JP2021040385A - Inverter device and inverter device control method - Google Patents

Abstract

To detect a zero-cross point of an output current with precision, to inhibit deviation of the frequency of an output from an inverter unit from the resonance frequency of a series resonance load even when performing output control, and further, to improve a characteristic of following the series resonance load having a fluctuating resonance frequency.SOLUTION: An inverter device is a voltage-type inverter that is connected to a series resonance load, and is subjected to PWM control. The inverter device includes an inverter unit that is connected to the series resonance load, and is driven by an inverter driving signal, and control means for controlling operation of the inverter unit. The control means performs control to adjust the frequency of the inverter driving signal to be substantially equal to the resonance frequency of the series resonance load, by using, as the inverter driving signal, a pulse signal having a pulse width shorter than the cycle of the resonance frequency, starting driving the inverter unit from a start point set at a frequency apart from the resonance frequency, and then frequency-shifting the frequency of the inverter driving signal to a frequency equal to or close to the resonance frequency through frequency control based on a voltage phase of a resonance capacitor included in the series resonance load.SELECTED DRAWING: Figure 4

Description

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

Generally, an inverter device is known as a power supply device connected to a series resonant load. Examples of the series resonance load include an induction heating circuit which is a series resonance circuit formed by connecting a heating coil for induction heating and a resonance capacitor in series.

Conventionally, in such an inverter device, an inverter control unit composed of a phase-locked loop (PLL) circuit has been used as an inverter control unit for controlling an inverter unit having an inverter circuit. The inverter section was controlled.

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

Note that FIG. 1A shows a configuration explanatory diagram showing the overall configuration of the inverter device controlled by the inverter control unit using the PLL circuit and connected to the series resonant load.

Further, FIG. 1B shows a detailed configuration explanatory diagram of the inverter control unit in the inverter device shown in FIG. 1A.

As shown in FIG. 1A, the inverter device 100 converts an alternating voltage supplied from the alternating current (AC) power supply 102 into a high frequency alternating current voltage of a desired voltage, and a series resonance load such as an induction heating circuit or the like. It is to supply to 200.

As the AC power supply 102, for example, a commercial AC power supply can be used. In that case, the inverter device 100 converts the commercial AC voltage into a high frequency AC voltage and supplies it to the series resonance load 200.

More specifically, the inverter device 100 is output from a converter unit 104 having a converter circuit that inputs an alternating current voltage supplied from the alternating current power supply 102, converts it into a DC (DC) voltage, and outputs the voltage, and the converter unit 104. An inverter unit 106 having an inverter circuit that inputs a DC voltage and reversely converts it to a high-frequency AC voltage and outputs it, and an output from the inverter unit 106 (here, the "output" from the inverter unit 106 is from the inverter unit 106. The output voltage "output voltage Vh", the current output from the inverter unit 106 "output current Ih", or the power output from the inverter unit 106 "output power") is detected. The converter unit 104 is based on the output sensor 108 that outputs the detection result as an output sensor signal, the output setting signal that is a signal for setting the output of the inverter unit 106 from the outside, and the output sensor signal output from the output sensor 108. The converter control unit 110 that feedback-controls the DC voltage to be converted, and the PLL circuit 112a that feedback-controls the operation of the inverter unit 106 based on the output sensor signal output from the output sensor 108 (see FIG. 1B). It is configured to have an inverter control unit 112 having the above.

Here, the converter circuit of the converter unit 104 is composed of, for example, a thyristor rectifier circuit, a chopper circuit, or the like. When an alternating current voltage is supplied from the alternating current (AC) power supply 102, the converter unit 104 controls to convert the alternating current voltage into a direct current voltage according to the signal output from the converter control unit 110.

Further, the inverter unit 106 includes, for example, an inverter circuit composed of transistors. The inverter unit 106 inputs the DC voltage output from the converter unit 104, converts the input DC voltage back into a high-frequency AC voltage by the ON (ON) / OFF (OFF) switching operation of the transistor, and outputs the DC voltage. Take control.

In the example shown in FIG. 1, the output sensor 108 provided in the output stage of the inverter unit 106 detects the output voltage Vh or the output current Ih, and uses the detection result as an output sensor signal to control the converter control unit 110 and the inverter. Output to unit 112.

As a result, in the inverter device 100, the output DC voltage value of the converter unit 104 is variably controlled so that the output (current or voltage) of the inverter unit 106 becomes the setting level indicated by the output setting signal.

Further, as described above, the inverter control unit 112 includes a PLL circuit 112a, and the PLL circuit 112a automatically controls the output of the inverter unit 106 to the resonance frequency of the series resonance load 200.

Here, FIG. 1B shows a detailed configuration of the inverter control unit 112. In the inverter control unit 112, the PLL circuit 112a outputs rectangular wave inverter drive signals Q and NQ, which are inverter drive signals for driving the inverter unit 106, in response to the output sensor signal input to the PLL circuit 112a.

In the present specification and claims, the "square wave inverter drive signals Q and NQ" are appropriately referred to simply as "inverter drive signals".

In the above configuration, in the inverter device 100, an AC voltage is input to the converter unit 104 from an AC power supply 102 such as a commercial AC power supply.

The converter unit 104, to which the AC voltage is input from the AC power supply 102, variably controls the DC voltage by the 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 output from the converter unit 104 and input into a high frequency voltage by the ON (ON) / OFF (OFF) switching operation of the transistors constituting the inverter circuit and outputs the voltage.

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

The converter control unit 110 controls to change the DC voltage value which is the output of the converter unit 104 so that the output of the inverter unit 106 becomes the set level indicated by the output setting signal.

Here, the inverter control unit 112 is automatically controlled by the PLL circuit 112a so that the output frequency of the inverter unit 106 becomes the resonance frequency of the series resonance load 200.

By the way, in the inverter device connected to the series resonant load, some methods are used in addition to the configuration shown in the conventional inverter device 100 described above for the output control circuit using the phase control of the high frequency voltage and the high frequency current. Has been done.

However, in any of the methods conventionally used, there is a problem that the output frequency of the inverter section deviates from the resonance frequency of the series resonant load when the output is controlled, which has been a practical problem. was there.

On the other hand, in the inverter device used for low power equipment, output control by a pulse width modulation (PWM) control method is also used.

Here, FIG. 2 shows a configuration explanatory diagram showing the overall configuration of the inverter device connected to the series resonance load while the output is controlled by the PWM control method.

In the following description, the configurations and actions that are the same as or equivalent to the configurations and actions described with reference to FIGS. 1 (a) and 1 (b) are the same as those used in FIGS. 1 (a) and 1 (b). The detailed configuration and description of the operation will be omitted by indicating the respective reference numerals.

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

As the AC power supply 102, for example, a commercial AC power supply can be used as in the above-mentioned inverter device 100. In that case, the inverter device 10 converts the commercial AC voltage into a high-frequency AC voltage and serializes it. It is supplied to the resonance load 200.

More specifically, the inverter device 300 inputs the AC voltage supplied from the AC power supply 102, converts it into a DC voltage by rectification by a diode, and outputs the converter unit 302, and the DC voltage output from the converter unit 302. The inverter unit 106 having an inverter circuit that inputs and reverse-converts to a high-frequency AC voltage and outputs it, and the output from the inverter unit 106 (here, the "output" from the inverter unit 106 is output from the inverter unit 106. The output sensor 108 that detects the current "output current Ih" or the power output from the inverter unit 106 (the output power) and outputs the detection result as an output sensor signal, and the inverter unit from the outside. It is configured to include a PWM control unit 304 that feedback-controls the inverter unit 106 based on an output setting signal that is a signal for setting the output of the 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 the waveform diagrams schematically shown in FIGS. 3A, 3B, and 3C.

