Switching Amp Patents


last updated: 26 November 2002



Class D Audio Amplifier
Patent No:6,420,930
Date filed:August 12, 2000
Issued::August 16, 2002
Inventor:Hideto Takagishi
Assignee:Monolithic Power Systems
Comments:A self-oscillating system that uses feedback after the filter; no integrator/noise shaping other than that in the output filter and feedback network; active circuitry is just a comparator and a power stage (as with referenced Anderson).
Method and Apparatus for Error Correction of Amplifier
Patent No:6,476,674
Date filed:January 24, 2001
Issued:November 5, 2002
InventorMichael Smedegaard-Pederden; James B. Reedy
Assignee:Momentum Data Systems
Comments:Another case of putting analog and switching amp in series, this time claiming both feedback and feedforward cases.
Switching Amplifier Incorporating Return-to-Zero Quaternary Power Switch
Patent No:6,472,933
Date filed:September 27, 1999
Issued:October 29, 2002
Inventor:Wei-Chan Hsu
Assignee:Waytech Investments
Comments:State transitions four four H bridge states chosen to reduce distortion; preferably driven from three-state sigma-delta
Circuit for Amplifying and Outputting Audio Signals
Patent No:6,469,575
Date filed:March 19, 2001
Issued:October 22, 2002
Inventor:Masahi Oki; Kazuhiro Okamoto
Assignee:Mitsubishi
Comments:Bridge is protected from short circuit by detecting voltage across switch.
Adaptive Pulse Frame Rate Frequency Control for Minimization of Electro-Magnetic Contamination in Integrated Switching Amplifier Systems
Patent No:6,456,127
Date filed:August 21, 2001
Issued:September 24, 2002
Inventor:Michael J. Tsecouras
Assignee:Texas Instruments
Comments:Adjust frequency of PWM so it won't interfere with the particular frequency the radio is tuned to.
Dynamic Switching Frequency Control for a Digital Switching Amplifier
Patent No:6,351,184
Date filed:July 24, 2000
Issued:February 26, 2002
Inventor:Guoquing Miao; Cary Delano
Assignee:Tripath Technology
Comments:Dynamically adjust loop delay to a predetermined value
DC Offset Calibration for a Digital Switching Amplifier
Patent No:6,316,992
Date filed:July 24, 2000
Issued:November 13, 2001
Inventor:Guoquing Miao; Cary Delano
Assignee:Tripath Technology
Comments:Measure loop and digitally store offsets in a Tripath amplifier
Methods and Apparatus for Noise Shaping a Mixed Signal Power Output
Patent No:6,297,697
Date filed:January 11, 2001
Issued:October 2, 2001
Inventor:Cary L. Delano; Adya S. Tripathi
Assignee:Tripath Technology
Comments:Switching between switching and linear amp near zero crossings and at clipping where linear amp doesn't impact efficiency,
Power Switching Output Stage with Dead Zone Minimization and Possibility of Parallel Synchronous Connection
Patent No:6,288,605
Date filed:January 18, 2000
Issued:September 11, 2001
Inventor:Edoardo Botti; Danilo Ranieri
Assignee:STMicroelectronics
Comments:Full bridges have event-driven cross-conduction control, allowing multiple half bridges to be directly paralleled with suitable logic.
Concept and Method to Enable Filterless, Efficient Operation of Class-D Amplifiers
Patent No:6,262,632
Date filed:November 16, 1999
Issued:July 17, 2001
Inventor: Marco Corsi; Wayne Tien-Feng Chen;Roy Clifton Jones; Dan Mavencamp; Kenneth Arcudia
Assignee:Texas Instruments
Comments:Zero crossing problems in full bridge reduced by shifting one half bridge in time so ramp PWM zero crossings are shifted in time.
Methods and Apparatus for Noise Shaping a Mixed Signal Power Output
Patent No:6,229,390
Date filed:November 2, 1999
Issued:May 8, 2001
Inventor:Cary L. Delano; Adya S. Tripathi
Assignee:Tripath Technology
Comments:Switching between switching and linear amp near zero crossings, clipping where linear amp doesn't impact efficiency,
Modulation Scheme for Filterless Switching Amplifiers
Patent No:6,211,728
Date filed:November 16, 1999
Issued:April 3, 2001
Inventor:Wayne Tien-Feng Chen; Marco Corsi; Roy Clifton Jones; Michael David Score
Assignee:Texas Instruments
Comments:. Claims are HILARIOUS. An H bridge. An H bridge where there are multiple output states. Where the current in the load is a function of the differential voltage. Where the output voltage is a function of duty cycleŠ DUHH!!!
Class D Amplifier with Pulse Width Modulation and a Very Low Power Consumption
Patent No:6,191,650
Date filed:June 29, 1999
Issued:February 20, 2001
Inventor:Lee Backram; Hans-Erik Backram; Borje Gustafsson
Assignee:G/N Netcom A/S
Comments:Simple open loop PWM full bridge
Power Amplifier
Patent No:6,188,276
Date filed:June 18, 1999
Issued:February 13, 2001
Inventor:Anastasios Simopoulos
Assignee:0
Comments:What looks like a half bridge is in fact a low side PWM switch that acts if the output is too high, a highside PWM switch that acts if the signal is too low, each with completely separate PWM modulators, error amps, etc.
Pulse-Width Modulation System
Patent No:6,175,272
Date filed:December 19, 1997
Issued:January 16, 2001
Inventor:Mark K. Takita
Assignee:Nikon
Comments:Supply rails of PWM output switched among multiple voltage rails
Switching Amplifier and Method for Operating Same
Patent No:6,172,558
Date filed:September 2, 1999
Issued:January 9, 2001
Inventor:Stefan Nowak; Robert Bleisteiner
Assignee:Siemens
Comments:In connecting series full bridges, the problem of CM capacitance is addressed
High Efficiency Power Amplifying Apparatus with Phase Compensation Circuit
Patent No:6,166,596
Date filed:March 31, 1999
Issued:December 26, 2000
Inventor:Katsuhiko Higashiyama; Tsuyoshi Sato
Assignee:Matsushita
Comments:Like earlier Higashiama scheme, a combination of linear amp and class D amp driving power supply. Split supply now uses just one switching amp plus two fixed DC supplies; a phase compensation network provides similar phase response in both signal paths.
Power Amplifier and Method for the Drive of a Power Amplifier
Patent No:6,160,445
Date filed:June 2, 1999
Issued:December 12, 2000
Inventor:Peter Schweighofer
Assignee:Siemens
Comments:Series connected (floating) full-bridges for multi-level output
Battery Polarity Insensitive Integrated Circuit Amplifier
Patent No:6,157,252
Date filed:September 9, 1998
Issued:December 5, 2000
Inventor:James Barclay Compton; Clyde Kip Brown Jr.
