阅读说明：本技术 逆变器装置和逆变器装置的控制方法 (Inverter device and control method of inverter device ) 是由 石间勉 田内良男 守上浩市 高田太郎 辻宽树 伊藤政浩 茂野大作 于 2019-01-11 设计创作，主要内容包括：即使进行输出控制逆变器部的输出的频率也不从谐振频率偏离,此外,改善对谐振频率变动的负载的跟随特性。在作为连接到谐振负载(200)而被PWM控制的电压型逆变器的逆变器装置(10)中,具有连接到谐振负载(200)而通过逆变器驱动信号(Q、NQ)驱动的逆变器部(106)以及控制逆变器部(106)的动作的控制单元(12),控制单元(12)在将比谐振负载(200)的谐振频率的周期短的脉冲宽度的脉冲信号作为逆变器驱动信号(Q、NQ)并把从谐振频率移开的频率作为起点来开始逆变器部(106)的驱动之后,以使逆变器驱动信号(Q、NQ)的频率频移到谐振频率或谐振频率附近而使逆变器驱动信号(Q、NQ)的频率与谐振频率大体一致的方式进行控制。(The frequency of the output of the inverter unit is not deviated from the resonance frequency even if the output control is performed, and the follow-up characteristic to the load of the resonance frequency variation is improved. An inverter device (10) as a voltage-type inverter connected to a resonant load (200) and PWM-controlled, comprising an inverter unit (106) connected to the resonant load (200) and driven by an inverter drive signal (Q, NQ), and a control means (12) for controlling the operation of the inverter unit (106), wherein the control means (12) controls the inverter drive signal (Q, NQ) to be a pulse signal having a pulse width shorter than the cycle of the resonant frequency of the resonant load (200) and controls the inverter drive signal (Q, NQ) so that the frequency of the inverter drive signal (Q, NQ) is shifted to the resonant frequency or the vicinity of the resonant frequency after the inverter drive signal (Q, NQ) starts driving the inverter unit (106) with the frequency shifted from the resonant frequency as the starting point.)

1. An inverter device as a voltage-type inverter connected to a resonant load and controlled by PWM, comprising:

an inverter unit connected to the resonant load and driven by an inverter drive signal; and

a control unit for controlling the operation of the inverter unit,

the control means controls the inverter drive signal to have a pulse width shorter than a cycle of a resonant frequency of the resonant load as the inverter drive signal and to start driving of the inverter section with a frequency shifted from the resonant frequency as a starting point, and then controls the inverter drive signal to have a frequency shifted to the resonant frequency or a vicinity thereof so that the frequency of the inverter drive signal substantially coincides with the resonant frequency.

2. The inverter device according to claim 1, wherein the short pulse width is a pulse width at which an output of the inverter unit becomes a lowest set output value of a set value indicated by an output set signal from outside.

3. The inverter device according to any one of claims 1 or 2, wherein the starting point is such that a region in which the frequency shift is performed is an inductive region based on a diode reverse recovery characteristic of an inverter circuit constituting the inverter portion.

4. The inverter device according to any one of claims 1, 2, or 3, characterized in that, in the inverter device,

the resonant load is a parallel resonant load,

the starting point is a frequency lower than the resonance frequency.

5. The inverter device according to claim 4, wherein an inductor is connected to an output stage of the inverter section in the inverter device.

6. The inverter device according to claim 5, wherein the control unit has a delay correction unit that corrects a delay of the voltage phase caused by the inductor.

7. The inverter device according to any one of claims 1, 2, or 3, characterized in that, in the inverter device,

the resonant load is a series resonant load,

the starting point is a frequency higher than the resonance frequency.

8. The inverter device according to claim 7, wherein the control section has a delay correction unit that corrects a circuit delay of the inverter section.

9. The inverter device according to any one of claims 1 or 2, characterized in that, in the inverter device,

the resonant load is a series resonant load,

the inverter section uses a SiC diode as a freewheeling diode in the inverter switching element,

the starting point is a frequency lower than the resonance frequency.

10. The inverter device according to any one of claims 1, 2, 3, 4, 5, 6, 7, 8, or 9, characterized in that in the inverter device, the starting point is a frequency shifted by 5% or more with respect to the frequency of the resonance frequency.

11. The inverter device according to any one of claims 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, wherein the control unit widens the pulse width of the inverter drive signal by PWM control after controlling so that the frequency of the inverter drive signal substantially coincides with the resonance frequency.

12. The inverter device according to any one of claims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11, wherein the control section has a lowest level checking means for checking that the output of the inverter section becomes an output level at which phase checking becomes possible.

13. The inverter device according to any one of claims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12, wherein the control section has a frequency checking means for checking that the output of the inverter section becomes a frequency of an output level at which phase checking becomes possible.

14. The inverter device according to any one of claims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or 13, wherein in the inverter device, an output terminal of the inverter device and a parallel resonance capacitor box are connected by an air-cooled coaxial cable, a converter is connected to the parallel resonance capacitor box, and a high-frequency current is transmitted to a heating coil.

15. The inverter device according to any one of claims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, or 14, wherein in the inverter device, the resonant load is constituted by a resonant circuit including a heating coil for induction heating and a resonant capacitor.

16. In a control method of an inverter device which is a voltage-type inverter connected to a resonant load and controlled by PWM, after driving of an inverter section is started with a frequency shifted from a resonant frequency of the resonant load as a starting point by using a pulse signal having a pulse width shorter than a cycle of the resonant frequency as an inverter driving signal, the frequency of the inverter driving signal is shifted to the resonant frequency or a vicinity of the resonant frequency so that the frequency of the inverter driving signal substantially coincides with the resonant frequency.

17. The method of controlling an inverter device according to claim 16, wherein the short pulse width is a pulse width at which the output of the inverter unit becomes a minimum set output value of a set value indicated by an output set signal from outside.

18. The method according to any one of claims 16 or 17, wherein the starting point is such that a region in which the frequency shift is performed is an inductive region based on a diode reverse recovery characteristic of an inverter circuit constituting the inverter unit.

19. The control method of the inverter apparatus according to any one of claims 16, 17, or 18, characterized in that, in the control method,

the resonant load is a parallel resonant load,

the starting point is a frequency lower than the resonance frequency.

20. The control method of the inverter apparatus according to claim 19, characterized in that in the control method, an inductor is connected to an output stage of the inverter section.

21. The control method of the inverter apparatus according to claim 20, characterized in that in the control method, a delay of a voltage phase caused by the inductor is corrected.

22. The control method of the inverter apparatus according to any one of claims 16, 17, or 18, characterized in that, in the control method,

the resonant load is a series resonant load,

the starting point is a frequency higher than the resonance frequency.

23. The method of controlling an inverter device according to claim 22, wherein a circuit delay of the inverter unit is corrected in the control method.

24. The control method of the inverter apparatus according to any one of claims 16 or 17, characterized in that, in the control method,

the resonant load is a series resonant load,

the inverter section uses a SiC diode as a freewheeling diode in the inverter switching element,

the starting point is a frequency lower than the resonance frequency.

25. The control method of an inverter device according to any one of claims 16, 17, 18, 19, 20, 21, 22, 23, or 24, characterized in that in the control method, the starting point is a frequency shifted by 5% or more with respect to the frequency of the resonance frequency.

26. The method of controlling an inverter device according to any one of claims 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25, wherein in the method of controlling, after controlling so that the frequency of the inverter drive signal substantially coincides with the resonance frequency, the pulse width of the inverter drive signal is widened by PWM control.

27. The method of controlling an inverter device according to any one of claims 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, or 26, wherein in the control method, it is checked that the output of the inverter section becomes an output level at which phase checking becomes possible.

28. The method of controlling an inverter device according to any one of claims 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, or 27, wherein in the method of controlling, a case where an output of the inverter section becomes a frequency of an output level at which phase detection becomes possible is detected.

29. The method of controlling an inverter apparatus according to any one of claims 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, or 28, wherein in the method of controlling, an output terminal of the inverter apparatus and a parallel resonant capacitor box are connected by an air-cooled coaxial cable, a converter is connected to the parallel resonant capacitor box, and a high-frequency current is transmitted to a heating coil.

30. The method of controlling an inverter apparatus according to any one of claims 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, or 29, wherein in the method of controlling, the resonant load is constituted by a resonant circuit including a heating coil for induction heating and a resonant capacitor.

