IGBT state monitoring and protection circuit

Abstract

The utility model discloses a kind of IGBT state monitoring and protection circuit, the current of constant current source output flows through the measured IGBT of conduction, the voltage of first comparator's in-phase input end is the voltage of the collector of measured IGBT, therefore, first comparator when determining the voltage of the collector of measured IGBT is greater than preset saturation voltage threshold, output first level, to make detection control circuit control measured IGBT to be turned off, protect measured IGBT, in addition, high-voltage isolation diode is connected between constant current source and power supply voltage, ensure that the output current of constant current source can flow through measured IGBT, while avoiding power supply voltage to pour into constant current source, to protect constant current source.Based on this, the voltage of the collector of measured IGBT is detected in the present application, to determine whether measured IGBT is in saturation state according to the voltage division of measured IGBT, and then protect measured IGBT.

Description

Technical Field

[0001] This utility model relates to the field of power electronics technology, and in particular to an IGBT condition monitoring and protection circuit. Background Technology

[0002] An IGBT (Insulated Gate Bipolar Transistor) is a semiconductor device widely used in power electronics, primarily in high-frequency switching power supplies, motor drives, and frequency converters. It combines the high input impedance of a MOSFET (Metal-Oxide-Semiconductor Transistor) with the low on-resistance of a bipolar transistor, offering advantages such as fast switching speed, low on-state voltage drop, and high withstand voltage. When the gate voltage is sufficiently high, the IGBT can be fully turned on. When the IGBT operates normally in saturation, the voltage Vce between its collector and emitter is the saturation voltage. The collector current Ic is close to its maximum value. However, when a short circuit occurs in the circuit, such as an abnormal load or a short circuit fault at the IGBT connection point, the IGBT's Vce will rise rapidly and far exceed the normal saturation voltage value, approaching the bus voltage. The collector current Ic will also increase to the short circuit current, causing the IGBT's instantaneous power loss to increase sharply. Not only will the IGBT itself be damaged, but the driver chip in the circuit may also be burned out.

[0003] Therefore, how to accurately measure the saturation voltage drop of IGBTs and protect the gate is a problem that urgently needs to be solved by those skilled in the art. Utility Model Content

[0004] The purpose of this invention is to provide an IGBT state monitoring and protection circuit that detects the collector voltage of the IGBT under test, determines whether the IGBT under test is in a saturated state based on the voltage division of the IGBT under test, and then protects the IGBT under test.

[0005] To solve the above technical problems, this utility model provides an IGBT condition monitoring and protection circuit, wherein the collector of the IGBT under test is connected to a power supply voltage, and the emitter of the IGBT under test is grounded; the IGBT condition monitoring and protection circuit includes:

[0006] A detection control circuit, wherein the first input terminal of the detection control circuit is connected to the output terminal of the first comparator, and the first output terminal of the detection control circuit is connected to the gate of the IGBT under test, for controlling the IGBT under test to turn off when a first level is received;

[0007] The first comparator has a non-inverting input connected to a constant current source and connected to the anode of a high-voltage isolation diode, and an inverting input connected to a preset saturation voltage threshold, for outputting the first level when the voltage at the non-inverting input is greater than the preset saturation voltage threshold.

[0008] The high-voltage isolation diode has its cathode connected to the collector of the IGBT under test.

[0009] Preferably, it further includes a second comparator;

[0010] The non-inverting input of the second comparator is connected to the gate of the IGBT under test, and the inverting input of the second comparator is connected to a preset on-state voltage threshold, which is used to output a second level when the voltage at its non-inverting input is greater than the preset on-state voltage threshold.

[0011] The second input terminal of the detection control circuit is connected to the output terminal of the second comparator, and the second output terminal of the detection control circuit is connected to the control terminal of the first comparator, for controlling the first comparator to start when a second level is received.

[0012] Preferably, it also includes a detection trigger switch transistor;

[0013] The control terminal of the detection trigger switch is connected to the second output terminal of the detection control circuit, the first terminal of the detection trigger switch is connected to the non-inverting input terminal of the first comparator, and the second terminal of the detection trigger switch is grounded.

[0014] The detection control circuit is also used to control the detection trigger switch to turn off when the second level is received.

