TECHNICAL FIELD

[1] The subject matter described herein, in general, relates to a voltage control device and, in particular, relates to a voltage regulator for controlling of voltage supplied to a load.

BACKGROUND

[2] In a vehicle, such as a two wheeler, electrical power is required to operate various AC and DC load devices. The power to be supplied to the load devices is generally generated by a generator coupled to an engine. The generator is typically a permanent magnet AC generator, which generates an AC voltage based on power provided by the engine. The AC voltage is provided to the various AC load devices, such as a head lamp, associated with the generator. To power the DC load devices, the AC voltage is converted to DC voltage and is used to charge a battery to which the various DC load devices, such as stoplight, are connected.

[3] As revolutions per minute (rpm) of the engine increases, the AC voltage provided to the various load devices, being in proportion to the engine rpm, also increases. However, the voltage provided to any of the load devices needs to be within a safe operating limit for that load device to function properly.

[4] For this purpose, a regulator is used to limit the effective AC voltage supplied to AC loads and to limit battery voltage. Also, it is known that switching ON / OFF of the DC load devices connected to battery affects the AC voltage supplied to AC loads which is observed as flickering of the head lamp. Thus, a regulator is needed for various purposes such as, to limit effective AC voltage applied to AC loads, to limit the battery voltage, and to limit variation in AC voltage due to switching ON/OFF of DC loads.

[5] For the purpose of regulating the AC voltage supplied to the load device various types of voltage regulators are used. The type of regulator used is primarily decided by the nature of how the regulating element (usually a silicon controlled rectifier) is connected with respect to the load. If the load is connected in series with the regulating element, it is called a Series Type regulator and if the load is connected in parallel to the regulating element, it is called a Shunt Type regulator.

SUMMARY

[6] The present subject matter relates to a Alternating Current (AC) voltage control device to regulate a voltage generated by an AC generator. In one implementation, the AC voltage control device includes a surrogate load and a surrogate voltage regulator. The surrogate voltage regulator is coupled to the surrogate load. The surrogate voltage regulator limits an AC voltage across the surrogate load to a predetermined level in response to fluctuation in an AC voltage supplied to the AC voltage control device.

[7] These and other features, aspects, and advantages of the present subject matter will be better understood with reference to the following description and appended drawings. This Summary is provided to introduce a selection of concepts in a simplified form. 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

[8] The detailed description is described 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.

[9] Fig. 1 illustrates a schematic diagram of a voltage control system, according to an embodiment of the present subject matter.

[10] Fig. 2 illustrates a schematic diagram of the voltage control system of Fig. 1, according to another embodiment of the present subject matter.

[11] Fig. 3 illustrates a schematic diagram of waveforms taken across an AC input, AC load and a surrogate load, according to an embodiment of the present subject matter.

[12] Fig. 4a and 4b illustrates a schematic diagram of waveforms taken at the input to the voltage control system in accordance with another embodiment of the present subject matter.

DETAILED DESCWPTION

[13] A typical application of a voltage regulator is to regulate the AC voltage generated in a vehicle such as a two wheeler. Conventionally voltage regulators regulate power supplied by a generator in a vehicle to a plurality of AC loads and a battery. The battery supplies power to various DC loads of the vehicle. When the DC loads draw power from the battery, voltage of the battery decreases and due to this the battery is to be charged. Charging of the battery draws a large amount of current from the generator, and due to an inductance effect in the generator, voltage generated by the generator gets affected. More particularly, the inductance causes a delay in the AC voltage waveform of the generator.

[14] The delay in the AC voltage waveform has an adverse effect on the voltage control of the AC loads. In other words, a turn on time of the AC loads in every cycle is delayed. Consequently, voltage provided to the AC loads decreases and a flickering in the AC loads, such as a head lamp, is observed. Thus, in the conventional voltage regulation systems, when the DC loads are operated with power supplied from the battery, the power supplied by the generator to the AC loads gets affected and often results in improper functioning of the AC loads.

[15] Disclosed herein is a voltage control system including an AC voltage control device that enables improved regulation of a voltage, supplied to one or more associated loads. The AC voltage control device limits fluctuations in the AC loads even when DC loads are switched ON/OFF and cause fluctuations in the AC voltage supplied by the generator.

