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US 8,427,126 B2Granted
Digital control of PWM converters with nonlinear gain scheduling
AssigneeSemtech Corporation
InventorsHao Peng, Chin Chang
Life of this patent
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Abstract
A system and method for controlling a digital pulse-width modulated power converter achieves a fast large-signal transient response while maintaining a slow response near the steady-state operating point in order to assure stability and to reduce the system's susceptibility to noise. Digital output error samples are processed through a gain scheduling block that applies a non-linear gain function to produce a weak loop response when the system is near its steady-state equilibrium point and a strong loop response when large transients are encountered. The resulting system maintains a fast transient response to large error signals while reducing noise and loop jittering and assuring loop stability.
Claims19
A digital pulse-width modulation (DPWM) control system comprising:
- a power stage for converting voltage comprising:
- an input voltage port;
- an output voltage port;
- and
- an input control port for receiving a DPWM control waveform;
- an error sampling block operatively coupled to the output voltage port of the power stage and comprising:
- an analog-to-digital converter;
- and
- an error comparison circuit;
- wherein the error sampling block is adapted to output a digitized error signal representing a voltage difference between the output voltage of the power stage and a reference voltage;
- a gain scheduling block adapted to apply a non-linear gain to the digitized error signal from the error comparison circuit to produce a gain-scheduled error signal;
- a compensator filter for filtering the gain-scheduled error signal;
- and
- a digital PWM module configured to receive the filtered gain-scheduled error signal and to output a DPWM control waveform that is operatively coupled to the input control port of the power stage;
- wherein the gain scheduling block is further adapted to apply a non-linear gain having a profile that:
- increases slowly with input amplitude for small input amplitudes;
- increases quickly with input amplitude for medium input amplitudes;
- and
- increases slowly with input amplitude for large input amplitudes.
16 more elements
A digital pulse-width modulation (DPWM) control system comprising:
- a power stage for converting voltage comprising:
- an input voltage port;
- an output voltage port;
- and
- an input control port for receiving a DPWM control waveform;
- an error sampling block operatively coupled to the output voltage port of the power stage and comprising:
- an analog-to-digital converter;
- and
- an error comparison circuit;
- wherein the error sampling block is adapted to output a digitized error signal representing a voltage difference between the output voltage of the power stage and a reference voltage;
- a gain scheduling block adapted to apply a non-linear gain to the digitized error signal from the error comparison circuit to produce a gain-scheduled error signal;
- a compensator filter for filtering the gain-scheduled error signal;
- and
- a digital PWM module configured to receive the filtered gain-scheduled error signal and to output a DPWM control waveform that is operatively coupled to the input control port of the power stage;
- wherein the gain scheduling block is further adapted to apply a non-linear gain having a profile that:
- increases linearly with a slope of α1 for input amplitudes less than a1;
- increases linearly with a slope of α2 for input amplitudes between and including a1 and a2;
- and
- increases linearly with a slope of α3 for input amplitudes greater than a2;
- wherein:
- α1 is less than or equal to α2;
- α2 is greater than or equal to α3;
- and
- a1 is less than a2.
21 more elements
A digital pulse-width modulation (DPWM) control system comprising:
- a power stage for converting voltage comprising:
- an input voltage port;
- an output voltage port;
- and
- an input control port for receiving a DPWM control waveform;
- an error sampling block operatively coupled to the output voltage port of the power stage and comprising:
- an analog-to-digital converter;
- and
- an error comparison circuit;
- wherein the error sampling block is adapted to output a digitized error signal representing a voltage difference between the output voltage of the power stage and a reference voltage;
- a gain scheduling block adapted to apply a non-linear gain to the digitized error signal from the error comparison circuit to produce a gain-scheduled error signal;
- a compensator filter for filtering the gain-scheduled error signal;
- and
- a digital PWM module configured to receive the filtered gain-scheduled error signal and to output a DPWM control waveform that is operatively coupled to the input control port of the power stage;
- wherein the gain scheduling block is further adapted to apply a non-linear gain having a profile that:
- is equal to zero for input amplitudes less than a1;
- and
- increases linearly for input amplitudes greater than or equal to a1.
15 more elements
A digital pulse-width modulation (DPWM) control system comprising:
- a power stage for converting voltage comprising:
- an input voltage port;
- an output voltage port;
- and
- an input control port for receiving a DPWM control waveform;
- an error sampling block operatively coupled to the output voltage port of the power stage and comprising:
- an analog-to-digital converter;
- and
- an error comparison circuit;
- wherein the error sampling block is adapted to output a digitized error signal representing a voltage difference between the output voltage of the power stage and a reference voltage;
- a gain scheduling block adapted to apply a non-linear gain to the digitized error signal from the error comparison circuit to produce a gain-scheduled error signal;
- a compensator filter for filtering the gain-scheduled error signal;
- and
- a digital PWM module configured to receive the filtered gain-scheduled error signal and to output a DPWM control waveform that is operatively coupled to the input control port of the power stage;
- wherein the gain scheduling block is further adapted to apply a non-linear gain having a profile that:
- increases linearly with a slope of α1 for input amplitudes less than a1;
- and
- remains constant at a gain of α1*a1 for amplitudes greater than or equal to a1.
