GB2246254A

GB2246254A - Protective equipment for a vehicle electrical supply system

Info

Publication number: GB2246254A
Application number: GB9114587A
Authority: GB
Inventors: Guenter Schramm; Walter Kohl; Rainer Mittag; Wenzel Novak
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1990-07-07
Filing date: 1991-07-05
Publication date: 1992-01-22
Anticipated expiration: 2011-07-05
Also published as: GB2246254B; DE4021667C2; DE4021667A1; FR2664443A1; FR2664443B1; GB9114587D0

Abstract

Equipment 14 for the overvoltage protection of a vehicle power supply includes a diagnostic circuit which automatically checks the equipment before the vehicle engine is started. If a fault is detected in the protective equipment 14 or in the diagnostic circuit itself or if an overvoltage occurs, this is indicated, for example by the ignition light 25, and generator excitation 16 prevented. If an overvoltage occurs while the vehicle is in use this is also indicated and generator excitation terminated. <IMAGE>

Description

1 - PROTECTIVE EQUIPMENT FOR A VEHICLE ELECTRICAL SUPPLY SYSTEM The

present invention relates to protective equipment for protection of a vehicle electrical supply system against voltage overload.

Equipment for the protection of motor vehicle power supply systems against excess voltage, with possibilities for indicating certain faults, are known. Thus, for example, in DE-OS 30 06 109 there is described a motor vehicle power supply, in which a battery is supplied by an alternating current generator (alternator) with an excitation winding and a rectifier system, wherein a voltage regulator keeps the generator output voltage constant through regulation of the excitation current. By way of charging checking equipment it is indicated when the generator voltage has a faulty value. Through this indication, the user is warned in good time and can avoid consequential damage such as, for example, drying-out of the battery or failure of the entire electrical system of the motor vehicle.

However, the functional capability of the equipment for the fault indication is not checked and it is therefore not recognised if the fault indication itself is not functioning.

According to the present invention there is provided protective equipment for protection of a vehicle electrical supply system against voltage overload, the equipment including diagnostic means to check the functional capability of the equipment before each start-up of the vehicle engine and to respond to recognition of at least one of faulty function of the equipment and presence of excess voltage by initiating an indication and preventing or terminating excitation of a generator 5 of the system.

Equipment embodying the invention may have the advantage that the equipment checks itself for functional capability on each starting operation and indicates at this instant if a faulty function is present. Furthermore, it can be indicated on starting if there is excess voltage liable to endanger the vehicle power supply.

An excitation of the generator is either prevented, or terminated if excitation has already taken place, in the case of a faulty function of the protective equipment as well as on the occurrence of excess voltage.

is An embodiment of the present invention will now be more particularly described by way of example with reference to the accompanying drawings, in which:

Fig. 1 Fig. 2 is a schematic circuit diagram of a motor vehicle power supply system; is a block schematic diagram of protective equipment embodying the invention and incorporated in the system of Fig. 1; Figs. 3a and 3b are parts of a detailed circuit diagram of the protective equipment; and Fig. 4 is a flow diagram illustrating operation of the protective equipment.

i i i i 1 1 3 - Referring now to the drawings, there is shown in Fig. 1 a vehicle electrical supply system comprising a generator 10, for example a polyphase current generator, with stator windings 11 which are connected by way of main current diodes with the generator terminal B+ and earth, a battery 50, and load devices 51 connected between B+ and earth. The stator windings 11 are connected by way of excitation diodes 13 with the generator terminal D+, which in turn is connected to the terminal D+ of protective equipment 14.

A terminal DF1 of the protective equipment 14 is connected with an excitation winding 16 of the generator 10 by way of a corresponding terminal DF1 of a voltage regulator 15, wherein a reverse current diode 17 is connected in parallel with the excitation winding 16.

The protective equipment 14 comprises a driver 18 for a relay 19, wherein the driver 18 is connected by way of a diode 20 with a voltage divider 21 and 22, which is associated either with a thyristor 23 as shown in Fig. 3 or a thyristor TH1 as shown in Fig. 1, wherein the thyristor TH1 (23) and the voltage divider 21 and 22 are connected by way of a further diode 24 with the relay 19. The ignition electrode of the thyristor TH1 (23) is connected with the junction of the voltage divider 21 and 22 and the driver 18.

