JP2019071242A - Electromagnetic induction heating device - Google Patents

Abstract

To provide an electromagnetic induction heating device capable of acquiring a zero-cross point or a frequency of an AC power source without performing rectification such as full wave rectification, with a relatively simple hardware configuration.SOLUTION: A part of configuration born by the hardware of zero-cross detection is realized by a software, by building zero-cross detection means 22 for detecting a zero-cross point of a signal source 1' in a microcomputer 11 for controlling electrification of heating means. Furthermore, a voltage of the signal source 1' at a neutral line N side and the voltage at a voltage line L side are divided, respectively, and a digital signal obtained therefrom by an A/D converter 21 is taken into the microcomputer 11. With such an arrangement, the zero-cross point of the voltage of the signal source 1' can be acquired by a relatively simple configuration of a voltage-dividing circuit 4 and the microcomputer 11, without performing rectification such as full wave rectification.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an electromagnetic induction heating apparatus provided with heating means for electromagnetically heating an object to be heated, and more particularly to an electromagnetic induction heating apparatus provided with a zero-cross detection function to control energization of the heating means.

  Generally, as shown in Patent Document 1, this type of electromagnetic induction heating device rectifies an AC voltage supplied from an AC power source with a zero cross detection means to detect a zero cross point, and transmits the timing of the zero cross to the control means It is disclosed that the control means controls the energization of the heating coil serving as the heating means.

Unexamined-Japanese-Patent No. 2009-295392

  In a conventional electromagnetic induction heating apparatus such as Patent Document 1, a rectifier for rectifying an AC voltage to detect the zero crossing point of an AC power supply, a photo coupler whose voltage value changes in synchronization with the timing of the zero crossing, etc. It is necessary to configure the zero-crossing detection circuit provided with the above-mentioned detection element by hardware. However, since such a circuit uses a plurality of elements, the addition of a detection circuit for performing zero-cross detection has been concerned with an increase in cost and a decrease in accuracy due to variations in components.

  In view of the above problems, the present invention provides an electromagnetic induction heating apparatus capable of acquiring the zero crossing point and frequency of an AC power supply without performing rectification such as full wave rectification with a small number of relatively simple hardware configurations. To that purpose.

  An electromagnetic induction heating apparatus according to claim 1 of the present invention comprises heating means for electromagnetic induction heating an object to be heated by receiving electric power from an AC power supply, control means for controlling energization to the heating means, and the AC power supply. A first voltage dividing circuit for dividing a voltage at one end side, a second voltage dividing circuit for dividing a voltage at the other end of the AC power supply, and an output signal from the first voltage dividing circuit And a second A / D converter for taking the output signal from the second voltage divider circuit into the control means, the control means comprising An AC power supply of the AC power supply by a digital signal acquired from the first A / D converter and a digital signal acquired from the second A / D converter to control energization of the heating means; Having a zero cross detection means to detect the zero cross point And butterflies.

  The electromagnetic induction heating apparatus according to claim 2 of the present invention is characterized in that the control means comprises power supply frequency acquisition means for measuring the timing of the zero crossing point to acquire the frequency of the AC power supply.

  According to the invention of claim 1, the zero cross detection means for detecting the zero cross point of the alternating current power supply is incorporated in the control means for controlling the energization of the heating means as a software configuration, thereby providing the hardware of the zero cross detection. By partially dividing the voltage at one end of the AC power supply and the voltage at the other end, and taking the digital signal obtained by the A / D converter from there into the control means. With a few relatively simple hardware configurations, it is possible to obtain the AC power supply's zero crossing point without rectification such as full wave rectification.

  According to the invention of claim 2, based on the zero crossing point detected by the zero crossing detection means, the timing is measured by the power supply frequency acquiring means incorporated as a software configuration in the control means as well as the zero crossing detection means. With a relatively simple hardware configuration, it is possible to obtain the frequency of the AC power supply without performing rectification such as full-wave rectification.

It is a block diagram of an electromagnetic induction heating device showing a 1st embodiment of the present invention. It is a block diagram of a zero crossing detection apparatus same as the above. FIG. 6 is a waveform diagram of digital signals acquired by the first A / D converter and the second A / D converter. It is a flowchart which shows the detection of the zero crossing point of a signal source same as the above, and the acquisition procedure of frequency. It is a flowchart which shows the detection of the zero crossing point of a specific signal source same as the above, and the acquisition procedure of frequency. It is a wave form diagram of the signal acquired by the same 1st A / D converter and 2nd A / D converter, and each numerical value calculated within a microcomputer. It is a flowchart which shows the acquisition procedure of the voltage of a signal source same as the above. FIG. 10 is an ideal voltage waveform diagram of a collector-emitter voltage of an IGBT, a detection signal from a trigger detection circuit, and a gate voltage of the IGBT according to a second embodiment of the present invention. It is a voltage waveform diagram of the voltage between the collector and the emitter of the IGBT, the detection signal from the trigger detection circuit, and the gate voltage of the IGBT at the same time when the short circuit current is generated. It is a voltage waveform diagram of the voltage between the collector and the emitter of the IGBT, the detection signal from the trigger detection circuit, and the gate voltage of the IGBT when the delay time is adjusted. In the 3rd Embodiment of this invention, it is the wave form diagram which measured the input current and input voltage when electromagnetic induction heating is turned ON. It is a circuit block diagram of the fault detection circuit which shows the 5th Embodiment of this invention, and its periphery. The same as above, the voltage of the signal source, the first digital value obtained by A / D converting the voltage of the first analog input port, and the voltage of the second analog input port when the diode for backflow failure fails are A / D. It is a wave form diagram of the converted 2nd digital value and the 2nd threshold. Same as above, when the peak hold circuit fails, the voltage of the signal source, the first digital value obtained by A / D converting the voltage of the first analog input port, and the voltage of the second analog input port are A / D converted It is a wave form diagram of the 2nd digital value and the 1st threshold.

  Hereinafter, each embodiment of the electromagnetic induction heating device in the present invention will be described with reference to the attached drawings. Note that, in all the drawings, common parts are given common reference numerals. Further, the electromagnetic induction heating device described here can be applied to a copying machine that heats a toner as an object to be heated, a cooker that heats a pan containing the object to be cooked, and the like.

  FIG. 1 is a block diagram showing a first embodiment of an electromagnetic induction heating device according to the present invention. In FIG. 1, reference numeral 1 denotes an alternating current (AC) power source such as a commercial power source, and 2 denotes a rectifying and smoothing circuit that rectifies and smooths AC power supplied from the AC power source 1 and converts it into DC power. Therefore, this rectifying and smoothing circuit 2 can be regarded as a DC power supply that supplies DC power. An input current detection circuit 3 for detecting an input current from an AC power supply 1 and a voltage dividing circuit 4 for dividing an AC voltage supplied from the AC power supply 1 are connected to the input side of the rectifying and smoothing circuit 2.

