A power supply unit and a method for checking the field-effect transistors of that power supply unit.

Abstract

The present invention relates to a method for checking at least one field effect transistor (11) connected as an active diode downstream of the output of a power supply unit (1) in a power supply, the method comprising the steps of generating a non-fully conducting state, in particular a blocking state, of the at least one field effect transistor (11), detecting a first value of a voltage drop (ΔU) across the switching path of the at least one field effect transistor (11) at a first set voltage of the power supply unit (1), setting a second voltage of the power supply unit (1), detecting a second value of a voltage drop (ΔU) across the switching path of the at least one field effect transistor (11) at the second set voltage of the power supply unit (1), and if both the first value of the voltage drop (ΔU) and the second value of the voltage drop (ΔU) are smaller in magnitude than a first predetermined positive threshold (U1), or if the first value of the voltage drop (ΔU) and / or the second value of the voltage drop (ΔU) are smaller in magnitude than a second predetermined positive threshold (U1), the method is checked. n ), wherein the second threshold is greater than the first threshold. The present invention further relates to a power supply device having a power supply unit (1) connected to at least one field effect transistor (11) connected as an active diode.

Description

[Technical Field]

[0001] The present invention relates to a power supply unit having a power supply unit to which at least one field-effect transistor is connected downstream as an active diode. The present invention further relates to a method for checking the at least one field-effect transistor connected as an active diode in a power supply unit. [Background technology]

[0002] To prevent reverse current from a power supply, a diode is typically connected in series with the connected load. Such diodes are especially important when two or more power supplies are connected in parallel at their outputs to supply power to the load. Supplying power to a load from power supplies connected in parallel is used, for example, when a higher current is required than what a single available power supply can supply. Another reason is that it can be a desirable redundant power supply, ensuring that the load can operate safely even if one of the power supplies fails.

[0003] In many cases, the diodes described above are already located within the power supply unit. These are then connected downstream to the actual power supply unit that generates the output voltage and supplies the output current. Due to their function, which is expressed as one and / or the other being able to supply power to the load in the case of parallel-connected power supplies, these diodes are also called "OR-coupled (ORing) diodes."

[0004] Because these OR-coupled diodes are located within the power path of the load, all the current supplied by the power supply flows through them. The forward voltage drop across silicon diodes is approximately 0.7 volts (V), which results in a power loss that cannot be ignored in power supplies with output currents of several tens of amperes (A) or more.

[0005] To reduce these power losses, it is known that one or more switched field-effect transistors (FETs) with additional drive circuits are used instead of passive silicon diodes, which may depend on the level of voltage applied to the output of the power supply unit relative to the set output voltage of the power supply unit. When a suitable field-effect transistor, especially a MOSFET transistor (metal-oxide-FET), is used, a contact resistance in the milliohm range can be achieved in the conduction state, thereby reducing the voltage drop to a few millivolts (mV) or tens of mV, thereby reducing power losses, while simultaneously providing the function of a diode through appropriate drive.

[0006] In particular, for power supplies intended for redundant use, a precise functional check of the field-effect transistors is desirable and useful in this situation to ensure power supply redundancy. For example, if the field-effect transistors are permanently conducting, it means that the power supplies are no longer isolated from each other, and in this case, a failure in one power supply may affect the others.

[0007] A driving circuit for a field-effect transistor used as an active diode is described in U.S. Patent Application Publication No. 7,038,433. In addition to driving the field-effect transistor to realize the active diode function, this circuit includes a test circuit that outputs a warning signal if the voltage drop across the switching path falls below a predetermined value, even though the field-effect transistor is switched off. A voltage drop that is too small is thought to indicate that the transistor's switching path has melted and is permanently experiencing low resistance.

[0008] The described method provides reliable results for power supplies operating in single-phase mode. However, when at least two power supplies are connected to each other at the output and operating in parallel, a measured voltage drop below the threshold may be due to the voltage levels supplied by both power supplies being so similar that the voltage drop cannot be measured. In this case, a defect in the OR-coupled FET may be mistakenly assumed.

[0009] Therefore, an object of the present invention is to describe a test method for OR-coupled FETs that provides reliable test results and eliminates the possibility of field-effect transistors that are actually functioning correctly being detected as defective.

