CN107484284B

CN107484284B - Electromagnetic oven

Info

Publication number: CN107484284B
Application number: CN201710702801.6A
Authority: CN
Inventors: 赵礼荣; 刘学宇; 孙鹏刚
Original assignee: Zhejiang Shaoxing Supor Domestic Electrical Appliance Co Ltd
Current assignee: Zhejiang Shaoxing Supor Domestic Electrical Appliance Co Ltd
Priority date: 2017-08-16
Filing date: 2017-08-16
Publication date: 2020-07-28
Anticipated expiration: 2037-08-16
Also published as: CN107484284A

Abstract

The invention provides an induction cooker, when an IGBT is switched on every time, a detection result obtained by a comparison current detection circuit detecting current flowing through the IGBT and a reference voltage are compared, a driving signal sent to a driving circuit is controlled according to the comparison result, meanwhile, when the IGBT is controlled to be switched off, the reference voltage or input voltage is adjusted for the next switching-on period of the IGBT according to sampling current and rated maximum current of the IGBT in the previous switching-on period, so that the switching-on duration of the IGBT when switched on every time is obtained according to the sampling current and the rated maximum current flowing through the IGBT when switched on last time, but not fixed preset duration, and the switching-on duration fluctuates along with the fluctuation of a mains supply, thereby realizing the wave-by-wave current limiting of the IGBT, and fully utilizing the IGBT when the IGBT is protected.

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. An Insulated Gate Bipolar Transistor (IGBT) is usually used as a switching device of the induction cooker. And when the control circuit sends a switching-on signal or a switching-off signal to the drive circuit of the IGBT, the drive circuit drives the IGBT to be switched on or switched off.

When the IGBT is turned on, as the IGBT on time gradually increases, the current flowing through the IGBT will gradually increase, which may cause the IGBT to be damaged when the current flowing through the IGBT is too large. In order to avoid the situation that the IGBT is conducted for too long time, the control circuit usually sets the duration of a conducting signal sent to the driving circuit by the control circuit according to the average current and the rated maximum current flowing through the IGBT, and then controls the conducting duration of the IGBT.

However, in the use process of the induction cooker, the commercial power for supplying power to the induction cooker may fluctuate. The fluctuating mains supply may affect the turn-on time of the IGBT at the preset turn-on duration, possibly causing damage to the IGBT.

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 a fluctuant mains supply may influence the turn-on time of an IGBT under a preset turn-on duration, and the IGBT may be damaged.

In one aspect, the present invention provides an induction cooker, including: the device comprises a control circuit, a driving circuit, an IGBT, a resonance circuit and a current detection circuit; wherein the content of the first and second substances,

the control circuit is connected with the drive circuit, the drive circuit is connected with the grid electrode of the IGBT, the collector electrode of the IGBT is connected with the first end of the resonance circuit, the second end of the resonance circuit is connected with a power supply, and the emitter electrode of the IGBT is grounded and connected with the power supply; the emitting electrode of the IGBT is connected with the power supply through a current detection circuit, and the output end of the current detection circuit is connected with the control circuit; the current detection circuit is used for detecting the current flowing through the IGBT;

the control circuit is used for controlling the duration of the conducting signal according to the detection result provided by the current detection circuit and the reference voltage when sending the conducting signal to the drive circuit, and adjusting the reference voltage according to the sampling current of the IGBT in the previous conducting period and the rated maximum current of the IGBT to obtain the adjusted reference voltage or adjusting the input voltage of the current detection circuit to obtain the adjusted input voltage when sending the turn-off signal to the drive circuit; the adjusted reference voltage is used as the reference voltage of the IGBT in the next conduction period so as to control the duration of a conduction signal in the next conduction period; and the adjusted input voltage is used as the input voltage of the current detection circuit in the next conduction period so as to control the duration of the conduction signal in the next conduction period.

When the IGBT is conducted every time, a detection result obtained by detecting the current flowing through the IGBT by the current detection circuit is compared with a reference voltage, a driving signal sent to the driving circuit is controlled according to the comparison result, meanwhile, when the IGBT is controlled to be turned off, the reference voltage or the input voltage is adjusted for the next conduction period of the IGBT according to the sampling current and the rated maximum current of the IGBT in the previous conduction period, the conduction time length when the IGBT is conducted every time is made to be obtained according to the sampling current and the rated maximum current flowing through the IGBT when the IGBT is conducted last time, the fixed preset time length is not, the conduction time length fluctuates along with the fluctuation of a mains supply, the wave-by-wave current limiting of the IGBT is realized, and the IGBT is fully utilized while being protected.

The induction cooker as described above, when the control circuit is used for adjusting the input voltage of the current detection circuit; the induction cooker further comprises: a charge and discharge circuit; the control circuit comprises a comparison circuit and a pulse width modulation circuit; wherein the content of the first and second substances,

the power supply input end of the charge and discharge circuit is connected with the pulse width modulation circuit, and the power supply output end of the charge and discharge circuit is connected with the power supply input end of the current detection circuit;

the output end of the current detection circuit is connected with the first input end of the comparison circuit, and the second input end of the comparison circuit receives the reference voltage;

the control circuit is used for sending a turn-off signal to the drive circuit if the voltage of the first input end of the comparison circuit is detected to be smaller than the voltage of the second input end when sending a turn-on signal to the drive circuit, and adjusting the width of a pulse output by the pulse width modulation circuit according to the sampling current of the IGBT in the previous turn-on period and the rated maximum current of the IGBT when sending the turn-off signal to the drive circuit so as to adjust the input voltage provided by the charge and discharge circuit to the current detection circuit.