Technical Field

The invention relates to an inverter device and a control method of the inverter device. More specifically, the present invention relates to an inverter device used by being connected to a resonant load and a control method of the inverter device.

Background

In general, an inverter device is known as a power supply device connected to a resonant load such as an induction heating circuit.

Conventionally, in such an inverter device, an inverter control unit including a Phase Locked Loop (PLL) circuit is used as an inverter control unit for controlling an inverter unit having an inverter circuit, and the inverter control unit controls the inverter unit.

A conventionally known inverter device controlled by an inverter control unit using a PLL circuit will be described with reference to fig. 1 (a) and (b).

Fig. 1 (a) is an explanatory view showing the overall configuration of an inverter device that is controlled by an inverter control unit using a PLL circuit and is connected to a resonant load.

Fig. 1 (b) is an explanatory diagram showing a detailed configuration of an inverter control unit in the inverter device shown in fig. 1 (a).

As shown in fig. 1 (a), an inverter device 100 converts an alternating current voltage supplied from an Alternating Current (AC) power supply 102 into a high-frequency alternating current voltage of a desired voltage and supplies the high-frequency alternating current voltage to a resonant load 200 such as an induction heating circuit.

Further, as the ac power source 102, for example, a commercial ac power source can be used, and in this case, the inverter device 100 converts a commercial ac voltage into a high-frequency ac voltage and supplies the high-frequency ac voltage to the resonant load 200.

More specifically, the inverter device 100 is configured to include: a converter unit 104 having a converter circuit for receiving an ac voltage supplied from an ac power supply 102 and converting the ac voltage into a Direct Current (DC) voltage and outputting the DC voltage, an inverter unit 106 having an inverter circuit for receiving a DC voltage output from the converter unit 104 and converting the DC voltage into a high-frequency ac voltage and outputting the high-frequency ac voltage, an output sensor 108 for detecting an output from the inverter unit 106 (here, the "output" from the inverter unit 106 means an "output voltage Vh" which is a voltage output from the inverter unit 106, an "output current Ih" which is a current output from the inverter unit 106, or an "output power" which is a power output from the inverter unit 106) and outputting a detection result as an output sensor signal, and a converter control unit 110 for feedback-controlling the DC voltage converted by the converter unit 104 based on an output setting signal which is a signal for externally setting the output from the inverter unit 106 and an output sensor signal which is output from the output sensor 108 And an inverter control unit 112 having a PLL circuit 112a (see fig. 1 (b)) for feedback-controlling the operation of the inverter unit 106 based on an output sensor signal output from the output sensor 108.

The converter circuit of converter unit 104 is constituted by, for example, a thyristor rectifier circuit, a chopper circuit, and the like.

Here, fig. 1 (b) shows a detailed configuration of the inverter control unit 112. In the inverter control unit 112, the PLL circuit 112a outputs a rectangular wave inverter drive signal Q, NQ, which is an inverter drive signal for driving the inverter unit 106, based on the output sensor signal input to the PLL circuit 112 a.

In the present specification and claims, the "rectangular wave inverter drive signal Q, NQ" is appropriately referred to as an "inverter drive signal".

In the above configuration, in the inverter device 100, an ac voltage is input from an ac power supply 102 such as a commercial ac power supply to the converter unit 104. The converter unit 104 to which an ac voltage is input from the ac power supply 102 variably controls a dc voltage by a control signal from the converter control unit 110, and outputs the dc voltage to the inverter unit 106.

The inverter unit 106 converts the dc voltage input from the converter unit 104 into a high-frequency voltage by switching ON/OFF of transistors constituting the inverter circuit.

As described above, the output sensor 108 is provided at the output stage of the inverter unit 106 in the inverter device 100, and the output sensor 108 detects the output from the inverter unit 106 (which is the output voltage Vh, the output current Ih, or the output power) and outputs the detection result to the converter control unit 110 and the inverter control unit 112 as an output sensor signal.

Converter control unit 110 performs control to vary the dc voltage value as the output of converter unit 104 so that the output of inverter unit 106 is at the set level indicated by the output set signal.

Here, the inverter control unit 112 performs automatic control by the PLL circuit 112a as follows: the frequency of the output of inverter unit 106 becomes the resonant frequency of resonant load 200.

In addition, in the inverter device connected to the resonant load, as for the output control circuit using the phase control of the high-frequency voltage and the high-frequency current, several methods are used in addition to the configuration shown in the above-described conventional inverter device 100.

However, any of the methods used in the past has the following problems: when the output control is performed, the characteristic that the frequency of the output of the inverter unit is shifted from the resonance frequency becomes a practical problem.

On the other hand, an inverter device used in a low power apparatus also uses output control using a Pulse Width Modulation (PWM) control method.

Here, fig. 2 is an explanatory view showing the overall configuration of an inverter device that performs output control by the PWM control method and is connected to a resonant load.

In the following description, the configurations and operations described with reference to fig. 1 (a) and (b) and the configurations and operations that are the same or equivalent to those described with reference to fig. 1 (a) and (b) are shown with the same reference numerals as those used in fig. 1 (a) and (b), and detailed descriptions thereof will be omitted.

As shown in fig. 2, the inverter device 300 is a device that converts an ac voltage supplied from an ac power supply 102 into a high-frequency ac voltage of a desired voltage and supplies the high-frequency ac voltage to a resonant load 200 such as an induction heating circuit.

As the ac power source 102, for example, a commercial ac power source can be used as in the case of the inverter device 100 described above, and in this case, the inverter device 10 converts a commercial ac voltage into a high-frequency ac voltage and supplies the high-frequency ac voltage to the resonant load 200.

More specifically, the inverter device 300 is configured to include: a converter unit 302 that receives an ac voltage supplied from an ac power supply 102 and converts the ac voltage into a dc voltage by rectification with a diode and outputs the dc voltage, an inverter unit 106 having an inverter circuit that receives the dc voltage output from the converter unit 302 and converts the dc voltage into a high-frequency ac voltage and outputs the high-frequency ac voltage, an output sensor 108 that detects an output from the inverter unit 106 (here, the "output" from the inverter unit 106 refers to an "output voltage Vh" that is a voltage output from the inverter unit 106, an "output current Ih" that is a current output from the inverter unit 106, or an "output power" that is power output from the inverter unit 106) and outputs a detection result as an output sensor signal, and a PWM control unit 304 that feedback-controls the inverter unit 106 based on an output setting signal that is a signal for externally setting the output from the inverter unit 106 and an output sensor signal output from the output sensor 108 .

In the above configuration, the operation of the inverter device 300 will be described with reference to waveform diagrams schematically shown in fig. 3 (a), (b), and (c).

In FIGS. 3 (a), (b), and (c),

waveform A: output of inverter unit 106 (output voltage Vh or output current Ih)

Waveform B: output of inverter unit 106 (output voltage Vh or output current Ih)

And C, waveform C: output of inverter unit 106 (output voltage Vh or output current Ih)

T: 1 cycle of the fundamental component of the output (output voltage Vh or output current Ih) of inverter unit 106

T/4: 1/4 cycles of the fundamental component of the output (output voltage Vh or output current Ih) of inverter unit 106

tw: pulse width of the inverter drive signal.

In inverter device 300, when driving is started (at the time of startup) by PWM control unit 304, inverter drive signal (rectangular wave inverter drive signal Q, NQ) having a narrow pulse width tw is driven at around the resonant frequency (fig. 3 a), and in order to variably control the output of inverter unit 106, the output of inverter unit 106 is variably controlled by varying pulse width tw by PWM control unit 304.

For example, in order to increase the output of the inverter unit 106, the pulse width tw is expanded by PWM control by the PWM control unit 304 as shown in fig. 3 (b) and 3 (c).

That is, in the conventional inverter device 300, the PWM control by the PWM control unit 304 controls the driving in the vicinity of the resonant frequency by using the PLL circuit or the like from the start-up time, and performs the PWM control in the frequency band.

Therefore, the conventional inverter device 300 has a problem that the follow-up characteristic with respect to the load whose resonant frequency fluctuates is deteriorated.

Further, the prior art known by the applicant of the present application at the time of patent application is not an invention related to a publicly known invention of a literature, and therefore there is no prior art literature information to be described in the specification of the present application.

