Insulated gate bipolar transistor driving circuit based on magnetic field detection

Abstract

The invention discloses an insulated gate bipolar transistor driving circuit based on magnetic field detection, which comprises an input level isolator 1, a gate driver 2, a gate resistor 3 and a magnetic field sensor 4, the magnetic field sensor 4 is used for detecting the magnetic field intensity of a collector or emitter output end line of the insulated gate bipolar transistor and outputting a trigger signal through an output end 41 of the insulated gate bipolar transistor when the magnetic field intensity exceeds a preset threshold value; and the output end of the gate driver 2 generates weak discharge current to carry out soft turn-off on the insulated gate bipolar transistor. The device can further comprise an open magnetic ring (5), and the magnetic field sensor (4) is placed at the notch position of the open magnetic ring (5) to detect the magnetic field intensity. The over-current protection circuit has the advantages of being simple in circuit structure, low in cost and capable of performing over-current protection with a relatively accurate threshold.

Description

Technical Field

[0001] This invention belongs to the field of electronic devices, and more specifically, relates to an insulated gate bipolar transistor driving circuit based on magnetic field detection. Background Technology

[0002] Insulated-gate bipolar transistors (IGBTs) are core semiconductor switching devices in various power electronic converters such as frequency converters, inverters, and uninterruptible power supplies (UPS). They require a drive circuit to control their insulated gate, causing them to turn on or off to achieve the conversion function of these devices. When the drive circuit of an IGBT experiences a power supply abnormality or overcurrent fault, it needs to quickly generate a protection action, performing a soft shutdown within 2-10 µs to prevent the IGBT from burning out due to overcurrent leakage.

[0003] Currently, most drive circuits use desaturation detection to trigger overcurrent protection. The principle is as follows: when the current flowing through the collector-emitter junction of the insulated gate bipolar transistor exceeds the rated value, the insulated gate bipolar transistor is desaturated, and the collector-emitter voltage begins to increase abnormally. When the voltage exceeds the 6-8V threshold, the gate drive circuit is triggered to produce a soft turn-off action, which reduces the gate voltage with a small current, thereby allowing the collector-emitter current to decrease to zero at a safe speed and turn off.

[0004] This type of desaturation protection circuit has significant limitations because the relationship between the collector-emitter saturation voltage and current exhibits considerable dispersion and is temperature-sensitive. At low and normal temperatures, even with an overcurrent of 3-5 times, the collector-emitter saturation voltage rarely exceeds 6V. However, at high temperatures, the collector-emitter saturation voltage, due to its positive temperature coefficient, more easily surpasses the 6-8V threshold. These characteristics make setting the protection threshold difficult; lowering the threshold to generate more sensitive protection often leads to false triggering. Therefore, it is necessary to develop an insulated-gate bipolar transistor (IGBT) driver circuit with more reasonable overcurrent protection action. Summary of the Invention

[0005] In view of the above-mentioned defects or improvement needs of the prior art, the present invention provides an insulated gate bipolar transistor driving circuit based on magnetic field detection to generate overcurrent protection action, which has the advantages of simple circuit structure, low cost and the ability to perform overcurrent protection with a relatively accurate threshold.

[0006] To achieve the above objectives, according to one aspect of the present invention, an insulated gate bipolar transistor (IGBT) driving circuit based on magnetic field detection is provided. The IGBT driving circuit includes an input level isolator (1), a gate driver (2), a gate resistor (3), and a magnetic field sensor (4). The input level isolator (1) converts the input signal at its input terminal (11) into an electrically isolated control signal and outputs it through its control terminal (12) to the input terminal (21) of the gate driver (2). When the input signal at the input terminal (21) of the gate driver (2) is high, a positive level is output through its output terminal (22); when the input signal at the input terminal (21) of the gate driver (2) is low, a negative level is output through its output terminal (22). The output terminal (22) of the gate driver (2) is electrically connected to the gate of the driven insulated gate bipolar transistor through the gate resistor (4). The magnetic field sensor (4) is used to detect the magnetic field strength of the collector or emitter output terminal line of the insulated gate bipolar transistor and output a trigger signal through its output terminal (41) when the magnetic field strength exceeds a preset threshold. The output terminal (41) of the magnetic field sensor (4) is electrically connected to the soft turn-off terminal (23) of the gate driver (2). When the soft turn-off terminal (23) of the gate driver (2) receives the trigger signal, regardless of whether the input terminal (21) of the gate driver (2) is high or low, a weak discharge current will be generated through the output terminal of the gate driver (2) to soft turn off the insulated gate bipolar transistor.

