IGBT (Insulated Gate Bipolar Translator) driving circuit and electromagnetic heating equipment

Abstract

The invention provides an IGBT (Insulated Gate Bipolar Translator) driving circuit and electromagnetic heating equipment, and the IGBT driving circuit comprises a main control circuit, a level conversion circuit, a speed adjustment circuit, a push-pull driving circuit and an IGBT, the main control circuit is provided with a first control end, and the level conversion circuit is provided with a second control end; the first control end of the main control circuit, the level conversion circuit, the speed adjusting circuit, the push-pull driving circuit and the grid electrode of the IGBT are connected in sequence, and the emitter electrode of the IGBT is grounded; and the speed adjusting circuit is used for controlling and slowing down the increasing speed of the driving voltage for driving the IGBT, so that the conduction current of the IGBT is reduced. The invention is used for solving the technical problem that the electromagnetic heating equipment is difficult to continuously work at a low-power gear because the current of the IGBT at the conduction moment is too large.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic heating, and in particular to an IGBT drive circuit and an electromagnetic heating device. Background Art

[0002] Electromagnetic heating equipment mainly heats through coil disk heating and electromagnetic induction (IH) coil heating, such as induction cookers, IH electric pressure cookers, IH rice cookers, etc. Insulated Gate Bipolar Transistor (IGBT) is the core device for energy conversion and transmission in electromagnetic heating equipment. The IGBT drive circuit provides a driving voltage to the gate of the IGBT to drive the IGBT on or off.

[0003] After the parameters of the coil disk, cookware, etc. are determined, the working state of the IGBT is also determined. Generally, when working in a high-power gear, the IGBT can still conduct at zero crossing, but when working in a low-power gear, the gate voltage of the IGBT is relatively high, and the on-state voltage will be relatively high, which makes the instantaneous on-state current of the IGBT very large. This will cause the IGBT to withstand a higher periodic pulse current, which can easily cause problems such as overheating and burning of the IGBT, affecting its service life.

[0004] Therefore, it is urgent to solve the problem that the current of IGBT is too large at the moment of turn-on, making it difficult to work continuously at low power level. Summary of the invention

[0005] The present invention provides an IGBT driving circuit and an electromagnetic heating device, which are used to solve the technical problem that the current of the IGBT is too large at the moment of conduction, making it difficult to realize the continuous operation of the electromagnetic heating device at a low power gear.

[0006] In order to achieve the above object, the present invention provides an IGBT drive circuit, comprising: a main control circuit, a level conversion circuit, a speed adjustment circuit, a push-pull drive circuit and an IGBT, wherein the main control circuit has a first control terminal, the first control terminal of the main control circuit, the level conversion circuit, the speed adjustment circuit, the push-pull drive circuit and the gate of the IGBT are connected in sequence, and the emitter of the IGBT is grounded;

[0007] The speed adjustment circuit is used to control and slow down the growth rate of the driving voltage driving the IGBT, so as to reduce the on-current of the IGBT.

[0008] The present invention provides an IGBT driving circuit. By setting a speed adjustment circuit, the growth rate of the driving voltage driving the IGBT can be slowed down, thereby extending the time that the push-pull driving circuit drives the IGBT in the amplification area, so that when the IGBT is turned on, the rising edge becomes slow, and the rising speed of the current passing through the IGBT becomes slow, thereby effectively reducing the transient on-current of the IGBT and reducing the life damage caused by the periodic pulse current borne by the IGBT.

[0009] In a possible implementation, it further includes a voltage sampling circuit, a first end of the voltage sampling circuit is electrically connected to the collector of the IGBT, a second end of the voltage sampling circuit is electrically connected to the speed adjustment circuit, and the voltage sampling circuit is used to collect the collector voltage of the IGBT and output the collector voltage of the IGBT to the speed adjustment circuit;

[0010] The speed adjustment circuit is configured to control the slowdown of the growth rate of the driving voltage driving the IGBT when the collector voltage of the IGBT is greater than or equal to a preset voltage threshold so as to reduce the on-current of the IGBT, and to speed up the growth rate of the driving voltage driving the IGBT when the collector voltage of the IGBT is less than the preset voltage threshold.

[0011] In a possible implementation, the main control circuit further includes a speed control circuit and a temperature sampling circuit, the main control circuit further has a second control terminal, the second control terminal of the main control circuit is connected to the input terminal of the speed control circuit, and the output terminal of the speed control circuit is connected to the speed adjustment circuit;

[0012] The first end of the temperature sampling circuit is connected to the pin of the IGBT, the second end of the temperature sampling circuit is connected to the main control circuit, and the temperature sampling circuit is used to collect the temperature of the IGBT;

[0013] The speed control circuit is used to control the speed adjustment circuit to be in an off state when the temperature value of the IGBT collected by the temperature sampling circuit is greater than or equal to a preset temperature value, and to control the speed adjustment circuit to be in an on state when the temperature value of the IGBT collected by the temperature sampling circuit is less than a preset temperature value.

