Hysteretic power converter with calibration circuit

Patent metadata

Field	Value
Publication number	US-10082811-B2
Application number	US-201514843496-A
Country	US
Kind code	B2
Filing date	Sep 2, 2015
Priority date	Nov 30, 2010
Publication date	Sep 25, 2018
Grant date	Sep 25, 2018

Abstract

A power converter includes a first load terminal used to supply a current to a load and a second load terminal used to return a feedback voltage based on the current. A calibration circuit supplies a calibrated voltage processed from the feedback voltage, and a hysteretic comparator controls a current level of the current based on a difference between the feedback voltage and the calibrated voltage.

First claim

What is claimed is:

1. A power converter, comprising:
a first load terminal configured to supply a current to a load;
a second load terminal configured to return a feedback voltage based on the current;
a calibration circuit configured to supply a calibrated voltage, the calibration circuit including a low pass filter and a voltage clamp;
the low pass filter being configured to receive the feedback voltage;
the calibration circuit being further configured to generate an unclamped voltage based on an output of the low pass filter; and
the voltage clamp being configured to limit a maximum value of the unclamped voltage resulting in a clamped voltage, the clamped voltage being output from the calibration circuit as the calibrated voltage; and

a hysteretic comparator circuit configured to control a current level of the current based on a difference between the feedback voltage and the calibrated voltage.

2. The power converter of claim 1 , wherein the calibration circuit comprises a charge pump configured to alter the unclamped voltage.

3. The power converter of claim 1 , wherein the calibration circuit comprises a comparator configured to adjust the unclamped voltage based on the output of the low pass filter and a reference voltage.

4. The power converter of claim 1 , wherein the low pass filter is further configured to average the feedback voltage.

5. The power converter of claim 1 , wherein the hysteretic comparator circuit comprises a hysteretic comparator.

6. The power converter of claim 1 , wherein the hysteretic comparator circuit comprises a first non-hysteretic comparator, a second non-hysteretic comparator, a first latch, and a second latch, wherein
each of the first non-hysteretic comparator and the second non-hysteretic comparator is configured to receive the feedback voltage, and
each of the first latch and the second latch is configured to receive an output of the first non-hysteretic comparator and an output of the second non-hysteretic comparator.

7. The power converter of claim 1 , wherein the load comprises a light emitting diode.

8. The power converter of claim 1 , wherein the feedback voltage is further based on a resistance value of a resistor.

9. The power converter of claim 1 , wherein the power converter further comprises a switch, a capacitor, and an inductor configured to supply the current by increasing an input voltage.

10. The power converter of claim 1 , wherein the power converter further comprises a switch, a capacitor, and an inductor configured to supply the current by decreasing an input voltage.

11. A method of controlling a load current of a hysteretic power converter, the method comprising:
supplying, with a first load terminal, the load current to a load;
returning, from a second load terminal, a feedback voltage based on the load current;
processing the feedback voltage with a calibration circuit to generate a calibrated voltage, the processing including:
low pass filtering the feedback voltage to form a filtered feedback voltage; and
generating an unclamped voltage based on the filtered feedback voltage;
clamping the unclamped voltage and so as to limit a maximum value of the unclamped voltage resulting in a clamped voltage; and
outputting the clamped voltage as the calibrated voltage; and

controlling, with a hysteretic comparator circuit, a current level of the load current based on a difference between the feedback voltage and the calibrated voltage.

12. The method of claim 11 , wherein the processing further includes:
comparing the filtered feedback voltage to a reference voltage based on a target load current.

13. The method of claim 11 , wherein the processing further includes:
adjusting the unclamped voltage using a charge pump.

14. The method of claim 11 , wherein the filtering further includes:
averaging the feedback voltage.

15. The method of claim 11 , wherein controlling the current level with a hysteretic comparator circuit comprises controlling the current level with a hysteretic comparator.

16. The method of claim 11 , wherein controlling the current level with a hysteretic comparator circuit comprises controlling the current level with a first non-hysteretic comparator, a second non-hysteretic comparator, a first latch, and a second latch, wherein
each of the first non-hysteretic comparator and the second non-hysteretic comparator receives the feedback voltage, and
each of the first latch and the second latch receives an output of the first non-hysteretic comparator and an output of the second non-hysteretic comparator.

17. The method of claim 11 , wherein supplying the load current to the load comprises supplying the load current to a light emitting diode.

18. A power converter circuit, comprising:
a load in series with a resistor;
a switch, a capacitor, and an inductor configured to receive an input voltage and supply a current to the load and the resistor, a voltage drop across the resistor representing a feedback voltage based on the current;
a calibration circuit configured to supply a calibrated voltage, the calibration circuit including a low pass filter and a voltage clamp;
the low pass filter being configured to receive the feedback voltage;
the calibration circuit being further configured to generate an unclamped voltage based on an output of the low pass filter; and

the voltage clamp being configured to limit a maximum value of the unclamped voltage resulting in a clamped voltage, the clamped voltage being output from the calibration circuit as the calibrated voltage; and
a hysteretic comparator circuit configured to control the switch, the capacitor, and the inductor so as to supply the current at a current level based on a difference between the feedback voltage and the calibrated voltage.

19. The power converter circuit of claim 18 , wherein the calibration circuit is further configured to generate the unclamped voltage based also on a reference voltage corresponding to a target current.

20. The power converter circuit of claim 18 , wherein the load comprises a light emitting diode.

Assignees

• Taiwan Semiconductor Mfg Co Ltd

Inventors

• Tai Chia-Liang
• Roth Alan
• Soenen Eric

Classifications

• G05F1/00

  Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems · CPC title

• G05F1/10

  Regulating voltage or current  (G05F1/02 takes precedence) · CPC title

• G05F1/40

  using discharge tubes or semiconductor devices as final control devices · CPC title

• G01R1/203

  Resistors used for electric measuring, e.g. decade resistors standards, resistors for comparators, series resistors, shunts (resistors in general H01C; microwave or radiowave terminations H01P1/26; coupling devices H01R) · CPC title

• G05F1/575 Primary

  characterised by the feedback circuit · CPC title