JPH0760735B2 - High frequency induction heating device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a high-frequency induction heating device, and particularly to a dental casting machine or the like.

(Prior Art) As a power source for a high frequency induction heating device, with the recent improvement in the high frequency technology of a semiconductor power conversion device, SIT and power MOSFE
High frequency inverter circuits using high-speed switching elements such as T have come into use.

On the other hand, a diode rectifier circuit has been conventionally used as a DC power source of a voltage type inverter circuit which is one of such high frequency inverter circuits. That is, connect the choke coil and a large-capacity DC capacitor to the output side (DC side) of the diode rectifier circuit to smooth the output of the diode rectifier circuit and supply it to the voltage source inverter circuit as a stable DC power supply. Has become.

(Problems to be Solved by the Invention) As described above, in the conventional high-frequency induction heating device, the smoothing circuit including the choke coil and the large-capacity DC capacitor is connected to the input side of the voltage source inverter circuit which is the power supply. Therefore, there is a problem that the input current to the voltage-type inverter circuit becomes pulsed, and not only the power supply power factor deteriorates but also harmonic interference may occur. Also,
Since there is a smoothing circuit composed of a choke coil and a large-capacity DC capacitor, it has been an obstacle to weight reduction and size reduction.

The present invention has been made in view of the above circumstances, and an object thereof is to directly supply the output of a single-phase diode rectifier circuit as a DC power source to a voltage source inverter circuit, thereby providing a choke coil, a large-capacity DC capacitor, or the like. It is an object of the present invention to provide a high-frequency induction heating device that can be omitted and can make the power supply current waveform a sine wave with a power factor of 1.

(Means for Solving the Problems) In order to solve the above problems, a high-frequency induction heating device of the present invention is connected to a rectifier circuit for full-wave rectifying a commercial power source and an output side of the rectifier circuit, and is turned on by a drive circuit. ON / OFF controlled full-bridge type switching element, matching transformer connected to the output side of this switching element, driving circuit driving the heating coil connected to the secondary side of this matching transformer, and this driving circuit , A frequency detection circuit for detecting the frequency during driving, a preset reference frequency that is a frequency that the drive circuit has in an initial state, and a fluctuating frequency detected by the frequency detection circuit, alternately in a predetermined cycle. Phase control for switching and outputting, and for sending a drive signal phase-locked to the output reference frequency or fluctuation frequency to the drive circuit And a 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 introduced, and a PLL circuit to which a signal whose phase is controlled by this phase shifter is introduced, and the phase shifter includes A power factor adjusting unit capable of arbitrarily controlling the phase is provided.

Further, in each of the above-mentioned configurations, a zero detection circuit for detecting the zero point of the full-wave rectified output from the rectification circuit, and the zero point detection of the full-wave rectified output detected by the zero-point detection circuit, in the vicinity of the zero point of the full-wave rectified output. And a start / stop circuit that sends out a start signal and a stop signal of the apparatus itself.

(Function) The commercial power supply is full-wave rectified by the rectifier circuit, and the full-wave rectified output of this rectifier circuit is supplied to the input side of the switching element connected in the full-bridge type. Each switching element is
Switching control is performed by each drive circuit provided corresponding to each, and the alternating current sent to the output side by this switching control is supplied to the primary side of the matching transformer. Therefore, on the secondary side of the matching transformer, for example, an alternating current converted at a ratio of 8: 1 flows, so that a driving circuit, for example, an LC series resonant circuit to which this alternating current is guided, is driven, that is, resonated, 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 the voltage frequency from the current or the voltage applied to the drive circuit at this time, and detects the detected current frequency or voltage frequency (hereinafter,
It is called fluctuating frequency. ) To the phase control circuit. A signal of a reference frequency from a reference frequency oscillator is guided to the phase control circuit, and the reference frequency and the fluctuation frequency are appropriately switched in a predetermined cycle and output. Then, by supplying the drive signal phase-locked to the output reference frequency or fluctuation frequency to each drive circuit, each drive circuit is driven and ON / OFF of the switching element is controlled with good timing.

