Hybrid sensing system for measuring switching voltage and switching current of power devices

Abstract

The present invention is a hybrid sensing system for measuring the switching voltage and switching current of a power device, including a power device driving circuit, a power circuit, a sensing element, an electric coupling signal processing circuit, a magnetic coupling signal processing circuit, an instrument operational amplifier circuit, an oscilloscope and multiple load resistors; a copper trace is used as the sensing end of the sensing element, and when the system is used to simultaneously measure the switching voltage and switching current of the power device, the sensing element is installed near the drain of the power device, and the sensing end of the sensing element is parallel to the drain lead of the power device, and a coupling capacitor is formed between the two; the output end of the sensing element is respectively connected to the electric coupling signal processing circuit and the instrument operational amplifier circuit, the instrument operational amplifier circuit is connected to the magnetic coupling signal processing circuit, and the electric coupling signal processing circuit and the magnetic coupling signal processing circuit are both connected to the oscilloscope. Non-contact measurement is achieved through the principle of electromagnetic coupling, and low intrusion and easy integration of current and voltage sensing technology are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of electromagnetic sensing, and in particular is a hybrid sensing system for measuring a switching voltage and a switching current of a power device. Background Art

[0002] Power semiconductor devices are the core of power electronic devices to achieve power conversion and circuit control. Their main uses include frequency conversion, rectification, voltage conversion, power amplification, power control, etc. Power semiconductor devices are widely used in many fields such as mobile communications, rail transportation, and new energy generation. With the continuous development of power semiconductor devices, their switching characteristics have attracted more and more attention. Switching voltage and current are the most basic parameters for analyzing the switching characteristics of power semiconductor devices, and are important prerequisites for power device switching loss calculation, life prediction, and real-time control. Therefore, accurate measurement of switching voltage and current is of great significance to give full play to the excellent performance of power devices and improve the operating reliability of power electronic devices.

[0003] With the rapid development of the third-generation power semiconductor technology, new challenges have been raised for voltage and current sensing technology, including low intrusion and easy integration.

[0004] 1) Low intrusion: The third generation of power semiconductor devices has a faster switching speed. The voltage and current change rate is large at the moment of opening and closing, which can easily cause excessive voltage spikes on the parasitic inductance of the switching circuit, thereby threatening the power device. Therefore, the sensor element needs to have a smaller insertion impedance and less intrusion on the original circuit. However, the existing voltage and current sensing technology is mainly based on contact measurement, that is, the sensor element is connected to the circuit to measure the voltage and current of the power device. The sensor element connected to the circuit will introduce a certain insertion inductance, which will affect the original circuit layout and the accuracy of the measurement results.

[0005] 2) Easy integration: With the rapid development of the third-generation power semiconductor technology, the demand for high power density of power electronic devices is getting higher and higher. Independently set sensor elements need to occupy more space in the device, which wastes space utilization and greatly increases manufacturing costs. Therefore, small size and easy integration are the development direction of sensing technology.

[0006] Traditional voltage sensing technology is mainly based on oscilloscope probes, such as differential voltage probes, passive differential probes, and optical isolation probes. Oscilloscope probes can meet the high-bandwidth and large-range measurement requirements of power devices, but oscilloscope probes often have a large volume, which is not conducive to integration in power electronic devices. Traditional current sensing technology is mainly based on Hall current sensors, which are currently the most widely used current sensors and are widely used in power electronic devices to collect system current information. However, with the rapid development of the third-generation power semiconductor technology, the trend of high power density and high switching speed makes it difficult for Hall current sensors to meet measurement requirements. In addition, coaxial shunts, magnetoresistive sensors, etc. are also used to sense current, but these sensors cannot simultaneously meet the measurement requirements of high bandwidth, low intrusion, and small volume.

[0007] In summary, the present application proposes a hybrid sensing system for measuring the switching voltage and switching current of power devices in response to the low-intrusion and easy-integration requirements of the third-generation power semiconductor devices for voltage and current sensing technology. Summary of the invention

[0008] In view of the deficiencies in the prior art, the technical problem to be solved by the present invention is to provide a hybrid sensing system for measuring the switching voltage and switching current of a power device.