When the IGBT is conducted every time, the comparison circuit compares the reference voltage with the detection result of the current detection circuit, controls the driving signal sent to the driving circuit according to the comparison result, and adjusts the width of the pulse output by the pulse width modulation circuit and the conduction time of the IGBT according to the sampling current and the rated maximum current when the driving circuit is expected to send a turn-off signal, thereby realizing the wave-by-wave current limiting of the IGBT and fully utilizing the IGBT while protecting the IGBT.

The induction cooker as described above, said current detection circuit comprising: a first voltage dividing element, a second voltage dividing element and a third voltage dividing element; wherein the content of the first and second substances,

a first end of the first voltage division element is connected with an emitter of the IGBT, a second end of the first voltage division element is respectively connected with the power supply and a first end of the second voltage division element, and a second end of the second voltage division element is respectively connected with a first input end of the comparison circuit and a first end of the third voltage division element;

and the second end of the third voltage division element is connected with the power output end of the charge and discharge circuit.

The current detection circuit in the induction cooker provided by the embodiment is simple in structure, low in cost and easy to realize.

In the above electromagnetic oven, the charging and discharging circuit includes: a fourth voltage dividing element and a first capacitor; wherein the content of the first and second substances,

the second end of the third voltage division element is respectively connected with the first end of the fourth voltage division element and the first end of the first capacitor, the second end of the fourth voltage division element is connected with the output end of the pulse width modulation circuit, and the second end of the first capacitor is grounded.

In the electromagnetic oven provided by the embodiment, the charging and discharging circuit is simple in structure, low in cost and easy to realize.

The induction cooker, the control circuit is used for adjusting the reference voltage; the induction cooker further comprises: a charge and discharge circuit; the control circuit comprises a comparison circuit and a pulse width modulation circuit; wherein the content of the first and second substances,

the power supply input end of the current detection circuit receives a preset voltage, and the output end of the current detection circuit is connected with the first input end of the comparison circuit;

the power supply input end of the charge and discharge circuit is connected with the pulse width modulation circuit, the power supply output end of the charge and discharge circuit is connected with the second input end of the comparison circuit, and the charge and discharge circuit is used for providing the reference voltage for the second input end of the comparison circuit;

the control circuit is used for sending a turn-off signal to the drive circuit if the voltage of the first input end of the comparison circuit is detected to be smaller than the voltage of the second input end when sending a turn-on signal to the drive circuit, and adjusting the width of a pulse output by the pulse width modulation circuit according to the sampling current of the IGBT in the previous turn-on period and the rated maximum current of the IGBT when sending the turn-off signal to the drive circuit so as to adjust the reference voltage provided by the charge and discharge circuit to the second input end of the comparison circuit.

a second terminal of the third voltage dividing element receives the preset voltage.

the second input end of the comparison circuit is respectively connected with the first end of the fourth voltage dividing element and the first end of the first capacitor, the second end of the fourth voltage dividing element is connected with the output end of the pulse width modulation circuit, and the second end of the first capacitor is grounded.

The induction cooker as described above, wherein the control circuit further comprises a driving signal generating circuit;

the output end of the comparison circuit is connected with the input end of the driving signal generation circuit, and the output end of the driving signal generation circuit is connected with the input end of the driving circuit;

the comparison circuit is used for controlling the driving signal generation circuit to stop outputting the conducting signal to the driving circuit when the first input end voltage is smaller than the second input end voltage.

The induction cooker as described above, further comprising: a second capacitor;

and the first end of the second capacitor is connected with the first input end of the comparison circuit, and the second end of the second capacitor is grounded.

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 schematic structural diagram nine of the induction cooker provided by the present invention.

Reference numerals:

11-a control circuit; 12-a drive circuit;

13-an IGBT; 14-a resonant circuit;

15-a current detection circuit; 16-a charge and discharge circuit;

17-a comparison circuit; 18-a pulse width modulation circuit;

19-a drive signal generating circuit; 20-a second capacitor;

151 — a first voltage dividing element; 152-a second voltage dividing element;

153-third voltage dividing element; 161-fourth voltage dividing element;

162 — first capacitance.

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: a control circuit 11, a drive circuit 12, an IGBT13, a resonance circuit 14, and a current detection circuit 15; an emitter of the IGBT13 is connected with a power supply through a current detection circuit 15, and an output end of the current detection circuit 15 is connected with the control circuit 11; the current detection circuit 15 is used for detecting the current flowing through the IGBT 13; the control circuit 11 is configured to, when sending an on signal to the driving circuit 12, control a duration of the on signal according to a detection result provided by the current detection circuit 15 and a magnitude of a reference voltage, and when sending an off signal to the driving circuit 12, adjust the reference voltage according to a sampling current of the IGBT13 in a previous on period and a rated maximum current of the IGBT13 to obtain an adjusted reference voltage, or adjust an input voltage of the current detection circuit 15 to obtain an adjusted input voltage; the adjusted reference voltage is used as the reference voltage of the IGBT13 in the next conduction period to control the duration of the conduction signal in the next conduction period; the adjusted input voltage is used as the input voltage of the current detection circuit 15 in the next conduction period to control the duration of the conduction signal in the next conduction period.

Illustratively, the gate of the IGBT13 is connected to the driving circuit 12, the collector of the IGBT13 is connected to the first terminal of the resonant circuit 14, the second terminal of the resonant circuit 14 is connected to the power supply, and the emitter of the IGBT13 is grounded and connected to the power supply through the current detection circuit 15. The power supply is exemplified by a rectified and filtered dc power supply of a mains supply. The power supply is connected to the current detection circuit 15, the resonance circuit 14, and the IGBT13, and forms a heating circuit of the induction cooker. When the IGBT13 is turned on, the resonant circuit 14 is charged, and when the IGBT13 is turned off, the resonant circuit 14 discharges to generate an alternating magnetic field, which cuts a pot placed on the induction cooker to heat the pot. The output voltage of the driver circuit 12 controls the turn-on and turn-off of the IGBT 13.

