JPH03216989A - High-frequency induction heating device - Google Patents

Abstract

PURPOSE:To omit a choke coil and a large-capacitance DC capacitor and form the power current wave-form into a sine wave with the power factor 1 by directly feeding the output of a single-phase diode rectifying circuit for a DC power source to a voltage type inverter circuit. CONSTITUTION:The commercial power source 1 is full-wave-rectified by a rectifying circuit 2, and the full-wave-rectified output of the rectifying circuit 2 is fed to the input sides of the switching elements 3a-3d connected in a full- bridge type. The switching elements 3a-3d are switching-controlled by driving circuits 28a-28d provided correspondingly to them, and the AC current fed to the output side by the switching control is fed to the primary side of a matching transformer 6. The AC current converted at the ratio 8:1, for example, flows in the secondary side of the matching transformer 6, and the high-frequency power is fed to a heating coil to generate the AC magnetic field. A smoothing circuit constituted of a choke coil and an electrolytic capacitor can be omitted, the whole device can be miniaturized and made lightweight, and the power current wave-form can be made into a sine wave with the power factor 1.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a high-frequency induction heating device, and is particularly used in dental casting machines and the like.

(Prior art) As a power source for high-frequency induction heating equipment, SIT and power M
High-frequency inverter circuits using high-speed switching elements such as OSFETs have come into use.

On the other hand, a diode rectifier circuit has conventionally been used as a DC power source for a voltage source inverter circuit, which is one of such high frequency inverter circuits.

In other words, on the output side (DC side) of the diode rectifier circuit,
A choke coil and a large-capacity DC capacitor are connected to smooth the output of the diode rectifier circuit and supply it to the voltage source inverter circuit as a stable DC power source.

(Problem to be solved by the invention) As described above, in the conventional high-frequency induction heating device, a smoothing circuit consisting of a choke coil and a large-capacity DC capacitor is connected to the input side of the voltage source inverter circuit that is the power source. As a result, the input current to the voltage source inverter circuit becomes pulsed, which poses problems such as not only worsening the power factor of the power supply but also the possibility of causing harmonic interference. Also,
The presence of a smoothing circuit consisting of a choke coil and a large-capacity DC capacitor has been an obstacle to reducing weight and size.

The present invention has been made in view of the above-mentioned circumstances, and its purpose is to directly supply the output of a single-phase diode rectifier circuit as a DC power source to a voltage source inverter circuit, so that choke coils, large-capacity DC capacitors, etc. An object of the present invention is to provide a high-frequency induction heating device that can omit the above-described configuration and make the power supply current waveform a sine wave with a power factor of l.

(Means for Solving the Problems) In order to solve the above problems, the high-frequency induction heating device of the present invention includes a rectifier circuit that full-wave rectifies a commercial power supply, and a drive circuit that is connected to the output side of this rectification port path. ON/OF
A full bridge switching element that is F-controlled, a matching transformer connected to the output side of this switching element, a drive circuit that drives a heating coil connected to the secondary side of this matching transformer, and a drive circuit that drives this drive circuit. a frequency detection circuit that detects the frequency of the time, a reference frequency that is a preset frequency that the drive circuit has in an initial state, and a fluctuating frequency detected by the frequency detection circuit, which are alternately switched at a predetermined period. The configuration includes a phase control circuit that outputs a drive signal that is phase-lost to the output reference frequency or variable frequency to the drive circuit.

Further, in the above configuration, the phase control circuit includes a phase shifter to which the fluctuating frequency from the frequency detection circuit is guided, and a PLL circuit to which the phase-controlled signal is guided by the phase shifter, and the phase shifter includes , a power factor adjustment section that can arbitrarily control the phase is provided.

Furthermore, in each of the above configurations, a zero point detection circuit detects the zero point of the full wave rectified output from the rectifier circuit, and based on the zero point detection of the full wave rectified output detected by this zero point detection circuit, the zero point of the full wave rectified output is detected. The configuration includes a start/stop circuit that sends a start signal and a stop signal for the device itself based on the smell.

