A constant current source for transient thermal testing of semiconductor devices

Abstract

The application discloses a constant current source for transient thermal test of a semiconductor device, and relates to the technical field of transient thermal test. The constant current source comprises a DCDC isolation power supply, an LDO voltage reduction module, a high-precision voltage reference module, a polarity conversion module, a 25.5MA-grade current source module, a 2A-grade current source module, a large / small current switching module and a BNC interface output module. The application can keep high precision under large current output, and can realize quick switching between large and small currents, so as to meet the requirements of transient thermal test.

Description

A constant current source for transient thermal testing of semiconductor devices Technical Field

[0001] This invention relates to the field of transient thermal testing technology, and in particular to a constant current source for transient thermal testing of semiconductor devices. Background Technology

[0002] In recent decades, the power levels of electronic systems have been continuously increasing. In electric and hybrid vehicles, 100 amps of current are switched at kilowatts of power, and trains even use kiloamps. Furthermore, power density has also increased. For example, a mobile phone typically generates only a few watts of electricity, but in the absence of ventilation, the temperature of its internal components can rapidly change from sub-zero outdoor temperatures to above 100°C. Therefore, characterizing the system's heat dissipation capacity has become a primary concern during the design phase. Additionally, thermal measurements are required during manufacturing and final failure analysis.

[0003] In power electronics, heat source devices are typically semiconductor devices, or more precisely, a thin dissipation layer within the semiconductor device. In many cases, a forward-biased pn junction exists within the semiconductor device; therefore, the heat source is traditionally referred to as a "junction." Since all parameters of a semiconductor device are temperature-dependent, this junction can also be used as a sensor. This allows for the recording of temperature changes at the hottest points within the semiconductor device structure. Although any power distribution over time can cause temperature transients, for simplicity, a power step—the instantaneous change between two power levels—is typically applied as the excitation. The temperature transient response to the power step is a transient change at a given time, the magnitude of which is influenced by the semiconductor device structure along the heat conduction path. In this way, a wealth of information about the semiconductor device structure can be obtained by evaluating the temperature transient profile. Due to the temperature dependence of the aforementioned parameters, rapidly generating stable power is a challenging task. Summary of the Invention

[0004] In view of this, the present invention provides a constant current source for transient thermal testing of semiconductor devices.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] A constant current source for transient thermal testing of semiconductor devices includes: a DC-DC isolated power supply and an LDO step-down module, a high-precision voltage reference module, a polarity conversion module, a 25.5mA current source module, a 2A current source module, a large and small current switching module, and a BNC interface output module.

[0007] The output terminals of the DC-DC isolated power supply and the LDO step-down module are respectively connected to the input terminal of the high-precision voltage reference module and the input terminal of the polarity conversion module;

[0008] The output terminal of the high-precision voltage reference module is connected to the input terminal of the 25.5mA range current source module and the input terminal of the 2A range current source module, respectively.

[0009] The output terminal of the polarity conversion module is connected to the input terminal of the 25.5mA current source module and the input terminal of the 2A current source module, respectively.

[0010] The output terminals of the 25.5mA current source module and the 2A current source module are both connected to the input terminal of the large and small current switching module.

[0011] The output terminal of the large and small current switching module is connected to the input terminal of the BNC interface output module.

[0012] Optionally, the 25.5mA current source module includes: a PWM and level input module, a high-speed and high-precision isolated level conversion module, a Butterworth analog quantity conversion module, a 50% turn-on threshold setting module, an adder accumulation data and error module, and a current output module;

[0013] The PWM and level input module is used to receive the enable signal and level signal from the FPGA; the output terminal of the PWM and level input module is connected to the first input terminal of the high-speed, high-precision isolated level conversion module; the output terminal of the high-precision voltage reference module is connected to the second input terminal of the high-speed, high-precision isolated level conversion module.

[0014] The output of the high-speed, high-precision isolated level conversion module is connected to the input of the Butterworth analog-to-digital converter module; the output of the Butterworth analog-to-digital converter module is connected to the first input of the current output module; the output of the adder accumulation data and error module is connected to the second input of the current output module; and the output of the 50% activation threshold setting module is connected to the first input of the adder accumulation data and error module.

