Circuit arrangement for producing an alternating voltage

Claim 2

A circuit arrangement for producing an alternating output voltage from a d.c. input voltage comprising: means for providing pulse width modulated signals at a high frequency; first and second voltage inverter circuit means, each controlled by said pulse width modulated signals at a high frequency, for producing the positive half waves of the alternating output voltage and the negative half waves of the output voltage respectively from a d.c. input signal; means for connecting the outputs of said first and second voltage inverter circuit means in series across a common load; first and second electronic power switches connected across the outputs of said first and second voltage inverter circuit means respectively; and means for controlling said power switches to short-circuit the output of the respective first and second voltage inverter circuit means during the time it is not producing output energy.

Claim 3

A circuit arrangement as defined in claim 1 wherein said means for providing pulse width modulated signals provides pulse width modulated rectangular signals.

Claim 4

A circuit arrangement as defined in claim 2 wherein said means for providing pulse width modulated rectangular signals includes a first signal generator means for producing an alternating reference voltage; a second signal generator means for producing a triangular voltage having a higher frequency than said reference voltage and having amplitudes of only one polarity; and comparison circuit means for comparing the momentary amplitude values of said reference voltage and said triangular voltage to produce said pulse width modulated rectangular signals.

Claim 5

A circuit arrangement as defined in claim 2 wherein said means for providing pulse width modulated rectangular signals includes: a first signal generator means for producing an alternating reference voltage; a second signal generator means for producing a triangular voltage having a higher frequency than said reference voltage and amplitude values of only one polarity; a first comparison circuit means, having its output connected to said first inverter circuit means, for comparing the momentary amplitude values of the output signals from said first and second signal generator means to produce a pulse width modulated rectangular output signal for controlling said first inverter circuit means; a third signal generator means for producing a triangular voltage of said higher frequency and having amplitude values of only the opposite polarity; and second comparison circuit means, having its output connected to said second inverter circuit means, for comparing the momentary amplitude values of the output signals from said first and third signal generator means to produce a pulse width modulated rectangular output signal for controlling said second inverter circuit means.

Claim 6

A circuit arrangement as defined in claim 2 wherein said means for providing pulse width modulated rectangular signals includes: a first signal generator means for producing an alternating reference voltage; a second signal generator means for producing a triangular voltage having a higher frequency than said reference voltage and amplitude values of only one polarity; a first comparison circuit means, having its output connected to said first inverter circuit means, for comparing the momentary amplitude values of the output signals from said first and second signal generator means to produce a pulse width modulated rectangular signal for controlling said first inverter circuit means; a polarity reversing circuit having its input connected to the output of said first signal generating means; and a second comparison circuit means, having its output connected to said second inverter circuit means, for comparing the momentary amplitude values of the output signals from said polarity reversing circuit and said second signal generating means to produce a pulse width modulated rectangular signal for controlling said second inverter circuit means.

Claim 7

A circuit arrangement as defined in claim 1 wherein said means for providing pulse width modulated signals includes an alternating reference voltage generator and means for converting the momentary amplitudes of said reference voltage to said pulse width modulated signals; and further comprising means for regulating the alternating output voltage of said circuit arrangement including means for comparing the momentary amplitude values of said alternating output voltage and said reference voltage to provide an output signal for controlling said reference voltage.

Claim 8

A circuit including a plurality of circuit arrangements as defined in claim 1 connected in parallel.

Claim 9

A circuit arrangement as defined in claim 1 wherein each of said first and second voltage inverter circuit means includes a transformer having a primary and a secondary winding, a transistor having its emitter-collector path in series with said primary winding and its base connected to the output of said means for providing pulse width modulated signals, a diode connected in series with said secondary winding and said common load, and a capacitor connected in parallel with the series connection of said secondary winding and said diode; wherein said secondary windings are connected in series; and wherein each of said first and second power switches is connected in parallel with said capacitor of a respective one of said first and second voltage inverter circuit means.

Claim 10

A circuit arrangement as defined in claim 8 wherein each of said first and second power switches is a transistor having its emitter-collector path connected in parallel with the associated said capacitor and its base connected to the output of said means for controlling said power switches.

Claim 11

A circuit arrangement as defined in claim 9 wherein said means for controlling said power switches includes: a respective further secondary winding for each of said transformers, said further secondary winding of each of said transformers having one end connected to the common junction of said series connected secondary windings and its other end connected via a diode to the base of the one of said transistors whose emitter-collector path is connected in parallel with the capacitor associated with the other of said transformers.