High-frequency heating apparatus
First Claim
1. A high frequency heating apparatus for driving a magnetron, comprising:
- a DC power supply which is constituted by an AC power supply, a rectifying circuit for rectifying an AC voltage of said AC power supply, and a smoothing capacitor for smoothing an output voltage of said rectifying circuit;
a series circuit constituted by two pieces of semiconductor switching elements;
a resonant circuit in which a primary winding of a leakage transformer and a capacitor are connected, said series circuit being connected parallel to said DC power supply, and one end of said resonant circuit being connected to a center point of said series circuit and the other end of said resonant circuit being connected to one end of said DC power supply in an AC equivalent circuit;
driving means for driving said semiconductor switching elements respectively by alternately turning on and off said semiconductor switching elements while providing a dead time for concurrently turning off said two semiconductor switching elements;
rectifying means connected to a secondary winding of said leakage transformer; and
the magnetron connected to said rectifying means;
a control signal forming circuit for forming a control signal from a difference between an input current of the AC power supply and a reference current, or a difference between a voltage to be applied to the magnetron and a reference voltage;
a frequency modulated signal forming circuit for correcting rectified voltage/rectified current which are obtained by rectifying the AC voltage/current of the AC power supply based upon the control signal of the control signal forming circuit;
a dead time forming circuit for generating a dead time control signal which enables the driving means to set said dead time depending on the output of the frequency modulated signal forming circuit; and
a control signal converting circuit configured to lower the value of said control signal when polarity of the control signal converting circuit is positive, the control signal converting circuit being disposed between and connected to said control signal forming circuit and said frequency modulated signal forming circuit.
2 Assignments
0 Petitions
Accused Products
Abstract
A purpose of the present invention is to provide an inverter circuit capable of suppressing an overshooting phenomenon of an input current at an instantaneous time when an initiating operation of the inverter circuit is switched to the normal operation thereof, and thus, capable of preventing damages of IGBTs and a magnetron.
In a high frequency heating apparatus comprising: a control signal forming circuit for forming a control signal from a difference between an input current of an AC power supply and a reference current; a frequency modulated signal forming circuit for correcting rectified voltage/rectified current which are obtained by rectifying the AC voltage/current of the AC power supply based upon the control signal of the control signal forming circuit; and a dead time forming circuit for receiving the output of the frequency modulated signal forming circuit, a control signal converting circuit having a function capable of further lowering the value of the control signal is provided between the control signal forming circuit and the frequency modulated signal forming circuit.
5 Citations
21 Claims
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1. A high frequency heating apparatus for driving a magnetron, comprising:
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a DC power supply which is constituted by an AC power supply, a rectifying circuit for rectifying an AC voltage of said AC power supply, and a smoothing capacitor for smoothing an output voltage of said rectifying circuit; a series circuit constituted by two pieces of semiconductor switching elements; a resonant circuit in which a primary winding of a leakage transformer and a capacitor are connected, said series circuit being connected parallel to said DC power supply, and one end of said resonant circuit being connected to a center point of said series circuit and the other end of said resonant circuit being connected to one end of said DC power supply in an AC equivalent circuit; driving means for driving said semiconductor switching elements respectively by alternately turning on and off said semiconductor switching elements while providing a dead time for concurrently turning off said two semiconductor switching elements; rectifying means connected to a secondary winding of said leakage transformer; and the magnetron connected to said rectifying means; a control signal forming circuit for forming a control signal from a difference between an input current of the AC power supply and a reference current, or a difference between a voltage to be applied to the magnetron and a reference voltage; a frequency modulated signal forming circuit for correcting rectified voltage/rectified current which are obtained by rectifying the AC voltage/current of the AC power supply based upon the control signal of the control signal forming circuit; a dead time forming circuit for generating a dead time control signal which enables the driving means to set said dead time depending on the output of the frequency modulated signal forming circuit; and a control signal converting circuit configured to lower the value of said control signal when polarity of the control signal converting circuit is positive, the control signal converting circuit being disposed between and connected to said control signal forming circuit and said frequency modulated signal forming circuit. - View Dependent Claims (4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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2. A high frequency heating apparatus for driving a magnetron, comprising:
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a DC power supply which is constituted by AC power supply, a rectifying circuit for rectifying an AC voltage of said AC power supply, and a smoothing capacitor for smoothing an output voltage of said rectifying circuit; two sets of series circuits, each of said series circuits being constituted by two pieces of semiconductor switching elements; a resonant circuit in which a primary winding of a leakage transformer and a capacitor are connected, said two sets of series circuits being connected parallel to said DC power supply respectively, and one end of said resonant circuit being connected to a center point of said one series circuit and the other end of said resonant circuit being connected to a center point of the other series circuit; driving means for driving said semiconductor switching elements respectively by alternately turning on and off said semiconductor switching elements while providing a dead time for concurrently turning off said two semiconductor switching elements; rectifying means connected to a secondary winding of said leakage transformer; and the magnetron connected to said rectifying means; a control signal forming circuit for forming a control signal from a difference between an input current of the AC power supply and a reference current, or a difference between a voltage to be applied to the magnetron and a reference voltage; a frequency modulated signal forming circuit for correcting rectified voltage/rectified current which are obtained by rectifying the AC voltage/current of the AC power supply based upon the control signal of the control signal forming circuit; a dead time forming circuit for generating a dead time control signal which enables the driving means to set said dead time depending on the output of the frequency modulated signal forming circuit; and a control signal converting circuit configured to lower the value of said control signal when polarity of the control signal converting circuit is positive, the control signal converting circuit being disposed between and connected to said control signal forming circuit and said frequency modulated signal forming circuit.
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3. A high frequency heating apparatus for driving a magnetron, comprising:
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a DC power supply which is constituted by an AC power supply, a rectifying circuit for rectifying an AC voltage of said AC power supply, and a smoothing capacitor for smoothing an output voltage of said rectifying circuit; a series circuit constituted by two pieces of semiconductor switching elements; a resonant circuit in which a primary winding of a leakage transformer and a capacitor are connected, said series circuit being connected parallel to said DC power supply, and said resonant circuit being connected to one of said semiconductor switching elements in a parallel manner; driving means for driving said semiconductor switching elements respectively by alternately turning on and off said semiconductor switching elements while providing a dead time for concurrently turning off said two semiconductor switching elements; rectifying means connected to a secondary winding of said leakage transformer; and the magnetron connected to said rectifying means; a control signal forming circuit for forming a control signal from a difference between an input current of the AC power supply and a reference current, or a difference between a voltage to be applied to the magnetron and a reference voltage; a frequency modulated signal forming circuit for correcting rectified voltage/rectified current which are obtained by rectifying the AC voltage/current of the AC power supply based upon the control signal of the control signal forming circuit; a dead time forming circuit for generating a dead time control signal which enables the driving means to set said dead time depending on the output of the frequency modulated signal forming circuit; and a control signal converting circuit configured to lower the value of said control signal when polarity of the control signal converting circuit is positive, the control signal converting circuit being disposed between and connected to said control signal forming circuit and said frequency modulated signal forming circuit.
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Specification