  Reference numeral 5 denotes a resonant coil as heating means for electromagnetic induction heating an object to be heated (not shown) with an alternating magnetic field on the output side of the rectifying and smoothing circuit 2 on the DC power supply side. The resonant coil 5 forms an LC resonant circuit 6 Resonant capacitors 7 are connected in parallel. Reference numeral 8 denotes a switching element such as an IGBT (Insulated Gate Bipolar Transistor), and the series circuit of the LC resonant circuit 6 and the switching element 8 described above is connected between the output side terminals of the rectifying and smoothing circuit 2. By connecting, the oscillation circuit 9 for supplying a high frequency current to the LC resonant circuit 6 is configured by interrupting the DC power from the rectifying and smoothing circuit 2 to the LC resonant circuit 6 with the switching operation of the switching element 8.

  The oscillation circuit 9 of the present embodiment uses a single-ended resonant high frequency inverter with a simple circuit configuration and a small number of parts. The single-ended resonant high frequency inverter uses a single switching element 8 and is widely used because of its low cost.

  Reference numeral 10 denotes a drive circuit connected to, for example, the gate of an IGBT which is a control terminal of the switching element 8. The drive circuit 10 sends a pulse drive signal to the control terminal of the switching element 8 in response to a control signal from the microcomputer 11, and the microcomputer 11 here is from the resonant coil 5 to the object to be heated. In order to perform the electromagnetic induction heating, the control means is provided as a control means for controlling the operation of the switching element 8 and hence the energization of the LC resonant circuit 6. Further, an input voltage detection circuit 12 is connected between the output side terminals of the rectifying and smoothing circuit 2 and detects a DC input voltage from the rectifying and smoothing circuit 2 to the oscillation circuit 9.

  FIG. 2 is a block diagram showing a configuration of the zero cross detection device 15 including the voltage dividing circuit 4 described above. 1 'is a signal source such as a commercial power source, for example, and corresponds to the AC power source 1 described above. When the distribution system of the signal source 1 ′ is a single-phase two-wire system, one end of the AC power supply 1 is a neutral wire N corresponding to the ground side, and the other end of the AC power supply 1 is a voltage line L corresponding to the ungrounded side. It becomes.

  The voltage dividing circuit 4 includes a first voltage dividing circuit 4A that divides the voltage on the neutral wire N side of the signal source 1 ′ and a second voltage dividing circuit that divides the voltage on the voltage line L side of the signal source 1 ′. And 4B. The first voltage dividing circuit 4A is configured by connecting voltage dividing resistors 16 and 17 in series between the neutral wire N and the ground line, and the first A / D converter incorporated in the microcomputer 9 The connection point of the voltage dividing resistors 16 and 17 is connected to the input terminal 21A. The second voltage dividing circuit 4B is configured by connecting voltage dividing resistors 18 and 19 in series between the voltage line L and the ground line, and a second A / D converter incorporated in the microcomputer 9 The connection point of the voltage dividing resistors 18 and 19 is connected to the input terminal 21B.

  When the distribution method of the signal source 1 ′ is a single-phase three-wire system, the voltage of one voltage line L from the signal source 1 ′ is divided by the first voltage dividing circuit 4A, and the other The voltage of the voltage line may be divided by the second voltage dividing circuit 4B. Further, voltage dividing resistors 16 and 17 may be connected between the neutral line N and the voltage line L, not between the neutral line N and the ground line.

  The first A / D converter 21A is for taking in the first output signal from the first voltage dividing circuit 4A to the microcomputer 11, and the first output signal is the first A / D converter 21A. Are converted to a first digital signal and sent to the microcomputer 11. The second A / D converter 21B is for taking in the second output signal from the second voltage dividing circuit 4B to the microcomputer 11, and the second output signal is the second A / D converter. The signal is converted into a second digital signal at 21 B and sent to the microcomputer 11. The first A / D converter 21A and the second A / D converter 21B constitute an A / D converter 21 for converting an analog output signal from the voltage dividing circuit 4 into a digital signal. In the present embodiment, the first A / D converter 21A and the second A / D converter 21B are included in the microcomputer 11. However, these may be configured separately from the microcomputer 11.

  The microcomputer 11 includes a CPU as an arithmetic processing means, a memory as a storage means, a timer as a clock means, an input / output device, etc., as well as the A / D converter 21 described above. It is provided as a wear configuration. The microcomputer 11 also calculates the actual input power to the oscillation circuit 9 from the detection data of the input current obtained by the input current detection circuit 3 and the detection data of the input voltage obtained by the input voltage detection circuit 12. The switching element 8 is repeatedly interrupted at the timing of the zero crossing obtained based on the output signal from the voltage dividing circuit 4 over the entire time such that the actual input power becomes the set power. To transmit the control signal to the drive circuit 10 so that the pulse drive signal can be transmitted from the drive circuit 10. Such a software function is realized by the microcomputer 11 reading a program stored in the memory as a storage medium, but in the present embodiment, the microcomputer 11 includes the zero cross detection means 22, the power frequency acquisition means 23, and the power supply in particular. A program for functioning as the voltage acquisition means 24 is provided.

  The zero cross detection means 22 compares the first digital signal obtained from the first A / D converter 21A with the second digital signal obtained from the second A / D conversion means 21B. The zero cross point at which the voltage of 'becomes zero is calculated, and the zero cross point of the signal source 1' is generated by the zero cross detection means 22, the voltage dividing circuit 4 and the A / D converter 21 incorporated in the microcomputer 11. A zero cross detection device 15 for detecting In this embodiment, by incorporating the zero cross detection means 22 in the microcomputer 11 that controls the energization of the resonant coil 5, a part of the hardware configuration necessary for zero cross detection like a conventional detection element is realized by software. There is. Furthermore, by incorporating the A / D converter 21 into the microcomputer together with the zero cross detection means 22, the hardware configuration of the zero cross detection device 15 can be only the voltage dividing circuit 4 and the microcomputer 11, and from the signal source 1 ' A conventional rectifier or the like that full-wave rectifies the voltage can also be eliminated.

  The power supply frequency acquisition means 23 measures the timing of the zero cross point calculated by the zero cross detection means 22, and calculates the frequency of the signal source 1 'from the time from one timing to the next timing. The power supply voltage acquiring unit 24 uses the zero crossing point calculated by the zero crossing detection unit 22 and the power supply frequency calculated by the power supply frequency acquiring unit 23 to generate a first digital within a predetermined time based on the zero crossing point. The absolute value of the difference between the value of the signal and the value of the second digital signal is integrated, and the power supply voltage value of the signal source 1 'is calculated from the integrated value.

  Next, a method of detecting the zero crossing point by the zero crossing detection means 22 will be described with reference to the waveform diagram of FIG. In FIG. 3, the value of the digital signal acquired by the first A / D converter 21A corresponding to the voltage generated on the neutral wire N, ie, “signal A”, and the voltage generated on the voltage line L Correspondingly, it shows the time change of the value of the digital signal acquired by the second A / D converter 21 B, that is, the “signal B”.

