JP3206498B2 - High frequency heating equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply for driving a magnetron of a high-frequency heating device using a magnetron.

[0002]

2. Description of the Related Art As shown in FIG. 15, a conventional high-frequency heating apparatus uses a circuit configuration called a one-piece voltage resonance type circuit. Reference numeral 51 denotes a commercial power supply, and 52 denotes a rectifier formed by full-wave rectification, which rectifies the commercial power to form a DC power supply. 53
And 54 are capacitors, 55 is the first winding 56 and the second
, A semiconductor switching element, 60 a magnetron, 64 a heater of the magnetron 60, 65 a heater 64 of the magnetron 60 and the third winding 58. Are coils connected in series. Power is transmitted from the first winding 56 to the third winding 58 and the magnetron 6
The heater current is supplied to the heater 64 via the coil 65. 61 is a drive circuit for driving the semiconductor switching element 59. The first winding 56 of the leakage type transformer 55 and the capacitor 54 constitute a resonance circuit, and the voltage waveform of the semiconductor switching element 59 becomes sinusoidal by this action. The collector voltage and current waveform of the semiconductor switching element 59 are as shown in FIGS.

The effect of this resonance circuit is that the current starts to flow after the voltage becomes zero, so that the switching loss at the time of ON (the portion where the voltage and the current overlap) is reduced. At the time of off, the current is sharply cut off, but since the voltage rises in a sine wave shape, the slope becomes gentle and the switching loss at the time of off is reduced. Thus, the resonance type circuit has an effect of reducing the switching loss of the semiconductor switching element.

Since the drive circuit 61 shown in FIG. 15 needs to supply an ON signal at the timing when the collector voltage of the semiconductor switching element 59 becomes zero, a comparison circuit 62 for comparing the voltage of the collector with the voltage of the capacitor 53 is provided. hand,
The intersection of the collector voltage and the capacitor voltage is detected. This circuit section detects the vicinity of zero voltage of the collector voltage by comparing the collector voltage with the voltage of the capacitor 53, transmits the signal to the drive circuit 61, and drives the semiconductor switching element 59 at a predetermined frequency. Create a signal.

The heater 64 of the magnetron 60 doubles as the cathode of the magnetron 60,
The temperature rises to about 000 K, and thermoelectrons are emitted from the heater 64. An appropriate temperature at which the heater 64 emits electrons is 1900K to 2100K. 1900K
In the following, since the heater temperature is low, a moding phenomenon due to insufficient electron emission ability is likely to occur, and the life of the magnetron 60 is significantly reduced. At 2100K or more, the alteration phenomenon of the heater 64 occurs and 1900K
As in the following cases, the life is significantly reduced. The magnetron 60 has a cut-off voltage at which oscillation starts at about -4 kV or more, and becomes low impedance of about 300Ω when oscillating. At a voltage of about −4 kV or less, the magnetron 60 does not oscillate, and its impedance becomes a value of 10 MΩ or more.

FIG. 16 shows the operation of the magnetron 60 from the start state to the oscillation state. When the semiconductor switching element 59 is turned on, a current flows through the first winding 56 of the leakage transformer 55, and a voltage is applied to the third winding 58, a heater current (FIG. 2B) starts to flow. The temperature of the heater 64 of the magnetron 60 rises as shown in FIG. When the temperature of the heater 64 rises to a range of 1900 K to 2100 K at which the magnetron 60 oscillates, the region shifts from a start-up region to an oscillation region as shown in FIG.

As described above, the conditions under which the magnetron 60 oscillates are as follows.
When 4 is kept at an appropriate temperature and a voltage equal to or higher than the cutoff voltage is applied, oscillation occurs.

In FIG. 17, during the ON period (state A) of the semiconductor switching element 59, the leakage type transformer 55
Current flows through the first winding 56, and the second winding 57, the third winding
, A voltage is generated in each of the windings 58. Third winding 58
The heater 6 of the magnetron 60 is
4 is supplied with a heater current necessary for the oscillation of the magnetron 60 via the coil 65. Then, the second winding 57
Is added to the initial voltage stored in the capacitor of the rectifier circuit 63, the magnetron 60 is energized with a negative voltage, and the magnetron 60 oscillates when the heater current reaches an appropriate temperature due to the heater current. The energized magnetron 60 generates microwaves to heat the food. When the semiconductor switching element 59 is turned off, the current flowing through the first winding 56 of the leakage type transformer 55 starts flowing toward the capacitor 54 to start a resonance operation (state B). At this time, the second winding 57 of the leakage type transformer 55 charges the capacitor of the rectifier circuit 63. The voltage waveform of the semiconductor switching element 59 and the voltage waveform of the first winding 56 are shown in FIG.
(C).

