JP3919258B2 - High frequency power supply for heating - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an inverter type high frequency power supply device capable of generating high power high frequency alternating current necessary for induction heating or the like.
[0002]
[Prior art]
In recent years, inverters using solid-state switching elements have become mainstream as means for generating high-frequency AC power. Inverter is the name of a mechanism that essentially switches the output polarity of the element to convert the DC input to AC and outputs it. Is also a general term for an integrated device. Incidentally, in an apparatus integrated in this way, the original inverter part that converts direct current into alternating current is referred to as an “inverse conversion part”.
[0003]
When large power of kW level is required, such as induction heating, ensuring power efficiency is a critical requirement in terms of economy, etc., so the output circuit composed of the output side of the inverter and the load must be in resonance. For this reason, normally, as illustrated in FIG. 12 or FIG. 13, an inductance L and a capacitance C coexist in the output circuit to form a resonance circuit corresponding to the target energization frequency, and from the inverter A configuration is adopted in which the output AC frequency is tracked to the resonance frequency of the circuit. In induction heating, an electromagnetic coil engaged with an object to be heated, that is, L is loaded, so the target frequency is f. ₀ 1 / 2π√ (LC) = f ₀ As illustrated in FIG. 12 or FIG. 13, an output circuit that is incorporated in series or in parallel is configured to conduct electricity. Accordingly, since the resonance frequency of the output circuit fluctuates due to the change in L due to the temperature rise of the object to be heated, a tracking operation for causing the inverter to output alternating current at the resonance frequency is particularly important. .
[0004]
As shown in the circuit example of FIG. 9, FIG. 10 or FIG. 11, the tracking operation is performed by the switching circuit 1, 1 ′ or 1 ″ in order to continue the switching operation. The signal input to the signal terminal 3 (3a, 3b) of the switching element 2 (2a, 2b) arranged on the lower stage side, that is, the DC low potential side, is not an external signal supplied programmatically, but a current detector 4 etc. This is performed by using the data regarding the periodic behavior of the output current obtained by the above in the form of feedback by adjusting the phase etc. For this reason, the control circuit 5 is regularly used to optimize the phase of the signal to be fed back. A PLL (Phase Locked Loop) mechanism 6 is built in. With the above configuration, it is possible to continue energization in a resonance state that reflects the resonance characteristics of the output circuit.
[0005]
The inverter power supply usually requires a mechanism for adjusting the output power. As a typical means for adjusting the output power, phase shift control for adjusting the firing angle of the thyristor of the forward conversion unit. A scheme can be exemplified.
[0006]
In recent years, the use of a PDM (Palse Density Modulation) method in which the switching operation in the inverse conversion unit is intermittently executed to increase or decrease the frequency rate of execution has been proposed, and its practical use has begun. When this PDM method is applied to a frequency tracking type inverter, the power loss accompanying the output adjustment is zero, and the output power adjustment in the forward conversion unit is not required. In addition to the simple rectifier circuit used, since the operation of adjusting the output can be performed by a signal level mechanism, it can be said to be an output power adjusting means having particularly great merit in the high power inverter power supply device.
[0007]
However, there are the following problems in introducing the PDM system into a frequency tracking type inverter power supply device. That is, when an output circuit having a small Q value (resonance sharpness = 2πfL / R) is formed, such as induction heating, the attenuation of the periodic current flowing through the output circuit is large, and therefore it occurs intermittently in the PDM system. In the quiescent period of the switching operation, the signal that causes the data to be fed back to the signal terminal quickly decays, causing a problem that the switching operation cannot be resumed normally and is interrupted. The problem caused by the attenuation of the output current can be solved if the pause period of the switching operation is not lengthened. However, in this case, the setting range of the execution frequency rate of the switching operation and the adjustment range of the output power can be reduced. It becomes unintentionally narrow and incompatible with the original purpose.
[0008]
[Problems to be solved by the invention]
In view of the prior art as described above, the present invention introduces the PDM system as an output power adjusting means to a frequency tracking type inverter type high frequency power supply apparatus, and also determines the execution frequency rate of the switching operation and thus the output power. It is an object of the present invention to provide a high-frequency power supply device that does not cause the above-described trouble due to attenuation of output current, regardless of how it is set.