  The microcomputer 11 is provided with a timer having a function as a counter i (see FIG. 4) and a memory for storing data necessary for detecting the zero cross point. Signal A from the first A / D converter 21A and the signal B from the second A / D converter 21B at each predetermined reading timing, and the number of times of reading The upper and lower relation between the signal A and the signal B when the signal A and the signal B are compared at the reading timing is recorded in the memory. Here, when the signal A is larger than the signal B continuously for a plurality of times (that is, when “signal A> signal B”) is set to state 1, the voltage of the signal B is larger than the voltage of the signal A continuously for a plurality of times. Assuming that time (ie, “signal B> signal A”) is state 2, the zero-crossing detecting means 22 detects the transition between state 1 and state 2, that is, the graph of signal A and the graph of signal B in FIG. The intersection point is detected as the zero crossing point of the signal source 1 ′.

  Also, the counter i increments its value by 1 (+1 count) at each reading timing as described above, and the power supply frequency acquiring means 23 counts the counter i when the change point between the state 1 and the state 2 is reached. It is configured to be stopped and to record the value of the counter i in the memory as periodic data. In the present embodiment, by setting the read timing to 1/40 or less of the cycle of the AC voltage supplied from the signal source 1 ′, sufficient accuracy can be secured. The zero cross point of the signal source 1 ′ can be detected stably regardless of the size and noise.

  Next, the operation of the above-described electromagnetic induction heating apparatus will be described based on the flowchart of FIG. In step S111, the zero cross detection means 22 of the microcomputer 11 counts the value of the counter i by +1 at the reading timing based on the timer, and then the process proceeds to step S112, and the zero cross detection means 22 performs the first A / D converter 21A. Thus, the signal A is acquired, and the process proceeds to step S113, and the zero-crossing detecting means 22 acquires the signal B by the second A / D converter 21B.

  In the subsequent step S114, the zero cross detection means 22 compares the signal A acquired in step S112 with the signal B acquired in step S113, and compares the result of comparison as to whether the signal A is larger than the signal B or not. It stores in the memory together with the numerical value of i, and proceeds to step S115. In step S115, in order to detect the zero crossing point of the signal source 1 ′, the zero cross detection means 22 determines a state 1 where the signal A is larger than the signal B continuously for a plurality of times based on the comparison result in step S114. It is determined whether or not there is a change point with the state 2 in which the signal B is larger than the signal A in succession several times.

  Here, if there is no change point between the state 1 and the state 2, the process proceeds to step S116 to stand by and returns to step S111 at the next reading timing. On the other hand, if there is a transition point between the state 1 and the state 2, it is determined that the transition point is the zero crossing point of the signal source 1 ', and the process proceeds to the next step S117.

  In step S117, the power supply frequency acquiring unit 23 of the microcomputer 11 reads the numerical value of the counter i at the transition point between the state 1 and the state 2 from the numerical value of the counter i stored in the memory together with the above comparison result. The numerical value of the counter i at this change point is overwritten and recorded as periodic data in the memory, and the process proceeds to step S118. In step S118, if the recorded cycle data is within the predetermined value, the power supply frequency acquiring unit 23 calculates the reciprocal of the value as the power supply frequency (1 / period data = power supply frequency). The predetermined numerical value is desirably a value larger than half of the number of times of reading of one cycle of the AC voltage supplied from the signal source 1 ′, and in the present embodiment, the number of times of reading of one cycle of the AC voltage is 40 times. Because of the above, it is desirable to make the predetermined numerical value larger than 20 when the number of times of reading is 40 times.

  In the following step S119, the microcomputer 11 clears the value of the counter i to 0, and also clears the comparison result stored in the memory until then and the value of the counter i corresponding to the comparison result. Then, the process proceeds to step S120 and waits, and at the next reading timing, the process returns to step S111 and the above-described flow is repeated.

  By configuring in this way, a part of the functions carried by the hardware can be realized by software (zero cross detection means 22) incorporated in the microcomputer 11, and a relatively simple hardware of a small number of hardware such as the voltage dividing circuit 4 and the microcomputer 11 can be realized. With the configuration, it is possible to acquire the zero crossing point of the signal source 1 ′ without performing rectification such as full wave rectification. Further, if a predetermined numerical value is used as a threshold, and the above-mentioned period data is within the predetermined value, the power supply frequency acquiring means 23 uses the period data recorded in the memory to obtain the value of the frequency of the signal source 1 ′. Can be calculated, and the frequency of the signal source 1 ′ can be stably acquired regardless of the magnitude and the noise of the voltage of the signal source 1 ′. Then, the microcomputer 11 sends a control signal to the drive circuit 10 at an optimal timing synchronized with the signal source 1 ′ based on the zero cross point obtained by the zero cross detection means 22 and the power supply frequency obtained by the power supply frequency acquisition means 23. it can.

  FIG. 5 is a flow chart specifically showing the above operation. The microcomputer 11 in this case compares the signal A and the signal B at the read timing in addition to the value of the counter i. The number of times of "signal B" and the number of times of "signal B> signal A" are also recorded in the memory. The electromagnetic induction heating apparatus having the above configuration will be described based on the flowchart of FIG. 5. In step S211, the zero cross detection means 22 of the microcomputer 11 counts +1 the value of the counter i at the reading timing based on the timer. After the shift, the signal A is acquired by the first A / D converter 21A, and the process proceeds to step S213, and the signal B is acquired by the second A / D converter 21B.

  In the subsequent step S214, the zero cross detection means 22 compares the signal A acquired in step S212 with the signal B acquired in step S213. Here, when signal A> signal B, the process proceeds to step S215, and when signal A> signal B is not satisfied, that is, when the voltage of signal A is less than the voltage of signal B, the process proceeds to step S220.

  In step S215, the zero cross detection means 22 determines whether the number of times “signal A> signal B” when comparing the signal A and the signal B at the read timing is less than a predetermined number. Here, when the number of “signal A> signal B” is less than four which is a predetermined number, the process proceeds to step S216, the number of “signal A> signal B” is counted by +1, and the process proceeds to step S217. The number of “signal A <signal B” is cleared to 0, and the process proceeds to step S218. In step S215, when the number of "signal A> signal B" is four or more which is a predetermined number, the process directly proceeds to step S218. The predetermined number of times is desirably a numerical value smaller than a value obtained by subtracting 1 from 1⁄2 of the number of readings of one cycle of the AC voltage supplied from the signal source 1 ′. Here, the predetermined number of times is set to “4” There is.

  In step S218, the zero cross detection means 22 determines whether the number of times of “signal A> signal B” is four times which is a predetermined number of times. Here, when the number of times of “signal A> signal B” is four which is a predetermined number, the process proceeds to step S219, the number of “signal A> signal B” is counted by +1, and the process proceeds to step S225. . If it is determined in step S219 that the number of times of "signal A> signal B" is not 4 as the predetermined number, the process proceeds to step S225 as it is.

  When the process proceeds to step S220, the same operation as the flow from step S215 is performed. Specifically, in step S220, the zero cross detection means 22 determines whether the number of times of “signal A <signal B” when comparing signal A and signal B at the read timing is less than a predetermined number of times. . Here, when the number of times of “signal A <signal B” is less than four which is a predetermined number, the process proceeds to step S221, the number of “signal A <signal B” is counted by +1, and the process proceeds to step S222. The number of “signal A> signal B” is cleared to 0, and the process proceeds to step S223. In step S220, when the number of times of “signal A <signal B” is four or more which is a predetermined number of times, the process directly proceeds to step S223.

