Audio frequency deadband system and method for switch mode regulators operating in discontinuous conduction mode

• US 10,038,379 B2
• Filed: 01/13/2017
• Issued: 07/31/2018
• Est. Priority Date: 06/18/2013
• Status: Active Grant

• Current Assignee: Intersil Americas LLC (Renesas Electronics Corporation)
• Original Assignee: Intersil Americas LLC (Renesas Electronics Corporation)
• Inventors: Houston, M. Jason, Laur, Steven P.
• Primary Examiner(s): Pham, Emily P
• Application Number:
  US15/406,525
• Publication Number:
  US 20170133933A1
• Time in Patent Office: 564 Days
• CPC Class Codes: H02M 1/0032 Control circuits allowing low power mode operation, e.g. in standby mode
• CPC Class Codes: H02M 1/08 Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load
• 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

A controller for controlling operation of a switching regulator including a modulator, a discontinuous conduction mode (DCM) controller, an audible DCM (ADCM) controller, and a sub-sonic discontinuous conduction mode (SBDCM) controller. The modulator generally operates in a continuous conduction mode. The DCM controller modifies operation to DCM during low loads. The ADCM controller detects when the switching frequency is less than a super-sonic frequency threshold and modifies operation to maintain the switching frequency at a super-sonic frequency level. The SBDCM controller detects a sub-sonic operating condition during ADCM operation and responsively inhibits operation of the ADCM mode controller to allow a SBDCM mode within a sub-sonic switching frequency range. The SBDCM operating mode allows for efficient connected standby operation. The SBDCM controller allows operation to return to other modes when the switching frequency increases above the subsonic level.

Claims

1. A controller for controlling operation of a switching regulator, comprising:

an audible discontinuous conduction mode controller that detects a switching frequency that is less than a super-sonic frequency threshold and that modifies a discontinuous conduction mode operation of the switching regulator to maintain said switching frequency at a super-sonic frequency level; and

a sub-sonic discontinuous conduction mode controller that detects a sub-sonic operating condition during an audible discontinuous conduction mode operation of the switching regulator and that responsively inhibits operation of said audible discontinuous conduction mode controller to allow a sub-sonic discontinuous conduction mode within a sub-sonic switching frequency range.

2. The controller of claim 1, wherein said sub-sonic discontinuous conduction mode controller comprises a timer and comparator circuit that compares a duration of a pulse on said at least one switch control signal with a predetermined timing threshold.

3. The controller of claim 1, wherein said sub-sonic discontinuous conduction mode controller comprises a timer and comparator circuit that enables operation of said audible discontinuous conduction mode controller when said switching frequency is greater than a predetermined sub-sonic frequency threshold.

4. The controller of claim 3, wherein said timer and comparator circuit compares a period of said pulse control signal with a predetermined sub-sonic threshold period.

5. The controller of claim 1, wherein said sub-sonic operating condition is associated with a switching frequency of approximately 100 Hertz.

6. The controller of claim 1, further comprising:

a modulator that develops a pulse control signal for controlling pulses on at least one switch control signal to operate in a continuous conduction mode; and

a discontinuous conduction mode controller that detects a low load condition and that modifies operation to operate in a discontinuous conduction mode while said low load condition is detected,

wherein the switching regulator develops a first pulse on a first switch control signal in response to said pulse control signal followed by a second pulse on a second control signal for a remainder of each period of said pulse control signal during said continuous conduction mode, wherein;

said discontinuous conduction mode controller prematurely terminates the second pulse on the second control signal while the low load condition is detected;

wherein said audible discontinuous conduction mode controller initiates a new switching cycle when a switching period of said pulse control signal is greater than a predetermined super-sonic threshold period; and

wherein said sub-sonic discontinuous conduction mode controller inhibits said audible discontinuous conduction mode controller from initiating a new cycle when said sub-sonic operating condition is detected, and allows said audible discontinuous conduction mode controller to initiate a new cycle when said switching period of said pulse control signal is less than a predetermined sub-sonic threshold period.