[0009]
[Means for Solving the Problems]
The configuration of the high frequency power supply device for heating according to the present invention, which has been made for the purpose of solving the above-mentioned problems, includes the switching circuit connected to the signal terminal of the switching element in the switching circuit. It was grasped by the current detector provided on the output side of Connect a circuit that feeds back data related to the cyclic behavior of the output current, and continuously perform switching operation that switches the output polarity in a pulse manner, and converts the input DC or pulsating power into high-frequency AC power and outputs it. A heating power supply apparatus having a control circuit including a microcomputer for adjusting a signal input to the signal terminal, and the switching operation is arbitrarily set in the control circuit. Output power adjustment mechanism configured to be executed intermittently at an execution frequency rate, and data on the periodic behavior of the output current As frequency and phase data as Once remembered The above In response to the microcomputer's determination that the output current has attenuated below a predetermined level necessary for normal restart after a pause in the intermittent execution of the switching operation , Instead of an immediate signal fed back from the current detector to the switching element, an oscillator signal that oscillates based on the stored periodic behavior data is fed back to the signal terminal of the switching element. An oscillation operation maintaining mechanism configured as described above, and In output power adjustment mechanism The switching operation frequency rate is set based on the rate signal transmitted from the rate generator. ^Four ~ 2 ¹⁶ By performing in units of cycles, the accuracy of output power adjustment related to the accuracy of heating is reduced to 1/2 of the full scale of output power. ^Four ~ 1/2 ¹⁶ It is characterized by the fact that it has been secured with the fineness of.
[0010]
That is, the device according to the present invention is a full bridge type using four switching elements (FIG. 9) or a half bridge type using two switching elements (FIG. ), Or a one-stone type switching circuit using one element (FIG. 11), and the frequency tracking configured to feed back data related to the periodic behavior of the output current to the signal terminal 3 of the switching element 2 Type high frequency power supply device. A control circuit 5 for adjusting a signal input to the signal terminal 3 is provided on the feedback input path. The control circuit 5 incorporates the PLL mechanism 6 as in a normal frequency tracking type inverter, and forms an element 2a that forms an energizing path with a positive output polarity and an energizing path that is negative. A dead time adjusting mechanism 7 is provided as necessary so that the element 2b to be turned on is not simultaneously turned on.
[0011]
Thus, as described in the configuration of the present invention, the device of the present invention is characterized in that the PDM system for adjusting the output power is added to the control circuit 5 in addition to the PLL mechanism 6 and the dead time adjusting mechanism 7. Output power adjusting mechanism (hereinafter referred to as “PDM mechanism”) 8 and an oscillation operation maintaining mechanism 9 that assists by transmitting stored data at any time to assist in the decay of the feedback signal caused by the attenuation of the output current. is there. With the above configuration, a PDM system capable of economically adjusting the output power can be introduced without the above-mentioned trouble, and the problem of the present invention is solved.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings. 1 is a circuit block diagram of an example of the high-frequency power supply device of the present invention, FIG. 2 is a functional block diagram of an example of the oscillation operation maintaining mechanism of the device of FIG. 1, and FIG. 3 is another example of the oscillation operation maintaining mechanism of the device of FIG. 4 is a functional block diagram of an example of the PDM mechanism of the apparatus of FIG. 1, FIG. 5 is an output mode diagram of the PDM mechanism of FIG. 4, and FIG. 6 is a switching operation by the PDM mechanism in a full bridge type switching circuit. FIG. 7 is an operation mode diagram illustrating a situation in which a half-bridge type switching circuit performs a switching operation by the PDM mechanism, and FIG. 8 is a function illustrating an example of a control circuit of the power supply device of the present invention. FIG. 9 is a circuit block diagram of an example of a conventional inverter type high frequency power supply circuit, FIG. 10 is a circuit block diagram of another example of a conventional inverter type high frequency power supply circuit, and FIG. FIG. 12 is a block diagram of an example of a resonance circuit in a known high frequency power supply device, and FIG. 13 is a block diagram of another example of the resonance circuit in the known high frequency power supply device.
[0013]
As illustrated in FIG. 1, the device of the present invention is configured to convert DC power input to the terminals 10 and 10 ′ into high-frequency AC power by the switching circuit 1 and output from the terminals 11 and 11 ′. It is. The switching element 2 (2a, 2b) provided in the switching circuit is a solid-state element having at least three basic terminals, and conducts current through the current inflow terminal 12 toward the current outflow terminal 13. In addition, it has a transfer characteristic that is turned ON / OFF according to a signal input to the signal terminal 3. Typical devices having the above characteristics include SIT (electrostatic induction transistor), IGBT (insulated gate bipolar transistor), FET (field effect transistor), and GTO (gate turn-off thyristor). Each of these elements has advantages and disadvantages, and may be selected from the same viewpoint as a normal inverter according to the requirements in specifications such as output frequency, power, voltage, or miniaturization.