Illustratively, the control circuit 11 is configured to output driving signals to the driving circuit 12 according to an operation instruction input by a user, wherein the driving signals include an on signal and an off signal. Since the operating voltage of the control circuit 11 is usually 5V, and the driving voltage of the IGBT13 is usually 15-20V, the control circuit 11 cannot directly drive the IGBT13, and the driving circuit 12 is usually provided between the control circuit 11 and the IGBT13, and shapes the driving signal output from the control circuit 11 and transmits the shaped driving signal to the IGBT13 to drive the IGBT13 to turn on or off.

Illustratively, when the control circuit 11 outputs a conduction signal, the IGBT13 is turned on, and as the conduction time of the IGBT13 increases, the current flowing through the IGBT13 gradually increases, in order to avoid the IGBT13 being damaged due to excessive current, the conventional induction cooker compares the average current obtained by sampling with the rated maximum current, obtains the duration of the conduction signal output by the control circuit 11 according to the magnitude between the average current and the rated maximum current, and controls the conduction time of the IGBT13 by controlling the duration of the conduction signal output by the control circuit 11, thereby limiting the increase of the current flowing through the IGBT 13. The rated maximum current is the maximum current that can flow in the rated IGBT13, and when the current flowing through the IGBT13 exceeds the rated maximum current for a while, the IGBT13 will be damaged. However, in the peak period of the mains supply, the voltage of the mains supply is high, and under the condition that the duration of the conducting signal is the same, the conducting duration of the IGBT13 may be long, and the current flowing through the IGBT13 has an overcurrent risk; in the valley period of the mains supply, the voltage of the mains supply is low, and under the condition that the duration of the conducting signal is the same, the conducting duration of the IGBT13 may be short, the current increase current flowing through the IGBT13 is small, and the IGBT13 is not fully utilized.

In order to solve the above technical problem, the control circuit 11 needs to adaptively adjust the on-time of the IGBT13 in each on-period of the IGBT13 to realize the wave-by-wave current limiting of the IGBT13, and make full use of the IGBT13 while protecting the IGBT 13.

In the present embodiment, the current detection circuit 15 is provided in the electromagnetic oven, for example. Specifically, the current detection circuit 15 is connected in series with the IGBT13, the current flowing through the current detection circuit 15 is the same as the current flowing through the IGBT13, the current detection circuit 15 can be used for detecting the current flowing through the IGBT13, and the output end of the current detection circuit 15 is connected to the control circuit 11 for outputting the detection result to the control circuit 11. The detection result may be a current value or a voltage value, and the following embodiments of the present application will describe the detection result as a voltage value.

Specifically, when the IGBT13 is turned on, the control circuit 11 compares the detection result provided by the current detection circuit 15 with the reference voltage, and for example, when the detection result is a voltage value, the detection result may be compared with the reference voltage, and according to the magnitude relationship between the detection result and the reference voltage, it may be selected to continuously send the on signal to the driving circuit 12; or choose to stop sending the on signal to the driver circuit 12 and instead send the off signal to the driver circuit 12, i.e. control the duration of the on signal.

For example, when the IGBT13 is not turned on, no current flows in the IGBT13, the magnitude relationship between the detection result collected by the current detection circuit 15 and the reference voltage is consistent with the magnitude relationship between the detection result and the reference voltage when the off signal is sent to the drive circuit 12, and the control circuit 11 sends the off signal to the drive circuit 12.

Illustratively, the control circuit 11 is specifically configured to perform current detection each time the IGBT13 is turned on, and when the control circuit 11 sends an off signal to the driving circuit 12, the control circuit 11 adjusts the reference voltage or the input voltage of the current detection circuit 15 according to the sampled current of the IGBT13 in the previous on-period and the rated maximum current of the current GBT 13. When the control circuit 11 adjusts the reference voltage, an adjusted reference voltage is obtained, and the adjusted reference voltage is used as a reference voltage of the IGBT13 in the next on-period to control the duration of the on-signal in the next on-period. When the control circuit 11 adjusts the input voltage, an adjusted input voltage is obtained, and the adjusted input voltage is used as the input voltage of the current detection circuit 15 in the next conduction period to control the duration of the conduction signal in the next conduction period.

For example, when the mains supply fluctuates and is in a peak time period of the mains supply, and the sampling current flowing through the IGBT13 is greater than the rated maximum current, it may be considered that the turn-on duration of the IGBT13 is longer, and the reference voltage is adaptively increased, so that in the next turn-on period, once the detection result is smaller than the increased reference voltage, a turn-off signal is sent to the driving circuit 12, thereby shortening the turn-on duration of the IGBT13, avoiding the damage to the IGBT13, which may be caused by the longer turn-on duration of the IGBT13 when the mains supply is at the peak, and protecting the IGBT 13; when the mains supply fluctuates and is in a trough period of the mains supply, and the sampling current flowing through the IGBT13 is smaller than the rated maximum current, it is indicated that the turn-on duration of the IGBT13 is short, and the reference voltage is adaptively reduced, so that in the next turn-on period, the detection result is smaller than the reduced reference voltage, and then a turn-off signal is sent to the driving circuit 12, so that the turn-on duration of the IGBT13 is prolonged, and the problems that when the mains supply is in a trough, the turn-on duration of the IGBT13 is short, and the utilization rate of the IGBT13 is low are avoided.