FIG. 18A shows a waveform of a commercial power supply 51,
Hz or 60 Hz. FIG. 4B shows an input current waveform supplied from the commercial power supply 51, and FIG.
Is the output voltage V1 of the DC power supply obtained by rectifying the commercial power supply 51 with the rectifier 52.

Although the capacitor 53 has the effect of rectifying the output voltage V1 of the DC power supply, the degree of smoothness is small because the capacitance value is small, and as shown in FIG. The waveform has a large ripple at the same cycle as the cycle. By setting such a degree of smoothness, the waveform distortion of the input current can be reduced.

The semiconductor switching element 59 has a frequency of 20 kHz.
18D, the resonance current of the frequency shown in FIG. 18D flows through the capacitor 53. However, the current at this frequency is
The filter action of the inductor 3 and the inductor 66 prevents the current from the commercial power supply 51 from being superimposed.

As described above, since the present circuit uses a single-type voltage resonance type circuit, the semiconductor switching element 59 is used.
It is necessary to give a drive signal at the timing of zero voltage.
However, as shown in the waveform diagram of FIG.
The voltage V1 applied to the resonance circuit formed by the capacitor 54 and the first winding 56 of the leakage type transformer 55 and the series circuit of the semiconductor switching element 59 is substantially zero.

[0013]

(Equation 1)

E: It has a large ripple that varies up to the commercial power supply voltage. Therefore, the cut-off voltage of the magnetron 60 does not reach during the period when the voltage V1 is low even if the voltage is boosted by the leakage type transformer.
At this time, the impedance of the magnetron 60 has a high impedance as described above. Since the high part of the voltage V1 reaches the cutoff voltage, the magnetron 6
The impedance of 0 becomes low. Thus, the voltage V1
Since the impedance of the magnetron 60 greatly changes depending on the magnitude of the above, the influence affects the switching operation at zero voltage. That is, the timing at which the voltage becomes zero differs depending on the magnitude of the voltage V1.
The operating frequency changes as shown in FIG.

Therefore, as described above, since the drive circuit 61 needs to supply an ON signal at the timing when the collector voltage of the semiconductor switching element 59 becomes zero, the comparison circuit 6 for comparing the voltage of the collector with the voltage of the capacitor 53 is required.
2 to detect the intersection of the collector voltage and the capacitor voltage, thereby detecting near zero voltage of the collector voltage and transmitting the signal to the drive circuit 61 to drive the semiconductor switching element 59 at a predetermined frequency. It is essential to do so. As a result, the operating frequency changes according to the voltage V1 as shown in FIG.

FIGS. 17A and 17B are waveform diagrams showing the collector current and the collector voltage of the semiconductor switching element 59 at the peak point of the voltage V1. In FIG. 7B, the collector voltage V2 generates a voltage that is about four times the commercial power supply voltage E for a period of time t2. This is due to the action of the resonance circuit. The value of this voltage is obtained as follows. When the semiconductor switching element 59 is operating,
Assuming that the current flowing through the first winding 56 of the leakage type transformer 55 is IL, the stored energy is expressed as WL = (IL2 × L1) / 2 (2) L1: inductance of the first winding. When the semiconductor switching element 59 is turned off, a current starts to flow from the first winding 56 of the leakage type transformer 55 toward the capacitor 54 and the first winding 5
Since the energy of No. 6 is transferred to the capacitor 54, the following equation is established.

WL = CV2 / 2 + α (3) C: capacitance of the capacitor 54 α: energy for charging the capacitor of the rectifier circuit 63 From this equation, the voltage V is

[0018]

(Equation 2)

[0019]

When the magnetron is started, a sufficient heater current must be supplied to the heater 64 of the magnetron 60. Therefore, the impedance of the coil 65 connected in series between the magnetron 60 and the third winding 58 is reduced. There is a need to lower it. The impedance of the coil 65 is represented by Z = ωL = 2πfL (5) L: inductance of the coil f: operating frequency of the drive circuit If f is reduced, the impedance of the coil 65 decreases, and a necessary and sufficient heater current for magnetron oscillation can be supplied.

