Power source unit for an automotive vehicle

Abstract: A power source unit for an automotive vehicle comprises an alternator, a rectification unit for converting an alternating current output of the alternator to a direct current, and outputting same through first and second output sections, a first power accumulation unit connected in parallel with a first load, for receiving a power supply through the first output section, a second power accumulation unit connected in parallel with a second load, for receiving a power supply through the second output section, an alternator output control unit for adjusting an output of the alternator depending upon a terminal voltage of the first power accumulating unit, to maintain the terminal voltage of the first power accumulating unit at a predetermined level, and a voltage control unit responsive to a drop in a terminal voltage of the second power accumulation unit to predetermined level, to permit a power supply to the second power accumulation unit through the rectification unit to thus maintain the terminal voltage of the second power accumulation unit at a predetermined level.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power source unit for an automotive vehicle, which is capable of parallel supply of mutually distinct supply voltages of power to a plurality of loads. More specifically, the invention relates to a power source unit for an automotive vehicle, which rectifies a power source voltage supplied from an alternator and drives a plurality of mutually distinct kinds of loads including a stator motor independently of each other. 2. Description of the Related Arts Japanese Unexamined Patent Publication (Kokai) 1-308133 (corresponding to EP-A-0 337 155) discloses a power source unit for an automotive vehicle which employs a plurality of power generators for a parallel supply of power source voltages for a plurality of mutually distinct vehicular loads. However, since spaces within engine rooms of automotive vehicles are strictly limited and the generators are generally driven by an output torque of engines via belts, orientations for installing the generators are quite limited, and therefore, only a few types of vehicles, which can provide sufficient space in the engine rooms, can employ a plurality of generators. In general, the conventional power source unit of the automotive vehicle generates a source voltage by means of a three-phase alternator, and rectifies the source voltage by means of a three-phase full-wave rectifier for charging a single battery. The battery voltage is used for driving a start-up load system, such as a starter motor, and other non start-up load systems in parallel. On the other hand, Japanese Unexamined Patent Publication (Kokai) 60-102825 (corresponding to US-A-4 491 779) discloses a two voltage outputs type power source unit for an automotive vehicle, in which two batteries are connected in series, connected to both ends of a three-phase full-wave rectifier. In addition, a junction between two batteries and a neutral point of the three-phase full-wave rectifier is connected via a three-phase silicon controller rectifier bridge. However, the electric load for an automotive vehicle is growing due to installation of a car telephone and so forth, and the above-mentioned type of power source unit, which has a pair of three-phase alternators and a single battery and will be hereafter referred to as "single battery type power source unit", may be subject to a problem of a drawing of a battery during an inoperative state of the engine, due to a large power consumption. Such a weak battery can affect the start-up characteristics of the engine. Of course, such a problem may be resolved by providing a vehicular power source unit which has a pair of three-phase alternators and a battery for a load which is associated with a vehicular engine driving system including a starter or starter motor and which will hereinafter be referred to as "engine drive associated load", and another vehicular power source unit which also has another pair of three-phase alternators and a battery for a load which is irrelevant to the engine driving, and thus will hereinafter be referred to as "non-engine drive associated load". However, such arrangement becomes too bulky. In addition, where one of the outputs of the two voltage outputs type vehicular power source unit is connected to the engine start-up system, all loads utilizing the same voltage level to the engine start-up system must be connected to the engine start-up system channel. Therefore, a load on the battery for an engine drive associated load cannot be effectively reduced. Furthermore, in order to charge batteries connected in series, the three-phase alternator to be employed in the vehicular power source unit must be designed for a high voltage. Moreover, document US-A-4 720 645 discloses a dual output three phase alternator having a stator and a field winding. First, second and third