Method and test system for electronic fuses

Abstract

The invention relates to a test method for detecting an operating state of an electronic fuse (1) switchable between at least a conducting state and a non-conducting state, which electrically connects an electrical load (3) to a supply voltage source (2), wherein the electrical load (3) can withstand a supply circuit break for a predetermined maximum circuit break duration. The switchable electronic fuse (1) is switched from the conducting state to the non-conducting state within a test time which is at most as long as the maximum circuit break duration of the electrical load (3). During the test time, a residual current flowing through the switchable electronic fuse (1) is detected by a test circuit (120) as an actual residual current value and compared to at least one target residual current value. When the actual residual current value is below the at least one target residual current value, a first operating state is assigned to the switchable electronic fuse (1); otherwise, another operating state is assigned. The invention also relates to a test system (100) for carrying out the test method.

Description

Technical Field

[0001] This invention relates to a method for testing switchable electronic fuses according to the preamble of claim 1. Furthermore, this invention also relates to a test system for testing switchable electronic fuses according to the preamble of claim 8. Background Technology

[0002] An electronic fuse is a semiconductor circuit used to limit or interrupt the current drawn by an electrical load. Similar to a conventional fusible fuse, an electronic fuse blows when an overcurrent condition (such as a short circuit in the electrical load) occurs, causing it to carry a current exceeding its rated current for a predetermined time. An electronic fuse that correctly blows under overcurrent conditions typically loses its conductivity permanently (irreversibly), but resettable electronic fuses are also known, which can return to their initial state after an overcurrent.

[0003] A switchable electronic fuse can electronically switch between an on and off state before an overcurrent condition occurs. For example, a switchable electronic fuse can be designed as a field-effect transistor, such as an n-channel metal-oxide-semiconductor field-effect transistor, which can switch between an on and off state by a voltage applied to its gate.

[0004] Due to manufacturing or operational malfunctions, or performance degradation caused by aging electronic fuses, the protected electrical load may not be able to safely disconnect from the power supply voltage in the event of an overcurrent. This can affect the operational safety of the electrical load. For example, if such an electrical load is a safety-critical electrical subsystem in a vehicle, it could impact the vehicle's operational safety. Therefore, it is necessary to regularly check the operational status of such electronic fuses.

[0005] Therefore, electronic fuses can be tested in operating modes where the electrical load is disconnected, such as when the vehicle is parked and safety-critical electrical subsystems are off. However, this method is not suitable for checking the operational status of electronic fuses during continuous operation and is therefore unsuitable for continuous monitoring.

[0006] Furthermore, a redundant second electronic fuse can be arranged in parallel with the first electronic fuse between the power supply voltage source and the electrical load to be protected. Subsequently, these two electronic fuses can be alternately disconnected from the electrical load for isolation testing without affecting the power supply to the electrical load. However, this redundancy increases manufacturing and operating costs, such as due to the need for more space on the circuit board or chip, and / or due to increased power consumption caused by the need to provide additional electronic fuses.

[0007] US document 2001 / 0034070 A1 describes a device and method for testing fuses in storage devices. A voltage that decays over time is applied across a control resistor. A comparator compares the voltage drop across the control resistor with a reference voltage. The time elapsed for the comparator to change its state is measured. The fuse is tested by applying a decaying voltage to the fuse under test and measuring the time required for the comparator to switch, comparing this measured time with the measured time. When the fuse's resistance value meets specifications, the comparator will switch its state within the time determined according to the control resistor. By adjusting the reference voltage of the comparator, the time required for the comparator to switch for fuses with compliant resistance values ​​can be shortened, thereby reducing the test time. However, this method is only suitable for testing non-switchable electrical connections, particularly for determining whether they possess sufficient conductivity (i.e., sufficiently low resistance). Summary of the Invention

[0008] Therefore, an improved testing method is needed to detect the operating status of switchable electronic fuses, particularly distinguishing between two states: a safe operating state, where the electrical load is reliably isolated from the power supply voltage under overcurrent conditions; and an unsafe operating state, where the electrical load cannot be reliably isolated from the power supply voltage under overcurrent conditions. Furthermore, it may be necessary to identify certain operating states in which, although the electrical load is isolated during overcurrent, certain parameters (such as disconnection time or residual conductivity remaining along the electronic fuse) do not reach their specified ratings.

[0009] The first aspect of the present invention aims to provide an improved method for testing switchable electronic fuses. According to the invention, this objective is achieved by a method having the features described in claim 1.

[0010] Another object of the present invention is to provide an improved test system for testing switchable electronic fuses. According to the present invention, this object is achieved by a test system having the features described in claim 8.

[0011] Advantageous designs of the present invention are the subject of the dependent claims.

[0012] The first aspect of the invention relates to a method for testing switchable electronic fuses.

[0013] For a switchable electronic fuse that can switch between at least one on state and one off state and connects at least one electrical load to a power supply voltage source, at least one first operating state with normal function and a second operating state with abnormal function can be distinguished.

[0014] In the first operating state, when the current absorbed by the electrical load exceeds a predetermined rated current intensity within a predetermined time, at least one electrical load is reliably disconnected from the power supply via an electronic fuse. In the second operating state, under these conditions, disconnection of the electrical load cannot be guaranteed or reliably achieved.

