JPH1154249A - Inverter for induction heating - Google Patents

Abstract

(57) [Summary] An inverter device for induction heating is provided with a function of automatically displaying whether or not the device and a heating coil are matched. SOLUTION: A control circuit 30 has comparators 41 and 43, a full-wave rectifier 42, an inversion circuit 44, delay circuits 45 and 46, AND circuits 47, 48, 51 and 52, a one-shot circuit 49,
50, an OR circuit 53, and a monitoring circuit 54, and a matching detector 31 and a display 32 are added to detect the detected value of CT8 and γ
From the frequency of the drive signals of the IGBTs 2a and 3a output from the control circuit, the induction heating inverter and the heating coil 2
Whether or not a match with 0 is obtained is detected by the match detecting means 31, and this is displayed on the display 32.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction heating inverter device used for a commercial electromagnetic cooker or the like.

[0002]

2. Description of the Related Art FIG. 4 is a circuit diagram showing a conventional example of this type of inverter device for induction heating. In FIG. 4, 1 is a DC power supply such as a rectified power supply, and 2 and 3 are IGBTs 2 respectively.
a, 3a and semiconductor switches in which diodes 2b, 3b are connected in anti-parallel, 4, 4 and 5 are resonance capacitors, 6 is a DC voltage detector for detecting the terminal voltage of DC power supply 1, and 7 is the output current of DC power supply 1. A DC current detector for detecting the output current of the inverter device for induction heating;
Reference numeral 10 denotes a control circuit. Reference numeral 20 denotes a heating coil connected to the output terminal of the heating inverter.
Numeral 1 denotes a pot as an object to be heated which is installed on the heating coil 20.

The control circuit 10 includes a power setting device 11 for setting the heating power of the pan 21, a power calculator 12 for calculating the power from the detected values of the DC voltage detector 6 and the DC current detector 7, and a power setting device. Power controller 13 which performs a calculation for adjusting the power to be output by the induction heating inverter device based on the deviation between the set value of the heater 11 and the calculated value of the power calculator 12.
And adjustment of the current to be output by the inverter based on the deviation between the output value of the power controller 13 and the current detection value (DC value) of the induction heating inverter obtained via the CT 8 and the rectifier 14. A current controller 15 that performs an operation, and a voltage and a current output by the inverter device are obtained from an output value of the current controller 15 and a current detection value (AC value) of the inverter device for induction heating obtained via CT8. A γ control circuit 16 that outputs a drive signal to the semiconductor switches 2 and 3 in which the phase angle (γ) is controlled to a desired value, and a pulse distribution that decomposes the drive signal into a drive signal to each of the semiconductor switches 2 and 3 Devices 17 and IGBTs 2a, 3a constituting semiconductor switches 2, 3 based on drive signals to the respective devices.
Gate drive circuit 18 that outputs a gate signal to each
It is composed of

[0004] Since the respective functions constituting the control circuit 10 can be constituted by a well-known technique, a detailed explanation of the structure will be omitted.

[0005]

When the conventional induction heating inverter device shown in FIG. 4 is used for a commercial electromagnetic cooker or the like, a kitchen equipment maker uses a heating coil 20 to change the shape and material of the pot 21 and the cooking equipment. The inverter device for induction heating is manufactured by an electrical equipment maker, and the inverter device is delivered to a kitchen equipment manufacturer.The inverter device is incorporated into the kitchen equipment, and the kitchen equipment manufacturer Often delivered to customers (restaurants, restaurants, etc.).

However, based on the above-mentioned distribution channel,
When manufacturing the heating coil 20, it is necessary for the kitchen equipment maker to determine particularly whether the inductance of the heating coil 20 matches the manufacturing specification of the inverter device for induction heating. Generally, there are few technicians who are familiar with the inverter device for induction heating in the kitchen equipment maker.
In the worst case when 0 does not match the induction heating inverter device supplied from the electric equipment manufacturer, the inverter device may be damaged. In addition, there is a problem that the remanufacturing of the heating coil 20 is blindly performed.

Conventionally, as a countermeasure against this problem, a technician of an electric equipment maker goes to a kitchen equipment maker, and the technician uses a measuring instrument such as an oscilloscope to measure the voltage and current output by the induction heating inverter. While monitoring the phase angle (γ), the heating coil 20 is made ready for remanufacturing. An object of the present invention is to solve the above-mentioned problems and to provide an induction heating inverter device for automatically displaying the above-mentioned matching result.

