Cycle converter power supply for microwave heating

Claim 2

A power supply for supplying pulsed current to a load at a frequency in excess of a prime alternating current source comprising a transformer adapted to be energized by said alternating current source at a first frequency and having at least two pairs of primary windings and a secondary winding, first semiconductor switching means connected in series with each pair of said primary windings and poled to conduct current through each of said pairs of windings in one direction on halfcycles of said source, second semiconductor switching means connected in series with each of said pairs of said primary windings and poled to conduct current through each of said pairs of primary windings in a direction opposite to that of said first semiconductor switching means, means initiating conduction altermately in said first and second semiconductor switching means to initiate current flow alternately in each direction in first one pair and then the other of said pairs of said primary windings thereby to convert current flow in said secondary winding to waves having a frequency in excess of the frequency of said source, and means for progressively terminating conduction in said first and second semiconductor switching means to terminate current flow alternately in each direction through said primary windings, thereby to provide in said secondary winding an envelope formed by said waves.

Claim 3

A frequency converter circuit for producing alternating current at a frequency in excess of the frequency of an alternating current prime power source comprising a transformer having four primary windings adapted to be directly energized by an alternating current source, and a secondary winding, a semiconductor switch connected in a pair of series circuits each having a pair of primary windings and in shunt with said prime power source and adapted to conduct in a manner to control the flow of current in a single direction therethrough, means for initiating conduction at discrete intervals at a frequency in excess of that of the prime power source in each semiconductor switch which is poled in one direction a preselected number of times according to a predetermined program, and means including a capacitor charging circuit connected from one series circuit to the other series circuit for discharging to render one of said semiconductor switches nonconducting in response to conduction in another of said semiconductor switches, thereby to provide in said secondary winding alternating current pulses which upon rectification approximate characteristics achieved by rectification of said prime power source.

Claim 4

A frequency converter circuit for producing alternating current at a frequency in excess of the frequency of an alternating current prime power source comprising a transformer having four primary windings adapted to be directly energized by an alternating current source, and a secondary winding, a semiconductor switch connected in a pair of series circuits each having a pair of primary windings and in shunt with said prime power source and adapted to conduct in a manner to control the flow of current in a single direction therethrough, means for initiating conduction at discrete intervals at a frequency in excess of that of the prime power source in each semiconductor switch which is poled in one direction a preselected number of times according to a predetermined program, and means including a capacitor charging circuit connected from one series circuit to the other series circuit for discharging to render one of said semiconductor switches nonconducting in response to conduction in another of said semiconductor switches, thereby to provide in said secondary winding alternating current pulses which upon rectification approximate characteristics achieved by rectification of said prime power source.

Claim 5

A power converter circuit for multiplying the frequency of an AC power source comprising a transformer including first and second pairs of primary windings magnetically coupled to a secondary winding, a pair of unidirectional switching means coupled back-to-back and connected in a series circuit with each pair of primary windings, each of said serially connected pairs of primary windings connected in shunt with an AC power source, means operative on a first half-cycle of said power source for initiating conduction of a first of said switching means serially connected to one of said pairs of primary windings and initiating nonconduction of a similarly poled second switching means in said other pair of primary windings, means on the second half-cycle of said AC power source for initiating conduction of a second of said switching means connected in shunt with said first switching means and nonconduction of similarly poled switching means in said second pair of primary windings, current from said AC power source during conductivity of each of said switching means coacting with said Pairs of primary windings to produce in said secondary winding a series of pulses at a frequency independent of said AC power source, and rectifying means coupled to said secondary winding for converting said pulses to a direct current flow having characteristics corresponding to those achieved by rectification of said AC power source.

Claim 6

A power converter circuit for multiplying the frequency of an AC power source comprising a transformer including first and second pairs of primary windings magnetically coupled to a secondary winding, a pair of unidirectional switching means coupled back-to-back and connected in a series circuit with each pair of primary windings, each of said serially connected pairs of primary windings connected in shunt with an AC power source, means operative on a first half-cycle of said power source for initiating conduction of a first of said switching means serially connected to one of said pairs of primary windings and initiating nonconduction of a similarly poled second switching means in said other pair of primary windings, means on the second half-cycle of said AC power source for initiating conduction of a second of said switching means connected in shunt with said first switching means and nonconduction of similarly poled switching means in said second pair of primary windings, current from said AC power source during conductivity of each of said switching means coacting with said Pairs of primary windings to produce in said secondary winding a series of pulses at a frequency independent of said AC power source, and rectifying means coupled to said secondary winding for converting said pulses to a direct current flow having characteristics corresponding to those achieved by rectification of said AC power source.

