CN115542106A - An Online Working Sampling Circuit - Google Patents

Abstract

An online working sampling circuit comprising: the second voltage sampling unit is suitable for acquiring a second conduction saturation voltage drop of the main power switching tube to be detected on line, and the second current sampling unit is suitable for acquiring a second conduction current of the main power switching tube to be detected on line; the second voltage sampling unit includes: the first-stage operational amplifier unit is used for being connected with a main power switch tube to be tested; and the amplitude modulation unit is electrically connected with the first-stage operational amplifier unit and comprises a subtracter and a proportional amplifier with adjustable transformation ratio, the voltage of a reference voltage end of the subtracter is adjustable, and the output end of the subtracter is connected with the input end of the proportional amplifier. The online working sampling circuit gives consideration to high test precision and low test cost.

Description

An Online Working Sampling Circuit

This application is a divisional case proposed on the basis of the invention patent with application number 202110268954.0 and titled "A High-Precision Junction Temperature Online Monitoring Method and System".

technical field

The invention relates to the field of power semiconductor device testing, in particular to an on-line working sampling circuit.

Background technique

Junction temperature is an important parameter to characterize the working state and health state of power semiconductor devices. The chip in the power semiconductor device is packaged inside the module and works in a high-voltage and high-current environment, so the junction temperature of the chip cannot be directly measured. Therefore, it is quite difficult to monitor the junction temperature of power semiconductor devices online under working conditions, and it is also a hot spot of current research.

The traditional detection methods of power semiconductor chip junction temperature are mainly based on the research of Si IGBT, including physical contact method, optical measurement method, model prediction method and thermal sensitive electrical parameters (Thermal Sensitive Electrical Parameters, TSEPs) extraction method. The heat-sensitive electrical parameter method uses the chip itself as a temperature sensor, and reflects the change of the average junction temperature of the chip by measuring the change of the temperature-sensitive electrical parameter, which can realize the non-invasive measurement of the power module under test. methods of monitoring.

The thermosensitive electrical parameter method is divided into many types according to different sensitive parameters. Among them, the method of measuring the junction temperature by using the conduction voltage drop under the condition of large current does not have high requirements on the measurement sequence, does not affect the original control algorithm of the controller, and has low hardware intrusion. It has been extensively carried out at the laboratory level. Research.

However, the current method of measuring the junction temperature using the conduction voltage drop under the condition of large current cannot take into account both high test accuracy and low test cost. Among them, the accuracy of the on-line saturation voltage drop test needs to be improved, and the test cost needs to be increased.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the inability to balance high test accuracy and low test cost in the prior art.

In order to solve the above technical problems, the present invention provides an online working sampling circuit, including: a second voltage sampling unit and a second current sampling unit, the second voltage sampling unit is suitable for obtaining the first voltage of the main power switch tube to be tested online Two conduction saturation voltage drops, the second current sampling unit is adapted to obtain the second conduction current of the main power switch tube to be tested online; the second voltage sampling unit includes: for connecting with the main power switch tube to be tested The first-stage operational amplifier unit; the amplitude modulation unit electrically connected with the first-stage operational amplifier unit, the amplitude modulation unit includes a subtractor and a proportional amplifier with adjustable transformation ratio, and the voltage of the reference voltage terminal of the subtractor is adjustable , the output end of the subtractor is connected to the input end of the proportional amplifier.

Optionally, the voltage at the output terminal of the subtractor is equal to the voltage at the input terminal of the subtractor minus the voltage at the reference voltage terminal.

Optionally, the second voltage sampling unit also includes: a first low-pass filter, the input end of the first low-pass filter is connected to the output end of the first-stage op-amp unit, and the first low-pass filter The output of a low-pass filter is connected to the input of the subtractor.

Optionally, the first-stage operational amplifier unit includes a first current-voltage conversion operational amplifier, a bias current source, a seventh diode, an eighth diode, a ninth diode, a first resistor, and a first resistor. Two resistors, the positive input terminal of the first current-voltage conversion operational amplifier is connected to the positive connection terminal of the seventh diode, the negative connection terminal of the eighth diode, and the positive connection terminal of the ninth diode ; The positive connection end of the eighth diode is connected to the negative connection end of the ninth diode, one end of the first resistor and the bias current source, and the other end of the first resistor is connected to the first current-voltage conversion operational amplifier The negative input terminal and one end of the second resistor, the other end of the second resistor is connected to the output terminal of the first current-voltage conversion operational amplifier, and the negative connection terminal of the seventh diode is used as the input terminal of the first-stage operational amplifier unit , the output terminal of the first current-voltage conversion operational amplifier is used as the output terminal of the first-stage operational amplifier unit.

Optionally, the resistance value of the first resistor is equal to the resistance value of the second resistor.

Optionally, the conduction voltage drop of the eighth diode is equal to the conduction voltage drop of the seventh diode.

Optionally, the distance between the eighth diode and the seventh diode is less than or equal to 10mm.

Optionally, the second voltage sampling unit further includes: an analog signal isolation unit, an input end of the analog signal isolation unit is connected to an output end of the proportional amplifier.

Optionally, the second voltage sampling unit also includes: a current discharge unit connected to the first-stage operational amplifier unit, and the current discharge unit is adapted to Discharging the current in the first stage operational amplifier unit.

Optionally, the current discharge unit includes a MOS transistor.

Optionally, the second current sampling unit is also used to calibrate the first conduction saturation voltage drop of the main power switch to be tested in an offline state.

Optionally, the main power switch tube to be tested is a working element of a power equipment module, and the power equipment module includes a converter circuit unit, a current sampling internal module and a main control module, and the converter circuit unit includes Several main power switch tubes, the output end of the current sampling internal module is suitable for connecting to the input end of the main control module, and the output end of the main control module is suitable for each main power switch tube in the converter circuit unit The working sequence is provided; the second current sampling unit is composed of the current sampling internal module.

