JP4882330B2 - Induction heating device - Google Patents

Description

  The present invention relates to an induction heating device used as an induction heating cooker or the like.

Conventionally, in this type of induction heating apparatus, it is known that the power supplied to the heating coil is controlled by a phase shift control method (for example, see Patent Document 1).
JP 2005-149915 A

  However, in the conventional phase shift control method, there are many reactive currents at low power, the efficiency of the inverter is lowered, and the efficiency of the induction heating device is lowered. Further, when the difference between the resonance frequency determined by the heating coil and the resonance capacitor and the driving frequency of the switching element is increased, the efficiency of the inverter is lowered and the efficiency of the induction heating device is also lowered. Furthermore, switching of the switching element occurs when there is a large amount of current flowing through the switching element. In this case, the power loss of the switching element increases, which causes destruction of the switching element, heat generation, and reduction in efficiency. It was a thing.

  The present invention solves the above-described conventional problems, and provides an induction heating apparatus that can supply large power to a heating coil, perform power control with high efficiency, and reduce power loss of a switching element. With the goal.

In order to solve the conventional problem, an induction heating device of the present invention includes a heating coil, a resonance capacitor connected in series with the heating coil, a direct current power source for supplying energy to the heating coil, and the heating coil. Connected between the positive electrode side of the DC power source and including a first diode, and connected between the heating coil and the negative electrode side of the DC power source and including a second diode. A second switching element connected between the resonant capacitor and the positive side of the DC power source and including a third diode; the resonant capacitor and the negative side of the DC power source; And a control circuit for supplying a drive signal to the first to fourth switching elements. The fourth switching element is connected to the first switching element and includes a fourth diode. The driving signals applied to the pair of the switching element and the second switching element, and the pair of the third switching element and the fourth switching element are alternately switched, and the first switching element, the fourth switching element, and the second switching element are switched. The switching element and the third switching element are driven with an arbitrary phase difference, and further, the switching elements are continuously turned on and off for a plurality of times, and then the drive signals are supplied to all the first to fourth switching elements at a constant cycle. The power control is performed by providing a stop period.

  Thereby, since the load connection part of an inverter can apply a positive power supply voltage and a negative power supply voltage alternately, a large electric power can be supplied to a heating coil. Further, the average power can be arbitrarily controlled with high efficiency by controlling the ratio between the switching element driving period and the switching element non-driving period and the phase difference of the driving signal generated from the control circuit. Furthermore, since the driving of the switching element is stopped during a period in which power is not supplied to the heating coil, no power loss occurs when switching the switching element, and the power can be controlled with high efficiency.

  The induction heating apparatus of the present invention can supply a large amount of power to the heating coil, and can arbitrarily control the average power with high efficiency, and does not cause power loss when switching the switching element, and has high efficiency. Can be controlled.

A first invention is connected between a heating coil, a resonant capacitor connected in series with the heating coil, a DC power supply for supplying energy to the heating coil, and a positive side of the heating coil and the DC power supply. A first switching element including a first diode; a second switching element including a second diode connected between the heating coil and a negative electrode side of the DC power supply; and the resonance capacitor; Connected between the positive side of the DC power source and a third switching element including a third diode, and connected between the resonant capacitor and the negative side of the DC power source, including a fourth diode And a control circuit for supplying a drive signal to the first to fourth switching elements, and a set of the first switching element and the second switching element. And a third switching alternately a driving signal applied to the set of the switching element and the fourth switching element, the first switching element and the fourth switching element, and the second switching element and the optional third switching element Induction heating in which driving is performed with a phase difference and the switching elements are continuously turned on / off for a plurality of times, and then power control is performed by providing drive signal stop periods for all the first to fourth switching elements at regular intervals. It is a device. This makes it possible to increase the resolution of the power supplied to the heating coil by using phase difference control in combination, so that it is easy to supply arbitrary power to the heating coil, and the power control interval can be narrowed. It is possible to improve convenience.

A heating coil; a resonant capacitor connected in series with the heating coil; a direct current power source for supplying energy to the heating coil; and a first diode connected between the heating coil and the positive electrode side of the direct current power source. A first switching element included, a second switching element connected between the heating coil and the negative electrode side of the DC power supply and including a second diode, the resonance capacitor, and a positive electrode side of the DC power supply And a third switching element including a third diode, and a fourth switching element including a fourth diode connected between the resonance capacitor and the negative electrode side of the DC power source. And a control circuit for supplying a drive signal to the first to fourth switching elements, a set of the first switching element and the second switching element, and a third The drive signals to be applied to the pair of the switching element and the fourth switching element are alternately switched, and the first switching element and the fourth switching element, and the second switching element and the third switching element are driven in the same phase, Furthermore, after the switching elements are continuously turned on / off for a plurality of times, the drive signal stop period is provided in all the first to fourth switching elements at a constant period, and the power control is performed. Can be controlled arbitrarily. Furthermore, since the switching element is stopped during the period when no power is supplied to the heating coil, power loss occurs when switching the switching element.
Therefore, power can be controlled with high efficiency.