For example, when the mains supply fluctuates and is in a peak time period of the mains supply, and the sampling current flowing through the IGBT13 is greater than the rated maximum current, it may be considered that the turn-on duration of the IGBT13 is longer, and the input voltage of the current detection circuit 15 is adaptively reduced, so that in the next turn-on period, the current detection circuit 15 indicates the current flowing through the IGBT13 using a smaller detection result, and once the detection result is smaller than the reference voltage, a turn-off signal is sent to the drive circuit 12, so that the turn-on duration of the IGBT13 is shortened, and it is avoided that when the mains supply is at the peak, the turn-on duration of the IGBT13 is longer, which may cause damage to the IGBT13, and the IGBT13 is protected; when the mains supply fluctuates and is in a trough period of the mains supply, the sampling current flowing through the IGBT13 is smaller than the rated maximum current, which indicates that the on-time of the IGBT13 is short, and the input voltage of the current detection circuit 15 can be adaptively increased, so that in the next on-period, the current detection circuit 15 uses a large detection result to indicate the current flowing through the IGBT13, and when the detection result is smaller than the reference voltage, a turn-off signal is sent to the drive circuit 12, so that the on-time of the IGBT13 is prolonged, and the problems that when the mains supply is in the trough, the on-time of the IGBT13 is short, and the utilization rate of the IGBT13 is low are solved.

In the two on-time control modes, the on-time of the IGBT13 at each on-time is obtained according to the sampling current and the rated maximum current flowing through the IGBT13 at the last on-time, instead of a fixed preset time, and the on-time fluctuates along with the fluctuation of the mains supply, thereby realizing wave-by-wave current limiting.

According to the induction cooker provided by the embodiment of the invention, when the IGBT is switched on every time, the comparison current detection circuit detects the detection result and the reference voltage obtained by the current flowing through the IGBT, the driving signal sent to the driving circuit is controlled according to the comparison result, meanwhile, when the IGBT is controlled to be switched off, the reference voltage or the input voltage is adjusted for the next switching-on period of the IGBT according to the sampling current and the rated maximum current of the IGBT in the previous switching-on period, so that the switching-on duration of the IGBT when switched on every time is obtained according to the sampling current and the rated maximum current flowing through the IGBT when switched on last time, but not a fixed preset duration, and the switching-on duration fluctuates along with the fluctuation of a mains supply, thereby realizing the wave-by-wave current limiting of the IGBT, and fully utilizing the IGBT when the IGBT is protected. Further, in conjunction with the embodiment shown in fig. 1, the present invention will be described in detail in conjunction with the following specific embodiments, respectively, according to the difference between the input voltage and the reference voltage of the control circuit 11 for adjusting the current detection circuit 15.

In a first aspect, the control circuit 11 is configured to adjust an input voltage of the current detection circuit 15. Fig. 2 is a schematic structural diagram of an induction cooker according to the second embodiment of the present invention, and the structure of the control circuit 11 is described in detail in this embodiment. As shown in fig. 2, the induction cooker further includes: a charge and discharge circuit 16; the control circuit 11 includes a comparison circuit 17 and a pulse width modulation circuit 18; wherein the content of the first and second substances,

the power supply input end of the charge and discharge circuit 16 is connected with the pulse width modulation circuit 18, and the power supply output end of the charge and discharge circuit 16 is connected with the power supply input end of the current detection circuit 15; the output end of the current detection circuit 15 is connected with the first input end of the comparison circuit 17, and the second input end of the comparison circuit 17 receives the reference voltage;

the control circuit 11 is configured to send an off signal to the drive circuit 12 when it is detected that the voltage of the first input terminal of the comparator circuit 17 is lower than the voltage of the second input terminal when sending the on signal to the drive circuit 12, and adjust the width of the pulse output from the pulse width modulation circuit 18 based on the sampling current of the IGBT13 in the previous on period and the rated maximum current of the IGBT13 when sending the off signal to the drive circuit 12, so as to adjust the input voltage supplied from the charge/discharge circuit 16 to the current detection circuit 15.

In the present embodiment, for example, a charging and discharging circuit 16 is added to the electromagnetic oven, and the control circuit 11 includes a comparison circuit 17 and a pulse width modulation circuit 18.

Specifically, a power supply input terminal of the charge/discharge circuit 16 is connected to an output terminal of the pulse width modulation circuit 18. The pulse width modulation circuit 18 is configured to output a pulse signal, where the width of a high level in the pulse signal is the width of a pulse. The charge and discharge circuit 16 may be exemplified by an integrating circuit, when the pulse width modulation circuit 18 outputs a high level, the charge and discharge circuit 16 starts charging, the voltage at the output terminal of the charge and discharge circuit 16 gradually rises, and when the pulse width modulation circuit 18 stops charging, the voltage at the output terminal of the charge and discharge circuit 16 stops rising. The width of the pulse output from the pulse width modulation circuit 18 determines the maximum value to which the voltage at the output terminal of the charge/discharge circuit 16 can be raised.

Specifically, the power output terminal of the charging and discharging circuit 16 is connected to the power input terminal of the current detection circuit 15, which affects the detection result of the current detection circuit 15. Therefore, the detection result of the current detection circuit 15 is affected by the current flowing through the IGBT13 and the voltage supplied from the charge and discharge circuit 16.

