Self-stabilized constant on-time control

Patent metadata

Field	Value
Publication number	US-10243465-B1
Application number	US-201816038018-A
Country	US
Kind code	B1
Filing date	Jul 17, 2018
Priority date	Mar 14, 2018
Publication date	Mar 26, 2019
Grant date	Mar 26, 2019

Abstract

Some apparatus and associated methods relate to a buck-derived switched mode power supply with constant on-time and configured to substantially maintain a steady-state average switch period in a time interval between a start of a load transient and the time when the inductor current returns to a steady state. In an illustrative example, the time interval may include a first and a second predetermined number of cycles after the start of the load transient. The switch period may be modulated, for example, by an amount calculated to supply a change in additional energy demand in the first number of cycles and an opposite amount in the subsequent second number of cycles calculated to maintain the average steady-state switch period over the time interval. In various examples, maintaining average switching period with constant on-time may minimize transient response times without sacrificing stability and without the need for complex compensation networks.

First claim

What is claimed is:

1. A buck-derived switched mode power supply, the apparatus comprising:
a main switch operative to selectively connect a first terminal of an input voltage source to an intermediate switch node;
an inductor coupled to the intermediate switch node and an output terminal configured to couple to a load;
a rectifier coupled to circulate inductor current returning from the load back to the intermediate switch node;
a processor operably coupled to control a conductivity state of the main switch; and,
a data store operably coupled to the processor and containing a program of instructions that, when executed by the processor, cause the processor to perform operations to substantially maintain an average period for the main switch, the operations comprising:
determine the on-time and switching cycle period during a period of the main switch control signal at the start of a load transient;
determine a first off-time adjustment that, when applied to the main switch, is effective to deliver the additional amount of energy demanded by the load transient;
during the first portion of a response time interval that begins with a start of a load transient and ends when the inductor current returns to a steady state, adjust the main switch off time according to the first off-time adjustment;
determine a second off-time adjustment that, when applied to the main switch during a second portion of the response time that comprises a remainder of the response time interval, is effective to maintain the average period for the main switch during the response time interval equal to the determined period at the start of the load transient;
during the second portion of the response time interval, adjust the main switch off time according to the second off-time adjustment; and,
maintain the determined on-time for the main switch during the response time interval.

2. The apparatus of claim 1 , wherein the second off-time adjustment has equal magnitude and opposite sign relative to the first off-time adjustment.

3. The apparatus of claim 1 , wherein the second off-time adjustment has a different magnitude and opposite sign relative to the first off-time adjustment.

4. The apparatus of claim 1 , wherein the operation to determine the first off time adjustment further comprises determining the offset to supply the change in additional energy demand in a first predetermined number of switching cycles.

5. The apparatus of claim 1 , wherein the operation to determine the second off time adjustment further comprises determining the offset effective to maintain the average period within a second predetermined number of switching cycles.

6. The apparatus of claim 1 , wherein the operation to determine the first off time adjustment further comprises determining the offset to supply the change in additional energy demand in a first predetermined number of switching cycles, the operation to determine the second off time adjustment further comprises determining the offset effective to maintain the average period within a second predetermined number of switching cycles, and the first and second number of predetermined switching cycles are equal.

7. The apparatus of claim 4 , wherein the first predetermined number of switching cycles is one.

8. The apparatus of claim 4 , wherein the first predetermined number of switching cycles is two.

9. The apparatus of claim 4 , wherein the first predetermined number of switching cycles is less than 10.

10. A buck-derived switched mode power supply controller, the apparatus comprising:
a controller comprising:
(a) a processor adapted to operatively couple to at least one phase of a buck-derived power supply (BDPS), each of the at least one BDPS comprises a main switch, an inductor, and a rectifier, wherein the processor is operably coupled to control a conductivity state of the main switch; and,
(b) a data store operably coupled to the processor and containing a program of instructions that, when executed by the processor, cause the processor to perform operations to substantially maintain an average period for the main switch, the operations comprising:
determine the on-time and switching cycle period during a period of the main switch control signal at the start of a load transient;
determine a first off-time adjustment that, when applied to the main switch, is effective to deliver the additional amount of energy demanded by the load transient;
during the first portion of a response time interval that begins with a start of a load transient and ends when the inductor current returns to a steady state, adjust the main switch off time according to the first off-time adjustment;
determine a second off-time adjustment that, when applied to the main switch during a second portion of the response time that comprises a remainder of the response time interval, is effective to maintain the average period for the main switch during the response time interval equal to the determined period at the start of the load transient;
during the second portion of the response time interval, adjust the main switch off time according to the second off-time adjustment; and,
maintain the determined on-time for the main switch during the response time interval.

11. The apparatus of claim 10 , wherein the second off-time adjustment has equal magnitude and opposite sign relative to the first off-time adjustment.

12. The apparatus of claim 10 , wherein the second off-time adjustment has a different magnitude and opposite sign relative to the first off-time adjustment.

13. The apparatus of claim 10 , wherein the operation to determine the first off time adjustment further comprises determining the offset to supply the change in additional energy demand in a first predetermined number of switching cycles, the operation to determine the second off time adjustment further comprises determining the offset effective to maintain the average period within a second predetermined number of switching cycles, and the first and second number of predetermined switching cycles are equal.

14. The apparatus of claim 10 , wherein the operation to determine the first off time adjustment further comprises determining the offset to supply the change in additional energy demand in a first predetermined number of switching cycles.

15. The apparatus of claim 10 , wherein the operation to determine the second off time adjustment further comprises determining the offset effective to maintain the average period within a second predetermined number of switching cycles.

16. The apparatus of claim 13 , wherein the first predetermined number of switching cycles is one.

17. The apparatus of claim 13 , wherein the first predetermined number of switching cycles is two.

18. The apparatus of claim 13 , wherein the first predetermined number of switching cycles is three.

19. The apparatus of claim 13 , wherein the first predetermined number of switching cycles is less than 10.

20. The apparatus of claim 10 , wherein the freewheeling rectifier comprises a synchronous rectifier operably controlled by the processor.

Assignees

• Alpha & Omega Semiconductor Cayman Ltd

Inventors

• Young Chris M

Classifications

• H02M1/00 Primary

  Details of apparatus for conversion · CPC title

• H02M1/14 Primary

  Arrangements for reducing ripples from DC input or output · CPC title

• H02M3/1588

  comprising at least one synchronous rectifier element (H02M3/1582, H02M3/1584 take precedence) · CPC title

• H02M3/158

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

• H02M3/1582 Primary

  Buck-boost converters (H02M3/1584 takes precedence) · CPC title