In the third invention, in particular, in the first or second invention, a period for supplying a drive signal to the first to fourth switching elements and a drive signal stop period for all the first to fourth switching elements are provided. The basic of the current flowing through the heating coil is controlled by making the sum of the period for supplying the drive signal to the switching element and the period for stopping the drive signal constant and controlling the drive ratio between the period for supplying the drive signal to the switching element and the drive signal stop period. By performing power control at a constant frequency, the fundamental frequency component of the current generated from the induction heating device is determined by the combined period of supplying and not supplying power to the heating coil. For this reason, power control can be performed at a constant frequency, and two different induction heating devices can be installed adjacent to each other so that no interference sound is generated.

  In particular, in any one of the first to third inventions, the fourth invention is characterized in that the drive signal stop period for all the first to fourth switching elements is longer than the period of one pulse of the control signal when the switching elements are driven. In a short case, when all the first to fourth switching elements are shifted from the drive signal stop state to the switching element drive state, the drive signals generated from the control circuit are transmitted to the first to fourth switching elements. The switching element is driven by generating a drive signal of the same switching element as the switching element that was being driven immediately before the drive signal stopped state, and a drive signal stop period is included in all the first to fourth switching elements. If the control signal is longer than one pulse period when the switching element is driven, all the first to fourth switching elements are switched from the drive signal stop state to the switching element. When switching to the driving state of the switching element, a switching element that is different from the switching element that has been driven immediately before the driving signal is stopped in all the first to fourth switching elements is generated from the control circuit. The switching element is driven to control the power by generating the drive signal. As a result, when the switching element shifts from the drive stop state to the drive state, power is supplied to the heating coil again in synchronization with the vibration of the current flowing in the heating coil. Can be increased. Also, when switching from the drive stop state to the drive state of the switching element, it is driven from the switching element in which current flows through the diode connected in parallel with the switching element, and the voltage applied to the snubber capacitor is short-circuited There is no longer to do. Therefore, the heat generated by the switching element is reduced, and the cooling device can be downsized. Furthermore, since the power loss at the time of switching of the switching element is reduced, the efficiency of the induction heating device can be increased.

  According to a fifth aspect of the invention, in particular, in any one of the first to fourth aspects of the invention, the fifth aspect includes means for detecting a frequency relationship between the resonance frequency of the heating load and the driving frequency of the switching element, and follows the change in the heating load. The switching element is driven by changing the frequency of the driving signal generated from the control circuit, and power control is performed by providing a driving signal stop period for all the first to fourth switching elements at a constant period, thereby heating When the load parameter of the heating coil changes due to replacement of an object, etc., the switching frequency of the switching element is reset to a frequency close to the resonance frequency determined by the load parameter of the heating coil and the resonant capacitor. Regardless of the condition, large power can be supplied to the heating coil with high power factor and high efficiency. In addition, since the fundamental frequency component of the current generated from the induction heating device is determined by the combined period of supplying power to the heating coil and the period of not supplying it, the drive frequency of the switching element changes due to replacement of the object to be heated. The power can be controlled at a constant frequency, and two different induction heating devices can be installed adjacent to each other so that no interference sound is generated.

  In particular, the sixth aspect of the invention relates to any one of the first to fifth aspects of the invention, in which the frequency of the drive signal generated from the control circuit is changed to drive the switching element in the vicinity of the resonance point of the heating load, and the fixed period In the first to fourth switching elements, the drive signal stop period is provided and power control is performed, so that the drive frequency of the switching element is determined by the heating coil and the resonance capacitor during the period of supplying power to the heating coil. Since the frequency is set close to, high power can be supplied to the heating coil with high power factor and high efficiency.

  In particular, in a seventh invention, in any one of the first to sixth inventions, the seventh invention includes a current detection means for detecting current, and the first to fourth switching elements are switched from the drive signal stop state to the switching elements. At the time of transition to the driving state, the driving signal generated from the control circuit is generated from the driving signal of the switching element through which current flows, and the switching element is driven to perform power control, so that the switching element is driven from the stopped state to the driving state. Since the electric power is supplied again to the heating coil in synchronization with the vibration of the current flowing through the heating coil when shifting to the step, the electric power supplied to the heating coil can be increased. Also, when switching from the drive stop state to the drive state of the switching element, it is driven from the switching element in which current flows through the diode connected in parallel with the switching element, and the voltage applied to the snubber capacitor is short-circuited There is no longer to do. Therefore, the heat generated by the switching element is reduced, and the cooling device can be downsized. Furthermore, since the power loss at the time of switching of the switching element is reduced, the efficiency of the induction heating device can be increased.