[0015] At least one electrical load is designed to withstand a power supply interruption (i.e. disconnection from the power supply voltage source) for a predetermined maximum interruption duration.

[0016] Maximum circuit breaking time refers to the longest time an electrical load can continue to operate without being powered by a supply voltage source, taking all tolerances into account, such as by using a buffer memory inside the electrical load.

[0017] In a test method for detecting the operating state of a switchable electronic fuse, the switchable electronic fuse is switched from a conducting state to a non-conducting state within a test time, wherein the test time is at most equal to the shortest maximum circuit-breaking time among all electrical loads powered by the switchable electronic fuse.

[0018] During the test period, the residual current flowing through the switchable electronic fuse in a non-conducting state will be detected as the actual residual current value and compared with at least one target residual current value. When the detected actual residual current value is below at least one target residual current value, the switchable electronic fuse will be assigned to a first (normal) operating state. If at least one target residual current value is less than or equal to the detected actual residual current value, the switchable electronic fuse will be assigned to another operating state.

[0019] This method enables functional safety testing of switchable electronic fuses without affecting the normal operation of the electrical loads they power, and without requiring the use of redundant structures in the switchable electronic fuses. This allows for particularly economical, energy-efficient, and precise functional testing of switchable electronic fuses.

[0020] In one embodiment of this method, the actual residual current value is detected by detecting the actual discharge duration of a capacitor connected in parallel to an electrical load and powered by a supply voltage source as it discharges through a resistor. The measured actual discharge duration value is compared with at least one target discharge duration value, which is measured for a switchable electronic fuse under specific operating conditions.

[0021] For example, a first target value can be determined for the discharge duration of a switchable electronic fuse in a fully functional operating state, and a second target value can be determined for the discharge duration in a still functional but degraded operating state. Subsequently, the actual discharge duration of the capacitor connected to the power supply voltage source through the switchable electronic fuse under test is detected and compared with the first and second target values. If the measured actual discharge duration is below the first target value, the switchable electronic fuse under test is assigned to a "functionally normal" operating state. If the measured actual discharge duration is below the second target value but not below the first target value, the switchable electronic fuse under test is assigned to a "functionally limited" operating state. If the detected actual discharge duration is not below the second target value, the switchable electronic fuse under test is assigned to a "functionally abnormal" operating state.

[0022] In an improved embodiment of this method, a measured voltage across the capacitor is detected and compared with a reference voltage, for example, using a comparator. The reference voltage may be provided, for example, by an adjustable reference voltage source.

[0023] During the period when the measured voltage is above the reference voltage and the electronic fuse has been switched to the non-conducting state, a clock signal with a predetermined clock period can be counted. The actual discharge duration can be determined by multiplying the count value by the duration of the clock signal period. For example, if the reference voltage is chosen low enough (close to the voltage value of the measured voltage of a fully discharged capacitor), the product of the count value and the period duration can be directly obtained. However, to shorten the measurement time, a higher reference voltage can be chosen, and a (correspondingly lower) count value can be extrapolated, which is obtained when the reference voltage is close to the measured voltage on a nearly fully discharged capacitor.

[0024] The counters required for time measurement according to the improved scheme are as easy to implement and inexpensive as high-precision clock generators, or they already exist. Furthermore, the counting process can be very easily limited to the time range of capacitor discharge through a resistor. Therefore, the counter circuit or counter module typically has a "capture" input that must be applied a positive (logic true) level and / or a rising edge (or falling edge) to trigger the counting process or detect the counter state. For example, this level and / or edge for such a "capture" input can be obtained from the output voltage of a comparator used to compare the measured voltage with a reference voltage. The logic connections (e.g., logic connections to the signal voltage that triggers a switchable electronic fuse to switch from an on state to a non-on state) are also very easy to implement, for example, via transistor-to-transistor (TTL) logic.

[0025] Therefore, the discharge duration can be used to easily determine whether the electronic fuse disconnects the electrical load as expected when switching from the conducting to the non-conducting state. If the actual discharge duration exceeds a predetermined range above or below the corresponding target discharge duration (indicating insufficient capacitor discharge speed), excessive leakage current of the switchable electronic fuse in the non-conducting state or a short circuit in the switchable electronic fuse can be detected. In this case, the operational safety of the electrical load will be threatened because it cannot disconnect from the supply voltage in the event of a fault (exceeding the rated current).

[0026] If the actual discharge duration is below the predetermined range, insufficient capacitor charging can be detected, for example, due to the switchable electronic fuse failing to conduct fully when controlled to be in the on state (i.e., the resistance along the electronic fuse is too high).

[0027] In an improved version of this method, the deviation of the current temperature value and / or the current supply voltage value and / or the capacitance value of the capacitor from the rated value and / or the resistance value of the resistor from the rated value is measured and used to correct the actual value of the discharge duration.

