Scr chopper circuit

Claim 2

A circuit for periodically interrupting the flow of energy from an electrical energy source through a load comprising: first electrical switch means connecting said source to said load having a conductive and a nonconductive state and adapted to be shifted from said conductive to said nonconductive state, a second electrical switch means having a conductive and nonconductive state and having a turnoff time exceeding the turnoff time of said first switch means, and transformer means having a primary and a secondary coil, one of said coils being connected in series with said second switch means and the series connection of said one coil and said second switch means being connected across said first switch means so that when a first signal is applied to the other coil of said transformer said second switch means assumes a conductive state and when said first signal is followed by a second signal of opposite polarity said second switch means conducts current in the reverse direction to cause said first switch means to assume said nonconducting state.

Claim 3

A circuit as in claim 1 wherein said second switch means is a diode.

Claim 4

A circuit as in claim 2 wherein said first switch means is an SCR.

Claim 5

A circuit as in claim 1 including means to produce said first and second signals and wherein said signals are pulses.

Claim 6

A circuit as in claim 1 wherein said energy source is a DC voltage source.

Claim 7

A circuit as in claim 1 including suppression circuit means connected in parallel with the first switch means including a serially connected resistor and inductance, a diode connected in parallel with said serially connected resistor and inductance and a capacitor connected in series with said diode and said serially connected resistor and inductance.

Claim 8

A circuit as in claim 1 including a diode connected in parallel with said load.

Claim 9

A circuit for producing a substantially square wave signal from a direct current voltage comprising: electronic switch means for receiving said direct current voltage and having a substantially conductive and a substantially nonconductive state, and means connected to said switch means for periodically shifting said switch means from said conductive to said nonconductive state and from said nonconductive to said conductive state including semiconductor means having a turnoff time greater than the turnoff time of said switch means and signal producing means for prodUcing a first signal to cause said semiconductor means to conduct current in a forward direction and a second subsequent signal to cause said semiconductor means to conduct current in a reverse direction to cause said switch means to shift from one to the other of said states before said semiconductor means ceases conducting current in said reverse direction.

Claim 10

A circuit for producing a substantially square wave signal from a direct current voltage comprising: electronic switch means for receiving said direct current voltage and having a substantially conductive and a substantially nonconductive state, and means connected to said switch means for periodically shifting said switch means from said conductive to said nonconductive state and from said nonconductive to said conductive state including semiconductor means having a turnoff time greater than the turnoff time of said switch means and signal producing means for prodUcing a first signal to cause said semiconductor means to conduct current in a forward direction and a second subsequent signal to cause said semiconductor means to conduct current in a reverse direction to cause said switch means to shift from one to the other of said states before said semiconductor means ceases conducting current in said reverse direction.

Claim 11

A circuit as in claim 8 wherein said signal-producing means includes first transformer means having a winding serially connected with said semiconductor means and said serially connected winding and said semiconductor means are connected in parallel with said switch means.

Claim 12

A circuit as in claim 9 wherein said semiconductor means is a diode.

Claim 13

A circuit as in claim 10 wherein said switch means is an SCR.

Claim 14

A circuit as in claim 11 wherein said signal-producing means further includes a pulse-producing means connected to another of the windings of said first transformer means for producing pulses to induce said first and second signals in said winding serially connected with said diode.

Claim 15

A circuit as in claim 12 wherein said pulse-producing means includes a first one-shot multivibrator adapted to produce a first pulse when a given signal is received, first transistor means connected to the output of said first multivibrator so that said first transistor means is driven into conduction by said first pulse, second transformer means connected to said first transistor means for including pulses in first and second winding when said first transistor is driven into conduction second transistor means connected to said first winding and third transistor means connected to said second winding so that said second and third transistor means are driven into conduction when said pulses are induced in said first and second windings direct current source means connected to said second and third transistors and to said another of said windings of said first transformer means so that said first signal is produced when said second and third transistors are driven into conduction, differentiating circuit means connected to said first transistor means so that when said first transistor means becomes nonconductive said second transformer means produces a signal which is passed to said differentiating means, a second one-shot multivibrator connected to said differentiating means adapted to produce a second pulse when a given signal is received from said differentiating means, fourth transistor means connected to said second multivibrator so that said fourth transistor means is driven into conduction by said second pulse, third transformer means connected to said fourth transistor means for inducing pulses in third and fourth winding when said fourth transistor is driven into conduction by said second pulse, fifth transistor means connected to said third winding and sixth transistor means connected to said fourth winding so that said fifth and sixth transistor means are driven into conduction when said pulses are induced in said third and fourth windings, said fifth and sixth transistors means being connected to said direct current source means so that said second signal is produced when said fifth and sixth transistor means are driven into conduction.