7. The controller of claim 1, further comprising:

a modulator that develops a pulse control signal for controlling pulses on at least one switch control signal to operate in a continuous conduction mode; and

a discontinuous conduction mode controller that detects a low load condition and that modifies operation to operate in a discontinuous conduction mode while said low load condition is detected,

wherein the switching regulator develops a first pulse on a first switch control signal in response to said pulse control signal followed by a second pulse on a second control signal for a remainder of each period of said pulse control signal during said continuous conduction mode, and wherein said discontinuous conduction mode controller comprises;

a detect circuit that detects when a current through an output inductor goes to zero and that asserts a zero signal indicative thereof; and

a first logic circuit for prematurely terminating the second pulse on the second control signal in response to said zero signal;

wherein said audible discontinuous conduction mode controller comprises a timer circuit that detects when a period of said pulse control signal exceeds a predetermined super-sonic threshold period and which asserts an audio detect signal indicative thereof, and a second logic circuit for initiating a third pulse on the second control signal in response to said audio detect signal; and

wherein said sub-sonic discontinuous conduction mode controller comprises a timer and comparator circuit that provides a sub-sonic enable signal when a duration of said third pulse on the second control signal is greater than a predetermined timing threshold, a third logic circuit for inhibiting said third pulse on the second control signal in response to said sub-sonic enable signal, and a timer and reset circuit that inhibits said sub-sonic enable signal from being provided when a period of said pulse control signal is less than a predetermined sub-sonic threshold period.

8. The controller of claim 1, wherein said predetermined super-sonic frequency threshold is 25 kilohertz and wherein said sub-sonic switching frequency range is up to 100Hertz.

9. The controller of claim 1, wherein said sub-sonic discontinuous conduction mode controller comprises:

a charge node;

a capacitor coupled between said charge node and a reference node;

a transconductance amplifier having an output that provides a current proportional to an output voltage to said charge node;

a comparator having a first input coupled to said charge node, having a second input receiving a voltage indicative of a difference between said output voltage and an input voltage, and having an output providing a sub-sonic enable signal;

a switch having current terminals coupled across said capacitor and having a control input receiving an operative pulse during said audible discontinuous conduction mode operation; and

wherein said switch is turned off during said operative pulse to enable charging of said capacitor, and is otherwise turned on to short said capacitor.

10. An electronic device, comprising:

a switching regulator, comprising;

an inductor;

a switch circuit, coupled to said inductor, that is configured to switch current through said inductor to convert an input voltage to an output voltage as controlled by a pulse control signal;

an error amplifier circuit that is configured to detect an error of the output voltage and to provide a compensation signal indicative thereof; and

a controller, comprising;

an audible discontinuous conduction mode controller that detects a frequency of said pulse control signal that is less than a predetermined super-sonic frequency threshold and that modifies discontinuous conduction mode operation to prevent a switching frequency of said switching regulator from operating within an audible frequency range; and

a sub-sonic discontinuous conduction mode controller that detects a sub-sonic operating condition during audible discontinuous conduction mode operation and that responsively inhibits operation of said audible discontinuous conduction mode controller to allow said switching regulator to operate at a sub-sonic discontinuous conduction mode.

11. The electronic device of claim 10, further comprising a processor and a memory coupled to said switching regulator.

12. The electronic device of claim 10, wherein said sub-sonic discontinuous conduction mode controller comprises a timer and comparator circuit that compares a duration of a pulse on said at least one switch control signal with a predetermined timing threshold.

13. The electronic device of claim 10, wherein said sub-sonic discontinuous conduction mode controller comprises a timer and comparator circuit that enables operation of said audible discontinuous conduction mode controller when said switching frequency is greater than a predetermined sub-sonic frequency threshold.

