CN107438299B

CN107438299B - Electromagnetic oven

Info

Publication number: CN107438299B
Application number: CN201710812314.5A
Authority: CN
Inventors: 周宇; 赵礼荣
Original assignee: Zhejiang Shaoxing Supor Domestic Electrical Appliance Co Ltd
Current assignee: Zhejiang Shaoxing Supor Domestic Electrical Appliance Co Ltd
Priority date: 2017-09-11
Filing date: 2017-09-11
Publication date: 2020-09-01
Anticipated expiration: 2037-09-11
Also published as: CN107438299A

Abstract

The present invention provides an induction cooker, comprising: control circuit, charge-discharge circuit, first triode and inductance. The input end of the charge-discharge circuit is connected with the second power supply, the output end of the charge-discharge circuit is connected with the driving circuit through an inductor, the charge-discharge circuit is further connected with the collector electrode of the first triode, the emitter electrode of the first triode is grounded, and the base electrode of the first triode is connected with the control circuit. The control circuit is used for sending a pulse signal with preset duration to the base electrode of the first triode when receiving the heating instruction, so that the voltage of the power supply provided by the charging and discharging circuit to the driving circuit is smaller than the voltage provided by the second power supply within the preset duration after the charging and discharging circuit receives the heating instruction. When the induction cooker provided by the invention is used for detecting a pot, the driving circuit works at a lower second driving voltage, so that the problem that the induction cooker is not provided with a pot during pot detection, and the IGBT is possibly damaged is avoided; the IGBT is further protected by arranging the inductor for energy storage buffering.

Description

Electromagnetic oven

Technical Field

The invention relates to the technical field of circuit structures, in particular to an induction cooker.

Background

The induction cooker has the advantages of safety, no open fire, high efficiency, energy conservation, cleanness and the like, and is common household electrical equipment. The induction cooker comprises a control circuit, a switching device and a resonance circuit, wherein the switching device of the induction cooker is usually an Insulated Gate Bipolar Transistor (IGBT). The working principle of the induction cooker is as follows: the control circuit controls the IGBT to be switched on and off rapidly, alternating current flows in the resonant circuit, the alternating current generates an alternating magnetic field, the alternating magnetic field is repeatedly cut at the bottom of the cookware, and annular current (eddy current) generated at the bottom of the cookware is heated, so that the cookware is heated.

If a pot is not placed above the microcrystalline panel of the induction cooker during heating of the induction cooker, heat energy converted from electric energy of a resonant circuit of the induction cooker can not be absorbed by the pot, and the NP junction temperature of the IGBT connected with the resonant circuit is too high, so that the IGBT is burnt out. Therefore, whether the pot has been placed on the electromagnetism stove needs to be detected before the electromagnetism stove begins to heat, need examine the pot before the electromagnetism stove heats promptly.

The common pot detection mode of the induction cooker comprises the following steps: the control circuit sends a pot detection pulse with preset time length to the IGBT, so that the IGBT is switched on and off within the preset time length, and a resonance signal is generated in the resonance circuit; the control circuit also detects a resonance signal in the resonance circuit by detecting the pan circuit, and determines whether a pan is placed on the induction cooker according to the resonance signal. However, the pot detection method in the prior art may still cause the junction temperature of the IGBT to be too high, and the IGBT is damaged.

Disclosure of Invention

In order to solve at least one problem mentioned in the background art, the invention provides an induction cooker, which solves the problem that the junction temperature of an IGBT is too high and is easy to damage when a pot is inspected by the existing induction cooker.

The present invention provides an induction cooker, comprising: the IGBT power supply comprises a driving circuit, an IGBT, a resonant circuit, a control circuit, a charging and discharging circuit, a first triode and an inductor, wherein the driving circuit is connected with a grid electrode of the IGBT, a collector electrode of the IGBT is connected with a first end of the resonant circuit, a second end of the resonant circuit and an emitter electrode of the IGBT are both connected with a first power supply source, and the emitter electrode of the IGBT is grounded;

the input end of the charge-discharge circuit is connected with a second power supply, and the output end of the charge-discharge circuit is respectively connected with the collector of the first triode and the first end of the inductor; the second end of the inductor is connected with the power input end of the driving circuit; the emitting electrode of the first triode is grounded, the base electrode of the first triode is connected with the control circuit, and the control circuit is also connected with the driving circuit;

the control circuit is used for sending a pulse signal with preset duration to the base electrode of the first triode when receiving the heating instruction, so that the voltage of the power supply provided by the charging and discharging circuit to the driving circuit is smaller than the voltage provided by the second power supply within the preset duration after the charging and discharging circuit receives the heating instruction.

