Switching regulator with transient recovery circuit

• US 6,605,931 B2
• Filed: 12/21/2001
• Issued: 08/12/2003
• Est. Priority Date: 11/07/2000
• Status: Expired due to Fees

• Current Assignee: Microsemi Corporation (Microchip Technology Incorporated)
• Original Assignee: Microsemi Corporation (Microchip Technology Incorporated)
• Inventors: Brooks, Steven W.
• Primary Examiner(s): STERRETT, JEFFREY L
• Application Number:
  US10/136,614
• Publication Number:
  US 20020180410A1
• Time in Patent Office: 599 Days
• Field of Search: 323/272, 323/282, 323/284, 323/285, 361/18, 363/55, 363/56.01
• US Class Current: 323/272
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators
• CPC Class Codes: H02M 3/1584 with a plurality of power processing stages connected in parallel

Abstract

A transient recovery circuit in a switching regulator responds to relatively quick changes in load currents to suppress output voltage overshoots or undershoots. The transient recovery circuit operates independently of a regular feedback circuit. The transient recovery circuit can be used in a single phase or a multiphase switching regulator. In one embodiment, the transient recovery circuit overrides a control voltage from the regular feedback circuit to control the duty cycle of a pulse-width modulation circuit in the switching regulator during transient conditions. In another embodiment, the transient recovery circuit controls a dedicated transient phase in a multiphase switching regulator. The transient recovery circuit is inactive during non-transient conditions.

Claims

1. A method of responding quickly to output transients for a multiphase switching regulator comprising:

comparing an output voltage of the multiphase switching regulator to a reference comparing voltage;

providing a minimum-load signal to turn on a first semiconductor switch in a dedicated phase of the multiphase switching regulator to drain excess output current when the output voltage is greater than the reference comparing voltage; and

providing a maximum-load signal to turn on a second semiconductor switch in the dedicated phase of the multiphase switching regulator to provide additional output current when the output voltage is less than the reference comparing voltage.

2. The method of claim 1, wherein catch diodes are associated with the respective semiconductor switches to suppress voltage spikes when the semiconductor switches turn off.

3. The method of claim 1, wherein the reference comparing voltage is equivalent to the multiphase switching regulator output voltage at steady state.

4. A switching regulator comprising:

a feedback circuit to generate a control voltage and to respond to slow changes in output current;

a transient recovery circuit to generate an inject signal and to respond to fast changes in the output current, wherein the transient recovery circuit is disabled during power down of the switching regulator; and

a pulse-width modulation circuit to control switching operations of the switching regulator, wherein the control voltage controls the duty cycle of the switching operations to regulate the output voltage of the switching regulator, and wherein the inject signal overrides the control voltage to control the duty cycle of the switching operations to suppress output voltage transients in response to fast changes in the output current.

5. A multiphase switching regulator comprising at least one phase configured for continuous operation to provide a regulated output voltage and at least one dedicated phase configured for intermittent operation to suppress output voltage transients in response to fast changes in output current.

6. The multiphase switching regulator of claim 5, wherein the at least one dedicated phase further comprising:

a first semiconductor switch coupled between ground and an input terminal of an inductor, wherein an output terminal of the inductor is coupled to the regulated output voltage; and

a first catch diode coupled between the input terminal of the inductor and a voltage source.

7. The multiphase switching regulator of claim 6, wherein a multiphase controller compares the regulated output voltage with a reference voltage and outputs a first signal to turn on the first semiconductor switch when the regulated output voltage is greater than the reference voltage.

8. The multiphase switching regulator of claim 5, wherein the at least one dedicated phase further comprising:

a second semiconductor switch coupled between a voltage source and an input terminal of an inductor, wherein an output terminal of the inductor is coupled to the regulated output voltage; and

a second catch diode coupled between the input terminal of the inductor and ground.

9. The multiphase switching regulator of claim 8, wherein a multiphase controller compares the regulated output voltage with a reference voltage and outputs a second signal to turn on the second semiconductor switch when the regulated output voltage is less than the reference voltage.

10. The multiphase switching regulator of claim 8 further comprising a capacitor coupled between the voltage source and ground, wherein the capacitor has a relatively large capacitive value and is placed close to the second semiconductor switch.

11. The multiphase switching regulator of claim 5, wherein the at least one dedicated phase is inactive during power up of the multiphase switching regulator.

12. The multiphase switching regulator of claim 5, wherein the at least one dedicated phase is inactive during power down of the multiphase switching regulator.

13. A multiphase switching regulator with a dedicated transient phase comprising:

a feedback circuit to generate a plurality of control voltages, wherein the feedback circuit responds relatively slowly to changes in output current;

a plurality of pulse-width modulation circuits to accept the plurality of control voltages and to control switching operations of respective regular phases in the multiphase switching regulator; and

a transient recovery circuit to generate at least one control signal for the dedicated transient phase, wherein the transient recovery circuit responds to relatively fast changes in the output current.

14. The multiphase switching regulator of claim 13, wherein the transient recovery circuit further generates inject signals to override one or more of the plurality of control voltages to increase transient correction speed.

15. The multiphase switching regulator of claim 13, wherein the dedicated transient phase uses an inductor with lower inductance than inductors of the regular phases.

16. The multiphase switching regulator of claim 13, wherein the dedicated transient phase is disabled during power up of the multiphase switching regulator.

17. The multiphase switching regulator of claim 13, wherein the dedicated transient phase is disabled during power down of the multiphase switching regulator.

18. A switching regulator comprising:

a feedback circuit to generate a control voltage and to respond to slow changes in output current;

a transient recovery circuit to generate an inject signal and to respond to fast changes in the output current, wherein the transient recovery circuit is disabled during power up of the switching regulator; and

a pulse-width modulation circuit to control switching operations of the switching regulator, wherein the control voltage controls the duty cycle of the switching operations to regulate the output voltage of the switching regulator, and wherein the inject signal overrides the control voltage to control the duty cycle of the switching operations to suppress output voltage transients in response to fast changes in the output current.