The technical solution of the present invention has the following beneficial effects:

In the online working sampling circuit provided by the technical solution of the present invention, the second voltage sampling unit in the online working sampling circuit tests to obtain the second conduction saturation voltage drop. Because the second voltage sampling unit includes: a first-stage op-amp unit connected to the main power switch tube to be tested; an amplitude modulation unit electrically connected to the first-stage op-amp unit, and the amplitude modulation unit includes a subtractor and a proportional amplifier, the output terminal of the subtractor is connected to the input terminal of the proportional amplifier. In this way, in the process of online sampling, the subtractor can be used to remove invalid range data, and then the data output by the subtractor can be amplified through the proportional amplifier, so that the accuracy of the second conduction saturation voltage drop sampled by the second voltage sampling unit is improved. The resolution of the second turn-on saturation voltage drop versus junction temperature is improved. In this solution, there is no need to rely on high-precision test voltage test instruments, so the test cost is reduced. In summary, this solution takes into account both high test accuracy and low test cost.

Further, the second current sampling unit is composed of the current sampling internal module. In this solution, the current sampling internal module of the power equipment module is used as the second current sampling unit, and the current sampling internal module is used to test and obtain the second conduction current during the online sampling process. In this way, there is no need to additionally arrange a module for sampling current, thus reducing the cost.

Description of drawings

In order to more clearly illustrate the specific implementation of the present invention or the technical solutions in the prior art, the following will briefly introduce the accompanying drawings that need to be used in the specific implementation or description of the prior art. Obviously, the accompanying drawings in the following description The drawings show some implementations of the present invention, and those skilled in the art can obtain other drawings based on these drawings without any creative work.

FIG. 1 is a relationship curve between T _j and V _CE under different conduction currents calibrated by junction temperature in the prior art;

Figure 2 is a typical three-phase bridge converter;

3 is a schematic diagram of a high-precision junction temperature online monitoring system provided by an embodiment of the present invention;

4 is a schematic diagram of a junction temperature calibration module provided by an embodiment of the present invention;

5 is a schematic diagram of a working sampling module provided by an embodiment of the present invention;

Fig. 6 is a schematic diagram of a power equipment module and a second voltage sampling unit provided by an embodiment of the present invention;

7 is a schematic diagram of online sampling provided by a second voltage sampling unit according to an embodiment of the present invention;

8 is a schematic diagram of online sampling provided by a second current sampling unit according to an embodiment of the present invention;

9 is a schematic diagram of the junction temperature calibration process of the main power switch tube on the standby side by the junction temperature calibration module provided by an embodiment of the present invention;

FIG. 10 is a flowchart of a high-precision junction temperature online monitoring method provided by an embodiment of the present invention;

FIG. 11 is a timing diagram of online sampling by the current sampling internal module provided by an embodiment of the present invention.

detailed description

As mentioned in the background art, the existing technology cannot balance high testing accuracy and low testing cost.

The current research on the large current conduction voltage drop method is basically limited to the theoretical level. It is believed that under a certain current, the conduction voltage drop and the junction temperature show a monotonic correlation. Through current and conduction voltage drop measurement, the mapping calculation of junction temperature can be realized. T _j =f(V _CE , I), where T _j is the junction temperature, V _CE is the conduction voltage drop, and I is the conduction current.

There are many problems in the practical engineering application of using the conduction voltage drop method to measure the junction temperature. For most power devices (the following is for the convenience of discussion, IGBT is used as an example, and a 1700V/1000A IGBT power module is selected as an example for intuitive expression. The mapping relationship between T _j and V _CE and I is shown in Figure 1. Different lines Represents the relationship curve between T _j and V _CE under different conduction currents. Different lines in Figure 1 show different conduction currents, and the conduction voltage drop V _CE for junction temperature T _j when the conduction current is 6.25mA The resolution of the conduction voltage drop V _CE to the junction temperature T j is -2.77mV/℃, and the resolution of the conduction voltage drop V _CE to the junction temperature T _j is -0.90mV/℃ when the conduction current is 200A. The resolution of the junction temperature T _j is _-0.15mV /°C, the conduction voltage drop V _CE is 0.56mV/°C when the conduction current is 300A, and the conduction voltage drop is 0.56mV/°C when the conduction current is 400A The resolution of V _CE for the junction temperature T _j is 1.07mV/°C, and the resolution of the conduction voltage drop V _CE for the junction temperature T _j is 1.62mV/°C when the conduction current is 500A, and the conduction current is 600A. The resolution of the voltage drop V _CE to the junction temperature T _j is 2.10mV/°C, and the resolution of the conduction voltage drop V _CE to the junction temperature T _j is 2.59mV/°C when the conduction current is 700A, and the conduction current is 800A The resolution of the conduction voltage drop V _CE to the junction temperature T _j is 3.09mV/°C, and the resolution of the conduction voltage drop V _CE to the junction temperature T _j is 3.54mV/°C when the conduction current is 900A, and the conduction current is at The resolution of the conduction voltage drop V _CE to the junction temperature T _j at 1000A is 4.02mV/°C.

It can be seen from Figure 1 that the resolution of the conduction voltage drop V _CE to the junction temperature T _j is not high, so the requirements for voltage sampling accuracy are high, and the conduction voltage drop V _CE is more affected by the conduction current I coupling than the junction temperature , so that for a conduction voltage drop of the order of 3V, the variation range of the conduction voltage drop V _CE in the temperature range of 25-150°C under a fixed current value is only about 0.5V.

A typical three-phase bridge converter is shown in Figure 2. The device under test is T6' in this example, and T6' is in the alternate on-off state in the working state. At the moment of stable conduction of T6', the current I ₆ flowing through T6' and the conduction voltage V _CE6 are sampled; when T6' is turned off and T5' is conducted, the voltage at both ends of T6' is the DC bus voltage Udc of the converter, generally 300-1000V, so it is necessary to isolate the high voltage to protect the circuit under test. However, for circuits with high isolation voltage and low measured voltage, it is difficult to guarantee the measurement accuracy.

It is greatly affected by current coupling and requires high accuracy of current sampling. The accuracy of current sampling heavily affects the accuracy of junction temperature estimation. To achieve a temperature resolution of 1°C in theory, the current sensor needs to have an accuracy of 0.2%. However, only laboratory measurement-level current sensors can meet the accuracy requirements. The current sensors used in most industrial equipment generally use open-loop Hall current sensors or precision resistors connected in series in the loop. The current measurement accuracy is generally about 3%. Far from being able to meet the requirements of junction temperature measurement accuracy. Table 1 shows the impact of voltage and current sampling errors on the junction temperature measurement results.

