Power device conduction voltage on-line monitoring circuit based on thermal compensation and error optimization

Abstract

The invention discloses a power device conduction voltage online monitoring circuit based on thermal compensation and error optimization. The power device conduction voltage online monitoring circuit comprises a low current source, a controlled voltage source, a first diode, a second diode and a resistor element. The low current source is connected with the input ends of the first diode and the second diode. The output end of the first diode is connected with a to-be-tested power device; the output end of the second diode is connected with a controlled voltage source; a resistor element is arranged between the first diode and the power device to be tested, and a resistor element is arranged between the second diode and the controlled voltage source; the controlled voltage source is used for controlling the current flow direction and adjusting the symmetry of the conduction time of the first diode and the second diode. According to the invention, the reliability problem of a power electronic system is solved, and technical support is provided for system design optimization, monitoring circuit improvement, system stability and reliability and high-precision parameter identification. And a new direction and possibility are provided for technical development and application of power device state monitoring.

Description

Technical Field

[0001] The present invention belongs to the field of circuit monitoring, and particularly relates to an on-line monitoring circuit for the conduction voltage of a power device based on thermal compensation and error optimization. Background Art

[0002] With the rapid development of new energy technologies, power converters are widely used in important fields such as energy, environment, transportation, aerospace, etc. However, the reliability problem of power electronic systems has become increasingly prominent, especially the reliability of power electronic converters, and the most vulnerable devices among them are power devices (such as MOSFETs and IGBTs). During operation, the complex and changeable environment causes the internal temperature of the device to fluctuate violently, thereby accelerating the aging process of the device and seriously threatening the stability and reliability of the system. By monitoring the aging failure state of the key devices of the power converter, the economic losses and even safety problems caused by system shutdown due to faults can be effectively avoided. Therefore, the health state monitoring of power devices is particularly important, and the conduction voltage drop is a key parameter characterizing the health state of power devices, and its change indicates the aging or fault tendency of the device. The real-time and on-line monitoring of the conduction voltage drop is of great significance for ensuring the operation stability of the system and extending the device life.

[0003] In modern power electronic systems, the research on the state monitoring of aging-sensitive parameters of power devices has become an important part of improving system reliability. Among them, the monitoring methods of the conduction voltage drop of power devices have attracted wide attention, and many monitoring means have been proposed successively. Although a variety of power device state monitoring methods have been proposed in recent years, the existing technologies mainly focus on off-line monitoring and are difficult to meet the real-time and on-line monitoring requirements at the circuit level. In addition, the existing on-line monitoring methods generally ignore the influence of temperature on the measurement accuracy, resulting in difficulties in achieving low power consumption and high-precision measurement. The error compensation caused by temperature change has become the main technical challenge for on-line monitoring systems. Summary of the Invention

[0004] Object of the Invention: The object of the present invention is to provide an on-line monitoring circuit for the conduction voltage of a power device based on thermal compensation and error optimization. By using the conduction voltage drop of a diode to offset the temperature change of the conduction voltage drop of the power device, the stability of the voltage at the measurement node is ensured, and the monitoring accuracy is improved. In addition, the present invention uses a controlled voltage source to control the conduction state of the second diode to ensure the symmetry of the conduction time of the first diode and the second diode, further ensuring the on-line monitoring accuracy. The present invention will promote the solution of the reliability problem of power electronic systems and provide technical support for system design optimization, monitoring circuit improvement, system stability and reliability, and achieving high-precision parameter identification.

