CN115201651A - On-state voltage drop on-line monitoring circuit and device for power device - Google Patents
On-state voltage drop on-line monitoring circuit and device for power device Download PDFInfo
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- 238000012544 monitoring process Methods 0.000 title claims abstract description 96
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Abstract
The invention relates to an on-state voltage drop on-line monitoring circuit and a device for a power device, which comprise a same-direction proportional operation circuit and a test current source I sense Diode D 1 High-voltage-resistant ultrafast recovery diode D 2 A clamping branch circuit formed by connecting a plurality of clamping diodes in series, and an anti-parallel bleeder diode D 5 (ii) a The same direction proportional operation circuit comprises an operational amplifier and a resistor R 1 Resistance R 2 (ii) a First clamping diode D on the clamping branch 3 Anode of the diode is connected with the same-direction input end of the operational amplifier of the same-direction proportional operation circuit and the diode D 1 Cathode, high voltage resistant ultrafast recovery diode D 2 The anode of (2); last clamping diode D 4 The cathode of the transistor is connected with the source electrode or the emitter electrode of the tested device; the anti-parallel bleeder diode D 5 Anode and last clamping diode D 4 Is connected with the cathode of the diode D 5 Is connected to the first clamping diode D 3 Of (2) an anode. The circuit reducesThe circuit reliability is enhanced while the cost is low.
Description
Technical Field
The invention belongs to the field of power semiconductor device state monitoring and reliability evaluation, and is mainly used for on-line monitoring of on-state voltage drop of a power semiconductor device, and further can be used for junction temperature information extraction and reliability evaluation.
Background
The power semiconductor device is one of the most critical components in a power electronic converter, and the safe operation thereof is crucial to the robustness and reliability of the power electronic converter system. According to the reliability research report of the power electronic system, the power device is the part with the highest failure rate in the converter system, and accounts for about 35 percent. In recent years, silicon carbide (SiC) materials have been receiving more and more attention from the power electronics industry due to their excellent physical and electrical properties, and SiC power devices are considered to be the most likely to replace silicon (Si) IGBT devices which are widely used at present due to their performance advantages such as low on-resistance and high switching frequency. However, the performance of the SiC power device in practical application is far from its theoretical performance, and is limited to some extent by state sensing technologies such as electricity, magnetism, and heat. Therefore, the online monitoring of the electrical parameters can realize the full utilization of the apparent capacity of the SiC power device and the safe operation under the complex limit condition.
On-state voltage drop of power devices (e.g. V of IGBT) CE V of MOSFET DS-on And V SD ) The method is widely applied to junction temperature monitoring and service life prediction of devices, and is an indispensable parameter for realizing device state monitoring and loss calculation. With the development of power converters to high frequency, high power and high density, in order to realize real-time monitoring of the state of a power device, the monitoring of the on-state voltage drop should meet the requirements on linearity, safety, accuracy and the like. Due to the existence of the overdrive problem and the limitation of a dynamic range, measurement equipment such as an oscilloscope and the like cannot accurately extract on-state voltage at the time of conducting a steady state in the switching process, and integration is not facilitated. Therefore, a special on-state voltage drop on-line monitoring circuit is needed to realize the on-state voltage on-line monitoring of the power device with low cost and high precision.