[0014] In a possible implementation, the first control end of the main control circuit is used to output a first control signal, and the second control end of the main control circuit is used to output a second control signal, and the second control signal is different from the first control signal.

[0015] In a possible implementation, the speed adjustment circuit includes a first transistor Q2, a capacitor element C1, a first diode D1, a first resistor R8 and a second resistor R4, the base of the first transistor Q2 is connected to the first end of the second resistor R4, the emitter of the first transistor Q2 is grounded, the collector of the first transistor Q2 is connected to the first end of the capacitor element C1 and the cathode of the first diode D1, the first end of the capacitor element C1 is connected to the cathode of the first diode D1, the second end of the capacitor element C1 is connected to the first end of the first resistor R8, the anode of the first diode D1 is grounded, the second end of the first resistor R8 is connected to the input end of the push-pull drive circuit and the level conversion circuit, and the second end of the second resistor R4 is connected to the voltage sampling circuit and the speed control circuit.

[0016] In one possible implementation, the speed control circuit includes a current limiting circuit R1 and a second transistor Q1, the first end of the current limiting circuit R1 is connected to the base of the second transistor Q1, the second end of the current limiting circuit R1 is connected to the second control end of the main control circuit, the emitter of the second transistor Q1 is grounded, and the collector of the second transistor Q1 is respectively connected to the second end of the second resistor R4 and the voltage sampling circuit.

[0017] In one possible implementation, the voltage sampling circuit includes a first voltage divider element R2 and a second voltage divider element R3, wherein the first end of the first voltage divider element R2 is connected to the collector of the IGBT, the second end of the first voltage divider element R2 is connected to the first end of the second voltage divider element R3 and the collector of the second transistor Q1, the first end of the second voltage divider element R3 is also connected to the second end of the second resistor R4, and the second end of the second voltage divider element R3 is grounded.

[0018] In a possible implementation, the push-pull driving circuit includes a third resistor R7, a third transistor Q4, a fourth transistor Q5, a fourth resistor R9 and a fifth resistor R10;

[0019] The first end of the third resistor R7 is connected to a first level VCC, the second end of the third resistor R7 is respectively connected to the output end of the level conversion circuit, the second end of the first resistor R8, the base of the third transistor Q4 and the base of the fourth transistor Q5, the collector of the third transistor Q4 is connected to the first level VCC, the emitter of the third transistor Q4 is respectively connected to the first end of the fourth resistor R9 and the first end of the fifth resistor R10, the emitter of the fourth transistor Q5 is connected to the second end of the fourth resistor R9, the collector of the fourth transistor Q5 is grounded, and the second end of the fifth resistor R10 is connected to the input end of the IGBT module (105).

[0020] In a possible implementation, the level conversion circuit includes a third voltage divider element R5, a fourth voltage divider element R6 and a fifth transistor Q3, the first end of the third voltage divider element R5 is connected to the first level VCC, the second end of the third voltage divider element R5 is connected to the first end of the fourth voltage divider element R6, the second end of the fourth voltage divider element R6 is connected to the base of the fifth transistor Q3, and the collector of the fifth transistor Q3 is connected to the second end of the third resistor R7, the second end of the first resistor R8, the base of the third transistor Q4 and the base of the fourth transistor Q5.

[0021] In a possible implementation, the third transistor Q4, the second transistor Q1 and the first transistor Q2 are NPN transistors, and the fourth transistor Q5 is a PNP transistor.

[0022] The present invention also provides an electromagnetic heating device, comprising the above-mentioned IGBT driving circuit.

[0023] The IGBT drive circuit and electromagnetic heating device provided by the present invention have a main control circuit that flexibly switches between two working modes according to the working temperature of the IGBT, and selects that when the temperature value collected by the temperature sampling circuit is greater than or equal to the preset temperature threshold, the second control end of the main control circuit outputs the second control signal, and when the temperature value collected by the temperature sampling circuit is less than the preset temperature threshold, the first control end of the main control circuit outputs the first control signal, thereby ensuring that the IGBT works in a relatively safe state.

[0024] In addition to the technical problems solved by the embodiments of the present invention described above, the technical features that constitute the technical solutions, and the beneficial effects brought about by the technical features of the technical solutions, other technical problems that can be solved by an IGBT drive circuit and an electromagnetic heating device provided by the embodiments of the present invention, other technical features included in the technical solutions, and the beneficial effects brought about by these technical features will be further described in detail in the specific implementation methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 A schematic diagram of the structure of an IGBT driving circuit provided by an embodiment of the present invention;

[0027] Figure 2 Another structural schematic diagram of an IGBT driving circuit provided by an embodiment of the present invention;

[0028] Figure 3 A schematic diagram of the structure of an IGBT driving circuit provided by an embodiment of the present invention;

[0029] Figure 4 A diagram showing the gate voltage of the IGBT and the driving waveform of the IGBT when the speed adjustment circuit of the IGBT driving circuit provided by the embodiment of the present invention is in the on state;

[0030] Figure 5 The diagram is a diagram of the gate voltage of the IGBT and the driving waveform of the IGBT when the speed adjustment circuit of the IGBT driving circuit provided by the embodiment of the present invention is in the disconnected state.