Disclosure of Invention

Problems to be solved by the invention

The present invention has been made in view of the above-described problems of the conventional art, and an object of the present invention is to provide the following: the present invention is intended to provide an inverter device and a control method for the inverter device, which do not deviate from a resonance frequency even if the frequency of the output of an inverter unit is output-controlled, and which further improve the follow-up characteristics for a load whose resonance frequency fluctuates.

Means for solving the problems

In order to achieve the above object, the present invention is an inverter device comprising: in the inverter device, which is a voltage-type inverter connected to a resonant load and PWM-controlled, a pulse signal having a pulse width shorter than a resonant frequency cycle (for example, a "minimum pulse width" described later) is used as an inverter drive signal (in the present specification and the claims, the "pulse signal having a pulse width shorter than the resonant frequency cycle" is appropriately referred to as a "narrow-width pulse signal"), and the inverter unit is started to be driven with a frequency shifted from the resonant frequency as a starting point, and the inverter drive signal is frequency-shifted to the resonant frequency or a vicinity of the resonant frequency by frequency control so that the frequency of the inverter drive signal substantially coincides with the resonant frequency.

Further, the present invention is an invention as follows: after the frequency of the inverter drive signal is substantially equal to the resonance frequency by the above control, the pulse width of the inverter drive signal is widened by the PWM control, and the output (which is the output voltage, the output current, or the output power) of the inverter unit is controlled to be a predetermined value.

Therefore, according to the present invention, even if the frequency of the output of the inverter unit is output-controlled, the frequency does not deviate from the resonance frequency, and the follow-up characteristic for the load varying in the resonance frequency can be improved.

That is, in the present invention, the frequency at the start of driving of the inverter drive signal is shifted from the resonance frequency and intentionally shifted so that the frequency of the inverter drive signal becomes the resonance frequency after the start of driving, whereby the resonance frequency can be automatically found by the frequency shift regardless of the shift of the resonance frequency on the resonance load side.

Here, it is preferable that a region in which the frequency of the inverter drive signal is shifted (in the present specification and the claims, "a region in which the frequency of the inverter drive signal is shifted" is appropriately referred to as a "frequency shift region") be determined as an inductive region in which the most appropriate diode reverse recovery characteristics for the inverter circuit are considered.

In other words, it is preferable that the starting point of the frequency shifted from the resonance frequency is determined so that the frequency shift region becomes an inductive region based on the diode reverse recovery characteristic of the inverter circuit.

That is, the inverter device according to the present invention is an inverter device as follows: the inverter device is a voltage-type inverter connected to a resonant load and controlled by PWM, and includes an inverter section connected to the resonant load and driven by an inverter drive signal, and a control unit for controlling an operation of the inverter section, wherein the control unit controls the inverter section so that a frequency of the inverter drive signal is shifted to or near the resonant frequency to substantially match the frequency of the inverter drive signal with the resonant frequency after starting driving of the inverter section with a frequency shifted from the resonant frequency by using a pulse signal having a pulse width shorter than a cycle of the resonant frequency of the resonant load as the inverter drive signal.

Further, an inverter device according to the present invention is a device as follows: in the inverter device according to the present invention, the short pulse width is set to a pulse width at which the output of the inverter unit becomes a minimum set output value of the set values indicated by the output set signal from the outside.

Further, an inverter device according to the present invention is a device as follows: in the inverter device according to the present invention, the starting point is such that a region in which the frequency shift is performed is an inductive region based on a diode reverse recovery characteristic of an inverter circuit constituting the inverter unit.

Further, an inverter device according to the present invention is a device as follows: in the inverter device according to the present invention, the resonant load is a parallel resonant load and the starting point is a frequency lower than the resonant frequency.

Further, an inverter device according to the present invention is a device as follows: in the inverter device according to the present invention described above, the inductor is connected to the output stage of the inverter section described above.

Further, an inverter device according to the present invention is a device as follows: in the inverter device according to the present invention, the control unit may include a delay correction unit that corrects a delay in a voltage phase caused by the inductor.

Further, an inverter device according to the present invention is a device as follows: in the inverter device according to the present invention, the resonant load is a series resonant load and the starting point is a frequency higher than the resonant frequency.

Further, an inverter device according to the present invention is a device as follows: in the inverter device according to the present invention, the control unit may include a delay correction unit that corrects a circuit delay of the inverter unit.

Further, an inverter device according to the present invention is a device as follows: in the inverter device according to the present invention described above, the resonant load is a series resonant load and the inverter unit uses a SiC diode as a flywheel diode in an inverter switching element and the starting point is a frequency lower than the resonant frequency.

Further, an inverter device according to the present invention is a device as follows: in the inverter device according to the present invention, the starting point is a frequency shifted by 5% or more from the frequency of the resonance frequency.

Further, an inverter device according to the present invention is a device as follows: in the inverter device according to the present invention, the control unit may control the inverter driving signal so that the frequency of the inverter driving signal substantially coincides with the resonance frequency, and then widen the pulse width of the inverter driving signal by PWM control.

Further, an inverter device according to the present invention is a device as follows: in the inverter device according to the present invention, the control unit includes a minimum level detection unit for detecting that the output of the inverter unit is an output level at which phase detection is possible.

Further, an inverter device according to the present invention is a device as follows: in the inverter device according to the present invention, the control unit may include a frequency checking unit for checking that the output of the inverter unit has a frequency at which a phase check becomes possible.

Further, an inverter device according to the present invention is a device as follows: in the inverter device according to the present invention described above, the output terminals of the inverter device and the parallel resonant capacitor box are connected by an air-cooled coaxial cable, the converter is connected to the parallel resonant capacitor box, and a high-frequency current is sent to the heating coil.

Further, an inverter device according to the present invention is a device as follows: in the inverter device according to the present invention described above, the resonant load is made up of a resonant circuit including a heating coil for induction heating and a resonant capacitor.

Further, the control method of the inverter device according to the present invention is a method of: in this control method of an inverter device as a voltage source inverter connected to a resonant load and PWM-controlled, after driving of an inverter unit is started with a frequency shifted from a resonant frequency of the resonant load as an inverter drive signal and a frequency shorter than a cycle of the resonant frequency as a starting point, the frequency of the inverter drive signal is shifted to the resonant frequency or a vicinity of the resonant frequency to substantially match the frequency of the inverter drive signal with the resonant frequency.

Further, the control method of the inverter device according to the present invention is a method of: in the method of controlling the inverter device according to the present invention, the short pulse width is set to a pulse width at which the output of the inverter unit becomes a minimum set output value of a set value indicated by an output set signal from the outside.

Further, the control method of the inverter device according to the present invention is a method of: in the method of controlling an inverter device according to the present invention, the starting point is such that a region in which the frequency shift is performed is an inductive region based on a diode reverse recovery characteristic of an inverter circuit constituting the inverter unit.

Further, the control method of the inverter device according to the present invention is a method of: in the method of controlling an inverter device according to the present invention, the resonant load is a parallel resonant load and the starting point is a frequency lower than the resonant frequency.

Further, the control method of the inverter device according to the present invention is a method of: in the above-described control method of the inverter apparatus according to the present invention, the inductor is connected to the output stage of the inverter section.

Further, the control method of the inverter device according to the present invention is a method of: in the control method of the inverter device according to the present invention described above, the delay of the voltage phase caused by the inductor described above is made to be corrected.

Further, the control method of the inverter device according to the present invention is a method of: in the method of controlling an inverter device according to the present invention, the resonant load is a series resonant load and the starting point is a frequency higher than the resonant frequency.

Further, the control method of the inverter device according to the present invention is a method of: in the above-described control method of the inverter device according to the present invention, the circuit delay of the inverter section is corrected.

Further, the control method of the inverter device according to the present invention is a method of: in the control method of the inverter device according to the present invention described above, the resonant load is a series resonant load and the inverter section uses a SiC diode as a flywheel diode in an inverter switching element and the starting point is a frequency lower than the resonant frequency.

Further, the control method of the inverter device according to the present invention is a method of: in the method of controlling an inverter device according to the present invention, the starting point is a frequency shifted by 5% or more from the resonant frequency.

Further, the control method of the inverter device according to the present invention is a method of: in the method of controlling the inverter device according to the present invention, after the control is performed so that the frequency of the inverter drive signal substantially coincides with the resonance frequency, the pulse width of the inverter drive signal is widened by the PWM control.

