Adjustable minimum peak inductor current level for burst mode in current-mode DC-DC regulators

• US 6,724,174 B1
• Filed: 09/12/2002
• Issued: 04/20/2004
• Est. Priority Date: 09/12/2002
• Status: Expired

• Current Assignee: Analog Devices International Unlimited Company (Analog Devices, Inc.)
• Original Assignee: Linear Technology Corporation (Analog Devices, Inc.)
• Inventors: Flatness, Randy Guy, Esteves, Joey Martin
• Primary Examiner(s): Riley, Shawn
• Application Number:
  US10/243,526
• Time in Patent Office: 586 Days
• Field of Search: 323/224, 323/284, 323/285, 323/282
• US Class Current: 323/224
• CPC Class Codes: H02M 1/0025 Arrangements for modifying reference values, feedback values or error values in the control loop of a converter
• CPC Class Codes: H02M 1/0035 using burst mode control
• CPC Class Codes: H02M 3/155 using semiconductor devices only
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

Switching regulator circuits and methods are provided for regulating output voltage that include an adjustable minimum peak inductor current level for Burst Mode in current-mode DC-DC regulators. Minimum peak inductor current level control is achieved during Burst Mode by allowing external control for adjusting the burst threshold level. A single pin can be used to distinguish between forced continuous and Burst Mode as well as set the burst threshold level during Burst Mode, or an alternate method of setting a variable burst threshold level can be implemented in which two pins are used, one for selecting the mode of operation and the other for setting the burst threshold level during Burst Mode. The above principles can be applied to both step-up and step-down regulator circuit configurations, as well as both synchronous switching regulators and non-synchronous switching regulators.

Claims

1. A switching regulator that supplies current at a regulated voltage to a load, said switching regulator that is capable of operating in Burst Mode, said switching regulator comprising:

an input terminal coupled to a source of input supply voltage;

an output terminal coupled to said load;

a control circuit coupled to said input terminal and to said output terminal, said control circuit that regulates the current that is supplied to said load; and

a minimum peak adjustment circuit coupled to a mode selection input and to said control circuit, said minimum peak adjustment circuit that adjusts the burst threshold level of said switching regulator when said switching regulator operates in Burst Mode.

2. The switching regulator of claim 1 wherein said switching regulator is a step-down regulator.

3. The switching regulator of claim 2 wherein said switching regulator is a non-synchronous switching regulator.

4. The switching regulator of claim 2 wherein said switching regulator is a synchronous switching regulator.

5. The switching regulator of claim 2 wherein said control circuit comprises:

a logic section;

an inductor coupled to said output terminal and to said control circuit; and

a main switch coupled to said logic section, said main switch that is controlled by said logic section.

6. The switching regulator of claim 5 wherein said control circuit further comprises an oscillator coupled to said logic section, said oscillator that provides an oscillatory signal to said logic section.

7. The switching regulator of claim 5 wherein said control circuit further comprises an error amplifier coupled to said output terminal, said error amplifier that adjusts its output voltage depending on load conditions.

8. The switching regulator of claim 5 wherein said control circuit further comprises:

a current comparator coupled to said logic section, said current comparator that produces a signal, said signal that instructs said logic section to turn OFF said switching element when a sense voltage increases above the output voltage of said error amplifier; and

a current amplifier coupled to said current comparator, said current amplifier that provides said current comparator with said sense voltage indicative of the current that flows through said inductor.

9. The switching regulator of claim 5 wherein said control circuit further comprises a burst comparator coupled to said logic section, said burst comparator that produces a signal, said signal that causes said switching regulator to enter into sleep mode when the voltage output from said error amplifier drops below a burst threshold level.

10. The switching regulator of claim 5 wherein said control circuit further comprises a synchronous switch coupled to said logic section and to said main switch, said synchronous switch that switches in opposition to said main switch.

11. The switching regulator of claim 10 wherein said control circuit further comprises a current reversal comparator coupled to said logic section, said current reversal comparator that produces a signal, said signal that causes said logic section to turn OFF said synchronous switch when the current through said synchronous switch reverses and when said switching regulator operates in Burst Mode.

12. The switching regulator of claim 5 wherein said minimum peak adjustment circuit comprises:

a mode selection input pin that selects the mode of operation for said switching regulator and that sets the burst threshold level;

a mode comparator that receives a signal from said mode selection input pin, said mode comparator that provides an output signal indicative of the signal from said mode selection input pin, said output signal that is supplied to said logic section; and

a transmission gate comprising transistors, said transmission gate coupled to said mode selection input pin and to a clamping circuit, the gates of said transmission gate transistors that receive input signals dependent on said output signal from said mode comparator, said transmission gate that provides said clamping circuit with a burst threshold level when said switching regulator operates in Burst Mode.

13. The switching regulator of claim 5 wherein said minimum peak adjustment circuit comprises:

a mode selection input pin that selects the mode of operation for said switching regulator;

a mode comparator that receives a signal from said mode selection input pin, said mode comparator that provides an output signal indicative of the signal from said mode selection input pin, said output signal that is supplied to said logic section; and

a burst threshold level selection pin that selects the burst threshold level when said switching regulator operates in Burst Mode, said burst threshold level selection pin coupled to a clamping circuit.