Further, in the above configuration, the phase control circuit includes a phase shifter to which the fluctuating frequency from the frequency detection circuit is introduced, and a PLL circuit to which a signal whose phase is controlled by this phase shifter is introduced, and the phase shifter includes A power factor adjusting unit that can arbitrarily control the phase is provided. That is, power control to the heating coil is performed by controlling the power factor of the inverter circuit including the switching element.

Furthermore, in each of the above configurations, the zero point of the full-wave rectified output from the rectifier circuit is detected by the power source zero-point detection circuit, and based on this zero point detection of the full-wave rectified output, the starting signal of the device itself near the zero point of the full-wave rectified output. And a stop signal from the start / stop circuit. That is, even if the start switch and stop switch provided in the device itself are turned on at any timing, the device itself actually starts or stops because it is near the zero point of the full-wave rectified output. The destruction of the element is prevented.

(Example) Hereinafter, the Example of this invention is described with reference to drawings.

[Embodiment 1] FIG. 1 is a circuit diagram showing an electrical configuration of a high-frequency induction heating device of the present invention corresponding to claim 1. However, in the present embodiment, a series resonance circuit type high frequency induction heating apparatus using a voltage source high frequency inverter circuit of 1 KW and 500 KHz is shown.

In the figure, each output of an AC 100V AC power supply (commercial power supply) 1 is a single-phase diode full-bridge rectifier circuit (hereinafter, simply referred to as a rectifier circuit) including four diodes 2a to 2d.
2 is connected to each input terminal of the rectifier circuit 2. Each output terminal of the rectifier circuit 2 is connected to four power MOSFETs 3a bridge-connected via a small-capacity (for example, 0.47 μF) capacitor C ₀ connected in parallel. It is connected to each input terminal of ~ 3d (switching element).

In the power MOSFETs 3a to 3d, the drain terminals of the power MOSFETs 3a and 3b are connected to each other and the source terminals of the power MOSFETs 3c and 3d are connected to each other. Is connected to the drain terminal of. Further, feedback diodes Da to Dd are connected between the drain terminal and the source terminal of each of the power MOSFETs 3a to 3d, and series circuits (snubber circuits) 4a to 4d of capacitors and diodes are connected. And these powers
The MOSFETs 3a to 3d and the feedback diodes Da to Dd form a voltage type high frequency inverter circuit. The middle point of the snubber circuit 4a is connected to the source terminal of the power MOSFET 3c via the resistor R1, the middle point of the snubber circuit 4b is connected to the source terminal of the power MOSFET 3d via the resistor R2, and the middle point of the snubber circuit 4c is connected. Is connected to the drain terminal of the power MOSFET 3a via the resistor R3, and the middle point of the snubber circuit 4d is the power source via the resistor R4.
It is connected to the drain terminal of the MOSFET 3b, and these snubber circuits 4a, 4c and resistors R1, R3 and the snubber circuits 4b, 4d and resistor R2,
R4 and spike voltage suppression circuits 5a and 5b are respectively configured.

The output ends of the bridge-connected power MOSFETs 3a to 3d are connected to both ends of the primary winding 6a of the matching transformer 6, and the secondary winding 6b of the matching transformer 6 has a capacitor C and A series resonance circuit with the heating coil L is connected.

In addition, the voltage detection unit 7 that detects the terminal voltage of the capacitor C
Of the switching circuit 13 which is a component of the phase control circuit 10.
Of the phase shifter 11 is connected to the switching control input of the phase shifter 11 and the output of the phase shifter 11 passes through one input of the comparator 21 and the switching circuit 13 and is a phase component of the PLL circuit 12. It is led to the detector 121. 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 unit 7. When the maximum value of the output (capacitor voltage) of the voltage detection unit 7 is 50 V or less, for example, the output of the reference frequency oscillator 14 is set to the PLL. When the voltage is sent to the circuit 12 and 50 V or more, the switching is performed so that the output of the phase shifter 11 is sent to the PLL circuit 12. Also,
The oscillation frequency of the reference frequency oscillator 14 is set to the resonance frequency (500 KHz in this embodiment) of the LC resonance circuit connected to the secondary winding of the matching transformer 6.

