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US3649902A
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Dc to ac inverter for producing a sine-wave output by pulse width modulation
Assignee: General Electric Co
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Filing: 1970-06-15
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Granted: 1972-03-14
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Expires: 1990-06-15
Abstract
Abstract A DC to AC bridge inverter circuit produces a sine wave output of low-harmonic content. One transistor of each pair of transistors in opposite arms of the inverter bridge is switched into conduction at the desired output frequency; i.e., 400 times per sec. for a 400 Hz. output. The remaining complementary transistor of each pair is switched on and off n times per alternation to produce n constant amplitude, variable width output pulses during each alternation. The duration of the conduction time of the complementary transistor is controlled so that the area of each pulse is equal to the area of the corresponding sinusoidal segment where each sinusoidal segment represents an angle phi , in electrical degrees equal to: phi 180*/n. These variable width output pulses are applied to a filter to produce a sinusoidal output having low-harmonic content. A clock-driven logic system controls the complementary transistor of each transistor pair turning it on n times per alternation and turning it off at different times during each interval to produce the desired sinusoidal pulse width modulation. The turnoff pulses are generated by a clock-driven divider and associated AND gates. Each of the AND gates is energized in response to a predetermined count from the divider to produce a turnoff pulse during each of the n intervals at a point in time during each interval such that the pulse width is proportional to the sine of the angle.
Inventors
- 👤 Robert A Dunbar
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 20:25
CPC Classifications
H; H02; H02M; H02M7/00; H02M7/42; H02M7/44; H02M7/48; H02M7/53; H02M7/537; H02M7/5387; H02M7/53871; H02M7/539
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
112 words
A DC to AC inverter for producing a time varying output waveform from a unidirectional supply comprising, a. a source of unidirectional voltage, b. bridge switching means comprising a plurality of switching devices connected in the arms of the bridge, said source of unidirectional voltage being coupled across one diagonal of said bridge, c. means for selectively actuating said switching devices in pairs to produce opposite alternations of the time varying output wave, d. pulse width modulating means including means to generate switching pulses for said switching devices to produce a plurality n of constant amplitude, variable width, pulses during the period of each alternation of the time varying output wave, including
Claim 2
Dependent Claim
112 words
A DC to AC inverter for producing a time varying output waveform from a unidirectional supply comprising, a. a source of unidirectional voltage, b. bridge switching means comprising a plurality of switching devices connected in the arms of the bridge, said source of unidirectional voltage being coupled across one diagonal of said bridge, c. means for selectively actuating said switching devices in pairs to produce opposite alternations of the time varying output wave, d. pulse width modulating means including means to generate switching pulses for said switching devices to produce a plurality n of constant amplitude, variable width, pulses during the period of each alternation of the time varying output wave, including
Claim 3
Dependent Claim
26 words
A first switching path for switching one of the switching devices in each pair at a rate equal to the desired output frequency of the wave,
Claim 4
Dependent Claim
26 words
A first switching path for switching one of the switching devices in each pair at a rate equal to the desired output frequency of the wave,
Claim 5
Dependent Claim
47 words
A second switching path for switching the other switching device in each pair on and off at n times the rate of said one switching device to produce n output pulses during each alternation, including means to produce n switching pulses for turning on said switching devices,
Claim 6
Dependent Claim
47 words
A second switching path for switching the other switching device in each pair on and off at n times the rate of said one switching device to produce n output pulses during each alternation, including means to produce n switching pulses for turning on said switching devices,
Claim 7
Dependent Claim
53 words
The inverter according to claim 1 wherein said wave is a sinusoidal wave and the area of each of said variable width pulses is equal to the area of a corresponding sinusoidal segment where each sinusoidal segment in each alternation is defined by an angle in electrical degrees equal to 180* over n.
Claim 8
Dependent Claim
47 words
A second switching path for switching the other switching device in each pair on and off at n times the rate of said one switching device to produce n output pulses during each alternation, including means to produce n switching pulses for turning on said switching devices,
Claim 9
Dependent Claim
47 words
A second switching path for switching the other switching device in each pair on and off at n times the rate of said one switching device to produce n output pulses during each alternation, including means to produce n switching pulses for turning on said switching devices,
Claim 10
Dependent Claim
76 words
Means to vary the time said other switching device is turned off to vary the width of the pulses including means to generate n switching pulses for turning off said switching devices, the time interval between each turn on and each turnoff switching pulse varying selectively to vary the width of the output pulses so that the area of each pulse is substantially equal to the area of the corresponding segment of the desired varying wave.
Claim 11
Dependent Claim
76 words
Means to vary the time said other switching device is turned off to vary the width of the pulses including means to generate n switching pulses for turning off said switching devices, the time interval between each turn on and each turnoff switching pulse varying selectively to vary the width of the output pulses so that the area of each pulse is substantially equal to the area of the corresponding segment of the desired varying wave.
Claim 12
Dependent Claim
146 words
The inverter according to claim 2 including, a. a source of clock pulses, b. means in said first path for producing first switching pulses from said clock pulses having a repetition rate equal to the desired output frequency, c. means for producing further switching pulses from said clock pulses having a repetition rate n times the rate of said first switching pulses for turning the other switching device in each pair on to drive it into conduction n times per alternation d. means for producing a turnoff switching pulse in response to said clock pulses a predetermined time after each of said further switching pulses to turn said other devices of n times per alternation, said predetermined time being chosen to vary the width of the output pulses so that the area of each pulse equals the area under a corresponding segment of the sinusoidal wave.
Claim 13
Dependent Claim
76 words
Means to vary the time said other switching device is turned off to vary the width of the pulses including means to generate n switching pulses for turning off said switching devices, the time interval between each turn on and each turnoff switching pulse varying selectively to vary the width of the output pulses so that the area of each pulse is substantially equal to the area of the corresponding segment of the desired varying wave.
Claim 14
Dependent Claim
76 words
Means to vary the time said other switching device is turned off to vary the width of the pulses including means to generate n switching pulses for turning off said switching devices, the time interval between each turn on and each turnoff switching pulse varying selectively to vary the width of the output pulses so that the area of each pulse is substantially equal to the area of the corresponding segment of the desired varying wave.
Claim 15
Dependent Claim
75 words
The inverter according to claim 3 wherein said means for producing the turnoff switching pulses includes a first group of n AND gates, means for successively enabling each of the n AND gates during each alternation, means to generate n timing pulses at varying times after the AND gates are enabled, means to impress said timing pulses to the individual AND gates to produce successive turnoff pulse from said AND gates which vary in time.
Claim 16
Dependent Claim
59 words
The inverter according to claim 4 wherein said timing pulse generating means comprises a further set of n AND gates, pulse counting means responsive to said clock pulses having a plurality of output terminals, means for connecting the AND gates to said output terminals so that the AND gates respond to varying predetermined counts to produce the timing pulses.
Claim 17
Dependent Claim
64 words
The inverter according to claim 5 including voltage regulating means to maintain the amplitude of the sinusoidal wave constant including means to produce a pulse train having a repetition rate proportional to the wave amplitude, means to apply said pulse train to said pulse counting means to vary the time required to reach said predetermined counts to change the position of said timing pulses.
References Cited (Backward Citations)
US3310730A
Cited
US3504264A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-03-14 | 1975-09-13 | 1976-03-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-03-14 | 1979-09-13 | 1980-03-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-03-14 | 1983-09-13 | 1984-03-14 | $7700.00 | Window Closed / Lapsed |