Patent US3886342A successfully refreshed from Google Patents.
US3886342A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Induction cooking unit having all pan safe operation, wide range power control and low start-up and shut-down transients
Assignee: Environment One Corp
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Filing: 1973-04-26
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Granted: 1975-05-27
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Expires: 1993-04-26
Abstract
Abstract An induction heating unit including inverter circuit means comprised by a gate controlled thyristor and commutation circuit coupled together in circuit relationship and excited from a set of power supply terminals connected to a source of excitation potential. An induction heating coil is coupled to and excited by the inverter circuit means in a manner such that the loading on the induction heating coil determines at least in part the operating frequency at which the inverter circuit means operates. Gating circuit means comprised by a gating signal generator and enabling circuit means are coupled to and control turn-on of the gate control thyristor with the gating circuit means comprising a feedback sensing circuit coupled to the induction heating coil for deriving a feedback trigger signal synchronized with the frequency of operation of the commutation circuit.
Inventors
- 👤 Jr Philip H Peters
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 19:16
CPC Classifications
H; H05; H05B; H05B6/00; H05B6/02; H05B6/06; H05B6/062; H05B2213/00; H05B2213/07
Claims Analysis
Total Claims: 29
Claim 1
Independent Claim
219 words
An induction heating unit including in combination inverter circuit means comprising gate controlled thyristor means and commutation circuit means coupled together in circuit relationship and excited from a set of power supply terminals, an induction heating coil coupled to and excited by said inverter circuit means in a manner such that the induction heating coil determines at least in part the operating frequency at which the inverter circuit means operates, and gating circuit means coupled to and controlling turn-on of said gate controlled thyristor means, said gating circuit means comprising feed back sensing circuit means coupled to said induction heating coil for deriving a feedback trigger signal synchronized with the frequency of operation of the inverter circuit circuit means, gating signal generator means for generating high frequency signal pulses having a repetition rate determined by the operation frequency for the inverter circuit means and of sufficient energy to insure turn-on of said gate controlled thyristor means, enabling means coupled to and enablIng initiation of operation of said gating signal generator means, and alternating current signal coupling circuit means intercoupling said last mentioned enabling means with said feedback sensing circuit means for synchronizing the operation of the gating signal generator means with changes in frequency of the inverter circuit means due to loading and unloading of the induction heating coil.
Claim 2
Dependent Claim
219 words
An induction heating unit including in combination inverter circuit means comprising gate controlled thyristor means and commutation circuit means coupled together in circuit relationship and excited from a set of power supply terminals, an induction heating coil coupled to and excited by said inverter circuit means in a manner such that the induction heating coil determines at least in part the operating frequency at which the inverter circuit means operates, and gating circuit means coupled to and controlling turn-on of said gate controlled thyristor means, said gating circuit means comprising feed back sensing circuit means coupled to said induction heating coil for deriving a feedback trigger signal synchronized with the frequency of operation of the inverter circuit circuit means, gating signal generator means for generating high frequency signal pulses having a repetition rate determined by the operation frequency for the inverter circuit means and of sufficient energy to insure turn-on of said gate controlled thyristor means, enabling means coupled to and enablIng initiation of operation of said gating signal generator means, and alternating current signal coupling circuit means intercoupling said last mentioned enabling means with said feedback sensing circuit means for synchronizing the operation of the gating signal generator means with changes in frequency of the inverter circuit means due to loading and unloading of the induction heating coil.
Claim 3
Dependent Claim
70 words
An induction heating unit according to claim 1 wherein the alternating current signal coupling circuit means comprises differentiating circuit means for differentiating the sensed value of the voltage appearing across the induction heating coil and supplying the same back to synchronize operation of the gating signal generator means with the changes in frequency of operation of the inverter circuit means due to loading and unloading of the induction heating coil.
