IGBT soft start control method, circuit and electromagnetic heating equipment

Abstract

The present invention relates to the field of electromagnetic heating technology, and discloses an IGBT soft-start control method, circuit, and electromagnetic heating equipment. The method comprises: obtaining the collector voltage of an IGBT device; when the collector voltage of the IGBT device is greater than a first voltage threshold, providing a first drive signal to the IGBT device during the IGBT device's turn-on phase; and providing a second drive signal to the IGBT device until the collector voltage of the IGBT device is less than a second voltage threshold, so that the IGBT device performs soft start and then normal conduction. The circuit comprises a control circuit, a drive circuit, a feedback circuit, an IGBT device, and a resonant circuit. The present invention controls the IGBT device in stages by collecting the collector voltage of the IGBT device, causing the IGBT device to perform soft start and then normal conduction, thereby reducing conduction losses and achieving continuous low-power heating operation of the electromagnetic heating equipment.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic heating, and in particular to an IGBT soft start control method, circuit and electromagnetic heating equipment. Background Art

[0002] In existing technology, electromagnetic heating products such as induction cookers, induction rice cookers, and pressure cookers mostly utilize single-tube IGBT devices for cost reasons. Under high-voltage or low-power operating conditions, these solutions experience insufficient input energy during resonance, causing the IGBT to turn on at a non-zero voltage. This results in a high on-voltage and high instantaneous on-current, which can lead to IGBT overheating and damage. During pot inspection and power startup, the IGBT's collector voltage is 1.4 times the AC mains voltage, resulting in an even higher on-voltage and instantaneous on-current. At high voltage, the instantaneous on-current can reach over 150A, exceeding the IGBT's specifications and posing a significant risk of device failure. Summary of the Invention

[0003] The purpose of the present invention is to provide an IGBT soft start control method, circuit and electromagnetic heating equipment to solve one or more technical problems existing in the prior art and at least provide a beneficial choice or create conditions.

[0004] In a first aspect, a method for controlling an IGBT soft start is provided, comprising the following steps:

[0005] Get the collector voltage of the IGBT device;

[0006] When the collector voltage of the IGBT device is greater than the first voltage threshold, a first driving signal is provided to the IGBT device during the turn-on phase of the IGBT device, and when the collector voltage of the IGBT device is less than the second voltage threshold, a second driving signal is provided to the IGBT device, so that the IGBT device performs soft start and normal turn-on successively;

[0007] The first voltage threshold is greater than or equal to the second voltage threshold, and the soft-start voltage of the IGBT device corresponding to the first drive signal is less than the drive voltage of the IGBT device corresponding to the second drive signal.

[0008] In a second aspect, an IGBT soft start control circuit is provided, comprising a control circuit, a drive circuit, a feedback circuit, an IGBT device and a resonant circuit;

[0009] The control circuit, the drive circuit and the base of the IGBT device are connected in sequence, the collector of the IGBT device is connected to the resonant circuit, one end of the feedback circuit is connected to the collector of the IGBT device, and the other end of the feedback circuit is connected to the control circuit or the drive circuit or the base of the IGBT device;

[0010] The control circuit outputs a driving voltage to the base of the IGBT device through the driving circuit;

[0011] The feedback circuit is used to obtain the collector voltage of the IGBT device, and when the collector voltage of the IGBT device is greater than a first voltage threshold, provide a first drive signal to the IGBT device during the turn-on phase of the IGBT device, and when the collector voltage of the IGBT device is less than a second voltage threshold, provide a second drive signal to the IGBT device, so that the IGBT device performs soft start and normal turn-on successively;

[0012] The first voltage threshold is greater than or equal to the second voltage threshold, and the soft-start voltage of the IGBT device corresponding to the first drive signal is less than the drive voltage of the IGBT device corresponding to the second drive signal.

[0013] According to one embodiment of the present invention, the feedback circuit includes a sampling subcircuit, an enabling subcircuit and a voltage-reducing subcircuit;

[0014] The collector of the IGBT device, the sampling sub-circuit, the enabling sub-circuit and one end of the buck sub-circuit are connected in sequence, and the other end of the buck sub-circuit is connected to the driving circuit or the base of the IGBT device.

[0015] According to one embodiment of the present invention, the sampling subcircuit includes a first sampling resistor and a second sampling resistor;

[0016] One end of the first sampling resistor is connected to the collector of the IGBT device, the other end of the first sampling resistor and one end of the second sampling resistor are respectively connected to the enabling sub-circuit, and the other end of the second sampling resistor is grounded.