Illustratively, the control circuit 11 adjusts the width of the pulse output by the pulse width modulation circuit 18 based on the sampled current and the rated maximum current of the IGBT13 during the previous conduction period. For example, the current sampling circuit may use an existing current sampling method, and the present invention is not limited thereto. If the sampling current is larger than the rated maximum current, the IGBT13 needs to be turned on for too long, the turn-on duration of the IGBT13 needs to be reduced, and the width of the pulse output by the pulse width modulation circuit 18 can be reduced, so that the charging time of the charge and discharge circuit 16 is shortened, the input voltage of the current detection circuit 15 is reduced, and the detection result of the current detection circuit 15, such as voltage, is reduced to be smaller than the reference voltage and takes shorter time, thereby reducing the turn-on duration of the IGBT 13. Illustratively, the width of the pulse output by the pulse width modulation circuit 18 may be increased if the sampled current is less than the nominal maximum current. By comparing the detection result of the current detection circuit 15 with the reference voltage and adjusting the width of the pulse output by the pulse width modulation circuit 18 every time the IGBT13 is turned on, the current limiting of the IGBT13 is realized wave by wave, and the IGBT13 is fully utilized while protecting the IGBT 13.

According to the induction cooker provided by the embodiment of the invention, when the IGBT is switched on every time, the comparison circuit compares the reference voltage with the detection result of the current detection circuit, the driving signal sent to the driving circuit is controlled according to the comparison result, and when the driving circuit is required to send a switching-off signal, the width of the pulse output by the pulse width modulation circuit is adjusted according to the sampling current and the rated maximum current, the switching-on time of the IGBT is adjusted, the wave-by-wave current limiting of the IGBT is realized, and the IGBT is fully utilized while the IGBT is protected.

Further, in combination with the embodiment shown in fig. 2, an embodiment of the present invention further provides an induction cooker. Fig. 3 is a third schematic structural diagram of the induction cooker according to the present invention, and the structure of the current detection circuit 15 is explained in detail in this embodiment. As shown in fig. 3, the current detection circuit 15 includes: a first pressure dividing element 151, a second pressure dividing element 152, and a third pressure dividing element 153; wherein the content of the first and second substances,

a first end of the first voltage dividing element 151 is connected to an emitter of the IGBT13, a second end of the first voltage dividing element 151 is connected to the power supply and a first end of the second voltage dividing element 152, respectively, and a second end of the second voltage dividing element 152 is connected to a first input end of the comparison circuit 17 and a first end of the third voltage dividing element 153, respectively; a second terminal of the third voltage dividing element 153 is connected to a power output terminal of the charge and discharge circuit 16.

Exemplarily, in the present embodiment, the current detection circuit 15 includes a first voltage division element 151, a second voltage division element 152, and a third voltage division element 153.

Specifically, the second voltage dividing element 152 is connected in series with the third voltage dividing element 153, and a first end of the second voltage dividing element 152 is connected to the first voltage dividing element 151. When the IGBT13 is turned on, the current flowing through the IGBT13 also flows through the first voltage-dividing element 151, so that the voltage drop across the first voltage-dividing element 151 can reflect the magnitude of the current, and since the first end of the first voltage-dividing element 151 is grounded, the voltage at the second end of the first voltage-dividing element 151 is negative, and the voltage can reflect the magnitude of the current. The third voltage dividing element 153, the second voltage dividing element 152 and the first voltage dividing element 151 form a voltage dividing branch, the voltage of the first end of the third voltage dividing element 153 is affected by the voltage provided by the charge and discharge circuit 16 and the voltage of the second end of the first voltage dividing element 151, and as the current increases, the voltage of the second end of the first voltage dividing element 151 acts on the first end of the third voltage dividing element 153, so that the voltage of the first end of the third voltage dividing element 153 decreases. The first terminal of the third voltage dividing element 153 is connected to the first input terminal of the comparison circuit 17, the second input terminal of the comparison circuit 17 receives the reference voltage provided by the control circuit 11, when the IGBT13 is not turned on, the voltage of the first input terminal of the comparison circuit 17 is greater than the voltage of the second input terminal, the comparison circuit 17 may exemplarily output a high level signal, and as the IGBT13 is turned on, the voltage of the first input terminal of the comparison circuit 17 gradually decreases until it is less than the reference voltage input by the second input terminal, at which time the comparison circuit 17 may exemplarily output a low level signal. The reference voltage may exemplarily be a voltage of the first terminal of the third voltage dividing element 153 when the maximum allowable current flows through the IGBT 13.

For example, when the control circuit 11 detects that the comparison circuit 17 outputs a low level signal when sending the on signal to the driving circuit 12, it stops outputting the on signal to the driving circuit 12, so that the current flowing through the IGBT13 is detected and limited within a preset range in each turn on of the IGBT 13.

Illustratively, the control circuit 11 further adjusts the width of the pulse output by the pulse width modulation circuit 18 according to the sampled current flowing through the IGBT13 and the rated maximum current obtained by the current sampling. For example, the current sampling circuit may use an existing current sampling method, and the present invention is not limited thereto. The rated maximum current may be the maximum allowable current of the IGBT13, the sampling current and the rated maximum current are compared, if the sampling current is greater than the rated maximum current, which means that the turn-on time of the IGBT13 is too long at this time, the turn-on time of the IGBT13 needs to be reduced, the width of the pulse output by the pulse width modulation circuit 18 can be reduced, so that the charging time of the integrating circuit is shortened, the time for reducing the voltage of the first end of the third voltage division element 153 to be less than the reference voltage is shortened, and the turn-on time of the IGBT13 is reduced. Illustratively, the width of the pulse output by the pulse width modulation circuit 18 may be increased if the sampled current is less than the nominal maximum current. By comparing the voltage at the first terminal of the third voltage division element 153 with the reference voltage and adjusting the width of the pulse output by the pulse width modulation circuit 18 each time the IGBT13 is turned on, the current limiting of the IGBT13 is realized wave by wave, and the IGBT13 is fully utilized while protecting the IGBT 13.