In an eighth aspect of the invention, in particular, in any one of the first to seventh aspects of the invention, the power supply for supplying energy to the heating coil is a full-wave rectification obtained by using a commercial power supply and a diode bridge instead of a DC power supply. By using a power supply or a half-wave rectified power supply, a circuit for converting from a commercial power supply to a DC smoothing power supply becomes unnecessary, and an inexpensive inverter can be formed by reducing the number of parts.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
1 and 2 show an induction heating apparatus according to Embodiment 1 of the present invention.

  As shown in FIG. 1, the induction heating device according to the present embodiment has a heating coil 16 that heats a heated object 10 such as a pan, a resonance capacitor 17 connected in series with the heating coil 16, and energy to the heating coil 16. , A first switching element 12 connected between the heating coil 16 and the positive side of the DC power source 11, and a second connected between the heating coil 16 and the negative side of the DC power source 11. Switching element 13, a third switching element 14 connected between the resonance capacitor 17 and the positive electrode side of the DC power supply 11, and a fourth switching element connected between the resonance capacitor 17 and the negative electrode side of the DC power supply 11. Element 15 and a control circuit 18 for supplying a drive signal to the first to fourth switching elements 12 to 15, and the first switching element 12 and the second switching element The drive signal given to the set of the element 13 and the set of the third switching element 14 and the fourth switching element 15 are alternately switched, and the first switching element 12, the fourth switching element 15, and the second switching element are switched. 13 and the third switching element 14 are driven in the same phase, and power control is performed by providing drive signal stop periods in all the first to fourth switching elements 12 to 15 at a constant cycle.

  Moreover, each switching element 12-15 comprises the full bridge type inverter, and the 1st-4th diode 12a-15a is connected to each switching element 12-15 in parallel, respectively. Further, a first snubber capacitor 19 and a second snubber capacitor 20 are connected in parallel to the switching elements 13 and 15, respectively, and a soft switching operation is performed by all the first to fourth switching elements 12 to 15. I am doing so.

  Next, operation | movement of the induction heating apparatus in the said structure is demonstrated.

  When the first switching element 12 and the fourth switching element 15 are turned on, the circuit loop of the DC power supply 11 → the first switching element 12 → the heating coil 16 → the resonance capacitor 17 → the fourth switching element 15 → the DC power supply 11 is changed. The DC power supply 11 and the heating coil 16 are connected to each other, and power is supplied to the heating coil 16. When the first switching element 12 and the fourth switching element 15 are simultaneously turned off after a certain period of time, the charge and discharge of the charges in the first snubber capacitor 19 and the second snubber capacitor 20 occur, and then flow to the heating coil 16. The current that has flowed flows through the diode 13a connected in parallel with the second switching element 13 and the diode 14a connected in parallel with the third switching element 14, and the heating coil 16 → resonance capacitor 17 → diode 14a → DC power supply 11 → diode. 13a → A circuit loop of the heating coil 16 is formed. If this state is maintained, a circuit loop of the DC power supply 11 → the third switching element 14 → the resonance capacitor 17 → the heating coil 16 → the second switching element 13 → the DC power supply 11 is formed after a certain period of time, and the DC power supply 11 And the heating coil 16 is connected, and power is supplied to the heating coil 16. In this state, a current in the reverse direction flows through the heating coil 16 from the initial state.

  Furthermore, the switching operation from the second switching element 13 to the first switching element 12 and from the third switching element 14 to the fourth switching element 15 is also performed by performing the same procedure as described above.

  Further, after repeating this operation a plurality of times, as shown in FIG. 2, by providing a drive signal stop period for all the first to fourth switching elements 12 to 15, no current flows through the heating coil 16 and heating is performed. Power is not supplied to the coil 16. In addition, after all the first to fourth switching elements 12 to 15 have passed the drive signal stop period, the switching elements are started again to start a series of operations.

  In the above control method, a positive power supply voltage and a negative power supply voltage can be applied alternately to the load connection portion of the inverter, so that large power can be supplied to the heating coil 16. Further, by using a full bridge type inverter, it is possible to supply a large amount of power to the heating coil 16 even when the power supply voltage is low. Therefore, the function of boosting the power supply voltage is unnecessary, and an inexpensive inverter is formed by reducing the number of parts. can do. Furthermore, since the driving of the switching elements 12 to 15 is stopped during a period in which power is not supplied to the heating coil 16, no power loss occurs when the switching elements 12 to 15 are switched, and the power can be controlled with high efficiency. .