[0017] According to one embodiment of the present invention, the enabling sub-circuit includes a first switching tube and a first resistor, wherein a first end of the first switching tube is connected to the step-down sub-circuit, a second end of the first switching tube is grounded, a triggering end of the first switching tube is connected to one end of the first resistor, and the other end of the first resistor is connected to the sampling sub-circuit; or

[0018] The enabling subcircuit includes a first switching tube, a first resistor and an operational amplifier, the positive input terminal of the operational amplifier is connected to the sampling subcircuit, the negative input terminal of the operational amplifier is connected to the reference voltage or the output terminal of the operational amplifier, the output terminal of the operational amplifier is connected to one end of the first resistor, the other end of the first resistor is connected to the trigger terminal of the first switching tube, the first end of the first switching tube is connected to the step-down subcircuit, and the second end of the first switching tube is grounded.

[0019] According to an embodiment of the present invention, the first switch tube is a triode or a MOS tube.

[0020] According to one embodiment of the present invention, the step-down sub-circuit includes a second resistor, one end of the second resistor is connected to the enabling sub-circuit, and the other end of the second resistor is connected to the base of the driving circuit or the GIBT device; or

[0021] The step-down subcircuit includes a voltage-stabilizing diode, an anode of the voltage-stabilizing diode is connected to the enabling subcircuit, and a cathode of the voltage-stabilizing diode is connected to the base of the driving circuit or the GIBT device.

[0022] According to one embodiment of the present invention, the feedback circuit includes a sampling subcircuit, an enabling subcircuit and a voltage-reducing subcircuit;

[0023] The collector of the IGBT device, the sampling subcircuit, the control circuit, the enabling subcircuit and one end of the buck subcircuit are connected in sequence, and the other end of the buck subcircuit is connected to the driving circuit or the base of the IGBT device.

[0024] According to one embodiment of the present invention, the control circuit, the drive circuit, the enabling sub-circuit and the buck sub-circuit are integrated into a package.

[0025] According to one embodiment of the present invention, the driving circuit includes a level conversion subcircuit and a push-pull driving subcircuit, and the control circuit, the level conversion subcircuit, the push-pull driving subcircuit and the gate of the IGBT device are connected in sequence.

[0026] According to one embodiment of the present invention, the level conversion sub-circuit includes a second transistor, a third resistor, a fourth resistor and a fifth resistor;

[0027] One end of the third resistor and one end of the fifth resistor are connected to a DC voltage, the other end of the third resistor and one end of the fourth resistor are connected to a control circuit, the other end of the fourth resistor is connected to the base of the second transistor, the other end of the fifth resistor and the input end of the push-pull drive sub-circuit are connected to the collector of the second transistor, and the emitter of the second transistor is grounded.

[0028] According to one embodiment of the present invention, the push-pull driving sub-circuit includes a third transistor, a fourth transistor, a sixth resistor and a seventh resistor;

[0029] The bases of the third and fourth transistors are connected to the output end of the level conversion sub-circuit, the collector of the third transistor is connected to a DC voltage, the emitter of the third transistor is connected to the gate of the IGBT device through a sixth resistor and to the emitter of the fourth transistor through a seventh resistor, the collector of the fourth transistor is grounded, the third transistor is an NPN transistor, and the fourth transistor is a PNP transistor.

[0030] In a third aspect, an electromagnetic heating device is provided, comprising the IGBT soft start control circuit described in the second aspect.

[0031] The beneficial effects of the present invention are as follows: the IGBT device is controlled in stages by collecting the collector voltage of the IGBT device; in the startup phase, when the collector voltage of the IGBT device exceeds the set value, the driving voltage of the IGBT device is reduced; then, when the collector voltage of the IGBT device is reduced to a normal level, the driving voltage of the IGBT device is restored, so that the IGBT device is soft-started and normally turned on in turn, thereby reducing the conduction loss of the IGBT device and realizing continuous low-power heating operation of the electromagnetic heating equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 FIG. 1 is a structural diagram of an IGBT soft start control circuit according to an embodiment of the present invention.

[0033] Figure 2 This is a second structural diagram of the IGBT soft start control circuit according to an embodiment of the present invention.

[0034] Figure 3 This is the third structural diagram of the IGBT soft start control circuit according to an embodiment of the present invention.