[16] It will also be appreciated by those skilled in the art that the words during, while, and when as used herein are not exact terms that mean an action takes place instantly upon an initiating action but that there may be some small but reasonable delay, such as a propagation delay, between the initial action and the reaction that is initiated by the initial action. Additionally, wherever the word "coupled" is used, it includes either direct or indirect electrical connection between or among the elements of the circuit.

[17] The present AC voltage control device uses a surrogate load and a surrogate voltage regulator to control voltage supplied by a generator to various load devices. In one embodiment, a voltage across the surrogate load is monitored and controlled, and, based on this; the voltage across AC loads is controlled. The present AC voltage control device controls the voltage across the AC load devices to limit it within their safe operating limits. Advantageously, the present voltage regulating device is simple in construction and inexpensive.

[18] The specification provided here explains in a detailed manner the voltage control system and an AC voltage control device to regulate power supply to various kinds of loads in a vehicle, such as a two wheeler and a four wheeler. For the ease of understanding, the voltage regulating system has been explained herein in the context of regulation of AC voltage generated by an AC generator However, it will be appreciated by one skilled in the art that the concept may extend to any other application of a typical voltage regulator without deviating from the scope and spirit of the invention. For example, the voltage regulating device may be implemented in voltage control modules of various electrical devices such as, gen -sets, and so on.

[19] Fig. 1 illustrates a schematic diagram depicting an implementation of a voltage control system 100, in accordance with an embodiment of the present subject matter. The voltage control system 100 includes an AC generator 102 for generating an AC voltage. The AC generator 102 powers an AC load 108 through an AC voltage regulator 104. In an implementation, the AC load 108 and the AC voltage regulator 104 are coupled in series through a switch SW 106. Thus, the present AC voltage regulator 104 is a series type regulator. The AC load 108 may include headlights of a two wheeler. The voltage control system 100 further includes an AC voltage control device 110 for detecting and controlling a voltage supplied by the AC generator 102 to the AC load 108. The AC voltage control device 110 includes a surrogate load 112 and a surrogate voltage regulator 114.

[20] The voltage control system 100 further includes a DC voltage control device 118 for detecting and controlling a voltage supplied to or derived from a battery 120. The DC voltage control device 118 is coupled to the battery 120 through a DC voltage regulator 116. In one implementation, the battery 120 is coupled to a DC load 124 through a switch SW122. The DC load 124 may include, but is not limited to, stoplight, or indicator light of a vehicle.

[21] In operation, the AC voltage across the AC load 108 may increase beyond operating limits of the AC load 108 as engine rpm increases. The AC voltage is hereinafter interchangeably referred to as voltage VL. The voltage VL needs to be controlled to operate the AC load 108 in its safe operating limits. For the purpose, the surrogate voltage regulator 114 operates in synchronization with the AC voltage regulator 104 such that an AC voltage applied to the AC load 108 is same as an AC voltage applied to the surrogate load 112. The surrogate load 112 represents the AC load 108 such that controlling a voltage across the surrogate load 112 controls the voltage VL across the AC load 108. More particularly, the voltage across the surrogate load 112 is monitored, and if the voltage exceeds a predetermined level, the surrogate voltage regulator 114 is switched off.

[22] The AC voltage regulator 104, coupled to the surrogate voltage regulator 114, simultaneously switches off with the surrogate voltage regulator 114. Thus, the surrogate voltage regulator 114 cuts off the supply to the AC load 108 from the AC generator 102. In this way, the AC load 108 is protected from an over voltage condition, which might damage the AC load 108.

[23] Further, the battery 120 is charged by the power supplied by the AC generator 102. The charging of the battery 120 is monitored and controlled by the DC voltage regulator 116 and the DC voltage control device 118. Hence the battery is also protected from overcharging.