[0014]
By inputting a predetermined voltage signal or current signal to each signal terminal 3 of the switching element 2, the switching circuit is caused to perform a switching operation for converting direct current into high frequency alternating current. That is, in the circuit example of FIG. 1, when a pair signal ({Yes, No}) for instructing an {ON, OFF} operation is input to the signal terminals 3a, 3b, the conduction of the element 2a is turned on. 2b becomes OFF, and an energization path via terminal 10 → terminal 11 → load 14 → terminal 11 ′ → terminal 10 ′ is formed (this is referred to as a “positive side energization path”). When a {No, Yes} pair signal is input to terminals 3a and 3b, an energization path ("negative-side energization path") is formed via terminal 10 → terminal 11 ′ → load 14 → terminal 11 → terminal 10 ′. By alternately executing the above two operations, the load 14 has a polarity from the terminal 11 to the terminal 11 ′ (“positive” polarity) and a polarity from the terminal 11 ′ to the terminal 11 (“ A negative (polarity) current flows alternately and AC energization is performed. Reference numeral 15 denotes a diode for always turning on conduction in the direction opposite to that of the switching element 2.
[0015]
In the case of the half bridge type and one stone type switching circuits shown in FIGS. 10 and 11, respectively, first, the conduction of the element 2a is turned on by the Yes signal input to the signal terminal 3a of the element 2a, and the positive half A wave current flows through the output circuit, and then a negative half-wave current flows due to the free oscillation of the output circuit, thereby completing one switching operation. Reference numeral 16 in FIGS. 10 and 11 denotes a capacitor for inducing the free vibration. Note that the apparatus of the present invention operates without any trouble even when pulsating power in which an AC component (ripple) is superimposed on DC is input to the terminals 10 and 10 '.
[0016]
Since the power supply device of the present invention is a frequency tracking type inverter type, the signal terminal 3 is not an external signal supplied programmatically, but the output grasped by the current detector 4 as described above. Data related to the periodic behavior of the current is input in a feedback manner. As described above, since the periodic behavior of the output current reflects the resonance characteristics of the output circuit, the operation of outputting alternating current is continued while tracking the resonance frequency of the output circuit by the feedback signal input. The
[0017]
Here, the signal input does not have to input the periodic behavior of the output current to the signal terminal 3 only by adjusting the polarity and the voltage level. That is, first, when the cyclic behavior transmitted from the detector 4 or the like is fed back to the signal terminal 3, a phase shift occurs due to floating L and C in the feedback path, and the AC output operation by the feedback signal is smoothly performed. Since the problem that it cannot be performed arises, signal processing for correcting the phase shift is required. The signal processing is performed by the PLL mechanism 6 incorporated in the control circuit 5 as described above. Data relating to the phase of the periodic behavior of the output current detected by the detector 4 or the like by the PLL mechanism 6 is correctly fed back to correct the phase shift, and the frequency data of the periodic behavior is adjusted in phase by the correction. Thus, the problem of phase shift is solved.
[0018]
The second problem regarding the feedback signal input is that the switching element 2a, 2b has a positive polarity conduction state and a negative polarity conduction state, which should be generated every half wave, respectively. Overlap occurs, and a minute period in which the circuit is short-circuited occurs, leading to power loss and further element damage. This problem is solved by the dead time adjusting mechanism 7 also incorporated in the control circuit 5. This mechanism 7 is a mechanism for controlling signals sent to the signal terminals 3a and 3b so that both the switching elements 2a and 2b are turned off only during a very short period during which there is a possibility of short circuit of the circuit. The dead time adjusting mechanism 7 is not necessary for a one-stone type switching circuit as shown in FIG.
[0019]
The above is a description of the components common to the conventional inverter and the operation thereof in the power supply device of the present invention. Next, components unique to the apparatus of the present invention and the operation thereof will be described.
