GB2550661A

GB2550661A - Electrical load ballasting

Info

Publication number: GB2550661A
Application number: GB1704613.7A
Authority: GB
Inventors: Jubber Edmond; Crawford Andrew; Chilton Nick; Cains Geoff
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2014-02-18
Filing date: 2014-02-18
Publication date: 2017-11-29
Anticipated expiration: 2034-02-18
Also published as: GB201704613D0; GB2550661B

Abstract

A communication protocol for use in a data network, e.g. for voltage regulation of an electrical power sub-system of a motor vehicle, comprises first and second control units A, B, communicatively coupled via said data network and each having a respective clock, the first control unit for switching a primary load 13 on or off and the second control unit for switching a ballast load 15 on or off. The communication protocol comprises the first control unit, on identifying a need to switch the primary load, determining a delay time to take account of delays within the data network, reading the time from its clock, determining a designated time based upon the determined delay and the read time, sending a message via the data network to the second control unit instructing the second control unit to switch the ballast load at the designated time and instructing a counter-timer within the first control unit to switch the primary load at the designated time, such that the primary load and the ballast load are switched in co-ordinated synchrony with one another. Synchronising switching of the loads in this way balances the load on the electrical power sub-system such that voltage spikes and voltage dips may be minimised or eradicated.

Description

ELECTRICAL LOAD BALLASTING

TECHNICAL FIELD

The present disclosure relates to electrical load ballasting. Embodiments of the invention relate to a method of voltage regulation of an electric circuit and particularly, but not exclusively, to a method of ballasting electrical load within an electric circuit of a vehicle. The invention finds advantageous application in electric circuits for vehicles wherein an alternator that is used to generate electrical energy can take time to respond to certain changes in electrical load.

Aspects of the invention relate to a method, to a system, to a vehicle, to a communications protocol and to a program.

BACKGROUND

In vehicles, an alternator, typically driven by the engine, is used to generate electrical energy which is supplied to components of the vehicle, including a rechargeable battery of a vehicle. It is known that a large drop in an electrical load, which is commonly referred to as a “load dump", can occur when a significant electrical load is suddenly disconnected from the electrical circuits. Such load dumps are typically characterised by a sudden and often unexpected disconnection of the battery. A sudden increase in voltage accompanies the “load dump”. Load dumps can therefore have a deleterious effect and can cause damage and failure of components coupled to the electrical circuits. Such “load dumps” can be characterised by their duration, which is typically up to about 400ms. Such load dumps and the accompanying voltage increase can damage components of the vehicle’s electrical system, importantly including Electronic Control Units (ECUs) of the vehicle. The ECUs and other controller units connected to the electrical circuit containing the rechargeable battery of a vehicle are protected from such load dumps. Protection systems for load dumps are known, for example from US 8,093,870 and EP 2,044,670.

In contrast, it has been identified by the applicant of the present disclosure that “over-voltage spikes” of much shorter duration, in the region of up to about 250ms can occur when an electrical load is disconnected from the electrical circuit of a vehicle. Similar “voltage dips” can occur when an electrical load is connected to the electrical circuit of a vehicle. An “overvoltage spike” (and to some extent also a “voltage dip”) can cause, components that may be less critical than the rechargeable battery or ECUs of the vehicle to completely or temporarily shut-down. Such a response may be due to the component failing in response to being exposed to a voltage that exceeds its specification or may be due to the activation of a protection mechanism for that component that is put into effect if that component is exposed to a voltage that exceeds its specification.

The present disclosure seeks to provide an improvement in the field of protection or management of electrical circuits that has particular application for vehicles which addresses or at least mitigates against the problems of the prior art. In addition the present disclosure provides a communications protocol that may be used in conjunction with the improvement in the field of protection or management of electrical circuits.

Aspects of the present disclosure may be utilised in applications other than for vehicles, for example it is foreseen that advantageous application may be found in systems where electrical generators are used, for example portable power generators and back-up power supplies.

The term “rechargeable battery” is used herein to refer to the battery used to power electrical components and may be distinguished from a rechargeable battery pack of an electric or hybrid vehicle which is used to provide power to the powertrain.

SUMMARY OF THE INVENTION

Aspects of the invention provide a method, a system, a vehicle, a communications protocol and a program.

According to an aspect of the invention for which protection is sought, there is provided a method of voltage regulation of an electric circuit having: (a) a generator providing an output voltage; (b) a primary load switchable between an on-state in which the primary load draws current from the electric circuit and an off-state in which the primary load does not draw current from the electric circuit; and (c) a ballast load switchable between an on-state in which the ballast load draws current from the electric circuit and an off-state in which the ballast load does not draw current from the electric circuit, the method comprising: (i) identifying that the primary load is required to be switched: a. from the on-state to the off-state or b. from the off-state to the on-state; and (ii) in response to said identifying: a. co-ordinating switching the ballast load between the off-state and the on-state with switching said primary load to its off-state; or b. co-ordinating switching the ballast load between the on-state and the off-state with switching said primary load to its on-state, such that the voltage of the electric circuit is regulated.

Optionally, the ballast load has a load-size that is less than the load size of the primary load. Optionally, said co-ordinating switching the ballast load is timed and/or arranged to reduce the size of any one instantaneous change in load on the electric circuit whilst at the same time facilitating a total change in load on the electric circuit that is equal to the load-size of the primary load.

Optionally, said co-ordinating switching the ballast load is timed and/or arranged to enable the generator to adjust its voltage output in response to the change in load over a period of time in order to mitigate against the occurrence of a voltage spike that would otherwise occur due to switching the primary load to the on-state or to the off-state in the absence of coordinating switching of the ballast load.

Optionally, upon identifying that the primary load is required to be switched from the on-state to the off-state, said step of co-ordinating switching comprises: (i) switching the primary load to the off-state such that said primary load is no longer drawing current from the electric circuit; (ii) switching said at least one ballast load to the on-state substantially synchronously with switching said primary load to the off-state; and thereafter (iii) switching said ballast load to the off-state.

Optionally, upon identifying that the primary load is required to be switched from the off-state to the on-state, said step of co-ordinating switching comprises: (i) switching said ballast load to the on-state before switching said primary load to the on-state; (ii) maintaining said ballast load in the on-state for a period of time sufficient to allow the generator to adjust its voltage output in response to switching said ballast load to the on-state; (iii) switching the primary load to the on-state such that the primary load is drawing current from the electric circuit; and (iv) switching the ballast load to the off-state substantially synchronously with switching the primary load to the on-state.

Optionally, the ballast load comprises a set of ballast loads. The set of ballast loads may comprise two or more ballast loads.

Optionally, in the method, upon identifying that the primary load is required to be switched from the on-state to the off-state, the method comprises co-ordinating switching all ballast loads of the set of ballast loads to the on-state with switching said primary load to its off-state; and comprises staggering switching the ballast loads of the set to the off-state.

Optionally, staggering switching the ballast loads of the set of ballast loads to the off-state comprises: (i) switching the set of ballast loads off in decreasing load-size order, starting with the largest ballast load of the set; or (ii) switching one or more ballast loads to the off-state and switching one or more other ballast loads of the set to the on-state in a timed and/or ordered sequence in order to stagger the reduction in load on the circuit in a step-wise manner.

Optionally, upon identifying that the primary load is required to be switched from the off-state to the on-state, the method comprises staggering switching the ballast loads of the set of ballast loads to the on-state; and subsequently comprises co-ordinating switching all ballast loads of the set of ballast loads to the off-state with switching said primary load to its on-state.

Optionally, staggering switching the ballast loads of the set of ballast loads to the on-state comprises: (i) switching the set of ballast loads on in increasing load-size order, starting with the smallest ballast load of the set; or (ii) switching one or more ballast loads to the on-state and then switching one or more other ballast loads of the set to the on-state whilst switching one or more ballast loads to the off-state in a timed and/or ordered sequence in order to stagger the increase in load on the circuit in a step-wise manner.