[0015] Optionally, the first input terminal of the current output module is used as the first output terminal and connected to the second input terminal of the adder accumulation data and error module to form a closed-loop negative feedback.

[0016] Optionally, the 2A current source module includes: a PWM and level input module, a high-speed and high-precision isolated level conversion module, a Butterworth analog quantity conversion module, a 50% turn-on threshold setting module, an adder accumulation data and error module, a current output module, and a drive amplifier circuit module;

[0017] The PWM and level input module is used to receive the enable signal and level signal from the FPGA; the output terminal of the PWM and level input module is connected to the first input terminal of the high-speed, high-precision isolated level conversion module; the output terminal of the high-precision voltage reference module is connected to the second input terminal of the high-speed, high-precision isolated level conversion module.

[0018] The output of the high-speed, high-precision isolation level conversion module is connected to the input of the Butterworth analog-to-digital converter module; the output of the Butterworth analog-to-digital converter module is connected to the first input of the current output module; the output of the adder accumulation data and error module is connected to the second input of the current output module; the output of the 50% threshold setting module is connected to the input of the adder accumulation data and error module; and the second output of the current output module is connected to the input of the drive amplifier circuit module.

[0019] Optionally, the DC-DC isolated power supply and LDO buck module include at least: a 24V to 12V isolated DC / DC converter and a three-pin positive voltage regulator;

[0020] The 24V to 12V isolated DC / DC converter is used to convert 24V voltage to 12V voltage;

[0021] The input terminal of the 24V to 12V isolated DC / DC converter is used to connect to a 24V DC power supply. The first output terminal of the 24V to 12V isolated DC / DC converter is connected to the input terminal of the large and small current switching module. The first output terminal of the 24V to 12V isolated DC / DC converter is connected to the input terminal of the three-pin positive voltage regulator.

[0022] The three-pin positive voltage regulator is used to convert 12V to 5V; the output of the three-pin positive voltage regulator is connected to the input of the high-precision voltage reference module and the input of the polarity conversion module, respectively.

[0023] Optionally, the high-precision voltage reference module is used to convert 5V voltage into 2.5V voltage; the output terminal of the high-precision voltage reference module is connected to the input terminal of the high-speed high-precision isolated level conversion module and the input terminal of the 50% turn-on threshold setting module, respectively.

[0024] Optionally, the polarity conversion module includes at least a power polarity inversion converter; the operating voltage of the power polarity inversion converter is 1.5V to 9.5V, the power polarity inversion converter chip has a built-in oscillation control circuit and four power MOSFET switches, and three capacitors are disposed around the power polarity inversion converter.

[0025] Optionally, the high-speed, high-precision isolated level conversion module includes at least a high-speed optocoupler; the core of the Butterworth analog-to-digital converter module is a dual operational amplifier.

[0026] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0027] The constant current source provided by this invention is a digital constant current source that uses a feedback control loop and a high-speed digital signal processor as the controller. It can maintain high accuracy under high current output and can also achieve rapid switching between large and small currents to meet the requirements of transient thermal testing. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 is a transient thermal test circuit diagram provided in an embodiment of the present invention;

[0030] Figure 2 is a schematic diagram of a constant current source for transient thermal testing of semiconductor devices provided in an embodiment of the present invention;

[0031] Figure 3 is a circuit diagram of the DC-DC isolated power supply and LDO step-down module provided in an embodiment of the present invention;

[0032] Figure 4 is a circuit diagram of the high-precision voltage reference module provided in an embodiment of the present invention;

[0033] Figure 5 is a circuit diagram of the polarity conversion module provided in an embodiment of the present invention;

[0034] Figure 6 is a circuit diagram of the 25.5mA current source module provided in an embodiment of the present invention;

[0035] Figure 7 is a circuit diagram of the 2A current source module provided in an embodiment of the present invention;

[0036] Figure 8 is a circuit diagram of the large and small current switching module provided in an embodiment of the present invention.

