Parallel-resonant bridge inverter

• US 6,229,718 B1
• Filed: 10/02/1989
• Issued: 05/08/2001
• Est. Priority Date: 10/05/1984
• Status: Expired due to Fees

• Current Assignee: Ole K Nilssen
• Original Assignee: Ole K Nilssen
• Inventors: Nilssen, Ole K.
• Primary Examiner(s): BERHANE, ADOLF D
• Application Number:
  US07/952,303
• Time in Patent Office: 4,236 Days
• Field of Search: 361/131 R, 315/209 R, 315/DIG. 7, 315/DIG. 5, 315/244, 315/209, 315/243, 315/219, 315/227 R, 315/200 R, 315/207, 315/208, 315/86, 315/307, 315/297, 315/246, 315/278 , 315/287, 315/224, 363/17, 363/98, 363/132, 363/36, 363/37, 363/136
• US Class Current: 363/37
• CPC Class Codes: H03K 3/30 using a transformer for feedback, e.g. blocking oscillator
• CPC Class Codes: H05B 41/2827 using specially adapted components in the load circuit, e.g. feed-back transformers, piezoelectric transformers; using specially adapted load circuit configurations
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps

Abstract

Power to a self-oscillating full-bridge inverter is supplied from a center-tapped DC voltage source through an inductor means having two separate windings on a common magnetic core—with one winding being positioned in each leg of the power supply. The full-bridge inverter, which comprises four switching transistors connected in usual full-bridge fashion, is loaded by way of a center-tapped parallel-tuned L-C circuit connected across the bridge output, thereby providing a sinusoidal voltage at its output. Due to the effect of the inductor means, the current provided to the bridge is substantially constant during a complete period of the inverter'"'"'s oscillation.

The arrangement is completely symmetrical, which provides for the center-tap of the DC voltage source to be at the same potential as the center-tap of the parallel-tuned L-C circuit.

Claims

1. An inverter powered from a constant-magnitude DC voltage by way of a first sub-assembly and providing, between a first and a second output terminal, an alternating output voltage having a periodic and substantially sinusoidal waveshape, said waveshape having a cyclical period, said first sub-assembly being operative to cause any current flowing from the DC voltage supply to the inverter to remain substantially constant during the time-length of said cyclical period, said inverter comprising:

a first and a second pair of series-connected switching transistors, each transistor having a control input terminal, said first pair of transistors each having a terminal that is connected with a first junction, said second pair of transistors each having a terminal that is connected with a second junction;

the first and second junctions being galvanically connected with the first and second output terminals, respectively; and

second sub-assembly connected between said junctions and in circuit with each transistor'"'"'s control terminal, said second sub-assembly comprising a tuned circuit and a third sub-assembly functional to cause said transistors to switch on and off in a time-pattern operative to cause said output voltage to have said periodic and substantially sinusoidal waveshape.

2. The inverter of claim 1 wherein said tuned circuit is a parallel-tuned circuit.

3. The inverter circuit of claim 1 wherein said output sub-assembly has an output center-tap.

4. The inverter of claim 3 wherein said DC voltage supply has a set of supply terminals between which there exists an effective short circuit for currents of frequency about equal to that of the alternating output voltage, whereby any alternating voltage existing between any one of said supply terminals and said output center-tap has substantially zero magnitude.

5. The inverter of claim 4 wherein said DC voltage supply has a supply center-tap and where said output center-tap is connected with said supply center-tap.

6. The inverter of claim 1 wherein said first sub-assembly comprises a current-transformer device operative to provide intermittent drive current to the control terminal of each of said transistors, the presence of said drive current being operative to turn a transistor on, the magnitude of said drive current being substantially proportional to the magnitude of the current flowing between said junctions.

7. The inverter of claim 6 wherein said current-transformer device is characterized by being saturable.

8. The inverter of claim 1 and circuitry operative to cause said waveshape to comprise a short period of substantially zero voltage magnitude.

9. The inverter of claim 1 wherein said first sub-assembly comprises two separate windings on a common magnetic core.

10. Inverter circuit operable to be powered from a constant-magnitude DC voltage supply and to provide, between a first and a second output terminal, a periodic alternating output voltage having an overall periodic waveshape that may be characterized as consisting of periods with sinusoidally varying voltage interconnected with periods of substantially non-varying voltage, said periodic waveshape having a complete period, said inverter circuit comprising:

a pair of DC input terminals;

a first and a second pair of series-connected switching transistors, each pair being connected across said DC input terminals, each transistor having control input terminals, said first pair of transistors each having a terminal that is connected with a first junction, said second pair of transistors each having a terminal that is connected with a second junction;

the first and second junctions being galvanically connected with the first and second output terminals, respectively;

a first sub-assembly connected in circuit between said DC voltage source and said pair of DC input terminals, said first sub-assembly being operative to prevent any current flowing between said DC voltage supply and said DC input terminals from changing by any substantial degree during the time-length of said complete period; and

a second sub-assembly connected between said junctions and in circuit with said control input terminals, said second sub-assembly being characterized by comprising a tuned circuit as well as a third sub-assembly operative to cause said transistors to switch on and off in a time-pattern that, in turn, is operative to cause said output voltage to attain said overall periodic waveshape.

11. The inverter circuit of claim 10 wherein said periods of substantially non-varying voltage have a time-length of near-zero duration.

12. The inverter of claim 10 wherein said second sub-assembly has a center-tap connected with a terminal of said DC voltage supply.