[24] Fig. 2 illustrates an exemplary circuit of the voltage control system 100, in accordance with an implementation of the present subject matter The AC voltage regulator 104 includes a switching element such as a thryistor. In one implementation, the thryistor is a silicon controlled rectifier (SCR). In one example, the AC voltage regulator 104 includes a silicon controlled rectifier SCR1. It will be understood by persons skilled in the art that other type of switching elements can also be used in place of a thryistor. In one embodiment, the AC voltage control device 110 includes the surrogate voltage regulator 114 and the surrogate load 112. In one example, the surrogate voltage regulator 114 is implemented using a silicon controlled rectifier SCR2 while the surrogate load 112 is a resistor RIO, referred to as surrogate resistor RIO. The silicon controlled rectifier SCR2, has its cathode connected to a gate of the silicon controlled rectifier SCR1. The AC voltage control device 110 further includes a diode D1 for supplying the first polarity half cycle of AC power from the AC generator 102. For ease of explanation, the first polarity half cycle is referred to as the negative half cycle of the AC generator 102. The diode D1 is connected to a capacitor C2 through a resistor R1. The base of a transistor Q1 is coupled to the capacitor C2 and the resistor R3. An emitter of the transistor Q1 is coupled to the gate of SCR2. A resistor R4 and a capacitor CI are associated with the SCR2. It will be understood by persons skilled in the art that other type of switching elements that are functionally equivalent to a transistor can also be used in place of a transistor.

[25] The silicon controlled rectifier SCR2 is further coupled to the surrogate resistor RIO. The silicon controlled rectifier SCR2 is also coupled to a capacitor-resistor (CR) circuit including a capacitor C3 and a resistor R8. The resistor R8 is coupled to a base of a transistor Q2 through a first voltage limiter device and a resistor R7. The collector of the transistor Q2 is coupled to the capacitor C2 and the resistor R3. In one embodiment, the first voltage limiter device is a zener diode Z1. It will be understood by persons skilled in the art that other type of voltage limiter device can also be used in place of a zener diode.

[26] The voltage control system 100 further includes a DC voltage regulator 116 and a DC voltage control device 118 coupled to the DC voltage regulator 116. The voltage control system 100 also includes a battery 120 coupled to the AC generator 102 through the DC voltage regulator 116. A DC load 124 is coupled to the battery 120 through a switch SW 122. The DC voltage regulator 116 includes a silicon controlled rectifier SCR3.

[27] The DC voltage control device 118 includes a resistor R11, which is coupled to an anode of the silicon controlled rectifier SCR3 and also to a gate of silicon controlled rectifier SCR3 through a diode D4 and a resistor R13. The DC voltage control device 118 further includes a second voltage limiter device and a diode D5. In one embodiment, the second voltage limiter device is a Zener diode Z2. In another embodiment, the Zener diode Z2 and the diode D5 are coupled in series. The diode D5 is also coupled to the diode D4 and the resistor R11. The DC voltage control device 118 further includes a resistor R12 and a capacitor C4 coupled to the silicon controlled rectifier SCR3 between a gate and a cathode of the silicon controlled rectifier SCR3.

[28] In operation, during opposing polarity half cycle of the AC generator 102, when the battery voltage is less than a predefined voltage across the diode D5 and Zener diode Z2, current is supplied to the gate of silicon controlled rectifier SCR3 via the diode D4, and the resistor R13. For ease of explanation, the opposing polarity half cycle is referred
to as positive half cycles of the AC generator 102. This switches on the silicon controlled rectifier SCR3 and the battery 120 gets charged. When the voltage of the battery 120 reaches the predefined voltage across diode D5 and Zener diode Z2, diode D4 switches off, which in turn stops a gate current of the silicon controlled rectifier SCR3. Thus, the silicon controlled rectifier SCR3 remains switched off and the battery 120 is not charged further, and hence the battery 120 is protected from overcharging. The predefined voltage is based on a breakdown potential of the Zener diode Z2.

When the battery voltage falls below the voltage across diode D5 and Zener diode Z2, the battery is again charged through the silicon controlled rectifier SCR3.
[30] In operation, during negative half cycles of the AC generator 102, the AC load 108 is supplied power.

[31] In one embodiment, the voltage control system 100 may be implemented such that the AC load 108 may be supplied power during the positive half cycle and the battery 120 may be charged during the negative half cycle of the AC generator 102.