Optionally, said set of ballast loads are switched on or off in a staggered or sequential manner such that a total current draw on the electric circuit is changed: (i) in a step-wise ramped manner; (ii) in a substantially linear ramped manner; (iii) such that the rate of change of the current draw has an “S”-shaped profile; and/or (iv) in a more gradual or smooth manner than would otherwise occur if the primary load was switched either to the on-state or to the off-state in the absence of also switching the ballast load to the off-state or to the on-state.

Optionally, each ballast load in the set of ballast loads has a different load-size to any of the other ballast loads in the set.

Optionally, said two or more ballast loads in the set of ballast loads have substantially the same size.

Optionally, the electric circuit comprises a variable current ballast load and wherein: (i) after co-ordinating switching the at least one ballast load between the off-state and the on-state with switching said primary load to its off-state the current drawn by said variable ballast load is steadily decreased; or (ii) before co-ordinating switching the at least one ballast load between the on-state and the off-state with switching said primary load to its on-state the current drawn by said variable ballast load is steadily increased.

Optionally, the ballast load is a dedicated ballast load provided only for the purpose of regulating the voltage of the electric circuit.

Optionally, the ballast load additionally functions as a second primary load when it is not functioning as a ballast load and wherein the method comprises: (i) co-ordinating switching a second ballast load between the off-state and the on-state with switching said second primary load to its off-state; or (ii) co-ordinating switching a second ballast load between the on-state and the off-state with switching said second primary load to its on-state.

According to another aspect of the invention for which protection is sought there is provided the method of voltage regulation according to any preceding paragraph when performed in a vehicle.

According to another further aspect of the invention for which protection is sought, there is provided a system comprising: a control system and an electric circuit having: (a) a generator providing an output voltage; (b) a primary load switchable between an on-state in which the primary load draws current from the electric circuit and an off-state in which the primary load does not draw current from the electric circuit; and (c) a ballast load switchable between an on-state in which the ballast load draws current from the electric circuit and an off-state in which the ballast load does not draw current from the electric circuit; the control system being configured and/or arranged for: (i) identifying that the primary load is required to be switched from the on-state to the off-state or from the off-state to the on-state; and in response thereto G) co-ordinating switching the ballast load between the off-state and the on-state with switching said primary load to its off-state; or co-ordinating switching the ballast load between the on-state and the off-state with switching said primary load to its on-state, such that the voltage of the electric circuit is regulated.

Optionally, the system of the immediately preceding paragraph is configured and/or arranged to perform the method according to any one of relevant preceding paragraphs.

According to yet another aspect of the invention for which protection sought there is provided a vehicle comprising a system for providing electrical power to components of the vehicle, the system comprising an electric circuit and the system being configured and/or arranged to carry out the method of any of the relevant preceding paragraphs.

Optionally, in said vehicle, said ballast load is provided by one or more of: (i) an electrical heater for a front windscreen of the vehicle; (ii) an electrical heater for a rear windscreen of the vehicle (iii) one or more heating elements for a driver or passenger seat; (iv) a heating element for a steering wheel; (v) an electrical heater for a side window of the vehicle; (vi) a glow plug (for an FBH and/or on a vehicle having a compression ignition engine, for example a diesel vehicle) ; and (vii) a heating element for the door mirrors.

According to a further aspect of the invention for which protection sought there is provided a program for a control system configured and/or arranged, such that when the program is running on one or more processors of the control system, the control system is capable of performing the method according to any of the above relevant preceding paragraphs.

According to yet an even further aspect of the invention for which protection sought there is provided a communications protocol for use in a data network comprising: a first control unit and a second control unit, the first and second control units being communicatively coupled via said data network, the first control unit for switching a first load on or off; and the second control unit for switching a second load on or off, wherein the communications protocol comprises: the first control unit: (i) determining a delay time; (ii) reading the real time off its clock; (iii) determining a designated time based upon said delay time and said real time; (iv) sending a message via said data network to the second control unit instructing the second control unit, at the designated time, either to switch the second load on or to switch the second load off; and (v) instructing a counter-timer within the first control unit, at the designated time, to switch the first load on or to switch the first load off, and thereby at the designated time the first and second control units switch the first and second loads respectively according to the instruction and in co-ordinated synchrony with one another.

According to yet another further aspect of the invention for which protection sought there is provided a vehicle comprising: a data network, a control system, and a system for providing electrical power to electrically-powered components of the vehicle including a primary load and a ballast load, wherein the system for providing electrical power to electrically-powered components of the vehicle comprises an electric circuit; wherein the control system comprises a first control unit for the primary load and a second control unit for the ballast load; wherein the control system is configured and/or arranged to carry out the communications protocol according to the preceding paragraph; and wherein the system for providing electrical power to electrically-powered components of the vehicle and the control system are configured and/or arranged to carry out the method according to any of the relevant preceding paragraphs.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: FIGURE 1 is diagram of a motor vehicle comprising an electrical power sub-system (not shown in Figure 1) for generating, distributing and storing electrical energy; FIGURE 2 is an electrical circuit diagram illustrating an electrical power sub-system of a motor vehicle for generating, distributing and storing electrical energy; FIGURE 3A is the electrical circuit diagram of Figure 2 illustrating switching off an electrical load; FIGURE 3B is a graphical representation of current and voltage against time for the electrical circuit shown in Figure 3A, wherein switching off the first load causes a voltage spike; FIGURE 4A is an electrical circuit diagram of a circuit according to another embodiment, additionally including three ballast loads of gradually decreasing size and illustrating the switching off of a primary electrical load and the synchronous switching on of the three ballast loads; FIGURE 4B is a graphical representation of current and voltage against time for the electrical circuit shown in Figure 4A and operated as described, wherein the voltage of the circuit is regulated when the primary load is switching off by synchronously switching on a series of ballast loads and in a step-wise manner ramping down the current drawn; FIGURES 5, 6 and 7 are electrical circuit diagrams illustrating a method of ballast loading according to an embodiment of the invention; FIGURE 8A is a graphical representation of current and voltage against time in a first load ballasting scenario; FIGURE 8B is a graphical representation of current and voltage against time in a second load ballasting scenario; FIGURE 8C is a graphical representation of current and voltage against time in a third load ballasting scenario; FIGURE 9A is the electrical circuit diagram of Figure 4A, now illustrating the switching on of a primary electrical load and the synchronous switching of three ballast loads; FIGURE 9B is a graphical representation of current and voltage against time for the electrical circuit shown in Figure 9A and operated as described, wherein the voltage of the circuit is regulated when the primary load is switching on by synchronously switching a series of ballast loads in a step-wise manner ramping up the current drawn; FIGURE 10 is schematic illustration of a control system for implementing at least part of the ballast loading or unloading methods of the disclosure to be implemented in a vehicle; and FIGURE 11 is schematic illustration of part of another control system for implementing at least part of a communications protocol that is used in methods of ballast loading or unloading according to an aspect of the disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

Detailed descriptions of specific embodiments of the methods, systems, vehicles and circuits of the present invention are disclosed herein. It will be understood that the disclosed embodiments are merely examples of the way in which certain aspects of the invention can be implemented and do not represent an exhaustive list of all of the ways the invention may be embodied. Indeed, it will be understood that the methods, systems, vehicles and circuits described herein may be embodied in various and alternative forms. The figures are not necessarily to scale and some features may be exaggerated or minimised to show details of particular components. Well-known components, materials or methods are not necessarily described in great detail in order to avoid obscuring the present disclosure. Any specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the invention.

