DE102010001713A1 - Method for detecting load drop in rectifier of generator arrangement i.e. starter generator of motor vehicle, involves estimating duration of voltage drop in rectifier based on characteristics of electrical parameter - Google Patents

Abstract

The method involves detecting load drop in a rectifier of a generator arrangement by using an evaluation unit based on electrical parameter e.g. electrical current or electrical voltage. Duration of the voltage drop in the rectifier is estimated based on characteristics of another electrical parameter, where the former electrical parameter corresponds to the latter electrical parameter. Adjustment of Zener-voltage in the rectifier is carried out during detection of the voltage drop. An independent claim is also included for a generator arrangement comprising a rectifier and an evaluation unit.

Description

The invention relates to a method for detecting a load drop or load dump in a rectifier, a generator arrangement and an evaluation unit for carrying out the method.

State of the art

For feeding DC systems from three-phase systems, such as, for example, in the public three-phase network, rectifiers are generally used. These rectifiers are usually constructed in bridge circuit. As rectifier elements are usually diodes that do not require any further drive circuit, since they automatically go at the right time in the conducting or blocking state.

Bridge rectifiers in six-pulse design are also used as rectifiers in automotive alternators. It should be noted that these generators have a pronounced inductive resistance. Furthermore, it should be noted that the rectifier has a predetermined by the diodes and the output current power loss. By circuitry measures, such as. By parallel switching of diodes, these losses can be reduced only slightly.

A critical failure in the design of an active rectifier is load dumping. This occurs when, with a correspondingly high-powered machine and a correspondingly high output current, the load on the generator abruptly decreases and can not be intercepted by capacitive elements in the electrical system, such as, for example, the battery.

This can occur, for example, when the load cable drops when the machine is fully energized with a maximum current output.

The generator can supply up to about 300 to 500 ms energy into the electrical system. This must be implemented in the rectifier in order to protect electrical components connected to the generator from damage due to overvoltage. This is done according to the prior art by implementing the rectifier diodes as power zener diodes.

Various methods are already known for detecting a load dump in passive rectifiers. This is from the publication DE 10 2006 032 736 A1 It is known to use a detector unit for detecting a load shutdown in a generator device with a generator and a rectifier bridge. For detection, a voltage and / or current measuring unit is provided. With this detector unit, a switch can be controlled, which is arranged between a DC supply voltage line and an energy storage. After detection of a load shutdown, the detector unit transmits the switch permeable, so that the energy formed by the load shutdown is stored in the energy store.

In the cited document is thus provided to store the excess energy that is generated during the load dump in a buffer.

In conventional diode rectifiers, this energy loss can be easily converted into heat. For this, the diodes offer a sufficiently good setup and connection technology with a comprehensive thermal connection. As is known, this is not completely replicated in MOSFET transistors, other measures must be taken to intercept the power loss.

In the event that diodes are replaced by active switches, for example by MOSFET transistors, to substantially reduce the losses, it is thus necessary to use new load-dump strategies.

As a remedial strategy in a load-dump event, two extreme positions are currently represented:
The amplification is carried out in a range of 25 V to 30 V. This ensures a sufficient safety distance to the normal operating conditions, such as double battery with 24 to 28 V guaranteed. The components used for the enhancement must implement a high electrical power loss or energy to heat in the load-dump case and buffer them.

In the pamphlets EP 0 777 309 A2 and JP 3 396 955 B2 In order to delete the load-dump energy, it is proposed to completely short-circuit a branch (highside or lowside). This is problematic that in case of a non-existent battery due to defect or cable waste the Power supply suddenly collapses. In this case, system critical conditions occur because the rectifier also draws its energy from the vehicle electrical system.

Furthermore, it should be noted that a motor vehicle without a battery, which has generated the load dump by the demolition of the starter auxiliary cable itself, with high probability emanates, which is not desired or technically meaningless.

The publication DE 10 2005 054 949 A1 describes a semiconductor integrated circuit with which an output of a MOS transistor can be protected from failure. The semiconductor integrated circuit has for this purpose an output MOS transistor which controls the current flowing through a load, a dynamic clamp circuit which clamps an overvoltage applied to the output MOS transistor, a delay circuit for generating a reference signal by setting a level of a gate voltage. A source voltage of the output MOS transistor and a clamp control circuit which causes the operation of the dynamic clamp circuit based on the reference signal when a counter electromotive force is applied to the output MOS transistor.