[0008]

According to the first invention, an arm circuit in which two sets of semiconductor switches are connected in series at both ends of a DC power supply and a circuit in which two resonance capacitors are connected in series are connected in parallel, respectively. An induction heating inverter device in which an intermediate point of the arm circuit and an intermediate connection point of the resonance capacitor are each used as an output terminal, and each of the semiconductor switches is turned on and off alternately based on a drive signal from a control circuit. In the circuit, it is determined whether or not the heating coil connected between the output terminals and the object to be heated placed on the heating coil are matched with the induction heating inverter device. Is displayed to the outside.

In a second aspect based on the first aspect, the matching detecting means outputs a logical "H" signal when a detected value of the current of the heating coil has a positive polarity; A full-wave rectifier for full-wave rectification of the detected value, a second comparator for outputting a logical "H" signal when the full-wave rectification value is equal to or less than a predetermined value, and an inverting circuit for inverting the output of the first comparator A first delay circuit that outputs a logic "H" with a predetermined time delay when the output of the first comparator changes from a logic "L" to a logic "H", and the output of the inverting circuit is a logic "L". ”To a logic“ H ”, a second delay circuit that outputs a logic“ H ”with a predetermined time delay, and outputs a logical product of the output of the second comparator and the output of the first delay circuit. A first AND circuit, a second AND circuit that outputs a logical product of an output of the second comparator and an output of the second delay circuit, A first one-shot circuit for outputting a logic "H" signal for a predetermined period when a drive signal of a semiconductor switch of an upper arm of the arm circuit is turned off from on, and a drive of a semiconductor switch of a lower arm of the arm circuit A second one-shot circuit that outputs a logical "H" signal for a predetermined period when the signal is turned off from on, and an AND of an output of the first AND circuit and an output of the first one-shot circuit is output. A third AND circuit, a fourth AND circuit that outputs the logical product of the output of the second AND circuit and the output of the second one-shot circuit, and the output of the third AND circuit and the fourth AND circuit. A logical sum circuit that outputs a logical sum of the output and a logical sum circuit that monitors the output of the logical sum circuit and sets a predetermined period from when the previous logical “H” signal is generated to when the current logical “H” signal is generated. Output display signal to outside when value exceeds And a monitoring circuit.

According to the present invention, as described later, by providing a matching monitoring means in the control circuit, it is possible to monitor the matching between the induction heating inverter device and the heating coil.

[0011]

FIG. 1 is a circuit diagram of an induction heating inverter device according to an embodiment of the present invention. Components having the same functions as those of the conventional circuit shown in FIG. ing. That is, the control circuit 30 of the induction heating inverter device shown in FIG.
2, power controller 13, rectifier 14, current controller 15, γ
Control circuit 16, pulse distributor 17, gate drive circuit 18
In addition, a matching detecting means 31 and a display 32 are provided.

Also, as the production specifications of the induction heating inverter device, the resonance capacitors 3 and 4 and the heating coil 20
Is set to about 20 kHz, and the change range of the frequency of the drive signal of the inverter device is set to about 50 kHz to about 25 kHz.
Is generally set, and the rating of each semiconductor element constituting the semiconductor switches 2 and 3 is also selected from the maximum heating power for the pan 21 at this time. That is, in a state where the capacitances of the resonance capacitors 3 and 4 are set in advance, for example, a kitchen appliance maker needs to set the inductance of the heating coil 20 to be equal to the resonance frequency based on the above-described distribution path. .

