Apparatus and method for DC-to-DC power conversion

• US 6,661,210 B2
• Filed: 01/23/2002
• Issued: 12/09/2003
• Est. Priority Date: 01/23/2002
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Kimball, Donald, Archambault, Joseph, Haley, Walter
• Primary Examiner(s): Berhane, Adolf D.
• Application Number:
  US10/054,831
• Publication Number:
  US 20030137286A1
• Time in Patent Office: 685 Days
• Field of Search: 323/265, 323/268, 323/269, 323/273, 323/277, 323/280, 323/281, 323/282, 323/351
• US Class Current: 323/268
• CPC Class Codes: H02M 1/0045 Converters combining the concepts of switch-mode regulation and linear regulation, e.g. linear pre-regulator to switching converter, linear and switching converter in parallel, same converter or same transistor operating either in linear or switching mode
• CPC Class Codes: H02M 3/1584 with a plurality of power processing stages connected in parallel

Abstract

A capacitorless DC-DC converter provides a controlled output voltage to a load, and includes a relatively wide bandwidth linear regulator placed in parallel with a switching regulator. Output signals from the linear regulator and switching regulator are added to form a combined output signal provided to the load. The switching regulator provides steady state current to the load, while the linear regulator provides higher-frequency transient current as needed. Because the linear regulator'"'"'s transient response compensates for the limited transient response of the switching regulator, the substantial low-ESR output capacitance that is customarily required by conventional switching regulators is not needed. Further, feedback to the linear regulator taken from the combined output signal causes it to generate anti-phase ripple compensation, thereby reducing the magnitude of switching ripple in the converter'"'"'s combined output signal.

Claims

1. A DC-to-DC converter for supplying a load with an output signal having a regulated voltage, the converter comprising:

a linear regulator circuit to generate a first signal having higher frequency transient current components;

a switching regulator circuit in parallel with the linear regulator circuit to generate a second signal having lower frequency and DC current components;

a summing node to combine the first and second signals to form the output signal; and

wherein the linear regulator circuit supplies a majority of transient current required by the load, and the switching regulator circuit provides a majority of steady-state current required by the load.

2. The DC-to-DC converter of claim 1, wherein the linear regulator circuit comprises an operational amplifier circuit to generate the first signal at the regulated voltage based on a reference signal and a feedback signal derived from the output signal, such that the first signal is responsive to voltage transients in the output signal.

3. The DC-to-DC converter of claim 2, further comprising a current sense element coupling the first signal from the operational amplifier circuit to the summing node.

4. The DC-to-DC converter of claim 3, further comprising a switching control circuit to generate a switching control signal, and wherein the switching regulator generates the second signal responsive to the switching control signal.

5. The DC-to-DC converter of claim 4, wherein the switching control circuit includes the current sense element, and further comprises:

a current sensing circuit to generate a current sense signal responsive to a differential voltage signal developed across the current sense element by the first signal; and

a comparator circuit to generate the switching control signal based on comparing the current sense signal to at least one comparator threshold derived from the reference signal.

6. The DC-to-DC converter of claim 5, wherein the current sensing circuit comprises:

a first sensing circuit DC-coupled to the current sense element to generate a first sense signal proportional lower frequency signal components of the differential voltage signal;

a second sensing circuit AC-coupled to the current sense element to generate a second sense signal proportional to higher frequency signal components of the differential voltage signal; and

an output circuit coupled to the first and second sensing circuits to generate the current sense signal as a wideband sense signal by combining the first and second sense signals.

7. The DC-to-DC converter of claim 6, wherein the comparator circuit comprises a hysteretic comparator circuit.

8. The DC-to-DC converter of claim 1, wherein the DC-to-DC converter further comprises a reference signal input to receive a reference signal that sets the regulated voltage of the output signal.

9. The DC-to-DC converter of claim 8, wherein the DC-to-DC converter further comprises a supply signal input to receive a supply signal that provides a supply voltage signal to the DC-to-DC converter, and wherein the DC-to-DC converter derives the output signal from the supply voltage signal.

10. The DC-to-DC converter of claim 9, wherein the switching regulator circuit is a buck converter that generates the second signal by stepping down the voltage of the supply signal to the regulated voltage.

11. The DC-to-DC converter of claim 1, wherein the linear regulator circuit comprises a linear amplifier having a bandwidth of about 30 MHz, and wherein the transient response of the DC-to-DC converter is about 33 nanoseconds.

12. The DC-to-DC converter of claim 11, wherein the linear amplifier comprises a dual-feedback amplifier circuit having a high-frequency feedback loop, and a low-frequency feedback loop.

13. The DC-to-DC converter of claim 12, wherein the frequency responses of the high- and low-frequency feedback loops are tuned to provide a desired transient response of the DC-to-DC converter.

14. The DC-to-DC converter of claim 12, wherein the high-frequency loop comprises an inner feedback loop, and the low-frequency loop comprises an outer feedback loop.

15. A method of generating an output signal at a regulated voltage as a combination of first and second signals, the method comprising:

generating the first signal using a linear regulator circuit having a first power conversion efficiency and configured to supply higher frequency current components of the output signal;

generating a second signal using a switching regulator circuit having a second power conversion efficiency relatively higher than the first power conversion efficiency and configured to supply lower frequency and DC current components of the output signal; and

combining the first and second regulated signals to form the output signal.