Claim 4
Dependent Claim
140 words
An induction heating unit according to claim 1 wherein the inverter circuit means comprises a high frequency chopper-inverter circuit means including inductor and capacitor commutating reactive components having an inductance L1 and capacitance C1, respectively, connected in series circuit relationship across the gate controlled thyristor means in parallel circuit relationship therewith and with the chopper-inverter circuit means thus comprised being connected across the set of power supply terminals for connection to the source of excitation potential through a filter inductor having an inductance L2, said commutating inductor and capacitor being series resonant at a predetermined natural commutating frequency that provides a combined thyristor conduction and commutating period t1 during each cycle of operation and said gating circuit means controlling the turn-on of the gate controlled thyristor means so as to render the thyristor conductive at a controlled frequency of operation.
Claim 5
Dependent Claim
132 words
An induction heating unit according to claim 3 further including a smoothing inductor having an inductance L3 and a smoothing capacitor having capacitance C3 connected in series circuit relationship across at least one of the capacitor and inductor commutating reactive components, said smoothing inductor and capacitor having values such that the combined reactive impedance of the capacitor commutating reactive component including the smoothing inductor and the smoothing capacitor is capacitive in nature and series resonates with the inductor commutating component to establish the combined thyristor conduction-commutating period t1, and wherein the smoothing inductor and capacitor shape the output current flowing through the smoothing inductor to a substantially sinusoidal wave shape having little or no radio frequency interference emission effects and improved power coupling, and the smoothing inductor comprises the induction heating coil.
Claim 6
Dependent Claim
84 words
An induction heating unit according to claim 4 further including shunt capacitor means and shunt capacitor switching means for switching said shunt capacitor means in parallel circuit relationship across said L3 induction heating coil at low power levels of operation for the induction heating unit whereby the current flowing through the L3 induction heating coil is reduced and the effective commutating capacitance C1 of the commutating capacitor is increased to thereby increase the t1 conduction and commutating time of the gate controlled thyristor means.
Claim 7
Dependent Claim
183 words
An induction heating unit according to claim 5 wherein the commutating capacitance C1 is comprised by a plurality of different capacitor elements and further includes C1 switching means for switching in different combinations of capacitor elements in accordance with a desired power level at which the induction heating unit is to operate, and wherein the shunt capacitor means is formed by utilizing appropriate ones of said capacitor elements switched into shunt circuit relationships with L3 induction heating coil at low power levels of operation by the shunt capacitor switching means. 7. An induction heating unit according to claim 6 wherein the source of excitation potential for the induction heating unit comprises full wave rectifier means designed for connection to a source of conventional commercial or residential alternating current and having the output thereof connected across a filter capacitor of a relatively small capacitance value C2, said parallel connected series commutated chopper-inverter circuit means being connected through the L2 filter inductor across the filter capacitor and a metal oxide thyristor transient voltage supressor device connected in parallel circuit relationsip across the chopper-inverter circuit means.
Claim 8
Dependent Claim
124 words
An induction heating unit according to claim 7, wherein the induction heating coil comprises a planar, spirally round induction heating coil, a flat insulating support member for supporting inductively heated cooking vessels disposed over the induction heating coil, electrostatic shield means formed on the under surface of the flat, insulating support member for electro-statically shielding the inductively heated cooking vessels from the induction heating coil, the electrostatic shielding means being electrically grounded, and temperature responsive means coupled to sense the operating temperature of at least the L3 induction heating coil, and means coupling the output from the temperature responsive means to control the operation of said gating circuit means to cause shut down of the induction heating unit upon an over-temperature condition being sensed.
Claim 9
Dependent Claim
133 words
An induction heating unit according to claim 8 wherein said gating signal generator means comprises a programable unijunction transistor having an anode, an anode-gate and a cathode, a timing capacitor connected in parallel circuit relationship across the anode-cathode of the programable unijunction transistor, output circuit means coupled to the cathode of the programable unijunction transistor for supplying a gating-on signal to said gate controlled thyristor means, adjustable charging resistor means connected in common to the anode and to the timing capacitor, biasing resistor means connected across the series connected charging resistor and programable unijunction transistor and having an intermediate point connected to the anode-gate of the programable unijunction transistor, and terminal means connected across and biasing resistor means for supplying the gating signal generator means with a low voltage direct current excitation potential.
