Circuits and techniques for improving regulation in a regulator having more than one mode of operation

Patent metadata

Field	Value
Publication number	US-9621036-B2
Application number	US-201414132534-A
Country	US
Kind code	B2
Filing date	Jan 9, 2014
Priority date	Jan 9, 2014
Publication date	Apr 11, 2017
Grant date	Apr 11, 2017

Abstract

A switching regulator control circuit comprises a first control circuit to control conduction of the switch according to a first mode of operation and having a regulation point and a second control circuit to control conduction of the switch according to a second mode of operation in response to a reference signal that is calibrated to have a predetermined relationship with respect to the regulation point of the first control circuit. In some embodiments, the reference signal is calibrated to be a predetermined amount greater than the regulation point of the first control circuit and may be calibrated during the first mode of operation or in response to a regulator start or restart event.

First claim

What is claimed is:

1. A switching regulator control circuit for controlling a switching regulator comprising at least one switch that conducts to transfer energy from an input source to an output at which a regulated output is provided, the switching regulator control circuit comprising:
a first control circuit to generate a first control signal to control conduction of the at least one switch during a first mode of operation and having a first input responsive to a first reference signal, a second input responsive to a feedback signal proportional to the regulated output, and an output at which the first control signal is provided; and
a second control circuit to generate a second control signal to control conduction of the at least one switch during a second mode of operation and having a first input responsive to a second reference signal, a second input responsive to the feedback signal, and an output at which the second control signal is provided; and
a regulation mode calibration circuit coupled between the first control circuit and the second control circuit for calibrating the second reference signal in response to the first control circuit.

2. The switching regulator control circuit of claim 1 wherein the first control circuit is a PWM control circuit and the second control circuit is a PFM control circuit.

3. The switching regulator control circuit of claim 1 further comprising a combining circuit responsive to the first control signal and the second control signal for generating at least one switch control signal for coupling to the at least one switch.

4. The switching regulator control circuit of claim 3 wherein the at least one switch control signal is a function of the first control signal when the first control signal is greater than a reference signal.

5. The switching regulator control circuit of claim 4 wherein the first control circuit comprises an error amplifier to provide the first control signal at a variable level when the first control signal is greater than the reference signal and at a fixed, clamp level when the first control signal is less than the reference signal.

6. The switching regulator control circuit of claim 1 wherein the second control circuit comprises a comparator to provide the second control signal.

7. The switching regulator control circuit of claim 1 wherein the regulation mode calibration circuit comprises a DAC to provide the second reference signal.

8. The switching regulator control circuit of claim 7 wherein the first control circuit has a regulation point and the DAC is adjusted to provide the second reference signal at a level that is a function of the regulation point of the first control circuit.

9. The switching regulator control circuit of claim 8 wherein the regulation mode calibration circuit further comprises a state machine to adjust the DAC until the second reference signal is at a predetermined amount greater than regulation point of the first control circuit.

10. The switching regulator control circuit of claim 9 wherein the DAC is adjusted during the first mode of operation.

11. The switching regulator control circuit of claim 10 wherein the DAC is continuously adjusted during the first mode of operation.

12. The switching regulator control circuit of claim 10 wherein the regulator is forced to operate in the first mode of operation to calibrate the second reference signal.

13. The switching regulator control circuit of claim 9 wherein the state machine increments the DAC, decrements the DAC, or both increments and decrements the DAC to provide the second reference signal at the predetermined amount greater than the regulation point of the first control circuit.

14. The switching regulator control circuit of claim 13 further comprising a delay counter to verify an adjustment to the DAC during a delay time period to avoid adjusting the second reference signal in response to transients in the regulation point of the first control circuit.

15. The switching regulator control circuit of claim 8 wherein the regulation mode calibration circuit further comprises a register to increment the DAC for a predetermined duration.

16. The switching regulator control circuit of claim 15 wherein the regulation mode calibration circuit adjusts the second reference signal only in response to a regulator start or restart event.

17. The switching regulator control circuit of claim 15 wherein the first control circuit comprises an error amplifier and wherein the error amplifier is coupled in a unity gain configuration when the regulation mode calibration circuit adjusts the second reference signal.

18. A switching regulator control circuit for controlling a switching regulator comprising at least one switch that conducts to transfer energy from an input source to an output at which a regulated output is provided, the switching regulator control circuit comprising:
a first control circuit to control conduction of the switch according to a first mode of operation and having a regulation point comprising an average level of the regulated output during the first mode of operation; and
a second control circuit to control conduction of the switch according to a second mode of operation and having at least one input responsive to a reference signal, wherein the reference signal is calibrated to be within a predetermined range of the regulation point of the first control circuit.

19. The switching regulator control circuit of claim 18 wherein the first mode of operation is PWM operation and the second mode of operation is PFM operation.

20. The switching regulator control circuit of claim 18 wherein the reference signal is calibrated to be a predetermined amount greater than the regulation point of the first control circuit.

21. The switching regulator control circuit of claim 18 wherein the reference signal is calibrated during the first mode of operation.

22. The switching regulator control circuit of claim 18 wherein the reference signal is calibrated only in response to a regulator start or restart event.

23. A method of controlling transitioning between two modes of operation in a regulator comprising:
determining a regulation point associated with a first mode of operation and a first control circuit, wherein the regulation point comprises an average level of a regulated output of the regulator during the first mode of operation; and
calibrating a reference signal used during a second mode of operation to be within a predetermined range of the regulation point associated with the first mode of operation, wherein the reference signal is an input to a second control circuit.

24. The method of claim 23 wherein the first mode of operation is PWM operation and the second mode of operation is PFM operation.

25. The method of claim 23 wherein calibrating the reference signal comprises setting the reference signal to a predetermined amount greater than the regulation point.

26. The method of claim 23 wherein calibrating the reference signal comprises maintaining the reference signal at the predetermined amount greater than the regulation point.

27. The method of claim 23 wherein the reference signal is calibrated when the regulator operates in the first mode of operation.

28. The method of claim 27 further comprising forcing the regulator to operate in the first mode of operation to calibrate the reference

Assignees

• Allegro Microsystems Llc

Inventors

• Wibben Joshua

Classifications

• H02M2001/0025

  Electricity · mapped topic

• Y02B70/16

  Cross-Sectional Technologies · mapped topic

• H02M2001/0045

  Electricity · mapped topic

• H02M2001/0032

  Electricity · mapped topic

• H02M3/156 Primary

  with automatic control of output voltage or current, e.g. switching regulators · CPC title