Proportional power control circuit

Claim 2

A power control circuit for controlling the average power applied to a load comprising: a. switching means having two power terminals, said device normally exhibiting a high impedance between said two power terminals, but capable of being excited to a quasistable lowimpedance state when a control signal is applied thereto and remaining in the low-impedance state so long as holding current flows through said power terminals or said control signal is applied to said switching means; b. means for connecting said switching means by said two power terminals in series with source of alternating current supply voltage and a load; c. zero crossing means for generating and applying to said switching means a control signal to cause said switching means to switch to said quasistable low-impedance state at the beginning of each half-cycle of applied alternating current supply voltage; d. generating means for generating a proportional control signal having a period substantially equal to that of a selected plurality of cycles of the alternating current supply voltage and whose character varies in accordance with the power requirements of the load; e. said generating means including means for generating a first voltage whose amplitude varies with time and having a period substantially equal to that of the selected plurality of cycles of alternating current supply voltage, means for generating a reference voltage whose amplitude varies as a function of the power requirement of the load, and comparison means responsive to one of the reference voltage and the ramp voltage being greater than the other for changing the character of the proportional control signal; and, f. means responsive to the character of the proportional control signal for selectively enabling and disabling said zero crossing means.

Claim 3

A power control circuit as defined iN claim 1 wherein the comparison means produces a proportional control signal which is of binary character.

Claim 4

A power control circuit as defined in claim 1 wherein said means for generating a first voltage comprises a pulse generator, a capacitor, means for charging said capacitor, and means for discharging the capacitor each cycle of the pulse generator to provide a ramp voltage.

Claim 5

A power control circuit as defined in claim 3 wherein said pulse generator is a relaxation oscillator comprising a second capacitor, means for charging said second capacitor to a predetermined level during the plurality of cycles of alternating current supply voltage, a silicon controlled rectifier having an anode and a cathode connected in circuit with said second capacitor for discharging said second capacitor when the silicon controlled rectifier switches to the low-impedance state, and an avalanche diode device connected between the anode and a gate electrode of the silicon controlled rectifier for switching the silicon controlled rectifier from a normally high-impedance state to a low-impedance state when the avalanche diode switches to a low-impedance state from a normally high-impedance state upon the potential applied across the diode becoming equal to its avalanche voltage, said avalanche voltage being substantially equal to said predetermined level.

Claim 6

A power control circuit as defined in claim 3 wherein said means for discharging the capacitor includes a silicon controlled rectifier operated in a sublatching mode, means connecting said silicon controlled rectifier for discharging said capacitor, and means for switching said silicon controlled rectifier to the low-impedance state each cycle of the pulse generator.

Claim 7

A power control circuit as defined in claim 1 wherein said comparison means comprises a silicon controlled rectifier connected for operation in a sublatching mode, means for applying said reference voltage to the cathode of said silicon controlled rectifier and means for applying said first voltage to the gate electrode of said silicon controlled rectifier, the anode of said silicon controlled rectifier being connected to source of supply voltage whereby said silicon controlled rectifier is rendered conductive responsive to the first voltage being more positive than said reference voltage.

Claim 8

A power control circuit as defined in claim 1 wherein said zero crossing means is effective for generating said control signal prior to the beginning of each half-cycle of alternating current supply voltage in which power is to be applied to the load.

Claim 9

A power control circuit as defined in claim 1 wherein said zero crossing circuit is effective for generating and applying to said switching means a control signal from a time prior to the beginning of each half-cycle in which power is to be applied to the load until substantially the end of said half-cycle.

Claim 10

A power control circuit as defined in claim 1 wherein said switching means comprises two oppositely poled silicon controlled rectifiers.

Claim 11

A power control circuit as defined in claim 1 wherein said switching means is a bilateral semiconductor switch.

Claim 12

A power control circuit as defined in claim 1 wherein said comparison means further includes DC restoration means.

Claim 13

A power control circuit as defined in claim 1 wherein said means for selectively enabling and disabling said zero crossing circuit comprises a silicon controlled rectifier effective when in the conductive state to prevent said control signal being applied to said switching means.

Claim 14

A power control circuit as defined in claim 1 wherein the plurality of cycles is 50 cycles.

Claim 15

A power control circuit for controlling the average power applied to a load comprising: a. switching means having two power terminals, said device normally exhibiting a high impedance between said two power terminals, but capable of being excited to a quasistable low-impedance state when a control signal is applied thereto and remaining in the low-impedance state so long as holding current flows through said power terminals or said control signal is applied to said switching means; b. means for connecting said switching means by said two power terminals in series with a source of alternating current supply voltage and a load; c. zero crossing means for generating and applying to said switching means a control signal to cause said switching means to switch to said quasistable low-impedance state at the beginning of each half-cycle of applied alternating current supply voltage; d. means for generating a proportional control signal having a period substantially equal to that of a plurality of cycles of the alternating current supply voltage and whose character varies in accordance with the power requirements of the load; e. means responsive to the character of the proportional control signal for selectively enabling and disabling said zero crossing means; and, f. said means responsive to the character of the proportional control signal for selectively enabling and disabling said zero crossing means including a silicon controlled rectifier, means connecting said silicon controlled rectifier for disabling said zero crossing means when said silicon controlled rectifier is in one conductivity state and means for applying the proportional control signal for controlling the conductivity state of the silicon controlled rectifier in accordance with the character of the proportional control signal.

