Power device failure detection method

Abstract

The invention relates to a power device failure detection method. The method comprises the following steps: acquiring a shell temperature, a forward conduction voltage drop and a forward conduction current of a power device in real time; and when the shell temperature, the forward conduction voltage drop and the forward conduction current meet preset conditions, determining that the power device fails. According to the power device failure detection method, the failure of the power device can be detected online in real time, the detection process is simple, and due to the fact that various parameters are combined for fusion and comparison, the accuracy is higher.

Description

Technical Field

[0001] The present invention relates to the field of charging modules, and more particularly to a method for detecting failure of a power device. Background Art

[0002] As the core component of electric vehicle charging devices, the stability and reliability of the charging module are extremely important to the charging device. When the charging module stops working or the input power is disconnected, the battery voltage may be higher than the voltage at the output of the charging module. At this time, it is necessary to install an anti-backflow diode inside the charging module to prevent current from flowing back from the battery end to the power end to avoid reverse current impacting the capacitor, MOS tube or controller on the power side, reducing the risk of short circuit or device breakdown. At the same time, the anti-backflow diode can ensure unidirectional current flow, preventing reverse current from causing voltage oscillation or false triggering of protection mechanisms (such as overvoltage / overcurrent protection). In addition, in fast charging and supercharging scenarios, when multiple charging modules need to be operated in parallel, if a module fails, other modules may form a reverse current through the faulty module in the absence of an anti-backflow diode. The internal components of the faulty module (such as inductors and capacitors) are damaged by overheating due to the reverse current.

[0003] However, in actual use, the backflow protection diode may fail for some reason, seriously affecting the operation of the charging module or even causing damage. However, current diode failure detection methods usually require removing the diode from the charging module and then testing it using specialized instruments or circuits. This is not only complicated and inconvenient, but also affects the normal operation of the charging module. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a power device failure detection method and apparatus in response to the above-mentioned defects of the prior art, which can detect power device failure online, thereby simplifying and facilitating the detection process.

[0005] The technical solution adopted by the present invention to solve the technical problem is to construct a power device failure detection method, comprising:

[0006] Real-time acquisition of power device case temperature, forward voltage drop, and forward current;

[0007] When the shell temperature, the forward conduction voltage drop, and the forward conduction current meet preset conditions, it is determined that the power device has failed.

[0008] In the power device failure detection method of the present invention, the real-time acquisition of the case temperature of the power device includes sampling the case temperatures of a plurality of power devices connected in parallel and taking the maximum case temperature thereof as the case temperature threshold;

[0009] The power device failure detection method further includes: when the case temperature, the forward conduction voltage drop, and the forward conduction current meet preset conditions, determining that the power device has failed; and calculating a minimum forward conduction voltage drop and a maximum forward conduction voltage drop based on the case temperature and the forward conduction current.

[0010] In the power device failure detection method of the present invention, the calculating of the minimum forward conduction voltage drop and the maximum forward conduction voltage drop based on the case temperature and the forward conduction current includes:

[0011] Obtaining a forward voltage drop theoretical value calculation formula based on the characteristics of the power device;

[0012] Calculating the maximum forward conduction voltage drop based on the first set shell temperature, the maximum forward conduction current and the forward conduction voltage drop theoretical value calculation formula;

[0013] Calculating the minimum forward conduction voltage drop based on the second set shell temperature, the reverse polarization saturation current and the forward conduction voltage drop theoretical value calculation formula;

[0014] The first set case temperature is lower than the second set case temperature.

[0015] In the power device failure detection method of the present invention, the power device includes a diode and a MOS tube;

[0016] When the power device includes a diode, obtaining the forward conduction voltage drop theoretical value calculation formula based on the characteristics of the power device includes: obtaining the forward conduction voltage drop theoretical value calculation formula by interpolation fitting according to the characteristic curve of the diode;

[0017] When the power device includes a MOS tube, the forward conduction voltage drop theoretical value calculation formula obtained based on the characteristics of the power device includes: obtaining the forward conduction voltage drop theoretical value calculation formula according to the forward conduction resistance, forward conduction current and case temperature of the MOS tube.