Claim 10
Dependent Claim
54 words
An induction heating unit according to claim 9 wherein the enabling means comprises transistor means having its emittor-collector connected in series-circuit relationship with the parallel connected biasing resistor means and series connected charging resistor and timing capacitor and programable unijunction transistor, and having its base connected to the output from feedback sensing circuit means.
Claim 11
Dependent Claim
56 words
An induction heating unit according to claim 10 further including operator controlled on-off switch means, and lock out circuit means controlled by said operator controlled on-off switch means and in turn coupled to and locking out operation of said gating signal generator means in response to the on-off condition of said operator controlled on-off switch means.
Claim 12
Dependent Claim
140 words
An induction heating unit according to claim 11 wherein the lockout circuit means comprises a set of opposite conductivity type transistors having the base of one transistor connected back to the emittor-collector of the opposite conductivity type transistor so that both transistors latch on or off in response to one of the transistors being turned on or off, one of said latching opposite conductivity type transistors being coupled across the charging capacitor in the gating signal generator means, and one of the transistors having its base electrode connected to have the highest switching potential applied thereto determined by the setting of the operator controlled on-off switch means whereby positive on-off switching of the clamp imposed acrosS the charging capacitor in the gating pulse signal generator means is achieved in response to on-off operation of the operator controlled on-off switch means.
Claim 13
Dependent Claim
133 words
An induction heating unit according to claim 1 wherein said gating signal generator means comprises a programable unijunction transistor having an anode, an anode-gate and a cathode, a timing capacitor connected in parallel circuit relationship across the anode-cathode of the programable unijunction transistor, output circuit means coupled to the cathode of the programable unijunction transistor for supplying a gating-on signal to said gate controlled thyristor means, adjustable charging resistor means connected in common to the anode and to the timing capacitor, biasing resistor means connected across the series connected charging resistor and programable unijunction transistor and having an intermediate point connected to the anode-gate of the programable unijunction transistor, and terminal means connected across said biasing resistor means for supplying the gating signal generator means with a low voltage direct current excitation potential.
Claim 14
Dependent Claim
54 words
An induction heating unit according to claim 13 wherein the enabling means comprises transistor means having its emittor-collector connected in series-circuit relationship with the parallel connected biasing resistor means and series connected charging resistor and timing capacitor and programable unijunction transistor, and having its base connected to the output from feedback sensing circuit means.
Claim 15
Dependent Claim
56 words
An induction heating unit according to claim 13 further including operator controlled on-off switch means, and lock out circuit means controlled by said operator controlled on-off switch means and in turn coupled to and locking out operation of said gating signal generator means in response to the on-off condition of said operator controlled on-off switch means.
Claim 16
Dependent Claim
140 words
An induction heating unit according to claim 15 wherein the lockout circuit means comprises a set of opposite conductivity type transistors having the base of one transistor connected back to the emittor-collector of the opposite conductivity type transistor so that both transistors latch on or off in response to one of the transistors being turned on or off, one of said latching opposite conductivity type transistors being coupled across the charging capacitor in the gating signal generator means, and one of the transistors having its base electrode connected to have the highest switching potential applied thereto determined by the setting of the operator controlled on-off switch means whereby positive on-off switching of the clamp imposed across the charging capacitor in the gating pulse signal generator means is achieved in response to on-off operation of the operator controlled on-off switch means.
Claim 17
Dependent Claim
56 words
An induction heating unit according to claim 1 further including operator controlled on-off switch means, and lock out circuit means controlled by said operator controlled on-off switch means and in turn coupled to and locking out operation of said gating signal generator means in response to the on-off condition of said operator controlled on-off switch means.