Claim 7

A power supply comprising a low frequency input line, a transformer having a secondary winding and four primary windings, a plurality of semiconductor switches connected in series with said primary windings and poled to interrupt current flow through said primary windings on half-cycles of said low frequency input line, a first pair of said primary windings connected in a first series circuit with each other and with a pair of back-to-back semiconductor switches and in shunt with said low frequency input line, a second pair of primary windings connected in a second series circuit with each other and with back-to-back semiconductor switches and in shunt with said low frequency input line, capacitor means connected from said first series circuit to said second series circuit and adapted to become charged in response to current flow alternately in said first and second series circuits, means in response to current flow in said second and said first series circuits to utilize the charge on said capacitor means to interrupt current flow respectively in said first and second series circuits, and timing means for progressively initiating conduction in said semiconductor switches to produce in said secondary winding a resultant current which upon rectification approximates the characteristics achieved by rectification of said low frequency input line.

Claim 8

A power supply comprising a low frequency input line, a transformer having a secondary winding and four primary windings, a plurality of semiconductor switches connected in series with said primary windings and poled to interrupt current flow through said primary windings on half-cycles of said low frequency input line, a first pair of said primary windings connected in a first series circuit with each other and with a pair of back-to-back semiconductor switches and in shunt with said low frequency input line, a second pair of primary windings connected in a second series circuit with each other and with back-to-back semiconductor switches and in shunt with said low frequency input line, capacitor means connected from said first series circuit to said second series circuit and adapted to become charged in response to current flow alternately in said first and second series circuits, means in response to current flow in said second and said first series circuits to utilize the charge on said capacitor means to interrupt current flow respectively in said first and second series circuits, and timing means for progressively initiating conduction in said semiconductor switches to produce in said secondary winding a resultant current which upon rectification approximates the characteristics achieved by rectification of said low frequency input line.

Claim 9

A power supply including frequency converter circuit for producing alternating current at a frequency in excess of the frequency of a prime power source comprising a transformer having four primary windings and a secondary winding, a semiconductor switch connected in circuit with each primary winding, means for initiating conduction in each smiconductor switch at discrete intervals to program current flow through said primary windings at a frequency in excess and independent of that of said prime power source, said latter means including a capacitor charging circuit connected to discharge across one of said semiconductor switches to render said semiconductor switch nonconducting in response to conduction of another of said semiconductor switches, thereby providing in said secondary winding alternating current pulses, and means for rectifying said pulses to provide a source of unidirectional power.

Claim 10

A power supply including frequency converter circuit for producing alternating current at a frequency in excess of the frequency of a prime power source comprising a transformer having four primary windings and a secondary winding, a semiconductor switch connected in circuit with each primary winding, means for initiating conduction in each smiconductor switch at discrete intervals to program current flow through said primary windings at a frequency in excess and independent of that of said prime power source, said latter means including a capacitor charging circuit connected to discharge across one of said semiconductor switches to render said semiconductor switch nonconducting in response to conduction of another of said semiconductor switches, thereby providing in said secondary winding alternating current pulses, and means for rectifying said pulses to provide a source of unidirectional power.

Claim 11

A power supply including a frequency converter circuit for producing alternating current at a frequency in excess of the frequency of a prime power source and suitable for rectification to said original prime power frequency comprising a transformer having four primary windings and a secondary winding, means for controlling current in said primary windings comprising a silicon controlled rectifier connected in series with the primary windings and said prime power source for conducting current in said primary windings at successive time intervals, pulse generating means connected to the silicon controlled rectifiers for initiating current conduction therein, means for varying the repetition rate of the pulse generating means to a value to provide in said secondary winding alternating current pulses at a frequency in excess of that of the prime power source, and means for rectifying said pulses to provide a unidirectional power source having the approximate characteristics achieved by rectification of said prime power source.

Claim 12

A power supply including a frequency converter circuit for producing alternating current at a frequency in excess of the frequency of a prime power source and suitable for rectification to said original prime power frequency comprising a transformer having four primary windings and a secondary winding, means for controlling current in said primary windings comprising a silicon controlled rectifier connected in series with the primary windings and said prime power source for conducting current in said primary windings at successive time intervals, pulse generating means connected to the silicon controlled rectifiers for initiating current conduction therein, means for varying the repetition rate of the pulse generating means to a value to provide in said secondary winding alternating current pulses at a frequency in excess of that of the prime power source, and means for rectifying said pulses to provide a unidirectional power source having the approximate characteristics achieved by rectification of said prime power source.