  In addition, since the fundamental frequency component of the current generated from the induction heating device is determined by the combined period of supplying power to the heating coil 16 and the period of not supplying it, the power can be controlled at a constant frequency and two different inductions can be controlled. Heating devices can be installed adjacent to each other so that no interference noise is generated.

  As described above, in the present embodiment, since the load connection portion of the inverter can alternately apply a positive power supply voltage and a negative power supply voltage, a large amount of power can be supplied to the heating coil 16. Further, the average power can be arbitrarily controlled with high efficiency by controlling the ratio of the driving period of the switching elements 12 to 15 and the non-driving period of the switching elements 12 to 15 and the phase difference of the driving signal generated from the control circuit 18. can do. Furthermore, since the driving of the switching elements 12 to 15 is stopped during a period in which power is not supplied to the heating coil 16, no power loss occurs when the switching elements 12 to 15 are switched, and the power can be controlled with high efficiency. .

(Embodiment 2)
FIG. 3 shows the voltage and current waveforms of the induction heating apparatus according to Embodiment 2 of the present invention. Since the circuit configuration is the same as that of the first embodiment, the description thereof is omitted.

  In the induction heating apparatus according to the present embodiment, a period for supplying a drive signal to the first to fourth switching elements and a drive signal stop period for all the first to fourth switching elements 12 to 15 are provided. The sum of the period during which the drive signal is supplied to -15 and the period during which the drive signal is stopped is constant, and the drive ratio between the period during which the drive signal is supplied to the switching elements 12-15 and the drive signal stop period is controlled to flow through the heating coil 16 The power control is performed with the current fundamental frequency constant.

  Next, the operation in the control method will be described.

  When the first switching element 12 and the fourth switching element 15 are turned on, the circuit loop of the DC power supply 11 → the first switching element 12 → the heating coil 16 → the resonance capacitor 17 → the fourth switching element 15 → the DC power supply 11 is changed. The DC power supply 11 and the heating coil 16 are connected to each other, and power is supplied to the heating coil 16. When the fourth switching element 15 is turned off after a certain period, the second snubber capacitor 20 is charged and discharged, and then the current flowing in the heating coil 16 is a diode connected in parallel with the third switching element 14. The circuit loop of the heating coil 16 → the resonance capacitor 17 → the diode 14a → the first switching element 12 → the heating coil 16 is formed.

  When the first switching element 12 is turned off after a certain period of time after the fourth switching element 15 is turned off, the first snubber capacitor 19 is charged and discharged, and then flows into the heating coil 16. The current flows through the diode 13a connected in parallel with the second switching element 13, and forms a circuit loop of the heating coil 16, the resonance capacitor 17, the diode 14a, the DC power supply 11, the diode 13a, and the heating coil 16. If this state is maintained, a circuit loop of the DC power supply 11 → the third switching element 14 → the resonance capacitor 17 → the heating coil 16 → the second switching element 13 → the DC power supply 11 is formed after a certain period of time, and the DC power supply 11 And the heating coil 16 is connected, and power is supplied to the heating coil 16. In this state, a current in the reverse direction flows through the heating coil 16 from the initial state.

  The switching operation from the second switching element 13 to the first switching element 12 and from the third switching element 14 to the fourth switching element 15 is also performed by performing the same procedure as described above.

  In addition, after repeating this operation a plurality of times, by providing a drive signal stop period for all the first to fourth switching elements 12 to 15, no current flows through the heating coil 16, and no power is supplied to the heating coil 16. Like that.

  In addition, after a drive signal stop period has passed through all the first to fourth switching elements 12-15, a series of operations is started by starting the switching elements 12-15 again.

  In the above control method, since the driving of the switching elements 12 to 15 is stopped during the period when the power is not supplied to the heating coil 16, no power loss occurs when switching the switching elements 12 to 15, and the power is controlled with high efficiency. be able to.

  In addition, since the fundamental frequency component of the current generated from the induction heating device is determined by the combined period of supplying power to the heating coil 16 and the period of not supplying it, the power can be controlled at a constant frequency and two different inductions can be controlled. Heating devices can be installed adjacent to each other so that no interference noise is generated.

  Furthermore, since the resolution of the power supplied to the heating coil 16 can be increased by using the phase difference control in combination, it is easy to supply arbitrary power to the heating coil 16 and the interval at which the power can be controlled is narrowed. It is possible to improve convenience.