14. The electronic device of claim 10, wherein the controller further comprises:

a modulator that receives said compensation signal and that provides said pulse control signal to control pulses on at least one switch control signal provided to said switch circuit to operate said switching regulator in a continuous conduction mode; and

a discontinuous conduction mode controller that detects a low load condition and that modifies operation of said switching regulator to operate in a discontinuous conduction mode while said low load condition is detected, wherein;

said discontinuous conduction mode controller comprises a comparator circuit that detects a zero current crossing of said inductor;

wherein said audible discontinuous conduction mode controller comprises a first timer circuit that detects when a period of said pulse control signal exceeds a predetermined super-sonic threshold period and that asserts an audible discontinuous conduction mode enable signal indicative thereof; and

wherein said sub-sonic discontinuous conduction mode controller comprises a second timer circuit that detects when a duration of one of said at said at least one switch control signal exceeds a predetermined threshold period indicative of said sub-sonic operating condition and that asserts a sub-sonic discontinuous conduction mode enable signal indicative thereof.

15. A controller for controlling operation of a switching regulator, comprising:

first circuitry that detects a switching frequency that is less than about 25 kilohertz and that modifies the discontinuous conduction mode operation of the switching regulator such that the switching frequency is maintained at a super-sonic frequency level; and

second circuitry that detects a low frequency operating condition during the discontinuous conduction mode operation of the switching regulator and that responsively inhibits operation of the first circuitry and to allow discontinuous conduction mode in an operating range of less than about 100 Hertz.

16. The controller of claim 15, wherein the second circuitry comprises a timer and comparator circuit that compares a duration of a pulse on said at least one switch control signal with a predetermined timing threshold.

17. The controller of claim 15, wherein the second circuitry comprises a timer and comparator circuit that enables operation of the first circuitry when the switching frequency is greater than a predetermined sub-sonic frequency threshold.

18. The controller of claim 17, wherein the timer and comparator circuit compares a period of the pulse control signal with a predetermined sub-sonic threshold period.

19. The controller of claim 15, further comprising:

a modulator that develops a pulse control signal for controlling pulses on at least one switch control signal to operate in a continuous conduction mode; and

a discontinuous conduction mode controller that detects a low load condition and that modifies operation to operate in a discontinuous conduction mode while said low load condition is detected,

wherein the switching regulator develops a first pulse on a first switch control signal in response to said pulse control signal followed by a second pulse on a second control signal for a remainder of each period of said pulse control signal during said continuous conduction mode, wherein;

said discontinuous conduction mode controller prematurely terminates the second pulse on the second control signal while the low load condition is detected;

wherein the first circuitry initiates a new switching cycle when a switching period of said pulse control signal is greater than a predetermined super-sonic threshold period; and

wherein the second circuitry inhibits the first circuitry from initiating a new cycle when the low frequency operating condition is detected, and allows the first circuitry to initiate a new cycle when said switching period of said pulse control signal is less than a predetermined sub-sonic threshold period.

20. The controller of claim 15, further comprising:

a modulator that develops a pulse control signal for controlling pulses on at least one switch control signal to operate in a continuous conduction mode; and

a discontinuous conduction mode controller that detects a low load condition and that modifies operation to operate in a discontinuous conduction mode while said low load condition is detected,

wherein the switching regulator develops a first pulse on a first switch control signal in response to said pulse control signal followed by a second pulse on a second control signal for a remainder of each period of said pulse control signal during said continuous conduction mode, and wherein said discontinuous conduction mode controller comprises;

a detect circuit that detects when a current through an output inductor goes to zero and that asserts a zero signal indicative thereof; and

a first logic circuit for prematurely terminating the second pulse on the second control signal in response to said zero signal;

wherein the first circuitry comprises a timer circuit that detects when a period of said pulse control signal exceeds a predetermined super-sonic threshold period and which asserts an audio detect signal indicative thereof, and a second logic circuit for initiating a third pulse on the second control signal in response to said audio detect signal; and

wherein the second circuitry comprises a timer and comparator circuit that provides a sub-sonic enable signal when a duration of said third pulse on the second control signal is greater than a predetermined timing threshold, a third logic circuit for inhibiting said third pulse on the second control signal in response to said sub-sonic enable signal, and a timer and reset circuit that inhibits said sub-sonic enable signal from being provided when a period of said pulse control signal is less than a predetermined sub-sonic threshold period.