AU597900B2 - Electronic voltage regulator circuit - Google Patents

Description

Auwtralia Form PATENTS ACT 1952 COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE Short Title: Int. Cl: Application Number: Lodged: Co~mplete Specification-Lodged: Accepted; Lapsed: Published: Pd ority: iriment conta~ns the Related Art: r ii~lSmd Inr TO BE COMPLETED BY APPLICANT Name of Applicant: ROBERT BOSCH (AUSTRALIA) PTY. LTD.

Address of Applicant, Cnr. Centre McNaughton Roads, Clayton, 3168, Victoria, Australia Actual Inventor: Address for Service: CALLINAN AND ASSOCIATES, Patent Attorneys, of 48-50 Bridge Road, Richmnd, State of Victoria, Australia.

Complete Specification for the Invention entitlod: 11RA41 lh he ,l lowing statement is a full description of this inventlon, Including the best method of performing It known IV T C- ote: The description Is to be typed In double spacing, pica typo faco, In an area not oxceeding 250 mm In depin and 160 mm In width. on tough white paper of good quality and it is to be inserted Inside this form, The present invention relates to an electronic voltage regulator circuit for multiphase alternators for vehicles and relates particularly, although not exclusively, to electronic voltage regulators for passenger vehicles having an internal combustion engine.

Most regulators with battery voltage sensing functions that are currently on the market do not have the feature that the alternator output is limited to a safe level should the battery charging wire from the alternator be decoupled. In the event of the battery charging wire t t from the alternator being decoupled, the battery voltage will fall below the regulating level of the regulator. The I t t battery sense function of the regulator will sense the low battery voltage and will supply field current to trie it alternator in order to generate a higher alternator output voltage to charge the battery to the regulating level.

Because the battery charging wire is decoupled, the battery will not be charged and consequently the alternator will continue to generate higher and higher output voltage.

Under this condition, the alternator output voltage can reach in excess of 30 volts. Depending on the wiring configuration of the vehicle, this unacceptably high alternator output voltage can be supplied directly to the rest of the electrical components in the car even if the battery cable is disconnected. Consequently, damage to instrumentation, electronic engine control systems, stereo systems, lights and even the wiring harness of the vehicle 2 ~PPI3~aUP-rV* I--rr--~li3 P i~ l~~ may occur and may even result in a fire hazard.

One solution to this problem is to alert the driver to such a dangerous condition by illumination of a warning light within the vehicle. In our Australian Patent Application No. 42820/85, the contents of which are incorporated herein, an embodiment of a suitable electronic regulator was described with reference to Figure 4 thereof.

In this embodiment the electronic regulator senses both the battery charging wire from the alternator and the battery sensing wire becoming decoupled by comparing the battery voltage level to the alternator output voltage. Comparator U1 compares alternator output voltage with the battery voltage, and the output of comparator U1 will go high when the alternator output voltage reaches a voltage level about 1 to 3 volts above the regulating level which is set by resistors R17 and R37 (after which the difference voltage level may be set by transistors R1 and R10). When the output of comparator U1 goes high, base current is supplied to transistor T14 via diode D7 and resistor R15, to turn on the warning light WL, warning the driver of the faulty condition. If the warning is not heeded and the vehicle continues to run in this condition, there is the possibility of damage occurring to the vehicle as described above.

It is an object of the present invention to provide a modification or improvement to the electronic voltage regulator circuit disclosed in Australian Patent Application No. 42820/85 whereby alternator output voltage -3is limited to a safe level when the battery charging wire from the alternator or the battery sensing wire are decoupled.

According to one aspect of the present invention there is provided an electronic voltage regulator circuit for multi-phase alternators for vehicles, said circuit including control means for controlling the switching of alternator field winding current and switch means for supplying field current to said field winding on power up of said regulator circuit, said control means switching current to said field winding when alternator voltage falls below a predetermied value and prevents flow of current to said field winding when said alternator voltage exceeds a further predetermined value, said switch means including a warning light or device to indicate when insufficient charging voltage is being generated or on detection of a fault conditiun in said alternator, said warning light or device not being in series with said field winding, said control means including a first sensing means for comparing battery voltage with a reference voltage to control operation of said switch means for providing a regulated alternator output voltage and a second sensing means for comparing alternator output voltage with battery voltage, whereby said second sensing means activates said switch means when a predetermined alternator output voltage is sensed to limit alternator output voltage to a safe level.

Preferably said control means switches current to said field winding when alternator voltage falls below a predetermined value and prevents flow of current to said field winding when said regulated voltage exceeds a further predetermined value.