[0010] A further objective is to provide a power supply configured to perform such a test method. Advantageous designs and further developments are the subject of the dependent claims. [Overview of the project]

[0011] The method according to the present invention is for checking at least one field-effect transistor connected as an active diode, connected downstream of the output of a power supply unit in a power supply device, and comprises the following steps of the invention: A non-complete conduction state, particularly an interrupted state, of the transistor is set, and a first value of the voltage drop across the switching path of the field-effect transistor is measured at a first set voltage of the power supply unit. Subsequently, a second voltage of the power supply unit, different from the first voltage, is set, and a second value of the voltage drop across the switching path of the field-effect transistor is measured at this second voltage. A defect in the field-effect transistor is detected and notified if both the first value of the voltage drop and the second value of the voltage drop are less in magnitude than a predetermined positive first threshold, or if the first value of the voltage drop and / or the second value of the voltage drop are greater than a predetermined positive second threshold, where the second threshold is greater than the first threshold.

[0012] When the voltage drop value lies between the first and second thresholds, the voltage drop indicates the commutation of load current from the switching path to the body diode. The body diode is an inherent diode in the field-effect transistor, connected in parallel with the switching path. The body diode conducts current in its forward direction even when the field-effect transistor is not conducting. Generally, switching transistors used as active diodes in power supplies are arranged so that the body diode has an OR coupling function, but in silicon diodes, the typical voltage drop is about 0.7V, which is not the advantageously small voltage drop that can be achieved with conductively connected field-effect transistors.

[0013] In the context of this application, even when referring to one or a field-effect transistor, this also refers to a sequence of several synchronous drive transistors. Regarding their switching distance, parallel-connected field-effect transistors may be used to achieve higher current-carrying capacity. Regarding their switching distance, series-connected field-effect transistors may be used to achieve safer switching operation.

[0014] Instead of, or in addition to, an external diode, particularly a Schottky diode, can be used in addition to the intrinsic body diode. Configurations with a field-effect transistor that lacks an intrinsic diode and is not provided with an external diode can also be checked by the method according to the present invention, with an optionally adapted threshold level.

[0015] The threshold values can be set, for example, to 0.3 V and 2 V, especially for checking a configuration with an internal or external diode connected in parallel with a field - effect transistor. If the second condition above is met in one of the two measurements, it means that the field - effect transistor is blocked as required, but its body diode is also not conducting. This is a rare but possible case of a fault detected by this method. In an advantageous design of this method, the first threshold value is about 0.3 V. More advantageously, the second threshold value is at least about 1.5 V, especially about 2 V.

[0016] If the voltage drop in the first measurement does not exceed the first threshold value, this may be due to a short - circuit in the switching path of the field - effect transistor. However, since the voltage is maintained externally, for example, by another power supply device connected in parallel, at the output, it is possible that no current transfer to the body diode occurred. However, by changing the nominal voltage before the second voltage - drop measurement, the output voltage from the relevant power supply device becomes different. If the field - effect transistor is then correctly switched off and the load current is diverted to the body diode, this is reflected in a corresponding large voltage difference. However, if no voltage drop exceeding the first threshold value is measured in this second measurement either, a defective field - effect transistor can be detected and notified according to the present invention.

[0017] The power supply unit of the power supply device according to the present invention may be, for example, an alternating - current (AC) / direct - current (DC) converter, often also called a power supply unit. In the context of this application, the term power supply unit also includes, but is not limited to, DC / DC converters as well as batteries and buffer modules for uninterruptible power supplies.

[0018] In an advantageous configuration of this method, the second voltage is approximately 1 V higher than the first voltage. Such a fixed amount for changing the nominal voltage of the power supply unit is technically easy to implement and is sufficient to clearly determine, after measuring the second value of the voltage drop, whether the first measured value of the voltage drop is lower than the first threshold value due simply to the externally applied voltage or is actually due to a defective field-effect transistor.

[0019] In an alternative variant of this method, the second voltage is approximately higher than the measured voltage at the output terminals of the power supply device by a second threshold value. Under these measurement conditions, it is possible to particularly reliably detect the correct transfer of current to the internal or external parallel diodes.

[0020] In a further advantageous design, the measurement and evaluation of the two voltage drops are repeatedly performed in order to reliably detect possible defects of the transistor. A defect of at least one field-effect transistor can be notified only when it is detected only after a predetermined number of repetitions, for example, three or more repetitions. In this way, a high certainty of defect detection is achieved.