[0015] Preferably, the detection control circuit includes a controller, a Schmitt trigger, and a push-pull circuit;

[0016] The first input terminal of the controller is connected to the output terminal of the first comparator, the second input terminal of the controller is connected to the output terminal of the second comparator, the first output terminal of the controller is connected to the input terminal of the Schmitt trigger, and the second output terminal of the controller is connected to the control terminal of the first comparator. It is used to output an IGBT turn-off signal when the first level is received, and to control the first comparator to start when the second level is received.

[0017] The output terminal of the Schmitt trigger is connected to the control terminal of the push-pull circuit. The first input terminal of the push-pull circuit is connected to a preset high level, the second input terminal of the push-pull circuit is connected to a preset low level, and the output terminal of the push-pull circuit is connected to the gate of the IGBT under test.

[0018] The Schmitt trigger is used to control the push-pull circuit to output the preset high level or the preset low level based on the IGBT control signal output by the controller, and to output the preset low level based on the IGBT turn-off signal.

[0019] Preferably, the push-pull circuit includes a first driving switch and a second driving switch;

[0020] The first terminal of the first driving switch is connected to the preset high level, the control terminal of the first driving switch is connected to the first output terminal of the Schmitt trigger, and the second terminal of the first driving switch is connected to the gate of the IGBT under test, so as to output the preset high level when the IGBT under test is turned on.

[0021] The first terminal of the second driving switch is connected to the gate of the IGBT under test, the second terminal of the second driving switch is connected to the preset low level, and the control terminal of the second driving switch is connected to the second output terminal of the Schmitt trigger, so as to output the preset low level when the IGBT under test is turned on.

[0022] Preferably, it also includes a pull-up resistor, a pull-down resistor, and a reverse protection diode;

[0023] The first end of the pull-up resistor is connected to the second end of the first driving switch and the non-inverting input of the second comparator, and the second end of the pull-up resistor is connected to the gate of the IGBT under test.

[0024] The first end of the pull-down resistor is connected to the gate of the IGBT under test, and the second end of the pull-down resistor is connected to the anode of the anti-reverse diode.

[0025] The cathode of the anti-reverse diode is connected to the first terminal of the second driving switch.

[0026] Preferably, it further includes a first driving resistor and a second driving resistor;

[0027] The first end of the first driving resistor is connected to the control terminal of the first driving switch, and the second end of the first driving resistor is connected to the first output terminal of the Schmitt trigger.

[0028] The first end of the second driving resistor is connected to the control terminal of the second driving switch, and the second end of the second driving resistor is connected to the second output terminal of the Schmitt trigger.

[0029] Preferably, the anode is connected to the control terminal of the IGBT under test, and the cathode is connected to the clamping diode with a preset high level.

[0030] Preferably, it also includes a filter capacitor and a filter resistor;

[0031] The first terminal of the filter capacitor is connected to the gate of the IGBT under test, and the second terminal of the filter capacitor is grounded.

[0032] The first end of the filter resistor is connected to the gate of the IGBT under test, and the second end of the filter resistor is grounded.

[0033] Preferably, it also includes a blanking capacitor with its first end connected to the anode of the high-voltage isolation diode and its second end grounded.

[0034] In summary, this application provides an IGBT state monitoring and protection circuit. After the current output from the constant current source flows through the conducting IGBT under test, the voltage at the non-inverting input of the first comparator is the collector voltage of the IGBT under test. Therefore, when the first comparator determines that the collector voltage of the IGBT under test is greater than a preset saturation voltage threshold, it outputs a first level to cause the detection control circuit to control the IGBT under test to turn off, thus protecting the IGBT. Furthermore, a high-voltage isolation diode is connected between the constant current source and the power supply voltage to ensure that the output current of the constant current source can flow through the IGBT under test while preventing the power supply voltage from flowing into the constant current source, thereby protecting the constant current source. Based on this, this application detects the collector voltage of the IGBT under test to determine whether the IGBT is in a saturation state based on the voltage division of the IGBT under test, thereby protecting the IGBT under test. Attached Figure Description

[0035] To more clearly illustrate the embodiments of this utility model, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 A schematic diagram of an IGBT condition monitoring and protection circuit provided in this application;

[0037] Figure 2 This application provides a schematic diagram of the specific structure of an IGBT condition monitoring and protection circuit. Detailed Implementation

[0038] The core of this invention is to provide an IGBT state monitoring and protection circuit that detects the collector voltage of the IGBT under test, determines whether the IGBT under test is in a saturated state based on the voltage division of the IGBT under test, and then protects the IGBT under test.