  In step S223, the zero cross detection means 22 determines whether the number of times of “signal A <signal B” is four times which is a predetermined number of times. Here, when the number of times of “signal A <signal B” is four which is a predetermined number, the process proceeds to step S224, the number of “signal A <signal B” is counted by +1, and the process proceeds to step S225. If it is determined in step S223 that the number of times of “signal A <signal B” is not 4 as the predetermined number, the process proceeds to step S225.

  In step S225, the microcomputer 11 determines whether the number of "signal A> signal B" is five or not, or whether the number of "signal A <signal B" is five or not. Here, when the number of times of “signal A <signal B” is five times, or when the number of times of “signal A> signal B” is five times, the process proceeds to step S226. When the number of "signal A <signal B" is not 5 times in step S225 or when the number of "signal A> signal B" is not 5 times, the process proceeds to step S230 and stands by, and the next time The process proceeds to step S211 at the read timing of the. Here, although the number of times is set to “5”, when the predetermined number of times is changed in step S215, the number of times may be the predetermined number of times +1.

  In step S226, the zero cross detection means 22 detects a zero cross point, that is, a change point between state 1 and state 2. Specifically, step S111 to step S119 of the flowchart of FIG. 4 are performed to detect a change point between state 1 and state 2. Then, the change point between the state 1 and the state 2 is detected, and when the value of the counter i is within the predetermined value, the process proceeds to step S227.

  In step S227, in order to calculate the power supply frequency, the power supply frequency acquiring unit 23 records the numerical value of the counter i as cycle data in the memory. Here, a value obtained by subtracting the numerical value of the counter i used as the cycle data last time from the current numerical value of the counter i is configured to be recorded in the memory. Instead of subtracting the value of the previous counter i, the value of the counter i may be cleared to 0 each time after recording in the memory as periodic data. When the power supply frequency acquiring unit 23 causes the memory to store the cycle data, the process proceeds to step S228.

  In step S228, the microcomputer 11 clears the number of "signal A> signal B" to zero, and in the next step S229, the microcomputer 11 clears the number of "signal A <signal B" to zero, and step S229 , And waits for the next reading timing, and returns to step S211 to repeat the above-described flow. By configuring in this way, part of the functions carried by the hardware is realized by software, and rectification such as full-wave rectification is performed with a relatively simple configuration of a small number of hardware such as voltage dividing circuit 4 and microcomputer 11. It is possible to acquire the zero crossing point of the signal source 1 ′ without. Also, by using a predetermined numerical value or a predetermined number of times as a threshold, the power supply frequency acquiring means 23 can calculate the frequency of the signal source 1 ′ using the cycle data recorded in the memory, and the magnitude of the voltage of the signal source 1 ′ Regardless of the sheath noise, the frequency of the signal source 1 ′ can be acquired stably.

  Next, a method of acquiring the voltage of the signal source 1 ′ by the power supply voltage acquiring means 24 will be described. Here, it is assumed that the calculation of the power supply frequency described above is performed in parallel with the power supply frequency acquisition unit 23.

  The operation until the voltage of the signal source 1 'is acquired will be described based on the waveform diagram of FIG. 6 and the flowchart of FIG. FIG. 6 (a) shows the time change of the value (“signal A”) of the digital signal acquired by the first A / D converter 21A, and FIG. 6 (b) shows the second A FIG. 6C shows the absolute value (“| A− of the value obtained by subtracting the signal B from the signal A, and the time change of the value of the digital signal (“ signal B ”) acquired by the D / D converter 21B. 6 (d) shows the time change of the integrated value of the absolute value | A-B |, and FIG. 6 (e) shows the power supply voltage acquisition means of the microcomputer 11. 24 shows the value of the power supply voltage recognized.

  In step S311 in FIG. 7, as described above, the zero cross detection means 22 of the microcomputer 11 counts +1 the value of the counter i at the reading timing based on the timer, then proceeds to step S312 and performs the first A / D conversion. The signal A is acquired by the unit 21A, and the process proceeds to step S113, and the signal B is acquired by the second A / D converter 21B.

  In step S314, the power supply voltage acquisition means 24 of the microcomputer 11 calculates the absolute value | A-B | of the signal A-signal B using the signal A acquired in step S312 and the signal B acquired in step S313, It transfers to step S315.

  In step S315, the absolute value | A−B | from the time of the zero crossing point at which the period of the signal source 1 ′ starts, ie, when the counter i is 0, to the present time is integrated and the value is recorded in the memory . In the following step S316, the power supply voltage acquiring means 24 determines whether the numerical value of the counter i is the same as the numerical value of the cycle data recorded in the memory by the power supply frequency acquiring means 23 in step S117 of the flowchart of FIG. Here, when the numerical value of the counter i is not the same as the numerical value of the cycle data, the process directly proceeds to step S320 without calculating the power supply voltage and stands by, and proceeds to step S311 at the next reading timing. On the other hand, when the numerical value of the counter i is the same as the numerical value of the cycle data, the power supply voltage acquiring means 24 starts the cycle data from the time when the integrated value of the absolute value | A-B | acquired in step S315 is 0. It is determined that the value of the signal source 1 ′ is half the period until it becomes the numerical value of and the process proceeds to step S317.

  In step S317, the power supply voltage acquiring unit 24 acquires a value obtained by dividing the integrated value by an eigen value dependent on a circuit constant for each frequency of the signal source 1 ′, and this value is used as a voltage of the signal source 1 ′ as a power supply. Record in memory. Then, in the next step S318, the numerical value of the counter i is cleared to 0, and the process proceeds to step S319. In step S319, the power supply voltage acquiring unit 24 clears the integrated value to 0, and the process proceeds to step S320 and waits. At the next read timing, the process returns to step S311 to repeat the above-described flow.

  In this series of operations, as shown in FIG. 6A, the first A / D converter 21A corresponds to the voltage generated on the neutral line N in the first half cycle of the signal source 1 ′. In the second half cycle following the first half cycle of the signal source 1 ′, the constant signal A is output to the microcomputer 11. On the other hand, as shown in FIG. 6B, the second A / D converter 21B outputs a constant signal B at 0 to the microcomputer 11 in the first half cycle of the signal source 1 ′. Thus, in the second half cycle of the signal source 1 ′, the signal B that changes in response to the voltage generated on the power supply line L is output to the microcomputer 11. Therefore, as shown in (c) of FIG. 6, the absolute value | A−B | of the signal A−signal B substantially corresponds to the absolute value of the instantaneous value of the signal source 1 ′. Therefore, as shown in (d) of FIG. 6, the absolute value | A−B | of signal A−signal B is set at each read timing of the microcomputer 11 starting from one zero cross point detected by the zero cross detection means 22. The power supply voltage acquiring unit 24 of the microcomputer 11 divides the integrated value immediately before the absolute value | A−B | by the characteristic value at the timing when the integration is performed and the zero cross detection unit 21 detects the next zero cross point. It becomes possible to recognize the value of the power supply voltage of 1 'every half cycle.

  Thus, in the present embodiment, the power supply voltage acquiring means 24 can calculate the voltage value of the signal source 1 ′ using the period data recorded in the memory, and is stable regardless of the voltage magnitude or noise of the signal source 1 ′. Thus, the voltage value of the signal source 1 ′ can be obtained.