Further, the control method of the inverter device according to the present invention is a method of: in the above-described control method of the inverter device according to the present invention, it is checked that the output of the inverter section becomes an output level at which phase detection becomes possible.

Further, the control method of the inverter device according to the present invention is a method of: in the above-described control method of the inverter device according to the present invention, it is checked that the output of the inverter section has a frequency of an output level at which phase detection becomes possible.

Further, the control method of the inverter device according to the present invention is a method of: in the above-described control method of the inverter device according to the present invention, the output terminals of the inverter device and the parallel resonant capacitor box are connected by an air-cooled coaxial cable, the converter is connected to the parallel resonant capacitor box, and a high-frequency current is transmitted to the heating coil.

Further, the control method of the inverter device according to the present invention is a method of: in the above-described control method of the inverter device according to the present invention, the resonant load is made up of a resonant circuit including a heating coil for induction heating and a resonant capacitor.

Effects of the invention

The present invention is configured as described above, and therefore, the following advantageous effects are obtained: the frequency of the output of the inverter unit is not deviated from the resonance frequency even if the output control is performed, and the follow-up characteristic for the load with the fluctuation of the resonance frequency can be improved.

Drawings

Fig. 1 (a) and (b) are explanatory views of the configuration of a conventionally known inverter device controlled by a PLL circuit. More specifically, fig. 1 (a) is a configuration explanatory diagram showing the overall configuration of an inverter device that is controlled by an inverter control unit using a PLL circuit and is connected to a resonant load. Fig. 1 (b) is a detailed configuration explanatory diagram of an inverter control unit in the inverter device shown in fig. 1 (a).

Fig. 2 is an explanatory view showing the configuration of the entire inverter device known in the related art, which is connected to a resonant load and performs output control by a PWM control method.

Fig. 3 (a), (b), and (c) are schematic waveform diagrams showing operations in the inverter device shown in fig. 2.

Fig. 4 is a structural explanatory diagram of an inverter device according to an example of the embodiment of the invention. More specifically, fig. 4 is a configuration explanatory diagram showing the overall configuration of the inverter device controlled by the control unit and connected to the resonant load.

Fig. 5 is a detailed configuration explanatory diagram of a control unit in the inverter shown in fig. 4.

Fig. 6 is a structural explanatory diagram of an inverter device according to an example of the embodiment of the invention. More specifically, fig. 6 is an explanatory view showing the configuration of the entire inverter device controlled by the control unit and connected to the parallel resonant load.

Fig. 7 (a), (b), (c), (d), and (e) are schematic waveform diagrams showing operations in the inverter device shown in fig. 6.

Fig. 8 is a structural explanatory diagram of an inverter device according to an example of the embodiment of the invention. More specifically, fig. 8 is an explanatory view showing the configuration of the entire inverter device controlled by the control unit and connected to the series resonant load.

Fig. 9 (a), (b), (c), (d), and (e) are schematic waveform diagrams showing operations in the inverter device shown in fig. 8.

Fig. 10 is a diagram illustrating a configuration of a control section in an inverter device according to an example of an embodiment of the present invention.

Fig. 11 is a diagram illustrating a configuration of a control unit in an inverter device according to an example of an embodiment of the present invention.

Fig. 12 is a structural explanatory diagram of an inverter device according to an example of the embodiment of the invention. More specifically, fig. 12 is an explanatory view showing the configuration of the entire inverter device controlled by the control unit and connected to the series resonant load.

Fig. 13 is an enlarged explanatory view of an inverter unit in the inverter device shown in fig. 12.

Fig. 14 (a) is a structural explanatory diagram schematically showing a power supply structure using an inverter device according to the present invention connected to a resonant load. Fig. 14 (b) is a configuration explanatory diagram schematically showing a power supply configuration using an inverter device according to the related art connected to a series resonant load. Fig. 14 (c) is a configuration explanatory diagram schematically showing a power supply configuration using an inverter device according to the related art connected to a parallel resonant load.

Fig. 15 (a) and (b) are explanatory views showing the structure of a resonant load for induction heating as an example of the resonant load. More specifically, fig. 15 (a) is an explanatory diagram showing a configuration of the series resonant load for induction heating in the case of the series resonant load. Fig. 15 (b) is an explanatory diagram showing a configuration of a parallel resonant load for induction heating as a case of the parallel resonant load.

Detailed Description

One example of an embodiment of an inverter device and a control method for an inverter device according to the present invention is described below in detail with reference to the accompanying drawings.

In the following description of the "embodiment", the same or equivalent structures and operations as those described with reference to the drawings of fig. 1 (a) and (b), fig. 2, and fig. 3 (a), (b), and (c), or those described with reference to the drawings of fig. 4 and below are shown with the same reference numerals as those used in fig. 1 (a) and (b), fig. 2, and fig. 3 (a), (b), and (c), respectively, and thus the detailed structures and operations will not be described.

(I) First embodiment

(I-1) Structure

Fig. 4 is an explanatory view showing a structure of an inverter device according to an example of the embodiment of the present invention. Fig. 4 shows an overall configuration of an inverter device controlled by a control unit and connected to a resonant load.

Fig. 5 is a diagram illustrating a detailed configuration of the control unit in the inverter device shown in fig. 4.

An inverter device 10 according to an example of an embodiment of the present invention is described with reference to fig. 4 and 5.

The inverter device 10 according to one example of the embodiment of the present invention is a PWM-controlled voltage-type inverter connected to the resonant load 200.

That is, the inverter device 10 converts an ac voltage supplied from the ac power supply 102 into a high-frequency ac voltage of a desired voltage and supplies the high-frequency ac voltage to the resonant load 200 such as an induction heating circuit.

As the ac power source 102, for example, a commercial ac power source can be used as in the conventional inverter device 100, and in this case, the inverter device 10 converts a commercial ac voltage into a high-frequency ac voltage and supplies the high-frequency ac voltage to the resonant load 200.

More specifically, the inverter device 10 includes a converter unit 302, and the converter unit 302 receives an ac voltage supplied from the ac power supply 102, converts the ac voltage into a dc voltage by rectification using a diode, and outputs the dc voltage.

That is, the converter unit 302 of the inverter device 10 is configured by a diode rectifier circuit that does not use a converter control unit, and receives an ac voltage from the ac power supply 102, converts the received ac voltage into a dc voltage, and outputs the dc voltage to the inverter unit 106.

The inverter unit 106 receives the dc voltage output from the converter unit 302, and inverts the dc voltage into a high-frequency ac voltage and outputs the high-frequency ac voltage.

An output sensor 108 that detects an output from the inverter unit 106 (here, "output" from the inverter unit 106 means "output voltage Vh" that is a voltage output from the inverter unit 106, "output current Ih" that is a current output from the inverter unit 106, or "output power" that is power output from the inverter unit 106) is provided at an output stage of the inverter unit 106, and outputs the detection result as an output sensor signal.

The inverter device 10 includes a control unit 12 as control means for controlling the operation of the inverter unit 106.

As shown in fig. 5, the controller 12 includes a PWM controller 12a and a frequency shift controller 12 b.

The control unit 12 performs feedback control on the inverter unit 106 based on an output setting signal, which is a signal for externally setting the output of the inverter unit 106, and an output sensor signal output from the output sensor 108.

That is, the control unit 12 varies the pulse width of the rectangular wave inverter drive signal Q, NQ, which is an inverter drive signal for driving the transistors of the voltage source inverter constituting the inverter unit 106, by the PWM control of the PWM control unit 12a so that the output from the inverter unit 106 becomes the output set value indicated by the output set signal, and varies the output of the high frequency ac voltage converted by the inverter unit 106.

The output from inverter unit 106 is input to external resonant load 200 via output sensor 108.

(I-2) operation

In the above configuration, the control unit 12 of the inverter device 10 performs the operation described below as an operation related to the implementation of the present invention.

That is, at the start of driving (at the time of starting) when the output from the inverter device 10 is started, the pulse width is sufficiently shorter than the resonance frequency cycle, for example, the pulse width of the lowest set output value (which is the output voltage, the output current, or the output power) that becomes the set value indicated by the output set signal from the outside (in the present specification and the present claims, "the pulse width of the lowest set output value that becomes the set value indicated by the output set signal from the outside" is appropriately referred to as "the lowest pulse width"), and the driving is started (started) by the rectangular wave inverter drive signal Q, NQ having a frequency shifted away from the resonance frequency of the resonant load 200 as the starting point.