[0021]

However, since the conventional magnetron drive power supply uses a single-type voltage resonance type circuit, the voltage applied to the semiconductor switching element is about four times the power supply voltage E by the action of the resonance circuit. And the period of occurrence t2 is determined by the resonance constant of the resonance circuit. Further, as described above, a sufficient heater current is required at the time of starting the magnetron, so that it becomes necessary to reduce the impedance of the coil. For this purpose, the operating frequency of the drive circuit must be lowered according to equation (5). Since the generation period of the collector voltage of the semiconductor switching element is fixed by the resonance constant of the resonance circuit, the generation period t1 of the collector current flowing through the semiconductor switching element must be increased in order to lower the operating frequency. Here, i = E / L1 * t1 (6) i: Collector current E: Commercial power supply voltage L1: Inductance of first winding t1: Collector current generation period Becomes larger, and when Expression (2) = Expression (3), (IL2 × L1) / 2 = CV2 / 2 + α (i = IL), and the collector voltage V also increases. Further, the relational expression between the number of turns of the first winding and the second winding and the voltage is as follows: n2 / n1 = VL2 / VL1 (7) n1: the number of turns of the first winding n2: the second winding The number of turns of the wire VL1: Voltage of the first winding VL2: Voltage of the second winding The relationship between the collector voltage and the first winding voltage has a close relationship as shown in FIGS. When the collector voltage V increases, the first winding voltage increases, and according to Expression (7), the second winding voltage necessarily increases. In order to obtain a sufficient heater current, an unnecessary collector voltage and second winding voltage are generated when the magnetron is started. As a result, the breakdown voltage of the semiconductor switching element must be sufficiently high, the breakdown voltage of each component of the rectifier circuit to which the second winding voltage is applied must be sufficiently high, and the starting time of the magnetron is long. Had issues.

[0022]

According to the present invention, there is provided a DC power supply obtained by rectifying a commercial power supply.
A magnetron and supplying a high voltage to the magnetron
A first winding connected to the DC power supply, a second winding, and a third winding, and a first winding on a primary side of the leakage transformer.
Connected first and second capacitors, and the first capacitor.
A first capacitor connected in series with the first winding .
1 semiconductor switching element and connected to the first winding
It has been a series connection between the second capacitor and the second semiconductor switching element, a drive circuit for driving the said first semiconductor switching element and the second semiconductor switching element, said second winding A rectifier circuit connected to the third winding and the magnetron;
And a coil connected in series between the first condenser and the second condenser.
The capacity of the second semiconductor switch is also set large.
The driving of the first semiconductor switching element is used as the switching element.
It is necessary to provide a signal with a delay time to the inverted signal of the dynamic signal.
When the second semiconductor switching element is turned on,
The distance can be adjusted arbitrarily and the magnetron is activated
Sometimes the first semiconductor switching from the driving circuit
Signal applied to the element and the second semiconductor switching element
The first semiconductor switching element.
The on-time of the pulse signal given to the second semiconductor
By making the on-time shorter than the on-time given to the switching element , in the conventional circuit, the off-time of the first semiconductor switching element, which was determined by the resonance circuit and could not be adjusted, can be arbitrarily adjusted. Can be reduced, the impedance of the coil connected between the magnetron heater and the third winding can be reduced, the heater current necessary and sufficient for magnetron oscillation can be obtained, and the magnetron can be started. Can be shortened.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a DC power supply obtained by rectifying a commercial power supply, a magnetron, and the magnetron.
For supplying a high voltage to the DC power supply, the leakage transformer having a first winding, a second winding, and a third winding, and one of the leakage transformers.
First and second capacitors connected to the first winding on the secondary side
And the first winding connected to the first capacitor.
A first semiconductor switching element connected in series to the first coil , a series connection of the second capacitor and a second semiconductor switching element connected to the first winding,
A drive circuit for driving the the semiconductor switching element and the second semiconductor switching element, said second winding before
A rectifier circuit connected to the magnetron ;
A coil connected in series between a winding and a heater of the magnetron , wherein the second capacitor is
While the capacity is set larger than the capacitor of No. 1,
A first semiconductor switch is provided to the second semiconductor switching element.
There is a delay time for the inversion signal of the driving signal of the switching element.
The second semiconductor switch.
The on-time of the switching element can be adjusted as desired.
At the time of starting the magnetron, the first
Semiconductor switching element, second semiconductor switching element
By reducing the frequency of the pulse signal given to the first semiconductor switching element and making the on-time of the pulse signal given to the first semiconductor switching element shorter than the on-time given to the second semiconductor switching element, the operation at the start of the magnetron Since the frequency can be reduced, the impedance of the coil connected between the heater of the magnetron and the third winding is reduced, so that the heater current required and sufficient for the magnetron heater can be obtained. The time required for starting the magnetron can be reduced.

