JP2002260835A - Induction cooker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an induction cooker that has an inverter circuit of the half bridge type of low cost and high performance. SOLUTION: In the electromagnetic cooker 1, which is an induction cooker, the DSP 9, which is a processor having built in the PWM function for driving three phase motor that generates a PWM signal for three phase based on the common carrier signal, generates the PWM signal of U-phase that has fixed the duty ratio and the PWM signal of- V-phase that has the relation of anti- phase with the PWM signal of this U-phase and has adjusted the duty ratio in accordance with the predetermined amount of heating so as not to overlap with each other, and outputs the PWM signal of- V-phase and PWM signal of U-phase to the IGBT 35a being a first switching element and the IGBT 34a being a second switching element of the half bridge type inverter circuit, and thereby, performs PWM control of switching ON/OFF alternately the IGBT 34a and 35a of both switching elements.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an induction heating cooker for supplying a high-frequency current to a heating coil by a half-bridge type inverter circuit.

[0002]

2. Description of the Related Art Conventionally, there has been an induction heating cooker such as an electromagnetic cooker or an electric rice cooker which is configured to supply a high-frequency current to a heating coil by an inverter circuit. Japanese Patent Application Laid-Open No. 8-138848 discloses FIG.
The electromagnetic cooker 100 provided with the one-stone type inverter circuit as shown in FIG. This electromagnetic cooker 100
A high-frequency current is supplied to the heating coil 102 by performing PWM control of the switching element 101.
A microcomputer (hereinafter, simply referred to as a microcomputer) 1 that outputs a command signal for controlling heating of the cooking device 103.
04 and a PWM circuit 105 that outputs a PWM (pulse width modulation) signal based on a command signal. In this case, the PWM circuit 105 is generally a combination of individual semiconductors or a circuit using an ASIC (application-specific integrated circuit).

However, in the case of a combination of individual semiconductors, there are problems such as an increase in the number of components and an increase in cost, and an increase in the mounting area of the components and an increase in the size of the electromagnetic cooker. Further, in the case of using an ASIC, the development cost is increased due to the long time required for the design and development, and the cost is increased. There were many problems such as many functions. In order to solve these problems, a general-purpose microcomputer having a PWM function for driving a single-type inverter circuit such as a semiconductor 38C3 group manufactured by Mitsubishi Electric has been commercialized.

[0004]

By the way, in an electromagnetic cooker provided with such a one-piece inverter circuit, it is necessary to increase the voltage applied to the switching element.
Therefore, the switching loss increases, and the breakdown voltage needs to be increased to, for example, about 900 V.
There was room for improvement, such as the waveform of the current flowing through the heating coil being greatly distorted.

For this reason, in recent years, an electromagnetic cooker provided with a half-bridge type inverter circuit (see FIG. 1) is becoming mainstream. Since this half-bridge type electromagnetic cooker can reduce the voltage applied to the two switching elements as compared with the one-stone type cooker, the switching loss is reduced and the withstand voltage is reduced to, for example, about 600 V. Can be. Further, there is a characteristic that distortion of a current waveform flowing through the heating coil is reduced, and further, there are advantages such as good controllability at a low heating amount (when the output is reduced). For example, JP-A-11-214139 discloses that
P for driving a half-bridge type inverter circuit
A configuration example of a microcomputer having a built-in WM function is disclosed. It is expected that an inexpensive electromagnetic cooker with improved performance can be provided by using such a microcomputer.

[0006] However, a microcomputer having a built-in PWM function for driving such a half-bridge type inverter circuit has not yet been commercialized as being unprofitable in the induction heating cooker market. . In addition, the development of such a microcomputer requires a long development period, and the development cost is high, so that it is unlikely that the microcomputer will be commercialized in the future. Therefore, PWM
As a function, a combination of individual semiconductors or a combination of ASICs must be used, and even if the performance of an induction heating cooker can be improved, it cannot be provided at a low cost.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an induction heating cooker having a low-cost and high-performance half-bridge type inverter circuit.

[0008]

According to a first aspect of the present invention, there is provided an induction heating cooker comprising: a resonance circuit comprising a heating coil and a resonance capacitor for heating the cooker; and a series circuit of first and second switching elements. At least one electromagnetic cooking unit paired with a half-bridge type inverter circuit that supplies a high-frequency current to the resonance circuit, and a PWM signal for a plurality of phases is generated based on a common carrier signal generated by a timer. Built-in PWM function for motor drive, this PWM
A processor for performing PWM control of the inverter circuit based on the M function.

According to such a configuration, since a processor having a PWM function for driving a motor is mass-produced and supplied at a low price, the PWM function is provided by an individual semiconductor or AS.
The manufacturing cost can be reduced as compared with the case where the IC is used. Moreover, by using a processor having a PWM function for driving the motor, it is not necessary to newly develop a microcomputer or the like having a PWM function for driving a half-bridge type inverter circuit. Development time can be shortened. Therefore, an induction heating cooker can be provided at low cost.

[0010] In the induction heating cooker according to the second aspect, the processor is configured to perform the following processing based on the common carrier signal.
The PWM function capable of generating a PWM signal equal to or greater than the “number of the electromagnetic cooking units + 1” phase is built in, and based on comparing the count value of the timer with a set comparison value, A fixed PWM signal for the "1" phase in which the mutually complemented PWM signals for the "number of the electromagnetic cooking units + 1" phase are output, and a duty ratio per cycle of the carrier signal is fixed. And the fixed PWM signal has an opposite phase relationship, and the variable PWM for the “number of the electromagnetic cooking units” phase in which the duty ratio per cycle of the carrier signal is adjustable so as not to overlap each other. And the fixed PWM signal is output to one switching element of the inverter circuit, and the variable PWM signal is output to the other switching element of the inverter circuit. By outputting the P
WM control is performed to control a heating amount to the cooker based on adjusting a duty ratio of the variable PWM signal.

According to this configuration, the PWM function for driving the motor can easily output the PWM signal based on the setting of the comparison value and the frequency of the carrier signal. Accordingly, a half-bridge type inverter circuit can be easily driven.
In addition, the power supply amount of the high-frequency current to the inverter circuit, that is, the heating amount can be adjusted only by fixing the frequency of the carrier signal and the duty ratio of the fixed PWM signal and changing the duty ratio of the variable PWM signal. The PWM control of the circuit is simple, and the control program can be easily created. Furthermore, since each PWM signal is generated based on a common timer, the fundamental frequency of the high-frequency current supplied to the plurality of heating coils can be made equal, and the occurrence of beats can be suppressed.