  As described above, in the present embodiment, the first switching element 12 and the fourth switching element 15, and the second switching element 13 and the third switching element 14 are driven with an arbitrary phase difference, and constant By providing a drive signal stop period to all the first to fourth switching elements 12 to 15 in a cycle and performing power control, the induction heating device can control power with high efficiency, and two different induction heating can be performed. The devices can be installed adjacent to each other so that no interference sound is generated. The power control interval can be narrowed and the convenience can be improved.

(Embodiment 3)
4 and 5 show voltage and current waveforms of the induction heating device according to Embodiment 3 of the present invention. Since the circuit configuration is the same as that of the first embodiment, the description thereof is omitted.

  In the induction heating apparatus according to the present embodiment, when the drive signal stop period is shorter than the period of one pulse of the control signal when driving the switching elements, the first to fourth switching elements 12 to 15 are first to fourth. The drive signal generated from the control circuit 18 is transferred to all the first to fourth switching elements 12 to 15 when the switching signal 12 is shifted from the drive signal stop state to the switching element drive state. The switching element is driven by generating a drive signal of the same switching element as the switching element that was being driven immediately before the stop state. Further, when the drive signal stop period of all the first to fourth switching elements 12 to 15 is longer than the period of one control signal pulse when the switching elements are driven, all the first to fourth switching elements 12 to 15 are used. At the time of transition from the drive signal stop state to the drive state of the switching element, the drive signal generated from the control circuit 18 is driven to all the first to fourth switching elements 12 to 15 immediately before the drive signal stop state. The power is controlled by driving the switching element by generating it from the drive signal of the switching element different from the switching element.

  That is, the drive signal stop period and the period of one pulse of the control signal when driving the switching element are detected in all the first to fourth switching elements 12 to 15 and reflected in the control. The waveform in FIG. 4 is a waveform when the drive signal stop period in all the first to fourth switching elements 12 to 15 is shorter than the period of one pulse of the control signal when driving the switching elements. The driving is started from the same switching element as the switching element that has been driven immediately before the driving signal is stopped in all the switching elements 12 to 15. 5 is a waveform when the drive signal stop period in all of the first to fourth switching elements 12 to 15 is longer than the period of one control signal pulse when the switching elements are driven. Driving is started from a switching element different from the switching element that was driven immediately before the drive signal is stopped in all the fourth switching elements 12 to 15.

  As described above, in this embodiment, when the switching elements 12 to 15 are shifted from the drive stop state to the drive state, power is again supplied to the heating coil 16 in synchronization with the vibration of the current flowing in the heating coil 16. Since the electric power is supplied, the electric power supplied to the heating coil 16 can be increased. In addition, when the switching elements 12 to 15 are shifted from the driving stop state to the driving state, the switching elements in which current is flowing in the diodes connected in parallel with the switching elements are driven and applied to the snubber capacitor. The voltage will not be short-circuited. Therefore, the heat generation of the switching elements 12 to 15 is reduced, and the cooling device can be downsized. Furthermore, since the power loss at the time of switching the switching elements 12 to 15 is reduced, the efficiency of the induction heating device can be increased.

(Embodiment 4)
FIG. 6 shows the voltage and current waveforms of the induction heating device in Embodiment 4 of the present invention. Since the circuit configuration is the same as that of the first embodiment, the description thereof is omitted.

  The induction heating device in the present embodiment includes means for detecting the frequency relationship between the resonance frequency of the heating load and the driving frequency of the switching elements 12 to 15, and a drive signal generated from the control circuit 18 following the change in the heating load. The switching elements 12 to 15 are driven by changing the frequency, and power control is performed by providing a drive signal stop period for all the first to fourth switching elements 12 to 15 at a constant cycle.

  That is, the driving frequencies of the switching elements 12 to 15 are different. For example, when a pan is heated by an induction heating device, the parameters of the heating coil 16 change depending on the material and shape of the pan, and the resonance frequency determined by the heating coil 16 and the resonance capacitor 17 also changes. When the resonance frequency changes, the driving frequency of the switching element is changed in order to make the relationship with the driving frequency of the switching element constant.

  As described above, in the present embodiment, when the load parameter of the heating coil 16 is changed due to replacement of the object to be heated 10 or the like, the load parameter of the heating coil 16 and the resonance capacitor whose driving frequency of the switching elements 12 to 15 is changed. Since the frequency close to the resonance frequency determined by 17 is reset, large power can be supplied to the heating coil 16 with high power factor and high efficiency regardless of replacement of the object to be heated 10 or the like. In addition, since the fundamental frequency component of the current generated from the induction heating device is determined by the combined period of supplying power to the heating coil 16 and the period of not supplying it, the switching elements 12 to 15 are driven by replacing the heated object 10 or the like. Even if the frequency changes, power control can be performed at a constant frequency, and two different induction heating devices can be installed adjacent to each other so that no interference sound is generated.