[0028] For example, a capacitor's actual capacitance might be less than its rated capacitance, resulting in a shorter actual discharge time. To prevent switchable electronic fuses from being incorrectly identified as faulty, a corrected (and correspondingly reduced) target discharge time is determined based on the capacitor's actual (corrected) capacitance. Such a correction can be obtained quite simply by scaling the target discharge time (by the ratio of the target to the actual capacitance) with sufficient approximation accuracy. Alternatively (computationally equivalent), the actual discharge time can also be scaled inversely.

[0029] Similarly, when the resistance value deviates from the rated value, the actual resistance value can be corrected.

[0030] Furthermore, the effects of temperature on switchable electronic fuses and / or other components, as well as the effects of power supply voltage fluctuations, can be accounted for by mathematically correcting the target discharge duration (or the actual discharge duration, which is computationally equivalent). In this process, such fluctuations or deviations may be incorporated into the calculation correction in a non-linear manner. Advantageously, a correction table, such as one that considers the operating temperature of the electronic fuse, can be established. This table stores a correction term for each of a series of temperature values, which should be applied to the detected actual discharge duration value in the form of addition, multiplication, or other functional relationships when the corresponding temperature is detected. Similarly, correction tables can be established for different power supply voltage values.

[0031] Such calibration tables can be stored in non-volatile memory and retrieved by the test and evaluation unit after the actual discharge duration has been detected in the manner described above. Specifically, such non-volatile memory can also store correction values ​​used to compensate for deviations in the actual resistance and / or capacitance values, which are measured once during the calibration step (for each switchable electronic fuse).

[0032] This improved embodiment allows the use of lower-precision components (resistors, capacitors) and enables the implementation of the method under a wide range of drastically different conditions, such as under fluctuating supply voltages and temperatures. Therefore, it improves the reliability of the method and makes its implementation simpler and less costly.

[0033] In one exemplary embodiment of this method, the test time (off time) for placing the switchable electronic fuse in a non-conducting state is limited to 100 microseconds. Because electrical loads, especially those used in automobiles, possess sufficiently large buffer memories (e.g., internal capacitors) to bridge such brief circuit breaks without restriction, this embodiment of the method allows for testing of electronic fuses under a wide range of operating conditions (with various electrical loads).

[0034] In one embodiment of this method, the detected actual residual current value (e.g., the actual residual current value calculated based on the actual discharge duration) is continuously stored. Based on this, a dynamically adjusted target residual current value is continuously calculated. The principle is that when the currently measured actual residual current value deviates significantly from historically measured actual residual current values, the switchable electronic fuse is assigned another operating state (i.e., an operating state different from the "normal" operating state). In this way, gradual processes that do not affect the function of the switchable electronic fuse (e.g., drift due to aging) can be distinguished from sudden changes that may lead to failure. This enables the detection of faulty switchable electronic fuses with extremely high specificity and sensitivity.

[0035] In one embodiment of this method, a switchable electronic fuse is arranged in the vehicle to supply power to electrical loads. Such electrical loads (e.g., control units, sensors for monitoring the vehicle's surroundings, or powertrain components) are particularly important for safety and reliability. Therefore, it is crucial to disconnect them in the event of a fault, such as exceeding their rated current value.

[0036] In one embodiment of this method, when the actual residual current value is below the first target residual current value, the switchable electronic fuse is assigned to a first operating state of "normal function". When the actual residual current value is between the first target residual current value and a second target residual current value (the second target residual current value is higher than the first target residual current value), it is assigned to a second operating state of "limited function". When the actual residual current value is above the second target residual current value, it is assigned to a third operating state of "malfunction".

[0037] Similarly, if the actual residual current value is determined based on the actual value of the discharge duration, the first (relatively small) target value and the second (relatively large) target value of the discharge duration can also be used as the basis for allocating the first to third operating states.

[0038] The advantage of this implementation is that it can promptly identify switchable electronic fuses that have degraded but are still functioning normally for the time being (for example, in the off-state, although the leakage current has increased, it is still within the predetermined tolerance range), so that they can be replaced during planned maintenance.

[0039] According to another aspect, the present invention relates to a test system for implementing the above-described method. According to the present invention, the test system includes a test circuit, a test control unit, and a test evaluation unit.

[0040] The test circuit is configured to detect the actual residual current flowing through the switchable electronic fuse when it is switched to the non-conducting state.

[0041] The test control unit is configured to switch the switchable electronic fuse from an on state to a non-on state within a predetermined test time.

[0042] The test evaluation unit is configured to compare the actual residual current value measured by the test circuit with at least one target residual current value.

[0043] The advantages of this testing system are consistent with the advantages of the method that can be implemented according to the first aspect of the invention.

[0044] In one implementation, the test circuit includes an RC component with a resistor and a capacitor connected in parallel therewith, as well as a comparator and a timer.

[0045] The RC component can be connected to a power supply voltage source via a switchable electronic fuse. A comparator is configured to compare the measured voltage applied to the RC component with a reference voltage, which can be provided, for example, by a preferred adjustable reference voltage source.

[0046] The timer is connected to the test control unit and the comparator and is configured to detect the time elapsed from when the test control unit switches the switchable electronic fuse from the on state to the off state until the comparator determines that the measured voltage on the RC component has reached or dropped below the reference voltage.