The protective equipment 14 is connected with a charging indicator lamp 25 by way of terminals KL15 and LK, but a different method of indication, for example a luminescent diode, can be provided.

Fig. 2 shows a schematic block diagram of the protective equipment 14 from which it can be seen that the protective equipment 14 is basically subdivided into a diagnostic device 26 and the actual protective device 27.

The diagnostic device 26 comprises a current supply unit 28, which has a first protective device, as well as an indicating circuit 29, a holding circuit 30, a field current switch 31, a logic system 32, a store 33, an electronic starting switch 34 and a test-switching protective device 35. The units 28 to 35 are interconnnected to the extent necessary. The diagnostic device 26 also includes terminals KL15, LK, DFl, D+ and D-, which are connected with the corresponding generator or on-board power supply terminals in the vehicle electrical system.

Those terminals if the generator, regulator or protective equipment 14 which are connected together carry the same notation.

The protective device 27 comprises an element for recognition of excess voltage 36, which is connected by way of a timing member 37 with the output stage with thyristor 38.

The connection of the protective device 27 with the diagnostic device 26 is effected by way of several lines, the exact terminals of these lines being evident from the detailed circuit diagram of Figs. 3a and 3b, which shows the circuit in two parts, wherein the lines at the points I, II, III and IV are connected correspondingly. A terminal KL15 is connected by way -of the charging indicator lamp 25 and a fuse 39 with a terminal OF1 of the regulator 15. In the case of the regulator 15, merely the output stage 15 is illustrated, which lies between the terminal DF1 and earth by way of the excitation winding 16 as well as the reverse current diode 17 connected in parallel therewith.

- Also connected to the terminal KL15 is the diagnostic device 26, which comprises the individual elements 28 to 33, as already described in connection with Fig. 2.

The circuit arrangement and the interconnection of the elements 28 to 33 is as follows:

The current supplt 28 comprises a first resistor Rl, which is connected on the one hand to the terminal KL15 and on the other hand by way of a Zener diode D1 and a capacitor Cl, which is connected in parallel with the Zener diode D1, to earth. Connected in parallel with the capacitor Cl is a series connection of a resistor R2 and a Zener diode D2, which is in turn connected in parallel with a capacitor C2. The current supply is connected to the indicating circuit 29 by way of the junction between the components C2, D2 and R2 and the sub-assemblies 29 and 31 to 38 are connected to the current supply 28 by way of the line 40.

The indicating circuit 29 comprises an integrated switching circuit IC1 with, altogether, eight inputs. In the circuit IC1, an input 4 is connected to the current supply unit 28 and an input 5 is connected by way of a capacitor 3 and an input 1 directly to earth.

Coupled between the input 8, which is connected directly with the input 4, and input 2 is a series connection of three resistor R3, R4 and R5, the junctions between the resistors being connected with inputs 7 and 6 of the integrated switching circuit IC1, wherein the input 6 is additionally connected by way of a capacitor 4 with earth.

The input 3 of the circuit IC1 leads by way of a resistor R6 to the base of a transistor T2, the emitter of which is connected with 6 - earth and the collector of which is connected by way of a resistor R8 with the input 8 of the circuit IC1 and also to the current supply unit 28. A series connection of a capacitor C5 and a resistor R7 is coupled between the collector of the transistor T2 and earth, wherein the junction between C5, R6 and R7 is connected with the base of the transistor T2.

A further connection leads from the collector of the transistor T2 to the base of a transistor T3, the emitter of which is connected to earth. A Zener diode D3 is connected in parallel with the collector-emitter path of the transistor T3, while the anode of the Zener diode D3 is connected to earth. The collector of the transistor T3 is connected by way of a resistor R10 and a Zener diode D4 with the base of a transistor T4, while the emitter of the transistor T4 is connected by way of a resistor R9 with the collector of the transistor T3. A further resistor R11 is connected between the base and the emitter of the transistor T4.

A further connection leads from the collector of the transistor T4 by way of a resistor R12 to the base of the transistor T1, the collector of this transistor T1 leading to the input 2 of the circuit IC1 and the emitter of the transistor T1 being connected to earth. In addition, the base of the transistor T1 is connected with earth by way of a parallel connection of a resistor R13 and a capacitor C6.