Referring now to Figure 1 there is shown a vehicle 70. Figure 2 illustrates an electrical circuit diagram of an electrical power sub-system 10, of the motor vehicle 70. The electrical power sub-system 10 generates and stores electrical energy, which is provided to electrically-powered components within the vehicle 70. This may be referred to as the “supply”. The electrically-powered components are referred to generally as “loads” or “primary loads”. The loads collectively may be referred to as the “demand” and may, for example, include, without limitation: front lights 18, rear lights 73, a rear heating element 16 for a rear windscreen 76, a front heating element 14 for a front windscreen 74, a driver mechanism (not shown) for electrically operated windows 78, an audio system (not shown), interior lights (not shown) and the like.

The electrical power sub-system 10 of the motor vehicle 70 (also referred to herein as “electrical circuit” and “circuit” 10) comprises three parts: a generator 12; one or more primary loads 14, 16, 18; and a rechargeable battery 20.

The generator 12 optionally takes the form of an alternator 12, which generates alternating current (A.C.). The alternating current is internally (locally) rectified to direct current (D.C) such that a direct current is output by the alternator 12. A regulator is typically associated with the alternator 12 to keep the voltage output by the alternator 12 substantially constant, even though there may be changes in the speed of an engine (not shown) of the vehicle 70 and/or in the electrical load on the electrical power sub-system 10. The alternator 12 may comprise a series of windings (coils) disposed within iron cores, which may have very high inductance. The output of the generator 12 (alternator) is regulated by measuring the delivered voltage (voltage output) by the generator 12 and adjusting a control current in the electro-magnet.

As the one or more primary loads 14, 16, 18 coupled to the circuit 10 are electrically connected and switched to an on-state (turned on) or are electrically disconnected and switched to an off-state (turned off) the control current of the generator 12 is increased or decreased as appropriate. In this way, a current output by the generator 12 substantially matches a present demand for current as determined by the number, type, size and active state (on or off) of the one or more primary loads 14, 16, 18 that are coupled to the circuit 10. Flowever, the response rate of the generator 12 is limited. The rate of response of the generator 12 to changes in a present demand for current is limited: naturally by the rate at which the control current can be increased (or decreased); and deliberately, for example, to avoid “hunting”.

In the illustrated example three primary loads 14, 16, 18 (corresponding to the heating element 14 for the front windscreen 74, heating element 16 for the rear windscreen 76, and the front lights 18) are shown, but it will be understood that a number of primary loads 14, 16, 18 that is less than or greater than three may be connected to the electrical power subsystem 10. The one or more primary loads 14, 16, 18 draw (large) currents from the electrical circuit 10. The current drawn by each of the primary loads 14, 16, 18 may be about 40 Amp, about 20 Amp and about 8 Amp respectively.

As used herein the term “switched on-state” refers to a state wherein a load 14, 16 or 18 is drawing some current (i.e. it is on) and the term “switched off-state” refers to a state wherein a load 14, 16 or 18 is not drawing any current (i.e. it is off). It will be recognised that in the case of a variable load, such as the front lights 18 the “switched on-state” may cover a range of states, for example, low, medium and high, in each of which current is drawn by the primary load 18 (the front lights 18).

The battery 20 either delivers current as necessary to make up a shortfall in required current if the generator 12 is not able to meet a present demand for current, or the battery 20 draws current in order to recover its charge so that at a later date, it can deliver current. In the illustrated example, a single rechargeable battery 20 is shown. It will be appreciated that in other arrangements an electrical power sub-system 10 may comprise more than one rechargeable battery and that each such rechargeable battery may be of a similar or different capacity. The rechargeable battery 20 is referred to herein as “battery” for simplicity. In Figure 2 it is shown how three primary loads 14, 16, 18, optionally of different load-sizes are each drawing current and how the battery 20 is delivering current to supplement the current delivered by the generator 12. The term “load-size” as used herein in relation to the one or more primary loads (and later in relation to one or more ballast loads) is used generally to indicate the electrical size of the load and may refer, where appropriate, to the current drawn by the load in its “on-state” in Amps (A). Where a load has a variable size, its current draw in an on-state may be variable.

At a later time, one or more of the primary loads 14, 16, 18, for example, primary load 14, may be switched to an off-state and may cease drawing current. In Figure 3A an electrical circuit 10 is shown wherein a heater 14 for the front windscreen 74 has been switched off. In such a situation, the primary load 14 is electrically disconnected.

As used herein the term "disconnected" is typically intended to refer to electrical disconnection and is typically not intended to mean physical disconnection in the sense of a component being removed or physically detached from the circuit 10. When the primary load 14 is disconnected, it remains “wired-in” and as such or otherwise is coupled to the electrical circuit 10. In this “off-state”, the primary load 14 ceases to draw current. The primary load 14 has been switched to the “off-state”, for example by moving a switch (S14) to an open-state to create an electrical disconnection of the primary load 14. Closing the switch (S14) electrically connects the primary load 14, which is then in an “on-state”.

It will be appreciated that switching a primary load from a current drawing “on-state” to a non-current drawing “off-state” may be facilitated by physically breaking the electrical circuit using a mechanical switching mechanism, or may be facilitated by an electrical switching mechanism, for example, such as but not limited to, a relay, an FET (Field Effect Transistor), MOSFET (Metal Oxide Semiconductor Field Effect Transistor), and the like.

One or more of the primary loads 14, 16, 18 may be controlled by a user-actuated control stick or button which may directly cause a switch to open and may cause the primary load 14, 16, 18 to be switched off (or vice versa). For example, in some embodiments of vehicle, the front lights 18 and rear lights 73 may be controlled in this way.

Alternatively, one or more of the primary loads 14, 16, 18 may be controlled by a user actuated control stick or button which may, indirectly, cause the primary load 14, 16,18 to be switched off or switched on, by means of an electrically controlled switching mechanism. For example, an in-vehicle cabin control button may be provided for the rear windscreen heater 16. Flowever, changing the position of that button to an “on-position” or to an “off-position” may merely cause a request message to be issued to a control module (for example a Body Control Module BCM, or an Auxiliary Fleating Control Module AFICM) that is provided for managing those requests and for controlling, inter alia, the rear windscreen heater 16. Such a control module may run a decision protocol to determine whether the request should be accepted or denied and in response to a decision to accept the request, the control module may effect electrically controlled switching to turn-on the rear windscreen heater 16, or vice versa, to turn it off.

Further alternatively, one or more of the primary loads 14, 16, 18 may not be user controlled and may be controlled only by a controller within the vehicle 70. Such components may also serve well as ballast loads as will be described below.

Irrespective of how it has been achieved, when a primary load 14 is switched to the off-state (see open switch S14 in Figure 3A), the primary load 14 stops drawing current from the circuit 10. This results in a drop in the total current being drawn by the components of the circuit 10 (this drop in current is shown graphically in Figure 3B). Flowever, the responsetime (delay) of the generator 12, due, inter alia, to its inductance, means that the output current of the generator 12 cannot suddenly reduce to the same degree. The rate of response of the generator 12 to changes in a present demand for current is not necessarily because its regulator is slow to respond but typically because the inductance of its windings has stored electrical energy which is provided as an excess current during the response period. The excess current generated as a result of “un-loading” the primary load 14 is shared between the remaining (switched on) loads 16, 18. This causes a spike in the voltage in the circuit 10. This is referred to as a voltage spike ‘VS’ (see Figure 3B).

This voltage spike (‘VS’) may have a duration in the region of about 250ms and is very much distinguished from a load dump as described above.

As the spike voltage rises (the term “spike voltage” is used to refer to the magnitude of the voltage of the “voltage spike”), the battery 20 may be able to take some of the excess current, though it is less able to do so when it is cold, or when it is degraded by age. Although, some of the remaining “switched-on” primary loads 16, 18 may have capacitance, which limits the rate at which the voltage across the capacitive primary loads can change, the cyclic current can nevertheless have a long-term deleterious effect and cause the primary load components 16, 18 that remain connected to the circuit during the voltage spike ‘VS’ to degrade more quickly than they otherwise might.