Table 1

Secondly, the junction temperature test process has high requirements for sampling timing and high requirements for noise suppression. In order to obtain accurate junction temperature, it is required that the voltage and current sampling must be kept synchronous; at the same time, because the converter works in the alternate conduction state, other switching actions generate high dv/dt and di/dt, which will cause great interference to the device under test. Therefore, it is necessary to control the sampling timing and add filtering to suppress interference in the sampling link; at the same time, the sampling and filtering processing algorithms should be controlled independently, and the normal control function for interference should not be used.

Based on the above problems, most of the research based on the high-current conduction voltage drop method is based on the measurement results of expensive and precise measurement equipment in the laboratory under specific timing and specific working conditions. For practical engineering applications, it is necessary to use lower cost and volume to realize the function of junction temperature measurement under the existing hardware conditions, and to meet certain accuracy requirements.

On this basis, an embodiment of the present invention provides a high-precision junction temperature online monitoring system 1, referring to FIG. 3 to FIG. 5, including:

A junction temperature calibration module 10, the junction temperature calibration module 10 includes a first voltage sampling unit 101 and a first current sampling unit 102, the junction temperature calibration module 10 is suitable for the main power switch tube to be tested in the junction temperature calibration process Injecting the current in the forward direction, and obtaining a mapping relationship between the first conduction saturation voltage drop and the first conduction current of the main power switch tube to be tested in an offline state, and the junction temperature of the main power switch tube to be tested;

A data fitting module 20, the data fitting module 20 is adapted to fit the data in the mapping relationship to obtain a characteristic function relationship, the characteristic function relationship is based on the first conduction saturation voltage drop and the first conduction current is the independent variable, and the junction temperature of the main power switch tube to be tested is the dependent variable;

A working sampling module 30, the working sampling module 30 includes a second voltage sampling unit 301 and a second current sampling unit 302, the second voltage sampling unit 301 is adapted to obtain the second conduction of the main power switch tube to be tested online Saturation voltage drop, the second current sampling unit 302 is adapted to obtain online the second conduction current of the main power switch tube to be tested;

Both the first voltage sampling unit 101 and the second voltage sampling unit 301 include: a first-stage op-amp unit connected to the main power switch tube to be tested; an amplitude modulation unit electrically connected to the first-stage op-amp unit, The amplitude modulation unit includes a subtractor and a proportional amplifier, the output of the subtractor is connected to the input of the proportional amplifier;

A test junction temperature acquisition unit 40, the test junction temperature acquisition unit 40 is adapted to acquire the junction temperature value corresponding to the second conduction saturation voltage drop and the second conduction current in the characteristic function relationship.

The junction temperature calibration module 10 can perform the junction temperature calibration step, and the junction temperature calibration step is performed when the main power switch tube to be tested is processed offline. The main power switch tube to be tested is a working element of the power equipment module, and the processing of the main power switch tube to be tested in an offline state refers to: in the power equipment module except the main power switch tube to be tested, other All active devices are turned off.

The working sampling module 30 can perform the steps of online sampling. On-line sampling refers to: testing the main power switch tube to be tested under the working state of the power equipment module, and applying an alternate conduction voltage to the grid of the main power switch tube to be tested.

The first voltage sampling unit 101 is adapted to obtain the first conduction saturation voltage drop of the main power switch tube to be tested in the offline state during the junction temperature calibration process, and the first current sampling unit 102 is adapted to obtain the junction temperature calibration process. The first conduction current of the main power switch tube to be tested in an offline state.

The second voltage sampling unit 301 is adapted to acquire the second conduction saturation voltage drop of the main power switch tube to be tested online, and the second current sampling unit 302 is adapted to acquire the second saturation voltage drop of the main power switch tube to be tested online. conduction current.

In this embodiment, the first voltage sampling unit 101 and the second voltage sampling unit 301 have the same structure.

The main power switch tube to be tested is a working element of the power equipment module.

Referring to Fig. 6, the power equipment module includes a converter circuit unit W, a current sampling internal module Q1 and a main control module 41, the converter circuit unit W includes several main power switch tubes, and the current sampling internal module Q1 The output end of the main control module 41 is adapted to be connected to the input end of the main control module 41, and the output end of the main control module 41 is adapted to provide working timing for each main power switch tube in the converter circuit unit W.

Referring to Fig. 6, the converter circuit unit W includes: a DC network, an AC network, and a bridge power switch tube circuit. There are several power switch tube units in the bridge power switch tube circuit, and each power switch tube unit includes: a main power switch tube unit A switch tube and a diode connected in antiparallel to the main power switch tube; the AC network includes a load inductor electrically connected to the main power switch tube, and the DC network includes a load resistor connected in series with the DC bus power supply U _dc .

In one embodiment, the converter circuit unit is a three-phase full-bridge converter circuit as an example for illustration. Referring to FIG. 6 , the bridge power switch circuit in the converter circuit unit W includes a first power switch tube unit, the second power switch tube unit, the third power switch tube unit, the fourth power switch tube unit, the fifth power switch tube unit and the sixth power switch tube unit. The first power switch tube unit includes a first main power switch tube T1 and a first diode D1 antiparallel to the first main power switch tube T1; the second power switch tube unit includes a second main power switch tube T2 and a first diode D1 connected in antiparallel with the first main power switch tube T1; The second diode D2 connected in antiparallel with the second main power switch tube T2; the third power switch tube unit includes a third main power switch tube T3 and a third diode connected in antiparallel with the third main power switch tube T3 D3; the fourth power switch tube unit includes a fourth main power switch tube T4 and a fourth diode D4 connected in antiparallel with the fourth main power switch tube T4; the fifth power switch tube unit includes a fifth main power switch tube T5 and the fifth diode D5 antiparallel to the fifth main power switch tube T5; the sixth power switch tube unit includes the sixth main power switch tube T6 and the sixth second diode D5 antiparallel to the sixth main power switch tube T6 Pole tube D6. The collector of the first main power switching tube T1, the collector of the third main power switching tube T3 and the collector of the fifth main power switching tube T5 are connected together and connected to the positive pole of the DC bus power supply U _DC , the second main power The emitter of the switching tube T2, the emitter of the fourth main power switching tube T4 and the emitter of the sixth main power switching tube T6 are connected together and connected to the negative pole of the DC bus power supply U _dc . The first main power switch tube T1, the second main power switch tube T2, the third main power switch tube T3, the fourth main power switch tube T4, the fifth main power switch tube T5 and the sixth main power switch tube T6 are all IGBTs (Insulated Gate Bipolar Transistor). In this embodiment, IGBT is selected as the main power switch tube to be tested. Of course, in other embodiments, power switch tubes such as MOSFETs can also be selected as the main power switch tube to be tested.