[0037] Figure 9 is a circuit schematic diagram of the BNC interface output module provided in an embodiment of the present invention;

[0038] Figure 10 is a circuit diagram of the transient thermal test in body diode mode provided in an embodiment of the present invention. Detailed Implementation

[0039] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0041] As shown in Figure 1, by using a stable high heating current I heat Quickly switch to low induced current I sense It can generate fairly accurate power changes to achieve transient thermal testing. Obviously, it is feasible to construct a fast-switching and stable current source. In view of this, this embodiment provides a constant current source for transient thermal testing of semiconductor devices.

[0042] For transient thermal testing, a high-precision, highly stable, and rapidly switchable controllable constant current source is crucial. With the rapid development of computer and communication technologies, the performance of electronic components is constantly being optimized, and power supply technology is undergoing significant innovation. Consequently, the overall performance of constant current sources is continuously improving, and DC constant current sources have entered the digital and intelligent era. Based on traditional DC constant current sources, microprocessors, analog-to-digital converters, and digital-to-analog converters can be used in conjunction with computer software programming to program-control the DC constant current source. Simultaneously, a highly efficient control algorithm can be designed using control theory to improve the accuracy of the output voltage and current. Furthermore, for high-precision programmable DC constant current sources, high precision is based on high stability of the output current; only when the output current has high stability can the DC constant current source guarantee constant current output. Traditional constant current power supplies use analog control methods without feedback loops, making it impossible to simultaneously achieve high stability and high current. The constant current source provided in this embodiment is a digital constant current source that uses a feedback control loop and a high-speed digital signal processor as the controller. It can maintain high accuracy under high current output. In addition, it can realize rapid switching between large and small currents to meet the requirements of transient thermal testing. For example, the maximum deviation of this constant current source after 10 minutes of operation at the 2A setting is ±1mA, and the maximum error at the 25.5mA setting is only at the 10 microamp level.

[0043] As shown in Figure 2, this embodiment provides a constant current source for transient thermal testing of semiconductor devices, including a DC-DC isolated power supply, an LDO step-down module, a high-precision voltage reference module, a polarity conversion module, a 25.5mA current source module, a 2A current source module, a large and small current switching module, and a BNC interface output module.

[0044] The output terminals of the DC-DC isolated power supply and the LDO step-down module are respectively connected to the input terminals of the high-precision voltage reference module and the polarity conversion module; the output terminal of the high-precision voltage reference module is connected to the input terminals of the 25.5mA current source module and the 2A current source module; the output terminal of the polarity conversion module is connected to the input terminals of the 25.5mA current source module and the 2A current source module; the output terminals of the 25.5mA current source module and the 2A current source module are both connected to the input terminal of the large and small current switching module; the output terminal of the large and small current switching module is connected to the input terminal of the BNC interface output module.

[0045] The 25.5mA current source module includes: a PWM and level input module, a high-speed, high-precision isolated level conversion module, a Butterworth analog quantity conversion module, a 50% threshold setting module, an adder accumulation data and error module, and a current output module.

[0046] The PWM and level input module is used to receive the enable signal and level signal of the FPGA; the output terminal of the PWM and level input module is connected to the first input terminal of the high-speed high-precision isolated level conversion module; the output terminal of the high-precision voltage reference module is connected to the second input terminal of the high-speed high-precision isolated level conversion module.

[0047] The output of the high-speed, high-precision isolated level conversion module is connected to the input of the Butterworth analog-to-digital converter module; the output of the Butterworth analog-to-digital converter module is connected to the first input of the current output module; the output of the adder accumulation data and error module is connected to the second input of the current output module; the output of the 50% threshold setting module is connected to the first input of the adder accumulation data and error module; the first input of the current output module serves as the first output and is connected to the second input of the adder accumulation data and error module, forming a closed-loop negative feedback.

[0048] The 2A current source module includes: a PWM and level input module, a high-speed, high-precision isolated level conversion module, a Butterworth analog quantity conversion module, a 50% threshold setting module, an adder accumulation data and error module, a current output module, and a drive amplifier circuit module.

[0049] The PWM and level input module is used to receive the enable signal and level signal of the FPGA; the output terminal of the PWM and level input module is connected to the first input terminal of the high-speed high-precision isolated level conversion module; the output terminal of the high-precision voltage reference module is connected to the second input terminal of the high-speed high-precision isolated level conversion module.

