A system for device turn-off time detection in a power electronic bridge arm assembly

Abstract

This invention discloses a device turn-off time detection system for power electronic bridge arm assemblies, relating to the field of critical timing detection technology for power electronic devices. The system mainly includes: determining the start time of the voltage rise process during the turn-off process of the device under test (DUT) based on the initial characteristics of the voltage rise across the collector-emitter junction during the turn-off process; determining the end time of the voltage rise process during the turn-off process of the DUT based on the zero-crossing reversal characteristics of the voltage drop across the collector-emitter junction during the turn-off process of the complementary device of the DUT; and determining the voltage rise time during the turn-off process of the DUT based on the start time and the initial time of the voltage rise process. This invention can accurately detect the voltage rise time during the turn-off process in power electronic bridge arm assemblies.

Description

Technical Field

[0001] This invention relates to the field of critical timing detection technology for power electronic devices, and in particular to a device turn-off time detection system for power electronic bridge arm assemblies. Background Technology

[0002] Power electronic devices, such as IGBTs, are core components for power conversion. They operate in two states—on and off—and have high switching frequencies. Power electronic devices are manufactured and packaged using microelectronic chip technology. During the switching and conduction processes, they generate losses and heat, bear high voltage and large current, and experience thermal shock during switching, causing thermomechanical effects that lead to fatigue, aging, and eventual failure.

[0003] Because power electronic devices undergo fatigue aging before failure, early warnings of faults can be provided based on the aging process, enabling pre-diagnosis and subsequent management. This improves the reliability of power electronic devices and prevents production accidents. Therefore, it is necessary to monitor the health status of power electronic devices during operation. This involves effectively extracting important information such as whether the device is functioning normally and whether aging has occurred by using parameters such as current, voltage, and temperature.

[0004] The key parameters of a device during the switching process reflect its operating characteristics. The junction temperature during device operation has a significant impact on the switching characteristics. Conversely, changes in the device's switching characteristic parameters also reflect the current junction temperature, which is of great importance to ensuring the safe operation of the device.

[0005] Studies have shown that the health status of power electronic devices is closely related to their switching characteristics. Once a device ages, whether it is the power chip or the package (component), its switching characteristics will change. Therefore, studying the switching characteristics of devices is of great significance for estimating junction temperature and analyzing the health status of power electronic devices.

[0006] Taking the turn-off process of power devices as an example, among the turn-off parameters of power electronic devices, the time period in which the voltage between the collector and emitter of the device rapidly rises from the saturation voltage drop during conduction to the DC bus voltage of the external circuit is an extremely critical time period. This time period can be determined by detecting two key moments: the start moment of the voltage rise between the collector and emitter of the device during the turn-off process and the end moment of the voltage rise process. The end moment of the voltage rise process refers to the moment when the voltage first rises to the DC bus voltage of the external circuit during the turn-off process. After this moment, the current of the corresponding device begins to decrease rapidly, while the voltage continues to rise.

[0007] During the turn-off process of power devices, the collector-emitter (CE) voltage and the current flowing through the device change over a wide range and for a short period of time. During the turn-on period of power devices, the saturation voltage drop is in the mV range, while during the turn-off process, the voltage rises to hundreds or even thousands of volts, and the current drops from the operating current to near zero instantaneously, with a current drop time of tens to hundreds of ns. Therefore, accurate detection of critical times during the device turn-off process has significant theoretical and engineering value for estimating the junction temperature of the device and analyzing its health status.

[0008] From an engineering application perspective, on the one hand, complex detection circuits can lead to significant errors. On the other hand, the voltage on a power device rises suddenly from near-zero turn-on voltage to the bus voltage, a difference of orders of magnitude (hundreds to thousands of times). Determining the voltage rise time by detecting the voltage over the entire operating cycle of the device results in substantial errors. Therefore, it is necessary to investigate methods for accurately detecting the voltage rise time of power devices during the turn-off process. Summary of the Invention

[0009] In view of this, the present invention provides a device turn-off time detection system for power electronic bridge arm assemblies.

[0010] To achieve the above objectives, the present invention provides the following solution: A device turn-off time detection system for a power electronic bridge arm assembly includes: a module for detecting the start time of the voltage rise process of the device under test during the turn-off process in the power electronic bridge arm assembly, a module for detecting the end time of the voltage rise process of the device under test during the turn-off process in the power electronic bridge arm assembly, and a module for detecting the voltage rise time of the device under test during the turn-off process in the power electronic bridge arm assembly. The power electronic bridge arm assembly's voltage rise detection module during the turn-off process of the device under test (DUT) is used to determine the start time of the voltage rise during the turn-off process of the DUT based on the characteristics of the voltage rise at the collector-emitter terminals during the turn-off process of the DUT. The power electronic bridge arm assembly's voltage rise detection module during the turn-off process of the device under test (DUT) is used to determine the end time of the voltage rise during the turn-off process of the DUT based on the zero-crossing reverse characteristic of the collector-emitter voltage drop during the turn-off process of the complementary device of the DUT. The voltage rise time detection module of the device under test in the power electronic bridge arm assembly is used to determine the voltage rise time of the device under test during the turn-off process based on the start time and end time of the voltage rise process of the device under test during the turn-off process.