[0018] In the power device failure detection method of the present invention, the forward voltage drop theoretical value calculation formula is obtained by interpolation fitting based on the characteristic curve of the diode, including:

[0019] The forward voltage drop theoretical value calculation formula is obtained by interpolation fitting based on the forward voltage drop-forward current-case temperature characteristic curve of the diode:

[0020]

[0021] Where V F0 represents the reference voltage drop of the diode; α represents the temperature coefficient; β represents the current correction factor; I0 represents the reverse bias saturation current; TC : Indicates the shell temperature; I F Represents the forward conduction current; V F(theory) It represents the theoretical value of the forward conduction voltage drop.

[0022] In the power device failure detection method of the present invention, the first set case temperature is 25° C.; the second set case temperature is 120° C.;

[0023] The maximum forward conduction voltage drop is expressed as:

[0024]

[0025] Where V F_max Represents the maximum forward conduction voltage drop; I F_max represents the maximum forward conduction current;

[0026] The minimum forward conduction voltage drop is expressed as:

[0027]

[0028] Where V F_min represents the maximum forward conduction voltage drop; I0 represents the reverse bias saturation current.

[0029] In the power device failure detection method of the present invention, the forward voltage drop theoretical value calculation formula obtained based on the forward resistance, forward current and case temperature of the MOS tube includes:

[0030] Calculating the effect of the shell temperature on the nominal on-resistance of the MOS tube to obtain a first variable resistance;

[0031] Calculating the influence of the forward conduction current on the nominal on-resistance of the MOS transistor to obtain a second variable resistance;

[0032] The forward resistance is obtained based on the first variable resistance and the second variable resistance, and the forward voltage drop theoretical value calculation formula is obtained based on the forward resistance and the forward current.

[0033] In the power device failure detection method of the present invention, calculating the effect of the case temperature on the nominal on-resistance of the MOS tube to obtain the first variable resistance includes calculating the first variable resistance based on the following formula:

[0034] R ds_on (T c )=R ds_on_25℃ ×[1+α×(T c -25℃)]

[0035] Among them, R ds_on(Tc) represents the first variable resistance, Tc represents the case temperature, R ds_on_25℃ represents the nominal on-resistance, and α represents the temperature coefficient;

[0036] Calculating the influence of the forward conduction current on the nominal on-resistance of the MOS transistor to obtain the second variable resistance includes calculating the second variable resistance based on the following formula:

[0037]

[0038] R ds_on (I ds_on ) represents the second variable resistance, I ds_on represents the forward conduction current, and β represents the current dependence coefficient;

[0039] The method of obtaining the forward resistance based on the first variable resistance and the second variable resistance and obtaining the forward voltage drop theoretical value calculation formula based on the forward resistance and the forward current includes calculating the forward voltage drop theoretical value based on the following formula:

[0040]

[0041] Wherein, Vds_on represents the theoretical value of the forward conduction voltage drop; R ds_on_25℃ represents the nominal on-resistance; α represents the temperature coefficient; I ds_on represents the forward conduction current, β represents the current dependence coefficient, and η represents the empirical index.

[0042] In the power device failure detection method of the present invention, the first set case temperature is 25° C.; the second set case temperature is 120° C.;

[0043] The maximum forward voltage drop is the forward current I detected when Tc=25°C. ds_on And the value obtained by substituting Tc=25°C into the forward conduction voltage drop theoretical value calculation formula;

[0044] The minimum forward conduction voltage drop is the forward conduction current I detected when Tc=120°C. ds_on And the value obtained by substituting Tc=120°C into the forward conduction voltage drop theoretical value calculation formula.

[0045] In the power device failure detection method of the present invention, the power device failure includes short circuit failure, open circuit failure, or parameter degradation, and when the case temperature, the forward conduction voltage drop, and the forward conduction current meet preset conditions, determining that the power device has failed includes:

[0046] Get the shell temperature threshold, minimum forward conduction voltage drop, and maximum forward conduction voltage drop;

[0047] When the forward conduction voltage drop is less than the minimum forward conduction voltage drop and the case temperature is greater than the case temperature threshold, it is determined that a short circuit failure occurs in the power device;

[0048] When the forward conduction voltage drop is greater than the maximum forward conduction voltage drop and the forward conduction current is approximately 0, determining that an open circuit failure occurs in the power device;

[0049] When the forward conduction voltage drop continuously deviates from the forward conduction voltage drop theoretical value and exceeds a set range and the shell temperature fluctuates abnormally, it is determined that parameter degradation occurs in the power device.

