Power Conditioning Unit

Field of the Invention:

This invention relates to an improved power conditioning unit for a vehicle with an internal combustion engine, particularly a regulator-cum-rectifier unit for charging a vehicle battery and for supplying to various AC and DC electric loads.

Background of the Invention:

Vehicles with an internal combustion engine conventionally have an alternating current generator coupled with a crankshaft of the engine for generating electrical power. The alternating voltage generated is rectified and regulated for charging a vehicle battery and for supplying to other DC (direct current) loads like horn and Turn Signal Lamp. The generated voltage is also regulated for supplying to AC (alternating current) loads, mainly lighting loads like headlamp and tail lamp. Voltage regulation is essential for maintaining the load terminal voltage within set limits. These limits are set to ensure safe and efficient operation of the electrical loads. A regulator-cum-rectifier unit conventionally performs the above mentioned functions of rectifying and regulating alternating voltage for the different electrical loads in a vehicle.

The rectification function can be achieved either by a half-wave rectifier or a full-wave rectifier. Semiconductor devices like diodes or SCRs (Silicon Controlled Rectifiers) convert the alternating current into unidirectional current which is thereafter filtered to reduce ripple and to provide direct current (DC) for charging a battery and for supplying to DC electric loads.

The voltage regulation function can be achieved either by shunt regulator or series regulator. In the case of a shunt regulator, an electronic switch is connected between the supply terminal and ground. Switching is performed to shunt the supply voltage to ground in order to maintain the RMS (Root Mean Square) terminal voltage within set limits. But this in turn increases power loss within the regulator. A series regulator is a better option wherein an electronic switch connected in series between the supply terminal and load terminal is switched to maintain RMS load terminal voltage within set limits.

The alternating current generator can have separate windings for supplying to AC loads and another set of windings for supplying to DC loads. Otherwise a fraction of the winding used for supplying to DC loads including battery could be used for supplying to AC loads, mainly lighting.

Japanese Patent publication JP1283029 titled "Lamp Voltage Control Circuit for Motorcycle" discloses a lamp voltage control circuit wherein a positive cycle voltage from alternating current generator is supplied for charging a battery and the negative cycle voltage is supplied for lamp lighting. There are no separate windings or connections in the AC generator for charging and lighting circuits. A single AC output from the generator is used for both battery charging and lamp lighting. Thyristors are connected in series between AC generator and battery, AC generator and lamp respectively to form series regulator circuits.

European patent application EP0936720 titled "Lamp Lighting and Battery Charging Control System of a Vehicle" also discloses a series regulator circuit for both charging side as well as lighting side. Lamp is lighted alternatively by a full-wave and a negative half-wave of the alternating voltage in every other cycle. The positive half cycle is used exclusively for charging a battery in every other cycle. The turning ON of the lamp switching device is delayed gradually as engine speed increases to prevent high voltage across lamp terminals during high engine speeds. The above mentioned series regulator circuits require a large number of components to prevent the DC load voltage from exceeding specified limits during high engine speeds. They are also prone to AC side lamp flickering during low engine speeds. A simple device with small number of components which can maintain the DC load voltage and AC load voltage within specified limits at all conditions will help in meeting customer requirements without increasing product cost.

Summary of the Invention:

An improved power conditioning unit for a vehicle with an internal combustion engine is disclosed comprising series regulator devices for both battery charging side and lamp lighting side. The positive half wave of the alternator output voltage is used for battery charging and the negative half wave is used for supplying to alternating current (AC) loads. A strict tolerance on the battery charging voltage is maintained even at high engine speed and low electrical load condition using a transistor based voltage control circuit. AC lamp flickering at low engine speed is reduced by the present AC voltage regulation circuit.

The nature and further characteristic features of the present invention will be made clearer from the following description made with reference to the accompanying drawings.

Brief Description of the Drawings:

Figure 1 illustrates a conventional two wheeler motorcycle.

Figure 2 shows a power conditioning unit connected with alternating voltage source
and electrical loads according to one embodiment of the present invention.

Detailed Description of the Drawings:

For illustration purpose a conventional motorcycle is described herein, wherein the power conditioning unit according to the present invention may be used. First, with reference to Figure 1 a motorcycle comprises of a frame (101), front fork (102) attached to a pivot tube (201) of the vehicle frame, a front wheel (103) attached to these front forks (102), a handle bar (104) connected to the front forks (102), a fuel tank (105) attached so as to straddle an upper part of the vehicle frame, a seat (106) attached to the upper rear portion of the vehicle frame, an engine unit (107) attached to the lower front section of the vehicle frame, a swing arm (108) attached to a lower rear section of the vehicle frame, suspended by a rear shock absorber (not shown) from the vehicle frame and a rear wheel attached to a rear end of swing arm (108). The intake system of the engine comprises of a fuel air metering device such as a carburettor (109), intake duct and an air cleaner. The exhaust system of the engine comprises of exhaust pipe and a muffler. The motorcycle is also provided with a side cover for covering a side section of the vehicle frame, a seat cover for covering a rear section of the vehicle frame below the seat, a front fender (110) for covering an upper part of the front wheel (103), and a rear fender (111) for covering an upper part of the rear wheel (112). The drive from the engine (107) is transmitted from the engine to the driven wheel sprocket mounted on the rear wheel hub mounted on the rear wheel assembly.