In order to solve the defect of online monitoring of on-state voltage drop of a measuring instrument, the invention patent with the application number of 202010694635.1 provides an on-state voltage drop online monitoring circuit with a diode for blocking large current, but a path is provided for test current through a NOT gate, a second driving module and an additional switching device, and the additional switching device needs to be synchronously and reversely controlled with a device to be tested during use, so that the complexity of control is increased, and the application cost is increased. The invention patent with application number 201611049398.3 proposes an on-state voltage drop clamp on-line monitoring circuit, but the clamp branch of the on-state voltage drop clamp on-line monitoring circuit consists of a diode series isolation power supply, and in fig. 1 of the patent, when a measured upper tube is conducted, the on-state voltage drop clamp on-line monitoring circuit needs to be realizedThe current I needs to be tested for the accurate monitoring of the on-state voltage drop sense All pass through D 2 、D 1 Then entering an upper pipe; if no 15V power supply is set, part of the test current I sense Will pass through D 3 、D 4 Flow is divided to cause a flow through D 2 、D 1 I of (A) sense When the values are not equal, the preset conditions of the operation circuit are damaged, and inaccurate monitoring is caused; after the power supply is arranged, when the upper tube is conducted, 15V voltage is provided to enable D 4 、D 3 The cathode potential is higher than the anode to avoid shunting, in addition, the power supply is known in the field to need to select an expensive isolation power supply with high common-mode transient immunity, otherwise, common-mode interference is introduced to cause circuit output oscillation, if the floating voltage resistant isolation power supply is selected, the requirements cannot be met, the circuit output can oscillate, and the output waveform cannot be used.
Therefore, an on-state voltage drop on-line monitoring circuit with low cost, high precision and simple control needs to be provided.
Disclosure of Invention
In order to solve the defects in the prior art, the invention aims to provide an on-state voltage drop on-line monitoring circuit and an on-state voltage drop on-line monitoring device for a power device, provide a technical support for reliability research of the power device, and clamp a higher voltage to a lower voltage circuit when a device to be detected is switched off on the premise of lower cost and simple control, so that the voltage at two ends of the power device can be monitored within a smaller voltage range, and the monitoring precision of the on-state voltage drop of the device to be detected is ensured.
The technical scheme adopted by the invention is as follows:
in a first aspect, the present invention provides an on-line voltage drop monitoring circuit for a power device, comprising a same-direction proportional operation circuit and a test current source I sense Diode D 1 High-voltage-resistant ultrafast recovery diode D 2 (ii) a The same direction proportional operation circuit comprises an operational amplifier and a resistor R 1 Resistance R 2 (ii) a The on-line voltage drop monitoring circuit is characterized by further comprising a clamping branch formed by serially connecting a plurality of clamping diodes and an anti-parallel bleeder diode D 5 On a clamped branchThe on-state voltage drop value of a single clamping diode is subtracted from the on-state voltage drop of the clamping diode and is not less than the theoretical highest on-state voltage drop of the tested device; first clamping diode D on the clamping branch 3 Anode connected to the same-direction input end of the operational amplifier of the same-direction proportional operation circuit and diode D 1 Cathode, high voltage resistant ultrafast recovery diode D 2 The anode of (1); last clamping diode D 4 The cathode is connected with the source electrode or the emitter electrode of the tested device; the anti-parallel bleeder diode D 5 Anode and last clamping diode D 4 Is connected with the cathode of the diode D 5 Is connected to the first clamping diode D 3 Of (2) an anode.
The power device to be measured is a SiC MOSFET or an IGBT, an anti-parallel diode is arranged on the IGBT, and an on-state voltage drop on-line monitoring circuit is connected between an emitter (E) and a collector (C) of the IGBT in parallel.
In a second aspect, the present invention provides a device, which uses the on-state voltage drop on-line monitoring circuit for power devices to measure the forward or/and reverse on-state voltage drop of the device under test.