Assignee:TEC
Comments:Primarily for hearing aids, CMOS circuit includes Class D amp and circuit to connect to battery of in either polarity.
Device for Amplifying Digital Signals
Patent No:6,140,875
Date filed:August 5, 1998
Issued:October 31, 2000
Inventor:Johannes A.T.M. Van Den Homberg; Kathleen J.P. Philips
Assignee:Philips
Comments:Continuous time feedback allows input of DSD stream into second order hysteretic loop. The use of feedforward of the digital stream supposedly reduces effects of clock jitter.
Power Amplifier with Soft Switching and Multilevel Switching Cells
Patent No:6,140,873
Date filed:July 28, 1999
Issued:October 31, 2000
Inventor:Wilhelmus D.H. Van Groningen
Assignee:Philips
Comments:A multilevel inverter for high voltage high power MRI applications
Class D Amplifiers Including Transition Zone Modulation
Patent No:6,127,885
Date filed:August 31, 1998
Issued:October 3, 2000
Inventor:Thomas Phillip Michael Colangelo
Assignee:Cello Ltd
Comments:At low outputs, slew rate of switching drops to low value, minimizing RFI and improving distortionŠ
Amplifiers
Patent No:6,124,757
Date filed:October 6, 1997
Issued:September 26, 2000
Inventor:Christopher Newey
Assignee:Harman Intl.
Comments:Digital to PWM; an FM modulation of the PWM adjusts for supply variation
Start-up Circuit For Self Oscillating Class D Modulator
Patent No:6,118,336
Date filed:October 30, 1998
Issued:September 12, 2000
Inventor:Stuart W. Pullen; Donald R. Preslar
Assignee:Intersil
Comments:Adding ENABLE and MUTE to a hysteretic converter.
Digital Input Switching Audio Power Amplifier
Patent No:6,107,876
Date filed:April 13, 1999
Issued:August 22, 2000
Inventor:Thomas Joseph Obrien
Assignee:Ravisent Technologies
Comments:Seria-Parallel-Oversample-Interpolate-LINEARIZER(??)-Noise Shaping-PWM all digital chain.
Variable Frequency Class D Modulator with Built In Soft Clipping and Frequency Limiting
Patent No:6,107,875
Date filed:October 15, 1998
Issued:August 22, 2000
Inventor:Stewart W. Pullen; Patrick A. Begley; Donald R. Preslar
Assignee:Intersil
Comments:Hysteretic loop has input limiting to prevent clipping, also prevents loop from modulating down to audio range at high output levels.
Audio Amplifier with Tracking Power Supply Utilizing Inductive Power Converter
Patent No:6,104,248
Date filed:March 31, 1999
Issued:August 15, 2000
Inventor:Robert W. Carver
Assignee:
Comments:Class G with dynamic rails from switcher, independent on each rail
Method and Device for Improved Class BD Amplification Having Single Terminal Alternating-Rail Dual-Sampling Technology
Patent No:6,097,249
Date filed:September 2, 1998
Issued:August 1, 2000
Inventor:James C. Strickland; Carlos A. Castrejon
Assignee:Rockford
Comments:Two bridges half bridges in series; output half bridge switches GND to +V or GND to -V depending on first half bridge
High Efficiency Power Amplifying Apparatus
Patent No:6,091,292
Date filed:March 31, 1999
Issued:July 18, 2000
Inventor:Katsuhiko Higashiyama; Tsuyoshi Sato
Assignee:Matsushita
Comments:Two switching Amps, offset in DC, supply low voltage rails for linear output amp. (Not exactly class GŠ)
PWM Controller with One Cycle Response
Patent No:6,084,450
Date filed:February 13, 1998
Issued:July 4, 2000
Inventor:K. Mark Smith; Zheren Lai; Keyue M. Smedley
Assignee:UC Regents
Comments:Self-oscillating scheme that eliminates frequency modulation
High Efficiency Class DB Power Amplifier
Patent No:6,078,214
Date filed:March 22, 1999
Issued:June 20, 2000
Inventor:Zhengwei Zhang
Assignee:Texas Instruments
Comments:H Bridge drives into caps rather than inductors, silly use of discrete time processing. (some body saw a description of using switchcaps as resistors, gives inherent ramp action for PWMŠ)
System for Enabling a Full-Bridge Switch-Mode Amplifier to Recover All Reactive Energy
Patent No:6,072,362
Date filed:July 10, 1998
Issued:June 6, 2000
Inventor:Daniel J. Lincoln
Assignee:Ameritherm
Comments:Variations on std. H bridge to reduce HF losses
High Power High Performance Pulse Width Modulation Amplifier
Patent No:6,064,259
Date filed:July 24, 1998
Issued:May 16, 2000
Inventor:Mark K. Takita
Assignee:Nikon
Comments:Well written but not clear what is new - a delay element is added into loop; a notch at the switching frequency in the LC output filter.
Signal Processing Apparatus with Selective Power Amplification
Patent No:6,028,944
Date filed:March 4, 1997
Issued:February 22, 2000
Inventor:Mitchell A. Markow; Rabah S. Hamdi
Assignee:Compaq
Comments:In laptop computer, low power switching amp is used under battery power, higher power linear amp under mains power.
Audio Amplifier System Using a Class D Amplifier
Patent No:6,028,943
Date filed:March 27, 1999
Issued:February 22, 2000
Inventor:Koichiro Nagato
Assignee:Matsushita
Comments:Two channels have switch freq. > 20kHz apart
Power Switched Amplifier
Patent No:6,028,476
Date filed:July 21, 1998
Issued:February 22, 2000
Inventor:Peter Schweighofer
Assignee:Siemens
Comments:Variable elements in output filter, for NMR
Class D Amplifier Input Structure
Patent No:6,016,075
Date filed:June 4, 1997
Issued:January 18, 2000
Inventor:David J. Hamo
Assignee:Lord Corp.
