CN113970596A - Stress wave extraction device and method suitable for power device - Google Patents
Stress wave extraction device and method suitable for power device Download PDFInfo
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- CN113970596A CN113970596A CN202111188263.6A CN202111188263A CN113970596A CN 113970596 A CN113970596 A CN 113970596A CN 202111188263 A CN202111188263 A CN 202111188263A CN 113970596 A CN113970596 A CN 113970596A
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Abstract
The device comprises a pulse testing circuit, a differential acoustic emission sensor and a waveform display device, wherein a coupling surface of the differential acoustic emission sensor is attached to the back surface of a power device to be tested of the pulse testing circuit, and the differential acoustic emission sensor is connected with the waveform display device. The method for extracting the stress wave suitable for the power device is also included. The invention can obviously inhibit pulse interference signals, and the output signals have high signal-to-noise ratio and higher extraction degree of stress waves.
Description
Technical Field
The invention relates to the technical field of nondestructive testing of power electronic devices, in particular to a stress wave extraction device and method suitable for a power device.
Background
The power device is a core device for converting electric energy, and the health state of the power device is directly related to the reliable operation of the system. The acoustic emission detection is a rapid, nondestructive and online detection, is widely applied to the power industry, and has potential application value in power device state evaluation. The power device can generate stress waves when the current is transient at the moment of switching on and switching off, and the acoustic emission sensor can measure stress wave signals, see reference documents [1] and [2 ]. The conventional method for extracting the stress wave of the power device is developed based on a single-ended acoustic emission sensor, however, the single-ended acoustic emission sensor is very easy to generate a pulse interference signal during measurement and is coupled into the stress wave, so that the signal-to-noise ratio of the stress wave is reduced. The mechanism of generation of the specific impulse interference signal is considered as electromagnetic interference by researchers, see reference [3 ].
To enhance the signal-to-noise ratio of the extracted stress wave, two strategies are currently applied, namely an electric field shielding technique and a digital filtering technique. The electric field shielding technology needs to use a grounded closed metal shell or a Faraday cage to shield the electric field of a power device and a module, and has the defects of high operation difficulty and complex device structure, which are shown in a reference document [1 ]; the digital filtering technique only uses a low-pass filter to filter the high-frequency signal to reduce the influence of the impulse interference signal, and has the disadvantages that the upper cut-off frequency of the low-pass filter is difficult to determine and the extracted signal is not good because the impulse interference signal has components in each frequency band, and the low-pass filter is difficult to completely filter the impulse interference signal mixed in the stress wave, see references [3], [4 ].
[1]Karkkainen T J,Talvitie J P,Kuisma M,et al.Acoustic Emission in Power Semiconductor Modules—First Observations[J].IEEE Transactions on Power Electronics,2014,29(11):6081–6086.
[2]Davari P,Kristensen O,Iannuzzo F.Investigation of acoustic emission as a non-invasive method for detection of power semiconductor aging[J].Microelectronics Reliability,2018,88–90:545–549.
[3] Any Yun ze, Zhouyang, Lemonta, etc. 30V stress wave theory and experimental research [ J ] China Motor engineering report 2021,41(16): 5683-.
[4]Li M,He Y,Meng Z,et al.Acoustic Emission Based Experimental Analysis of Mechanical Stress Wave in IGBT Device[J].IEEE Sensors Journal,2020,20(11):6064–6074.
Disclosure of Invention
The technical problem to be solved by the present invention is to overcome the above drawbacks of the background art, and to provide a device and a method for extracting a stress wave suitable for a power device, which can significantly suppress a pulse interference signal, and the output signal has a high signal-to-noise ratio and a high degree of extraction of the stress wave.
The technical scheme adopted by the invention for solving the technical problem is that the stress wave extraction device suitable for the power device comprises a pulse testing circuit, a differential acoustic emission sensor and a waveform display device, wherein a coupling surface of the differential acoustic emission sensor is attached to the back surface of the power device to be tested of the pulse testing circuit, and the differential acoustic emission sensor is connected with the waveform display device.
Furthermore, the differential acoustic emission sensor comprises two first piezoelectric ceramics and two second piezoelectric ceramics with opposite polarities, a metal shell and a lead terminal, wherein the first piezoelectric ceramics and the second piezoelectric ceramics are arranged in the metal shell, and two paths of signals output by the two piezoelectric ceramics are led out through the lead terminal.