  As described above, in the electromagnetic induction heating device of the present embodiment, the resonance coil 5 as the heating unit that receives the electric power from the signal source 1 ′ as the AC power supply 1 and heats the object to be heated by electromagnetic induction As a control means for controlling the power supply of the current source, a first voltage dividing circuit 4A for dividing the voltage on the neutral wire N side as one end side of the signal source 1 ′, and the other end side of the signal source 1 ′ A second voltage dividing circuit 4B for dividing the voltage on the side of the voltage line L, a first A / D converter 21A for taking the output signal from the first voltage dividing circuit 4A into the microcomputer 11, and And a second A / D converter 21B for taking in an output signal from the voltage dividing circuit 4B to the microcomputer 11. In particular, the microcomputer 11 controls the energization of the resonance coil 5 by Digital signal obtained from the first A / D converter 21A When, by the digital signal obtained from the second A / D converter 21B, and a zero-cross detection means 22 for detecting a zero cross point of the signal source 1 '.

  In this case, the zero cross detection means 22 for detecting the zero cross point of the signal source 1 ′ is incorporated as a software configuration into the microcomputer 11 for controlling the energization of the resonance coil 5 to perform the zero cross detection hardware. The department is realized by software. Further, the voltage on the neutral line N side of the signal source 1 ′ and the voltage on the voltage line L side are divided respectively, and the digital signal obtained by the A / D converter 21 is taken in from the microcomputer 11. This makes it possible to obtain the zero crossing point of the signal source 1 'without rectification such as full wave rectification with a few relatively simple hardware configurations.

  Further, in the present embodiment, the power supply frequency acquisition unit 23 acquires the frequency of the signal source 1 ′ by measuring the time from one zero cross point to the next zero cross point according to the timing of the zero cross point detected by the zero cross detection unit 22. Are incorporated in the microcomputer 11 together with the cellocross detection means 22.

  In this case, based on the zero-crossing point detected by the zero-crossing detecting means 22, the timing is measured by the power supply frequency acquiring means 23 incorporated as a software configuration into the microcomputer 11 as with the zero-crossing detecting means 22. With a simple hardware configuration, it is possible to obtain the frequency of the signal source 1 ′ without performing rectification such as full-wave rectification.

1 and 8 to 10 show a second embodiment of the electromagnetic induction heating device of the present invention. The electromagnetic induction heating device here has the oscillation circuit 9 of the single end system shown in FIG. 1, and the switching element 8 to be the switch means of the oscillation circuit 9 is configured using an IGBT. A trigger detection circuit (not shown) that generates a trigger detection signal is connected between the emitters. The trigger detection circuit sends an ON (on) or OFF (off) trigger detection signal according to the level of the collector-emitter voltage V _CE of the IGBT to the microcomputer 11. The microcomputer 11 of this embodiment is an IGBT collector - variable that emitter voltage V _CE becomes near 0V, the detection of the trigger OFF receiving the detection signal from the trigger detection circuit, the trigger delay time is a delay time until the gate of the IGBT is turned oN Thus, the short circuit current is reduced.

FIG. 8 shows ideal voltages of “V _CE ” which is a voltage between the collector and the emitter of the IGBT, “trigger” which is a detection signal from the trigger detection circuit, and “IGBT gate” which is a gate voltage of the IGBT. The graph of the waveform is shown. Conventionally, in an induction heating controller using a single-ended method for copying machines, when the gate of the IGBT is turned on by a pulse drive signal from the drive circuit 10, the collector-emitter voltage V _CE of the IGBT is reduced to 0V. Otherwise, short-circuit current may occur in the IGBT, which may lead to energy loss and, in the worst case, destruction of the device. Therefore, as shown in FIG. 8, the microcomputer 11 turns on the IGBT gate when the collector-emitter voltage V _CE of the IGBT becomes close to 0 V after a predetermined delay time has elapsed from the trigger OFF edge. The IGBT is driven by the drive circuit 11 so that the oscillation circuit 9 becomes zero cross oscillation.

However, in practice, the delay timing from the trigger OFF to the gate ON of the IGBT fluctuates depending on the frequency and the magnitude of the collector-emitter voltage V _CE of the IGBT. Although the microcomputer 11 performs control to adjust the delay time according to the gate ON time output from the drive circuit 10 to the IGBT, the adjustment for which the AC voltage of the AC power supply 1 is recorded in the memory of the microcomputer 11 and when it is increased or decreased from the center of the input voltage, in the vicinity of zero cross point of the AC voltage, may shift if trigger timing by the trigger detecting circuit, a collector of IGBT - emitter voltage V _CE of IGBT near 0V gate It did not turn ON, and the short circuit current was large.

This will be described based on FIG. 9. As in the case of FIG. 8, the microcomputer 11 causes the drive circuit 10 to drive the IGBT when a predetermined delay time elapses from the detection of the trigger OFF by the trigger detection circuit. However, if the trigger OFF timing by the trigger detection circuit is deviated, the collector-emitter voltage V _CE of the IGBT is 0 V at the timing when the gate of the IGBT is turned ON even if the delay time has elapsed from the trigger OFF edge. The short circuit current still occurred.

Therefore, in this embodiment, as shown in FIG. 10, IGBT collector - emitter voltage V _CE, and the partial pressure-averaging by a resistor and a capacitor at a partial pressure-averaging circuit 28, and the partial pressure-averaging By taking the voltage into the microcomputer 11, the delay time from the detection of the trigger OFF to the ON of the IGBT gate is optimized based on the table value or the calculation formula recorded in advance in the memory of the microcomputer 11. Is configured to be changed to Specifically, in this embodiment, the collector of IGBT - to emitter voltage V _CE partial pressure-averaged to capture the microcomputer 11, a series circuit of a resistor and a capacitor as a divided voltage-averaging circuit 28, The switching element 8 is connected between the collector and the emitter of the IGBT, and the connection point between the resistor and the capacitor is connected to the input port of the microcomputer 11. The other configuration can be the same as that of the first embodiment.

The operation of the electromagnetic induction heating apparatus having the above configuration will be described based on FIG. 10. The microcomputer 11 outputs an output signal obtained by dividing and averaging the collector-emitter voltage V _CE of the IGBT by the voltage dividing and averaging circuit 28. Once captured, the microcomputer 11, a collector of IGBT - from the output signal which is information relating to emitter voltage V _CE, and calculates the optimal delay time. Information of _{V CE,} as used herein, the collector of IGBT - from emitter voltage _{V CE} falls, since Triggered OFF trigger detection circuit detects the collector of IGBT - emitter voltage _{V CE} is 0V The information is not particularly limited as long as it is information for calculating an optimal delay time until it becomes near. After calculating the optimal delay time, the microcomputer 11 sets the delay time, and turns on the gate of the IGBT at a timing when this delay time has elapsed from the trigger OFF edge. As a result, the occurrence of a short circuit current can be suppressed, and the IGBT can be driven at an optimal timing.

