Inverse Charge Current Mode (IQCM) Control for Power Converter

• US 20160301303A1
• Filed: 04/04/2016
• Published: 10/13/2016
• Est. Priority Date: 04/07/2015
• Status: Active Grant

• Current Assignee: Virginia Tech Intellectual Properties, Inc.
• Original Assignee: Virginia Tech Intellectual Properties, Inc.
• Inventors: Bari, Syed, Lee, Fred C., Li, Qiang
• Granted Patent: US 10,673,328 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators
• CPC Class Codes: H02M 3/1566 with means for compensating against rapid load changes, e.g. with auxiliary current source, with dual mode control or with inductance variation

Abstract

an amount of charge transferred by a power converter is estimated by developing a signal that is a combination of signals representing an output voltage of a power converter and an inductor current of the power converter, charging a capacitor with a current proportional to that signal and comparing a voltage developed across the capacitor due to that charging to develop a signal for initiating a pulse to control input of power from a voltage source to the power converter. By using a signal developed in this way, response to both step-up and step-down transients can be improved and, in multi-phase embodiments, ripple cancellation problems such as noise susceptibility and loss of pulse generation can be entirely avoided.

Claims

1. A power converter comprising

a pulse generator for generating pulses for controlling connection of said power converter to a power source,

a circuit for developing a control voltage corresponding to a combination of output voltage and inductor current of said power converter,

a transconductance amplifier for developing a current proportional to said combination of output voltage and inductor current for charging a capacitor, and

a control circuit responsive to a voltage on said capacitor reaching a threshold for controlling said pulse generator.

2. The power converter as recited in claim 1, wherein said pulse generator comprises

a current source,

a capacitor in series with said current source,

a comparator for comparing a voltage developed on said capacitor with a threshold,

a latch that is set in response to said control circuit and reset in response to said comparator, and

a capacitor discharge switch responsive to said pulse generator connected in parallel with said capacitor.

3. The power converter as recited in claim 1, wherein said pulse generator comprises

a current source,

a capacitor in series with said current source,

a comparator for comparing a voltage developed on said capacitor with a threshold,

a bistable latch that is set in response to said control circuit and reset in response to said comparator,

a capacitor discharge switch responsive to said pulse generator connected in parallel with said capacitor, and

a logic circuit responsive to an output of said latch and an output of said comparator for controlling said capacitor discharge switch.

4. The power converter as recited in claim 1, further comprising

a comparator responsive to said control voltage and a signal representing said inductor current for disabling said pulse generator when said signal representing said control voltage exceeds said control voltage.

5. The power converter as recited in claim 1, further comprising

a plurality of said pulse generators, and

a phase manager for distributing and output of said control circuit.

6. The power converter as recited in claim 5, wherein said each of said plurality of pulse generators comprises

a current source,

a capacitor in series with said current source,

a comparator for comparing a voltage developed on said capacitor with a threshold,

a bistable latch that is set in response to said control circuit and reset in response to said comparator, and

a capacitor discharge switch responsive to said pulse generator connected in parallel with said capacitor.

7. The power converter as recited in claim 5, wherein each of said plurality of said pulse generators comprises

a current source,

a capacitor in series with said current source,

a comparator for comparing a voltage developed on said capacitor with a threshold,

a bistable latch that is set in response to said control circuit and reset in response to said comparator,

a capacitor discharge switch responsive to said pulse generator connected in parallel with said capacitor, and

a logic circuit responsive to an output of said latch and an output of said comparator for controlling said capacitor discharge switch.

8. The power converter as recited in claim 5, further comprising

a comparator responsive to said control voltage and a signal representing said inductor current for disabling said pulse generator when said signal representing said control voltage exceeds said control voltage.

9. The power converter as recited in claim 2, further comprising

a circuit for adding an offset voltage to said control voltage, and

wherein said control circuit further comprises

a further circuit for developing a control voltage corresponding to a combination of output voltage and inductor current of said power converter,

a further transconductance amplifier for developing a current proportional to said combination of output voltage and inductor current for charging a capacitor, and

a further control circuit responsive to a voltage on said capacitor reaching a threshold for setting said latch.

10. The power converter as recited in claim 9, further including

a plurality of said pulse generators,

a plurality of said latches,

a phase manager for distributing an output of said control circuit for setting each of said plurality of latches, and

a plurality of comparators for comparing a signal representing a combination of said output voltage of said converter and a signal representing inductor current with a ramp voltage for resetting each of said plurality of latches.

11. The power converter as recited in claim 2, further including

a logic circuit responsive to a clock for gating a signal to set said latch.

12. The power converter as recited in claim 1, further including

an integrator for smoothing said signal representing said inductor current.

13. The power converter as recited in claim 1, wherein said pulse generator supplies pulses of a constant duration.

14. The power converter as recited in claim 1, wherein said pulse generator supplies pulses of a constant frequency.

15. The power converter as recited in claim 2, wherein said pulse generator comprises

a current source,

a capacitor in series with said current source,

an integrator for smoothing said signal representing said inductor current,

a comparator for comparing a voltage developed on said capacitor with a threshold,

a capacitor discharge switch responsive to said comparator in parallel with said capacitor.

16. A method of controlling a power converter, said method comprising steps of

Developing a voltage representing a combination of output voltage of said power converter and an inductor current of said power converter,

charging a capacitor with a current proportional to said voltage developed in said developing step,

comparing a voltage developed across said capacitor by said charging step with a threshold, and

controlling a switch driver for applying input power to an inductor of said power converter in accordance with a result of said comparing step.

17. The method as recited in claim 16, wherein said power converter is a multi-phase power converter

18. The method as recited in claim 16, wherein said power converter is a constant on time (COT) power converter.

19. The method as recited in claim 16, wherein said power converter is a constant frequency power converter.

20. The method as recited in claim 16, wherein said power converter is a variable on-time, variable frequency power converter.