When the induction cooker is heated each time, the charging and discharging circuit is firstly controlled to be charged to a second preset voltage which is smaller than the first preset voltage, and the second preset voltage is provided for the driving voltage, so that the driving circuit works at the lower second driving voltage when the induction cooker detects a pot, and the problem that the induction cooker is damaged due to the fact that a pot is not placed on the induction cooker when the pot is detected, and the current on the IGBT is possibly larger, and the junction temperature of the IGBT is too high is avoided; meanwhile, energy storage buffering is carried out through the inductor, and the change of current flowing through the inductor is restrained, so that the power input end of the driving circuit receives stable voltage, and the IGBT is further protected.

In the induction cooker, the number of the inductors is at least one, and the inductors are connected in series.

The induction cooker as described above, further comprising: a low-pass filter circuit;

and the second end of the inductor is connected with the power input end of the driving circuit through the low-pass filter circuit.

The low-pass filter circuit is arranged at the power input end of the driving circuit, so that interference signals are filtered, and the driving circuit and the IGBT are protected.

The induction cooker as described above, said low pass filter circuit comprising: a first current limiting element and a first capacitor;

the second end of the inductor is connected with the first end of the first current limiting element; and the second end of the first current limiting element is respectively connected with the first end of the first capacitor and the power input end of the driving circuit, and the second end of the first capacitor is grounded. The low-pass filter circuit is simple in structure and low in cost.

In the above electromagnetic oven, the charging and discharging circuit includes: a second capacitor and a second current limiting element;

the first end of the second capacitor and the first end of the second current limiting element are both connected with the second power supply, and the second end of the second capacitor is grounded;

and the second end of the second current limiting element is respectively connected with the collector of the first triode and the first end of the inductor.

The charge and discharge circuit comprises a capacitor and a current limiting element, and is simple in structure and low in cost.

The induction cooker as described above, further comprising: a third current limiting element;

the control circuit is connected with the base electrode of the first triode through the third current limiting element.

The third current limiting element plays a role in current limiting and is used for protecting the first triode.

The induction cooker as described above, further comprising: a pot detection circuit; the pot detection circuit is respectively connected with the control circuit and the resonance circuit;

the pot detection circuit is used for detecting a resonance signal in the resonance circuit within the preset time after the control circuit receives the heating instruction;

the control circuit is specifically used for determining whether a cooker is placed on the induction cooker or not according to the resonance signal detected by the cooker detection circuit; when no cooker is placed on the induction cooker, the IGBT is controlled to be turned off; when the cooker is placed on the induction cooker, the first triode is controlled to be turned off, so that the voltage provided by the output end of the charging and discharging circuit and the power input end of the driving circuit is equal to the voltage provided by the second power supply.

The first driving voltage is provided for the driving circuit when the induction cooker is heated, and the second driving voltage smaller than the first driving voltage is provided for the driving circuit when the pot is detected, so that the current flowing through the IGBT is small in the pot detection process, the over-high junction temperature of the IGBT is avoided, and the IGBT is protected.

The induction cooker, the control circuit comprises a pulse width modulation circuit, and the pulse width modulation circuit is connected with the third current limiting element;

the control circuit is specifically configured to control the pulse width modulation circuit to provide a pulse signal with a preset duration to the base of the first triode when the control circuit receives a heating instruction.

The induction cooker as described above, the driving circuit includes a level conversion circuit and a push-pull driving circuit;

the second end of the first current limiting element is respectively connected with the power input end of the level switching circuit and the power input end of the push-pull driving circuit;

the level switching circuit is respectively connected with the control circuit and the push-pull driving circuit, and the push-pull driving circuit is also connected with the grid electrode of the IGBT.

The induction cooker as described above, said level conversion circuit comprising: a fourth current limiting element and a second triode;

a first end of the fourth current limiting element is connected with a second end of the first current limiting element, and a second end of the fourth current limiting element is respectively connected with the push-pull driving circuit and a collector of the second triode; and the base electrode of the second triode is connected with the output port of the control circuit, and the emitting electrode of the second triode is grounded.

The level conversion circuit is used for level conversion, and is simple in structure and low in cost.

The induction cooker as described above, further comprising: a rectification filter circuit;

and the second end of the resonance circuit and the emitting electrode of the IGBT are connected with a mains supply through the rectification filter circuit.

The construction of the present invention and other objects and advantages thereof will be more apparent from the following description of the preferred embodiments taken in conjunction with the accompanying drawings.