[0007] Furthermore, the insulated gate bipolar transistor driving circuit based on magnetic field detection also includes an open magnetic ring (5), which is sleeved on the collector or emitter output terminal line of the insulated gate bipolar transistor. The magnetic field sensor (4) is placed at the notch of the open magnetic ring (5) to detect the magnetic field strength of the collector or emitter output terminal line of the insulated gate bipolar transistor.

[0008] Furthermore, the insulated gate bipolar transistor driving circuit based on magnetic field detection also includes an isolation power supply (6), which is used to generate a driving voltage with an insulation strength of not less than 1000 volts to power the gate driver (2).

[0009] Furthermore, the level isolator (1) is a high-speed optocoupler, the anode or cathode of the light-emitting diode of the high-speed optocoupler serves as the input terminal (11) of the level isolator (1), the phototube emitter of the high-speed optocoupler serves as the output terminal (12) of the level isolator (1), and the phototube emitter of the high-speed optocoupler is electrically connected to the working resistor (13).

[0010] Furthermore, the gate driver (2) includes an input resistor (24), a positive-level transistor (25), a negative-level transistor (26), a soft-turn-off transistor (271), a soft-turn-off resistor (273), a bypass transistor (272), and a bleed resistor (28). The input terminal (21) of the gate driver (2) is electrically connected to the base of the positive-level transistor (25) and the base of the negative-level transistor (26) through the input resistor (24). The emitters of the positive-level transistor (25) and the negative-level transistor (26) are connected together as the output terminal (22) of the gate driver (2). The collector of the negative-level transistor (26) is connected to the bleed resistor (28). The collector and emitter of the bypass transistor (272) are connected in parallel across the bleed resistor (28). The base of the bypass transistor (272) is connected to the collector of the soft-shutdown transistor (271). The soft-shutdown resistor (273) is connected across the base of the positive level transistor (25) and the base of the bypass transistor (272). The base of the soft-shutdown transistor (271) serves as the soft-shutdown terminal (23) of the gate driver (2). The collector of the positive level transistor (25) is connected to the positive power supply (291). The emitter of the soft-shutdown transistor (271), the emitter of the bypass transistor (272), and the negative terminal of the bleed resistor (28) are all connected to the negative power supply (292).

[0011] Furthermore, the magnetic field sensor (4) includes a Hall element (42), an amplifier (44), and a comparator (43). The output terminal of the Hall element (42) is electrically connected to the amplifier (44), and the output terminal of the amplifier (44) is electrically connected to the comparator (43). The comparator (43) is used to generate a trigger signal according to a threshold set by the comparator, and the output terminal of the comparator serves as the output terminal (41) of the magnetic field sensor (4).

[0012] Furthermore, the open magnetic ring (5) is a high permeability manganese zinc ferrite magnetic ring, the relative permeability of the open magnetic ring (5) is not less than 500, the width of the notch position of the open magnetic ring (5) is not less than 3mm, and the nominal magnetic field direction of the open magnetic ring (5) is parallel to the circumferential direction of the notch position of the open magnetic ring (5).

[0013] Furthermore, the isolation power supply (6) includes a half-bridge converter (61), a high-frequency isolation transformer (62), a rectifier circuit (63), a first DC capacitor (641), and a second DC capacitor (642). The square wave voltage output by the half-bridge converter (61) is electrically connected to the input terminal of the high-frequency isolation transformer (62). After being electrically isolated and converted by the high-frequency isolation transformer (62), the voltage is then converted by the rectifier circuit (63) to form a positive power supply (291) output terminal and a negative power supply (292) output terminal. At the same time, the first DC capacitor (641) and the second DC capacitor (642) provide filtering and support for the positive power supply output (291) and the negative power supply output (292) respectively. The other end of the first DC capacitor (641) and the other end of the second DC capacitor (642) are connected together to form a common terminal (643), which is used as a common reference terminal for the positive power supply (291) output terminal and the negative power supply (292) output terminal.