The output of the VCO (voltage controlled oscillator) 123, which is a constituent element of the PLL circuit 12, is led to the trigger input of the flip-flop 15 and the trigger input of the monostable multivibrator 16, and the Q output of the flip-flop 15 and Two outputs
The output of the monostable multivibrator 16 is led to one input of each of the AND circuits 17 and 18, and the other input of the two AND circuits 17 and 18, respectively. Also, flip-flop 15
Q output of is connected to the phase detector 121 to form a feedback loop. Further, the monostable multivibrator 16 is connected to a commutation delay angle control volume VRβ for controlling the commutation delay angle. Then, the output of the AND circuit 17 and the output of the AND circuit 18 are guided as gate signals to the drive circuits 28a to 28d that drive the power MOSFETs 3a to 3d provided corresponding to the gate signals. Although not shown, the drive power supply for each of the drive circuits 28a to 28d is different from the drive power supply for the inverter circuit in order to perform stable operation. The power MOSFET 3a is shown in FIG.
An example of the circuit configuration of the drive circuits 28a to 28d for driving .about.3d at 500 KHz is shown. In order to drive the power MOSFETs 3a to 3d at a high frequency, a 1: 1 pulse transformer is used to insulate them from the main circuit.

That is, the high-frequency induction heating apparatus of this embodiment uses the full-wave rectified voltage from the single-phase diode full-bridge rectifier circuit 2 as the DC power source, and only the small-capacity capacitor C ₀ on its output side (DC side). By connecting it and omitting the smoothing circuit such as choke coil and electric field capacitor used in the conventional device, stable operation can be obtained as a high frequency induction heating device, and the power supply current waveform is a sine wave with a power factor of 1. It can be made into waves. The full-wave rectified voltage
Fluctuations of 100Hz (or 120Hz) have little effect on the heating properties of metals.

Next, the operation of the high-frequency induction heating device having the above configuration will be described with reference to the timing chart of FIG. However, FIG. 3 shows the signal waveform of each part of the phase control circuit 10.

By turning on the start switch (not shown) of the high frequency induction heating device, the AC100V voltage from the commercial power source 1 is full-wave rectified in the rectifier circuit 2 and then the power MOSFETs 3a to 3d.
Is supplied to the input terminal of the switching element. The power MOSFETs 3a to 3d appropriately drive the drive circuits 28a to 28d by a gate signal from the phase control circuit 10 to be described later, so that the power MOSFETs 3a and 3d and the power MOSFETs 3b and 3d, respectively.
An alternating current flows through the primary winding of the matching transformer 6 because 3c and 3c are alternately conducted. As a result, the matching transformer 6
A high-frequency current is supplied to the LC resonance circuit via the secondary winding of the, and an alternating magnetic field is generated in the heating coil L.

On the other hand, when the start switch is turned on, the voltage detection circuit 7
Output (capacitor voltage: v _C ) is less than 50V,
The switching circuit 13 outputs the output of the reference frequency oscillator 14 to the PLL circuit 12
The connection has been switched to send to. Here, the frequency oscillated from the reference frequency oscillator 14 is a natural frequency of the LC resonance circuit (resonance frequency: in the present embodiment.
Since the power MOSFETs 3a to 3d have a constant time (that is, the time until the output of the voltage detection circuit 7 exceeds 50V: several msec) from the time when the start switch is turned on.
Up to, the ON / OFF operation is controlled in the state of the oscillation frequency from the reference frequency oscillator 14. That is, since a high frequency current flows through the heating coil L in the resonance state, efficient high frequency induction heating is performed.