In a further preferred embodiment a field winding turn off means is provided which prevents current being supplied to said field winding on opening of an ignition or main power switch.

order that the invention may be more clearly understood and readily put into practical effect, a -4-

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preferred non-limitative embodiment constructed in accordance with the invention will now be described with reference to the accompanying drawing, in which:- Figs. 1A to 1D show an embodiment of an electronic voltage regulator circuit made in accordance with the present invention.

Turning now to Figs. 1A to ID an embodiment of the invention will now be described. This embodiment has the capability of providing a regulated voltage under almost any circumstances. The complexity of the circuit requires the major components to be incorporated into an integrated circuit which in turn is incorporated in a hybrid circuit.

The operation of the component parts will not be described individually. The overall operation of the circuit together with the fault detection and modes of regulation will be described. Whilst an engine is running, the three phase current generated by the stator windings of the alternator are rectified by six power diodes. This current charges up the battery end supplies to the various loads required by the vehicle, The regulator senses the battery voltage and controls this voltage by switching the alternator excitation field current to the field winding on and off. Whilst battery voltage remains below the regulated voltage, power Darlington T15 is switched on. If the battery voltage exceeds the specified limit, power Darlington transistor T15 is switched off, causing output voltage to drop. These regulator cycles are repeated so II r' L r quickly, that the output voltage is maintained constant at the desired regulated level.

The basic voltage regulation is achieved by sensing the battery voltage and scaling it down using resistors R37 and R17 and diode D6. This scaled down voltage is compared to a reference voltage by comparator U2.

If the battery voltage is smaller than the regulated limit, transistor T8 is switched off, allowing transistors T6 and T7 to be turned on and hence to switch on power Darlington transistor T15. If battery voltage is larger than the .desired regulated voltage, transistor T8 is turned on via resistor R18. Transistors T6 ard T7 are turned off which blocks the current to the base of T15, i.e. the Darlington transistor is turned off. The function of resistor R16 and capacitor Cl1 is to provide the hysterisis loop which determines the upper and lower specified limits of regulated voltage.

The regulator has two basic modes, namely active and standby. In the standby mode pin 10 of the integrated circuit (pin 6 of the hybrid circuit) senses the on/off conditions of the ignition switch for the I.C. circuitry to determine the active/standby mode. Standby mode represents the or'ndition in which the engine is not running and the ignition switch is in the off position. In this mode, transistor T2 is turned off and transistor T4 is on, which turns off transistors T6 and T7 and power Darlington transistor T15. Hence, no current flows through the field -6 winding. Under this condition, the I.C. draws very little quiescofat current to prevent the battery from discharging quickly. This is done by using small current sources to drive the transistors (represented by resistors R2, R5, R6, R7, R8 and R9).

In the active mode two different situations occur.

In the normal active mode the warning light driver T14 is switched off. Transistor T2 is on, transistor T4 is off and therefore the switching of Darlington transistor T15 is controlled by the battery voltage level. The other situation arises when the engine is not running but the ignition switch is closed. To reduce the power dissipation through the field winding the duty cycle of the current therethrough can be controlled. A 50% duty cycle oscillator, formed by operational amplifier U4 resistors R5, R19, R20, R21 and R22, capacitor C4 and diodes D22 and D42, controls transistor T5 which in turn switches power Darlington transistor T15 accordingly. When the phase voltage threshold is reached, output of operational amplifier goes low causing oscillator output current to be diverted away from transistor T5 through diode D13; hence the field will remain on fully until switched off by other means, such as regulation level being exceeded. To avoid the situation where the regulator may become a high frequency oscillation source the frequency of the 50% duty cycle oscillator must not be too high. In other words, the product of R21 C4 and R22 C4 cannot be too low. The values of R21 and R22 can be -7 made higher by using low current source. By doing this C4 can be made at about 680Pf which can be made in the I.C.

Capacitors C3 and C5 together with resistor R3, transistor T8, resistor R35, transistors T6 and T7 form low pass filters, which prevent the regulator from being a high frequency oscillation source.

The various fault conditions will now be described. On detection of one or more of the belowmentioned faults the warning light driver transistor will be turned on which will cause illumination of the warning light. Diode D39 is included to provide enough current to turn on transistor T2 during a fault condition. The various fault conditions monitored by the regulator are as follows:- 1. Battery to alternator cable broken whilst driving Under normal operation, the battery is connected to the alternator output via the cable. Also, under normal operation the battery to alternator voltage difference is less than the threshold limit. However, if the cable is broken, the battery voltage is dropped below the lower regulated limit, causing the Darlington transistor to turn on because of the normal battery sense regulation. Therefore, alternator output voltage will build up until the non-inverting voltage of comparator Ul is greater than its inverting voltage causing the warning light to be turned on.