[0011] A device turn-off time detection system for a power electronic bridge arm assembly, the power electronic bridge arm assembly including an upper bridge arm device and a lower bridge arm device, wherein the upper bridge arm device and the lower bridge arm device are referred to as complementary devices, the device turn-off time detection system includes: an upper bridge arm device voltage change characteristic detection module connected in parallel across the collector-emitter terminals of the upper bridge arm device, a lower bridge arm device voltage change characteristic detection module connected in parallel across the collector-emitter terminals of the lower bridge arm device, and a time reading module connected to both the upper bridge arm device voltage change characteristic detection module and the lower bridge arm device voltage change characteristic detection module; The upper arm device voltage change characteristic detection module is used to output a level signal indicating the start of the voltage rise across the collector-emitter terminals of the upper arm device and a level signal indicating the end of the voltage rise across the collector-emitter terminals of the upper arm device. The voltage change characteristic detection module of the lower bridge arm device is used to output a level signal indicating the start of the voltage rise across the collector-emitter terminals of the lower bridge arm device and a level signal indicating the end of the voltage rise across the collector-emitter terminals of the lower bridge arm device. The time reading module is used for: When the operating state is that the output current of one bridge arm is greater than zero, the voltage rise time of the upper bridge arm device during the turn-off process is determined according to the level signal that marks the start of the voltage rise across the collector-emitter terminals of the upper bridge arm device and the level signal that marks the end of the voltage rise across the collector-emitter terminals of the lower bridge arm device. When the operating state is that the output current of one bridge arm is less than or equal to zero, the voltage rise time of the lower bridge arm device during the turn-off process is determined based on the level signal indicating the start of the voltage rise across the collector-emitter terminals of the lower bridge arm device and the level signal indicating the end of the voltage rise across the collector-emitter terminals of the upper bridge arm device.

[0012] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects: This invention fully utilizes the characteristic that power electronic devices (converters) are generally constructed using bridge arm circuits, and proposes a device turn-off time detection system for power electronic bridge arm assemblies. This system solves the problem of measuring the end of the voltage rise time of a device by utilizing the zero-crossing characteristic of a complementary anti-parallel diode connected in series with the device under test. This system is applicable to both inverters composed of symmetrical upper and lower bridge arms and DC / DC converters composed of asymmetrical bridge arm circuit modules, and has advantages such as simple method, high time detection accuracy, and simple and low-cost detection circuit. The power electronic bridge arm assembly is either a power electronic bridge arm circuit or a power electronic bridge arm module. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 This is a structural diagram of the power electronic bridge arm assembly provided in an embodiment of the present invention; Figure 2 This is a graph showing the relationship between voltage rise time and junction temperature provided in an embodiment of the present invention. Figure 3 This is a graph showing the relationship between voltage rise time and aging, provided in an embodiment of the present invention. Figure 4 Voltage and current waveforms of the power electronic bridge arm assembly provided in this embodiment of the invention; Figure 5 Voltage and current waveform diagrams of the bridge arm assembly applied in an inverter according to embodiments of the present invention; Figure 6 This is a schematic diagram of the structure of a device turn-off time detection system in a power electronic bridge arm assembly provided in an embodiment of the present invention; Figure 7 This is a structural diagram of the upper bridge arm device voltage change characteristic detection module provided in an embodiment of the present invention; Figure 8 A schematic diagram of a sampling circuit unit for voltage variation characteristics across the collector and emitter terminals of an upper bridge arm device provided in an embodiment of the present invention; Figure 9 The schematic diagram of the sampling circuit unit for the voltage change characteristics between the collector and emitter terminals of the lower bridge arm device and the detection unit for the voltage change characteristics between the collector and emitter terminals of the lower bridge arm device provided in the embodiments of the present invention; Figure 10 A schematic diagram of an isolated output unit provided in an embodiment of the present invention; Figure 11 A schematic diagram of a time reading module provided in an embodiment of the present invention; Figure 12 This is a structural block diagram of a device turn-off time detection system for power electronic bridge arm assemblies provided in an embodiment of the present invention. Detailed Implementation

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0017] Figure 1 This is a structural diagram of a typical power electronic bridge arm assembly containing two IGBT devices. Figure 1 In the middle, L c1(int) L e1(int) and L g1(int) These represent the parasitic inductances of the power collector C1, power emitter E1, and power gate G1 of the upper bridge arm device, respectively; L c2(int) L e2(int) and L g2(int) These represent the parasitic inductances of the power collector C2, power emitter E2, and power gate G2 of the lower bridge arm device, respectively; R g1(int) L is the drive resistor built into the upper bridge arm device. ge1(int) The parasitic inductance of the auxiliary emitter e1 of the upper bridge arm device; R g2(int) L is the drive resistor built into the lower bridge arm device. ge2(int) The parasitic inductance of the auxiliary emitter e1 of the lower bridge arm device; L E1 L is the parasitic inductance between the chip emitter e1(int) and the power emitter E1 of the upper bridge arm device. E2 L is the parasitic inductance between the chip emitter e2(int) and the power emitter E2 of the lower bridge arm device. C1 L is the parasitic inductance between the chip collector C1(int) and the power collector C1 of the upper bridge arm device. C2 This is the parasitic inductance between the chip collector C2(int) and the power collector C2 of the lower bridge arm device.

[0018] In power converters (such as inverters), a bridge arm assembly consisting of two power electronic devices connected in series can be further extended to a three-phase inverter circuit. In each bridge arm assembly, the collector C1 of the upper bridge arm device (upper tube) is connected to the positive bus of the converter, and the emitter E2 of the lower bridge arm device (lower tube) is connected to the negative bus of the converter. The emitter E1 of the upper bridge arm is connected together with the collector C2 of the lower bridge arm, and then connected to the load or external circuit.