[0014] Overall, the technical solutions conceived in this invention have beneficial effects compared with the prior art: (1) This invention employs a magnetic field sensor to detect the magnetic field around the collector or emitter line of the driven insulated gate bipolar transistor (IGBT). This magnetic field is proportional to the current flowing through the collector or emitter line. When this current exceeds a certain threshold, the output of the magnetic field sensor causes the comparator inside the magnetic field sensor to flip, thereby generating a trigger signal. This trigger signal is used to generate a soft turn-off action through the combination of a soft turn-off transistor and a bypass transistor in the gate driver, allowing the driven IGBT to turn off under a safe current slope condition, thus ensuring the safety of the device. Compared with the existing technology that uses desaturation detection to generate protection action, since the magnetic field and the line current are linearly related, the uncertainty of the saturation voltage drop of the IGBT is avoided. Although the Hall element itself also has nonlinearity and temperature drift, the overcurrent threshold can still be relatively accurate within an error range of ±20%.

[0015] (2) The present invention uses an open magnetic ring to cover the output cable of the insulated gate bipolar transistor under test, so that the magnetic field at the opening position is only related to the current on the cable. Any interference magnetic field generated by the external cable will cancel each other out in the magnetic circuit, thus having a strong anti-interference capability. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the driving circuit for desaturation detection in the prior art; Figure 2 This is a schematic diagram of an insulated gate bipolar transistor driving circuit according to an embodiment of the present invention; Figure 3 This is a schematic diagram of an embodiment of the input level isolator of the present invention; Figure 4 This is a schematic diagram of an embodiment of the gate driver of the present invention; Figure 5 This is a schematic diagram of an embodiment of the magnetic field sensor of the present invention; Figure 6 This is a schematic diagram of an embodiment of the isolated power supply of the present invention. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0018] In the description of the embodiments of this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. The terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion.

[0019] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0020] Figure 1 This is a schematic diagram of the driving circuit for desaturation detection in the prior art.

[0021] like Figure 2As shown, this embodiment of the invention provides an insulated gate bipolar transistor (IGBT) driving circuit based on magnetic field detection, comprising an input level isolator 1, a gate driver 2, a gate resistor 3, and a magnetic field sensor 4. An isolation power supply 6 generates a driving power supply with an insulation strength of not less than 1000 volts to power the gate driver 2. The input level isolator 1 converts the input signal at its input terminal 11 into an electrically isolated control signal 12, and outputs it to the input terminal 21 of the gate driver 2 through its control terminal 12. When the input terminal 21 of the gate driver 2 is high, a positive level is output through the output terminal 22, which can be set to not less than 15V. When the input terminal 21 of the gate driver 2 is low, a negative level is output through the output terminal 22. The voltage can be set to no higher than -7V. The output terminal 22 of the gate driver 2 is electrically connected to the gate of the driven insulated gate bipolar transistor through the gate resistor 4. The magnetic field sensor 4 is used to detect the magnetic field strength of the collector or emitter output terminal line of the insulated gate bipolar transistor and outputs a trigger signal through its output terminal 41 when the magnetic field strength exceeds a preset threshold. The output terminal 41 of the magnetic field sensor 4 is electrically connected to the soft turn-off terminal 23 of the gate driver 2. When the soft turn-off terminal 23 of the gate driver 2 receives the trigger signal, regardless of whether the input terminal 21 of the gate driver 2 is high or low, a weak discharge current will be generated through the output terminal of the gate driver 2 to softly turn off the driven insulated gate bipolar transistor.

