초록 ▼

The present invention is an improved induction heating apparatus and more particularly a improved oscillation control circuit. The induction heating apparatus includes at least one induction coil, with a parallel capacitance forming an LC oscillation circuit. A set of at least one semiconductor swit

The present invention is an improved induction heating apparatus and more particularly a improved oscillation control circuit. The induction heating apparatus includes at least one induction coil, with a parallel capacitance forming an LC oscillation circuit. A set of at least one semiconductor switching devices enables a power source to be coupled to the LC oscillation circuit. This power source is preferably a half wave rectified AC voltage. A control circuit periodically switches ON the semiconductor switching devices to couple the half wave rectified AC voltage to the LC oscillation circuit thereby stimulating electrical oscillations. The control circuit includes an initialization circuit for inhibiting the first coupling of the half wave rectified AC voltage to the LC oscillation circuit while the half wave rectified AC voltage is greater than a predetermined amount. In the preferred embodiment this is achieved by delaying this initial energization until a leading edge of a pulse of the half wave rectified AC voltage. This serves to protect the semiconductor switching devices from possible initial overcurrent conditions.

대표청구항 ▼

An induction heating apparatus comprising: at least one induction coil having first and second terminals; a capacitance connected in parallel with said at least one induction coil; a rectifier circuit adapted for connection to a source of alternating current electrical power for producing half wave

An induction heating apparatus comprising: at least one induction coil having first and second terminals; a capacitance connected in parallel with said at least one induction coil; a rectifier circuit adapted for connection to a source of alternating current electrical power for producing half wave rectified alternating current electrical power having a pulsating voltage; at least one semiconductor switching device having a conducting state and a nonconducting state for selectively connecting said half wave rectified alternating current electrical power across said first and second terminals of said at least one induction coil; a control circuit including a triggerable one shot circuit having a trigger input, a reset input and an output connected to said at least one semiconductor switching device for generating a predetermined voltage at said output for a predetermined trigger interval upon receipt of a trigger signal at said trigger input in the absence of a reset signal at said reset input, said predetermined voltage at said output placing said at least one semiconductor switching device in said conducting state for said predetermined trigger interval thereby stimulating electrical oscillation within the combination of said at least one induction coil and said capacitance; a trigger circuit responsive to the voltage of said half wave rectified alternating current power source, and the voltage at said first terminal of said at least one induction coil, and connected to said trigger input of said trigger one shot circuit for generating a trigger signal for application to said trigger input of said triggerable one shot circuit upon detection of a predetermined relationship between the voltage of said half wave rectified alternating current power source and the voltage at said first terminal of said at least one induction coil, an initialization circuit responsive to said half wave rectified alternating current electrical power source and connected to said reset input of said trigger one shot circuit for generating said reset signal thereby inhibiting said trigger one shot circuit upon initial energization of said induction heating apparatus until the leading edge of one of the pulses of said pulsating voltage of said half wave rectified alternating current electrical power.