Thyristor off-time controlled induction heating apparatus by differentiated thyristor anode potential
First Claim
1. An induction heating apparatus for supplying constant power to a variable heating load comprising a thyristor connected to receive power from a power source, a commutating circuit including an induction heating coil and a capacitor connected to said thyristor for commutating same, a fixed time constant differentiator connected across the anode and cathode terminals of said thyristor for differentiating a potential developed across said anode and cathode terminals to develop a load power responsive signal, a smoothing circuit for converting said load power responsive signal into a corresponding d-c signal, means for generating a deviation signal representative of the deviation of said d-c signal from a reference value corresponding to a reference power level, and means for supplying the gating control terminal of said thyristor with gating pulses at a frequency in the ultrasonic range with the period between successive ones of said gating pulses being variable as a function of said deviation signal.
0 Assignments
0 Petitions
Accused Products
Abstract
An induction heating apparatus including a thyristor adapted to receive power from a power source, a gating control circuit for generating gating pulses for application to the gating control terminal of the thyristor, a commutating circuit which commutates off the thyristor, and a differentiator connected across the anode and cathode terminals of the thyristor to detect the power consumption of an inductively heated cooking ware. The gating control circuit comprises a gating pulse generator and a smoothing circuit for filtering the signal from the differentiator into a d-c signal which is compared with a reference level to detect the deviation of the power consumption from the reference value. The gating pulse generator is responsive to a potential at the anode of the thyristor to initiate timing action to determine the interpulse period or turn-off time of the thyristor and also responsive to the deviation of power consumption to vary the interpulse period.
24 Citations
7 Claims
- 1. An induction heating apparatus for supplying constant power to a variable heating load comprising a thyristor connected to receive power from a power source, a commutating circuit including an induction heating coil and a capacitor connected to said thyristor for commutating same, a fixed time constant differentiator connected across the anode and cathode terminals of said thyristor for differentiating a potential developed across said anode and cathode terminals to develop a load power responsive signal, a smoothing circuit for converting said load power responsive signal into a corresponding d-c signal, means for generating a deviation signal representative of the deviation of said d-c signal from a reference value corresponding to a reference power level, and means for supplying the gating control terminal of said thyristor with gating pulses at a frequency in the ultrasonic range with the period between successive ones of said gating pulses being variable as a function of said deviation signal.
Specification