CN110870190B - Inverter device and control method for inverter device - Google Patents

Inverter device and control method for inverter device Download PDF

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Publication number
CN110870190B
CN110870190B CN201980003588.7A CN201980003588A CN110870190B CN 110870190 B CN110870190 B CN 110870190B CN 201980003588 A CN201980003588 A CN 201980003588A CN 110870190 B CN110870190 B CN 110870190B
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inverter
frequency
inverter device
output
control method
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CN110870190A (en
Inventor
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
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SPC Electronics Corp
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SPC Electronics Corp
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B6/00—Heating by electric, magnetic or electromagnetic fields
    • H05B6/02—Induction heating
    • H05B6/06—Control, e.g. of temperature, of power
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Inverter Devices (AREA)
  • General Induction Heating (AREA)

Abstract

Even if the frequency of the output control inverter unit is not deviated from the resonance frequency, the following characteristics of the load with respect to the fluctuation of the resonance frequency are improved. In an inverter device (10) which is a voltage-type inverter connected to a resonant load (200) and PWM-controlled, the inverter device comprises an inverter unit (106) connected to the resonant load (200) and driven by an inverter drive signal (Q, NQ), and a control unit (12) for controlling the operation of the inverter unit (106), the control unit (12) controls the inverter unit so that the frequency of an inverter drive signal (Q, NQ) is shifted to a resonance frequency or a vicinity of the resonance frequency and the frequency of an inverter drive signal (Q, NQ) substantially coincides with the resonance frequency after starting the driving of the inverter unit (106) by using a pulse signal having a pulse width shorter than the period of the resonance frequency of the resonant load (200) as an inverter drive signal (Q, NQ) and a frequency shifted from the resonance frequency as a starting point.

Description

Inverter device and control method for inverter device
Technical Field
The present invention relates to an inverter device and a control method of the inverter device. In more detail, the present invention relates to an inverter device and a control method of the inverter device that are connected to a resonant load for use.
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, as an inverter control unit that controls an inverter unit having an inverter circuit, an inverter control unit composed of a phase locked loop (PLL: phase Locked Loop) circuit is used, and the inverter unit is controlled by the inverter control unit.
A description will be given of a conventionally known inverter device controlled by an inverter control unit using a PLL circuit, with reference to fig. 1 (a) and (b).
Fig. 1 (a) is a structural explanatory diagram showing the entire configuration of an inverter device controlled by an inverter control unit using a PLL circuit and connected to a resonant load.
Fig. 1 (b) is a detailed structural explanatory diagram 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 source 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.
As the ac power source 102, for example, a commercial ac power source is used, and in this case, the inverter device 100 converts the commercial ac voltage into a high-frequency ac voltage and supplies the high-frequency ac voltage to the resonant load 200.
In more detail, the inverter device 100 is configured to have: the inverter unit 104 having a converter circuit that receives an alternating current voltage supplied from the alternating current power supply 102 and converts the same into a Direct Current (DC) voltage and outputs the same, the inverter unit 106 having an inverter circuit that receives a direct current voltage outputted from the converter unit 104 and inverts the same into a high-frequency alternating current voltage and outputs the same, the converter control unit 110 that detects an output from the inverter unit 106 (here, "output" from the inverter unit 106 means "output voltage Vh" as a voltage outputted from the inverter unit 106 or "output current Ih" as a current outputted from the inverter unit 106 or "output power" as a power outputted from the inverter unit 106), and the inverter unit 112 having an output sensor 108 that outputs a detection result as an output sensor signal, an output setting signal as a signal outputted from the outside that sets the output of the inverter unit 106, and a DC voltage converted by the converter unit 104 based on the output sensor signal outputted from the output sensor 108, and the inverter control unit 112 having a feedback control function (see fig. 1 b) that performs feedback control to the inverter unit 106 based on the output sensor signal outputted from the output sensor 108.
The converter circuit of the converter unit 104 is constituted by, for example, a thyristor rectifier circuit, a chopper circuit, or the like.
Fig. 1 (b) shows a detailed configuration of the inverter control unit 112. In the inverter control section 112, the PLL circuit 112a outputs a rectangular wave inverter drive signal Q, NQ as an inverter drive signal for driving the inverter section 106, based on an output sensor signal input to the PLL circuit 112 a.
In the present specification and the present claims, the "rectangular wave inverter drive signal Q, NQ" is merely referred to as "inverter drive signal" as appropriate.
In the above configuration, in the inverter device 100, an ac voltage is input from an ac power source 102 such as a commercial ac power source to the converter unit 104. The converter unit 104 to which the ac voltage is input from the ac power supply 102 variably controls the 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 ON/OFF switching operation of transistors constituting the inverter circuit.
As described above, the output stage of the inverter unit 106 in the inverter device 100 is provided with the output sensor 108, and the output sensor 108 detects the output from the inverter unit 106 (which is the output voltage Vh or 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.
The converter control unit 110 performs control to vary the dc voltage value as the output of the converter unit 104 so that the output of the inverter unit 106 becomes 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 the inverter 106 becomes the resonance frequency of the resonant load 200.
In addition, in the inverter device connected to the resonant load, several methods are used for the output control circuit for phase control using the high-frequency voltage and the high-frequency current, in addition to the configuration shown in the above-described conventional inverter device 100.
However, any of the methods used heretofore has the following problems: when the output control is performed, the frequency of the output of the inverter unit is deviated from the resonance frequency, which is a practical problem.
On the other hand, in an inverter device used for a low-power device, output control using a pulse width modulation (PWM: pulse Width Modulation, pulse width modulation) control method is also used.
Fig. 2 is a structural explanatory diagram showing the overall configuration of an inverter device that performs output control by a PWM control method and is connected to a resonant load.
In the following description, the same or corresponding structures and operations as those described with reference to fig. 1 (a) and (b) are denoted by the same reference numerals as those used in fig. 1 (a) and (b), and detailed description of the structures and operations is omitted.
As shown in fig. 2, the inverter device 300 converts an ac voltage supplied from the ac power source 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 in the same manner as the inverter device 100 described above, and in this case, the inverter device 10 converts the commercial ac voltage into a high-frequency ac voltage and supplies the high-frequency ac voltage to the resonant load 200.