[0020]
In the circuit illustrated in FIG. 1, first, the PDM mechanism 8 incorporated in the control circuit 5 causes the switching operation for alternately turning on the switching elements 2 a and 2 b to be executed intermittently at a set execution frequency rate. And a mechanism for controlling signals sent to the signal terminals 3a and 3b. Since the output power is generally proportional to the execution frequency rate, the output power can be adjusted by adjusting the execution frequency rate. As described above, even if the switching operation is executed intermittently, unlike the phase shift control method and the like, the power loss in the output power adjustment is caused by the power transformer primary side while the switching operation is suspended. It is economical with only a small loss.
[0021]
Next, in the power supply device of the present invention, the oscillation operation maintaining mechanism newly introduced to solve the problems associated with the introduction of the PDM system will be described.
2 and 3 are block diagrams showing an example of an installation mode of the oscillation operation maintaining mechanism in the device of the present invention. That is, the microcomputer (hereinafter referred to as a microcomputer) 17 stores the frequency and the like as data relating to the periodic behavior of the output current, and causes the oscillator 18 to perform oscillation based on the stored data, so that the output current is at a predetermined level. When the microcomputer 17 determines that the signal has attenuated below, a signal for instructing the switch 19 to transmit to the switch 19 is transmitted from the microcomputer 17. Upon receiving this signal, the PLL mechanism 6 receives an immediate signal from the output current detector 4. Instead, the oscillation signal of the oscillator 18 is input, and as a result, the transmission of the feedback signal is continued without stopping.
[0022]
Here, the usability of the power supply apparatus of the present invention is greatly affected by how finely the execution frequency rate of the switching operation can be adjusted by the PDM mechanism 8. In other words, taking heat treatment by induction heating as an example, it is generally requested that heating exceeding 1000 ° C. be performed with an accuracy of ± 25 ° C. The accuracy of the heating is strong to the output power adjustment accuracy of the power supply device. In order to obtain such heating accuracy, it is desirable to adjust the output power in steps smaller than 5% of the full scale. If this is to be realized by the PDM method, the switching operation is performed. It is necessary to set the frequency rate in units of 20 or more cycles of the switching operation.
[0023]
Accordingly, in the power supply device of the present invention, the setting of the execution frequency rate of the switching operation by the PDM mechanism can be performed in any manner with the following configuration. That is, in the apparatus of the present invention, it is recommended that the PDM mechanism be configured using the rate generator 20 as shown in the block diagram of FIG. As is well known, the rate generator has a parameter n = 2. ^P This is a mechanism that can receive a numerical value m instructed in the following range and transmit a rate signal m / n for instructing sampling of m times in n times in a substantially time-distributed manner. In the example of FIG. 4, the reference pitch command from the pulse oscillator 21 and the rate command (m, n) from the microcomputer 22 are transmitted to the rate generator 20, and m / n sampling rate signals are distributed and transmitted in time series. This is configured such that this is converted into a signal for controlling the operation of the switching elements 2a and 2b by the amplifier 23 and transmitted. For example, the PDM mechanism shown in FIG. ^Five = 32 and operating, and m is changed between 0 and 32, m / n = 0/32, 1/32, 2/32..., 31/32, 32/32 = 0, 3.1, 6.3,..., 97, 100% of a rate signal is transmitted and converted into a signal for commanding the suspension of the switching operation to control the operation of the switching circuit. The intermittent switching operation as shown in FIG. Contrary to the above example, the rate signal may be converted into a signal for instructing execution of the switching operation and controlled. In this case, the relationship between the rate signal and the PDM signal is opposite to that in the example of FIG.
[0024]
According to the PDM mechanism using the rate generator, the parameter n is set to 2 ⁷ Even when the frequency of execution of the switching operation is adjusted in units of 128 periods by setting = 128, the time required for one unit of the adjustment is as low as the output frequency of the switching circuit is 500 Hz. However, it is only 0.26 s, and fine output power adjustment in 1/128, that is, in increments of 0.8% of full scale, can be easily performed without substantially accompanying time-series pulsation. The execution frequency rate in the PDM operation using the rate generator is set to 2 for the above reason. ^Four It is desirable to carry out in units of = 16 or more. On the other hand, 2 ¹⁶ Even if it is set with a period unit exceeding 65536, there are few practical advantages. ^Four ~ 2 ¹⁶ It is better to set in units of periods.
[0025]
A method for causing the switching circuit 1, 1 ′, or 1 ″ shown in FIG. 9, FIG. 10, or FIG. 11 to perform the intermittent switching operation based on the PDM signal as described above is arbitrary. Two methods can be exemplified.