[0035] Figure 4 This is a fourth structural diagram of the IGBT soft start control circuit according to an embodiment of the present invention.

[0036] Figure 5 This is the fifth structural diagram of the IGBT soft start control circuit according to an embodiment of the present invention.

[0037] Figure 6 This is the sixth structural diagram of the IGBT soft start control circuit according to an embodiment of the present invention.

[0038] Figure 7 FIG7 is a seventh structural diagram of an IGBT soft start control circuit according to an embodiment of the present invention.

[0039] Figure 8 FIG8 is an eighth structural diagram of an IGBT soft start control circuit according to an embodiment of the present invention.

[0040] Figure 9 This is a ninth structural diagram of the IGBT soft start control circuit according to an embodiment of the present invention.

[0041] Figure 10 FIG10 is a structural diagram of an IGBT soft start control circuit according to an embodiment of the present invention.

[0042] Figure 11FIG11 is a structural diagram of an IGBT soft start control circuit according to an embodiment of the present invention.

[0043] Figure 12 Flowchart of an IGBT soft start control method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0044] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the present invention will be further described below in conjunction with the embodiments and drawings.

[0045] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on the present invention.

[0046] In the description of the present invention, "several" means an indefinite quantity, "multiple" means more than two, "greater than," "less than," "exceed," etc. are understood to exclude the number itself, and "above," "below," "within," etc. are understood to include the number itself. The use of "first" and "second" is solely for the purpose of distinguishing technical features and should not be understood to indicate or imply relative importance, or to implicitly indicate the number of technical features indicated, or to implicitly indicate the order of the technical features indicated. Furthermore, "and / or" appearing throughout the text represents three parallel solutions. For example, "A and / or B" represents a solution where A satisfies, a solution where B satisfies, or a solution where both A and B satisfy.

[0047] In the description of the present invention, the terms "comprises," "comprising," or any other variations thereof are intended to cover a non-exclusive inclusion, and may include elements not expressly listed, in addition to the listed elements.

[0048] According to a first aspect of the present invention, an IGBT soft-start control method is provided.

[0049] like Figure 12 As shown, the IGBT soft start control method provided by the embodiment of the present invention includes the following steps:

[0050] Step S100: Obtain the collector voltage of the IGBT device.

[0051] Step S200: When the collector voltage of the IGBT device is greater than the first voltage threshold, a first drive signal is provided to the IGBT device during the turn-on phase of the IGBT device, and when the collector voltage of the IGBT device is less than the second voltage threshold, a second drive signal is provided to the IGBT device, so that the IGBT device performs soft start and normal turn-on successively.

[0052] The first voltage threshold is greater than or equal to the second voltage threshold, and the soft-start voltage of the IGBT device corresponding to the first drive signal is less than the drive voltage of the IGBT device corresponding to the second drive signal.

[0053] Specifically, in the IGBT device control scenario, the collector voltage of the IGBT device is obtained and it is determined whether the collector voltage of the IGBT device is greater than a first voltage threshold. When the collector voltage of the IGBT device is greater than the first voltage threshold, a first drive signal is output during the turn-on phase of the IGBT device, and the drive voltage of the IGBT device is adjusted to reduce the drive voltage of the IGBT device. The IGBT device is soft-started, and the collector voltage of the IGBT device is kept obtained. When the collector voltage of the IGBT device is less than a second voltage threshold, a second drive signal is output to increase the drive voltage of the IGBT device and restore it to a normal state, so that the IGBT device is turned on normally, thereby achieving the drive voltage of the IGBT device being low first and then high, and the IGBT device is soft-started and turned on normally in sequence.

[0054] It should be noted that the soft start voltage is the driving voltage of the IGBT device during the soft start phase. The soft start voltage gradually increases from zero to the rated driving voltage, and the IGBT device completes the soft start.

[0055] According to a second aspect of the present invention, an IGBT soft start control circuit is provided.

[0056] like Figure 1 As shown, the IGBT soft start control circuit provided by the embodiment of the present invention includes a control circuit 100 , a drive circuit 200 , a feedback circuit 300 , an IGBT device 400 and a resonant circuit 500 .

[0057] Among them, the bases of the control circuit 100, the drive circuit 200 and the IGBT device 400 are connected in sequence, the collector of the IGBT device 400 is connected to the resonant circuit 500, one end of the feedback circuit 300 is connected to the collector of the IGBT device 400, and the other end of the feedback circuit 300 is connected to the base of the drive circuit 200 or the IGBT device 400.