(Embodiment 5)
FIG. 7 shows the voltage and current waveforms of the induction heating device in Embodiment 5 of the present invention. Since the circuit configuration is the same as that of the first embodiment, the description thereof is omitted.

  The induction heating apparatus in the present embodiment changes the frequency of the drive signal generated from the control circuit 18 to drive the switching elements 12 to 15 near the resonance point of the heating load, and the first to fourth in a constant cycle. All the switching elements 12 to 15 are provided with a drive signal stop period to perform power control.

  That is, if the difference between the resonance frequency determined by the heating coil 16 and the resonance capacitor 17 and the driving frequency of the switching elements 12 to 15 is large, it is difficult to supply power to the heating coil 16. Therefore, in order to supply a large amount of power to the heating coil 16, the driving frequency of the switching elements 12 to 15 is driven at a frequency close to the resonance frequency determined by the heating coil 16 and the resonance capacitor 17.

  As described above, in the present embodiment, during the period in which power is supplied to the heating coil 16, the driving frequency of the switching elements 12 to 15 is set to a frequency close to the resonance frequency determined by the heating coil 16 and the resonance capacitor 17. Large power can be supplied to the coil 16 with high power factor and high efficiency.

(Embodiment 6)
FIG. 8 shows an induction heating apparatus according to Embodiment 6 of the present invention. Since the circuit configuration is the same as that of the first embodiment, the description thereof is omitted.

  The induction heating device in the present embodiment includes current detection means 21 that detects current, and at the time of transition from the drive signal stop state to the drive state of the switching elements in all the first to fourth switching elements 12 to 15, The drive signal generated from the control circuit 18 is generated from the drive signal of the switching element through which a current flows, and the switching element is driven to perform power control.

  In addition, voltage detecting means 22 for detecting the voltage value applied to the resonant capacitor 17 is provided, and the switching element is driven by changing the timing of the drive signal generated from the control circuit 18 based on the detected value, so as to have a constant cycle. Thus, all of the first to fourth switching elements 12 to 15 are provided with a drive signal stop period to perform power control.

  That is, by providing the current detection means 21, the direction of the current flowing through the circuit and the magnitude of the current are detected, and which switching element of the first to fourth switching elements 12-15 is flowing through the current is detected. Detected. Further, the voltage detection means 22 is provided to detect the direction and magnitude of the voltage applied to the resonant capacitor 17 and the like.

  In the above configuration, when the switching elements 12 to 15 are shifted from the drive stop state to the drive state, power is supplied to the heating coil 16 again in synchronization with the vibration of the current flowing in the heating coil 16. The electric power supplied to the heating coil 16 can be increased.

  In addition, when the switching elements 12 to 15 are shifted from the driving stop state to the driving state, the switching elements in which current is flowing in the diodes connected in parallel with the switching elements are driven and applied to the snubber capacitor. The voltage will not be short-circuited. Therefore, the heat generated by the switching element is reduced, and the cooling device can be downsized.

  Moreover, since the power loss at the time of switching of the switching elements 12-15 decreases, the efficiency of an induction heating apparatus can be made high.

  Further, the period during which power is supplied to the heating coil 16 is set to a frequency close to the resonance frequency determined by the heating coil 16 and the resonance capacitor 17 based on the detected value. Electric power can be supplied with high power factor and high efficiency.

  Furthermore, when an abnormal voltage value or current value is detected, the driving of the switching element can be stopped so that power is not supplied to the heating coil 16, so that the safety of the induction heating device can be improved. it can.

  Note that the current detection means 21 and the voltage detection means 22 may be only one without providing both.

  As described above, in the present embodiment, at least one of the current detection means 21 and the voltage detection means 22 is provided, and the switching element is changed by changing the timing of the drive signal generated from the control circuit 18 based on the detected value. 12 to 15 are driven, and a drive signal stop period is provided for all of the first to fourth switching elements 12 to 15 at a constant period to perform power control, whereby a large power is supplied to the heating coil 16 with a high power factor. It can supply with high efficiency, a cooling device can be reduced in size, the efficiency of an induction heating apparatus can be made high, and the safety | security of an induction heating apparatus can be improved.

(Embodiment 7)
FIG. 9 shows an induction heating apparatus according to Embodiment 7 of the present invention. Since the circuit configuration is the same as that of the first embodiment, the description thereof is omitted.

  The induction heating apparatus in the present embodiment includes power detection means 23 that detects power consumption, and detects power consumed by the induction heating apparatus or power consumed by the heating coil 16.