The device is a double-pulse circuit and is provided with two tested devices, and each tested device is connected with an on-state voltage drop on-line monitoring circuit in parallel, which comprises a grid drive circuit, a bus capacitor and a bus voltage V DC A device under test; a circuit formed by the bus voltage, the bus capacitor, the inductive load and the tested device can carry large voltage and large current, and is called as a power main circuit; the devices to be tested used are respectively Q 1 、Q 2 (ii) a The grid drive is connected with a drive circuit, the drive circuit is a circuit for providing a control signal for the switching tube, and the grid drive outputs the drive signal to control the lower tube Q 2 The switch (2) has a driving frequency of 50-300 kHZ and a high-tube Q 1 The grid of which is low or floating, is operated by its body diode only in the freewheeling stage, and the upper transistor Q 1 Test current source I of connected on-state voltage drop on-line monitoring circuit sense And source or emitter connection position of the device under test and the lower tube Q 2 Is connected to the drain or collector of; and a lower tube Q 2 Test current of connected on-state voltage drop on-line monitoring circuitSource I sense The connection position of the source electrode or the emitter electrode of the SiC MOSFET to be tested is grounded; upper tube Q 1 Parallel inductive load, lower tube Q 2 The grid of the grid is connected with the grid driver; the bus voltage and the bus capacitor are connected in parallel on the upper tube Q 1 And a lower tube Q 2 To (c) to (d);
when the driving signal outputs a high level, the lower tube Q 2 On, bus voltage V DC And an inductive load L load And a lower tube Q 2 Form a closed loop when the lower tube Q 2 The voltage at both ends is the on-state voltage drop, and when the driving circuit outputs a low level, the lower tube Q 2 Is turned off when the inductive load L load Continuously upward pipe Q 1 Discharging, current passing through the upper tube Q 1 The body diode or the anti-parallel diode form a closed loop, and the tube Q is arranged at the moment 1 The voltage at both ends is the voltage drop of the body diode or the anti-parallel diode.
Compared with the prior art, the invention has the beneficial technical effects that:
(1) The invention provides an on-state voltage drop on-line monitoring circuit for a power device, and provides a method for only using multi-diode series connection as a clamping branch, so that the monitoring error caused by the traditional single-diode clamping branch is optimized, the problem of output waveform oscillation caused by using a double-diode series power supply as the clamping branch is solved, the cost is reduced, and the reliability of the circuit is enhanced.
(2) In the on-line voltage drop monitoring circuit for the power device, the voltage of the in-phase input end of the operational amplifier has a voltage peak at the conduction moment in the monitoring process, the reason is caused by the switching voltage overshoot of the device to be monitored and the reverse recovery current of the clamping branch, and the negative voltage overshoot can cause the monitoring circuit to work under the abnormal condition, so that the reliability of the whole on-line voltage drop monitoring circuit is reduced. The invention provides a reverse parallel bleeder diode D in a clamping branch 5 The voltage spike existing in the clamping branch is suppressed, the comparison effect of the waveform V homodromous input of the homodromous input end of the operational amplifier is shown in fig. 5, when the bleeder diode is not arranged, a larger voltage spike exists, the voltage spike is greatly reduced after the bleeder diode is arranged, and the effect of suppressing the voltage spike is proved to be obvious.
(3) For a MOSFET device, the body diode related parameters contained in its own structure can also characterize the junction temperature information and the aging degree of the MOSFET. The on-state voltage drop on-line monitoring circuit provided by the invention can monitor the voltage drop of the body diode of the MOSFET when the MOSFET continues current, and realizes the function of extracting two different voltage parameters (the forward on-state voltage drop of the MOSFET and the voltage drop of the body diode) by the on-state voltage drop on-line monitoring circuit. The on-state voltage drop on-line monitoring circuit is used for respectively monitoring the tested devices at different positions, so that the forward on-state voltage drop and/or the voltage drop of the body diode of the switching tube with the follow current function can be monitored.
(4) The on-state voltage drop on-line monitoring circuit for the power device is simple and reliable, has high monitoring precision, can isolate high voltage, and can be normally used in a converter. Practical verification proves that the on-state voltage drop on-line monitoring circuit provided by the invention can normally work at the maximum switching frequency of 300kHz, and the working frequency of the traditional on-state voltage drop on-line monitoring circuit is dozens of kHz.
In summary, the invention provides an on-state voltage drop online monitoring circuit of a power device based on multi-diode series clamping, and a clamping branch circuit adopts a multi-diode series clamping mode, so that additional control signals and drivers are not needed, the reliability is improved, and the cost is reduced. And after a plurality of clamping diodes are connected in series in the application, a special power supply does not need to be additionally arranged, shunting can be inhibited, the cost is reduced, and the stability of the monitoring circuit is improved.