Drawings

FIG. 1 is a first schematic structural diagram of an induction cooker according to the present invention;

FIG. 2 is a schematic structural diagram II of the induction cooker provided by the invention;

FIG. 3 is a third schematic structural view of an induction cooker according to the present invention;

FIG. 4 is a fourth schematic structural view of an induction cooker according to the present invention;

FIG. 5 is a schematic structural diagram of an induction cooker according to a fifth embodiment of the present invention;

FIG. 6 is a sixth schematic structural view of an induction cooker according to the present invention;

FIG. 7 is a seventh schematic structural view of an induction cooker according to the present invention;

fig. 8 is a schematic structural diagram eight of the induction cooker provided by the invention;

FIG. 9 is a ninth schematic structural view of an induction cooker according to the present invention;

fig. 10 is a schematic structural diagram ten of the induction cooker provided by the present invention.

Reference numerals:

14-a control circuit; 11-a drive circuit;

12-an IGBT; 13-a resonant circuit;

15-charge and discharge circuit; 16-a first triode;

17-inductance; 18-a low-pass filter circuit;

19-a first current limiting element; 20-a first capacitance;

21-a second capacitance; 22-a second current limiting element;

23-a third current limiting element; 24-pot detection circuit;

25-a pulse width modulation circuit; 26-a level shift circuit;

27-push-pull drive circuit; 28-a fourth current limiting element;

29-a second triode; 30-a rectifying and filtering circuit.

Detailed Description

Fig. 1 is a schematic structural diagram of an induction cooker according to the present invention. As shown in fig. 1, the induction cooker provided by the present invention includes:

the driving circuit 11, the IGBT12, the resonance circuit 13, the control circuit 14, the charging and discharging circuit 15, the first triode 16 and the inductor 17; wherein,

the driving circuit 11 is respectively connected with the control circuit 14 and the gate of the IGBT12, the collector of the IGBT12 is connected with the first end of the resonant circuit 13, the second end of the resonant circuit 13 and the emitter of the IGBT12 are both connected with the first power supply, and the emitter of the IGBT12 is grounded;

the input end of the charge and discharge circuit 15 is connected with a second power supply, and the output end of the charge and discharge circuit 15 is respectively connected with the collector of the first triode 16 and the first end of the inductor 17; a second end of the inductor 17 is connected with a power input end of the driving circuit 11;

the emitter of the first triode 16 is grounded, the base of the first triode 16 is connected with the control circuit 14, and the control circuit 14 is used for sending a pulse signal with preset duration to the base of the first triode 16 when receiving a heating instruction, so that the voltage of the power supply provided by the charging and discharging circuit 15 to the driving circuit 11 is smaller than the voltage provided by the second power supply within the preset duration after receiving the heating instruction.

Illustratively, the gate of the IGBT12 is connected to the driving circuit 11, the collector of the IGBT12 is connected to the first terminal of the resonant circuit 13, the second terminal of the resonant circuit 13 is connected to the first power supply, and the emitter of the IGBT12 is grounded and connected to the first power supply. The first power supply is illustratively a rectified and filtered dc power supply of a mains supply. The first power supply is connected to the resonant circuit 13 and the IGBT12 to form a heating circuit of the induction cooker. When the IGBT12 is turned on, the resonant circuit 13 is charged, and when the IGBT12 is turned off, the resonant circuit 13 discharges to generate an alternating magnetic field, which cuts a pot placed on the induction cooker to heat the pot.

Illustratively, the control circuit 14 controls the on and off of the IGBT12 by controlling the output terminal voltage of the driving circuit 11. Since the operating voltage of the control circuit 14 is usually 5V, the maximum voltage of the signal that the control circuit 14 can output is 5V, and the driving voltage when the IGBT12 is turned on is usually 15 to 20V, so the control circuit 14 cannot directly drive the IGBT12 to turn on. The driving circuit 11 is generally disposed between the control circuit 14 and the IGBT12, and is configured to shape and amplify the driving signal output by the control circuit 14, and send the shaped and amplified driving signal to the IGBT12 to drive the IGBT12 to turn on or off. Illustratively, the control circuit 14 is configured to output driving signals to the driving circuit 11 according to an operation instruction input by a user, and the driving signals include an on signal and an off signal. For example, when the control circuit 14 outputs a turn-on signal to the drive circuit 11, the output terminal of the drive circuit 11 outputs a high level, for example, 15 to 20V, so that the IGBT12 is turned on; when the control circuit 14 outputs a turn-off signal to the drive circuit 11, the output terminal of the drive circuit 11 outputs a low level, for example, 0V, so that the IGBT12 turns off. For example, when the IGBT12 is turned on, as the driving voltage of the IGBT12 increases, the current flowing through the IGBT12 increases, and as the current increases, the power supplied by the resonant circuit 13 increases.