Here, in FIGS. 3 (a), (b) and (c),
Waveform A: Output of inverter unit 106 (output current Ih)
Waveform B: Output of inverter unit 106 (output current Ih)
Waveform C: Output of inverter unit 106 (output current Ih)
T: 1 cycle of the fundamental wave component of the output (output voltage Vh or output current Ih) of the inverter unit 106 T / 4: 1/4 cycle of the fundamental wave component of the output (output voltage Vh or output current Ih) of the inverter unit 106 tw: The pulse width of the inverter drive signal.

In the inverter device 300, when the drive is started (at the start) by the PWM control of the PWM control unit 304, the inverter drive signals (rectangular wave inverter drive signals Q and NQ) having a narrow pulse width tw are used to drive the inverter device 300 in the vicinity of the resonance frequency (FIG. 3). (A)) In order to variably control the output of the inverter unit 106, the pulse width tw is variably controlled by the PWM control of the PWM control unit 304 to variably control the output of the inverter unit 106.

For example, in order to increase the output of the inverter unit 106, as shown in FIGS. 3B and 3C, the pulse width tw is widened by the PWM control of the PWM control unit 304.

That is, in the conventional inverter device 300, the drive is controlled in the vicinity of the resonance frequency of the series resonance load 200 by using the PLL circuit or the like from the start by the PWM control of the PWM control unit 304, and the PWM control is performed in that frequency band. Was there.

Therefore, the conventional inverter device 300 has a problem that it is inferior in tracking characteristics to the series resonance load 200 in which the resonance frequency fluctuates.

Further, when the pulse width tw of the inverter drive signal is narrow as in the waveform A and the waveform B of the output current Ih, there is a problem that the sine waveform is broken and the accurate zero cross point cannot be detected.

Since the prior art that the applicant of the present application knows at the time of filing the patent application is not an invention related to a document known invention, there is no prior art document information to be described in the specification of the present application.

The present invention has been made in view of various problems in the conventional technique as described above, and an object of the present invention is to make the zero cross point detection of the output current accurate and to control the output. An attempt is made to provide an inverter device and a control method for the inverter device in which the output frequency of the inverter unit does not deviate from the resonance frequency of the series resonance load and the tracking characteristics for the series resonance load in which the resonance frequency fluctuates are improved. Is.

In order to achieve the above object, the present invention has a pulse width shorter than the period of the resonance frequency of the series resonance load in an inverter device which is a voltage type inverter connected to a series resonance load and controlled by PWM (for example, "for example," The pulse signal of the "minimum pulse width" (in the present specification and the scope of the present patent claim, the "pulse signal having a pulse width shorter than the period of the resonance frequency of the series resonance load" is appropriately referred to as a "narrow pulse signal". ) Is used as the inverter drive signal to start driving the inverter section starting from a frequency distant from the resonance frequency of the series resonance load, and the resonance that constitutes the series resonance load to obtain an accurate zero cross point. After shifting the frequency of the inverter drive signal to the resonance frequency of the series resonance load or near the resonance frequency by frequency control based on the voltage phase of the capacitor, the frequency of the inverter drive signal is approximately the same as the resonance frequency of the series resonance load by phase control. The output (output voltage, output current, or output power) of the inverter unit is preset by controlling the inverter to be fixed and then widening the pulse width of the inverter drive signal by PWM control. It is controlled so that it becomes a value.

Therefore, according to the present invention, the zero cross point detection of the output current is made accurate, and the output frequency of the inverter unit does not deviate from the resonance frequency of the series resonance load even if the output control is performed, and the resonance frequency is set. It becomes possible to improve the tracking characteristics for a fluctuating series resonance load.

That is, in the present invention, the frequency at the start of driving the inverter drive signal is intentionally separated from the resonance frequency of the series resonance load, and the frequency of the inverter drive signal becomes the resonance frequency of the series resonance load after the start of the drive. By shifting the frequency to, no matter how the resonance frequency on the series resonance load side shifts, the resonance frequency of the series resonance load can be automatically found by the frequency shift.

Here, a region for frequency-shifting the frequency of the inverter drive signal (in the scope of the present specification and claims, the "region for frequency-shifting the frequency of the inverter drive signal" is appropriately referred to as a "frequency shift region"). Is preferably determined in the inductive region in consideration of the optimum diode reverse recovery characteristic for the inverter circuit.

In other words, it is preferable to determine the starting point of the frequency distant from the resonance frequency of the series resonant load 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 that is a voltage type inverter that is connected to a series resonance load and is PWM-controlled. The control means has a control means for controlling the operation of the above, and the control means uses a pulse signal having a pulse width shorter than the period of the resonance frequency of the series resonance load as the inverter drive signal and a frequency distant from the resonance frequency as a starting point. After starting the drive of the inverter unit, the frequency of the inverter drive signal is frequency-shifted to the resonance frequency or the vicinity of the resonance frequency by frequency control based on the voltage phase of the resonance capacitors constituting the series resonance load, and the inverter The frequency of the drive signal is controlled so as to substantially match the resonance frequency.

Further, in the inverter device according to the present invention, the short pulse width is a pulse width at which the output of the inverter unit is the minimum set output value of the set value indicated by the output setting signal from the outside. It was made to be.

Further, in the inverter device according to the present invention, the starting point of the inverter device according to the present invention is such that the frequency shift region is an inductive region based on the diode reverse recovery characteristic of the inverter circuit constituting the inverter unit. It was done.

Further, the inverter device according to the present invention is the inverter device according to the present invention described above, in which the starting point is set to a frequency higher than the resonance frequency.

Further, the inverter device according to the present invention further corrects the delay time from the phase center position of the inverter drive signal to the zero crossing point of the voltage waveform of the resonance capacitor, which is delayed by 1/2 cycle, in the inverter device according to the present invention. It is designed to have a delay correction means to be used.

Further, the inverter device according to the present invention is a delay correction means for correcting the delay time to the zero crossing point of the voltage waveform of the resonance capacitor adjacent to the phase center position of the inverter drive signal in the above-mentioned inverter device according to the present invention. It is designed to have.

Further, the inverter device according to the present invention is the above-mentioned inverter device according to the present invention, and the delay correction means is a first delay correction means for correcting a 1/2 cycle delay of the fundamental wave component of the output voltage of the inverter unit. It is intended to have.

Further, the inverter device according to the present invention is the above-mentioned inverter device according to the present invention, in which the delay correction means includes a second delay correction means for correcting the circuit delay of the inverter unit.

Further, the inverter device according to the present invention is the above-mentioned inverter device according to the present invention, and the inverter unit uses a SiC diode as a freewheel diode in the inverter switching element.

Further, in the inverter device according to the present invention, the starting point of the inverter device according to the present invention is set to a frequency separated by 5% or more from the frequency of the resonance frequency.

Further, in the inverter device according to the present invention, the control means controls the frequency of the inverter drive signal so as to substantially match the resonance frequency, and then performs PWM control to control the inverter drive signal. The pulse width of the inverter is widened.

Further, the inverter device according to the present invention has the lowest level detecting means for detecting that the output of the inverter unit has reached an output level at which phase detection is possible in the above-mentioned inverter device according to the present invention. It was made like this.

Further, the inverter device according to the present invention is the above-mentioned inverter device according to the present invention, in which the series resonance load is composed of a series resonance circuit in which a heating coil for induction heating and a resonance capacitor are connected in series. Is.

Further, the control method of the inverter device according to the present invention is a control method of an inverter device which is a voltage type inverter connected to a series resonance load and PWM-controlled, and is a pulse signal having a pulse width shorter than the period of the resonance frequency of the series resonance load. Is used as the inverter drive signal, and after the inverter unit is started to be driven starting from a frequency distant from the resonance frequency, the frequency of the inverter drive signal is changed by frequency control based on the voltage phase of the resonance capacitors constituting the series resonance load. The frequency is shifted to the resonance frequency or the vicinity of the resonance frequency so that the frequency of the inverter drive signal is controlled so as to substantially match the resonance frequency.

