phase in response to the overcurrent protection signal being asserted and cause the reference voltage signal to track the feedback voltage signal when the reference voltage control phase is enabled.

8. The device of claim 7 , wherein the overcurrent control stage is configured to detect the overcurrent condition in response to an output current of the converter exceeding a threshold for the output current.

9. The device of claim 7 , wherein the reference voltage control stage is configured to cause the reference voltage signal to track the feedback voltage signal by selecting, from a plurality of reference voltage levels, a reference voltage level that is closest to a voltage level of the feedback voltage signal and setting the voltage level of the reference voltage signal to the reference voltage level of the plurality of reference voltage levels.

10. The device of claim 7 , wherein the reference voltage control stage is configured to:
determine that a voltage level of the reference voltage signal that tracks the feedback voltage signal has returned to its voltage level prior to enablement of the reference voltage control phase; and
disable the reference voltage control phase in response to determining that the voltage level of the reference voltage signal that tracks the feedback voltage signal has returned to its voltage level prior to the enablement of the reference voltage control phase.

11. The device of claim 10 , wherein the reference voltage control stage is configured to set the voltage level of the reference voltage signal to a static reference voltage level when the reference voltage control phase is disabled.

12. The device of claim 7 , wherein the reference voltage control stage includes:
a comparator having an inverting input for receiving the reference voltage signal, a non-inverting input for receiving the feedback voltage signal and an output for providing a comparison signal;
control logic having an input coupled to the output of the comparator and an output for providing a counter signal, the control logic being configured to determine a logical value for the counter signal based on whether the comparison signal

Assignees

• St Microelectronics Srl

Inventors

• Vicquery Jeanpierre
• VOLPI Emilio

Classifications

• H02M1/32

  Means for protecting converters other than automatic disconnection · CPC title

• H02M3/157 Primary

  with digital control · CPC title

• H02M3/158 Primary

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

• H02M1/08

  Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters · CPC title

• H02M1/0025

  Arrangements for modifying reference values, feedback values or error values in the control loop of a converter · CPC title