Comments:Use a differential amp for feedback from full bridge
Class D Amplifier with Reduced Clock Requirement and Related Methods
Patent No:6,014,055
Date filed:February 6, 1998
Issued:January 11, 2000
Inventor:David B. Chester
Assignee:Intersil
Comments:Digital input amp; oversampled, noise shaped, then digital to PWM via separate PWMs for MSB and LSBs
Current Mode Switching for Tristate Amplifiers in Magnetic Bearing Control System
Patent No:6,005,316
Date filed:December 10, 1998
Issued:December 21, 1999
Inventor:Timothy A. Harris
Assignee:Revolve Magnetic Bearings
Comments:Two bit PWM signal controls Bridge switching pattern
Method and Apparatus for Processing an Analog Signal
Patent No:5,994,954
Date filed:March 4, 1997
Issued:November 30, 1999
Inventor:David Smith; Ross Nimmo
Assignee:Texas Instruments
Comments:WOW In 1997, using a ramp and a comparator, TI patents the pulse width modulatorŠ
Method and Apparatus for Improved Power Transfer Efficiency of an Amplifier System
Patent No:5,990,751
Date filed:October 16, 1997
Issued:November 23, 1999
Inventor:Mark K. Takita
Assignee:Nikon
Comments:Class G with dynamic rails from switcher, independent on each rail
Method and Apparatus for High Efficiency Power Amplification
Patent No:5,990,735
Date filed:April 1, 1998
Issued:November 23, 1999
Inventor:Bernard Eugene Sigmon; Ronald Gene Myers
Assignee:Motorola
Comments:Multiple converters on single chip combined (prior to transmitter)
Audio Direct from Power Supply
Patent No:5,986,498
Date filed:April 14, 1998
Issued:November 16, 1999
Inventor:Manuel D. Rodriguez
Assignee:Harman Intl.
Comments:Traffo coupled; followed by polarity switch
Multiple Channel Class D Audio Amplifier
Patent No:5,982,231
Date filed:July 23, 1997
Issued:November 9, 1999
Inventor:Mehmet K. Nalbant
Assignee:Linfinity
Comments:Two full bridges on a chip?
Method and Apparatus for Performance Improvement by Qualifying Pulses in an Oversampled Noise-Shaping Signal Processor
Patent No:5,974,089
Date filed:July 22, 1997
Issued:October 26, 1999
Inventor:Adya S. Tripathi; Cary L. Delano
Assignee:Tripath
Comments:Qualifying logic follows Delta-Sigma
Class D amplifier with Switching Control
Patent No:5,963,086
Date filed:August 8, 1997
Issued:October 5, 1999
Inventor:David S. Hall
Assignee:Velodyne
Comments:Two extra switches, another L, to control recirculating energy
Class-D Amplifier No Low Pass Filter Feedback with Zero Phase Delay
Patent No:5,949,282
Date filed:February 25, 1998
Issued:September 7, 1999
Inventor:Huey Nguyen; Hideto Takagishi
Assignee:National Semiconductor
Comments:HILARIOUS!
Pulse Width Modulator with Automatic Gain Control Over-Voltage Modulator and Limiter
Patent No:5,917,369
Date filed:February 25, 1998
Issued:June 29, 1999
Inventor:Huey Nguyen
Assignee:National Semiconductor
Comments:Processing of overloads, and for some reason trying to prevent full modulation by imposing artificial max D.
Method and Apparatus for compensating for delays in Modulator Loops
Patent No:5,909,153
Date filed:February 5, 1998
Issued:June 1, 1999
Inventor:Cary L. Delano; Adya S. Tripathi
Assignee:Tripath
Comments:Oh boy! The introduction of zeros in the loop to improve stability. (Avoiding of course any such basic explanation for the techniques usedŠ)
High Efficiency Power Amplifier using Combined Linear and Switching Techniques with Novel Feedback System
Patent No:5,905,407
Date filed:July 30, 1997
Issued:May 18, 1999
Inventor:Pallab Midya
Assignee:Motorola
Comments:Switching amp is used as current dumper in combined Linear/Switching scheme.
Delta-Sigma Pulse Width Modulator Control Circuit
Patent No:5,901,176
Date filed:October 16, 1997
Issued:May 4, 1999
Inventor:Richard S. Lewison
Assignee:Hewlett-Packard
Comments:Converting Delta-Sigma to PWM
High Power Efficiency Audio Power Amplifier with Digital Audio and Volume Inputs
Patent No:5,898,340
Date filed:October 20, 1996
Issued:April 27, 1999
Inventor:Manjirnath A. Chatterjee; Gregory R. Simon
Assignee:0
Comments:Volume control sets supply rails for switching amp
Class D Hearing Aid Amplifier with Feedback
Patent No:5,815,581
Date filed:October 19, 1995
Issued:September 29, 1998
Inventor:Olle Andersson
Assignee:Mitel
Comments:Interesting IC design of PWM based amplifier; feedback directly from switches
Silent Start Class D Amplifier
Patent No:5,805,020
Date filed:June 27, 1996
Issued:September 8, 1998
Inventor:George Edward Danz; Larry A. King; John K. Fogg
Assignee:Harris
Comments:A switch(or variable element) kills the gain of the loop integrator at start-up in a conventional PWM loop
Single Output Dual Supply Class D Amplifier
Patent No:5,798,672
Date filed:July 9, 1996
Issued:August 25, 1998
Inventor:Marco Masini; Claudio Tavazzani; Stephania Boioccchi
Assignee:SGS-Thomson
Comments:Extension of multivibrator-type modulator to have supply feedforward; IC realization for split-supply sensing.
Single Pole Negative Feedback for Class D Amplifier
Patent No:5,796,302
Date filed:July 9, 1996
Issued:August 18, 1998
Inventor:Marco Masini; Stephania Boioccchi; Edoardo Botti
Assignee:SGS-Thomson
Comments:Multivibrator based PWM with feedback from the switching output
Method and Apparatus for Oversampled, Noise Shaping, Mixed-Signal Processing
Patent No:5,777,512
Date filed:June 19, 1996
Issued:July 7, 1998
Inventor:Adya S. Tripathi; Cary L. Delano
Assignee:Tripath
Comments:Cont. time Delta Sigma w/state & output FB
Switching Amplifier Closed Loop Dual Comparator Modulation Technique
Patent No:5,767,740
Date filed:September 27, 1996
Issued:June 16, 1998
Inventor:John K. Fogg
Assignee:Harris
Comments:Two comparators to get Full bridge signals, Differential feedback.
Method of Driving a Class D Audio Power Amplifier Using Non-Overlapping Edge Drive Signals
Patent No:5,729,175
Date filed:April 26, 1996
Issued:March 17, 1998
Inventor:Enrique Ferrer
Assignee:Motorola
Comments:Wow! Moto patents using deadtime to prevent shoot-through!