[0047] This test circuit allows for the detection of the actual discharge time of a capacitor through a resistor, which can then be used to determine the actual residual current value by switching the switchable electronic fuse to a non-conductive state. Furthermore, in addition to comparing the actual residual current value with the target residual current value, the measured actual discharge time can also be compared with the target discharge time value corresponding to the target residual current value.

[0048] Therefore, this embodiment can check the actual residual current value in a particularly simple and accurate way, thereby checking the functionality of the switchable electronic fuse.

[0049] In one embodiment, the test evaluation unit includes an analog-to-digital converter (ADC) configured to detect the supply voltage and / or, in conjunction with a temperature sensor, detect the temperature of the switchable electronic fuse. Alternatively or supplementarily, the test evaluation unit according to this embodiment also includes non-volatile memory for storing at least one calibration value and / or at least one previously measured actual residual current value.

[0050] The advantage of this embodiment is that, when testing electronic fuses, fluctuations in the operating temperature or supply voltage of the electronic fuse, as well as manufacturing tolerances of electronic components (such as resistors and capacitors in RC assemblies), can be taken into account. Therefore, it is possible to achieve highly specific and sensitive testing of electronic fuses while maintaining a particularly simple and low-cost testing system structure. Other advantages are consistent with those of corresponding embodiments of the method according to the first aspect of the invention. Attached Figure Description

[0051] Embodiments of the present invention will now be explained in more detail with reference to the accompanying drawings.

[0052] in:

[0053] Figure 1 A test system for switchable electronic fuses is schematically illustrated.

[0054] Figure 2 The curve illustrating the change of test voltage over time during the testing phase is shown schematically.

[0055] Figure 3 A flowchart illustrating the testing and evaluation of measurements on a switchable electronic fuse is shown schematically.

[0056] Corresponding parts in all the accompanying figures are labeled with the same reference numerals. Detailed Implementation

[0057] Figure 1 A test system 100 is shown purely illustratively and schematically for checking the operational status of a switchable electronic fuse 1 disposed between a power supply voltage source 2 and an electrical load 3.

[0058] In this embodiment, the switchable electronic fuse 1 is configured as an n-channel metal-oxide-semiconductor field-effect transistor (NMOS FET), but other forms of semiconductor switching elements can also be used. In this example, the source 1.S of the NMOS FET is connected to the supply voltage source 2. The drain 1.D is connected to the electrical load 3 through a diode 4. The current in the diode 4 flows from the switchable electronic fuse 1 to the electrical load 3.

[0059] The power supply source 2 can be configured, for example, as a vehicle battery of a vehicle not specifically shown, which typically outputs a power supply voltage of 8 to 17 volts. As an alternative or supplement, the power supply voltage source 2 can also be a component of the vehicle's electrical on-board network. The electrical load 3 can be configured, for example, as a control unit, active sensor, actuator, or other electrical drive subsystem of the vehicle.

[0060] Electrical load 3 must be continuously supplied with voltage It is powered, but the supply voltage can be bridged (e.g., with the help of internal capacitors or other buffer memory). The circuit is interrupted for a period of time. Typically, this solution can bridge power outages with a maximum interruption duration of approximately 100 microseconds.

[0061] The test system 100 includes a microcontroller 110 with external circuitry (typically together with a switchable electronic fuse 1) arranged on a circuit board not shown in detail. The microcontroller 110 includes a timer 111, a non-volatile memory 112, and a multi-channel analog-to-digital converter (ADC) 113.

[0062] In addition, the microcontroller 110 also has Figure 1 The execution unit, not shown in detail, is used to execute program instructions. The program code that this execution unit can execute includes electronic fuse testing software 114 and application software 115, which can be stored in the shared program memory of the microcontroller 110 or in their own independent program memories. Figure 1 The program memory of the microcontroller 110 is not shown in detail. For example, the non-volatile memory 112 may be constructed as flash memory and configured to be used for both storing program instructions and non-volatile data storage.

[0063] The multi-channel ADC 113 samples the supply voltage on the first channel. The value is sampled on the second channel from the value of the peripheral temperature sensor 101. The temperature sensor 101 detects the temperature of the circuit board on which the electronic fuse 1 and the external circuitry of the microcontroller 110 are arranged.

[0064] The timer 111 can be configured, for example, as a resettable counter that counts the internal clock of the microcontroller 110 in response to timer activation.

[0065] In addition, the microcontroller 110 provides signal voltage under the program instructions of the electronic fuse testing software 114. This voltage is directed to the gate 1.G of the switchable electronic fuse 1. Using the signal voltage... The switchable electronic fuse 1 can be in the on state (e.g., in the on state). (when volts) and non-conducting state (e.g. in) Switching between (volts).

[0066] An RC assembly 102 and 103 is arranged between the drain 1.D of the switchable electronic fuse 1 and ground. The RC assembly consists of a resistor 102 and a capacitor 103 connected in parallel with it, and has a time constant. The time constant is equal to the resistance value. With capacitor capacitance The product ( ).