[0050] The output of the high-speed, high-precision isolated level conversion module is connected to the input of the Butterworth analog-to-digital converter module; the output of the Butterworth analog-to-digital converter module is connected to the first input of the current output module; the output of the adder accumulation data and error module is connected to the second input of the current output module; the output of the 50% threshold setting module is connected to the input of the adder accumulation data and error module; and the second output of the current output module is connected to the input of the drive amplifier circuit module. The first input of the current output module serves as the first output, and is connected to the second input of the adder accumulation data and error module, forming a closed-loop negative feedback.

[0051] This constant current source, through programmable PWM regulation via an FPGA, can achieve two current output levels: 0-25.5mA and 0-2A. This is to achieve the low induced current I required for transient thermal testing. sense and high heating current I heat .

[0052] Figure 3 shows the DC-DC isolated power supply and LDO step-down module. As the power supply at the front end of the system, to improve anti-interference performance and ensure reliability, U2, a 24V to 12V isolated DC / DC converter, is used. There is no direct electrical connection between the input and output circuits of the power supply; the input and output are in an isolated high-impedance state with no current loop. To obtain a stable 5V voltage, an LM78M05 three-pin positive voltage regulator is used to convert 12V to 5V. This regulator employs built-in current limiting, thermal shutdown, and safe operating area protection, which makes it virtually unaffected by output overload. The VIN24V terminal is supplied with an external 24V DC power supply, input to port 2 of U2. After being converted from DC / DC to +12V, it is output through port 4 of U2 and connected to the +12V terminal of the current switching module shown in Figure 8. The +5V output terminal, after being regulated to 5V by VR1 and LDO, serves as the 5V power supply output and is connected to the +5V input terminals of other modules, such as the +5V input terminal of the high-precision voltage reference module shown in Figure 4.

[0053] The high-precision voltage reference module, as shown in Figure 4, uses the REF192 precision bandgap voltage reference to convert the 5V voltage obtained from the LDO buck circuit into a 2.5V high-precision reference voltage source. This provides the voltage reference for the high-speed, high-precision isolated level conversion module and the 50% turn-on threshold setting module. The input is the DC-DC isolated power supply and the +5V output terminal of the LDO buck module, which are then connected to input terminal VS (number 2) of U1 in the high-precision voltage reference module. Output terminal OUTPUT (number 6) provides a +2.5V voltage.

[0054] As shown in Figure 5, U6 in the polarity conversion module is a high-efficiency power supply polarity inversion converter from the ICL7660 series, capable of outputting negative voltage. Its operating voltage is 1.5V-9.5V. The chip consists of a built-in oscillation control circuit and four power MOSFET switches, requiring only three external capacitors to output a negative voltage with the opposite polarity to the input voltage. For example, in this design requiring ±5V, using this converter, when the input voltage V+ = 5V, the VOUT output voltage is -5V. Wherein, CAP+ is the positive terminal of the energy storage capacitor, CAP- is the negative terminal, LV is the low-voltage control terminal (disabled), OSC is the oscillator port (disabled), V+ is the positive power input terminal, VOUT is the negative voltage output terminal, GND is the power ground, and NC is empty. The input is the +5V output terminal of the DC-DC isolated power supply and the LDO buck module, connected to the V+ port of U6. The output is the VOUT port, outputting a -5V voltage.

[0055] Figure 6 shows the circuit schematic of the 25.5mA current source module. It receives a 25.5mA signal and a 25.5mA enable signal (PWM25.5mA, IEN25.5mA terminals) from the FPGA's PWM signal input, and outputs a current of 0-25.5mA (OUT25.5mA terminal). Additionally, a 3.3V level (VIN3.3V terminal) provided by the FPGA is required as a level conversion input.