[0039] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0040] Please refer to Figure 1 , Figure 1 This is a schematic diagram of the structure of an IGBT condition monitoring and protection circuit provided in this application. Figure 1 In this circuit, IDesat is a constant current source, the collector of the IGBT under test is connected to the power supply voltage VCC, and the emitter of the IGBT under test is grounded; the IGBT condition monitoring and protection circuit includes:

[0041] The detection control circuit 1 has its first input terminal connected to the output terminal of the first comparator U1, and its first output terminal connected to the gate of the IGBT under test. It is used to control the IGBT under test to turn off when it receives the first level.

[0042] The first comparator U1 has a non-inverting input connected to a constant current source and connected to the anode of a high-voltage isolation diode D1. The inverting input of the first comparator U1 is connected to a preset saturation voltage threshold Vref1, which is used to output a first level when the voltage at the non-inverting input is greater than the preset saturation voltage threshold Vref1.

[0043] High-voltage isolation diode D1, the cathode of which is connected to the collector of the IGBT under test.

[0044] When the IGBT under test is turned on and operating in saturation, its impedance is low. The voltage between the collector and emitter of the IGBT is the preset saturation voltage threshold Vref1, which is typically around 2V to 5V. However, when the load is short-circuited, the voltage Vce between the collector and emitter of the IGBT under test rises sharply until it approaches the power supply voltage VCC. This increased Vce is directly applied across the collector and emitter of the IGBT under test, making it unable to maintain its low-resistance saturation state. This forces the IGBT to exit saturation, and the impedance between the collector and emitter is no longer in the milliohm range, but may be several ohms or even higher. The current on the IGBT under test, i.e., the collector current Ic, is no longer controlled solely by the gate voltage, but is simultaneously controlled by Vce and the voltage Vge between the gate and emitter. At this point, the IGBT under test suffers huge power loss and may be permanently damaged due to overheating in a very short time.

[0045] Based on this, a first comparator U1 is provided in this application. The non-inverting input terminal of the first comparator U1 is connected to the collector of the IGBT under test through a high-voltage isolation diode D1, and the output current of the constant current source also flows to the IGBT under test through the high-voltage isolation diode D1. Therefore, the voltage at the non-inverting input terminal of the first comparator U1 is the voltage of the collector of the IGBT under test, which is also the voltage difference between the collector and emitter of the IGBT under test. The purpose of connecting the constant current source to the IGBT under test via the high-voltage isolation diode D1 is to provide a stable and controllable test condition for the IGBT under test to accurately measure the voltage difference Vce between the collector and emitter of the IGBT under test, i.e., to measure the saturation voltage drop of the IGBT under test. This allows the first comparator U1 to determine whether the IGBT under test is in the desired saturation state. Specifically, when the IGBT under test is conducting at a high current, directly measuring the voltage difference Vce between the collector and emitter of the IGBT under test can lead to a situation where, at the moment of a short circuit fault, the collector current becomes extremely large and difficult to control. Under such extreme current conditions, voltage measurement poses a significant risk to the measurement circuit itself. The measurement result may be unstable due to the large current or it may be difficult to set an accurate preset saturation voltage threshold Vref1. Furthermore, the protection action of the IGBT under test requires time, during which time the IGBT under test is already undergoing devastating losses. The function of the constant current source is to force a known test current to flow through the collector-emitter channel of the IGBT under test at a specific, safe, and low current level, thereby measuring Vce. Under this stable low current injected by the constant current source, the first comparator U1 measures the collector-emitter voltage Vce of the IGBT under test to determine the saturation state. If the IGBT under test is healthy and driving normally, that is, if the IGBT under test is in a saturation state, even if only tens of milliamps of current flow, the Vce of the IGBT under test will be very low, for example, less than 1-2V. The first comparator U1 will compare the measured Vce with the preset saturation voltage threshold Vref1. If Vce < the preset saturation voltage threshold Vref1, the first comparator U1 outputs the second level, and the detection control circuit 1 can determine that the IGBT under test is in a normal state. If the IGBT under test enters a desaturation state, such as due to an internal short circuit, load short circuit, or insufficient drive, the Vce of the IGBT under test will increase significantly at the instant the constant current source injects output current into the IGBT under test. The set value may be close to the power supply voltage VCC. At this time, the measured Vce > the preset saturation voltage threshold Vref1. The first comparator U1 outputs the first level, and the detection control circuit 1 immediately controls the IGBT under test to turn off in order to protect the gate of the IGBT under test.