According to the second aspect of the present invention, there is provided the first aspect.
In addition to the invention, driving the first winding voltage reference signal and the comparison
A comparator circuit for outputting a signal to the dynamic circuit, by changing the first semiconductor switching element ON time ratio of the second semiconductor switching element, so that the first winding voltage becomes a predetermined value, the With the configuration in which the driving circuit is controlled from the comparison circuit, the withstand voltage of the first semiconductor switching element can be reduced, and the voltage generated in the second winding is also reduced. The withstand voltage can be lowered. Furthermore, since the impedance of the coil connected between the heater and the third winding of the magnetron is reduced, a heater current necessary and sufficient for magnetron oscillation is obtained, and the time required for starting the magnetron is reduced. Shortening can be realized.

[0025]

Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1 FIG. 1 is a circuit diagram of a magnetron driving power supply according to an embodiment of the present invention.

In FIG. 1, 1 is a DC power supply, 7 is a first capacitor, 8 is a second capacitor, 9 is a second semiconductor switching element, 6 is a first semiconductor switching element, 10 is a driving circuit, Is a leakage type transformer composed of a first winding 2, a second winding 3, and a third winding 4, 11
Denotes a full-wave voltage rectifier circuit, 12 denotes a magnetron, 13 denotes a coil, and 14 denotes a heater.

The drive circuit 10 generates a signal of a predetermined frequency and a duty, and supplies a drive signal to the first semiconductor switching element 6 and the second semiconductor switching element 9. The second semiconductor switching element 9 is provided with a signal obtained by adding a delay time to an inverted signal of the drive signal of the first semiconductor switching element 6.

The operation of this circuit will be described with reference to FIGS. First, when the first semiconductor switching element 6 is turned on, an equivalent circuit of a main circuit portion after the DC power supply 1 is as shown in FIG. 2A, and the collector current Ic is changed to the first circuit of the leakage type transformer 5. It is supplied from the third capacitor 17 through the winding 2 (state (a) in FIG. 3A). At this time, the third winding 4 of the leakage type transformer 5
Power is transmitted to the heater 14 and the heater 14 starts to supply a heater current via the coil 13. The output of the second winding 3 starts charging the capacitor 16 of the full-wave voltage doubler rectifier circuit 11. Since the capacitor 15 stores the initial voltage V2, the voltage V3 of the capacitor 16 has the following relationship: V2 + V3> Vcut (8) Vcut: magnetron cut-off voltage, and the temperature of the heater 14 is equal to the heater current. When the temperature reaches an appropriate temperature, the magnetron 12 can be oscillated.