Referring to FIG. 6 , the converter circuit unit _W further includes: _a first load inductance LA, one end of the first load inductance LA and the emitter of the first main power switch T1 and the collector of the second main power switch T2 Electrical connection; the first load resistor R _A connected in series with the first load inductor LA, the other end of the first load inductor LA is connected to one end of the first load resistor _{R A ;} the second load inductor _{L B ,} the second load One end of the inductance L _B is electrically connected to the emitter of the third main power switch tube T3 and the collector of the fourth main power switch tube T4; the second load resistor R _B connected in series with the second load inductance L _B , the second load The other end of the inductance L _B is connected to one end of the second load resistor R _B ; the third load inductance L _C , one end of the third load inductance L _C is connected to the emitter of the fifth main power switch tube T5 and the sixth main power switch tube The collector of T6 is electrically connected; the third load resistance R _C is connected in series with the third load inductance L _C , and the other end of the third load inductance L _C is connected to one end of the third load resistance R _C ; the first load resistance R _A The other end of the second load resistor _RB and the other end of the third load resistor R _C are connected together. In this embodiment, the sixth main power switch tube T6 is selected as the main power switch tube to be tested. Of course, in other embodiments, other main power switch tubes can also be arbitrarily selected as the main power switch tube to be tested.

The power equipment module further includes: a CPU (Central Processing Unit) 42 . The main control module 41 , CPU (Central Processing Unit) 42 and the test junction temperature acquisition unit 40 are integrated together to form the structure of the control unit.

FIG. 7 shows a specific circuit structure of the second voltage sampling unit 301 . The second voltage sampling unit 301 includes a bias current source Y11.

The second voltage sampling unit 301 includes: a first-stage operational amplifier unit Y1 connected to the main power switch tube to be tested; an amplitude modulation unit Y3 electrically connected to the first-stage operational amplifier unit Y1, and the amplitude modulation unit Y3 It includes a subtractor Y31 and a proportional amplifier Y32, the output terminal of the subtractor Y31 is connected to the input terminal of the proportional amplifier Y32.

In this embodiment, the second voltage sampling unit 301 includes: a first-stage operational amplifier unit Y1, a first low-pass filter Y2, an amplitude modulation unit Y3, an analog signal isolation unit Y4, and a current discharge unit S1. The input end of the first low-pass filter Y2 is connected to the output end of the first-stage operational amplifier unit Y1, and the output end of the first low-pass filter Y2 is connected to the input end of the subtractor Y31. The voltage signal at the output of the proportional amplifier Y32 is greater than the voltage signal at the input of the proportional amplifier Y32. The input end of the analog signal isolation unit Y4 is connected to the output end of the proportional amplifier Y32.

The current discharge unit S1 is connected to the first-stage operational amplifier unit Y1, and the current discharge unit S1 is suitable for discharging the power in the first-stage operational amplifier unit Y1 when the main power switch tube to be tested is turned off. current. The current drain unit S1 includes a MOS transistor.

The output terminal of the analog signal isolation unit Y4 is suitable for outputting the conduction voltage. Specifically, when the second voltage sampling unit 301 performs online sampling, the output terminal of the analog signal isolation unit Y4 outputs the second conduction saturation voltage drop.

The first-stage operational amplifier unit Y1 includes a first current-voltage conversion operational amplifier Y12, a bias current source Y11, a seventh diode D7, an eighth diode D8, a ninth diode D9, a first resistor R1, the second resistor R2, the positive input terminal of the first current-voltage conversion operational amplifier Y12 is connected to the positive connection terminal of the seventh diode D7, the negative connection terminal of the eighth diode D8, the ninth and second The positive connection end of the pole tube D9, and the current discharge unit S1. The positive connection end of the eighth diode D8 is connected to the negative connection end of the ninth diode D9, one end of the first resistor R1 and the bias current source Y11, and the other end of the first resistor R1 is connected to the first current-voltage converter The negative input terminal of the operational amplifier Y12 and one terminal of the second resistor R2, the other terminal of the second resistor R2 is connected to the output terminal of the first current-voltage conversion operational amplifier Y12, and the negative connection terminal of the seventh diode D7 serves as The input terminal of the first-stage operational amplifier unit Y1 and the output terminal of the first current-voltage conversion operational amplifier Y12 are used as the output terminal of the first-stage operational amplifier unit Y1.

In this embodiment, taking the sixth main power switch T6 as an example to be tested, correspondingly, the negative connection end of the seventh diode D7 is connected to the collector of the sixth main power switch T6 .

In this embodiment, the current discharge unit S1 includes a MOS transistor, the source of the MOS transistor is connected to the negative connection terminal of the eighth diode D8, the drain of the MOS transistor is grounded, and the voltage applied to the gate of the MOS transistor is It is opposite to the voltage applied on the gate of the main power switch tube to be tested.

In this embodiment, when the main power switch tube to be tested is turned on, that is, when the sixth main power switch tube T6 is turned on, the potential difference between the M point and the GNDH point is the result of the sixth main power switch tube T6. At this time, the first-stage operational amplifier unit Y1 converts the conduction voltage drop Vce of this certificate according to a ratio of 1:1 and outputs it to the subsequent circuit to achieve impedance isolation. When the fifth main power switch tube T5 is turned on, the potential difference between point M and point GNDH is the DC bus voltage Udc. At this time, the seventh diode D7 is cut off. Due to the existence of the first-stage operational amplifier unit Y1, the voltage sampling The unit 101 can prevent overvoltage damage to the subsequent circuit during the online sampling process.