Although, the current will reduce very quickly, in response to the change in present current demand such that the voltage spike ‘VS’ will have a very short duration (typically in the region of only 250ms), this can nevertheless disrupt the primary loads (components) that remain connected and switched on to the circuit 10.

Similarly, when a new primary load is first connected, the extra current is not immediately available from the generator 12 and this causes the supply voltage to fall. This again may be referred to as a voltage spike (or a voltage dip). When the supply voltage falls, any inductive loads connected and switched on will continue to draw the same current; any resistive loads connected and switched on draw a little less current, in proportion to the voltage; and any capacitive loads, deliver temporary current, which serves to prop up the voltage. At the same time the battery 20 may adjust its performance and if drawing current, the battery 20 may draw less current; or if delivering current, the battery 20 may deliver more current; or swap from drawing current to delivering current.

The voltage falls very quickly, as the capacitances drain, and the insufficient generator 12 current is shared between the resistive primary loads 14, 16, 18. The generator 12 output then gradually increases, and the voltage recovers.

When a primary load 14, 16, 18 is disconnected and switched to an off-state, such that it no longer draws current, the generator 12 cannot immediately reduce its output, so a voltage spike ‘VS’ occurs (see Figure 3B). The effect of switching off a load (un-loading), which causes a short-lived rise in voltage, is similar to the voltage fall that occurs upon switching a load on (loading), but typically, the effect is more severe when un-loading, for at least the following reasons: (i) The battery 20 is better at delivering current, than it is at accepting current and therefore the battery 20 is worse at clamping voltage spikes ‘VS’, than it is at supporting voltage spikes (which may also be referred to as “voltage dips”); (ii) An Electronic Control Unit (ECU) of the vehicle 70 may be configured to detect under-voltage (which occurs during loading) and may merely become tolerant of the predicted reduced performance of components 14, 16, 18 controlled by the ECU. In contrast, an over-voltage situation caused by switching off a primary load may trigger the ECU to take default action to protect itself or to protect the connected components 14, 16, 18 it controls (for example, by temporarily switching off front lights 18 in response to an “over-voltage spike” that may occur as a direct consequence of the simultaneous disconnection (switching off) of the front and rear windscreen heaters 14, 16, in order to protect the front lights 18); and (iii) For any given primary load, the voltage spike ‘VS’ when it turns off, is larger than the dip when it turns on. This can be demonstrated mathematically by consideration of a scenario wherein, upon connecting a second similar resistive primary load, a present current demand is doubled and this causes the voltage to drop, temporarily, by half (e.g. 12V drops to 6V, which results in a change of 6V). On the other hand, disconnecting (switching off) one of two similar resistive primary loads causes the present current demand to halve and this causes the voltage to increase, temporarily, by double (e.g. 12V increases to 24V, which results in a change of 12V).

The size of the voltage step change, typically depends upon the load-size of the primary load 14, 16 18 being switched on or off (which may be referred to as a “switching load”), compared with the load-size of loads 16, 18 which remain on (which may be referred to as the “residual loads”). For example, a sudden drop in current draw of 10 Amps typically has less effect when 100 Amps is being drawn, than when only 20 Amps is being drawn. A worst-case is when all connected and switched on primary loads 14, 16, 18 are turned off together (i.e. substantially at the same time).

The size of the voltage step change also depends upon how the residual loads 16, 18 react to the change in voltage occurring as a result of loading or un-loading the switching load 14. For example, an inductive load remaining on, although it is drawing several Amps, keeps drawing that much current as the voltage fluctuates and as such can provide no help or assistance in damping the voltage change.

The present disclosure provides a method of voltage regulation of the electrical circuit 10 which reduces the effect of such voltage spikes ‘VS’. The method comprises providing at least one ballast load 16 that is coupled to the electric circuit 10.

The term “coupled” as used herein may be used to refer to an electrical load 16 that is wired to the electrical circuit 10, optionally by means of one or more wiring harnesses disposed within the vehicle 70, such that it is available to be switched on (turned on) and switched off-state (turned off). As such, the at least one coupled ballast load 16 is switchable between an electrically connected “on-state” in which the at least one ballast load 16 draws current from the electrical circuit 10 and an electrically disconnected “off-state” in which the at least one ballast load 16 does not draw current from the electrical circuit 10.

When a large primary load 14 is turned off, a set of one or more ballast loads 16, 18, which collectively draw slightly less current than the current drawn by the larger primary load, is turned on. After allowing the generator 12 to adjust to the new lower current requirement, the one or more ballast loads 16, 18 are switched to an off-state in an ordered and timed manner.

The switching off of each of the ballast loads 16, 18 can be similarly sequenced, timed and arranged, with a large ballast load turning off, having a set of smaller “sub-ballast” loads turning on, to minimise the step in current change each time.

Using a set of ballast loads, (a set may comprise a plurality of ballast loads i.e. more than one ballast load) of decreasing size, careful management of a voltage spike that would otherwise occur can be achieved.

For example, consider a circuit 10’ (see Figure 4A), in which a primary load 13 draws 8 (eight) Amps when the primary load 13 is electrically connected to the circuit 10’ and is in a switched on-state. Simply switching the load to an off-state would result in an 8 Amp drop in current drawn from the circuit 10’ and would result in a voltage spike ‘VS’ (similar to the voltage spike ‘VS’ that is illustrated in Figure 3B). In the present disclosure however, the overall change in current of 8 Amp can be more gradually achieved by ramping-down the current change, optionally in a staggered, stepwise manner and optionally, for example, in substantially uniform steps of about 1 Amp each, using a set of ballast loads 21 (see dotted ring in Figure 4A).

The set of ballast loads 21 may comprise two or more ballast loads 15, 17, 19 and in the illustrated embodiment of Figure 4A, the set of ballast loads 21 comprises three different sized ballast loads: a first ballast load 15 of about 4 Amp; a second ballast load 17 of about 2 Amp; and a third ballast load 19 of about 1 Amp. As such, the set of ballast loads 21 comprises three ballast loads 15, 17, 19, each of a different size. The three ballast loads can be arranged in a sequence of decreasing value and optionally do not have a substantially equal difference between them.

The largest of the ballast loads, the first ballast load 15, draws a current (in the on-state) that is less than the current that is drawn by the primary load 13 (in the on-state). In other words, the largest ballast load 15 has a smaller size (also referred to as “load-size”, meaning the current draw in the on-state) than the load-size of the primary load 13. (In the Figures, loads are illustrated by rectangular boxes of different size to illustrate that the loads have a different load-size. Flerein where reference is made to the “size” of a load reference is being made to the current drawn by the load and not to the physical dimension of the load component.)

Optionally, the sum of the load-sizes of each of the ballast loads 15, 17, 19 in the set of ballast loads 21 is less than the load size of the primary load 13. In this example, the primary load 13 has a load size of about 8 Amp whereas the largest ballast load 15 in the set 21, i.e., the first ballast load 15, has a load size of only 4 Amp (which optionally happens to be about 50% of the load-size of the primary load). The total load-size of the ballast load set 21 (i.e., the sum of the load-sizes of the individual ballast loads 15, 17, 19 in the set of ballast loads 21 is also optionally less than the load-size of the primary load 13 (4+2+1 < 8). This is beneficial because in order to create a gradual current ramping. The set of ballast loads 21 needs to be able to transition the large current step (the original 8 Amp step that would give rise to a voltage spike ‘VS’ if the primary load is disconnected without ballasting) by splitting it into two or more smaller steps.

In other envisaged embodiments only a single ballast load is used and its load-size is less than the load size of the primary load it is ballasting. Where the ballast load comprises a set of ballast loads, in some embodiments, the total load-size of the set is about equal to (and optionally slightly less than or slightly greater than) the load size of the primary load.