[32] In one implementation, during the negative half cycles of the AC generator 102, the diode D1 conducts and charges the capacitor C2 through the resistor R1. The capacitor C2 and the resistor R3 are designed to give a delay. The delay is provided to avoid undesirable fluctuations in the AC generator voltage, which may lead to the flickering of the AC load 108. After this delay, the transistor Q1 is switched ON and provides sufficient gate current to switch ON the silicon controlled rectifier SCR2. The switching ON of the silicon controlled rectifier SCR2 simultaneously switches ON the silicon controlled rectifier SCRl, through the resistor R5.
10

[33] Switching ON of the silicon controlled rectifier SCR2 also applies the AC voltage across the surrogate resistor RIO. The AC voltage applied across the surrogate resistor RIO charges the capacitor C3 through the resistor R9 and the diode D3. Thus, the DC voltage across C3 represents the effective voltage across the surrogate resistor RIO, which in turn represents the effective voltage across the AC load 108. When the effective voltage across the capacitor C3 increases beyond the predetermined level of limiting voltage, the Zener diode Z1 conducts and switches ON the transistor Q2. The predetermined level is based on the breakdown potential of Zener Diode Z1.

[34] Switching ON of the transistor Q2 switches OFF the transistor Ql. Consequently, the silicon controlled rectifier SCR2 is switched OFF and hence the silicon controlled rectifier SCRl is also switched OFF. Further, when the effective voltage across the capacitor C3 drops below the limiting voltage by discharging through the resistor R8 and the resistor R6, the transistor Q2 is switched OFF. This, in turn, switches ON the transistor Ql and through the diode Dl, the silicon controlled rectifier SCR2 and the silicon controlled rectifier SCRl are switched ON again.

[35] Thus, the voltage applied to the AC load 108 is limited by switching ON and OFF the silicon controlled rectifier SCRl determined by the effective voltage across the surrogate resistor R10.

[36] In one embodiment, when the DC load 124 is switched ON or OFF by the switch SW 122, the AC voltage control device 110 would still detect the effective voltage across the surrogate resistor RIO and correspondingly switches ON or OFF the silicon controlled rectifier SCR1. Thus, the effect of the DC load 124 affecting the AC load 108 does not arise in the present configuration of the voltage control system 100.

[37] Fig. 3 illustrates a schematic diagram of waveforms taken across the AC input, the AC load 108 and a surrogate load 112, according to an embodiment of the present subject matter. More particularly. Fig. 3 shows two set of waveforms 302 and 304. The waveforms 302 depict the voltage across AC input, the AC load 108, and the surrogate load 112 when the DC load 124 coupled to the battery 120 is switched OFF. The waveforms 304 depict the voltage across AC input, the AC load 108, and the surrogate load 112 when the DC load 124 coupled to the battery 120 is switched ON. The waveforms 302 represent the waveform with DC load OFF and include a waveform 3 which is an input AC voltage available at output terminals of the AC generator 102, a waveform 1 which is a voltage across the AC load 108, and a waveform 2 which is a voltage across the surrogate load 112.

[38] The other set of waveforms 304 are the "Waveform with DC load ON". The waveforms 304 include a waveform 3 which is the input AC voltage available at output terminals of the AC generator 102, a waveform 1 which is the voltage across the AC load 108, and a waveform 2 which is the voltage across the surrogate load 112. It is evident from Fig. 3 that a waveform of voltage taken across the AC load 108 is not affected because of the switching ON or OFF of the DC loads 124.