sets of diodes are present. Each set of diodes comprises three diodes each being connected to different alternator winding terminals; two of the sets have a common cathode, and one set has a common anode. Moreover, the two sets having the common cathode form first and second output sections for supplying rectified alternating current to two batteries, respectively. Document US-A-3 624 480 discloses a dual output three phase alternator having a stator and a field winding. First, second and third sets of rectifiers are present. Each set of rectifiers comprises three rectifiers each being connected to different alternator winding terminals; two of the sets have a common cathode, and one sets has a common anode. The first set having a common cathode comprises uncontrolled diodes and forms the first output section, the second set having a common cathode comprises silicon controlled rectifiers and forms the second output section. The first and second output sections supply two batteries which are connected in series. SUMMARY OF THE INVENTION With the above-mentioned problems in mind, an object of the present invention is to provide a power source unit for an automotive vehicle, which is capable of a parallel supply of mutually distinct supply voltages for a plurality of load and exhibits an easy installation ability and economical cost. The aforementioned and other objects are achieved by a power source unit for an automotive vehicle, according to Claim 1. Namely, the power source unit for the automotive vehicle, according to the present invention, has a plurality of rectifiers, and a plurality of kinds of loads connected to the respective rectifiers, for independently controlling a voltage to be supplied for respective loads. The means for controlling a supply voltage comprises the alternator output control means and the voltage control means, and, optionally, a boosting transformer means. Accordingly, a plurality of mutually distinct kinds of load can be driven independently and in parallel. BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be more fully understood from the detailed discussion given herebelow and from the accompanying drawings of the preferred embodiments of the present invention, which, however, should not be taken to limit the invention, but are for elucidation and understanding only. In the drawings: Fig. 1 is a circuit diagram of one embodiment of a power source unit for an automotive vehicle according to the present invention; Fig. 2 is a circuit diagram of one embodiment of a voltage control means; Fig. 3 is a circuit diagram of another embodiment of a voltage control means to be employed in the present invention; Fig. 4 is a circuit diagram of an electromagnetic coil driver circuit; Fig. 5 is a circuit diagram of another and practical embodiment of a power source unit for an automotive vehicle according to the invention; and Fig. 6 is a circuit diagram of a further embodiment of a power source unit for an automotive vehicle according to the invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a power source unit for an automotive vehicle, according to the present invention, will be discussed hereafter with reference to the accompanying drawings. Fig. 1 shows one practical embodiment of a vehicular power source unit, according to the invention, as a block diagram. The vehicular power source unit comprises an alternator 1 as a power generator, which is driven by an engine, a rectification means 30 which converts an alternating current output of the alternator 1 to a direct current output and outputs the direct current output through first and second output sections, a first power accumulation means 7 connected in parallel with a first load 8 receiving power supply through the first output section LH 1 , a second power accumulation means 9 connected in parallel with a second load 10 receiving power supply through the second output section LH 2 , an alternator output control means 6 which adjusts the output of the alternator 1 depending upon a terminal voltage of the first power accumulating means 7 to maintain the terminal voltage of the first power accumulating means 7 which receives power supply through the first output section LH 1 of the rectification means 30 at a predetermined level, and a voltage control means 11 responsive to a drop in a terminal voltage of the second power accumulation means 9 to a predetermined level to permit a power supply to the second power accumulation means 9 through the second output section LH 2 of the rectification means 30 to thus maintain the terminal voltage of the second power accumulation means 9 at a predetermined level. A practical embodiment of the rectification means 30 according to the invention will be discussed with reference to Fig. 1. The rectification means 30 preferably comprises a higher level diode half bridge 2 having anodes respectively connected to respective output terminals of the alternator 1 independently of each