Switching regulator with transient recovery circuit

• US 6,356,063 B1
• Filed: 11/07/2000
• Issued: 03/12/2002
• Est. Priority Date: 11/07/2000
• Status: Expired due to Fees

• Current Assignee: Microsemi Corporation (Microchip Technology Incorporated)
• Original Assignee: Linfinity Microelectronics, Inc. (Microchip Technology Incorporated)
• Inventors: Brooks, Steven W.
• Primary Examiner(s): Sterrett, Jeffrey
• Application Number:
  US09/708,268
• Time in Patent Office: 490 Days
• Field of Search: 323/282, 323/284, 323/285, 361/18, 363/55, 363/56.01
• US Class Current: 323/284
• 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 and 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. The transient recovery circuit is inactive during non-transient conditions. The transient recovery circuit can be used in a single phase or a multiphase switching regulator.

Claims

1. A switching regulator comprising:

means for bypassing a feedback circuit of the switching regulator to suppress an overshoot in the output voltage of the switching regulator by causing a minimum duty cycle operation of the switching regulator; and

means for bypassing the feedback circuit to suppress an undershoot in the output voltage of the switching regulator by causing a maximum duty cycle operation.

2. A multiphase switching regulator comprising:

a feedback circuit to generate a plurality of control voltages for respective phases and respond to slow changes in output current;

a transient recovery circuit to generate a plurality of inject signals for the respective phases and respond to rapid changes in the output current; and

a plurality of pulse-width modulation circuits to control switching operations in the respective phases, wherein the control voltages control the duty cycles of the switching operations to regulate the output voltage of the multiphase switching regulator, and the inject signals override the respective control voltages to control the duty cycles of the switching operations to suppress output voltage transients in response to rapid changes in the output current.

3. A multiphase switching regulator comprising:

a feedback circuit to generate a plurality of control voltages for respective phases and respond to slow changes in output current;

a transient recovery circuit to generate inject signals for one or more dedicated phases and respond to rapid changes in the output current, wherein the one or more dedicated phases comprise a subset of the phases in the multiphase switching regulator; and

a plurality of pulse-width modulation circuits to control switching operations in the respective phases, wherein the control voltages control the duty cycles of the switching operations to regulate the output voltage of the multiphase switching regulator, and the inject signals override the control voltages for the one or more dedicated phases to control the duty cycles of the respective switching operations to suppress output voltage transients in response to rapid changes in the output current.

4. The multiphase switching regulator of claim 3 wherein the one or more dedicated phases use inductors with lower inductance than inductors used in the other phases.

5. A switching regulator comprising:

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

a transient recovery circuit to generate an inject signal and respond to fast changes in the output current, wherein said transient recovery circuit further comprises;

a reference generator to generate a comparing voltage;

a first detector to detect an output voltage overshoot;

a second detector to detect an output voltage undershoot;

a force minimum unit to configure the inject signal to correspond to minimum duty cycle operation in response to the output voltage overshoot; and

a force maximum unit to configure the inject signal to correspond to maximum duty cycle operation in response to the output voltage undershoot; 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.

6. The switching regulator of claim 5 wherein the reference generator is a low pass filter with an input terminal coupled to the output voltage of the switching regulator.

7. The switching regulator of claim 5 wherein the reference generator is a digital-to-analog converter.

8. The switching regulator of claim 5 wherein said first detector and said second detector have hysteresis.

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

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

bypassing a feedback of the switching regulator to operate the switching regulator at maximum duty cycle when the output voltage is less than the reference comparing voltage by a first limit; and

bypassing the feedback to operate the switching regulator at minimum duty cycle when the output voltage is greater than the reference comparing voltage by a second limit.

10. The method of claim 9 wherein an external resistor is used to adjust the first limit and the second limit.

11. The method of claim 9 wherein the reference comparing voltage is equivalent to the switching regulator output voltage at steady state.