[0050] The power device failure detection method of the present invention is implemented by obtaining the shell temperature, forward conduction voltage drop and forward conduction current of the power device in real time. When the shell temperature, the forward conduction voltage drop and the forward conduction current meet preset conditions, the power device is determined to have failed. The power device failure can be detected online in real time. The detection process is simple and the accuracy is higher due to the fusion comparison of multiple parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0052] Figure 1 It is a principle block diagram of a preferred embodiment of the power device failure detection method of the present invention;

[0053] Figure 2 It is a logic diagram of the judgment process of the power device failure detection method of the present invention;

[0054] Figure 3 It is a principle block diagram of the power device failure detection device of the present invention. DETAILED DESCRIPTION

[0055] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0056] Figure 1 FIG. 1 is a principle block diagram of a preferred embodiment of the power device failure detection method of the present invention. Figure 1 As shown, in step S1, the case temperature, forward voltage drop, and forward current of the power device are acquired in real time. In a preferred embodiment of the present invention, the case temperature Tc of the power device can be acquired in real time by using a temperature acquisition circuit, and the forward voltage drop sampling circuit and the forward current sampling circuit can be used to respectively acquire the forward voltage drop V of the power device.F and forward current I F In a preferred embodiment of the present invention, the power device may include various types of power devices, such as diodes, MOS tubes, IGBT tubes, and the like.

[0057] In step S2, when the case temperature, the forward voltage drop, and the forward current meet preset conditions, the power device is determined to be faulty. For example, in a preferred embodiment of the present invention, whether the power device is faulty is determined based on the case temperature, the forward voltage drop, the forward current, as well as a case temperature threshold, a minimum forward voltage drop, and a maximum forward voltage drop. In a preferred embodiment of the present invention, determining whether the power device is faulty based on the case temperature, the forward voltage drop, the forward current, as well as a case temperature threshold, a minimum forward voltage drop, and a maximum forward voltage drop comprises: sampling the case temperatures of a plurality of power devices connected in parallel and using the maximum case temperature as the case temperature threshold; calculating the minimum forward voltage drop and the maximum forward voltage drop based on the case temperature and the forward current; and determining whether the power device has a short circuit failure, an open circuit failure, or parameter degradation based on the case temperature, the forward voltage drop, the forward current, the case temperature threshold, the minimum forward voltage drop, and the maximum forward voltage drop.

[0058] In a further preferred embodiment of the present invention, the calculation of the minimum forward conduction voltage drop and the maximum forward conduction voltage drop based on the shell temperature and the forward conduction current includes: obtaining a forward conduction voltage drop theoretical value calculation formula based on the characteristics of the power device; calculating the maximum forward conduction voltage drop based on a first set shell temperature, the maximum forward conduction current and the forward conduction voltage drop theoretical value calculation formula; calculating the minimum forward conduction voltage drop based on a second set shell temperature, the reverse polarization saturation current and the forward conduction voltage drop theoretical value calculation formula; the first set shell temperature is less than the second set shell temperature.

[0059] In a preferred embodiment of the present invention, when the forward conduction voltage drop is less than the minimum forward conduction voltage drop and the shell temperature is greater than the shell temperature threshold, the power device is judged to have a short circuit failure; when the forward conduction voltage drop is greater than the maximum forward conduction voltage drop and the forward conduction current is approximately 0, the power device is judged to have an open circuit failure; when the forward conduction voltage drop continuously deviates from the forward conduction voltage drop theoretical value beyond a set range and the shell temperature fluctuates abnormally, the power device is judged to have parameter degradation.

[0060] Short-circuit failure typically refers to a power device losing its ability to block reverse current; open-circuit failure refers to a power device losing its ability to conduct current, manifested by extremely large or infinite internal resistance, preventing current from flowing through it; and parameter degradation refers to the gradual deterioration of a power device's electrical performance and parameters. Parameter degradation may cause the device to be unable to effectively perform its original function, thereby affecting the performance of the entire circuit. Therefore, in a further preferred embodiment of the present invention, different alarm levels can be set for different failures. For example, parameter degradation only provides an alarm indication, while short-circuit and open-circuit failures simultaneously provide an alarm indication and disable the output, prohibiting further operation.