According to a third aspect of the present invention, there is provided an induction heating cooker comprising current phase detecting means for detecting a phase of a current flowing through the heating coil, and the processor generates a PWM signal based on the common carrier signal. The same number of PWM functions for driving the motor as possible are built in the electromagnetic cooking unit, and the PWM functions are mutually complemented based on a comparison between the count value of the timer and a set comparison value for each of the PWM functions. The fixed PWM signal having a fixed duty ratio per cycle of the carrier signal and the first fixed PWM signal are configured to output a PWM signal corresponding to the “1” phase obtained as described above. , And outputs the fixed PWM signal to one switching element of the inverter circuit, and outputs the fixed PWM signal to the other switching element of the inverter circuit. The PWM control is performed by outputting the inverted PWM signal to the switching element, and the phase of the current detected by the current phase detector is compared with the phase of the fixed PWM signal or the inverted PWM signal. The amount of heating of the cooker is controlled based on adjusting the frequency of the carrier signal.

According to such a configuration, the PWM function for driving the motor can easily output the PWM signal based on the setting of the comparison value and the frequency of the carrier signal. By adjusting the frequency of the carrier signal, the PWM control of the half-bridge type inverter circuit can be easily performed. Moreover, fixed P
By simply fixing the duty ratios of the WM signal and the inverted PWM signal and adjusting the frequency of the carrier signal, the amount of high-frequency current supplied to the inverter circuit, that is, the amount of heating, can be adjusted, so that PWM control of the inverter circuit is simple. Yes, the control program can be easily created. Also, for example, the P generated for each inverter circuit
When the comparison value of the WM signal is shared, the number of registers for setting the comparison value can be reduced.

According to a fourth aspect of the present invention, there is provided an induction heating cooker comprising a resonance circuit comprising a heating coil and a resonance capacitor for heating the cooker, and a series circuit of first and second switching elements, wherein the resonance circuit has a high frequency. It has one or more electromagnetic cooking units that are paired with a half-bridge type inverter circuit that supplies current, and the same number of timers as the electromagnetic cooking units. Each of the timers is independent based on each carrier signal generated by each of the timers. A high-speed arithmetic processing type processor having a built-in PWM function for driving a motor capable of generating a modified PWM signal; an inverted signal generating means for generating an inverted signal of the PWM signal; Delay means for delaying, wherein the processor compares the counter value with a set comparison value for each of the timers. Stomach, has been mutually complement each other "1"
A fixed PWM signal having a fixed duty ratio per cycle of each carrier signal, wherein the fixed PWM signal is provided to one of the switching elements of the inverter circuit. And outputs an inverted PWM signal obtained by inverting the fixed PWM signal to the other switching element of the inverter circuit, thereby performing PWM control of the inverter circuit and detecting the inverted PWM signal by the current phase detection unit. The amount of heating of the cooker is controlled based on adjusting the frequency of the carrier signal while comparing the phase of the current with the phase of the fixed PWM signal.

According to such a configuration, the same effect as the third aspect can be obtained. Moreover, one having a plurality of timers
A processor with one built-in PWM function
The cost is lower than that of a processor having a built-in function, and the inversion signal generation means and the delay means are low in cost.

According to a fifth aspect of the present invention, there is provided an induction heating cooker comprising a snubber capacitor for reducing switching loss of the first and second switching elements, and a third switching element for controlling energization of the snubber capacitor. A snubber circuit configured, wherein the processor controls the energization of the third switching element by using the PWM signal for performing PWM control of the first and second switching elements as a trigger. According to such a configuration, the processor having the PWM function for driving the motor can perform the energization control of the snubber circuit in a software manner. Moreover, a program for controlling the snubber circuit can be easily formed.

An induction heating cooker according to a sixth aspect of the present invention includes an emergency stop means for detecting an abnormality in an external state and outputting an emergency stop signal, wherein the processor is adapted to receive the emergency stop signal from outside. Is characterized by comprising output stopping means for forcibly stopping the output of the PWM signal. According to such a configuration, for example, when an abnormality occurs in an external state such as a power supply, the abnormality can be immediately detected and the PWM control of the inverter circuit can be stopped. Accidents can be prevented beforehand.

In the induction heating cooker according to claim 7, the emergency stop means is configured to output the emergency stop signal when an input voltage to the inverter circuit is abnormally high. I do. According to such a configuration, when an abnormality occurs in the drive source of the inverter circuit,
Immediately detecting this, the PWM control of the inverter circuit can be stopped, and the same effect as in claim 6 can be obtained.

In the induction heating cooker according to the present invention, the emergency stop means is configured to output the emergency stop signal when a drive voltage of the processor is abnormally low. According to such a configuration, when an abnormality occurs in the drive source of the processor, the abnormality can be immediately detected and the PWM control of the inverter circuit can be stopped, and the same effect as that of claim 6 can be obtained.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] Hereinafter, an induction heating cooker according to the present invention is applied to an electromagnetic cooker having two heating coils and a half-bridge type inverter circuit. A first embodiment will be described with reference to FIGS.

FIG. 2 shows the appearance of the electromagnetic cooker 1. In FIG. 2, a top plate 3 made of heat-resistant glass is provided on the upper surface of the main body 2 having a rectangular shape. On the upper surface of the top plate 3, two circular heating ports 4 a for placing a cooker and 4b is printed. Heating coils 5a and 5b (not shown) are provided below the top plate 3 where the heating ports 4a and 4b are located.
(See FIG. 1).

On the right side of the front part of the main body 2, an operation section 6 having a heating start button 6a, a heating stop button 6b, a heating amount setting button 6c, a heating amount display section 6d, etc.
a and 4b. An electric circuit board (not shown) for controlling the drive of the electromagnetic cooker 1 is mounted on the back side of the operation unit 6. In addition, an opening / closing door 7 of a roaster built in the main body 2 is provided on the front left side of the main body 2.