The emitter of the transistor T4 is connected by way of a diode D5 with the fuse 39, the voltage regulator terminal DFI and the holding circuit 30. The holding circuit 30, which is connected by way of the field current switch 31 with the line 40, comprises a transistor T5, the emitter of which is connected to earth by way of the resistor R14 and the collector of which is connected with the relay 19 as well as with a diode D6, connected in parallel therewith, of the field current switch 31. The base of the transistor T5 is coupled to earth by way of a series connection of two diodes D7 and D8 as well as a resistor 15 connected in parallel therewith. Moreover, a connection with the logic system 32 exists by way of a further resistor R16 and a connection with the line 41, which in its turn leads to the regulator terminal DFl, exists by way of a diode D9, a Zen er diode D10 and a resistor R17. A capacitor C7 is connected between the cathode of the Zener diode D10 and earth.

The line 41 is connected by way of a contact, which is disposed within the holding circuit 30, of the relay 19 either through a diode 16 with earth or, after switching-over of the relay 19, with the store 33 as well as with the terminal D+.

The store 33 comprises a transistor T9, the base of which is connected by way of a diode D13 and a resistor R25 with earth, wherein the series connection of a Zener diode D14 and a diode 15 is so connected between the cathode of the diode D13 and the resistor R25 that the cathodes of the Zener diode D14 and the diode D15 are connected together and the anode of the diode D15 is connected with a terminal of the switch Schl.

The collector of the transistor T9 is connected by way of a resistor R23 as well as a resistor R22 and the capacitor C8, which are connected in parallel with the resistor R23, with a thyristor TH1.

The mutual electrode of the thyristor TH1 is connected to earth and the control electrode is similarly connected with earth by way of a is resistor R27. The store 33 is driven by the logic system 32, wherein the connection between the store 33 and the logic system 32 takes place starting from the emitter of the transistor T9, which is connected with the emitter of a further transistor T6 of the logic system 32. A further connection between the system 32 and the store 33 is provided by way of the resistors R21 and R19 starting from the junction between the resistor R23 and the capacitor C8.

The logic circuit 32 is connected with the current supply unit 28 by way of a line 40 starting from the collector of the transistor T6. A resistor R18 is connected between the collector of the transistor T6 and the base of the transistor T6, the base of the transistor T6 moreover being connected to the cathode of the Zener diode 011, the anode of which is connected to earth. A further connection leads from the emitter of the transistor T6 to the emitter of a transistor T7, the collector of the transistor T7 being connected with the emitter of a transistor T8 and the collector of the transistor T8 by way of a diode D12 with the resistor R16 of the holding circuit 30.

The base of the transistor T7, is as already mentioned, connected by way of the resistor R22 with the store 33, a resistor R19 being connected between the base and the emitter of the transistor T7. A further resistor R20 connects the base of the transistor T8 with the emitter of the two transistors T6 and T9 and also with the electronic starter switch 34.

The electronic starter switch 34 comprises two transistors T10 and T11, the emitters of which are connected by way of the line 40 to the current supply unit 28. The base of the transistor T11 and the i i i 11 i'I i i i 1 i i i 1 i collector of the transistor T10 are connected with each other, and also with earth by way of a resistor R29. A resistor R28 and a capacitor C9 are connected between the emitter and the base of the transistor 10. 5 A connection leads from the collector of the transistor T11 by way of a resistor R31 to the test circuit 35 and by way of a diode D19 to the store 33. The junction between the resistor R31 and the diode 019 is applied to earth by way of a further diode D21 and a resistor R33, and the other connection of the resistor R31 is similarly connected with earth by way of a series connection of a diode D20, a resistor R32 and capacitor C10. In that case, a further connection leads from the cathode of the diode D20 by way of a diode D18 to the base of the transistor T8 of the logic system 32. A further resistor R30 is connected between earth and the junction of the cathodes of the diodes D20 and D18. A Zener diode D17, the cathode of which is connected with the base of the transistor T10 and the anode of which is connected with the cathode of the diode D21, serves for voltage limitation. The test circuit 35 consists of a transistor T12, the emitter of which is connected to the resistor R31 of the electronic starter switch 34. A resistor R34 is connected between the emitter of the transistor T12 and the base of the transistor T12, and the base of the transistor T12 is connected with earth by way of a further resistor R35.

