Electronic inverter having precharging control affording high frequency switching at low output

Claim 2

In an electronic inverter system, the combination comprising: two power switching circuits joined together and supplied from an adjustable direct current source and connected at their junction to an output terminal for supplying alternating current to a load device. each said power switching circuit comprising an electronic gate controlled power switching device and a commutating inductor in series and a commutating capacitor in parallel therewith and a blocking diode between such parallel circuit and the associated side of the adjustable direct current source for blocking discharge of the commutating capacitors into the latter, the two commutating inductors being magnetically coupled; a separate precharging direct current source connected across the commutating capacitors of the two power switching circuits for charging them; a firing circuit for selectively firing said power switching devices into conduction. each of said commutating capacitors being effective upon firing of the associated power switching device for discharging through the latter and through the associated commutating inductor thereby to induce a voltage in the other commutating inductor to bias its associated power switching device off; precharging control means comprising a recoup transformer having primary and secondary windings responsive to the energy stored in one of said commutating inductors for charging the commutating capacitor in the other power switching circuit; and feedback control means operable when said precharging control means has charged said commutating capacitor to a predetermined level for feeding back the remainder of the stored energy into the adjustable direct current source.

Claim 3

The invention defined in claim 1, wherein said precharging control means also comprises; a first unidirectional circuit in which said one commutating inductor causes a current to flow through the primary winding of said recoup transformer; and a second unidirectional circuit in which the secondary winding of said recoup transformer causes a current to flow to charge the commutating capacitor in said other power switching circuit.

Claim 4

The invention defined in claim 1, wherein said feedback control means comprises: voltage level detector means coupled to said recoup transformer and being responsive to the voltage thereon when said commutating capacitor voltage reaches said predetermined level to provide an operating signal; and means responsive to said operating signal for completing a feedback path from the secondary winding of said recoup transformer to said adjustable direct current source.

Claim 5

The invention defined in claim 3, wherein said voltage level detector means coupled to said recoup transformer comprises: a pair of control windings on said recoup transformer; a pair of voltage spillover circuits connected to the respective control windings, each being effective to provide a firing current pulse when the voltage on its control winding exceeds a given value indicative of said predetermined level of charge on the respective commutating capacitor; and a pair of gate controlled feedback switching devices for completing opposite polarity paths from the secondary winding of said recoup transformer to said adjustable direct current source, said feedback switching devices being controlled by the firing current pulses of the respective voltage spillover circuits.

Claim 6

The invention defined in claim 4, wherein each said voltage spillover circuit comprises: a gate controlled firing pulse switching device; a zener diode responsive to the voltage on the associated control winding for passing a current to the gate of said firing pulse switching device to render it conducting; and a firing pulse transformer responsive to conduction of said firing pulse switching device for applying a firing current pulse to the assoCiated feedback switching device.

Claim 7

In an electronic inverter having at least one controllable half-bridge including upper and lower power control portions connectable at their junction to a load device; the combination comprising: an adjustable direct voltage source for supplying operating voltage to the inverter; each portion of the half-bridge comprising a blocking diode, a controllable electronic power switching device and a commutating inductor in series connection between one side of said source and the load junction, the commutating inductors being magnetically coupled together. a pair of commutating capacitors connected individually across the power switching device and commutating inductor of each portion of the half-bridge; a separate precharging direct current source connected across said commutating capacitors; said blocking diodes being poled to block discharge of said commutating capacitors into said adjustable direct voltages source; a firing circuit for selectively firing said power switching devices into conduction; one of said commutating capacitors being effective upon firing of the associated ''''off'''' power switching device ''''on'''' for discharging through the latter and through the associated first commutating inductor thereby to induce a voltage in the second commutating inductor to bias the associated power switching device off; a recoup transformer having primary and secondary windings and a pair of control windings; means comprising said recoup transformer responsive to the energy stored in said first commutating inductor for charging the other commutating capacitor to a predetermined voltage level; and means comprising a voltage level detector responsive to the voltage on one of said control windings when said other commutating capacitor reaches said predetermined voltage level for feeding back the remaining stored energy from said recoup transformer secondary winding to said adjustable direct voltage source.

Claim 8

In an electronic inverter having at least one controllable half-bridge including upper and lower power control portions connectable at their junction to a load device; the combination comprising: an adjustable direct voltage source for supplying operating voltage to the inverter; each portion of the half-bridge comprising a blocking diode, a controllable electronic power switching device and a commutating inductor in series connection between one side of said source and the load junction, the commutating inductors being magnetically coupled together. a pair of commutating capacitors connected individually across the power switching device and commutating inductor of each portion of the half-bridge; a separate precharging direct current source connected across said commutating capacitors; said blocking diodes being poled to block discharge of said commutating capacitors into said adjustable direct voltages source; a firing circuit for selectively firing said power switching devices into conduction; one of said commutating capacitors being effective upon firing of the associated ''''off'''' power switching device ''''on'''' for discharging through the latter and through the associated first commutating inductor thereby to induce a voltage in the second commutating inductor to bias the associated power switching device off; a recoup transformer having primary and secondary windings and a pair of control windings; means comprising said recoup transformer responsive to the energy stored in said first commutating inductor for charging the other commutating capacitor to a predetermined voltage level; and means comprising a voltage level detector responsive to the voltage on one of said control windings when said other commutating capacitor reaches said predetermined voltage level for feeding back the remaining stored energy from said recoup transformer secondary winding to said adjustable direct voltage source.

Claim 9

The invention defined in claim 6, wherein said means comprising said recoup transformer also comprises: a first unidirectionally conducting circuit wherein said first commutating inductor causes current flow through the primary winding of said recoup transformer. and a second unidirectionally conducting circuit wherein said primary and secondary windings cause current flow to the other commutating capacitor to charge the same.

Claim 10

The invention defined in claim 6, wherein: said other commutating capacitor is effective upon firing of the associated ''''off'''' power switching device ''''on'''' for discharging through the latter and through the associated second commutating inductor thereby to induce a voltage in the first commutating inductor to bias the associated power switching device off; and said combination also comprises: second means comprising said recoup transformer responsive to the energy stored in said second commutating inductor for charging said one commutating capacitor to said predetermined voltage level; and means comprising a second voltage level detector responsive to the voltage on the other control winding when said one commutating capacitor reaches said predetermined voltage level for feeding back the remaining stored energy from said recoup transformer secondary winding to said adjustable direct current source.

Claim 11

The invention defined in claim 8, wherein said second means comprising said recoup transformer also comprises; a third unidirectionally conducting circuit wherein said second commutating inductor causes current flow through the primary winding of said recoup transformer; and a fourth unidirectionally conducting circuit wherein said primary and secondary windings cause current flow to said one commutating capacitor to charge the same.