Further, the control method of the inverter device according to the present invention is the above-mentioned control method of the inverter device according to the present invention. In the above-mentioned short pulse width, the output of the inverter unit is the minimum set output of the set value indicated by the output setting signal from the outside. The pulse width is set to be a value.

Further, the control method of the inverter device according to the present invention is the same as the control method of the inverter device according to the present invention, wherein the starting point is an induction based on the diode reverse recovery characteristic of the inverter circuit in which the frequency shift region constitutes the inverter section. It is intended to be a sexual region.

Further, in the control method of the inverter device according to the present invention, in the above-mentioned control method of the inverter device according to the present invention, the starting point is set to a frequency higher than the resonance frequency.

Further, the control method of the inverter device according to the present invention is the control method of the inverter device according to the present invention, from the phase center position of the inverter drive signal to the zero cross point of the voltage waveform of the resonance capacitor delayed by 1/2 cycle. The delay time is corrected.

Further, the control method of the inverter device according to the present invention corrects the delay time to the zero cross point of the voltage waveform of the resonance capacitor adjacent to the phase center position of the inverter drive signal in the control method of the inverter device according to the present invention. It is something that I tried to do.

Further, the control method of the inverter device according to the present invention is such that the control method of the inverter device according to the present invention corrects a 1/2 cycle delay of the fundamental wave component of the output voltage of the inverter unit.

Further, the control method of the inverter device according to the present invention is such that the circuit delay of the inverter section is corrected in the control method of the inverter device according to the present invention.

Further, in the control method of the inverter device according to the present invention, in the above-mentioned control method of the inverter device according to the present invention, the inverter unit uses a SiC diode as a freewheel diode in the inverter switching element.

Further, in the control method of the inverter device according to the present invention, in the above-mentioned control method of the inverter device according to the present invention, the starting point is set to a frequency separated by 5% or more from the frequency of the resonance frequency. ..

Further, in the control method of the inverter device according to the present invention, in the above-mentioned control method of the inverter device according to the present invention, after controlling the frequency of the inverter drive signal so as to substantially match the resonance frequency, the inverter is driven by PWM control. The pulse width of the signal is widened.

Further, the control method of the inverter device according to the present invention is such that in the above-mentioned control method of the inverter device according to the present invention, it is detected that the output of the inverter unit has reached an output level at which phase detection is possible. is there.

Further, in the control method of the inverter device according to the present invention, in the above-mentioned control method of the inverter device according to the present invention, the series resonance load is composed of a series resonance circuit in which a heating coil for induction heating and a resonance capacitor are connected in series. It is intended to be done.

Since the present invention is configured as described above, the output frequency of the inverter section may deviate from the resonance frequency of the series resonant load even if the output current is accurately detected at the zero crossing point and the output is controlled. In addition, it has an excellent effect that it is possible to improve the tracking characteristic for a series resonance load in which the resonance frequency fluctuates.

1A and 1B are configuration explanatory views of a conventionally known inverter device controlled by an inverter control unit using a PLL circuit. More specifically, FIG. 1A is a configuration explanatory diagram showing the entire configuration of an inverter device controlled by an inverter control unit using a PLL circuit and connected to a series resonant load. Further, FIG. 1B is a detailed configuration explanatory view of an inverter control unit in the inverter device shown in FIG. 1A. FIG. 2 is a configuration explanatory view showing the entire configuration of a conventionally known inverter device connected to a series resonance load while output control is performed by a PWM control method. 3A, 3B, and 3C are schematic waveform diagrams showing the operation of the inverter device shown in FIG. FIG. 4 is a configuration explanatory view of an inverter device (first embodiment) according to an example of the embodiment of the present invention. More specifically, FIG. 4 is a configuration explanatory view showing the entire configuration of the inverter device controlled by the control unit and connected to the series resonant load. FIG. 5 is a detailed configuration explanatory view of a control unit in the inverter device shown in FIG. FIG. 6 is a configuration explanatory view of an inverter device (third embodiment) according to an example of the embodiment of the present invention. More specifically, FIG. 6 is a configuration explanatory view showing the entire configuration of the inverter device controlled by the control unit and connected to the series resonant load. 7 (a), (b), (c), (d), and (e) are schematic waveform diagrams showing the operation of the inverter device shown in FIG. FIG. 8 is a configuration explanatory view of an inverter device (fourth embodiment) according to an example of the embodiment of the present invention. More specifically, FIG. 8 is a configuration explanatory view showing the entire configuration of the inverter device controlled by the control unit and connected to the series resonant load. 9 (b') and 9 (c') are schematic waveform diagrams showing the operation of the inverter device shown in FIG. 10 (a), (b), (c), (d), and (e) are schematic waveform diagrams showing the operation of the inverter device (fifth embodiment) according to an example of the embodiment of the present invention. 11 (b') and 11 (c') are schematic waveform diagrams showing the operation of the inverter device according to the sixth embodiment. FIG. 12 is a configuration explanatory view of a control unit in an inverter device (seventh embodiment) according to an example of the embodiment of the present invention. FIG. 13 is an enlarged explanatory view of an inverter unit in an inverter device (eighth embodiment) according to an example of the embodiment of the present invention. FIG. 14 is a configuration explanatory view showing a case where an induction heating resonance load is connected as an example of a series resonance load as a ninth embodiment of an inverter device according to an example of the embodiment of the present invention.

Hereinafter, an example of the embodiment of the inverter device and the control method of the inverter device according to the present invention will be described in detail with reference to the accompanying drawings.

In the following description of the section "Modes for Carrying Out the Invention", with reference to FIGS. 1 (a) (b), 2 and 3 (a) (b) (c). The configurations and actions described, or the configurations and actions that are the same as or equivalent to the configurations and actions described with reference to the respective figures in FIGS. 4 and 4 below, are described in FIGS. 1 (a) and 1 (b), FIGS. 2 and 3 (a). ) (B) (c) or the same reference numerals as those used in FIGS. 4 and 4 and below, respectively, and the detailed configuration and description of the operation will be omitted.

(I) First Embodiment of the present invention

(I-1) Configuration

FIG. 4 shows a configuration explanatory diagram of an inverter device (first embodiment) according to an example of the embodiment of the present invention. Note that FIG. 4 shows the overall configuration of the inverter device controlled by the control unit and connected to the series resonant load.

Further, FIG. 5 shows a detailed configuration explanatory diagram of the control unit in the inverter device shown in FIG.

The inverter device according to the first embodiment of the present invention will be described with reference to FIGS. 4 and 5.

The inverter device 10 according to the first embodiment of the present invention is a PWM-controlled voltage-type inverter connected to the series resonance load 200.

The series resonance load 200 is configured by connecting the resonance capacitor 202 and the series resonance inductor 204 in series.

The resonance capacitor 202 is located on the inner side of the inverter device 10, while the series resonant inductor 204 is located on the outer side of the inverter device 10.

The inverter device 10 converts the AC voltage supplied from the AC power supply 102 into a high-frequency AC voltage of a desired voltage and outputs it with a variable pulse width by PWM control of the voltage-type inverter circuit in the inverter unit 106, and passes it through the resonance capacitor 202. By outputting to the series resonance inductor 204, a high frequency AC voltage is supplied to the series resonance load 200 such as an induction heating circuit.

As the AC power supply 102, for example, a commercial AC power supply can be used as in the conventional inverter device 100. In that case, the inverter device 10 converts the commercial AC voltage into a high frequency AC voltage and serializes it. It is supplied to the resonance load 200.

Generally, the power source used as a commercial AC power source includes a single-phase AC power source or a three-phase AC power source.

More specifically, the inverter device 10 includes a converter unit 302 that inputs an AC voltage supplied from the AC power supply 102, converts it into a DC voltage by rectification by a diode, and outputs the AC voltage.

That is, the converter unit 302 of the inverter device 10 is composed of a diode rectifier circuit that does not use the converter control unit, an AC voltage is input from the AC power supply 102, and the input AC voltage is converted into a DC voltage to be converted into the inverter unit. Output to 106.