[0061] The power device failure detection method of the present invention is implemented by acquiring the case temperature, forward conduction voltage drop and forward conduction current of the power device in real time, and when the case temperature, the forward conduction voltage drop and the forward conduction current meet preset conditions, the power device is determined to have failed. The power device failure can be detected online in real time, the detection process is simple, and various failure types can be accurately identified.

[0062] Figure 2 This is a logic diagram of the judgment process of the power device failure detection method of the present invention. Figure 2 Based on the teachings of the present invention, those skilled in the art can apply it to any other types of diodes, IGBTs, transistors and other power devices, and will not be elaborated here.

[0063] Since the anti-backflow diode needs to pass a large current and withstand a high reverse voltage, the material of the anti-backflow diode is usually a diode based on silicon material, and germanium material diodes are basically not used. Therefore, the anti-backflow diodes mentioned in this embodiment are all silicon-based diodes, and the relevant parameters are all set and calculated based on silicon material diodes.

[0064] First, the temperature acquisition circuit is used to collect the shell temperature Tc of the anti-backflow diode in real time, and the diode forward voltage drop sampling circuit and the diode forward current sampling circuit are used to collect the diode forward conduction voltage drop V F And forward current I F . Since the current flowing through the anti-backflow diode is large during operation, it usually generates a lot of heat, resulting in a high temperature. The usual measure is to add a heat sink to the diode to dissipate the heat of the anti-backflow diode. At the same time, in high-power charging module applications, the anti-backflow diodes are often connected in parallel. Therefore, the anti-backflow diodes working in parallel will have inconsistent temperatures due to different heat dissipation conditions, current sharing and other factors. In a preferred embodiment of the present invention, a multi-point detection scheme is adopted to sample the shell temperature T of the diodes near multiple parallel diodes. C1,T C2 ...T CN , take the maximum value of the sampling and set it as the case temperature threshold T of the diode during normal operation C_max .

[0065] Using the diode's own forward conduction voltage drop V F With the forward current I F and shell temperature T C The theoretical forward conduction voltage drop V is calculated from the relationship F The maximum value of V F_max and minimum value V F_min , the above theory V F The value is the forward voltage drop of the diode itself - forward current - case temperature (V F -I F -T C) The characteristic curve is obtained by interpolation fitting. That is, the forward voltage drop theoretical value calculation formula is obtained by interpolation fitting based on the forward voltage drop-forward current-case temperature characteristic curve of the diode.

[0066]

[0067] Where V F0 represents the reference voltage drop of the diode, which can be obtained from the diode specification sheet; α represents the temperature coefficient, which is a negative value for silicon diodes and is -2mV / °C; β represents the current correction factor and is 60mV; I0 represents the reverse bias saturation current (for example, the reverse bias saturation current at 25°C specified in the diode specification sheet); T C : represents the shell temperature (i.e., the temperature acquisition circuit acquires the shell temperature Tc of the anti-backflow diode in real time); I F represents the forward conduction current (i.e., the sampling current of the diode forward current sampling circuit); V F(theory) It represents the theoretical value of the forward conduction voltage drop.

[0068] At the maximum output current I O_max In the charging module, when the number of anti-backflow diodes connected in parallel is N, the maximum forward conduction current IF_max passing through a single anti-backflow diode is:

[0069]

[0070] Shell temperature T C =T C_max =25℃, forward current I F =I F_max The forward voltage drop of the diode is the maximum forward voltage drop V F_max , that is, to obtain the maximum forward conduction voltage drop:

[0071]

[0072] Similarly, take the shell temperature T C =120℃, forward current I F =I0, the diode forward voltage drop is the minimum forward voltage drop V F_min , that is, to obtain the minimum forward conduction voltage drop:

[0073]

[0074] Then, based on the case temperature Tc, the forward conduction voltage drop V F , the forward conduction current I F And the shell temperature threshold T C_max , minimum forward conduction voltage drop V F_min and maximum forward voltage drop V F_max Determine whether the power device is failed. Of course, in the preferred embodiment of the present invention, when calculating the minimum forward conduction voltage drop V F_min and maximum forward voltage drop V F_max You can also choose any other suitable set temperature according to the actual situation, such as calculating the minimum forward conduction voltage drop V F_min When selecting T C =100℃, 135℃; and in calculating the maximum forward conduction voltage drop V F_max When selecting T C =20°C, 30°C, etc., all of which fall within the protection scope of the present invention.