(Function) The commercial power supply is full-wave rectified by a rectifier circuit, and the full-wave rectified output of this rectifier circuit is supplied to the input side of the Swissotting element connected in a full bridge type. Each switching element is
Switching control is performed by each drive circuit provided correspondingly, and the alternating current sent to the output side by this switching control is supplied to the primary side of the matching transformer. Therefore, since an alternating current converted at a ratio of, for example, 8:1 flows through the secondary side of the matching transformer, a drive circuit formed of, for example, an LC series resonant circuit to which this alternating current is led is driven, that is, resonates. High frequency power is supplied to the heating coil to generate an alternating magnetic field. On the other hand, the frequency detection circuit detects the current frequency or voltage frequency from the current flowing or the voltage applied to the drive circuit at this time, and applies the detected current frequency or voltage frequency (hereinafter referred to as fluctuation frequency) to the phase control circuit. lead to. A reference frequency signal from a reference frequency oscillator is guided to the phase control circuit, and the reference frequency and the variable frequency are appropriately switched at a predetermined period and output. Then, by supplying a drive signal that is phase-lost to the output reference frequency or variable frequency to each of the drive circuits,
Drive each drive circuit to turn on/off the switching element
To control FF in a timely manner.

Further, in the above configuration, the phase control circuit includes a phase shifter to which the fluctuating frequency from the frequency detection circuit is guided, and a PLL circuit to which the phase-controlled signal is guided by the phase shifter, is equipped with a power factor adjustment section that can arbitrarily control the phase. That is, power to the heating coil is controlled by controlling the power factor of an inverter circuit made up of switching elements.

Furthermore, in each of the above configurations, the power supply zero point detection circuit detects the zero point of the full-wave rectified output from the rectifier circuit, and based on the zero point detection of the full-wave rectified output, the starting signal of the device itself is generated near the zero point of the full-wave rectified output. and a stop signal from the start/stop circuit.

In other words, even if you turn on the start switch and stop switch provided on the device itself at any timing, the device itself will actually start or stop near the zero point of the full-wave rectified output, so the switch・Damage of the 2-ch element is prevented.

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

[Embodiment 1] FIG. 1 is a circuit diagram showing the electrical configuration of a high-frequency induction heating device of the present invention corresponding to claim 1.

However, in this embodiment, I KW. This figure shows a series resonant circuit type high-frequency induction heating device using a 500 KHz voltage-type high-frequency inverter circuit.

In the same figure, ACIOOV AC power supply (commercial power supply) ■
Each output of the rectifier circuit 2 is connected to each input terminal of a single-phase diode full bridge rectifier circuit (hereinafter simply referred to as a rectifier circuit) 2 consisting of four diodes 2a to 2d. The end is connected to a small capacitor (e.g. 0
．． Four power MOSFETs 3 a to 3 d are bridge-connected via a capacitor C0 of 47 μF).
(switching element).

Power MOSFETs 3a to 3d are power MOSFETs
The drain terminals of the SFETs 3a and 3b and the source terminals of the power MOSFETs 3c and 3d are connected to each other, and the power MOSFETs 3a and 3b are connected to each other.
The source terminal of the power MOSFET 3c is connected to the drain terminal of the power MOSFET 3c, and the source terminal of the power MOSFET 3b is connected to the drain terminal of the power MOSFET 3d. Moreover, a feedback diode D a − is connected between the drain terminal and source terminal of each power MOSFET 3 a to 3 d.
D d is connected, and series circuits (snubber circuits) 43 to 4 d of capacitors and diodes are also connected. These power MOSFETs 3a to 3d and feedback diodes Da to Dd constitute a voltage source high frequency inverter circuit.

Further, the middle point of the snubber circuit 4a is connected to the source terminal of the power MOSFET 3c via the resistor Rl, and the middle point of the snubber circuit 4b is connected to the source terminal of the power MOSFET 3c via the resistor R2.
The middle point of the snubber circuit 4C is connected to the drain terminal of the power MOSFET 3a through a resistor R3, and the middle point of the snubber circuit 4d is connected to the drain terminal of the power MOSFET 3b through a resistor R4. These snubber circuits 4a, 4c and resistors Rl,
R3, snubber circuits 4b, 4d, and resistors R2, R4,
They constitute spike voltage suppression circuits 5a and 5b, respectively.