[0067] Measurement voltage on RC components 102 and 103 The voltage is detected by comparator 104 and compared with the reference voltage provided by reference voltage source 105. Comparison. When measuring voltage. Greater than or equal to the reference voltage At that time, the comparator output voltage at the output terminal of comparator 104 It will display a high level (corresponding to a positive value, e.g.) (Volts). When measuring voltage Less than the reference voltage At that time, the comparator output voltage at the output terminal of comparator 104 It will be displayed at a low level (corresponding to a relatively small value, for example) volt).

[0068] exist Figure 1 In the embodiment shown, the test system 100 includes a test circuit 120, a test control unit 121, and a test evaluation unit 122.

[0069] In this example, the test circuit 120 consists of a clock generator 111, RC components 102 and 103 (with resistor 102 and capacitor 103), a comparator 104, and a reference voltage source 105.

[0070] In this example, the test control unit 121 is composed of a microcontroller 110 equipped with electronic fuse testing software 114. In this example, the test evaluation unit 122 consists of a microcontroller 110 with an ADC 113 and non-volatile memory 112, and a temperature sensor 101. Of course, the test control unit 121 and the test evaluation unit 122 can also be implemented independently.

[0071] The following will combine Figure 2 The working principle of the test system 100 is explained in detail. The figure schematically shows the signal voltage. Measure voltage and comparator output voltage The curve.

[0072] At the first moment The electronic fuse testing software 114 will output the signal voltage. Reduce (e.g. from) Volts dropped (Volts), causing the switchable electronic fuse 1 to switch from the on state to the off state via the NMOS FET. Diode 4 prevents the internal capacitor or buffer memory of the electrical load 3 from continuing to supply power to capacitor 103 in RC components 102, 103.

[0073] With signal voltage The reduction in voltage causes the electronic fuse test software 114 to synchronously start the timer 111.

[0074] Subsequently, capacitor 103 discharges through resistor 102, causing the measured voltage to... From the supply voltage The value begins to decrease in the form of a decaying exponential function.

[0075]

[0076] Until its second moment Reduced to reference voltage Values ​​below.

[0077] When at the reference voltage Below, the comparator output voltage It will switch from a high level (corresponding to a logic value of 1 or "true") to a low level (corresponding to a logic value of 0 or "false"). Therefore, at the second moment... Timer 111 is stopped (e.g., by the comparator output voltage). (Applied to the capture input of the counter of timer 111).

[0078] Therefore, the value of timer 111 (i.e., the second moment) The count value represents the discharge of capacitor 103 to the reference voltage through resistor 102. Discharge duration of value .

[0079] In the third moment The electronic fuse testing software 114 will again test the signal voltage. Elevate (e.g. from) Volts rise to (Volts), causing electronic fuse 1 to switch from a non-conducting state to a conducting state by turning on the NMOS FET. Therefore, from the third moment... Initially, electrical load 3 will be powered by power supply voltage source 2 again.

[0080] First moment With the third moment The time intervals between them are carefully set to ensure the duration of power outage for electrical load 3. Although long enough for capacitor 103 to discharge to the reference voltage of comparator 104. However, it is much shorter than the maximum circuit breaker duration for which electrical load 3 can remain de-energized without affecting normal operation. This avoids affecting the operation of electrical load 3.

[0081] In the third moment With signal voltage As the voltage rises, the electronic fuse test software 114 resets the timer 111 to zero.

[0082] Second moment Next, the electronic fuse testing software 114 evaluates the discharge duration T value provided by the timer 111. For example, the discharge duration measured in this way can be used as an evaluation tool. Value and target value The target value is derived from the correlation of the above-mentioned discharge processes in comparison:

[0083]

[0084] In different operating environments, especially in vehicles, the power supply voltage Significant changes may occur. Furthermore, resistance values ​​may vary due to manufacturing tolerances or aging processes. and / or capacitance value There may be deviations from their respective ratings. In addition, the switching characteristics of the switchable electronic fuse 1 and the discharge characteristics of the RC components 102 and 103 may also change with temperature.

[0085] Therefore, advantageously, when evaluating the switchable electronic fuse 1, not only the measured discharge duration T should be considered, but also at least the factors used to accurately determine the resistance value should be taken into account. and / or capacitance value The correction value, and especially (at the first moment) Measured power supply voltage value .

[0086] Here, we can refer to the above information regarding the power supply voltage. The change in capacitance of resistor 102 and / or capacitor 103 The correlation is used to determine a corrected target value. Used in relation to discharge duration Comparison:

[0087]

[0088] Similarly, temperature-induced changes can also be considered, for example, by detecting the switching characteristic curve of the switchable electronic fuse 1.

[0089] Correction value (e.g., correction value for resistor 102) and / or the capacitance correction value of capacitor 103 It can be advantageously detected during the calibration step and stored in non-volatile memory 112.

[0090] In one implementation, the measured discharge duration can also be... The values ​​are continuously stored in non-volatile memory 112 at specific time intervals or for specific past periods. By comparing the currently measured values ​​with historical data, the electronic fuse testing software 114 can detect the gradual degradation of the switchable electronic fuse 1 as early as possible, especially when its function can still be guaranteed temporarily.