[0005] Technical solution: An on-line monitoring circuit for the conduction voltage of a power device based on thermal compensation and error optimization according to the present invention includes a low-current source, a controlled voltage source, a first diode, a second diode, and a resistance element;

[0006] The input terminals of the first diode and the second diode are respectively connected to the low-current source; the low-current source is used to provide a stable small current to monitor the conduction voltage drop of the power device;

[0007] The first diode and the second diode are respectively connected to the power device to be measured and the controlled voltage source, and are used to provide reverse voltage protection when the power device is turned off and achieve a thermal compensation effect;

[0008] The output terminal of the first diode is connected to the power device to be measured;

[0009] The output terminal of the second diode is connected to the controlled voltage source;

[0010] Resistance elements are provided between the first diode and the power device to be measured, and between the second diode and the controlled voltage source; the resistance elements are used to set the voltage level of the measurement node to improve signal stability;

[0011] The controlled voltage source is used to control the current flow direction and adjust the symmetry of the conduction times of the first diode and the second diode.

[0012] Further, the controlled voltage source includes an inverter, an operational amplifier, and a voltage follower. Among them, the inverter is used to invert the switching signal; the input signal is amplified by the operational amplifier to ensure that the auxiliary voltage V aux is greater than the voltage V at the point to be measured x so as to effectively control the current source flow direction; the voltage follower plays an isolation protection role to ensure the stability and reliability of the system.

[0013] Further, the low-current source is in the milliampere level. To reduce the influence of the monitoring circuit on the measurement of the conduction voltage drop and ensure that the normal operation of the power device in the power converter will not be affected during the on-line monitoring process;

[0014] By adjusting the output voltage of the controlled voltage source to control the conduction state of the second diode D2, so as to ensure that the conduction times of the first diode D1 and the second diode D2 are equal, thereby realizing conduction time error compensation, and thus improving the measurement accuracy of the conduction voltage drop of the power device.

[0015] Further, the temperature coefficients of the first diode and the second diode are opposite to the conduction voltage drop of the power device to be measured. When the temperature rises, the increase in the conduction voltage drop of the power device causes the node voltage V x to rise, while the decrease in the forward voltage drop of the diode can partially offset this change, so that the node voltage Vx Maintain relative stability, achieve the thermal compensation effect and reduce the influence of temperature changes on the measurement accuracy.

[0016] The present invention also discloses a monitoring method for an on-line monitoring circuit of the conduction voltage of a power device based on thermal compensation and error optimization. When the second diode is reversely turned off, the low current source flows through the first diode, and at this time, the power device to be measured is turned on; when the second diode is forwardly turned on, the low current source flows through the second diode, and at this time, the power device to be measured is turned off; when the device to be measured is turned on, the measurement node voltage is

[0017]

[0018] wherein, V R1 represents the voltage of the first resistor, V D1 represents the voltage of the first diode, V on represents the conduction voltage drop of the power device to be measured;

[0019] When the device to be measured is turned off, the measurement node voltage is

[0020]

[0021] wherein, V R2 represents the voltage of the second resistor, V D2 represents the voltage of the second diode;

[0022] Therefore, the conduction voltage drop of the power device is

[0023]

[0024] Beneficial effects: Compared with the prior art, the present invention has the following remarkable advantages:

[0025] (1) Performance advantages: Compared with the off-line monitoring method, the present invention has real-time, non-invasive and dynamic monitoring capabilities. It does not require shutting down and disassembling the equipment, and can continuously monitor the conduction voltage drop of the power device during the normal operation of the circuit, and can reflect the state and health trend of the power device in real time, improving the reliability and safety of the system. Compared with the traditional on-line monitoring method, the present invention has the characteristics of low power consumption, thermal compensation and error optimization. The present invention adopts a low current source design to ensure that the monitoring circuit does not affect the normal working state of the power device and avoids the influence of additional thermal effects introduced during the on-line measurement process; the present invention utilizes the negative temperature coefficient of the diode to achieve thermal compensation, thereby reducing the influence of temperature on the measurement result of the conduction voltage drop; by controlling the controllable voltage source, the conduction time error compensation of the diode is realized, further improving the measurement accuracy. The on-line monitoring method of the conduction voltage drop with thermal compensation and error optimization proposed by the present invention provides an efficient and low-cost solution for the long-term reliability research and life prediction of power devices, and can be widely applied to various power electronic systems and intelligent monitoring platforms.