Claim 18

A method as in claim 14 including the steps of producing said first signal as a first pulse and producing said second signal as a second pulse of Polarity opposite to said first pulse.

Claim 19

A circuit for periodically interrupting the flow of energy from an electrical energy source through a load comprising: first electrical switch means connecting said source to said load having a conductive and a nonconductive state and adapted to be shifted from said conductive to said nonconductive state, a second electrical switch means electrically connected to said first switch means having a conductive and nonconductive state and having a turnoff time when shifting from said conductive to said nonconductive state exceeding the turnoff time of said first switch means when shifting from said conductive to said nonconductive state, and means for causing current to flow through said second switch means first in a forward direction so that said second switch means assumes said conductive state and next causing current to flow through said second switch means in a reverse direction to cause said first switch means to assume said nonconductive state before said second switch means assumes said nonconductive state.

Claim 20

A circuit for periodically interrupting the flow of energy from an electrical energy source through a load comprising: first electrical switch means connecting said source to said load having a conductive and a nonconductive state and adapted to be shifted from said conductive to said nonconductive state, a second electrical switch means electrically connected to said first switch means having a conductive and nonconductive state and having a turnoff time when shifting from said conductive to said nonconductive state exceeding the turnoff time of said first switch means when shifting from said conductive to said nonconductive state, and means for causing current to flow through said second switch means first in a forward direction so that said second switch means assumes said conductive state and next causing current to flow through said second switch means in a reverse direction to cause said first switch means to assume said nonconductive state before said second switch means assumes said nonconductive state.

Claim 21

A circuit for periodically interrupting the flow of energy from an electrical energy source through a load comprising: first electrical switch means connecting said source to said load having a conductive and a nonconductive state and adapted to be shifted from said conductive and said nonconductive state, a second electrical switch means having a conductive and nonconductive state and having a turnoff time exceeding the turnoff time of said first switch means, a controlling source of alternating current, a capacitor connected to said controlling source and connected to said second switch means so that said capacitor is charged by said controlling source to cause current to flow in a forward direction through said second switch means, causing said second switch means to assume said conductive state, and an inductance connected to said second switch means so that after current flows through said second switch means in a forward direction current flows through said second switch means in a reverse direction causing said first switch means to assume a nonconductive state before said second switch means assumes a nonconductive state.

Claim 22

A circuit for periodically interrupting the flow of energy from an electrical energy source through a load comprising: first electrical switch means connecting said source to said load having a conductive and a nonconductive state and adapted to be shifted from said conductive and said nonconductive state, a second electrical switch means having a conductive and nonconductive state and having a turnoff time exceeding the turnoff time of said first switch means, a controlling source of alternating current, a capacitor connected to said controlling source and connected to said second switch means so that said capacitor is charged by said controlling source to cause current to flow in a forward direction through said second switch means, causing said second switch means to assume said conductive state, and an inductance connected to said second switch means so that after current flows through said second switch means in a forward direction current flows through said second switch means in a reverse direction causing said first switch means to assume a nonconductive state before said second switch means assumes a nonconductive state.

Claim 23

A circuit as in claim 17 wherein said capacitor, said second switch means, and said inductor are connected in a series combination and said combination is connected in parallel with said first switch means.

Claim 24

A circuit as in claim 18 including third switch means connected in series with said capacitor, said second switch means and said inductor.

Claim 25

A circuit as in claim 18 wherein said second switch means is a long recovery diode.

Claim 26

A circuit as in claim 18 wherein said first switching means is an SCR.

Claim 27

A circuit as in claim 18 including fourth switching means connecting said controlling source to said capacitor.