The first, second and third ballast loads 15, 17, 19 are turned off and on as necessary in a staggered manner in order to gradually ramp the current down to mitigate against a sharp drop in current draw and to thereby smooth-out the voltage spike ‘VS’. The following optionally and exemplary sequence of operations of the primary load 13 and first, second and third ballast loads 15, 17, 19 show how a single 8 Amp drop in current is manipulated into a series of 1 Amp step-changes over a slightly longer time period to thus mitigate against the occurrence of a voltage-spike ‘VS’ and thus regulate the voltage (see Figure 4B).

In Figure 4B, a graphical representation of the change in current achieved by the illustrative and non-limiting example above is shown. In contrast to the large drop in current shown in Figure 3B, switching a series of one or more ballast loads 15, 17, 19 between the on-state and the off-state in a staggered, timed and ordered sequence can result in a far more gradual, albeit stepped, change in current which can at least reduce the size of voltage fluctuations or which can eradicate a voltage spike entirely.

It will be appreciated that in practice, component tolerance and variation may mean that the primary load 13 and the one or more ballast loads 15, 17, 19 may not be exactly in the ratio 8, 4, 2, 1 and so the step-wise change in reducing current that has been described as occurring in equal 1 Amp steps would more likely occur in unequal steps, but nevertheless, the principle holds and it can be seen how a more gradual ramping down of the current from an 8 Amp draw to a zero current draw can be achieved using a set of ballast loads.

The nominally Ί” and “2” Amp second and third ballast loads may be actually 1.4 Amp and 2.4 Amp second and third ballast loads respectively, making a total of 3.8 Amp. The “small” ballast loads may in fact have a larger size than the nominally “4” Amp “large” first ballast load, which may only be a 3.6 Amp load. If so, it is envisaged that in some embodiments, one or more portions of the above or a similar ballasting sequence may need to be reversed, so that the progressive change in current is nevertheless a gradually decreasing current or may be skipped, for example if the change in current would anyway be acceptably small.

In other embodiments the ratio of the total load size of the one or more ballast loads to the load size of the primary load may be different to that of this exemplary embodiment. In other embodiments, a set of ballast loads may comprise two or more ballast loads. In some embodiments, two or more ballast loads of a set may actually have a similar load size, and may be used in combination and in the alternative to one another in dependence upon system requirements.

It will be understood from the description of the circuit 10’ of Figure 4A in which three ballast loads 15, 17, 19 are utilised that the methods of the present disclosure in one aspect may provide for the ramping-down of the current drawn from the circuit 10' to be carried out over a slightly longer time period (compared to a single “step”-change, such as that shown in Figure 3B) which may allow the generator 12 to adjust its output.

The ramping-down of the current drawn from the circuit 10’ may be carried out in a step-wise manner, comprising of steps of sufficient number and of sufficiently small size that the profile of the ramped current may in fact be considered as having a generally linear profile. For example, see Figure 4B, wherein a series of incremental changes in the current tend towards a linear profile. In some envisaged embodiments, it is advantageous to minimise also the rate of change of the current into an “S”-shaped profile. In other embodiments where one or more variable ballast loads are utilised a curved profile of the change in current can be achieved.

In some embodiments, a ballasting sequence is timed and arranged to achieve a current profile wherein initially the change in the load current is slow, so the generator 12 can start adjusting, then have a period of fairly steady change, and finishing the sequence “gently” for the generator 12 to settle again. For any given current step, the voltage change depends on the remaining load and as such the ballasting sequence is optionally required to be more precise when the residual load is smaller. A timed arrangement and order of a ballasting sequence may be determined in dependence upon the performance and/or characteristics of the regulator in the generator 12.

It will be appreciated that in other embodiments the number of primary loads 13 hosted by a circuit may be greater than one and typically in a vehicle 70, a plurality of primary loads can be electrically connected to and will draw current from the electrical power sub-system 10, 10’ at any one time.

Whether a primary load is drawing current depends upon whether it is in an on-state. Whether a primary load is in an on-state may be dependent upon any one or more or any combination of factors, including, but not limited to: • the ambient temperature and environment the vehicle 70 is in (which may affect, for example whether components such as front lights 18, front and rear windscreen heaters 14, 16, front and rear windscreen wipers, door mirror heaters (not shown) and vehicle cabin heaters are required); • the operational status of the vehicle 70 (which may affect, for example whether components such as rear lights 73, reverse lights, brake lights, indicator lights, electric-power assisted steering (EPAS) system, adjustable suspension system, camera modules (used in park-aid and other vehicle systems) are required and to what extent); • the number of occupants of the vehicle, (which may affect, for example, the power consumption of a heating, ventilation and air conditioning system (HVAC system)); and • occupant activity (which may affect, for example, whether electric windows, electric sunroofs, an audio system, an in-car navigation and/or communications system is operated).

As such demand on the circuit 10, 10’ changes considerably during use of the vehicle 70. A control system 500 (see Figure 5) is provided and may in some arrangements form part of an ECU of the vehicle 70. The control system 500 is provided to control or manage loading and un-loading of the electrical power sub-system 10, of the vehicle 70. The control system 500 is configured and/or arranged to carry out the method of the present disclosure to ballast the loading and un-loading of the primary load(s) of the electrical power sub-system 10, to mitigate against voltage spikes ‘VS’.

As such a communications control link C2, C3 may exist (directly or indirectly) between electrically (and optionally software controlled) switches S16, S18 associated with loads on the circuit 10 that can act as a ballast loads 16, 18. A communications control link C1, C2, C3 may also exist (directly or indirectly) between electrically (and optionally software controlled) switches S14, S16, S18 associated with any load on the circuit 10 that is required, at certain times, to be treated, as a primary load 14, 16,18.

In some embodiments, specific ballast loads may be incorporated in order to provide dedicated, fast-switched ballast loads. In other embodiments, existing components of the vehicle 70 that are primary loads some of the time can also be utilised as ballast loads for ballasting the switching of one or more other primary loads.

In the presently illustrated arrangement, all shown loads may be primary loads 14, 16, 18 and smaller loads 16, 18 can act as ballast loads for the primary load 14. In this illustrative example, load 14 is treated as the only primary load 14. Primary load 14 has the largest load-size and therefore cannot be useful as a ballast load for either of the smaller load-sized components 16, 18. However, it can be appreciated that a typical electrical power subsystem of the vehicle 70 has many more than three electrically connected loads and in practice, even the larger primary load 14 may be useful as a ballast load for an even larger sized primary load (not shown).

In envisaged arrangements, the control system 500 is provided with data relating to one or more vehicle 70 parameters and, for example, “knows” the present status (on/off) of each primary load(s) 14 and the present status (on/off) of each ballast loads 16, 18; their load-size, and how "good” the battery 20 is. The control system 500 is additionally configured and/or arranged in such embodiments to decide: how to carry out the ballast loading; which ballast loads to use; and how precise the ballast loading needs to be in order for an appropriate smoothing effect to be achieved given the circumstances. For example, to avoid noise affecting the quality of sound output by the infotainment system, a voltage smoothing threshold may be adopted that is specific for when the infotainment system is active. In accordance with that, ballast loading and unloading may be conducted in a specific manner. However, once the infotainment system is switched off, a different, optionally less smooth, voltage smoothing threshold (requirement) may be adopted by the control system 500.

The method of the present disclosure also comprises identifying or knowing that one primary load 14 of said one or more primary loads 14, 16, 18 is required to be switched from the on-state to the off-state or that one primary load 14 of said one or more primary loads 14, 16, 18 is required to be switched from the off-state to the on-state. In other words, the control system 500 is also provided with communication or data signals so that it knows the “intended status” (going on/going off) of said one or more primary loads 14, 16, 18.

Optionally, the identification of the intended status may be performed based upon an instruction received by the control system 500 to switch a primary load component 14, 16, 18 on or off. Additionally or alternatively, the identification may be achieved by a message being sent to the control system 500 from another control module (not shown) comprised within the vehicle 70. The other control module may directly control electronic (and optionally software controlled) switching of a primary load component comprised in its system.