Drawings
Fig. 1 is a circuit topology diagram of an on-state voltage drop on-line monitoring circuit for a power device according to the present invention.
Fig. 2 is a connection diagram of an on-state voltage drop on-line monitoring circuit for a power device according to the present invention when applied to the following example.
Fig. 3 shows the monitoring results of the forward on-state voltage drop and the body diode voltage drop of the SiC MOSFET, where (a) is the monitoring output result of the forward on-state voltage drop of the MOSFET, and (b) is the monitoring output result of the body diode voltage drop when the MOSFET continues current in the reverse direction.
Fig. 4 is a schematic diagram of the power main circuit and the proposed on-state voltage drop on-line monitoring circuit in the embodiment.
Fig. 5 is a graph comparing the effect of the voltage waveform of the input terminal in the same direction when the anti-parallel bleeder diode is not provided and is provided.
Detailed Description
To facilitate an understanding of the invention, reference will now be made to the accompanying drawings and descriptive matter in general terms. Preferred embodiments of the present application are shown in the drawings. The invention may be implemented in different contexts or configurations and is not limited to the embodiments shown herein.
The circuit topology structure of the on-state voltage drop on-line monitoring circuit for the power device is shown in fig. 1, the device to be tested is taken as a SiC MOSFET for explanation in the embodiment, and the circuit topology structure comprises a clamping branch formed by connecting a plurality of clamping diodes in series, a homodromous proportional operation circuit (processing circuit) and an anti-parallel bleeder diode D 5 Testing current source I sense Diode D 1 High-voltage-resistant ultrafast recovery diode D 2 (ii) a The same direction proportional operation circuit comprises an operational amplifier and a resistor R 1 Resistance R 2 ；
The on-state voltage drop value of a single clamping diode subtracted by the on-state voltage drop of all the clamping diodes on the clamping branch circuit is not less than the theoretical highest on-state voltage drop of the tested device; first clamping diode D on the clamping branch 3 Anode of the diode is connected with the same-direction input end of the operational amplifier of the same-direction proportional operation circuit and the diode D 1 Cathode, high voltage resistant ultrafast recovery diode D 2 The anode of (1) provides a path for the test current when turned off and plays a role of voltage stabilizing and clamping for the operational amplifier, and the last clamping diode D 4 The cathode of the test current source is connected with the source electrode of the SiC MOSFET to be used as a test current source I sense Providing a complete closed loop; the anti-parallel bleeder diode D 5 Anode and last clamping diode D 4 Is connected with the cathode of the diode D 5 Is connected to the first clamping diode D 3 The anode of (D) provides a path for reverse recovery current to play a role of inhibiting reverse recovery voltage, and is connected with the bleeder diode D in an anti-parallel way 5 The reverse overshoot of the switching voltage of the device to be tested can be eliminated, and the reverse recovery current of the plurality of clamping diodes connected in series is discharged so as to inhibit the voltage spike of the equidirectional input end of the operational amplifier.
High-voltage-resistant ultrafast recovery diode D 2 The cathode of the operational amplifier is connected with the drain terminal of the tested SiC MOSFET to prevent the load current from entering the processing circuit, and the anode of the operational amplifier is connected with the same-direction input end of the operational amplifier. Diode D 1 The cathode of the operational amplifier is connected with the same-direction input end of the operational amplifier, and the anode of the operational amplifier is connected with the resistor R 1 And a test current source I sense The output terminal of (1) providing a path for the test current; resistance R 1 And the other end thereof is connected to the inverting input terminal of the operational amplifier. Resistance R 2 One end of the second switch is connected with the inverting input end of the operational amplifier, and the other end of the second switch is connected with the output end of the operational amplifier to provide a loop for the feedback signal. Test current source I for providing test small current sense The reference ground of the SiC MOSFET to be tested is the source of the SiC MOSFET to be tested, so that the short circuit risk caused by non-common ground connection can be avoided.