14. The switching regulator of claim 1 wherein said switching regulator is a step-up regulator.

15. The switching regulator of claim 14 wherein said switching regulator is a non-synchronous switching regulator.

16. The switching regulator of claim 14 wherein said switching regulator is a synchronous switching regulator.

17. The switching regulator of claim 14 wherein said control circuit comprises:

a logic section;

an inductor coupled to said input terminal and to said output terminal; and

a main switch coupled to said logic section, said main switch that is controlled by said logic section.

18. The switching regulator of claim 17 wherein said control circuit further comprises a diode coupled to a node that connects said inductor and said main switch and to said output terminal.

19. The switching regulator of claim 17 wherein said control circuit further comprises an oscillator coupled to said logic section, said oscillator that provides an oscillatory signal to said logic section.

20. The switching regulator of claim 17 wherein said control circuit further comprises an error amplifier coupled to said output terminal, said error amplifier that adjusts its output voltage depending on load conditions.

21. The switching regulator of claim 17 wherein said control circuit further comprises:

a current comparator coupled to said logic section, said current comparator that produces a signal, said signal that instructs said logic section to turn OFF said switching element when a sense voltage increases above the output voltage of said error amplifier; and

a current amplifier coupled to said current comparator, said current amplifier that provides said current amplifier with a sense voltage indicative of the current that flows through said inductor.

22. The switching regulator of claim 17 wherein said control circuit further comprises a burst comparator coupled to said logic section, said burst comparator that produces a signal, said signal that causes said switching regulator to enter into sleep mode when the voltage output from said error amplifier drops below a burst threshold level.

23. The switching regulator of claim 17 wherein said minimum peak adjustment circuit comprises:

a mode selection input pin that selects the mode of operation for the regulator and sets the burst threshold level;

a mode comparator that receives a signal from said mode selection input pin, said mode comparator that provides an output signal indicative of the signal from said mode selection input pin, said output signal that is supplied to said logic section; and

a transmission gate comprising transistors, said transmission gate coupled to said mode selection input pin and to a clamping circuit, the gates of said transmission gate transistors that receive input signals dependent on said output signal from said mode comparator, said transmission gate that provides said clamping circuit with a burst threshold level when said switching regulator operates in Burst Mode.

24. The switching regulator of claim 17 wherein said minimum peak adjustment circuit comprises:

a mode selection input pin that selects the mode of operation for said switching regulator;

a mode comparator that receives a signal from said mode selection input pin, said mode comparator that provides an output signal indicative of the signal from said mode selection input pin, said output signal that is supplied to said logic section; and

a burst threshold level selection pin that selects the burst threshold level when said switching regulator operates in Burst Mode, said burst threshold level selection pin coupled to a clamping circuit.

25. In a step-down switching regulator that provides an output current to a load at a regulated voltage, a method for varying the minimum peak inductor current level for said switching regulator when operating in Burst Mode, the method comprising:

coupling an input terminal to a source of input supply voltage;

coupling an output terminal to said load;

regulating said output current to said load;

providing an adjustable burst threshold level, said burst threshold level controlling said minimum peak inductor current level; and

causing said switching regulator to enter into sleep mode when a control voltage level drops below said burst threshold level.

26. The method of claim 25 wherein said burst threshold level is adjustable through the use of a single mode selection input pin, said switching regulator operating in Burst Mode, said method comprising selecting the mode of operation for said switching regulator and setting the burst threshold level based on a signal from a single mode selection input pin.

27. The method of claim 25 wherein said burst threshold level is adjustable through the use of two separate mode selection input pins, said switching regulator operating in Burst Mode, said method comprising:

selecting the mode of operation for said switching regulator based on a signal from a single mode selection input pin; and

setting the burst threshold level for said switching regulator based on a signal from a burst threshold level selection input, said burst threshold level selection pin coupled to a clamping circuit.

28. In a step-up switching regulator that provides an output current to a load at a regulated voltage, a method for varying the minimum peak inductor current level for said switching regulator when operating in Burst Mode, the method comprising:

coupling an input terminal to a source of input supply voltage;

coupling an output terminal to said load;

regulating said output current to said load;

providing an adjustable burst threshold level, said burst threshold level controlling said minimum peak inductor current level; and

causing said switching regulator to enter into sleep mode when a control voltage level drops below said burst threshold level.

29. The method of claim 28 wherein said burst threshold level is adjustable through the use of a single mode selection input pin, said switching regulator operating in Burst Mode, said method comprising selecting the mode of operation for said switching regulator and setting the burst threshold level based on a signal from a single mode selection input pin.

30. The method of claim 28 wherein said burst threshold level is adjustable through the use of two separate mode selection input pins, said switching regulator operating in Burst Mode, said method comprising:

selecting the mode of operation for said switching regulator based on a signal from a single mode selection input pin; and

setting the burst threshold level for said switching regulator based on a signal from a burst threshold level selection input, said burst threshold level selection pin coupled to a clamping circuit.