[0046] It should be noted that when the IGBT under test is in saturation, its internal structure is in a deeply conductive state, forming a low-resistance path (Rce(sat)) between the collector and emitter. This is an inherent physical property of the IGBT as a switching device. The voltage at the non-inverting input of the first comparator U1 is the product of the constant current source output current I_test and Rce(sat), that is, Vce is the voltage drop across Rce generated by I_test. At this time, the power supply voltage VCC is not part of this detection loop. The power supply voltage VCC is usually kept connected during the detection period to prepare for subsequent main power operation. However, during the brief moment (microseconds) of the constant current source IDesat output current, I_test is provided by the constant current source IDesat, not by VCC.

[0047] The functions of the high-voltage isolation diode D1 are as follows: when the IGBT under test is turned off and its collector voltage is the power supply voltage VCC, it prevents the power supply voltage VCC from flowing into the constant current source, thus protecting the constant current source; when the IGBT under test is turned on and its collector voltage is low, i.e., at the preset saturation voltage threshold Vref1, it allows the constant current source to inject its output current into the collector of the IGBT under test through the high-voltage isolation diode D1.

[0048] It should be noted that the detection control circuit 1 can output a corresponding control signal to control the IGBT under test according to the PWM signal used to control the IGBT under test, so that the IGBT under test is turned on or off according to the PWM signal in each cycle.

[0049] It should also be noted that the preset saturation voltage threshold Vref1 is determined based on the characteristics of the IGBT under test. The preset saturation voltage threshold Vref1 can be the same or different for different IGBTs under test. In order to protect the IGBT under test, the preset saturation voltage threshold Vref1 can also be designed with a certain degree of redundancy. For example, the preset saturation voltage threshold Vref1 can be designed to be less than the power supply voltage VCC to reduce the probability of the IGBT under test being burned out.

[0050] The first level can be a high level.

[0051] In summary, this application detects the collector voltage of the IGBT under test to determine whether the IGBT is in a saturated state based on the voltage drop across the IGBT, thereby protecting the IGBT under test.

[0052] Based on the above embodiments:

[0053] Please refer to Figure 2 , Figure 2 This is a schematic diagram illustrating the specific structure of an IGBT condition monitoring and protection circuit provided in this application. Figure 1 and Figure 2 Q in the figure represents the IGBT being tested.

[0054] In a preferred embodiment, a second comparator U2 is also included;

[0055] The non-inverting input of the second comparator U2 is connected to the gate of the IGBT under test, and the inverting input of the second comparator U2 is connected to a preset turn-on voltage threshold Vref2, which is used to output a second level when the voltage at its non-inverting input is greater than the preset turn-on voltage threshold Vref2.

[0056] The second input terminal of the detection control circuit 1 is connected to the output terminal of the second comparator U2, and the second output terminal of the detection control circuit 1 is connected to the control terminal of the first comparator U1, which is used to control the first comparator U1 to start when the second level is received.

[0057] Since the IGBT under test is an N-channel IGBT, it will turn on when the gate voltage is sufficiently large, such as when the voltage difference between the gate and emitter is not less than the preset turn-on voltage threshold Vref2. Based on this, the second comparator U2 can compare the gate voltage of the IGBT under test with the preset turn-on voltage threshold Vref2. When the gate voltage of the IGBT under test is greater than the preset turn-on voltage threshold Vref2, it can be determined that the IGBT under test is turned on, thereby causing the detection control circuit 1 to activate the first comparator U1, thus enabling the detection of the collector voltage of the IGBT under test, that is, the voltage drop Vce between the collector and emitter. Conversely, when the gate voltage of the IGBT under test is not greater than the preset turn-on voltage threshold Vref2, the second comparator U2 can output a third level, causing the detection control circuit 1 to deactivate the first comparator U1 to reduce power consumption.

[0058] The second level can be a high level, and the third level can be a low level.

[0059] Specifically, the detection control circuit 1 can control the power supply terminal or ground terminal of the first comparator U1 to disconnect, so that the first comparator U1 stops working.