In more detail, the inverter device 300 is configured to have: the inverter unit 302 that receives an ac voltage supplied from the ac power supply 102 and converts the ac voltage into a dc voltage by rectification by a diode and outputs the dc voltage, the inverter unit 106 that has an inverter circuit that receives the dc voltage outputted from the inverter unit 302 and converts the dc voltage into a high-frequency ac voltage and outputs the high-frequency ac voltage, the PWM control unit 304 that detects an output from the inverter unit 106 (herein, "output" from the inverter unit 106 means "output voltage Vh" that is a voltage outputted from the inverter unit 106 or "output current Ih" that is a current outputted from the inverter unit 106 or "output power" that is a power outputted from the inverter unit 106) and outputs a detection result thereof as an output sensor signal, and that performs feedback control of the inverter unit 106 based on an output setting signal that is a signal that externally sets an output of the inverter unit 106 and the output sensor signal outputted from the output sensor 108.
In the above configuration, the operation of the inverter device 300 will be described with reference to the waveform diagrams schematically shown in fig. 3 (a), (b), and (c).
In fig. 3 (a), (b) and (c),
waveform a: the output of the inverter 106 (output voltage Vh or output current Ih)
Waveform B: the output of the inverter 106 (output voltage Vh or output current Ih)
Waveform C: the output of the inverter 106 (output voltage Vh or output current Ih)
T: 1 period of fundamental component of output (output voltage Vh or output current Ih) of inverter unit 106
T/4: 1/4 period of the fundamental component of the output (output voltage Vh or output current Ih) of the inverter section 106
tw: pulse width of inverter drive signal.
In the inverter device 300, when driving is started by PWM control of the PWM control unit 304 (at the time of starting), the inverter driving signal (rectangular wave inverter driving signal Q, NQ) having a narrow pulse width tw is driven around the resonance frequency (fig. 3 a), and in order to variably control the output of the inverter unit 106, the pulse width tw is made variable by PWM control of the PWM control unit 304, so that the output of the inverter unit 106 is variably controlled.
For example, as shown in fig. 3 (b) and 3 (c), the PWM control unit 304 expands the pulse width tw by PWM control in order to increase the output of the inverter unit 106.
That is, in the conventional inverter device 300, the PWM control unit 304 controls the driving in the vicinity of the resonance frequency from the start-up using a PLL circuit or the like by the PWM control, and the PWM control is performed in this frequency band.
Therefore, the conventional inverter 300 has a problem of deterioration in following characteristics of the load with respect to the fluctuation of the resonance frequency.
The prior art known to the applicant of the present application at the time of patent application is not an application related to the known application of the literature, and thus 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 application
The present application has been made in view of the above-described various problems of the conventional technology, and its object is the following application: the present application is intended to provide an inverter device and a control method for the inverter device, which do not deviate from a resonance frequency even when the frequency of the output of an inverter unit is controlled by the output, and which improve the following characteristics of a load whose resonance frequency varies.
Means for solving the problems
In order to achieve the above object, the present application is an inverter device comprising: in this inverter device as a voltage-type inverter that is PWM-controlled to be connected to a resonant load, a pulse signal having a pulse width shorter than a resonant frequency period (for example, a "minimum pulse width" described later) (in the present specification and the present claims, a "pulse signal having a pulse width shorter than a resonant frequency period" is appropriately referred to as a "narrow-width pulse signal") is used as an inverter drive signal, and driving of an inverter unit is started with a frequency shifted from the resonant frequency as a starting point, and the inverter drive signal is controlled to be shifted to the resonant frequency or the vicinity of the resonant frequency by frequency control so that the frequency of the inverter drive signal substantially coincides with the resonant frequency.
The present invention is also an invention as follows: after the frequency of the inverter drive signal and the resonance frequency are substantially matched by the control, the control is performed so that the pulse width of the inverter drive signal is widened by PWM control and the output of the inverter unit (which is the output voltage, the output current, or the output power) becomes a predetermined value.
Therefore, according to the present invention, even when the output of the output control inverter unit is performed, the frequency does not deviate from the resonance frequency, and the following characteristics of the load to which the resonance frequency fluctuates can be improved.
That is, in the present invention, by shifting the frequency at the start of driving of the inverter drive signal from the resonance frequency and intentionally shifting the frequency of the inverter drive signal after the start of driving so that the frequency becomes the resonance frequency, it becomes possible to automatically find the resonance frequency by the 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 present claims, "a region in which the frequency of the inverter drive signal is shifted" is appropriately referred to as a "shift region") be determined as an inductive region in which the most appropriate diode reverse recovery characteristic for the inverter circuit is considered.
In other words, it is preferable that the start 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 as a voltage-type inverter connected to a resonant load and PWM-controlled includes an inverter section connected to the resonant load and driven by an inverter drive signal, and a control means for controlling the operation of the inverter section, wherein the control means starts driving the inverter section with a pulse signal having a pulse width shorter than a period of a resonant frequency of the resonant load as the inverter drive signal and a frequency shifted from the resonant frequency as a starting point, and then shifts the frequency of the inverter drive signal to the resonant frequency or the vicinity of the resonant frequency so that the frequency of the inverter drive signal substantially coincides with the resonant frequency.
Further, the 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 is the lowest set output value of the set value indicated by the output set signal from the outside.
Further, the inverter device according to the present invention is a device as follows: in the inverter device according to the present invention, the start point is such that the frequency shift region is an inductive region based on a diode reverse recovery characteristic of an inverter circuit constituting the inverter section.
Further, the 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, the 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, the 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 have a delay correction unit that corrects a delay of the voltage phase caused by the inductor.
Further, the 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, the 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 delay correction means for correcting a circuit delay of the inverter unit.
Further, the 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, the inverter section uses a SiC diode as a flywheel diode in an inverter switching element, and the start point is a frequency lower than the resonant frequency.
Further, the inverter device according to the present invention is a device as follows: in the inverter device according to the present invention, the start point is set to a frequency shifted by 5% or more from the frequency of the resonance frequency.
