Dc-ac converter

Claim 2

A DC-AC converter comprising a transistor, a source of DC voltage connected in series with the emitter-collector path of the transistor, a resistor connected between the emitter and base of the transistor so as to lie outside of the emitter-collector DC current path of the transistor, a transformer having a primary winding, a coupling winding and a secondary winding, a coupling capacitor connected between the coupling winding of the transformer and the base of the transistor, a second capacitor whose capacitance is larger than that of the coupling capacitor, means connecting the second capacitor in series with the coupling capacitor and in shunt with said resistor in the connection between the emitter and the base of the transistor.

Claim 3

A DC-AC converter as claimed in claim 1, characterized in that the ratio between the capacitance of the second capacitor and that of the coupling capacitor lies in the range between 5 to 1 and 20 to 1 and is preferably approximately 10 to 1.

Claim 4

A DC-AC converter as claimed in claim 1 wherein a load including a discharge lamp is connected to the secondary winding of the transformer, and means connecting the primary winding and the coupling winding to the collector of the transistor.

Claim 5

A converter as claimed in claim 1 further comprising means connecting one terminal of the coupling winding to the collector of the transistor and the other terminal to said coupling capacitor so that the coupling capacitor is connected between the collector and base electrodes of the transistor.

Claim 6

A converter comprising, a transistor having emitter, base and collector electrodes, a pair of terminals adapted to be connected to a source of DC supply voltage, a traNsformer having a primary, secondary and auxiliary winding, means connecting said primary winding in series with the transistor across said terminals, first and second capacitors, means connecting the auxiliary winding and the first capacitor in series between the collector and base electrodes of the transistor, a resistor, means connecting said resistor and said second capacitor in parallel between the base and emitter of the transistor in a manner such that the emitter current of the transistor bypasses said resistor and second capacitor and said first and second capacitors are series connected to form a capacitive voltage divider for a voltage developed in said auxiliary winding, the capacitance of said second capacitor being greater than the capacitance of the first capacitor, and means for coupling the secondary winding to a load.

Claim 7

A converter comprising, a transistor having emitter, base and collector electrodes, a pair of terminals adapted to be connected to a source of DC supply voltage, a traNsformer having a primary, secondary and auxiliary winding, means connecting said primary winding in series with the transistor across said terminals, first and second capacitors, means connecting the auxiliary winding and the first capacitor in series between the collector and base electrodes of the transistor, a resistor, means connecting said resistor and said second capacitor in parallel between the base and emitter of the transistor in a manner such that the emitter current of the transistor bypasses said resistor and second capacitor and said first and second capacitors are series connected to form a capacitive voltage divider for a voltage developed in said auxiliary winding, the capacitance of said second capacitor being greater than the capacitance of the first capacitor, and means for coupling the secondary winding to a load.

Claim 8

A converter as claimed in claim 5 wherein said primary winding, said auxiliary winding and said first capacitor are serially connected, in the order named, between the collector and base electrodes of the transistor, and one of said supply terminals is connected to the junction point between said primary and auxiliary windings.

Claim 9

A converter as claimed in claim 5 further comprising means for disconnecting the base electrode of the transistor from the supply terminals during operation of the converter thereby to isolate the base-emitter path of the transistor from any DC current flow from the supply terminals.

Claim 10

A converter as claimed in claim 5 wherein the ratio of the capacitance of the second capacitor to the capacitance of the first capacitor lies in the range between 5 to 1 and 20 to 1.