The collector of the transistor T12 is followed by a series connection of a resistor R36, a resistor R37, a diode D23 and a Zener i I 1 i i - diode D22, wherein the diode D23 and the Zener D22 are connected to each other by way of their cathodes and are furthermore connected to the collector of a transistor T13. The collector of the transistor T13 is connected to earth and its base is also connected with earth by way of a resistor R38 and with the collector of a transistor T14, the base of which is connected with the junction between the resistor R37 and the diode D23 and the emitter of which is connected with the junction between the resistor R36 and the resistor R37. A capacitor C11 is connected between the emitter and the base of the transistor T14.

The test circuit 35 is connected with the element 36 for excess voltage recognition in such a manner that a return path exists from the emitter of the transistor D12 to the collector of the transistor T14 by way of a diode D24, a temper ature-dependent resistor R40 and a resistor R39.

A Zener diode D25 and a diode D26, which are connected to each other by way of their cathodes, are arranged between the resistor R39 and the base of a transistor T15. The emitter of the transistor T15 is connected to the terminal D+ and the collector is connected to earth by way of the resistor R43. A resistor R42 and a capacitor C12 are arranged in the base-emitter circuit of the transistor T15.

The temper ature-dependent resistor R40 together with a further resistor R41 form the input resistance of the excess voltage recognition element 36.

Denoted by 37 is a timing member which comprises a variable resistor R44 and a Zener diode D27, wherein the junction between the 1 resistor R44 and the diode 027 is connected to a capacitor C13, the other electrode of which is connected to earth. The anode of the Zener diode D27 is connected with earth by way of a resistor R45.

The output stage 38 is so connected by way of the line 40 of the current supply unit 28 that the emitter of a transistor T17 and one side of a resistor R46 are connected directly to the line 40, wherein the base of the transistor T17 is connected with the resistor R46 by way of the resistor R47 and at the same time with the collector of a transistor T16, the emitter of which is connected to earth and the base of which is connected to the anode of the diode D27 of the timing member 37.

The collector of the transistor T17 is connected by way of a resistor R48 to the control electrode of a thyristor TH2, which is connected between the terminal 0+ and earth. Moreover, the control electrode of the thyristor TH2 is connected by way of a resistor RSO to a terminal N, and a resistor R49 and a capacitor C14 are connected between the control electrode and earth. The operation of the circuit arrangement shall now be explained by reference to a flow diagram illustrated in Fig. 4. 20 After closure of the engine ignition switch (not shown), a diagnosis initially takes place, at the end of which it is either recognised that the system is in order or it is recognised and indicated that a fault has arisen. The diagnosis is started after closure of the ignition switch on switching-on of the vehicle, for which purpose a test voltage is applied from terminal KL15 to the voltage divider 21 and 22 of the excess voltage protection device 27.

In the flow diagram of Fig. 4, this is illustrated by the steps S1 to S3. In that case, the test voltage is produced in the step 53 and applied to the voltage divider in a step S4.

Step S5 represents a decision step; it if is recognised that the voltage divider is not in order, it is decided by "no" and a fault indication F is initiated. The feed of the signal for the fault indication takes place by way of a summation point S. If the voltage divider is in order, it is indicated by "yes" and the ignition of the thyristor 23 takes place. In the flow diagram, this is denoted by the step S6. After ignition of the thyristor, the test voltage goes towards 0 volts. The terminal D+ is short-circuited in step S7 and it is checked in decision step 58 whether the voltage UD+ goes towards zero. If the voltage UD+ does not go towards zero, a fault indication F is initiated, which can be provided by, for example, the charging indicator lamp.

If, on the other hand, it is recognised in step S8 that the voltage UD+ goes towards zero, it is decided in step S9 to cancel the short-circuit at D+, which corresponds to a step S10, and at the same time to switch on the field current relay 19 in a step S11. For this purpose, the test voltage is initially switched off so that the thyristor 23 goes out and thereby switches on the field current relay.