[0075] After the failure of the anti-backflow diode, it usually manifests as the following situations: short-circuit failure: the PN junction of the diode is short-circuited, causing it to lose its ability to normally block the reverse current; open-circuit failure: the PN junction of the diode is open-circuited and loses its conduction ability, which manifests as its internal resistance being extremely large or infinite, resulting in the inability of current to pass; parameter degradation: the electrical performance and parameters of the diode gradually decrease. Parameter degradation may cause the diode to be unable to effectively perform its original function, thereby affecting the performance of the entire circuit.

[0076] The following relationship can be used to determine when a diode is short-circuited:

[0077] Short circuit failure: When V F <V F_min And T C >T C_max When triggered;

[0078] The following relationship can be used to determine when a diode is open:

[0079] Open circuit failure: When V F >V F_maxAnd I F Triggered when ≈0;

[0080] The following relationship can be used to judge when parameter degradation occurs:

[0081] Parameter degradation: When V F Triggered when the deviation from the theoretical value is ±10% and the Tc fluctuates abnormally. The abnormal fluctuation can be set according to the actual situation, such as the number of changes, the difference exceeding the set value, etc.

[0082] When the above faults and anomalies occur, graded alarm output is performed according to the severity of the fault. For example, parameter degradation only gives an alarm indication, while for short circuit and open circuit, the output is turned off and further operation is prohibited at the same time as the alarm indication.

[0083] The power device failure detection method of the present invention can detect whether the power device has failed in real time online. The detection process is simple, and due to the combination of multiple parameter fusion comparison, the accuracy is higher. The parameter detection, judgment, and triggering of abnormal alarm output can reach the millisecond level. It can also adaptively learn and dynamically update the threshold, adapt to various diode models and compatible diode aging scenarios (different brands and models of diodes have V F0 The software only needs to associate and adjust the diode model with the threshold value to adapt to the use of different types of diodes); strong scalability: it supports parallel monitoring of multiple diodes and can be applied to the health management of power devices such as IGBTs, MOS tubes and other devices.

[0084] The MOS transistor failure detection method is similar to the diode failure detection method, also including real-time acquisition of the MOS transistor's case temperature, forward voltage drop, and forward current. Failure is determined based on these values, along with the case temperature threshold, minimum forward voltage drop, and maximum forward voltage drop. The only difference lies in the calculation process of the minimum and maximum forward voltage drops. This process is described below.

[0085] In a preferred embodiment of the present invention, the effect of the case temperature on the nominal on-resistance of the MOS transistor is calculated to obtain a first variable resistance; the effect of the forward current on the nominal on-resistance of the MOS transistor is calculated to obtain a second variable resistance; the forward on-resistance is obtained based on the first variable resistance and the second variable resistance, and the forward voltage drop theoretical value calculation formula is obtained based on the forward on-resistance and the forward current. The minimum forward voltage drop and the maximum forward voltage drop are then calculated based on the forward voltage drop theoretical value calculation formula.

[0086] Taking MOS transistors as an example, the forward conduction voltage drop of MOS transistors is affected by the forward conduction resistance, case temperature, and forward conduction current as follows:

[0087] V ds_on =I ds_on ×R ds_on (T c ,I ds_on )

[0088] Where Vds_on represents the theoretical value of the forward conduction voltage drop, R ds_on (Tc, I ds_on ) represents the forward conduction resistance. ds_on It is the temperature and current dependent on-resistance, and its value varies with the case temperature T c and current I ds_on change.

[0089] The temperature effect of the forward on-resistance Rds_on of the MOS tube increases with increasing temperature. The typical model is:

[0090] R ds_on (T c )=R ds_on_25℃ ×[1+α×(T c -25℃)].

[0091] Therefore, the influence of the shell temperature on the nominal on-resistance of the MOS tube can be calculated according to the formula to obtain the first variable resistance; wherein, R ds_on (Tc) represents the first variable resistance; Tc represents the shell temperature; R ds_on_25℃ It represents the nominal on-resistance, which is usually provided in the device data sheet. α represents the temperature coefficient. Typical values are: silicon (Si) MOS tube: 0.4-0.7% / °C.

[0092] Silicon carbide (SiC) MOS tube: 0.2~0.4% / ℃.