Claim 18
Dependent Claim
126 words
An induction heating unit according to claim 1 wherein the source of excitation potential to which the power supply terminals are to be connected provides a periodic undulating excitation potential that drops substantially to zero periodically, and the induction heating unit further includes zero point pulse generator means coupled to the power supply terminals for producing a pulsed output signal at the occurrence of each substantial zero point in the periodic undulating excitation potential, and zero point coincidence circuit means coupled to and controlling operation of said enabling means and in turn coupled to and controlled by said zero point pulse generator means for conditioning said gating signal generator means for operation only at or near the periodic zero point in the periodic undulating excitation potential.
Claim 19
Dependent Claim
112 words
An induction heating unit according to claim 18 wherein said zero point coincidence circuit means comprises a bilateral on-off latching switch circuit means having two stable states of operation and capable of being switched from one to the other of its stable states of operation only at or near a zero point in the periodic undulating excitation potential and inhibit circuit means intercoupling said bilateral on-off latching switch circuit means to the gating signal generator means for inhibiting further operation of said gating signal generator means upon the bilateral on-off latching switch means being switched to an off condition only at or near a zero point of the periodic undulating excitation potential.
Claim 20
Dependent Claim
56 words
An induction heating unit according to claim 18 further including operator controlled on-off switch means, and lock out circuit means controlled by said operator controlled on-off switch means and in turn coupled to and locking out operating of said gating signal generator means in response to the on-off condition of said operator controlled on-off switch means.
Claim 21
Dependent Claim
163 words
An induction heating unit according to claim 20 wherein the lockout circuit means comprises a set of opposite conductivity type transistors having the base of one transistor connected back to the emitter-collector of the opposite conductivity type transistor so that both transistors latch on or off in response to one of the transistors being turned on or off, one of said latching transistors being coupled to said bilateral on-off latching switch circuit means for enabling operation of the bilateral on-off latching switch circuit means at the next zero point of the periodic undulating excitation potential and having its base electrode connected to have a switching on-off potential applied thereto by the operator controlled on-off switch means whereby positive on-off switching of the inhibit imposed on said gating pulse signal generator means by the inhibit circuit means is achieved in response to on-off operation of the operator controlled on-off switch means only at or near a zero point of the supply undulating excitation potential.
Claim 22
Dependent Claim
160 words
An induction heating unit according to claim 20 wherein said gating signal generator means comprises a programable unijunction transistor having an anode, an anode-gate and a cathode, a timing capacitor connected in parallel circuit relationship across the anode-cathode of the programable unijunction transistor, output circuit means coupled to the cathode of the programable unijunction transistor for supplying a gating-on signal to said gate controlled thyristor means, adjustable charging resistor means connected in common to the anode and to the timing capacitor, biasing resistor means connected across the series connected charging resistor and programable unijunction transistor and having an intermediate point connected to the anode-gate of the programable unijunction transistor and said enabling means comprises transistor means having its emitter-collector connected in series circuit relationship with the parallel connected biasing resistor means and the series connected charging resistor and parallel connected timing capacitor and programable unijunction transistor, and having its base connected to the output from the feedback sensing circuit means.
Claim 23
Dependent Claim
70 words
An induction heating unit according to claim 22 wherein the alternating current signal coupling circuit means comprises differentiating circuit means for differentiating the sensed value of the voltage appearing across the induction heating coil and supplying the same back to synchronize operation of the gating signal generator means with the changes in frequency of operation of the inverter circuit means due to loading and unloading of the induction heating coil.