[0056] After the FPGA's PWM signal and level input, it passes through the high-speed, high-precision isolated level conversion module shown in Figure 6(a). This module uses a high-speed optocoupler HCPL-0630-500E to convert the 3.3V high-speed signal into a 5V signal. The circuit is simple to build and can produce a good waveform. In addition, the optocoupler also provides isolation. This high-speed, high-precision isolated level conversion module has four inputs. The VIN 3.3V terminal is connected to ports A1 and A2 of U3, and the PWM 25.5MA and IEN 25.5MA terminals are connected to ports K1 and K2, respectively. The 5V level PWM 25.5MA signal is output through VO1, and the 5V level I 25.5MAEN signal is output through VO2. Then, the high-speed level is converted by a high-speed, low-impedance MOSQ1, making the high level almost close to 2.5V (absolutely close). This third-generation lateral MOSFET (LD-MOS) design minimizes on-state losses and enables ultra-fast switching, making it ideal for efficient power delivery. It utilizes a chip-scale package (CSP) to increase power density by combining low impedance with minimal RDS(ON) per pin area. The OPAR197 features high output current drive capability and low input bias voltage, making it an excellent reference buffer that provides an accurate buffered output with ample drive current for transients.

[0057] The inputs of this high-speed, high-precision isolated level conversion module are the five source ports S (B3, B2, B1, A3, A2) and one gate port G (A1) of Q1. The +2.5V input terminal is connected to the +2.5V output terminal of the high-precision voltage reference module, and A1 is connected to one end of the 5V PWM 25.5mA signal output by R11. The outputs of this high-speed, high-precision isolated level conversion module are three drain ports (C1, C2, C3), outputting a 2.5V high-level signal, which is connected to one end of R7 and R14.

[0058] The other end of R14 in this high-speed, high-precision isolated level conversion module is connected to input port 3 of a Butterworth analog-to-digital converter module based on the U4 (OPA2197IDR) dual operational amplifier shown in Figure 6(b). Ports 1, 2, and 3 on the left side of U4 form a voltage follower to increase signal driving force; ports 5, 6, and 7 on the right side of U4 form a Butterworth low-pass filter, converting the PWM signal input at port 3 into a linear voltage output at port 7, which is connected to the right side of R32.

[0059] The right side of R32 in the Butterworth analog-to-digital converter module is connected to input terminal 3 of U5 in the current output module shown in Figure 6(c). Input terminal 2 of U5 is connected to the left side of R28 in the adder's data accumulation and error module. The current output module uses U5 as a comparator to compare the signals at terminals 3 and 2 of U5, outputting an accurate signal. This signal is then amplified by Q2 to obtain a 25.5mA output current, which is output from the OUT25.5mA terminal. Furthermore, port 3 of Q2 in the current output module is connected to one side of R19 in the adder's data accumulation and error module, forming a closed-loop negative feedback.

[0060] As shown in Figure 6(d), the 50% threshold setting module adjusts the reference level via a precision sliding rheostat, and then achieves a high-precision output of the 50% threshold setting through the U9 precision buffer. The +2.5V input terminal of the 50% threshold setting module is connected to the +2.5V output terminal of the high-precision voltage reference module. The output at port 6 of the U9 precision buffer is connected to the left side of R18, and is connected in parallel with the feedback signal of the output current to port 5 of U7 as shown in Figure 6(e) for error accumulation. The adder accumulation data and error module collects data from the 50% threshold setting module and compares it with the output current feedback data to reduce errors. The input of the adder accumulation data and error module is port 3 of U7, which is the output from the current output module. The output is port 7 of U7, which serves as negative feedback and is output to the left side of R12 of the current output module.

[0061] Figure 7 shows the circuit diagram of the 2A current source module. A driver amplifier circuit module is added to the current output module of the 25.5mA current source module to amplify the current. The input of the driver amplifier circuit module is port 1 of Q5, and the output is the OUT2A terminal, outputting a 2A DC current. Specifically, Figure 7(a) shows the high-speed, high-precision isolated level conversion module in the 2A current source module; Figure 7(b) shows the Butterworth analog converter module in the 2A current source module; Figure 7(c) shows the 50% threshold setting module in the 2A current source module; Figure 7(d) shows the adder accumulation data and error module in the 2A current source module; and Figure 7(e) shows the driver amplifier circuit module in the 2A current source module.

