WO2013035108A1

WO2013035108A1 - System and method for controlling power generation for electrical loads in a vehicle

Info

Publication number: WO2013035108A1
Application number: PCT/IN2012/000587
Authority: WO
Inventors: Raju Pandurangan; Umashankar Raman
Original assignee: India Nippon Electricals Limited
Priority date: 2011-09-05
Filing date: 2012-09-05
Publication date: 2013-03-14

Abstract

The present subject matter described herein relates to methods (400) and systems (200, 218, 300) for controlling electrical power supply for a plurality of electrical loads in a vehicle. According to one embodiment, the power supply system includes an AC generator (102) that generates an AC voltage having a positive half and a negative half. An ignition control system (112) includes a DC voltage regulator (114) having a first switching device (116) that converts the AC voltage received from the AC generator (102) to a DC voltage and an ignition control unit (122) that enables generation of an actuation signal when the speed of the engine is higher than a predetermined level. A load voltage regulator (202) having a second switching device (106) and a third switching device (206) for supplying positive and negative halves of the AC voltage to the plurality of electrical loads is provided.

Description

SYSTEM AND METHOD FOR CONTROLLING POWER GENERATION FOR ELECTRICAL

LOADS IN A VEHICLE

TECHNICAL FIELD

[0001] The subject matter described herein, in general, relates to systems and methods for controlling electrical power generated for electrical loads, and, in particular, relates to systems and methods for controlling power supply in vehicles with spark ignited internal combustion engine.

BACKGROUND

[0002] Generally, in vehicles, and more specifically, in two-wheeled vehicles, electrical power is supplied to various devices by a generator coupled to an engine, through the crankshaft. In such cases, a permanent magnet generator, acting as an AC generator, is used for providing electrical power required for ignition, and to power other electrical loads of vehicle such as headlamp, brake-lamp, turn-signal indicators and horn. Of these electrical loads, the headlamp is a constant load since it is operated continuously at a stretch whereas the brake-lamp, turn-signal indicators and horns are intermittent loads since they are used for a short period of time. [0003] In operation, the electrical power output of the generator is a function of the engine speed, the strength of the magnetic field, number of poles and size of the armature. The powering of engine functions, such as ignition, and powering of the electrical loads of the two-wheeled engine is done separately. This is done to ensure that during starting, the starting of the engine is not affected, as the generator initially will not support all loads.

[0004] Other electrical loads are normally required during the operation of the vehicle, especially when the vehicle is in motion. Hence, these loads are not as critical during starting when compared to the ignition, which is essential for vehicle start-up.

[0005] An ignition control unit is provided in order to control the occurrence of spark. It normally consists of an electronic control circuit that stores and transforms the electrical energy derived from the AC generator into a high voltage pulse capable of generating a spark in the sparkplug of the internal combustion engine that causes the ignition. SUMMARY

[0006] The present subject matter described herein relates to methods and systems for controlling electrical power supply for a plurality of electrical loads in a vehicle. According to one embodiment, the power supply system includes an AC generator that generates an AC voltage. The AC voltage thus generated, includes a positive half and a negative half. The system also includes an ignition control system, which further includes a DC voltage regulator having a first switching device that converts the AC voltage received from the AC generator to a DC voltage and an ignition control unit to control the ignition of the engine. The ignition control unit further enables generation of an actuation signal based on the speed of the engine. A load voltage regulator for supplying electrical power to the plurality of electrical loads is provided. The load voltage regulator has a second switching device, which is configured to conduct the negative half of the AC voltage and a third switching device configured to conduct the positive half of the AC voltage. The third switching device of the load voltage regulator conducts the positive half of the AC voltage after receiving the actuation signal from the ignition control unit.

[0007] These and other features of the present subject matter will be better understood with reference to the following description. This summary is provided to introduce a selection of concepts in a simplified form, as per one embodiment of the present subject matter. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

BRIEF DESCRIPTION OF DRAWINGS

[0008] The detailed description is provided with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to reference like features and components. For simplicity and clarity of illustration, elements in the figures are not necessarily to scale. [0009] Fig. 1 illustrates a schematic diagram of a conventional power supply control system. [0010] Fig. 2 illustrates a schematic diagram of a power supply control system in accordance to one embodiment of the present subject matter.

