Stabilized power converter having quantized duty cycle
First Claim
1. A method for stabilizing a power converter against oscillations due to a mismatch between an output voltage setpoint and available ones of a plurality of quantized duty cycles, comprising the steps:
- generating a reference voltage for indicating a desired output voltage setpoint;
comparing the reference voltage to an actual output voltage of the power converter to derive an error signal;
varying the pulsewidth of a first pulsewidth modulated control signal in accordance with the error voltage, the first pulsewidth modulated control signal having a first frequency;
converting the first pulsewidth modulated control signal to at least one second pulsewidth modulated control signal for varying a conduction time of a converter switching means so as to make the actual output voltage conform to the desired output voltage, the step of converting including a step of quantizing the pulsewidth to one of a plurality of quantized duty cycles; and
injecting a dither signal such that the dither signal appears in the error signal, the dither signal having a second frequency that is less than the first frequency and greater than a bandwidth frequency of the power converter, the dither signal functioning to effectively increase the number of possible duty cycles by a factor given by the ratio of the second frequency to the bandwidth frequency.
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Accused Products
Abstract
A multi-slice power converter (10) employs a digital circuit (22) to generate phase-delayed pulse width modulated (PWM) signals, which results in the duty cycle of the PWM signals having only a certain number of possible values. The quantization of the duty cycle is shown to result in two types of instabilities which are unique to power converters having a digital control loop, in addition to the conventional analog-type of instabilities. This invention provides novel methods and apparatus for stabilizing the digital control loop of the power converter through the use of a periodic dither signal having a frequency that is less than the PWM frequency and greater than a bandwidth frequency of the converter. The dither signal functions to effectively increase the number of possible duty cycles by a factor given by the ratio of the dither frequency to the bandwidth frequency.
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Citations
10 Claims
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1. A method for stabilizing a power converter against oscillations due to a mismatch between an output voltage setpoint and available ones of a plurality of quantized duty cycles, comprising the steps:
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generating a reference voltage for indicating a desired output voltage setpoint; comparing the reference voltage to an actual output voltage of the power converter to derive an error signal; varying the pulsewidth of a first pulsewidth modulated control signal in accordance with the error voltage, the first pulsewidth modulated control signal having a first frequency; converting the first pulsewidth modulated control signal to at least one second pulsewidth modulated control signal for varying a conduction time of a converter switching means so as to make the actual output voltage conform to the desired output voltage, the step of converting including a step of quantizing the pulsewidth to one of a plurality of quantized duty cycles; and injecting a dither signal such that the dither signal appears in the error signal, the dither signal having a second frequency that is less than the first frequency and greater than a bandwidth frequency of the power converter, the dither signal functioning to effectively increase the number of possible duty cycles by a factor given by the ratio of the second frequency to the bandwidth frequency. - View Dependent Claims (2, 3, 4)
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5. A power converter, comprising:
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means for generating a reference voltage for indicating a desired output voltage setpoint; means for comparing the reference voltage to an actual output voltage of the power converter to derive an error signal; means for varying the pulsewidth of a first pulsewidth modulated control signal in accordance with the error voltage, the first pulsewidth modulated control signal having a first frequency; means for converting the first pulsewidth modulated control signal to at least one second pulsewidth modulated control signal for varying a conduction time of a converter switching means so as to make the actual output voltage conform to the desired output voltage, said converting means comprising means for quantizing the pulsewidth to one of a plurality of quantized duty cycles; and means for stabilizing said power converter against oscillations due to a mismatch between the output voltage setpoint and available ones of the plurality of quantized duty cycles; wherein said converting means further comprises means for generating a plurality of the second pulsewidth modulated control signals for varying a conduction time of a corresponding plurality of converter switching means individual ones of which are associated with a corresponding plurality of power stage slices, individual ones of the plurality of second pulsewidth modulated control signals being offset in phase from one another and each having a pulsewidth equal to one of the plurality of quantized duty cycles.
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6. A power converter, comprising:
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means for generating a reference voltage for indicating a desired output voltage setpoint; means for comparing the reference voltage to an actual output voltage of the power converter to derive an error signal; means for varying the pulsewidth of a first pulsewidth modulated control signal in accordance with the error voltage, the first pulsewidth modulated control signal having a first frequency; means for converting the first pulsewidth modulated control signal to at least one second pulsewidth modulated control signal for varying a conduction time of a converter switching means so as to make the actual output voltage conform to the desired output voltage, said converting means comprising means for quantizing the pulsewidth to one of a plurality of quantized duty cycles; and means for stabilizing said power converter against oscillations due to a mismatch between the output voltage setpoint and available ones of the plurality of quantized duty cycles; wherein said stabilizing means comprises means for generating a dither signal that appears in the error signal, the dither signal having a second frequency that is less than the first frequency and greater than a bandwidth frequency of the power converter, the dither signal functioning to effectively increase the number of possible duty cycles by a factor given by the ratio of the second frequency to the bandwidth frequency. - View Dependent Claims (7)
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8. A power converter, comprising:
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means for generating a reference voltage for indicating a desired output voltage setpoint; means for comparing the reference voltage to an actual output voltage of the power converter to derive an error signal; means for varying the pulsewidth of a first pulsewidth modulated control signal in accordance with the error voltage, the first pulsewidth modulated control signal having a first frequency; means for converting the first pulsewidth modulated control signal to at least one second pulsewidth modulated control signal for varying a conduction time of a converter switching means so as to make the actual output voltage conform to the desired output voltage, said converting means comprising means for quantizing the pulsewidth to one of a plurality of discrete quantized duty cycles; and means for stabilizing said power converter against oscillations due to a mismatch between the output voltage setpoint and available ones of the plurality of quantized duty cycles. - View Dependent Claims (9)
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10. A power converter, comprising:
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means for generating a reference voltage for indicating a desired output voltage setpoint; means for comparing the reference voltage to an actual output voltage of the power converter to derive an error signal; means for varying the pulsewidth of a first pulsewidth modulated control signal in accordance with the error voltage, the first pulsewidth modulated control signal having a first frequency; means for converting the first pulsewidth modulated control signal to at least one second pulsewidth modulated control signal for varying a conduction time of a converter switching means so as to make the actual output voltage conform to the desired output voltage, said converting means comprising means for quantizing the pulsewidth to one of a plurality of quantized duty cycles; and means for stabilizing said power converter against oscillations due to a mismatch between the output voltage setpoint and available ones of the plurality of quantized duty cycles; wherein said power converter is responsive to an input signal for setting a magnitude of the reference voltage, and wherein an output of said power converter is coupled to an RF power amplifier within a satellite communications payload for providing operating power to said RF power amplifier, said RF power amplifier outputting a downlink communications signal to a downlink transmitter antenna.
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Specification