[0093] In the case of forward current, the on-resistance R ds_on It will further change due to self-heating effects or mobility modulation, which is modeled as:

[0094]

[0095] Therefore, the influence of the forward conduction current on the nominal on-resistance of the MOS tube can be calculated according to the formula to obtain the second variable resistance; R ds_on (I ds_on ) represents the second variable resistance, I ds_on represents the forward conduction current, β represents the current dependence coefficient, and the typical value range is: Silicon (Si) MOS tube: 1×10 -3~5×10 -3 (1 / A n ); Silicon carbide (SiC) MOS tube: 5×10 -4 ~2×10 -3 (1 / A n );η represents the empirical index, and the typical value range is: silicon (Si) MOS tube: 0.7~1.2; silicon carbide (SiC) MOS tube: 0.5~0.9.

[0096] Therefore, combined with the above formula, the relationship between the MOS tube forward conduction voltage drop Vds_on, the case temperature Tc and the forward conduction current Ids_on can be expressed as:

[0097]

[0098] Wherein, Vds_on represents the theoretical value of the forward conduction voltage drop; R ds_on_25℃ represents the nominal on-resistance; α represents the temperature coefficient; I ds_on represents the forward conduction current, β represents the current dependence coefficient, and η represents the empirical index.

[0099] Thus, we can obtain the calculation formula of the theoretical value of the forward conduction voltage drop of the MOS tube. Similar to the above embodiment, the shell temperature T C =25℃, I ds_on The forward conduction current I is detected when Tc = 25°C. ds_on Substituting into the above formula, we can get the maximum forward voltage drop V F_max ; Take shell temperature T C =120℃, I ds_on The forward conduction current I detected at Tc = 120°C ds_on Substituting into the above formula, we can obtain the minimum forward voltage drop V F_mix Of course, other shell temperatures can also be selected for calculation.

[0100] Similarly, the following relationship can be used to determine when a MOS tube is short-circuited:

[0101] Short circuit failure: When V F <V F_min And T C >T C_max When triggered;

[0102] The following relationship can be used to determine when a MOS tube is open:

[0103] Open circuit failure: When V F >V F_max And I F Triggered when ≈0;

[0104] The following relationship can be used to judge when parameter degradation occurs:

[0105] Parameter degradation: When V F Triggered when the deviation from the theoretical value is ±10% and the Tc fluctuates abnormally. The abnormal fluctuation can be set according to the actual situation, such as the number of changes, the difference exceeds the set value, etc.

[0106] The power device failure detection method of the present invention can detect whether a power device has failed in real time online. The detection process is simple, and due to the combination of multiple parameter fusion comparisons, the accuracy is higher. The parameters detection, judgment, and triggering of abnormal alarm output can reach the millisecond level. It can also adaptively learn and dynamically update thresholds to adapt to various MOS tubes. It has strong scalability: it supports parallel monitoring of multiple MOS tubes and can be applied to various types of power devices.

[0107] Figure 3 FIG. 1 is a block diagram of the principle of the power device failure detection device of the present invention, wherein an anti-flooding diode is used as an example for explanation. Figure 3 As shown, the power device failure detection device of the present invention includes a case temperature detection unit Tc, a forward voltage drop detection unit VF, a forward current detection unit IF, a digital processing unit, and an alarm output unit. The case temperature detection unit Tc can be implemented by using an NTC resistor divider to sample the case temperature of the tube. The forward voltage drop detection unit VF can use a differential amplifier connected across the two sides of the anti-backflow diode to detect the voltage across the diode. The forward current detection unit IF can use a Hall current sensor or a shunt connected in series within the main circuit of the anti-backflow diode to sample the current within the diode.

[0108] The digital processing unit is used to execute the aforementioned power device failure detection method, that is, to determine whether the power device has failed based on the shell temperature, the forward conduction voltage drop, the forward conduction current, the shell temperature threshold, the minimum forward conduction voltage drop, and the maximum forward conduction voltage drop. Here, the digital processing unit internally stores a VF-IF-Tc database of diodes of corresponding models, stores normal parameter range values under different working conditions, performs threshold judgment on the collected data values, executes an analysis algorithm to determine whether the diode is abnormal, and generates abnormal alarm information. The alarm output unit performs a multi-level alarm output function, and outputs alarm signals to the outside through logic level flipping, LED indicator light, buzzer or dry junction. A person skilled in the art can construct a digital processing unit and an alarm output unit based on the aforementioned power device failure detection method, and will not be repeated here.

