High gain phase control circuit

Claim 2

A phase control circuit for controlling a thyristor to provide current across a load, said circuit comprising: a source of alternating current; a full-wave rectifier for converting said alternating current to provide a positive sine wave voltage during each half cycle of said alternating current: a relaxation oscillator including a switching device having a negative resistance characteristic and a charging capacitor therefor; circuit means including a zener diode having its anode connected to the negative side of said full-wave rectifier, and a p-n-p transistor having its emitter connected to the positive side of said full-wave rectifier and its base connected to the cathode of said zener diode, said p-n-p transistor conducting current on its collector to charge said charging capacitor during the time the sine wave voltage on its emitter is at a level to cause the voltage on its base to reach the breakdown voltage of said zener diode; a charging circuit including a first and second resistor and a timing capacitor connected in series between the collector of said p-n-p transistor and the negative side of said full-wave rectifier, and a n-p-n transistor having its collector connected to the collector of said p-n-p transistor, its emitter connected to said charging capacitor and its base connected to the common junction of said first and second resistor, the current from said p-n-p transistor providing for charging said charging capacitor through said n-p-n transistor as said timing capacitor charges on each half cycle until said charging capacitor reaches the triggering voltage level of said switching device, whereby said relaxation oscillator provides an output pulse to fire said thyristor; and feedback circuit means responsive to current supplied by said thyristor each half cycle to provide a feedback signal for resetting said timing capacitor by discharging it each half cycle to a preset value to thereby control the time required each half cycle for the charging circuit to charge said charging capacitor to the triggering level of said switching device.

Claim 3

A phase control circuit for controlling a thyristor to provide current across a load, said circuit comprising; a source of alternating current; a first full-wave rectifier for converting said alternating current to provide a positive sine wave voltage during each half cycle of said alternating current; a relaxation oscillator including a switching device having a negative resistance characteristic and a charging capacitor therefor; circuit means for synchronizing the operation of sAid relaxation oscillator with the alternating current during each half cycle thereof, said circuit means including a zener diode having its output connected to the return side of said first full-wave rectifier, and a first transistor having its input terminal connected to the output of said first full-wave rectifier and its base terminal connected to the input of said zener diode, said first transistor starting to conduct current on its output terminal to charge said charging capacitor when the positive sine wave voltage rises to a level to cause the voltage on its base terminal to reach the breakdown voltage of said zener diode and said first transistor ceasing to conduct charging current when said positive sine wave voltage falls to a level to cause the voltage on its base terminal to drop below the breakdown voltage of said zener diode; a charging circuit including a series circuit comprising a first and second resistor and a timing capacitor, said series circuit connected between the output terminal of said first transistor and the return side of said first rectifier, and a second transistor having its input terminal connected to the output terminal of said first transistor, its output terminal connected to said charging capacitor, and its base terminal connected to the common junction of said first and second transistor, the current from said first transistor providing for charging said charging capacitor by initially heavily conducting and then more slowly conducting through said second transistor as the timing capacitor charges until said charging capacitor reaches the triggering level of said switching device, whereby said relaxation oscillator provides an output pulse to control said thyristor; and feedback means including a third transistor having its base terminal connected to the return side of said first full-wave rectifier and its input terminal connected to said timing capacitor, a current transformer responding to the current applied to the load by said thyristor, and a second full-wave rectifier responsive to the output of said current transformer to provide a feedback signal, and second rectifier being connected across the base terminal and output terminal of said third transistor, and said timing capacitor being discharged through said third transistor to a preset initial value in accordance with said feedback signal after the switching device has been triggered during each half cycle.