Class D Amplifier and Method
Patent No:5,672,998
Date filed:August 9, 1995
Issued:September 30, 1997
Inventor:Harold Allen Wittlinger
Assignee:Harris
Comments:Rather than using feedback to analog input, feedback is taken to a point after analog to single bit (ramp PWM in this case)
Digital Signal Processing for Linearization of Small Input Signals to a Tri-state Power Switch
Patent No:5,617,058
Date filed:November 13, 1995
Issued:April 1, 1997
Inventor:Andrew A. Adrian; Michael S Danielson; David B. Meyers; Leo Spiegel
Assignee:Apogee
Comments:Digital in; DSP compensates for low level distortion
Output Transformerless Amplifier Impedance Matching Apparatus
Patent No:5,612,646
Date filed:March 30, 1995
Issued:March 18, 1997
Inventor:David W. Berning
Assignee:
Comments:Push pull triode amp uses h.f. DC:DC techniques to couple high voltage output to loudspeaker load. (I guess a bunch of ferrite cores plus power devices are improvement over a large iron core transformerŠ)
Switching Amplifier with Impedance Transformation Output Stage
Patent No:5,610,553
Date filed:March 2, 1994
Issued:March 11, 1997
Inventor:Larry Kirn
Assignee:0
Comments:Unusual output has too many switches, but can drive load beyond nominal supply rails
Pulse Width Modulated Amplifier
Patent No:5,594,386
Date filed:April 21, 1995
Issued:January 14, 1997
Inventor:Timothy A. Dhuyvetter
Assignee:Sipex
Comments:Hysteretic loop closed with state feedback alone.
Stereo Audio Codec
Patent No:5,589,830
Date filed:November 2, 1994
Issued:December 31, 1996
Inventor:Alfredo R. Linz; Carlin D. Cabler; Glen W. Brown; Martin P. Soques
Assignee:AMD
Comments:Solid presentation of digital audio processing in well written patent
Digital Pulse Width Modulation Power Amplifier with Noise and Ripple Shaping
Patent No:5,559,467
Date filed:January 27, 1995
Inventor:September 24, 1996
Inventor:Keyue M. Smedley
Assignee:Regents of UC
Comments:Digital in, noise shaped, converted to PWM. No output feedback, but a feedforward of supply rails is implemented.
Reducing Switching Losses in a Phase-Modulated Switch-Mode Amplifier
Patent No:5,541,827
Date filed:May 17, 1995
Issued:July 30, 1996
Inventor:Lars P. Allfather
Assignee:Doble
Comments:Phase mod the half bridges, use overlapping clocks on secondary
Stabilization of Closed Loop Power Controllers
Patent No:5,521,549
Date filed:July 19, 1994
Issued:May 28, 1996
Inventor:Robert G. Nelson
Assignee:
Comments:Applies high order loop (similar to Modgil) to ramp type PWM loops
Composite Bridge Amplifier with Output overload and Thermal Protection
Patent No:5,510,753
Date filed:November 22, 1994
Issued:April 23, 1996
Inventor:John B. French
Assignee:Blade Technologies
Comments:Single ended power stage followed by a non-switching Full Bridge that merely sets the output polarity. Also includes over-current, overtemp protection
Pulse Width Modulation Amplifier
Patent No:5,508,663
Date filed:September 20, 1994
Inventor:April 16, 1996
Inventor:Fumiyasy Konno
Assignee:Matsushita
Comments:To eliminate the High DC offset caused by DC loop with high DC gain operational amplifiers (!?!), the DC gain of the loop amp is reduced to unity and inputs and feedback are AC coupled. (i.e open loop at DC to improve offset???)
Power Amplifier Circuit for Audio Signal and Audio Device Using the Same
Patent No:5,483,197
Date filed:September 26, 1994
Inventor:January 9, 1996
Inventor:Kei Nishioka; Masanori Fujisawa; Katsumi Kusaba
Assignee:Rohm
Comments:Full bridge linear amp has its supplies provided dynamically by a switching amp
Very Low Power Loss Amplifier for Analog Signals Utilizing Constant Frequency Zero Voltage Switching Multi-resonant Converter
Patent No:5,479,337
Date filed:November 30, 1993
Issued:December 26, 1995
Inventor:William C. Voigt
Assignee:Kaiser Aerospace
Comments:Multi-resonant loading of bridge to get low switching losses
Switching Regulator and Amplifier System
Patent No:5,442,317
Date filed:March 10, 1995
Issued:August 15, 1995
Inventor:Robert E. Stengel; David E. Muri; Enrique Ferrer
Assignee:Motorola
Comments:Input signal controls a DC:DC that supplies a full bridge. If DC:DC has continuous output, the bridge supplies only direction signal. If DC:DC has discrete outputs, then Bridge uses PWM
Distortion Compensation for a Pulsewidth-Modulated Circuit
Patent No:5,438,694
Date filed:August 9, 1993
Issued:August 1, 1995
Inventor:David L. Muri; Robert E. Stengel
Assignee:Motorola
Comments:Digital storage of distortion characteristics to predistort PWM. (Look-up table /microcontroller approach).
Means and Method of Enhancing Signal Resolution and Dynamic Range Extension in a Pulse Width Modulated Amplifier.
Patent No:5,422,597
Date filed:4/31/94
Issued:June 6, 1995
Inventor:Robert E. Stengel; David E. Muri; Enrique Ferrer
Assignee:Motorola
Comments:Output stages with large devices or tiny devices are selectively used as output requires to maximize efficiency
Class'D' Audio Speaker Amplifier with State Variable Feedback
Patent No:5,410,592
Date filed:June 4, 1993
Issued:April 25, 1995
Inventor:Randall M. Wagner; Yogi L. Mistry
Assignee:Harris
Comments:State Variable voltage and current feedback
Pulse Width Modulation Speaker Amplifier
Patent No:5,398,003
Date filed:March 30, 1994
Issued:March 14, 1998
Inventor:Lawrence F. Heyl; Steven E. Austin
Assignee:Apple Computer
Comments:Open loop amplifier with volume control, PCM input, Offset elimination (on input signal), dynamic range control, etc.
Output Limiter for Class D BiCMOS Hearing Aid Output Amplifier
Patent No:5,389,829
Date filed:September 30, 1992
Issued:February 14, 1995
Inventor:Ciro Milazzo
Assignee:Exar
Comments:limiter is digital pulse qualification following modulator that enforces a minimum/maximum duty cycle.