[0109] When the power device failure detection device or power device failure detection method of the present invention is applied to the anti-backflow diode at the output end of a 40kW charging module of an electric vehicle, the maximum output voltage within the module output voltage range is 1000Vdc, the maximum output current of the module is 133A, and the anti-backflow diode model is 1600V / 60A and four are used in parallel. The diode reverse withstand voltage VR = 1600V. Tc_max = 125°C (this value can be dynamically adjusted and decreases at a rate of 0.8°C / °C as the ambient temperature increases); V F Normal range: 1.0V ± 0.08V (@IF = 60A, Tc = 80°C). Failure response: Level 1 alarm (VF deviation > 15%): Illuminates the yellow LED and reports the alarm to the system. Level 2 alarm (short circuit / open circuit): Triggers a relay to disconnect the circuit and sounds a buzzer. Additionally, the alarm information can be sent to the operation and maintenance platform via the 4G module, prompting inspection and replacement of the anti-backflow diode.

[0110] The power device failure detection device or power device failure detection method of the present invention monitors the forward conduction voltage drop, its shell temperature and the forward conduction current of the power device in real time, combines the parameter change trend under dynamic working conditions, builds a multi-dimensional failure criterion model, and combines the dynamic threshold algorithm to accurately identify short circuit, open circuit and parameter degradation failure modes. Preferably, contact multi-point comprehensive temperature measurement and high-precision differential voltage sampling and current sampling technology can be used to synchronously obtain the working status data of the power device. The forward conduction voltage drop and temperature correlation characteristics are adaptively analyzed by the microprocessor. When it is detected that the voltage drop deviates from the nominal range and the temperature rise rate is abnormal, the power device is judged to have failed and a graded alarm is triggered. Therefore, early fault warning can be achieved during the continuous operation of the equipment, and traditional passive protection can be upgraded to predictive maintenance, filling the technical gap of intelligent failure detection of anti-backflow power devices and significantly improving system reliability.

[0111] Although the present invention is described by way of specific embodiments, it will be understood by those skilled in the art that various modifications and equivalent substitutions may be made to the present invention without departing from the scope of the present invention. Furthermore, various modifications may be made to the present invention for specific circumstances or materials without departing from the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed, but is intended to encompass all embodiments falling within the scope of the claims.

[0112] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for detecting power device failure, characterized in that: include: Real-time acquisition of power device case temperature, forward voltage drop, and forward current; When the shell temperature, the forward conduction voltage drop, and the forward conduction current meet preset conditions, it is determined that the power device has failed.

2. The power device failure detection method according to claim 1, characterized in that: The real-time acquisition of the shell temperature of the power device includes sampling the shell temperatures of a plurality of power devices connected in parallel and taking the maximum shell temperature thereof as the shell temperature threshold; The power device failure detection method further comprises: when the shell temperature, the forward conduction voltage drop, and the forward conduction current meet preset conditions, determining that the power device is before failure; A minimum forward conduction voltage drop and a maximum forward conduction voltage drop are calculated based on the case temperature and the forward conduction current.

3. The power device failure detection method according to claim 2, characterized in that: The calculating of the minimum forward conduction voltage drop and the maximum forward conduction voltage drop based on the shell temperature and the forward conduction current includes: Obtaining a forward voltage drop theoretical value calculation formula based on the characteristics of the power device; Calculating the maximum forward conduction voltage drop based on the first set shell temperature, the maximum forward conduction current and the forward conduction voltage drop theoretical value calculation formula; Calculating the minimum forward conduction voltage drop based on the second set shell temperature, the reverse polarization saturation current and the forward conduction voltage drop theoretical value calculation formula; The first set case temperature is lower than the second set case temperature.

4. The power device failure detection method according to claim 3, characterized in that: The power devices include diodes and MOS tubes; When the power device includes a diode, obtaining the forward conduction voltage drop theoretical value calculation formula based on the characteristics of the power device includes: obtaining the forward conduction voltage drop theoretical value calculation formula by interpolation fitting according to the characteristic curve of the diode; When the power device includes a MOS tube, the forward conduction voltage drop theoretical value calculation formula obtained based on the characteristics of the power device includes: obtaining the forward conduction voltage drop theoretical value calculation formula according to the forward conduction resistance, forward conduction current and case temperature of the MOS tube.