[0026] (2) Application advantages: The present invention has higher measurement accuracy and stability, reduces the influence of temperature fluctuations on measurement results, can monitor the on-state voltage drop of power devices in real time under the normal operation of the power converter, avoids the cumbersome offline shutdown monitoring, meets a wide range of practical application scenarios, is particularly suitable for the requirements of power converter circuit-level status monitoring, and improves the reliability and applicability of status monitoring.

[0027] (3) Cost advantages: Compared with traditional offline monitoring methods, the present invention has a simple structure, can directly monitor the on-state voltage drop information of the power device to be measured online, avoids expensive experimental costs and time-consuming experimental processes, saves the materials, manpower and cost inputs required for experiments, speeds up the experimental design cycle, and reduces the economic burden during the development process. It greatly reduces the overall design cost in the design stage and provides a more cost-effective solution for the research and development and production of power converters. Description of the Drawings

[0028] Figure 1 is an on-line monitoring circuit for the on-state voltage of a power device based on thermal compensation and error optimization proposed by the present invention.

[0029] Figure 2 is a schematic diagram of the on-resistance and on-state voltage drop varying with temperature; among them, (a) is a schematic diagram of the MOSFET on-resistance R DS(on) varying with temperature in the present invention; 2(b) is the forward on-state voltage drop V of the diode in the present invention F varying with temperature.

[0030] Figure 3 is a schematic diagram of the working mode of the monitoring circuit in the present invention; among them, (a) is a working mode diagram when the power device to be measured is on, and (b) is a working mode diagram when the power device to be measured is off.

[0031] Figure 4 is a measurement waveform diagram of the monitoring circuit in the present invention when the power device to be measured is operating normally in the converter. Detailed Embodiments

[0032] The technical solution of the present invention will be further described below in conjunction with the drawings.

[0033] An on-line monitoring circuit for the on-state voltage of a power device based on thermal compensation and error optimization of the present invention includes the following two parts:

[0034] Part 1: Thermal compensation using the temperature characteristics of a diode: The present invention utilizes the property that the forward voltage drop of a diode has a temperature coefficient opposite to that of the conduction voltage drop of a power device. When the power converter operates for a period of time, the power device heats up, its conduction voltage drop increases, and the forward voltage drop of the diode decreases due to the influence of heat transfer. The changes in these two parts cancel each other out, so that the voltage V at the measurement node x remains relatively stable, thereby realizing thermal compensation for the conduction voltage drop of the power device to be measured and greatly reducing the influence of temperature changes on the measurement accuracy.

[0035] Part 2: Controlled voltage source ensures the symmetry of the conduction time of the diode: The present invention uses a controlled voltage source to control the conduction state of the second diode. When the second diode is reversely turned off, a low-current source flows through the first diode, and at this time the power device to be measured is conducting; when the second diode is forward-conducting, the low-current source flows through the second diode, and at this time the power device to be measured is turned off. The same conduction time of the two diodes is used to ensure that the aging states of the diodes are the same, and the degrees of decrease in the forward conduction voltage drops of the diodes affected by temperature rise are the same, thereby reducing the influence of the forward voltage drop of the diodes on the voltage at the measurement node during the normal operation of the power converter and ensuring the accuracy of the voltage at the measurement node.

[0036] In view of the problems existing in the existing power device state monitoring, the present invention proposes an on-line monitoring circuit for the conduction voltage of a power device based on thermal compensation and error optimization as shown in Figure 1 . The following describes each part of this method.

[0037] 1. Thermal compensation using the temperature characteristics of a diode

[0038] In the present invention, since devices such as power transistors (taking MOSFET as an example) and diodes generate losses during actual operation, and the losses are released in the form of heat, the result is an increase in the junction temperature. The change in temperature affects the values of electrical parameters such as the on-resistance R of the MOSFET DS(on) and the forward conduction voltage drop V of the diode F . Among them, according to Figure 2 (a), Figure 2 (b) measurement results show that the on-resistance R of the MOSFET DS(on) increases with the increase in temperature, and the forward conduction voltage drop V of the diode F decreases with the increase in temperature. Therefore, the present invention performs thermal compensation for the opposite temperature characteristics of the MOSFET and the diode to ensure the stability of the voltage at the measurement node.

