JP5275783B2 - Control device for electromagnetic induction heating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To alternately drive two switching elements by using an inexpensive logic circuit or the like without using a complex integrated circuit in a control device for an electromagnetic induction heater. <P>SOLUTION: In a control device for an electromagnetic induction heater, a first signal, a second signal and a third signal are output from a microcomputer of a control circuit 40, wherein a potential H is applied from the time t0 to the time t1 and a potential L is applied from the time t1 to the time t4 by the first signal, the potential H is applied from the time t0 to the time t2 and the potential L is appled from the time t2 to the time t4 by the second siganal, and the potential H is applied from the time t0 to the time t3 and the potential L is applied from the time t3 to the time t4 by the third siganl. A first control signal for turning on a switching element 17 from the time t0 to the time t1 is formed based on the first signal output from the microcomputer of the control circuit 40 and maintaining the potential H from the time t0 to the time t1, and a second control signal for turning on a switching element 18 from the time t2 to the time t3 is formed based on an OR signal output from an OR circuit 55a and maintaining the potential L from the time t2 to the time t3. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a control device for an electromagnetic induction heating device.

Patent Document 1 includes a resonance capacitor, an induction heating coil that forms a series resonance circuit together with the resonance capacitor, and two switching elements. By alternately turning on these two switching elements, a high-frequency current is supplied to the induction heating coil. A control device for controlling an electromagnetic induction heating device including a half-bridge type inverter circuit to be supplied is disclosed. This control device includes an inverter drive circuit that outputs a drive signal for driving two switching elements, and the inverter drive circuit receives a control signal for alternately turning on the two switching elements from the control arithmetic circuit for a predetermined period of time. The driving signals that are alternately input to each of the two switching elements are output.
JP 2004-253297 A

  In the control device of the electromagnetic induction heating device disclosed in Patent Document 1, each drive signal output from the inverter drive circuit to each switching element is as high as 20 kHz to 50 kHz. In order to change the output of the induction heating coil, the inverter drive circuit Therefore, it is necessary to finely change the frequency of each drive signal output to each switching element. In order to output such a drive signal from the inverter drive circuit, the control signal input to the inverter drive circuit must also be a high-speed signal that changes in frequency finely. However, the control arithmetic circuit has to be provided with a complicated integrated circuit for changing a signal output from the microcomputer to a high-speed signal. It is also possible to create control signals using the microcomputer software built in the control arithmetic circuit. However, since high-speed processing is required, a high-performance microcomputer is required and the cost increases. If the output timing of the control signal is slightly shifted due to other serial communication processing or display processing, the two switching elements of the inverter circuit may be energized at the same time and the switching element of the inverter circuit may be destroyed. . The present invention aims to solve such problems.

  In order to solve the above-described problems, the present invention includes a resonance capacitor, an induction heating coil that forms a series resonance circuit together with the resonance capacitor, and two switching elements, and the two switching elements are turned on alternately so that the induction heating coil is turned on. A control device for controlling an electromagnetic induction heating device including a half-bridge type inverter circuit for supplying a high-frequency current to a first control signal for turning on one of the two switching elements; After one switching element has been turned on, a second control signal for turning on the other switching element is input every cycle time T consisting of time t0 to time t4, so that the two switching elements are alternately turned on. A driving circuit that outputs a driving signal to be output to each other and a binary signal that takes a first potential and a second potential. The first potential is applied from time t0 to time t1 and the second potential is applied from time t1 to time t4 and the binary signal, and the first potential is applied from time t0 to time t2, and the second potential is applied. A second signal applied from time t2 to time t4, a third signal comprising a binary signal, the first potential applied from time t0 to time t3, and the second potential applied from time t3 to time t4; Logic of a control circuit including a microcomputer that outputs a signal, an inverter that inverts and outputs a third signal output from the control circuit, and a signal output from the second signal output from the control circuit and the inverter And a first control signal that is turned on from time t0 to time t1 based on the fact that the first signal output from the control circuit is at the first potential from time t0 to time t1. , OR A control device for an electromagnetic induction heating device, characterized in that the second control signal is turned on from time t2 to time t3 based on the fact that the logical sum signal output from the path is the second potential from time t2 to time t3. Is to provide.