And the power MOSFET 3a connected in Brissoge
~3d is connected to the primary winding 6a of the matching transformer 6.
A series resonant circuit including a capacitor C and a heating coil L is connected to the secondary winding 6b of the matching transformer 6.

Also, a voltage detection section 7 that detects the terminal voltage of the capacitor C
The output of the phase shifter 11 is connected to the switching control input of the switching circuit 13, which is a component of the phase control circuit 10, and is also guided to the phase shifter 11.
and one input of the switching circuit 13, the PLL circuit 1
2 is guided to a phase detector 121, which is a component of No. 2.

Further, the output of the reference frequency oscillator 14 is led to the other input of the switching circuit 13. The switching circuit 13 performs switching control based on the output of the voltage detection section 7.
When the maximum value of the output (capacitor voltage) of the voltage detection section 7 is, for example, 50V or less, the output of the reference frequency oscillator 14 is sent to the PLL circuit 12, and when it is 50V or more, the output of the phase shifter 11 is sent to the PLL circuit 12. The switching is performed so as to transmit the data. Further, the oscillation frequency of the reference frequency oscillator l4 is set to the resonant frequency of the LC resonant circuit connected to the secondary winding of the matching transformer 6 (500 KHz in this embodiment).

■CO (which is a component of the PLL circuit 12
The output of the voltage controlled oscillator) 123 is
5 and the trigger input of the monostable multivibrator I6, and the Q and Q outputs of the Frisopflosob 15 are connected to one input of each of the two AND circuits 17 and 18 to the trigger input of the monostable multivibrator I6. The outputs are respectively led to the other inputs of two AND circuits 17 and 18. Further, the Q output of the Frisopflosop 15 is connected to a phase detector 121 to form a feedback loop. In addition, the monostable multi-by break 16 includes a commutation delay angle control volume V for controlling the commutation delay angle.
Rβ is connected. The output of the AND circuit 17 and the output of the AND circuit 18 are used as gate signals for each of the power MOSFETs 3 provided correspondingly.
They are led to drive circuits 28a to 28d that drive circuits a to 3d. Although not shown in the drawings, the driving power source for each of the drive circuits 28a to 28d is a separate power source from the driving power source for the inverter circuit in order to perform stably.

Further, FIG. 2 shows drive circuits 28a to 2 for driving the power MOSFETs 3a to 3d at 500 KHz.
An example of the circuit configuration of 8d is shown. Power MOSFET 3
In order to drive components a to 3d at high frequencies, a 1:1 pulse transformer is used to insulate them from the main circuit.

That is, the high-frequency induction heating device of this embodiment uses the full-wave rectified voltage from the single-phase diode Flubri-7 rectifier circuit 2 as the DC power source, and also
and small capacitor C. By connecting only the power source and omitting smoothing circuits such as choke coils and electrolytic capacitors used in conventional devices, stable operation as a high-frequency induction heating device can be obtained, and the power supply current waveform can be adjusted to a power factor of 1. This can be made into a sine wave. Note that a 100 Hz (or 120 Hz) fluctuation in the full-wave rectified voltage has almost no effect on the heating characteristics of metal.

Next, the operation of the high frequency induction heating device having the above configuration will be explained with reference to the timing chart of FIG. 3.

However, FIG. 3 shows signal waveforms of each part of the phase control circuit 10.

Turn on the start switch (not shown) of the high-frequency induction heating device
By doing so, the ACIOOV voltage from the commercial power supply 1 is full-wave rectified in the rectifier circuit 2, and then the power MO
It is supplied to the input terminal of the switching element consisting of SFET3a to 3d. In the power MOSFETs 3 a to 3 d, the power MOSFETs 3 a and 3 d and the power MOSFETs 3 b and 3 c are alternately brought into conduction by appropriately driving each drive circuit 283 to 28 d with a gate signal from the phase control circuit 10 described later. Therefore, an alternating current flows through the primary winding of the matching transformer 6. As a result, a high frequency current is supplied to the LC resonance circuit through the secondary winding of the matching transformer 6, and an alternating magnetic field is generated in the heating coil.