The inverter unit 106 inputs the DC voltage output from the converter unit 302, converts it back to a high-frequency AC voltage, and outputs the voltage.

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 that controls the PWM control unit 12a.

The output stage of the inverter unit 106 is provided with a current sensor 14 that detects the output current, which is the current output from the inverter unit 106, and outputs the detection result as a current level signal to the PWM control unit 12a of the control unit 12. ing.

Further, the resonance capacitor 202 of the series resonance load 200 detects the phase of the voltage in the resonance capacitor 202, and outputs the detection result as a resonance capacitor voltage phase signal to the frequency shift control unit 12b of the control unit 12. Is provided.

The control unit 12 is based on an output setting signal which is a signal for setting the output of the inverter unit 106 from the outside, a current level signal output from the current sensor 14, and a resonance capacitor voltage phase signal output from the voltage sensor 16. , The inverter unit 106 is feedback-controlled.

That is, the control unit 12 configures the inverter unit 106 by PWM control of the PWM control unit 12a, which is controlled by the frequency shift control unit 12b, so that the output from the inverter unit 106 becomes the output setting value indicated by the output setting signal. The pulse widths of the rectangular wave inverter drive signals Q and NQ, which are the inverter drive signals for driving the transistors of the voltage-type inverter circuit, are changed to change the output of the high-frequency AC voltage converted by the inverter unit 106.

The output from the inverter unit 106 is input to the series resonance load 200 via the current sensor 14.

(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 (starting) when the output from the inverter device 10 is started, the pulse width is sufficiently shorter than the period of the resonance frequency of the series resonance load 200, for example, the minimum set value indicated by the output setting signal from the outside. Pulse width that becomes the set output value (output voltage or output current or output power) (In the present specification and the present patent claim, "a pulse that is the minimum set output value of the set value indicated by the output setting signal from the outside". The width is appropriately referred to as the "minimum pulse width"), and the drive is started (started) by the rectangular wave inverter drive signals Q and NQ starting from a frequency sufficiently distant from the resonance frequency of the series resonance load 200. ).

Further, the resonance capacitor voltage phase signal output from the voltage sensor 16 is input to the frequency shift control unit 12b.

Therefore, even if the resonance frequency of the series resonance load 200 fluctuates, the frequency shift control unit 12b of the control unit 12 starts driving the rectangular wave inverter drive signals Q and NQ based on the resonance capacitor voltage phase signal. The frequency shift is performed to shift the frequency of the above to the resonance frequency, and automatic tracking to the resonance frequency of the fluctuating series resonance load 200 becomes possible.

Then, in the inverter device 10, after the PWM control unit 12a of the control unit 12 has the frequencies of the square wave inverter drive signals Q and NQ close to the resonance frequency (resonance point) or the resonance frequency of the series resonance load 200, the external device 10 is used. The pulse width of the square wave inverter drive signals Q and NQ is widened by PWM control so that the output of the set value indicated by the output setting signal from is obtained.

That is, the inverter device 10 has the minimum set output value (output voltage, output current, or output power) of the set value indicated by the output setting signal from the outside as the rectangular wave inverter drive signals Q and NQ which are the inverter drive signals. Is output, and a pulse signal (narrow pulse signal) having a pulse width sufficiently shorter than the period of the resonance frequency of the series resonance load 200 (for example, the minimum pulse width described above) is used, and the narrow pulse signal is connected in series. After starting from a frequency sufficiently distant from the resonance frequency of the resonance load 200, the frequency is shifted to the resonance frequency or the vicinity of the resonance frequency using the resonance capacitor voltage phase signal, and then the series resonance load 200 is controlled by frequency control. Control to a square wave frequency.

After that, the inverter device 10 widens the pulse width of the narrow pulse signal by PWM control, and becomes an output (output voltage or output current or output power) of a set value indicated by an output setting signal from the outside. To do so.

(I-3) Action Effect

Therefore, according to the inverter device 10 described above, the zero cross point detection of the output current is made accurate, and the output frequency of the inverter unit does not deviate from the resonance frequency of the series resonance load 200 even if the output is controlled. Further, it is possible to improve the tracking characteristic of the series resonance load 200 whose resonance frequency fluctuates.

Further, in the inverter device 10 described above, since the output can be controlled by the inverter unit 106, the thyristor rectifier circuit and the chopper circuit are not used as the converter circuit of the converter unit as in the conventional technique.

Therefore, the inverter device 10 has an improvement in power factor and a significant improvement in output response speed as compared with the conventional technology using a thyristor rectifier circuit or a chopper circuit (according to the experiment of the inventor of the present application, the response speed is higher. , It has been greatly improved from 100 ms in the conventional technique to 10 ms.) It becomes possible to reduce the cost and improve the reliability by drastically reducing the number of parts.

Further, in the inverter device 10, the start frequency, which is the frequency at the start (start) of driving the inverter drive signal, is set to a frequency sufficiently distant from the resonance frequency of the series resonance load 200, and then the frequency of the inverter drive signal is set to the series resonance load 200. Since the frequency is shifted so as to approach the resonance frequency of, the tracking characteristic to the series resonance load 200 whose resonance frequency fluctuates is greatly improved, and when a plurality of series resonance loads 200 having different resonance frequencies are switched and connected. Can be dealt with without any problem.

Here, it is preferable that the region (frequency shift region) in which the frequency is shifted by the frequency shift control unit 12b is determined to be an inductive region in consideration of the diode reverse recovery characteristic that is optimal for the inverter circuit.

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

According to the experiment by the inventor of the present application, the start frequency, which is the frequency at the start of driving the inverter drive signal, is a frequency separated by 5% or more from the frequency of the resonance frequency of the series resonance load 200 (for example, in series). Assuming that the resonance frequency of the resonance load 200 is 20 kHz, a frequency 5% or more away from the frequency of the resonance frequency of the series resonance load 200 is a frequency of 19 kHz or less or a frequency of 21 kHz or more). was gotten.

When the start frequency is set to a frequency 5% or more away from the frequency of the resonance frequency of the series resonance load 200, that is, when the start frequency is separated from the frequency of the resonance frequency of the series resonance load 200 by 5% or more, It may be separated to the low frequency side of the resonance frequency of the series resonance load 200 (in the frequency direction lower than the resonance frequency of the series resonance load 200) (for example, assuming that the resonance frequency of the series resonance load 200 is 20 kHz, the series resonance A frequency 5% or more away from the low frequency side of the resonance frequency of the load 200 is a frequency of 19 kHz or less), or a high frequency side of the resonance frequency of the series resonance load 200 (higher than the resonance frequency of the series resonance load 200). It may be separated in the frequency direction (for example, if the resonance frequency of the series resonance load 200 is 20 kHz, the frequency 5% or more away from the resonance frequency of the series resonance load 200 on the high frequency side becomes a frequency of 21 kHz or more. .).

According to the knowledge of the inventor of the present application, the start frequency is set away from the frequency of the resonance frequency of the series resonance load 200 (for example, the resonance frequency of the series resonance load 200) as in the inverter device 10 according to the present invention described above. After starting the driving of the inverter unit 106 by the narrow pulse signal from the start frequency, the narrow pulse signal is frequency-shifted to the resonance frequency of the series resonance load 200. There is no conventional technique for starting PWM control for widening the pulse width of the narrow pulse signal at the resonance frequency of the series resonance load 200.

(II) Second Embodiment of the present invention

Next, the inverter device and the control method of the inverter device according to the second embodiment of the present invention will be described.

The control method of the inverter device and the inverter device according to the second embodiment of the present invention is the same as the control method of the inverter device and the inverter device according to the first embodiment of the present invention described above. The method of controlling the frequency shift according to 12b is different.