  In such a control device for the electromagnetic induction heating device, the first potential is applied from the time t0 to the time t1 and includes the binary signal taking the first potential and the second potential, and the second potential is applied from the time t1 to the time t4. The first signal is applied from the time t0 to the time t2, and the second signal is applied from the time t2 to the time t4. The second signal is formed from the binary signal. A control circuit including a microcomputer that outputs a third signal in which a first potential is applied from time t0 to time t3 and a second potential is applied from time t3 to time t4, and a third signal output from the control circuit And a logical sum circuit that outputs a logical sum signal of the second signal output from the control circuit and the signal output from the inverter, and a first output from the control circuit. Signal from time t0 to time t1 The first control signal is turned on from time t0 to time t1 based on the first potential, and the logical sum signal output from the OR circuit is the second potential from time t2 to time t3. Since the second control signal is turned on from time t2 to time t3, the first control signal is provided by a control circuit including a microcomputer without using a complicated integrated circuit, an inexpensive logic circuit such as an inverter and an OR circuit, or the like. And the second control signal can be generated.

  In the control device for the electromagnetic induction heating device configured as described above, a delay circuit that delays and outputs the third signal between the control circuit and the inverter and a signal output from the delay circuit are shaped. It is preferable to provide a shaping circuit that outputs to the inverter. In this case, even if the second signal is output from the control circuit with a slight delay, it is input from the inverter to the OR circuit. Since the signal has the first potential for the time delayed by the delay circuit from time t0, the signal output from the OR circuit takes the first potential without delay from time t0, and the drive circuit receives the first potential. A control signal for simultaneously turning on the first and second switching elements is not input, and the first and second switching elements are not simultaneously turned on and destroyed.

  In the control device for the electromagnetic induction heating apparatus configured as described above, the first to third signals are preferably signals generated from the clock of the microcomputer of the control circuit. No load is applied to output the first to third signals, and the microcomputer can execute other control processing even if it is not of high performance.

  Hereinafter, an embodiment of a control device for an electromagnetic induction heating device of the present invention will be described with reference to the drawings. The control device 20 of this electromagnetic induction heating device includes resonance capacitors 13 and 14, an induction heating coil 15 that forms a series resonance circuit together with the resonance capacitors 13 and 14, and two IGBTs (switching elements) 17 and 18. An electromagnetic induction heating device including a half-bridge type inverter circuit 16 that supplies a high-frequency current to the induction heating coil 15 by alternately turning on the two IGBTs 17 and 18 is controlled. The first control signal for turning on one of the two IGBTs 17 and 18 and the second control signal for turning on the other IGBT 18 after the IGBT 17 is turned on end at time t0 to time t4. Each of the drive signals that are alternately turned on by the two IGBTs 17 and 18 by being input at every cycle time T. The drive circuit 31, 32 that outputs and a binary signal that takes the first potential and the second potential, the potential H (first potential) is applied from time t0 to time t1, and the potential L (second potential) is timed. A first signal that is applied from t1 to time t4, a binary signal, and a second signal that is applied with a potential H from time t0 to time t2 and is applied with a potential L from time t2 to time t4. And a control circuit 40 including a microcomputer that outputs a third signal in which a potential H is applied from time t0 to time t3 and a potential L is applied from time t3 to time t4, and a first output from the control circuit 40. An inverter 54 that inverts and outputs the three signals, and an OR circuit 55a that outputs a logical sum signal of the second signal output from the control circuit 40 and the signal output from the inverter 54. First output from 40 The first control signal is turned on from time t0 to time t1 based on the fact that the signal is the first potential from time t0 to time t1, and the logical sum signal output from the logical sum circuit 55a is from time t2 to time t3 Based on the fact that the potential is the second potential until it is delayed to t3 ′ by the delay circuit 52 in the embodiment, it is turned on from time t2 to time t3 (delayed to t3 ′ by the delay circuit 52 in this embodiment). The second control signal is used.

  Between the control circuit 40 and the inverter 54 of the control device 20, a delay circuit 52 that delays and outputs the third signal, and a shaping circuit that shapes the signal output from the delay circuit 52 and outputs the signal to the inverter 54. 53 is provided. Below, the control apparatus 20 of an electromagnetic induction heating apparatus is explained in full detail.

  FIG. 1 is a circuit diagram of the electromagnetic induction heating device of this embodiment. In FIG. 1, a rectifier circuit 11 rectifies the output of a commercial AC power supply and converts it into a DC voltage. The smoothing capacitor 12 smoothes the voltage converted into direct current. The resonance capacitors 13 and 14 form a series resonance circuit with the induction heating coil 15. The inverter circuit 16 is a half-bridge type in which IGBTs 17 and 18 as switching elements are connected in series, and supplies the high frequency current to the induction heating coil 15 by alternately turning on these two IGBTs 17 and 18. is there. The protection capacitors 19 and 19 are for protecting the IGBTs 17 and 18.