[0022] This invention employs a magnetic field sensor to detect the magnetic field surrounding the collector or emitter circuit of a driven insulated-gate bipolar transistor (IGBT). This magnetic field is proportional to the current flowing through the collector or emitter circuit. When this current exceeds a certain threshold, the magnetic field sensor output causes the comparator inside the sensor to flip, generating a trigger signal. This trigger signal is used to trigger a soft-shutdown action via a combination of a soft-shutdown transistor and a bypass transistor within the gate driver, allowing the driven IGBT to turn off under safe current slope conditions, thus ensuring device safety. Compared to existing technologies that use desaturation detection to generate protection actions, this invention avoids the uncertainty of the saturation voltage drop of the IGBT because the magnetic field and line current have a linear relationship. Although the Hall element itself exhibits nonlinearity and temperature drift, it still ensures relatively accurate overcurrent threshold within an error range of ±20%.

[0023] Furthermore, the insulated gate bipolar transistor (IGBT) driving circuit that generates overcurrent protection based on magnetic field detection also includes an open magnetic ring 5. The open magnetic ring 5 is sleeved on the collector or emitter output terminal line of the IGBT, and the magnetic field sensor 4 is placed at the notch of the open magnetic ring 5 to detect the magnetic field strength of the collector or emitter output terminal line of the IGBT.

[0024] In this embodiment of the invention, an open magnetic ring is used to enclose the output cable of the insulated gate bipolar transistor under test, so that the magnetic field at the opening position is only related to the current on the cable. Any interference magnetic field generated by the external cable will cancel each other out in the magnetic circuit, thus providing a strong anti-interference capability.

[0025] Furthermore, the insulated gate bipolar transistor driving circuit that generates overcurrent protection based on magnetic field detection also includes an isolation power supply 6, which is used to generate a driving voltage with an insulation strength of not less than 1000 volts to power the gate driver 2.

[0026] like Figure 3 The input level isolator 1 shown in this embodiment of the invention is constructed using a high-speed optocoupler. The anode or cathode of the light-emitting diode of the high-speed optocoupler serves as the input terminal 11 of the input level isolator 1, and the emitter of the phototube of the high-speed optocoupler serves as the output terminal 12 of the input level isolator 1, with a matching working resistor 13 at the emitter of the phototube.

[0027] like Figure 4 The diagram shows a gate driver 2 according to an embodiment of the present invention. The gate driver 2 includes an input resistor 24, a positive-level transistor 25, a negative-level transistor 26, a soft-turn-off transistor 271, a soft-turn-off resistor 273, a bypass transistor 272, and a bleeder resistor 28. The gate driver 2's input terminal 21 is connected to the base of the positive-level transistor 25 and the base of the negative-level transistor 26 through the input resistor 24. The emitters of the positive-level transistor 25 and the negative-level transistor 26 are electrically connected together as the output terminal of the gate driver 2. The collector of the negative-level transistor 26 is connected to the bleeder resistor 28. Resistor 28, the collector and emitter of the bypass transistor 272 are connected in parallel to the discharge resistor 28, the base of the bypass transistor 272 is electrically connected to the collector of the soft turn-off transistor 271, the soft turn-off resistor 273 is connected across the base of the positive level transistor 25 and the base of the bypass transistor 272, the base of the soft turn-off transistor 271 serves as the soft turn-off terminal 23 of the gate driver 2, the collector of the positive level transistor 25 is electrically connected to the positive power supply 291, and the emitter of the soft turn-off transistor 271, the emitter of the bypass transistor 272, and the negative terminal of the discharge resistor 28 are all connected to the negative power supply 292.

[0028] In the gate driver 2, the bleed resistor 28, the bypass transistor 272, and the soft-turn-off transistor 271 are used in combination to control the absorption current generated by the negative-level transistor 26. When the bypass transistor 272 is turned on, the bleed resistor 28 is bypassed, allowing the negative-level transistor 26 to generate a large absorption current, enabling the drive circuit to turn off the insulated-gate bipolar transistor (IGBT) at the fastest speed. When the soft-turn-off transistor 271 is turned on, the bypass transistor 272 is turned off, the bleed resistor 28 is not bypassed, and the negative-level transistor 26 can only generate a limited absorption current. The drive circuit can only turn off the IGBT at a limited speed, thereby suppressing the turn-off voltage spike. This design cleverly utilizes the high-speed, high-current driving capability of the negative-level transistor 26, generating the required two turn-off capabilities simply by whether the bleed resistor 28 is bypassed. Compared to a separately designed soft-turn-off circuit, this simplifies the circuit design and logic switching process and reduces the required components.