On the other hand, when the starting switch is turned ON, the output of the voltage detection circuit 7 (capacitor voltage: vc) is 50 V or less, so the switching circuit 13 switches the output of the reference frequency oscillator 14 to the PLL circuit 12. The connection has been switched. Here, since the frequency oscillated from the reference frequency oscillator 14 is a unique frequency of the LC resonant circuit (in this embodiment, the two resonant frequencies are 500 KHz), the power MOSFETs 3 a to 3 d operate from the time when the starting switch is turned on. The ON/OFF operation is controlled at the oscillation frequency from the reference frequency oscillator 14 until a certain fixed period of time (ie, several milliseconds until the output of the voltage detection circuit 7 exceeds 50V). That is, since a high frequency current flows through the heating coil in a resonant state, efficient high frequency induction heating is performed.

After this, when the output V (of the voltage detection circuit 7 exceeds 50 V), the switching circuit l3 switches the connection from the reference frequency oscillator 14 side to the phase shifter l1 side. The output will be done manually.

The phase shifter 11 inputs the output of the voltage detection circuit 7, that is, the capacitor voltage ゎ, and outputs T0 for the output current 10.
A signal [FIG. 3(C)] whose phase is delayed by a certain amount is generated, and this signal is input to the phase detector 121 of the PLL circuit 12 via the comparator 2l.

As shown in Fig. 3+d), the VCO 123 of the PLL circuit 12 operates at a frequency (2 times the driving frequency of the inverter circuit).
100Hz), and this signal is delayed by delay time T0 and
5 and the trigger input of the monostable multivibrator 16. In Frisopflosop 15, the led VCO 1
Q output is the signal obtained by dividing the output of 23 into 2 [Figure 3 (f)]
and Q output [Figure 3 (g)], and output Q output from AN
The D circuit 17 and the Q output are sent to the AND circuit 18, respectively.

In addition, in the monostable multi-bi break l6, by adjusting the volume VRβ, a signal that rises after the commutation delay angle β from the rise of the output signal of V C 0123 is created [Fig. 3 (e)]. signal to each AN
It is sent to D circuits 17 and 18. Each AND circuit 17.18
Now, by taking the AND of these signals, AND
From the circuit 17, the gate signal G shown in FIG.
Further, the gate signal G2 shown in FIG. 3(1) is sent from the AND circuit 18 to the corresponding drive circuits 28a,
28d and 28b. 28c. Each of the drive circuits 28a to 28d receives gate signals G, , G. Each power MOSFET3 a based on
Switching ~3d. That is, power MOSF
The ON/OFF operations of ET 3 a to 3 d are controlled in a state in which the phase is controlled by the fluctuating frequency of the LC resonant circuit.

Then, when the output vc of the voltage detection circuit 7 becomes lower than the set voltage of 50V again, the connection of the switching circuit 13 is switched to the reference frequency oscillator l4 side, and each power MOSFET 3a to 3d is activated by the same gate signal as above. Swiss isoching will be performed.

That is, the switching control of the power MOSFETs 3a to 3d is performed by the reference frequency oscillator l every lQmsec.
Open loop control by 4 and phaser l1 and PLL
The feedback control by the circuit 12 is repeated. This change every 10 msec is the resonant frequency 500
From the perspective of KHz, it can be regarded as a continuous steady state.

[Embodiment 2] FIG. 4 is a circuit diagram showing the electrical configuration of the high frequency induction heating device of the present invention corresponding to claims 2 and 3. however,
In this example, IKW, 500κ is used as in Example 1 above.
This figure shows a series resonant circuit type high-frequency induction heating device using a Hz voltage-type high-frequency inverter circuit. In the following description, the same reference numerals are given to the parts whose circuit configurations are the same as those of the first embodiment, and the description thereof will be omitted here.