When the resistance value of the first resistor R1 is equal to the resistance value of the second resistor R2, the potential difference between point N and GNDH point V _N =2Va—V _b =2V _CE +2V _D7 —(V _CE +V _D7 +V _D8 ) = _VCE

In order to offset the interference of the voltage drop of the seventh diode D7 on the measurement, the eighth diode D8 is set as a high-voltage fast recovery diode of the same type as the seventh diode D7, and it is required that the seventh diode D7 and the eighth diode The positions of the diodes D8 are arranged close to each other, and the ambient temperature is similar, so as to eliminate the inconsistency between the temperature-induced voltage drop of the seventh diode D7 and the temperature-induced voltage drop of the eighth diode D8.

When T6 is turned off, the MOS transistor provides a discharge circuit for the bias current source Y11.

In a specific embodiment, the conduction voltage drop of the eighth diode D8 is equal to the conduction voltage drop of the seventh diode D7.

In a specific embodiment, the distance between the eighth diode D8 and the seventh diode D7 is less than or equal to 10mm. The seventh diode D7 and the eighth diode D8 are arranged close to each other, and the ambient temperature is similar to eliminate the inconsistency between the temperature-induced voltage drop of the seventh diode D7 and the temperature-induced voltage drop of the eighth diode D8 .

The first low-pass filter Y2 includes a third resistor R3, a fourth resistor R4, a first capacitor C1, a second capacitor C2 and a second operational amplifier Y21, one end of the third resistor R3 is connected to the first stage operational amplifier unit Y1 connected to the output end of the third resistor R3, the other end of the third resistor R3 is connected to one end of the fourth resistor R4 and one end of the first capacitor C1, the other end of the first capacitor C1 is connected to the negative input end of the second operational amplifier Y21, the second The positive input end of the second operational amplifier Y21 is connected to the other end of the fourth resistor R4 and one end of the second capacitor C2, the other end of the second capacitor is grounded, the negative input end of the second operational amplifier Y21 is connected to the output end of the second operational amplifier Y21 connect.

The first low-pass filter Y2 filters out high-frequency interference generated during the switching process of the main power switch tube (T1-T6 in this example).

The subtractor Y31 has a reference voltage terminal, the voltage V _REF of the reference voltage terminal is adjustable, and the voltage at the output terminal of the subtractor Y31 is equal to the voltage at the input terminal of the subtractor Y31 minus the voltage V _REF at the reference voltage terminal .

The amplitude modulation unit Y3 adjusts the voltage range input to the amplitude modulation unit Y3 to a proper range and outputs it.

Most sampling circuits have a fixed magnification. It can be seen from Figure 1 (three-dimensional corresponding relationship between conduction voltage-junction temperature-current) that the section with temperature resolution only occupies a very narrow part of the entire measurement range. In this embodiment, in order to improve the temperature resolution, the subtractor Y31 is used to remove the invalid range data. In this embodiment, the invalid range data refers to data lower than V _REF . After removing the invalid range data, adjust the potential difference V _P between the P point and the GNDH point to the range required by the subsequent stage circuit through the proportional amplifier Y32 with adjustable ratio.

When the characteristic curve of the main power switch tube to be tested is known, select a high-precision voltage reference chip as the reference value of V _REF ; when the main power switch tube to be tested is uncertain, or the main power switch tube to be tested When the characteristic range of the switch tube changes greatly with the current, the programmable voltage signal is selected as the reference value of V _REF .

The analog signal isolation unit Y4 implements the analog signal isolation function, which is used to isolate strong electrical interference and ensure the safe operation of equipment and personnel safety. The isolation method of the analog signal isolation unit Y4 can be selected from high-resistance isolation, optocoupler isolation, magnetic isolation, or capacitive isolation.

Referring to Fig. 8, the second current sampling unit 302 includes: a Hall sampling unit 4203, a second initial operational amplifier unit 4201 and a second low-pass filter 4202, and the current input terminal of the Hall sampling unit 4203 is suitable for The main power switch tube is electrically connected, when the main power switch tube to be tested is an IGBT, the current input terminal of the Hall sampling unit 4203 is suitable for electrical connection with the collector and emitter of the main power switch tube to be tested, When the main power switch tube to be tested is a MOSFET, the current input end of the Hall sampling unit 4203 is adapted to be electrically connected to the source or drain of the main power switch tube to be tested. The two voltage output terminals of the Hall sampling unit 4203 are electrically connected to the first input terminal and the second input terminal of the second initial operational amplifier unit 4201 respectively, and the output terminal of the second initial operational amplifier unit 4201 is connected to the second low-pass The input terminal of the filter 4202 is connected, and the output terminal of the second low-pass filter 4202 is suitable for obtaining the second conduction current of the main power switch tube to be tested online.

The Hall sampling unit 4203 includes a first magnetic core, the first magnetic core is a ring structure and has a gap, the first Hall element is placed in the gap of the first magnetic core, and the first Hall element is placed in the first magnetic core There is a first guide rod, the first magnetic core surrounds the first guide rod, specifically, the first guide rod is suitable for electrical connection with the power switch tube of the master to be tested, and one end of the first guide rod serves as the first Hall sampling unit's current input.

The second initial operational amplifier unit 4201 is adapted to output the differential voltage output by the Hall sampling unit 4203 as a single-ended fixed voltage.

In this embodiment, the structure of the second low-pass filter 4202 is consistent with the structure of the aforementioned first low-pass filter Y42, and will not be described in detail.

In this embodiment, the second low-pass filter 4202 is used to adjust the delay of the second current sampling unit 302, so that the working sampling module 30 samples the second conduction saturation voltage drop and the second conduction voltage of the main power switch tube to be measured. Current signal synchronization. FIG. 9 is a schematic diagram of a process of calibrating the junction temperature of the main power switch tube on the standby side by the junction temperature calibration module provided by an embodiment of the present invention.

Referring to FIG. 9, a half-bridge single-pulse test circuit is built with the main power switch tube (DUT) to be tested. The junction temperature calibration module 10 includes: a voltage source 60; a capacitor C; a heating platform 64; the fifth main power switch tube, the fifth Diode, resistor 63 , sixth main power switch tube T6 and sixth diode D6 ; first voltage sampling unit 101 and first current sampling unit 102 .