[0060] It should be noted that the preset turn-on voltage threshold Vref2 is determined based on the turn-on voltage of the IGBT under test and the preset high-level voltage value. Therefore, the preset turn-on voltage threshold Vref2 is adjustable, and this application does not limit it.

[0061] In a preferred embodiment, a detection trigger switch Q3 is also included;

[0062] The control terminal of the detection trigger switch Q3 is connected to the second output terminal of the detection control circuit 1, the first terminal of the detection trigger switch Q3 is connected to the non-inverting input of the first comparator U1, and the second terminal of the detection trigger switch Q3 is grounded.

[0063] The detection control circuit 1 is also used to control the detection trigger switch Q3 to turn off when the second level is received.

[0064] In this embodiment, a detection trigger switch Q3 is also provided. When the IGBT under test is turned off and no detection is required, the detection trigger switch Q3 can be in the on state, thereby grounding the output current of the constant current source. When the IGBT under test is turned on and detection of the IGBT under test is required, the detection control circuit 1 controls the detection trigger switch Q3 to turn off, so that the output current of the constant current source is transmitted to the IGBT under test.

[0065] Based on this, the detection control circuit 1 can also flexibly control the conduction and cutoff of the detection trigger switch Q3 according to the detection requirements.

[0066] In a preferred embodiment, the detection control circuit 1 includes a controller, a Schmitt trigger U3, and a push-pull circuit;

[0067] The first input terminal of the controller is connected to the output terminal of the first comparator U1, the second input terminal of the controller is connected to the output terminal of the second comparator U2, the first output terminal of the controller is connected to the input terminal of the Schmitt trigger U3, and the second output terminal of the controller is connected to the control terminal of the first comparator U1. It is used to output an IGBT turn-off signal when a first level is received, and to control the first comparator U1 to start when a second level is received.

[0068] The output of Schmitt trigger U3 is connected to the control terminal of the push-pull circuit. The first input terminal of the push-pull circuit is connected to a preset high level, and the output terminal of the push-pull circuit is connected to the gate of the IGBT under test.

[0069] Schmitt trigger U3 is used to control the push-pull circuit to output a preset high level or a preset low level based on the IGBT control signal output by the controller, and to output a preset low level based on the IGBT turn-off signal.

[0070] The detection control circuit 1 in this embodiment includes a controller, a Schmitt trigger U3, and a push-pull circuit. The controller can output an IGBT control signal according to the control requirements of the IGBT under test or the power supply requirements of the load. The IGBT control signal can be a PWM (Pulse Width Modulation) signal. The Schmitt trigger U3 controls the push-pull circuit according to the PWM signal. For example, when the rising edge of the PWM signal is detected, the Schmitt trigger U3 controls the push-pull circuit to output a preset high level, thereby turning on the IGBT under test. When the falling edge of the PWM signal is detected, the Schmitt trigger U3 controls the push-pull circuit to output a preset low level, thereby turning on the IGBT under test. Based on this, the conduction time of the IGBT under test in each control cycle corresponds to the duty cycle of the PWM, thereby realizing the control of the IGBT under test.

[0071] When the controller receives the first level, it determines that the collector voltage of the IGBT under test is abnormal, and then outputs an IGBT turn-off signal. At this time, the controller only outputs the IGBT turn-off signal and does not have an IGBT control signal. Therefore, the Schmitt trigger U3 only controls the push-pull circuit to output a preset low level, thereby turning off the IGBT under test to protect it.

[0072] The preset high level can be, but is not limited to, 14V, and the preset low level can be, but is not limited to, -8V, to ensure the conduction and turn-off of the IGBT under test, while avoiding damage to the gate voltage of the IGBT under test due to excessive voltage.

[0073] It should be noted that the preset turn-on voltage threshold Vref2 is greater than the preset low level, but not greater than the preset high level.

[0074] The Schmitt trigger U3 can also operate by being powered by a preset high level, and this application does not limit this.

[0075] In a preferred embodiment, the push-pull circuit includes a first driving switch Q1 and a second driving switch Q2;

[0076] The first terminal of the first driving switch Q1 is connected to a preset high level. The control terminal of the first driving switch Q1 is connected to the first output terminal of the Schmitt trigger U3. The second terminal of the first driving switch Q1 is connected to the gate of the IGBT under test. It is used to output a preset high level when the IGBT under test is turned on.