[001 1 ] Fig. 2 A illustrates an exemplary schematic diagram of a power supply control system in accordance with an embodiment of the present subject matter. [0012] Fig. 3 illustrates a schematic diagram of a power supply control system in accordance to another embodiment of the present subject matter.

[0013] Fig. 4 illustrates a schematic flow diagram of a method for controlling power supply to various loads of a two-wheeled vehicle in accordance to an embodiment of the present subject matter. [0014] Fig. 5 illustrates an electrical load voltage characteristic curve in accordance with an embodiment of the present subject matter.

DETAILED DESCRIPTION

[0015] The present subject matter describes systems and methods for controlling power supply in a two-wheeled vehicle operated by a spark-ignited internal combustion engine. It would be noted that the present description is provided with reference to two-wheeled vehicles. However, as would be appreciated by a person skilled in the art, other wheeled vehicles would also be included within the scope of the present subject matter. [0016] Conventional power supply systems employed in two-wheeled vehicles are capable of generating AC voltage through an alternator or an AC generator. The AC voltage generated includes a positive half and a negative half. Typically, the positive half of the AC voltage generated by the AC generator is utilized by an ignition control system of the vehicle for engine ignition. Any other demands in the form of other loads, such as powering of electrical components are addressed through the negative half of the generated AC voltage. Further, conventional systems also enabled power supply to the engine ignition system, independent of the other load requirements of the vehicle. One such conventional system is illustrated in Fig. ί . [0017] Fig. 1 illustrates a schematic diagram of a conventional power supply control system. A conventional electrical system 100 consists of various vehicle loads 104 such as the headlamps, brake lamp, turn indicators and horn. The loads 104 are powered by negative half of the AC voltage generated from an AC generator 102. The positive half of the AC voltage powers an ignition control system 1 12 for the purpose of producing a spark for the operation of internal combustion engine of the vehicle. The ignition control system 1 12 has a DC voltage regulator 1 14 that converts the AC voltage received from the generator 102 to a regulated DC voltage with the help of a first switching device 1 16. The DC voltage regulator 1 14 further includes a DC voltage controller 118 and a capacitor 120. The regulated DC voltage is then utilized for spark ignition of the internal combustion engine with the help of an ignition control unit 122, ignition coil 124 and a spark plug 126.

[0018] The negative half of the AC voltage is applied to the vehicle loads 104 through a load voltage regulator 1 10 of the electrical system 100. The load voltage regulator 110 has a second switching device 106 that power the loads 104 by conducting during the negative half of the AC generator output.

[0G 9] Furthermore, in the aforementioned configuration, the load requirements addressed through the positive half of the AC voltage are not the same as the load requirements addressed by the negative half of the AC voltage even though each of the halves are capable of addressing equal load requirements individually. For example, the load requirement in a typical two wheeled vehicle for ignition is about 10 watts whereas for that of other loads 104 are in the range of 80 to 100 watts. Hence it is obvious that the load distribution amongst positive and negative halves do not facilitate the use of generated power efficiently. Thus it is desirable to provide a power supply control system that can efficiently utilize the positive half of the generated AC voltage and that provides an AC generator of less capacity, less weight and occupies less space.

[0020] In another conventional system, an ignition control unit, say for example an ignition control unit 122 as illustrated in Fig.l, along with various vehicle loads such as headlamp, brake-lamp, turn indicators and horn are provided along with a battery (not shown in the figure) and an electrical generator, say for example an AC generator 102 as illustrated in Fig.l . The ignition control unit 122 in this case is powered by the battery, while the other vehicle loads 104 are operated from the power generated by the electrical generator 102. This system also includes a DC voltage regulator, say for example a DC voltage regulator 1 14 as illustrated in Fig.l, for charging the battery. The problem with this power supply configuration is that the ignition control unit 122 cannot be operated in the absence of the battery. Further, in the absence of the battery, at the time of engine start-up, when the speed of the engine is low, the DC voltage provided by the DC voltage regulator 114 is not sufficient to operate the ignition control unit 122 and hence ease of engine start-up is affected.

[0021] In yet another known conventional system, the vehicle power supply system uses an AC generator 102 with two separate windings, one winding to provide power exclusively to the ignition control unit 122 even when operated without a battery (not shown in the figure) and the other winding to power various other loads 104 of the vehicle 104. An ignition control system, say for example an ignition control system 112 as illustrated in Fig.l, is provided with a dedicated DC voltage regulator 114 and a capacitor 120. The capacitor 120 stores electrical energy derived from an exclusive winding of the AC generator 102 for the operation of the ignition control unit 122. Since the AC generator 102 of this power supply system uses two separate windings for the operation of ignition control unit 122 and other vehicle loads 104, the size of the AC generator 102 will be larger compared to the other known AC generators 102. Hence there is a requirement to effectively and efficiently use the AC generator output and also provide adequate power to ignition control unit 122 during start-up.