After this, when the output v _C of the voltage detection circuit 7 exceeds 50 V, the switching circuit 13 changes its connection from the reference frequency oscillator 14 side to the phase shifter.
Switch to 11 side. As a result, the output of the phase shifter 11 is input to the PLL circuit 12.

The phase shifter 11 receives the output of the voltage detection circuit 7, that is, the capacitor voltage v _C as an input, and creates a signal [Fig. 3 (c)] that is delayed in phase by γ _{0 with} respect to the output voltage i ₀ . Is input to the phase detector 121 of the PLL circuit 12 via the comparator 21. As shown in FIG. 3 (d), the VCO 123 of the PLL circuit 12 has a frequency (10
0 Hz) is output, and this signal is delayed by the delay time γ ₀ and supplied to the flip-flop 15 and the trigger input of the monostable multivibrator 16. The flip-flop 15 outputs a signal obtained by dividing the guided VOC123 output by two from the Q output [FIG. 3 (f)] and the output [FIG. 3 (g)], and outputs the Q output to the AND circuit 17. Output is A
It is sent to each ND circuit 18. In addition, in the monostable multivibrator 16, by adjusting the volume VRβ, the commutation delay angle β from the rise of the output signal of the VCO123.
Create a signal [Fig. 3 (e)] that rises after that,
This signal is sent to each AND circuit 17, 18. Each AND circuit 17,18
Then, by taking the logical product of these signals, the gate signal G ₁ shown in FIG.
From D circuit 18 sends a gate signal G ₂ shown in FIG. 3 (i), the drive circuit 28a corresponding to the respective, 28d and 28b, to 28c. Each drive circuit 28a~28d, each power MOSFET on the basis of the gate signals G _1, G _2, which was derived corresponding to each
Switching 3a to 3d. That is, the power MOSFET 3a
For 3d, ON / OFF operation is controlled in a state where the phase is locked to the fluctuation frequency of the LC resonance circuit.

When the output v _C of the voltage detection circuit 7 becomes equal to or lower than the set voltage of 50 V again, the switching circuit 13 is connected to the reference frequency oscillator.
Switching to the 14 side, switching of the power MOSFETs 3a to 3d is performed by the same gate signal as above.

That is, the switching control of the power MOSFETs 3a to 3d is
The open loop control by the reference frequency oscillator 14 and the feedback control by the phase shifter 11 and the PLL circuit 12 are repeated every 10 msec. This change every 10 msec
From a resonance frequency of 500 KHz, it can be regarded as a continuous steady state.

[Embodiment 2] FIG. 4 is a circuit diagram showing an electrical configuration of a high frequency induction heating apparatus of the present invention corresponding to Claims 2 and 3. However,
In the present embodiment, a high frequency induction heating apparatus of a series resonance circuit type using a 1 KW, 500 KHz voltage type high frequency inverter circuit is shown as in the first embodiment. In the following description, the parts having the same circuit configurations as those of the first embodiment are designated by the same reference numerals, and the description thereof will be omitted here.

That is, in the present embodiment, in the circuit configuration shown in the first embodiment, the phase shifter 11 is connected to the power factor angle adjusting volume VRγ for adjusting the power factor angle, and the output of the commercial power source 1 is increased. A voltage detection circuit 25 for detecting the voltage is connected to the side. The output of the voltage detection circuit 25 is led to a power source zero point detection circuit 26 that detects the zero point of the voltage from the detected voltage waveform, and the output of the power source zero point detection circuit 26 is the device itself from the guided signal. Are led to a start / stop circuit 27 which produces start and stop signals for instructing start and stop. Then, the start signal and the stop signal from the start / stop circuit 27 are respectively guided to one inputs of two newly provided AND circuits 19 and 20, and the outputs of the AND circuits 19 and 20 are Drive circuits 28a to 28d for driving the power MOSFETs 3a to 3d provided corresponding to the respective power MOSFETs
Have been led to. 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 apparatus according to the present embodiment includes the phase shifter 11
By controlling the power factor of the power supply, the full bridge type switching element can be stably power-controlled to control the heating on the load side, and the start and stop of the device itself can be controlled by the power supply. The power MOSFETs 3a to 3d are prevented from being broken or the like by being configured to operate near the zero point of the voltage.