Thus, even if the resonant frequency of resonant load 200 fluctuates, it is possible to automatically follow the fluctuating resonant frequency by performing frequency shift from the start of driving (at the time of startup) to shift the frequency of rectangular wave inverter drive signal Q, NQ to the resonant frequency by frequency shift control unit 12b of control unit 12.

In the inverter device 10, the PWM control unit 12a of the control unit 12 expands the pulse width of the rectangular wave inverter drive signal Q, NQ by PWM control so that the frequency of the rectangular wave inverter drive signal Q, NQ becomes the resonance frequency (resonance point) or the vicinity thereof and thereafter becomes the output of the set value indicated by the output set signal from the outside.

That is, the inverter device 10 outputs a minimum set output value (which is an output voltage, an output current, or output power) of a set value indicated by an external output set signal as a rectangular wave inverter drive signal Q, NQ as an inverter drive signal, and uses a pulse signal (narrow width pulse signal) having a pulse width sufficiently shorter than a resonance frequency cycle (for example, the minimum pulse width mentioned above) so as to start with a frequency obtained by shifting the narrow width pulse signal from the resonance frequency as a starting point, and then shifts the frequency to the resonance frequency or the vicinity thereof, and thereafter controls the frequency to the resonance frequency by frequency control.

After that, the inverter device 10 widens the pulse width of the narrow-width pulse signal by PWM control so as to be an output (which is an output voltage or an output current or an output power) of a set value indicated by an output setting signal from the outside.

(I-3) Effect

Therefore, according to the inverter device 10 described above, even if the frequency of the output of the inverter unit is output-controlled, the frequency does not deviate from the resonance frequency, and the follow-up characteristic for the load with respect to the fluctuation of the resonance frequency can be improved.

In the inverter device 10 described above, since the output control can be performed in the inverter unit 106, there is no case where a thyristor rectifier circuit or a chopper circuit is used as a converter circuit of the converter unit as in the conventional technique.

Therefore, when compared with the conventional technology using a thyristor rectifier circuit or a chopper circuit, the inverter device 10 can achieve an improvement in power factor of the power supply, a significant improvement in output response speed (according to the experiment of the inventors of the present application, the response speed is improved from 100ms in the conventional technology to 10 ms), a reduction in cost due to a significant reduction in the number of components, and an improvement in reliability.

Further, since the inverter device 10 sets the start frequency, which is the frequency at the start of driving (at the start) of the inverter drive signal, to a frequency shifted from the resonance frequency and then shifts the frequency of the inverter drive signal so as to approach the resonance frequency, the follow-up characteristic of the resonant load 200 with respect to the resonance frequency fluctuation is greatly improved, and the inverter device can be applied without any problem even when a plurality of resonant loads 200 having different resonance frequencies are connected by switching.

Further, since the resonant load 200 can be used as the same voltage-type inverter regardless of whether it is a parallel resonant load or a series resonant load, the inverter device can be made universal.

Here, it is preferable that the region (frequency shift region) in which the frequency shift is performed by the frequency shift control unit 12b is determined as an inductive region in consideration of the diode reverse recovery characteristics most suitable for the inverter circuit.

In other words, it is preferable that the start frequency is determined so that the frequency shift region becomes an inductive region based on the diode reverse recovery characteristic of the inverter circuit.

According to the experiment of the inventors of the present application, a good result was obtained when the frequency at the start of driving (at the time of starting) as the inverter driving signal, that is, the starting frequency, was set to a frequency shifted by 5% or more from the frequency of the resonance frequency (for example, when the resonance frequency was set to 20kHz, the frequency shifted by 5% or more from the frequency of the resonance frequency was set to a frequency of 19kHz or less or a frequency of 21kHz or more).

When the starting frequency is shifted by 5% or more from the frequency of the resonance frequency, that is, when the starting frequency is shifted by 5% or more from the frequency of the resonance frequency, the starting frequency may be shifted on the low frequency band side of the resonance frequency (in the frequency direction lower than the resonance frequency) (for example, when the resonance frequency is set to 20kHz, the frequency shifted by 5% or more on the low frequency band side of the resonance frequency is 19kHz or less), or may be shifted on the high frequency band side of the resonance frequency (in the frequency direction higher than the resonance frequency) (for example, when the resonance frequency is set to 20kHz, the frequency shifted by 5% or more on the high frequency band side of the resonance frequency is 21kHz or more).

Furthermore, according to the findings of the inventors of the present application, there is no conventional technique such as PWM control in which the start frequency is shifted from the frequency of the resonance frequency (for example, shifted from the frequency of the resonance frequency by 5% or more.) and the drive of the inverter unit is started by the narrow-width pulse signal from the start frequency, then the narrow-width pulse signal is shifted to the resonance frequency, and then the pulse width of the narrow-width pulse signal is expanded at the resonance frequency, as in the inverter device 10 according to the present invention described above.

(II) second embodiment

(II-1) Structure

Fig. 6 is an explanatory view showing a structure of an inverter device according to an example of the embodiment of the present invention. Fig. 6 shows the overall configuration of the inverter device controlled by the control unit and connected to the parallel resonant load.

When the inverter device 20 according to one example of the embodiment of the present invention is explained while referring to fig. 6, the inverter device 20 is connected to the parallel resonant load 22.

Further, the parallel resonant load has a characteristic of being inductive in a range of a frequency lower than a resonant frequency, while the voltage-type inverter understands that a switching operation by the inductance is more stable than a capacitive operation due to a reverse recovery characteristic of a current of a diode connected in parallel to an inverter element.

Therefore, the inverter device 20 according to the present invention sets a frequency lower than the resonance frequency of the parallel resonant circuit 22 (for example, a frequency lower than the resonance frequency by 5% or more) as the start frequency of the inverter drive signal, and shifts the frequency of the inverter drive signal from the start frequency to the resonance frequency so that the frequency of the inverter drive signal is locked at the resonance frequency.

In the following description of the inverter device 20, reference numeral 24 denotes an inductor, reference numeral 26 denotes a voltage sensor, and reference numeral 28 denotes a control unit.

The voltage sensor 26 is a component corresponding to the output sensor 108, and detects a voltage and outputs a signal indicating the detected voltage as an output sensor signal.

The control unit 28 is configured to include a frequency shift circuit 30, a Voltage-controlled oscillator (VCO) circuit 32, a narrow-width pulse signal generation circuit 34, an output circuit 36, a phase comparison circuit 38, a delay setting circuit 40, a lock completion circuit 42, a detector circuit 44, an error amplifier filter 46, a triangular wave generation circuit 48, and a PWM circuit 50.

Here, since the inverter device 20 can be applied to a technique of an inverter device known in the related art except that the control unit 28 includes the frequency shift circuit 30 to shift the frequency of the inverter drive signal and to switch the signal in association with the implementation of the present invention, a detailed description of the configuration other than the frequency shift of the frequency of the inverter drive signal and to switch the signal will be omitted.

(II-2) action

In the above configuration, the operation of the inverter device 20 will be mainly described with respect to the operation of the control unit 28 related to the implementation of the present invention.

The control unit 28 inputs an output ON (ON) signal from the outside to the frequency shift circuit 30, outputs a signal to the VCO circuit 32 so that the inverter unit 106 starts to be driven from a frequency lower than the resonance frequency of the parallel resonant load 22 (for example, a frequency lower by 5% or more than the resonance frequency), inputs a frequency signal of the output from the VCO circuit 32 to the narrow width pulse signal generation circuit 34, generates a narrow width pulse signal of the frequency of the output from the VCO circuit 32 by the narrow width pulse signal generation circuit 34, and outputs the narrow width pulse signal to the output circuit 36. In the output circuit 36, the signal of the narrow-width pulse signal generation circuit 34 is switched to the signal of the PWM circuit 50 by the signal of the lock completion circuit 42.

Here, it is preferable that the pulse width of the narrow-width pulse signal generated by the narrow-width pulse signal generation circuit 34 is set so that the output value output from the inverter unit 106 becomes the lowest set output value (which is the output voltage, the output current, or the output power) of the set values indicated by the output setting signal from the outside.

Fig. 7 (a), (b), (c), (d), and (e) show waveform diagrams schematically illustrating operations of the inverter device 20.