Next, FIG. 1 is a block diagram showing an electric configuration of the electromagnetic cooker 1. As shown in FIG. In FIG. 1, although not shown, the control circuit 8 is composed of an electric circuit mainly composed of a microcomputer (hereinafter, simply referred to as a microcomputer). The electric control of the entire cooking device 1 is performed. The control circuit 8 includes an operation unit 6 and a DSP (digital signal processor) serving as a processor.
9 is connected to switches 12a and 12b for controlling conduction of PWM signals output from the DSP 9 to the drive circuits 11a and 11b, based on a heating command from the operation unit 6. , The DSP 9 and the conduction control of the switches 12a and 12b.

FIG. 3 shows a PW for driving a three-phase motor.
FIG. 2 is a block diagram showing an internal configuration of a general-purpose DSP 9 having a built-in M function. The DSP 9 has a high-speed operation processing type structure, and a main CPU (Central Processing Unit) 13
A serial communication function 10 for communicating with other microcomputers, an external interrupt function 14, a timer interrupt function 15,
An I / O function 16, a ROM 17, a RAM 18, an A / D converter 19, a watchdog timer function 20, and a PWM function 21 for generating three-phase (U, V, and W phases) PWM signals are connected.

The PWM function 21 includes a timer 21a for generating a carrier signal, a compare register 21b for storing a set comparison value, a comparison unit 21c for comparing the count value of the timer 21a with the comparison value, and a comparison unit 21c. Signal generation unit 21d that generates a three-phase PWM signal based on the output from the controller, a dead time generation unit 21e that generates a dead time based on the three-phase PWM signal, and a three-phase PWM signal including the dead time Which outputs PWM signals of U, _U, V, _V, W and _W phases (under bar means inverted phase) including inverted phase based on
It is composed of a signal output section 21f.

The DSP 9 operates by receiving an oscillation signal of a predetermined period from an oscillation circuit (not shown). Then, a PWM signal and a set control signal are generated and output based on the DSP control program written in the ROM 17.

Returning to FIG. 1, the U-phase PWM signal output terminal of the PWM signal output unit 21f of the DSP 9 is connected to the switch 12
a and 12b, are commonly connected to the drive circuits 11a and 11b, and the _V and _W phase PWM signal output terminals are
They are individually connected to the drive circuits 11a and 11b via the switches 12a and 12b. In DSP9,
A snubber control signal for controlling the energization of the IGBTs 23a and 23b, which are the third switching elements of the snubber circuits 22a and 22b described later, is generated, and the terminal set to output the snubber control signal is a switch 12
are commonly connected to the drive circuits 11a and 11b via the terminals a and 12b. Further, the A / D converter 19 of the DSP 9
Are current detectors 24a and 24b and voltage detectors 25a, 25b and 45 as emergency stop means (all described later).
It is connected to the.

The control circuit 8, the DSP 9, the switches 12a and 12b, the operation unit 6, the oscillation circuit, the drive circuit 1
1a and 11b, current detectors 24a and 24b, and
The voltage detectors 25, 25b, and 45 are configured to operate when a predetermined DC voltage is supplied from a constant voltage circuit (not shown).

Next, the configuration of the electromagnetic cooking units 26a and 26b will be described. Since the electromagnetic cooking units 26a and 26b are equivalent, only the electromagnetic cooking unit 26a will be described.
The electromagnetic cooking unit 26b is denoted by the reference numeral only, and the description is omitted. The commercial power supply 27 is connected to an AC input terminal of a rectifier circuit 28 composed of a diode bridge, and a DC output terminal of the rectifier circuit 28 is connected to a series circuit including a coil 29 and a smoothing capacitor 30. The rectifier circuit 28, the coil 29, and the smoothing capacitor 3
The DC voltage source 31 is constituted by 0.

A DC bus 32 is connected to a common connection point between the coil 29 and the smoothing capacitor 30, and a DC bus 33 is connected to the other end of the smoothing capacitor 30. Between the DC buses 32 and 33, a series circuit in which the emitter of the IGBT 34a as the second switching element and the collector of the IGBT 35a as the first switching element are connected such that the collector of the IGBT 34a is on the bus 32 side. Connected. The gates of the IGBTs 32 and 33 are connected to the V- and U-phase PWMs of the drive circuit 11a.
Connected to signal output terminal. (Note that the electromagnetic cooking unit 26
The gates of the IGBTs 34b and 35b in b are connected to the W and U phase PWM signal output terminals of the drive circuit 11b. In addition, freewheel diodes 36 and 37 are connected in parallel to the IGBTs 34a and 35a such that the anodes are on the emitter side. And
The IGBTs 34a and 35a and the freewheel diodes 36 and 37 form a half-bridge type inverter circuit 38a.

Between the output terminal 39 of the inverter circuit 38 and the bus 33, a heating coil 5a and a resonance capacitor 40 are provided.
Are connected in series to a resonance circuit 46a.
A diode 41 is connected in parallel to the resonance capacitor 40 such that the anode is on the bus 33 side.
The output terminal 39 of the inverter circuit 38 and the bus 33
Between one end of the snubber capacitor 42 and the IGBT 23a
Is connected so that the other end of the snubber capacitor 42 is on the output terminal 39 side. The snubber control signal output terminal of the drive circuit 11a is connected to the base of the IGBT 23a, and a diode 43 is connected between the collector and the emitter such that the anode is on the emitter side.
Note that this snubber circuit 22a is composed of IGBTs 34a and 35
This is for reducing the switching loss at the time of a. The DC voltage source 31, the inverter circuit 38, the snubber circuit 22a, the heating coil 5a and the like constitute an electromagnetic cooking unit 26a.

By the way, a current transformer 44 is inserted in the bus on the AC input terminal side of the rectifier circuit 28, and the current transformer 44 is connected to the current detector 24a. The current transformer 44 and the current detector 24a detect the input current to the inverter circuit 38 and
9 is output.

The bus 32 is connected to the voltage detector 25. The voltage detection unit 25 detects an input voltage to the inverter circuit 38 and outputs the detected voltage to the DSP 9, and outputs an emergency stop signal to the DSP 9 when the input voltage is higher than a predetermined voltage value (abnormally high). It is supposed to.