Pulsewidth-Modulated Amplifier Having Analog Mode
Patent No:5,382,915
Date filed:July 6, 1993
Issued:January 17, 1995
Inventor:David L. Muri; Robert E. Stengel
Assignee:Motorola
Comments:Dual mode amplifier switches to analog mode for low signal levels
Closed Loop Power Controller
Patent No:5,352,986
Date filed:January 22, 1993
Issued:October 4, 1994
Inventor:Onkar S. Modgil; Robert G. Nelson; Margaret S. Reif
Assignee:Digital Fidelity
Comments:Higer order loop in triangle PWM (high loop gain in-band)
Amplification Circuit
Patent No:5,347,230
Date filed:June 17, 1992
Issued:September 13, 1994
Inventor:Masao Noro
Assignee:Yamaha
Comments:Class G with self-tracking PWM rails
Pulse Width Modulation Amplifier
Patent No:5,262,733
Date filed:March 9, 1992
Issued:November 16, 1993
Inventor:Yasafumi Nakajima; Toshihiko Oohashi
Assignee:Matsushita
Comments:Simple ramp PWM but ramp is proportional to supply for gain feedforward
Four Quadrant Current Mode Switching Amplifier
Patent No:5,225,789
Date filed:April 17, 1992
Issued:July 6, 1993
Inventor:Steven L. Caine, Mahlon D. Kimbrough
Assignee:Nortel
Comments:current traffo reports current info; odd power architecture
Switching Amplifier
Patent No:5,218,315
Date filed:January 6, 1992
Issued:June 8, 1993
Inventor:Wheeler M. Turner
Assignee:Infinity
Comments:hysteretic modulator with additional pole plus a delay element in the loop
Pulse Duration Amplifier System Having Distortion Reduction
Patent No:5,216,376
Date filed:June 10, 1992
Issued:June 1, 1993
Inventor:Hilmer J. Swanson
Assignee:Harris
Comments:Multiple amplifiers paralleled; feedforward correction for supply variations
Class D loop
Patent No:5,160,896
Date filed:February 18, 1992
Issued:November 3, 1992
Inventor:David P. McCorkle
Assignee:Harman Intl.
Comments:Hyst. Loop w/ supply and input dependent hysteresis, CM/DM filtering, muting, sleep functionality
Dual Feedback Control for a High-Efficiency Class-D Power Amplifier Circuit
Patent No:5,118,997
Date filed:August 16, 1991
Issued:June 2, 1992
Inventor:Sayed-Amr A. El Hamamsy
Assignee:GE
Comments:For ballast operation; two control loops adjust resonant network to optimize efficiency
Class D MOSFET Amplifier and Voltage Supply Balance Circuit Therefor
Patent No:5,117,198
Date filed:April 8, 1991
Issued:May 26, 1992
Inventor:Kenneth Morrenz
Assignee:
Comments:Avoiding body diode conduction by splitting output inductor; similar scheme can be used to control supply pumping
Power Amplifier for Feeding an Inductor with Switched Transistors
Patent No:5,113,145
Date filed:February 27, 1991
Issued:May 12, 1992
Inventor:Karl-Heniz Ideler; Stefan Nowak; Gunter Petzold
Assignee:Siemens
Comments:Interesting high power scheme; changes to bridge to aid parallel ling, mechanical/thermal design
Minimum Pulse Width Switching Power Amplifier
Patent No:5,077,540
Date filed:June 14, 1990
Issued:December 31, 1991
Inventor:F. Joseph Keith; Eric H. Maslin
Assignee:U. of Virginia
Comments:Minimum pulse width digital qualification in a loop with loop closed around output current
Switching Amplifier
Patent No:5,077,539
Date filed:December 26, 1990
Issued:December 31, 1991
Inventor:John R. Howett
Assignee:Apogee
Comments:3 state, optional 4th state is analog amp, selected based on _signal_level_
Composite Bridge Amplifier with Output overload and Thermal Protection
Patent No:5,075,634
Date filed:November 23, 1990
Issued:December 24, 1991
Inventor:John B. French
Assignee:Blade Technologies
Comments:Half Bridge provides PWM, direction into load is from baseband fullbridge steering.
Switching Amplifier
Patent No:5,014,016
Date filed:April 13, 1989
Issued:May 7, 1991
Inventor:James R. Anderson
Assignee:Beltone
Comments:Basic PWM full bridge. Two half bridges modulated independently; three state switching results.
Audio Amplifier with Phase Modulated Pulse Width Modulation
Patent No:4,992,751
Date filed:October 17, 1989
Issued:February 12, 1991
Inventor:Brian E. Attwod; Larry E. Hand; Fred C. Santillano
Assignee:Peavey
Comments:Excellent teaching; Shows development of PM bridge using diode/FET bidirectional switches. System shown is open loop.
Ultra Efficient Switching Power Amplifier
Patent No:4,980,649
Date filed:July 8, 1989
Issued:December 25, 1990
Inventor:Zdzislaw Gulezynski
Assignee:
Comments:Transformer plus two bidirectional switches allow four quadrant output; bad class B and odd switching
Pulse Width Modulation Amplifier Circuit
Patent No:4,968,948
Date filed:July 14, 1989
Issued:November 6, 1990
Inventor:Aiko Tokumo; Masayuki Kato; Takeshi Sato; Tatsuzo Hasegawa
Assignee:Pioneer
Comments:Two sides of bridge driven from in-phase clocks; common mode choke with low (audio freq) cutoff can be used.
Pulse Width Modulation Amplifier Circuit
Patent No:4,952,884
Date filed:August 3, 1989
Issued:August 28, 1990
Inventor:Aiko Tokumo; Masayuki Kato; Takeshi Sato; Tatsuzo Hasegawa
Assignee:Pioneer
Comments:Radiation is reduced by wobble (FM the carrier with random signal)
Pulse Width Modulation Amplifier Circuit
Patent No:4,949,048
Date filed:November 3, 1989
Issued:August 14, 1990
Inventor:Aiko Tokumo; Masayuki Kato; Takeshi Sato; Tatsuzo Hasegawa
Assignee:Pioneer
Comments:Two sides of bridge driven from separate modulators from quadrature clocked PWMs
Digital Audio Amplifier
Patent No:4,724,396
Date filed:August 21, 1984
Issued:January 13, 1986
Inventor:Wilson E. Taylor; Larry R. Hand
Assignee:Peavey
Comments:Improved version of Peavey's clipping detection via missing pulses; limiting scheme based on reducing gain near clipping.