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

However, FIG. 5 is a signal waveform diagram of each part of the phase control circuit 10,
6 (a) and 6 (b) are diagrams showing the relationship between the inverter output voltage v ₀ and the output current i _0, and FIGS. 7 (a) and 7 (b) are diagrams showing the relationship between the power supply voltage v _S and the power supply current i _S. FIG. 8 is a timing chart of start / stop showing the relationship.

By turning on the start switch (not shown) of the high frequency induction heating device, the AC100V voltage from the commercial power source 1 is full-wave rectified in the rectifier circuit 2 and then the power MOSFETs 3a to 3d.
Is supplied to the input terminal of the switching element. The power MOSFETs 3a to 3d appropriately drive the drive circuits 28a to 28d by a gate signal from the phase control circuit 10 to be described later, so that the power MOSFETs 3a and 3d and the power MOSFETs 3b and 3d, respectively.
3c and 3c are alternately conducted, 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 via the secondary winding of the matching transformer 6, and an alternating magnetic field is generated in the heating coil L.

On the other hand, when the start switch is turned on, the voltage detection circuit 7
Since its output v _C is 50 V or less, the connection of the switching circuit 13 is switched so as to send the output of the reference frequency oscillator 14 to the PLL circuit 12. Here, since the frequency oscillated from the reference frequency oscillator 14 is the unique frequency of the LC resonance circuit, the power MOSFETs 3a to 3d are
From the time of ON to a certain time (that is, the time until the output of the voltage detection circuit 7 exceeds 50V: several msec), it is turned ON / OFF in the state of the oscillation frequency from the reference frequency oscillator 14.
The operation is controlled. That is, in the resonance state, the heating coil L
Since a high frequency current flows through the high frequency, efficient high frequency induction heating is performed.

After this, when the output v _C of the voltage detection circuit 7 exceeds 50 V, the switching circuit 13 changes its connection from the reference frequency oscillator 14 side to the phase shifter.
Switch to 11 side. As a result, the output of the phase shifter 11 is input to the PLL circuit 12.

If the power factor angle is adjusted to γ by adjusting the power factor angle adjusting volume VRγ of the phaser 11, the phaser
In 11, the output of the voltage detection circuit 7, that is, the capacitor voltage
v _C as input to create abreast signal only gamma-gamma ₀ for the output current i ₀ phase [Figure 5 (c)], PLL circuit this signal via a comparator 21 and switching circuit 13 Input to 12 phase detectors 121. As shown in FIG. 5 (d), the VCO 123 of the PLL circuit 12 has a drive frequency of 2 of the inverter circuit.
It is set to output a double frequency (100 Hz), and this signal is delayed by γ-γ ₀ and supplied to the trigger inputs of the flip-flop 15 and the monostable multivibrator 16. The flip-flop 15 outputs a signal obtained by dividing the guided output of the VCO 123 by 2 from the Q output [Fig. 5 (f)] and the output [Fig. 5 (g)], and outputs the Q output from the AND circuit 17
Then, the output is sent to the AND circuit 18, respectively. Further, in the monostable multivibrator 16, by adjusting the commutation delay angle control volume VRβ, a signal [Fig. 5 (e)] which rises after the commutation delay angle β from the rising of the output signal of the VCO 123 is generated. Create this signal,
Send to 18. In each AND circuit 17, 18, the logical product of these signals is taken, so that the AND circuit 17 shows in FIG.
, And the gate signal G ₂₂ shown in FIG. 5 (i) from the AND circuit 18 via the AND circuits 19 and 20 provided corresponding to the gate signal G ₁₁ shown in FIG.
28a, 28d and 28b, 28c. Each drive circuit 28a-2
8d is the gate signals G ₁₁ and G ₂₂ that are guided correspondingly.
The power MOSFETs 3a to 3d are switched based on the above.
That is, the power MOSFETs 3a to 3d are ON / OFF-controlled while being phase-locked to the fluctuation frequency of the LC resonance circuit.