[0021] Preferably, there is a waiting time between two consecutive repetitions of this method, and in particular with respect to its length, it includes a random component. The random component can be calculated, for example, based on the individual identifier of the power supply device, particularly the serial number.

[0022] The random component prevents the detection of a fault in the field-effect transistor when there are at least two identical power supplies connected in parallel on the output side. This is because the two power supplies perform the method described above, and accordingly, during the performance of this method, they change the nominal voltage for measuring the second voltage drop in precisely synchronous manner. This case is not impossible when two identical power supplies are redundantly connected not only on the output side but also on the input side, and the input voltage is supplied simultaneously, i.e., they are switched on simultaneously. Due to the simultaneous startup of the power supplies, the method according to this application is also performed synchronously at first. The random component prevents the power supplies from performing measurements with the same time structure when the measurement is repeated.

[0023] The power supply device of the type described at the beginning of the present invention features a control unit configured to perform the method described above. The advantages described in relation to this method are obtained. Therefore, the control unit performing this method can be part of the control unit of the power supply unit. At least one field-effect transistor is part of the OR coupling module, where the power supply unit and the OR coupling module may be located in separate housings or in a common housing.

[0024] The present invention will be described in detail below with reference to exemplary embodiments shown in the drawings. [Brief explanation of the drawing]

[0025] [Figure 1] Figure 1 shows a schematic block diagram of the power supply unit. [Figure 2] Figure 2 shows a flowchart illustrating a first exemplary embodiment of a test method for testing an OR-coupled field-effect transistor. [Figure 3] Figure 3 shows a flowchart illustrating a second exemplary embodiment of a method for monitoring an OR-coupled field-effect transistor. [Modes for carrying out the invention]

[0026] Figure 1 shows a block diagram of a power supply unit comprising a power supply unit 1 and a so-called OR coupling (ORing) module 10. Note that the two units described above, the power supply unit 1 and the OR coupling module 10, can be arranged integrally within the power supply unit housing or in separate housings.

[0027] Power supply unit 1 converts the input voltage into an output voltage, which can be a DC voltage and / or AC voltage depending on the model. Often, the AC voltage of the lighting mains power supply is used as the input voltage. In this case, power supply unit 1 is also referred to as a power supply unit. The output voltage is usually a DC output voltage adjusted to a predetermined value, the so-called nominal voltage. Under normal operation of power supply unit 1, the output voltage deviates significantly from the nominal voltage only when the output current of the power supply unit exceeds its maximum value.

[0028] The power supply unit has an input terminal 2, which is also the input to the power supply unit 1, and the input current to the power supply unit 1 is supplied through this input terminal. In this embodiment, since the power supply unit 1 receives, for example, a single-phase AC power supply on the input side, there are two input terminals 2. Also, the number of input terminals 2 may be more than 2, such as when the power supply unit is connected to a three-phase AC main power supply.

[0029] The output voltage of power supply unit 1 is available here at output 3, which has two poles. The power supply unit has output terminals 4 to which a load powered by power supply unit 1 can be connected.

[0030] The OR coupling module 10 is connected between the power supply unit 1 and the output terminal 4, i.e., the load. It includes a field-effect transistor 11 (hereinafter referred to as FET 11), and the full load current flows through its switching path (i.e., between the source terminal S and the drain terminal D). In the illustrated embodiment, the FET 11 is an n-channel enhancement type that is in a closed state when not driven. In principle, it is also possible to use other types or combinations of one or more field-effect transistors.

[0031] In the illustrated example, the negative output of power supply unit 1 is directly connected to the negative output terminal 4 of the power supply, and the positive output 3 is connected to the positive output terminal 4 of the power supply via FET 11. In an alternative design, the positive output terminal 4 may be directly connected to power supply unit 1, and the negative output terminal 4 may be connected via a field-effect transistor. In this case, a level-adjusted threshold may need to be used.

[0032] The OR coupling module 10 has a control unit 12 that controls the FET 11 via its gate input G. To ensure the OR coupling function of the OR coupling module 10, the control unit 12 compares the voltage at output terminal 4 with the voltage at output 3 of power supply unit 1 for this purpose. These voltages are U i and U o This is shown in Figure 1. Voltage U i This represents the output voltage of power supply unit 1, and therefore the input voltage of the OR coupling module. Voltage U o This is the voltage applied to output terminal 4. Voltage U o Voltage U i If the value exceeds a certain level, the control unit 12 disables the FET 11 to prevent current from flowing back from the output terminal 4 to the power supply unit 1. The corresponding test leads connected to the control unit 12 are not shown in Figure 1 for simplicity of representation.