[0031] Description of reference numerals:

[0032] 10- Main control circuit;

[0033] 20-level conversion circuit;

[0034] R5-the third voltage dividing element;

[0035] R6-the fourth voltage dividing element;

[0036] Q3-fifth transistor;

[0037] 30-speed adjustment circuit;

[0038] Q2-the first transistor;

[0039] C1-capacitor element;

[0040] D1-first diode;

[0041] R8-first resistor;

[0042] R4 - second resistor;

[0043] 40-push-pull driving circuit;

[0044] R7-the third resistor;

[0045] Q4-the third transistor;

[0046] Q5-the fourth transistor;

[0047] R9-the fourth resistor;

[0048] R10-fifth resistor;

[0049] 50-IGBT;

[0050] 60- voltage sampling circuit;

[0051] R2-first voltage dividing element;

[0052] R3-the second voltage dividing element;

[0053] 70-speed control circuit;

[0054] R1-current limiting circuit;

[0055] Q1-the second transistor;

[0056] 80- temperature sampling circuit;

[0057] R11-sixth resistor;

[0058] R20-seventh resistor;

[0059] VCC-first level;

[0060] VDD-second level. DETAILED DESCRIPTION

[0061] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0062] Considering that when IGBT50 is saturated and turned on, the impact current generated is large, and the current flowing through IGBT50 is too large, which can easily damage IGBT50 and generate a lot of noise. In order to improve the working state of IGBT, the common practice is to minimize the working time of IGBT in low power gear, which limits the use of low power gear and the user experience is poor.

[0063] In view of the above background, the IGBT driving circuit and electromagnetic heating device provided by the present invention, by setting a speed adjustment circuit 30, when the speed adjustment circuit 30 is in the on state, the speed adjustment circuit 30 works, which can extend the time for driving the IGBT50 in the amplification area, reduce the transient on-current of the IGBT50, and reduce the noise of the IGBT50.

[0064] The IGBT driving circuit and electromagnetic heating device provided by the embodiments of the present invention are described below with reference to the accompanying drawings.

[0065] refer to Figure 1 As shown, the present invention provides an IGBT driving circuit, including: a main control circuit 10, a level conversion circuit 20, a speed adjustment circuit 30, a push-pull driving circuit 40 and an IGBT50, the main control circuit 10 has a first control end, the first control end of the main control circuit 10, the level conversion circuit 20, the speed adjustment circuit 30, the push-pull driving circuit 40 and the gate of the IGBT50 are connected in sequence, and the emitter of the IGBT50 is grounded; the speed adjustment circuit 30 is used to control and slow down the growth rate of the driving voltage driving the IGBT50, so as to reduce the conduction current of the IGBT50.

[0066] The present invention provides an IGBT driving circuit, which slows down the growth rate of the driving voltage driving IGBT50 by setting a speed adjustment circuit 30, and correspondingly extends the push-pull driving circuit 40 to extend the time for driving IGBT50 in the amplification area, so that when IGBT50 is turned on, the rising edge becomes slow, and the rising speed of the current passing through IGBT50 becomes slow, thereby effectively reducing the transient on-current of IGBT50 and reducing the life damage caused by the periodic pulse current borne by IGBT50.

[0067] The present invention provides an IGBT driving circuit, which controls the rising speed of the current passing through the IGBT50 by setting a speed adjustment circuit 30. Therefore, the current when the IGBT50 is turned on is smaller than the current when the IGBT50 is turned on in the existing electromagnetic heating equipment, thereby protecting the service life of the IGBT50 and saving costs.

[0068] The main control circuit 10 includes a control unit (Micro Control Unit, MCU), which provides a pulse signal so that the push-pull drive circuit 40 can provide a drive signal to the IGBT 50 according to the pulse signal.

[0069] Since the main control circuit 10 usually operates at 5V, and the turn-on voltage of the IGBT 50 is greater than 9V, and the IGBT 50 usually operates at 18V, it is necessary to adjust the driving voltage provided by the main control circuit 10 to achieve control of the IGBT 50, which needs to be achieved through the level conversion circuit 20 and the push-pull driving circuit 40. The level conversion circuit 20 is used to convert the driving voltage provided by the main control circuit 10, and the push-pull driving circuit 40 is used to shape the polarity of the driving voltage received from the level conversion circuit 20.

[0070] In one possible implementation, reference Figure 2 As shown, the IGBT driving circuit provided in this embodiment further includes a voltage sampling circuit 60, a first end of the voltage sampling circuit 60 is electrically connected to the collector of the IGBT 50, a second end of the voltage sampling circuit 60 is electrically connected to the speed adjustment circuit 30, and the voltage sampling circuit 60 is used to collect the collector voltage of the IGBT 50 and output the collector voltage of the IGBT 50 to the speed adjustment circuit 30. The speed adjustment circuit 30 is configured to control the slowdown of the growth rate of the driving voltage driving the IGBT 50 when the collector voltage of the IGBT 50 is greater than or equal to the preset voltage threshold, so as to reduce the conduction current of the IGBT 50, and to speed up the growth rate of the driving voltage driving the IGBT 50 when the collector voltage of the IGBT 50 is less than the preset voltage threshold.