A voltage detector 45 is connected to a drive voltage input terminal (not shown) of the DSP 9. The voltage detector 45 detects the drive voltage of the DSP 9 and outputs an emergency stop signal to the DSP 9 when the drive voltage is lower than a predetermined voltage value (abnormally low).

<Explanation of Operation of Electromagnetic Cooker 1> Next, the operation of the electromagnetic cooker 1 will be described. Since the operations of the electromagnetic cooking units 26a and 26b are equivalent, only the operation of the electromagnetic cooker 26a will be described, and the explanation of 26b will be described. Shall be omitted.
Here, it is assumed that a heating start command is output from the operation unit 6 when the user presses the heating start button 6a, and the switches 12a and 12b are set to ON by the control circuit 8.

FIG. 4 shows a timing chart of each PWM signal generated based on the carrier signal. The DSP 9 repeats the operation of counting up the timer 21a in the PWM function 21 from zero to a predetermined value and resetting the timer 21a when the timer 21a reaches the predetermined value, whereby a carrier signal (for example, a triangular wave) having a constant period T (for example, 46 μs) is repeated.
Is generated (see FIG. 4A). Note that the carrier signal is not limited to a triangular wave.
May be configured as an up-down counter to generate a sawtooth wave.

First, a method of generating a U-phase PWM signal as a fixed PWM signal output to the gate of the IGBT 35a will be described. The compare register 21b stores the U-phase P
A comparison value in which the duty ratio of the WM signal is fixed to 50% is set in advance. In the comparing unit 21c, the comparison value is compared with the count value of the timer 21a.
The signal generation unit 21d generates a U-phase original signal that falls from a high level to a low level when the count value of the timer is zero, and rises from a low level to a high level when the count value matches the comparison value (FIG. 4). (B)).

In the dead time generation section 21e, based on the U-phase original signal, a U-shaped signal having a predetermined width as shown in FIG.
A phase dead time signal is generated, and the U phase dead time signal is added to the U phase original signal. PWM signal output unit 21
In FIG. 4F, the U-phase PWM signal which is low during the U-phase dead time period as shown in FIGS.
In addition, a _U-phase PWM signal having a complementary relationship with the PWM signal is generated. The U-phase PWM thus generated
The signal is output to the gate of IGBT 35a via drive circuit 11a. That is, the IGBT 35a uses the U-phase PW
Intermittent on / off control is performed at period T by the M signal.

Next, a method of generating a _V-phase PWM signal as a variable PWM signal to be output to the gate of the IGBT 34a will be described. The duty ratio of the V-phase comparison value set in the compare register can be adjusted from 50% to 100% by the external interrupt function 14. Then, by adjusting the duty ratio, the amount of high-frequency current supplied to the heating coil 5a is adjusted, that is, the amount of heating of the cooker placed in the heating port 4a is controlled. As described above, in the DSP 9, the fixed PW for the “1” phase
_V and _W corresponding to the U-phase PWM signal corresponding to the M signal and the variable PWM signal corresponding to the “number of electromagnetic cooking units” phase
A phase PWM signal is generated.

In the control circuit 8, the heating amount set by the heating amount setting button 6c is stored, and the set heating amount is output to the external interrupt function 14 of the DSP 9. DS
At P9, the amount of input power to the inverter circuit 38a is estimated and set based on integrating the input voltage value and the input current value to the inverter circuit 38a detected by the voltage detection unit 25a and the current detection unit 24a. A comparison value of the V phase for supplying an electric energy corresponding to the heating amount to the heating coil 5a is set. Then, in the same manner as in the case of the U-phase, a PWM signal of the _V phase, which is a fixed PWM signal, is generated through the comparison unit 21c, the PWM signal generation unit 21d, the dead time generation unit 21e, and the PWM signal output unit 21f. The PWM signal is transmitted to the IGB via the drive circuit 11a.
Output to the gate of T34a (FIGS. 4F to 4I)
reference).

Next, a method of generating a snubber control signal to be output to the gate of the IGBT 23a will be described. This snubber control signal is triggered by a point in time when the U-phase PWM signal rises from a low level to a high level as a trigger for a predetermined time Tα.
(E.g., 3 μs), the signal is generated such that the time when the _V-phase PWM signal falls from the high level to the low level becomes a trigger after a predetermined time Tβ (eg, 3 μs) elapses (FIG. 4 (j)). )reference). The snubber control signal is transmitted to the CPU 5 of the DSP 9.
1 is generated in a software manner by the DSP control program.

The IGBT 23a responds to this snubber control signal for a predetermined time T after the IGBT 35a is turned on.
It turns on after elapse of α, and turns off after a certain time Tβ elapses after the IGBT 34a turns off. Thereby, IGB
When T34a and 35a shift from the on state to the off state, the voltage change between each collector and emitter is moderated to prevent the occurrence of switching loss, and the IGB
The short-circuit current is also prevented from flowing through the snubber capacitor 42 when T35a is turned on.

The U-phase PWM signal is output to the gate of the IGBT 35b of the electromagnetic cooking unit 26b.
The _W-phase PWM signal generated in the same manner as the _V-phase PWM signal is output to the gate of T34b. Similarly to the snubber control signal, a snubber control signal that goes high based on the U-phase PWM signal and goes low level based on the _W-phase PWM signal is output to the gate of the IGBT 23b (see FIG. 4). 4 (k) to (o)).

As described above, in the electromagnetic cooking units 26a and 26b, the IGBTs 34a and 35a or the IGBTs
While alternately turning on 34b and 35b, _V and _
By adjusting the duty ratio of the W-phase PWM signal, a high-frequency current is supplied to the heating coils 5a and 5b,
The cookers placed in the heating ports 4a and 4b are heated.

While the PWM control of the electromagnetic cooking units 26a and 26b is being performed, the inverter circuits 38 in the voltage detection units 25a and 25b are used.
Abnormality detection of the input voltage to a and 38b and the drive voltage of the DSP 9 is performed. When an abnormality is detected and an emergency stop signal is output, the DSP serving also as an output stop unit
In No. 9, the output of all the PWM signals is forcibly stopped (to a low level), and the PWM control for the inverter circuits 38a and 38b is stopped.