Consider for example a scenario wherein the heating element 14 for the front windscreen 74 is the primary load 14 and is managed by another control module such as a body control module (BCM). In response to a user actuation of an in-cabin control button, the control module (BCM) for the load 14 decides that the primary load 14 should be switched on (or switched off) and acts upon that decision. As such, one or more control systems within the vehicle 70, in this case the BCM know, in advance of switching the load 14 on or off, that switching on the load 14 or switching off the load 14 is about to occur. In other words, the intended status of the primary load 14 is known and this is optionally additionally communicated to the control system 500 so that the control system 500 can cause ballast loading to be conducted in order to regulate the voltage of the electrical power sub-system 10, 10’ of the motor vehicle 70 to protect that electrical power sub-system 10, 10’ when the BCM switches the primary load 14 on or off.

In response to identifying that switching the primary load 14 is about to occur, the methods disclosed herein require co-ordinated switching of the at least one ballast load 16 between its on-state and its off-state, with switching said one (primary) load 14 to the on-state or to the off-state, such that the voltage of the electric circuit 10, 10’ can be regulated. The manner in which at least one ballast load 16 is operated may be determined by whether a (primary) load 14 is being switched on, in which case operation of the at least one ballast load in a “ballast loading” sequence is required or whether a (primary) load 14 is being switched off, in which case operation of the at least one ballast load in a “ballast un-loading” sequence is required.

In envisaged embodiments of the disclosure, when a primary load 14 switches off, because it does not need to be on, or it must be off, only one smaller ballast load is switched on. Reference is now made to Figures 5 to 7 in order to describe and illustrate how a method of the disclosure can be effective at ballasting an electrical power sub-system 10 of a vehicle 70, when a primary load 14 is switched off, using only one ballast load 16. In some arrangements, and as shown here, the use of a single ballast load 16 is suitable to achieve a sufficient smoothing of the drop in drawn current to prevent the occurrence of a harmful voltage spike ‘VS’ in some scenarios.

Reference is now made to Figure 5 wherein the circuit 10 is shown and wherein a single ballast load 16 is shown moving between the off-state and the on-state. In this scenario the load 18 is a residual load 18 and is not active in the ballast un-loading sequence. The dotted lines are used to show the movement of the switches S14 and S16 associated with the primary load 14 and the single ballast load 16. A switch S18 associated with the residual load 18 remains closed during the illustrated sequence of ballast un-loading.

In Figure 5, switch S14 is moving from a closed position to an open position (as denoted by the arrow) as the primary load 14 is disconnected and switched into an off-state wherein it no longer draws current. The ballast load 16 is switched on in co-ordinated synchrony with the primary load 14 being switched from the on-state into the off-state.

The primary load 14 has a current of 40 Amp and the ballast load 16 has a current of about 50% of the primary load 14 i.e. the ballast load has a current of about 20 Amp. The current change will be stepped in two steps each of 20 Amp as the current draw changes from 40 to 20 to zero. The surplus current is smaller (only ever 20 Amp and not 40 Amp), and it may be shared between more loads (16, 18), which factors together and in combination contribute towards a smaller voltage spike ‘VS’.

Furthermore a time delay can be factored in at the intermediate current step (of say, 20 Amp) which gives the generator 12 further time to respond to the change in the present current demand. Though the ballast load 16 switch-off may cause a second voltage spike, it and any first voltage spike are both smaller than the single voltage spike ‘VS’ that would otherwise have occurred if the ballast load 16 had not been switched on and off in timed and co-ordinated arrangement.

In Figure 6, it is shown that the primary load 14 is in the off-state and the ballast load 16 is in the on-state. After a suitable delay, the ballast load 16 may also be switched into the off-state (see Figure 7). In this way, the ballast load 16 turning on has transitioned the current drop so that rather than the full impact of the full drop of current draw (due to the primary load 14 switching off) being felt by the circuit 10, the current drop is staged in two steps. Once the inductive energy in the generator 12 is dissipated, the output current then settles down to a lower value appropriate for the new load on the circuit 10 (from residual load 18).

It will be appreciated that timing of the switching (on or off) of the ballast-load is an important factor. As illustrated in Figure 8A, in an ideal scenario, the timing of the ballast load switching on (and all of the ballast loads where a set of more than one ballast loads is used) is completely simultaneous with the switching off of the primary load. In such an arrangement, the resultant voltage spike is significantly reduced (see VS1 in Figure 8A).

Figures 8B and 8C illustrate situations wherein the timing is out and the voltage is not regulated or is not regulated as well as it might be. In Figure 8B, both the primary load and the ballast load are switched in an overlapping manner such that they are both in the on-state for a period of time, causing an initial increase in drawn current and then a more significant current drop as they are both switched off. In Figure 8C the primary load has been turned off before the ballast load is switched on. In the scenarios of Figures 8B and 8C, the voltage spikes VS2 and VS3 are not reduced and the methods of the present disclosure have not been put into effect due to a time mis-match.

Notwithstanding the scenarios of Figures 8B and 8C, it will be recognised that perfect timing is not critical to obtaining a reduction in the voltage spike and regulation of the circuit voltage. However, the closer the timing is to perfectly simultaneous, the better.

In some situations the electrical impedance or the capitance of primary and/or a ballast loads may need to be taken in to consideration in computing the timing of the switching of ballast loads. A capacitive primary or ballast load will suddenly draw high current when switched on and then the current draw will tail off. An inductive primary or ballast load will gradually ramp up its current draw to the steady running current when it is switched on. The current draw of primary and/or ballast loads may therefore have a ramp. The rate at which current ramps may differ when the primary and/or ballast loads are switched on compared to when it is switched off and the ramp rates may be different depending upon the load. Whether a component is suitable for use as a ballast load may therefore depend upon a number of factors including: the abruptness or ramp rate of its current draw when it is switched on; the abruptness or ramp rate of its current draw when it is switched off; the abruptness or ramp rate of a primary load when it is switched on; and the abruptness or ramp rate of a primary load when it is switched off.

For example, the inrush current of a filament bulb such as front light 18 is typically 4 x a running current, and such a primary load 18 may need ballasting when it is switched from its off-state to its on-state in order to avoid a voltage dip. However, it may not need ballasting when it is switched from its on-state to its off-state because at that point, the current draw has already significantly reduced (to its running current). A further consideration is that the current draw of a primary or ballast load may vary with conditions. For example, the current draw of a glow-plug is dependent upon its temperature. If the change in current draw is significant, then this must be accounted for when it is being decided what ballast loads to use, and in what ballasting sequence.

It will be appreciated that certain ballast loads may have a necessary minimum “on” time. Additionally and as described, a primary load can serve as a ballast load for another (larger) primary load. A load that is already on, can nevertheless be used as a ballast load, by first turning it off.

It has been described above that “voltage dips” or “negative voltage spikes” can occur during loading of a circuit and although, as also described above, the effect of loading, namely a dip in voltage may be less disadvantageous, the effects can nevertheless be minimised or eradicated by ballasting a primary load that is being switched on. In a “ballast loading” scenario, it is identified that a primary load is required to be switched from the off-state to the on-state.

In response to identifying the intended status of the primary load, i.e., that it is going to be switched on, one or a set of ballast loads is switched on, in advance of switching the primary load on. The ballast load (or set of ballast loads) is again preferably smaller (in total load-size) than the primary load. When a set of ballast loads (which have a total current draw that is less than the current of the primary load to be switched on) are used, they are switched on, in an organised sequence, optionally one after the other or staggered, to gradually, in a controlled, ordered and step-wise manner, ramp-up the current demand on the circuit 10. Once the ballast load(s) are all switched on a slight delay period may be included and thereafter all of the ballast loads are switched off in co-ordinated synchrony with the switching on of the primary load.