[0022] However, in the conventional systems, the power consumed by the ignition control system 112 operated from the positive half of the AC voltage is relatively low as compared to the other vehicle loads 104 such as a headlamp and other intermittent loads. Further, in the conventional systems, the positive half of the AC voltage available is not efficiently utilized.

[0023] On the other hand, such systems fully utilize the negative half of the

AC voltage to operate various vehicle loads 104 such as headlamps and other intermittent loads. In such cases, the negative half of the AC voltage caters to the entire load requirement of the vehicle other than ignition, after the start of the vehicle. More often than not, the electrical power capacity of the AC generator 102 used in the conventional systems is much higher than the actual electrical power requirement of the vehicle. In order for the load requirements to be adequately addressed, the capacity of the AC generator 102 for a specific electric load of the vehicle may be high. Therefore, a higher capacity AC generator 102 is unnecessarily utilized, which consequently results in the overall increase in size and weight of the AC generator 102, thereby increasing the cost.

[0024] System and methods for controlling the power generation in vehicles are described. In an embodiment, the power supply control system of the present subject matter is provided for a two-wheeled vehicle such as a moped that functions without a battery. In one embodiment, the power supply control system of the present subject matter facilitates optimal utilization of AC generator voltage, without affecting the functioning of ignition control system 112 and engine start-up.

[0025] In an embodiment, the positive half of the AC voltage is converted into

DC voltage and utilized for generating an ignition spark to start the internal combustion engine. Once the engine is started, the speed attained by the engine and the corresponding voltage generated by the AC generator are monitored. When the engine speed increases beyond a preset reference speed at which point the electrical power due to the generated AC voltage is sufficient to cater to the power requirement of the ignition control system, an actuation signal is generated. The actuation signal enables the power switches in the load voltage regulator to conduct the positive half of the AC voltage in addition to the negative half, for supplying power to other electrical loads such as a headlamp of the vehicle.

[0026] The present subject matter provides a system that effectively utilizes both the positive and the negative halves of the AC voltage when the engine speed increases beyond a preset speed, thereby enabling efficient utilization of the generated power.

[0027] Thus, the power supply control system of the present subject matter advantageously provides a method of optimal utilization of an AC generator with reduced electrical power capacity specific for the electric load requirement of the vehicle. The power supply control system of the present subject matter also enables reduction in size and weight of the AC generator as the power in the positive half of the AC voltage available for engine ignition is also effectively and efficiently utilized for various other electrical loads. In an embodiment, the power supply control system of the present subject matter is provided for a two-wheeled vehicle such as a moped that functions without a battery. In one embodiment, the power supply control system of the present subject matter facilitates optimal utilization of AC voltage, without affecting the start-up of the spark ignited internal combustion engine of the vehicle.

[0028] Fig. 2 illustrates a schematic diagram of a power supply control system

200 in accordance to an embodiment of the present subject matter. The control system 200 has a load voltage regulator 202, and an ignition control system 1 12 coupled across an AC generator 102. Plurality of vehicle loads 104 are connected in series with a plurality of power switching devices 106 and 206 of the load voltage regulator 202. In one embodiment, the pair of power switching devices 106 and 206 is in a parallel-connected configuration. The load voltage regulator 202 further includes a load voltage controller 208 that controls the operation of the switching devices 106 and 206. The switching devices 106 and 206 can be a combination of thyristors, MOSFETs or IGBTs. In one embodiment of the present subject matter, the switching devices 106 and 206 are thyristors. In one implementation, the thyristor is a silicon controlled rectifier (SCR). It will be understood by persons skilled in the art that other type of switching elements can also be used in place of a thyristor. Further, it will be comprehended that the pair of switching devices can be replaced by a single switching device which is functionally equivalent to the paired devices.

[0029] The parallel-connected switching devices 106 and 206 are configured in such a way that each switching device in the pair will conduct only one half of the AC voltage.