[0091] For example, the operating state of the switchable electronic fuse 1 can be determined as a value in the list {"normal function", "normal function but degraded performance", "abnormal function"}, and transmitted to the application software 115 by the electronic fuse testing software 114.

[0092] Application software 115 can trigger a fault response based on this value, such as disabling certain functions of the vehicle controlled by the relevant electrical load 3, or issuing a warning message.

[0093] according to Figure 2 The voltage-time curve diagram shown will illustrate this in more detail. Figure 1 The schematic circuit shown illustrates the working principle. Figure 2 The upper part shows the signal voltage. The time curve shows the measured voltage in the middle. The time curve shows the comparator output voltage at the bottom. Time curves, all curves are along the time axis draw.

[0094] In (power supply voltage) (Connection or application) moment signal voltage The voltage will switch to a higher value (typically between 10 and 15 volts), sufficient to turn on the switchable electronic fuse 1, which is configured as an NMOS FET. Correspondingly, the measured voltage applied to the RC components 102 and 103... The supply voltage will be approximated. The value is (minus only the negligible voltage drop compared to the source-drain path, which is typically 100 millivolts to 1 volt).

[0095] Comparator 104 will measure voltage With reference voltage Compare. Reference voltage. It is set to a value slightly above zero. For example, the reference voltage can be determined in this way. Calculate the voltage drop across RC components 102 and 103 resulting from the leakage current that is just within the allowable range when the switchable electronic fuse 1 is in the off state. If this voltage drop is not exceeded, the switchable electronic fuse 1 is considered to be functioning correctly. Typically, for this purpose, a reference voltage is used. Approximately the supply voltage Values ​​range from 10% to 20%.

[0096] Therefore, when the switchable electronic fuse 1 is functioning normally (i.e., in the on state), the measured voltage... This will be much greater than the reference voltage. Therefore, the output of comparator 104 exhibits a higher comparator output voltage. Positive voltage value (the specific value depends on the circuit technology and the supply voltage of comparator 104, typically 2 to 5 volts).

[0097] At the first moment The electronic fuse test software 114 running on the microcontroller 110 will trigger a brief shutdown of the switchable electronic fuse 1 to test its functionality. Therefore, at the third moment... Previously (i.e., during shutdown duration) (internal), signal voltage It will be set to a low level, which is equivalent to 0 volts or close to 0 volts.

[0098] Therefore, for a properly functioning switchable electronic fuse 1, the source-drain current will be completely or almost completely cut off. Subsequently, capacitor 103 discharges through resistor 102, at which point the voltage across capacitor 103 (equal to the measured voltage)... It will proceed according to the time constants of RC components 102 and 103 as described above. The determined decay exponential function decreases. During this process, a period known as the discharge duration occurs. After the time period, at the second moment The voltage value will drop to the reference voltage. The output of comparator 104 will synchronously or with only a slight delay receive the comparator output voltage. The high level switches to the low level.

[0099] Shutdown duration The setting is long enough so that (when the switchable electronic fuse 1 is functioning correctly) the measured voltage can be reliably observed. The attenuation. Practice has shown that reducing the shutdown duration... Set as discharge duration Several times the value is advantageous during this period, when the switchable electronic fuse 1 functions properly (especially when it has sufficiently good cut-off performance), the measured voltage... It will be from the power supply voltage Reduced to reference voltage .

[0100] Meanwhile, shutdown duration It is set to be so short that electrical load 3 can tolerate the supply voltage during this period. The failure will not affect the electrical load 3. Herein and below, electrical load 3 will be considered even under the supply voltage... It can still operate safely without being affected even when missing (i.e., considering electrical load 3 and supply voltage). The time period (under the premise of possible tolerances and other tolerances) is called the maximum circuit breaker duration.

[0101] For example, based on the known maximum circuit breaker duration, the shutdown duration can be... Select a fraction of the maximum interrupt duration (e.g., half or one-third). Then, connect RC components 102, 103 and the reference voltage. Designed to withstand the maximum permissible leakage current and maximum permissible supply voltage of the switchable electronic fuse 1 in the off state. Below, capacitor 103 discharges through resistor 102 for a period of time. Internal discharge to reference voltage This discharge duration is only the turn-off duration. A small portion (e.g., one-fifth or one-tenth).

[0102] To determine the discharge duration For example, it can be used Figure 1 Another comparator, not shown in detail, may generate a capture signal by converting to transistor-to-transistor logic (TTL). When the signal voltage... When the comparator output voltage is low, While remaining at a high level, the capture signal will present a high level and / or a rising edge; conversely, it will present a low level and / or a falling edge. With such a capture signal, a counting process of a known clock signal can be triggered on timer 111 during a high level and / or rising edge, and stopped during a low level and / or falling edge. In this case, the count value of timer 111 multiplied by the period duration of the known clock signal is exactly equal to the discharge duration. Of course, the counting process will also stop if the count value of timer 111 exceeds the maximum count value. In addition, application software 115 can also send start and / or stop signals to timer 111 to trigger and / or end the counting process.