15 more elements
A power conversion system comprising:
- a switching converter comprising:
- an input voltage port;
- an output voltage port;
- an output filter operatively connected to the output voltage port;
- and
- a switch element for selectively connecting the input voltage port to the output filter;
- an error circuit adapted to produce a voltage corresponding to a difference between the output voltage of the switching converter and a reference voltage;
- an analog-to-digital converter (ADC) adapted to digitize the difference voltage produced by the error circuit to produce a digital error sample;
- a gain scheduling block adapted to scale the digital error sample by a non-linear gain function to produce a gain-scheduled error signal, wherein the non-linear gain function comprises a piecewise linear function having at least a first slope and a second slope, wherein the non-linear gain function increases slowly with input amplitude for small input amplitudes, increases quickly with input amplitude for medium input amplitudes, and increases slowly with input amplitude for large input amplitudes;
- a compensator filter for filtering the gain-scheduled error signal;
- and
- a digital pulse width modulation module configured to receive the filtered gain-scheduled error signal and to generate a control waveform that is operatively coupled to the switch element of the switching converter.
9 more elements
In a digital pulse-width-modulator-controlled power system including a switching power converter, an analog-to-digital converter, a compensator filter, and a digital pulse-width modulator, a method of controlling an output voltage of the switching power converter comprises the steps of:
- comparing the output voltage of the switching power converter to a reference voltage to create a difference error signal;
- digitizing the difference error signal with the analog-to-digital converter to create a plurality of digital error samples;
- applying a non-linear gain scheduling function to the plurality of digital error samples to produce a plurality of gain-scheduled error samples;
- filtering the plurality of gain-scheduled error samples to produce a pulse-width-modulator driving signal;
- driving the digital pulse width modulator with the pulse-width modulator driving signal to produce a switching waveform;
- and
- operatively coupling the switching waveform to the switching power converter;
- wherein the output voltage of the switching power converter is controlled such that it tracks the reference voltage;
- and wherein the step of applying a non-linear gain scheduling function to the plurality of digital error samples further comprises:
- applying a gain that increases linearly with a slope of α1 to ones of the plurality of error samples having amplitudes less than a1;
- applying a gain that increases linearly with a slope of α2 to ones of the plurality of error samples having amplitudes between and including a1 and a2;
- and
- applying a gain that increases linearly with a slope of α3 to ones of the plurality of error samples having amplitudes greater than a2, wherein:
- α1 is less than or equal to α2;
- α2 is greater than or equal to α3;
- and
- a1 is less than a2.
14 more elements
In a digital pulse-width-modulator-controlled power system including a switching power converter, an analog-to-digital converter, a compensator filter, and a digital pulse-width modulator, a method of controlling an output voltage of the switching power converter comprises the steps of:
- comparing the output voltage of the switching power converter to a reference voltage to create a difference error signal;
- digitizing the difference error signal with the analog-to-digital converter to create a plurality of digital error samples;
- applying a non-linear gain scheduling function to the plurality of digital error samples to produce a plurality of gain-scheduled error samples;
- filtering the plurality of gain-scheduled error samples to produce a pulse-width-modulator driving signal;
- driving the digital pulse width modulator with the pulse-width modulator driving signal to produce a switching waveform;
- and
- operatively coupling the switching waveform to the switching power converter;
- wherein the output voltage of the switching power converter is controlled such that it tracks the reference voltage;
- and wherein the step of applying a non-linear gain scheduling function to the plurality of digital error samples further comprises:
- applying a gain of zero to ones of the plurality of error samples having amplitudes less than a1;
- and
- applying a gain that increases linearly to ones of the plurality of error samples having amplitudes greater than or equal to a1.
9 more elements
In a digital pulse-width-modulator-controlled power system including a switching power converter, an analog-to-digital converter, a compensator filter, and a digital pulse-width modulator, a method of controlling an output voltage of the switching power converter comprises the steps of:
- comparing the output voltage of the switching power converter to a reference voltage to create a difference error signal;
- digitizing the difference error signal with the analog-to-digital converter to create a plurality of digital error samples;
- applying a non-linear gain scheduling function to the plurality of digital error samples to produce a plurality of gain-scheduled error samples;
- filtering the plurality of gain-scheduled error samples to produce a pulse-width-modulator driving signal;
- driving the digital pulse width modulator with the pulse-width modulator driving signal to produce a switching waveform;
- and
- operatively coupling the switching waveform to the switching power converter;
- wherein the output voltage of the switching power converter is controlled such that it tracks the reference voltage;
- and wherein the step of applying a non-linear gain scheduling function to the plurality of digital error samples further comprises:
- applying a gain that increases linearly with a slope of α1 to ones of the plurality of error samples having amplitudes less than a1;
- and
- applying a constant gain equal to α1*a1 to ones of the plurality of error samples having amplitudes less than a1.
9 more elements
Dependencies are inferred from the claim text.