[0026]
FIG. 6 and FIG. 7 show the situation where the two systems are applied to full-bridge and half-bridge switching circuits, respectively. Here, the PDM signal is a repetition of time series sampling {1, 0, 0, 0} (“1” indicates execution, “0” indicates pause, ie, the execution frequency rate is 25%). An example of instructing will be described.
[0027]
First, the first method is the simplest method, and the sampling of {1, 0, 0, 0} is performed on the positive current path of the switching circuit (in the full bridge illustrated in FIG. High potential side element 2a ₁ And the element 2a on the lower stage side, that is, the DC low potential side ₂ The half bridge consists of the upper element 2a) and the negative current path (similarly, 2b for the full bridge ₁ And 2b ₂ In the half bridge, all the switching elements (consisting of the lower element 2b) are simply operated as {ON, OFF, OFF, OFF}. On the other hand, the negative side is sent half a wave). According to this method, in response to the OFF operation, the lower-side switching element is also turned off, and the current path of the output circuit is changed to make it difficult for the current to flow. The current attenuation is greater than the level commensurate with the Q value of the original output circuit.
[0028]
If the oscillation operation maintaining mechanism is not provided, if the current of the output circuit is greatly attenuated in this way, the next switching operation cannot be normally resumed. However, in the case of the device according to the present invention, since the oscillation operation maintaining mechanism 9 is provided, even if the current of the output circuit is greatly attenuated as described above, the switching operation of the circuit is normally performed with the assistance of the mechanism. Will be revived.
[0029]
Next, the second method is a method in which the sampling of {1, 0, 0, 0} is performed so that the lower side switching elements are continuously turned on in response to the above “0”. According to this method, the switching operation for converting direct current to alternating current changes as {ON, OFF, OFF, OFF}, but in the OFF state of the switching operation, the lower element is in the ON state. The current path of the output circuit is almost the same as when the switching operation is in the ON state. That is, even when the switching operation is turned off, the free oscillation current of the output circuit attenuates at a level commensurate with the Q value of the original output circuit. That is, since the output current does not stop as early as the first method, even if there is no oscillation operation maintaining mechanism, if the Q value of the output circuit is not particularly small, the next switching operation is resumed normally. Since the device according to the present invention has the oscillation operation maintaining mechanism 9, the switching operation is normally resumed regardless of the Q value of the output circuit.
[0030]
As described above, the power supply device according to the present invention includes the PLL mechanism 6 and the dead time adjustment mechanism 7 similar to those of the ordinary frequency tracking type inverter power supply, and the PDM mechanism 8 and the oscillation operation maintaining mechanism 9 as new components. Is deployed. The individual configurations of these mechanisms are as described above, but many combinations are possible for the overall configuration of the control circuit that combines the mechanisms. An example of the arrangement is shown in a block diagram in FIG. Note that the first method can be applied to a monolithic switching circuit.
[0031]
Further, when the control circuit 5 of the device of the present invention is configured to set the sampling rate, which is a command item in the PDM mechanism 8, based on a change in the frequency of the output current, In operations such as induction heating performed using the inventive device, changes such as the temperature rise of the object to be heated, which is the cause of the frequency change, can be fed back to the output power. For example, if the sampling rate is set in the form of a function of the difference between the current tracking frequency f and the reference frequency fo derived from the difference between the current temperature T and the target temperature To, An operation schedule that performs rapid heating with 100% output power and then maintains a stable temperature with the adjusted output power is realized in a pseudo program manner.
[0032]
In the feedback type output power adjustment, if the circuit configuration shown in FIG. 8 is adopted, data on the current tracking frequency f is transmitted from the PLL mechanism 6 to the microcomputer 17 through the path shown in FIG. The data relating to the reference frequency fo input to the microcomputer 17 can be converted into a sampling rate in a desired function relationship in the microcomputer 17 and transmitted to the rate generator 20.
[0033]
In the power supply device of the present invention, there are no particular restrictions on the circuit configuration relating to the output frequency and output power, and there are a wide range of specifications ranging from several hundred Hz to several hundred KHz, several hundred W to several hundred kW depending on the performance of the switching element used. Things can be provided.