[0033] In the circuit symbol for FET11, a diode is depicted between the source terminal S and the drain terminal D of FET11. This diode, also known as a body diode, is inherent to field-effect transistors. The diode is oriented so that FET11 can perform OR coupling even when its gate terminal G is not driven. However, the typical voltage drop for a silicon diode is about 0.7 volts, which is not a favorably small voltage drop that can be achieved with a conductively connected FET11.

[0034] In the illustrated embodiment, the control unit 12 has a control terminal 13, which, in addition to driving the gate of the FET 11, is connected to the power supply unit 1 and controls the output voltage U of the power supply unit 1. i This can be changed. This function is used as part of the test method described below. In another design, a control unit 12 located within the OR coupling module 10 may drive the FET 11 for the OR coupling function, where the control terminal 13 can independently influence the switching state of the FET 11 in the context of the test method described below. In particular, if the OR coupling module 10 is integrated with the power supply unit 1, it should be noted that the function of the control unit 12 can also be fully or partially performed by the control unit of the power supply unit 1.

[0035] Figure 2 shows an exemplary embodiment of a method for checking the function of a field-effect transistor used as an active diode in an OR coupling module, in flowchart form. This method can be implemented, for example, in the power supply shown in Figure 1, and will be explained using the structure and reference numerals shown in Figure 1 as an example.

[0036] When this method is performed, power supply unit 1 is in a normal operating state, and the voltage U at its output 3 is iIt is assumed that a preset voltage, the nominal voltage, is provided. This method assumes no further preconditions. In particular, the power supply device to be inspected may operate without a load, may operate with only the load, or may operate in parallel connection with at least one other power supply device. When the power supply device is actively involved in supplying current to the load, the FET 11 of the OR coupling module 10 is driven to conduct by the control unit 12 via the gate terminal G. In another design of this method, this can also be investigated in advance by appropriate measurements.

[0037] In the first step S1 of this method, the FET 11 is switched to the off state, for example, by the control unit 12, when the gate terminal G is no longer driven. This can be directly realized by appropriate drive logic within the control unit 12. When the power supply device operates in parallel connection, the off state of the FET 11 can also be achieved by reducing the nominal voltage of the power supply unit by, for example, 1 volt or more, thereby detecting the operating situation where the field effect transistor 11 is blocked to avoid reverse current in the OR coupling module 10. In that case, the control unit 12 disables the FET 11 by its OR coupling function.

[0038] In the subsequent step S2, the voltage ΔU = U i -U o dropping across the switching path (source-drain path) of the FET 11 is determined, for example, from measuring the respective voltages U i and U o . ΔU is hereinafter referred to as the voltage difference or voltage drop.

[0039] Then, in the next step S3, it is confirmed that the magnitude of the measured voltage difference ΔU| is greater than or equal to a first positive threshold U1, which is in the range of approximately 0.3 volts. If so, it means that the FET 11 is turning off, causing a load current through the body diode of the FET 11 and a corresponding voltage drop in relation to this, or that the body diode is preventing current from flowing to the power supply unit 1. However, this indicates that the actual switching path of the FET 11 is functioning and, in particular, does not exhibit any short-circuit behavior (also called a short circuit) that would occur after the FET 11 melts.

[0040] If |ΔU|>=U1 is detected as a magnitude, the method branches to step S4, indicating that FET11 is functioning. The method then proceeds to step S9, where the field-effect transistor 11 is again made conductive, and the switching path carries the load current with correspondingly low losses.

[0041] In step S3, if the magnitude of the measured voltage difference ΔU is determined to be smaller than the specified first threshold U1, then nothing can be said at the initial stage about the normal function of the FET 11. According to the present invention, in the subsequent step S5, the nominal voltage of the power supply unit 1, i.e., the output voltage U of the power supply unit, i For example, via the control output 13, it can be increased by a certain amount, specifically, by, for example, 1 volt.