The clamping diodes of the clamping branch circuits are ultrafast recovery diodes, and the plurality of clamping diodes are sequentially connected in series according to the sequence that the cathode of the last clamping diode is connected with the anode of the next clamping diode.
In FIG. 1, Q 2 Is a tested SiC MOSFET; i is sense For testing current sources, which supply a stable milliampere-level test current, D 2 And D 4 The high-voltage resistant ultrafast recovery diode is selected, the high-voltage resistant ultrafast recovery diode can work in a high-voltage environment only if the breakdown voltage of the diode is high, the high-voltage resistant ultrafast recovery diode is selected, the reverse recovery time is short (nanosecond level), the reverse recovery current is small, the breakdown voltage is high and is higher than the high voltage borne by two ends of a tested device when the tested device is turned off, the high current of a main power circuit (a high-current loop where the tested device is located, the prior art is adopted), the high current of a power part is prevented from entering a processing circuit, and the effect of protecting the post-level processing circuit is achieved.
When the on-state voltage drop on-line monitoring circuit is turned off, the clamp branch clamps the voltage of the operational amplifier equidirectional input terminal to a low voltage levelAnd the function of voltage stabilization clamping is realized. The clamping branch is connected with a homodromous proportional operation circuit at the back, wherein R 1 And R 2 The high-precision resistors with the same low resistance value are selected, the precision of the high-precision resistors is higher than 0.1%, and the purpose is to ensure the operation precision of the same-direction proportional operation circuit. R 2 As a feedback resistor, if the resistance value is too high, the feedback is delayed, so that the self-oscillation of the operational amplifier occurs to influence the quality of an output waveform. At the same time, R 1 、R 2 The resistance values should be the same so that the output value of the same direction proportional operation circuit is equal to the on-state voltage drop value of the tested device.
Testing current source I sense For on-line monitoring and testing of voltage drop, a test current source I sense The voltage stabilizing chip is connected in series with the adjusting resistor to form the constant small test current output, and the output current value can be changed by adjusting the resistance value. The voltage stabilization chip outputs a test current including a test current source I sense And the power supply of the operational amplifier is realized by a power supply module with an isolation function, the power supply module with the isolation function is a common isolation power supply module, an expensive isolation power supply with high common-mode transient immunity is not needed, and the interference problem caused by common ground can be avoided.
According to actual needs, the number of the clamping diodes connected in series in the clamping branch circuit is adjusted to obtain a proper value clamping voltage, the number of the clamping diodes is equal to the sum of the clamping voltage value divided by the number of forward conduction voltage drop values of the single clamping diode, and the forward conduction voltage drop values of all the clamping diodes on the clamping branch circuit are equal. The clamping voltage can be adjusted according to the number of the clamping diodes, the theoretically highest on-state voltage drop of the tested device is certain, and the on-state voltage drop value of a single clamping diode is subtracted from the on-state voltage drop of all the clamping diodes and is not less than the theoretically highest on-state voltage drop of the tested device, so that the voltage-stabilizing clamping function is realized.
Examples
The on-state voltage drop on-line monitoring circuit is implemented in a built double-pulse circuit and comprises two tested devices, and each tested device is connected with the on-state voltage drop on-line monitoring circuit in parallel. A double-pulse hardware platform as shown in fig. 4 is built, and the hardware platform comprises a grid drive and a busCapacitor, bus voltage V DC The invention provides a device to be tested and an on-state voltage drop on-line monitoring circuit. A circuit consisting of the bus voltage, the bus capacitor, the inductive load and the SiC MOSFET to be tested can carry large voltage and large current, and is called a power main circuit. The device under test used is two SiC MOSFETs, Q 1 、Q 2 . The circuit connection mode of the embodiment is shown in figure 2. The grid electrode is connected with a driving circuit in a driving mode, and the driving circuit is a circuit for providing control signals for the switching tube. Gate drive output drive signal controlled lower tube Q 2 The switch (2) has a driving frequency of 50-300 kHZ and a high-tube Q 1 The gate of which is given a low level or floating and its body diode is operated only during the freewheeling phase. In this embodiment, the clamp voltage is set to about 4V, and 7 clamp diodes are provided.