[0019] By detecting the collector current I before the device under test is turned off cDuring device turn-off, the voltage V across the collector-emitter junction (such as the upper transistor C1E1) is... CE voltage rise time t rv The dynamic operating point (I) of the device turn-off characteristics c t rv The above operating characteristics (operating point) reflect the typical performance of the device during turn-off at the current junction temperature and can be used to characterize the current junction temperature and health status of the device, such as... Figure 2 As shown, t rv - I c The relationship between characteristics and device junction temperature Figure 3 For t rv - I c The relationship between characteristics and device aging.

[0020] The operation of a bridge arm includes two typical operating states. First, when the bridge arm output current is greater than zero and the upper bridge arm device is turned on, the current flows from E1C2 (the midpoint of the bridge arm) to the load or external circuit. When the bridge arm output current is greater than zero and the upper bridge arm device is turned off, the anti-parallel diode of the lower bridge arm device is turned on, and the freewheeling current flows from E1C2 to the load or external circuit. Second, when the bridge arm output current is less than zero and the lower bridge arm device is turned on, the current flows from the load or external circuit to E1C2. When the bridge arm output current is less than zero and the lower bridge arm device is turned off, the anti-parallel diode of the upper bridge arm device is turned on, and the freewheeling current flows from the load or external circuit to E1C2.

[0021] When the output current of one bridge arm is greater than zero (current flows from the upper bridge arm device -E1C2 to the load or external circuit), the upper bridge arm device is controlled to change from the on (current flowing) state to the off state. During this process, the voltage and current waveforms of the upper and lower bridge arm devices are as follows: Figure 4 As shown in (a), (b), (c), and (d) in the diagram. For the operating state where the bridge arm output current is less than zero, the lower bridge arm device is controlled to change from the on state to the off state, and the principle is the same.

[0022] The upper bridge arm device consists of IGBT device VT1 and anti-parallel diode VD1, and the lower bridge arm device consists of IGBT device VT2 and anti-parallel diode VD2. Figure 4 The voltage V across the upper arm device CE is given for four typical common-mode operations: on-state, off-state, off-state, and on-state. CE1 Current I on the device VT1 and I VD1 The voltage V across the CE terminals of the lower bridge arm device CE2 Current I on the device VT2 and I VD2 .

[0023] The upper and lower bridge arm devices of a bridge arm assembly are defined as complementary devices. The voltage across the capacitor (CE) during the off-state of the device under test (upper bridge arm device) is (V...). CE1 The voltage rises suddenly from near zero during turn-on to the bus voltage (and continues to rise, then drops back to the bus voltage after a voltage overshoot). Therefore, at the start of the voltage rise across the CE terminals during the turn-off process of the upper arm device, the voltage V... CE There is a significant increase (abrupt change), which can be obtained by sampling and detecting the CE voltage of this device.

[0024] In an operating state where the output current (flowing from E1C2 to the load or external circuit) of one bridge arm is greater than zero, the upper bridge arm device is the device under test (DUT), and the voltage across the CE terminal (V) is [value missing] during the off-state of the DUT (upper bridge arm device). CE1 During the voltage rise process, when the voltage rises to the bus voltage (and continues to rise, then drops back to the bus voltage after a voltage overshoot), this is defined as the end of the rise of the upper bridge arm device. At this time, the complementary device (lower bridge arm device) connected in series with this device (upper bridge arm device) is connected together with this device as a bridge arm between the positive and negative buses. Therefore, during the voltage rise of this device, the voltage of the complementary device decreases. When the voltage across the CE terminal of this device reaches the DC bus voltage (i.e., the end of the voltage rise during the turn-off process), the voltage of the complementary device reaches zero and continues to decrease to negative. At this time, the anti-parallel diode on the complementary device conducts. Therefore, during the turn-off process of this device, the voltage across the CE terminal (V...) CE1 At the end of the rise, the CE voltage (V) of the complementary device (lower arm device) can be measured. CE2 Obtained through sampling and detection.

[0025] The following describes the operating state where the output current of one bridge arm (flowing from the load or external circuit to the E1C2 terminal of the bridge arm) is less than zero. In this state, the lower bridge arm device is the device under test (DUT), and the voltage across the CE terminals (V) is [value missing] during the DUT's (lower bridge arm device's) off-state period. CE2 During the voltage rise process, when the voltage rises to the bus voltage (and continues to rise, then drops back to the bus voltage after a voltage overshoot), this is also defined as the end of the rise of the lower bridge arm device. At this time, the complementary device (upper bridge arm device) connected in series with this device (lower bridge arm device) is connected together with this device as a bridge arm between the positive and negative buses. Therefore, during the voltage rise of this device, the voltage of the complementary device decreases. When the voltage across the CE terminal of this device reaches the DC bus voltage (i.e., the end of the voltage rise during the turn-off process), the voltage of the complementary device reaches zero and continues to decrease to negative. At this time, the anti-parallel diode on the complementary device conducts. Therefore, during the turn-off process of this device, the voltage across the CE terminal (V...) CE2 At the end of the rise, the CE voltage (V) of the complementary device (upper arm device) can be measured. CE1Obtained through sampling and detection.

[0026] Therefore, when one bridge arm's output current (flowing from E1C2 to the load or external circuit) is greater than zero, the voltage rise time during the turn-off process of the upper bridge arm device can be detected; when one bridge arm's output current (flowing from the load or external circuit to the E1C2 terminal of the bridge arm) is less than zero, the voltage rise time during the turn-off process of the lower bridge arm device can be detected. Regardless of whether the bridge arm output current is positive or negative, it is necessary to detect the voltage change characteristics of the upper and lower bridge arm devices.