That is, in this embodiment, in the circuit configuration shown in the first embodiment, a power factor angle adjustment volume VRr for adjusting the power factor angle is connected to the phase shifter 11, and the output of the commercial power supply 1 is connected to the phase shifter 11. On the side, there is a voltage detection circuit 25 for detecting the voltage.
is connected.

The output of this voltage detection circuit 25 is sent to a power supply zero point detection circuit 26 that detects the zero point of the voltage from the detected voltage waveform.
The output of the power supply zero point detection circuit 26 is led to a start/stop circuit 27 which creates a start signal and a stop signal for instructing the start and stop of the device itself from the led signal. The start signal and stop signal from this start/stop circuit 27 are respectively guided to one input of two newly provided AND circuits 19 and 20, and each A
The outputs of the ND circuits 19 and 20 are led to drive circuits 28a to 28d that drive the respective power MOSFETs 3a to 3d provided correspondingly.

Further, the output of the AND circuit 17 is connected to the other input of the AND circuit 19, and the output of the AND circuit 18 is connected to the other input of the AND circuit 20.

That is, the high frequency induction heating device of this embodiment has a phase shifter 1.
By adopting a configuration in which the power factor of l can be arbitrarily controlled, it is possible to stably control the power of the full brissage type switching element and control heating on the load side, as well as start and stop the device itself. By configuring it to operate near the zero point of the power supply voltage, the power MOSFET 3
This prevents destruction of parts a to 3d.

Next, the operation of the high frequency induction heating device having the above configuration will be explained with reference to FIGS. 5 to 8.

However, FIG. 5 is a signal waveform diagram of each part of the phase control circuit 10, and FIG. 6 (al, (bl) is the inverter output voltage V.
A diagram showing the relationship between and output current 10, FIG. 7(a),
(bl is a diagram showing the relationship between the power supply voltage 2 and the power supply current i, and FIG. 8 is a start/stop timing chart.

Turn on the start switch (not shown) of the high-frequency induction heating device
By doing this, the ACIOOV voltage from the commercial power supply l is full-wave rectified in the rectifier circuit 2, and then
It is supplied to the input end of the switching device consisting of SFETs 3a to 3d. The power MOSFETs 3 a to 3 d are connected to the power MOSFETs 3 a and 3 d by appropriately driving each drive circuit 28 a to 28 d with a gate signal from a phase control circuit 10 described later.
7-MOSFETs 3b and 3C are alternately conductive, and an alternating current flows through the primary winding of the matching transformer 6.

As a result, a high frequency current is supplied to the LC resonance circuit through the secondary winding of the matching transformer 6, and an alternating magnetic field is generated in the heating coil.

On the other hand, when the starting switch is turned on, the output of the voltage detection circuit 7 is ■. is less than 50V, so the connection of the switching circuit l3 is switched so that the output of the reference frequency oscillator l4 is sent to the PLL 111112. Here, since the frequency oscillated from the reference frequency oscillator 14 is a unique frequency of the LC resonant circuit, the power MOS
The FETs 3a to 3d control the oscillation frequency from the reference frequency oscillator 14 for a certain period of time (i.e., the time until the output of the voltage detection circuit 7 exceeds 50V: several msec) from the time when the starting switch is turned on. ON in state
/OFF operation is controlled. That is, since a high frequency current flows through the heating coil in a resonant state, efficient high frequency induction heating is performed.

Thereafter, when the output voltage of the voltage detection circuit 7 exceeds 50V, the switching circuit 13 switches the connection from the reference frequency oscillator I4 side to the phase shifter 11 side. As a result, the output of the phase shifter 1l is input to the PLL circuit 12.

Here, assuming that the power factor angle is adjusted to T by adjusting the power factor angle adjustment volume VRγ of the phase shifter l1, the output of the voltage detection circuit 7, that is, the capacitor voltage vc, is input to the phase shifter l1, and γ - γ for output current 10
. A signal [FIG. 5(C)] whose phase is delayed by
Input to LL circuit 120 phase detector 121. The VCO 123 of the PLL circuit 12, as shown in FIG. 5(d),
Frequency twice the driving frequency of the inverter circuit (100H
z), and this signal is T-γ. The signal is delayed by 30 minutes and then supplied to the trigger inputs of the Frisopflosop 15 and the monostable multi-by-break 16.