Claim 4

A phase control circuit for controlling a thyristor to provide current across a load, said circuit comprising; a source of alternating current; a first full-wave rectifier for converting said alternating current to provide a positive sine wave voltage during each half cycle of said alternating current; a relaxation oscillator including a switching device having a negative resistance characteristic and a charging capacitor therefor; circuit means for synchronizing the operation of sAid relaxation oscillator with the alternating current during each half cycle thereof, said circuit means including a zener diode having its output connected to the return side of said first full-wave rectifier, and a first transistor having its input terminal connected to the output of said first full-wave rectifier and its base terminal connected to the input of said zener diode, said first transistor starting to conduct current on its output terminal to charge said charging capacitor when the positive sine wave voltage rises to a level to cause the voltage on its base terminal to reach the breakdown voltage of said zener diode and said first transistor ceasing to conduct charging current when said positive sine wave voltage falls to a level to cause the voltage on its base terminal to drop below the breakdown voltage of said zener diode; a charging circuit including a series circuit comprising a first and second resistor and a timing capacitor, said series circuit connected between the output terminal of said first transistor and the return side of said first rectifier, and a second transistor having its input terminal connected to the output terminal of said first transistor, its output terminal connected to said charging capacitor, and its base terminal connected to the common junction of said first and second transistor, the current from said first transistor providing for charging said charging capacitor by initially heavily conducting and then more slowly conducting through said second transistor as the timing capacitor charges until said charging capacitor reaches the triggering level of said switching device, whereby said relaxation oscillator provides an output pulse to control said thyristor; and feedback means including a third transistor having its base terminal connected to the return side of said first full-wave rectifier and its input terminal connected to said timing capacitor, a current transformer responding to the current applied to the load by said thyristor, and a second full-wave rectifier responsive to the output of said current transformer to provide a feedback signal, and second rectifier being connected across the base terminal and output terminal of said third transistor, and said timing capacitor being discharged through said third transistor to a preset initial value in accordance with said feedback signal after the switching device has been triggered during each half cycle.

Claim 5

The invention in accordance with claim 2 including a potentiometer connected across the current transformer to vary the magnitude of the feedback signal and thereby vary the point in time during the half cycle when said relaxation oscillator provides an output pulse.

Claim 6

The invention in accordance with claim 2 including a fourth resistor for connecting the output of said first rectifier with the timing capacitor.

Claim 7

A phase control circuit for controlling a thyristor to provide current across a load, said circuit comprising: a source of alternating current; a full-wave rectifier for converting said alternating current to provide a positive sine wave voltage during each half cycle of said alternating current; a relaxation oscillator including a switching device having a negative resistance characteristic and a charging capacitor therefor; circuit means for synchronizing the operation of said relaxation oscillator with the alternating current during each half cycle thereof, said circuit means including a zener diode having its output connected to the return side of said full-wave rectifier, and a first transistor having its input terminal connected to the output of said full-wave rectifier and its base terminal connected to the input of said zener diode, said first transistor starting to conduct current on its output terminal to charge said charging capacitor when the positive sine wave voltage causes the voltage on its base terminal to reach the breakdown voltage of said zener diode and said first transistor ceasing to conduct charging current when the positive sine wave voltage causes the voltage on its base terminal to drop below the breakdown voltage of said zener diode; a charging circuit including a first and second resistor and a timing capacitor connected in series between the output terminal of said first transistor and the return side of said full-wave rectifier, and a second transistor having its input terminal connected to the output terminal of said first transistor, its output terminal connected to said charging capacitor, and its base terminal connected to the common junction of said first and second resistor, the current from said first resistor providing for charging said charger capacitor by initially conducting heavily and then more slowly through said second transistor as said timing capacitor charges until said charging capacitor reaches the triggering voltage level of said switching device, whereby said relaxation oscillator provides an output pulse to control said thyristor; feedback means responsive to current supplied by said thyristor each half cycle to provide a feedback signal for resetting said charging circuit to thereby control the time required each half cycle for the charging circuit to charge said charging capacitor to the triggering level of the switching device; a thermistor connected across one of the resistors in said charging circuit; a third resistor in the return line of said first rectifier for sensing the current therein when said zener diode conducts; and a fourth transistor having its input terminal connected to the base of said second transistor, its output terminal connected to the return side of said first rectifier, and its base terminal connected to the junction of said zener diode and said third resistor.