[0027] Figure 5 The waveforms of the collector-emitter voltage and the current on the upper and lower bridge arm devices are simulated.

[0028] This invention provides a device turn-off time detection system for power electronic bridge arm assemblies. The critical turn-off time of the power electronic device refers to the time period during the turn-off process where the voltage between the collector and emitter of the device rapidly rises from the saturation voltage drop during conduction to the DC bus voltage of the external circuit. This time period can be determined by detecting two critical moments: the start time of the voltage rise between the collector and emitter during the turn-off process and the end time of the voltage rise process. The end time of the voltage rise process refers to the moment when the voltage first rises to the DC bus voltage of the external circuit during the turn-off process. At this time, the current of the corresponding device begins to decrease rapidly, while the voltage continues to rise.

[0029] Many power electronic converters use two devices connected together as their basic circuit unit (such as the inverter bridge of an inverter). These two devices can be independent of each other and form a bridge arm circuit through external connections, or they can be packaged together as a module. For ease of explanation, the upper bridge arm device and the lower bridge arm device in this power electronic bridge arm assembly are referred to as complementary devices.

[0030] For a power electronic converter, such as an IGBT inverter, which consists of an upper bridge arm device and a lower bridge arm device, the upper and lower bridge arms are two power electronic devices connected in series to form a bridge arm assembly. The collector C1 of the upper bridge arm is connected to the DC positive bus, and the emitter E2 of the lower bridge arm is connected to the DC negative bus. After the emitter E1 of the upper bridge arm device is connected to the collector C2 of the lower bridge arm device, E1C2 is connected to the load or other components of the application circuit.

[0031] like Figure 6As shown, the device turn-off critical time detection system in the power electronic bridge arm assembly provided in this embodiment of the invention includes: an upper bridge arm device voltage change characteristic detection module 1 connected in parallel across the collector-emitter (C1-E1) terminals of the upper bridge arm device; a lower bridge arm device voltage change characteristic detection module 2 connected in parallel across the collector-emitter (C2-E2) terminals of the lower bridge arm device; and a time reading module 3 connected to both the upper bridge arm device voltage change characteristic detection module 1 and the lower bridge arm device voltage change characteristic detection module 2.

[0032] The upper bridge arm device voltage change characteristic detection module 1 is used to output a level signal indicating the start of the voltage rise across the collector-emitter terminals of the upper bridge arm device and a level signal indicating the end of the voltage rise across the collector-emitter terminals of the upper bridge arm device.

[0033] The lower bridge arm device voltage change characteristic detection module 2 is used to output a level signal indicating the start of the voltage rise across the collector-emitter terminals of the lower bridge arm device and a level signal indicating the end of the voltage rise across the collector-emitter terminals of the lower bridge arm device.

[0034] The time reading module 3 is used for: When the operating state is that the output current of one bridge arm is greater than zero, the voltage rise time of the upper bridge arm device during the turn-off process is determined according to the level signal that marks the start of the voltage rise across the collector-emitter terminals of the upper bridge arm device and the level signal that marks the end of the voltage rise across the collector-emitter terminals of the lower bridge arm device. When the operating state is that the output current of one bridge arm is less than or equal to zero, the voltage rise time of the lower bridge arm device during the turn-off process is determined based on the level signal indicating the start of the voltage rise across the collector-emitter terminals of the lower bridge arm device and the level signal indicating the end of the voltage rise across the collector-emitter terminals of the upper bridge arm device.

[0035] Figure 7 The diagram shows the structure of the upper bridge arm device voltage change feature detection module 1. The upper bridge arm device voltage change feature detection module 1 includes: a sampling circuit unit 11 for voltage change features across the collector-emitter terminals of the upper bridge arm device, a voltage change feature detection unit 12 for voltage change across the collector-emitter terminals of the upper bridge arm device, and a first isolation output unit 13. The upper bridge arm device collector-emitter voltage change characteristic sampling circuit unit 11 is used to sample the voltage change characteristics of the upper bridge arm device collector-emitter in real time during the process of the upper bridge arm device from the on state to the off state, and obtain the sampling result; the upper bridge arm device collector-emitter voltage change characteristic sampling circuit unit 11 includes: (1) sampling the characteristic information of the voltage rise at the upper bridge arm device collector-emitter, which occurs during the process of the device from the on state to the device off state; (2) sampling the characteristic information of the voltage decrease to zero and become negative during the process of the device from the off state to the anti-parallel diode conduction (freewheeling).

[0036] The collector-emitter voltage change characteristic detection unit 12 of the upper bridge arm device is used to process the sampling results output by the collector-emitter voltage change characteristic sampling circuit unit 11 of the upper bridge arm device to obtain the voltage rise start characteristic of the upper bridge arm device during the turn-off process, and the characteristic of the voltage crossing zero (from positive zero crossing to negative voltage) of the collector-emitter of the upper bridge arm device during the change from the turn-off state to the conduction state of the anti-parallel diode.

[0037] The upper bridge arm device collector-emitter voltage change characteristic detection unit 12 includes an upper bridge arm device collector-emitter voltage rise change characteristic detection unit 121 and an upper bridge arm device collector-emitter voltage reverse zero crossing characteristic detection unit 122.

[0038] The collector-emitter voltage rise change feature detection unit 121 of the upper bridge arm device is used to detect the feature of a sudden rise in the collector-emitter voltage of the upper bridge arm device. During the process of the upper bridge arm device changing from the on state (current flowing through the upper bridge arm device, outputting current to the external circuit or load through the bridge arm midpoint C2E1) to the off state, the output signal of the upper bridge arm device collector-emitter voltage change feature sampling circuit unit 11 is processed to determine the start time of the rise in the collector-emitter voltage, and a level flip signal marking the start of the rise in the collector-emitter voltage of the upper bridge arm device is output.