[39] Fig. 4a illustrates a schematic diagram of AC waveforms 402 taken across the AC generator 102 in accordance with another embodiment of the present subject matter. The AC waveform 402 depicted in the figure illustrates voltage across the AC generator 102 while the DC load 124 is switched OFF. The dotted line "L" represents the predetermined level set by Zener diode Z1. The voltage waveform 404 across capacitor C3 represents the effective voltage across resistor RIO. The charging of the capacitor C3 when the voltage across the surrogate load RIO reduces below the predetermined level set by Zener diode Z1 is depicted by the line 406 and the discharging when DC voltage across RIO increases above the predetermined level set by Zener diode Z1 is depicted by the line 408. [00040] When the voltage across capacitor C3 is above the predetermined level, the transistor Q2 is switched ON, as depicted by ON time indicator 410. Similarly, time instances 412 represent two instances of AC waveforms 402. At time instances 412, it may be observed that the voltage across capacitor C3 is below the predetermined level, the transistor Q2 switches OFF and the transistor Q1 switches ON making the surrogate voltage regulator 114 and consequently AC voltage regulator 104 ON. The time at which Q2 switches OFF varies automatically to maintain effective voltage across capacitor C3 and hence across the AC load 108. The AC waveform 402 depicted in the Fig. 4b illustrates voltage across the AC generator 102 while the DC load 124 is switched ON. When the voltage across capacitor C3 is not reduced below the predetermined level as illustrated by waveform 414, the AC voltage regulator is not switched ON. In one implementation, at the two instances of the AC waveform 402 represented by time instances 412, the control logic remains same as in figure 4a. It is observed that when the voltage 404 across the capacitor C3 is below the predetermined level, the transistor Q2 switches OFF and transistor Q1 switches ON making the surrogate voltage regulator 114 and consequently AC voltage regulator 104 ON. The time at which transistor Q2 switches OFF varies automatically to maintain effective voltage across capacitor C3 and hence across the AC load 108. Thus the waveforms depicted in Fig. 4a and 4b illustrate how the AC load 108 is switched ON to maintain the effective voltage across the AC load 108 when DC load 124 is switched ON and OFF.

[41] The description of the voltage control system and AC voltage control device of the present subject matter is not restricted to the embodiments that are mentioned above in the description.

[42] Although the subject matter has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternate embodiments of the subject matter, will become apparent to persons skilled in the art upon reference to the description of the subject matter. It is therefore contemplated that such modifications can be made without departing from the spirit or scope of the present subject matter as defined.

claim:

1. An Alternating Current (AC) voltage control device (110) comprising:
a surrogate load (112); and

a surrogate voltage regulator (114) coupled to the surrogate load (112), wherein the surrogate voltage regulator (114) is configured to limit an AC voltage across the surrogate load (112) to a predetermined level in response to fluctuation in an AC voltage supplied to the AC voltage control device (110).

2. The AC voltage control device (110) as claimed in claim 1, wherein the surrogate voltage regulator (114) is coupled to a first voltage limiter device for limiting the AC voltage across the surrogate load (112) to the predetermined level.

3. The AC voltage control device (110) as claimed in claim 2, wherein the predetermined level is based on a breakdown potential of the first voltage limiter device.

4. The AC voltage control device (110) as claimed in claim 2, wherein the first voltage limiter device is coupled to at least one switching element to switch the surrogate voltage regulator (114).

5. The AC voltage control device (110) as claimed in claim 1, wherein the surrogate voltage regulator (114) is a thryistor.

6. A system (100) comprising:

an AC generator (102);

an AC load (108) coupled to the AC generator (102);

an AC voltage regulator (104) coupled to the AC load (108) to control an AC voltage across the AC load (108); and

an AC voltage control device (110) coupled to the AC voltage regulator (104) to limit the AC voltage across the AC load (108) to a predetermined level in response to fluctuation in an AC voltage supplied by the AC generator (102).

7. The voltage control system (100) as claimed in claim 6, wherein the voltage control system (100) further comprises:

a battery (120) coupled to the AC generator (102), wherein the battery (120) is charged by the AC generator (102);

a Direct Current (DC) load (124) coupled to the battery (120);

a DC voltage regulator (116) coupled to the DC load (124) to control a DC voltage across the DC load (124); and

a DC voltage control device (118) coupled to the battery (120) to limit charging of the battery (120) to a predefined voltage.

8. The voltage control system (100) as claimed in claim 7, wherein the DC voltage control device (118) comprises a second voltage limiter device, wherein the second voltage limiter device is configured to control the charging of the battery (120) to the predefined voltage.

9. The voltage control system (100) as claimed in claim 8, wherein the predefined voltage is based on a breakdown potential of the second voltage limiter device.

10. A vehicle comprising:

an AC generator (102);

an AC load (108) coupled to the AC generator (102);

an AC voltage regulator (104) coupled to the AC load (108) to control an AC
voltage across the AC load (108); and

an AC voltage control device (110) coupled to the AC voltage regulator (104)to limit the AC voltage across the AC load (108) to a predetermined level in response
to fluctuation in AC voltage supplied by the AC generator (102).