For example, in the conventional electromagnetic oven, when the control circuit 14 receives a heating instruction input by a user, the control circuit 11 is first controlled to provide a high level of 15-20V to the IGBT12, and the IGBT12 is driven to be turned on to perform pot detection. If the cookware is detected, the control circuit 14 further controls the driving circuit 11 to output a driving signal; if no pot is detected, the control circuit 14 further controls the driving circuit 11 to output a shutdown signal. However, if no pot is placed on the induction cooker during pot detection, the electric energy of the resonant circuit 13 cannot be absorbed by the pot and can only be converted into heat energy, so that the junction temperature of the IGBT12 is too high, and the IGBT12 is damaged.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows: the current flowing through the IGBT12 is reduced by reducing the driving voltage provided by the driving circuit 11 to the driving circuit 11, so that the electric energy generated by the resonant circuit 13 when the induction cooker detects a pan is reduced, and the over-high junction temperature of the IGBT12 is avoided. Considering that the magnitude of the high level provided by the driving circuit 11 to the IGBT12 depends on the voltage magnitude of the power input terminal of the driving circuit 11, the present invention provides an induction cooker, wherein the high level output by the driving circuit 11 is controlled to be lower than the high level output by the driving circuit 11 when the induction cooker is heated when the induction cooker is used for pot detection.

For example, as shown in fig. 1, in the induction cooker provided in this embodiment, a charging and discharging circuit 15, a first triode 16 and an inductor 17 are added in the induction cooker. The input end of the charge and discharge circuit 15 is connected to a second power supply, and the voltage value of the second power supply is the maximum voltage value that the charge and discharge circuit 15 can provide. The voltage value of the second power supply is referred to as the first driving voltage. The output end of the charge and discharge circuit 15 is connected to the first end of the inductor 17, and the second end of the inductor 17 is connected to the power input end of the driving circuit 11. The inductor 17 is used for energy storage buffering, and the output end of the charging and discharging circuit 15 supplies a stable voltage to the power input end of the driving circuit 11 by suppressing the change of the current flowing through the inductor 17. The voltage applied by the driver circuit 11 determines the magnitude of the high level provided by the driver circuit 11 to the gate of the IGBT12, that is, determines the magnitude of the current flowing through the IGBT 12. When the voltage supplied from the output terminal of the charge and discharge circuit 15 to the power supply input terminal of the driver circuit 11 decreases, the current flowing through the IGBT12 will be caused to decrease.

Illustratively, the output terminal of the charging and discharging circuit 15 is further connected to the collector of the first transistor 16, the emitter of the first transistor 16 is grounded, and the base of the first transistor 16 is connected to the control circuit 14. The control circuit 14 is used for controlling the first transistor 16 to be turned on and off. When the control circuit 14 provides a low-high level signal to the first transistor 16, the first transistor 16 is turned on, and at this time, the charging and discharging circuit 15 is grounded through the first transistor 16, and the charging and discharging circuit 15 and the first transistor 16 form a discharging path. The longer the control circuit 14 provides a low high signal to the first transistor 16, the lower the voltage provided at the output of the charge and discharge circuit 15. When the control circuit 14 provides a low level signal to the first transistor 16, the first transistor 16 is turned off, and at this time, the discharge path formed by the charge and discharge circuit 15 and the first transistor 16 is disconnected, and the charge and discharge circuit 15 is charged. The control circuit 14 controls the duration of the charging and discharging circuit 15 by controlling the duration of the on and off of the first transistor 16, so that the voltage at the output terminal of the charging and discharging circuit 15 reaches a preset value, which is called a second driving voltage.

Illustratively, when the control circuit 14 receives the heating command, the control circuit 14 sends a pulse signal to the base of the first transistor 16 for a preset duration, wherein a high level of the pulse signal is used to turn on the first transistor 16, and a low level of the pulse signal is used to turn off the first transistor 16. The duty ratio of the pulse signal determines the magnitude of the second driving voltage provided at the output terminal of the charge and discharge circuit 15. Within the preset time, the induction cooker is in a pot detection state, and at this time, the voltage of the power supply provided by the charging and discharging circuit 15 to the driving circuit 11 is a second driving voltage which is smaller than a first driving voltage provided by a second power supply. When the preset duration is over, if the cookware is detected, the induction cooker is switched to a heating state; if the cookware is not detected, the induction cooker is switched to a pause working state. By providing the input voltage for the driving circuit 11 through the charging and discharging circuit 15, the current flowing through the IGBT12 is small when the pot is inspected by the induction cooker, and the problem that the junction temperature of the IGBT12 is too high and can be damaged is avoided.