[0039] The reverse zero-crossing characteristic detection unit 122 of the collector-emitter voltage of the upper bridge arm device is used to detect the characteristic of the voltage turning negative after crossing zero. It processes the output signal of the sampling circuit unit 11 of the collector-emitter voltage change characteristic of the upper bridge arm device to determine the moment when the voltage across the collector-emitter decreases to zero and turns negative, and outputs a level flip signal that marks the end of the rise of the voltage across the collector-emitter of the upper bridge arm device.

[0040] The first isolation output unit 13 is used to electrically isolate the output result of the voltage change characteristic detection unit 12 at the collector-emitter terminals of the upper bridge arm device, and output a level signal indicating the start of the voltage rise at the collector-emitter terminals of the upper bridge arm device and a level signal indicating the end of the voltage rise at the collector-emitter terminals of the upper bridge arm device.

[0041] Figure 8 This is an example of an implementation scheme for a voltage change characteristic sampling circuit unit across the collector-emitter terminals of an upper bridge arm device. The voltage change characteristic sampling circuit unit 11 across the collector-emitter terminals of the upper bridge arm device can be a voltage change characteristic sampling circuit composed of multiple resistors connected in series, or a voltage change characteristic sampling circuit composed of multiple resistors and capacitors connected in series, or other sampling circuits having the two functions described above.

[0042] Figure 8 (a) is a typical sampling circuit scheme, where D1 and D2 are two diodes with the same conduction characteristics. When the IGBT is turned on, current flows from the current source I... a Starting from D1, D2, and IGBT to form a loop. Assuming the current flowing through D1 and D2 is equal, and that D1 and D2 have the same conduction characteristics, external environment, and junction temperature, then we have... VD1=VD2; Vout=Vb-VD2=Vb-(Va-Vb)=2Vb-Va; Where (Va-Vb) is the voltage VD1 of diode D1.

[0043] If R1=R2, then the output voltage of the operational amplifier is equal to the voltage drop across the CE terminals of the IGBT under test.

[0044] When the IGBT is in the turn-off process, the current source Ia flows through D1, D3, and D4 to form a circuit, with Zener diode D3 performing the voltage clamping function. D3 and D4 clamp the voltage Vb at the non-inverting input of the operational amplifier to a stable value, ensuring that it is not affected by the turn-off voltage within the diode's tolerance range.

[0045] Va = VD1 + Vb Vb = VD3 + VD4 During the IGBT turn-off process, the voltage output of the op-amp is Vout = VD3 + VD4 - VD1.

[0046] Figure 8 (b) shows the voltage Vce waveform across CE during the controlled transition of the upper bridge arm IGBT from the on state to the off state in the operating mode where the current flowing to the load or external circuit is positive in the bridge arm circuit. Figure 8 The sampling circuit output signal Vout corresponds to (a).

[0047] Figure 8 (c) is the voltage waveform across CE of the lower bridge arm IGBT from the off state to the conduction of the anti-parallel diode in the working mode where the current flows to the load or the external circuit is positive (voltage decreases and crosses zero to become negative).

[0048] This scheme can obtain information about the on-state voltage drop of the device and the change in voltage across the CE terminals after the device turns off, based on the output signal of the operational amplifier. It can also obtain information about the characteristic information of the voltage across the CE terminals decreasing to zero and turning negative during the process of the device transitioning from the off state to the on state of the anti-parallel diode.

[0049] The lower bridge arm device voltage change feature detection module 2 includes: a sampling circuit unit 21 for voltage change features at the collector-emitter terminals of the lower bridge arm device, a voltage change feature detection unit 22 for voltage change at the collector-emitter terminals of the lower bridge arm device, and a second isolation output unit 23.

[0050] The sampling circuit unit 21 for the voltage change characteristics of the collector-emitter terminals of the lower bridge arm device is used to sample the voltage change characteristics of the collector-emitter terminals of the lower bridge arm device in real time during the process of the lower bridge arm device changing from the on state to the off state, and obtain the sampling results. The sampling circuit unit 21 for the voltage change characteristics of the collector-emitter terminals of the lower bridge arm device includes: (1) sampling the voltage rise start characteristic information of the lower bridge arm device, which occurs during the process of the device changing from the on state to the off state; (2) sampling the voltage decrease to zero and become negative of the lower bridge arm device, which occurs during the process of the device changing from the off state to the anti-parallel diode conduction (freewheeling).

[0051] The voltage change characteristic detection unit 22 at the collector-emitter terminals of the lower bridge arm device includes a voltage rise change characteristic detection unit 221 at the collector-emitter terminals of the lower bridge arm device and a voltage reverse zero crossing characteristic detection unit 222 at the collector-emitter terminals of the lower bridge arm device.

[0052] The collector-emitter voltage rise change characteristic detection unit 221 of the lower bridge arm device is used to detect the sudden rise characteristic of the collector-emitter voltage of the lower bridge arm device. During the process of the lower bridge arm device changing from the on state (current flowing through the lower bridge arm device, current input from the external circuit or load to the midpoint E1C2 of the bridge arm) to the off state, the output signal of the collector-emitter voltage change characteristic sampling circuit unit 21 of the lower bridge arm device is processed to determine the starting time of the collector-emitter voltage rise, and a level flip signal marking the start of the collector-emitter voltage rise of the lower bridge arm device is output.