[0071] In this embodiment, the collector voltage of IGBT50 is collected by the voltage sampling circuit 60, and the collected collector voltage of IGBT50 is compared with the preset voltage threshold by the speed adjustment circuit 30, so that the working state of IGBT50 can be determined, and it can be judged whether IGBT50 is working in a low power gear or a high power gear.

[0072] When the collector voltage of IGBT50 is greater than or equal to the preset voltage threshold, it means that the collector voltage of IGBT50 is relatively high. At this time, if it is started at a low power gear, the current passing through IGBT50 is relatively large, causing IGBT50 to withstand a higher periodic pulse current, which will affect the service life of IGBT50. Therefore, this embodiment controls and slows down the growth rate of the driving voltage that drives IGBT50 to reduce the on-current of IGBT50.

[0073] When the collector voltage of IGBT50 is less than the preset voltage threshold, it means that the collector voltage of IGBT50 is small. At this time, if it is started at a low power gear, the current passing through IGBT50 will not have a great impact on the service life of IGBT50, thereby accelerating the growth rate of the driving voltage of driving IGBT50.

[0074] In one possible implementation, the IGBT drive circuit provided in this embodiment further includes a speed control circuit 70 and a temperature sampling circuit 80. The main control circuit 10 also has a second control end. The second control end of the main control circuit 10 is connected to the input end of the speed control circuit 70, and the output end of the speed control circuit 70 is connected to the speed adjustment circuit 30. The first end of the temperature sampling circuit 80 is connected to the pin of the IGBT50, and the second end of the temperature sampling circuit 80 is connected to the main control circuit 10. The temperature sampling circuit 80 is used to collect the temperature of the IGBT50.

[0075] The speed control circuit 70 is used to control the speed adjustment circuit 30 to be in an off state when the temperature value of the IGBT50 collected by the temperature sampling circuit 80 is greater than or equal to the preset temperature value, and to control the speed adjustment circuit 30 to be in an on state when the temperature value of the IGBT50 collected by the temperature sampling circuit 80 is less than the preset temperature value.

[0076] By setting the temperature sampling circuit 80 to collect the temperature of the IGBT50 and transmitting the sampled temperature value to the main control circuit 10, the main control circuit 10 compares the temperature value collected by the temperature sampling circuit 80 with the preset temperature threshold to select whether to disconnect the speed adjustment circuit 30.

[0077] When the temperature value collected by the temperature sampling circuit 80 is greater than or equal to the preset temperature threshold, it indicates that the temperature of the IGBT50 is relatively high. At this time, if the speed adjustment circuit 30 controls to slow down the growth rate of the driving voltage driving the IGBT50, the time for driving the IGBT50 to be in the amplification zone will be correspondingly prolonged. Although the transient on-current of the IGBT50 can be effectively reduced, the turn-on loss of the IGBT50 is serious. Therefore, it is selected to speed up the turn-on speed of the driving signal of the IGBT50, thereby reducing the turn-on loss of the IGBT50.

[0078] When the temperature value collected by the temperature sampling circuit 80 is less than the preset temperature threshold, it indicates that the temperature of the IGBT50 is relatively low. At this time, the speed adjustment circuit 30 can be used to control the growth rate of the driving voltage for driving the IGBT50 to be slowed down, thereby extending the time that the driving IGBT50 is in the amplification area and reducing the instantaneous current passing through the IGBT50. The turn-on loss of the IGBT50 is relatively small, thereby preventing the problem of heating and damage to the IGBT50.

[0079] In a possible implementation, the first control terminal of the main control circuit 10 is used to output a first control signal, and the second control terminal of the main control circuit 10 is used to output a second control signal, and the second control signal is different from the first control signal.

[0080] The first control terminal of the main control circuit 10 outputs a first control signal, for example, a pulse signal is outputted through a programmable pulse generator (PPG for short). The level conversion circuit 20 receives the first control signal, and converts the low-voltage PPG signal into a high-voltage signal that can drive the IGBT50. The high-voltage signal is converted into a voltage signal with a dual slope on the rising edge by the speed adjustment circuit 30, and is controlled through the push-pull drive circuit 40 to control the growth rate of the drive voltage of the IGBT50.

[0081] The second control signal may be an outputtable CTR signal.