That is, the inverter device according to the second embodiment of the present invention has the same configuration as the inverter device 10 according to the first embodiment of the present invention as a component. Therefore, in the following description, the present invention Only the points different from the inverter device 10 according to the first embodiment of the invention will be described.

In the control method of the inverter device and the inverter device according to the second embodiment of the present invention, the start frequency, which is the frequency at the start (start) of driving the inverter drive signal, is set to the high frequency side of the resonance frequency of the series resonance load 200 ( It is separated in a frequency direction higher than the resonance frequency of the series resonance load 200 (for example, if the resonance frequency of the series resonance load 200 is 20 kHz, it is on the high frequency side of the resonance frequency of the series resonance load 200. Frequencies separated by 5% or more are frequencies of 21 kHz or more).

That is, the series resonance circuit constituting the series resonance load 200 has a characteristic of being inductive in a range where the frequency is higher than the resonance frequency of the series resonance circuit.

On the other hand, in the voltage type inverter circuit constituting the inverter unit 106, the inductive switching operation is more stable than the capacitive switching operation due to the reverse recovery characteristic of the current of the diode connected in parallel with the inverter element. doing.

Therefore, in the inverter device and the control method of the inverter device according to the second embodiment, a frequency higher than the resonance frequency of the series resonance circuit constituting the series resonance load 200 (for example, a frequency higher than 5%) is started. The frequency is shifted as the frequency to lower the frequency so that the frequency is locked (fixed) at the resonance frequency of the series resonance circuit constituting the series resonance load 200.

(III) Third Embodiment of the present invention

(III-1) Composition

FIG. 6 shows a configuration explanatory diagram of an inverter device (third embodiment) according to an example of the embodiment of the present invention. Note that FIG. 6 shows the overall configuration of the inverter device controlled by the control unit and connected to the series resonant load.

Explaining the inverter device according to the third embodiment of the present invention with reference to FIG. 6, the inverter device 20 according to the third embodiment of the present invention is connected to the series resonance load 200.

By the way, the series resonance load 200 has a characteristic of being inductive in a range higher than the resonance frequency of the series resonance circuit constituting the series resonance load 200, while the voltage type inverter which is the inverter unit 106 is parallel to the inverter element. From the reverse recovery characteristics of the current of the diode connected to, it is known that the switching operation in inductive is more stable than the capacitance.

Therefore, the inverter device 20 according to the third embodiment of the present invention has an inverter having a frequency higher than the resonance frequency of the series resonance circuit 200 (for example, a frequency 5% or more higher than the resonance frequency of the series resonance circuit 200). The start frequency of the drive signal is set, and the frequency is shifted from this start frequency to lower the frequency of the inverter drive signal to the resonance frequency of the series resonance circuit 200, and the frequency of the inverter drive signal is locked by the resonance frequency of the series resonance circuit 200. ing.

Hereinafter, the inverter device 20 will be described. Reference numeral 22 is a variable control of the pulse widths of the square wave inverter drive signals Q and NQ, which are the inverter drive signals for driving the transistors of the voltage type inverter circuit constituting the inverter unit 106. This is a control unit that outputs to the inverter unit 106.

The control unit 22 includes a frequency shift circuit 30, a voltage control oscillator (VCO) circuit 32, a narrow pulse signal generation circuit 34, an output circuit 36, a phase comparison circuit 38, and a delay correction circuit 40. A lock completion circuit 42, a detection circuit 44, an error amplifier filter 46, a triangular wave generation circuit 48, and a PWM circuit 50 are included.

Here, the delay correction circuit 40 includes a T / 2 delay correction circuit 40a as a component thereof.

As will be described in detail later, "T / 2" means "1/2 period of the fundamental wave component of the output voltage of the inverter unit 106". In the inverter device 20 according to the third embodiment of the present invention, more specifically, it means "1/2 period of the resonance capacitor voltage waveform output from the voltage sensor 16."

In the inverter device 20, in connection with the implementation of the present invention, the control unit 22 includes a frequency shift circuit 30, a point where the frequency of the inverter drive signal is frequency-shifted, a point where the signal is switched, and a T / 2 delay correction circuit. Since the conventionally known technology of the inverter device can be applied except that the delay correction circuit 40 having the 40a is provided, the frequency of the inverter drive signal is shifted and the signal is switched. A detailed description of the configuration other than the above point and the point of delay correction will be omitted.

(III-2) Operation

In the above configuration, the operation of the inverter device 20 will be described focusing on the operation of the control unit 22 related to the implementation of the present invention.

The inverter device 20 detects the phase of the voltage waveform of the resonance capacitor 202 of the series resonance circuit constituting the series resonance load 200 by the voltage sensor 16, and obtains the detection result of the resonance capacitor voltage phase signal as the phase of the control unit 22. It is one input to the comparison circuit 38.

The other input of the control unit 22 to the phase comparison circuit 38 is an output signal obtained by inputting the output signal of the VCO circuit 32 to the delay correction circuit 40 and correcting the delay.

The phase comparison circuit 38 of the control unit 22 uses the above-mentioned delay-corrected output signal as a comparison signal and tracks it to the series resonance frequency of the series resonance load 200.

Here, the delay time corrected by the delay correction circuit 40 is from the phase center position of the pulses of the rectangular wave inverter drive signals Q and NQ, which are the inverter drive signals, to the zero cross point of the voltage waveform of the resonance capacitor 202 delayed by 1/2 cycle. It is a value substantially equal to the delay time td (td = T / 2 + Δt) of.

As will be described in detail later, “Δt” means “circuit delay of the inverter circuit constituting the inverter unit 106”.

Further, the detection circuit 44 of the control unit 22 inputs a current level signal, detects it, and then outputs the signal to the error amplifier filter 46, while the error amplifier filter 46 inputs an output setting signal.

Then, the pulse widths of the square wave inverter drive signals Q and NQ are controlled by the PWM circuit 50 so that the current level signal becomes the level of the output setting signal in the error amplifier filter 46.

More specifically, in the control unit 22 of the inverter device 20, an output ON (ON) signal from the outside is input to the frequency shift circuit 30, and a frequency higher than the resonance frequency of the series resonance load 200 (for example, the series resonance load 200). A signal is output to the VCO circuit 32 so as to start driving the inverter unit 106 from the resonance frequency of 5% or more.), And the frequency signal from the output of the VCO circuit 32 is the narrow pulse signal generation circuit 34. The narrow pulse signal of the frequency of the output of the VCO circuit 32 is generated by the narrow pulse signal generation circuit 34 and output to the output circuit 36.

In the output circuit 36, the signal of the narrow 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, the pulse width of the narrow pulse signal generated by the narrow pulse signal generation circuit 34 is such that the output value output from the inverter unit 106 is the minimum set output value (the minimum set output value of the set value indicated by the output setting signal from the outside). It is preferable to set the output voltage, output current, or output power).

The pulse width of the narrow pulse signal generated by the narrow pulse signal generation circuit 34 does not have to be constant, and may be determined by, for example, the minimum ratio of the period.

That is, when the pulse width of the narrow pulse signal is constant (fixed), the output ratio increases as the frequency increases and the minimum level increases. Therefore, it is preferable to set the pulse width to the minimum ratio of the period.

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

In each of FIGS. 7 (a), (b), (c), (d), and (e), the waveform D, the waveform E, the waveform F, the waveform G, and the waveform H are the resonance capacitor voltage waveforms detected by the voltage sensor 16. Is.

Further, in each of FIGS. 7 (a), (b), (c), (d), and (e), the waveform I, the waveform J, the waveform K, the waveform L, and the waveform M are the currents (output currents) detected by the current sensor 14. ) It is a waveform.

FIG. 7A shows the waveform of the narrow pulse signal (narrow pulse drive signal waveform) which is the inverter drive signal at the start frequency at the start of drive (start) and the current sensor 14 as the output of the inverter unit 106. The phase difference between the output current waveform (waveform I) and the resonance capacitor voltage waveform (waveform D) detected by the voltage sensor 16 as the output of the inverter unit 106 is shown.