FIG. 2 is a detailed circuit diagram showing an example of the configuration of the matching detecting means 31 shown in FIG. This matching detecting means 31
Is a comparator 41 that outputs a logical "H" signal when the detected value of the current of the heating coil 20 via the CT8 has a positive polarity, a full-wave rectifier 42 that performs full-wave rectification on the detected value, A comparator 43 for outputting a logical "H" signal when the value is equal to or less than a predetermined value, and an inverting circuit 44 for inverting the output of the comparator 41
And a delay circuit 45 that outputs a logic "H" with a predetermined delay when the output of the comparator 41 changes from a logic "L" to a logic "H", and the output of the inversion circuit 44 is a logic "L". And a delay circuit 46 which outputs the logic "H" with the same time delay as the delay circuit 45 when the logic becomes "H", and a logic which outputs the logical product of the output of the comparator 43 and the output of the delay circuit 45. A product circuit 47, a logical product circuit 48 that outputs a logical product of the output of the comparator 43 and the output of the delay circuit 46, and a logic circuit for a predetermined period when the drive signal of the IGBT 2a of the semiconductor switch 2 is turned off from on. A one-shot circuit 49 for outputting an "H"signal; and a one-shot circuit 49 when the drive signal of the IGBT 3a of the semiconductor switch 3 is turned off from on.
A one-shot circuit 50 that outputs a logical "H" signal for the same period as
AND circuit 51 that outputs a logical product of the output of the AND circuit 48, an AND circuit 52 that outputs the logical product of the output of the AND circuit 48 and the output of the one-shot circuit 50, and the logical product of the output of the AND circuit 51 A logical OR circuit 53 that outputs a logical OR with the output of the circuit 52, and a monitor of the output of the logical OR circuit 53, from the generation of the previous logical "H" signal to the generation of the current logical "H" signal. Display 32 when the period of
And a monitoring circuit 54 for outputting a display signal to the monitor.

The operation of the matching detecting means 31 shown in FIG.
This will be described below with reference to the operation waveform diagram shown in FIG. FIG. 3 (a) shows the detected value of CT8, IGBT2a
Alternatively, when the diode 3b is in a conductive state, a current of a positive polarity flows. That is, when the detected value of CT8 is positive polarity, the output of the comparator 41 becomes a logical "H" signal as shown in FIG. 3B, and the sine-wave dashed line in FIG. V _C is the output of the comparator 43
When the output value of the full-wave rectifier 42 is equal to or less than the comparison value V _C , the output of the comparator 43 becomes a logical “H” signal as shown in FIG.

The period T ₁ in FIG. 3B indicates the delay time of the delay circuit 45, and the delay time of the delay circuit 45 is higher than when the output of the comparator 41 changes from logic “L” to logic “H”. T ₁ times delayed by a logic "H", the output of the comparator 41 outputs a logic "H" signal until the logic "L". Incidentally, this period T ₁ is the frequency of the drive signal 5
It is set slightly shorter than the time based on the half cycle at 0 kHz.

That is, the frequency of the normal drive signal (25 to
In the range of 50 kHz), the AND circuits 47 and 48 output the logical "H" signals during the last period of the positive polarity and the last period of the negative polarity of the detected value of CT8, respectively, as shown in FIG. I do. In addition, the drive signals of the IGBTs 2a and 3a are changed with respect to the elapse of the detected value of the CT8 shown in FIG.
The one-shot circuits 49 and 50 output a logical "H" signal at the timings shown in FIGS. At this time, the time T ₂ is set to a time period corresponding to the phase angle (γ).

That is, the output of the OR circuit 53 is
As shown in FIG. 3 (N), the outputs of the AND circuits 47 and 48 (FIG.
(D, e) and the outputs of the one-shot circuits 49 and 50 (see FIG. 3 (h) and (h)) to output a logical "H" signal. Further, in the monitoring circuit 54, the OR circuit 53
Output is generated the previous logic "H" signal from the measures time until generation of the current logic "H" signal, the measured time is less than time period T _3, FIG. 3 (j) The logic "H" signal is continuously output as shown in FIG.
₃ timed T ₃ and later when it exceeds outputs a logic "L" signal. The timed T ₃ is the frequency of the drive signal 2
It is set slightly longer than the time based on the half cycle at 5 kHz.

The operation of the induction heating inverter device of the present invention having the above-described matching detection means 31 will be described below. On the basis of the above-mentioned distribution route, for example, a heating coil 20 manufactured by a kitchen equipment maker is connected to an output terminal of an inverter device for induction heating, and a pot 21 is placed on the heating coil 20. When the set value of 11 is set to a desired value and a heating command is issued to the inverter device, a drive signal is issued to each of the IGBTs 2a and 3a by the control circuit 30, and the set value of the power setter 11 and the calculation of the power calculator 12 are performed. The frequency of the drive signal is gradually reduced from 50 kHz so that the deviation from the value becomes zero, and the inverter device settles at the frequency of the drive signal whose deviation becomes zero.

At this time, if the inductance of the heating coil 20 is larger than a desired value and is not consistent with the production specification of the induction heating inverter device, even if the frequency of the drive signal reaches 20 kHz, the power setting device The deviation between the set value of 11 and the calculated value of the power calculator 12 does not become zero,
As a result, beyond the time period T ₃ of the monitoring circuit 54, the output of the monitoring circuit 54 outputs a logic "L" signal, the indicator 32 is turned on.