[0009] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0010] A hybrid sensing system for measuring the switching voltage and switching current of a power device, characterized in that the system comprises a power device driving circuit, a power circuit, a sensing element, an electric coupling signal processing circuit, a magnetic coupling signal processing circuit, an instrument operational amplifier circuit, an oscilloscope and a plurality of load resistors; the power device driving circuit is connected to the power circuit, a power device is arranged in the power circuit, and a copper trace is used as the sensing end of the sensing element;

[0011] When the system is used to simultaneously measure the switching voltage and switching current of a power device, the sensing element is installed near the drain of the power device, the sensing end of the sensing element is parallel to the drain lead of the power device, and a coupling capacitor is formed between the sensing end of the sensing element and the drain lead of the power device; a load resistor R is connected between the two output ends of the sensing element. m4 At the same time, any output terminal of the sensor element is connected to the load resistor R m3 Connect the load resistor R m3 grounded; the output end of the sensing element is respectively connected to the electric coupling signal processing circuit and the instrument operational amplifier circuit, the instrument operational amplifier circuit is connected to the magnetic coupling signal processing circuit, and the electric coupling signal processing circuit and the magnetic coupling signal processing circuit are both connected to the oscilloscope;

[0012] Firstly, power is supplied to the power device driving circuit, the electric coupling signal processing circuit, and the magnetic coupling processing circuit, then power is supplied to the power circuit, and finally a driving signal is applied to the power device driving circuit;

[0013] The frequency domain response of the sensing element voltage sensing satisfies the following formula:

[0014]

[0015] Where s represents the frequency domain; u1′(s), u ou ′(s) respectively represent the drain voltage of the power element and the output voltage of the sensing element when the switching voltage and switching current of the power device are measured simultaneously; C couple ' represents the coupling capacitance formed between the sensing end of the sensing element and the drain of the power device when the switching voltage and switching current of the power device are measured simultaneously, and its size is:

[0016]

[0017] In the formula, ε r is the dielectric constant of the medium, k is the electrostatic force constant; h3 and w' respectively represent the wiring length and wiring width of the sensing end of the sensing element when the switching voltage and switching current of the power device are measured simultaneously, and l4 is the distance between the drain lead of the power device and the sensing end of the sensing element;

[0018] When measuring the switching voltage and switching current of a power device at the same time, the frequency domain response of the current sensing of the sensing element satisfies the following equation:

[0019]

[0020] In formula (6), i1′(s), u oi ′(s) respectively represent the current flowing through the drain lead of the power device and the output voltage of the sensing element when the switching voltage and switching current of the power device are measured simultaneously, l5 is the voltage between the sensing end of the sensing element and the load resistance R m4 The distance between them; M is the mutual inductance, μ0 is the vacuum permeability;

[0021] The output voltage u of the sensor element ou ′(s) is integrated and amplified by the electric coupling signal processing circuit, and the current sensing u of the sensing element oi ′(s) is integrated and amplified by a magnetic coupling signal processing circuit. The two amplified signals are displayed in real time on an oscilloscope. The switching voltage and switching current of the power device are characterized by setting the sensitivity of the oscilloscope.

[0022] When the system is used to measure the switching voltage of a power device, the sensor element is installed near the drain of the power device. The sensing end of the sensor element is parallel to the drain lead of the power device. A coupling capacitor is formed between the sensing end of the sensor element and the drain of the power device. The output end of the sensor element is connected to the load resistor R m1 One end of the load resistor R m1 The other end is grounded; the electrically coupled signal processing circuit is connected to the output end of the sensor element and the oscilloscope respectively, and the switching voltage of the power device is characterized by setting the sensitivity of the oscilloscope;

[0023] The frequency domain response of the sensing element voltage sensing satisfies the following formula:

[0024]

[0025] Among them, u1(s), u ou (s) respectively represent the drain voltage of the power element and the output voltage of the sensing element when measuring the switching voltage of the power device; C couple It indicates that when measuring the switching voltage of a power device, the coupling capacitance formed between the sensing end of the sensing element and the drain of the power device is:

[0026]

[0027] Among them, h1 and w represent the wiring length and wiring width of the sensing end of the sensor element when measuring the switching voltage of the power device, respectively, and l1 is the distance between the drain lead of the power device and the sensing end of the sensor element.