other and supplying a first power source voltage to the first load 8 and the first power accumulation means 7, a switching half bridge 4 having anodes respectively connected to respective output terminals of the alternator 1 independently of each other and supplying a second power source voltage to the second load 10 and the second power accumulation means 9, and a lower level diode half bridge 3 having cathodes respectively connected to respective of the output terminals of the alternator 1 independently of the other and anodes commonly connected to the lower level side of the first and second loads 8 and 10. In the shown embodiment, the lower level diode half bridge 3 forms a two voltage output type rectifier together with the higher level diode half bridge 2 and the switching half bridge 4. The first power source voltage and the second power source voltage can be at the same level or at different levels. As the first and second power accumulation means 7 and 9, batteries or capacitors can be employed. The alternator output control means 6 detects the first power source voltage for controlling power generation in the alternator 1 based thereon. The voltage control means 11 detects the second power source voltage of the rectifier and controls the conduction of the switching half bridge 4. Accordingly, the first power source voltage can be maintained at a rated voltage by controlling the power generation of the alternator 1. Also, the second power source voltage is maintained at a rated voltage by controlling the conduction of the switching half bridge 4. As discussed above, the practical embodiment of the vehicular power source unit is provided with the alternator output control means 6 for controlling the power generation of the alternator 1 by detecting the first power source voltage, and the voltage control means 11 for controlling the switching half bridge 4 between conductive state and non-conductive state by detecting the second power source voltage. The shown embodiment of the power source unit successfully and advantageously establishes a parallel and mutually independent drive of two different kinds of loads with a single alternator 1, and has a simply constructed circuit. In addition, in the shown embodiment, the first load 8 which receives the first power source voltage from the higher level diode half bridge 2, is a non-engine drive associated load, such as a fan motor, a head lamp and so forth, regardless of engine driving. In the practical embodiment, the first power accumulation means 7 comprises the battery which is employed for driving a non-engine drive associated load. Preferably, the rated voltages of the first and second loads 8 and 10 are set at 12 V. On the other hand, the second load 10, which receives power supply from the switching half bridge 4, is an engine drive associated load, such as the starter motor, spark ignition system and so forth. The second power accumulation means 9 comprises a battery for driving the engine drive associated load. Furthermore, the switching half bridge 4 in the shown embodiment preferably comprises a silicon controlled rectifier half bridge. As discussed above, the invention employs the construction comprising the battery 9 for the engine drive associated load 10, wherein the battery 9 is connected in parallel with the engine drive associated load 10 to receive a power supply from the silicon controlled rectifier half bridge 4, and the battery 7 for the non-engine drive associated load 8 connected in parallel with the non-engine drive associated load 8 to receive a power supply from the higher level diode half bridge 4. Further preferably, the shown embodiment of the power source unit employs the alternator output control means 6 which performs feedback control of the field current of the alternator 1, which is e.g. a three-phase alternator, depending upon variation of the electric potential at the terminal of the battery 7 for the non start-up load, and a voltage control means 11 which serves as rectifier switching means for suppressing fluctuation of an electric potential at the terminal of the battery 9 for a start-up load by opening and closing the silicon controlled rectifier half bridge 4 depending upon a potential variation at the terminal of the battery 9 for the engine drive associated load 10. In the construction of Fig. 1, each output end of stator coils la of the three-phase alternator 1, which is driven by the automotive engine, is connected to respective anodes of the higher level diode half bridge 2 and the switching half bridge 4, and to a cathode of the lower level diode half bridge 3, forming the rectification means 30. The higher level diode half bridge 2 and the lower level diode half bridge 3 comprise a silicon diode. On the other hand, the switching half bridge 4 comprises a thyristor (SCR). In practice, the common cathode of the higher level diode half bridge 2 is connected to the power supply line LH 1 . The common cathode