Digitally Driven Switching Power Amp System
Patent No:4,683,439
Date filed:January 9, 1986
Issued:July 28, 1987
Inventor:Jay W. Atherton; Raymond A. Castor; Leonard F Christie; Robert C. Engerman
Assignee:Honeywell
Comments:Open loop digital amp; shows conversion to PWM, for digitally synthesized signals
Apparatus and Method for Muting an Output Signal in a Switching Amplifier
Patent No:4,673,889
Date filed:December 16, 1985
Issued:June 16, 1987
Inventor:Carlo Cini; Claudin Diazzi; Pietro Erratico
Assignee:SGS Microelettronica
Comments:Muting and turn-on pop reduction by gating and clamping points in the loop
Power Control System
Patent No:4,673,888
Date filed:September 2, 1986
Issued:June 16, 1987
Inventor:Rudolph H. Engelman; Thad Early
Assignee:Electro-Voice
Comments:Multi-level switching to drive loudspeaker
Digital Driver for Fixed Power Amplifier
Patent No:4,673,887
Date filed:January 3, 1986
Issued:June 16, 1987
Inventor:Jay W. Atherton
Assignee:Honeywell
Comments:analog->digital->phase modulated->full bridge
Digital Audio Amplifier Having High Power Output Level and Low Distortion
Patent No:4,600,891
Date filed:August 21, 1984
Issued:July 15, 1986
Inventor:Wilson E. Taylor; Larry R. Hand
Assignee:Peavey
Comments:NICE teaching, detects overload by missing pulses, Compensates for body diode errors, sophisticated output filter, nested feedback
Switching Amplifier System
Patent No:4,573,018
Date filed:April 19, 1984
Issued:February 25, 1986
Inventor:Fred Mirow
Assignee:
Comments:Traffo coupled power stage followed by polarity switch; basically DC:DC with split variable outputs and a post-filter switch to tie load to the proper polarity. A really bad class-B PWM approach
Flyback Modulated Power Amplifier
Patent No:4,571,551
Date filed:February 28, 1984
Issued:February 18, 1986
Inventor:Wesley H. Trager
Assignee:Washington Innovative Technology
Comments:Flyback control is odd: Don't switch while body diode conducts; forces output current to drop to zero every cycle (why?)
Power Amplifier
Patent No:4,560,946
Date filed:March 21, 1984
Issued:December 24, 1985
Inventor:Kenji Yokoyama
Assignee:Nippon Gakki
Comments:High voltage, high efficiency amp drives one end of load, a low voltage high quality amp drives the other.
Switching Amplifier for Digital Power Amplification
Patent No:4,560,944
Date filed:April 18, 1984
Issued:December 24, 1985
Inventor:Andreas Furrer
Assignee:Brown Boveri
Comments:Another multi-level switching scheme, with interesting interleaving.
Switching Amplifier with MOSFET Driver Circuit
Patent No:4,554,512
Date filed:November 19, 1985
Issued:November 19, 1985
Inventor:Michael E. Aiello
Assignee:Aerotech
Comments:PWM full bridge uses RF carrier through tiny gate drive transformers for level shift
Pulse Width Modulation Amplifier Circuit
Patent No:4,531,096
Date filed:September 28, 1983
Issued:July 23, 1985
Inventor:Kenji Yokoyama
Assignee:Nippon Gakki
Comments:Adds BBM, second order loop amplifier, feedback from switches
Pulse Width Modulation Circuit with Carrier Signal Frequency Control
Patent No:4,524,335
Date filed:March 10, 1983
Issued:June 18, 1985
Inventor:Kenji Yokoyama
Assignee:Nippon Gakki
Comments:PWM frequency is made a function of signal; Triangle PWM emulates hysteretic loop? Justification is actually funny.
High Efficiency Feedforward-Error-Correction Amplifier
Patent No:4,523,152
Date filed:March 30, 1983
Issued:June 11, 1985
Inventor:Peter Garde
Assignee:Unisearch Ltd.
Comments:Analog amp corrects errors in switching output; in final version analog amp doubles as loop error amp (as with Walker)
Switching Amplifier
Patent No:4,510,457
Date filed:January 10, 1983
Issued:April 9, 1985
Inventor:Andreas Furrer; Johann Milavec
Assignee:Brown Boveri
Comments:Multiple amps summed on secondaries
Protection Circuit for Switching Amplifier
Patent No:4,509,101
Date filed:August 15, 1983
Issued:April 2, 1985
Inventor:Kenji Yokoyama
Assignee:Nippon Gakki
Comments:Current limiting scheme senses current from the rails
Pulse Width Modulation Circuit with Carrier Signal Frequency Control
Patent No:4,504,793
Date filed:January 4, 1983
Issued:March 12, 1985
Inventor:Kenji Yokoyama
Assignee:Nippon Gakki
Comments:A feedback loop is placed around a ramp PWM, improving linearity (imagine that!)
Method and Apparatus for Amplifying an Analog low Frequency Signal by a Switching Amplifier
Patent No:4,488,121
Date filed:January 28, 1982
Issued:November 11, 1984
Inventor:Andreas Furrer; Vaclau Mertl; Johann Milavec; Herbert Stemmler
Assignee:Brown Boveri
Comments:Multi-level switched amp. One of the worst-taught patents I've ever seen!
Pulse Width Modulated Power Amp
Patent No:4,484,145
Date filed:December 8, 1981
Issued:November 20, 1984
Inventor:Tord L. Haulin
Assignee:Ericsson
Comments:Using PWM on push-pull primary, fixed 50% or zero on independent bilateral secondary switches
Phase Modulated Switchmode Power Amplifier and Waveform Generator
Patent No:4,479,175
Date filed:August 13, 1982
Issued:October 23, 1984
Inventor:Robert A. Gille; Norman G. Planer; Zoltan Zansky
Assignee:Honeywell
Comments:Four switch Phase modulation scheme, shown as push-pull. Four quadrant output at fixed frequency and fixed (50%) duty cycle. Henceforth referenced in relation to co-inventor Zansky, who promoted this scheme.
Power Amplifier
Patent No:4,476,436
Date filed:August 25, 1981
Issued:October 9, 1984
Inventor:Akio Koizumi; Hiroshi Yamagishi
Assignee:Sony
Comments:Amplitude modulating the base drive for bipolar PWM
Hybrid Pulse Width Modulated Audio Amplifier
Patent No:4,471,314
Date filed:June 15, 1981
Issued:September 11, 1984
Inventor:Charles R. Lindberg
Assignee:
Comments:Put any switching amp on a hybrid substrate (how novel!)