Further, the inverter device according to the present invention is a device as follows: in the inverter device according to the present invention, the control unit controls the inverter drive signal so that the frequency of the inverter drive signal substantially matches the resonance frequency, and then widens the pulse width of the inverter drive signal by PWM control.
Further, the 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 minimum level check unit configured to check that an output of the inverter unit is an output level at which phase check is possible.
Further, the 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 configured to check whether the output of the inverter unit is a frequency of an output level at which phase checking is possible.
Further, the 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 terminal of the inverter device and the parallel resonant capacitor box are connected by an air-cooled coaxial cable, and the inverter is connected to the parallel resonant capacitor box and high-frequency current is transmitted to the heating coil.
Further, the 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 constituted by 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 the control method of the inverter device as the voltage inverter connected to the resonant load and PWM-controlled, after driving of the inverter unit is started with a pulse signal having a pulse width shorter than a period of a resonant frequency of the resonant load as an inverter driving signal and a frequency shifted from the resonant frequency as a starting point, the frequency of the inverter driving signal is shifted to the resonant frequency or the vicinity of the resonant frequency, and the frequency of the inverter driving signal is controlled to substantially coincide with the resonant frequency.
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, the short pulse width is set to a pulse width at which the output of the inverter unit is the lowest set output value of the set value indicated by the 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 control method of the inverter device according to the present invention, the start point is such that the frequency shift region is an inductive region based on a diode reverse recovery characteristic of an inverter circuit constituting 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, 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 control method of 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, 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 above-described inductor is caused to be 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, 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 control method of the inverter device according to the present invention described above, the circuit delay of the inverter section described above 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, the resonant load is a series resonant load, the inverter section uses a SiC diode as a flywheel diode in an inverter switching element, and the start 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 control method of the inverter device according to the present invention, the start point is set to a frequency shifted by 5% or more from the frequency of the resonance frequency.
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, the pulse width of the inverter drive signal is widened by PWM control after the control is performed so that the frequency of the inverter drive signal substantially coincides with the resonance frequency.
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, it is possible to check that the output of the inverter section is an output level at which phase checking is possible.
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, the output of the inverter section is checked for the frequency of the output level at which the phase check becomes possible.
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 output terminal of the inverter device and the parallel resonant capacitor box are connected by an air-cooled coaxial cable, and the inverter is connected to the parallel resonant capacitor box and 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 control method of the inverter device according to the present invention, the resonant load is constituted by 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: even if the frequency of the output control inverter unit is not deviated from the resonance frequency, the following characteristics of the load with respect to the fluctuation of the resonance frequency can be improved.
Drawings
Fig. 1 (a) and (b) are explanatory diagrams of the configuration of a conventionally known inverter device controlled by a PLL circuit. In more detail, fig. 1 (a) is a structural explanatory diagram showing the overall configuration of an inverter device controlled by an inverter control section using a PLL circuit and connected to a resonant load. Fig. 1 (b) is a detailed structural explanatory diagram of an inverter control unit in the inverter device shown in fig. 1 (a).
Fig. 2 is a structural explanatory diagram showing the overall configuration of a conventionally known inverter device in which output control is performed by a PWM control system and the inverter device is connected to a resonant load.
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 an embodiment of the present invention. In more detail, fig. 4 is a structural explanatory diagram showing the overall structure of the inverter device controlled by the control unit and connected to the resonant load.
Fig. 5 is a detailed structural explanatory diagram of a control unit in the inverter device shown in fig. 4.
Fig. 6 is a structural explanatory diagram of an inverter device according to an example of an embodiment of the present invention. In more detail, fig. 6 is a structural explanatory diagram showing the overall structure of the 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 an embodiment of the present invention. In more detail, fig. 8 is a structural explanatory diagram showing the overall structure of the 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 structural explanatory diagram of a control section in an inverter device according to an example of an embodiment of the present invention.
Fig. 11 is a structural explanatory diagram of a control section 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 an embodiment of the present invention. In more detail, fig. 12 is a structural explanatory diagram showing the overall structure of the inverter device controlled by the control unit and connected to the series resonant load.
Fig. 13 is an enlarged explanatory view of an inverter section 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 schematic structural explanatory diagram showing a power supply structure of an inverter device according to the related art using a series resonant load. Fig. 14 (c) is a schematic structural explanatory diagram showing a power supply structure of an inverter device according to the related art using a parallel resonant load.
Fig. 15 (a) and (b) are structural explanatory diagrams showing a resonant load for induction heating as an example of the resonant load. In more detail, fig. 15 (a) is a structural explanatory diagram showing a series resonant load for induction heating in the case of being a series resonant load. Fig. 15 (b) is a structural explanatory diagram showing a parallel resonant load for induction heating in the case of being a parallel resonant load.
Detailed Description
An example of an embodiment of an inverter device and a control method of the inverter device according to the present invention will be described in detail below with reference to the accompanying drawings.
In the following description of the "specific embodiment", the same or equivalent structures and functions as those described with reference to fig. 1 (a) and (b), fig. 2, and fig. 3 (a), (b), and (c), or those described with reference to fig. 4 below, are denoted by the same reference numerals as those used in fig. 1 (a) and (b), fig. 2, and fig. 3 (a), (b), and (c), or fig. 4 below, respectively, and detailed description thereof will be omitted.
(I) First embodiment
(I-1) Structure
Fig. 4 is a schematic diagram illustrating an exemplary inverter device according to an embodiment of the present invention. Fig. 4 shows the entire configuration of the inverter device controlled by the control unit and connected to the resonant load.
Fig. 5 is a detailed structural explanatory diagram of a control unit in the inverter device shown in fig. 4.
An exemplary inverter device 10 according to an embodiment of the present invention will be 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 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 in the same manner as the conventional inverter device 100, and in this case, the inverter device 10 converts the 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 source 102, converts the ac voltage into a dc voltage by rectification with 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, receives an ac voltage from the ac power source 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, inversely converts the dc voltage to 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 (herein, "output" from the inverter unit 106 means "output voltage Vh" that is a voltage output from the inverter unit 106 or "output current Ih" that is a current output from the inverter unit 106 or "output power" that is a power output from the inverter unit 106) and outputs a detection result thereof as an output sensor signal is provided at an output stage of the inverter unit 106.