  The control device 20 of the electromagnetic induction heating device includes a drive circuit 30 and a control circuit 40 that outputs first to third signals. The drive circuit 30 includes first and second drive circuits 31 and 32. The drive circuits 31 and 32 alternate with each IGBT 17 and 18 at each cycle time T starting from the time t0 and ending at the time t4. The first and second drive signals for turning on are output. The first and second drive circuits 31 and 32 use photocouplers. When a control signal of potential L is input to each of the drive circuits 31 and 32, the built-in LED is lit, and when this LED is lit In addition, a potential H of 15 V is output to each of the IGBTs 17 and 18 to be turned on. The first drive signal is turned on again after the second drive signal is turned on until the second drive signal is turned on after the first drive signal is turned on. Before the start, a dead time is set so that both IGBTs 17 and 18 do not turn on at the same time.

  The control circuit 40 outputs first to third signals composed of binary signals that take a potential H and a potential L in order to output drive signals from the drive circuits 31 and 32. The first to third signals are signals generated by the clock of the microcomputer of the control circuit 40. As shown in FIGS. 2A to 2C, the first signal changes the potential H from time t0 to time t1. The signal is applied and the potential L is applied from the time t1 to the time t4, and the second signal is the signal that the potential H is applied from the time t0 to the time t2 and the potential L is applied from the time t2 to the time t4. The third signal is a signal in which the potential H is applied from time t0 to time t3 and the potential L is applied from time t3 to time t4.

  Between the control circuit 40 and the drive circuits 31 and 31, there are an inverter 51, a delay circuit 52, a shaping circuit 53 including a Schmitt trigger, an inverter 54, an OR circuit 55a, and an inverter 55b. A negative OR circuit 55 and an inverter 56 are provided.

  The first signal output from the microcomputer of the control circuit 40 is input to the first drive circuit 31 as a signal inverted by the inverter 51 (shown in (f) of FIG. 2). The third signal output from the microcomputer of the control circuit 40 becomes a signal delayed by the delay circuit 52 (shown in (d) of FIG. 2). The signal is shaped by the shaping circuit 53 and the inverter is inverted. The signal inverted by 54 (shown in (e) of FIG. 2) is output to the negative OR circuit 55. As shown in FIG. 2 (e), the potential of the signal output after being inverted by the inverter 54 is changed at the timing delayed from the time t3 to the time t3 ′ as compared with the third signal. Yes. The second signal output from the microcomputer of the control circuit 40 and the signal output from the inverter 54 are inverted as a logical sum signal by the negative OR circuit 55 and output to the inverter 56. The inverted signal (shown in FIG. 2G) is input to the second drive circuit 32.

  When the clock frequency of the microcomputer of the control circuit 40 in this embodiment is 20 MHz, the microcomputer clock outputs a signal in which one count is 50 ns. In the microcomputer of the control circuit 40, if the dead time is 1.75 μs and the delay time delayed by the delay circuit 52 is 0.35 μs, this dead time corresponds to 35 counts of a signal based on the clock of the microcomputer. The time corresponds to 7 counts of the signal by the microcomputer clock. When the frequency of the first and second control signals is 20 kHz and 40 kHz, the number of clocks of the microcomputer in the first to third signals and the period time T is calculated as shown in Table 1 below.

  As shown in Table 1 above, the first and second control signals can be divided into 250 frequencies between 20 kHz and 40 kHz. In the vicinity of 20 kHz, which is close to the resonance point between each of the resonance capacitors 13 and 14 and the induction heating coil 15, the heating output of the induction heating coil 15 changes greatly even if the frequency of each drive signal changes slightly, but the frequency of each control signal is changed. By making fine changes, the drive signals output from the drive circuits 31 and 32 can be finely changed and outputted in the same manner, so that the heating output of the induction heating coil 15 can be set finely. When the microcomputer of the control circuit 40 has a clock frequency of 16 MHz, the first and second control signals can divide the frequency by 200 between frequencies of 20 kHz to 40 kHz.