[0042] After the requested change, the output voltage U i After an optional waiting time required by power supply unit 1 to supply power, the measurement in step S2 is repeated in step S6, i.e., the voltage difference ΔU across the switching distance of FET 11 is measured again. Then, it is checked again whether this voltage difference is greater than a predetermined positive first threshold U1. If so, the method branches back to step S4 to indicate that FET 11 is functioning normally.

[0043] The reason for doing this is that the difference in the measurement results in steps S2 and S6 corresponds to the voltage U at the output. o This indicates that the current transition to the body diode did not occur in steps S2 / S3 because it was maintained externally, for example, by an additional power supply connected in parallel. However, after increasing the nominal voltage, the output voltage of the power supply in question is different. If FET11 is properly switched off and the load current is commutated to the body diode, this is reflected in the voltage difference ΔU and is not smaller in magnitude than the first threshold, in which case this method branches to step S4.

[0044] However, if, in step S6, despite increasing the nominal voltage, a differential voltage ΔU exceeding the first threshold cannot be measured, that is, if no current is transmitted to the body diode despite the increase in nominal voltage, this indicates a short circuit in the switching path of the field-effect transistor 11 and must therefore be considered defective. This will be communicated in the subsequent step S8 after the evaluation of the differential voltage ΔU in step S7.

[0045] In the next step S8, in addition to notifying the faulty FET, the nominal voltage of power supply unit 1 is reset to the previous nominal voltage that was set at the start of this method, and this method ends in step S9, where the field-effect transistor 11 is driven again.

[0046] The notification specified in step S8 can be displayed, for example, on the OR coupling module 10 or the power supply unit in the form of a signal indicator, such as a corresponding light-emitting diode. Alternatively, the transmission of a data message via the communication network to which the power supply unit is connected can also be considered a notification.

[0047] In designs corresponding to this method, steps S1 through S8 can be advantageously executed in a time ranging from a few milliseconds (ms) to a maximum of 10 ms. This is advantageous when power supplies are used to supply power to industrial equipment, which are often designed according to the IEC 61131-2 standard, requiring the device to function without limitations for 10 ms even without power. Therefore, if this described test cycle is executed faster than the specified 10 ms, it will not affect the functionality of the connected device.

[0048] Therefore, a smooth transition from step S1 to S8 is achieved without any waiting time, and / or the output voltage U of power supply unit 1 is controlled. i It may be advantageous to consider the expected rise-off ramp according to its time response.

[0049] Figure 3 shows another exemplary embodiment of a test method for field-effect transistors in an OR coupling module, similarly in flowchart form. Again, the flowchart is explained with reference to the power supply shown in Figure 1.

[0050] Furthermore, as explained in relation to Figure 2, this method is initiated on the condition that the power supply unit 1 is set to a predetermined nominal voltage applied to its output 3.

[0051] In order to enable this method to start when the power supply is switched on, in step S11, a specific start delay is first set via a loop structure. A predetermined time T > T Start Only after time T has elapsed does this method proceed to step S12. Start Due to the resulting startup delay, for example, if the power has just been turned on, the power supply unit 1 can start up and begin stable operation.

[0052] In step S12, voltage U is applied to the upstream and downstream sides of the OR coupling module 10, respectively. i and U oThe voltage ΔU is measured, and even considering a measurement error of, for example, 0.05V, it is checked whether the voltage at output 4 of the power supply unit is greater than the voltage at output 1 of the power supply unit. i -U o From this relationship, it is checked whether |ΔU| > 0.05V. This can result from, for example, another power supply unit connected in parallel that has a slightly increased output voltage despite being set to the same high nominal voltage. However, voltage U o U i The fact that it is greater than already indicates that FET11 is not short-circuited. This method then branches to step S16, and FET11 is considered to be functioning.

[0053] This method proceeds from step S16 to step S17, where FET11 is switched on again as needed, and the time memory variable is set back to value 0. Then this method returns to step S11, and there is a waiting time T until step S12 is processed again. Start It waits again only after that. Therefore, the repetition frequency of this method is time T. Start It can also be defined by [this method].

[0054] If the condition is not met in step S12, for example, if the voltage at output 3 is exactly the same as the voltage at output terminal 4, this method branches to step S13, and the voltage U i It is checked whether the voltage is greater than the set nominal voltage of power supply unit 1. If so, this indicates that the power supply is applying a higher voltage to output terminal 4, which is also seen at output 3 of power supply unit 1. This indicates a short circuit in FET 11, and for this reason the method branches to step S23, where a variable used to count the number of fault cases detected is incremented by a value of 1, and the time the test was performed is set to the variable T test It will be stored in memory.