When the inductance of the heating coil 20 is smaller than a desired value and is not consistent with the production specification of the induction heating inverter device, the heating coil 20 is driven before the frequency of the drive signal reaches 20 kHz. At this point, the logical "H" signal output from the OR circuit 53 disappears, and the output from the monitoring circuit 54 becomes the logical "L" signal. Is output, and the display 32 is turned on.

Although not shown in FIG. 1, when the matching detecting means 31 operates and the output becomes a logical "L" signal, the inverter device for induction heating is stopped by this signal. Is common.

[0022]

According to the present invention, as described above, by providing the matching monitoring means in the control circuit of the inverter device for induction heating, the result of matching between the inverter device and the heating coil can be automatically displayed. it can.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an induction heating inverter device showing an embodiment of the present invention.

FIG. 2 is a partial detailed circuit diagram of FIG. 1;

FIG. 3 is an operation waveform diagram of FIG. 2;

FIG. 4 is a circuit diagram of an induction heating inverter device showing a conventional example.

[Explanation of symbols]

1: DC power supply, 2, 3: semiconductor switch, 2a, 3a ...
IGBT, 2b, 3b: diode, 4, 5: resonance capacitor, 6: DC voltage detector, 7: DC current detector, 8
... CT, 10, 30 ... Control circuit, 11 ... Power setting device, 1
2: Power calculator, 13: Power regulator, 14: Rectifier, 1
5 current regulator, 16 gamma control circuit, 17 pulse distributor, 18 gate drive circuit, 20 heating coil, 21
Pan, 31: matching detection means, 32: display, 41, 43 ...
Comparator, 42 full-wave rectifier, 44 inverting circuit, 45, 4
6 delay circuit, 47, 48, 51, 52 ... AND circuit
49, 50: one-shot circuit, 53: OR circuit, 5
4: Monitoring circuit.

Claims (2)

[Claims] 1. An arm circuit in which two sets of semiconductor switches are connected in series at both ends of a DC power supply and a circuit in which two resonance capacitors are connected in series, respectively, are connected in parallel, and an intermediate point of the arm circuit and the resonance capacitor are connected. An intermediate connection point as an output terminal, and an inverter device for induction heating in which each of the semiconductor switches is turned on and off alternately based on a drive signal from a control circuit, wherein the control circuit is connected between the output terminals. A heating coil; and a matching detection means for determining whether or not the object to be heated placed on the heating coil is matched with the induction heating inverter device, and displaying the determination result to the outside. An inverter device for induction heating, characterized in that: 2. The induction heating inverter device according to claim 1, wherein said matching detection means outputs a logic "H" signal when a detected value of a current of said heating coil has a positive polarity. ,
A full-wave rectifier for full-wave rectifying the detected value, and a second rectifier for outputting a logical "H" signal when the full-wave rectified value is equal to or less than a predetermined value.
A comparator, an inverting circuit for inverting an output of the first comparator, and outputting a logic "H" with a predetermined delay when the output of the first comparator changes from a logic "L" to a logic "H" A second delay circuit that outputs a logic "H" with a predetermined delay when the output of the inversion circuit changes from a logic "L" to a logic "H"; A first AND circuit that outputs a logical product of the output and the output of the first delay circuit; and a second AND circuit that outputs the logical product of the output of the second comparator and the output of the second delay circuit.
An AND circuit, and a first one-shot circuit that outputs a logic “H” signal for a predetermined period when a drive signal of a semiconductor switch of the upper arm of the arm circuit is turned off from on,
A second one-shot circuit for outputting a logic "H" signal for a predetermined period when a drive signal of a semiconductor switch of a lower arm of the arm circuit is turned off from on, a first AND circuit and an output of the first AND circuit; A third AND circuit that outputs an AND of the output of the shot circuit, a fourth AND circuit that outputs an AND of the output of the second AND circuit and the output of the second one-shot circuit, A logical sum circuit that outputs the logical sum of the output of the product circuit and the output of the fourth logical product circuit, and monitors the output of the logical sum circuit to determine the current logical level “H” after the previous logical “H” signal is generated. A monitoring circuit for outputting a display signal to the outside when a period until a signal is generated exceeds a predetermined value.