The structure of the first voltage sampling unit 101 refers to the structure of the second voltage sampling unit 301 , and will not be described in detail.

In the process of junction temperature calibration using the junction temperature calibration module 10, the power equipment module is in the state of stopping work, the main power switch tube to be tested remains on, and the bias current source of the first voltage sampling unit 101 is in the state of the main power switch to be tested. The power switch tube injects current in the forward direction, the first voltage sampling unit 101 outputs the first conduction saturation voltage drop, and the first current sampling unit 102 tests the first conduction current of the main power switch tube to be tested. The bias current source of the first voltage sampling unit 101 has a forward injection current of 5mA-200mA, such as 5mA, 10mA, 50mA, 100mA, 150mA or 200mA, so that the constant current is small and can Avoid heating due to excessive conduction current inside the main power switch tube to be tested.

Specifically, during the junction temperature calibration process using the junction temperature calibration module 10, the main power switch tube to be tested is placed on the heating platform 64, specifically, the chip corresponding to the main power switch tube to be tested is placed on the heating platform 64, the main power switch tube to be tested is heated to a predetermined temperature by the heating platform 64, the gate of the main power switch tube to be tested is turned on, and the bias current source of the first voltage sampling unit 101 The tube injects current in the forward direction. In the process of calibrating the main power switch tube to be tested by the junction temperature calibration module 10, by adjusting the temperature of the heating platform 64, the first conduction saturation of the main power switch tube to be tested at different junction temperatures _Tj1 can be obtained The mapping data of the voltage drop V _CE1 and the first conduction current _ID1 , so as to obtain the first conduction saturation voltage drop V _CE1 and the first conduction current of the main power switch to be tested in the off-line state and in the conduction state A first mapping relationship between _{ID1 and the junction temperature T j1 of} the main power switch tube to be tested. The junction temperature of the main power switch tube to be tested in the first mapping relationship is calibrated by the temperature of the heating platform 64 .

The characteristic function relationship fitted by the data fitting module 20 may be a polynomial or a trigonometric function. It should be noted that, in this embodiment, there is no limitation on the specific data fitting module 20, as long as the data fitting module 20 realizes fitting to the characteristic function relationship according to the mapping relationship.

In one embodiment, the first current sampling unit 102 and the second current sampling unit 302 are the same current sampling unit, and for the detailed structure of the first current sampling unit 102 , refer to the foregoing description of the second current sampling unit 302 . The output terminal of the second low-pass filter in the first current sampling unit 102 is suitable for outputting the first conduction current of the main power switch tube to be tested during the junction temperature calibration process.

Since the first current sampling unit 102 and the second current sampling unit 302 are the same current sampling unit, the first conduction current tested in the junction temperature calibration process brings a determination error, and the second current tested in the online sampling process The conduction current also brings a determination error, so that the determination error in the second conduction current cancels the determination error in the first conduction current, so that the accuracy of the current test is improved, and the test junction temperature acquisition unit finally obtains The accuracy of junction temperature values has been improved.

It should be noted that, in other embodiments, the first current sampling unit and the second current sampling unit may be different sampling units.

In one embodiment, both the first current sampling unit 102 and the second current sampling unit 302 are composed of the current sampling internal module Q1. In this solution, the current sampling internal module in the power equipment module is used as the first current sampling unit 102 and the second current sampling unit 302, that is to say, the current sampling internal module is used to test and obtain the second current sampling unit 302 during the junction temperature calibration process. The first conduction current, the second conduction current is obtained by using the current sampling internal module test during the online sampling process. In this way, an additional module for sampling current needs to be provided, thus reducing the cost.

In one embodiment, the sampling error of the current sampling internal module Q1 is less than or equal to 3%. In this embodiment, even if the sampling error of the current sampling internal module Q1 is large, it can also achieve high sampling accuracy for the current, that is, the determination error of the first conduction current and the second conduction current In the process, it is compensated, so that the accuracy of the junction temperature value of the final test of the test junction temperature acquisition unit is improved.

In this embodiment, the first current sampling unit 102 includes an open-loop Hall current sensor; the second current sampling unit 302 includes an open-loop Hall current sensor.

In this embodiment, the junction temperature calibration module uses the forward injection current of the main power switch tube to be tested, and obtains the first conduction saturation voltage drop and the first conduction voltage drop of the main power switch tube to be tested in the offline state. The mapping relationship between the current and the junction temperature of the main power switch tube to be tested. The working sampling module is used to acquire the second conduction saturation voltage drop and the second conduction current of the main power switch tube to be tested online. The first voltage sampling unit in the junction temperature calibration module tests to obtain the first conduction saturation voltage drop. The second voltage sampling unit in the working sampling module is tested to obtain the second conduction saturation voltage drop. Since the first voltage sampling unit and the second voltage sampling unit both include: a first-stage op-amp unit connected to the main power switch tube to be tested; an amplitude modulation unit electrically connected to the first-stage op-amp unit, the The amplitude modulation unit includes a subtractor and a proportional amplifier, and the output terminal of the subtractor is connected to the input terminal of the proportional amplifier. In this way, no matter in the process of junction temperature calibration or online sampling, the subtractor can be used to remove the invalid range data, and then the data output by the subtractor can be amplified through the proportional amplifier, so that the first voltage sampling unit in the mapping relationship The resolution of the sampled first turn-on saturation voltage drop versus junction temperature is improved. The second on-saturation voltage drop is acquired by using the second voltage sampling unit, and the second voltage sampling unit has the same structure as the first voltage sampling unit. Since the resolution of the first conduction saturation voltage sampled by the first voltage sampling unit to the junction temperature in the mapping relationship is improved, the test junction temperature acquisition unit is used to obtain the second conduction saturation voltage drop and the second conduction saturation voltage. After the junction temperature value corresponding to the characteristic function relationship is passed through the current, the accuracy of the junction temperature acquired by the junction temperature acquisition unit is tested to be improved. Moreover, in this solution, there is no need to rely on a high-precision test voltage test instrument, so that the test cost is reduced. In summary, this solution takes into account both high test accuracy and low test cost.