And the differential acoustic emission sensor is connected with the waveform display equipment through the preamplifier.
Furthermore, a small amount of vacuum grease sealing coupling agent is coated on the coupling surface of the differential acoustic emission sensor and is attached to the back surface of the power device to be tested of the pulse testing circuit.
Furthermore, the two piezoelectric ceramics output two paths of signals through a twin-core BNC coaxial cable, and the differential acoustic emission sensor is provided with a twin-core BNC output interface.
Further, the preamplifier is provided with a double-core BNC input interface and a single-core BNC output interface, and the double-core BNC output interface of the differential acoustic emission sensor is connected with the double-core BNC input interface of the preamplifier through a double-core BNC coaxial cable.
Furthermore, a double-core BNC output interface of the differential acoustic emission sensor is connected with the waveform display equipment through a coaxial cable patch cord of the double-core BNC-single-core BNC.
Further, the preamplifier is provided with a single-core BNC input interface and a single-core BNC output interface, and the double-core BNC output interface of the differential acoustic emission sensor is connected with the single-core BNC input interface of the preamplifier through a coaxial cable transfer line of the double-core BNC-single-core BNC.
A stress wave extraction method suitable for a power device comprises the following steps:
(1) controlling the power device to be switched on and off, and releasing stress waves;
(2) collecting stress waves released by the power device in the step (1) by using a differential acoustic emission sensor;
(3) carrying out differential processing on the acquired signals;
(4) and (4) outputting the signal processed in the step (3) to a waveform display device.
Further, the step (3) further comprises amplifying the signal after the difference processing.
Compared with the prior art, the invention has the following advantages:
the invention discovers a generation mechanism of a pulse interference signal in a stress wave signal, wherein the pulse interference signal in the stress wave signal is formed by crosstalk generated by voltage transient of a power device and coupling the crosstalk into a sensor, and designs a corresponding stress wave extraction device and a method aiming at the discovery; compared with the traditional electric field shielding technology based on the single-ended acoustic emission sensor, the device has the advantages that the size is saved, the operation difficulty is simplified, and the cost is reduced; compared with a digital filtering technology based on a single-ended acoustic emission sensor, the method can prevent voltage coupling interference signals changing around the sensor from being transmitted to the sensor from the source, and solves the problem that pulse interference signals cannot be completely decoupled.
Drawings
Fig. 1 is a schematic structural diagram of a stress wave extraction device according to an embodiment of the present invention.
Fig. 2 is a stress wave generating circuit diagram of the power device of the embodiment shown in fig. 1.
Fig. 3 is an internal configuration diagram of the differential acoustic emission sensor according to the embodiment shown in fig. 1.
FIG. 4 is a stress wave test comparison graph of the differential acoustic emission sensor and the conventional single-ended acoustic emission sensor of the embodiment shown in FIG. 1.
Fig. 5 is a schematic diagram of the mechanism of generation of the impulse interference signal discovered by the present invention.
The device comprises a coupling surface 1, a lead terminal 2, a metal shell 3, a first piezoelectric ceramic 4, a second piezoelectric ceramic 5, a power device to be tested 2, 6, a vacuum grease sealing coupling agent 7, a differential acoustic emission sensor 8, a preamplifier 9, a waveform display device 10, and a collecting-emitting voltage V of an IGBT 11ceCollector-emitter current I of 12-IGBTce13-stress wave, 14-pulse interference signal, 15-voltage signal, 16-conductor, 17-distributed capacitance.
Detailed Description
The invention is described in further detail below with reference to the figures and specific embodiments.
The invention discovers through research that when a voltage signal 15 around the single-ended acoustic emission sensor changes, a distributed capacitance 17 is generated between a conductor 16 nearby and a lead terminal 2 inside the sensor due to the existence of potential difference, the voltage signal 15 changing around is coupled into the sensor through the distributed capacitance 17 to form crosstalk, and when the voltage signal 15 changing around is loaded in the form of square waves, the crosstalk is conveniently expressed as a pulse interference signal 14 (the mechanism is shown in fig. 5). Because the power device to be measured has voltage transient when being switched on and switched off, the pulse interference signal 14 measured when the stress wave 13 of the power device is measured by using the single-ended acoustic emission sensor is not an electromagnetic wave signal, but the transient of the voltage of the power device is coupled to a crosstalk signal generated in the acoustic emission sensor.