[0034]
【The invention's effect】
The present invention is as described above, and the power supply device according to the present invention performs the output power adjustment in the frequency tracking type inverter by the PDM method, and at the time of PDM control, the operation of feeding back the data related to the output current to the switching circuit, An oscillation operation maintaining mechanism capable of storing the above data and transmitting it at any time is provided and supported so as not to stop due to the attenuation of the output current during the switching operation pause.
[0035]
The output power adjustment by the PDM method can simplify the configuration of the forward conversion unit in the power supply device in which the forward conversion unit is integrated, and the output power adjustment mechanism can be configured by a signal level structure, thereby reducing the cost of the device. In addition, since the power loss accompanying power adjustment is zero because the device of the present invention is a frequency tracking type inverter, a particularly large economic effect is brought about in a high power power supply device. In addition, the above feature is advantageous for downsizing the power supply device.
[0036]
In addition, by introducing the oscillation operation maintaining mechanism, it is possible to introduce the PDM output adjustment method having excellent economy as described above without any trouble without reducing the fine adjustment function.
[0037]
That is, according to the present invention, by introducing the PDM output power adjustment method and the oscillation operation maintaining mechanism together, it is possible to finely adjust the output power, and it is a compact and economical frequency tracking type inverter type high frequency. A power supply device can be realized.
[Brief description of the drawings]
FIG. 1 is a circuit block diagram of an example of a high frequency power supply device of the present invention.
2 is a functional block diagram of an example of an oscillation operation maintaining mechanism of the apparatus of FIG.
FIG. 3 is a functional block diagram of another example of the oscillation operation maintaining mechanism of the apparatus of FIG.
4 is a functional block diagram of an example of a PDM mechanism of the apparatus of FIG.
5 is an output mode diagram of the PDM mechanism of FIG. 4;
FIG. 6 is an operation mode diagram illustrating a situation in which a switching operation by a PDM mechanism is performed in a full bridge type switching circuit.
FIG. 7 is an operation mode diagram illustrating a state in which a switching operation by a PDM mechanism is performed in a half-bridge type switching circuit.
FIG. 8 is a functional block diagram showing an example of a control circuit of the power supply device of the present invention.
FIG. 9 is a circuit block diagram of an example of a conventional inverter type high frequency power supply circuit.
FIG. 10 is a circuit block diagram of another example of a conventional inverter type high frequency power supply circuit.
FIG. 11 is a circuit block diagram of another example of a conventional inverter type high frequency power supply circuit.
FIG. 12 is a block diagram illustrating an example of a resonance circuit in a known high-frequency power supply device.
FIG. 13 is a block diagram of another example of a resonance circuit in a known high-frequency power supply device.
[Explanation of symbols]
1 Switching circuit
2 Switching element
3 Signal terminals
4 Current detector
5 Control circuit
6 PLL mechanism
7 Dead time adjustment mechanism
8 PDM mechanism (output power adjustment mechanism)
9 Oscillation operation maintenance mechanism
10, 10 'input terminal
11, 11 'output terminal

Claims (2)

A circuit that feeds back data related to the periodic behavior of the output current obtained by the current detector provided on the output side of the switching circuit is connected to the signal terminal of the switching element in the switching circuit, and the output polarity is changed in a pulsed manner. A heating power supply device that continuously performs switching operation for switching, converts input DC or pulsating power into high-frequency AC power, and outputs the high-frequency AC power for adjusting a signal input to the signal terminal An output power adjusting mechanism configured to intermittently execute the switching operation at an execution frequency rate set arbitrarily, and a control circuit including a microcomputer, and the output current between the periodic behavior temporarily stores the frequency and phase of the data as data relating to, said output current of said switching operation Specific wherein the attenuated below a predetermined level required for successful recovery after rest periods in the execution undergoing microcomputer judgment, the current detector from the place immediately signal is fed back to the switching element said temporarily stored An oscillation operation maintaining mechanism configured to feed back an oscillator signal that oscillates based on the periodic behavior data to the signal terminal of the switching element, and an execution frequency rate of the switching operation in the output power adjustment mechanism Is set in units of 2 ⁴ to 2 ¹⁶ cycles of the switching operation based on the rate signal transmitted from the rate generator, so that the accuracy of output power adjustment related to the accuracy of heating is reduced to 1 / full scale of output power. A high frequency power supply for heating, which is secured with a fineness of 2 ⁴ to 1/2 ¹⁶   The high frequency power supply device for heating according to claim 1, wherein the execution frequency rate of the switching operation is set based on a frequency change of the output current.

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