[0058] In actual use, the control circuit 100 outputs a drive voltage to the base of the IGBT device 400 via the drive circuit 200. The feedback circuit 300 is used to obtain the collector voltage of the IGBT device 400. When the collector voltage of the IGBT device 400 is greater than a first voltage threshold, a first drive signal is provided to the IGBT device 400 during the turn-on phase of the IGBT device 400. When the collector voltage of the IGBT device 400 is less than a second voltage threshold, a second drive signal is provided to the IGBT device 400 to sequentially perform a soft start and a normal turn-on of the IGBT device 400. The first voltage threshold is greater than or equal to the second voltage threshold, and the soft start voltage of the IGBT device corresponding to the first drive signal is less than the drive voltage of the IGBT device corresponding to the second drive signal. Both the first voltage threshold and the second voltage threshold are preset values.

[0059] Specifically, upon receiving a start-up instruction, the control circuit 100 , such as an MCU (microprocessor), outputs a control signal to the drive circuit 200 to control the drive circuit 200 to output a drive voltage to the IGBT device 400 to turn on the IGBT device 400 . The feedback circuit 300 is connected to the collector of the IGBT device 400 to determine whether the collector voltage of the IGBT device 400 is greater than a first voltage threshold. When the collector voltage of the IGBT device 400 is greater than the first voltage threshold, the feedback circuit 300 outputs a first drive signal to the control circuit 100 or the drive circuit 200 or the base of the IGBT device 400 during the turn-on phase of the IGBT device 400 to reduce the drive voltage of the IGBT device 400, and the IGBT device 400 is soft-started until the collector voltage of the IGBT device is less than the second voltage threshold. The feedback circuit 300 outputs a second drive signal to restore the drive voltage of the IGBT device 400 to a normal state, and the IGBT device 400 is normally turned on, thereby achieving the goal that the drive voltage of the IGBT device 400 is first low and then high, and the IGBT device 400 is soft-started and normally turned on in sequence.

[0060] That is, the IGBT soft-start control circuit provided by the present invention uses a feedback circuit 300 to monitor the collector voltage generated by the collector of the IGBT device 400 at the moment when the control circuit 100 starts the IGBT device 400 through the drive circuit 200. The feedback circuit 300 compares the sampled collector voltage of the IGBT device 400 with a first voltage threshold and a second voltage threshold. When the collector voltage of the IGBT device 400 exceeds the first voltage threshold, the feedback circuit 300 outputs a first drive signal for reducing the drive voltage of the IGBT device 400, thereby reducing the drive voltage and conduction current of the IGBT device 400, causing the IGBT device 400 to soft-start. After the soft-start stage, the collector voltage of the IGBT device 400 decreases. When the collector voltage of the IGBT device 400 is less than the second voltage threshold, the feedback circuit 300 outputs a second drive signal for restoring the drive voltage of the IGBT device 400, thereby increasing the drive voltage of the IGBT device 400 to a normal level, causing the IGBT device 400 to conduct normally.

[0061] To further explain the IGBT soft-start control circuit provided by the present invention, the IGBT soft-start control circuit provided by the present invention is described below in conjunction with actual embodiments.

[0062] like Figure 2 As shown, according to one embodiment of the present invention, the feedback circuit 300 includes a sampling sub-circuit 310 , an enabling sub-circuit 320 and a voltage-reducing sub-circuit 330 .

[0063] The collector of the IGBT device 400 , the sampling sub-circuit 310 , the enabling sub-circuit 320 and one end of the buck sub-circuit 330 are connected in sequence, and the other end of the buck sub-circuit 330 is connected to the base of the driving circuit 200 or the IGBT device 400 .

[0064] In this embodiment, the sampling sub-circuit 310 sends the collected collector voltage of the IGBT device 400 to the enabling sub-circuit 320. The enabling sub-circuit 320 enables the IGBT device 400 based on the collector voltage, the first voltage threshold, and the second voltage threshold. When the collector voltage of the IGBT device 400 exceeds the first voltage threshold, the enabling sub-circuit 320 enables the step-down sub-circuit 330. The step-down sub-circuit 330 outputs a first drive signal to the drive circuit 200 or the base of the IGBT device 400 to reduce the drive voltage and conduction current of the IGBT device 400, thereby soft-starting the IGBT device 400. When the collector voltage of the IGBT device 400 is less than the second voltage threshold, the enabling sub-circuit 320 is not enabled, and the output terminal of the disabled step-down sub-circuit 330 is in a low-level state (the second drive signal). The drive voltage of the IGBT device 400 gradually returns to a normal level, and the IGBT device 400 is normally turned on.