The inverter device 10 includes a control unit 12 as a control means for controlling the operation of the inverter unit 106.
As shown in fig. 5, the control unit 12 includes a PWM control unit 12a and a frequency shift control unit 12b.
The control unit 12 performs feedback control of the inverter unit 106 based on an output setting signal that 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 changes the pulse width of the rectangular wave inverter drive signal Q, NQ, which is an inverter drive signal for driving transistors of the voltage-type inverter constituting the inverter unit 106, by PWM control of the PWM control unit 12a so that the output from the inverter unit 106 becomes an output setting value indicated by the output setting signal, and changes the output of the high-frequency ac voltage converted by the inverter unit 106.
The output from the inverter 106 is input to the external resonant load 200 via the output sensor 108.
(I-2) action
In the above configuration, the control unit 12 of the inverter device 10 performs operations described below as operations related to the implementation of the present invention.
That is, at the start of driving (at the start-up) of the output from the inverter device 10, the pulse width is sufficiently shorter than the resonance frequency period, for example, the pulse width (in the present specification and the present claims, "the pulse width which becomes the lowest set output value of the set value shown by the output set signal from the outside" is appropriately referred to as "the lowest pulse width") which becomes the lowest set output value of the set value shown by the output set signal from the outside "is the pulse width which becomes the lowest set output value of the set value shown by the output set signal from the outside" is the lowest set output value ", and the rectangular wave inverter driving signal Q, NQ having the frequency shifted from the resonance frequency of the resonant load 200 as the start point starts (start-up) driving.
Accordingly, even if the resonance frequency of the resonant load 200 fluctuates, the frequency shift control unit 12b of the control unit 12 shifts the frequency of the rectangular wave inverter drive signal Q, NQ to the resonance frequency from the start of driving (at the start), thereby enabling automatic following of the fluctuating resonance frequency.
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 as to output a set value indicated by an output setting signal from the outside after the frequency of the rectangular wave inverter drive signal Q, NQ reaches or is near the resonance frequency.
That is, the inverter device 10 outputs a minimum set output value (which is an output voltage, an output current, or an output power) of a set value shown by an output set signal from the outside as an inverter drive signal, that is, a rectangular wave inverter drive signal Q, NQ, and uses a pulse signal (narrow width pulse signal) having a pulse width sufficiently shorter than a resonance frequency period (for example, the minimum pulse width described above), starts the narrow width pulse signal from a frequency obtained by moving the narrow width pulse signal away from the resonance frequency, and then shifts the frequency to the resonance frequency or the vicinity of the resonance frequency, and then controls the frequency to the resonance frequency by frequency control.
Thereafter, 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, an output current, or an output power) of a set value shown by an output set signal from the outside.
(I-3) Effect
Therefore, according to the inverter device 10 described above, even if the frequency of the output control inverter unit is not deviated from the resonance frequency, the following characteristics of 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 a converter unit as in the conventional art.
Therefore, when compared with the conventional technique using a thyristor rectifier circuit and a chopper circuit, the inverter device 10 can achieve improvement of the power factor of the power supply, substantial improvement of the output response speed (according to the experiment of the present inventors, the response speed is greatly improved from 100ms to 10ms in the conventional technique), reduction of the cost due to substantial reduction of the number of components, and improvement of the reliability.
Further, since the inverter device 10 shifts the start frequency, which is the frequency at the start of driving (at the start) of the inverter drive signal, to a frequency that is shifted from the resonance frequency and then shifts the frequency of the inverter drive signal to approach the resonance frequency, the following characteristics of the resonance load 200 that fluctuates in resonance frequency are greatly improved, and even when a plurality of resonance loads 200 having different resonance frequencies are switched and connected, the inverter device can cope with a problem.
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 used in general.
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 most appropriate diode reverse recovery characteristic for the inverter circuit.
In other words, the start-up frequency is preferably 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 experiments of the present inventors, good results were obtained when the frequency at the start of driving (at the start) of the inverter driving signal, that is, the start 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 19kHz or less or 21kHz or more).
When the start-up frequency is set to a frequency that is 5% or more away from the frequency of the resonance frequency, that is, when the start-up frequency is set to a frequency that is 5% or more away from the frequency of the resonance frequency, the start-up frequency may be shifted away 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 that is 5% or more away on the low-frequency band side of the resonance frequency is 19kHz or less), or the start-up frequency may be shifted away 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 that is 5% or more away on the high-frequency band side of the resonance frequency is 21kHz or more).
Further, according to the findings of the present inventors, there is no conventional technique such as the above-described inverter device 10 according to the present application in which the start frequency is shifted from the frequency of the resonance frequency (for example, shifted by 5% or more with respect to the frequency of the resonance frequency) and the drive of the inverter section is started from the start frequency by the narrow-width pulse signal, and 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.
(II) second embodiment
(II-1) Structure
Fig. 6 is a schematic diagram illustrating an exemplary inverter device according to an embodiment of the present invention. Fig. 6 shows the entire 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 described with reference 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 lower in frequency than the resonant frequency, and on the other hand, it is understood that the voltage-type inverter is stable in switching operation by the inductance as compared with the capacitance due to the reverse recovery characteristic of the current of the diode connected in parallel to the inverter element.
Accordingly, 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, shifts the frequency from the start frequency to raise the frequency of the inverter drive signal to the resonance frequency, and locks the frequency of the inverter drive signal 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 described above, 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: voltage-controlled oscillator) circuit 32, a narrow-width pulse signal generating circuit 34, an output circuit 36, a phase comparing circuit 38, a delay setting circuit 40, a lock-up completion circuit 42, a detection circuit 44, an error amplifier filter 46, a triangular wave generating circuit 48, and a PWM circuit 50.
Here, regarding the inverter device 20, 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, and since the technology of the inverter device known from the related art can be applied, a detailed description about other structures than the frequency shift of the inverter drive signal and the signal switching is omitted.
(II-2) action
In the above configuration, the operation of the inverter device 20 will be described mainly with respect to the operation of the control unit 28 according to the embodiment 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 as to start driving of the inverter unit 106 from a frequency lower than the resonance frequency of the parallel resonant load 22 (for example, a frequency lower than the resonance frequency by 5% or more), inputs a frequency signal from the output of the VCO circuit 32 to the narrow width pulse signal generating circuit 34, generates a narrow width pulse signal of the output frequency of the VCO circuit 32 by the narrow width pulse signal generating 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 generating circuit 34 is switched from the signal of the lock-out completion circuit 42 to the signal of the PWM circuit 50.