[0053] The reverse zero-crossing characteristic detection unit 222 of the collector-emitter voltage of the lower bridge arm device is used to detect the characteristic of the voltage turning negative after crossing zero. It processes the output signal of the sampling circuit unit 11 of the collector-emitter voltage change characteristic of the lower bridge arm device to determine the moment when the voltage across the collector-emitter decreases to zero and turns negative, and outputs a level flip signal that marks the end of the rise of the voltage across the collector-emitter of the lower bridge arm device.

[0054] The second isolation output unit 23 is used to electrically isolate the output result of the voltage change characteristic detection unit 12 at the collector-emitter terminals of the lower bridge arm device, and output a level signal indicating the start of the voltage rise at the collector-emitter terminals of the lower bridge arm device and a level signal indicating the end of the voltage rise at the collector-emitter terminals of the lower bridge arm device.

[0055] The voltage change characteristic sampling circuit unit 21 at the collector-emitter terminals of the lower bridge arm device can be a voltage change characteristic sampling circuit composed of multiple resistors connected in series, or a voltage change characteristic sampling circuit composed of multiple resistors and capacitors connected in series, or other sampling circuits having the two functions mentioned above.

[0056] Figure 9 This is a schematic diagram of the detection principle of either the sampling circuit unit 21 for the voltage change characteristics across the collector-emitter junction of the lower bridge arm device or the detection unit 22 for the sudden voltage change characteristics across the collector-emitter junction of the lower bridge arm device. Figure 8 Taking the sampling circuit corresponding to (a) as an example, Figure 9 (a) and (b) illustrate the detection principle of the collector-emitter voltage change characteristic sampling circuit unit 21 of the lower bridge arm device, which compares the output Vout of the collector-emitter voltage through the voltage change characteristic sampling circuit with the voltage rise characteristic reference value Vcex (see...). Figure 9 (b) yields the characteristic signal Vout' of the voltage abrupt change across the collector-emitter junction (see [reference]). Figure 9 (a) where ε is a very small value, and twice ε is usually called the hysteresis width of the comparator.

[0057] Figure 9 (c) and (d) illustrate the detection principle of the collector-emitter voltage change characteristic detection unit 22 of the lower bridge arm device, which compares the output Vout of the voltage change characteristic sampling circuit across the collector-emitter terminals with the zero-crossing voltage characteristic reference value Vcex (see...). Figure 9 (d)), the characteristic signal Vout' of the voltage jump across the collector-emitter terminals is obtained (see (d)). Figure 9 (c)).

[0058] like Figure 10The diagram shows a typical implementation principle of the first isolation output unit 13 or the second isolation output unit 23. This isolation output unit employs an optocoupler isolation scheme. When the input signal reverses from low to high (or from high to low), it passes through an optocoupler circuit with an isolated power supply, outputting a signal that reverses from high to low (or from low to high), which is then sent to the next stage circuit (time reading module 3). The output level-flipping signal of the first isolation output unit 13 or the second isolation output unit 23 locks in the starting moment of the voltage rise during the turn-off process of the device under test (DUT) corresponding to the input signal, and also locks in the ending moment of the voltage rise (the moment when the voltage of the complementary device of the DUT drops to zero and becomes negative).

[0059] The time reading module 3 includes an upper bridge arm device time reading module 31 and a lower bridge arm device time reading module 32.

[0060] The upper bridge arm device time reading module 31 is used to determine the voltage rise time of the upper bridge arm device during the turn-off process based on the output level signal that marks the start of the voltage rise across the collector-emitter terminals of the upper bridge arm device and the level signal that marks the end of the voltage rise across the collector-emitter terminals of the lower bridge arm device when the working state is that the output current of one bridge arm is greater than zero. The lower bridge arm device time reading module 32 is used to determine the voltage rise time of the lower bridge arm device during the turn-off process based on the output level signal indicating the start of the voltage rise across the collector-emitter terminals of the lower bridge arm device and the level signal indicating the end of the voltage rise across the collector-emitter terminals of the upper bridge arm device when the working state is that the output current of one bridge arm is less than or equal to zero.

[0061] use Figure 11 Explain the basic working principle of the time reading module 3. Figure 11 (a), (b), and (c) illustrate the basic principle of how the time reading module 3 obtains the critical time of voltage rise during the turn-off process of the upper bridge arm device by taking the working mode in which the output current of one bridge arm (flowing from E1C2 to the load or external circuit) is greater than zero.

[0062] For a bridge arm with a positive output current (flowing from E1C2 to the load or external circuit), the upper bridge arm device is turned on and off to control the magnitude of the current flowing through the device (i.e., the circuit output current), while the lower bridge arm device has a diode connected in anti-parallel to provide a freewheeling path. Figure 11 In (a), V ce1 The figure shows the voltage waveform across the CE terminals of the upper bridge arm device as it transitions from the on state to the off state. The figure also indicates the starting moment of the voltage rise during the off-state process of the upper bridge arm device. Figure 11 In (b), V ce2The figure shows the voltage waveform across the CE terminals of the lower bridge arm device as it transitions from the off state to the on state of the anti-parallel diode. The figure also highlights the characteristic of the lower bridge arm device voltage decreasing to zero and then reversing, corresponding to the end of the upper bridge arm device voltage rise. The time reading module 3 is used to determine the upper bridge arm device turn-off process V based on the outputs (level inversion signals) of the first isolation output unit 13 and the second isolation output unit 23. CE Voltage rise time. Figure 11 In (c), the Vrise waveform provides a characteristic signal representing the rise time of the upper bridge arm device voltage, which can be obtained by processing the output signals of the first isolation output unit 13 and the second isolation output unit 23. In terms of timing, the characteristic moment when the upper bridge arm device CE voltage begins to rise is earlier, and the characteristic moment when the lower bridge arm device CE voltage decreases to zero and becomes negative is later.