Disclosure of the invention

Against this background, a method for detecting a load drop with the features of claim 1, a generator arrangement according to claim 8 and an evaluation unit according to claim 10 are presented. Embodiments result from the dependent claims.

It is thus detected on the basis of a first electrical variable, a load drop and additionally estimated based on a course of a second electrical variable, the duration of the load drop. As electrical variables, the electrical voltage and / or the electric current come into consideration. It is thus made a current and / or voltage measurement. If the load drop is detected by means of a current measurement, the duration of the load drop can be estimated based on the course of this current or based on the history of a detected voltage. If the load drop is detected by a voltage measurement, the duration of the load drop can be estimated based on the history of this voltage or based on the history of a detected current.

With the presented method, the current measurement can thus also be used to estimate the duration of the load dump in order to initiate other measures for minimizing power loss for a limited period of time. The beginning of a load dump can be detected quickly in order to immediately initiate a countermeasure, such as an intelligent enhancement, and thus avoid the power loss peak at the beginning.

In this way, a quick detection of a load dump is possible before, at least in embodiments of the method, the voltage has risen to 32 V, so that by introducing a fast backlash the maximum value of 34 V can be significantly reduced. This leads to a significant cost reduction, since the dielectric strength of the control unit located on the electrical system can be reduced by the corresponding amount.

In order to limit the loss energy to be converted, for example, an "intelligent enhancement" is proposed. This provides a remedial strategy to reduce the power that must be applied to a load dump in a rectifier. In this case, the output to the electrical system power is limited by the so-called amplification in the rectifier, the power loss, due to the physics of the generator, proportional to the Zener voltage.

Further advantages and embodiments of the invention will become apparent from the accompanying drawings and the description.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination indicated, but also in other combinations or in isolation, without departing from the scope of the present invention.

Brief description of the drawings

1 shows in a diagram the power output in a load dump.

2 shows in a diagram a measured output current in a load dump.

3 shows a schematic representation of an embodiment of the generator assembly.

4 shows in a diagram the relationship between excitation current and output current.

5 shows in a diagram the timing of excitation current and generator current at Abregelung.

6 shows in a flow chart a possible sequence of the method described.

7 shows the relationship between peak power dissipation and Zener voltage.

8th shows a communication process in a bracketing.

9 shows a possible implementation of the method described.

10 shows a further implementation of the method.

11 shows yet another implementation of the method.

Embodiments of the invention

The invention is schematically illustrated by means of embodiments in the drawings and will be described in detail below with reference to the drawings.

• – Störung auf der Batterieleitung
• – Spannungsrippel auf Bat+ aufgrund defekter oder fehlender Batterie
• – Jump-Start
• – Load-Dump

In principle, a distinction must be made between the following special operating states when detecting a load dump:

• - Malfunction on the battery cable
• - Voltage ripple on Bat + due to defective or missing battery
• - Jump start
• - Load dump

With a load dump, a very fast voltage rise occurs from a normal active controller operation. At the time of the load dump, the stator continues to deliver power. Since in extreme cases the current output is interrupted in the electrical system, this power must be implemented in the rectifier. Due to the voltage increase and the approximately continuous current output of the stator, the output power of the stator increases steeply. An example of a measured power output is in 1 shown.

In 1 is shown the history of performance before and after a load dump. In particular, the measured power output of a stator of an electrical machine during load dumping is shown. At an ordinate 10 is the power P in W and an abscissa 12 the time t is plotted in s. The load dump takes place at time t = 0.1 s.

A curve 14 shows the power that the generator delivers to the electrical system. Another curve 16 shows the power the rectifier must pick up during the load dump. The load dump event starts at 0.1 s. The curve 16 follows approximately an e-function with the time constant tau, which is determined by the exciter circuit of the generator.

In conventional diode rectifiers, the load dump detection is at the same voltage level as the fusing operation. This is typically above 28V to have a safe distance to the jump start.

By measuring the external current output behind the rectifier, the load dump detection can be shortened. Furthermore, it is possible to estimate the expected length of the load dump, since this is a function of the current jump.

In 2 a measured current curve is shown in a load dump. The diagram shows an example of a measured output current downstream of the rectifier during a load dump. At the ordinate 30 is the current in A and on the abscissa 32 the time in s applied.

The generator current IG results from: I _G = I _D1plus + I _D2plus + I _D3plus + I _D4plus + I _D5plus

In 3 is shown in a schematic representation of an embodiment of the generator arrangement described, the total with the reference numeral 50 is designated. In the illustration is a generator 52 , a rectifier 54 , which is constructed as a bridge rectifier, and an evaluation unit 56 shown with current and voltage detection. Furthermore, a drive unit 58 for active rectification or a belt driven starter generator.