[0082] In one possible implementation, reference Figure 3 As shown, the speed adjustment circuit 30 includes a first transistor Q2, a capacitor element C1, a first diode D1, a first resistor R8 and a second resistor R4. The base of the first transistor Q2 is connected to the first end of the second resistor R4, the emitter of the first transistor Q2 is grounded, the collector of the first transistor Q2 is connected to the first end of the capacitor element C1 and the cathode of the first diode D1, the first end of the capacitor element C1 is connected to the cathode of the first diode D1, the second end of the capacitor element C1 is connected to the first end of the first resistor R8, the anode of the first diode D1 is grounded, the second end of the first resistor R8 is connected to the input end of the push-pull drive circuit 40 and the level conversion circuit 20, and the second end of the second resistor R4 is connected to the voltage sampling circuit 60 and the speed control circuit 70.

[0083] refer to Figure 4 and Figure 5 As shown, the horizontal axis represents time and the vertical axis represents voltage, wherein the dotted line is a graph of the voltage of the gate C of IGBT50 changing with time, and the solid line is the waveform of the driving signal of IGBT50, that is, a graph of the voltage of the gate of IGBT50 changing with time.

[0084] refer to Figure 3 and Figure 4 As shown, under the action of the speed adjustment circuit 30, the rising edge of the driving signal of the IGBT50 is divided into two stages. The first stage 91 is when the first transistor Q2 is turned on, and the corresponding rising edge slope is the charging slope of the capacitor element C1; the second stage 92 is when the first transistor Q2 is turned off, and the corresponding rising edge slope jumps from the charging voltage to the slope of the first level VCC.

[0085] refer to Figure 4As shown, the working principle of the speed adjustment circuit 30 is: when the base voltage of the first transistor Q2 is greater than the turn-on voltage of the first transistor Q2, the first transistor Q2 is turned on, and the voltage of the first level VCC charges the capacitor C1 through the first resistor R8, and the voltage at the second end of the first resistor R8 begins to rise, that is, the voltage at point a begins to rise, and the voltage signal at point a is output to the IGBT50 through the push-pull drive circuit 40, and the IGBT50 begins to turn on. After the IGBT50 is turned on, the gate C voltage of the IGBT50 begins to decrease. When the gate C voltage of the IGBT50 decreases to a certain value, the first transistor Q2 is in a cut-off state, and the voltage at the second end of the first resistor R8 increases to the voltage of the first level VCC, and the drive voltage output by the push-pull drive circuit 40 to the gate of the IGBT50 also increases accordingly, and the gate of the IGBT50 reaches the input end of the IGBT50.

[0086] In one possible implementation, the speed control circuit 70 includes a current limiting circuit R1 and a second transistor Q1, the first end of the current limiting circuit R1 is connected to the base of the second transistor Q1, the second end of the current limiting circuit R1 is connected to the second control end of the main control circuit 10, the emitter of the second transistor Q1 is grounded, and the collector of the second transistor Q1 is respectively connected to the second end of the second resistor R4 and the voltage sampling circuit.

[0087] In a possible implementation, the current limiting circuit R1 may be composed of one or more resistors connected in parallel or in series.

[0088] The main control circuit 10 can control the conduction and shutdown of the second transistor Q1 by outputting high and low levels. Exemplarily, when the second control terminal of the main control circuit 10 outputs a high level of 5V, the voltage difference between the base and the emitter of the second transistor Q1 exceeds the conduction voltage of the second transistor Q1, so that the second transistor Q1 is turned on, and the speed adjustment circuit 30 is disconnected and does not work, so the rising speed of the current of the IGBT50 will not be controlled. When the second control terminal of the main control circuit 10 outputs a low level of 0-1V, the voltage difference between the base and the emitter of the second transistor Q1 is less than the conduction voltage of the second transistor Q1, so that the second transistor Q1 is not turned on. At this time, the speed adjustment circuit 30 works, so that the rising speed of the current of the IGBT50 becomes slow.

[0089] By providing a current limiting circuit R1 between the main control circuit 10 and the base of the second transistor Q1 , the main control circuit 10 can be protected to prevent excessive current from passing through the main control circuit 10 and causing damage to the main control circuit 10 .

[0090] In one possible implementation, the voltage sampling circuit 60 includes a first voltage divider element R2 and a second voltage divider element R3, wherein the first end of the first voltage divider element R2 is connected to the collector of the IGBT50, the second end of the first voltage divider element R2 is connected to the first end of the second voltage divider element R3 and the collector of the second transistor Q1, the first end of the second voltage divider element R3 is also connected to the second end of the second resistor R4, and the second end of the second voltage divider element R3 is grounded.

[0091] In a possible implementation, the temperature sampling circuit 80 includes a thermistor RT1, a first end of the thermistor RT1 is connected to the main control circuit 10 and the first end of the seventh resistor R20, respectively, and a second end of the seventh resistor R20 is connected to the second level VDD. A second end of the thermistor RT1 is connected to a pin of the IGBT 50. The thermistor RT1 transmits the detected temperature value of the IGBT 50 to the main control circuit 10.