The embodiment of the invention provides an induction cooker, which comprises: charge-discharge circuit, first triode and inductance. The input end of the charge-discharge circuit is connected with the second power supply, the output end of the charge-discharge circuit is connected with the driving circuit through an inductor, the charge-discharge circuit is further connected with the collector electrode of the first triode, the emitter electrode of the first triode is grounded, and the base electrode of the first triode is connected with the control circuit. The control circuit is used for sending a pulse signal with preset duration to the base electrode of the first triode when receiving the heating instruction, so that the voltage of the power supply provided by the charging and discharging circuit to the driving circuit in the preset duration after the heating instruction is received is smaller than the voltage provided by the second power supply. When the induction cooker is heated each time, the charging and discharging circuit is firstly controlled to be charged to a second preset voltage which is smaller than the first preset voltage, and the second preset voltage is provided for the driving voltage, so that the driving circuit works at the lower second driving voltage when the induction cooker detects a pot, and the problem that the induction cooker is damaged due to the fact that a pot is not placed on the induction cooker when the pot is detected, and the current on the IGBT is possibly larger, and the junction temperature of the IGBT is too high is avoided; meanwhile, energy storage buffering is carried out through the inductor, and the change of current flowing through the inductor is restrained, so that the power input end of the driving circuit receives stable voltage, and the IGBT is further protected.

Further, in the above embodiment, the inductance 17 may be at least one, and a plurality of inductances 17 are connected in series. For example, the inductor 17 in this embodiment may refer to a single inductor, or may refer to an inductor network obtained by connecting a plurality of inductors in series.

Further, in combination with the embodiment shown in fig. 1, the embodiment of the invention also provides an induction cooker. Fig. 2 is a schematic structural diagram of an induction cooker according to a second embodiment of the present invention, in which the induction cooker further includes a low-pass filter circuit for filtering out interference signals. As shown in fig. 2, in this embodiment, the induction cooker further includes: a low-pass filter circuit 18; a second terminal of the inductor 17 is connected to a power input terminal of the driver circuit 11 via a low pass filter circuit 18.

Illustratively, referring to fig. 2, the power supply provided through the inductor 17 is filtered by adding a low-pass filter circuit 18 to the power supply input terminal of the driving circuit 11, so as to filter the fluctuation and interference signals of the dc power supply, thereby further protecting the driving circuit 11 and the IGBT 12.

The induction cooker provided by the embodiment is provided with the low-pass filter circuit at the power input end of the driving circuit, and is used for filtering interference signals and protecting the driving circuit and the IGBT.

Illustratively, on the basis of the embodiment shown in fig. 2, the invention further provides an induction cooker, and the structure of the low-pass filter circuit is explained in detail. Fig. 3 is a schematic structural diagram of a third electromagnetic oven provided in the present invention, and as shown in fig. 3, the low-pass filter circuit 18 includes: a first current limiting element 19 and a first capacitor 20.

A second terminal of the inductor 17 is connected to a first terminal of a first current limiting element 19; a second terminal of the first current limiting element 19 is connected to a first terminal of the first capacitor 20 and a power input terminal of the driving circuit 11, respectively, and a second terminal of the first capacitor 20 is grounded.

Illustratively, referring to the embodiment shown in fig. 3, in this embodiment, the low-pass filter circuit 18 includes: a first current limiting element 19 and a first capacitor 20. A second terminal of the inductor 17 is connected to a first terminal of a first current limiting element 19; a second terminal of the first current limiting element 19 is connected to a first terminal of the first capacitor 20 and a power input terminal of the driving circuit 11, respectively, and a second terminal of the first capacitor 20 is grounded. Illustratively, the first current limiting element 19, as well as other current limiting elements in the following embodiments of the present invention, may be a resistor.

The low-pass filter circuit provided by the embodiment has the advantages of simple structure and low cost.

Further, in combination with the embodiment shown in fig. 3, an embodiment of the present invention further provides an induction cooker. Fig. 4 is a schematic structural diagram of an induction cooker according to the present invention, and the structure of the charge/discharge circuit 15 is explained in detail in this embodiment. As shown in fig. 4, the charge and discharge circuit 15 includes: a second capacitor 21 and a second current limiting element 22;

a first end of the second capacitor 21 and a first end of the second current limiting element 22 are both connected with a second power supply, and a second end of the second capacitor 21 is grounded; a second terminal of the second current limiting element 22 is connected to the collector of the first transistor 16 and to a first terminal of the inductor 17, respectively.