For example, the voltage dividing element may be a resistor, a capacitor, an inductor, a diode, a transistor, a temperature sensor, or other components with a certain resistance, which is not limited in the present invention.

According to the induction cooker provided by the embodiment of the invention, when the IGBT is conducted every time, the comparison circuit compares the reference voltage with the voltage of the first end of the third voltage division element for indicating the current in the IGBT, the driving signal sent to the driving circuit is controlled according to the comparison result, the turn-off signal is sent to the driving circuit, the width of the pulse output by the pulse width modulation circuit is adjusted according to the sampling current and the rated maximum current, the conduction time of the IGBT is adjusted, the wave-by-wave current limiting of the IGBT is realized, and the IGBT is fully utilized while the IGBT is protected. In the electromagnetic oven provided by the embodiment, the current detection circuit is simple in structure, low in cost and easy to realize.

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 16 is explained in detail in this embodiment. The charge and discharge circuit 16 includes: a fourth voltage dividing element 161 and a first capacitor 162; wherein the content of the first and second substances,

the second terminal of the third voltage divider 153 is connected to the first terminal of the fourth voltage divider 161 and the first terminal of the first capacitor 162, respectively, the second terminal of the fourth voltage divider 161 is connected to the output terminal of the pulse width modulation circuit 18, and the second terminal of the first capacitor 162 is grounded.

Illustratively, the charge and discharge circuit 16 is constituted by a capacitor and a voltage dividing element. A first terminal of the fourth voltage dividing element 161 is connected to a first terminal of the first capacitor 162, a second terminal of the first capacitor 162 is grounded, and a second terminal of the fourth voltage dividing element 161 is connected to an output terminal of the pulse width modulation circuit 18. The pulse width modulation circuit 18 is configured to output a pulse signal, where the width of a high level in the pulse signal is the width of a pulse. Therefore, the fourth voltage dividing element 161 and the first capacitor 162 constitute an integrating circuit, when the pulse width modulation circuit 18 outputs a high level, the first capacitor 162 starts to be charged, the voltage at the first end of the first capacitor 162 gradually rises, and when the pulse width modulation circuit 18 stops being charged, the voltage at the first end of the first capacitor 162 stops rising. The width of the pulse output by the pulse width modulation circuit 18 determines the maximum value to which the voltage at the first terminal of the first capacitor 162 can be raised.

In a second aspect, the control circuit 11 is used for adjusting a reference voltage, and in conjunction with the embodiment shown in fig. 1, the embodiment of the present invention further provides an induction cooker. Fig. 5 is a fifth schematic structural diagram of the induction cooker according to the present invention, and the structure of the control circuit 11 is explained in detail in this embodiment. As shown in figure 5 of the drawings,

the electromagnetism stove still includes: a charge and discharge circuit 16; the control circuit 11 includes a comparison circuit 17 and a pulse width modulation circuit 18; wherein the content of the first and second substances,

the power supply input end of the current detection circuit 15 receives a preset voltage, and the output end of the current detection circuit 15 is connected with the first input end of the comparison circuit 17;

a power supply input end of the charge and discharge circuit 16 is connected with the pulse width modulation circuit 18, a power supply output end of the charge and discharge circuit 16 is connected with a second input end of the comparison circuit 17, and the charge and discharge circuit 16 is used for providing reference voltage for the second input end of the comparison circuit 17;

the control circuit 11 is configured to send an off signal to the driving circuit 12 when detecting that the voltage of the first input terminal of the comparison circuit 17 is lower than the voltage of the second input terminal when sending the on signal to the driving circuit 12, and adjust the width of the pulse output by the pulse width modulation circuit 18 according to the sampling current of the IGBT13 in the previous on period and the rated maximum current of the IGBT13 when sending the off signal to the driving circuit 12, so as to adjust the reference voltage provided by the charging and discharging circuit 16 to the second input terminal of the comparison circuit 17.

Exemplarily, similar to the embodiment shown in fig. 2, the difference is that in this embodiment, the voltage provided by the charge and discharge circuit 16 is connected as a reference voltage to the input terminal of the comparison circuit 17. The power input of the current detection circuit 15 receives a fixed preset voltage. At this time, the detection result of the current detection circuit 15 is affected only by the current flowing through the IGBT 13. For example, when the sampling current flowing through the IGBT13 is greater than the rated maximum current, it indicates that the turn-on duration of the IGBT13 is long, the reference voltage provided by the charge and discharge circuit 16 is adaptively increased, and once the detection result is less than the reference voltage, a turn-off signal is immediately sent to the drive circuit 12, so that the turn-on duration of the IGBT13 is reduced, the maximum value that the current flowing through the current detection circuit 15 can reach is reduced, and the IGBT13 is protected; when the sampling current flowing through the IGBT13 is smaller than the rated maximum current, it is indicated that the turn-on duration of the IGBT13 is short, and the reference voltage provided by the charge and discharge circuit 16 is adaptively reduced, so that the turn-on duration of the IGBT13 is increased, the maximum value that can be reached by the circuit flowing through the current detection circuit 15 is increased, and the IGBT13 is fully utilized.