5. The power device failure detection method according to claim 4, characterized in that: The forward voltage drop theoretical value calculation formula is obtained by interpolation fitting based on the characteristic curve of the diode, including: The forward voltage drop theoretical value calculation formula is obtained by interpolation fitting based on the forward voltage drop-forward current-case temperature characteristic curve of the diode: Where V F0 represents the reference voltage drop of the diode; α represents the temperature coefficient; β represents the current correction factor; I0 represents the reverse bias saturation current; T C : Indicates the shell temperature; I F Represents the forward conduction current; V F(theory) It represents the theoretical value of the forward conduction voltage drop.

6. The power device failure detection method according to claim 5, characterized in that: The first set shell temperature is 25°C; the second set shell temperature is 120°C; The maximum forward conduction voltage drop is expressed as: Where V F_max Represents the maximum forward conduction voltage drop; I F_max represents the maximum forward conduction current; The minimum forward conduction voltage drop is expressed as: Where V F_min represents the maximum forward conduction voltage drop; I0 represents the reverse bias saturation current.

7. The power device failure detection method according to claim 4, characterized in that: The forward voltage drop theoretical value calculation formula obtained according to the forward resistance, forward current and shell temperature of the MOS tube includes: Calculating the effect of the shell temperature on the nominal on-resistance of the MOS tube to obtain a first variable resistance; Calculating the influence of the forward conduction current on the nominal on-resistance of the MOS transistor to obtain a second variable resistance; The forward resistance is obtained based on the first variable resistance and the second variable resistance, and the forward voltage drop theoretical value calculation formula is obtained based on the forward resistance and the forward current.

8. The power device failure detection method according to claim 7, characterized in that: Calculating the influence of the shell temperature on the nominal on-resistance of the MOS tube to obtain a first variable resistance includes calculating the first variable resistance based on the following formula: R ds_on (T c )=R ds_on_25℃ ×[1+α×(T c -25℃)] Among them, R ds_on (Tc) represents the first variable resistance, Tc represents the case temperature, R ds_on_25℃ represents the nominal on-resistance, and α represents the temperature coefficient; Calculating the influence of the forward conduction current on the nominal on-resistance of the MOS transistor to obtain the second variable resistance includes calculating the second variable resistance based on the following formula: R ds_on (I ds_on ) represents the second variable resistance, I ds_on represents the forward conduction current, and β represents the current dependence coefficient; The method of obtaining the forward resistance based on the first variable resistance and the second variable resistance and obtaining the forward voltage drop theoretical value calculation formula based on the forward resistance and the forward current includes calculating the forward voltage drop theoretical value based on the following formula: Wherein, Vds_on represents the theoretical value of the forward conduction voltage drop; R ds_on_25℃ represents the nominal on-resistance; α represents the temperature coefficient; I ds_on represents the forward conduction current, β represents the current dependence coefficient, and η represents the empirical index.

9. The power device failure detection method according to claim 8, characterized in that: The first set shell temperature is 25°C; the second set shell temperature is 120°C; The maximum forward voltage drop is the forward current I detected when Tc=25°C. ds_on And the value obtained by substituting Tc=25°C into the forward conduction voltage drop theoretical value calculation formula; The minimum forward conduction voltage drop is the forward conduction current I detected when Tc=120°C. ds_on And the value obtained by substituting Tc=120°C into the forward conduction voltage drop theoretical value calculation formula.

10. The power device failure detection method according to any one of claims 1 to 9, characterized in that: The power device failure includes short circuit failure, open circuit failure or parameter degradation; When the shell temperature, the forward conduction voltage drop, and the forward conduction current meet preset conditions, determining that the power device has failed includes: Get the shell temperature threshold, minimum forward conduction voltage drop, and maximum forward conduction voltage drop; When the forward conduction voltage drop is less than the minimum forward conduction voltage drop and the case temperature is greater than the case temperature threshold, it is determined that a short circuit failure occurs in the power device; When the forward conduction voltage drop is greater than the maximum forward conduction voltage drop and the forward conduction current is approximately 0, determining that an open circuit failure occurs in the power device; When the forward conduction voltage drop continuously deviates from the forward conduction voltage drop theoretical value and exceeds a set range and the shell temperature fluctuates abnormally, it is determined that parameter degradation occurs in the power device.

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