When the series resonance load 200 is connected to the inverter device 20, the phase of the resonance capacitor voltage is T / 2 (90 °) behind the output current, and in the frequency range above the resonance frequency of the series resonance load 200, the phase is delayed. It is known that the output current phase lags behind the phase center position of the narrow pulse drive signal waveform.

Here, in the phase comparison circuit 38, the phase detection pulse position, which is a half-delayed pulse of the period from the phase center position of the narrow pulse drive signal waveform, which is the inverter drive signal, is set as point A, and the resonance capacitor voltage waveform to be compared is compared. With the zero crossing point of (see FIGS. 7A and 7B) as point B (see FIGS. 7A and 7B), the phase difference between point A and point B is compared, and the phase difference is zero (0) or a preset phase difference. Lock at the frequency of (see FIG. 7 (c)).

On the other hand, the frequency signal from the VCO circuit 32 is input to the T / 2 delay correction circuit 40a constituting the delay correction circuit 40, and corrects the phase delay of the resonance capacitor voltage of the series resonance circuit constituting the series resonance load 200. After that, it is input to the phase comparison circuit 38.

The phase comparison circuit 38 compares the phase of the input resonance capacitor voltage phase signal with the frequency signal from the VCO circuit 32 delayed-corrected by the delay correction circuit 40, and the output from the VCO circuit 32 is the series resonant load 200. The frequency of the VCO circuit 32 is feedback-controlled so as to be the resonance frequency of.

Specifically, the inverter unit 106 is driven by an inverter drive signal of a narrow pulse signal having a frequency distant from the resonance frequency of the series resonance load 200, for example, a frequency 5% or more higher than the resonance frequency as the start frequency ( (See FIG. 7 (a)), the frequency of the inverter signal is frequency-shifted and lowered (see FIG. 7 (b)).

Then, the phase comparison circuit 38 locks the frequency of the inverter drive signal at the resonance frequency of the series resonance load 200 (see FIG. 7C), and the lock completion circuit 42 detects the lock completion and sends the output circuit 36. Output a signal.

By this signal, the operation by the narrow pulse signal shifts to the PWM operation, and the output circuit 36 outputs an inverter drive signal in which the pulse width tw is widened by PWM control from the narrow pulse signal, and the output of the inverter unit 106 is output. It rises (ups) to the output of the set value set by the output setting signal (see FIGS. 7 (d) and 7 (e)).

(IV) Fourth Embodiment of the present invention

FIG. 8 shows a configuration explanatory diagram of an inverter device (fourth embodiment) according to an example of the embodiment of the present invention. Note that FIG. 8 shows the overall configuration of the inverter device controlled by the control unit and connected to the series resonant load.

Explaining the inverter device 60 according to the fourth embodiment of the present invention with reference to FIG. 8, in the inverter device 60 according to the fourth embodiment of the present invention, the delay correction circuit 40 in the control unit 62 is T / 2. It differs from the inverter device 20 according to the third embodiment of the present invention in that it is configured to include the delay correction circuit 40a and the Δt delay correction circuit 40b.

Here, it is known that a circuit delay Δt occurs in the inverter circuit constituting the inverter unit 106.

Therefore, in the inverter device 60 according to the fourth embodiment of the present invention, the delay correction circuit 40 is provided with the Δt delay correction circuit 40b in order to correct the circuit delay Δt of the inverter circuit constituting the inverter unit 106. The delay correction circuit 40 is configured to have a T / 2 delay correction circuit 40a and a Δt delay correction circuit 40b.

9 (b') and 9 (c') show waveforms when there is a circuit delay Δt, and such a circuit delay Δt is corrected by the Δt delay correction circuit 40b.

Note that FIG. 9 (b') shows a waveform diagram when there is a circuit delay Δt in FIG. 7 (b), and FIG. 9 (c') shows a waveform when there is a circuit delay Δt in FIG. 7 (c). The figure is shown.

(V) Fifth Embodiment of the present invention

Next, the inverter device and the control method of the inverter device according to the fifth embodiment of the present invention will be described.

The method for controlling the inverter device and the inverter device according to the fifth embodiment of the present invention is different from the method for controlling the inverter device and the inverter device according to the third embodiment of the present invention described above in the phase comparison circuit 38. The method of detecting the phase difference in is different.

That is, the inverter device according to the fifth embodiment of the present invention has the same configuration as the inverter device 20 according to the third embodiment of the present invention as a component. Therefore, in the following description, the present invention Only the points different from the inverter device 20 according to the third embodiment of the invention will be described.

In the inverter device according to the fifth embodiment of the present invention, the phase of the voltage waveform of the resonance capacitor 202 of the series resonance circuit constituting the series resonance load 200 is detected by the voltage sensor 16, and the resonance capacitor which is the detection result is detected. The voltage phase signal is used as one input to the phase comparison circuit 38.

The other input to the phase comparison circuit 38 is an output signal obtained by inputting the output signal of the VCO circuit 32 to the delay correction circuit 40 and correcting the delay.

Here, the delay time corrected by the delay correction circuit 40 is a zero cross of the voltage waveform of the resonance capacitor 202 adjacent to the phase center position from the phase center position of the pulse of the rectangular wave inverter drive signals Q and NQ which are the inverter drive signals. It is a value substantially equal to the delay time td (td = Δt) to the point.

Here, FIGS. 10 (a), (b), (c), (d), and (e) show a schematic waveform diagram showing the operation of the inverter device according to the fifth embodiment of the present invention.

In each of FIGS. 10 (a), (b), (c), (d), and (e), the waveform D', the waveform E', the waveform F', the waveform G', and the waveform H'are detected by the voltage sensor 16. It is a resonance capacitor voltage waveform.

Further, in each of FIGS. 10 (a), (b), (c), (d), and (e), the waveform I', the waveform J', the waveform K', the waveform L', and the waveform M'are detected by the current sensor 14. This is the current (output current) waveform.

In the inverter device 20 according to the third embodiment of the present invention, the voltage of the resonance capacitor 202 is oscillating, and therefore, as shown in FIGS. 10 (a), (b), (c), (d), and (e), FIGS. Even if the zero crossing point of the B'point, which is T / 2 earlier than the B point shown in 7 (a), (b), (c), (d), and (e), is detected, there is no practical inconvenience. .. The point A'is the center of the pulse phase.

Specifically, the inverter drive signal of the narrow pulse signal having a frequency distant from the resonance frequency of the series resonance load 200, for example, a frequency 5% or more higher than the resonance frequency of the series resonance load 200 as the start frequency, causes the inverter unit 106. The drive is started (see FIG. 10 (a)), and the frequency of the inverter signal is frequency-shifted and lowered (see FIG. 10 (b)).

Then, the phase comparison circuit 38 locks the frequency of the inverter drive signal at the resonance frequency of the series resonance load 200 (see FIG. 10C), and the lock completion circuit 42 detects the lock completion and sends the output circuit 36. Output a signal.

By this signal, the operation by the narrow pulse signal shifts to the PWM operation, and the output circuit 36 outputs an inverter drive signal in which the pulse width tw is widened by PWM control from the narrow pulse signal, and the output of the inverter unit 106 is output. It rises (ups) to the output of the set value set by the output setting signal (see FIGS. 10 (d) and 10 (e)).

(VI) Sixth Embodiment of the present invention

Next, the inverter device and the control method of the inverter device according to the sixth embodiment of the present invention will be described.

The method for controlling the inverter device and the inverter device according to the sixth embodiment of the present invention is different from the method for controlling the inverter device and the inverter device according to the fourth embodiment of the present invention described above in the phase comparison circuit 38. Only the method of detecting the phase difference in is different.

Here, the method of detecting the phase difference in the phase comparison circuit 38 is the same as the method of controlling the inverter device and the inverter device according to the fifth embodiment of the present invention described above. ) The detailed description will be omitted by referring to the description in "Fifth Embodiment of the present invention".