When the first semiconductor switching element 6 is turned off, the equivalent circuit becomes as shown in FIG. 2B, and the current flowing through the first winding 2 of the leakage type transformer 5 is supplied to the first capacitor 7. Start to flow towards. At this time, the output of the second winding 3 of the leakage type transformer 5 is
5 is started (state (b) in FIG. 3A). At this time,
When Expression (8) is satisfied, the magnetron 12 starts oscillating again. The current of the first winding 2 of the leakage transformer 5 is as shown in FIG. The voltage of the first semiconductor switching element 6 is as shown in FIG. When this voltage reaches the initial voltage of the second capacitor 8, the diode constituting the second semiconductor switching element 9 turns on,
The charging of the second capacitor 8 is started. The equivalent circuit at this time is as shown in FIG. Second capacitor 8
Since the capacitance of the first semiconductor switching element 6 is larger than that of the first capacitor 7, the slope of the voltage of the first semiconductor switching element 6 sharply becomes gentle, and the state shifts to the state C in FIG. From the first winding 2 of the leakage type transformer 5 to the second
The current flowing toward the capacitor 8 of
When the current flows from the second capacitor 8 toward the first winding, the state shifts to state d. At this point, it is necessary to turn on the transistor constituting the second semiconductor switching element 9. When the transistor forming the second semiconductor switching element 9 is cut off at an arbitrary time T1, the state shifts to a state E in which current starts to flow from the first capacitor 7 toward the first winding of the leakage type transformer 5. At this time, the slope of the voltage of the first semiconductor switching element 6 becomes steep, and decreases toward zero due to the energy of the first capacitor 7. When the first semiconductor switching element 6 is driven again when this voltage becomes zero, the same operation is repeated from the state A, and the switching operation for reducing the switching loss can be realized. Thereafter, the state A to the state E are repeated, but the heater current is continuously supplied from the third winding 4 to the heater 14, and an appropriate heater temperature is maintained.

FIG. 4A shows a voltage waveform of a commercial power supply having a frequency of 50 or 60 Hz. FIG. 3B shows an input current waveform supplied from a commercial power supply, and FIG. 3C shows an output voltage of the DC power supply 1 obtained by rectifying the commercial power supply with a rectifier.

The third capacitor 17 has the effect of rectifying the output voltage of the DC power supply, but has a small capacitance value and therefore has a low degree of smoothness. As shown in FIG. The waveform V1 has a large ripple at the same cycle as the cycle V1. By setting such a degree of smoothness, the waveform distortion of the input current can be reduced.

The first semiconductor switching element 6 is given by
Since the operation is performed at a frequency of about kHz, the oscillating current having the frequency shown in FIG. However, the current at this frequency
The filter action of the capacitor 17 and the inductor 17 prevents the input current from being superimposed. As described above, this circuit includes the second semiconductor switching element 9.
Is characterized in that the on-time T1 of the transistor constituting can be set arbitrarily. In order to realize the switching of the first semiconductor switching element 6 at zero voltage, for example, the operation of the area E in FIG. 3 becomes important. The voltage at which the voltage of the first semiconductor switching element 6 decreases toward zero is determined by the energy of the first capacitor 7, so that the voltage of the first semiconductor switching element 6 only reaches zero. Energy must be stored in the first capacitor 7. Energy is represented by equation (3), but since the capacitance value C is invariable, energy can be replaced by voltage. First
The voltage of the capacitor 7 is determined by the voltage of the second capacitor 8. That is, it can be determined by the on-time of the transistor constituting the second semiconductor switching element 9. Therefore, even if the first semiconductor switching element 6 is operated at a constant frequency with respect to the change of the voltage V1,
By adjusting the ON time of the transistor constituting the semiconductor switching element 9, the first capacitor 7 can store as much energy as the zero voltage of the first semiconductor switching element 6 can store.

As described above, the off time of the first semiconductor switching element 6, which cannot be realized by the conventional circuit configuration,
In other words, the ON time of the second semiconductor switching element 9 can be set arbitrarily, and the operating frequency at the time of starting the magnetron can be reduced, so that the connection between the heater 14 of the magnetron 12 and the third winding 4 can be made. Coil 1
3, the heater current necessary and sufficient for starting the magnetron is obtained, and the magnetron 12
Can be reduced in time required for activation.

Embodiment 2 In FIG. 5, the same reference numerals are used for the same elements as those in FIG. The basic circuit operation is the same as in the first embodiment.
Reference numeral 19 compares the voltage value of the first semiconductor switching element 6 with a reference voltage value, and outputs the output signal to the drive circuit 1.
This is a comparison circuit that outputs 0. A pulse signal to be given to the first semiconductor switching element 6 and the second semiconductor switching element 9 is set by the output signal of the comparison circuit 19, and the on-time of the first semiconductor switching element 6 and the second semiconductor switching element 9 is set. The drive circuit 10 controls the first semiconductor switching element 6 and the second semiconductor switching element 9 so that the voltage ratio of the first winding 2 becomes a predetermined value. As described above, the on-time ratio of the first semiconductor switching element 6 and the second semiconductor switching element 9 that cannot be realized by the conventional circuit configuration can be controlled so that the voltage of the first winding 2 becomes a predetermined value. Therefore, the withstand voltage of the first semiconductor switching element can be reduced, and the voltage applied from the second winding 3 to the full-wave voltage rectifier circuit 11 can also be kept low.
The withstand voltage of each component can also be reduced. Furthermore, the off-time of the first semiconductor switching element 6, in other words, the on-time of the second semiconductor switching element 9 can be set arbitrarily, and the operating frequency at the time of starting the magnetron can be reduced. The impedance of the coil 13 connected between the coil 14 and the third winding 4 is reduced, so that a sufficient and sufficient heater current for starting the magnetron is obtained, and the time required for starting the magnetron 12 can be reduced.