In order to stop the heating of the cooker, the user only has to press the heating stop button 6b of the operation unit 6. In this case, the control circuit 8 controls the switches 12a and 12b.
b is set to off, and all IGBTs 34a, 34b,
35a, 35b, 23a and 23b are turned off, and supply of the high-frequency current to the heating coils 5a and 5b is stopped.

FIG. 5 shows each of the IGBTs 34a, 34b,
5 shows a timing chart of a PWM signal output to gates of 35a, 35b, 23a and 23b.
As described above, in the first embodiment, the DSP 9 estimates the input electric energy based on detecting the input voltage value and the input current value to the inverter circuits 38a and 38b,
PWM control of the IGBTs 34a and 34b by adjusting the duty ratio of the _V-phase and _W-phase PWM signals so that a high-frequency current corresponding to the heating amount set by the heating amount setting button 6c is supplied to the heating coils 5a and 5b. To do. In addition, the IGBTs 35a and 35a are commonly used with a U-phase PWM signal having a fixed duty ratio.
b) PWM control is performed. Furthermore, U-phase PWM
The energization control of the IGBTs 23a and 23b of the snubber circuits 22a and 22b is performed by a snubber control signal that becomes high level at the time of rising of the signal and becomes low level at the time of falling of the PWM signal of _V phase or _W phase. .

According to such a configuration, since the DSP 9 having the PWM function 21 for driving the motor is mass-produced and supplied at a low price, the DSP 9 is compared with the case where the PWM function 21 is formed by an individual semiconductor or an ASIC. Thus, the manufacturing cost of the electromagnetic cooker 1 can be reduced. Moreover, by using the DSP 9 having the PWM function 21 for driving the motor,
It is not necessary to newly develop a microcomputer having a PWM function for driving the half-bridge type inverter circuits 38a and 38b, and the development period of the electromagnetic cooker 1 can be shortened. Therefore, the electromagnetic cooker 1 including the high-performance half-bridge type inverter circuits 38a and 38b can be provided at low cost.

The PWM function 21 for driving the motor is
Since the PWM signal can be easily generated based on the setting of the comparison value and the frequency of the carrier signal, the compare register 2 can be generated in a different manner from the case where the motor is normally driven.
By adjusting the comparison value of 1b, the half-bridge type inverter circuits 38a and 38b can be easily driven. In addition, since the frequency of the carrier signal and the comparison value of the U phase are fixed, and the comparison values of the V and W phases are merely adjusted, the amount of electric power of the high-frequency current supplied to the inverter circuits 38a and 38b, that is, the heating amount can be adjusted. The PWM control of the inverter circuits 38a and 38b is simple, and the control program can be easily created.

Since the PWM signal of each phase is generated based on the common timer 21a, the two heating coils 5
The fundamental frequencies of the high-frequency currents supplied to a and 5b can be made equal, and the occurrence of beats can be suppressed.

Further, such a general-purpose motor driving P
In the DSP 9 having the WM function 21, the snubber circuit 22a
And 22b. Moreover, a control program for controlling the snubber circuits 22a and 22b can be simplified.

Further, when the input voltage to the inverter circuits 38a and 38b is abnormally high or when the drive voltage of the DSP 9 is abnormally low, it is detected immediately and the PWM control of the inverter circuits 38a and 38b is stopped. Therefore, it is possible to prevent a failure of the inverter circuits 38a and 38b and an accident associated therewith.

[Second Embodiment] Hereinafter, a second embodiment in which the induction cooking device of the present invention is applied to an electromagnetic cooking device having two heating coils and having a half-bridge type inverter circuit. An example will be described with reference to FIGS. The same parts as those in the first embodiment are denoted by the same reference numerals and the description thereof will be omitted, and only different parts will be described below.

First, FIG. 6 is a block diagram showing an electric configuration of the electromagnetic cooker 50. In FIG. 6, DS
P51 is a general-purpose P51 having two PWM functions 52a and 52b built therein so that two three-phase motors can be driven (see FIG. 7). Note that these PWM functions 52a and 5a
2b has the same configuration as the PWM function 21 shown in the first embodiment. Then, both of these PWM functions 52a and 52b are provided with electromagnetic cooking units 53a and 53b, respectively.
b is used for PWM control. For example, the connection configuration of the PWM function 52a and the electromagnetic cooking unit 53a will be described.
And _U are connected to the drive circuit 11a via the switch 12a. The connection configuration of the PWM function 52b and the electromagnetic cooking unit 53b is the same as the above.

Next, the configuration of the electromagnetic cooking units 53a and 53b will be described. Since the electromagnetic cooking units 53a and 53b are equivalent, only the electromagnetic cooking unit 53a will be described.
The electromagnetic cooking unit 53b is denoted by the reference numeral only, and the description is omitted.

In the electromagnetic cooking unit 53a, the bus bar 32,
A resonance capacitor 54 is connected between the heating coil 5a and a common connection point of the resonance capacitor 40. The IGBTs 34a and 35b of the inverter circuit 38a
, Snubber capacitors 55 and 56 are connected between the collector and the emitter. Further, IGBTs 34a and 3
A current transformer 57 is interposed between the common connection point 5a and the heating coil 5a, and the current transformer 57 is connected to a current phase detection unit 58a as current phase detection means.
The current transformer 57 and the current phase detector 5
At 8a, the phase of the input current to the heating coil 5a is detected and output to the DSP 9. The heating coil 5a and the resonance capacitors 40 and 54 constitute a resonance circuit 59a having a predetermined resonance frequency, and the heating coil 5b and the resonance capacitors 40 and 54 constitute a resonance circuit 59b having a predetermined resonance frequency. Have been.

<Description of Operation of Electromagnetic Cooker 50> Next, the operation of the electromagnetic cooker 50 will be described. In the second embodiment, since the operations of the electromagnetic cooking units 53a and 53b are equivalent, only the 53a will be described, and the description of the 53b will be omitted. Here, when the user presses the heating start button 6a, a heating command is output from the operation unit 6, and the control circuit 8 switches the switches 12a and 12a.
It is assumed that b is set to ON.