The detailed description of the preferred embodiment will be explained with reference to Fig 2. The output of an alternating voltage source 10 is connected with alternating current (AC) load 20 through a first series voltage regulating device 30. The output of the alternating voltage source 10 is also connected with direct current (DC) load 40 and battery 50 through a second series voltage regulating device 60. An AC voltage control circuit 70 senses the AC load 20 voltage and switches ON and OFF the first series voltage regulating device 30 in order to maintain the AC load 20 voltage within a predetermined first limit. A DC voltage control circuit 80 senses the DC load 40 and switches ON and OFF the second series voltage regulating device 60 in order to maintain the DC load 40 voltage within a predetermined second limit. The positive half wave in the alternator 10 output is used for supplying to DC load 40 and for battery 50 charging by using thyristor S1 as the first voltage regulating device 30. The negative half wave in the alternator 10 output is used for supplying to AC load 20 by using thyristor S2 as the second voltage regulating device 60. At low engine speeds, the alternating voltage source 10 output is low. The transistor T2 is turned ON during the negative half cycle of the alternator 10 output as the base-emitter junction of transistor T2 is reverse biased through diode D2, Zener Z3 and resistor R8. The capacitor C2 and resistor R7 help in ensuring that the transistor T2 base-emitter voltage is within permissible levels and is free from high frequency noise signals. With transistor T2 in ON condition, Silicon Controlled Rectifier (SCR) S1 is turned ON using the collector current through resistor R9. Resistor R10 and capacitor C3 ensure that the SCR S1 gate voltage is within permissible limits and is free from high frequency noise signals. The Zener Z1 and Zener Z2 reverse breakdown voltages are chosen such that transistor T1 remains OFF for alternator 10 negative peak voltage below specified first limit. When the alternator 10 output peak negative voltage increases beyond a predefined first limit at high engine speeds, the transistor T1 turns ON and connects the transistor T2 base to ground. This in turn prevents the turn ON of SCR S1. The AC voltage across AC load 20 is thus maintained to be within a specified first limit. Resistors R1, R2, R3, R4 and R5 help in providing proper reference voltage for Zener diodes Z1 and Z2. Diodes D1 and D2 ensure reverse voltage protection for transistor T1.

In the DC side, the voltage across battery 50 and DC load 40 is maintained within a specified second limit using transistors T3 and T4. When the DC load 40 voltage is within the specified second limit, the transistor T4 remains OFF. The transistor T3 emitter-base junction is forward biased using resistors R11 and R12. The transistor T3 emitter current turns ON the SCR S2 during each positive half cycle of alternator 10 output voltage. When the DC load 40 voltage exceeds the specified second limit, the transistor T4 turns ON due to reverse break down of Zener Z4. Turn ON of transistor T4 in turn connects the base of transistor T4 to ground and prevents turn ON of SCR S2. The capacitor C4 provides proper reference voltage for transistor T4 and allows precise turn OFF of transistor T3 as soon as the DC load 40 voltage exceeds specified second limit. Resistor R14 and capacitor C5 maintain the SCR S2 gate-cathode voltage within permissible limits and prevent high frequency noise from affecting SCR S2 gate cathode junction. Capacitor C6 provides a proper reference of the DC load 40 voltage in the absence of battery 50.

The AC voltage control circuit 70 and DC voltage control circuit 80 together maintain the AC load 20 and DC load 40 voltages within specified limits. The transistor based voltage control circuits 70 and 80 prevents the DC load 40 voltage from exceeding the specified second limit even at high engine speed and low electrical load condition. At low engine speeds, the AC voltage control circuit 70 does not lead to lamp flickering as the negative half cycles are not unnecessarily eliminated. The power conditioning circuit can operate without battery 50 and also with loads 20 and 40 switched in an irregular manner.

Other embodiments of the disclosed invention with changes in the AC voltage control
circuit 70 and DC voltage control circuit 80 are possible without deviating from the
scope of the invention.

It is further to be noted "that the present invention is not limited to the described embodiment and many other changes and modifications may be made without
departing from the scope of the appended claims.

We Claim:

1. An improved power conditioning unit for a vehicle with an internal combustion
engine comprising:

an alternator wherein the positive half cycle of the voltage generated is used for supplying to DC loads and the negative half cycle of voltage generated is used for supplying to AC loads;

a first series regulator device for battery charging and for supplying to DC loads;

a second series regulator device for supplying to AC loads;

wherein

a transistor based AC voltage control device senses the AC load voltage and controls a first voltage regulating device to maintain the AC load voltage within a specified first limit and

a transistor based DC voltage control device senses the DC load voltage and controls a second voltage regulating device to maintain the DC load voltage within a specified second limit.

2. The improved power conditioning unit as claimed in claim 1, wherein the said DC loads includes a vehicle battery

3. The improved power conditioning unit as claimed in claim 1, wherein the said first and second series regulator devices are Silicon Controlled Rectifiers.

4. The improved power conditioning unit as claimed in claim 3, wherein the said AC voltage control device comprises at least one Zener diode for controlling a transistor supplying to the gate of a Silicon Controller Rectifier.

5. The improved power conditioning unit as claimed in claim 3, wherein the said DC voltage control device comprises at least one Zener diode for controlling a transistor supplying to the gate of a Silicon Controlled Rectifier.

6. The improved power conditioning unit as claimed in claim 1, wherein the said AC loads comprises of lamps for lighting.

7. The improved power conditioning unit as claimed in claim 1, wherein the said AC load and DC load are switched in an irregular manner.