Pulse Width Modulated Signal Amplifier
Patent No:4,458,208
Date filed:April 9, 1982
Issued:July 3, 1984
Inventor:Miki Abe
Assignee:Sony
Comments:PWM loop is held in low gain open loop during startup
Dual Mode Amplifier
Patent No:4,446,440
Date filed:January 26, 1982
Issued:May 1, 1984
Inventor:R. Frank Bell
Assignee:Hewlett-Packard
Comments:PWM at high levels, switches to linear for small signals
Class D Pulse Width Modulated Amplifier
Patent No:4,439,738
Date filed:October 12, 1981
Issued:March 27, 1984
Inventor:Jay W. Atherton
Assignee:Honeywell
Comments:Transformer coupled, a switch shorts the transformer during deadtime
Power Amplifier
Patent No:4,430,625
Date filed:June 23, 1981
Issued:February 7, 1984
Inventor:Kenji Yokoyama
Assignee:Nippan Gakki
Comments:Linear amp with Class G output has additional dynamic class D amp to drive nominal supplies in the class G to improve efficiency. (Only would go true class G if PWM amp failed to keep up with the signal swing).
Pulse Width Modulation Amplifier
Patent No:4,415,863
Date filed:March 24, 1981
Issued:November 15, 1983
Inventor:Akio Tokumo
Assignee:Pioneer
Comments:Ramp PWM uses feedback from switching output
Pulse Width Modulated Amplifier
Patent No:4,415,862
Date filed:March 24, 1981
Issued:November 15, 1983
Inventor:Yoshiro Konugi
Assignee:Pioneer
Comments:Two stereo channels have common clock, but produce outputs that are 90 degrees out, to minimize switching interaction.
Amplifier Employing Digital Modulator Circuit
Patent No:4,403,197
Date filed:October 26, 1981
Issued:September 6, 1983
Inventor:Hilmer I. Swanson
Assignee:Harris
Comments:Binary weighted signals summed into transmitter, PWM between Digital values for more resolution
Pulse Width Modulated Power Amplifier with Differential Connecting Line Voltage Drop Comparator
Patent No:4,403,196
Date filed:April 22, 1981
Inventor:September 6, 1983
Inventor:Paul E. Grandmont
Assignee:US Air Force
Comments:Compensates for cabling drop: If one has access to load, why not just close the loop there???
Audio Power Amp with Class-D Push-Pull Output Stage
Patent No:4,390,849
Date filed:April 28, 1981
Issued:July 28, 1983
Inventor:Leslie Miskin
Assignee:ITT
Comments:Digital input takes high order bits to PWM, lower bits drive A/D that modifies pulse amplitude. Walker is referenced, as are Vanderkooy & Lipshitz, who extended Walkers current dumper to a switching amp.
Power Amplifier Connection
Patent No:4,390,846
Date filed:January 21, 1981
Issued:June 28, 1983
Inventor:Gunnar Cragfors; Jurgen Bosson
Assignee:ASEA Actiebolag
Comments:Linear Amp corrects output via feedback; Switching amp driven from error signal in linear amp.
Digitally Driven Combination Coils for electrodynamics Acoustic Transducer
Patent No:4,360,707
Date filed:November 24, 1980
Issued:November 23, 1982
Inventor:Joel R. Joseph; William F. Bleeke
Assignee:CTS
Comments:Two single ended anti-phase drives for opposing coils on loudspeaker.
Pulse Width Modulated Signal Amplifier
Patent No:4,347,481
Date filed:May 19, 1980
Issued:March 31, 1982
Inventor:Tadao Yoshida
Assignee:Sony
Comments:Separate supplies for (bipolar) switches and freewheeling diodes to minimize the difference in output voltage as a function of current direction
Multi-Channel Audio Power Amplifier
Patent No:4,346,349
Date filed:May 7, 1980
Issued:August 24, 1982
Inventor:Kenji Yokoyama
Assignee:Nippon Gakki
Comments:Summing a switching (LF) and linear (HF) amp in single loop. Neglects to reference PJ Walker!
Pulse-Width Modulator Circuit
Patent No:4,337,438
Date filed:February 13, 1980
Issued:June 29, 1982
Inventor:Water Guggenbuhl; Mathis Halder
Assignee:LGZ Landis
Comments:A notch filter in the output low-pass includes a means to force the oscillator to stay tuned to the notch.
PWM Signal Power Amplifier
Patent No:4,249,136
Date filed:May 22, 1979
Issued:February 3, 1981
Inventor:Tadao Suzuki; Tadeo Yoshida
Assignee:Sony
Comments:Feedback from output closes around integrator, comparator, output stage. (First order loop)
Linearized Three state Switching Amplifier
Patent No:4,240,036
Date filed:April 13, 1979
Issued:December 15, 1980
Inventor:Thomas P. Kohler
Assignee:GE
Comments:This is class AB approach to improve prior art, well-known three-state switching approach
Class D Amplifier System
Patent No:4,178,556
Date filed:April 19, 1978
Issued:December 11, 1979
Inventor:Brian E. Attwood
Assignee:0
Comments:Nested feedback loops around triangle type PWM
Pulse Width Modulated Signal Amplifier with Protective Means
Patent No:4,167,710
Date filed:October 28, 1977
Issued:September 11, 1979
Inventor:Tadao Suzuki; Tadeo Yoshida
Assignee:Sony
Comments:Supply pumping on LF signals is detected and the amp is shut down if supply exceeds a max value. (First Sony patent showing MOS output stage)
Polyphase PDM Amplifier
Patent No:4,164,714
Date filed:September 26, 1977
Issued:August 14, 1979
Inventor:Hilmer J. Swanson
Assignee:Harris
Comments:Multiple PWMs from n-phase clocks summed (into transmitter)
Amplifier Systems
Patent No:4,162,455
Date filed:January 4, 1978
Issued:July 24, 1979
Inventor:David R. Birt
Assignee:Communications Patents Ltd.
Comments:Two power stages with anti-phase ripple feed load.
High Efficiency Amplifier
Patent No:4,153,882
Date filed:March 24, 1978
Issued:May 8, 1979
Inventor:Charles B. Fisher; Sidney T. Fisher
Assignee:0
Comments:Multi-level based on switching multiple transformer taps on both primary and secondary for Nyquist rate conversion
Negative Feedback Amplifier of PWM-Type
Patent No:4,144,502
Date filed:October 26, 1977
Issued:March 13, 1979
Inventor:Yuji Ikeda
Assignee:Sansui
Comments:Basic scheme with feedback from the load. Adding ESR to the cap introduces a zero which helps stability.
Pulse Width Modulated Amplifier
Patent No:4,059,807
Date filed:October 29, 1975
Issued:November 22, 1977
Inventor:Osamu Hamade
Assignee:Sony
Comments:Absolute classic PWM amp; single integrator in loop with Ramp PWM modulator, feedback from after output filter.