Further, the first current sampling unit and the second current sampling unit are the same current sampling unit. The first conduction current tested during the junction temperature calibration process brings a certain error, and the second conduction current tested during the online sampling process also brings a certain error, so that the determination error in the second conduction current has a significant impact on the first A determination error in the conduction current is offset, so that the accuracy of the current test is improved, and thus the accuracy of the final junction temperature value obtained by the test junction temperature acquisition unit is improved.

Further, both the first current sampling unit and the second current sampling unit are composed of the current sampling internal module. In this solution, the current sampling internal module of the power equipment module is used as the first current sampling unit and the second current sampling unit, that is to say, the current sampling internal module is used to test and obtain the first current sampling unit during the junction temperature calibration process. During the online sampling process, the current sampling internal module test is used to obtain the second conduction current. In this way, there is no need to additionally arrange a module for sampling current, thus reducing the cost.

Correspondingly, another embodiment of the present invention also provides a high-precision junction temperature online monitoring method, referring to FIG. 10 , including the following steps:

S01: Use the junction temperature calibration module to inject forward current into the main power switch tube to be tested, and obtain the first conduction saturation voltage drop and the first conduction current of the main power switch tube to be tested in the offline state The mapping relationship between the junction temperature of the measured main power switch tube;

S02: Use the data fitting module to fit the data in the mapping relationship to obtain the characteristic function relationship, the characteristic function relationship takes the first conduction saturation voltage drop and the first conduction current as independent variables, and takes the to-be-measured The junction temperature of the main power switch tube is the dependent variable;

S03: Obtain the second conduction saturation voltage drop and the second conduction current of the main power switch tube to be tested online by using the working sampling module;

S04: Using the test junction temperature acquisition unit to obtain a junction temperature value corresponding to the second conduction saturation voltage drop and the second conduction current in the characteristic function relationship.

During the forward injection current process of the main power switch tube to be tested, the main power switch tube to be tested is suitable for being placed on the heating platform 64, and the junction temperature of the main power switch tube to be tested in the mapping relationship is determined by the heating Temperature calibration of platform 64 .

The working sampling module 30 is used to acquire the second conduction saturation voltage drop and the second conduction current of the main power switch tube to be tested online, specifically, the second voltage sampling unit 301 is used to acquire the main power switch tube to be tested online The second conduction saturation voltage drop V _CE2 is obtained online by using the second current sampling unit 302 to obtain the second conduction current _ID2 of the main power switch tube to be tested.

In one embodiment, both the first current sampling unit and the second current sampling unit are composed of the current sampling internal module, and both the first conduction current and the second conduction current adopt the current sampling internal module Test acquisition.

The current sampling internal module samples current for the main control module during a first characteristic period, and the current sampling internal module samples a second conduction current during a second characteristic period. The first characteristic period and the second characteristic period are spaced apart from each other. In this way, the data of the second conduction current and the current data sampled for the main control module do not interfere with each other.

Referring to FIG. 11 , during the working process of the power equipment module, the main control module 41 uses the carrier wave as the time standard to perform timing control. In this embodiment, the main power switch tube to be tested is the lower bridge, and the specific sixth main power switch tube is the lower bridge. Correspondingly, the fifth main power switch tube is the upper bridge of the sixth main power switch tube, and the upper bridge The timing sequence imposed on the upper bridge is opposite to the timing sequence imposed on the lower bridge. When the carrier overflow is interrupted, the main control module 41 performs relevant analog sampling and calculation; when the carrier underflow is interrupted, the sampling of the second conduction current is performed. During the second conduction current sampling process, the second conduction saturation voltage drop V _CE2 is sampled synchronously.

The converter circuit unit includes several half bridges, and each half bridge is composed of two main power switch tubes connected in series; in at least one half bridge, when one main power switch tube is used as the main power switch tube to be tested, the other The main power switch tube is used as the opposite tube of the main power switch tube to be tested. When the power equipment module is in the working state, alternate first high level and first low level are applied to the pair of main power switch tubes to be tested. The first characteristic period has a first start moment, and the first start moment is selected as an intermediate moment of the time period corresponding to any first high level.

When the power equipment module is in the working state, alternate second high level and second low level are applied to the main power switch tube to be tested; the second characteristic period has a second starting moment, and the second starting moment is selected The middle moment of the time period corresponding to any second high level.

When the second high level is applied to the main power switch tube to be tested, the first low level is applied to the opposite tube of the main power switch tube to be tested, and the second low level is applied to the main power switch tube to be tested. Usually, a first high level is applied to the pair of the main power switch tubes to be tested.

In this embodiment, the accuracy of the junction temperature value finally output by the test junction temperature acquisition unit is relatively high. In a specific embodiment, the resolution of the junction temperature value finally output by the test junction temperature acquisition unit is less than or equal to 1 °C, such as 0.8 °C, 1 °C.

Another embodiment of the present invention also provides an online working sampling circuit, including: a second voltage sampling unit and a second current sampling unit, and the second voltage sampling unit is suitable for obtaining the second voltage of the main power switch tube to be tested online. Turn-on saturation voltage drop, the second current sampling unit is adapted to obtain the second conduction current of the main power switch tube to be tested online; the second voltage sampling unit includes: used to connect with the main power switch tube to be tested A first-stage operational amplifier unit; an amplitude modulation unit electrically connected to the first-stage operational amplifier unit, the amplitude modulation unit includes a subtractor and a proportional amplifier with adjustable transformation ratio, the voltage of the reference voltage terminal of the subtractor is adjustable, The output terminal of the subtractor is connected with the input terminal of the proportional amplifier.

The voltage at the output terminal of the subtractor is equal to the voltage at the input terminal of the subtractor minus the voltage at the reference voltage terminal.

The second voltage sampling unit also includes: a first low-pass filter, the input end of the first low-pass filter is connected to the output end of the first-stage operational amplifier unit, and the first low-pass filter The output terminal of the device is connected with the input terminal of the subtractor.