If no field interruption is recognised, the generator is excited in step S12. If, on the other hand, it is recognised that the field is interrupted, a fault indication takes place.

If a fault is recognised in the above-described diagnostic sequence, then a fault indication takes place in accordance with the 1 1 i i i - 13 flow diagram starting from the steps 55, S8 and S12. If, however, the diagnosis as far as the step S12 indicates that the system is in order, the normal generator operation is carried out.

The functional sequence in the protective device 27 is as 5 follows:

After excitation of the generator, the excess voltage protection device measures the voltage at the terminal D+ in a step S13. If the condition UD+ = URegel is fulfilled in a step S14, this is registered in a further step 515 and a statement follows in a step S16 that the system is in order. At the same time, the step S11 remains activated by feedback from the step 515.

If, however, it is recognised in step 514 that UD+ is greater than the voltage URegel, the excess voltage protection is activated in step S17. After a response delay time represented by the step S18, the generator is short-circuited by the thyristor 23 at D+/D- and the field current relay 19 is switched off, upon which a fault indication takes place and the charging indicator lamp 25 lights up. In the flow diagram, this state of affairs is shown by a step S19 which represents a decision step, a step S20 which denotes the short-circuit of D+, and a step S21 which represents the step "switch off field current relay".

The exact functional sequence will now be explained by reference to the complete circuit illustrated in Fig. 3. For this purpose, it is indicated below what takes place in the blocks 29 to 38.

1. Diagnosis The diagnosis is switched on by way of the terminal KL15 before engine starting.

14 - B] ock 34: The transistor T11 conducts by way of the base resistor R29. Positive potential is fed from the collector of the transistor T11 by way of the decoupling diode D20 to the diode D18. Transistor T10 blocks.

32: Transistor T8 blocks.

34: The blocks 35, 36, 37 and 38 are switched on by way of the resistor R31.

35: The diode D24 decouples the diagnostic circuit from the terminal D+ Gen' 35:

32: Resistor R18, diode 11 and transistor T6 stabilise the voltage for the blocks 32 and 33. Thereby, it is ensured that any voltage collapses at the terminal W5, for example during the starting operation, do not lead to unintended extinction of the thyristor TH1 or to switching-off of the logic system and thereby to interruption of the field current by the relay 19 in block C.

33: Transistor T9 conducts by way of the diode D13 and the resistor R25.

32: After the ignition of thyristor TH1, the transistor T7 conducts by way of the resistor R21.

At the same time, the transistor T12, T13 and T14 become conductive by way of the resistor R31 of the block 34. Transistor T13 places the resistor R39 in parallel with the resistor R41 and thereby simulates an excess voltage in block 36. Transistor 15 therefore becomes conductive and, by way of the resistor R44 of the timing member 37, charges the capacitor C13 of that member.

z 1 1 z 1 i i i i 1 38: When the voltage across the capacitor C13 reaches the value of the sum of the voltages UD27 + UBE T16, then the transistors T16 and T17 become conductive, whereby the thyristor THS2 ignites.

35: After the ignition of the thyristor TH2, the voltage at the anode 34:

of the diode D24 falls to the value U024 + UTH2.

The transistor T10 becomes conductive by way of the diodes D21 and D17, whereupon the transistor T11 blocks and the current falls below the holding current of the thyristor TH2 of the block 38.

38: When the holding current of the thyristor TH2 is fallen below, the thyristor TH2 blocks. Thereby, the transistors T16 and T17 also block, since voltage is no longer present at the transistor T15. Transistor T11 in block 34 also blocks. The transistors T16 and T17 thereupon lie at the terminal KL15, as there is no voltage at terminal D+ in the case of standstill of the generator.

35: The transistors T12, T13 and T14 block. The parallel connection of the resistors R39 and R41 is therefore cancelled.

32: If the transistor T11 blocks in block 34, the transistor T8 becomes conductive by way of the diode D18 and resistor R30.

The resistor R32 and the capacitor C10 serve for the smoothing of voltage collapses at the terminal KL15. This is denoted as bouncing of the ignition switch.

If the transistors T7 and T8 are in conductive state by reason of the diagnostic sequence described up to now, the field current switch 31, the transistor T5, is driven by way of the diode D12 and the resistor R16.