Pulse Width Modulated Signal Amplifier
Patent No:4,021,745
Date filed:December 16, 1975
Issued:March 3, 1977
Inventor:Tadao Suzuki; Tadeo Yoshida
Assignee:Sony
Comments:Single integrator loop with feedback from switches; loop integrator also integrates square clock to create [ramp + integrated error] signal
Switching Amplifier System
Patent No:4,016,501
Date filed:December 29, 1975
Issued:April 5, 1977
Inventor:Leon Jasinski; Francis Robert Steed
Assignee:Motorola
Comments:Half bridge with unipolar PWM into directional switching Bridge around load.
Pulse Width Modulated Signal Amplifier
Patent No:4,015,213
Date filed:February 23, 1976
Issued:March 29, 1977
Inventor:Osamu Hamade
Assignee:Sony
Comments:Loop similar to hysteretic with feedback from switch output, but on-time is set by linear ramp; off-time by the loop integrator.
Pulse Width Modulated Signal Amplifier
Patent No:4,004,246
Date filed:March 3, 1975
Issued:January 18, 1977
Inventor:Osamu Hamade
Assignee:
Comments:Full Bridge PWM with differential feedback from load
Pulse Width Modulated Signal Amplifier
Patent No:3,999,143
Date filed:December 16, 1975
Issued:December 21, 1976
Inventor:Tadao Yoshida; Tadao Suzuki
Assignee:Sony
Comments:Bipolars lack body diodes. A scheme for connecting diodes to a rail lower than nominal VDD; eliminating the step change going from sourcing to sinking.
Distortion Free Amplifier
Patent No:3,970,953
Date filed:January 10, 1975
Issued:July 20, 1976
Inventor:P.J> Walker; Michael Peter Albinson
Assignee:Acoustic Mfg Co
Comments:Quad 405 Current Dumping amp; Using small high quality feedforward amp to correct for current dumper (Class B in original patent) Both in Walker's published work and in other inventors' this was extended to using a PWM plus linear amp.
High Efficiency Switching Power Amplifier
Patent No:3,931,581
Date filed:September 30, 1974
Issued:January 6, 1976
Inventor:Louis J.Kush Jr.; Claus P. Janota, Richard D. Koontz, Leon H. Sibul
Assignee:Navy
Comments:Bipolar H bridge w/ base drive traffos; BBM, for LF sonar
Amplification System
Patent No:3,648,186
Date filed:March 24, 1970
Issued:March 7, 1972
Inventor:Leonard R. Kahn
Assignee:Kayn Research
Comments:PWM modulates class C amp, which gives power gain. RF output is detected back to baseband. Two opposing schemes give (class B) bipolar output. (OK, I admit - this makes the list as my token vacuum tube switching amp!)
Power Amplifier
Patent No:3,636,380
Date filed:September 4, 1970
Issued:January 18, 1972
Inventor:Vernon A. Anderson
Assignee:US Navy
Comments:Self oscillating loop where active stages are comparator and power output. Feedback from switches fed back through unspecified feedback network.
High Efficiency Power Amplifier
Patent No:3,585,517
Date filed:May 1, 1968
Issued:June 15, 1971
Inventor:Roger B. Herbert
Assignee:Westinghouse
Comments:Class BD scheme with direct coupled bipolar full-bridge, three state switching, Ramp based PWM with feedback
Class D Linear Audio Amplifier
Patent No:3,579,132
Date filed:November 14, 1969
Issued:May 18, 1971
Inventor:James A. Ross
Assignee:LTV Ling Altec
Comments:A means to drive transformer coupled drive signals of Full, Half bridges zero to 100% duty cycle; basic open loop ramp PWM architecture
Simplified Pulse Width Modulated Amplifier
Patent No:3,509,479
Date filed:November 29, 1966
Issued:April 28, 1970
Inventor:George C. Gucker; Paul H. Daitch
Assignee:Sperry
Comments:Feedback PWM (square wave injected into Gm-C integrator cap); Output stage is 3-state half bridge (Zero state is low Z)
High Efficiency RF Power Amplification with Modulation Signal Controlled ON-OFF Switch Varied Amplifier DC Potential
Patent No:3,413,570
Date filed:February 23, 1966
Issued:November 26, 1968
Inventor:Warren B. Breune; Tom L. Dennis Jr.; Edgar O. Schoenike
Assignee:Collins Radio
Comments:Switching Amp provides signal dependent rails for AM RF Amplifier
Solid State Switching Type Linear Amplifier
Patent No:3,400,334
Date filed:November 12, 1964
Issued:September 3, 1968
Inventor:James A. Ross; Tadeusz W. Maciejowski; Thomas R. Parkhill
Assignee:Ling-Temco-Vought
Comments:Ramp type open loop PWM with transformer coupled bipolar half bridge
Two-State Power Amplifier with Transitional Feedback
Patent No:3,336,538
Date filed:August 13, 1964
Issued:August 15, 1967
Inventor:Norman H. Crowhurst
Assignee:0
Comments:THREE state amplifier actually. Power stage is transformer coupled push-pull. At zero crossing, minimum pulse widths drive in either direction and are amplitude modulated (very advanced, unique.) Zero state is high Z. Feedback system with ramp modulator.
Modulator-Demodulator Amplifier
Patent No:3,253,228
Date filed:April 12, 1962
Issued:May 24, 1966
Inventor:Joseph Montner
Assignee:Aerojet
Comments:Open loop amp for inverters uses 3 state output; Power stage is transformer coupled bipolar push-pull, PWM modulator is ether ramp type or mag amp PWM (!!)
Control Apparatus Including a Switch and Both Positive and Negative Feedback
Patent No:3,225,216
Date filed:September 6, 1962
Issued:December 21, 1965
Inventor:John H. Grabowski
Assignee:Honeywell
Comments:Pos. feedback around switch gives more solid switching, but hysteresis. A global NFB can reduce the hysteresis. Additional NFB (delayed) creates a negative hysteresis in the form of a PWM. Interesting description of self-oscillating PWM modulator.
Controller Circuitry with pulse Width Modulator
Patent No:3,090,929
Date filed:December 18, 1959
Issued:May 21, 1963
Inventor:Francis T. Thompson
Assignee:Westinghouse
Comments:Minor loop feedback (I.e. local state feedback) linearizes modulator
Electric Signal Transmission System
Patent No:2,491,969
Date filed:October 14, 1946
Issued:December 20, 1949
Inventor:Paul Francois Marie Gloess
Assignee:Sadir Carpentier
Comments:Actually for distributing digital PWM signals; but is a feedback PWM scheme for improved linearity