Once the light is on, transistor T5 will be 8 i r, _~tiL_ i C i ~iW1 turned on, hence power Darlington transistor is switched off. This will restrict, the alternator output to about 18V.

2. Battery to alternator cable broken before engine is running When the cable is broken before the engine is running, no voltage can be built up as there is no initial self-excitation current.

Transistor T1 is then turned off, current will flow through resistor Rll and diode D1 to turn on transistor T 1 4, which in turn switches on the warning light. However, if running engine at high speed, alternator output voltage will be built up as described in fault condition 7. described later. This will turn off the warning light.

When the engine returns to idle speed, warning light is on again.

3. Battery sensing wire broken Under normal operation, the inverting voltage of comparator Ul is greater than its non-inverting voltage.

Accordingly no current flows through diode D7 and resistor R15 to turn on warning light driver transistor T14. If the battery sensing wire is broken, the inverting terminal of comparator U1 drops to zero. This drop enables transistor T14 and hence the warning light to be turned on via diode D7 and resistor R15. Under this condition, transistor T5 is on and power Darlington -9 _F transistor T15 is switched off. This will prevent the alternator output voltage from rising too high.

4. Alternator overload As mentioned before, the output current of the alternator is used to charge up the battery and supply to the loads. However, if the load is so heavy that current demanded exceeds the output current rating of the alternator, the battery voltage will drop below {I the desired level even if the power Darlington transiscor T15 is fully on. This is an overload situation. Under this situaion, the inverting I terminal voltage of comparator U3 is larger than its non-inverting terminal voltage, hence turning off transistor Tll and trigger pin 1 of the I.C.

to logic high level. Otherwise, under normal operation, pin 1 of I.C. would be at logic low level. Pin 1 can be monitored by additional circuitry if a separate indication of overload is required. As previously described under normal operation, when the battery voltage is at the upper regulated limit, transistor T8 is turned on and Darlington transistor T15 is turned off. When the battery voltage drops to the lower limit, transistor T8 is turned off and Darlington transistor T15 is on. In other words, either the output of comparator U2 or collector of transistor 10 'In 'r r -r -r 1 11 1 TlO is at a logic low level. This level forbids current flow through diodes D2, D3 and D4. Hence the warning light is off. However, due to the large power dissipation in Darlington transistor T15, it is likely that T15 will not be working properly after a prolonged overload. Darlington transistor T15 may then fail to turn off when transistor T8 is on. If this is the case, the battery will be overcharged. Under this l0, condition, high logic level will be maintained at cathode of diodes D8 and D4 which enables transistor T14 to be turned on by permitting the current to flow through resistor R 4 and diodes D2, D3 and D4 to drive the warning light.

5. One or more alternator positive power diodes short circuit The phase voltage at the ignition switch on position is high enough to set output of comparator U5 to low logic level. This will turn off the warning light before the engine is cranking. Indirectly, this indicates the fault con' 'tion is in the alternator regulator unit.

6. Alternator negative power diodes short circuit or phase sensing wire broken Under these conditions, the average phase voltage at the inverting terminal of comparator U5 will be smaller than the non-inverting voltage. This enables transistor T14 to be turned on by 11 iLn

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i permitting the current to flow through diode and resistor R29 to drive the warning light.

7. Warning light burnt out When the warning bulb is burnt out, there is no field current during cranking of the starter motor. However, it can generate a small amount of phase voltage due to the self-excited characteristic of the field winding. This phase voltage will be high enough to turn on transistor T2 and turn off transistor °0 T4, hence allowing field current through the field o winding at high speed. As a result, output 0 0 0 0 Bvoltage is built up to the regulated level.

00 0 From the above it is clear that this embodiment 0 0 has extensive error correction capability and allows 6 operation of the alternator under extremely adverse conditions. The above description is a repetition of the embodiment shown in Figure 4 of Australian Patent tit Application No. 42820/85 and has been included for St Scompleteness. The improvements or modifications which form the basis of this invention will now be deoribed. The S ohanges will, in addition to warning the driver, also switch the current to the field winding, limiting the alternator output voltage to a safe level, thus preventing any further damage to the electrical components in the vehicle when "e battery charging wire from the alternator or the battery sensing wire are deooupled.

A branch containing diode D43 has be n adde 12 ij the output of comparator U! to the base of transistor T5 via resistor R13. When the battery charging wire from the alternator or the battery sensing wire are decoupled, the V battery voltage sensed wil.l fall below the regulating .evel of the regulator. The batt~ery voltage sensed by the battery sensing wire is compared by the regulating level which is set by the reference voltage at the inverting input of comparator U2. This low battery voltage caus, 3 the output of comparator U2 to go low switching transistor T8 off, ii 10 which enabltes base curre t~ to be supplied to transistor T6 via resistor' R3 and diode D5, turning transistor T6 on.