34:

- 16 31: The relay energises and connects the lamp with the terminal D+. Preliminary excitation current can therefore flow and the generator becomes excited. The components T5, R14, D7, D8 and R15 form a current regulator. Thereby, a 12 volt relay can be used, the maintaining voltage of which lies below 6 volts. Consequently, it is ensured that any voltage collapses at the terminal KL15, up to a height of 6 volts, do not lead to deenergisation of the relay 19.

2. Generator Excitation If the voltage at the terminal D+ becomes greater than the voltage drop across the diodes D14 and D15, then the transistor 9 in the block 33 blocks and the current falls below the holding current of thyristor TH1, which leads to the thyristor TH1 blocking. The relay in block 31 is maintained by way of the resistor R17, the diode D9 and the diode D10. The transistor T7 is blocked by way of the resistor R21 in block 32. The thyristor TH1 and the logic systems T7 and T8 are switched off.

Standstill of Generator On standstill of the generator, the voltage falls below the Zener voltage of the Zener diode D10 in block 31, whereby the relay 19 is de-energised, current flows by way of the diode D16 and the indicator lamp 25 lights up.

i z 1 i i 1 1 - 17 Fault in the diagnostic sequence If an interruption occurs with the components in the blocks 31 to 38, either the thyristor TH1 in block 33 is not ignited or the transistors T7 or T8 in block 32 do not become conductive. Thereby, the relay REL1 in block 31 cannot be energised and, since the current path by way of the diode D16 is of lower resistance than the current path by way of the excitation winding and the regulator, it is ensured that the generator is not excited.

Polarity Error Protection If the terminals KL15 and the lamp terminal LA are interchanged, the lamp current is interrupted by the fuse 39, which corresponds to an indirect fault indication.

3. Excess voltage protection device If excess voltage arises at the terminal D+, the following sequence is initiated:

Block 36: It is recognised by way of the voltagedivider R40 and R41 that excess voltage prevails at D+. If the voltage UD25+ UD26 + UBET15 is reached, transistor T15 becomes conductive. 20 37: The capacitor C13 is charged up to a voltage UD27 + UBET16 by way of the resistor R44.

18 - 30:

38: The transistors T16 and T17 become conductive, and the thyristor TH2 is ignited and short-circuits the generator at the terminals D+ and D-. The grid current derives from the terminal KL15 because of the diagnostic circuit.

The relay REL1, which is no longer driven by way of the maintaining circuit R17, D10 and D9, de-energises and shortcircuits the terminal DF1 by way of the rest contact and the diode D16. The diode-D16 then produces a voltage drop in the short-circuited field circuit. Thereby, the remnant (shortcircuit) current in the excitation circuit reduces. The static short-circuit current through the thyristor TH2 and thus the arising dissipative power are appreciably reduced thereby. After a standstill of the generator, the system is operationally ready again.

3. Indicating Circuit (interruption of excitation) Block 29: An astable trigger stage with an integrating switching circuit 1C1 oscillates at a frequency of 1 hertz. The resistor R9 is switched between the terminals DFl and D- by way of the 20 transistors T2 and T3 as well as the diode D5. In that case, the following diagnostic cases are possible:

Case 1: Positive diagnosis, standstill of generator:- 1 1 i 1 Either the terminal DFl or the terminal LA is connected with D+ by way of the relay contact of block 31. A preliminary excitation current flows through the field winding 16. The resistor R9 is connected in parallel with the terminal DFl at the oscillation frequency of the circuit IC1. Thereby, impairment of the engine starting rotational speed is prevented and the system is ready for operation.

Case 2: Positive diagnosis after the starting operation:- The excitation current is led from terminal D+ by way of the relay contact of the relay 19 to the terminal DF1. The holding circuit in block 31 is activated. The resistor R9 is connected under the control of the circuit IC1 to the generator terminal D+ Gen. Due to the voltage drop across the resistor R9, the transistor T4 becomes conductive and transistor T1 likewise conducts and effects a reset in the circuit IC1. Consequently, the transistor T3 isblocked and the dissipative power at the resistor R9 is substantially reduced.