  That is, the detection of the power detection means 23 increases the drive frequency of the switching elements 12 to 15 when power equal to or higher than the set value is supplied, and switches to the switching elements 12 to 15 when power equal to or lower than the set value is supplied. The power supplied to the heating coil 16 is set by lowering the drive frequency of 15 and performing power control by providing a drive signal stop period for all the first to fourth switching elements 12 to 15 at a constant cycle. Since it is possible to match the electric power, any desired calorific value can be stably obtained.

  In addition, when power equal to or higher than the set value is supplied by the detection of the power detection means 23, the first switching element 12 and the fourth switching element 15, and the second switching element 13 and the third switching element. 14 is widened, and when power equal to or lower than the set value is supplied, the first switching element 12 and the fourth switching element 15, and the second switching element 13 and the third switching element 14 are The power supplied to the heating coil 16 is adjusted to the set power by reducing the phase difference and performing power control by providing a drive signal stop period in all the first to fourth switching elements 12 to 15 at a constant cycle. Therefore, any desired calorific value can be stably obtained.

  Further, by the detection of the power detection means 23, a drive signal stop period is provided for all of the first to fourth switching elements 12 to 15 at a constant cycle according to the set power, or the first to fourth switching devices at a constant cycle. If it is desired to supply a large amount of power to the heating coil 16 by switching power control by switching whether to perform control only by phase shift without providing a drive signal stop period for all the fourth switching elements 12 to 15, By switching so as not to provide the drive signal stop period for all of the first to fourth switching elements 12 to 15, the power is larger than providing the drive signal stop period for all of the first to fourth switching elements 12 to 15. Therefore, the power control value can be increased.

  As described above, in the present embodiment, by providing the power detection means 23, it is possible to stably obtain a desired amount of heat generation and increase the value of power control.

(Embodiment 8)
FIG. 10 shows an induction heating apparatus according to the eighth embodiment of the present invention. Since the circuit configuration is the same as that of the first embodiment, the description thereof is omitted.

  In the induction heating apparatus according to the present embodiment, the power source for supplying energy to the heating coil 16 is a full-wave rectified power source or a half-wave rectified power source obtained by using a commercial power source 24 and a diode bridge 25 instead of the DC power source 11. did. A smoothing capacitor 26 is provided in parallel with the power supply.

  As described above, in the present embodiment, the power source for supplying energy to the heating coil 16 is a commercial power source using a full-wave rectified power source or a half-wave rectified power source obtained by using a commercial power source and a diode bridge. A circuit for converting from DC to a DC smoothing power supply is unnecessary, and an inexpensive inverter can be formed by reducing the number of parts. In addition, since the control method according to the present embodiment can supply a large amount of power to the heating coil 16, it is possible to obtain the necessary power without using a constant voltage power source. Therefore, it is not necessary to perform a smooth operation of the commercial power supply, and the power factor of the induction heating device can be increased.

  In addition, the structure in each Embodiment 1-8 can be suitably combined as needed, and is not limited to the structure of Embodiment itself. Moreover, although the full bridge type inverter was shown as an inverter, other inverters can also be applied.

  As described above, the induction heating device according to the present invention can supply a large amount of power to the heating coil, can arbitrarily control the average power with high efficiency, and can generate a power loss when switching the switching element. Therefore, it can be applied to not only home appliances such as IH cooking heaters and IH rice cookers but also all devices that heat by induction heating including commercial products such as metal quenching. It is. Furthermore, this control method has great industrial applicability because the burden on the switching element is small even when the switching element is driven at a high frequency, and a metal having a low specific resistance such as aluminum can be easily heated.

The circuit diagram which shows the induction heating apparatus in Embodiment 1 of this invention The figure which shows the voltage waveform and current waveform in the same induction heating device The figure which shows the voltage waveform and current waveform of the induction heating apparatus in Embodiment 2 of this invention The figure which shows the voltage waveform and current waveform of the induction heating apparatus in Embodiment 3 of this invention. The figure which shows the voltage waveform and current waveform different from FIG. 4 of the same induction heating apparatus The figure which shows the voltage waveform and current waveform of the induction heating apparatus in Embodiment 4 of this invention. The figure which shows the voltage waveform and current waveform of the induction heating apparatus in Embodiment 5 of this invention. The circuit diagram which shows the induction heating apparatus in Embodiment 6 of this invention The circuit diagram which shows the induction heating apparatus in Embodiment 7 of this invention The circuit diagram which shows the induction heating apparatus in Embodiment 8 of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Heated object 11 DC power supply 12 1st switching element 12a 1st diode 13 2nd switching element 13a 2nd diode 14 3rd switching element 14a 3rd diode 15 4th switching element 15a 4th Diode 16 Heating coil 17 Resonant capacitor 18 Control circuit 19 First snubber capacitor 20 Second snubber capacitor 21 Current detection means 22 Voltage detection means 23 Power detection means 24 Commercial power supply 25 Diode bridge 26 Smoothing capacitor