(Embodiment 3) In FIG. 7, the same reference numerals are used for the same elements as those in FIG.

The output of the second winding 3 of the leakage type transformer 5 is rectified by the half-wave voltage rectifier circuit 30, and the DC voltage energizes the magnetron 12. FIG. 8A shows a current waveform of the first semiconductor switching element 6, and FIG.
FIG. 3C shows a current waveform of the first winding 2, FIG. 4C shows a voltage waveform of the first semiconductor switching element 6, and FIG. 4D shows a voltage waveform of the first winding 2. When the first semiconductor switching element 6 is on (state a in FIG. 8), a current flows through the first winding 2 of the leakage type transformer 5 and the second winding 3
7, a voltage is generated in the direction of the arrow in FIG. 7, and this voltage and the voltage stored in the capacitor of the half-wave voltage rectifier circuit 30 are added to energize the magnetron 12. When the first semiconductor switching element 6 is turned off, the current flowing through the first winding 2 of the leakage transformer 5 starts flowing toward the first capacitor 7 (state B in FIG. 8), and When the voltage reaches the initial voltage of the second capacitor 8, a current also starts flowing through the second capacitor 8. In the state c in FIG. 8, the voltage applied to the first semiconductor switching element 6 is not clamped. This is the same as in the first embodiment. From the second capacitor 8 to the leakage transformer 5
The current starts to flow toward the primary side of (a state d in FIG. 8),
When the second semiconductor switching element 9 is turned off at an arbitrary time T1, the current becomes only from the first capacitor 7, and the voltage of the first semiconductor switching element 6 decreases toward zero with a steep gradient (FIG. State 8). During the period from state B to state E, the voltage generated in the second winding 3 of the leakage transformer 5 causes the half-wave multiple voltage rectifier circuit 30
Is charged.

Embodiment 4 In FIG. 9, the same reference numerals are used for the same elements as those in FIG.

The output of the second winding 3 of the leakage type transformer 5 is rectified by a full-wave rectifier circuit 31, and the DC voltage energizes the magnetron 12. FIG. 8A shows the current waveform of the first semiconductor switching element 6, and FIG.
FIG. 3C shows a voltage waveform of the first semiconductor switching element 6, and FIG. 4D shows a voltage waveform of the first coil 2. When the first semiconductor switching element 6 is on (state a in FIG. 8), a current flows through the first winding 2 of the leakage type transformer 5 and the second winding 3 shown in FIG.
A voltage is generated in the direction of the arrow, and the magnetron 12 is energized. When the first semiconductor switching element 6 is turned off,
The current flowing in the first winding 2 of the leakage type transformer 5 starts flowing toward the first capacitor 7 (state B in FIG. 8), and the voltage of this capacitor becomes the second capacitor 8
The current applied to the first capacitor 6 is clamped by the current flowing to the second capacitor 8 when the voltage reaches the initial voltage (state C in FIG. 8) as in the first embodiment. It is. When a current starts to flow from the second capacitor 8 toward the primary side of the leakage type transformer 5 (state d in FIG. 8) and the second semiconductor switching element 9 is turned off at an arbitrary time T1, the first capacitor 7, the first semiconductor switching element 6
At a steep slope and drops toward zero (state e in FIG. 8). During the period from state B to state E, the voltage generated in the second winding 3 of the leakage type transformer 5 is rectified by the full-wave rectifier circuit 31 to energize the magnetron 12.

(Embodiment 5) In FIG. 11, the same reference numerals are used for elements equivalent to those in FIG.