[0065] like Figure 3 As shown, according to one embodiment of the present invention, the sampling sub-circuit 310 includes a first sampling resistor RS1 and a second sampling resistor RS2. One end of the first sampling resistor RS1 is connected to the collector of the IGBT device 400, the other end of the first sampling resistor RS1 and one end of the second sampling resistor RS2 are respectively connected to the enabling sub-circuit 320, and the other end of the second sampling resistor RS2 is grounded.

[0066] In this embodiment, when the collector of the IGBT device 400 is energized, a voltage difference is formed across the first sampling resistor RS1. When the enabling sub-circuit 320 connected to the first sampling resistor RS1 detects that the collector voltage of the IGBT device 400 exceeds the first voltage threshold, the step-down sub-circuit 330 is enabled.

[0067] like Figure 4 As shown, according to one embodiment of the present invention, the enabling sub-circuit 320 includes a first switch Q1 and a first resistor R1. A first terminal of the first switch Q1 is connected to the step-down sub-circuit 330, a second terminal of the first switch Q1 is grounded, a trigger terminal of the first switch Q1 is connected to one terminal of the first resistor R1, and the other terminal of the first resistor R1 is connected to the sampling sub-circuit 310.

[0068] In this embodiment, the sampling signal obtained by the sampling sub-circuit 310 by sampling the collector voltage of the IGBT device 400 flows to the trigger terminal of the first switch tube Q1. When the collector voltage of the IGBT device 400 exceeds the first voltage threshold, the sampling signal output by the sampling sub-circuit 310 triggers the first switch tube Q1 to turn on, grounding the step-down sub-circuit 330 connected to the drive circuit 200 or the base of the IGBT device 400, thereby lowering the drive voltage of the IGBT device 400. Conversely, when the collector voltage of the IGBT device 400 is less than the second voltage threshold, the first switch tube Q1 gradually enters the cut-off state. When the first switch tube Q1 is cut off, the step-down sub-circuit 330 fails to turn on, and the drive voltage of the IGBT device 400 is maintained at a normal level.

[0069] like Figure 5 As shown, according to one embodiment of the present invention, the enabling sub-circuit 320 includes a first switch Q1, a first resistor R1, and an operational amplifier U1. The positive input terminal of the operational amplifier U1 is connected to the sampling sub-circuit 310, the negative input terminal of the operational amplifier U1 is connected to the reference voltage Vref, the output terminal of the operational amplifier U1 is connected to one end of the first resistor R1, the other end of the first resistor R1 is connected to the trigger terminal of the first switch Q1, the first end of the first switch Q1 is connected to the step-down sub-circuit 330, and the second end of the first switch Q1 is grounded.

[0070] In this embodiment, the sampling signal obtained by the sampling sub-circuit 310 sampling the collector voltage of the IGBT device 400 flows to the positive input terminal of the operational amplifier U1 and is compared with the reference voltage Vref input from the negative input terminal of the operational amplifier U1. When the sampling signal corresponding to the collector voltage of the IGBT device 400 exceeds the reference voltage Vref, the operational amplifier U1 outputs a high-level signal and triggers the first switch tube Q1 to turn on. After the first switch tube Q1 turns on, the step-down sub-circuit 330 lowers the drive voltage of the IGBT device 400. Conversely, when the collector voltage of the IGBT device 400 is less than the reference voltage Vref, the operational amplifier U1 outputs a low-level signal, the first switch tube Q1 is turned off, the step-down sub-circuit 330 fails to turn on, and the drive voltage of the IGBT device 400 is maintained at a normal level.

[0071] like Figure 6 As shown, according to one embodiment of the present invention, Figure 5 The difference between the provided embodiments is that the negative input terminal of the operational amplifier U1 is connected to the output terminal of the operational amplifier U1, forming an inverting amplifier circuit, which has the function of amplifying the input signal and outputting it in an inverted state.

[0072] above Figures 4 to 6 In an embodiment, the first switch tube Q1 is a triode or a MOS tube. When the first switch tube Q1 is a triode, the first end of the first switch tube Q1 is the collector, the second end of the first switch tube Q1 is the emitter, and the trigger end in the first switch tube Q1 is the base. When the first switch tube Q1 is a MOS tube, the first end of the first switch tube Q1 is the drain, the second end of the first switch tube Q1 is the source, and the trigger end in the first switch tube Q1 is the gate.