Claim 8

A phase control circuit for controlling a thyristor to provide current across a load, said circuit comprising: a source of alternating current; a full-wave rectifier for converting said alternating current to provide a positive sine wave voltage during each half cycle of said alternating current; a relaxation oscillator including a switching device having a negative resistance characteristic and a charging capacitor therefor; circuit means for synchronizing the operation of said relaxation oscillator with the alternating current during each half cycle thereof, said circuit means including a zener diode having its output connected to the return side of said full-wave rectifier, and a first transistor having its input terminal connected to the output of said full-wave rectifier and its base terminal connected to the input of said zener diode, said first transistor starting to conduct current on its output terminal to charge said charging capacitor when the positive sine wave voltage causes the voltage on its base terminal to reach the breakdown voltage of said zener diode and said first transistor ceasing to conduct charging current when the positive sine wave voltage causes the voltage on its base terminal to drop below the breakdown voltage of said zener diode; a charging circuit including a first and second resistor and a timing capacitor connected in series between the output terminal of said first transistor and the return side of said full-wave rectifier, and a second transistor having its input terminal connected to the output terminal of said first transistor, its output terminal connected to said charging capacitor, and its base terminal connected to the common junction of said first and second resistor, the current from said first resistor providing for charging said charger capacitor by initially conducting heavily and then more slowly through said second transistor as said timing capacitor charges until said charging capacitor reaches the triggering voltage level of said switching device, whereby said relaxation oscillator provides an output pulse to control said thyristor; feedback means responsive to current supplied by said thyristor each half cycle to provide a feedback signal for resetting said charging circuit to thereby control the time required each half cycle for the charging circuit to charge said charging capacitor to the triggering level of the switching device; a thermistor connected across one of the resistors in said charging circuit; a third resistor in the return line of said first rectifier for sensing the current therein when said zener diode conducts; and a fourth transistor having its input terminal connected to the base of said second transistor, its output terminal connected to the return side of said first rectifier, and its base terminal connected to the junction of said zener diode and said third resistor.

Claim 9

A phase control circuit for controlling a high powered thyristor to provide current across a load comprising: a relaxation oscillator including a switching device having a negative resistance characteristic and a charging capacitor thereacross; a supply of alternating current; a full-wave rectifier circuit for converting said alternating current to provide a positive sine wave voltage during each half cycle of the alternating current; a zener diode; a first transistor circuit having its emitter connected to the output of said rectifier circuit and having its base connected to conduct through said zener diode, the output of said zener diode being connected to the return side of said rectifier means, said first transistor circuit conducting charging circuit on its collector when the positive sine wave voltage causes its base to reach the breakdown voltage of said zener diode; a charging circuit including a second transistor having a voltage divider resistor connected to the base thereof and a timing capacitor; said voltage divider resistor having one end thereof connected to the collector of said second gating transistor and the other end thereof connected by said timing capacitor to the return side of said rectifier means, said charging circuit responding to the charging current from said first transistor to initially heavily charge the charging capacitor of said relaxation oscillator to a level dependent upon the charge left stored on said timing capacitor during the last half cycle, and thereafter to more slowly charge said charging capacitor; said relaxation oscillator collapsing to provide a firing pulse to fire said thyristor and provide a current to said load when the charging capacitor reaches the triggering potential of said switching device; a feedback circuit responsive to the current passing to said load to provide a feedback signal; said feedback circuit including means for discharging said timing capacitor in accordance with said feedback signal during the latter portion of each half cycle; and means for adjusting said feedback circuit to vary said feedback signal to thereby reset the point in time during each half cycle that said charging capacitor in said relaxation oscillator reaches the triggering potential of said switching device.

Claim 10

A phase control circuit for controlling a high powered thyristor to provide current across a load comprising: a relaxation oscillator including a switching device having a negative resistance characteristic and a charging capacitor thereacross; a supply of alternating current; a full-wave rectifier circuit for converting said alternating current to provide a positive sine wave voltage during each half cycle of the alternating current; a zener diode; a first transistor circuit having its emitter connected to the output of said rectifier circuit and having its base connected to conduct through said zener diode, the output of said zener diode being connected to the return side of said rectifier means, said first transistor circuit conducting charging circuit on its collector when the positive sine wave voltage causes its base to reach the breakdown voltage of said zener diode; a charging circuit including a second transistor having a voltage divider resistor connected to the base thereof and a timing capacitor; said voltage divider resistor having one end thereof connected to the collector of said second gating transistor and the other end thereof connected by said timing capacitor to the return side of said rectifier means, said charging circuit responding to the charging current from said first transistor to initially heavily charge the charging capacitor of said relaxation oscillator to a level dependent upon the charge left stored on said timing capacitor during the last half cycle, and thereafter to more slowly charge said charging capacitor; said relaxation oscillator collapsing to provide a firing pulse to fire said thyristor and provide a current to said load when the charging capacitor reaches the triggering potential of said switching device; a feedback circuit responsive to the current passing to said load to provide a feedback signal; said feedback circuit including means for discharging said timing capacitor in accordance with said feedback signal during the latter portion of each half cycle; and means for adjusting said feedback circuit to vary said feedback signal to thereby reset the point in time during each half cycle that said charging capacitor in said relaxation oscillator reaches the triggering potential of said switching device.