As described above, in the electromagnetic induction heating device according to the present embodiment, the IGBT 11 serving as the switching element 8 during electromagnetic induction heating in which the microcomputer 11 performs energization control of the resonant coil 5 serving as heating means by switching to the switching element 8. collector - emitter voltage V _CE, and the partial pressure-averaged by configured partial pressure-averaging circuit 28 by a resistor and a capacitor, the microcomputer 11 and the voltage was taken into the microcomputer 11, the partial pressure-averaging circuit 28 The microcomputer 11 incorporates a software configuration that changes to optimize the delay time from the trigger input, which is trigger OFF detection, to the gate output when the gate of the IGBT is turned on, based on the voltage level of the output signal sent to There is.

  Therefore, even when the trigger timing by the trigger detection circuit deviates, the microcomputer 11 can perform the zero cross oscillation by optimally varying the delay time by using the output signal from the voltage dividing / averaging circuit 28. It is possible to reduce the occurrence of short circuit current.

  The configuration of a third embodiment of the electromagnetic induction heating device according to the present invention will be described with reference to FIG. 1 described above. Also in the electromagnetic induction heating device here, the switching element 8 is configured using an IGBT, and when the microcomputer 11 performs energization control of the resonant coil 5, detection data of the input current obtained by the input current detection circuit 3 and Based on the detection data of the input voltage obtained by the input voltage detection circuit 12, the actual input power to the oscillation circuit 9 is calculated, and the drive circuit 10 is controlled so that the actual input power becomes the set power. A signal is sent to cause the IGBT to perform switching operation. At that time, when the IGBT is turned on, the input voltage detected by the input voltage detection circuit 12 drops compared to when the IGBT is turned off, and the input voltage is further dropped by the amount of input current to the oscillation circuit 9 Since the amount is also different, in the present embodiment, the microcomputer 11 is provided with a software drop amount correction means that corrects the drop amount of the input voltage according to the input current amount. The other configuration is the same as the electromagnetic induction heating device of the first embodiment or the second embodiment.

  In an induction heating controller using a single-ended resonant high frequency inverter, that is, an electromagnetic induction heating apparatus using a single switching element 8, when the gate of the IGBT is turned on, a voltage drop occurs in the input voltage. Therefore, conventionally, the microcomputer 11 determines the voltage offset amount by calculating “input voltage at rated power” − “input voltage during electromagnetic induction heating OFF”, and while the electromagnetic induction heating is OFF, detects the input voltage By offsetting the voltage drop by the determined voltage offset amount on the calculation result of the input voltage based on the detection signal of the circuit 12, the deviation of the voltage correction is corrected. However, the actual amount of voltage drop is not uniform, and fluctuates depending on the ON time of the gate of the IGBT. Therefore, even when the electromagnetic induction heating is ON, deviation of the input voltage calculation result occurs due to the voltage drop.

  In order to solve this problem, for example, by correcting the voltage drop amount according to the ON time of the gate of the IGBT, the deviation of the input voltage calculation result due to the voltage drop can be reduced and the input power calculation accuracy can be improved. Conceivable. However, even if the on time of the gate of the IGBT is the same, the amount of voltage drop differs depending on the level of the input voltage, and the above-mentioned correction accuracy is not sufficient.

  Therefore, in the present embodiment, focusing on the fact that the voltage drop amount increases in proportion to the amount of input current, the characteristics of the voltage drop amount according to the input current are measured in advance, and a data table or a calculation formula is calculated. It is recorded in the memory (ROM) of the microcomputer 11. Then, when the microcomputer 11 performs the switching operation of the IGBT, the voltage drop correction means corrects the drop of the input voltage according to the amount of the input current based on the table or calculation formula stored in the memory while the IGBT is ON. By doing this, the deviation of the input voltage calculation result due to the voltage drop is reduced, and the calculation accuracy of the input voltage is improved.

  FIG. 11 shows a waveform diagram in which the input current and the input voltage are measured when the IGBT and hence the electromagnetic induction heating is turned on in the electromagnetic induction heating device of the present embodiment. In the figure, the electromagnetic induction heating is turned off from on A large input current flows through the oscillation circuit 9 including the IGBT after switching to the point A, and after the point B when the electromagnetic induction heating switches from ON to OFF, the amount of input current to the oscillating circuit 9 is the point A It fluctuates to about half of the On the other hand, the amount of voltage drop of the input voltage increases in proportion to the amount of input current, and when the input current after point A is large, the amount of voltage drop of the input voltage is also large. When the current is small, the voltage drop amount of the input voltage is also reduced to about half after point A.

  In this embodiment, the “input current-voltage drop amount” characteristic as shown in FIG. 11 is measured in advance, a data table or a calculation formula is calculated, and is recorded in the ROM (not shown) of the microcomputer 11. In addition, voltage dividing and averaging circuits (not shown) for input voltage and input current, both of which are composed of a resistor and a capacitor, are provided, and voltage division and average for these input voltage and input current are provided. Based on the data table or calculation formula recorded in the ROM, the voltage drop correction means incorporated in the microcomputer 11 takes in the output signal which has been divided and averaged by the conversion circuit into the microcomputer 11 and the electromagnetic induction heating is ON. The offset amount of the voltage drop is determined according to the amount of input current calculated from the output signal from the voltage division and averaging circuit for input current, and calculated from the output signal from the voltage division and averaging circuit for input voltage The offset amount of the determined voltage drop is corrected with respect to the input voltage. Therefore, the accuracy of the input power calculation result calculated by the product of the input voltage calculation result and the input current calculation result can be improved. The input current to the oscillation circuit 9 may be calculated using the detection signal obtained by the input current detection circuit 3 instead of the output signal of the voltage division and averaging circuit for input current. The input voltage of the oscillation circuit 9 may be calculated using a detection signal obtained by the input voltage detection circuit 12 instead of the output signal of the voltage dividing / averaging circuit for voltage.

  As described above, in the electromagnetic induction heating apparatus according to the present embodiment, the microcomputer 11 performs switching control to the switching element 8 to control the energization of the resonance coil 5 serving as heating means during electromagnetic induction heating, both by the resistor and the capacitor. A data table or the like stored in ROM, for example, which becomes the memory of the microcomputer 11, by taking the divided output signals respectively divided and averaged by the voltage division and averaging circuits for input voltage and input current configured Based on the formula, the amount of input current obtained by the output signal from the voltage division and averaging circuit for the input current determines the voltage drop offset amount of the input voltage that matches the amount of the input current. Therefore, the deviation amount of the calculation result of the input voltage due to the voltage drop can be corrected inside the microcomputer 11, and the calculation accuracy of the input power can be improved.

  A fourth embodiment of the electromagnetic induction heating device of the present invention will be described with reference to the aforementioned FIG. 1 and FIG. The electromagnetic induction heating device here averages the values of the input voltage and the input current for each power supply cycle of the AC power supply 1 based on the zero cross point, instead of the feedback every 100 ms of the conventional input voltage and input current, The microcomputer 11 is configured to perform feedback. The other configuration is common to the electromagnetic induction heating device of the first embodiment.