[0073] like Figure 7 As shown, according to one embodiment of the present invention, the step-down sub-circuit 330 includes a second resistor R2 , one end of the second resistor R2 is connected to the enabling sub-circuit 320 , and the other end of the second resistor R2 is connected to the driving circuit 200 .

[0074] In this embodiment, the second resistor R2 serves as a voltage divider resistor. When the enabling sub-circuit 320 is enabled, the second resistor R2 is grounded, so that the DC voltage on the driving circuit 200 is partially output to the gate of the IGBT device 400 and partially flows to the ground, thereby lowering the driving voltage of the IGBT device 400.

[0075] like Figure 8 As shown, according to one embodiment of the present invention, Figure 7 The difference between the provided embodiment is that the step-down sub-circuit 330 includes a Zener diode ZD1 , the anode of the Zener diode ZD1 is connected to the enabling sub-circuit 320 , and the cathode of the Zener diode ZD1 is connected to the base of the GIBT device.

[0076] like Figure 10 As shown, according to one embodiment of the present invention, another feedback circuit 300 structure is provided. The feedback circuit 300 includes a sampling sub-circuit 310, an enabling sub-circuit 320, and a buck sub-circuit 330. The collector of the IGBT device 400, the sampling sub-circuit 310, the control circuit 100, the enabling sub-circuit 320, and one end of the buck sub-circuit 330 are sequentially connected, and the other end of the buck sub-circuit 330 is connected to the base of the drive circuit 200 or the IGBT device 400.

[0077] In this embodiment, the sampling subcircuit 310 sends the collected collector voltage of the IGBT device 400 to the control circuit 100. The control circuit 100 triggers the enabling subcircuit 320 to enable the IGBT device 400 based on the collector voltage, the first voltage threshold, and the second voltage threshold. When the collector voltage of the IGBT device 400 exceeds the first voltage threshold, the control circuit 100 controls the enabling subcircuit 320 to enable the step-down subcircuit 330. The step-down subcircuit 330 outputs a first drive signal to the drive circuit 200 or the base of the IGBT device 400, reducing the drive voltage and conduction current of the IGBT device 400, thereby soft-starting the IGBT device 400. When the collector voltage of the IGBT device 400 is less than the second voltage threshold, the control circuit 100 controls the enabling subcircuit 320 to disable the IGBT device 400. The output terminal of the disabled step-down subcircuit 330 is in a low-level state (the second drive signal), and the drive voltage of the IGBT device 400 gradually returns to a normal level, causing the IGBT device 400 to conduct normally.

[0078] The sampling sub-circuit 310, the enabling sub-circuit 320, and the buck sub-circuit 330 described in this embodiment may adopt the same structure as the sampling sub-circuit 310, the enabling sub-circuit 320, and the buck sub-circuit 330 described in the above embodiment. The principles of the sampling sub-circuit 310, the enabling sub-circuit 320, and the buck sub-circuit 330 are the same as those in the above embodiment and are not further described here.

[0079] like Figure 9 As shown, according to one embodiment of the present invention, the driving circuit 200 includes a level conversion sub-circuit 210 and a push-pull driving sub-circuit 220, and the control circuit 100, the level conversion sub-circuit 210, the push-pull driving sub-circuit 220 and the gate of the IGBT device 400 are connected in sequence.

[0080] The level conversion sub-circuit 210 includes a second transistor Q2, a third resistor R3, a fourth resistor R4, and a fifth resistor R5. One end of the third resistor R3 and one end of the fifth resistor R5 are connected to a DC voltage, the other end of the third resistor R3 and one end of the fourth resistor R4 are connected to the control circuit 100, the other end of the fourth resistor R4 is connected to the base of the second transistor Q2, the other end of the fifth resistor R5 and the input end of the push-pull drive sub-circuit 220 are connected to the collector of the second transistor Q2, and the emitter of the second transistor Q2 is grounded.

[0081] The push-pull drive sub-circuit 220 includes a third transistor Q3, a fourth transistor Q4, a sixth resistor R6, and a seventh resistor R7. The bases of the third transistor Q3 and the fourth transistor Q4 are connected to the output of the level conversion sub-circuit 210, the collector of the third transistor Q3 is connected to a DC voltage, the emitter of the third transistor Q3 is connected to the gate of the IGBT device 400 via the sixth resistor R6, and to the emitter of the fourth transistor Q4 via the seventh resistor R7. The collector of the fourth transistor Q4 is grounded. The third transistor Q3 is an NPN transistor, and the fourth transistor Q4 is a PNP transistor.