[0092] In a possible implementation, the push-pull driving circuit 40 includes a third resistor R7, a third transistor Q4, a fourth transistor Q5, a fourth resistor R9, and a fifth resistor R10;

[0093] Among them, the first end of the third resistor R7 is connected to the first level VCC, the second end of the third resistor R7 is respectively connected to the output end of the level conversion circuit 20, the second end of the first resistor R8, the base of the third transistor Q4 and the base of the fourth transistor Q5, the collector of the third transistor Q4 is connected to the first level VCC, the emitter of the third transistor Q4 is respectively connected to the first end of the fourth resistor R9 and the first end of the fifth resistor R10, the emitter of the fourth transistor Q5 is connected to the second end of the fourth resistor R9, the collector of the fourth transistor Q5 is grounded, and the second end of the fifth resistor R10 is connected to the input end of the IGBT50.

[0094] Exemplarily, the third transistor Q4 is an emitter follower, and the voltage of the emitter of the third transistor Q4 is substantially the same as the base voltage of the third transistor Q4, so changing the base voltage of the third transistor Q4 achieves the purpose of changing the output voltage of the push-pull drive circuit 40. The third transistor Q4 is turned on when the base receives a high level, and is turned off when the base receives a low level. The fourth transistor Q5 is turned off when the base receives a high level, and is turned on when the base receives a low level. Therefore, the third transistor Q4 and the fourth transistor Q5 are always in a state where one is turned on and the other is turned off.

[0095] When the third transistor Q4 is turned on, the voltage of the emitter of the third transistor Q4 is close to the base voltage of the third transistor Q4, and the push-pull driving circuit 40 provides a driving voltage lower than the first level VCC to the gate C of the IGBT 50, so that the IGBT 50 is turned on. When the fourth transistor Q5 is turned on, it can be considered that the gate C of the IGBT 50 is grounded through the fourth transistor Q5, that is, the fourth transistor Q5 provides a low level to the gate C of the IGBT 50, so that the IGBT 50 is turned off.

[0096] The push-pull driving circuit 40 in this embodiment uses two transistors connected in series, which has a simple structure and low cost.

[0097] In a possible implementation, the level conversion circuit 20 includes a third voltage-dividing element R5, a fourth voltage-dividing element R6 and a fifth transistor Q3, wherein a first end of the third voltage-dividing element R5 is connected to a first level VCC, a second end of the third voltage-dividing element R5 is connected to a first end of the fourth voltage-dividing element R6, a second end of the fourth voltage-dividing element R6 is connected to a base of the fifth transistor Q3, and a collector of the fifth transistor Q3 is connected to a second end of the third resistor R7, a second end of the first resistor R8, a base of the third transistor Q4 and a base of the fourth transistor Q5.

[0098] In a possible implementation, the first level VCC is a direct current power source.

[0099] When the main control circuit 10 provides a high level to the base of the fifth transistor Q3, the fifth transistor Q3 is turned on, and the input end of the push-pull drive circuit 40 connected to the collector of the fifth transistor Q3 receives a low level, so that the IGBT50 is turned off; when the main control circuit 10 provides a low level to the base of the fifth transistor Q3, the fifth transistor Q3 is turned off, and the input end of the push-pull drive circuit 40 connected to the collector of the fifth transistor Q3 receives a high level provided by the speed adjustment circuit 30, so that the IGBT50 is turned on.

[0100] In a possible implementation, the third transistor Q4, the second transistor Q1 and the first transistor Q2 are NPN transistors, and the fourth transistor Q5 is a PNP transistor.

[0101] In order to prevent the IGBT 50 from being damaged when the gate of the IGBT 50 is open or the gate of the IGBT 50 is damaged, a sixth resistor R11 is provided between the gate and the emitter of the IGBT 50 to protect the IGBT 50. In addition, a voltage zener diode DW11 is provided in parallel with the sixth resistor R11 to protect the IGBT 50. When the voltage of the push-pull drive circuit 40 driving the IGBT 50 is too high, the voltage zener diode DW11 is broken down, so that the driving voltage cannot be applied to the IGBT 50, and the driving voltage applied to the IGBT 50 is stabilized within a limited value, thereby effectively protecting the IGBT 50 from being burned out.

[0102] The present invention provides an IGBT driving circuit having the following working principle: the gate C voltage of the IGBT50 is provided to the base of the first transistor Q2 after being divided by the first voltage dividing element R2 and the second voltage dividing element R3; when the base voltage of the first transistor Q2 is greater than the turn-on voltage of the first transistor Q2, the first transistor Q2 is turned on, and the voltage of the first level VCC charges the capacitor C1 through the third resistor R7 and the first resistor R8, and the voltage at point a starts to rise. The second end of the first resistor R8 is point a. The voltage signal at point a is output to IGBT50 through the push-pull drive circuit 40. IGBT50 starts to conduct. After IGBT50 is conducted, the gate C voltage of IGBT50 starts to drop. When the gate C voltage of IGBT50 drops to a certain value, the first transistor Q2 is in the cut-off state. The voltage at the second end of the first resistor R8 rises to the voltage of the first level VCC. The drive voltage output to the gate of IGBT50 by the push-pull drive circuit 40 also rises accordingly. The gate of IGBT50 reaches the input end of IGBT50. The present application solves the problem of limited use of the low-power gear by intermittently heating the electromagnetic heating device at a low-power gear, controlling and reducing the working time of the IGBT at a low-power gear, thereby presenting to the user that the electromagnetic heating device works continuously at a low-power gear and improving the use effect.