[0062] Figure 8 shows the circuit schematic of the current switching module. This module has three input terminals: OUTZF, VIN24V, and +12V. OUTZF provides the high and low voltage levels from the FPGA. If the input is high, the relay is energized, reversing the on-state direction. If the input is low, the on-state direction is correct. VIN24V is the external 24V DC voltage input. The +12V terminal is connected to the DC-DC isolated power supply and the +12V output terminal of the LDO step-down module. The module has two output terminals: OUTA and OUTB. OUTA and OUTB are connected to input ports 1 and 2 of the BNC interface output module shown in Figure 9.

[0063] The output terminal of the BNC interface output module provides an output connection at the other end of this device.

[0064] The inputs to the entire constant current source are VIN24V, AGND, VIN3.3V, PWM25.5MA, IEN25.5MA, OUTZF, PWM2A, and IEN2A. When the inputs are VIN24V (24V), AGND (ground), VIN3.3V (3.3V), PWM25.5MA (PWM signal), IEN25.5MA (enable signal), and OUTZF (high level), the output terminals OUTA and OUTB output a current of 0–25.5MA. When the inputs are VIN24V (24V), AGND (ground), VIN3.3V (3.3V), PWM25.5MA (PWM signal), IEN25.5MA (enable signal), and OUTZF (low level), the output terminals OUTA and OUTB output a current of -25.5–0MA. These two outputs can be used as low-current tests for thermal applications, depending on the required current level. sensor The system provides the induced current. When the input is VIN24V (24V), AGND (ground), VIN3.3V (3.3V), PWM 2A (PWM signal), IEN 2A (enable signal), and OUTZF (high level), the output terminals OUTA and OUTB output a current of 0-2A. When the input is VIN24V (24V), AGND (ground), VIN3.3V (3.3V), PWM 2A (PWM signal), IEN 2A (enable signal), and OUTZF (low level), the output terminals OUTA and OUTB output a current of -2-0A. These two outputs can be used as high current for thermal testing, depending on the required current level. heat The supply of heating current.

[0065] This constant current source can be applied to various test modes for transient thermal testing. As shown in Figure 10, the "body diode" mode test is used as an example. Power MOSFETs have an inherent reverse diode between their source and drain. Thermal testing of this "body diode" is very simple; for typical devices, the test steps are as follows:

[0066] a) Mount the device under test on a cooling plate (temperature controllable) and connect the device to the test equipment using the 4-wire method;

[0067] b) Inputs: VIN24V (24V), AGND (ground), VIN3.3V (3.3V), PWM 2A (PWM signal), IEN 2A (enable signal), OUTZF (high level). Outputs: OUTA and OUTB output 0-2A current. The required IA is applied by changing the PWM 2A signal of the FPGA. heat Apply to the device under test;

[0068] c) After heating stabilizes, input VIN24V (24V), AGND (ground), VIN3.3V (3.3V), PWM25.5MA (PWM signal), (enable signal) IEN25.5MA, OUTZF (high level). Output terminals OUTA and OUTB output 0-25.5MA current, transferring the current from I... heat Switch to I sensor And after selecting a suitable t MD Post-record V F ;

[0069] d) For transient tests, ΔV needs to be recorded continuously. F (t), at t M (I sensor The testing process requires collecting data from at least 50 points.

[0070] This constant current source can provide heating current I for transient thermal testing. heat and test current I sensor It enables rapid switching between them, providing constant current source hardware for transient thermal testing.

[0071] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple; relevant parts can be referred to the method section.