16. The method of claim 15, further comprising deriving a feedback signal for the linear regulator circuit from the output signal, such that the linear regulator circuit provides transient current responsive to voltage transients in the output signal.

17. The method of claim 16, wherein deriving the feedback signal further comprises feeding back switching voltage ripple to the linear regulator such that the linear regulator outputs a ripple compensation signal as a component of the first signal, and wherein the ripple compensation signal attenuates switching voltage ripple induced in the output signal by operation of the switching regulator circuit.

18. The method of claim 15, further comprising generating a switching control signal for controlling the switching regulator circuit based on sensing current in the first signal such that the switching regulator operates to reduce the amount of low frequency and DC current supplied by the linear regulator circuit.

19. The method of claim 15, further comprising:

sensing a magnitude of the current supplied by the first signal; and

generating a switching control signal for the switching regulator circuit responsive to the magnitude of the current supplied by the first signal.

20. The method of claim 19, wherein generating the switching control signal responsive to the magnitude of the current supplied by the first signal comprises generating the switching control signal such that the switching regulator circuit increases the current supplied by the second signal as the magnitude of the current supplied by the first signal increases.

21. The method of claim 19, wherein generating the switching control signal responsive to the magnitude of the current supplied by the first signal comprises increasing the effective on-time of the switching regulator circuit with increasing magnitude of the current supplied by the first signal.

22. The method of claim 19, further comprising setting a sensing bandwidth for sensing the current supplied by the first signal such that the switching regulator circuit has a desired responsiveness with regard to changes in the current supplied by the first signal.

23. A radio base station (RBS) for use in a wireless communication network, the RBS comprising:

signal processing resources to perform at least one of transmit signal processing and receive signal processing; and

at least one DC-to-DC converter for powering at least a portion of the signal processing resources, said DC-to-DC converter comprising;

a linear regulator circuit to generate a first signal having higher frequency transient current components;

a switching regulator circuit in parallel with the linear regulator circuit to generate a second signal having lower frequency and DC current components;

a summing node to combine the first and second signals to form an output signal having a regulated voltage; and

wherein the linear regulator circuit supplies a majority of transient current required by the signal processing resources powered by the output signal, and the switching regulator circuit provides a majority of steady-state current required by the signal processing resources powered by the output signal.

24. The RBS of claim 23, wherein the linear regulator circuit comprises an operational amplifier circuit to generate the first signal at the regulated voltage based on a reference signal and a feedback signal derived from the output signal, such that the first signal is responsive to voltage transients in the output signal.

25. The RBS of claim 24, further comprising a current sense element coupling the first signal from the operational amplifier circuit to the summing node.

26. The RBS of claim 25, further comprising a switching control circuit to generate a switching control signal, and wherein the switching regulator generates the second signal responsive to the switching control signal.

27. The RBS of claim 26, wherein the switching control circuit includes the current sense element, and further comprises:

a current sensing circuit to generate a current sense signal responsive to a differential voltage signal developed across the current sense element by the first signal; and

a comparator circuit to generate the switching control signal based on comparing the current sense signal to at least one comparator threshold derived from the reference signal.

28. The RBS of claim 27, wherein the current sensing circuit comprises:

a first sensing circuit DC-coupled to the current sense element to generate a first sense signal proportional lower frequency signal components of the differential voltage signal;

a second sensing circuit AC-coupled to the current sense element to generate a second sense signal proportional to higher frequency signal components of the differential voltage signal; and

an output circuit coupled to the first and second sensing circuits to generate the current sense signal as a wideband sense signal by combining the first and second sense signals.

29. The RBS of claim 28, wherein the comparator circuit comprises a hysteretic comparator circuit.

30. The RBS of claim 23, wherein the DC-to-DC converter further comprises a reference signal input to receive a reference signal that sets the regulated voltage of the output signal.

31. The RBS of claim 30, wherein the DC-to-DC converter further comprises a supply signal input to receive an input supply signal that provides a supply voltage signal to the DC-to-DC converter, and wherein the DC-to-DC converter derives the output signal from the supply voltage signal.

32. The RBS of claim 31, wherein the switching regulator circuit is a buck converter that generates the second signal by stepping down the voltage of the supply signal to the regulated voltage.

33. The RBS of claim 23, wherein the linear regulator circuit comprises a linear amplifier having a bandwidth of about 30 MHz, and wherein the transient response of the DC-to-DC converter is about 33 nanoseconds.

34. The RBS of claim 33, wherein the linear amplifier comprises a dual-feedback amplifier circuit having a high-frequency feedback loop, and a low-frequency feedback loop.

35. The RBS of claim 34, wherein the frequency responses of the high- and low-frequency feedback loops are tuned to provide a desired transient response of the DC-to-DC converter.

36. The RBS of claim 34, wherein the high-frequency feedback loop comprises an inner feedback loop, and the low-frequency feedback loop comprises an output feedback loop.

37. The RBS of claim 23, wherein the RBS further comprises at least one sub-rack, and wherein the sub-rack carries at least a portion of the signal processing resources, and further wherein each sub-rack carries said at least one DC-to-DC converter configured to power at least a portion of the signal processing resources carried on the sub-rack.

38. The RBS of claim 23, wherein the RBS further comprises at least one additional power supply, and wherein the at least one additional power supply generates a supply signal for supplying said at least one DC-to-DC converter.