[0103] In addition, the comparator output voltage can be... The signal is directly fed to the inverting capture input of timer 111, causing timer 111 to activate at the second time step. By the third moment The time period between (the comparator output voltage during this time period) The clock signal is counted while the signal is at a low level. In this embodiment, the discharge duration... Known precise shutdown duration (triggered by electronic fuse test software 114) The difference between the actual measurement time period and the actual measurement time period is calculated.

[0104]

[0105] Figure 3 A flowchart illustrating the analysis performed by electronic fuse testing software 114 is shown schematically and purely illustratively. The process begins at starting point A and ends at ending point E.

[0106] Starting from point A, in the first step S1, the supply voltage is read. The current value and the current temperature value measured by temperature sensor 101 (typically located near switchable electronic fuse 1). Both values ​​are sampled and discretized by ADC 113.

[0107] In the second step S2, at the second time... signal voltage The voltage is lowered to a low level, thereby turning off the switchable electronic fuse 1 (entering a non-conducting state). At the same time, timer 111 is started in the second step S2.

[0108] In the subsequent first decision step E1, it is checked whether the time recorded by timer 111 for the switchable electronic fuse 1 to be in the off state has reached or exceeded the predetermined discharge duration. In other words: the current time will be checked. Is it earlier than the third moment? .

[0109] If the shutdown duration has not yet been reached. In the subsequent third step S3, the method will pause for a predetermined waiting time and then execute the first decision step E1 again. The predetermined waiting time is set short enough to ensure that the predetermined shutdown duration can be detected with extremely high accuracy. The desired waiting time has been achieved. Preferably, the predetermined waiting time is one clock cycle of the clock signal supplied to and counted by the timer 111.

[0110] If the predetermined shutdown duration is determined in the first decision step E1 If this condition is met, then in the subsequent fourth step S4, the switchable electronic fuse 1 will be switched back to the on state (i.e., the conductive state).

[0111] Subsequently, in step S5, the discharge duration is read. For example, the result of multiplying the counter value by the clock cycle; this counter is based on the comparator output voltage. High level and signal voltage At the low level, the first moment With the second moment The clock signal is counted within the time interval.

[0112] In the subsequent sixth step S6, the resistance values ​​of RC components 102 and 103 are referenced. and capacitance value Calibration data, and / or supply voltage The current value (i.e., the value measured in the first step S1) and / or the temperature measured by the temperature sensor 101, are used to determine the reading of the discharge duration. Adjustments will be made.

[0113] For example, in ( Figure 3 During the calibration process (not shown in detail), a resistance value relative to the rated resistance can be detected. deviation and the rated capacitance value deviation This data is then stored in non-volatile memory 112. Furthermore, curves describing the time-switching characteristics of the NMOS FET constituting the electronic fuse 1, and / or curves describing the source-drain leakage current of the switchable electronic fuse 1 as a function of temperature, can also be stored in non-volatile memory 112. This data will be read in step S6 and used to adjust the read discharge duration. This allows for the determination of the corrected discharge duration. This value describes the behavior of the switchable electronic fuse 1 and is unaffected by manufacturing tolerances, temperature, and supply voltage. The impact.

[0114] In the subsequent second decision step E2, the discharge duration, after the above correction, will be... Compare with the first threshold. If the discharge duration... Below this first threshold, the switchable electronic fuse 1 is considered to be functionally unrestricted. Subsequently, in the first output step A1, the first output code "functional" will be output (this code can of course be encoded in bit mode or literal form).

[0115] If the discharge duration If the discharge duration is not below the first threshold, then in the third decision step E3, following the second decision step E2, the discharge duration will be checked. Is it below the second threshold (which is set to be greater than the first threshold)?

[0116] If the discharge duration Below this second threshold, the switchable electronic fuse 1 is considered functionally limited. For example, this might mean that the switchable electronic fuse 1 can only be considered functional with a certain probability for a certain remaining service life, and should be replaced before the end of that remaining service life. Subsequently, in the second output step A2, a second output code "functionally limited" (which can of course be encoded in bit mode or literal form) different from the first output code is output.

[0117] If the discharge duration If the discharge duration is not below the first threshold, then in the third decision step E3, following the second decision step E2, the discharge duration will be checked. Is it below the second threshold (which is set to be greater than the first threshold)?

[0118] If the discharge duration If the value is not below the second threshold, the switchable electronic fuse 1 is considered to be malfunctioning. Subsequently, in the third output step A3, a third output code "malfunctioning" is output, which is different from the first and second output codes (this code can of course be encoded in bit mode or literal form).

[0119] The thresholds used in the second and third decision steps, E2 and E3, can be determined, in particular, through methods such as statistical analysis. For example, the discharge duration can be continuously monitored for a sufficiently large sample of switchable electronic fuses. The value of . Then, for a subset of the failed switchable electronic fuses 1 in this sample, a value related to the discharge duration can be retrospectively determined. The relevant threshold is used to detect a sufficiently large proportion of failures in a timely manner without causing an unacceptably high number of false alarms (i.e., switchable electronic fuse 1 marked as about to fail according to the threshold, but which is actually still functioning normally).