[0028] When the system is used to measure the switching current of a power device, the sensor element is installed near the source of the power device, the sensing end of the sensor element is parallel to the source lead of the power device, and a load resistor R is connected between the two output ends of the sensor element. m2 ; The magnetic coupling signal processing circuit is connected to the output end of the sensor element and the oscilloscope respectively, and the switching current of the power device is characterized by setting the sensitivity of the oscilloscope;

[0029] The frequency domain response of the current sensing of the sensing element is as follows;

[0030]

[0031] In the formula, u oi (s), i1(s) represent the output voltage of the sensor element and the current flowing through the source lead of the power device when measuring the switching current of the power device, respectively. h2 is the wiring length of the sensing end of the sensor element. l2 represents the distance between the source lead of the power device and the sensing end of the sensor element. l3 represents the distance between the sensing end of the sensor element and the load resistor R m2 The distance between.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. This measurement system installs the sensor element near the power device, energizes the sensor element and the power device, and uses the electromagnetic coupling principle to indirectly characterize the switching voltage and switching current information of the power device by measuring the changes in the electric field and magnetic field, thereby realizing non-contact measurement. Compared with the traditional contact measurement method of connecting the sensor element to the original circuit, the present invention greatly reduces the impact of the inserted inductor on the original circuit, avoids the problem of the sensor element causing interference to the original circuit, and realizes low interference of current and voltage sensing technology.

[0034] 2. The measurement system can sense the switch voltage and switch current separately, and can also receive the electric field signal and magnetic field signal generated by the primary side circuit at the same time, realizing the function of a sensor element to measure voltage and current signals at the same time, thereby greatly reducing the volume of the sensor element. In addition, the sensor element can be integrated on the printed circuit board using printed circuit board technology to form a whole with the driver board of the power device, realizing the integrated design of the sensor element and the driver board, and promoting the development of power electronic devices towards high power density and integration. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The schematic diagram of the system is shown below;

[0036] Figure 2 A block diagram for measuring the switching voltage of a power device;

[0037] Figure 3 It is the schematic diagram of the electrical coupling between the sensing end of the sensor element and the drain of the power device;

[0038] Figure 4 A block diagram for measuring the switching current of a power device;

[0039] Figure 5 It is the principle diagram of magnetic coupling between the source of the power device and the sensing end of the sensor element;

[0040] Figure 6 A structural block diagram for simultaneously measuring the switching voltage and switching current of a power device;

[0041] Figure 7 This is the schematic diagram of the electromagnetic coupling between the sensing end of the sensor element and the drain of the power device. DETAILED DESCRIPTION

[0042] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments, but this is not intended to limit the scope of protection of the present application.

[0043] The present invention is a hybrid sensing system (referred to as the system) for measuring the switching voltage and switching current of a power device, the system comprising a power device driving circuit, a power circuit, a sensing element, an electric coupling signal processing circuit, a magnetic coupling signal processing circuit, an instrument operational amplifier circuit, an oscilloscope and a plurality of load resistors; the power device driving circuit is connected to the power circuit, a power device is arranged in the power circuit, and a copper trace is used as the sensing end of the sensing element;

[0044] Figure 1 This is the schematic diagram of the system. The sensor element uses the electromagnetic coupling principle to sense the voltage at both ends of the power device and the current flowing through it. The output voltage of the sensor element is integrated and amplified by the electric coupling signal processing circuit, thereby obtaining a voltage signal proportional to the measured voltage to represent the switching voltage of the power device; similarly, the output circuit of the sensor element is processed by the magnetic coupling signal processing circuit, thereby obtaining a voltage signal proportional to the measured current to represent the switching current of the power device;

[0045] When the system is used to measure the switching voltage of a power device, such as Figure 2 As shown, the sensing element is installed near the drain of the power device, the sensing end of the sensing element is parallel to the drain lead of the power device, and a coupling capacitor is formed between the sensing end of the sensing element and the drain of the power device; the output end of the sensing element is connected to the load resistor R m1 One end of the load resistor R m1 The other end of the load resistor R m1 Used to receive the output signal of the sensor element; the electrically coupled signal processing circuit is connected to the output end of the sensor element and the oscilloscope through a coaxial transmission line, and the oscilloscope is used to display the measured switching voltage of the power device in real time;