[0063] In an operating mode where the output current (flowing from the load or external circuit to E1C2) of one bridge arm is less than zero, the switching on and off of the lower bridge arm device controls the magnitude of the current flowing through the device, while the anti-parallel diode of the upper bridge arm device provides a freewheeling path. Similarly, the lower bridge arm device turn-off process V is determined based on the output results of the first isolation output unit 13 and the second isolation output unit 23. CE Critical timing of voltage rise. In terms of timing, the characteristic moment when the CE voltage of the lower bridge arm device begins to rise is earlier, and the characteristic moment when the CE voltage of the upper bridge arm device decreases to zero and becomes negative is later.

[0064] This system is applicable to modules such as bridge inverters and DC / DC asymmetric bridge inverters, as well as bridge arm circuits composed of single-tube modules or asymmetric bridge arm circuits.

[0065] Example 2 like Figure 12 As shown, this embodiment of the invention provides a device turn-off time detection system for a power electronic bridge arm assembly, including: a detection module 100 for detecting the start time of the voltage rise process of the device under test during the turn-off process in the power electronic bridge arm assembly, a detection module 200 for detecting the end time of the voltage rise process of the device under test during the turn-off process in the power electronic bridge arm assembly, and a detection module 300 for detecting the voltage rise time of the device under test during the turn-off process in the power electronic bridge arm assembly.

[0066] The start time of voltage rise during the turn-off process of the device under test (the device corresponding to the upper or lower bridge arm) is obtained by detecting the voltage change characteristics across the device under test. The end time of voltage rise during the turn-off process of the device under test (the moment when the device voltage reaches the bus voltage) can be obtained by detecting the voltage change characteristics across the complementary device corresponding to the device under test. The power electronic bridge arm assembly includes a voltage rise detection module 100 for detecting the start time of the voltage rise during the turn-off process of the device under test (DUT). This module is used to determine the start time of the voltage rise during the turn-off process of the DUT based on the characteristics of the voltage rise at the collector and emitter terminals during the turn-off process. The module 200 for detecting the end of the voltage rise during the turn-off process of the device under test (DUT) in the power electronic bridge arm assembly is used to determine the end of the voltage rise during the turn-off process of the DUT based on the zero-crossing and reverse characteristics of the collector-emitter voltage drop during the turn-off process of the complementary device. This is because the end of the voltage rise during the turn-off process of the DUT (the moment when the device voltage first reaches the bus voltage) corresponds precisely to the moment when the voltage drop of the complementary device crosses zero and becomes negative (the anti-parallel diode of the device turns on).

[0067] The voltage rise time detection module 300 of the device under test in the power electronic bridge arm assembly is used to determine the voltage rise time of the device under test during the turn-off process based on the start time and end time of the voltage rise time of the device under test during the turn-off process.

[0068] This invention addresses the problem of voltage overshoot during the voltage rise across the collector and emitter (CE) terminals of a device during turn-off, making it difficult to detect when the voltage rise reaches the external bus voltage. It proposes utilizing the zero-crossing characteristic of a complementary device connected in series with the device under test (DUT), an anti-parallel diode, to solve the problem of measuring the end of the voltage rise. This system is applicable to both inverters composed of symmetrical upper and lower bridge arms and DC / DC converters composed of asymmetrical bridge arm circuit modules.

[0069] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0070] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A device turn-off time detection system for power electronic bridge arm assemblies, characterized in that, The power electronic bridge arm assembly includes an upper bridge arm device and a lower bridge arm device, and the upper bridge arm device and the lower bridge arm device are referred to as complementary devices. The device turn-off time detection system includes: an upper bridge arm device voltage change characteristic detection module connected in parallel across the collector-emitter terminals of the upper bridge arm device, a lower bridge arm device voltage change characteristic detection module connected in parallel across the collector-emitter terminals of the lower bridge arm device, and a time reading module connected to both the upper bridge arm device voltage change characteristic detection module and the lower bridge arm device voltage change characteristic detection module. The upper arm device voltage change characteristic detection module is used to output a level signal indicating the start of the voltage rise across the collector-emitter terminals of the upper arm device and a level signal indicating the end of the voltage rise across the collector-emitter terminals of the upper arm device. The voltage change characteristic detection module of the lower bridge arm device is used to output a level signal indicating the start of the voltage rise across the collector-emitter terminals of the lower bridge arm device and a level signal indicating the end of the voltage rise across the collector-emitter terminals of the lower bridge arm device. The time reading module is used for: When the operating state is that the output current of one bridge arm is greater than zero, the voltage rise time of the upper bridge arm device during the turn-off process is determined according to the level signal that marks the start of the voltage rise across the collector-emitter terminals of the upper bridge arm device and the level signal that marks the end of the voltage rise across the collector-emitter terminals of the lower bridge arm device. When the operating state is that the output current of one bridge arm is less than or equal to zero, the voltage rise time of the lower bridge arm device during the turn-off process is determined based on the level signal indicating the start of the voltage rise across the collector-emitter terminals of the lower bridge arm device and the level signal indicating the end of the voltage rise across the collector-emitter terminals of the upper bridge arm device.