Case 3: Interruption in the excitation circuit, standstill of the generator:- Initially, the diagnosis continues and the relay 19 in the block 30 is de-energised. The transistor T9 in block 33 blocks by way of the lamp contact LA, the working contact of the relay REL1 and the diodes D15 and 14.

29:

33: Since the transistor T9 blocks, thyristor TH1 also blocks. The logic system T7 and T8 in block 32 is thus cancelled.

31: The relay 19 initially remains in the energised state by way of the resistor R17 and the diodes D10 and D9. This branch is loaded through the resistor R9, base current is drawn off at the transistor T5 and transistor T5 therefore blocks.

31: The relay 19 de-energ-ises and the indicator lamp 29 receives current by way of the diode D16 and lights up.

Case 4: Interruption of excitation during vehicle travel operation:If an interruption occurs in the generator excitation during the travel operation, then in.

Block 31:

29:

The holding circuit is no longer supplied from terminal D+.

By reason of the pulsed loading by the resistor R9, base current is withdrawn from the transistor T5, for which reason transistor T5 blocks and the relay 19 de-energises. Current is therefore fed to the indicator lamp 25 by way of the diode D16 and the lamp lights up.

28: The Zener diode D1 as well as the resistors R1 and R2 protect the diagnostic part against voltage peaks.

In the case of an emergency switch-off of the engine, the thyristor TH2 in block 38 can also be ignited externally by way of the -1 i j 1 It 1 i i 1 j! 1 i resistor R50. At this point, for example, an input for safety devices of the vehicle can be provided so that an emergency switch-off can be initiated through these further safety devices.

After successful checking of the diagnostic equipment, the protection and error recognition systems remain active in normal operation of the generator, so that any faults in the on-board power supply are indicated, protection against excess voltages is maintained and the generator is deexcited, optionally on the occurrence of a particular fault.

In order to contain circuit cost, the equipment is designed for the fault case "interruption of components and also of the conductor paths". If the circuit is constructed as an integrated circuit, apart from interruptions a short-circuit in the respective circuit components can also be recognised.

i i i i

Claims

1. Protective equipment for protection of a vehicle electrical supply system against voltage overload, the equipment including diagnostic means to check the functional capability of the equipment before each start-up of the vehicle engine and to respond to recognition of at least one of faulty function of the equipment and presence of excess voltage by initiating an indication and preventing or terminating excitation of a generator of the system.

2. Equipment as claimed in claim 1, the diagnostic means being arranged to check the functionally capability of the equipment 10 automatically.

3. Equipment as claimed in either claim 1 or claim 2, the equipment being arranged to initiate said indication by causing illumination of a battery charge warning lamp of the system or of a respective warning lamp of the system.

4. Equipment as claimed in any one of the preceding claims, comprising protective means arranged separately from the diagnostic means and connected thereto by connecting means.

5. Equipment as claimed in claim 4, wherein at least a substantial part of each of the diagnostic means and the protective means is 20 provided by an integrated circuit.

1 i 1 i i i i j 1

6. Equipment as claimed in any one of the preceding claims, the equipment being arranged to initiate said indication in response to short circuiting of, or interruption of an excitation circuit for,the generator when at full excitation.

7. Equipment as claimed in claim 6, wherein the system voltage is generated without a battery and the generator is so arranged that short circuiting thereof occurs after occurrence of voltage overload exceeding a threshold value.

8. Equipment as claimed in any one of the preceding claims, the equipment being so arranged that, when the generator is excited, recognition and indication of faults in the system takes place after recognition of the functional capability of the equipment.

9. Equipment as claimed in claim 1, wherein the generator has an excitation winding and rectifier means and the system includes a battery, a voltage regulator and consumers.

10. Protective equipment substantially as hereinbefore described with reference to the accompanying drawings.

11. A motor vehicle provided with protective equipment as claimed in any one of the preceding claims for the electrical system of the vehicle.

Published 1992 at The Patent Office. Concept House. Cardiff Road. NewportGwent NP9 I RH Further copies rnav be obtained Irom Sales Branch. Unit 6. NineMile Point. Cumfelinfach. Cross Keys. Newport- N'P1 7HZ. Printed by Multiplex technique5 lid Si Nlar Cra. Kew