In one embodiment, the first-stage operational amplifier unit includes a first current-voltage conversion operational amplifier, a bias current source, a seventh diode, an eighth diode, a ninth diode, a first resistor and the second resistor, the positive input terminal of the first current-voltage conversion operational amplifier is connected to the positive connection terminal of the seventh diode, the negative connection terminal of the eighth diode, and the positive connection terminal of the ninth diode Connecting end; the positive connecting end of the eighth diode is connected to the negative connecting end of the ninth diode, one end of the first resistor and the bias current source, and the other end of the first resistor is connected to the first current-voltage conversion operational amplifier The negative input end of the device and one end of the second resistor, the other end of the second resistor is connected to the output end of the first current-voltage conversion operational amplifier, and the negative connection end of the seventh diode is used as the first-stage operational amplifier unit The input terminal and the output terminal of the first current-to-voltage conversion operational amplifier serve as the output terminal of the first-stage operational amplifier unit.

In one embodiment, the resistance of the first resistor is equal to the resistance of the second resistor.

In one embodiment, the conduction voltage drop of the eighth diode is equal to the conduction voltage drop of the seventh diode.

In one embodiment, the distance between the eighth diode and the seventh diode is less than or equal to 10 mm.

In one embodiment, the second voltage sampling unit further includes: an analog signal isolation unit, an input terminal of the analog signal isolation unit is connected to an output terminal of the proportional amplifier.

In one embodiment, the second voltage sampling unit also includes: a current discharge unit connected to the first-stage operational amplifier unit, and the current discharge unit is suitable for switching off the main power switch to be tested. Discharging the current in the first-stage operational amplifier unit when it is off.

In one embodiment, the current drain unit includes a MOS transistor.

In one embodiment, the second current sampling unit is also used to calibrate the first conduction saturation voltage drop of the main power switch to be tested in an offline state.

In one embodiment, the main power switch tube to be tested is a working element of a power equipment module, and the power equipment module includes a converter circuit unit, a current sampling internal module and a main control module, and the converter circuit The unit includes several main power switch tubes, the output terminal of the current sampling internal module is suitable for connecting to the input terminal of the main control module, and the output terminal of the main control module is suitable for supplying the main power in the converter circuit unit The switching tube provides working timing. The second current sampling unit is composed of the current sampling internal module.

Regarding the online working sampling circuit of the embodiment, refer to the content of the aforementioned working sampling module, and will not be described again.

Apparently, the above-mentioned embodiments are only examples for clear description, rather than limiting the implementation. For those of ordinary skill in the art, other changes or changes in different forms can be made on the basis of the above description. It is not necessary and impossible to exhaustively list all the implementation manners here. And the obvious changes or changes derived therefrom are still within the scope of protection of the present invention.

Claims (12)

1. An online working sampling circuit, characterized in that, comprising: A second voltage sampling unit and a second current sampling unit, the second voltage sampling unit is adapted to acquire the second conduction saturation voltage drop of the main power switch tube to be tested online, and the second current sampling unit is adapted to acquire online The second conduction current of the main power switch tube to be tested; The second voltage sampling unit includes: a first-stage op-amp unit used to be connected to the main power switch tube to be tested; an amplitude modulation unit electrically connected to the first-stage op-amp unit, and the amplitude modulation unit includes a subtractor and a transformer A ratio-adjustable proportional amplifier, the voltage of the reference voltage terminal of the subtractor is adjustable, and the output terminal of the subtractor is connected to the input terminal of the proportional amplifier. 2. The online working sampling circuit according to claim 1, wherein the voltage at the output terminal of the subtractor is equal to the voltage at the input terminal of the subtractor minus the voltage at the reference voltage terminal. 3. The online working sampling circuit according to claim 1, wherein the second voltage sampling unit also includes: a first low-pass filter, the input terminal of the first low-pass filter is connected to the The output terminal of the first-stage op-amp unit is connected, and the output terminal of the first low-pass filter is connected with the input terminal of the subtractor. 4. online work sampling circuit according to claim 1, is characterized in that, described first stage op-amp unit comprises the first current-voltage conversion op-amp, bias current source, the 7th diode, the 82nd pole tube, the ninth diode, the first resistor and the second resistor, the positive input terminal of the first current-voltage conversion operational amplifier is connected to the positive connection terminal of the seventh diode, the negative terminal of the eighth diode To the connection terminal, the positive connection terminal of the ninth diode; the positive connection terminal of the eighth diode is connected to the negative connection terminal of the ninth diode, one end of the first resistor and the bias current source, the first The other end of the resistor is connected to the negative input terminal of the first current-voltage conversion operational amplifier and one terminal of the second resistor, the other end of the second resistor is connected to the output terminal of the first current-voltage conversion operational amplifier, and the seventh diode The negative connection terminal is used as the input terminal of the first-stage operational amplifier unit, and the output terminal of the first current-voltage conversion operational amplifier is used as the output terminal of the first-stage operational amplifier unit. 5. The online working sampling circuit according to claim 4, wherein the resistance value of the first resistor is equal to the resistance value of the second resistor. 6. The online working sampling circuit according to claim 4 or 5, characterized in that the conduction voltage drop of the eighth diode is equal to the conduction voltage drop of the seventh diode. 7. The online working sampling circuit according to claim 4 or 5, characterized in that the distance between the eighth diode and the seventh diode is less than or equal to 10 mm. 8. The online working sampling circuit according to any one of claims 1 to 4, wherein the second voltage sampling unit further comprises: an analog signal isolation unit, the input terminal of the analog signal isolation unit is connected to the Proportional amplifier output connection. 9. The online working sampling circuit according to any one of claims 1 to 4, wherein the second voltage sampling unit further comprises: a current discharge unit connected to the first-stage operational amplifier unit, The current discharge unit is adapted to discharge the current in the first-stage operational amplifier unit when the main power switch tube to be tested is turned off. 10. The online working sampling circuit according to claim 9, characterized in that, the current discharge unit comprises a MOS transistor. 11. The on-line working sampling circuit according to claim 1, wherein the second current sampling unit is also used to calibrate the first conduction saturation voltage drop of the main power switch tube to be tested in an offline state. 12. The online working sampling circuit according to claim 1, wherein the main power switch tube to be tested is a working element of a power equipment module, and the power equipment module includes a converter circuit unit, a current sampling internal module and a main control module, the converter circuit unit includes several main power switch tubes, the output terminal of the current sampling internal module is suitable for connecting to the input terminal of the main control module, and the output terminal of the main control module is suitable for To provide working timing for each main power switch tube in the converter circuit unit; The second current sampling unit is composed of the current sampling internal module.

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