When the output v _C of the voltage detection circuit 7 becomes equal to or lower than the set voltage of 50 V again, the switching circuit 13 is connected to the reference frequency oscillator.
Switching to the 14 side, switching of the power MOSFETs 3a to 3d is performed by the same gate signal as above.

That is, the switching control of the power MOSFETs 3a to 3d is
The open loop control by the reference frequency oscillator 14 and the feedback control by the phase shifter 11 and the PLL circuit 12 are repeated every 10 msec. This change every 10 msec
From a resonance frequency of 500 KHz, it can be regarded as a continuous steady state.

FIG. 7 (a) shows the inverter output voltage v ₀₉₅ at a power factor of 95%.
_Shows the waveform relationship between the output current i ₀₉₅ and the output current i _095, and FIG. 7B shows the waveform relationship between the inverter output voltage v ₀₆₇ and the output current i ₀₆₇ at a power factor of 67%. 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 FIG. 7B, the output voltage v ₀₆₇ and the output current i ₀₆₇ vibrate during switching. Therefore, in the present device, the spike voltage suppressing circuits 5a and 5b suppress the oscillation of the output voltage v ₀₆₇ and the output current I ₀₆₇ and prevent the switching elements from being destroyed.

Further, FIG. 8 (a) shows the waveform relationship between the power supply voltage v _S95 and the power supply current i _S95 at the power factor of 95% during the inverter operation, and FIG. 8 (b) shows the power factor of 67 during the inverter operation. Power supply voltage in%
v _Shows the waveform relationship between _S67 and power supply current i _S67 . From the figure, by connecting only the small-capacity (0.47 μF) capacitor C ₀ to the output side (DC side) of the single-phase diode full-bridge rectifier circuit 2, the power supply current becomes a sine wave with a power factor of 1. .

On the other hand, the start control and the stop control when the start switch and the stop switch of this device are operated are performed by the voltage detection circuit 25, the power source zero detection circuit 26, the start / stop circuit 27, and the AND circuits 19, 20.
Done by

That is, as shown in FIG. 8, the power source zero point detection circuit 26 detects the power source zero point from the power source voltage v _S detected by the voltage detection circuit 25, and outputs a pulse signal every 10 msec as a zero point detection signal. (Fig. 8 (c)). And
When the start switch is turned ON (that is, a start command is issued) at an arbitrary time t1, the start / stop circuit 27 causes the time t1 to change.
At the time t2 when the next zero-point detection signal is input from, the starting signal [indicated at H level in FIG. 8 (e)]. ]] Is transmitted. Since this start signal is given to one input of the AND circuits 19 and 20, each AND of the phase control circuit 10 is in the period when the start signal shown by the H level is given from the AND circuits 19 and 20. The gate signals from the circuits 17 and 18 are sent to the corresponding drive circuits 28a to 28d. And
When the stop switch is turned on at time t3 (that is, a stop command is issued), the start / stop circuit 27 outputs a stop signal (shown at L level) at time t4 when the next zero point detection signal is input from time t3. Send out. This stop signal is AN
Since the signal is given to one input of the D circuits 19 and 20, the sending of the gate signal from the AND circuits 19 and 20 to the drive circuits 28a to 28d is stopped. In this way, the voltage detection circuit 25, the power source zero detection circuit 26, the start / stop circuit 27 and the AND
By adding the circuits 19 and 20, it is possible to start and stop the device itself near the zero point of the power supply regardless of the actual ON operation of the start switch and stop switch, so that a large current suddenly flows in the switching element. Since the current does not flow into the device, the switching element is prevented from being destroyed when the device is started and stopped, and safe starting and stopping is performed.