[0103] refer to Figure 3 and Figure 4 As shown, when working, under the action of the speed adjustment circuit 30, the rising edge of the driving signal of the IGBT50 is divided into two stages: a first stage 91 and a second stage 92, wherein the first stage 91 is when the first transistor Q2 is turned on, and the corresponding rising edge slope is the charging slope of the capacitor element C1; the second stage 92 is when the first transistor Q2 is turned off, and the corresponding rising edge slope jumps from the charging voltage to the slope of the first level VCC.

[0104] The higher the gate C voltage of IGBT50, the longer the duration of the first stage 91, which makes the voltage of IGBT50 rise more slowly. At this time, the IGBT50 is in the amplification area for a longer time, and the current of IGBT50 rises more slowly, thereby effectively reducing the transient on-current of IGBT50. However, the longer the duration of the first stage 91 is, the greater the conduction loss of IGBT50 is, and the higher the temperature rise of IGBT50 is.

[0105] When the temperature rise of IGBT50 reaches the preset temperature threshold, the second control terminal of the main control circuit 10 outputs a second control signal, which may be a CTR signal, the second transistor Q1 is turned on, the first transistor Q2 is turned off, and due to the presence of the first diode D1, the capacitor C1 will no longer be charged or discharged, and the voltage at the second end of the first resistor R8 becomes the output voltage of the first level VCC, i.e., the reference voltage. Figure 5 As shown, the rising edge of the IGBT50 driving signal becomes a single slope. When the second transistor Q1 is turned on, the first transistor Q2 is turned off, that is, the speed adjustment circuit 30 is disconnected and does not work, so the rising speed of the current of the IGBT50 will not be controlled.

[0106] When the temperature of the IGBT 50 is lower than the preset temperature threshold, the second transistor Q1 is not turned on. At this time, the speed adjustment circuit 30 works to control the rising speed of the current of the IGBT 50 to be slow.

[0107] The present invention also provides an electromagnetic heating device, comprising the above-mentioned IGBT driving circuit.

[0108] In this embodiment, the main control circuit 10 flexibly switches between two working modes according to the working temperature of the IGBT 50, and selects that when the temperature value collected by the temperature sampling circuit 80 is greater than or equal to the preset temperature threshold, the second control terminal of the main control circuit 10 outputs the second control signal, and when the temperature value collected by the temperature sampling circuit 80 is less than the preset temperature threshold, the first control terminal of the main control circuit 10 outputs the first control signal, to ensure that the IGBT 50 works in a relatively safe state.

[0109] Those skilled in the art can understand that all or part of the steps of implementing the above-mentioned method embodiments can be completed by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When the program is executed, the steps of the above-mentioned method embodiments are executed; and the aforementioned storage medium includes: ROM, RAM, disk or optical disk and other media that can store program codes.

[0110] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, they can be fixedly connected, detachably connected, or integrated; they can be mechanically connected, electrically connected, or can communicate with each other; they can be directly connected, or indirectly connected through an intermediate medium, so that the internal communication of two elements or the interaction relationship between two elements can be achieved. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0111] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An IGBT driving circuit, characterized in that: include: A main control circuit (10), a level conversion circuit (20), a speed adjustment circuit (30), a push-pull drive circuit (40) and an IGBT (50), wherein the main control circuit (10) has a first control end, the first control end of the main control circuit (10), the level conversion circuit (20), the speed adjustment circuit (30), the push-pull drive circuit (40) and the gate of the IGBT (50) are connected in sequence, and the emitter of the IGBT (50) is grounded; The speed adjustment circuit (30) is used to control and slow down the growth rate of the driving voltage driving the IGBT (50), so as to reduce the on-current of the IGBT (50).

2. The IGBT driving circuit according to claim 1, characterized in that: It also includes a voltage sampling circuit (60), wherein a first end of the voltage sampling circuit (60) is electrically connected to the collector of the IGBT (50), and a second end of the voltage sampling circuit (60) is electrically connected to the speed adjustment circuit (30), and the voltage sampling circuit (60) is used to collect the collector voltage of the IGBT (50) and output the collector voltage of the IGBT (50) to the speed adjustment circuit (30); The speed adjustment circuit (30) is configured to control the slowing down of the growth rate of the driving voltage driving the IGBT (50) when the collector voltage of the IGBT (50) is greater than or equal to a preset voltage threshold, so as to reduce the on-current of the IGBT (50), and to speed up the growth rate of the driving voltage driving the IGBT (50) when the collector voltage of the IGBT (50) is less than the preset voltage threshold.