[0055] After fault detection in step S23, the program branches to step S25, where it is checked whether the number of fault cases has reached a certain number, for example, three. If not, the program branches to the next step S26, where FET11 is switched on again (if it was previously switched off), and the test time is (again if necessary) set to variable T test The value is stored in memory, and (optionally) the voltage at output 3 of power supply unit 1 is reset to its nominal value.

[0056] Subsequently, in the next step S27, a waiting loop is executed, and only after a certain waiting period has elapsed does this method branch back to step S12. The meaning of the waiting time in step S27 will be explained in more detail below.

[0057] If the condition in step S13 is not met, the method proceeds to step S14, where FET11 is switched off. The time this occurs is again stored as the test time, and the current flowing before this shutdown is also stored. This current value is measured by power supply unit 1 as part of the overcurrent protection circuit and is therefore normally available within power supply unit 1. Turning off FET11 in step S14 corresponds to turning off the field-effect transistor in step S1 of the exemplary embodiment in Figure 2.

[0058] In the subsequent step S15, the voltage ΔU dropping across both ends of the FET11 is measured and evaluated. In this exemplary embodiment, three cases are distinguished. In the first case, the voltage at the output terminal 4 is lower than a predetermined voltage value than the voltage at the output 3 of the power supply unit 1, that is, ΔU > U2, where U2 is a positive value of several volts, for example, 2V. When this condition is satisfied, it means that the FET11 is cut off and its body diode is also non-conductive. This is a fault state that is rare but can be detected and counted in step S24. After step S24, this error is processed in steps S25 and subsequent steps in the same manner as the short-circuit error of the FET11 in step S23.

[0059] Another case that can occur in step S15 is when the magnitude of the voltage difference ΔU is less than or equal to the further threshold U2 but greater than or equal to a first positive threshold U1 of about 0.3V, which was also the subject of the query in step 3 of FIG. 2. In this case, the method branches to step S16, where the field-effect transistor 11 is considered to be functioning. Subsequently, after the waiting time T Start the method enters a new execution via steps S17 and S11.

[0060] In the third case of step S15, the magnitude of the voltage difference ΔU is smaller than the first threshold U1, that is, |ΔU| < U1, and then the method continues to step S18.

[0061] In step S18, the current flowing through the output of the power supply unit 1 is measured again. If it is determined that the current was greater than a predetermined threshold before the FET11 was turned off in step S14 but has now dropped to zero, this also indicates correct operation, particularly correct switching off of the source-drain path of the field-effect transistor. In this case, the method also branches to step S16, where the FET11 is considered to be functioning.

[0062] If the condition of step S18 is not satisfied, this may be because the time between step S14 and step S18 is too short, which may, for example, make the current measurement result in step S18 incorrect. Therefore, until the minimum waiting time is reached, this method branches to step S19 and executes steps S15 and S18 many times, so that FET11 may be considered to be functioning in step S16. After repeated execution, even if it is determined in step S19 that the turn-off time of FET11 in step S14 has been long enough so far and accurate measurement is possible considering the measurement time constants of steps S15 and S18, or if not, this method branches to step S20.

[0063] In step S20, the voltage at output 3 of power supply unit 1 is increased by a predetermined amount, for example, by 1 volt again. Subsequently, steps S21 and S22 similar to steps S15 and S19 are executed. In step S21, three different cases for the voltage difference ΔU are distinguished again, which exactly correspond to the distinction in step S15. In the first case (ΔU>U2) described here, this method branches to step S24, and in the second case (U1<|ΔU|<=U2) described here, it branches to step S16. After sufficient waiting time, in the third case, that is, when the potential difference is less than the first threshold value (ΔU<U1) in both the measurement in step S15 and the measurement in step S22, this method branches to step S23, and FET11 is diagnosed as a short circuit and counted as a failure.

[0064] Next, in step S25, if it is determined that this error state occurs reproducibly more frequently, for example, more than twice, this error is also notified externally in step S28. Thus, this method ends.