In the inverter device and the control method of the inverter device according to the sixth embodiment of the present invention, the delay correction circuit 40 has a T / 2 delay correction circuit 40a and a Δt delay correction circuit 40b to correct the circuit delay Δt. In that respect, it differs from the inverter device and the control method of the inverter device according to the fifth embodiment of the present invention.

As described above, it is known that a circuit delay Δt occurs in the inverter circuit constituting the inverter unit 106.

The circuit delay Δt of the inverter circuit constituting the inverter unit 106 may be corrected by the Δt delay correction circuit 40b constituting the delay correction circuit 40.

11 (b') and 11 (c') show waveforms when there is a circuit delay Δt, and such a circuit delay Δt is corrected by the Δt delay correction circuit 40b.

Note that FIG. 11 (b') shows a waveform diagram when there is a circuit delay Δt in FIG. 10 (b), and FIG. 11 (c') shows a waveform when there is a circuit delay Δt in FIG. 107 (c). The figure is shown. The point A'' is the phase center position of the narrow pulse signal waveform.

(VII) Seventh Embodiment of the present invention

FIG. 12 shows a configuration explanatory diagram of a control unit in an inverter device (seventh embodiment) according to an example of the embodiment of the present invention.

The inverter device 70 according to the seventh embodiment of the present invention is not different from the configuration of the inverter device 60 according to the fourth embodiment of the present invention except for the control unit 72. Therefore, the illustration and detailed description of other configurations other than the control unit 72 will be omitted.

The control unit 72 of the inverter device 70 according to the seventh embodiment of the present invention is in addition to the configuration of the control unit 62 as compared with the control unit 62 of the inverter device 60 according to the fourth embodiment of the present invention described above. The lowest level detection circuit 74 is provided, and the two are different in this respect.

In the inverter device 60 according to the fourth embodiment of the present invention, when the frequency deviates from the series resonance frequency of the series resonance load 200, the resonance capacitor voltage or the output current level decreases, and the output of the inverter unit 106 is accurate. Phase detection becomes impossible.

Therefore, in the inverter device 70 according to the seventh embodiment of the present invention, the control unit 72 is provided with the lowest level detection circuit 74, and the output of the inverter unit 106 can be phase-detected by the lowest level detection circuit 74. When the output level is reached, the phase comparison is started.

That is, in the inverter device 70 according to the seventh embodiment of the present invention, the detection circuit 44 of the control unit 72 is configured to detect the resonance capacitor voltage or the output current level of the series resonance load 200 by the pulse drive signal. The output from the detection circuit 44 is the lowest level detection circuit 74
Enter.

The lowest level detection circuit 74 detects the resonance capacitor voltage or output current level of the series resonance load 200 by the pulse drive signal which is an inverter drive signal, and when the level becomes equal to or higher than a preset level, the resonance frequency of the series resonance load 200 The operation of the phase comparison circuit 38 is started so as to control the frequency shift to the vicinity.

(VIII) Eighth Embodiment of the present invention

FIG. 13 shows an enlarged explanatory view of the inverter unit in the inverter device (eighth embodiment) according to an example of the embodiment of the present invention.

The inverter device according to the eighth embodiment of the present invention has an inverter unit 106 as compared with the configuration of the inverter device according to the first to seventh embodiments of the present invention described with reference to FIGS. 4 to 11. The two are different in that they are provided with an inverter unit 406 instead of the above.

As shown in FIG. 13, the inverter section 406 of the inverter device uses a SiC diode as the recirculation diode (freewheel diode) 406b in the inverter switching element 406a.

More specifically, as shown in FIG. 13, in the inverter switching element 406a of the inverter unit 406, a SiC diode is used as the freewheel diode 406b connected in reverse parallel to the semiconductor switching element 406c.

In the inverter device according to the eighth embodiment of the present invention, the frequency of the pulse drive signal, which is a sufficiently short inverter drive signal that can secure the minimum set output value (output current or output power), is set to be higher than the resonance frequency. The frequency of the pulse drive signal, which is the inverter drive signal, is adjusted by starting from a high frequency (for example, a frequency 5% or more higher than the resonance frequency) and performing frequency control by a frequency shift that lowers the frequency to the vicinity of the resonance frequency. Control to resonance frequency.

That is, in the inverter device according to the eighth embodiment of the present invention described above, a SiC diode is used as the freewheel diode 406b of the inverter switching element 406a.

Therefore, due to its characteristics, there is almost no recovery time during current regeneration, so diode recovery short-circuit current when PWM switching is turned on in a series resonant circuit can be prevented, and inverter noise and inverter loss can be reduced. Become.

(IX) A ninth embodiment of the present invention

In the inverter device according to the ninth embodiment according to the present invention, the series resonance circuit constituting the series resonance load 200 according to each of the above-described embodiments of the present invention (first to eighth embodiments) is used for induction heating. It is configured to be composed of a series resonance circuit composed of a heating coil and a resonance capacitor.

That is, as the series resonance load 200 connected to the inverter device according to the present invention including the inverter device according to each embodiment of the present invention (first to eighth embodiments) described above, various configurations are used. For example, a series resonant load for induction heating as shown in FIG. 14 may be connected to the inverter device according to the present invention.

Here, FIG. 14 shows a heating coil (induction heating coil L) and a resonance capacitor for induction heating, which is an example of a series resonance load, as a ninth embodiment of the inverter device according to an example of the embodiment of the present invention. A configuration explanatory diagram showing a case where an induction heating resonance load including a series resonance circuit for induction heating connected in series with C is connected is shown.

In the case of induction heating, since the output current becomes large, a matching transformer may be inserted in the output.

(X) Description of Other Embodiments and Modifications

It should be noted that the above-described embodiment is merely an example, and the present invention can be implemented in various other embodiments. That is, the present invention is not limited to the above-described embodiment, and various omissions, replacements, and changes can be made without departing from the gist of the present invention.

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

(X-1) In the above-described embodiment, when the start frequency is separated from the resonance frequency of the series resonance load 200, specifically, it is exemplified that the start frequency is separated from the resonance frequency of the series resonance load 200 by 5% or more.

However, the present invention is not limited to being separated from the resonance frequency of the series resonance load 200 by 5% or more, and may be separated from the resonance frequency of the series resonance load 200 by less than 5%.

That is, the value of "5%" is a suitable value empirically obtained by the inventor of the present application through experiments, but the present invention is not limited to the value of "5%", and the start frequency is a series resonance load. It suffices to be away from the resonance frequency of 200.

By separating the start frequency from the resonance frequency of the series resonance load 200, it is possible to automatically find the resonance frequency of the series resonance load 200 by frequency shift, no matter how the resonance frequency on the series resonance load 200 side deviates. ..

Here, the frequency shift region (frequency shift region) is preferably determined to be an inductive region in consideration of the diode reverse recovery characteristic that is optimal for the inverter circuit, and according to an experiment by the inventor of the present application, 5% or more from the resonance frequency. Was the area of.

(X-2) In the above-described embodiment, the description of the specific circuit configuration and the like in each configuration is omitted, but it goes without saying that a conventionally known circuit configuration corresponding to each configuration may be used.

(X-3) In the above-described embodiment, the description of specific circuit constants and the like in each configuration is omitted, but it goes without saying that conventionally known circuit constants corresponding to each configuration may be used.

(X-4) Of course, the above-described embodiments and the above-described embodiments (X-1) to (X-3) may be combined as appropriate.

The present invention can be used for an inverter device which is a power supply device connected to a series resonance load such as an induction heating circuit.