[0077] The first terminal of the second driving switch Q2 is connected to the gate of the IGBT under test, the second terminal of the second driving switch Q2 is connected to a preset low level, and the control terminal of the second driving switch Q2 is connected to the second output terminal of the Schmitt trigger U3 to output a preset low level when the IGBT under test is turned on.

[0078] In the push-pull circuit, the on / off state of the first driving switch Q1 controls the conduction and off state of the circuit between the preset high level and the gate of the IGBT under test. The on / off state of the second driving switch Q2 controls the conduction and off state of the circuit between the preset low level and the gate of the IGBT under test. Therefore, at most one of the first driving switch Q1 and the second driving switch Q2 can be turned on at any given time. That is, the gate of the IGBT under test can only be connected to the preset high level or the preset low level, and cannot be connected to both the preset high level and the preset low level at the same time.

[0079] like Figure 2 As shown, the first driving switch Q1 can be a PMOS and the second driving switch Q2 can be an NMOS. When both the first and second outputs of the Schmitt trigger U3 output a low level, the first driving switch Q1 is turned on and the second driving switch Q2 is turned off. The circuit between the preset high level and the gate of the IGBT under test is connected, and the IGBT under test is turned on because its gate is connected to the preset high level. When both the first and second outputs of the Schmitt trigger U3 output a high level, the first driving switch Q1 is turned off and the second driving switch Q2 is turned on. The circuit between the preset low level and the gate of the IGBT under test is connected, and the IGBT under test is turned off because its gate is connected to the preset low level.

[0080] Based on this, Schmitt trigger U3 can convert the PWM signal into a square wave signal for more precise control. For example, when the PWM signal is high, Schmitt trigger U3 outputs a high level, and when the PWM signal is low, Schmitt trigger U3 outputs a low level. Based on this, the push-pull circuit can be controlled more precisely, thereby achieving more precise control of the IGBT under test.

[0081] In a preferred embodiment, it also includes a pull-up resistor R3, a pull-down resistor R4, and a reverse protection diode D3;

[0082] The first end of the pull-up resistor R3 is connected to the second end of the first driving switch Q1 and the non-inverting input of the second comparator U2, and the second end of the pull-up resistor R3 is connected to the gate of the IGBT under test.

[0083] The first end of the pull-down resistor R4 is connected to the gate of the IGBT under test, and the second end of the pull-down resistor R4 is connected to the anode of the reverse protection diode D3.

[0084] The cathode of the anti-reverse diode D3 is connected to the first terminal of the second driving switch Q2.

[0085] Pull-up resistor R3 pulls the gate voltage of the IGBT under test to a preset high level when the first drive switch Q1 is turned on, so that the IGBT under test is turned on. Pull-down resistor R4 pulls the gate voltage of the IGBT under test to a preset low level when the second drive switch Q2 is turned on, so that the IGBT under test is turned off.

[0086] The anti-reverse diode D3 is positioned between the first terminal of the pull-down resistor R4 and the first terminal of the second drive switch Q2, ensuring that the circuit between the gate of the IGBT under test and the preset low level can only conduct in one direction, thus ensuring the accuracy of the control of the IGBT under test.

[0087] In a preferred embodiment, it further includes a first driving resistor R1 and a second driving resistor R2;

[0088] The first end of the first driving resistor R1 is connected to the control terminal of the first driving switch Q1, and the second end of the first driving resistor R1 is connected to the first output terminal of the Schmitt trigger U3.

[0089] The first end of the second driving resistor R2 is connected to the control terminal of the second driving switch Q2, and the second end of the second driving resistor R2 is connected to the second output terminal of the Schmitt trigger U3.

[0090] In this embodiment, by setting a first driving resistor R1 at the control terminal of the first driving switch Q1 and a second driving resistor R2 at the control terminal of the second driving switch Q2, the switching speeds of the first driving switch Q1 and the second driving switch Q2 are balanced, and losses and noise are optimized, while achieving the functions of current limiting and anti-oscillation.

[0091] In a preferred embodiment, the anode is connected to the gate of the IGBT under test, and the cathode is connected to a clamping diode D2 with a preset high level.

[0092] By connecting a clamping diode D2 between the gate of the IGBT under test and a preset high level, the gate voltage of the IGBT under test is clamped and limited to within the preset high level. This prevents the IGBT under test from being falsely turned on due to excessively high gate voltage. Furthermore, it provides a fast discharge channel for gate charge when the IGBT under test is turned off, reducing turn-off losses.