Claim 13

A power supply including a frequency converter circuit comprising a transformer having a secondary winding and at least two pairs of magnetically coupled primary windings, a semiconductor switch connected in series with each of said primary windings and a prime power source, means for progressively triggering each of said semiconductor switches into conduction at discretE intervals to program current flow from said prime power source alternately through each pair of said primary windings at a frequency in excess and independent of that of said prime power source to produce in said secondary winding a plurality of square waves having a modulation envelope which follows the waveshape of the prime power frequency, said latter means including a capacitor charging circuit connected to discharge across one of said semiconductor switches in a first pair of primary windings to render said one of said semiconductor switches nonconducting in response to conduction of another of said semiconductor switches in a second pair of primary windings, and means to rectify said square waves to provide a direct current wave similar in character to that achieved through rectification of said prime power source.

Claim 14

A power supply including a frequency converter circuit comprising a transformer having a secondary winding and at least two pairs of magnetically coupled primary windings, a semiconductor switch connected in series with each of said primary windings and a prime power source, means for progressively triggering each of said semiconductor switches into conduction at discretE intervals to program current flow from said prime power source alternately through each pair of said primary windings at a frequency in excess and independent of that of said prime power source to produce in said secondary winding a plurality of square waves having a modulation envelope which follows the waveshape of the prime power frequency, said latter means including a capacitor charging circuit connected to discharge across one of said semiconductor switches in a first pair of primary windings to render said one of said semiconductor switches nonconducting in response to conduction of another of said semiconductor switches in a second pair of primary windings, and means to rectify said square waves to provide a direct current wave similar in character to that achieved through rectification of said prime power source.

Claim 15

A power supply as set forth in claim 6 in which the means for varying the repetition rate of the pulse generating means includes a voltage sensitive element operatively connected to said pulse generating means and a voltage sensing circuit connected in shunt with said prime power source to feed input voltage variations to said voltage sensitive element.

Claim 16

A power supply including a frequency converter circuit comprising a transformer having a secondary winding and first and second pairs of primary windings adapted to be connected to a prime power source, back-to-back semiconductor switches connected in series with each of said first and second pairs of primary windings, means for triggering said semiconductor switches which are poled in one direction a preselected number of times to provide a plurality of waves during said first half-cycle, means for triggering a preselected number of times said semiconductor switches which are poled in the opposite direction during said second half-cycle to provide a plurality of waves during said second half-cycle corresponding to the number of waves produced during said first half-cycle, and means for rectifying the waves of said first and second half-cycles to provide a direct current wave having wave characteristics equivalent to those achieved through rectification of said prime power source.

Claim 17

A power supply including a frequency converter circuit comprising a transformer having a secondary winding and first and second pairs of primary windings adapted to be connected to a prime power source, back-to-back semiconductor switches connected in series with each of said first and second pairs of primary windings, means for triggering said semiconductor switches which are poled in one direction a preselected number of times to provide a plurality of waves during said first half-cycle, means for triggering a preselected number of times said semiconductor switches which are poled in the opposite direction during said second half-cycle to provide a plurality of waves during said second half-cycle corresponding to the number of waves produced during said first half-cycle, and means for rectifying the waves of said first and second half-cycles to provide a direct current wave having wave characteristics equivalent to those achieved through rectification of said prime power source.

Claim 18

A power supply including a frequency converter circuit for producing alternating current at a frequency in excess of a prime power source and adapted for rectification to said original prime power frequency comprising a transformer having first and second pairs of primary windings magnetically coupled to each other and to a secondary winding, a semiconductor switch poled in a first direction connected in series with each pair of primary windings and said power source and adapted to conduct at successive intervals in a manner to control current flow therethrough in a first direction, another semiconductor switch poled in a second direction connected in series with each pair of primary windings and said power source and adapted to conduct at successive intervals in a manner to control current flow in a second direction, means for initiating conduction in each semiconductor switch in discrete intervals independent of the frequency of the prime power source and in excess of the frequency thereof to provide alternating current waves in said secondary winding, said latter means including a capacitor charge circuit connected to discharge across one of said semiconductor switches to render said one of said semiconductor switches nonconducting in response to conduction of another of said semiconductor switches, and means for rectifying said alternating current waves to provide a rectified wave approximating the characteristics achieved by rectification of said prime power source.