of the switching half bridge 4 is connected to the power supply line LH 2 . The common anode of the lower level diode half bridge 3 is connected to a grounding line LL. Between the power supply line LH 1 and the grounding line LL, load, regardless of starting up of the engine, such as a head lamp and thus referred to as a non-engine drive associated load 8, and the battery 7 are connected in parallel to each other. Between the power supply line LH 2 and the grounding line LL, the load related to a starting up of the engine, such as a starter motor, ignition system and so forth and thus referred to as the engine drive associated load 10, and the battery 9 are connected in parallel to each other. Furthermore, between the power supply line LH 2 and the grounding line LL, an electromagnetic coil 5 of the three-phase alternator 1 and the alternator output control means 6 are connected in series. To both ends of the electromagnetic coil 5, a protection diode (flywheel diode) 12 is connected in parallel. The construction and operation of the alternator output control means 6 is widely known and thus a detailed discussion thereof is omitted. In the basic construction, the alternator output control means 6 may comprise a comparator 6b which compares the potential at the terminal of the battery 7 with a constant reference potential to output a high voltage when the terminal potential is lower than the reference potential, an emitter grounding type transistor 6a which is switched between conductive state and non-conductive state by the comparator 6b to establish and block supply of exciting current for the electromagnetic coil 5. The alternator output control means 6 performs feedback control of the exciting current for the electromagnetic coil 5 with taking the terminal potential of the battery 7 as control parameter, and thus maintains the terminal potential of the battery 7 constant. Respective cathodes of the switching half bridge 4 are positive terminals of the battery 9 via the second power supply line LH 2 . The negative terminal of the battery 9 is grounded. The second load 10 is connected in parallel with the battery 9. The voltage control circuit 11 receives power supply from the battery 9, and has output terminal supplying gate voltage for each SCR of the switching half bridge 4. The voltage control circuit 11 employed in the present invention will be discussed in detail with reference to Fig. 2. The voltage control circuit 11 has a comparator 20 which compares the terminal voltage V 9 of the battery 9 with a constant reference voltage V ref to output a predetermined HIGH level output voltage Vc when the terminal voltage V 9 is lower than the reference voltage V ref , and to output a predetermined LOW level output voltage Vc when the terminal voltage V 9 is higher than or equal to the reference voltage V ref , a boosting circuit 21 which boosts the output voltage Vc of the comparator 20 to produce a gate trigger voltage Vg (Vg 1 to Vg 3 ) to be applied to the gate of the SCR half bridge 4. The boosting circuit 21 may comprise a DC-DC converter which outputs the gate trigger voltage Vg, which has a voltage level higher than the HIGH level output voltage Vc of the comparator 20, in a predetermined magnitude. For electrical separation and limiting electric current between gates of the SCR half bridge 4, series circuits of the resistors 22 to 24 and diodes 25 to 27 are provided between each gate and the boosting circuit 21. Accordingly, the voltage control circuit 11 sets the gate trigger voltage Vg at HIGH level when the terminal voltage V 9 of the battery 9 is lower than the reference voltage V ref to turn OFF each SCR, and sets the gate trigger voltage Vg at LOW level when the terminal voltage V 9 is higher than or equal to the reference voltage V ref to turn ON each SCR. Therefore, the voltage control circuit 11 performs a feedback control taking the terminal potential V 9 as control parameter to maintain the terminal potential at a constant level. Each of the reference voltages are supplied from a voltage regulator circuit (rated output 12 V). Fig. 3 shows another embodiment of the voltage control means 11 to be employed in the present invention. In the drawing, the reference numeral 30 denotes a known DC-DC converter which boosts the second power source voltage of the second power supply line LH 2 to output from the output terminal 30a. The reference numeral 31 and 32 denote transistors, 33 denotes a comparator, 34, 35 and 36 denote diodes, 37 denotes a constant voltage diode, and 38, 39, 40, 41, 42, 43, 44, 45 and 46 denote resistors. A divided voltage of the output voltage V 9 of the battery 9, which is divided by the resistors 45 and 46, and the reference voltage output from the junction between the resistor 44 and the constant voltage diode 37 are compared by the comparator 33. When the voltage V 9 of the battery 9 is lower than the predetermined level, the output of the comparator 33 becomes "1" (HIGH level) to turn on the emitter grounding NPN type transistor 32 via the resistor 43. To the collector of the NPN type transistor 32, the direct current V dc boosted by the DC-DC converter 30 via the resistors 42 and 41 flows. A junction 31a is connected to the base of a PNP transistor 31. The emitter of the PNP transistor 31 is connected to the output terminal of the DC-DC converter 30. Accordingly, in response to turning ON the transistor 32, the potential at the junction 31a is lowered. Then, the transistor 31 turns ON. By this, the gate trigger voltage Vg 1 supplied from the collector of the PNP transistor 31 via the diode 34 and the resistor 38 to one of SCR of the switching half bridge 4, becomes HIGH level. Similarly, the gate trigger voltages Vg 2 and Vg 3 are supplied to the remaining two SCR of the switching half bridge 4, respectively, via the diode 35 and the resistor 39 and via the diode 36 and the resistor 40. Then, the switching half bridge 4 becomes conductive so that the highest voltage level of the phase voltage of the alternator 1 is supplied to the second power supply line LH 2 when a highest phase voltage of the alternator 1 is higher than the second power source voltage. Contrary to this, when the voltage of the battery 9 becomes higher than the predetermined value, the output of the comparator 33 becomes "0" (LOW level). Then, in the reversed process, the transistors 32 and 31 turn OFF. Since the SCR of the switching half bridge 4 are connected to the alternating current output terminal of the alternator 1, the gate trigger voltages Vg 1 , Vg 2 and Vg 3 become LOW level. Then, the reverse voltage arises between the anode and cathode to turn the SCR OFF. Then, the SCR is maintained OFF until the next occurrence of a HIGH level gate trigger voltage Vg 1 , Vg 2 or Vg 3 . The operation of the above-mentioned vehicular power source unit will be discussed herebelow. When the engine (not shown) starts running, the three-phase alternator 1 starts generation to output a three-phase alternating current voltage. The higher level diode half bridge 2 applies a three-phase rectified voltage to the non-engine drive associated load 8 and the battery 7 via the first power supply line LH 1 . The alternator output control circuit 6 turns OFF the transistor 6a by the comparator 6b when the detected voltage of the battery 7 is higher than the reference voltage, and turns ON the transistor 6a when the voltage of the battery 7 is lower than the reference voltage. By this, the current flowing through the electromagnetic coil 5 is intermittently controlled to adjust the output voltage of the alternator 1 to the constant value. In the normal case, the aforementioned reference voltage is set so that the first power source voltage of the first power supply line LH 1 is maintained at +12 V. In the aforementioned operation, even when the terminal potential of the battery 7 fluctuates due to intermittently turning ON and OFF of the non-engine drive associated load 8, the discharge of the battery 7 and so forth, the alternator output control circuit 6 feedback controls the terminal potential of the battery 7 at a constant level. On the other hand, the voltage control circuit 11 detects the voltage of the battery 9 and controls the switching half bridge 4 to be ON and OFF to maintain the voltage of the battery 9 at a predetermined level. In the normal operation, the switching half bridge 4 is controlled so that the second power source voltage of the second power supply line LH 2 can be maintained at +12 V. Therefore, even when the voltage of the battery 9 is fluctuated by intermitting of the engine drive associated load 10 or the discharge of the battery 9, the voltage control circuit 11 feedback controls the terminal potential of the battery 9 at the constant level. In the shown embodiment, the alternator 1 may be constructed to have a stator winding 1a and a field winding 5, and to convert the alternating current output generated at the stator winding 1a into a direct current output. In the alternative, the alternator 1 may have a switching means which controls the power supply for the field winding of the alternator to control the switching means in response to a fluctuation of the terminal voltage of the first power accumulation means and thereby to adjust the output voltage of the alternator 1 for maintaining the terminal voltage of the first power accumulation means 7 to which the power from the first output section LH 1 of the rectification means 30 is supplied. On the other hand, in the present invention, by controlling a conduction ratio of the alternator output control means 6 and the voltage control means 11, a level difference of the terminal voltages of the first and second power accumulation means 7 and 9 can be freely set. In such a case, it is desirable to connect the power accumulation means having the higher terminal voltage to the start-up system. Although the foregoing discussion is