[0093] As a preferred embodiment, it also includes a detection resistor Rref, the first terminal of which is connected to the inverting input terminal of the first comparator U1 and the second terminal of which is grounded.

[0094] A detection resistor Rref is connected to the inverting input of the first comparator U1 to keep the inverting input in a high-impedance floating state when it is not powered on or disconnected, and to couple environmental electromagnetic noise to the floating pin to avoid the comparator from flipping erroneously due to voltage drift exceeding the threshold.

[0095] In a preferred embodiment, a filter capacitor C4 and a filter resistor R6 are also included;

[0096] The first terminal of the filter capacitor C4 is connected to the gate of the IGBT under test, and the second terminal of the filter capacitor C4 is grounded.

[0097] The first terminal of the filter resistor R6 is connected to the gate of the IGBT under test, and the second terminal of the filter resistor R6 is grounded.

[0098] In this embodiment, a filter capacitor C4 and a filter resistor R6 are also provided at the gate of the IGBT under test to make the gate voltage of the IGBT under test smoother and more accurate, so as to avoid the IGBT under test being mistakenly turned on or off due to voltage fluctuations in the circuit, and improve the accuracy of the control of the IGBT under test.

[0099] As a preferred embodiment, it also includes a blanking capacitor C3 with its first terminal connected to the anode of the high-voltage isolation diode D1 and its second terminal grounded.

[0100] When the IGBT under test switches from the off state to the on state, the voltage Vce between its collector and emitter undergoes a complex decline process. Specifically, there is a delay phase: before the gate voltage Vge of the IGBT under test rises to the preset turn-on voltage threshold Vref2, Vce remains basically unchanged and is close to the power supply voltage VCC. The next phase is the Miller plateau phase: when the gate voltage Vge exceeds the preset turn-on voltage threshold Vref2, the IGBT under test starts to conduct, and Vce begins to decline. When Vce declines to near the load voltage (such as the bus voltage), it enters the "Miller plateau" region. At this time, the Miller capacitance between the collector and gate of the IGBT under test is charged, Vge pauses its rise, and Vce declines slowly. Since Vce is still at a relatively high level during this process, if the detection of the IGBT under test is started at this time, it will be mistakenly judged as the IGBT under test not being in a saturated state, that is, an incorrect judgment that the IGBT under test is in a faulty state. Finally, there is the saturation conduction phase: after the Miller plateau ends, Vce rapidly declines to the preset saturation voltage threshold Vref1.

[0101] Based on this, the blanking capacitor C3 set in this embodiment can filter out high-frequency noise, provide a cleaner detection signal for the first comparator U1, improve the stability of the first comparator U1, avoid false triggering of the first comparator U1 due to signal fluctuations, and at the same time generate a real fault for the IGBT under test, that is, maintain a fast response when Vce is continuously high.

[0102] In addition, a first voltage-stabilizing capacitor C1 can be provided between the connection point between the second terminal of the second driving switch Q2 and the preset low level and the ground terminal; a second voltage-stabilizing capacitor C2 can be connected in parallel between the first terminal of the first driving switch Q1 and the second terminal of the first driving switch Q1; a protection capacitor C5 can be connected in parallel between the collector and the emitter of the IGBT under test; and a current-limiting resistor R5 can be provided between the non-inverting input terminal of the first comparator U1 and the anode of the high-voltage isolation diode. This application does not limit this.

[0103] It should also be noted that, in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, article, or apparatus that includes said element.

[0104] The above description of the disclosed embodiments enables those skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An IGBT state monitoring and protection circuit, characterized by, The collector of the IGBT under test is connected to the power supply voltage, and the emitter of the IGBT under test is grounded; the IGBT condition monitoring and protection circuit includes: A detection control circuit, wherein the first input terminal of the detection control circuit is connected to the output terminal of the first comparator, and the first output terminal of the detection control circuit is connected to the gate of the IGBT under test, for controlling the IGBT under test to turn off when a first level is received; The first comparator has a non-inverting input connected to a constant current source and connected to the anode of a high-voltage isolation diode, and an inverting input connected to a preset saturation voltage threshold, for outputting the first level when the voltage at the non-inverting input is greater than the preset saturation voltage threshold. The high-voltage isolation diode has its cathode connected to the collector of the IGBT under test.