13. The inverter of claim 10 wherein said third sub-assembly comprises two inductively coupled but separate windings, one of said windings being connected with one of said DC input terminals;

the other one of said windings being connected with the other one of said DC input terminals.

14. An arrangement comprising:

DC voltage source operative to provide a constant-magnitude DC voltage between a first and a second DC terminal;

the DC voltage source having a center-tap;

the first DC terminal having a first DC potential with respect to the center-tap;

the second DC terminal having a second DC potential with respect to the center-tap;

the absolute magnitude of the first DC potential being approximately equal to that of the second DC potential;

an inverter having;

(i) a B+ input terminal and a B−

input terminal; and

(ii) a first and a second transistor, each having a first and a second terminal;

the first terminal of the first transistor being directly connected with the B−

terminal;

the second terminal of the first transistor being directly connected with the first terminal of the second transistor as well as with an inverter output terminal;

the second terminal of the second transistor being directly connected with the B+ terminal;

the two transistors being substantially identical to each other; and

an inductor device having a first and a second winding;

the first winding having a first and a second terminal;

the second winding having a first and a second terminal;

the first winding being coupled with the second winding such that the instantaneous magnitude of any voltage present between the first and second terminal of the first winding is substantially equal to that of any voltage present between the first and the second terminal of the second winding;

the first terminal of the first winding being connected with the first DC terminal;

the second terminal of the first winding being connected with the B+ terminal;

the second terminal of the second winding being connected with the second DC terminal;

the first terminal of the second winding being connected with the B−

terminal;

the arrangement being operative to provide an AC voltage between the inverter output terminal and the center-tap.

15. The arrangement of claim 14 wherein the AC voltage has a fundamental period that is substantially shorter than that of the power line voltage present on an ordinary electric utility power line.

16. The arrangement of claim 15 wherein a first current of a first instantaneous magnitude is flowing through the first winding and a second current of a second instantaneous magnitude is flowing through the second winding;

the sum of the first instantaneous magnitude and the second instantaneous magnitude remaining substantially constant over the duration of said fundamental period.

17. The arrangement of claim 14 wherein the inverter also has a third and a fourth transistor as well as another inverter output terminal;

another AC voltage being provided between the other inverter output terminal and the center-tap.

18. The arrangement of claim 14 wherein the AC voltage has a substantially sinusoidal waveform.

19. The arrangement of claim 14 wherein any alternating voltage existing between the first DC terminal and the second DC terminal, as well as between the first DC terminal and the center-tap, is of negligible magnitude.

20. The arrangement of claim 19 wherein the AC voltage has a substantially sinusoidal waveform.

21. An arrangement comprising:

DC voltage source operative to provide a constant-magnitude DC voltage between a first and a second DC terminal;

any alternating voltage existing between the first and second DC terminals being of negligible magnitude;

inverter circuit having;

(i) a B+ input terminal and a B−

input terminal; and

(ii) a first and a second transistor, each having a first and a second terminal;

the first terminal of the first transistor being directly connected with the B-terminal;

the second terminal of the first transistor both being connected with an inverter output terminal;

the second terminal of the second transistor being directly connected with the B+ terminal;

the first transistor being substantially identical to the second transistor; and

an inductor having a first and a second winding;

the first winding having a first and a second terminal;

the second winding having a first and a second terminal;

the first winding being coupled with the second winding such that the instantaneous magnitude of any voltage present between the first and second terminal of the first winding is substantially equal to that of any voltage present between the first and the second terminal of the second winding;

the first terminal of the first winding being galvanically connected with the first DC terminal;

the second terminal of the first winding being galvanically connected with the B+ terminal;

the second terminal of the second winding being galvanically connected with the second DC terminal;

the first terminal of the second winding being galvanically connected with the B−

terminal;

the arrangement being operative to provide an AC voltage between the inverter output terminal and the center-tap.

22. The arrangement of claim 21 further characterized in that any alternating voltage existing between the center-tap and either one of the DC terminals is of negligible magnitude.

23. The arrangement of claim 22 wherein the AC voltage is further characterized as being of substantially sinusoidal waveform.

24. The arrangement of claim 21 wherein the DC voltage source is connected with a source of ordinary AC power line voltage by way of a rectifier assembly.

26. The arrangement of claim 24 wherein the first and second output terminals are galvanically connected to each other.

25. An arrangement comprising:

a first and a second DC terminal between which is provided a constant-magnitude DC voltage; and

an inverter connected with the DC terminals by way of a first sub-assembly and operative to provide, between a first and a second output terminal, an alternating output voltage having a periodic and substantially sinusoidal waveshape;

the waveshape having a cyclical period;

the first sub-assembly being operative to cause any current flowing from the DC terminals to the inverter to remain substantially constant during the duration of the cyclical period;

the inverter being further characterized by including;

a first and a second pair of series-connected switching transistors;

each transistor having a control input terminal;

the first pair of transistors each having a terminal that is galvanically connected with a first junction;

the second pair of transistors each having a terminal that is galvanically connected with a second junction;

the first and second junctions being galvanically connected with the first and second output terminals, respectively; and

a second sub-assembly connected between the junctions as well as in circuit with each transistor'"'"'s control terminal;

the second sub-assembly including a tuned circuit as well as a third sub-assembly functional to cause the transistors to switch on and off in a time-pattern operative to cause the output voltage to have said periodic and substantially sinusoidal waveshape.