The output of the second winding 3 of the leakage type transformer 5 is rectified by the half-wave voltage rectifier circuit 32, and the DC voltage energizes the magnetron 12. 12A is a current waveform of the first semiconductor switching element 6, FIG. 12B is a current waveform of the first winding 2, FIG. 12C is a voltage waveform of the first semiconductor switching element 6, and FIG. Figure (d) shows the first
3 is a voltage waveform of the winding 2 of FIG. When the first semiconductor switching element 6 is turned on (state a in FIG. 12), a current flows through the first winding 2 of the leakage type transformer 5 and flows through the second winding 3 in the direction of the arrow in FIG. , And the voltage stored in the capacitor of the half-wave voltage rectifier circuit 32 is added to energize the magnetron 12. First
When the semiconductor switching element 6 is turned off, the current flowing through the first winding 2 of the leakage type transformer 5 becomes the first current.
12 (state b in FIG. 12), and when the voltage of this capacitor reaches the initial voltage of the second capacitor 8, a current also starts to flow in the second capacitor 8 (state in FIG. 12). C) The clamping of the voltage applied to the first semiconductor switching element 6 is the second
This is the same as the embodiment. When a current starts to flow from the second capacitor 8 toward the primary side of the leakage type transformer 5 (state d in FIG. 12) and the second semiconductor switching element 9 is turned off at an arbitrary time T1, the first capacitor 7
And the voltage of the first semiconductor switching element 6 decreases toward zero with a steep gradient (state e in FIG. 12). During the period from state B to state E, the voltage of the second winding 3 of the leakage type transformer 5 charges the capacitor of the half-wave voltage rectifier circuit 32.

Embodiment 6 In FIG. 13, the same reference numerals are used for the same elements as those in FIG.

The output of the second winding 3 of the leakage transformer 5 is rectified by a full-wave rectifier circuit 33, and the DC voltage energizes the magnetron 12. 14A shows a current waveform of the first semiconductor switching element 6, FIG. 14B shows a current waveform of the first winding 2, FIG. 14C shows a voltage waveform of the first semiconductor switching element 6, FIG. 4D shows the first winding 2.
FIG. When the first semiconductor switching element 6 is turned on (state a in FIG. 14), a current flows through the first winding 2 of the leakage type transformer 5 and flows through the second winding 3 in the direction of the arrow in FIG. Generates a voltage, and energizes the magnetron 12. When the first semiconductor switching element 6 is turned off, the current flowing in the first winding 2 of the leakage type transformer 5 starts flowing toward the first capacitor 7 (state B in FIG. 14), and When the voltage reaches the initial voltage of the second capacitor 8, the current starts to flow also in the second capacitor 8 (state C in FIG. 14), so that the voltage applied to the first semiconductor switching element 6 is not clamped. This is the same as the first embodiment. Second capacitor 8
Current starts flowing toward the primary side of the leakage type transformer 5 (state d in FIG. 14), and when the second semiconductor switching element 9 is turned off at an arbitrary time T1, the current flowing only from the first capacitor 7 And the voltage of the first semiconductor switching element 6 decreases toward zero with a steep gradient (state E in FIG. 14). During this period from state b to state d,
The voltage generated in the second winding 3 of the leakage type transformer 5 is rectified by the full-wave rectifier circuit 33 and the magnetron 12
Energize.

[0044]

As described above, according to the present invention, the operating frequency at the time of starting the magnetron can be reduced.
Since the impedance of the coil connected between the heater and the third winding of the magnetron is reduced, a sufficient and sufficient heater current for magnetron oscillation is obtained, and the time required for starting the magnetron can be reduced. It has the effect of.

In addition, since the withstand voltage of the first semiconductor switching element can be reduced and the voltage generated in the second winding can be reduced, the withstand voltage of each component of the rectifier circuit can be reduced.

Further, since the impedance of the coil connected between the heater of the magnetron and the third winding is reduced, a heater current necessary and sufficient for magnetron oscillation is obtained, and the time required for starting the magnetron is reduced. It has the effect that it can be shortened.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a power supply for driving a magnetron of a high-frequency heating device according to a first embodiment of the present invention.