[0029] like Figure 5 The diagram shows a magnetic field sensor 4 according to an embodiment of the present invention. The magnetic field sensor 4 includes a Hall element 42, an amplifier 44, and a comparator 43. The output terminal of the Hall element 42 is electrically connected to the amplifier 44, and the output terminal of the amplifier 44 is electrically connected to the comparator 43. The amplifier 44 generates a trigger signal according to a threshold set by the comparator, and the output terminal of the comparator serves as the output terminal 41 of the magnetic field sensor 4. The Hall element 42 is mounted on a notch in an open magnetic ring 5. The open magnetic ring 5 is made of a high-permeability manganese-zinc ferrite magnetic ring with a relative permeability of not less than 500. A notch at least 3 mm wide is cut into the magnetic ring to mount the Hall element 42, and its nominal magnetic field direction is parallel to the circumferential direction of the notch in the open magnetic ring 5. The Hall element is used to detect magnetic fields. During installation, one mounting surface must be aligned with the direction of the magnetic field to be measured to accurately detect the strength of the magnetic field. The direction perpendicular to this mounting reference surface is called the nominal magnetic field direction of the Hall element. This reference mounting surface of the Hall element must be aligned with the circumferential direction of the notch.

[0030] like Figure 6The diagram shows the isolated power supply 6 of the present invention. The isolated power supply 6 includes a half-bridge converter 61, a high-frequency isolation transformer 62, a rectifier circuit 63, a DC capacitor 641, and a DC capacitor 642. The square wave voltage output by the half-bridge converter 61 is connected to the input terminal of the high-frequency isolation transformer 62. After being electrically isolated and converted by the high-frequency isolation transformer 62, the voltage is then rectified by the rectifier circuit 63 to form a positive power output 291 and a negative power output 292. At the same time, the DC capacitors 641 and 642 provide filtering and support for the positive power output 291 and the negative power output 292, respectively. The other end of the first DC capacitor 641 and the other end of the second DC capacitor 642 are connected together to form a common terminal 643, which is used as a common reference terminal for the output terminals of the positive power supply 291 and the negative power supply 292.

[0031] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An insulated gate bipolar transistor drive circuit based on magnetic field detection, characterized by, The insulated gate bipolar transistor drive circuit comprises an input level isolator (1), a gate driver (2), a gate resistor (3) and a magnetic field sensor (4), the input level isolator (1) converts the input signal at its input end (11) into an electrically isolated control signal and outputs it to the input end (21) of the gate driver (2) through its control end (12), the gate driver (2) outputs a positive level through its output end (22) when the input signal at its input end (21) is high, and outputs a negative level through its output end (22) when the input signal at its input end (21) is low, the output end (22) of the gate driver (2) is electrically connected to the gate of the driven insulated gate bipolar transistor through the gate resistor (3), and the magnetic field sensor (4) is used to detect the magnetic field strength of the collector or emitter output end circuit of the insulated gate bipolar transistor and outputs a trigger signal through its output end (41) when the magnetic field strength exceeds a preset threshold, and the output end (41) of the magnetic field sensor (4) is electrically connected to the soft shutdown end (23) of the gate driver (2), when the soft shutdown end (23) of the gate driver (2) receives a trigger signal, the gate driver (2) will generate a weak discharge current through its output end to soft shutdown the insulated gate bipolar transistor, regardless of whether the input end (21) of the gate driver (2) is high or low.

2. An insulated gate bipolar transistor drive circuit based on magnetic field detection as claimed in claim 1, characterized in that, It also comprises an open magnetic ring (5) which is sleeved on the collector or emitter output end circuit of the insulated gate bipolar transistor, and the magnetic field sensor (4) is placed at the gap position of the open magnetic ring (5) to detect the magnetic field strength of the collector or emitter output end circuit of the insulated gate bipolar transistor.