In fig. 7 (a), (b), (c), (D), and (E), the waveform D, the waveform E, the waveform F, the waveform G, and the waveform H are waveforms of the voltage (capacitor voltage Vc) detected by the voltage sensor 26.

Fig. 7 (a) shows a phase difference between a waveform (waveform D) of a voltage (capacitor voltage Vc) detected by the voltage sensor 26 as an output of the inverter section 106 at a start frequency at the start of driving (at the time of starting) and a narrow-width pulse signal as an inverter driving signal.

In the case where the parallel resonant load 22 is connected to the inverter device 20, it is understood that the phase of the inverter drive signal is delayed compared to the phase of the capacitor voltage Vc in a frequency domain below the resonant frequency.

Here, in the phase comparison circuit 38, a point a at which 1/4 is delayed in the period of the pulse of the inverter drive signal is set as the pulse position of the phase detection pulse, a zero-crossing point of the capacitor voltage Vc phase waveform (waveform E) to be compared is set as a point B (see fig. 7 (B)), the phase difference between the point a and the point B is compared, and the phase difference is locked at a frequency at which the phase difference becomes zero (0) or a predetermined phase difference (see fig. 7 (c)).

On the other hand, the waveform signal from the voltage sensor 26 and the frequency signal from the VCO circuit 32 are input to the phase comparator circuit 16, and the respective phases are compared, thereby controlling the frequency of the VCO circuit 32 so as to be the resonance frequency.

Specifically, the driving of the inverter unit 106 is started by an inverter driving signal of a narrow-width pulse signal having a frequency shifted from the resonance frequency (for example, a frequency lower than the resonance frequency by 5% or more) as a start frequency (see fig. 7 a), and the frequency of the inverter signal is shifted and increased (see fig. 7 b).

Then, the frequency of the inverter drive signal is locked at the resonance frequency by the phase comparison circuit 38 (refer to fig. 7 (c)), and the lock completion circuit 42 checks that the locking is completed and outputs a signal to the output circuit 36. Based on this signal, the output circuit 36 outputs an inverter drive signal in which the pulse width tw is expanded from the narrow-width pulse signal by PWM control, and the output of the inverter unit 106 rises to the output of the set value set by the output set signal (see fig. 7 (d) and (e)).

That is, the inverter device 20 connects the parallel resonant load 22 as a resonant load, uses, as a rectangular wave inverter drive signal Q, NQ which is an inverter drive signal, a pulse signal (narrow width pulse signal) having a pulse width sufficiently shorter than a resonant frequency cycle and outputting a minimum set output value (which is an output voltage, an output current, or an output power) of a set value indicated by an external output set signal, and performs frequency control using a frequency shift for raising the frequency to the resonant frequency or a frequency near the resonant frequency after starting with a frequency obtained by shifting the narrow width pulse signal from the resonant frequency (for example, a frequency lower by 5% or more than the resonant frequency), thereby controlling the frequency of the inverter drive signal to the resonant frequency.

Thereafter, in the inverter device 20, the pulse width of the narrow-width pulse signal is widened by the PWM control so as to be an output (which is an output voltage or an output current or an output power) of a set value indicated by an output setting signal from the outside.

(II-3) Effect

Therefore, the inverter device 20 also has the same operational effects as those described in (I-3) above with respect to the inverter device 10.

(II-4) other characteristic Structure in the second embodiment

(ア) in the inverter device 20, an inductor 24 for preventing harmonic current is connected between the inverter unit 106 and the voltage sensor 26, which is the output stage of the inverter unit 106.

That is, in the inverter device 20, when the inverter unit 106 as a voltage source inverter is connected to the parallel resonant load 22, a harmonic current flows due to a voltage of a harmonic component of the rectangular wave voltage, and therefore the inductor 24 for preventing the current is connected in series to the output stage of the inverter unit 106.

Although the output voltage of the inverter unit 106 is a rectangular wave, it is generally known that a rectangular wave is composed of a synthesized waveform of a sine wave and an odd harmonic, and when the rectangular wave is connected to the parallel resonant load 22 as it is, the odd harmonic component has a high frequency and thus the reactance of the capacitor decreases, the harmonic current increases, the current waveform distortion occurs, or the loss deterioration of the transistor as the switching element of the inverter unit 106 occurs.

Therefore, in the inverter device 20, the inductor 24 is connected to the output stage of the inverter unit 106 for the purpose of suppressing such harmonic currents.

(イ) the control unit 28 of the inverter device 20 is provided with a delay setting circuit 40 for setting a signal delay time when an output signal from the VCO circuit 32 is input to the phase comparison circuit 38 and phase comparison is performed.

That is, in the inverter device 20, when the inverter unit 106 as a voltage source inverter is connected to the parallel resonant load 22, since a harmonic current flows due to the voltage of the harmonic component of the rectangular wave voltage, the inductor 24 is connected in series in order to prevent the current, but a delay occurs in the voltage phase at the time of resonance due to the inductor component caused by the series connection of the inductor 24.

In order to correct the delay of the voltage phase, the control unit 28 of the inverter device 20 is provided with a delay setting circuit 40 that delays the phase of the pulse input to the drive side of the phase comparison circuit 38, and performs delay correction.

(III) third embodiment

(III-1) Structure

Fig. 8 is an explanatory view showing a structure of an inverter device according to an example of the embodiment of the present invention. Fig. 8 shows the overall configuration of an inverter device controlled by a control unit and connected to a series resonant load.

When an inverter device 60 according to an example of the embodiment of the present invention is described while referring to fig. 8, the inverter device 60 is connected to a series resonant load 62.

Further, while the series resonant load has a characteristic of being inductive in a range of a frequency higher than a resonant frequency, the voltage-source inverter is understood to have a switching operation by the inductance being more stable than a capacitive one due to a reverse recovery characteristic of a current of a diode connected in parallel to an inverter element.

Therefore, the inverter device 20 according to the present invention sets a frequency higher than the resonance frequency of the series resonant circuit 22 (for example, a frequency higher than the resonance frequency by 5% or more) as the start frequency of the inverter drive signal, and shifts the frequency of the inverter drive signal from the start frequency to the resonance frequency so that the frequency of the inverter drive signal is locked at the resonance frequency.

In the following description of the inverter device 60, reference numeral 64 denotes a current sensor, and reference numeral 66 denotes a resonant capacitor of the series resonant load 62.

The current sensor 64 is a component corresponding to the output sensor 108 described above, and detects a current and outputs a signal indicating the detected current as an output sensor signal.

The configuration of the control unit 28 is the same as that of the inverter device 20 described above, and therefore, a detailed description thereof is omitted.

(III-2) operation

In the above configuration, the operation of the inverter device 60 will be mainly described with respect to the operation of the control unit 28 related to the implementation of the present invention.

The control unit 28 inputs an output ON (ON) signal from the outside to the frequency shift circuit 30, outputs a signal to the VCO circuit 32 so that the inverter unit 106 starts to be driven from a frequency higher than the resonance frequency of the series resonant load 62 (for example, a frequency higher by 5% or more than the resonance frequency), inputs a frequency signal from the output of the VCO circuit 32 to the narrow width pulse signal generation circuit 34, generates a narrow width pulse signal of the frequency of the output of the VCO circuit 32 by the narrow width pulse signal generation circuit 34, and outputs the narrow width pulse signal to the output circuit 36. In the output circuit 36, the signal of the narrow-width pulse signal generation circuit 34 is switched to the signal of the PWM circuit 50 by the signal of the lock completion circuit 42.

Here, it is preferable that the pulse width of the narrow-width pulse signal generated by the narrow-width pulse signal generation circuit 34 is set so that the output value output from the inverter unit 106 becomes the lowest set output value (which is the output voltage, the output current, or the output power) of the set values indicated by the output setting signal from the outside.

Fig. 9 (a), (b), (c), (d), and (e) show waveform diagrams schematically illustrating operations of the inverter device 60.

In fig. 9 (a), (b), (c), (d), and (e), the waveform I, the waveform J, the waveform K, the waveform L, and the waveform M are current (output current) waveforms detected by the current sensor 64.

Fig. 9 (a) shows a phase difference between a current (output current) waveform (waveform I) detected by the current sensor 64 as an output of the inverter section 106 at a start frequency at the start time (at the time of start) of driving and a narrow-width pulse signal as an inverter driving signal.

In the case where the series resonant load 62 is connected to the inverter device 60, it is understood that the phase of the output current is delayed compared to the phase of the inverter drive signal in the frequency domain above the resonant frequency.