given for an example in which the load connected in parallel to the first power accumulation means 7 is a non-engine drive associated load and the load connected in parallel to the second power accumulation means 9 is the engine drive associated load, the present invention should not be limited to the shown arrangement and can be reversed. Furthermore, in the shown embodiment, the first and second loads 8 and 10 are respectively the engine drive associated load and the non-engine drive associated load, but the alternator output control means 6 can control the terminal voltage of the first power accumulation means 7 to the first predetermined voltage level, and the voltage control means 11 can control the terminal voltage of the second power accumulation means 9 to the second predetermined voltage level which is lower than the first predetermined voltage level. Next, a second embodiment of the vehicular power source unit according to the present invention will be discussed with reference to Fig. 5. In the second embodiment, the construction of the vehicular power source unit has substantially the same basic construction as the first embodiment of Fig. 1. This embodiment is differentiated from the former embodiment by the presence of a third power supply line LH 3 for outputting a third power source voltage, in addition to the first and second power supply lines LH 1 and LH 2 . For adapting to this, another rectification means 71 which is different from the rectification means 30, and a boosting transformer 74 are provided. Namely, in the shown embodiment, the three-phase alternating current voltage output from the alternator 1 is fed to the boosting transformer 74. The boosting transformer 74 boosts the alternating current voltage and is rectified by the three-phase full-wave rectifier 71. A high voltage rectified by the three-phase full-wave rectifier 71 is fed to the third load 72 via the third power supply line LH 3 . The third load 72 in the shown embodiment can be a defrosting heater or other high voltage loads. In order to reduce resistance loss, a boosting and three-phase full-wave rectification are performed. In the shown embodiment, to utilize the third load 72, a relay which incorporates a relay driver circuit 73c is provided. The relay is driven to make the contacts 73a and 73b conductive. As a result, the three-phase alternating current voltage, which is boosted by the boosting transformer 74, is subject to a full-wave rectification by the full-wave rectifier 71 and then supplied to the third load 72 as the third power source voltage (+100 V). Fig. 4 shows one example of the relay circuit 73c to be employed in the shown embodiment of the power source unit according to the invention. The reference numeral 50 denotes a known flip-flop circuit, 51 denotes a timer circuit, 52 denotes an electromagnetic coil, 53 and 54 denote transistors, 55 denotes a flywheel diode, 56 denotes a diode, 57 is a constant voltage diode, 58, 59, 60, 61 and 62 denote resistors, 70 denotes an operation switch, 80 denotes a comparator. The operation switch 70 comprises a push-ON switch which is maintained ON while depressed. To operate the operation switch 70 for operating the third load 22, the battery voltage V 9 is applied to the input terminal of the flip-flop 50, and the level at the output terminal 50a becomes "1". Then, the emitter grounding transistor 53 is turned ON via the resistor 58. Here, the flip-flop 50 is a type which reverses the position at the transition at which the input voltage switches from "0" to "1". The battery voltage V 9 is applied to the collector of the transistor 53 via the electromagnetic coil of the relay 52. Then, the transistor 53 is turned ON. The relay 52 is then turned ON to close the contacts 73a and 73b to drive the third load 22. To turn OFF the third load 22, the operation switch 70 is again turned ON. Also, it is possible to turn the third load 22 OFF by feeding back the output voltage Vf of the flip-flop 50 to the input terminal thereof via the timer 51 and the diode 56. By this, the output voltage Vf of the flip-flop 50 varies from "0" to "1". After a predetermined delay time, feedback voltage at the input terminal of the flip-flop 50 varies to "1" (HIGH level). At this time, when the voltage Ve at input terminal of the flip-flop 50 is "0", the output voltage Vf of the flip-flop 50 turns into "0" to open the contacts 73a and 73b of the relay. Accordingly, this timer 51 can serve as a protection device which limits power supply period for the third load 72. Further, when the voltage V 9 of the battery 9 becomes lower than or equal to the predetermined voltage, the following circuit operation is performed to turn OFF the contacts 73a and 73b of the relay to give a higher priority to charging the battery 9. Namely, a divided voltage of the voltage V 9 of the battery 9, which is divided by resistors 60 and 61, and a reference voltage output from a junction between the resistor 