When the driving signal outputs a high level, the lower tube Q 2 On, bus voltage V DC And an inductive load L load And a lower tube Q 2 Form a closed loop when the lower tube Q 2 The voltage across is its on-state voltage drop. When the driving circuit outputs a low level, the lower tube Q 2 Is turned off when the inductive load L load Last upward pipe Q 1 Discharging, current passing through the upper tube Q 1 The body diode forms a closed loop, at this time the upper tube Q 1 The voltage across is the voltage drop of its body diode.
When the on-line voltage drop monitoring circuit provided by the invention is connected to two ends of the lower tube in parallel, the on-line voltage drop monitoring circuit can be arranged on the Q of the lower tube 2 The on-state voltage drop is monitored when the switch is switched on. On-line voltage drop monitoring circuit for lower tube Q 2 The output value is lower tube Q when the switch is switched on 2 The on-state pressure drop value of (d); and when the circuit is switched off, the output value is the clamp voltage value set by the clamp branch circuit.
When the on-line voltage drop monitoring circuit is connected with the lower tube Q 2 At both ends, the lower tube Q can be monitored 2 The on-state voltage drop of the conduction. The on-state voltage drop monitoring circuit provided by the invention monitors the on-state voltage drop V of the tested device DS Monitoring, the result being shown in (a) of FIG. 3, when the lower pipe Q is present 2 When the voltage drop monitoring circuit is switched on, the output of the voltage drop monitoring circuit is the on-state voltage drop value of the voltage drop monitoring circuit, and the voltage drop monitoring circuit is connected with the lower tube Q 2 When the circuit is turned off, the output value of the monitoring circuit is clampedAnd voltage value, the function of voltage stabilization and clamping is realized. When the on-state voltage drop on-line monitoring circuit measures the voltage drop of the body diode, the measuring principle is basically consistent with the forward voltage drop of the measuring switch tube.
When the on-line voltage drop monitoring circuit is connected with the upper tube Q 1 At both ends, the upper tube Q can be monitored 1 And the on-state voltage drop of the body diode during reverse freewheeling. The on-line voltage drop monitoring circuit monitors the upper tube Q 1 On-state voltage drop V of body diode SD The monitoring result is shown in (b) in fig. 3. When current flows, the output value of the on-state voltage drop monitoring circuit is the upper tube Q 1 The reverse voltage drop of the body diode is negative and the absolute value is the upper tube Q 1 The on-state voltage drop of the body diode; at the moment of non-freewheeling, the output value is the clamping voltage, and the function of voltage stabilization and clamping is realized. In FIG. 3, I load To pass through an inductive load L load Current waveform of (V) g Is a lower tube Q 2 Drive waveform of (V) DS Is the voltage between the drain and source, V SD Is the voltage between the source and drain.
The output voltage of the same direction proportion operation circuit is the voltage drop of the body diode of the upper tube to be tested and the on-state voltage drop of the lower tube respectively. When the tested SiC MOSFET is switched on, the output of the operation circuit is the on-state voltage drop value of the tested SiC MOSFET, and when the tested SiC MOSFET is switched off, the output of the operation circuit is the set clamping voltage value. And inputting the voltage signal into a digital processing unit for processing so as to extract the state information of the device to be tested.