Further, in combination with the embodiment shown in fig. 5, an embodiment of the present invention further provides an induction cooker. Fig. 6 is a schematic structural diagram six of the induction cooker provided by the present invention, and in this embodiment, a structure of the current detection circuit 15 is described in detail, and the structure of the current detection circuit 15 is the same as the current detection structure in the embodiment shown in fig. 3, and has the same technical effect, which is not described again in the present invention. As shown in fig. 6, the current detection circuit 15 includes: a first pressure dividing element 151, a second pressure dividing element 152, and a third pressure dividing element 153; wherein the content of the first and second substances,

a first end of the first voltage dividing element 151 is connected to an emitter of the IGBT13, a second end of the first voltage dividing element 151 is connected to the power supply and a first end of the second voltage dividing element 152, respectively, and a second end of the second voltage dividing element 152 is connected to a first input end of the comparison circuit 17 and a first end of the third voltage dividing element 153, respectively; a second terminal of the third voltage division element 153 receives a preset voltage.

Further, in combination with the embodiment shown in fig. 6, an electromagnetic oven is further provided in the embodiment of the present invention. Fig. 7 is a seventh schematic structural diagram of the induction cooker according to the present invention, and the structure of the charge/discharge circuit 16 is explained in detail in this embodiment. The structure of the charge and discharge circuit 16 is the same as that of the charge and discharge circuit in the embodiment shown in fig. 4, and has the same technical effect, which is not described again in the present invention. As shown in fig. 7, the charge and discharge circuit 16 includes: a fourth voltage dividing element 161 and a first capacitor 162; wherein the content of the first and second substances,

a second input terminal of the comparator 17 is connected to a first terminal of the fourth voltage divider 161 and a first terminal of the first capacitor 162, respectively, a second terminal of the fourth voltage divider 161 is connected to an output terminal of the pulse width modulation circuit 18, and a second terminal of the first capacitor 162 is grounded.

Further, in combination with any one of the embodiments shown in fig. 2 to 7, an embodiment of the present invention further provides an induction cooker. Fig. 8 is a schematic structural diagram eight of the induction cooker according to the present invention, and the structure of the control circuit 11 is explained in detail in this embodiment. Exemplarily, fig. 8 shows a structure of the induction cooker provided by the present embodiment on the basis of fig. 7. As shown in fig. 8, the control circuit 11 further includes a drive signal generation circuit 19;

the output end of the comparison circuit 17 is connected with the input end of the driving signal generation circuit 19, and the output end of the driving signal generation circuit 19 is connected with the input end of the driving circuit 12;

the comparison circuit 17 is configured to control the drive signal generation circuit 19 to stop outputting the on signal to the drive circuit 12 when the first input terminal voltage is smaller than the second input terminal voltage.

Illustratively, the control circuit 11 includes a driving signal generating circuit 19, the driving signal generating circuit 19 is configured to send an on driving signal and an off driving signal to the driving circuit 12, and when the driving signal generating circuit 19 sends the on driving signal to the driving circuit 12, the IGBT13 is driven to be turned on. The driving signal generating circuit 19 is further connected to the output terminal of the comparing circuit 17, when the comparing circuit 17 detects that the voltage of the second terminal of the second voltage dividing element 16 is smaller than the reference voltage, the output terminal of the comparing circuit 17 outputs a low level signal, after receiving the low level signal, the driving signal generating circuit 19 stops sending the on driving signal, the IGBT13 is turned off, when the IGBT13 is turned off, no current flows in the first voltage dividing element 151, the voltage of the second terminal of the second voltage dividing element 152 rises, and the voltage of the second terminal of the second voltage dividing element 152 is greater than the reference voltage, so that the output terminal of the comparing circuit 17 outputs a high level signal, for example, the output terminal of the comparing circuit 17 outputs a high impedance state. The signal output from the output terminal of the comparison circuit 17 does not affect the output of the drive signal generation circuit 19, and the drive signal generation circuit 19 transmits the on drive signal to the drive circuit 12 when it receives the next command to turn on the IGBT 13. Illustratively, the drive signal generation circuit 19 is a programmable pulse generator.

Further, in combination with any one of the embodiments shown in fig. 2 to 8, an embodiment of the present invention further provides an induction cooker. Fig. 9 is a schematic structural diagram nine of the induction cooker provided by the present invention, and in this embodiment, the induction cooker further includes a second capacitor 20 for filtering out an interference signal. Exemplarily, fig. 9 shows a structure of the induction cooker provided by the present embodiment on the basis of fig. 8. As shown in fig. 9, the induction cooker further includes: a second capacitor 20;

a first terminal of the second capacitor 20 is connected to a first terminal of the third voltage dividing element 153, and a second terminal of the second capacitor 20 is grounded.

Illustratively, referring to fig. 9, the control circuit 11 and the comparing circuit 17 may be further protected by adding a capacitor to the second terminal of the second voltage dividing element 152 to filter the fluctuating dc power and filter the fluctuating and interfering signals of the dc power.

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 control circuit (11), a driving circuit (12), an IGBT (13) and a resonant circuit (14), wherein the control circuit (11) is connected with the driving circuit (12), the driving circuit (12) is connected with a grid electrode of the IGBT (13), a collector electrode of the IGBT (13) is connected with a first end of a resonant circuit (14), a second end of the resonant circuit (14) is connected with a power supply, and an emitter electrode of the IGBT (13) is grounded and connected with the power supply; it is characterized by also comprising: a current detection circuit (15); the emitter of the IGBT (13) is connected with the power supply through a current detection circuit (15), and the output end of the current detection circuit (15) is connected with the control circuit (11);

the current detection circuit (15) is used for detecting the current flowing through the IGBT (13);

the control circuit (11) is configured to, when sending a turn-on signal to the drive circuit (12), control a duration of the turn-on signal according to a detection result provided by the current detection circuit (15) and a reference voltage, and when sending a turn-off signal to the drive circuit (12), adjust the reference voltage according to a sampling current of the IGBT (13) in a previous turn-on period and a rated maximum current of the IGBT (13) to obtain an adjusted reference voltage, or adjust an input voltage of the current detection circuit (15) to obtain an adjusted input voltage; the adjusted reference voltage is used as the reference voltage of the IGBT (13) in the next conduction period so as to control the duration of a conduction signal in the next conduction period; and the adjusted input voltage is used as the input voltage of the current detection circuit (15) in the next conduction period so as to control the duration of the conduction signal in the next conduction period.