Illustratively, as shown in fig. 4, the charging and discharging circuit 15 includes a second capacitor 21 and a second current limiting element 22. A first end of the second capacitor 21 and a first end of the second current limiting element 22 are used as input ends of the charge and discharge circuit 15, and are both connected with the second power supply. The second terminal of the second capacitor 21 is connected to ground. A second terminal of the second current limiting element 22 is connected to a collector of the first transistor 16 and a first terminal of the inductor 17, respectively, as an output terminal of the charging and discharging circuit 15. When the first transistor 16 is turned on, the second capacitor 21, the second current limiting element 22 and the first transistor 16 form a discharging circuit, and the charging and discharging circuit 15 operates in a discharging state. When the first transistor 16 is turned off, the second capacitor 21 starts to charge. When the first transistor 16 is turned off for a long enough time, the charging voltage of the second capacitor 16 will reach the first driving voltage provided by the second power supply. Through controlling the respective duration of turning on and off of first triode 16, the voltage that the output of steerable charge-discharge circuit 15 provided to make the electromagnetism stove examine when the pot, second drive voltage that drive circuit 11 provided IGBT12 is less than the first drive voltage that drive circuit 11 provided IGBT12 when first electromagnetism stove heats, has guaranteed not to place the pan on the electromagnetism stove when examining the pot, and the electric current that flows through IGBT is less, thereby protection IGBT. Illustratively, the current limiting element may be a resistor.

The charge and discharge circuit provided by the embodiment comprises the capacitor and the current limiting element, and is simple in structure and low in cost.

Further, with reference to the embodiment shown in fig. 4, an embodiment of the present invention further provides an induction cooker, wherein a third current limiting element for limiting current is disposed on a base side of the first transistor to protect the first transistor. Fig. 5 is a schematic structural diagram of a fifth electromagnetic oven provided in the present invention, as shown in fig. 5, in this embodiment, the electromagnetic oven further includes: a third current limiting element 23; the control circuit 14 is connected to the base of the first transistor 16 via a third current limiting element 23.

Exemplarily, referring to fig. 5, the induction cooker in the present embodiment is provided with a third current limiting element 23 on the base side of the first transistor 16 for suppressing an overcurrent flowing into the base of the first transistor 16, thereby protecting the first transistor 16.

Further, with reference to the embodiment shown in fig. 5, the embodiment of the present invention further provides an induction cooker, and the pot detection principle of the induction cooker is described in detail. Fig. 6 is a schematic structural diagram six of the induction cooker provided by the present invention, as shown in fig. 6, the induction cooker further includes: a pot detection circuit 24; the pot detection circuit 24 is respectively connected with the control circuit 14 and the resonance circuit 13;

the pot detection circuit 24 is used for detecting a resonance signal in the resonance circuit 13 within a preset time length after the control circuit 14 receives the heating instruction;

the control circuit 14 is specifically configured to determine whether a pot is placed on the induction cooker according to the resonance signal detected by the pot detection circuit 24; when no cookware is placed on the induction cooker, the IGBT12 is controlled to be turned off; when a cooker is placed on the induction cooker, the first triode 16 is controlled to be turned off, so that the voltage provided by the output end of the charging and discharging circuit 15 to the power input end of the driving circuit 11 is equal to the voltage provided by the second power supply.

Illustratively, in conjunction with fig. 6, the present embodiment provides an electromagnetic oven further provided with a pan detection circuit 24. The pot detection circuit 24 is respectively connected with the control circuit 14 and the resonance circuit 13. The pan detection circuit 24 is configured to start detecting a resonance signal in the resonance circuit 13 when the control circuit 14 receives a heating instruction, and a detection duration is the same as a preset duration of the pulse signal sent to the base of the first transistor 16. The control circuit 14 judges whether a pot is placed on the induction cooker according to the pulse number included in the resonance signal detected by the pot detection circuit 24. When control circuit 14 confirmed not having placed the pan on the electromagnetism stove, control circuit 14 control IGBT12 turn off for the electromagnetism stove can't heat, with protection IGBT 12. When the control circuit 14 detects that the cookware is placed on the induction cooker, the control circuit 14 controls the first triode 16 to be turned off, so that the charging and discharging circuit 15 cannot discharge, the voltage output by the output end of the charging and discharging circuit 15 reaches a first preset voltage, namely, the voltage provided by the power input end of the driving circuit 11 is equal to the voltage provided by the second power supply.

The induction cooker provided by the embodiment provides the first driving voltage for the driving circuit during heating, and provides the second driving voltage smaller than the first driving voltage for the driving circuit during pot detection, so that the current flowing through the IGBT is small in the pot detection process, the junction temperature of the IGBT is prevented from being too high, and the IGBT is protected.

Further, in conjunction with the embodiment shown in fig. 6, the embodiment of the present invention further provides an induction cooker, and the structure of the control circuit 14 is described in detail. Fig. 7 is a seventh schematic structural diagram of the induction cooker provided by the present invention, as shown in fig. 7, the control circuit 14 includes a pulse width modulation circuit 25, and the pulse width modulation circuit 25 is connected to the third current limiting element 23; the control circuit 14 is specifically configured to control the pulse width modulation circuit 25 to provide a pulse signal with a preset duration to the base of the first transistor 16 when receiving the heating instruction.