[0030] During the start of the engine, the AC generator voltage available to an ignition control unit 122 of the ignition control system 1 12 is critical for generating an ignition spark of sufficient energy for starting the engine. Hence, until the engine rotation reaches a preset reference speed, the other electrical loads 104 are solely powered by the negative half of the AC voltage by the operation of second switching device 106. [0031] When the engine speed increases beyond the preset speed, the AC voltage output of the generator stabilizes and consequently the ignition control unit 122 provides an actuation signal through a signal line 216 to the load voltage controller 208. The actuation signal is provided for the purpose of enabling the third switching device 206 to conduct the positive half of the AC voltage for powering the other electrical loads 104 of the vehicle.

[0032] The actuating signal generated by the ignition control unit 122 to switch ON or activate the third switching device 206 facilitates the optimum utilization of electrical power available during the positive half of the AC voltage for the purpose of lighting the lamp loads and other intermittent loads. Hence, the power supply control system 200 of the present subject matter is operable for an AC generator of specific power capacity and can efficiently provide electrical power to the lamp loads and other intermittent loads, which are considerably higher as compared to conventional power supply configuration 100.

[0033] In one embodiment, the AC generator 102 is a permanent magnet electrical machine that is mechanically connected to the crankshaft of the engine. The electrical power output of the generator 102 is a function of the engine speed, the strength of the magnetic field in the generator 102, the number of poles and the size of the armature. The output of the AC generator 102 is a current of alternating polarity comprising a negative half and a positive half.

[0034] The ignition control system 1 12 consists of a DC voltage regulator

114, an ignition control unit 122 powered by the DC voltage regulator 114 and an ignition coil 124. The DC voltage regulator 1 14 converts the AC voltage received from the AC generator 102 into a DC voltage of appropriate voltage level for the safe operation of the electronic devices in the ignition control system 1 12. The DC voltage regulator 114 consists of a power switching device such as a thyristor 1 16. In an embodiment, the first switching device 116 can be a silicon control rectifier 116. The regulator 1 14 further comprises a DC voltage controller circuit 118 and a capacitor 120. The first switching device 1 16 rectifies the AC voltage and provides a DC voltage, which is smoothened by the capacitor 120. The DC voltage controller 1 18 controls the conduction period of the first switching device 1 16 by providing appropriate signal to the gate terminal of the first switching device 116 in order to regulate the output DC voltage. In an embodiment, the DC voltage regulator 114 is combined with the load voltage regulator 202 as a single integral unit for convenience in mounting on the vehicle. [0035] The ignition control unit 122 consists of an electronic circuit that stores electrical energy in a storage device, monitors various engine parameters such as the engine speed, throttle position, manifold air pressure, temperature etc., and releases the stored energy at an appropriate instant of time through the primary winding of the ignition coil 124. The ignition coil 124 transforms the voltage appearing across its primary winding into a very high voltage across its secondary winding, which is fed to the spark plug 126 of the engine for generating an ignition spark. If the ignition circuit is a capacitor discharge type, the ignition energy is stored in the capacitor of the ignition circuit. In case of inductive discharge type ignition circuit, the ignition energy is stored in the magnetic circuit of the ignition coil 124.

[0036] In one embodiment, the ignition control unit 122 of the present subject matter, in addition to the basic function of generating an ignition signal for producing a spark in the spark plug of the engine, also performs additional tasks of monitoring the engine speed and the corresponding voltage generated by the AC generator 102. When the engine speed increases beyond a preset reference speed, the ignition control unit 122 generates an actuation signal that is fed through a signal line 216 to the load voltage controller 208 of the load voltage regulator 202.

[0037] The load voltage regulator 202 of the power supply system 200 of the present subject matter provides regulated voltage of suitable voltage level to the vehicle electrical loads such as the headlamp, the brake-lamp, turn signal indicators and horn. It primarily consists of a pair of parallel-connected power switching devices 106 and 206, and a load voltage controller 208 for regulating the voltage across the electrical loads 104 within safe operating levels, i.e. a range of operating voltage within which the performance of the loads is optimal and no failure occur. The parallel combination of second switching device 106 and third switching device 206 are connected in reverse polarization such that the cathode terminal of the first device is connected to the anode terminal of the second device and vice versa. The second switching device 106 is configured to conduct only the negative half of the AC voltage while the third switching device 206 is configured to conduct the positive half of the AC voltage.