Frisov flop I5 outputs a signal obtained by dividing the frequency of the output of VCO 123 by two as Q output [Fig. 5(f)]. The Q output is sent to the ND circuit 17 and the Q output is sent to the AND circuit 18, respectively.

In addition, in the monostable multi-bi break 16, by adjusting the commutation delay angle control volume VRβ, the VCO
A signal [FIG. 5(e)] that rises after a commutation delay angle β after the rise of the output signal of I23 is created, and this signal is sent to each AND circuit 17 and 18. In each AND circuit 17 and 18, by taking the logical product of these signals, the AND circuit 17 outputs the gate signal G11 shown in FIG. 5(h), and the AND circuit 18 outputs the gate signal G11 shown in FIG.
The gate signal G2■ shown in FIG. Each of the drive circuits 28a to 28d receives a corresponding gate signal G. Each power M based on G2■
Switch OSFETs 3a to 3d. That is, the ON/OFF operations of the power MOSFETs 3 a to 3 d are controlled in a state in which the phase of the power MOSFETs 3 a to 3 d is controlled by the varying frequency of the LC circuit.

Then, when the output V of the voltage detection circuit 7 becomes lower than the set voltage of 50V again, the connection of the switching circuit 13 is switched to the reference frequency oscillator 14 side, and each power MOSFET 3a to 3d is activated by the same gate signal as above. Suinoching will be carried out.

That is, the switching control of the power MOSFETs 3a to 3d is performed by the reference frequency oscillator l every lomsec.
Open loop control by 4, phase shifter 11 and PLL
The feedback control by the circuit 12 is repeated. This change every lQmsec is the resonant frequency 500
From Kllz's point of view, it can be regarded as a continuous steady state.

Figure 7 (al is the inverter output voltage v at a power factor of 95%
0,, and the output current 10,5.
b) is the inverter output voltage V O6 at a power factor of 67%?
and output current i. 6, shows the waveform relationship with. From the figure, it can be seen that the phase control by the phase shifter 11 and the PLL circuit 12 is performed well, and the operation is stable.

In addition, in the same figure (b), the output voltage ■ during switching. , 7 and the output current 10, . Therefore, in this device, the spike voltage suppression circuits 5a, 5b
The output voltage V. ．． , and output current l. h, vibrations are suppressed and damage to the switching elements is prevented.

In addition, Fig. 8(a) shows a power factor of 95% during inverter operation.
The waveform relationship between the power supply voltage V 395 and the power supply current i, .
The power supply voltage V Sh'l in % and the power supply current i, . , shows the waveform relationship with . From the same figure, a small capacitance (0.4
7μF) capacitor C. By connecting only
The power supply current is a sine wave with a power factor l.

On the other hand, the voltage detection circuit 25 performs start control and stop control when the start switch and stop switch of this device are operated.
Power supply zero point detection circuit 26, start/stop circuit 27 and AND
This is done by circuit 19.20.

That is, as shown in FIG. 8, the power supply zero point detection circuit 26
Then, the power supply voltage V detected by the voltage detection circuit 25
, the power supply zero point is detected and the zero point detection signal is 10m.
Sending out a pulse signal every sec [Figure 8 (C)]
. Then, when the start switch is turned on (that is, commanded to start) at an arbitrary time H, the start/stop circuit 2
7 sends out a start signal [shown at H level in FIG. 8 (el)] at time t2 when the next zero point detection signal is input from time t1. given the input of AND
From the circuits 19 and 20, each AND of the phase control circuit 10 is output during the period when the start signal shown at the l1 level is applied.
The gate signals from circuits 17, 18 will be sent to each corresponding drive circuit 28a-28d. and,
At time t3, the stop switch is turned ON (i.e.
command to stop), the start/stop circuit 27 starts at time t3.
to the time when the next zero point detection signal is input (at 4,
A stop signal (indicated by L level) is sent. Since this stop signal is given to one input of the AND circuit 19.20, it is sent from the AND circuit 19.20 to each drive circuit 2.
Sending of gate signals to 83 to 28d will be stopped. In this way, the voltage detection circuit 25, the power supply zero point detection circuit 26, the start/stop circuit 27, and the AND circuit 19.20
By adding , it is possible to start and stop the device itself near the power supply zero point, regardless of the actual ON operation of the start switch and stop switch, so that large currents do not suddenly flow through the switch element. Since there is no such thing, the switching element is prevented from being destroyed when starting and stopping the device, and safe starting and stopping can be performed.