Preferably, the term “in co-ordination with” means simultaneously with, but the term “in-coordination with” is used herein to refer to substantially simultaneously or substantially in synchrony with to a sufficient degree that a voltage spike or voltage dip can be minimised. Optionally in some embodiments, “in co-ordination with” may mean the ballast load (or set of ballast loads) and the primary load switching within the same time period, which time period is optionally between 10ms and about 100ms.

Reference is now made to Figures 9A and 9B, wherein the circuit 10’ comprises a primary load 13 which optionally may be about 8 Amp and first, second and third ballast loads 15, 17, 19 of 4 Amp, 2 Amp and 1 Amp respectively.

The first, second and third ballast loads 15, 17, 19 are turned on and off as necessary to gradually ramp the current up to mitigate against a sharp increase in current draw on the circuit 10’ and to thereby smooth-out the voltage dip that would otherwise occur if the primary load 13 is simply switched on without ballasting. The following optionally and exemplary sequence of operations of the primary load 13 and first, second and third ballast loads 15, 17, 19 show how a single 8 Amp increase in current is manipulated into a series of 1 Amp step-changes over a slightly longer time period to thus mitigate against the occurrence of a voltage-dip and thus regulate the voltage (see Figure 9B).

In Figure 9B, a graphical representation of the change in current achieved by the illustrative and non-limiting example above is shown. Switching a series of one or more ballast loads 15, 17, 19 between the on-state and the off-state in an organised and staggered sequence can result in a far more gradual, albeit stepped, change in current which can at least reduce the size of voltage fluctuations or which can eradicate a voltage dip entirely.

Once, the ballast load (or in this case the set of ballast loads 15, 17, 19) have all been switched-on, and optionally after a suitable delay if necessary, all of the ballast loads 15, 17, 19 are switched off (at least substantially simultaneously with one another) in co-ordination with the primary load being switched on. As before with ballast un-loading, when switching between the ballast load 15, 17, 19 and the primary load 13 in a “loading” scenario, timing is an important factor.

In other envisaged embodiments, two substantially equal primary loads (not shown) are switched by using pulse-width modulation (PWM). Some large loads in the motor vehicle 70 are optionally PWM-switched. Pulse width modulation refers to switching the load on and off repeatedly. As such, PWM-switched loads are on for a variable proportion of the time. The vehicle 70 optionally comprises heated door mirrors (not shown), which are one such load and for example, are sometimes on for several seconds, every thirty seconds, wherein the “several” seconds is varied with a heating demand.

In some embodiments, the switching of two PWM-switched loads is synchronised, so that a first PWM-switched load switching to an off-state ballasts a second PWM-switched load turning to the on-state. In certain embodiments where the first and second substantially equal PWM-switched loads each have a 50% duty cycle, the first load turning on additionally ballasts the second load turning off and there is no un-ballasted switching.

In yet other envisaged embodiments, a large load (optionally between about 20 Amp and about 40 Amp) that is a naturally split-load with a single control, is modified to enable separate control of each of the split-loads. For example, in one embodiment, the heating element 14 for the front windscreen 74 of the vehicle 70, which typically comprises a left-side heating element disposed within the left-side of the front windscreen and a right-side heating element disposed within the right-side of the front windscreen switched on and switched off together, are modified for separate control. This may be achieved, for example, by adding a second switching device such as a relay or in other embodiments where two switching devices (for example relays) are already used, by adding a second ECU output. This enables the ECU to independently control and switch the left-side heating element and the right side heating element, so that they can be switched sequentially and either ballast one another and/or provide separate load ballasts for other components within the vehicle 70.

It will be appreciated upon reading the foregoing that various changes may be made within the scope of the present invention, for example, in other embodiments of the invention it is envisaged that the ballast load or a set of one or more ballast loads may be selected from a range of electrically-powered components within the vehicle 70. Advantageously, a switched load may be preferably utilised as a ballast load for another electrically-powered component (primary load) if that switched load: • is switched electronically (rather than by a user or in dependence upon a condition); • is operated by a sensor signal instructing (requesting) the ECU to do so; • has a known current; and • can be delayed, on or off, by a second or more, without it being obvious or noticeable to a user of the vehicle 70.

As used herein the term “noticeable to a user” may encompass “noticeable to other users”. The term “noticeable to a user” is not necessarily limited to being visually noticeable to a user (such as a light), but for example, may include audibly noticeable (such as a beep), and noticeable by contact (such as a haptic warning, a vibration, or change in temperature). In so far switching on a load would cause a noticeable change that can be detected within the short time period it would be on for, that load may not be suitable as a ballast load. A load that when switched on (or off) causes a significant or noticeable noise, vibration, sound and/or other effect that can be sensed or detected by the user or another user of the vehicle may not be used as a ballast load. For example, it is undesirable to use brake lights as ballast loads.

Optionally, “non-visual” components that may serve well as ballast loads include, without limitation: the heating element(s) 14 for the front windscreen 74; the heating element(s) 16 for the rear windscreen 76; one or more heating elements for a driver or passenger seat; a heating element for a steering wheel; one or more glow plugs that may be used on a Fuel Burning Fleater (FBFI) and/or on a vehicle comprising a compression ignition engine (diesel powered vehicle); and one or more heating elements for the door mirrors.

Additionally, some types of electronically-controlled glow heater are fully variable, and their switching on and off for short periods (1-2 seconds maximum) is not obvious (noticeable) to the user of the vehicle 70 and so these and similar components, such as glow plugs for an FBFI are used as variable ballast loads in some embodiments of the invention. Such a variable ballast load offers beneficial performance because it can be switched abruptly and in co-ordination with switching a primary load, and (before or after) ramped slowly thus smoothing current gradually and completely (or near completely removing) a voltage spike or voltage dip.

The methods of the present disclosure also include using as a ballast load, a load that is already on, performing its normal function. This is achieved by turning the ballast load off, just before the ballast switching event; and then switching the ballast back on in coordination with switching the primary load to the off-state. As such a ballast load in an on-state can be used in a ballast un-loading scenario by turning it off just before the switching event, allowing the generator 12 to settle; performing the simultaneous (co-ordinated) switching event; and then in this case, leaving the ballast load on afterwards.

In a further aspect of the present disclosure a method, system and control algorithm is provided to facilitate efficient communication between a control system 500 which manages the ballast loading and ballast un-loading methods described herein.

As discussed above, co-ordinating the opposite switching of the ballast load and primary load is important. Primary and ballast loads which must be operated substantially simultaneously are required to be synchronised within a time period that is shorter than the response time of the generator 12, otherwise the voltage spike ‘VS’ will not be shortened. Additionally, loads which must be operated substantially simultaneously should, preferably, be operated sufficiently closely in time to one another that natural capacitances of the electrical power sub-system 10 keep the electrical power sub-system 10 steady so the voltage spike ‘VS’ is lower.

Optionally, ballast loads of a set that are operated in a timed and ordered sequence are required to be operated with a sufficient, but preferably minimised time spacing between to enable the generator 12 to adjust to the graduated change in current being effected.

Components (loads) in a vehicle 70 that are suitable for use as ballast loads are typically operated by Electronic Control Units (ECUs), sometimes via relays (or other suitable electronic switches such as FETs), which react to electrical input signals to effect switching. Whilst small delays are acceptable in still achieving co-ordinated switching of primary and ballast loads, there is nevertheless a necessity to switch primary and ballast loads very close together. In many scenarios, the primary and ballast loads will be operated by different ECUs and this can give rise to difficulties. ECUs in a vehicle 70 typically communicate via serial data buses. Messages sent via the serial data buses are constrained by loading (message rate), and latency (message delay). The latency can be variable dependent upon the traffic on the serial data buses.

To minimise cost and design change, it is desirable if existing systems can be utilised without significant modification in order to facilitate performance of the new ballasting techniques described above.