[0038] The load voltage controller 208 consists of a load voltage sensing circuit 212, a voltage control circuit 214, and a switch driver circuit 210. The voltage sensing circuit 212 monitors a voltage appearing at the output terminal of the load voltage regulator 202, which is same as the voltage across the vehicle electrical loads 104 such as the headlamp (and other intermittent electrical loads) and provides a corresponding signal to the voltage control circuit 214. The voltage control circuit 214 compares the signal provided by the load voltage sensing circuit 212 with a reference voltage value and generates an enabling or a disabling signal, which is fed to the switch driver circuit 210 to either turn ON or OFF the second and third switching devices 106 and 206. The function of the switch driver circuit 210 is to supply a signal of suitable voltage and current levels to the control terminal (gate terminal) of the switching devices 106 and 206, when it receives an enabling signal from the voltage control circuit 214. In case of the power switches being thyristors, the switch driver circuit 210 provides enabling signal to the gate terminal of the thyristors. As soon as the polarity of the AC generator voltage is reversed, the thyristors are automatically turned OFF. [0039] In an alternative embodiment, the second and third switching devices

106 and 206 are MOSFETs or IGBTs. In this case, the gate driver circuit provides both enabling and disabling signal of appropriate voltage and current levels to the control terminal of the switching devices 106 and 206.

[0040] During the operation of electrical loads, when the voltage appearing across the electrical load is less than a preset voltage level, the voltage control circuit 214 in conjunction with the switch driver circuit 210 causes the switching devices 106 and 206 to turn ON. In an embodiment, the preset voltage level, for example, can be equivalent to zener characteristic voltage. If the voltage across the electrical loads increases beyond the preset voltage level, the voltage control circuit 214 provides a control signal to the switch driver circuit 210 to turn OFF the switching devices 106 and 206. The actuation signal generated from the ignition control unit 122 and fed through a signal line 216 is provided to the switch driver circuit 210 associated with the control terminal (gate) of the switching device 206.

[0041] At the time of start of the spark ignited internal combustion engine, the actuation signal that is fed through the signal line 216 will be set to disable the operation of the switching device 206. This inhibits the operation of switch driver circuit 210 connected to the control terminal (gate) of the third switching device 206. As a result, the switching device 206 will not be turned ON and the positive half of the AC voltage is exclusively utilized by the ignition control unit 122, while the lamp loads and the other intermittent loads are powered by the negative half of the AC voltage through the second switching device 106. When the engine rotation increases beyond a preset speed, the actuation signal fed through the signal line 216 from the ignition control unit 122 is set to enable operation of the switching device 206. This actuation signal in conjunction with the corresponding switch driver circuit 210 will cause the switching device 206 to turn ON.

[0042] Thus, after the generation of actuation signal from the ignition control unit 122 and fed through a signal line 216 to the switch driver circuit 210, the vehicle electrical loads 104 are provided electrical power during both the negative and positive halves of the AC voltage.

[0043] Fig. 2 A illustrates an exemplary schematic diagram 218 of the power supply control system 200 described in Fig. 2, in accordance with an embodiment of the present subject matter. In the exemplary embodiment of the power supply control system 218 as shown in Fig. 2 A, the load voltage regulator 202 includes a pair of power switching devices 106 and 206 connected in parallel with opposite polarization. The switching device 106 conducts during the negative half of the AC generator voltage. In an implementation, the load voltage controller 208 of the embodiment described in Fig.2, can include two separate load voltage controllers dedicated for independently controlling the operation of the pair of power switching devices 106 and 206. In an embodiment, the operation of the switching device 106 is controlled by a load voltage controller 220.

[0044] In an embodiment, the operation of the switching device 206, especially during the positive half of the AC generator output, is independently controlled by an exclusive load voltage controller 222. The load voltage controllers 220, 222 for the power switching devices 106 and 206 work in tandem such that the overall effective voltage value across the electrical loads 104 is maintained within a predetermined limit i.e. the safe operating level of voltage across the electrical loads. In an embodiment, the predetermined limit of voltage in each of the load voltage controllers 220 and 222 is selected in such a manner that the cumulative effect causes the voltage across the electrical loads 104 to be within the safe operating level of voltage.