Aiming at the discovery, the invention designs a stress wave extraction device suitable for a power device, and referring to fig. 1, the stress wave extraction device of the embodiment specifically comprises a pulse test circuit, a differential acoustic emission sensor 8 and a waveform display device 10, wherein a coupling surface 1 of the differential acoustic emission sensor 8 is coated with a small amount of vacuum grease sealing coupling agent 7 and is attached to the back surface of a power device 6 to be tested of the pulse test circuit so as to reduce the dissipation of stress waves in the interface propagation process, the differential acoustic emission sensor 8 is connected with a preamplifier 9, and the preamplifier 9 is connected with the waveform display device 10. In this embodiment, the power device 6 to be measured is an Insulated Gate Bipolar Transistor (IGBT). The power device of the invention shall include a single device or a power module with a plurality of chips packaged inside.
The IGBT to be tested of the pulse test circuit generates a collector-emitter voltage V of the IGBT when being switched once11 and collector-emitter current I of IGBT ce12 and generates a stress wave 13 and a pulsed interference signal 14.
Pulse test circuit As shown in FIG. 2, bus voltage V dc100V, 100uH, the lower tube VT is supplied with the load inductance L via a drive circuit2(i.e., IGBT to be tested) applying a single pulse voltage control signal, wherein the on-time T ison40us, gate-firing voltage V at turn-onge12V, gate voltage V when turning offgeUpper tube VT of-5V1By applying Vge-5V remains off; when VT2When the switch is on, the current increases linearly from 0 to path I due to the inductor L, and when VT is2When the circuit is turned off, the current flows to a path II due to the flowing VT2The current is instantaneously reduced to 0, and the stress wave is released.
Referring to fig. 3, the differential acoustic emission sensor 8 includes two first piezoelectric ceramics 4, two second piezoelectric ceramics 5, a metal housing 3 and a lead terminal 2, the two first piezoelectric ceramics 4 and the two second piezoelectric ceramics 5 are disposed in the metal housing 3, the differential acoustic emission sensor 8 has a two-core BNC output interface, a stress wave 13 and a pulse interference signal 14 generated after a voltage around the differential acoustic emission sensor 8 changes can generate two stress waves with opposite phases and two pulse interference signals with the same phase after passing through the first piezoelectric ceramics 4 and the second piezoelectric ceramics 5, and the two signals output by the two piezoelectric ceramics through the two-core BNC coaxial cable are led out through the lead terminal 2.
The preamplifier 9 is a 40dB preamplifier, the preamplifier 9 is provided with a twin-core BNC input interface and a single-core BNC output interface, two paths of signals output by the twin-core BNC coaxial cables of the two piezoelectric ceramics are input into the preamplifier 9 through the twin-core BNC input interface, an internal circuit of the preamplifier firstly carries out differential operation on the two paths of signals in the twin-core BNC coaxial cables, because the phases of stress waves in two paths of signal lines are opposite, the phases of interference signals are the same, the interference signals are offset after the two paths of signals are differenced, the gain of the stress wave signals is improved, the pulse interference signals are inhibited, and finally, the signals after the stress waves are amplified by 40dB are output.
In a specific application, the signal can be output to a preamplifier with a single-core BNC input interface by using a coaxial cable patch cord of the dual-core BNC-single-core BNC, the dual-core BNC-single-core BNC coaxial cable patch cord performs differential processing on two paths of signals, and the preamplifier performs amplification processing on the signals.
The signal output by the preamplifier 9 is connected to a waveform display device 10 through a BNC coaxial cable, and the waveform display device 10 is an upper computer system composed of an acoustic emission instrument (converting an analog signal into a digital signal), acoustic emission software (realizing further extraction of signal characteristics), and a display (for displaying waveforms), so as to acquire a stress wave of the IGBT to be measured, which does not contain a pulse interference signal at the turn-off time.
In a specific application, the preamplifier 9 may be omitted, the dual-core BNC output interface of the differential acoustic emission sensor is connected to the waveform display device 10 through the coaxial cable patch cord of the dual-core BNC-single-core BNC, and the coaxial cable patch cord of the dual-core BNC-single-core BNC performs differential processing on the two signals.