Here, it is preferable to set the pulse width of the narrow-width pulse signal generated by the narrow-width pulse signal generating circuit 34 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 value shown by the output set signal from the outside.
Fig. 7 (a), (b), (c), (d), and (e) schematically show waveforms of operations in the inverter device 20.
In fig. 7 (a), (b), (c), (D), and (E), waveforms D, E, F, G, and H are waveforms of voltages (capacitor voltages Vc) detected by the voltage sensor 26.
Fig. 7 a shows a phase difference between a waveform (waveform D) of the voltage (capacitor voltage Vc) detected by the voltage sensor 26 as an output of the inverter section 106 at the start frequency at the start of driving (at the start-up time) 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 the frequency domain below the resonant frequency.
Here, in the phase comparison circuit 38, the a point, which is the position of 1/4 of 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 capacitor voltage Vc phase waveform (waveform E) to be compared is set as the B point (see fig. 7 (B)), the phase difference between the a point and the B point is compared, and the phase difference is locked at a frequency at which the phase difference becomes zero (0) or a preset 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 comparison circuit 16, and the phases are compared, so that the frequency of the VCO circuit 32 is controlled to be the resonance frequency.
Specifically, the inverter unit 106 starts to drive by using an inverter drive signal of a narrow-width pulse signal having a frequency shifted from the resonance frequency (for example, a frequency lower by 5% or more than the resonance frequency) 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 lock is completed and outputs a signal to the output circuit 36. Based on this signal, an inverter drive signal whose pulse width tw is extended from the narrow-width pulse signal by 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 setting signal (see fig. 7 (d) and (e)).
That is, the inverter device 20 connects the parallel resonant load 22 as a resonant load, uses a pulse signal (narrow width pulse signal) having a pulse width sufficiently shorter than the resonant frequency period, which is a minimum set output value (which is an output voltage, an output current, or an output power) of a set value indicated by an output set signal from the outside, as the rectangular wave inverter driving signal Q, NQ, which is an inverter driving signal, starts with a frequency obtained by moving the narrow width pulse signal away from the resonant frequency (for example, a frequency lower than the resonant frequency by 5% or more), and then performs frequency control by using a frequency shift to raise the frequency to the resonant frequency or the vicinity of the resonant frequency, and controls the frequency of the inverter driving signal to the resonant frequency.
Thereafter, in the inverter device 20, the pulse width of the narrow-width pulse signal is widened by PWM control so as to be an output (which is an output voltage, an output current, or an output power) of a set value shown by an output set signal from the outside.
(II-3) Effect
Accordingly, 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 features of the second embodiment
In the inverter device 20, an inductor 24 for preventing a harmonic current is connected between the inverter unit 106 and the voltage sensor 26, which is an output stage of the inverter unit 106.
That is, in the inverter device 20, when the inverter unit 106, which is a voltage-type 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 for preventing the current is connected in series to the output stage of the inverter unit 106.
Although the output voltage of the inverter 106 is a rectangular wave, it is generally known that the rectangular wave is composed of a synthesized waveform of a sine wave and an odd-numbered harmonic, and when the rectangular wave is connected to the parallel resonant load 22 while the rectangular wave is kept, the reactance of the capacitor becomes small due to the higher frequency of the odd-numbered harmonic component, the harmonic current increases, and the current waveform is distorted, or the loss of the transistor as the switching element of the inverter 106 is deteriorated, or the like.
Accordingly, the inductor 24 is connected to the output stage of the inverter unit 106 in the inverter device 20 with the aim of suppressing such harmonic currents.
When the output signal from the VCO circuit 32 is input to the phase comparison circuit 38 to perform phase comparison, the control unit 28 of the inverter device 20 is provided with a delay setting circuit 40 for setting the signal delay time.
That is, in the inverter device 20, when the inverter unit 106, which is a voltage-type 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 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 for delaying the pulse phase input to the driving side of the phase comparison circuit 38, thereby performing delay correction.
(III) third embodiment
(III-1) Structure
Fig. 8 is a schematic diagram illustrating an exemplary inverter device according to an embodiment of the present invention. Fig. 8 shows the entire configuration of the inverter device controlled by the control unit and connected to the series resonant load.
When the inverter device 60 according to one example of the embodiment of the present invention is described with reference to fig. 8, the inverter device 60 is connected to the series resonant load 62.
Further, the series resonant load has a characteristic of being inductive in a range higher than the resonant frequency, and on the other hand, it is understood that the voltage-type inverter is stable compared with the capacitive switching operation by the inductive switching operation due to the reverse recovery characteristic of the current of the diode connected in parallel to the inverter element.
Accordingly, 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, shifts the frequency from the start frequency to lower the frequency of the inverter drive signal to the resonance frequency, and locks the frequency of the inverter drive signal at the resonance frequency.
In the following description of inverter device 60, reference numeral 64 denotes a current sensor, and reference numeral 66 denotes a resonant capacitor of series resonant load 62.
The current sensor 64 is a component equivalent 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 thus a detailed description thereof will be omitted.
(III-2) action
In the above configuration, the operation of the inverter device 60 will be described mainly with respect to the operation of the control unit 28 according to the embodiment 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 as to start driving of the inverter unit 106 from a frequency higher than the resonance frequency of the series resonant load 62 (for example, a frequency higher than the resonance frequency by 5% or more), inputs a frequency signal from the output of the VCO circuit 32 to the narrow width pulse signal generating circuit 34, generates a narrow width pulse signal of the output frequency of the VCO circuit 32 by the narrow width pulse signal generating 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 generating circuit 34 is switched from the signal of the lock-out completion circuit 42 to the signal of the PWM circuit 50.
Here, it is preferable to set the pulse width of the narrow-width pulse signal generated by the narrow-width pulse signal generating circuit 34 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 value shown by the output set signal from the outside.
Fig. 9 (a), (b), (c), (d), and (e) schematically show waveforms of operations in the inverter device 60.