2. The induction hob according to claim 1, characterized in, that when the control circuit (11) is used to adjust the input voltage of the current detection circuit (15); the induction cooker further comprises: a charge/discharge circuit (16); the control circuit (11) comprises a comparison circuit (17) and a pulse width modulation circuit (18); wherein the content of the first and second substances,

the power supply input end of the charging and discharging circuit (16) is connected with the pulse width modulation circuit (18), and the power supply output end of the charging and discharging circuit (16) is connected with the power supply input end of the current detection circuit (15);

the output end of the current detection circuit (15) is connected with the first input end of the comparison circuit (17), and the second input end of the comparison circuit (17) receives the reference voltage;

the control circuit (11) is used for sending a turn-off signal to the drive circuit (12) if the voltage of the first input end of the comparison circuit (17) is detected to be smaller than the voltage of the second input end when sending the turn-on signal to the drive circuit (12), and adjusting the width of the pulse output by the pulse width modulation circuit (18) according to the sampling current of the IGBT (13) in the previous turn-on period and the rated maximum current of the IGBT (13) when sending the turn-off signal to the drive circuit (12) so as to adjust the input voltage provided by the charging and discharging circuit (16) to the current detection circuit (15).

3. The induction hob according to claim 2, characterized in, that the current detection circuit (15) comprises: a first pressure dividing element (151), a second pressure dividing element (152) and a third pressure dividing element (153); wherein the content of the first and second substances,

a first end of the first voltage division element (151) is connected with an emitter of the IGBT (13), a second end of the first voltage division element (151) is respectively connected with the power supply and a first end of the second voltage division element (152), and a second end of the second voltage division element (152) is respectively connected with a first input end of the comparison circuit (17) and a first end of the third voltage division element (153);

and a second end of the third voltage division element (153) is connected with a power output end of the charge and discharge circuit (16).

4. The induction hob according to claim 3, characterized in, that the charge and discharge circuit (16) comprises: a fourth voltage dividing element (161) and a first capacitor (162); wherein the content of the first and second substances,

the second end of the third voltage division element (153) is respectively connected with the first end of the fourth voltage division element (161) and the first end of the first capacitor (162), the second end of the fourth voltage division element (161) is connected with the output end of the pulse width modulation circuit (18), and the second end of the first capacitor (162) is grounded.

5. The induction hob according to claim 1, characterized in, that the control circuit (11) is used for adjusting the reference voltage; the induction cooker further comprises: a charge/discharge circuit (16); the control circuit (11) comprises a comparison circuit (17) and a pulse width modulation circuit (18); wherein the content of the first and second substances,

the power supply input end of the current detection circuit (15) receives a preset voltage, and the output end of the current detection circuit (15) is connected with the first input end of the comparison circuit (17);

the power supply input end of the charging and discharging circuit (16) is connected with the pulse width modulation circuit (18), the power supply output end of the charging and discharging circuit (16) is connected with the second input end of the comparison circuit (17), and the charging and discharging circuit (16) is used for providing the reference voltage for the second input end of the comparison circuit (17);

the control circuit (11) is used for sending a turn-off signal to the drive circuit (12) if the voltage of the first input end of the comparison circuit (17) is detected to be smaller than the voltage of the second input end when sending the turn-on signal to the drive circuit (12), and adjusting the width of a pulse output by the pulse width modulation circuit (18) according to the sampling current of the IGBT (13) in the previous turn-on period and the rated maximum current of the IGBT (13) when sending the turn-off signal to the drive circuit (12) so as to adjust the reference voltage provided by the charging and discharging circuit (16) to the second input end of the comparison circuit (17).

6. The induction hob according to claim 5, characterized in, that the current detection circuit (15) comprises: a first pressure dividing element (151), a second pressure dividing element (152) and a third pressure dividing element (153); wherein the content of the first and second substances,

a second terminal of the third voltage dividing element (153) receives the preset voltage.

7. The induction hob according to claim 6, characterized in, that the charge and discharge circuit (16) comprises: a fourth voltage dividing element (161) and a first capacitor (162); wherein the content of the first and second substances,

the second input end of the comparison circuit (17) is respectively connected with the first end of the fourth voltage division element (161) and the first end of the first capacitor (162), the second end of the fourth voltage division element (161) is connected with the output end of the pulse width modulation circuit (18), and the second end of the first capacitor (162) is grounded.

8. The induction hob according to any one of the claims 2 to 7, characterized in, that the control circuit (11) further comprises a drive signal generation circuit (19);

the output end of the comparison circuit (17) is connected with the input end of the driving signal generation circuit (19), and the output end of the driving signal generation circuit (19) is connected with the input end of the driving circuit (12);

the comparison circuit (17) is used for controlling the driving signal generation circuit (19) to stop outputting the conducting signal to the driving circuit (12) when the first input end voltage is smaller than the second input end voltage.

9. The induction cooking hob according to any one of the claims 2 to 7, characterized in, that the induction cooking hob further comprises: a second capacitance (20);

the first end of the second capacitor (20) is connected with the first input end of the comparison circuit (17), and the second end of the second capacitor (20) is grounded.