[0120] The term "output code" specifically refers to transmitting such output codes to application software 115. For example, if electronic fuse testing software 114 determines that the output code is "limited functionality," application software 115 can issue a warning and / or prompt that the switchable electronic fuse 1 should be replaced by a certain date. If electronic fuse testing software 114 determines that the output code is "malfunctioning," application software 115 can shut down the safety-critical subsystem powered by the switchable electronic fuse 1.

[0121] After the first, second, and third output steps A1, A2, and A3, the discharge duration will be calculated in the seventh step S7. The value is stored in non-volatile memory 112. The method then reaches endpoint E.

[0122] To simplify the illustration, it is assumed that steps S5, S6, and S7, decision steps E2 and E3, and output steps A1, A2, and A3 are all executed sequentially after step S4, in which the switchable electronic fuse 1 is switched back to the on state (i.e., the conductive state). In principle, it can also be envisioned that the discharge duration... Once determined (i.e., from the second moment) (Upon starting) immediately perform the above steps. This has the following technical advantages: the reconnection of the electronic fuse can depend on the discharge duration. The assessment results. For example, an electronic fuse deemed malfunctioning may be completely unreactivatable.

Claims

1. A test method for detecting the operating state of an electronic fuse (1) capable of switching between at least an on state and a non-on state, the electronic fuse electrically connecting an electrical load (3) to a power supply voltage source (2), wherein, The electrical load (3) is capable of withstanding a power supply interruption for a predetermined maximum interruption duration. Its features are, - The test time of the switchable electronic fuse (1) is not longer than the maximum breaking time of the electrical load (3). The internal state switches from the conducting state to the non-conducting state; - at the test time During this period, the residual current flowing through the switchable electronic fuse (1) is detected by the test circuit (120) and used as the actual residual current value. - Compare with at least one target residual current value; Specifically, when the actual residual current value is below the at least one target residual current value, a first operating state is assigned; otherwise, another operating state is assigned.

2. The test method according to claim 1, Its features are, The actual residual current value is determined by detecting the discharge duration of the capacitor (103) powered by the switchable electronic fuse (1) and connected in parallel to the electrical load (3) through the resistor (102). The actual residual current value is measured and the discharge duration corresponding to the target residual current value determined for each operating state of the switchable electronic fuse (1) is calculated. At least one target value is compared.

3. The test method according to claim 2, Its features are, Detecting the measured voltage on the capacitor (103) And the measured voltage With reference voltage Compare, and in the measured voltage At the reference voltage The clock signal is counted during the aforementioned period, and the discharge duration is determined by multiplying the count value by the duration of the clock signal period. The actual value.

4. The test method according to any one of claims 2 to 3, Its features are, Measure the current temperature and / or supply voltage. The current value, and the deviation of the capacitance value of the capacitor (103) and / or the resistance value of the resistor (102) from their respective rated values, and the measurement results are used to correct the discharge duration. The actual value.

5. The test method according to any one of the preceding claims, Its features are, The target residual current value is adjusted according to the previously recorded actual residual current value as follows: when the currently measured actual residual current value deviates significantly from the previously recorded actual residual current value, the switchable electronic fuse (1) will be assigned to another working state.

6. The test method according to any one of the preceding claims, Its features are, The switchable electronic fuse (1) is installed in the vehicle to supply power to the electrical load (3).

7. The test method according to any one of the preceding claims, Its features are, in, When the actual residual current value is below the first target residual current value, the system is assigned a first operating state of "normal function"; when the actual residual current value is between the first target residual current value and a higher second target residual current value, the system is assigned a second operating state of "limited function"; when the actual residual current value is above the second target residual current value, the system is assigned a third operating state of "abnormal function".

8. A test system (100) for performing the method according to any one of the preceding claims, comprising a test circuit (120), a test control unit (121), and a test evaluation unit (122). Its features are: - The test circuit (120) is used to detect the actual residual current value flowing through the switchable electronic fuse (1) in a non-conducting state; - The test control unit (121) is configured to perform a test at a predetermined time. The switchable electronic fuse (1) is switched between an on state and a non-on state. The test evaluation unit (122) is configured to compare the actual residual current value detected by the test circuit (120) with at least one target residual current value.

9. The test system (100) according to claim 8. Its features are, The test circuit (120) includes RC components (102, 103), a comparator (104), and a timer (111). The RC components (102, 103) include a resistor (102) and a capacitor (103) connected in parallel with the resistor (102). - The RC components (102, 103) can be connected to the power supply voltage source (2) through the switchable electronic fuse (1); - Wherein, the comparator (104) is used to measure the voltage applied to the RC components (102, 103). With reference voltage Compare, and -The timer (111) is started by the test control unit (121) when the switchable electronic fuse (1) switches from the on state to the off state, and the timer is used to measure the voltage. Reaching or dropping to the reference voltage The time is stopped by the comparator (104).

10. The test system (100) according to claim 7 or 8. Its features are, The test evaluation unit (122) includes - Analog-to-digital converter (113). ○ Used to detect the power supply voltage The actual value, and / or ○ Used to detect the temperature of the switchable electronic fuse (1) by means of a temperature sensor (101); - and / or non-volatile memory (112) for storing at least one calibration value and / or at least one actual residual current value.

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