[0046] First, power is supplied to the power device driving circuit and the electrically coupled signal processing circuit; second, power is supplied to the power circuit, and finally, a driving signal is applied to the power device driving circuit to ensure that all circuits work normally;

[0047] Figure 3 The schematic diagram of the electrical coupling between the sensing end of the sensor element and the drain of the power device is shown in Figure 2. Based on this, the frequency domain response of the voltage sensing of the sensor element is:

[0048]

[0049] Among them, s represents the frequency domain, u1(s), u ou (s) respectively represent the drain voltage of the power element and the output voltage of the sensing element when measuring the switching voltage of the power device, C couple is the coupling capacitor, and its size is:

[0050]

[0051] Among them, ε r is the dielectric constant of the medium, k is the electrostatic force constant, h1 and w are the length and width of the line at the sensing end of the sensor element, respectively, and l1 is the distance between the drain lead of the power device and the sensing end of the sensor element;

[0052] From equation (1), it can be seen that the frequency response of the voltage sensing of the sensor element is a first-order high-pass, and the medium frequency f1 = 1 / (2πR m1 C couple ), due to the coupling capacitor C couple It is often very small, resulting in a large cutoff frequency value, so the voltage sensing of the sensing element exhibits differential characteristics within the normal working frequency band;

[0053] The electrically coupled signal processing circuit integrates and amplifies the output voltage of the sensor element; the amplified voltage signal is connected to the oscilloscope through the coaxial transmission line, and the switching voltage of the power device is characterized by setting the sensitivity of the oscilloscope to complete the measurement of the switching voltage of the power device. The oscilloscope displays the switching voltage of the power device in real time.

[0054] The electrically coupled signal processing circuit belongs to the prior art, and includes an active analog circuit, an operational amplifier circuit and a two-terminal power supply circuit; a high-performance operational amplifier circuit is used to ensure the sampling speed and bandwidth of the electrically coupled signal processing circuit; due to the existence of parasitic inductance, during the switching process of the power device, there will often be large voltage / current oscillations and negative voltage / current, so a two-terminal power supply circuit is used to power the operational amplifier to obtain a complete voltage waveform of the power device.

[0055] When the system is used to measure the switching current of a power device, such as Figure 4 As shown, the sensor element is installed near the source of the power device, the sensing end of the sensor element is parallel to the source lead of the power device, and a load resistor R is connected between the two output ends of the sensor element. m2 to receive the output signal; the magnetic coupling signal processing circuit is connected to the output end of the sensor element and the oscilloscope through a coaxial transmission line;

[0056] First, power is supplied to the power device driving circuit and the magnetic coupling signal processing circuit, then power is supplied to the power circuit, and finally a driving signal is applied to the power device driving circuit to ensure that all circuits work normally;

[0057] Figure 5 is the magnetic coupling principle diagram between the source of the power device and the sensing end of the sensor element; according to Ampere's loop law and Faraday's law of electromagnetic induction, the frequency domain response of the current sensing of the sensor element is calculated by formula (3);

[0058]

[0059] In the formula, u oi (s), i1(s) represent the output voltage of the sensor element and the current flowing through the source lead of the power device when measuring the switching current of the power device, respectively. M is the mutual inductance coefficient, μ0 is the vacuum magnetic permeability, h2 is the wiring length of the sensing end of the sensor element, l2 represents the distance between the source lead of the power device and the sensing end of the sensor element, and l3 represents the distance between the sensing end of the sensor element and the load resistance R m2 The distance between them; From formula (3), it can be seen that the frequency response of the current sensing of the sensor element presents a differential characteristic;

[0060] The output voltage of the sensor element is integrated and amplified by a magnetic coupling signal processing circuit. The magnetic coupling signal processing circuit belongs to the prior art and will not be described in detail here. The amplified voltage signal is displayed on an oscilloscope. By setting the sensitivity of the oscilloscope to characterize the switching current of the power device, the switching current of the power device can be measured.