[0039] The present invention provides the basis and support for monitoring the conduction voltage drop with millivolt-level accuracy by using the thermal compensation effect between devices.

[0040] 2. Efficiently solve the conduction voltage drop of the power device to be measured

[0041] Taking the monitoring of the on - voltage drop of the MOSFET in the Buck circuit (in CCM mode) as an example, a low - current source is used to provide a stable small current to ensure low - power consumption monitoring of the on - voltage drop of the device under test. When the switching transistor is on, as Figure 3 (a) shows, at this time, the driving signal is at a high level to control the controlled voltage source, making the second diode reverse - biased. The low - current source flows through the first diode branch, and the voltage of the node under test is When the switching transistor is off, as Figure 3 (b) shows, at this time, the driving signal is at a low level, the controlled voltage source is 0V, the second diode loses the control of the controlled voltage source and conducts forward. Since the switching transistor is off and the first diode is reverse - biased, the low - current source flows through the second diode branch, and the voltage of the node under test is According to the values of the voltage of the node under test in different switching states, as Figure 4 shown, the on - voltage drop of the power transistor under test can be obtained as The on - voltage drop of the power device under test can be obtained without separately measuring the on - voltage drop of the diode in the monitoring circuit, which simplifies the calculation of the monitoring circuit and improves the monitoring efficiency and accuracy.

[0042] The above embodiments are only used to illustrate the technical idea of the present invention, and the protection scope of the present invention cannot be limited thereby. Any modification made on the basis of the technical solution according to the technical idea proposed by the present invention falls within the protection scope of the present invention.

Claims

1. An on-line monitoring circuit for the conduction voltage of a power device based on thermal compensation and error optimization, characterized in that, It includes a low-current source, a controlled voltage source, a first diode, a second diode, and a resistor element; The low-current source is respectively connected to the input ends of the first diode and the second diode; The output end of the first diode is connected to the power device under test; The output end of the second diode is connected to the controlled voltage source; A resistor element is provided between the first diode and the power device under test, and a resistor element is provided between the second diode and the controlled voltage source; The controlled voltage source is used to control the current flow direction and adjust the symmetry of the conduction times of the first diode and the second diode.

2. The on-line monitoring circuit for the turn-on voltage of a power device based on thermal compensation and error optimization according to claim 1, wherein The controlled voltage source includes an inverter, an operational amplifier, and a voltage follower connected in sequence. Among them, the inverter is used to invert the switch signal; the input signal is amplified by the operational amplifier to make the auxiliary voltage V aux greater than the voltage V at the point to be measured x to control the current source to flow.

3. The on-line monitoring circuit for the conduction voltage of a power device based on thermal compensation and error optimization according to claim 1, characterized in that, The low-current source is at the milliamp level.

4. The on-line monitoring circuit for the turn-on voltage of a power device based on thermal compensation and error optimization according to claim 1, wherein The temperature coefficients of the first diode and the second diode are opposite to the conduction voltage drop of the power device under test.

5. A monitoring method for an on-line monitoring circuit of the conduction voltage of a power device based on thermal compensation and error optimization, characterized in that, When the second diode is reversely turned off, the low-current source flows through the first diode, and at this time the power device under test is turned on; when the second diode is forward-conducting, the low-current source flows through the second diode, and at this time the power device under test is turned off; when the device under test is turned on, the measurement node voltage is Among them, V R1 represents the first resistor voltage, V D1 represents the first diode voltage, V on represents the conduction voltage drop of the power device under test; When the device under test is turned off, the measurement node voltage is Among them, V R2 represents the second resistor voltage, V D2 represents the second diode voltage; Therefore, the conduction voltage drop of the power device is

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