Here, in the phase comparison circuit 38, the point C at which 1/4 is delayed in the period of the pulse of the inverter drive signal is set as the pulse position of the phase detection pulse, the zero-crossing point of the output current phase waveform (waveform J) to be compared is set as the point D (see fig. 9 (b)), the phase difference between the point C and the point D is compared, and the phase difference is locked at a frequency at which the phase difference becomes zero (0) or a predetermined phase difference (see fig. 9 (C)).

On the other hand, the waveform signal from the current sensor 64 and the frequency signal from the VCO circuit 32 are input to the phase comparator circuit 16, and the respective phases are compared, thereby controlling the frequency of the VCO circuit 32 so as to be the resonance frequency.

Specifically, the driving of the inverter unit 106 is started by an inverter driving signal of a narrow-width pulse signal having a frequency shifted from the resonance frequency (for example, a frequency higher by 5% or more than the resonance frequency) as a start frequency (see fig. 9 (a)), and the frequency of the inverter signal is shifted and decreased (see fig. 9 (b)).

Then, the frequency of the inverter drive signal is locked at the resonance frequency by the phase comparison circuit 38 (refer to fig. 9 (c)), and the lock completion circuit 42 checks that the locking is completed and outputs a signal to the output circuit 36. By this signal, the inverter drive signal whose pulse width tw is extended from the narrow-width pulse signal by the PWM control is output from the output circuit 36, and the output of the inverter unit 106 rises to the output of the set value set by the output set signal (see fig. 9 (d) and (e)).

In the inverter device 60 to which the series resonant load 62 is connected, the delay setting circuit 40 is used to correct the circuit delay of the inverter unit 106.

That is, the inverter device 60 connects the series resonant load 62 as a resonant load, uses, as a rectangular wave inverter drive signal Q, NQ which is an inverter drive signal, a pulse signal (narrow width pulse signal) having a pulse width sufficiently shorter than a resonant frequency cycle and outputting a minimum set output value (which is an output voltage, an output current, or an output power) of a set value indicated by an external output set signal, and performs frequency control using a frequency shift for lowering the frequency to the resonant frequency or a frequency near the resonant frequency after starting with a frequency obtained by shifting the narrow width pulse signal from the resonant frequency (for example, a frequency higher by 5% or more than the resonant frequency) as a starting point, thereby controlling the frequency of the inverter drive signal to the resonant frequency.

Thereafter, in the inverter device 60, the pulse width of the narrow-width pulse signal is widened by the PWM control so as to be an output (which is an output voltage or an output current or an output power) of a set value indicated by an output setting signal from the outside.

(III-3) Effect

Therefore, the inverter device 60 also has the same operational effects as those described in (I-3) above with respect to the inverter device 10.

(IV) fourth embodiment

Fig. 10 is an explanatory diagram showing a configuration of a control unit in an inverter device according to an example of the embodiment of the present invention.

In the fourth embodiment, since the configuration other than the control unit is not different from the configurations of the inverter devices 20 and 60 according to the second and third embodiments described above and the inverter device 400 according to the seventh embodiment described below, illustration and description of the configuration other than the control unit are omitted.

When compared with the control unit 28 in each of the above-described embodiments (second, third, and seventh embodiments), the control unit 70 of the inverter device according to the fourth embodiment includes the minimum level check circuit 72 in addition to the configuration of the control unit 28, and these are different from each other in this point.

In the inverter devices 20, 60, 400 according to the second, third, and seventh embodiments, the output level (resonance voltage or resonance current) decreases when the frequency is shifted from the resonance frequency, and it becomes impossible to perform a correct phase check from the output of the inverter section 106.

Therefore, in the inverter device according to the fourth embodiment, the lowest level check circuit 72 is provided at the control section 70, and a check is made that the output of the inverter section 106 becomes an output level at which phase check becomes possible at the lowest level check circuit 72, so that phase comparison is started.

That is, the inverter device according to the fourth embodiment is a device as follows: the lowest level check circuit 72 of the control unit 70 checks the level of the output (which is the output voltage, the output current, or the output power) of the resonant load by the pulse drive signal as the inverter drive signal, and starts the operation of the phase comparison circuit 38 controlled to be near the resonant frequency when the level is equal to or higher than a predetermined level.

(V) fifth embodiment

Fig. 11 is an explanatory diagram showing a configuration of a control unit in an inverter device according to an example of the embodiment of the present invention.

In the fifth embodiment, since the configuration other than the control unit is not different from the configurations of the inverter devices 20 and 60 according to the second and third embodiments described above and the inverter device 400 according to the seventh embodiment described below, illustration and description of the configuration other than the control unit are omitted.

When compared with the control unit 28 in each of the above-described embodiments (second, third, and seventh embodiments), the control unit 80 of the inverter device according to the fifth embodiment includes the lowest level frequency check circuit 82 in addition to the configuration of the control unit 28, and these are different from each other in this point.

In the inverter devices 20, 60, 400 according to the second, third, and seventh embodiments, the output level (resonance voltage or resonance current) decreases when the frequency is shifted from the resonance frequency, and it becomes impossible to perform a correct phase check from the output of the inverter section 106.

Therefore, in the inverter device according to the fifth embodiment, the lowest level frequency check circuit 82 is provided in the control section 80, and the case where the output of the inverter section 106 becomes the frequency (lowest level frequency) of the output level at which the phase check becomes possible at the lowest level frequency check circuit 82 is checked so that the phase comparison is started.

That is, the inverter device according to the fifth embodiment is a device as follows: the lowest level frequency check circuit 82 of the control unit 80 checks that the frequency of the pulse drive signal, which is the inverter drive signal, has reached a predetermined frequency (lowest level frequency) when the frequency is shifted, and starts the operation of the phase comparison circuit 38 at the check time.

(VI) sixth embodiment

An inverter device according to an example of a sixth embodiment of the present invention is a device as follows: the present invention includes both the lowest level checking circuit 72 in the fourth embodiment and the lowest level frequency checking circuit 82 in the fifth embodiment.

In the sixth embodiment, the structure is not different from that in the above-described embodiments (second, third, fourth, and fifth embodiments) and the seventh embodiment described later except that the lowest level check circuit and the lowest level frequency check circuit are both provided in the control unit, and therefore, the above-described embodiments (second, third, fourth, and fifth embodiments) and the seventh embodiment described later are applied to the description thereof, and illustration and description thereof are omitted.

(VII) seventh embodiment

Fig. 12 is an explanatory view showing a structure of an inverter device according to an example of the embodiment of the present invention. Fig. 12 shows an overall configuration of an inverter device controlled by a control unit and connected to a series resonant load.

Fig. 13 is an enlarged explanatory view of an inverter unit in the inverter device shown in fig. 12.

As compared with the configuration of the inverter device 60 according to the third embodiment shown in fig. 8, the inverter device 400 shown in fig. 12 (an inverter device according to an example of the seventh embodiment of the present invention) differs in that an inverter unit 406 is provided instead of the inverter unit 106.

As shown in fig. 13, the inverter unit 406 of the inverter device 400 is an inverter unit that: so that SiC diodes are used as the circulating current diodes (free-wheeling diodes) 406b in the inverter switching elements 406 a.

In more detail, as shown in fig. 13, in the inverter switching element 406a of the inverter section 406, a SiC diode is made to be used as the flywheel diode 406b connected in antiparallel with the semiconductor switching element 406 c.

In the inverter device 400 according to the seventh embodiment, the resonant load forms the series resonant circuit 62, and the frequency of the pulse drive signal, which is a sufficiently short inverter drive signal capable of securing the minimum set output value (which is the output voltage, the output current, or the output power), is set to a frequency lower than the resonant frequency (for example, a frequency lower by 5% or more than the resonant frequency) and started with the frequency lower than the resonant frequency as a starting point, and frequency control is performed using a frequency shift for raising the frequency to the vicinity of the resonant frequency. The frequency of a pulse drive signal as an inverter drive signal is controlled to a resonance frequency.

That is, in the inverter device 400, a SiC diode is used as the flywheel diode 106b of the inverter switching element 106 a.

Therefore, according to the characteristics, since there is almost no recovery time in the current regeneration, the inverter operation using the capacitance (C-characteristic) can be performed in the series resonant circuit, and the resonant frequency can be shifted to a higher frequency from a lower frequency (C-characteristic region).