10 Inverter device 12 Control unit (control means)
12a PWM control unit (control means)
12b Frequency shift control unit (control means)
14 Current sensor 16 Voltage sensor 20 Inverter device 22 Control unit (control means)
30 Frequency shift circuit 32 Voltage controlled oscillator (VCO: Voltage-controlled oscillator) circuit 34 Narrow pulse signal generation circuit 36 Output circuit 38 Phase comparison circuit 40 Delay correction circuit (delay correction means)
40a T / 2 delay correction circuit (first delay correction means)
40b ΔT delay correction circuit (second delay correction means)
42 Lock completion circuit 44 Detection circuit 46 Error amplifier / filter 48 Triangle wave generation circuit 50 PWM circuit 60 Inverter device 62 Control unit (control means)
70 Inverter device 72 Control unit (control means)
74 Lowest level detection circuit (Lowest level detection means)
100 Inverter device 102 AC (AC) power supply 104 Converter section 106 Inverter section 108 Output sensor 110 Converter control section 112 Control section 112a PLL circuit 200 Series resonance load 202 Resonance capacitor 204 Series resonance inductor 300 Inverter device 302 Converter section 304 PWM control section 406 Inverter section 406a Inverter switching element 406b Recirculation diode (free wheel diode)
406c Semiconductor switching element L Induction heating coil C Resonant capacitor Vh Output voltage Ih Output current Q Rectangular wave inverter drive signal NQ Rectangular wave inverter drive signal T 1 cycle of the fundamental wave component of the inverter unit output (output voltage or output current) 2 1/2 cycle of the fundamental wave component of the output voltage of the inverter section T / 4 1/4 cycle of the fundamental wave component of the output (output voltage or output current) of the inverter section Δt Circuit delay of the inverter circuit constituting the inverter section tw Rectangular wave inverter drive signal Q, NQ pulse width

Claims (26)

In an inverter device that is a voltage-type inverter that is PWM-controlled by connecting to a series resonance load.
The inverter section, which is connected to the series resonance load and driven by the inverter drive signal,
It has a control means for controlling the operation of the inverter unit.
The control means uses a pulse signal having a pulse width shorter than the period of the resonance frequency of the series resonance load as the inverter drive signal, starts driving the inverter unit from a frequency distant from the resonance frequency, and then starts driving the inverter unit in series. The frequency of the inverter drive signal is frequency-shifted to the resonance frequency or the vicinity of the resonance frequency by frequency control based on the voltage phase of the resonance capacitor constituting the resonance load, and the frequency of the inverter drive signal substantially matches the resonance frequency. An inverter device characterized by being controlled in such a manner. In the inverter device according to claim 1,
The short pulse width is an inverter device characterized in that the output of the inverter unit is a pulse width at which the output of the inverter unit is the minimum set output value of the set value indicated by the output setting signal from the outside. In the inverter device according to any one of claims 1 or 2.
The starting point is an inverter device characterized in that the frequency shift region is an inductive region based on the diode reverse recovery characteristic of the inverter circuit constituting the inverter unit. In the inverter device according to any one of claims 1, 2 or 3.
The inverter device is characterized in that the starting point is a frequency higher than the resonance frequency. In the inverter device according to any one of claims 1, 2, 3 or 4, further
An inverter device comprising a delay correction means for correcting a delay time from the phase center position of the inverter drive signal to the zero crossing point of the voltage waveform of the resonant capacitor, which is delayed by 1/2 cycle. In the inverter device according to any one of claims 1, 2, 3 or 4, further
An inverter device comprising a delay correction means for correcting a delay time to a zero crossing point of a voltage waveform of the resonance capacitor adjacent to a phase center position of the inverter drive signal. In the inverter device according to any one of claims 5 or 6.
The inverter device is characterized in that the delay correction means includes a first delay correction means for correcting a 1/2 cycle delay of a fundamental wave component of the output voltage of the inverter unit. In the inverter device according to any one of claims 5, 6 or 7.
The inverter device is characterized in that the delay correction means includes a second delay correction means for correcting the circuit delay of the inverter unit. In the inverter device according to any one of claims 1, 2, 3, 4, 5, 6, 7 or 8.
The inverter unit is an inverter device characterized in that a SiC diode is used as a freewheel diode in an inverter switching element. In the inverter device according to any one of claims 1, 2, 3, 4, 5, 6, 7, 8 or 9.
The inverter device is characterized in that the starting point is a frequency separated from the frequency of the resonance frequency by 5% or more. In the inverter device according to any one of claims 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10.
The control means is an inverter device characterized in that after controlling the frequency of the inverter drive signal so as to substantially match the resonance frequency, the pulse width of the inverter drive signal is widened by PWM control. In the inverter device according to any one of claims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or 11.
The control means is an inverter device including a minimum level detecting means for detecting that the output of the inverter unit has reached an output level at which phase detection is possible. In the inverter device according to any one of claims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12.
The series resonance load is an inverter device characterized by being composed of a series resonance circuit in which a heating coil for induction heating and a resonance capacitor are connected in series. In the control method of an inverter device, which is a voltage-type inverter that is PWM-controlled by connecting to a series resonance load,
A pulse signal having a pulse width shorter than the period of the resonance frequency of the series resonance load is used as an inverter drive signal, and after starting driving of the inverter portion from a frequency distant from the resonance frequency, the resonance capacitor constituting the series resonance load The frequency of the inverter drive signal is shifted to the resonance frequency or the vicinity of the resonance frequency by frequency control based on the voltage phase, and the frequency of the inverter drive signal is controlled to substantially match the resonance frequency. How to control the frequency controller. In the control method of the inverter device according to claim 14,
A control method for an inverter device, wherein the short pulse width is a pulse width at which the output of the inverter unit is the minimum set output value of the set value indicated by an output setting signal from the outside. In the control method of the inverter device according to any one of claims 14 or 15.
The starting point is a control method for an inverter device, wherein the frequency shift region is an inductive region based on the diode reverse recovery characteristic of the inverter circuit constituting the inverter unit. The method for controlling an inverter device according to any one of claims 14, 15 or 16.
A control method for an inverter device, wherein the starting point is a frequency higher than the resonance frequency. The control method for an inverter device according to any one of claims 14, 15, 16 or 17.
A control method for an inverter device, characterized in that the delay time from the phase center position of the inverter drive signal to the zero crossing point of the voltage waveform of the resonant capacitor delayed by 1/2 cycle is corrected. The control method for an inverter device according to any one of claims 14, 15, 16 or 17.
A control method for an inverter device, characterized in that the delay time to the zero crossing point of the voltage waveform of the resonant capacitor adjacent to the phase center position of the inverter drive signal is corrected. In the control method of the inverter device according to any one of claims 18 or 19.
A control method for an inverter device, which is characterized by correcting a 1/2 cycle delay of a fundamental wave component of the output voltage of the inverter unit. The method for controlling an inverter device according to any one of claims 18, 19 or 20.
A control method for an inverter device, characterized in that the circuit delay of the inverter section is corrected. The control method for an inverter device according to any one of claims 14, 15, 16, 17, 18, 19, 20 or 21.
The inverter unit is a control method for an inverter device, characterized in that a SiC diode is used as a freewheel diode in an inverter switching element. The method for controlling an inverter device according to any one of claims 14, 15, 16, 17, 18, 19, 20, 21 or 22.
A control method for an inverter device, wherein the starting point is a frequency that is 5% or more away from the frequency of the resonance frequency. The control method for an inverter device according to any one of claims 14, 15, 16, 17, 18, 19, 20, 21, 22 or 23.
A control method for an inverter device, which comprises controlling the frequency of the inverter drive signal so as to substantially match the resonance frequency, and then widening the pulse width of the inverter drive signal by PWM control. The control method for an inverter device according to any one of claims 14, 15, 16, 17, 18, 19, 20, 21, 22, 23 or 24.
A control method for an inverter device, characterized in that it detects that the output of the inverter unit has reached an output level at which phase detection is possible. The control method for an inverter device according to any one of claims 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24 or 25.
The series resonance load is a control method of an inverter device, characterized in that the series resonance load is composed of a series resonance circuit in which a heating coil for induction heating and a resonance capacitor are connected in series.

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