[0045] The voltage across the electrical load 104 due to the positive half of the

AC generator voltage is monitored by a load voltage sensing circuit 212. In one implementation, the load voltage sensing circuit 212 has a diode D4, a resistor Rl 1 and a capacitor - resistor combination circuit that includes a capacitor C2 and a resistor R10. The capacitor C2 is charged to the peak value of a positive half of the voltage across the vehicle electrical load 104. This voltage is fed as an input to a voltage control circuit 214 that controls the voltage supplied to the power switch 206. [0046] In one embodiment, the voltage control circuit 214 includes a zener diode Zl and a pair of cascading transistor circuits wired around transistors T2 and T3 that acts as electronic switches. The breakdown voltage value of the zener diode Zl is selected based on the peak positive voltage across the electrical load 104. The transistor T2 is configured in such a manner that during the ON state, current flows through the base terminal of the transistor T2. Further, the ON state of the transistor T2 induces a flow of current through the base of a transistor T4 of a power switch driver circuit 210, which in-turn results in the flow of drive current through the - transistor T4 to the control (gate) terminal of the power switch 206. In one implementation, when the voltage across the capacitor C2 of the voltage sensing circuit 212 is higher than the breakdown voltage rating of the zener diode Zl, current flows through the base of transistor T3. As a result, the transistor T3 is turned ON, which short circuits the current flowing through the base of the transistor T2. Consequently, transistors T2 and T4 are both turned OFF and the drive current to the power switch 206 is cut-off. Thus, the zener diode Zl monitors the voltage detected by the voltage sensing circuit 212 and appropriately controls the operation of the power switch 206 to maintain the voltage across the electrical load 104 within a predetermined limit.

[0047] The power switch driver circuit 210 includes a pair of cascading switch circuits configured around the transistors Tl and T4. The actuating signal from the ignition control circuit 122 is fed to the base of the transistor Tl through a signal line 216. Until the engine speed reaches a preset limit, the actuation signal in this particular configuration is normally high, high enough to drive the transistor Tl into ON state. The ON state of the transistor Tl will drive the transistor T2 in the voltage control circuit 214, into an OFF state. As a result, the flow of current through the base of the transistor T4 in the switch driver circuit will be zero, forcing the transistor T4 into OFF state. While the transistor T4 is in the OFF state, there will be no drive signal to the control (gate) terminal of the power switch 206 and hence the supply of power to the electrical load 104 due to the positive half of the AC generator voltage is cut-off.

[0048] When the engine speed increases beyond a preset limit, the ignition control unit 122 causes the actuation signal to transit from a high state to a low state or vice versa. As a result, transistor Tl is turned OFF and transistors T2 and T4 are turned ON causing a flow of drive current to the power switching device 206. In an embodiment, the output voltage of the AC generator depends on the engine speed and the preset limit of the engine speed is that point on the voltage characteristic of the AC generator, when the AC generator voltage stabilizes. When higher current is drawn from the AC generator before reaching the preset limit of the engine speed, the operation of the ignition control unit 122 will be affected due to a fall in AC generator voltage. On the other hand, after attaining the preset limit of the engine speed, higher current can be drawn from the AC generator without affecting the operation of the ignition control unit 122. [0049] Thus the generation of an actuation signal, which in this case is the transition of the signal from the normally high state to a low state when being fed to the switch driver circuit 210 through a signal line 216, causes electrical power from the AC generator to be supplied to the vehicle electrical load 104 during both the positive and the negatives halves of the generator output voltage. In another embodiment, the generation of the actuation signal involves transition of the signal from the low state to the high state.

[0050] In the foregoing description of schematic diagram 218, the operation of each of the power switches 106 and 206 are controlled by independent load voltage control circuits 220 and 222 respectively. However, it will be understood by persons skilled in the art that in another implementation, each of the power switching devices 106 and 206 and the corresponding load voltage control circuits 220 and 222 can be respectively replaced by a single power switch and a single load voltage control circuit.

[0051] Fig. 3 illustrates a schematic diagram of a power supply control system in accordance to another embodiment of the present subject matter. In the present embodiment, the control system 300 is provided with a battery 302. Under operating circumstances, when the battery 302 is disconnected from the vehicle electrical system, the operation of the ignition control system 112 and the engine start-up is not affected since the ignition control unit 122 is powered by the positive half of AC generator through the DC voltage regulator 1 14. In other words, in vehicles operated by electric start mechanism with the help of battery, such as the battery 302, any failure of the electric start mechanism caused due to the draining of the battery or a loose connection of the battery cables or disconnection of the battery from the vehicle electrical system, the operation of the ignition control system 112 as described in this embodiment of the present subject matter is implemented. The actuation signal through a signal line 216 is provided to the load voltage regulator 202 when the engine speed increases beyond the preset level and when a DC voltage output of the DC voltage regulator 114 is sufficiently high for the stable operation of the ignition control unit 122.

