High-frequency heating apparatus
First Claim
1. A high frequency heating apparatus for driving a magnetron, comprising,a direct current power supply;
- a series circuit comprising a pair of semiconductor switching elements; and
a resonance circuit connected with a primary coil of a leakage transformer and a capacitor;
in which the series circuit is connected to the direct current power supply in parallel, and, in an AC equivalent circuit, an end of the resonance circuit is connected to an intermediate point of one end of the series circuit and the other end is connected to an end of the direct current power supply, and further comprising,a drive means for driving the respective semiconductor switching elements;
a rectifying means, which is connected to a secondary coil of the leakage transformer; and
a magnetron, which is connected to the rectifying means,wherein a variable dead time preparation circuit which allows a period for which respective semiconductor switching elements are simultaneously turned off to vary in response to a switching frequency is provided,wherein the variable dead time preparation circuit allows the dead time to increase in response to a rise in the switching frequency when the switching frequency is greater than or equal to a predetermined switching frequency, andwherein the variable dead time preparation circuit allows the dead time to remain constant or to increase minutely as a function of the switching frequency when the switching frequency is less than the predetermined switching frequency.
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Accused Products
Abstract
A resonance type high frequency heating apparatus comprising; a direct current power supply; a series connection circuit consisting of a pair of semiconductor switching elements connected in parallel to the direct current power supply; another series connection circuit having a primary coil of a leakage transformer and a capacitor connected to both ends of one of the pair of semiconductor switching elements; and a drive means for driving each of the pair of semiconductor switching elements; wherein a variable dead time preparation circuit is provided in the drive means, and the variable dead time preparation circuit enables dead time to remain constant at below a predetermined frequency and causes the dead time to increase sharply at a point above a predetermined frequency.
7 Citations
12 Claims
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1. A high frequency heating apparatus for driving a magnetron, comprising,
a direct current power supply; -
a series circuit comprising a pair of semiconductor switching elements; and a resonance circuit connected with a primary coil of a leakage transformer and a capacitor; in which the series circuit is connected to the direct current power supply in parallel, and, in an AC equivalent circuit, an end of the resonance circuit is connected to an intermediate point of one end of the series circuit and the other end is connected to an end of the direct current power supply, and further comprising, a drive means for driving the respective semiconductor switching elements; a rectifying means, which is connected to a secondary coil of the leakage transformer; and a magnetron, which is connected to the rectifying means, wherein a variable dead time preparation circuit which allows a period for which respective semiconductor switching elements are simultaneously turned off to vary in response to a switching frequency is provided, wherein the variable dead time preparation circuit allows the dead time to increase in response to a rise in the switching frequency when the switching frequency is greater than or equal to a predetermined switching frequency, and wherein the variable dead time preparation circuit allows the dead time to remain constant or to increase minutely as a function of the switching frequency when the switching frequency is less than the predetermined switching frequency. - View Dependent Claims (4, 5, 6, 7, 8, 9, 10, 11)
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2. A high frequency heating apparatus for driving a magnetron, comprising,
a direct current power supply; -
two sets of series circuits each consisting of a pair of semiconductor switching elements; and a resonance circuit connected with a primary coil of a leakage transformer and a capacitor; in which two sets of the series circuits are respectively connected to the direct current power supply in parallel, and an end of the resonance circuit is connected to an intermediate point of the one end of series circuits and the other end thereof is connected to an intermediate point of the other direct current power supply, and further comprising, a drive means for driving the respective semiconductor switching elements; a rectifying means, which is connected to a secondary coil of the leakage transformer; and a magnetron, which is connected to the rectifying means, wherein a variable dead time preparation circuit which allows a period for which respective semiconductor switching elements are simultaneously turned off to vary in response to a switching frequency is provided, wherein the variable dead time preparation circuit allows the dead time to increase in response to a rise in the switching frequency when the switching frequency is greater than or equal to a predetermined switching frequency, and wherein the variable dead time preparation circuit allows the dead time to remain constant or increase minutely as a function of the switching frequency when the switching frequency is less than the predetermined switching frequency.
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3. A high frequency heating apparatus for driving a magnetron, comprising,
a direct current power supply; -
a series circuit consisting of a pair of semiconductor switching elements; and a resonance circuit connected with a primary coil of a leakage transformer and a capacitor; in which the series circuit is connected to the direct current power supply in parallel, and the resonance circuit is connected in parallel to one of the semiconductor switching elements, and further comprising, a drive means for driving the respective semiconductor switching elements; a rectifying means, which is connected to a secondary coil of the leakage transformer; and a magnetron, which is connected to the rectifying means, wherein a variable dead time preparation circuit which allows a period for which respective semiconductor switching elements are simultaneously turned off to vary in response to a switching frequency is provided, wherein the variable dead time preparation circuit allows the dead time to increase in response to a rise in the switching frequency when the switching frequency is greater than or equal to a predetermined switching frequency, and wherein the variable dead time preparation circuit allows the dead time to remain constant or increase minutely as a function of the switching frequency when the switching frequency is less than the predetermined switching frequency.
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12. A high frequency heating apparatus for driving a magnetron, which is comprised of a frequency-controlled type resonance inverter circuit having at least an arm including semiconductor switching elements;
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the high frequency heating apparatus further comprises a variable dead time preparation circuit, which allows a period for which the respective semiconductor switching elements are simultaneously turned off to vary in response to a switching frequency; wherein, the variable dead time preparation circuit prepares a dead time based on plus and minus offset voltages which vary by a first slope in proportion to an increase in the switching frequency and further vary from a predetermined switching frequency by a second slope, wherein the variable dead time preparation circuit allows the dead time to increase in response to a rise in the switching frequency when the switching frequency is greater than or equal to the predetermined switching frequency, and wherein the variable dead time preparation circuit allows the dead time to remain constant or increase minutely as a function of the switching frequency when the switching frequency is less than the predetermined switching frequency.
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Specification