[0082] In this embodiment, the level conversion sub-circuit 210 receives a drive signal output by the control circuit 100. The level of the drive signal changes alternately, causing the third transistor Q3 and the fourth transistor Q4 of the push-pull drive sub-circuit 220 to be alternately turned on. Specifically, when the drive signal is at a low level, the second transistor Q2 and the fourth transistor Q4 are turned off, and the third transistor Q3 is turned on to output a DC voltage as a drive voltage for driving the IGBT device 400. Conversely, the second transistor Q2 and the fourth transistor Q4 are turned on, and the third transistor Q3 is turned off, and no drive voltage is output to the IGBT device 400.

[0083] According to the IGBT soft start control circuit of the embodiment of the present invention, the IGBT device 400 is controlled in stages by collecting the collector voltage of the IGBT device 400. In the startup stage, when the collector voltage of the IGBT device 400 exceeds the set value, the driving voltage of the IGBT device 400 is reduced. Subsequently, when the collector voltage of the IGBT device 400 is reduced to a normal level, the driving voltage of the IGBT device 400 is restored, so that the IGBT device 400 is soft-started and normally turned on in turn, thereby reducing the conduction loss of the IGBT device 400 and realizing continuous low-power heating operation of the electromagnetic heating equipment.

[0084] like Figure 11 As shown, according to one embodiment of the present invention, the control circuit 100, the drive circuit 200, the enabling sub-circuit 320 and the buck sub-circuit 330 are integrated into a package, and after integration, they can form a control chip to reduce the system volume.

[0085] According to a third aspect of the present invention, an electromagnetic heating device is provided.

[0086] The electromagnetic heating device includes the IGBT soft start control circuit of the second aspect. The specific structure of the IGBT soft start control circuit refers to the above embodiment. Since the electromagnetic heating device adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, which will not be repeated here.

[0087] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. An IGBT soft start control method, characterized in that: The following steps are involved: Get the collector voltage of the IGBT device; When the collector voltage of the IGBT device is greater than the first voltage threshold, a first driving signal is provided to the IGBT device during the turn-on phase of the IGBT device, and when the collector voltage of the IGBT device is less than the second voltage threshold, a second driving signal is provided to the IGBT device, so that the IGBT device performs soft start and normal turn-on successively; Wherein, the first voltage threshold is greater than or equal to the second voltage threshold, and the soft-start voltage of the IGBT device corresponding to the first drive signal is less than the drive voltage of the IGBT device corresponding to the second drive signal; Wherein, for the feedback circuit, the feedback circuit is driven to monitor the collector voltage of the IGBT device, and the collector voltage generated by the collector of the IGBT device at the moment when the IGBT device is started by the driving circuit; Comparing the sampled collector voltage of the IGBT device with a first voltage threshold and a second voltage threshold through the feedback circuit; When the collector voltage of the IGBT device exceeds a first voltage threshold, controlling the output of the first driving signal for reducing the driving voltage of the IGBT device, thereby reducing the driving voltage and on-current of the IGBT device and causing the IGBT device to soft-start; After the soft start stage, the collector voltage of the IGBT device drops. When the collector voltage of the IGBT device is less than the second voltage threshold, the control output is used to restore the driving voltage of the IGBT device. The driving voltage of the IGBT device is increased to a normal level, so that the IGBT device is normally turned on.

2. An IGBT soft start control circuit, characterized in that: Including control circuit, drive circuit, feedback circuit, IGBT device and resonant circuit; The control circuit, the drive circuit and the base of the IGBT device are connected in sequence, the collector of the IGBT device is connected to the resonant circuit, one end of the feedback circuit is connected to the collector of the IGBT device, and the other end of the feedback circuit is connected to the control circuit or the drive circuit or the base of the IGBT device; The control circuit outputs a driving voltage to the base of the IGBT device through the driving circuit; The feedback circuit is used to obtain the collector voltage of the IGBT device, and when the collector voltage of the IGBT device is greater than a first voltage threshold, provide a first drive signal to the IGBT device during the turn-on phase of the IGBT device, and when the collector voltage of the IGBT device is less than a second voltage threshold, provide a second drive signal to the IGBT device, so that the IGBT device performs soft start and normal turn-on successively; Wherein, the first voltage threshold is greater than or equal to the second voltage threshold, and the soft-start voltage of the IGBT device corresponding to the first drive signal is less than the drive voltage of the IGBT device corresponding to the second drive signal; The feedback circuit includes a sampling subcircuit, an enabling subcircuit and a buck subcircuit; The collector of the IGBT device, the sampling sub-circuit, the enabling sub-circuit and one end of the buck sub-circuit are connected in sequence, and the other end of the buck sub-circuit is connected to the drive circuit or the base of the IGBT device; The driving circuit includes a level conversion subcircuit and a push-pull driving subcircuit. The control circuit, the level conversion subcircuit, the push-pull driving subcircuit and the gate of the IGBT device are connected in sequence.

