Abstract Circuitry for converting direct current at one voltage level to direct current at another voltage level by the use of alternately fired transistor switches or the like feeding into a transformer, and incorporating flyback transformer means to prevent large current spikes and dissipated energy when the ON times of the transistors overlap, when the transistor switches are driven with pulses of unequal widths, or when the transformer primary turns on either side of a center tap are unequal. The basic concept of the invention is to connect a winding of an inductive energy storing flyback transformer in series with one or more chopper switches so that when the switch or switches are closed, the switch current is limited by the presence of the energy storing flyback transformer. When the switches are open, the stored energy of the flyback transformer is allowed to transfer current to a load through a diode.
A chopper inverter comprising a pair of terminals adapted for connection to a source of direct current, a transformer having primary and secondary windings, at least one pair of switch devices for alternately connecting one terminal of said direct current source to opposite ends of the primary winding of said transformer, an output smoothing capacitor, means including a rectifier connecting the secondary winding of said transformer across said output smoothing capacitor, a flyback transformer having primary and secondary windings, means including the primary winding of said flyback transformer for connecting a center tap on the primary winding of said first-mentioned transformer to said other input terminal, and unidirectional current means connecting the secondary winding of said flyback transformer to said output smoothing capacitor.
Claim 2
Dependent Claim
123 words
A chopper inverter comprising a pair of terminals adapted for connection to a source of direct current, a transformer having primary and secondary windings, at least one pair of switch devices for alternately connecting one terminal of said direct current source to opposite ends of the primary winding of said transformer, an output smoothing capacitor, means including a rectifier connecting the secondary winding of said transformer across said output smoothing capacitor, a flyback transformer having primary and secondary windings, means including the primary winding of said flyback transformer for connecting a center tap on the primary winding of said first-mentioned transformer to said other input terminal, and unidirectional current means connecting the secondary winding of said flyback transformer to said output smoothing capacitor.
Claim 3
Dependent Claim
11 words
The inverter of claim 1 wherein said switch devices comprise transistors.
Claim 4
Dependent Claim
25 words
The inverter of claim 1 including the series combination of a resistor and capacitor connected in shunt with the primary winding of said flyback transformer.
Claim 5
Dependent Claim
53 words
The inverter of claim 1 wherein said unidirectional current device connecting the secondary winding of said flyback transformer to said output smoothing capacitor is poled to conduct current when both switch device in said pair of switch device are open and stored energy discharges through said unidirectional current device into said smoothing capacitor.
Claim 6
Dependent Claim
25 words
The inverter of claim 1 wherein said rectifier connecting said primary winding of the first-mentioned transformer to said smoothing capacitor is a full-wave bridge rectifier.