Claims (8)

A heating coil; a resonant capacitor connected in series with the heating coil; a direct current power source for supplying energy to the heating coil; and a first diode connected between the heating coil and the positive electrode side of the direct current power source. A first switching element included, a second switching element connected between the heating coil and the negative electrode side of the DC power supply and including a second diode, the resonance capacitor, and a positive electrode side of the DC power supply And a third switching element including a third diode, and a fourth switching element including a fourth diode connected between the resonance capacitor and the negative electrode side of the DC power source. And a control circuit for supplying a drive signal to the first to fourth switching elements, a set of the first switching element and the second switching element, and a third Alternately switched drive signal supplied to the switching element and the fourth set of switching elements, a first switching element and the fourth switching element, and a second driving switching element and the third switching element at an arbitrary phase difference In addition, an induction heating apparatus that performs power control by providing a drive signal stop period for all the first to fourth switching elements at a constant period after the switching elements are continuously turned on and off a plurality of times. A heating coil; a resonant capacitor connected in series with the heating coil; a direct current power source for supplying energy to the heating coil; and a first diode connected between the heating coil and the positive electrode side of the direct current power source. A first switching element included, a second switching element connected between the heating coil and the negative electrode side of the DC power supply and including a second diode, the resonance capacitor, and a positive electrode side of the DC power supply And a third switching element including a third diode, and a fourth switching element including a fourth diode connected between the resonance capacitor and the negative electrode side of the DC power source. And a control circuit for supplying a drive signal to the first to fourth switching elements, a set of the first switching element and the second switching element, and a third The drive signals to be applied to the pair of the switching element and the fourth switching element are alternately switched, and the first switching element and the fourth switching element, and the second switching element and the third switching element are driven in the same phase, Furthermore, the induction heating apparatus that performs power control by providing a drive signal stop period for all the first to fourth switching elements at a constant cycle after performing on / off control of the switching elements continuously a plurality of times . A period for supplying drive signals to the first to fourth switching elements, and all of the first to fourth switches;
A driving signal stop period is provided in the switching element, the sum of the period in which the drive signal is supplied to the switching element and the sum of the drive signal stop period is constant, and the drive ratio between the period in which the drive signal is supplied to the switching element and the drive signal stop period is controlled. The induction heating apparatus according to claim 1 , wherein power control is performed with a constant fundamental frequency of a current flowing through the heating coil . When the drive signal stop period for all of the first to fourth switching elements is shorter than the period of one pulse of the control signal when driving the switching elements, the first to fourth switching elements are switched from the drive signal stop state. When switching to the drive state of the element, the drive signal generated from the control circuit is driven by the same switching element as the switching element that has been driven immediately before the drive signal is stopped in all the first to fourth switching elements. When the switching element is driven by generating a signal and the drive signal stop period of all the first to fourth switching elements is longer than the period of one control signal pulse when the switching element is driven, the first to first Generated from the control circuit when transitioning from the drive signal stop state to the switching element drive state for all 4 switching elements Power is controlled by generating a drive signal from a switching element different from the switching element that was driven immediately before the drive signal is stopped in all the first to fourth switching elements. The induction heating apparatus according to any one of claims 1 to 3. A means for detecting the frequency relationship between the resonance frequency of the heating load and the driving frequency of the switching element is provided, and the switching element is driven by changing the frequency of the driving signal generated from the control circuit following the change of the heating load, The induction heating apparatus according to any one of claims 1 to 4, wherein power control is performed by providing a drive signal stop period for all of the first to fourth switching elements in a cycle. The frequency of the drive signal generated from the control circuit is changed to drive the switching element near the resonance point of the heating load, and the first to fourth switching elements are provided with a drive signal stop period at a certain period to control the power. The induction heating apparatus according to any one of claims 1 to 5, wherein: Switching that includes current detection means for detecting current, and that causes all of the first to fourth switching elements to pass a drive signal generated from the control circuit when transitioning from the drive signal stop state to the drive state of the switching element. The induction heating apparatus according to any one of claims 1 to 6, wherein power control is performed by driving a switching element generated from a drive signal of the element. Power detection means for detecting power consumption is provided, and drive signal stop periods are provided for all of the first to fourth switching elements at a constant cycle according to the set power, or the first to fourth at a constant cycle. The induction heating apparatus according to any one of claims 1 to 7, wherein power control is performed by switching whether to perform control only by phase shift without providing a drive signal stop period for all of the switching elements.