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US 5,901,176 AGranted
Delta-sigma pulse width modulator control circuit
AssigneeHewlett-Packard Company
InventorRichard S. Lewison
Life of this patent
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Abstract
A delta sigma pulse width modulator control circuit uses a delta sigma modulator as a first stage to create a sequence of pulses representing an input control signal. A pulse width modulator weighs each pulse, accumulates the sequence of weighted pulses and defines a pulse width modulated output signal from the accumulated pulses. The pulse width modulated signal is given a randomly generated offset to the time of pulse value transition and an adjacent pulse value matching technique is used to reduce harmonically related noise generation.
Claims16
A control circuit for controlling power delivered to a load with reduced spurious electromagnetic energy generation, comprising:
- a delta sigma modulator accepting a first signal and generating a second signal representing said first signal with a plurality of digital pulses;
- and
- a pulse width modulator coupled to said delta sigma modulator, accumulating said second signal over a first time period, and generating a third signal coupled to the load and having a first magnitude value, said first magnitude value lasting for a second time period related to said second signal, said pulse width modulator further comprises:
- a pulse counter that multiplies each pulse of said plurality of digital pulses with a weight, said weight determined by position of each pulse relative to commencement of said first time period, thereby creating a plurality of weighted pulses, and said pulse counter accumulates said weighted pulses over said first time period,
- a low pass filter, coupled to said pulse counter, to generate a filtered bit stream, and
- a waveform generator, coupled to said low pass filter to generate, from said filtered bit stream, said third signal including a third time period greater than and encompassing said second time period.
3 more elements
A control circuit for controlling power delivered to a load with reduced spurious electromagnetic energy generation, comprising:
- a delta sigma modulator accepting a first signal and generating a second signal representing said first signal with a plurality of digital pulses thereby creating second signal pulses;
- and
- a pulse width modulator coupled to said delta sigma modulator, accumulating said second signal over a first time period, and generating a third signal coupled to the load and having a first magnitude value, said first magnitude value lasting for a second time period related to said second signal, said pulse width modulator further comprises:
- a pulse counter that multiplies each pulse of said plurality of digital pulses with a weight, said weight determined by position of each pulse relative to commencement of said first time period, thereby creating a plurality of weighted pulses, and said pulse counter accumulates said weighted pulses over said first time period,
- a low pass filter, coupled to said pulse counter, to generate a filtered bit stream,
- a waveform generator, coupled to said low pass filter to generate, from said filtered bit stream, said third signal including a third time period greater than and encompassing said second time period,
- a pulse width indicator to indicate when an accumulation of said second signal pulses create lasting for greater than 50% of said third time period, and a pulse protocol inverter coupled to said pulse width indicator to transform said third signal from an active high first magnitude value protocol to an active low first magnitude value protocol.
4 more elements
A method of controlling power delivered to a load with reduced spurious electromagnetic energy generation, comprising the steps of:
- accepting a first signal input to a delta sigma modulator;
- generating a second signal representing said first signal with a plurality of digital pulses;
- accumulating said second signal over a first time period, further comprising the steps of:
- multiplying each pulse of said plurality of digital pulses with a weight, said weight determined by position of each pulse relative to the commencement of said first time period, thereby creating a plurality of weighted pulses,
- accumulating over said first time period said weighted pulses to generate an accumulated second signal,
- setting a third time period equal to said first time period, and
- generating, from said accumulated second signal, a third signal, said third signal including said third time period which is greater than and which encompasses a second time period;
- and coupling said third signal to the load and having a first magnitude value, said first magnitude value lasting for said second time period related to said second signal.
5 more elements
A method of controlling power delivered to a load with reduced spurious electromagnetic energy generation, comprising the steps of:
- accepting a first signal input to a delta sigma modulator;
- generating a second signal representing said first signal with a plurality of digital pulses;
- accumulating said second signal over a first time period, further comprises the steps of:
- multiplying each pulse of said plurality of digital pulses with a weight, said weight determined by position of each pulse relative to the commencement of said first time period, thereby creating a plurality of weighted pulses;
- accumulating over said first time period said weighted pulses;
- generating a second time period related to said second signal;
- setting a third time period equal to said first time period;
- generating, from the accumulated number of weighted pulses, a third signal, said third signal including said third time period which is greater than and which encompasses said second time period, said third signal having a first magnitude value, said first magnitude value lasting for said second time period;
- indicating when the accumulated number of weighted pulses create said second time period lasting for greater than 50% of said third time period;
- receiving an indication when said second time period exceeds 50% of said third time period;
- transforming said third signal from an active high first magnitude value protocol to an active low first magnitude value protocol upon receiving said indication;
- and
- coupling said third signal to the load.
10 more elements
Dependencies are inferred from the claim text.