In fig. 9 (a), (b), (c), (d), and (e), waveforms I, J, K, L, and 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) checked by the current sensor 64 as an output of the inverter section 106 at a start frequency at the start of driving (at the start-up time) 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, which is the position of 1/4 of 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 the frequency at which the phase difference becomes zero (0) or the preset 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 comparison circuit 16, and the phases are compared, so that the frequency of the VCO circuit 32 is controlled to be the resonance frequency.
Specifically, the inverter unit 106 is started to drive by an inverter drive signal of a narrow-width pulse signal having a frequency shifted from the resonance frequency (for example, a frequency 5% or more higher than the resonance frequency) as a start frequency (see fig. 9 (a)), and the frequency of the inverter signal is shifted and lowered (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 lock 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 PWM control is outputted 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 setting 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 a pulse signal (narrow width pulse signal) having a pulse width sufficiently shorter than the resonant frequency period, which is a minimum set output value (which is an output voltage, an output current, or an output power) of a set value indicated by an output set signal from the outside, as the rectangular wave inverter driving signal Q, NQ, which is an inverter driving signal, starts with a frequency obtained by shifting the narrow width pulse signal away from the resonant frequency (for example, a frequency 5% or more higher than the resonant frequency), and then performs frequency control by shifting the frequency down to the resonant frequency or the vicinity of the resonant frequency, and controls the frequency of the inverter driving signal to the resonant frequency.
Thereafter, in the inverter device 60, the pulse width of the narrow-width pulse signal is widened by PWM control so as to be an output (which is an output voltage, an output current, or an output power) of a set value shown by an output set signal from the outside.
(III-3) Effect
Accordingly, 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 a structural explanatory diagram of a control unit in an inverter device according to an example of the embodiment of the present invention.
In this fourth embodiment, the configuration of the inverter device 20, 60 according to the second and third embodiments and the configuration of the inverter device 400 according to the seventh embodiment described below are not different from each other with respect to the configuration other than the control unit, and therefore 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 is provided with a minimum level detection circuit 72 in addition to the configuration of the control unit 28, and differs in this respect.
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 correct phase verification from the output of the inverter section 106.
Therefore, in the inverter device according to the fourth embodiment, the lowest level verification circuit 72 is provided in the control section 70, and the case where the output of the inverter section 106 becomes the output level at which the phase verification becomes possible at the lowest level verification circuit 72 is verified, so that the phase comparison is started.
That is, the inverter device according to the fourth embodiment is a device as follows: the lowest level verification circuit 72 of the control unit 70 verifies 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, which is the inverter drive signal, and when the level is equal to or higher than the preset level, the phase comparison circuit 38 controlled to be in the vicinity of the resonant frequency is started to operate.
(V) fifth embodiment
Fig. 11 is a structural explanatory diagram of a control unit in an inverter device according to an example of the embodiment of the present invention.
In this fifth embodiment, the configuration of the inverter device 20, 60 according to the second and third embodiments and the configuration of the inverter device 400 according to the seventh embodiment described below are not different from each other with respect to the configuration other than the control unit, and therefore 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 is provided with a lowest level frequency checking circuit 82 in addition to the configuration of the control unit 28, and differs in both respects.
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 correct phase verification from the output of the inverter section 106.
Therefore, in the inverter device according to the fifth embodiment, the lowest level frequency checking 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 checking 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 verification circuit 82 of the control unit 80 verifies that the frequency of the pulse drive signal, which is the inverter drive signal, has reached a preset frequency (lowest level frequency) when the frequency is shifted, and starts the operation of the phase comparison circuit 38 at the verification time point.
(VI) sixth embodiment
An inverter device according to an example of the sixth embodiment of the present invention is a device as follows: the present invention is provided with both the lowest level verification circuit 72 in the fourth embodiment and the lowest level frequency verification circuit 82 in the fifth embodiment.
In the sixth embodiment, since the control unit is provided with both the minimum level detection circuit and the minimum level frequency detection circuit, the other configurations are not different from those of the above-described embodiments (second, third, fourth, and fifth embodiments) and the seventh embodiment described later, and therefore the description of the above-described embodiments (second, third, fourth, and fifth embodiments) and the seventh embodiment described later is omitted.
(VII) seventh embodiment
Fig. 12 is a structural explanatory diagram of an inverter device according to an example of the embodiment of the present invention. Fig. 12 shows the entire configuration of the 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.
When compared with the configuration of the inverter device 60 according to the third embodiment described above 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) is different in that an inverter portion 406 is provided instead of the inverter portion 106.
As shown in fig. 13, the inverter unit 406 of the inverter apparatus 400 is an inverter unit as follows: so that a SiC diode is used as a circulating current diode (flywheel diode) 406b in the inverter switching element 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 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 series resonant circuit 62 is formed by the resonant load, and the frequency of the pulse drive signal, which is a sufficiently short inverter drive signal capable of securing the lowest 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 5% or more lower than the resonant frequency) and started up from the frequency, so that frequency control is performed by utilizing the frequency shift in which the frequency is increased to the vicinity of the resonant frequency. The frequency of the pulse drive signal as the inverter drive signal is controlled to be the 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, since there is little recovery time during current regeneration due to the characteristics, the series resonant circuit can perform an inverter operation using the capacitance (C-property), and can be shifted to a resonant frequency with a high frequency starting from a low frequency (C-property region).
(VIII) eighth embodiment
Next, an inverter device according to an example of the eighth embodiment of the present invention will be described with reference to fig. 14 (a), (b), and (c).
Here, fig. 14 (a) is a structural explanatory diagram schematically showing a power supply structure using the inverter device according to the present invention connected to a resonant load.
Fig. 14 (b) is a schematic structural explanatory diagram showing a power supply structure of an inverter device according to the related art using a series resonant load.
Further, fig. 14 (c) is a schematic structural explanatory diagram showing a power supply structure of an inverter device according to the related art using a parallel resonant load.
The power supply structure of the inverter device 10, 20, 60, 400 connected to the resonant load according to the present invention described above using the power supply shown in fig. 14 (a) is the following power supply structure: for induction heating purposes, 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 are connected by an air-cooled coaxial cable 504, and a small-sized inverter (hand-held inverter) 506 is connected to the parallel resonant capacitor box 502 so that a high-frequency current is transmitted to the heating coil 508.