3. An insulated gate bipolar transistor drive circuit based on magnetic field detection as defined in claim 1, characterized in that It also comprises an isolation power supply (6) which is used to generate a driving voltage of not less than 1000 volts for the gate driver (2).

4. An insulated gate bipolar transistor drive circuit based on magnetic field detection as defined in claim 1, characterized in that, The level isolator (1) is a high-speed optocoupler, the anode or cathode of the light-emitting tube of the high-speed optocoupler serves as the input end (11) of the level isolator (1), the emitter of the phototube of the high-speed optocoupler serves as the output end (12) of the level isolator (1), and the emitter of the phototube of the high-speed optocoupler is electrically connected to a working resistor (13).

5. An insulated gate bipolar transistor drive circuit based on magnetic field detection as defined in claim 1, characterized in that, The gate driver (2) includes an input resistor (24), a positive level transistor (25), a negative level transistor (26), a soft-off transistor (271), a soft-off resistor (273), a bypass transistor (272) and a bleeder resistor (28), the input end (21) of the gate driver (2) is electrically connected to the base of the positive level transistor (25) and the base of the negative level transistor (26) through the input resistor (24), the emitter of the positive level transistor (25) and the emitter of the negative level transistor (26) are connected together as the output end (22) of the gate driver (2), the collector of the negative level transistor (26) is connected to the bleeder resistor (28), the collector and the emitter of the bypass transistor (272) are connected in parallel across the bleeder resistor (28), the base of the bypass transistor (272) is connected to the collector of the soft-off transistor (271), the soft-off resistor (273) is connected across the base of the positive level transistor (25) and the base of the bypass transistor (272), the base of the soft-off transistor (271) is the soft-off end (23) of the gate driver (2), the collector of the positive level transistor (25) is connected to a positive power supply (291), and the emitter of the soft-off transistor (271), the emitter of the bypass transistor (272) and the negative terminal of the bleeder resistor (28) are commonly connected to a negative power supply (292).

6. An insulated gate bipolar transistor drive circuit based on magnetic field detection as defined in claim 1, characterized in that The magnetic field sensor (4) includes a Hall element (42), an amplifier (44) and a comparator (43), the output of the Hall element (42) is electrically connected to the amplifier (44), the output of the amplifier (44) is electrically connected to the comparator (43), the comparator (43) is used to generate a trigger signal according to a comparator set threshold, and the output of the comparator is the output (41) of the magnetic field sensor (4).

7. An insulated gate bipolar transistor drive circuit based on magnetic field detection as defined in claim 2, characterized in that The open magnetic ring (5) adopts a high permeability manganese-zinc ferrite magnetic ring, the relative permeability of the open magnetic ring (5) is not less than 500, the width of the notch position of the open magnetic ring (5) is not less than 3mm, and the nominal magnetic field direction of the open magnetic ring (5) is parallel to the ring direction of the notch position of the open magnetic ring (5).

8. An insulated gate bipolar transistor drive circuit based on magnetic field detection as defined in claim 3, characterized in that, The isolation power supply (6) includes a half-bridge converter (61), a high-frequency isolation transformer (62) and a rectifier circuit (63), a first DC capacitor (641) and a second DC capacitor (642), the square wave voltage output by the half-bridge converter (61) is electrically connected to the input end of the high-frequency isolation transformer (62), after electrical isolation and voltage conversion through the high-frequency isolation transformer (62), the positive power supply (291) output end and the negative power supply (292) output end are formed through the rectifier circuit (63), at the same time, the first DC capacitor (641) and the second DC capacitor (642) are used to provide filtering and supporting functions for the positive power supply output (291) and the negative power supply output (292) respectively, and the other end of the first DC capacitor (641) and the other end of the second DC capacitor (642) are connected together to form a common end (643) which is used as a common reference end of the positive power supply (291) output end and the negative power supply (292) output end.

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