Alternatively to the in 3 As shown, the current can also, as by 2 clarified, evaluated via evaluation of the current in the bridge branches.

By plausibilizing a measured current drop with a measured voltage increase, the load dump detection can respond earlier than previously known load dump detections, which, for example, respond to Ubat> 28 V.

It should also be noted that the following parameters can be considered as input parameters: speed, temperature, excitation current, clamp voltage, machine type, condition of the battery and topology of the exciter circuit. If necessary, these or a subset of them are to be stored in maps in order to evaluate the current jump accordingly. Alternatively, the time duration can also be determined by means of a calculation algorithm.

In 4 the measured relationship between excitation current and output current is shown in a 5-phase claw pole generator. It is at the ordinate 100 the generator current in A and on the abscissa 102 the excitation current is plotted in A.

A first turn 104 shows the dependence at 1800 revolutions per minute (rpm), a second curve 106 at 3000 umin and a third turn 108 at 1800 rpm. It is dependent on the current speed to recognize a linear proximity in a first approximation between the excitation current and output current of the generator.

In 5 is a time course of the excitation current and generator current at Abregulation reproduced. At a first ordinate 150 is the excitation current in A, at a second ordinate 151 the generator current in A and on the abscissa 152 the time is plotted in ms.

A first turn 154 shows the course of the excitation current, a second curve 156 the course of the generator current at 6000 rpm, a curve 158 the course of the generator current at 3600 rpm and a curve 160 the course of the generator current at 1800 rpm.

At a first time 162 The load dump starts at a second time 164 this ends. At the second ordinate 151 is with it 170 the generator current just before the load-dump event and at 174 read the generator current shortly after the load dump event. A block 180 illustrates the estimated duration of the load dump event.

5 shows the principal estimation of the load dump duration. If the speed and the output current are known immediately before the load-dump event and after the occurrence of the load-dump event, the load-dump duration can be easily estimated in wide speed ranges. In 5 For the sake of simplification, it was assumed that the speed does not change within the estimated time duration of about 70 ms. In the present example, an initial current of 130 A and a target current of about 65 A at a speed of 6000 Uman was set. This results in an estimated time duration of about 75 ms.

The described method can be implemented in combination with a so-called "intelligent enhancement". In this case, the occurring power loss is minimized by reducing the clamped voltage in a load-dump event. Thus, for example, in the load dump, the clamp voltage can ideally be set to 9 V, since in this case, on the one hand, the supply of the electrical system is ensured and, on the other hand, the occurring power loss in the power electronics is substantially minimized. Compared to a load-dump voltage of 27 V, a reduction by factor 3 is achieved. However, this requires that the state of the low clamp voltage is left in time to switch back in the normal control range of 14V. Ideally, a switchback is needed just before the end of the natural load-dump phase.

In 6 a possible procedure of the method is described in a flow chart. This method can be used, for example, in belt-driven starter generators, synchronous rectifiers or in other drives with powers of typically more than 1 kW in motor vehicles.

In a first step 200 a load-dump event, eg. By voltage measurement, detected and started a timer or timer. In a second step 202 the current jump behind the rectification of the machine is determined. In a third step 204 the expected time load dump length is determined. Subsequently, in a fourth step 206 the initiation of countermeasures. This can, for example, the clamping of the load-dump voltage to a low value of z. B. 7 to 10 V, a short circuit of all Lowside- or LS-switch, a short circuit of all highside or HS switch and / or a selective short circuit of individual phases after Bat- include. In a fifth step 208 the remedial measures are terminated shortly before the expiration of the expected length, for example 1 to 10 ms. The time is determined with the help of the timer. in a sixth step 210 is transferred to the normal control mode.

The method can be used, for example, in a SAR (synchronous active rectifier), in a belt-driven starter generator (RSG) or an integrated starter generator (iSGR).

In the 1 The peak of the power output occurring is proportional to the Zener voltage. The aim is to keep the Zener voltage as low as possible in terms of power loss optimization. In 7 shows the relationship between peak power dissipation over Zener voltage at 230 A output current.