Emitter current from transistor T6 will turn transistor T7 V on which supplies base current to Darlington transistor to switch it on. When Darlington transistor T15 switches on it supplies current to the field excitation winding of the alterntor, increasing the output voltage of the ij alternator. The alternator output voltage, which is 1 compared to tne battery voltage level by comparator Ul, will cause the output of comparator Ul to go high when the alternator, output voltage exceeds the battery voltage level by more than about 1 to 3 volts a level which is set by resistors Rl and RIO. When the output of comparator U1 goes high, the warning light WL WOi go on due to base current supplied to transistor TlI via resistor R15 and diode D7 from the output of comparator Ul. Base current supplied to transistor T5 via the new branch containing diode D43 will turn transistor T5 on when the output of comparator U1 -s 13 I high. Transistors T6 and T7 will switch off, turning Darlington transistor T15 off, switching off the field current to the alternator. Once the alternator output voltage has fallen below the voltage level set about 1 to 3 volts above the regulating level, the output of comparator Ul will go low, turning off transistor T5 along with the warning lamp, allowing transistors T6 and T7 to turn on.

Darlington transistor T15 will then go on, supplying field current to the alternator to increase the alternator output voltage to about 1 to 3 volts above the regulating level.

In this way, a safe back up regulating vrltage is realised, preventing any further damage to the vehicle's electrical system and simultaneously warning the driver of the fault via the warning light WL.

The functions of Zl (diodes D23, D24, D25), Z2 (diodes D26, D27, D28), diodes D15, D16, D17, D29 to D37, resistor R23, transistor T9 are to protect the I.C.

from damage caused by voltage peak transient and load dump battery voltage. Zl, Z2, D29 to D31, D32 to D34 will clamp pin 3, 4, 1, 5 of I.C. to about 24V respectively during voltage peak transient. The function of filters F1 and F2 is to filter-off the high frequency interference from an Sexternal source. This interference will affect the regulated voltage and switching frequency. The roll-off frequencies of low pass filters Rl, Fl and R37, F2 are matched, to prevent the warning lamp from turning on under working condition.

14 rrsry It is believed that the invention and many of its attendant advantages will be understood from the foregoing description and it will be apparent that various changes may be made in the form, construction and arrangement of the parts and that changes may be made in the form, construction and arrangement of the circuit described without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the form hereinbefore described being merely a preferred embodiment thereof.

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Claims (5)

1. An electronic voltage regulator circuit for multi-phase alternators for vehicles, said circuit including control means for controlling the switching of alternator field winding current and switch means for supplying field current to I said field winding on power up of said regulator circuit, said control means switching current to said field winding when alternator voltage falls below a predetermined value and prevents flow of current to said field winding when said alternator voltage exceeds a further predetermined value, said switch means including a warning light or device to indicate when insufficient charging voltage is being generated or on detection of a fault condition in said alternator, said warning light or device not being in series with said field winding, said control means including a first sensing means for comparing battery voltage with a II reference voltage to control operation of said switch means for providing a If regulated alternator output voltage and a second sensing means for comparing alternator output voltage with battery voltage, whereby said second sensing means activates said switch means when a predetermined alternator output voltage is sensed to limit alternator output voltage to a safe level. Ii2. The electronic voltage regulator circuit as claimed in claim 1, wherein 1 said control means switches current to said field winding when alternator voltage falls below a predetermined value and prevents flow of current to said field winding when said egulated voltage exceeds a further predetermined value. ii3. The electronic voltage regulator circuit as claimed in claim 1 or 2, wherein a field winding turn off means is provided which prevents current being supplied to said field winding on opening of an ignition or main power switch.

4. The electronic voltage regulator circuit as claimed in any preceding claim, wherein said switch means includeo, a power transistor to supply current 'I n A 4 to said field winding. -16- 0 r

5. The electronic voltage regulator circuit of any preceding claim, wherein said warning light or device is transistor activated.

6. The electronic voltage regulator circuit of any preceding claim, wherein said switch means for supplying field current to said field on power up of said regulator circuit, includes an oscillator to reduce power dissipation through the field winding if the motor of the vehicle is not running but th1e ignition switch has been activated.

7. An electronic voltage regulator circuit substantially as hereinbefore described with reference to the accompanying drawings. DATED this 13th day of February, 1990. ROBERT BOSCH (AUSTRALIA) PTY. LTD. By its Patent Attorneys: CALLINAN LAWRIE -17- ;P~-NT O~ ,i