Power supply having improved over-voltage protection

Claim 2

A power supply as defined in claim 1 wherein said reference diode is adapted to conduct when said reflected voltage exceeds said predetermined value, said blocking diode being forward biased responsive to said reference diode being in conduction, the combination of said conducting diodes providing a low impedance current path from said drive winding to said fuse for supplying current that is sufficient to blow said fuse.

Claim 3

A power supply as defined in claim 1 wherein current regulator means are provided connected to the base terminal of said switching transistor for driving said switching transistor, and said control circuit includes first over-voltage detecting means connected across said load including comparater transistor switching means, first optical coupler means including a light-emitting semiconductor having its cathode connected to the collector of said comparator switching means and its anode connected to the high voltage side of said rectification means and a light-sensitive photo-transistor having an emitter and a collector, a voltage divider network connected between said source and said current regulator means for supplying drive current thereto, first diode means having its anode connected to the midpoint of said voltage divider network and its cathode connected to the collector of said photo-transistor for shunting said drive current from said current regulator means, and peak current transistor means having its collector connected to a reference voltage through second diode means reversed biased with respect to said reference voltage and its emitter connected to said current regulator means through third diode means poled to shunt said drive current from said current regulator means for regulating said switching transistor.

Claim 4

A power supply as defined in claim 3 wherein said first over-voltage detecting means includes a second reference diode having its anode connected to the low voltage side of said rectification means and its cathode connected to the collector of said comparator switching means for further regulating the conduction state of said switching transistor.

Claim 5

A power supply as defined in claim 3 wherein said control circuit further includes second over-voltage detecting means including thyristor means having anode, cathode and control leads with said anode lead connected to the high voltage side of said rectification means, said control lead connected through a second reference diode to the high voltage sIde of said rectification means, second optical coupler means including a light-emitting semiconductor having its cathode connected to the low voltage side of said rectification means and its anode connected to the cathode lead of said thyristor means and a light-sensitive photo-rectifier having its anode lead connected to the high voltage side of said oscillator and its cathode lead connected to the base of said second transistor for further regulating the conduction state of said switching transistor.

Claim 6

A dc to dc power supply circuit connectible between a dc source and a dc load and including in combination: oscillator means connectible to said source for producing an ac potential, rectification means connected between said oscillator means and said dc load for converting ac potential to dc potential for application to said load, semiconductor switching means connected to said oscillator means and having a primary switching transistor connected between said oscillator means and said source and a secondary control transistor operative to render said switching transistor non-conductive when said control transistor is conductive, current regulator means connected to the base terminal of said switching transistor for driving said switching transistor, first over-voltage detecting means connected across said load including comparator transistor switching means having its collector connected to the low voltage side of said rectification means through a first reference diode having its cathode connected to said collector, first optical coupler means including a light-emitting semiconductor having its cathode connected to the collector of said comparator switching means and its anode connected to the high voltage side of said rectification means and a light-sensitive photo-transistor having an emitter and a collector, a voltage divider network connected between said source and said current regulator means for supplying drive current thereto, first diode means having its anode connected to the midpoint of said voltage divider network and its cathode connected to the collector of said photo-transistor for shunting said drive current from said current regulator means, peak current transistor means having its collector connected to a reference voltage through second diode means reversed biased with respect to said reference voltage and its emitter connected to said current regulator means through third diode means poled to shunt said drive current from said current regulator means, and second over-voltage detecting means including thyristor means having anode, cathode and control leads with the anode lead thereof connected to the high voltage side of said rectification means, the control lead thereof connected to a second reference diode in turn connected to the high voltage side of said rectification means, second optical coupler means including a light-emitting semiconductor having its cathode connected to the low voltage side of said rectification means and its anode connected to the cathode lead of said thyristor means and a light-sensitive photo-rectifier having its anode lead connected to the high voltage side of said oscillator means and its cathode lead connected to the base of said secondary control transistor whereby said first over-voltage detecting means through said first reference diode or said first optical coupler means and said second over-voltage detecting means through said second optical coupler means are effective to regulate the conduction state of said switching transistor.

Claim 7

A dc to dc power supply circuit connectible between a dc source and a dc load and including in combination: oscillator means connectible to said source for producing an ac potential, rectification means connected between said oscillator means and said dc load for converting ac potential to dc potential for application to said load, semiconductor switching means connected to said oscillator means and having a primary switching transistor connected between said oscillator means and said source and a secondary control transistor operative to render said switching transistor non-conductive when said control transistor is conductive, current regulator means connected to the base terminal of said switching transistor for driving said switching transistor, first over-voltage detecting means connected across said load including comparator transistor switching means having its collector connected to the low voltage side of said rectification means through a first reference diode having its cathode connected to said collector, first optical coupler means including a light-emitting semiconductor having its cathode connected to the collector of said comparator switching means and its anode connected to the high voltage side of said rectification means and a light-sensitive photo-transistor having an emitter and a collector, a voltage divider network connected between said source and said current regulator means for supplying drive current thereto, first diode means having its anode connected to the midpoint of said voltage divider network and its cathode connected to the collector of said photo-transistor for shunting said drive current from said current regulator means, peak current transistor means having its collector connected to a reference voltage through second diode means reversed biased with respect to said reference voltage and its emitter connected to said current regulator means through third diode means poled to shunt said drive current from said current regulator means, and second over-voltage detecting means including thyristor means having anode, cathode and control leads with the anode lead thereof connected to the high voltage side of said rectification means, the control lead thereof connected to a second reference diode in turn connected to the high voltage side of said rectification means, second optical coupler means including a light-emitting semiconductor having its cathode connected to the low voltage side of said rectification means and its anode connected to the cathode lead of said thyristor means and a light-sensitive photo-rectifier having its anode lead connected to the high voltage side of said oscillator means and its cathode lead connected to the base of said secondary control transistor whereby said first over-voltage detecting means through said first reference diode or said first optical coupler means and said second over-voltage detecting means through said second optical coupler means are effective to regulate the conduction state of said switching transistor.

Claim 8

A power supply as defined in claim 6 including means for supplying the base current for said switching transistor including a drive winding having a reflected voltage proportional to the voltage of a secondary winding, fuse means positioned in the base of said switching transistor for open circuiting said base circuit to thereby cut off said switching transistor, and a current supply circuit for said fuse means comprising a blocking diode in series with a third reference diode positioned Between said drive winding and said fuse, said diodes normally blocking current flow in both directions, said current supply circuit being adapted to conduct current to blow said fuse when said reflected voltage exceeds a predetermined value.

Claim 9

A power supply as defined in claim 7 wherein said third reference diode is adapted to conduct when said reflected voltage exceeds said predetermined value, said blocking diode being forward biased responsive to said third reference diode being in conduction, the combination of said conducting diodes providing a low impedance current path from said drive winding to said fuse for supplying current that is sufficient to blow said fuse.