DC to AC inverter with unregulated input and regulated output
First Claim
1. A DC to AC inverter for an unregulated DC voltage source comprisingtwo stepped waveform generating means connected to said source, each stepped waveform generating means being capable of delivering from said source one half the total desired voltage amplitude in the form of phase displaced, digitally controlled, stepped waveforms that approach a sine wave, each of said waveform generating means comprising a source of clock pulses at a substantially constant frequency and a step counter responsive to said clock pulses for timing said steps;
- means for additively combining said stepped waveforms to produce an output voltage,means for sensing said output voltage and producing a feedback signal proportional to its amplitude,means for comparing said feedback signal with a reference signal to produce an error signal proportional to the difference therebetween, andmeans responsive to said error signal for inhibiting said clock pulses from reaching the step counter of one of said two-stepped waveform generating means, thereby phase shifting the stepped waveform of one stepped waveform generating means relative to the other to reduce said error signal.
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Accused Products
Abstract
An inverter for producing regulated AC voltage from an unregulated DC voltage source, such as a battery, employs two stepped voltage waveform generating means independently controlled in phase to produce waveform outputs that approach sine waves which are additively combined to produce an AC output voltage whose amplitude is sensed to produce a feedback signal for comparison with a reference voltage to produce an error signal that causes one stepped waveform generating means to so shift in phase relative to the other as to reduce the error. Each stepped voltage waveform generating means is capable of producing at least half the total desired AC output voltage, so that the DC voltage source may drop by as much as 50% and the desired AC output voltage can still be maintained by shifting the relative phase between the stepped waveforms.
41 Citations
16 Claims
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1. A DC to AC inverter for an unregulated DC voltage source comprising
two stepped waveform generating means connected to said source, each stepped waveform generating means being capable of delivering from said source one half the total desired voltage amplitude in the form of phase displaced, digitally controlled, stepped waveforms that approach a sine wave, each of said waveform generating means comprising a source of clock pulses at a substantially constant frequency and a step counter responsive to said clock pulses for timing said steps; -
means for additively combining said stepped waveforms to produce an output voltage, means for sensing said output voltage and producing a feedback signal proportional to its amplitude, means for comparing said feedback signal with a reference signal to produce an error signal proportional to the difference therebetween, and means responsive to said error signal for inhibiting said clock pulses from reaching the step counter of one of said two-stepped waveform generating means, thereby phase shifting the stepped waveform of one stepped waveform generating means relative to the other to reduce said error signal. - View Dependent Claims (2, 3, 4, 5)
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6. An inverter for producing regulated AC voltage at a desired amplitude level from an unregulated DC voltage source comprising
two stepped waveform generating means for producing from said DC voltage separate stepped waveforms approaching a sine wave at the same frequency, each step being equal to said DC voltage multiplied by some predetermined constant, each of said waveform generating means comprising a source of clock pulses at a substantially constant frequency and a step counter responsive to said clock pulses for timing said steps; -
means for additively combining said separate stepped waveforms to produce an AC output voltage, means for sensing and filtering said output voltage to produce a DC feedback signal proportional to the amplitude of said AC output voltage, means for comparing said feedback signal with a reference signal to produce an error signal when the amplitude of said output voltage is below said desired level, and means responsive to said error signal for inhibiting said clock pulses from reaching the step counter of one of said two-stepped waveform generating means, thereby shifting the phase of one of said stepped waveform generating means relative to the other to reduce said error signal. - View Dependent Claims (7, 8, 9, 10)
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11. In combination,
an unregulated DC voltage source coupled to a load by a pair of means for generating stepped waveforms at the same frequency, each generating means comprising a source of clock pulses at a substantially constant frequency, a step counter responsive to said clock pulses, and a count decoding means connected to said step counter for timing and controlling the amplitude of said steps of each stepped waveform generating means, each stepped waveform generating means being comprised of two transformers having turn ratios of X: - 1 and about 2.68X;
1 and being capable of delivering six-step waveforms of half the desired AC voltage to said load, and said pair of stepped waveform generating means producing two phase displaced stepped waveforms, each stepped waveform approximating a sine wave,means for additively combining said two stepped waveforms, means for sensing the amplitude of the AC voltage applied to said load, means responsive to said sensing means for generating an error signal proportional to the amplitude difference between the AC voltage applied to said load and said desired AC voltage, and means responsive to said error signal for adjusting the relative phase shift between said two stepped waveforms, to reduce said error signal toward zero. - View Dependent Claims (12)
- 1 and about 2.68X;
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13. In combination,
an unregulated DC voltage source coupled to a load by a pair of means for generating stepped waveforms at the same frequency, each generating means comprising a source of clock pulses at a substantially constant frequency and a step counter responsive to said clock pulses for timing said steps of each stepped waveform generating means, and each generating means being capable of delivering half the desired AC voltage to said load, said pair of stepped waveform generating means producing two phase displaced stepped waveforms, each stepped waveform approximating a sine wave, means for additively combining said two stepped waveforms, means for sensing the amplitude of the AC voltage applied to said load, means responsive to said sensing means for generating an error signal proportional to the amplitude difference between the AC voltage applied to said load and said desired AC voltage, and means responsive to said error signal for adjusting the relative phase shift between said two stepped waveforms, to reduce said error signal toward zero, wherein said adjusting means is comprised of means responsive to said error signal for inhibiting said clock pulses from reaching the step counter of one of said two stepped waveform generating means.
Specification