Circuits and methods for synchronizing non-constant frequency switching regulators with a phase locked loop

• US 6,774,611 B2
• Filed: 07/15/2002
• Issued: 08/10/2004
• Est. Priority Date: 04/06/2001
• Status: Expired due to Term

• Current Assignee: Analog Devices International Unlimited Company (Analog Devices, Inc.)
• Original Assignee: Linear Technology Corporation (Analog Devices, Inc.)
• Inventors: Flatness, Randy G., Umminger, Christopher B.
• Primary Examiner(s): Vu, Bao Q.
• Application Number:
  US10/197,357
• Publication Number:
  US 20020180413A1
• Time in Patent Office: 757 Days
• US Class Current: 323/282
• CPC Class Codes: H02M 3/1584 with a plurality of power processing stages connected in parallel

Abstract

Methods for synchronizing non-constant frequency switching regulators with a phase locked loop are disclosed. The methods enable non-constant frequency switching regulators to be synchronized with a phase locked loop to achieve constant frequency operation in steady state while retaining the advantages of non-frequency operation to improve transient response and operate over a wider range of duty cycles. In addition, the methods enable multiple non-constant frequency regulators to be synchronized and operated in parallel to deliver higher power levels to the output than a single switching regulator.

Claims

1. A switching voltage regulator circuit that operates at a constant frequency over a wide range of duty cycles, the circuit comprising:

a non-constant frequency switching voltage regulator, comprising;

a one shot-timer comprising inputs and an output to control the duty cycle of the switching voltage regulator circuit; and

a phase-locked loop connected to the inputs and the output of the one-shot timer to control the one-shot timer, causing the steady state switching frequency of the switching voltage regulator circuit to be constant.

2. The switching voltage regulator circuit of claim 1, wherein the non-constant frequency switching regulator comprises a non-constant frequency synchronous switching regulator.

3. The switching voltage regulator circuit of claim 1, wherein the non-constant frequency switching regulator comprises a non-constant frequency non-synchronous switching regulator.

4. The switching voltage regulator circuit of claim 2, wherein the non-constant frequency switching regulator comprises one of:

a step-down switching regulator;

a step-up switching regulator; and

a buck-boost switching regulator.

5. The switching voltage regulator circuit of claim 2, wherein the phase-locked loop comprises:

a first rising edge triggered data flip flop;

a second rising edge triggered data flip flop;

an AND gate coupled between the first and the second flip flops;

an amplifier coupled between the second flip flop and the one-shot timer; and

a loop filter to extract the DC average value from the second flip flop.

6. The switching voltage regulator circuit of claim 5, wherein the first rising edge triggered data flip flop comprises a clock input coupled to a reference clock.

7. The switching voltage regulator circuit of claim 5, the second rising edge triggered data flip flop comprises a clock input coupled to the output of the one-shot timer.

8. The switching voltage regulator circuit of claim 1, wherein the phase-locked loop controls the on-time of the one-shot timer.

9. The switching voltage regulator circuit of claim 1, wherein the phase-locked loop controls the off-time of the one-shot timer.

10. The switching voltage regulator circuit of claim 1, wherein the non-constant frequency switching regulator comprises a hysteretic switching regulator, wherein the hysteresis is adjusted by the phase-locked loop.

11. A method for operating a switching voltage regulator circuit at a constant frequency over a wide range of duty cycles, the method comprising:

providing a non-constant frequency switching regulator comprising a timer having inputs and an output; and

synchronizing the non-constant frequency switching regulator with a phase-locked loop circuit connected to the inputs and the output of the timer to control the timer, causing the steady state switching frequency of the switching voltage regulator circuit to be constant.

12. The method of claim 11, wherein providing a non-constant frequency switching regulator comprises providing a non-constant frequency synchronous switching regulator.

13. The method of claim 11, wherein providing a non-constant frequency switching regulator comprises providing a non-constant frequency non-synchronous switching regulator.

14. The method of claim 11, wherein synchronizing the non-constant frequency switching regulator with a phase-locked loop circuit comprises:

providing a first rising edge triggered data flip flop in the phase-locked loop circuit;

providing a second rising edge triggered data flip flop in the phase-locked loop circuit;

connecting an AND gate between the first and the second flip flops;

connecting an amplifier between the second flip flop and the timer; and

extracting the DC average value from the second flip flop with a loop filter.

15. The method of claim 14, wherein providing a first rising edge triggered data flip flop comprises providing a clock input coupled to a reference clock.

16. The method of claim 14, wherein providing a second rising edge triggered data flip flop in the phase-locked loop circuit comprises providing a clock input coupled to the output of the timer.

17. The method of claim 11, wherein synchronizing the non-constant frequency switching regulator with a phase-locked loop circuit to control the timer comprises controlling the on-time of the timer.

18. The method of claim 11, wherein synchronizing the non-constant frequency switching regulator with a phase-locked loop circuit to control the timer comprises controlling the off-time of the timer.

19. The method of claim 11, further comprising controlling the duty cycle of the switching voltage regulator circuit using current-mode control.

20. The method of claim 11, further comprising controlling the duty cycle of the switching voltage regulator circuit using voltage-mode control.

21. The method of claim 11, further comprising controlling the duty cycle of the switching voltage regulator circuit using a hybrid of current-mode and voltage-mode control.