In the representation is at the ordinate 300 the power loss in kW and at the abscissa 302 the zener voltage is plotted in V. 7 shows different voltage ranges, which are characterized by the following features. first area 310 : Zener voltage <8 V; the power supply in the electrical system breaks down second area 312 : 8 V <Zener voltage <18 V; normal operating range third area 314 : 15 V <Zener voltage <18 V; normal operating range above control voltage of the voltage regulator fourth area 316 : Zener voltage> 18 V; above normal operating range with high power dissipation

Known diode rectifiers operate in the voltage range above 18 V. This ensures that the amplification only takes place outside the normal operating mode.

Since active rectifiers can operate for a limited time, ie intelligently controlled, the Zener voltage can be reduced by the described method. Here is the third area 314 between 15 and 18 V is preferred, since the regulator operates normally in this voltage range, all electronic devices continue to work stably and the power dissipation is significantly lower than in the fourth range 316 with more than 18V. An actively controllable intelligent enhancement, which is activated when a load dump is detected and deactivated again when it falls below 15 V Ubat, is necessary.

As a further variant, the occurring power loss can be optimized by the Zener voltage is reduced to 8 V. Thus, the power loss can be kept even lower while maintaining the supply voltage. Without communication to the voltage regulator, the controller would detect too low a voltage and accordingly stimulate the generator. Therefore, in the voltage range of 8 to 15 V, additional communication to the controller and an appropriate controller response is necessary.

Possible controller responses are fast regulation, freewheeling and regulation to 8.5 V.

In 8th is a possible exchange between a rectifier 350 and a voltage regulator 352 shown. In a first step 360 a load dump is detected and a message 362 "Load Dump detected, stapling activated to 8V ". In a second step 364 the controller temporarily regulates to 8.5 V.

Is in one step 366 Ubat> 8.5 V, the controller starts with a control set point of 13.8 V and it will be a message 368 "8.5 V exceeded, controller works normally" sent. in one step 370 the clip is disabled to 8V.

In 9 is a possible implementation of the invention reproduced. The illustration shows a transistor 400 that has a logic 402 and a driver 404 can be controlled. Furthermore, a comparator 408 and a first zener diode 410 and a diode 412 intended. In this embodiment, a fixed Zener voltage can be added.

In 10 is again a transistor 430 , represented by a logic 432 is to be controlled. With the logic 432 Several Zener voltages can be switched on. This can be done according to the situation or application depending on the wishes of the customer. In this case, there is a first Zener diode 434 with a diode connected in series 438 and a second zener diode 436 with a diode connected in series 440 to disposal. The control of the transistor 430 takes place via a comparator 458 ,

In 11 can be a transistor 450 with a logic 452 , By bridges of individual zener diodes can be varied. In this case by bridges of a first Zener diode 454 and a second zener diode 456 with a diode connected in series 460 , The transistors 462 and 464 Beyond the logic 452 controlled, the transistor 464 the Zener path is activated or deactivated and the transistor 462 the first zener diode 454 can short circuit. As a result, the Zener voltage in the Zener distance can be about the Zener voltage of the Zener diode 454 be redutiert. The Transitor 450 is via a comparator 458 driven.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102006032736 A1 [0007]
• EP 0777309 A2 [0012]
• JP 3396955 B2 [0012]
• DE 102005054949 A1 [0014]

Claims (10)

Method for detecting a load drop in a rectifier ( 54 ), in which the load drop is detected on the basis of a first electrical quantity and the duration of the load drop is estimated on the basis of a course of a second electrical quantity. The method of claim 1, wherein the first electrical quantity corresponds to the second electrical quantity. Method according to Claim 1 or 2, in which an electric current is measured as the first electrical variable. Method according to Claim 1 or 2, in which an electrical voltage is measured as the first electrical variable. Method according to one of claims 1 to 4, in which a countermeasure is initiated upon detection of a load drop. Method according to Claim 5, in which, as a countermeasure, an adjustment of the zener voltage in the rectifier ( 54 ) is made. Method according to one of claims 1 to 6, which in a generator arrangement ( 50 ) with a generator ( 52 ), a rectifier ( 54 ) and an evaluation unit ( 56 ) is carried out. Generator arrangement with a generator ( 52 ), a rectifier ( 54 ) and an evaluation unit ( 56 ), whereby the evaluation unit ( 56 ) is adapted to detect a load drop on the basis of a detected first electrical quantity and to estimate the duration of the load drop based on the course of a second electrical variable. Generator arrangement according to Claim 8, in which a voltage regulator ( 352 ) is provided. Evaluation unit, which is designed to detect a load drop on the basis of a detected first electrical variable and estimate the duration of the load drop based on a course of a second electrical variable.

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