Claim 19

A power supply including a frequency converter circuit for producing alternating current at a frequency in excess of a prime power source and adapted for rectification to said original prime power frequency comprising a transformer having first and second pairs of primary windings magnetically coupled to each other and to a secondary winding, a semiconductor switch poled in a first direction connected in series with each pair of primary windings and said power source and adapted to conduct at successive intervals in a manner to control current flow therethrough in a first direction, another semiconductor switch poled in a second direction connected in series with each pair of primary windings and said power source and adapted to conduct at successive intervals in a manner to control current flow in a second direction, means for initiating conduction in each semiconductor switch in discrete intervals independent of the frequency of the prime power source and in excess of the frequency thereof to provide alternating current waves in said secondary winding, said latter means including a capacitor charge circuit connected to discharge across one of said semiconductor switches to render said one of said semiconductor switches nonconducting in response to conduction of another of said semiconductor switches, and means for rectifying said alternating current waves to provide a rectified wave approximating the characteristics achieved by rectification of said prime power source.

Claim 20

A power supply having a frequency converter circuit for producing rectified alternating current having characteristics suitable for connection to a magnetron type load and at a frequency compatible with minimum size components suited for use in a microwave oven comprising a transformer adapted to be connected to a prime power source and having A plurality of pairs of primary windings and a second winding, a rectifier connected to the secondary winding, a magnetron type load connected to the rectifier, semiconductor switches operatively connected in series with each pair of primary windings and said prime power source for conducting current through respective pairs of said primary windings at successive time intervals, a first semiconductor switch in each of said pairs of primary windings poled to permit current flow in one direction and a second semiconductor switch in each of said pairs of primary windings to permit current flow in the opposite direction, and trigger circuit means for initiating conduction in said first of said semiconductor switches which are poled in one direction a preselected number of times to provide a plurality of current waves during a first half-cycle and for initiating conduction a preselected number of times in said second of said semiconductor switches which are poled in the opposite direction during a second half-cycle to provide a plurality of current waves during said second half-cycle corresponding to the number of waves produced during said first half-cycle and at a frequency in excess of the frequency of said prime power source and independently thereof to provide in said secondary winding an envelope formed by said waves, said rectifier providing rectification of said waves to provide for said magnetron type load rectified current waves having characteristics corresponding to those achieved by rectification of said prime power source.

Claim 21

A power supply having a frequency converter circuit for producing rectified alternating current having characteristics suitable for connection to a magnetron type load and at a frequency compatible with minimum size components suited for use in a microwave oven comprising a transformer adapted to be connected to a prime power source and having A plurality of pairs of primary windings and a second winding, a rectifier connected to the secondary winding, a magnetron type load connected to the rectifier, semiconductor switches operatively connected in series with each pair of primary windings and said prime power source for conducting current through respective pairs of said primary windings at successive time intervals, a first semiconductor switch in each of said pairs of primary windings poled to permit current flow in one direction and a second semiconductor switch in each of said pairs of primary windings to permit current flow in the opposite direction, and trigger circuit means for initiating conduction in said first of said semiconductor switches which are poled in one direction a preselected number of times to provide a plurality of current waves during a first half-cycle and for initiating conduction a preselected number of times in said second of said semiconductor switches which are poled in the opposite direction during a second half-cycle to provide a plurality of current waves during said second half-cycle corresponding to the number of waves produced during said first half-cycle and at a frequency in excess of the frequency of said prime power source and independently thereof to provide in said secondary winding an envelope formed by said waves, said rectifier providing rectification of said waves to provide for said magnetron type load rectified current waves having characteristics corresponding to those achieved by rectification of said prime power source.

Claim 22

A power supply as set forth in claim 11 in which capacitors are connected in a series circuit with said semiconductor switches and adapted to provide commutation pulses in response to both charge and discharge of said capacitors.

Claim 23

A power supply as set forth in claim 11 in which said transformer is a high reactance type adapted to vary its output with variation in frequency in response to said trigger circuit means independent of the frequency of said prime power source, means for sensing for voltage variations in said prime power source, and means in response to said voltage variations to vary the frequency of output of said trigger circuit means thereby to provide a control voltage which varies the frequency of conduction of said semiconductor switches in a manner to compensate for said voltage variations.