59 and the constant voltage diode 57 are compared by the comparator 80. When the voltage V 9 of the battery 9 is lower than the predetermined value, the output of the comparator 33 becomes "1" (HIGH level) to turn the transistor 54 ON. By the transistor 54, the output terminal of the flip-flop 50 turns into LOW level irrespective of the state of input of the flip-flop 50. In response to this, the transistor 53 turns OFF to shunt the power supply for the electromagnetic coil 52 of the relay. The resistor 62 is employed for discharging the input terminal of the flip-flop 50 to low level when the operation switch 70 is OFF, or when the output voltage of the timer 51 becomes LOW level. Accordingly, since the voltage of the battery 9 is detected as a condition to turn OFF the third load 72, when an abnormal drop of the voltage of the battery 9 for driving the engine is detected, the generated power of the alternator 1 can be supplied to the second load 10 with a higher priority. It should be appreciated that, although the shown embodiment applies the three-phase rectified voltage to the third load 72, it is possible to apply the three phase alternating current voltage or a single phase alternating current. Though the foregoing embodiment employs the first load 8 and the second load 10 operable at equal voltage (+12 V), the first power source voltage can be set at higher voltage than the second power source voltage by duty controlling the switching half bridge 4. In this case, contrary to the above, the starter motor which operates well at a high voltage, may be employed as the first load 8, and electronic circuit products, which operate well at a low voltage, may be employed as the second load 10. Next, a third embodiment of the vehicular power source unit, according to the present invention, will be discussed with reference to Fig. 6. The shown embodiment is formed by modifying the foregoing first embodiment. For this, a reactor 90 is disposed between the output terminal of the switching bridge 4 and the second power supply line LH 2 . Furthermore, the output terminal of the switching half bridge 4 is connected to cathode of a diode 100. The anode of the diode 100 is grounded. In the shown embodiment, with the shown construction, the voltage control circuit 11 is designed so that a periodic pulse signal having a predetermined period is input to respective SCRs of the switching half bridge 4 for cyclically or periodically turning the latter ON and OFF. By periodically turning the SCR half bridge circuit 4 ON and OFF, the switching half bridge 4 outputs a pulse voltage proportional to the gate trigger voltages Vg 1 , Vg 2 and Vg 3 . The pulse voltages are then smoothed by the reactor 90 and the diode 100. Therefore, a voltage proportional to the duty cycle of the pulse can be applied to the battery 9. The following is a summary of the advantages achieved by the present invention. (a) With a single alternator, three kinds of load can be driven in parallel and independently of each other. Therefore, the vehicular electric load can be separated into a driving system (for example electric load associated with the engine, and a non-driving system for independent connections for respective power sources). With such a construction, since the electric load of the driving system is not used while the vehicle is maintained in the standstill condition, the battery cannot be exhausted except for a self-discharge. Therefore, this solves the problem of a difficulty of starting up the engine due to a weak battery. (b) As discussed with respect to the second embodiment, since a high voltage and a low voltage can be easily generated from the output voltage of the alternator, load with a different rated voltage can be connected to the first power supply system (first power supply line LH 1 ) and the second power supply system (second power supply line LH 2 ). (c) Since the power generation at the alternator 1 is controlled based on the voltage of the battery 7 which supplies power to the first load 8 which does not drive the engine. Therefore, even when the starter motor is in actuation to cause large voltage fluctuation in the battery 9, a supply voltage for the first load 8 does not fluctuate and can be maintained stable. Therefore, such a stable power supply via the first power supply line LH 1 can be used for the electric equipment, such as an audio set and so forth, which requires a stable power supply. (d) Upon starting up the engine, the battery 9 can be discharged down to the allowable minimum voltage which does not cause difficulties in the driving of the engine. (e) The third load 72 can be additionally connected in parallel to the first and second loads 8 and 10, independently of the other. Furthermore, when the voltage of the battery 9 becomes lower than a predetermined value, a power supply for the third load 72 is inhibited. The driving of the third load 72 will not cause difficulties when driving the engine.

