# US 9,520,785 B2 · Nonlinear control loop for DC-DC converters

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- Number: US 9,520,785 B2
- Document ID: US9520785B2
- Status: Granted
- Kind: B2
- Application number: 12/620,076
- Filed: 2009-11-17
- Published: 2011-05-19
- Granted: 2016-12-13
- Earliest claimed: 2009-11-17
- Assignees: Infineon Technologies Austria AG
- Applicants: Stefano Marsili; Dietmar Straeussnigg; Luca Bizjak; Robert Priewasser; Matteo Agostinelli
- Inventors: Stefano Marsili; Dietmar Straeussnigg; Luca Bizjak; Robert Priewasser; Matteo Agostinelli
- Web page: https://patentgrep.com/patent/US9520785B2

## CPC

- H02M 3/1582: {Buck-boost converters (H02M3/1584 takes precedence)}
- H02M 1/0003: {Details of control, feedback or regulation circuits}
- H02M: APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF (transformers H01F; dynamo-electric converters H02K47/00; controlling transformers, reactors or choke coils, control or regulation of electric motors, generators or dynamo-electric converters H02P)

## Abstract

A nonlinear converter, such as a DC-DC converter, includes a nonlinear controller configured to receive an output voltage and a current, and configured to generate a PWM signal. The PWM signal is generated based on setting the converter to a first phase associated with both buck and boost modes when a clock signal is asserted, and selecting a second phase associated with the buck mode of the converter, if a sliding function signal achieves a first predetermined relationship with respect to a buck threshold before a next clock signal is asserted, or selecting a third phase associated with the boost mode of the converter, if the sliding function signal achieves a second predetermined relationship with respect to a boost threshold before a next clock signal is asserted. The nonlinear converter may include a power stage configured to provide the output voltage and a coil current to the nonlinear controller.

## Claims

### Claim 1

A nonlinear converter, comprising:
a nonlinear controller configured to receive an output voltage and configured to generate a PWM signal based on:
setting the converter to a first phase associated with both buck and boost modes of the converter, when a clock signal is asserted; and
selecting a second phase associated with the buck mode of the converter, if a sliding function signal achieves a first predetermined relationship with respect to a buck threshold before a next clock signal is asserted, or
selecting a third phase associated with the boost mode of the converter, if the sliding function signal achieves a second predetermined relationship with respect to a boost threshold before a next clock signal is asserted,
a power stage configured to generate the output voltage for the nonlinear controller based on the PWM signal from the nonlinear controller,
wherein the sliding function signal is generated by a sliding function of the converter, the sliding function comprising a summation of feedback variables from the power stage,
wherein the feedback variables comprise the output voltage, a coil current, and a processed value that is a function of the output voltage.

### Claim 2 (depends on 1)

The nonlinear converter of claim 1, wherein the nonlinear controller is configured to receive a current.

### Claim 3 (depends on 1)

The nonlinear converter of claim 1, comprising a DC-DC converter.

### Claim 4 (depends on 1)

The nonlinear converter of claim 1, wherein the first phase that is generated when the clock signal is asserted, comprises one of a buck ON and a boost OFF phase corresponding to a common phase shared by or associated with both the buck and boost modes.

### Claim 5 (depends on 4)

The nonlinear converter of claim 4, wherein selecting the second phase comprises selecting a buck OFF mode after the common phase is set by the clock signal and before a next clock signal is asserted, and selecting the third phase comprises selecting a boost ON mode after the common phase is set by the clock signal and before a next clock signal is asserted.

### Claim 6 (depends on 1)

The nonlinear converter of claim 1, wherein one or more of the buck threshold and the boost threshold comprise a compensation waveform.

### Claim 7 (depends on 6)

The nonlinear converter of claim 6, wherein the compensation waveform comprises a sawtooth waveform.

### Claim 8 (depends on 1)

The nonlinear converter of claim 1, wherein both the buck threshold and the boost threshold comprise sawtooth waveforms that intersect before a next clock signal is asserted.

### Claim 9 (depends on 1)

The nonlinear converter of claim 1, wherein the sliding function signal achieving the first predetermined relationship with respect to the buck threshold comprises the value of the sliding function signal equaling, crossing or exceeding a first predetermined value of the buck threshold, and the sliding function signal achieving the second predetermined relationship with respect to the boost threshold comprises the value of the sliding function signal equaling, crossing or exceeding a second predetermined value of the boost threshold.