Claim 24

A power supply for operating a magnetron including a frequency converter circuit for producing alternating current at a frequency in excess of the frequency of a prime power source comprising a transformer having a secondary winding and first and second pairs of primary windings magnetically coupled to each other and directly connected in shunt with said prime power source, semiconductor switching means connected in a series circuit with each of said primary windings and said prime power source, said semiconductor switching means poled to control current flow therethrough alternately in each direction in each pair of said semiconductor switches; means for initiating conduction alternately in the first of said pairs of windings and in the second of said pairs of windings to provide in said secondary winding first and second envelopes of alternating current pulses; capacitor means including a pair of capacitors connected in a series circuit with said first and second of said pairs of primary windings and adapted to apply a charge on both said capacitors to interrupt current flow in said first and second of said pairs of windings, means charging said capacitors in response to current flow through said first of said pairs of windings and said second of said pairs of windings, means for rectifying said pulses to provide a source of unidirectional power resembling that achieved through rectification of the prime power source, and a magnetron connected to said source of unidirectional power.

Claim 25

A power supply for operating a magnetron including a frequency converter circuit for producing alternating current at a frequency in excess of the frequency of a prime power source comprising a transformer having a secondary winding and first and second pairs of primary windings magnetically coupled to each other and directly connected in shunt with said prime power source, semiconductor switching means connected in a series circuit with each of said primary windings and said prime power source, said semiconductor switching means poled to control current flow therethrough alternately in each direction in each pair of said semiconductor switches; means for initiating conduction alternately in the first of said pairs of windings and in the second of said pairs of windings to provide in said secondary winding first and second envelopes of alternating current pulses; capacitor means including a pair of capacitors connected in a series circuit with said first and second of said pairs of primary windings and adapted to apply a charge on both said capacitors to interrupt current flow in said first and second of said pairs of windings, means charging said capacitors in response to current flow through said first of said pairs of windings and said second of said pairs of windings, means for rectifying said pulses to provide a source of unidirectional power resembling that achieved through rectification of the prime power source, and a magnetron connected to said source of unidirectional power.

Claim 26

A power supply as set forth in claim 14 in which said transformer is a high reactance type adapted to vary its output with variation In frequency of said prime power source, means for sensing voltage variations in said prime power source, and means in response to said voltage variations to provide a control signal to vary the frequency of conduction of said semiconductor switches in a manner to compensate for said voltage variation and provide said magnetron with a substantially constant source of power.

Claim 27

A power supply including a frequency converter circuit for producing alternating current at a frequency in excess of the frequency of an alternating current power source comprising a transformer having first and second pairs of primary windings magnetically coupled to each other and to a secondary winding, a pair of semiconductor switches connected in a series circuit with each of said pairs of primary windings and said power source, each pair of semiconductor switches poled to control current flow therethrough alternately in each direction, means for alternately initiating conduction in the first of said pairs of primary windings and in the second of said pairs of primary windings to provide in said secondary winding first and second envelopes of alternating current pulses, capacitance means including a pair of capacitors connected in a series circuit with said first and second pairs of primary windings and adapted to apply a charge on both said capacitors to interrupt current flow in said first and second of said pairs of primary windings, means charging said capacitors in response to current flow through said first of said pairs of primary windings and said second of said pairs of primary windings, thereby to provide in said secondary winding an envelope containing alternating current pulses independent of the frequency of said alternating current power source, and means to rectify said pulses in said envelope to provide a source of unidirectional power having characteristics approximating those achieved by rectification of said alternating current power source.

Claim 28

A power supply including a frequency converter circuit for producing alternating current at a frequency in excess of the frequency of an alternating current power source comprising a transformer having first and second pairs of primary windings magnetically coupled to each other and to a secondary winding, a pair of semiconductor switches connected in a series circuit with each of said pairs of primary windings and said power source, each pair of semiconductor switches poled to control current flow therethrough alternately in each direction, means for alternately initiating conduction in the first of said pairs of primary windings and in the second of said pairs of primary windings to provide in said secondary winding first and second envelopes of alternating current pulses, capacitance means including a pair of capacitors connected in a series circuit with said first and second pairs of primary windings and adapted to apply a charge on both said capacitors to interrupt current flow in said first and second of said pairs of primary windings, means charging said capacitors in response to current flow through said first of said pairs of primary windings and said second of said pairs of primary windings, thereby to provide in said secondary winding an envelope containing alternating current pulses independent of the frequency of said alternating current power source, and means to rectify said pulses in said envelope to provide a source of unidirectional power having characteristics approximating those achieved by rectification of said alternating current power source.

Claim 29

A power supply as set forth in claim 16 in which said transformer is a high reactance type adapted to vary its output with variation in frequency of said alternating current power source, and means in response to voltage variations of said alternating current power source to provide a control voltage to vary the frequency of conduction of each pair of said semiconductor switches to compensate for said voltage variations.