2. The IGBT state monitoring and protection circuit of claim 1, wherein, It also includes a second comparator; The non-inverting input of the second comparator is connected to the gate of the IGBT under test, and the inverting input of the second comparator is connected to a preset on-state voltage threshold, which is used to output a second level when the voltage at its non-inverting input is greater than the preset on-state voltage threshold. The second input terminal of the detection control circuit is connected to the output terminal of the second comparator, and the second output terminal of the detection control circuit is connected to the control terminal of the first comparator, for controlling the first comparator to start when a second level is received.

3. The IGBT state monitoring and protection circuit of claim 2, wherein, It also includes detecting the trigger switch transistor; The control terminal of the detection trigger switch is connected to the second output terminal of the detection control circuit, the first terminal of the detection trigger switch is connected to the non-inverting input terminal of the first comparator, and the second terminal of the detection trigger switch is grounded. The detection control circuit is also used to control the detection trigger switch to turn off when the second level is received.

4. The IGBT state monitoring and protection circuit of claim 2, wherein, The detection and control circuit includes a controller, a Schmitt trigger, and a push-pull circuit. The first input terminal of the controller is connected to the output terminal of the first comparator, the second input terminal of the controller is connected to the output terminal of the second comparator, the first output terminal of the controller is connected to the input terminal of the Schmitt trigger, and the second output terminal of the controller is connected to the control terminal of the first comparator. It is used to output an IGBT turn-off signal when the first level is received, and to control the first comparator to start when the second level is received. The output terminal of the Schmitt trigger is connected to the control terminal of the push-pull circuit. The first input terminal of the push-pull circuit is connected to a preset high level, the second input terminal of the push-pull circuit is connected to a preset low level, and the output terminal of the push-pull circuit is connected to the gate of the IGBT under test. The Schmitt trigger is used to control the push-pull circuit to output the preset high level or the preset low level based on the IGBT control signal output by the controller, and to output the preset low level based on the IGBT turn-off signal.

5. The IGBT state monitoring and protection circuit of claim 4, wherein, The push-pull circuit includes a first driving switch and a second driving switch. The first terminal of the first driving switch is connected to the preset high level, the control terminal of the first driving switch is connected to the first output terminal of the Schmitt trigger, and the second terminal of the first driving switch is connected to the gate of the IGBT under test, so as to output the preset high level when the IGBT under test is turned on. The first terminal of the second driving switch is connected to the gate of the IGBT under test, the second terminal of the second driving switch is connected to the preset low level, and the control terminal of the second driving switch is connected to the second output terminal of the Schmitt trigger, so as to output the preset low level when the IGBT under test is turned on.

6. The IGBT state monitoring and protection circuit of claim 5, wherein, It also includes pull-up resistors, pull-down resistors, and reverse protection diodes; The first end of the pull-up resistor is connected to the second end of the first driving switch and the non-inverting input of the second comparator, and the second end of the pull-up resistor is connected to the gate of the IGBT under test. The first end of the pull-down resistor is connected to the gate of the IGBT under test, and the second end of the pull-down resistor is connected to the anode of the anti-reverse diode. The cathode of the anti-reverse diode is connected to the first terminal of the second driving switch.

7. The IGBT state monitoring and protection circuit of claim 5, wherein, It also includes a first driving resistor and a second driving resistor; The first end of the first driving resistor is connected to the control terminal of the first driving switch, and the second end of the first driving resistor is connected to the first output terminal of the Schmitt trigger. The first end of the second driving resistor is connected to the control terminal of the second driving switch, and the second end of the second driving resistor is connected to the second output terminal of the Schmitt trigger.

8. The IGBT state monitoring and protection circuit of claim 4, wherein, It also includes connecting the anode to the control terminal of the IGBT under test, and connecting the cathode to the clamping diode with a preset high level.

9. The IGBT state monitoring and protection circuit according to any one of claims 1 to 8, characterized in that, It also includes filter capacitors and filter resistors; The first terminal of the filter capacitor is connected to the gate of the IGBT under test, and the second terminal of the filter capacitor is grounded. The first end of the filter resistor is connected to the gate of the IGBT under test, and the second end of the filter resistor is grounded.

10. The IGBT state monitoring and protection circuit according to any one of claims 1 to 8, characterized in that, It also includes a blanking capacitor with its first end connected to the anode of the high-voltage isolation diode and its second end grounded.

Images