Circuits and methods for adjustable peak inductor current and hysteresis for burst mode in switching regulators

• US 20080030178A1
• Filed: 08/04/2006
• Published: 02/07/2008
• Est. Priority Date: 08/04/2006
• Status: Active Grant

• Current Assignee: Analog Devices International Unlimited Company (Analog Devices, Inc.)
• Original Assignee: Linear Technology Corporation (Analog Devices, Inc.)
• Inventors: Esteves, Joey Martin, Leonard, Jason
• Granted Patent: US 7,990,120 B2
• Time in Patent Office: Days
• US Class Current: 323/282
• CPC Class Codes: H02M 1/0032 Control circuits allowing low power mode operation, e.g. in standby mode
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators
• 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 and adjustable burst comparator hysteresis for Burst Mode operation in switching regulators. Control over minimum peak inductor current level and burst comparator hysteresis is achieved during Burst Mode operation by allowing external user control of the burst threshold level and the burst comparator hysteresis. A single user-accessible input pin, two user-accessible input pins, or three user-accessible input pins may be used to distinguish between forced continuous and Burst Mode operations, set a burst threshold level, and set a burst comparator hysteresis during Burst Mode operation. The present invention may be applied to buck, boost, buck-boost, or any other suitable regulator circuit configuration. The present invention also may be employed with synchronous and non-synchronous switching regulators.

Claims

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

an input terminal;

an output terminal coupled to said load;

a control circuit coupled to said input and output terminals, said control circuit regulating the current supplied to said load; and

an adjustment circuit coupled to said control circuit, said adjustment circuit permitting a user to set a burst threshold level and a hysteresis 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 1 wherein said switching regulator is a non-synchronous switching regulator.

4. The switching regulator of claim 1 wherein said switching regulator is a synchronous switching regulator.

5. The switching regulator of claim 1 wherein said control circuit comprises:

a logic section;

an inductor; and

a main switch coupled to said logic section, said main switch 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 providing 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 having an error amplifier output signal and said error amplifier adjusting said error amplifier output signal depending on load conditions.

8. The switching regulator of claim 7 wherein said control circuit further comprises:

a current comparator coupled to said logic section, said current comparator producing a current comparator signal that instructs said logic section to turn OFF said main switch when a sense signal compares in a predetermined manner with said error amplifier output signal; and

a current amplifier coupled to said current comparator, said current amplifier providing said current comparator with said sense signal indicative of the current flowing through said inductor.

9. The switching regulator of claim 7 wherein said control circuit further comprises a burst comparator coupled to said logic section, said burst comparator producing a burst comparator signal that causes said switching regulator to enter into sleep mode when said error amplifier output signal crosses a level that trips said burst comparator.

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 switching 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 producing a current reversal comparator signal when said switching regulator operates in Burst Mode that causes said logic section to turn OFF said synchronous switch when current through said synchronous switch undergoes a current reversal condition.

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

a mode selection input pin through which the user may select a mode of operation for said switching regulator and set said burst threshold level;

a mode comparator that receives a mode selection signal from said mode selection input pin, said mode comparator providing a mode comparator output signal indicative of said mode selection signal, wherein said mode comparator output signal 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, said transmission gate receiving signals dependent on said mode comparator output signal, said transmission gate providing said clamping circuit with said burst threshold level when said switching regulator is operating in Burst Mode.

13. The switching regulator of claim 12, wherein said transmission gate further is coupled to a burst comparator, said transmission gate providing said burst comparator with a signal related to said mode selection signal from said mode selection input pin to set said hysteresis when said switching regulator is operating in Burst Mode.

14. The switching regulator of claim 5 wherein said adjustment circuit comprises:

a mode selection input pin through which the user may select a mode of operation for said switching regulator, said mode selection input pin providing a mode selection signal;

a mode comparator that receives said mode selection signal, said mode comparator providing a mode comparator output signal indicative of said mode selection signal, said mode comparator output signal supplied to said logic section; and

a burst threshold level and hysteresis selection pin through which the user may set said burst threshold level and said hysteresis of said switching regulator when said switching regulator operates in Burst Mode, said burst threshold level and hysteresis selection pin coupled to a clamping circuit.

15. The switching regulator of claim 5 wherein said adjustment circuit comprises:

a mode selection input pin through which the user may select a mode of operation for said switching regulator, said mode selection input pin providing a mode selection signal;

a mode comparator that receives said mode selection signal, said mode comparator providing a mode comparator output signal indicative of said mode selection signal, said mode comparator output signal supplied to said logic section;

a burst threshold level selection pin through which the user may set said burst threshold level of said switching regulator when said switching regulator operates in Burst Mode; and

a burst hysteresis selection pin through which the user may set said hysteresis of said switching regulator when said switching regulator operates in Burst Mode.

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

17. The switching regulator of claim 5 wherein said control circuit further comprises a diode disposed between said inductor and said output terminal.

18. In a switching regulator that provides output current to a load at a regulated voltage, a method for operating said switching regulator in Burst Mode, the method comprising:

coupling an input terminal to a source of input voltage;

coupling an output terminal to said load;

providing an adjustable burst threshold level, said burst threshold level controlling a minimum peak inductor current level of said switching regulator;

providing an adjustable hysteresis when said switching regulator operates in Burst Mode;

regulating the output current to said load;

enabling sleep mode by tripping a burst comparator; and

de-asserting sleep mode by untripping said burst comparator, said hysteresis controlling when said burst comparator untrips.

19. The method of claim 18 wherein said method further comprises:

setting a mode of operation for said switching regulator based on an input signal from a single input pin; and

setting said burst threshold level and said hysteresis of said switching regulator based on said input signal.

20. The method of claim 18 wherein said method further comprises:

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

setting said burst threshold level and said hysteresis of said switching regulator based on an input signal from a burst threshold level and hysteresis selection input pin.

21. The method of claim 18 wherein said method further comprises:

setting a mode of operation for said switching regulator based on a mode selection signal from a mode selection input pin;

setting said burst threshold level based on a signal from a burst threshold level selection input pin; and

setting said hysteresis of said switching regulator based on a signal from a hysteresis selection input pin.

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

an input terminal;

an output terminal coupled to said load;

a control circuit coupled to said input and output terminals, said control circuit regulating the output current; and

an adjustment circuit coupled to said control circuit, said adjustment circuit permitting a user to set at least a hysteresis of said switching regulator when said switching regulator operates in Burst Mode.

23. The switching regulator of claim 22, wherein said adjustment circuit further permits the user to set a burst threshold level of said switching regulator when said switching regulator operates in Burst Mode.

24. The switching regulator of claim 23, wherein said adjustment circuit further permits the user to select a mode of operation for said switching regulator, said mode of operation being either forced continuous or Burst Mode.

25. A switching regulator that supplies output current at a regulated voltage to a load, said switching regulator capable of operating in a first operational mode having at least a length of time dependent on load conditions in which active switching elements are made to remain OFF, said switching regulator comprising:

an input terminal;

an output terminal coupled to said load;

a control circuit coupled to said input and output terminals, said control circuit regulating the current supplied to said load; and

an adjustment circuit coupled to said control circuit, said adjustment circuit permitting a user to set a burst threshold level and a hysteresis of said switching regulator when said switching regulator operates in said first operational mode.

26. The switching regulator of claim 25, wherein said control circuit is configured to turn OFF additional components of said switching regulator during when the active switching elements are made to remain OFF.