Claims: A power source unit for an automotive vehicle, comprising an alternator (1) having a field winding (5) and being driven by an engine, a rectification means (30) for converting an alternating current output of the alternator (1) to a direct current output and outputting the direct current output through first and second output sections, said rectification means (30) including a lower level diode half-bridge having a common anode (3) and first (2) and second (4) higher level diode half-bridges each having a common cathode forming said first and second output sections, first power accumulation means (7) connected in parallel with a first load (8) and arranged for receiving a power supply through the first output section, and a second power accumulation means (9) connected in parallel with a second load (10) and arranged for receiving a power supply through the second output section, said second higher level diode half-bridge (4) being a silicon controlled rectifier half-bridge, an alternator output control means (6) being provided for adjusting an output of the alternator (1) depending upon a terminal voltage of the first power accumulating means (7) to maintain the terminal voltage of the first power accumulating means (7), which receives power supply through said first output section, at a first predetermined voltage level, said first and second power accumulation means (7, 9) being parallely charged respectively through said rectification means (30) and a voltage control means (11) being provided for opening and closing said silicon controlled rectifier half-bridge (4) in response to a drop in a terminal voltage of the second power accumulation means (9) to a second predetermined voltage level, to permit a power supply to the second power accumulation means (9) through the second output section and to maintain the terminal voltage of the second power accumulation means (9) at a third predetermined voltage level. A power source unit as set forth in claim 1, characterized in that said first load (8) is irrelevant to a starting of the engine, and said second load (10) is a load related to a starting of the engine. A power source unit according to one of claims 1 or 2, characterized by further comprising a stator winding (1a) being arranged within said alternator (1) for generating said alternating current output, a first, controllable switching means (6a) being arranged within said alternator output control means (6) for controlling a power supply for said field winding (5) to thereby adjust the output of said alternator (1), and a second switching means (20; 31, 32, 33) being arranged within said voltage control means (11), being responsive to said drop in said terminal voltage of said second power accumulating means (9) and being employed for permitting said power supply to said second power accumulation means (9). A power source unit as set forth in one of claims 1 to 3, characterized in that said first predetermined voltage level equals said third predetermined voltage level. A power source unit as set forth in one of claims 1 to 3, characterized in that said first predetermined voltage level is greater than said third predetermined voltage level. A power source unit as set forth in claim 3, characterized in that a conduction ratio of said first (6a) and second (20; 31, 32, 33) switching means is controlled for adjusting a level difference of terminal voltages at said first (7) and second (9) power accumulating means. A power source unit as set forth in claim 6, characterized in that one of said first (7) and second (9) power accumulating means having a higher terminal voltage is connected to a load associated with a system for starting the engine. A power source unit as set forth in claim 7, characterized in that said first (8) and second (10) loads are respectively a load associated with a system for starting the engine and a load irrelevant to a starting of the engine, said alternator output control means (6) controlling the terminal voltage of said second power accumulation means (9) to said third predetermined voltage level. A power source unit as set forth in claim 8, characterized in that said third predetermined voltage level is lower than said first predetermined voltage level. A power source unit as set forth in claim 1, characterized by a boosting transformer (74) connected to said alternator (1), a rectifier means (71) being adapted to rectify the alternating current voltage based on the output of said boosting transformer (74), said rectifier means (71) having a third output section connected to a third load (72). A power source unit as set forth in claim 10, characterized in that said second power accumulation means (9) includes a relay driver circuit (73c) for driving said third output section. A power source unit as set forth in claim 1, characterized by further comprising a reactor means (90) disposed between the output section of said alternator output control means (6) and said second power accumulation means (9), and a diode (100) disposed between said output section of said alternator output control means (6) and the ground. A power source unit as set forth in claim 3, characterized in that said field winding (5) is actuated by electric power supplied from said second power accumulation means (9) related to starting of the engine. A power source unit as set forth in claim 13, characterized in that said field winding (5) is connected in parallel with said second power accumulation means (9) through said first switching means (6a) serially connected to said stator winding (1a).

Inventors: ITO YOSHIHIRO, TORII KOSHI, ITO, YOSHIHIRO, TORII, KOSHI
Applicants: DENSO CORP, DENSO CORPORATION
Application year: 1991
Main classification: H02J7
IPC codes: H02J7