In each of the above embodiments, the voltage waveform across the capacitor C is detected as a means for detecting the LC resonance frequency, but it is also possible to detect the current flowing through the LC resonance circuit,
It is possible to configure the frequency to be determined from the detected waveform.

(Effects of the Invention) The high-frequency induction heating device of the present invention is configured to use the full-wave rectified output from the rectifier circuit as a power source for driving the inverter circuit. Since the circuit can be omitted, the entire device can be made smaller and lighter, and the power supply current waveform can be made into a sine wave with a power factor of 1. In addition, since the power factor of the inverter circuit is controlled as a heating control method on the load side, a wide range of power control can be performed. Furthermore, since the apparatus itself is configured to start and stop near the zero point of the power supply voltage, it is possible to prevent the switching elements from being destroyed during starting and stopping.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing the electrical configuration of the high frequency induction heating device of the present invention corresponding to claim 1, and FIG. 2 is a power MOSP.
Circuit diagram illustrating an example of a drive circuit that drives a BT, 3rd
The figure is a signal waveform diagram of each part of the phase control circuit, FIG. 4 is a circuit diagram showing the electrical configuration of the high frequency induction heating device of the present invention corresponding to claims 2 and 3, and FIG. 5 is a diagram of the phase control circuit. Signal waveform diagram of each part, Figure 6 (al. (b) is a diagram showing the relationship between inverter output voltage ■. and output current l., Figure 7 (a). (bl is power supply voltage ■, and power supply current A diagram showing the relationship with iS, and FIG. 8 is a timing chart of start/stop. l... AC power supply (commercial power supply) 2... Single-phase diode full bridge rectifier circuit 3a ~
3d...-Power MOSFET 6...Matching transformer 7...Voltage detection circuit IO...Phase control circuit 11...Phase shifter 12...PLL circuit 121...Phase detector 122...Low bus Filter 123...VCO (voltage controlled oscillator) 13...Switching circuit 14...Reference frequency oscillator l5...Frisobufurosob 16...Monostable multivibrake 17-20...AND circuit 25...Voltage Detection circuit 26...Power supply zero point detection circuit 27...Start/stop circuit VRβ...Volume for commutation delay angle control VRr...
Power factor angle adjustment volume

Claims (1)

[Claims] 1) A rectifier circuit that performs full-wave rectification of a commercial power supply; A full-bridge switching element connected to the output side of this rectifier circuit and controlled ON/OFF by a drive circuit; A matching transformer connected to the output side, a drive circuit that drives a heating coil connected to the secondary side of this matching transformer, a frequency detection circuit that detects the frequency when this drive circuit is driven, and a preset A reference frequency, which is a frequency that the drive circuit has in its initial state, and a fluctuation frequency detected by the frequency detection circuit are alternately switched and outputted at a predetermined period, and a phase is set to the output reference frequency or fluctuation frequency. A high-frequency induction heating device comprising: a phase control circuit that sends a locked drive signal to the drive circuit. 2) The phase control circuit includes a phase shifter to which the fluctuating frequency from the frequency detection circuit is guided, and a PLL circuit to which the phase-controlled signal is guided by the phase shifter, and the phase shifter includes an arbitrary 2. The high-frequency induction heating device according to claim 1, further comprising a power factor adjusting section capable of phase control. 3) A power supply zero point detection circuit that detects the zero point of the full-wave rectified output from the rectifier circuit; Claim 1 or Claim 2 further comprising a start/stop circuit that sends out its own start signal and stop signal.
The high frequency induction heating device described in .