Digital Hybrid V2 Control for Buck Converters

• US 20110316508A1
• Filed: 08/12/2010
• Published: 12/29/2011
• Est. Priority Date: 06/28/2010
• Status: Active Grant

• Current Assignee: Virginia Tech Intellectual Properties, Inc. (Virginia Polytechnic Institute and State University)
• Original Assignee: Virginia Tech Intellectual Properties, Inc. (Virginia Polytechnic Institute and State University)
• Inventors: Lee, Fred C., Cheng, Kuang-Yao, Yu, Feng, Mattavelli, Paolo
• Granted Patent: US 8,575,911 B2
• Time in Patent Office: Days
• US Class Current: 323/282
• CPC Class Codes: H02M 1/0012 Control circuits using digital or numerical techniques in DC/DC converters H02M3/157, H02M3/33515; in DC-AC converters H02M7/53873
• 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 1/14 Arrangements for reducing ripples from dc input or output
• CPC Class Codes: H02M 3/1588 comprising at least one synchronous rectifier element H02M3/1582, H02M3/1584 take precedence
• 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

Stabilization of a switching voltage regulator employing V² control against ripple oscillation instability when the equivalent series resistance (ESR) of an output capacitor is small is provided by providing both an external ramp and an internal ramp (only the latter of which requires an approximation of inductor current) in the control feedback path, preferably including both inner and outer feedback loops. Approximation of inductor current using such an arrangement is non-critical and may be estimated based on power input voltage. Drift of a circuit providing such an inductor current estimation is preferably avoided by adjusting control duty cycle or slew rate of the positive-going ramp portion of the estimated inductor current triangular waveform.

Claims

1. A switched power converter comprising

switches for supplying input voltage power to an inductor, and

a feedback circuit for controlling said switches in accordance with a signal representing an output voltage of said power converter, said feedback circuit comprising

an external ramp generator for adding a first ramp waveform to said signal representing said output voltage, said first ramp waveform having a slope which produces approximately unity gain of said power converter at a switching frequency above a frequency causing a peak in gain of said power converter, and

an internal ramp generator for adding a second ramp waveform to said signal representing said output voltage, said second ramp waveform having a magnitude which produces approximately unity gain of said power converter at a switching frequency above a frequency above a frequency causing a minimum in gain of said power converter.

2. A power converter as recited in claim 1, wherein said internal ramp generator estimates current in said inductor from said input voltage.

3. A power converter as recited in claim 2,wherein said internal ramp generator detects minima in said ramp waveform and adjusts a positive-going portion of said ramp waveform to compensate for drift.

4. A power converter as recited in claim 3, wherein said positive-going portion of said ramp waveform is adjusted in duration.

5. A power converter as recited in claim 3, wherein said positive-going portion of said ramp waveform is adjusted in slope or slew rate.

6. A power converter as recited in claim 3, wherein said ramp generator includes a counter for adjusting said positive-going portion of said ramp waveform.

7. A power converter as recited in claim 1, wherein said internal ramp generator is responsive to a direct measurement of inductor current.

8. A power converter as recited in claim 7, wherein said direct measurement of inductor current is represented by a voltage developed on a direct current resistance of said inductor.

9. A triangular waveform generator comprising a multiplexer and a low pass filter, said multiplexer providing a first input parameter value or a second input parameter to said low pass filter in accordance with a control signal, wherein a level of said triangular waveform is adjusted by comparison of a value of said waveform at a detected minimum thereof with a reference value to compensate for drift.

10. A triangular waveform generator as recited in claim 9 wherein a duty cycle of said control signal is adjusted by said comparison.

11. A triangular waveform generator as recited in claim 9 wherein a slew rate of a rising portion of said triangular waveform is adjusted by said comparison.

12. A triangular waveform generator as recited in claim 9 wherein said low pass filter includes a counter.

13. A triangular waveform generator as recited in claim 9 wherein said second input parameter is a substantially fixed value.

14. A triangular waveform generator as recited in claim 9 wherein said first input parameter represents an input voltage to a switching voltage regulator including a V² control arrangement.