### Claim 10

A nonlinear DC-DC converter, comprising:
a power stage configured to provide a coil current and an output voltage based on a PWM signal; and
a nonlinear controller configured to receive the output voltage and the coil current from the power stage, and configured to generate the PWM signal based on:
setting the DC-DC converter to a first phase associated with both buck and boost modes of the converter when a clock signal is asserted; and
selecting a second phase associated with the buck mode of the DC-DC converter, if a sliding function signal achieves a first predetermined relationship with respect to a buck threshold before a next clock signal is asserted, or
selecting a third phase associated with the boost mode of the DC-DC converter, if the sliding function signal achieves a second predetermined relationship with respect to a boost threshold before a next clock signal is asserted,
wherein the sliding function signal is generated by a sliding function of the converter, the sliding function comprising a summation of feedback variables from the power stage,
wherein the feedback variables comprise the output voltage, a coil current, and a processed value that is a function of the output voltage.

### Claim 11 (depends on 10)

The nonlinear converter of claim 10, wherein both the buck threshold and the boost threshold comprise sawtooth waveforms that intersect.

### Claim 12 (depends on 10)

The nonlinear converter of claim 10, wherein the sliding function signal achieving the first predetermined relationship with respect to the buck threshold comprises the value of the sliding function signal equaling a first predetermined value of the buck threshold, and the sliding function signal achieving the second predetermined relationship with respect to the boost threshold comprises the value of the sliding function signal equaling a second predetermined value of the boost threshold.

### Claim 13 (depends on 10)

The nonlinear converter of claim 10, wherein the power stage is configured to scale the power of the output voltage.

### Claim 14

A nonlinear DC-DC converter, comprising:
a power stage configured to provide a coil current and an output voltage based on a PWM signal; and
a nonlinear controller configured to receive the output voltage and the coil current from the power stage, and configured to generate the PWM signal based on:
setting the DC-DC converter to a first phase associated with both buck and boost modes of the converter when a clock signal is asserted; and
selecting a second phase associated with the buck mode of the DC-DC converter, if a sliding function signal achieves a first predetermined relationship with respect to a buck threshold before a next clock signal is asserted, or
selecting a third phase associated with the boost mode of the DC-DC converter, if the sliding function signal achieves a second predetermined relationship with respect to a boost threshold before a next clock signal is asserted,
wherein the sliding function signal functions in accordance with a sliding function represented by:
S(x)=(Vo−Vref)+α2iL+α3∫(Vo−Vref)dt
where:
S(x)=the sliding function,
Vo=the output voltage from the power stage,
Vref=a reference voltage,
α2=a first multiplier coefficient,
α3=a second multiplier coefficient,
iL=the coil current from the power stage.

### Claim 15

A nonlinear DC-DC converter, comprising:
a measuring component configured and operable to measure a coil current and an output voltage during operation of the DC-DC converter;
a first summing component operable to obtain the difference between the output voltage and a reference voltage;
a first amplifier operable to scale the coil current, thereby providing a scaled coil current;
a second amplifier operable to scale an integral of the difference between the output voltage and the reference voltage thereby providing an integral product;
a second summing component operable to sum the difference between the output voltage and the reference voltage, the scaled coil current, and the integral product in order to provide a sliding function used by the DC-DC converter.

### Claim 16 (depends on 15)

The nonlinear DC-DC converter of claim 15, further comprising
a comparator configured to compare and determine if a value of the sliding function has achieved one of a first predetermined relationship with respect to a buck threshold, or a second predetermined relationship with respect to a boost threshold;
a latch configured to receive an output of the comparator and to reset the latch based on the result of the comparison determination and to provide a PWM signal at the output of the latch; and
an oscillator operable to provide a clock signal used to set the latch upon each assertion of the clock signal, wherein the DC-DC converter is set to a first phase associated with both buck and boost modes of the converter when the clock signal is asserted;
wherein the DC-DC converter is operable to provide a PWM signal at the output of the latch based on the comparison determination of if the value of the sliding function has achieved one of the first predetermined relationship with respect to a buck threshold before a next clock signal is asserted, or the second predetermined relationship with respect to the boost threshold before a next clock signal is asserted, and
wherein the DC-DC converter is configured to operate in one of the buck or boost modes using the PWM signal and based on the measured coil current and output voltage as used by the sliding function.

### Claim 17 (depends on 16)

The nonlinear DC-DC converter of claim 16, further comprising a switch mode power stage configured to scale the power of the output voltage based on the PWM signal, and to provide the coil current.

### Claim 18 (depends on 17)

The nonlinear DC-DC converter of claim 17, wherein the PWM signal controls the switch mode power stage of the DC-DC converter to operate in one of the buck or boost modes based on the measured coil current and output voltage, and wherein after setting the PWM signal to the first phase associated with both buck and boost modes of the converter using the clock signal, only one of the buck and boost modes is selected between successive clock signal assertions.