Claim 16

A power control circuit for controlling the average power applied to a load comprising: a. switching means having two power terminals, said device normally exhibiting a high impedance between said two power terminals, but capable of being excited to a quasistable low-impedance state when a control signal is applied thereto and remaining in the low-impedance state so long as holding current flows through said power terminals or said control signal is applied to said switching means; b. means for connecting said switching means by said two power terminals in series with a source of alternating current supply voltage and a load; c. zero crossing means for generating and applying to said switching means a control signal to cause said switching means to switch to said quasistable low-impedance state at the beginning of each half-cycle of applied alternating current supply voltage; d. means for generating a proportional control signal having a period substantially equal to that of a plurality of cycles of the alternating current supply voltage and whose character varies in accordance with the power requirements of the load; e. means responsive to the character of the proportional control signal for selectively enabling and disabling said zero crossing means; and, f. said means responsive to the character of the proportional control signal for selectively enabling and disabling said zero crossing means including a silicon controlled rectifier, means connecting said silicon controlled rectifier for disabling said zero crossing means when said silicon controlled rectifier is in one conductivity state and means for applying the proportional control signal for controlling the conductivity state of the silicon controlled rectifier in accordance with the character of the proportional control signal.

Claim 17

A power control circuit for controlling the average power applied to a load comprising: a. switching means having two power terminals, said device normally exhibiting a high impedance between said two power terminals, but capable of being excited to a quasistable low-impedance state when a control signal is applied thereto and remaining in the low-impedance state so long as holding current flows through said power terminals or said control signal is applied to said switching means; b. means for connecting said switching means by said two power terminals in series with a source of alternating current supply voltage and a load; c. a first capacitor; d. means for charging said first capacitor during one half-cycle of each cycle of applied alternating current supply voltage; e. means for preventing discharge of said capacitor except through control means connected to apply a control signal to said switching means whereby a control signal will be applied to said switching means of a character to cause said switching means to switch to the low-impedance state during another half-cycle immediately following the one half-cycle prior to the beginning of the other half-cycle; f. generating means for generating a proportional control signal having a period substantially equal to that of a selected plurality of cycles of the alternating current supply voltage and whose character varies in accordance with the power requirements of the load; and g. means responsive to the character of the proportional control signal for selectively enabling and disabling said control means.

Claim 18

A power control circuit for controlling the average power applied to a load comprising: a. switching means having two power terminals, said device normally exhibiting a high impedance between said two power terminals, but capable of being excited to a quasistable low-impedance state when a control signal is applied thereto and remaining in the low-impedance state so long as holding current flows through said power terminals or said control signal is applied to said switching means; b. means for connecting said switching means by said two power terminals in series with a source of alternating current supply voltage and a load; c. a first capacitor; d. means for charging said first capacitor during one half-cycle of each cycle of applied alternating current supply voltage; e. means for preventing discharge of said capacitor except through control means connected to apply a control signal to said switching means whereby a control signal will be applied to said switching means of a character to cause said switching means to switch to the low-impedance state during another half-cycle immediately following the one half-cycle prior to the beginning of the other half-cycle; f. generating means for generating a proportional control signal having a period substantially equal to that of a selected plurality of cycles of the alternating current supply voltage and whose character varies in accordance with the power requirements of the load; and g. means responsive to the character of the proportional control signal for selectively enabling and disabling said control means.

Claim 19

A power control circuit as defined in claim 15 wherein said means for preventing discharge of said capacitor comprises a plurality of diode rectifier devices.

Claim 20

A power control circuit as defined in claim 15 wherein said zero crossing means further includes a second capacitor, means connecting said second capacitor to be charged during a one half-cycle responsive to conduction of said switching means during the preceding other half-cycle and means connecting said second capacitor for being discharged to apply a control signal to said switching means from the time prior to beginning of the one half-cycle to cause the switching means to switch to the low-impedance state at the beginning of the one half-cycle.

Claim 21

A power control circuit as defined in claim 17 wherein said zero crossing means further includes a second switching means connected for controlling the application of a control signal To the first-mentioned switching means.

Claim 22

A power control circuit as defined in claim 15 further including means for slaving said switching means for conduction during a one half-cycle immediately following another half-cycle in which the switching means is rendered conductive.