As shown in fig. 3, the on-state voltage drop on-line monitoring circuit can output the on-state voltage drop value when the device under test is turned on, and the output waveform has a small peak and a good quality. The on-state voltage drop monitoring circuit has accurate monitoring value of on-state voltage drop monitored, good waveform quality and high reliability, and can clamp high voltage at two ends of the on-state voltage drop monitoring circuit at a low voltage level when a tested device is turned off, thereby improving the safety of the monitoring circuit and greatly improving the monitoring accuracy. Through example verification, the circuit provided by the invention can operate at the switching frequency of 300kHZ set by the signal generator, and meets the monitoring requirement of a wide bandgap power device.
As can be seen from fig. 4, the on-state voltage drop on-line monitoring circuit provided by the present invention occupies a small space, is easy to integrate, and can be integrated into a driving circuit or a power module in the future. The module of the on-line voltage drop monitoring circuit can be 4cm or even smaller, and can be integrated on a driving plate in future application, so that the occupied space can be further reduced.
FIG. 5 (a) shows a state where the anti-parallel bleeder diode D is not provided 5 The voltage waveform of the homodromous input end of the operational amplifier is represented by a dotted circle in the figure, the voltage peak value at the position is marked by a dotted circle in the figure, the voltage peak value at the position caused by the switch voltage overshoot and the reverse recovery current is too large, the risk of damaging the processing current exists, the reliability of a monitoring circuit is not ensured, and the anti-parallel bleeder diode D is not arranged 5 At the instant the device under test turns on, there is a large voltage overshoot. FIG. 5 (b) is a view showing an antiparallel bleeder diode D 5 When the voltage waveform of the equidirectional input end of the operational amplifier is set, when the anti-parallel bleeder diode D is set 5 Thereafter, the voltage spike is significantly improved and there is no significant voltage overshoot, indicating that the voltage overshoot is suppressed.
Nothing in this specification is said to apply to the prior art.
Claims (8)
1. An on-line voltage drop monitoring circuit for power device comprises a homodromous proportional operation circuit and a test current source I sense Diode D 1 High-voltage-resistant ultrafast recovery diode D 2 (ii) a The same direction proportional operation circuit comprises an operational amplifier and a resistor R 1 Resistance R 2 (ii) a The on-line voltage drop monitoring circuit is characterized by further comprising a clamping branch formed by serially connecting a plurality of clamping diodes and an anti-parallel bleeder diode D 5 Subtracting the on-state voltage drop value of a single clamping diode from the on-state voltage drops of all the clamping diodes on the clamping branch circuit, wherein the theoretical highest on-state voltage drop of the tested device is not less than the theoretical highest on-state voltage drop of the tested device; first clamping diode D on the clamping branch 3 Anode of the diode is connected with the same-direction input end of the operational amplifier of the same-direction proportional operational circuit and the diode D 1 Cathode, high voltage resistant ultrafast recovery diodeD 2 The anode of (2); last clamping diode D 4 The cathode of the transistor is connected with the source electrode or the emitter electrode of the tested device; the anti-parallel bleeder diode D 5 Anode and last clamping diode D 4 Is connected with the cathode of the diode D 5 Is connected to the first clamping diode D 3 Of (2) an anode.
2. The on-state voltage drop on-line monitoring circuit for power device as claimed in claim 1, wherein the anti-parallel bleeder diode D 5 The reverse overshoot of the switching voltage of the device to be tested can be eliminated, and the reverse recovery current of the plurality of clamping diodes connected in series is discharged so as to inhibit the voltage spike of the equidirectional input end of the operational amplifier.
3. The on-line voltage drop monitoring circuit for power device as claimed in claim 1, wherein the high voltage tolerant ultrafast recovery diode D 2 The cathode of the operational amplifier is connected with a drain electrode or a collector electrode terminal of the tested device to prevent load current from entering the processing circuit, and the anode of the operational amplifier is connected with the homodromous input end of the operational amplifier; diode D 1 The cathode of the operational amplifier is connected with the same-direction input end of the operational amplifier, and the anode of the operational amplifier is connected with the resistor R 1 And a test current source I sense The output terminal of (2) provides a pass for the test current; resistance R 1 The other end of the first resistor is connected to the inverting input end of the operational amplifier; resistance R 2 One end of the operational amplifier is connected with the reverse input end of the operational amplifier, and the other end of the operational amplifier is connected with the output end of the operational amplifier to provide a loop for a feedback signal; test current source I for providing test small current sense The reference ground of the device to be tested is the source electrode or the emitter electrode of the device to be tested, and the risk of short circuit caused by non-common ground connection is avoided.