  The microcomputer 11 serving as the induction heating control device performs a switching operation of the switching element 8 to thereby supply a high frequency current to the resonant capacitor 7 and the resonant coil 5 which is a heating coil. At that time, conventionally, the detection data of the input current obtained by the input current detection circuit 3 and the detection data of the input voltage obtained by the input voltage detection circuit 12 are fed back to the microcomputer 11 every 100 ms. The microcomputer 11 is adjusting so that the designated power which is the input power of is within the tolerance. However, in this configuration, the fluctuation of the frequency of the AC power supply 1 is not taken into consideration, and in addition to the method described above, the average value of detection data of input current and input voltage for 50 ms acquired at random timing is used. It was necessary to calculate in the microcomputer 11.

  Therefore, in the present embodiment, the value of the input current obtained by the detection signal from the input current detection circuit 3 and the input voltage detection circuit 12 with the feedback to the microcomputer 11 on the basis of the zero cross point detected by the zero cross detection means 22 The feedback means (not shown) for performing feedback to the microcomputer 11 is incorporated as a software configuration of the microcomputer 11, for example, by averaging the value of the input voltage obtained by the detection signal of FIG. . Therefore, as shown in FIGS. 1 and 2, the induction heating control device of the present embodiment is supplied from the AC power supply 1 at the front stage of the rectifying and smoothing circuit 2 in addition to the current detection circuit 3 and the input voltage detection circuit 12. A zero cross detection device 15 is provided that detects a zero cross point at which the value of the AC voltage is zero. The configuration of the voltage dividing circuit 4 may be the same as that of the first embodiment. Although not shown, the A / D converter converts the detection signal from the input current detection circuit 3 into a digital signal of the input current, and A / D converts the detection signal from the input voltage detection circuit 12 into a digital signal of the input voltage. D-converter, and the feedback means takes values of these digital signals several times between one zero-crossing point detected by the zero-crossing detecting means 22 and the next zero-crossing point, and averages the values of the respective digital signals. The value may be fed back to the microcomputer 11.

  Next, the operation of the above configuration will be described. First, when the zero cross detection means 22 detects the zero cross point of the AC power supply 1 as described in the first embodiment, the feedback means detects the read timing of the microcomputer 11 every time The detection data of the input current obtained by the input current detection circuit 3 and the detection data of the input voltage obtained by the input voltage detection circuit 12 are taken in, and their values are recorded in the memory of the microcomputer 11. Thereafter, when the zero cross detection means 22 detects the zero cross point again, the microcomputer 11 averages the values of the input current and the input voltage recorded so far for every cycle of the AC power supply 1 based on the zero cross point. The average value is used to perform feedback to the microcomputer 11 to adjust the designated power, which is the actual input power to the oscillation circuit 9, within the tolerance. With such a configuration, feedback to the microcomputer 11 can be stably performed regardless of fluctuations in the frequency of the AC power supply 1, and the accuracy of input power that is an integrated value of input current and input voltage is improved. It can be done.

  As described above, in the electromagnetic induction heating apparatus according to the present embodiment, the resonant circuit 6 including the resonant coil 5 and the resonant capacitor 7, the switching element 8 for supplying high frequency current to the resonant circuit 6, and the switching element 8 are driven. Drive circuit 10, an input current detection circuit 3 for detecting an input current, an input voltage detection circuit 12 for detecting an input voltage, a zero cross detection device 15 for detecting a zero cross point, an A / D converted input current and The microcomputer converts the digital value of the input voltage to the cycle of the AC power supply 1 based on the zero-crossing point, and uses the average value of the A / D-converted digital values during the cycle of the AC power supply 1 on the zero-crossing basis. And 11) feedback means for performing feedback. Therefore, regardless of the fluctuation of the frequency of the AC power supply 1, the feedback to the microcomputer 11 can be stably performed, and the accuracy of the power can be improved.

  12 to 14 show a fifth embodiment of the electromagnetic induction heating device of the present invention. The electromagnetic induction heating device here is a failure detection circuit that detects a short-circuit failure of a reverse current prevention diode, and software realizes a part of the function of hardware and A / D conversion acquired by two analog input ports. By comparing the values, it is configured to detect a failure of the backflow prevention diode.

  In the past, it was necessary to configure a fault detection circuit to detect a short circuit fault in the backflow prevention diode, and in the fault detection circuit, it was necessary to add a large number of elements such as a comparator, resulting in an increase in cost. there were. Therefore, in the present embodiment, a part of the function of the hardware in the failure detection circuit is realized by software, and a short circuit failure detection circuit for a backflow prevention diode with a relatively simple configuration and high safety is configured.

  FIG. 12 is a circuit block diagram showing the main configuration of the present embodiment. 1 '' is a signal source and outputs a voltage obtained by full-wave rectification of AC voltage (FIG. 13, FIG. 14) 31 is a diode for backflow prevention to be subjected to failure detection; The voltage is output from the cathode of the diode 31 in connection with the signal source 1 ′ ′. A failure detection circuit 32 detects whether or not the diode 31 has a failure. A pair of input terminals of the failure detection circuit 32 are connected to the anode and the cathode of the diode 31.

  Next, the configuration of the failure detection circuit 32 will be described. 33A is a first voltage dividing circuit that divides the voltage on the cathode side of the diode 31 and 33B is a second voltage dividing circuit that divides the voltage on the anode side of the diode 31 is there. These constitute a voltage dividing circuit 33 that divides the voltage before and after the diode 31. The input side terminal of the first voltage dividing circuit 33A is connected to the cathode of the diode 31, and the output side terminal of the first voltage dividing circuit 33A is connected to the first analog input port 37A of the microcomputer 11. The positive electrode side of the electrolytic capacitor 35 is connected between the input terminal of the first voltage dividing circuit 33A and the cathode of the diode 31, and the negative electrode side of the electrolytic capacitor 35 is connected to the ground terminal.

  The first voltage divider circuit 33A is not particularly limited as long as it is configured to divide the voltage on the cathode side of the diode 31, and may be configured as the first voltage divider circuit 4A in the first embodiment. In this case, the diode 31, the electrolytic capacitor 35 and the first voltage dividing circuit 33A function as a peak hold circuit, and at that time, the diode 31 functions as a rectifier circuit and the electrolytic capacitor 35 holds a peak value to a ground capacitor. The resistances of the first voltage dividing circuit 33A to be connected correspond to discharge circuits for discharging the voltage of the electrolytic capacitor 35, respectively.

  The input terminal of the second voltage divider circuit 33B is connected to the anode of the diode 31, and the output terminal of the second voltage divider circuit 33B is connected to the input terminal of the peak hold circuit 36. The output of the peak hold circuit 36 The side terminal is connected to the second analog input port 37 B of the microcomputer 11. The second voltage dividing circuit 33B is not particularly limited as long as it is configured to divide the voltage on the anode side of the diode 31. The second voltage dividing circuit 33B may be configured as the second voltage dividing circuit 4B in the first embodiment.