FIG. 8 shows PWM signals generated by the PWM functions 52a and 52b based on respective carrier signals.
4 shows a timing chart of signals. Hereinafter, P
The operation of the WM function 52a will be described as an example. DSP5
In step 1, as in the first embodiment, a carrier signal (for example, a triangular wave) having a predetermined period T1 is generated by a timer (not shown) (see FIG. 8A). However, by adjusting the count value (reset value) for resetting the timer by the timer interrupt function 15, the period T1 of the carrier signal is adjusted.
(Frequency) is adjustable.

As in the first embodiment, a U-phase PWM as a fixed PWM signal is stored in a compare register (not shown).
A comparison value in which the duty ratio of the signal is fixed to 50% is set in advance. As a result, a U-phase original signal is generated (see FIG. 8B), a U-phase dead time signal is generated (see FIG. 8C), the U-phase PWM signal and the inverted PWM signal are generated.
A PWM signal of the _U phase, which is a signal, is generated (FIG. 8D).
And (e)). Then, the U-phase and _U-phase PWM signals of the cycle T1 are output to the IGBTs 34a and 35a,
When the IGBTs 34a and 35a are turned on alternately, a high-frequency current is supplied to the heating coil 5a.
Heating to the cooker placed in a is performed.

The gates of the IGBTs 34b and 35b of the electromagnetic cooking unit 53b have U-phase fixed PWM signals, which are generated by the PWM function 52b based on carrier signals of a predetermined period T2, in the same manner as the PWM function 52a. P
The PWM signal of the _U phase, which is the WM signal and the inverted PWM signal, is output (see FIGS. 8F to 8J). As described above, in the DSP 51, each of the PWM functions 52a and 52b
In each case, the U-phase P corresponding to the fixed PWM signal for “1” phase
WM signal and _U-phase PWM corresponding to inverted PWM signal
A signal is generated.

The control of the heating amount by the DSP 51 is as follows.
This is performed as follows. First, when the heating amount set in the control circuit 8 is output to the external interrupt function of the DSP 51, the DSP 9 estimates the input electric energy to the inverter circuit 38a in the same manner as in the first embodiment. Then, so that the input power amount becomes the power amount according to the heating amount,
The frequency control of the U-phase and _U-phase PWM signals is performed.

Specifically, when the input electric energy is lower than the electric energy corresponding to the heating amount, the phase of the high-frequency current and the P
By bringing the phase of the PWM signal closer to the resonance frequency of the resonance circuit 59a,
Increase the input power. Conversely, when the input electric energy is higher than the electric energy corresponding to the heating amount, the phase of the high-frequency current is separated from the phase of the PWM signal, and the frequency of the PWM signal is changed to the resonance frequency of the resonance circuit 59a. Away from the input power to reduce the amount of input power.

As described above, in the electromagnetic cooking units 53a and 53b, the IGBTs 34a and 35a or the IGBTs
While turning on 34b and 35b alternately, the PWM
By adjusting the frequency of the signal, a high-frequency current is supplied to the heating coils 5a and 5b, and the cookers placed at the heating ports 4a and 4b are heated.

FIG. 9 is a timing chart of a PWM signal output to the bases of the IGBTs 34a, 34b, 35a and 35b in the electromagnetic cookers 53a and 53b. As described above, in the second embodiment, the DSP 5
In step 1, the phase difference between the phases of the high-frequency current supplied to the heating coils 5a and 5b and the phases of the U and _U-phase PWM signals is detected, and the phase difference corresponding to the heating amount set by the heating amount setting button 6c The high frequency current is applied to the heating coils 5a and 5
b of the PWM signal to be supplied to
2 to adjust IGBTs 34a, 34b, 35a and 35
b) PWM control is performed.

According to such a configuration, the PWM functions 52a and 52b for driving the motor can easily output the PWM signal based on the comparison value and the setting of the period T1 and T2 of the carrier signal. The half-bridge type inverter circuits 38a and 38b can be easily driven by fixing the comparison value and adjusting the periods T1 and T2 of the carrier signal by a method different from the method for driving the motor. Moreover, the amount of high-frequency current supplied to the inverter circuits 38a and 38b, that is, the amount of heating can be adjusted only by fixing the comparison value of each phase and changing the periods T1 and T2 of the carrier signal. The PWM control of 38b is simple, and the control program can be easily created.

Third Embodiment Hereinafter, a third embodiment in which the induction heating cooker of the present invention is applied to an electromagnetic cooker having two heating coils and having a half-bridge type inverter circuit will be described. An example will be described with reference to FIGS. The same parts as those in the second embodiment are denoted by the same reference numerals and the description thereof will be omitted, and only different parts will be described below.

First, FIG. 10 is a block diagram showing an electric configuration of the electromagnetic cooker 70. In FIG.
The DSP 71 includes a PWM function 73 including two timers 72a and 72b, the same number as the electromagnetic cooking units 53a and 53b, so that, for example, in an active inverter circuit, PWM control and PAM control of one three-phase motor can be performed. It is built-in general purpose.

FIG. 11 is a block diagram showing the internal configuration of the DSP 71. In FIG. 11, the PWM function 73 includes timers 72a and 72 for generating a carrier signal.
b, compare registers 74a and 74b for storing the set comparison values, comparison units 75a and 75b for comparing the count values of the timers 72a and 72b with the comparison values, based on the outputs from the comparison units 75a and 75b, PWM for generating independent PWM signals (PAM signals are also possible)
Signal generating unit 76, a PWM for outputting these PWM signals
It comprises a signal output unit 77.

The PWM function 73 generates and outputs a "1" -phase PWM signal (for example, corresponding to the U-phase PWM original signal of the second embodiment) for each of the timers 72a and 72b. Has become. Then, for example, the PWM function 73
And the connection configuration of the electromagnetic cooking unit 53a will be described.
The U-phase PWM signal output terminal of the PWM signal output unit 77
While connected to the IGBT 34a via the delay unit 79a serving as a delay unit, the switch 12a, and the drive circuit 11a,
Inverted signal generator 78a as an inverted signal generator, delay unit 7
9a, the switch 12a, and the IG through the drive circuit 11a.
It is connected to the BT 35a. The connection configuration of the PWM function 73 and the electromagnetic cooking unit 53b is the same as the above.