4. The on-state voltage drop on-line monitoring circuit for the power device as claimed in claim 1, wherein the clamping diodes of the clamping branch are ultrafast recovery diodes, and the plurality of clamping diodes are connected in series in the order of connecting the cathode of the previous clamping diode to the anode of the next clamping diode.
5. The on-state voltage drop on-line monitoring circuit for the power device as claimed in claim 1, wherein when the on-state voltage drop on-line monitoring circuit is turned off, the clamping branch clamps the voltage at the non-inverting input terminal of the operational amplifier to a low voltage level, so as to realize a voltage stabilizing and clamping function; the clamp branch is connected with a homodromous proportional operation circuit at the back, wherein R 1 And R 2 Selecting high-precision resistors, R, of the same low resistance 1 、R 2 The resistance values should be the same so that the output value of the same direction proportional operation circuit is equal to the on-state voltage drop value of the tested device.
6. The on-line voltage drop monitoring circuit for the power device as claimed in claim 1, wherein the device to be tested is a SiCSMOSFET or an IGBT, an anti-parallel diode is arranged on the IGBT, and the on-line voltage drop monitoring circuit is connected between an emitter (E) and a collector (C) of the IGBT in parallel.
7. An apparatus, characterized in that the apparatus uses the on-state voltage drop on-line monitoring circuit for power device as claimed in any one of claims 1-6 to measure the forward or/and reverse on-state voltage drop of the device under test.
8. The device of claim 7, wherein the device is a double pulse circuit having two devices under test, and an on-state voltage drop on-line monitoring circuit is connected in parallel to each device under test, and comprises a gate driver, a bus capacitor, and a bus voltage V DC A device under test; a circuit formed by the bus voltage, the bus capacitor, the inductive load and the tested device can carry large voltage and large current, and is called a power main circuit; the devices to be tested used are respectively Q 1 、Q 2 (ii) a The grid drive is connected with a drive circuit, the drive circuit is a circuit for providing a control signal for the switching tube, and the grid drive outputs the drive signal to control the lower tube Q 2 The switch (2) has a driving frequency of 50-300 kHZ and a high-tube Q 1 The gate of which is given a low level, or floating, only during the freewheeling phase by its body diode,and the upper pipe Q 1 Test current source I of connected on-state voltage drop on-line monitoring circuit sense And the source electrode or the emitter electrode of the tested device is connected with the lower tube Q 2 Is connected to the drain or collector of; and a lower tube Q 2 Test current source I of connected on-state voltage drop on-line monitoring circuit sense The source electrode or emitter electrode connecting position of the tested device is grounded; upper tube Q 1 Parallel inductive load, lower tube Q 2 The grid of the grid is connected with the grid driver; the bus voltage and the bus capacitor are connected in parallel on the upper tube Q 1 And a lower tube Q 2 To (c) to (d);
when the driving signal outputs a high level, the lower tube Q 2 On, bus voltage V DC And an inductive load L load And a lower tube Q 2 Form a closed loop when the lower tube Q 2 The voltage at both ends is the on-state voltage drop, and when the driving circuit outputs a low level, the lower tube Q 2 Is turned off when the inductive load L load Continuously upward pipe Q 1 Discharging, current passing through the upper tube Q 1 The body diode or the anti-parallel diode form a closed loop, and the tube Q is arranged at the moment 1 The voltage at both ends is the voltage drop of the body diode or the anti-parallel diode.
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