Illustratively, referring to fig. 7, the control circuit 14 includes a pulse width modulation circuit 25, and the pulse width modulation circuit 25 is connected to the first transistor 16 through the third current limiting element 23.

The pulse width modulation circuit 25 is configured to output a pulse signal, where a width of a high level in the pulse signal is a width of a pulse. By adjusting the duty ratio of the pulse signal, the magnitude of the second driving voltage provided by the charge and discharge circuit 15 can be adjusted.

Further, in conjunction with the embodiment shown in fig. 7, the embodiment of the present invention further provides an induction cooker, and the structure of the driving circuit 11 is described in detail. Fig. 8 is a schematic structural diagram eight of the induction cooker provided by the present invention, as shown in fig. 8, in this embodiment, the driving circuit 11 includes: a second end of the first current limiting element 19 is connected with a power input end of the level converting circuit 26 and a power input end of the push-pull driving circuit 27 respectively;

the level shift circuit 26 is connected to the control circuit 14 and the push-pull drive circuit 27, respectively, and the push-pull drive circuit 27 is also connected to the gate of the IGBT 12.

Illustratively, the push-pull drive circuit 27 is used to provide a drive voltage to the IGBT 12. In consideration of the fact that the operating voltage of the push-pull drive circuit 27 does not coincide with the operating voltage of the control circuit 14, a level shift circuit 26 may be added between the control circuit 14 and the push-pull drive circuit 27. Illustratively, the level shifter 26 may be configured to shift a high level of about 5V provided by the control circuit 14 to a low level of 0V, and to shift a low level of 0V provided by the control circuit 14 to a high level of 15-20V. Alternatively, the level shift circuit 26 may be configured to shift a high level of about 5V provided by the control circuit 14 to a high level of 15-20V, and shift a low level of 0V provided by the control circuit 14 to a low level of 0V.

Further, in conjunction with the embodiment shown in fig. 8, the embodiment of the present invention further provides an induction cooker, and the structure of the level shift circuit 26 is described in detail. Fig. 9 is a schematic structural diagram nine of the induction cooker provided by the present invention, as shown in fig. 9, in this embodiment, the level conversion circuit 26 includes: a fourth current limiting element 28 and a second transistor 29;

a first end of the fourth current limiting element 28 is connected to a second end of the first current limiting element 19, and a second end of the fourth current limiting element 28 is connected to the push-pull driving circuit 27 and a collector of the second transistor 29, respectively;

the base of the second transistor 29 is connected to the output port of the control circuit 14, and the emitter of the second transistor 29 is grounded.

For example, the level shift circuit 26 shown in fig. 9 can be used to shift a high level of about 5V provided by the control circuit 14 to a low level of 0V, and shift a low level of 0V provided by the control circuit 14 to a high level of 15-20V. The level shifter circuit 26 includes a fourth current limiting element 28 and a second transistor 29. The fourth current limiting element 28 is connected to the second terminal of the first current limiting element 19 and the collector of the second transistor 29, respectively, and the emitter of the second transistor 29 is grounded. The base of the second transistor 29 is connected to the control circuit 14. The principle of the control circuit 14 controlling the on and off of the IGBT12 is: when the control circuit 14 provides a high level to the base of the second transistor 29, the second transistor 29 is turned on, and the push-pull driving circuit 27 connected to the collector of the second transistor 29 receives a low level, so that the IGBT12 is turned off; when the control circuit 14 supplies a low level to the base of the second transistor 29, the second transistor 29 is turned off, and the push-pull driving circuit 27 connected to the collector of the second transistor 29 receives the high level supplied through the fourth current limiting element 28, so that the IGBT12 is turned on.

The level shift circuit 26 provided in this embodiment is used for level shifting, and has a simple structure and low cost.

Further, in combination with the embodiment shown in fig. 9, an electromagnetic oven is further provided in the embodiment of the present invention. Fig. 10 is a schematic structural diagram of an induction cooker provided by the present invention, and as shown in fig. 10, the induction cooker further includes: a rectifying-filtering circuit 30; the second terminal of the resonant circuit 13 and the emitter of the IGBT12 are both connected to the mains supply via the rectifying-filtering circuit 30.