[0061] When the system is used to simultaneously measure the switching voltage and switching current of a power device, such as Figure 6 As shown, the sensing element is installed near the drain of the power device, the sensing end of the sensing element is parallel to the drain lead of the power device, and a coupling capacitor is formed between the sensing end of the sensing element and the drain lead of the power device; a load resistor R is connected between the two output ends of the sensing element m4 At the same time, any output terminal of the sensor element is connected to the load resistor R m3 Connect the load resistor R m3 grounding; the output end of the sensing element is respectively connected to the electric coupling signal processing circuit and the instrument operational amplifier circuit through a coaxial transmission line, the instrument operational amplifier circuit is connected to the magnetic coupling signal processing circuit, and the electric coupling signal processing circuit and the magnetic coupling signal processing circuit are respectively connected to the oscilloscope through a coaxial transmission line; since the measuring point is at the drain level of the power device, and the drain level often has a large common mode voltage, the instrument operational amplifier circuit is used to minimize the influence of the common mode signal on the measurement result, and the instrument operational amplifier circuit belongs to the prior art;

[0062] First, power is supplied to the power device driving circuit, the electric coupling signal processing circuit, and the magnetic coupling processing circuit. Then, power is supplied to the power circuit. Finally, a driving signal is applied to the power device driving circuit to ensure that all circuits work normally.

[0063] Figure 7 The electromagnetic coupling principle diagram between the sensing end of the sensor element and the drain of the power device. The frequency domain response of the voltage sensing of the sensor element is:

[0064]

[0065] Among them, u1′(s), u ou′(s) respectively represent the drain voltage of the power element and the output voltage of the sensing element when the switching voltage and switching current of the power device are measured simultaneously, C couple ' is the coupling capacitance formed between the sensing end of the sensor element and the drain of the power device, and its size is:

[0066]

[0067] Wherein, h3 and w' respectively represent the length and width of the sensing end of the sensing element when measuring the switching voltage and switching current of the power device at the same time, and l4 is the distance between the drain lead of the power device and the sensing end of the sensing element;

[0068] When measuring the switching voltage and switching current of a power device simultaneously, the frequency domain response of the current sensing of the sensing element is:

[0069]

[0070] In formula (6), i1′(s), u oi ′(s) respectively represent the current flowing through the drain lead of the power device and the output voltage of the sensing element when the switching voltage and switching current of the power device are measured simultaneously, l5 is the voltage between the sensing end of the sensing element and the load resistance R m4 The distance between

[0071] From equations (4) and (6), it can be seen that within the normal working frequency band, the voltage sensing and current sensing of the sensing element both exhibit differential characteristics;

[0072] The output voltage u of the sensor element ou ′(s) is integrated and amplified by the electric coupling signal processing circuit, and the current sensing u of the sensing element oi ′(s) is integrated and amplified by a magnetic coupling signal processing circuit. The two amplified signals are displayed in real time on an oscilloscope. The switching voltage and switching current of the power device are characterized by setting the sensitivity of the oscilloscope.

[0073] Any matters not described in the present invention are applicable to the prior art.