3. The IGBT soft start control circuit according to claim 2, characterized in that: The sampling subcircuit includes a first sampling resistor and a second sampling resistor; One end of the first sampling resistor is connected to the collector of the IGBT device, the other end of the first sampling resistor and one end of the second sampling resistor are respectively connected to the enabling sub-circuit, and the other end of the second sampling resistor is grounded.

4. The IGBT soft start control circuit according to claim 2, characterized in that: The enabling subcircuit includes a first switch tube and a first resistor, wherein a first end of the first switch tube is connected to the step-down subcircuit, a second end of the first switch tube is grounded, a trigger end of the first switch tube is connected to one end of the first resistor, and the other end of the first resistor is connected to the sampling subcircuit; or The enabling subcircuit includes a first switching tube, a first resistor and an operational amplifier, the positive input terminal of the operational amplifier is connected to the sampling subcircuit, the negative input terminal of the operational amplifier is connected to the reference voltage or the output terminal of the operational amplifier, the output terminal of the operational amplifier is connected to one end of the first resistor, the other end of the first resistor is connected to the trigger terminal of the first switching tube, the first end of the first switching tube is connected to the step-down subcircuit, and the second end of the first switching tube is grounded.

5. The IGBT soft start control circuit according to claim 4, characterized in that: The first switching tube is a triode or a MOS tube.

6. The IGBT soft start control circuit according to claim 2, characterized in that: The step-down subcircuit includes a second resistor, one end of the second resistor is connected to the enabling subcircuit, and the other end of the second resistor is connected to the driving circuit or the base of the GIBT device; or The step-down subcircuit includes a voltage-stabilizing diode, an anode of the voltage-stabilizing diode is connected to the enabling subcircuit, and a cathode of the voltage-stabilizing diode is connected to the base of the driving circuit or the GIBT device.

7. The IGBT soft start control circuit according to claim 2, characterized in that: The feedback circuit includes a sampling subcircuit, an enabling subcircuit and a buck subcircuit; The collector of the IGBT device, the sampling subcircuit, the control circuit, the enabling subcircuit and one end of the buck subcircuit are connected in sequence, and the other end of the buck subcircuit is connected to the driving circuit or the base of the IGBT device.

8. The IGBT soft start control circuit according to any one of claims 2 or 7, characterized in that: The control circuit, drive circuit, enabling sub-circuit and buck sub-circuit are integrated and packaged in one piece.

9. The IGBT soft start control circuit according to claim 2, characterized in that: The level conversion sub-circuit includes a second triode, a third resistor, a fourth resistor and a fifth resistor; One end of the third resistor and one end of the fifth resistor are connected to a DC voltage, the other end of the third resistor and one end of the fourth resistor are connected to a control circuit, the other end of the fourth resistor is connected to the base of the second transistor, the other end of the fifth resistor and the input end of the push-pull drive sub-circuit are connected to the collector of the second transistor, and the emitter of the second transistor is grounded.

10. The IGBT soft start control circuit according to claim 2, characterized in that: The push-pull driving sub-circuit includes a third transistor, a fourth transistor, a sixth resistor and a seventh resistor; The bases of the third and fourth transistors are connected to the output end of the level conversion sub-circuit, the collector of the third transistor is connected to a DC voltage, the emitter of the third transistor is connected to the gate of the IGBT device through a sixth resistor and to the emitter of the fourth transistor through a seventh resistor, the collector of the fourth transistor is grounded, the third transistor is an NPN transistor, and the fourth transistor is a PNP transistor.

11. An electromagnetic heating device, characterized in that: The IGBT soft start control circuit comprises the IGBT soft start control circuit according to any one of claims 2 to 10.

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