3. The IGBT driving circuit according to claim 2, characterized in that: It also includes a speed control circuit (70) and a temperature sampling circuit (80), the main control circuit (10) also having a second control end, the second control end of the main control circuit (10) is connected to the input end of the speed control circuit (70), and the output end of the speed control circuit (70) is connected to the speed adjustment circuit (30); A first end of the temperature sampling circuit (80) is connected to a pin of the IGBT (50), a second end of the temperature sampling circuit (80) is connected to a main control circuit (10), and the temperature sampling circuit (80) is used to collect the temperature of the IGBT (50); The speed control circuit (70) is used to control the speed adjustment circuit (30) to be in an off state when the temperature value of the IGBT (50) collected by the temperature sampling circuit (80) is greater than or equal to a preset temperature value, and to control the speed adjustment circuit (30) to be in an on state when the temperature value of the IGBT (50) collected by the temperature sampling circuit (80) is less than the preset temperature value.

4. The IGBT driving circuit according to claim 3, characterized in that: The first control end of the main control circuit (10) is used to output a first control signal, and the second control end of the main control circuit (10) is used to output a second control signal, wherein the second control signal is different from the first control signal.

5. The IGBT driving circuit according to claim 3, characterized in that: The speed adjustment circuit (30) comprises a first transistor (Q2), a capacitor element (C1), a first diode (D1), a first resistor (R8) and a second resistor (R4); the base of the first transistor (Q2) is connected to the first end of the second resistor (R4); the emitter of the first transistor (Q2) is grounded; the collector of the first transistor (Q2) is connected to the first end of the capacitor element (C1) and the cathode of the first diode (D1); the first end of the capacitor element (C1) is connected to the cathode of the first diode (D1); the second end of the capacitor element (C1) is connected to the first end of the first resistor (R8); the anode of the first diode (D1) is grounded; the second end of the first resistor (R8) is connected to the input end of the push-pull drive circuit (40) and the level conversion circuit (20); and the second end of the second resistor (R4) is connected to the voltage sampling circuit (60) and the speed control circuit (70).

6. The IGBT driving circuit according to claim 5, characterized in that: The speed control circuit (70) comprises a current limiting circuit (R1) and a second transistor (Q1), wherein a first end of the current limiting circuit (R1) is connected to a base of the second transistor (Q1), a second end of the current limiting circuit (R1) is connected to the second control end of the main control circuit (10), an emitter of the second transistor (Q1) is grounded, and a collector of the second transistor (Q1) is respectively connected to a second end of the second resistor (R4) and the voltage sampling circuit (60).

7. The IGBT driving circuit according to claim 6, characterized in that: The voltage sampling circuit (60) comprises a first voltage dividing element (R2) and a second voltage dividing element (R3), wherein a first end of the first voltage dividing element (R2) is connected to the collector of the IGBT (50), a second end of the first voltage dividing element (R2) is connected to a first end of the second voltage dividing element (R3) and a collector of the second transistor (Q1), a first end of the second voltage dividing element (R3) is also connected to a second end of the second resistor (R4), and a second end of the second voltage dividing element (R3) is grounded.

8. The IGBT driving circuit according to claim 7, characterized in that: The push-pull driving circuit (40) comprises a third resistor (R7), a third transistor (Q4), a fourth transistor (Q5), a fourth resistor (R9) and a fifth resistor (R10); The first end of the third resistor (R7) is connected to a first level (VCC), the second end of the third resistor (R7) is respectively connected to the output end of the level conversion circuit (20), the second end of the first resistor (R8), the base of the third transistor (Q4) and the base of the fourth transistor (Q5), the collector of the third transistor (Q4) is connected to the first level (VCC), the emitter of the third transistor (Q4) is respectively connected to the first end of the fourth resistor (R9) and the first end of the fifth resistor (R10), the emitter of the fourth transistor (Q5) is connected to the second end of the fourth resistor (R9), the collector of the fourth transistor (Q5) is grounded, and the second end of the fifth resistor (R10) is connected to the input end of the IGBT (50).

9. The IGBT driving circuit according to claim 8, characterized in that: The level conversion circuit (20) comprises a third voltage-dividing element (R5), a fourth voltage-dividing element (R6) and a fifth transistor (Q3); a first end of the third voltage-dividing element (R5) is connected to the first level (VCC); a second end of the third voltage-dividing element (R5) is connected to a first end of the fourth voltage-dividing element (R6); a second end of the fourth voltage-dividing element (R6) is connected to a base of the fifth transistor (Q3); and a collector of the fifth transistor (Q3) is connected to a second end of the third resistor (R7), a second end of the first resistor (R8), a base of the third transistor (Q4) and a base of the fourth transistor (Q5).

10. The IGBT driving circuit according to claim 9, characterized in that: The third transistor (Q4), the second transistor (Q1) and the first transistor (Q2) are NPN transistors, and the fourth transistor (Q5) is a PNP transistor.

11. An electromagnetic heating device, characterized in that: The invention comprises the IGBT driving circuit as described in any one of claims 1 to 10.

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