[0065] After a failure is detected in step S23, starting from step S22, in principle, a second parallel-connected power supply with the same failure detection as the present invention for the field-effect transistor of the OR combination module is operating. Exactly synchronized with the execution of this method, in step S20, there is still a possibility that a failure is detected only because its nominal voltage has been increased. In that case, both power supply devices measure the voltage difference of ΔU < U1 in their respective ways in steps S15 and S21.

[0066] When two identical power supply devices are redundantly connected not only on the output side but also on the input side and the input voltage is supplied simultaneously, that is, when they are switched on simultaneously, this case is not unlikely to occur. When the power supply devices start up simultaneously, the monitoring method also starts up synchronously.

[0067] In order to prevent both power supply devices from measuring again in the same time configuration when the measurement is repeated, in step S27, a random component is added to the aforementioned waiting time.

[0068] Preferably, this random component is not purely computational (pseudo-random), and in its algorithm, various characteristics of the power supply, for example, the serial number that is individual for each power supply, are used. Also, the state of the least significant bit of the analog-to-digital converter can be used as a true random component within the algorithm for the random number generator.

Explanation of Signs

[0069] 1 Power supply unit 2 Input connection 3 Output 4 Output connection 10 OR connection module 11 Field-effect transistor 12 Control unit 13 Control connection U i Voltage at the output of the power supply unit U oVoltage at the output terminal of the power supply unit Source terminal of S FET Drain terminal of D FET G FET gate terminal Steps of the S1-S8 method Steps of the S11-S28 method

Claims

1. A method for checking at least one field-effect transistor (11) connected downstream of the output of a power supply unit (1) in a power supply device and connected as an active diode, A step of generating a non-complete conduction state of at least one field-effect transistor (11), A step of detecting a first value of the voltage drop (ΔU) across the switching path of the at least one field-effect transistor (11) at a first voltage of the power supply unit (1), A step of setting a second voltage higher than the first voltage of the power supply unit (1), A step of detecting a second value of the voltage drop (ΔU) across the switching path of the at least one field-effect transistor (11) at the second voltage of the power supply unit (1), and Both the first value and the second value of the voltage drop (ΔU) are greater than a predetermined positive first threshold (U １ If the first value and / or the second value of the voltage drop (ΔU) is less than a predetermined positive second threshold (U ｎ A step in which a defect in at least one field-effect transistor (11) is detected and notified if the second threshold is greater than the first threshold, Methods that include...

2. The method according to claim 1, wherein the non-complete conduction state is an interrupted state.

3. The first threshold (U １ The method according to claim 1 or 2, wherein the voltage is 0.3 volts.

4. The second threshold (U ２ The method according to any one of claims 1 to 3, wherein the voltage is 1.5 volts or more.

5. The second threshold (U ２ The method according to claim 4, wherein the voltage is 2 volts.

6. The method according to any one of claims 1 to 5, wherein the second voltage is 1 volt higher than the first voltage.

7. The second voltage is greater than the measured voltage at the output terminal (4) of the power supply device than the second threshold (U ２ The method according to any one of claims 1 to 5, wherein the value is only higher.

8. A method according to any one of claims 1 to 7, which is carried out repeatedly.

9. The method according to claim 8, wherein a defect in at least one field-effect transistor (11) is not notified until it is detected after a predetermined number of iterations.

10. The method according to claim 9, wherein the predetermined number of repetitions before a defect is notified is at least three.

11. The method according to any one of claims 8 to 10, wherein a waiting time exists between two consecutive iterations of the method.

12. The method according to claim 11, wherein the waiting time includes a random time component.

13. The method according to claim 12, wherein the random time component is calculated based on the individual identifiers of the power supply unit.

14. The method according to claim 13, wherein the identifier includes a serial number.

15. A power supply device having a power supply unit (1) to which at least one field-effect transistor (11) that can be switched as an active diode is connected downstream, characterized in that there is a control unit (12) configured to perform the method according to any one of claims 1 to 14.

16. The power supply device according to claim 15, wherein the at least one field-effect transistor (11) is part of an OR coupling module (10).

17. The power supply device according to claim 16, wherein the power supply unit and the OR coupling module (10) are arranged in separate housings.

18. The power supply device according to claim 16, wherein the power supply unit and the OR coupling module (10) are arranged in a common housing.

19. The power supply device according to claim 18, wherein the control unit (12) that performs the above method is part of the control device of the power supply unit (1).

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