[0052] Fig. 4 illustrates a schematic flow diagram of a method 400 of controlling power supply to various loads of a two-wheeled vehicle in accordance to an embodiment of the present subject matter.

[0053] The order in which the method is described is not intended to be construed as a limitation, and any number of the described method blocks can be combined in any order to implement the method, or an alternative method. Additionally, individual blocks may be deleted from the method without departing from the spirit and scope of the methods, systems and devices described herein. Furthermore, the method can be implemented in any suitable hardware, software, firmware, or combination thereof.

[0054] Referring to Fig. 4, at block 402, AC voltage having a positive half and a negative half is generated by an AC generator of a two-wheeled vehicle. In one embodiment, the AC generator generates the AC voltage by a mechanical torque created at a crankshaft to which the AC generator is coupled. [0055] At block 404, the positive half of the AC voltage thus generated is converted to DC voltage of appropriate voltage level by a DC voltage regulator. The converted DC voltage is then utilized for the purpose of ignition to start the engine.

[0056] At block 406, after starting the engine and when the engine speed is less than a preset level, the negative half of the AC voltage is conducted by a switching device configured to conduct only the negative half of the AC voltage and utilized for supplying power to other vehicle loads. At block 408, the engine speed and the corresponding voltage generated by the AC generator is monitored and at block 410, an actuation signal from an ignition control unit is enabled, when the engine speed increases beyond a preset level. Further, at block 410, on receiving the actuation signal from the ignition control unit, another switching device in the load voltage regulator configured to conduct only the positive half of the AC voltage is actuated.

[0057] At block 412, electrical power is supplied to all the constant and intermittent vehicle loads by utilizing both the positive and the negative halves of the AC voltage.

[0058] Fig.5 illustrates a graphical representation of magnitude of AC voltage across the electrical load 104 as a function of the engine speed in accordance with an embodiment of the present subject matter. Voltage curve 502 indicates the effective voltage appearing across the load 104.

[0059] The engine speed range is split into two parts by a threshold speed 504 i.e. the preset level of the engine speed. The speed range below the threshold speed 504, indicated by a region 506, constitutes an engine start-up range. Similarly, the speed range above the threshold speed 504, indicated by a region 508, constitutes an available speed range of the engine when the operation of the engine ignition system is stabilized.

[0060] As illustrated, in the engine start-up range 506, the vehicle electrical loads 104 are powered by only one half of the AC generator output voltage indicated by a lower portion of the load voltage curve 502. When the engine speed increases beyond the threshold speed 504, an actuation signal represented by a voltage plot 516, provided by the ignition control unit 122 to the load voltage regulator 202, causes the load voltage regulator 202 to conduct both halves of the generated AC voltage for powering the vehicle electrical loads 104.

[0061] A voltage curve 510 indicates the effective voltage across the electrical loads when powered by only one half of the AC generator voltage. An upper voltage curve 512 represents the electrical load voltage when operated by both the negative and positive halves of the AC generator voltage.

[0062] The shaded portion 514 in Fig. 5 indicates an additional power that is available to vehicle electrical loads without compromising the performance of the ignition control system 1 12.

[0063] Thus, an advantageous method for controlling power supply to various vehicle loads in a vehicle, in particular for a two-wheeled vehicle is provided. This method provides for complete utilization of power in the positive half of the AC voltage along with the negative half by means of conditionally enabling load voltage switching devices based on an actuating signal from the ignition control unit.

[0064] Although embodiments for methods and systems for power supply control have been described in a language specific to structural features and/or methods, it is to be understood that the invention is not necessarily limited to the specific features or methods described.

Claims

We claim:

1. A system for controlling electrical power supply (200, 218, 300) for a plurality of electrical loads (104) in a vehicle having a spark ignited internal combustion engine, the system (200, 218) comprising:

an AC generator (102) to generate an AC voltage, wherein the AC voltage comprises a positive half and a negative half;

an ignition control system (1 12) to control the ignition of the engine, wherein the ignition control system (112) comprises a DC voltage regulator (114) having a first switching device (116) that converts the AC voltage received from the AC generator (102) to a DC voltage, and an ignition control unit (122) that enables generation of an actuation signal based on the speed of the engine; and

a load voltage regulator (202) for supplying electrical power to the plurality of electrical loads (104) comprising a second switching device (106) configured to conduct the negative half of the AC voltage, and a third switching device (206) configured to conduct the positive half of the AC voltage, wherein the third switching device (206) conducts the positive half of the AC voltage after receiving the actuation signal from the ignition control unit (122).