(VIII) eighth embodiment

Next, an inverter device according to an example of an eighth embodiment of the present invention will be described with reference to fig. 14 (a), (b), and (c).

Here, a configuration explanatory diagram schematically showing a power supply configuration using an inverter device according to the present invention connected to a resonant load is shown in fig. 14 (a).

Fig. 14 (b) is an explanatory diagram schematically showing a power supply configuration using an inverter device according to the related art connected to a series resonant load.

Fig. 14 (c) is an explanatory view schematically showing a power supply configuration using an inverter device according to the related art connected to a parallel resonant load.

The power supply structure using the inverter device 10, 20, 60, 400 connected to the resonant load according to the present invention described above shown in fig. 14 (a) is a power supply structure as follows: the output terminals 500 of the inverter devices 10, 20, 60, 400 according to the present invention connected to the resonant load and the parallel resonant capacitor box 502 can be connected by an air-cooled coaxial cable 504, and a small-sized converter (hand-held converter) 506 is connected to the parallel resonant capacitor box 502 so that a high-frequency current is transmitted to the heating coil 508, which can be used for the purpose of induction heating.

In the application of induction heating, there is a case where heating work is manually performed by increasing the distance from an inverter device to a heating coil, and conventionally, as shown in fig. 14 (b), a water-cooled cable 602 is connected to an output terminal 600a of an inverter device 600 according to the related art connected to a series resonant load to be extended, and impedance conversion is performed at a small-sized converter (a hand-held converter) 606 through a relay box 604 to transmit a high-frequency current to a heating coil 608.

Alternatively, conventionally, as shown in fig. 14 (c), an inverter device 700 according to the related art connected to a parallel resonant load is used, an air-cooling coaxial cable 702 is connected to an output terminal 700a of the inverter device 700 to be extended, impedance conversion is performed at a small-sized converter (a hand-held converter) 706 through a relay box 704, and a high-frequency current is transmitted to a heating coil 708.

However, in the case of using the inverter device 600 according to the related art connected to the series resonant load as shown in fig. 14 (b), since a harmonic current flows in the stray capacitance reciprocating in the water-cooled cable 602, there is a limit to the extension distance, and generally the limit of the extension distance is about 50 m.

Further, when the distance of the air-cooling coaxial cable 702 is extended using the inverter device 700 according to the related art connected to the parallel resonant load as shown in fig. 14 (c), the following is the case: since the series reactor in the inverter device 700 is large and heavy, the power supply itself is also large and heavy, and cannot be easily used as a small power supply in a work site.

On the other hand, in the configuration using the inverter devices 10, 20, 60, and 400 according to the present invention connected to the resonant load as shown in fig. 14 (a), since a voltage-type inverter that does not require a large dc reactor is used, a small-sized power supply configuration can be achieved, and by connecting the air-cooling coaxial cable 504 to this power supply configuration, a small-sized power supply that can easily extend the air-cooling coaxial cable 504 even at 200m or more can be configured.

The parallel resonance capacitor box 502 is a capacitor box formed of parallel resonance capacitors.

As the small-sized current transformer (hand-held current transformer) 506, a current transformer having the same structure as the small-sized current transformers (hand-held current transformers) 606 and 706, which are conventional structures, can be used.

Similarly, the heating coil 508 may be the same as the heating coils 608 and 708 having the conventional configuration.

(IX) ninth embodiment

An inverter device according to an example of a ninth embodiment of the present invention is an inverter device as follows: the resonant circuit constituting the resonant load 200, the parallel resonant load 22, or the series resonant load 62 in each of the above embodiments is constituted by a resonant circuit including a heating coil and a resonant capacitor for induction heating.

That is, as the resonant load 200, the parallel resonant load 22, or the series resonant load 62 connected to the inverter device according to the present invention including the inverter devices 10, 20, 60, and 400, various configurations can be used, and for example, resonant loads for induction heating as shown in fig. 15 (a) and (b) may be connected to the inverter device according to the present invention.

Fig. 15 (a) is an explanatory view showing a configuration of the series resonant load for induction heating in the case of the series resonant load.

Fig. 15 (b) is an explanatory view showing a configuration of a parallel resonant load for induction heating, which is a parallel resonant load. In the configuration shown in fig. 15 (b), a filter for removing harmonics is connected in series to the parallel resonant load for induction heating.

In the inverter device 20 shown in fig. 6, the filter is connected as an inductor 24 in the inverter device 20.

(X) description of other embodiments and modifications

The above embodiments are merely examples, and the present invention can be implemented in various other embodiments. That is, the present invention is not limited to the above-described embodiments, and various omissions, substitutions, and changes may be made without departing from the spirit of the present invention.

For example, the above-described embodiment may be modified as shown in the following (X-1) to (X-4).

(X-1) in the above-described embodiment, it is exemplified that the starting frequency is shifted from the resonance frequency by 5% or more in particular.

However, the present invention is not limited to the invention which is shifted by 5% or more from the resonance frequency, and may be made to be shifted by less than 5% from the resonance frequency.

That is, the value of "5%" is a preferable value that the inventors have found by experiments, but the present invention is not limited to the value of "5%" as long as the starting frequency is shifted from the resonance frequency.

By shifting the starting frequency from the resonant frequency, the resonant frequency can be automatically found by the frequency shift regardless of the deviation of the resonant frequency on the resonant load side.

Here, it is preferable that the region in which the frequency shift is performed (frequency shift region) be determined as an inductive region in which the most appropriate diode reverse recovery characteristics for the inverter circuit are taken into consideration, and the region be 5% or more from the resonant frequency according to an experiment performed by the inventors of the present application.

(X-2) in the above-described embodiment, although the specific circuit configuration and the like in each configuration are not described, it is needless to say that a conventionally known circuit configuration corresponding to each configuration may be used.

(X-3) in the above-described embodiment, although the specific circuit constants and the like in each configuration are not described, it is needless to say that conventionally known circuit constants corresponding to each configuration may be used.

(X-4) As to the above-mentioned embodiments and the embodiments shown in (X-1) to (X-3), it is needless to say that the combination may be appropriately made.

Industrial applicability

The present invention can be applied to an inverter device as a power supply device connected to a resonant load such as an induction heating circuit.

Description of reference numerals

10 an inverter device; 12a control unit (control means); 12a PWM control unit (control means); 12b a frequency shift control unit (control means); 20 an inverter device; 22 a parallel resonant circuit; 24 an inductor; 26 a voltage sensor; 28 a control unit (control means); 30 a frequency shift circuit; a 32-Voltage Controlled Oscillator (VCO) circuit; 34 a narrow width pulse signal generating circuit; 36 output circuits; 38 a phase comparison circuit; 40 delay setting circuit; 42 locking the completion circuit; 44 a detector circuit; 46 an error amplifier filter; a 48 triangular wave generating circuit; a 50 PWM circuit; 60 an inverter device; 62 series resonant load; a 64 current sensor; 66 a resonant capacitor; 70 a control unit (control means); 72 a lowest level check circuit (lowest level check unit); 80 a control unit (control means); 82 a lowest level frequency checking circuit (frequency checking unit); 100 an inverter device; 102 an Alternating Current (AC) power source; 104 a converter section; 106 an inverter section; 108 an output sensor; 110 a converter control section; 112a control unit; 112a PLL circuit; 200 resonant load; 300 an inverter device; 302 a converter section; 304 PWM control section; 400 an inverter device; 406 an inverter section; 406a inverter switching elements; 406b a circulating diode (freewheeling diode); 406c a semiconductor switching element; 500 output terminals; 502 parallel resonant capacitor box; 504 air-cooling the coaxial cable; 506 a current transformer; 508 a heating coil; 600 an inverter device; 600a output terminal; 602 water-cooled cables; 604 a relay box; 606 a current transformer; 608 heating coils; 700 an inverter device; 700a output terminal; 702 air-cooling the coaxial cable; 704 a relay box; 706 a current transformer; 708 heating coils; vh output voltage; ih, outputting current; a Q-square wave inverter drive signal; NQ rectangular wave inverter drive signals; t1 cycle of the fundamental component of the output (output voltage or output current) of the inverter section; 1/4 cycles of the fundamental wave component of the output (output voltage or output current) of the T/4 inverter section; the pulse width of tw rectangular wave inverter drive signal Q, NQ.