  As described above, in the control device 20 of the electromagnetic induction heating device, the potential H is applied from the time t0 to the time t1, and the potential L is applied from the time t1 to the time t4. The first signal consisting of a binary signal and a potential H is applied from time t0 to time t2 and the potential L is applied from time t2 to time t4, and the potential H consisting of a binary signal is applied to time t0. To a time t3 and a control circuit 40 having a microcomputer that outputs a third signal to which the potential L is applied from a time t3 to a time t4, and a third signal output from the control circuit 40 is inverted and output. And an OR circuit 55a that outputs a logical sum signal of the second signal output from the control circuit 40 and the signal output from the inverter 54, and the first output from the control circuit 40. Signal Based on the potential H from time t0 to time t1, the first control signal is turned on from time t0 to time t1, and the logical sum signal output from the OR circuit 55a is from time t2 to time t3 ′ (this embodiment). Then, based on the fact that the potential is L from the delay circuit 52 to t3 to t3 ′, it is delayed from time t2 to time t3 ′ (in this embodiment, from t3 to t3 ′ by the delay circuit 52). The first control signal is turned on by the control circuit 40 having a microcomputer without using a complicated integrated circuit, an inexpensive logic circuit such as the inverter 54 and the OR circuit 55a, and the like. The second control signal can be generated.

  A delay circuit 52 that delays and outputs the third signal between the control circuit 40 and the inverter 54, and a shaping circuit 53 that shapes the signal output from the delay circuit 52 and outputs the signal to the inverter 54. Therefore, even if the second signal is output from the control circuit 40 with a slight delay, the signal input from the inverter 54 to the OR circuit 55a is the time delayed by the delay circuit 52 from the time t0. Therefore, the signal output from the OR circuit 55a takes the potential H without delay from the time t0, and the control signals for simultaneously turning on the IGBTs 17 and 18 are input to the drive circuits 31 and 32. The IGBTs 17 and 18 are not turned on and destroyed at the same time.

  Further, since the first to third signals are signals generated from the clock of the microcomputer of the control circuit 40, the microcomputer of the control circuit 40 does not take a load to output the first to third signals. It is possible to execute other control processes even if they are not of high performance.

It is a circuit block diagram of the electromagnetic induction heating apparatus using the control apparatus of this invention. It is a timing chart of the signal output from the 1st-3rd signal output from the microcomputer of a control circuit, and each circuit.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Electromagnetic induction heating device, 13, 14 ... Resonance capacitor, 15 ... Induction heating coil, 16 ... Inverter circuit, 17, 18 ... Switching element (IGBT), 20 ... Control device, 30 (31, 32) ... Drive circuit, 40 ... control circuit, 52 ... delay circuit, 53 ... shaping circuit, 54 ... inverter, 55a ... OR circuit.

Claims (3)

A resonance capacitor, an induction heating coil that forms a series resonance circuit with the resonance capacitor, and a half bridge that includes two switching elements and alternately turns on the two switching elements to supply a high-frequency current to the induction heating coil A control device for controlling an electromagnetic induction heating device comprising an inverter circuit of a shape,
A first control signal for turning on one of the two switching elements and a second control signal for turning on the other switching element after the one switching element has been turned on are at time t0. A drive circuit that outputs a drive signal to each of the two switching elements to be alternately turned on by being input every cycle time T consisting of a time t4,
A first signal comprising a binary signal taking a first potential and a second potential, wherein the first potential is applied from the time t0 to the time t1, and the second potential is applied from the time t1 to the time t4. And a second signal comprising the binary signal, wherein the first potential is applied from the time t0 to the time t2, and the second potential is applied from the time t2 to the time t4, and from the binary signal. A control circuit including a microcomputer that outputs a third signal in which the first potential is applied from the time t0 to the time t3 and the second potential is applied from the time t3 to the time t4;
An inverter that inverts and outputs the third signal output from the control circuit;
A logical sum circuit that outputs a logical sum signal of the second signal output from the control circuit and the signal output from the inverter;
The first control signal to be turned on from the time t0 to the time t1 based on the fact that the first signal output from the control circuit is the first potential from the time t0 to the time t1,
The logical sum signal output from the logical sum circuit is the second control signal that is turned on from the time t2 to the time t3 based on the second potential from the time t2 to the time t3. Control device for electromagnetic induction heating device.   2. The control device for an electromagnetic induction heating device according to claim 1, wherein a delay circuit that delays and outputs the third signal is formed between the control circuit and the inverter, and a signal output from the delay circuit is shaped. And a shaping circuit for outputting to the inverter.   3. The electromagnetic induction heating device control device according to claim 1, wherein the first to third signals are signals generated from a clock of a microcomputer of the control circuit. 4. Control device.

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