[0072] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A constant current source for transient thermal testing of semiconductor devices, characterized in that, include: The system includes a DC-DC isolated power supply, an LDO step-down module, a high-precision voltage reference module, a polarity conversion module, a 25.5mA current source module, a 2A current source module, a high / low current switching module, and a BNC interface output module. The outputs of the DC-DC isolated power supply and the LDO step-down module are connected to the inputs of the high-precision voltage reference module and the polarity conversion module, respectively. The output of the high-precision voltage reference module is connected to the inputs of the 25.5mA current source module and the 2A current source module, respectively. The output terminal of the polarity conversion module is connected to the input terminal of the 25.5mA current source module and the input terminal of the 2A current source module, respectively; the output terminals of the 25.5mA current source module and the 2A current source module are both connected to the input terminal of the large and small current switching module; the output terminal of the large and small current switching module is connected to the input terminal of the BNC interface output module. The 25.5mA current source module includes: a PWM and level input module, a high-speed, high-precision isolated level conversion module, a Butterworth analog-to-digital converter module, a 50% threshold setting module, an adder accumulation data and error module, and a current output module. The PWM and level input module receives the FPGA's enable signal and level signal. The output of the PWM and level input module is connected to the first input of the high-speed, high-precision isolated level conversion module. The output of the high-precision voltage reference module is connected to the second input of the high-speed, high-precision isolated level conversion module. The output of the high-speed, high-precision isolated level conversion module is connected to the input of the Butterworth analog-to-digital converter module. The output of the Butterworth analog-to-digital converter module is connected to the first input of the current output module. The output of the adder accumulation data and error module is connected to the second input of the current output module. The output of the 50% threshold setting module is connected to the first input of the adder accumulation data and error module. The 2A current source module includes: a PWM and... The system comprises a level input module, a high-speed, high-precision isolated level conversion module, a Butterworth analog-to-digital converter module, a 50% threshold setting module, an adder accumulation data and error module, a current output module, and a drive amplifier circuit module. The PWM and level input modules receive enable and level signals from the FPGA. The output of the PWM and level input modules is connected to the first input of the high-speed, high-precision isolated level conversion module. The output of the high-precision voltage reference module is connected to the second input of the high-speed, high-precision isolated level conversion module. The output of the high-speed, high-precision isolated level conversion module is connected to the input of the Butterworth analog-to-digital converter module. The output of the Butterworth analog-to-digital converter module is connected to the first input of the current output module. The output of the adder accumulation data and error module is connected to the second input of the current output module. The output of the 50% threshold setting module is connected to the input of the adder accumulation data and error module. The second output of the current output module is connected to the input of the drive amplifier circuit module.

2. The constant current source for transient thermal testing of semiconductor devices according to claim 1, characterized in that, The first input terminal of the current output module serves as the first output terminal and is connected to the second input terminal of the adder's accumulated data and error module, forming a closed-loop negative feedback.

3. The constant current source for transient thermal testing of semiconductor devices according to claim 1, characterized in that, The DC-DC isolated power supply and LDO step-down module include at least: a 24V to 12V isolated DC / DC converter and a three-pin positive voltage regulator; the 24V to 12V isolated DC / DC converter is used to convert 24V voltage to 12V voltage; the input terminal of the 24V to 12V isolated DC / DC converter is used to connect to a 24V DC power supply, the first output terminal of the 24V to 12V isolated DC / DC converter is connected to the input terminal of the large and small current switching module, and the first output terminal of the 24V to 12V isolated DC / DC converter is connected to the input terminal of the three-pin positive voltage regulator; the three-pin positive voltage regulator is used to convert 12V voltage to 5V voltage; the output terminal of the three-pin positive voltage regulator is connected to the input terminal of the high-precision voltage reference module and the input terminal of the polarity conversion module, respectively.

4. A constant current source for transient thermal testing of semiconductor devices according to claim 1, characterized in that, The high-precision voltage reference module is used to convert 5V voltage into 2.5V voltage; the output terminal of the high-precision voltage reference module is connected to the input terminal of the high-speed high-precision isolated level conversion module and the input terminal of the 50% opening threshold setting module, respectively.

5. A constant current source for transient thermal testing of semiconductor devices according to claim 1, characterized in that, The polarity conversion module includes at least a power polarity inversion converter; the operating voltage of the power polarity inversion converter is 1.5V-9.5V, the power polarity inversion converter chip has a built-in oscillation control circuit and four power MOSFET switches, and three capacitors are arranged around the power polarity inversion converter.

6. A constant current source for transient thermal testing of semiconductor devices according to claim 1, characterized in that, The high-speed, high-precision isolated level conversion module includes at least a high-speed optocoupler; the core of the Butterworth analog-to-digital converter module is a dual operational amplifier.

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