Claims

1. A hybrid sensing system for measuring switching voltage and switching current of a power device, characterized in that: The system includes a power device driving circuit, a power circuit, a sensing element, an electric coupling signal processing circuit, a magnetic coupling signal processing circuit, an instrument operational amplifier circuit, an oscilloscope and a plurality of load resistors; the power device driving circuit is connected to the power circuit, a power device is arranged in the power circuit, and a copper trace is used as the sensing end of the sensing element; When the system is used to simultaneously measure the switching voltage and switching current of a power device, the sensing element is installed near the drain of the power device, the sensing end of the sensing element is parallel to the drain lead of the power device, and a coupling capacitor is formed between the sensing end of the sensing element and the drain lead of the power device; a load resistor R is connected between the two output ends of the sensing element. m4 At the same time, any output terminal of the sensor element is connected to the load resistor R m3 Connect the load resistor R m3 grounded; the output end of the sensing element is respectively connected to the electric coupling signal processing circuit and the instrument operational amplifier circuit, the instrument operational amplifier circuit is connected to the magnetic coupling signal processing circuit, and the electric coupling signal processing circuit and the magnetic coupling signal processing circuit are both connected to the oscilloscope; Firstly, power is supplied to the power device driving circuit, the electric coupling signal processing circuit, and the magnetic coupling processing circuit, then power is supplied to the power circuit, and finally a driving signal is applied to the power device driving circuit; The frequency domain response of the sensing element voltage sensing satisfies the following formula: Where s represents the frequency domain; u1′(s), u ou ′(s) respectively represent the drain voltage of the power element and the output voltage of the sensing element when the switching voltage and switching current of the power device are measured simultaneously; C couple ' represents the coupling capacitance formed between the sensing end of the sensing element and the drain of the power device when the switching voltage and switching current of the power device are measured simultaneously, and its size is: In the formula, ε r is the dielectric constant of the medium, k is the electrostatic force constant; h3 and w' respectively represent the wiring length and wiring width of the sensing end of the sensing element when the switching voltage and switching current of the power device are measured simultaneously, and l4 is the distance between the drain lead of the power device and the sensing end of the sensing element; When measuring the switching voltage and switching current of a power device at the same time, the frequency domain response of the current sensing of the sensing element satisfies the following equation: In formula (6), i1′(s), u oi ′(s) respectively represent the current flowing through the drain lead of the power device and the output voltage of the sensing element when the switching voltage and switching current of the power device are measured simultaneously, l5 is the difference between the sensing end of the sensing element and the load resistance R m4 The distance between them; M is the mutual inductance, μ0 is the vacuum permeability; The output voltage u of the sensor element ou ′(s) is integrated and amplified by the electric coupling signal processing circuit, and the current sensing u of the sensing element oi ′(s) is integrated and amplified by a magnetic coupling signal processing circuit. The two amplified signals are displayed in real time on an oscilloscope. The switching voltage and switching current of the power device are characterized by setting the sensitivity of the oscilloscope.

2. The hybrid sensing system for measuring the switching voltage and switching current of a power device according to claim 1, characterized in that: When the system is used to measure the switching voltage of a power device, the sensor element is installed near the drain of the power device. The sensing end of the sensor element is parallel to the drain lead of the power device. A coupling capacitor is formed between the sensing end of the sensor element and the drain of the power device. The output end of the sensor element is connected to the load resistor R m1 One end of the load resistor R m1 The other end is grounded; the electrically coupled signal processing circuit is connected to the output end of the sensor element and the oscilloscope respectively, and the switching voltage of the power device is characterized by setting the sensitivity of the oscilloscope; The frequency domain response of the sensing element voltage sensing satisfies the following formula: Among them, u1(s), u ou (s) respectively represent the drain voltage of the power element and the output voltage of the sensing element when measuring the switching voltage of the power device; C couple It indicates that when measuring the switching voltage of a power device, the coupling capacitance formed between the sensing end of the sensing element and the drain of the power device is: Among them, h1 and w represent the wiring length and wiring width of the sensing end of the sensor element when measuring the switching voltage of the power device, respectively, and l1 is the distance between the drain lead of the power device and the sensing end of the sensor element.

3. The hybrid sensing system for measuring the switching voltage and switching current of a power device according to claim 1, characterized in that: When the system is used to measure the switching current of a power device, the sensor element is installed near the source of the power device, the sensing end of the sensor element is parallel to the source lead of the power device, and a load resistor R is connected between the two output ends of the sensor element. m2 ; The magnetic coupling signal processing circuit is connected to the output end of the sensor element and the oscilloscope respectively, and the switching current of the power device is characterized by setting the sensitivity of the oscilloscope; The frequency domain response of the current sensing of the sensing element is as follows: In the formula, u oi (s), i1(s) represent the output voltage of the sensor element and the current flowing through the source lead of the power device when measuring the switching current of the power device, respectively. h2 is the wiring length of the sensing end of the sensor element. l2 represents the distance between the source lead of the power device and the sensing end of the sensor element. l3 represents the distance between the sensing end of the sensor element and the load resistor R m2 The distance between.

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