2. The system (200, 218, 300) as claimed in claim 1, wherein the ignition control unit (122) generates the actuation signal when the engine speed increases beyond a predetermined level.

3. The system (200, 218, 300) as claimed in claim 1, wherein the second switching device (106) and the third switching device (206) are connected in parallel to each other.

4. The system (200, 218, 300) as claimed in claim 1, wherein the second switching device (106) and the third switching device (206) are connected in reverse polarities to each other.

5. The system (200, 218, 300) as claimed in claim 1, wherein the load voltage regulator (202) comprises at least one of a load voltage sensing circuit (212), a load voltage control circuit (214), and a switch driver circuit (210).

6. The system (200, 218, 300) as claimed in claim 1, wherein the second switching device (106) and the third switching device (206) are selected from a group consisting of at least one or a combination of a thyristor, a MOSFET and an IGBT.

7. The system (200, 218, 300) as claimed in claim 1 , wherein the plurality of electrical loads (104) is selected from a group consisting of at least one or a combination of a headlamp, a tail lamp and a turn-signal indicator.

8. The system (200, 218, 300) as claimed in claim 1, wherein the plurality of electrical loads (104), the second switching device (106), the third switching device

(206), and the AC generator (102) are connected in series.

9. The system (200, 218, 300) as claimed in claim 1, wherein the ignition control system (112) and the load voltage regulator (202) are functionally integrated into a single module.

10. The system (200, 218, 300) as claimed in claim 1, wherein the ignition control system (112) comprises a battery (302) for providing power to the ignition control unit (122) during the ignition of the engine.

11. The system (200, 218, 300) as claimed in claim 1, wherein the ignition control unit (122) causes the actuation signal to transit from a first state to a second state when the engine speed is greater than a predetermined level.

12. The system (200, 218, 300) as claimed in claim 11, wherein the first state is at least one of a high state and a low state, and wherein the second state is at least one of a high state and a low state.

13. The system (200, 218, 300) as claimed in claim 5, wherein the switch driver circuit (210) receives the actuation signal through a signal line (216) and supplies electrical power from the AC generator (102) to the plurality of electrical loads (104) through the conducting of the third switching device (206), during both the positive and the negatives halves of the AC voltage.

14. The system (200, 218, 300) as claimed in claim 13, wherein the voltage across the plurality of electrical loads (104) is monitored by a load voltage sensing circuit

(212).

15. The system (200, 218, 300) as claimed in claim 5, wherein the load voltage control circuit (214) comprises at least one zener diode (Zl) that controls the operation of the third switching device (206) based on the monitoring of the voltage detected by the voltage sensing circuit (212).

16. The system (200, 218, 300) as claimed in claim 15, wherein the third switching device (206) and a second switching device (106) maintains the voltage across the plurality of electrical loads (104) within a predetermined limit.

17. A method for controlling electrical power supply (400) for a plurality of electrical loads in a vehicle having a spark ignited internal combustion engine, the method comprising:

generating (402) an AC voltage having a positive half and a negative half by an AC generator;

converting (404) the positive half of the AC voltage to a DC voltage by a first switching device and utilizing for ignition of the spark ignited internal combustion engine;

conducting (406) the negative half of the AC voltage by a second switching device;

monitoring (408) the speed of the engine by an ignition control unit and enabling (410) generation of an actuation signal based on the monitored speed; and conducting, on receiving the actuation signal, by a third switching device, the positive half of the AC voltage.

18. The method as claimed in claim 17, wherein the enabling (410) further comprises providing the actuation signal when the monitored speed of the engine increases beyond a predetermined level.

19. The method as claimed in claim 17, wherein the method further comprises supplying (412) electrical power to the plurality of electrical loads in the vehicle by utilizing both the positive half and the negative half of the AC generator output.

20. The method as claimed in claim 17, wherein the method further comprises controlling the operation of the third switching device for maintaining the voltage across the plurality of electrical loads.