  In this embodiment, the output signal from the first voltage dividing circuit 33A taken into the first analog input port 37A when the failure detection circuit 32 is normal and neither the diode 31 nor the peak hold circuit 36 fails. And the voltage of the output signal from the peak hold circuit 36 taken into the second analog input port 37B are substantially equal. Further, the microcomputer 11 includes an A / D converter (not shown), and voltages from the first analog input port 37A and the second analog input port 37B are converted into digital signals by the A / D converter, The value is recorded in the memory (not shown) of the microcomputer 11. The microcomputer 11 generates a first threshold value and a second threshold value respectively from these recorded A / D conversion values, and is necessary for detecting a short circuit failure of the diode 31 for backflow prevention and detecting the short circuit failure. As a software configuration for detecting a failure of the peak hold circuit 36, failure detection means 39 is provided. The other configuration is common to the first embodiment.

  Next, an electromagnetic induction heating apparatus provided with the failure detection circuit 32 of the above configuration will be described in detail with reference to the waveform diagrams of FIG. 13 and FIG.

  FIG. 13 is a waveform diagram for explaining a detection method at the time of a short circuit failure of the diode 31. As shown in FIG. Here, before and after the occurrence of a short circuit failure of the diode 31, the voltage of the signal source 1 ′ ′, the first digital value obtained by A / D converting the voltage of the first analog input port 37A, the second digital input port 37B The figure shows a second digital value obtained by A / D converting the voltage and a time change of a second threshold value calculated from the second digital value The second threshold value is a voltage value of the second analog input port 37B. And is generated to be ΔV lower than a second digital value obtained from this voltage value.

  First, when neither the diode 31 nor the peak hold circuit 36 fails, as described above, the voltage of the first analog input port 37A and the voltage of the second analog input port 37B are substantially equal. Therefore, the microcomputer 11 compares the first digital value obtained by A / D converting the voltage of the first analog input port 37A with the second threshold. In this case, the first digital value is higher than the second threshold. Therefore, it is determined that neither the diode 31 nor the peak hold circuit 36 has failed.

  On the other hand, when the diode 31 causes a short circuit failure, the voltage of the first analog input port 37A drops with respect to the voltage of the second analog input port 37B. Therefore, when the first digital value corresponding to the voltage of the first analog input port 37A falls below the second threshold, the microcomputer 11 detects this and determines that the diode 31 has a short circuit failure. Thus, the microcomputer 11 A / D converts the second threshold value generated from the second digital value obtained by A / D converting the voltage of the second analog input port 37B and the voltage of the first analog input port 37A. By comparing the first digital value, it is possible to reliably detect that the diode 31 has a short circuit failure, regardless of the rating of the diode 31.

  FIG. 14 is a waveform diagram for explaining a detection method at the time of failure of the peak hold circuit 36. As shown in FIG. Here, before and after the occurrence of a short circuit failure of the diode 31, the voltage of the signal source 1 ′ ′, the first digital value obtained by A / D converting the voltage of the first analog input port 37A, the second digital input port 37B The second digital value obtained by A / D converting the voltage and the time change of the first threshold calculated from the first digital value indicate the voltage value of the first analog input port 37A. And is generated to be lower by Δv than the first digital value obtained from this voltage value.

  First, when neither the diode 31 nor the peak hold circuit 36 fails, as described above, the voltage of the first analog input port 37A and the voltage of the second analog input port 37B are substantially equal. Therefore, the microcomputer 11 compares the second digital value obtained by A / D converting the voltage of the second analog input port 37B with the first threshold. In this case, the second digital value is higher than the first threshold. Therefore, it is determined that the diode 31 and the peak hold circuit 36 have not failed and are normal.

  On the other hand, when the peak hold circuit 36 breaks down and loses its function, the voltage of the second analog input port 37B decreases with respect to the voltage of the first analog input port 37, as shown in FIG. It will Therefore, when the second digital value corresponding to the voltage of the second analog input port 37B becomes lower than the first threshold, the microcomputer 11 detects this and the peak hold circuit 36 breaks down and loses its function. It is determined that Thus, the microcomputer 11 A / D converts the first threshold value generated from the first digital value obtained by A / D converting the voltage of the first analog input port 37 and the voltage of the second analog input port 37B. By comparing the second digital value, it is possible to detect a failure of the peak hold circuit 36 which is a part of the failure detection circuit 32, and to reliably monitor the normality of the failure detection circuit 32. .

  As described above, in the present embodiment, the resonance coil 5 as heating means for heating the object to be heated by receiving electric power from the signal source 1 ′ ′ and control means for controlling energization of the resonance coil 5 In the electromagnetic induction heating apparatus including the microcomputer 11, the first voltage dividing circuit 33A for dividing the voltage on the cathode side of the diode 31 and the second voltage dividing circuit 33B for dividing the voltage on the anode side of the diode 31 And a peak hold circuit 36 for holding the peak of the voltage divided by the second voltage divider circuit 33B, and the voltage divided by the first voltage divider circuit 33A is taken into the first analog input port 37A. , The voltage holding the peak in the peak hold circuit 36 is taken into the second analog input port 37B, and a short circuit failure of the diode 31 for backflow prevention and the short circuit failure A software configuration for detecting the failure of the peak hold circuit 36 required for the detection, incorporates as a failure detecting means 39 to the microcomputer 11.

  In this case, the failure detection means 39 for detecting the failure of the diode 31 and the peak hold circuit 36 is incorporated in the microcomputer 11 for controlling the energization of the resonance coil 5 as a software configuration, and the hardware is responsible for the failure detection. To realize part of the software. Further, the voltages on the cathode side and the anode side of the diode 31 are respectively divided and taken into the first analog input port 37A and the second analog input port 37B of the microcomputer 11. This makes it possible to detect a short circuit failure of the backflow preventing diode 31 with a relatively simple configuration of a small number of hardware without using a comparator. In addition, since the failure of the peak hold circuit 36 necessary for detecting a short circuit failure can also be detected here, the short circuit failure detection function can be operated more safely by always monitoring the soundness of the short circuit failure detection function, A highly safe short circuit fault detection function can be provided.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, the components of the first to fifth embodiments may be combined to constitute an electromagnetic induction heating apparatus. In addition, the configuration and shape of each part of the first to fifth embodiments are not limited to those illustrated, and can be appropriately modified.

1 'Signal source (AC power supply)
4A first voltage dividing circuit 4B second voltage dividing circuit 5 resonant coil 11 microcomputer (control means)
21A 1st A / D converter 21B 2nd A / D converter 22 zero cross detection means 23 power supply frequency acquisition means L voltage line N neutral line

Claims (2)

Heating means for receiving a power from an AC power supply and electromagnetically heating an object to be heated;
Control means for controlling energization of the heating means;
A first voltage dividing circuit that divides a voltage at one end of the AC power supply;
A second voltage dividing circuit that divides a voltage of the other end side of the AC power supply;
A first A / D converter for taking an output signal from the first voltage dividing circuit into the control means;
A second A / D converter for taking an output signal from the second voltage dividing circuit into the control means;
The control means is configured to use a digital signal acquired from the first A / D converter and a digital signal acquired from the second A / D converter to control energization of the heating means. An electromagnetic induction heating apparatus comprising a zero cross detection means for detecting a zero cross point of the AC power supply.   The electromagnetic induction heating apparatus according to claim 1, wherein the control means comprises power supply frequency acquisition means for measuring the timing of the zero crossing point to acquire the frequency of the AC power supply.

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