2A is a main part equivalent circuit diagram when the semiconductor switching element of the magnetron driving power supply is on; and FIG. 2B is a main part equivalent circuit diagram when the semiconductor switching element of the magnetron driving power supply is off. 2) Equivalent circuit diagram of main parts when the diode of the magnetron driving power supply is turned on and charging of the second capacitor 8 is started.

FIG. 3 is a waveform diagram of a main circuit portion of the magnetron driving power supply.

FIG. 4 is an envelope waveform diagram of a main circuit portion of the power supply for driving the magnetron.

FIG. 5 is a circuit diagram of a power supply for driving a magnetron of a high-frequency heating device according to a second embodiment of the present invention.

FIG. 6 is a waveform diagram of a main circuit section of the magnetron driving power supply.

FIG. 7 is a circuit diagram of a power supply for driving a magnetron of a high-frequency heating device according to a third embodiment of the present invention.

FIG. 8 is a waveform diagram of a main circuit portion of the power supply for driving the magnetron.

FIG. 9 is a circuit diagram of a power supply for driving a magnetron of a high-frequency heating device according to a fourth embodiment of the present invention.

FIG. 10 is a waveform diagram of a main circuit section of the magnetron driving power supply.

FIG. 11 is a circuit diagram of a power supply for driving a magnetron of a high-frequency heating device according to a fifth embodiment of the present invention.

FIG. 12 is a waveform diagram of a main circuit portion of the power supply for driving the magnetron.

FIG. 13 is a circuit diagram of a power supply for driving a magnetron of a high-frequency heating device according to a sixth embodiment of the present invention.

FIG. 14 is a waveform diagram of a main circuit portion of the magnetron driving power supply.

FIG. 15 is a circuit diagram of a power supply device for driving a magnetron of a conventional high-frequency heating device.

FIG. 16 is an operation waveform diagram from a start region to an oscillation region of a magnetron.

FIG. 17 is a waveform diagram of a main circuit portion of a conventional magnetron driving power supply.

FIG. 18 is a waveform diagram illustrating a circuit operation of a conventional magnetron driving power supply.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 DC power supply 2 1st winding 3 2nd winding 4 3rd winding 5 Leakage type transformer 6 1st semiconductor switching element 7 1st capacitor 8 2nd capacitor 9 2nd semiconductor switching element 10 Drive circuit 11 Rectifier circuit 12 Magnetron 13 Coil 14 Heater 15 Comparison circuit

Continuing on the front page (72) Inventor Daisuke Villa 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Kenji Yasui 1006 Oji Kadoma Kadoma City Osaka Pref. References JP-A-63-66893 (JP, A) JP-A-5-199768 (JP, A) JP-A-4-62787 (JP, A) JP-A-49-70503 (JP, A) (58) Field surveyed (Int.Cl. ⁷ , DB name) H05B 6/66-6/68

Claims (2)

(57) [Claims] 1. A DC power supply obtained by rectifying a commercial power supply,
A magnetron and supplying a high voltage to the magnetron
A first winding connected to the DC power supply, a second winding, and a third winding, and a first winding on a primary side of the leakage transformer.
Connected first and second capacitors, and the first capacitor.
A first capacitor connected in series with the first winding .
1 semiconductor switching element and connected to the first winding
It has been a series connection between the second capacitor and the second semiconductor switching element, a drive circuit for driving the said first semiconductor switching element and the second semiconductor switching element, said second winding provided with a rectifier circuit connected to said magnetron, and a coil connected in series between the heater of the third winding and the magnetron, the second capacitor from the first capacitor
The capacity of the second semiconductor switch is also set large.
The driving of the first semiconductor switching element is used as the switching element.
It is necessary to provide a signal with a delay time to the inverted signal of the dynamic signal.
When the second semiconductor switching element is turned on,
Between the first semiconductor switching element and the second semiconductor switching element from the drive circuit at the time of starting the magnetron. A high-frequency heating apparatus having a configuration in which an on-time of a given pulse signal is shorter than an on-time given to the second semiconductor switching element. Wherein on the first winding voltage reference signal and compared with a comparison circuit for outputting a signal to the drive times <br/> circuit, a first semiconductor switching element and the second semiconductor switching element The high-frequency heating apparatus according to claim 1 , wherein the comparison circuit controls the drive circuit so that the first winding voltage becomes a predetermined value by changing a time ratio.