Hysteretic power converter with calibration circuit

• US 10,082,811 B2
• Filed: 09/02/2015
• Issued: 09/25/2018
• Est. Priority Date: 11/30/2010
• Status: Active Grant

• Current Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Original Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Inventors: Tai, Chia-Liang, Roth, Alan, Soenen, Eric
• Primary Examiner(s): Zhang, Jue
• Assistant Examiner(s): Dang, Trinh Q
• Application Number:
  US14/843,496
• Publication Number:
  US 20150370273A1
• Time in Patent Office: 1,119 Days
• Field of Search: 323282
• CPC Class Codes: G01R 1/203 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 Class Codes: G05F 1/00 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 Class Codes: G05F 1/10 Regulating voltage or current G05F1/02 takes precedence; for electric railways B60M3/02
• CPC Class Codes: G05F 1/40 using discharge tubes or semiconductor devices as final control devices
• CPC Class Codes: G05F 1/56 using semiconductor devices in series with the load as final control devices G05F1/461 takes precedence
• CPC Class Codes: G05F 1/575 characterised by the feedback circuit
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators

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.

Claims

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.