In each of the above-described embodiments, the voltage waveform across the capacitor C is detected as a means for detecting the LC resonance frequency. However, the current flowing through the LC resonance circuit is detected and the frequency is obtained from the detected waveform. Can be configured as follows.

(Effects of the Invention) Since the high-frequency induction heating device of the present invention is configured to use the full-wave rectified output from the rectifier circuit as the drive power source for the inverter circuit, it is possible to smooth the choke coil, electrolytic capacitor, etc. used in the conventional device. Since the circuit can be omitted, the size and weight of the entire device can be reduced, and the power supply current waveform can be a sine wave with a power factor of 1. In addition, since the load side heating control method is configured to control the power factor of the inverter circuit, a wide range of power control can be performed. Furthermore, since the device itself is started and stopped near the zero point of the power supply voltage, the switching element is prevented from being broken during starting and stopping.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram showing an electrical configuration of a high frequency induction heating device of the present invention corresponding to claim 1, and FIG. 2 is a circuit diagram showing an example of a drive circuit for driving a power MOSFET. , FIG. 3 is a signal waveform diagram of each part of the phase control circuit, FIG. 4 is a circuit diagram showing an electric configuration of the high frequency induction heating apparatus of the present invention corresponding to claims 2 and 3, and FIG. Signal waveform diagram of each part of the control circuit, FIG. 6 (a), (b) is the inverter output voltage
Diagram showing the relationship between v ₀ and output current i ₀ , FIG. 7 (a),
FIG. 8B is a diagram showing the relationship between the power supply voltage v _S and the power supply current i _S, and FIG. 8 is a timing chart of start / stop. 1 ... AC power supply (commercial power supply) 2 ... Single-phase diode full-bridge rectifier circuit 3a to 3d ... Power MOSFET 6 ... Matching transformer 7 ... Voltage detection circuit 10 ... Phase control circuit 11 ... Phaser 12 ... PLL circuit 121 ... Phase detector 122 ... Low-pass filter 123 ... VCO (voltage controlled oscillator) 13 ... Switching circuit 14 ... Reference frequency oscillator 15 ... Flip-flop 16 ... Monostable multivibrator 17-20 ... AND circuit 25 ... Voltage detection circuit 26 ... Power source zero detection circuit 27 ... Start / stop circuit VRβ… Volume for commutation delay angle control VRγ… Volume for power factor angle adjustment

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-62-287590 (JP, A)

Claims (3)

[Claims] 1. A rectifier circuit for full-wave rectifying a commercial power source, a full-bridge type switching element connected to the output side of the rectifier circuit and ON / OFF controlled by a drive circuit, and an output side of the switching element. A matching transformer connected thereto, a drive circuit for driving the heating coil connected to the secondary side of the matching transformer, a frequency detection circuit for detecting a frequency when the drive circuit is driven, and the preset drive circuit The reference frequency, which is the frequency in the initial state, and the fluctuation frequency detected by the frequency detection circuit are alternately switched in a predetermined cycle and output, and the phase locked drive to the output reference frequency or fluctuation frequency is performed. A high frequency induction heating device, comprising: a phase control circuit for sending a signal to the drive circuit. 2. The phase control circuit includes a phase shifter to which a fluctuating frequency from the frequency detection circuit is introduced, and a PLL circuit to which a signal whose phase is controlled by the phase shifter is introduced.
The high frequency induction heating apparatus according to claim 1, wherein the phase shifter is provided with a power factor adjusting unit capable of arbitrarily controlling a phase. 3. A power source zero point detection circuit for detecting a zero point of the full wave rectified output from the rectifier circuit, and a zero point of the full wave rectified output based on the zero point detection of the full wave rectified output detected by the power source zero point detection circuit. 3. A start / stop circuit for transmitting a start signal and a stop signal of the device itself in the vicinity thereof.
The high frequency induction heating device according to.