In the induction heating application, there is a case where a heating operation is performed manually by lengthening the distance from the inverter device to the 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 conventional art connected to a series resonant load, and is lengthened, impedance transformation is performed at a small-sized inverter (hand-held inverter) 606 by a relay box 604, and a high-frequency current is transmitted to a heating coil 608.
Alternatively, as shown in fig. 14 (c), in the prior art inverter device 700 connected to a parallel resonant load, an air-cooled coaxial cable 702 is connected to an output terminal 700a of the inverter device 700 to be extended, and impedance conversion is performed at a small-sized inverter (hand-held inverter) 706 by a trunk 704, so that a high-frequency current is transmitted to a heating coil 708.
However, in the case of using the inverter device 600 according to the conventional technique connected to the series resonant load as shown in fig. 14 (b), since the harmonic current flows in the stray capacitance of the water cooling cable 602, there is a limit in the extension distance, and in general, the limit of the extension distance is about 50 m.
Further, in the case of extending the distance of the air-cooled coaxial cable 702 using the inverter device 700 according to the related art connected to the parallel resonant load as shown in fig. 14 (c), the case is as follows: since the series reactor in the inverter device 700 is large and heavy, the power supply itself is also large and heavy, and thus cannot be easily used as a small power supply at the work site.
On the other hand, in the configuration using the inverter device 10, 20, 60, 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 power supply configuration can be made, and by connecting the air-cooled coaxial cable 504 to this power supply configuration, a small power supply that can easily lengthen the air-cooled coaxial cable 504 even at 200m or more can be constituted.
The parallel resonance capacitor box 502 is a capacitor box made up of a parallel resonance capacitor.
As the small-sized current transformer (hand-held current transformer) 506, the same current transformers as those of the small-sized current transformers (hand-held current transformers) 606 and 706 having a conventional structure can be used.
Similarly, the heating coil 508 may be configured as the heating coils 608 and 708 in the conventional manner.
(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 made up of a resonant circuit including a heating coil for induction heating and a resonant capacitor.
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, 400, various structures can be used, for example, it is also possible to make the resonant load for induction heating as shown in fig. 15 (a), (b) be connected to the inverter device according to the present invention.
Fig. 15 (a) is a structural explanatory diagram showing a series resonant load for induction heating in the case of the series resonant load.
Fig. 15 (b) is a structural explanatory diagram showing a parallel resonant load for induction heating in the case of the parallel resonant load. In the configuration shown in fig. 15 (b), the filter for removing the harmonic is connected in series to the parallel resonant load for induction heating.
In the inverter device 20 shown in fig. 6, a filter is wired as the inductor 24 in the inverter device 20.
(X) description of other embodiments and modifications
The above embodiments are merely examples, and the present application can be implemented in various other ways. That is, the present application 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 application.
For example, the above-described embodiment may be modified as shown in the following (X-1) to (X-4).
(X-1) in the above embodiment, it is exemplified that the start-up frequency is shifted from the resonance frequency by more than 5% in particular.
However, the present application is not limited to the application of more than 5% shift from the resonance frequency, and may be made less than 5% shift from the resonance frequency.
That is, the value "5%" is a preferable value that the present inventors have found experimentally, but the present application is not limited to the value "5%" as long as the start-up frequency is shifted from the resonance frequency.
By moving the start-up frequency away from the resonance frequency, it becomes possible to automatically find the resonance frequency by frequency shift regardless of the deviation of the resonance frequency on the resonance load side.
Here, it is preferable that the region (frequency shift region) in which the frequency shift is performed is determined as an inductive region in consideration of the most appropriate diode reverse recovery characteristic for the inverter circuit, and the region is preferably 5% or more from the resonance frequency according to the experiment performed by the present inventors.
(X-2) although the explanation of specific circuit configurations and the like in each configuration is omitted in the above-described embodiment, a conventionally known circuit configuration corresponding to each configuration may be used.
(X-3) although the explanation of specific circuit constants and the like in each structure is omitted in the above-described embodiment, conventionally known circuit constants corresponding to each structure may be used, of course.
(X-4) As to the above-described embodiments and the embodiments shown in the above-described (X-1) to (X-3), it is needless to say that the above-described embodiments may be appropriately combined.
Industrial applicability
The present application can be used for an inverter device as a power supply device connected to a resonant load such as an induction heating circuit.
Description of the reference numerals
An inverter device 10; 12a control unit (control unit); 12a PWM control section (control unit); 12b frequency shift control unit (control unit); 20 an inverter device; 22 parallel resonant circuits; a 24 inductor; a 26 voltage sensor; 28 control part (control unit); 30 a frequency shift circuit; a 32 Voltage controlled oscillator (VCO: voltage-controlled oscillator) circuit; 34 a narrow width pulse signal generating circuit; a 36 output circuit; a 38 phase comparison circuit; a 40 delay setting circuit; 42 locking the completion circuit; a 44 detection circuit; an error amplifier filter 46; a 48 triangular wave generation circuit; 50 A PWM circuit; a 60 inverter device; 62 series resonant loads; a 64-current sensor; 66 a resonant capacitor; 70 a control unit (control unit); 72 a lowest level verification circuit (lowest level verification unit); 80 control part (control unit); 82 a lowest level frequency check circuit (frequency check unit); 100 inverter devices; a 102 Alternating Current (AC) power source; 104 a converter section; 106 an inverter section; 108 outputting a sensor; 110 a converter control unit; 112 control part; 112a PLL circuitry; 200 resonant load; 300 inverter devices; 302 a converter section; 304 A PWM control unit; 400 inverter devices; 406 an inverter section; 406a inverter switching elements; 406b loop diode (freewheeling diode); 406c a semiconductor switching element; 500 output terminals; 502 a parallel resonant capacitor box; 504 air cooling the coaxial cable; 506 a current transformer; 508 heating coils; 600 inverter devices; 600a output terminals; 602 water-cooling the cable; 604 a trunk; 606 a current transformer; 608 heating coils; 700 inverter device; 700a output terminals; 702 air cooling the coaxial cable; 704 a relay box; 706 a current transformer; 708 a heating coil; vh output voltage; ih output current; a Q rectangular wave inverter drive signal; NQ rectangular wave inverter drive signals; 1 period of the fundamental component of the output (output voltage or output current) of the T inverter section; 1/4 period of the fundamental component of the output (output voltage or output current) of the T/4 inverter section; the tw rectangular wave inverter driving signal Q, NQ.