Illustratively, the mains power supplies the heating loop formed by the IGBT12 and the resonant circuit 13 through the rectifier filter circuit 30. The rectifying and filtering circuit 30 is specifically configured to rectify a 220V ac mains supply into a dc power, filter out possible resonances in the power grid, and provide a stable current and voltage to the resonant circuit 13. The rectifying and filtering module 30 may be composed of a rectifying bridge and a filtering device.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An induction hob, comprising: the IGBT driving circuit comprises a driving circuit (11), an IGBT (12) and a resonant circuit (13), wherein the driving circuit (11) is connected with a grid electrode of the IGBT (12), a collector electrode of the IGBT (12) is connected with a first end of the resonant circuit (13), a second end of the resonant circuit (13) and an emitter electrode of the IGBT (12) are both connected with a first power supply, and the emitter electrode of the IGBT (12) is grounded; it is characterized by also comprising: the device comprises a control circuit (14), a charging and discharging circuit (15), a first triode (16) and an inductor (17); wherein,

the input end of the charging and discharging circuit (15) is connected with a second power supply, and the output end of the charging and discharging circuit (15) is respectively connected with the collector of the first triode (16) and the first end of the inductor (17); the second end of the inductor (17) is connected with the power input end of the driving circuit (11); the emitting electrode of the first triode (16) is grounded, the base electrode of the first triode (16) is connected with the control circuit (14), and the control circuit (14) is also connected with the driving circuit (11);

the control circuit (14) is used for sending a pulse signal with a preset time length to the base electrode of the first triode (16) when a heating instruction is received, so that the voltage of the power supply provided by the charging and discharging circuit (15) to the driving circuit (11) is smaller than the voltage provided by the second power supply within the preset time length after the heating instruction is received, and the induction cooker is in a pot detection state within the preset time length;

the electromagnetism stove still includes: a pot detection circuit (24); the pot detection circuit (24) is respectively connected with the control circuit (14) and the resonance circuit (13);

the pot detection circuit (24) is used for detecting a resonance signal in the resonance circuit (13) within the preset time after the control circuit (14) receives a heating instruction;

the control circuit (14) is specifically used for determining whether a cooker is placed on the induction cooker or not according to the resonance signal detected by the cooker detection circuit (24); when no cookware is placed on the induction cooker, the IGBT (12) is controlled to be turned off; when the cooker is placed on the induction cooker, the first triode (16) is controlled to be turned off, so that the voltage provided by the output end of the charging and discharging circuit (15) to the power input end of the driving circuit (11) is equal to the voltage provided by the second power supply.

2. The induction hob according to claim 1, characterized in, that the inductance (17) is at least one, each of the inductances (17) being connected in series.

3. The induction cooker of claim 2, further comprising: a low-pass filter circuit (18);

the second end of the inductor (17) is connected with the power input end of the driving circuit (11) through the low-pass filter circuit (18).

4. The induction hob according to claim 3, characterized in, that the low-pass filter circuit (18) comprises: a first current limiting element (19) and a first capacitor (20);

the second end of the inductor (17) is connected with the first end of the first current limiting element (19); the second end of the first current limiting element (19) is respectively connected with the first end of the first capacitor (20) and the power input end of the driving circuit (11), and the second end of the first capacitor (20) is grounded.

5. The induction hob according to claim 4, characterized in, that the charge and discharge circuit (15) comprises: a second capacitor (21) and a second current limiting element (22);

the first end of the second capacitor (21) and the first end of the second current limiting element (22) are both connected with the second power supply, and the second end of the second capacitor (21) is grounded;

and the second end of the second current limiting element (22) is respectively connected with the collector of the first triode (16) and the first end of the inductor (17).

6. The induction cooker of claim 5, further comprising: a third current limiting element (23);

the control circuit (14) is connected with the base of the first triode (16) through the third current limiting element (23).

7. The induction hob according to claim 6, characterized in, that the control circuit (14) comprises a pulse width modulation circuit (25), the pulse width modulation circuit (25) being connected with the third current limiting element (23);

the control circuit (14) is specifically configured to control the pulse width modulation circuit (25) to provide a pulse signal with a preset duration to the base of the first triode (16) when receiving a heating instruction.

8. The induction cooking stove according to claim 7, characterized in that the drive circuit (11) comprises a level shift circuit (26) and a push-pull drive circuit (27);

the second end of the first current limiting element (19) is respectively connected with the power supply input end of the level switching circuit (26) and the power supply input end of the push-pull driving circuit (27);

the level conversion circuit (26) is respectively connected with the control circuit (14) and the push-pull drive circuit (27), and the push-pull drive circuit (27) is also connected with the grid electrode of the IGBT (12).

9. The induction cooking stove according to claim 8, characterized in that the level conversion circuit (26) comprises: a fourth current limiting element (28) and a second triode (29);

a first end of the fourth current limiting element (28) is connected with a second end of the first current limiting element (19), and a second end of the fourth current limiting element (28) is respectively connected with the push-pull driving circuit (27) and a collector of the second triode (29);

the base electrode of the second triode (29) is connected with the output port of the control circuit (14), and the emitter electrode of the second triode (29) is grounded.