Claim 24
Dependent Claim
214 words
An induction heating unit according to claim 23 wherein the inverter circuit means comprises a high frequency chopper-inverter circuit means including inductor and capacitor commutating reactive components having an inductance L1 and cApacitance C1, respectively, connected in series circuit relationship across the gate controlled thyristor means in parallel circuit relationship therewith and with the chopper-inverter circuit means thus comprised being connected across the set of power supply terminals for connection to the source of excitation potential through a filter inductor having an inductance L2, said commutating inductor and capacitor being tuned to series resonance at a predetermined natural commutating frequency that provides a combined thyristor conduction and commutating period t1 during each cycle of operation and said gating circuit means controlling the turn-on of the gate controlled thyristor means so as to render the thyristor conductive at a controlled frequency of operation that provides an operation period T for the chopper-inverter circuit means including a quiescent charging period t2 in each cycle of operation where T t1 + t2 such that the value omega 2t2 equals substantially pi /2 radians at the operating frequency or greater and where omega 2 equals 1/ Square Root L2C1 whereby the reapplied forward voltage across the thyristor means following each conduction interval is maintained substantially independent of load.
Claim 25
Dependent Claim
133 words
An induction heating unit according to claim 24 further including a smoothing inductor having an inductance L3 and a smoothing capacitor having capacitance C3 connected in series circuit relationship across at least one of the capacitor and inductor commutating reactive components, said smoothing inductor and capacitor having values such that the combined reactive, impedance of the capacitor commutating reactive component including the smoothing inductor and the smoothing capacitor is capacitive in nature and series resonates with the inductor commutating components to establish the combined thyristor conduction-commutating period t1, and wherein the smoothing inductor and capacitor shape the output current flowing through the smoothing inductor to a substantially a sinusoidal wave shape having little or no radio frequency interference emission effects and improved power coupling, and the smoothing inductor comprises the induction heating oil.
Claim 26
Dependent Claim
84 words
An induction heating unit according to claim 25 further including shunt capacitor means and shunt capacitor switching means for switching said shunt capacitor means in parallel circuit relationship across said L3 induction heating coil at low power levels of operation for the induction heating unit whereby the current flowing through the L3 induction heating coil is reduced and the effective commutating capacitance C1 of the commutating capacitor is increased to thereby increase the t1 conduction and commutating time of the gate controlled thyristor means.
Claim 27
Dependent Claim
90 words
An induction heating unit according to claim 26 wherein the commutating capacitance C1 is comprised by a plurality of different capacitor elements and further includes C1 switching means for switching in different combinations of capacitor elements in accordance with a desired power level at which the induction heating unit is to operate, and wherein the shunt capacitor means is formed by utilizing appropriate ones of said capacitor elements switched into shunt circuit relationships with L3 induction heating coil at low power levels of operation by the shunt capacitor switching means.
Claim 28
Dependent Claim
92 words
An induction heating unit according to claim 27 wherein the source of excitation potential for the induction heating unit comprises full wave rectifier means designed for connection to a source of conventional commercial or residential alternating current and having the output thereof connected across a filter capacitor of a relatively small capacitance value C2, said parallel connected series commutated chopper-inverter circuit means being connected through the L2 filter inductor across the filter capacitor and a metal oxide thyristor transient voltagE supressor device connected in parallel circuit relationship across the chopper-inverter circuit means.
Claim 29
Dependent Claim
124 words
An induction heating unit according to claim 28 wherein the induction heating coil comprises a planar, spirally wound induction heating coil, a flat insulating support member for supporting inductively heated cooking vessels disposed over the induction heating coil, electrostatic shield means formed on the under surface of the flat, insulating support member for electro-statically shielding the inductively heated cooking vessels from the induction heating coil, the electrostatic shielding means being electrically grounded, and temperature responsive means coupled to sense the operating temperature of at least the L3 induction heating coil, and means coupling the output from the temperature responsive means to control the operation of said gating circuit means to cause shut down of the induction heating unit upon an over-temperature condition being sensed.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-05-26 | 1978-11-25 | 1979-05-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-05-26 | 1982-11-25 | 1983-05-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-05-26 | 1986-11-25 | 1987-05-27 | $7700.00 | Window Closed / Lapsed |