Claim 11

A phase control circuit for controlling a high powered thyristor to provide current across a load comprising: a relaxation oscillator including a programmable unijunction transistor and a charging capacitor therefor; an alternating current supply; a full-wave rectifier for converting said alternating current to provide a positive sine wave voltage during each half cycle of said alternating current; a zener diode having its output connected to the return side of said full-wave rectifier; a first transistor having its input connected to the output of said full-wave rectifier and having its base connected to the input of said zener diode so as to conduct through said zener diode during the time the positive sine wave voltage causes the voltage in its base to exceed the breakdown voltage of said zener diode; a second transistor having its input connected to the output of said first transistor and having its output connected to said charging capacitor; a voltage control circuit for the base of said second transistor, said voltage control circuit connected between the output of said first transistor and the return side of said full-wave rectifier, and said voltage control circuit including a timing capacitor; said second transistor conducting current from said first transistor to charge said charging capacitor of said relaxation oscillator in accordance with the rise of the potential produced on the base of said second transistor by said voltage control circuit, the time for charging said charging capacitor during each half cycle to the triggering level of said programmable unijunction transistor being dependent on an initial charge stored on said timing capacitor; said relaxation oscillator collapsing to provide an output pulse to fire said thyristor when said charging capacitor reaches the triggering voltage level of said programmable unijunction transistor; a feedback circuit responsive to the current passing through said thyristor to said load during each half cycle to provide a feedback signal to discharge said timing capacitor down to its initial charge; and manual means for resetting said feedback circuit to change the initial charge on said timing capacitor and thereby adjust the point in time during each half cycle that said charging capacitor reaches the triggering voltage level of said programmable unijunction transistor.

Claim 12

A phase control circuit for controlling a high powered thyristor to provide current across a load comprising: a relaxation oscillator including a programmable unijunction transistor and a charging capacitor therefor; an alternating current supply; a full-wave rectifier for converting said alternating current to provide a positive sine wave voltage during each half cycle of said alternating current; a zener diode having its output connected to the return side of said full-wave rectifier; a first transistor having its input connected to the output of said full-wave rectifier and having its base connected to the input of said zener diode so as to conduct through said zener diode during the time the positive sine wave voltage causes the voltage in its base to exceed the breakdown voltage of said zener diode; a second transistor having its input connected to the output of said first transistor and having its output connected to said charging capacitor; a voltage control circuit for the base of said second transistor, said voltage control circuit connected between the output of said first transistor and the return side of said full-wave rectifier, and said voltage control circuit including a timing capacitor; said second transistor conducting current from said first transistor to charge said charging capacitor of said relaxation oscillator in accordance with the rise of the potential produced on the base of said second transistor by said voltage control circuit, the time for charging said charging capacitor during each half cycle to the triggering level of said programmable unijunction transistor being dependent on an initial charge stored on said timing capacitor; said relaxation oscillator collapsing to provide an output pulse to fire said thyristor when said charging capacitor reaches the triggering voltage level of said programmable unijunction transistor; a feedback circuit responsive to the current passing through said thyristor to said load during each half cycle to provide a feedback signal to discharge said timing capacitor down to its initial charge; and manual means for resetting said feedback circuit to change the initial charge on said timing capacitor and thereby adjust the point in time during each half cycle that said charging capacitor reaches the triggering voltage level of said programmable unijunction transistor.