Claims (30)

1. An inverter device for a voltage-type inverter PWM-controlled to be connected to a resonant load, 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 unit starts driving of the inverter unit using a pulse signal having a pulse width shorter than a period of a resonance frequency of the resonance load as the inverter driving signal and a frequency shifted from the resonance frequency as a start point, and then controls the inverter driving signal so that the frequency of the inverter driving signal is shifted to the resonance frequency or the vicinity of the resonance frequency and the frequency of the inverter driving signal substantially matches the resonance 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 section becomes a lowest set output value of a set value indicated by an output set signal from the outside.
3. The inverter device according to any one of claims 1 or 2, wherein in the inverter device, the start point makes a region where the frequency shift is performed an inductive region based on a diode reverse recovery characteristic of an inverter circuit constituting the inverter section.
4. The inverter device according to any one of claim 1 or 2, wherein, in the inverter device,
the resonant load is a parallel resonant load,
the origin is a frequency lower than the resonance frequency.
5. The inverter device according to claim 4, wherein in the inverter device, an inductor is connected to an output stage of the inverter section.
6. The inverter device according to claim 5, wherein the control section has a delay correction unit that corrects a delay of a voltage phase caused by the inductor in the inverter device.
7. The inverter device according to any one of claim 1 or 2, wherein, in the inverter device,
the resonant load is a series resonant load,
the origin 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 in the inverter device.
9. The inverter device according to any one of claim 1 or 2, wherein, in the inverter device,
The resonant load is a series resonant load,
the inverter section uses SiC diodes as flywheel diodes in the inverter switching elements,
the origin is a frequency lower than the resonance frequency.
10. The inverter device according to any one of claims 1 or 2, wherein in the inverter device, the start point is a frequency shifted by 5% or more with respect to a frequency of the resonance frequency.
11. The inverter device according to any one of claims 1 or 2, wherein the control unit widens a pulse width of the inverter drive signal by PWM control after controlling so that a frequency of the inverter drive signal substantially coincides with the resonance frequency.
12. The inverter device according to any one of claims 1 or 2, wherein the control section has a lowest level verification unit that verifies that an output of the inverter section becomes an output level at which phase verification becomes possible in the inverter device.
13. The inverter device according to any one of claims 1 or 2, wherein the control section has a frequency checking unit that checks a case where an output of the inverter section becomes a frequency of an output level at which phase checking becomes possible in the inverter device.
14. The inverter device according to any one of claims 1 or 2, wherein in the inverter device, an output terminal of the inverter device and a parallel resonance capacitor box are connected with an air-cooled coaxial cable, a current transformer 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 or 2, 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 PWM-controlled, a pulse signal having a pulse width shorter than a period of a resonant frequency of the resonant load is used as an inverter driving signal, and a frequency shifted from the resonant frequency is used as a starting point to start driving of an inverter unit, and then the frequency of the inverter driving signal is shifted to the resonant frequency or the vicinity of the resonant frequency so that the frequency of the inverter driving signal substantially coincides with the resonant frequency.
17. The control method of an inverter device according to claim 16, wherein in the control method, the short pulse width is a pulse width at which an output of the inverter section becomes a lowest set output value of a set value indicated by an output set signal from outside.
18. The control method of an inverter apparatus according to any one of claims 16 or 17, wherein in the control method, the start point makes a region where the frequency shift is performed an inductive region based on a diode reverse recovery characteristic of an inverter circuit constituting the inverter section.
19. The control method of an inverter device according to any one of claims 16 or 17, wherein, in the control method,
the resonant load is a parallel resonant load,
the origin is a frequency lower than the resonance frequency.
20. The control method of an inverter apparatus according to claim 19, wherein in the control method, an inductor is connected to an output stage of the inverter section.
21. The control method of an inverter apparatus according to claim 20, characterized in that in the control method, a delay in a voltage phase caused by the inductor is corrected.
22. The control method of an inverter device according to any one of claims 16 or 17, wherein, in the control method,
the resonant load is a series resonant load,
the origin is a frequency higher than the resonance frequency.
23. The control method of an inverter apparatus according to claim 22, characterized in that in the control method, a circuit delay of the inverter section is corrected.
24. The control method of an inverter device according to any one of claims 16 or 17, wherein, in the control method,
the resonant load is a series resonant load,
the inverter section uses SiC diodes as flywheel diodes in the inverter switching elements,
the origin is a frequency lower than the resonance frequency.
25. The control method of an inverter apparatus according to any one of claims 16 or 17, 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 control method of an inverter apparatus according to any one of claims 16 or 17, characterized in that in the control method, after 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 PWM control.
27. The control method of an inverter apparatus according to any one of claims 16 or 17, characterized in that in the control method, it is checked that an output of the inverter section becomes an output level at which phase checking becomes possible.
28. The control method of an inverter apparatus according to any one of claims 16 or 17, characterized in that in the control method, a case is checked in which an output of the inverter section becomes a frequency of an output level at which phase check becomes possible.
29. The control method of an inverter apparatus according to any one of claims 16 or 17, characterized in that in the control method, an output terminal of the inverter apparatus and a parallel resonance capacitor box are connected with an air-cooled coaxial cable, a current transformer is connected to the parallel resonance capacitor box and a high-frequency current is transmitted to a heating coil.
30. The control method of an inverter apparatus according to any one of claims 16 or 17, wherein in the control method, the resonant load is constituted by a resonant circuit including a heating coil for induction heating and a resonant capacitor.
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JP2022016299A (en) * 2020-07-10 2022-01-21 島田理化工業株式会社 Non-contact power supply inverter device, control method of non-contact power supply inverter device, non-contact power transmission device, non-contact power transmission and reception device, non-contact power supply system, and non-contact power transmission and reception system

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