<Description of Operation of Electromagnetic Cooker 70> Next, the operation of the electromagnetic cooker 70 will be described. In the third embodiment, as in the second embodiment, a fixed PWM signal and an inverted PWM signal are generated and the frequency of each PWM signal is adjusted, so that the inverter circuits 38a and 38b have the same PWM.
Since the WM control is performed, the description of the PWM control is omitted, and only the operation of generating the fixed PWM signal and the inverted PWM signal will be described. In addition, since the operations of generating the PWM signals of the electromagnetic cooking units 53a and 53b are the same, only the 53a side will be described, and the description of the 53b side will be omitted.

In the DSP 71, similarly to the first embodiment, a carrier signal (for example, a triangular wave) having a predetermined period T1 is generated by the timer 72a (corresponding to FIG. 8A).
However, by adjusting the count value (reset value) for resetting the timer by the timer interrupt function 15, the period T1 (frequency) of the carrier signal can be adjusted. In the compare register 74a, similarly to the first embodiment, a comparison value in which the duty ratio of the U-phase PWM signal, which is a fixed PWM signal, is fixed at 50% is set in advance. As a result, a U-phase original signal is generated (FIG. 8B).
) Is output.

The U-phase original signal output to the delay unit 79a is:
The delay unit 79a takes into account the delay time (low level) corresponding to the dead time when the waveform rises, and sets a fixed PWM.
A U-phase PWM signal as a signal is generated, and the IGBT 34a
(Corresponding to FIG. 8D). The U-phase original signal output to the inverted signal generation unit 78a is inverted between the low level and the high level by the inverted signal generation unit 78a, and the delay unit 79a delays the dead time corresponding to the dead time when the waveform rises. (Low level) is added to generate a _U-phase PWM signal, which is an inverted PWM signal, and the IGBT 35a
(Equivalent to FIG. 8E). As described above, in the DSP 71, for each of the timers 72a and 72b,
A fixed PWM signal for “1” phase is generated.

With such a configuration, the electromagnetic cooking units 53a and 53b can use the IG
BT34a and 35a or IGBT34b and 35b
By alternately turning on, while adjusting the frequency of the PWM signal, a high-frequency current is supplied to the heating coils 5a and 5b, and the cookers placed at the heating ports 4a and 4b are heated.

Thus, the same effect as the third aspect can be obtained. In addition, the DSP 71 having one PWM function 73 having two timers 72a and 72b is less expensive than the DSP 51 having two PWM functions 52a and 52b, and the inverted signal generators 78a and 78b and the delay Since the parts 79a and 79b can also be configured at low cost, the manufacturing cost of the electromagnetic cooker 79 can be further reduced.

The present invention is not limited to the embodiment described above and shown in the drawings.
Extension is possible. In the embodiment of the present invention, the induction heating cooker is applied to the electromagnetic cooker. However, the present invention is not limited to this, and may be applied to, for example, an electric rice cooker and a microwave oven. In the embodiment of the present invention, the processor is applied to the DSP. However, the present invention is not limited to this. For example, the processor may be applied to a RISC microcomputer having a built-in PWM function.
In short, any processor can be used as long as it is inexpensive and is a high-speed arithmetic processing type with a built-in PWM function for motor drive, and can perform PWM control of a half-bridge type inverter circuit using this PWM function. .

In the embodiment of the present invention, the processor is applied to a DSP having a PWM function for driving a three-phase motor. However, the present invention is not limited to this. For example, a processor having a PWM function for driving a single-phase motor is provided. It may be applied to a DSP. Further, the phase of the PWM signal for controlling the first switching element and the second switching element is not limited to that shown in the embodiment, and any phase may be used.

In the embodiment of the present invention, the switching element is applied to the IGBT. However, the present invention is not limited to this. For example, the switching element may be applied to a MOSFET or a bipolar transistor. Although the snubber circuit is provided in the first embodiment of the present invention, this snubber circuit may be provided as needed. Although the emergency stop means and the output stop means are provided in the embodiment of the present invention, the emergency stop means and the output stop means may be provided as necessary.

In the embodiment of the present invention, the input power amount is estimated by integrating the input voltage value and the input current value to the inverter circuit detected by the voltage detection unit and the current detection unit, and the input power amount is set. The duty ratio or the frequency of the PWM signal is adjusted so that the amount of power corresponds to the amount of heat generated, but the present invention is not limited to this. For example, without providing the voltage detection unit and the current detection unit , Heating amount and P
The correspondence between the duty ratio and the frequency of the WM signal may be converted into data and recorded in advance, and the duty ratio or the frequency may be set with reference to the correspondence.

[0079]

As is apparent from the above description, the induction heating cooker according to the present invention has a motor drive for generating a PWM signal for "the number of electromagnetic cooking units + 1" phase based on a common carrier signal. A fixed PWM signal for a “1” phase with a fixed duty ratio by a processor having a built-in PWM function,
The fixed PWM signal has an opposite phase relationship, and the variable PWM for the “number of electromagnetic cooking units” phase in which the duty ratio is adjusted according to the set heating amount so as not to overlap each other.
And PWM control for alternately turning on and off both switching elements of the half-bridge type inverter circuit based on these PWM signals. Therefore, when the PWM function is configured by an individual semiconductor or an ASIC, In addition, the manufacturing cost can be reduced, and a control program for performing PWM control of the inverter circuit can be developed in a short period of time. Therefore, an induction circuit having an inexpensive and high-performance half-bridge type inverter circuit can be provided. A cooking device can be provided.

[Brief description of the drawings]

FIG. 1 is an electric block diagram of an electromagnetic cooker according to a first embodiment of the present invention.

FIG. 2 is a perspective view of an electromagnetic cooker.

FIG. 3 is an electric block diagram showing an internal configuration of the DSP.

FIG. 4 is a timing chart of each PWM signal generated based on a carrier signal.

FIG. 5 is a timing chart of a PWM signal output to each switching element.

FIG. 6 is a view corresponding to FIG. 1, showing a second embodiment of the present invention;

FIG. 7 is a diagram corresponding to FIG. 3;

FIG. 8 is a diagram corresponding to FIG. 4;

FIG. 9 is a diagram corresponding to FIG. 5;

FIG. 10 is a view corresponding to FIG. 1, showing a third embodiment of the present invention.

FIG. 11 is a diagram corresponding to FIG. 3;

FIG. 12 is a diagram corresponding to FIG. 1 showing a conventional example.