Fig. 4 shows stress wave signals generated by the IGBT to be measured, which are measured by using the conventional single-ended acoustic emission sensor and the differential acoustic emission sensor under the same conditions, where the signals measured by the single-ended acoustic emission sensor are significantly subjected to severe pulse interference, and the signals measured by the differential acoustic emission sensor significantly suppress pulse interference signals, so that the degree of extraction of the stress waves is high, which can prove that a good effect can be generated when the differential acoustic emission sensor is applied to the extraction of the stress waves of the power device.
The embodiment of the method for extracting the stress wave suitable for the power device comprises the following steps:
(1) and controlling the power device to be switched on and off, and releasing the stress wave. The method for controlling the on-off of the power device outputs at least one square wave voltage control signal to the grid electrode of the power device.
(2) Collecting stress waves released by the power device in the step (1) by using a differential acoustic emission sensor;
(3) carrying out differential processing and amplification processing on the signals acquired in the step (2) through a preamplifier;
(4) and (4) outputting the signals processed in the step (3) to waveform display equipment.
The stress wave extraction device has simple and flexible structure and simple method operation, can extract without a digital filtering technology, effectively reduces the time cost of extraction, can inhibit pulse interference signals from a source generated by pulse interference, enables the output signals to have high signal-to-noise ratio and strong applicability, and can provide a powerful means for stress wave research of future power devices.
Various modifications and variations of the present invention may be made by those skilled in the art, and they are also within the scope of the present invention provided they are within the scope of the claims of the present invention and their equivalents.
What is not described in detail in the specification is prior art that is well known to those skilled in the art.
Claims (10)
1. The utility model provides a stress wave extraction element suitable for power device which characterized in that: the device comprises a pulse testing circuit, a differential acoustic emission sensor and waveform display equipment, wherein a coupling surface of the differential acoustic emission sensor is attached to the back surface of a power device to be tested of the pulse testing circuit, and the differential acoustic emission sensor is connected with the waveform display equipment.
2. The stress wave extraction device suitable for a power device according to claim 1, wherein: the differential acoustic emission sensor comprises two first piezoelectric ceramics with opposite polarities, a second piezoelectric ceramics, a metal shell and a lead terminal, wherein the first piezoelectric ceramics and the second piezoelectric ceramics are arranged in the metal shell, and two paths of signals output by the two piezoelectric ceramics are led out through the lead terminal.
3. The stress wave extraction device suitable for a power device according to claim 2, wherein: the acoustic emission sensor is connected with the waveform display device through the preamplifier.
4. The stress wave extraction device suitable for a power device according to claim 1 or 2, wherein: and the coupling surface of the differential acoustic emission sensor is coated with a vacuum grease sealing coupling agent and is attached to the back surface of a power device to be tested of the pulse testing circuit.
5. A stress wave extraction device suitable for use in a power device according to claim 3, wherein: the two piezoelectric ceramics output two paths of signals through a double-core BNC coaxial cable, and the differential acoustic emission sensor is provided with a double-core BNC output interface.
6. A stress wave extraction device suitable for use in a power device according to claim 3, wherein: the preamplifier is provided with a double-core BNC input interface and a single-core BNC output interface, and the double-core BNC output interface of the differential acoustic emission sensor is connected with the double-core BNC input interface of the preamplifier through a double-core BNC coaxial cable.
7. The stress wave extraction device suitable for a power device according to claim 2, wherein: and a double-core BNC output interface of the differential acoustic emission sensor is connected with the waveform display equipment through a coaxial cable patch cord of the double-core BNC-single-core BNC.
8. The stress wave extraction device suitable for a power device according to claim 5, wherein: the preamplifier is provided with a single-core BNC input interface and a single-core BNC output interface, and the double-core BNC output interface of the differential acoustic emission sensor is connected with the single-core BNC input interface of the preamplifier through a coaxial cable transfer line of the double-core BNC-single-core BNC.
9. A stress wave extraction method suitable for a power device is characterized by comprising the following steps: the method comprises the following steps:
(1) controlling the power device to be switched on and off, and releasing stress waves;
(2) collecting stress waves released by the power device in the step (1) by using a differential acoustic emission sensor;
(3) carrying out differential processing on the acquired signals;
(4) and (4) outputting the signal processed in the step (3) to a waveform display device.
10. The method of claim 9 for extracting a stress wave for a power device, wherein: and the step (3) further comprises the step of amplifying the signals after the difference processing.
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