SQUARE WAVE DRIVEN POWER AMPLIFIER

• US 3,815,030 A
• Filed: 07/13/1973
• Issued: 06/04/1974
• Est. Priority Date: 07/13/1973
• Status: Expired due to Term

• Current Assignee: Heber J. Morrison
• Original Assignee: Heber J. Morrison
• Inventors: Morrison, Heber J.
• Primary Examiner(s): Heyman, John S.
• Assistant Examiner(s): Davis, B. P.
• Application Number:
  US05/379,156
• Time in Patent Office: 326 Days
• Field of Search: 328/27,28,14,62 307/229
• US Class Current: 327/129
• CPC Class Codes: H03F 3/2178 using more than one switch or switching amplifier in parallel or in series H03F3/2173, H03F3/2175 take precedence

Abstract

A high power semiconductor amplifier which may be used as a power amplifier for low frequency apparatus such as radio transmitters and/or welding apparatus. A plurality of transistor driven amplifier sections are commonly driven by a square wave source and are coupled in parallel to a common load through loosely electro-magnetic coupled transformers or inductances forming the power combiner circuit. The loose coupling provides a desired low distributive capacitance and high leakage inductive reactance. Each amplifier driver section moreover is coupled to the transformer by a DC blocking capacitor having a selected capacitance value so that a series resonant circuit is formed with the combiner circuit leakage reactance near the center of the operating frequency band. Furthermore, the combiner circuit is coupled to the load by means of a harmonic filter having a series inductance input which acts to present a high reactive impedance to harmonics in the square wave voltage applied thereto so that a substantially sine wave of voltage and current is applied to the load.

Claims

1. A relatively high power amplifier comprising in combination:

a square wave signal source;

a plurality of signal amplifier sections commonly coupled to the output of said square wave signal source, each amplifier section operating to individually provide an amplified square wave output;

inductive combining circuit means having a relatively low distributed capacitance and a relatively high leakage reactance, coupled to said plurality of amplifier sections and providing a relatively high power square wave output;

respective capacitance coupling means coupling the square wave output of each of said plurality of amplifier sections to said combining circuit means, each coupling means having a selected capacitance value which in combination with said leakage reactance of said combining circuit means is adapted to resonate in the operating frequency band of said square wave signal source;

a resonant network having a low impedance to the fundamental frequency of the square wave output of said combining circuit means while attenuatng the harmonic frequencies of said fundamental frequencies and thereby provide a sine wave output of current and voltage; and

a load coupled to the harmonic filter and being responsive to the sine wave of current and voltage provided thereby.

2. The power amplifier as defined by claim 1 wherein said respective capacitance coupling means comprises a respective series connected capacitor coupled between the output of each of said plurality of amplifier sections to said combining circuit means and wherein each said capacitor series resonates with the leakage reactance at said combining circuit means.

3. The high powered amplifier as defined by claim 2 wherein said combining circuit means comprises transformer means.

4. The power amplifier as defined by claim 3 wherein said transformer means comprises a loose electro-magnetically coupled transformer having a plurality of primary windings individually coupled to said plurality of amplifier sections and a common output winding coupled to said resonant network.

5. The power amplifier as defined by claim 4 wherein all of said plurality of primary windings are coupled to the respective amplifier sections in the same polarity relationship.

6. The power amplifier as defined by claim 2 wherein said combining circuit means comprises a respective plurality of transformers, each having a loosely coupled primary winding and secondary winding, wherein each of said primary windings is coupled to the respective amplifier section in the same mutual polarity relationship, and wherein the secondary winding of said plurality of transformers are connected in series aiding circuit relationship across said harmonic network and said load, said resonant network and said load being connected in series.

7. The power amplifier as defined by claim 2 wherein said inductive combining circuit means comprises a respective plurality of transformers, each having a primary and a secondary winding and being constructed to have relatively loose electromagnetic coupling therebetween thereby providing relatively low distributive capacitance and relatively high leakage reactance, each primary winding being coupled to the output of a respective signal amplifier section and said secondary winding of said plurality of transformers being selectively connected to said resonant network.

8. The power amplifier as defined by claim 7 wherein each primary winding is coupled to the respective amplifier section in the same mutual polarity.

9. The power amplifier as defined by claim 8 wherein the plurality of secondary windings are coupled in parallel in the same polarity sense to the resonant network.

10. The power amplifier as defined by claim 7 wherein the plurality of transformers are comprised of air core transformers.

11. The power amplifier as defined by claim 2 wherein said resonant network and said load are connected in series and wherein said inductive combining circuit means comprises a first inductor for each of said signal amplifier sections connected to each said capacitor, said series combination being connected to said resonant network, and a second inductor for each of said signal amplifying sections coupled between one side of the load and said respective amplifying section.