[Explanation of symbols]

In the drawings, 1, 50 and 70 are electromagnetic cookers (induction heating cookers), 5a and 5b are heating coils, 6 is an operation unit, 8 is a control circuit, and 9, 51 and 71 are DSPs (processors, output stopping means). , 13 are a CPU, 21, 52a, 52b and 73 are PWM functions, 21a, 72a and 72b are timers, 22
a and 22b are snubber circuits, 23a and 23b are IGBTs
(Third switching element), 24a and 24b are current detection units, 25a, 25b and 45 are voltage detection units (emergency stop means), 26a, 26b, 53a and 53b are electromagnetic cooking units,
34a, 34b are IGBTs (second switching elements), 35a, 35b are IGBTs (first switching elements), 38a, 38b are half-bridge type inverter circuits, 46a, 46b, 59a, 59b are resonance circuits,
58a, 58b are current phase detectors (current phase detectors)
Is shown.

────────────────────────────────────────────────── ─── of the front page continued (51) Int.Cl. ⁷ identification mark FI theme Court Bu (reference) H02M 7/48 H02M 7/48 D (72 ) inventor Hitoshi Takimoto Seto City, Aichi Prefecture Anada-cho, 991 address, Ltd. East Inside Shiba Aichi Factory (72) Inventor Hidetake Hayashi 991 Anada-cho, Seto-shi, Aichi F-term in Higashishiba Aichi Factory (reference) 3K051 AA02 AC03 AC07 AC26 AD12 CD02 CD05 5H007 BB04 BB11 CA01 CB04 CB17 CB22 CC23 DA04 DB01 DC02 DC05 EA02

Claims (8)

[Claims] 1. A half-bridge type inverter comprising a resonance circuit comprising a heating coil for heating a cooker and a resonance capacitor, and a series circuit of first and second switching elements and supplying a high-frequency current to the resonance circuit. One or more electromagnetic cooking units forming a pair with a circuit; and a PWM for driving a motor that generates PWM signals for a plurality of phases based on a common carrier signal generated by a timer.
An induction heating cooker having a built-in function and a processor for performing PWM control of the inverter circuit based on the PWM function. 2. The processor according to claim 2, wherein the processor has a built-in PWM function capable of generating a PWM signal of “the number of the electromagnetic cooking units + 1” or more phases based on the common carrier signal. Based on the comparison between the count value and the set comparison value, mutually complementary PWM signals for the “number of electromagnetic cooking units + 1” phase are configured to be output, and 1 of the carrier signal is output. A fixed PWM signal for "1" phase having a fixed duty ratio per cycle, and the fixed PWM signal
A variable PWM signal corresponding to the “number of the electromagnetic cooking units” phase in which the duty ratio per cycle of the carrier signal is set to be adjustable so as not to overlap with the M signal is generated. The PWM control is performed by outputting the fixed PWM signal to one switching element of the inverter circuit and outputting the variable PWM signal to the other switching element of the inverter circuit. The induction heating cooker according to claim 1, wherein an amount of heating to the cooker is controlled based on adjusting a duty ratio of a PWM signal. 3. A motor driving PWM capable of generating a PWM signal based on the common carrier signal, comprising: a current phase detecting means for detecting a phase of a current flowing through the heating coil. The same number of functions are built in as the electromagnetic cooking unit,
For each WM function, based on comparing the count value of the timer with a set comparison value, mutually complementary PWM signals of “1” phase are output, and the carrier signal A fixed PWM signal having a fixed duty ratio per cycle and an inverted PWM signal having a mutually complementary relationship with the first fixed PWM signal are generated. One of the switching elements of the inverter circuit includes: The PWM control is performed by outputting a fixed PWM signal and outputting the inverted PWM signal to the other switching element of the inverter circuit, and the phase of the current detected by the current phase detection means; Adjusting the frequency of the carrier signal while comparing the phase of the fixed PWM signal or the inverted PWM signal with the phase of the carrier signal, Induction heating cooker of claim 1, wherein the controlling the amount. 4. A half-bridge type inverter comprising a resonance circuit comprising a heating coil for heating a cooker and a resonance capacitor, and a series circuit comprising first and second switching elements and supplying a high-frequency current to the resonance circuit. It has one or more electromagnetic cooking units that make a pair with a circuit, and the same number of timers as the electromagnetic cooking units. Based on each carrier signal generated by each of the timers, it is possible to generate an independent PWM signal. A high speed arithmetic processing type processor having a built-in PWM function for driving a motor, an inversion signal generation means for generating an inversion signal of the PWM signal, and a delay means for delaying the PWM signal and the inversion signal, The processor complements each other for each of the timers based on comparing the counter value with a set comparison value. And generating a fixed PWM signal having a fixed duty ratio per one cycle of each of the carrier signals, wherein one of the switching elements of the inverter circuit includes the fixed PWM signal. The PWM control of the inverter circuit is performed by outputting a PWM signal and outputting an inverted PWM signal obtained by inverting the fixed PWM signal to the other switching element of the inverter circuit. Induction heating cooking, wherein a heating amount to the cooker is controlled based on adjusting a frequency of the carrier signal while comparing a phase of the detected current with a phase of the fixed PWM signal. vessel. 5. A snubber circuit comprising a snubber capacitor for reducing a switching loss of the first and second switching elements, and a third switching element for controlling energization of the snubber capacitor, The processor controls the energization control of the third switching element so that a short circuit current does not flow through the third switching element by using the PWM signal for performing PWM control of the first and second switching elements as a trigger. The induction heating cooker according to any one of claims 1 to 4, wherein the cooking is performed. 6. An emergency stop means for detecting an abnormality in an external state and outputting an emergency stop signal, wherein the processor outputs the PWM signal when the emergency stop signal is input from outside. 2. An output stopping means for forcibly stopping the power supply.
6. The induction heating cooker according to any one of claims 1 to 5. 7. The induction heating cooking according to claim 6, wherein the emergency stop means is configured to output the emergency stop signal when the input voltage to the inverter circuit is abnormally high. vessel. 8. The induction heating cooker according to claim 6, wherein the emergency stop means is configured to output the emergency stop signal when a drive voltage of the processor is abnormally low.