2. The device turn-off time detection system for power electronic bridge arm assemblies according to claim 1, characterized in that, The upper bridge arm device voltage change feature detection module includes: an upper bridge arm device collector-emitter voltage change feature sampling circuit unit, an upper bridge arm device collector-emitter voltage change feature detection unit, and a first isolation output unit; The sampling circuit unit for the voltage change characteristics of the collector-emitter terminals of the upper bridge arm device is used to sample the voltage change characteristics of the collector-emitter terminals of the upper bridge arm device in real time during the process of the upper bridge arm device changing from the on state to the off state, and obtain the sampling results. The voltage change characteristic detection unit at the collector-emitter terminals of the upper bridge arm device is used to process the sampling results output by the sampling circuit unit of the voltage change characteristic sampling circuit at the collector-emitter terminals of the upper bridge arm device to obtain the voltage rise start characteristic during the turn-off process of the upper bridge arm device and the zero-crossing characteristic of the voltage at the collector-emitter terminals of the upper bridge arm device during the change from the turn-off state to the conduction state of the anti-parallel diode. The first isolation output unit is used to electrically isolate the output result of the voltage change characteristic detection unit at the collector-emitter terminals of the upper bridge arm device, and output a level signal indicating the start of the voltage rise at the collector-emitter terminals of the upper bridge arm device and a level signal indicating the end of the voltage rise at the collector-emitter terminals of the upper bridge arm device.

3. The device turn-off time detection system for power electronic bridge arm assemblies according to claim 2, characterized in that, The sampling results determined by the sampling circuit unit for the voltage change characteristics at the collector and emitter terminals of the upper bridge arm device include the initial characteristic information of the voltage rise at the collector and emitter terminals of the upper bridge arm device and the characteristic information of the voltage decrease to zero and become negative at the collector and emitter terminals of the upper bridge arm device.

4. The device turn-off time detection system for power electronic bridge arm assemblies according to claim 2, characterized in that, The voltage change characteristic detection unit across the collector-emitter terminals of the upper bridge arm device includes a voltage rise change characteristic detection unit and a voltage reverse zero crossing characteristic detection unit. The voltage rise change feature detection unit at the collector-emitter terminals of the upper bridge arm device is used to process the sampling results output by the voltage change feature sampling circuit unit at the collector-emitter terminals of the upper bridge arm device, determine the start time of the voltage rise at the collector-emitter terminals of the upper bridge arm device, and output a level flip signal that marks the start of the voltage rise at the collector-emitter terminals of the upper bridge arm device. The reverse zero-crossing characteristic detection unit of the collector-emitter voltage of the upper bridge arm device is used to process the sampling results output by the sampling circuit unit of the collector-emitter voltage change characteristic of the upper bridge arm device, determine the moment when the voltage across the collector-emitter of the upper bridge arm device decreases to zero and becomes negative, and output a level flip signal that marks the end of the rise of the voltage across the collector-emitter of the upper bridge arm device.

5. A device turn-off time detection system for power electronic bridge arm assemblies according to claim 1, characterized in that, The lower bridge arm device voltage change feature detection module includes: a lower bridge arm device collector-emitter voltage change feature sampling circuit unit, a lower bridge arm device collector-emitter voltage change feature detection unit, and a second isolation output unit; The sampling circuit unit for the voltage change characteristics of the collector-emitter terminals of the lower bridge arm device is used to sample the voltage change characteristics of the collector-emitter terminals of the lower bridge arm device in real time during the process of the lower bridge arm device changing from the on state to the off state, and obtain the sampling results. The voltage change characteristic detection unit at the collector-emitter terminals of the lower bridge arm device is used to process the sampling results output by the sampling circuit unit of the voltage change characteristic sampling circuit at the collector-emitter terminals of the lower bridge arm device to obtain the voltage rise start characteristic during the turn-off process of the lower bridge arm device and the zero-crossing characteristic of the voltage at the collector-emitter terminals of the lower bridge arm device during the change from the turn-off state to the conduction state of the anti-parallel diode. The second isolation output unit is used to electrically isolate the output result of the voltage change characteristic detection unit across the collector-emitter terminals of the lower bridge arm device, and output a level signal indicating the start of the voltage rise across the collector-emitter terminals of the lower bridge arm device and a level signal indicating the end of the voltage rise across the collector-emitter terminals of the lower bridge arm device.

6. A device turn-off time detection system for power electronic bridge arm assemblies according to claim 5, characterized in that, The sampling results determined by the sampling circuit unit for the voltage change characteristics across the collector-emitter terminals of the lower bridge arm device include the initial characteristic information of the voltage rise across the collector-emitter terminals of the lower bridge arm device and the characteristic information of the voltage decrease to zero and become negative.

7. A device turn-off time detection system for power electronic bridge arm assemblies according to claim 5, characterized in that, The voltage change characteristic detection unit across the collector-emitter terminals of the lower bridge arm device includes a voltage rise change characteristic detection unit and a voltage reverse zero crossing characteristic detection unit. The voltage rise change feature detection unit at the collector-emitter terminals of the lower bridge arm device is used to process the sampling results output by the voltage change feature sampling circuit unit at the collector-emitter terminals of the lower bridge arm device, determine the start time of the voltage rise at the collector-emitter terminals of the lower bridge arm device, and output a level flip signal that marks the start of the voltage rise at the collector-emitter terminals of the lower bridge arm device. The reverse zero-crossing characteristic detection unit of the collector-emitter voltage of the lower bridge arm device is used to process the sampling results output by the sampling circuit unit of the collector-emitter voltage change characteristic of the lower bridge arm device, determine the moment when the voltage across the collector-emitter of the lower bridge arm device decreases to zero and becomes negative, and output a level flip signal that marks the end of the rise of the voltage across the collector-emitter of the lower bridge arm device.

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