In the present disclosure methods of communication via a serial bus network utilising two or more ECUs are provided. In embodiments described below, the two or more ECUs may be required to share information, so they each have a knowledge of real time or may use dedicated counter-timer features, to switch outputs at precise times. As used herein, the term “real time” which is circulated around the ECUs on the vehicle for load-ballasting may not correlate to or have a useful relationship with, for instance, Greenwich Mean Time.

In a first embodiment consider, two loads: a primary load; and a single ballast load, that are switched by different control modules, for example a first Electronic Control Unit (ECU) ‘A’ for the primary load and a second ECU ‘B’ for the ballast load (see Figure 10).

In a peer-to-peer protocol for achieving the co-ordinated switching, the first ECU ‘A’ sends a message to instruct the second ECU ‘B’ when to switch the ballast load. The first ECU ‘A’ would know in terms of data, how long the second ECU Έ’ will take to process that message; and would know in real-time, when that message is actually sent. The first ECU ‘A’ will then know when the ECU ‘B’ will execute the switch of the ballast load and can coordinate the switching of the primary load accordingly.

In a further embodiment, a master-slave protocol for achieving the co-ordinated switching is utilised, in which, a master ECU tells each of the first ECU ‘A’ and the second ECU Έ’ when to switch the primary and ballast loads. The master ECU does this using a single message. Assuming that the first ECU ‘A’ and the second ECU Έ’ are on the same serial data bus, then the single message will reach the first ECU ‘A’ and the second ECU Έ’ at the same time. However, the first ECU ‘A’ and the second ECU Έ’ would then have to process messages with the same delay in order for the switching of the primary load and ballast load to be co-ordinated. Disadvantageously a significant difference between the processing delay of the first ECU ‘A’ and the processing delay of second ECU ‘B’ could result in the switching of the primary and ballast loads not being optimally co-ordinated. However, co-ordinated switching may be achievable by this method.

The master-slave type protocol may be utilised in some embodiments even when a system “master” (for example a control system 500) is controlling a load i.e., the system master is controlling a second ballast load. In such an arrangement, it is envisaged that the master would delegate the issuing of a command to start switching to the second ECU ‘B’. The second ECU Έ’ would message the first ECU ‘A’ and then the second ECU ‘B’, the master and the first ECU ‘A’, would all react to the message. In certain arrangements, this communication protocol may be acceptable and may provide sufficiently co-ordinated switching of loads that the load ballasting techniques described above can be carried out effectively.

However, in a further embodiment of the present disclosure a more precise communications protocol is provided. A first ECU ‘A’ is illustrated in Figure 11, in which a microprocessor is provided which has a repeated cycle (referred to herein as “main processor cycle”). During the main processor cycle, the microprocessor reads inputs, processes them, then drives outputs, for example, switches loads. A cycle time of the repeated main processor cycle may be padded or clocked, so that the main processor cycle runs at a constant rate each and every time it is repeated.

When the first ECU ‘A’ is required to carry out actions at a rate that is faster than the rate at which the main processor cycle is repeated, a Counter-Timer provided inside the microprocessor is used. For example, to switch an output at 100 Hertz and 20 % duty, a count from 0 to 100 at a rate of 10 kHz is carried out and the output switched ON” at a count of 0, and “OFF” at a count of 20.

The first ECU ‘A’ can be interrupted, for example, by a CAN transceiver (not shown), that listens for a particular message on the ECU’s serial data bus. As such, normal behaviour of the first ECU ‘A’ can be interrupted to cause the first ECU ‘A’ to carry out a particular action. The first ECU ‘A’ can also be prompted to react suddenly to an event rather than waiting for the point in the main processor cycle when an input would normally be read.

In the further embodiment, a second ECU ‘B’ (not shown in Figure 11) is similarly configured to the first ECU ‘A’. When the first ECU ‘A’ has a requirement for the second ECU Έ’ to switch the ballast load, so that the switching of the primary load controlled by the first ECU ‘A’ can be co-ordinated with switching the ballast load controlled by the second ECU ‘B’:

The first ECU ‘A’: (vi) Reads from its database, a worst-case delay time (M + N) and optionally adds a margin to generate a delay factor ‘X’; (vii) Reads the real time T off its clock; (viii) Sends a message on the serial data bus to the second ECU Έ’ instructing the second ECU ‘B’ to switch the ballast load at a “designated time” (T + X); (ix) Instructs its own Counter-Timer feature to switch the primary load at the designated time (T + X); and

The second ECU ‘B’: (i) At time T + M, with the bus becoming free, receives the message from the first ECU ‘A’; (ii) At time T + M + N, reaching the relevant point in its main microprocessor cycle, instructs its Counter-Timer feature to switch the ballast load at the designated time (T + X); then

At the designated time (T + X), the Counter-Timers of both the first and second ECUs ‘A’ and ‘B’ switch their loads, (the primary and ballast load respectively).

In this way, the primary and ballast loads are switched simultaneously and in synchrony with one another irrespective of the time taken to send and receive the message (providing the communication time does not exceed the delay factor ‘X’ (the worst case message delay time plus the added margin)).

Optionally, throughout the messaging protocol described above, another ECU or one of the first or second ECUs ‘A’, Έ’, may send out time-stamp signals as “interrupt” messages. Optionally, time-stamp signals may be sent at a rate of once per second, other send rates for time-stamp signals may be appropriate. The first and second ECUs ‘A’, ‘B’ upon receiving the time-stamp messages would act immediately on the interrupt and immediately reset a clock. In this way synchronisation of the Counter Time Function can be achieved.

In some embodiments and in dependence upon the capability of the two of more control units (ECU ‘A’, ECU ‘B’) controlling the primary and ballast loads coupled to the electrical power sub-system, several commands, or indeed the commands for a whole ballasting sequence are stored in the appropriate ECUs (the first and second and other ECUs). The ECUs all carry out their actions at the “designated time”, with no further communication being necessary.

It will be appreciated that, whilst the messaging protocol described above, that permits coordinated or simultaneous operation of devices without necessarily requiring simultaneous sending or receiving of command signals, has particular benefit in conjunction with switching the operation of ballast loads with primary loads to reduce or mitigate against voltage spikes or voltage dips, the messaging protocol may have advantageous application in other areas.

For example, international regulations require vehicles to be equipped with a control which, when activated, flashes the left and right directional signals (indicator lights), front and rear, all simultaneously and in phase with one another. Typically, dedicated wiring is provided to achieve this. Flowever, the messaging protocol disclosed herein permits the co-ordinated and simultaneous switching on of the indicator lights and hazard lights on the corners of vehicle without the need for dedicated wiring. Many other applications of this messaging protocol may be found, and in some applications outside of vehicles, the messaging protocol may also be advantageous.

Conversely, the messaging protocol described herein may be utilised to allow an ECU to report the exact time it saw or received a signal, even though that ECU may not be able to communicate that report immediately.

It will be appreciated upon reading the foregoing that various changes may be made within the scope of the present invention, for example, in other embodiments of the disclosure, the first and second ECUs ‘A’ and ‘B’ that control the primary load and the ballast load respectively are on different serial data buses. This may be the case where a controller area network (CAN) is used. The principle described above may operate in this scenario, optionally with a time-signal being passed over in the form of a time-signal message. When an ECU receives the time-signal message, it must process it immediately, using an “interrupt”.

Optionally, when an ECU resets its clock based upon receipt of a time-signal message with a time-signal “T”, the ECU may actually reset its clock to “T + t”, wherein “t” is the time the ECU knows it takes itself, to carry out the clock resetting activity.

In envisaged arrangements, ECUs on a bus, may already synchronise an internal clock frequency, so that the bus signals are at the same frequency. In other embodiments, the interval between time signals could be used to trim the speed of the clock, depending on the adjustment which was needed when the last time-signal was received.

In envisaged embodiments one or more ECUs only ballast their own loads, and use their normal output scheduling to time the switching of the loads that they control.

In other embodiments two or more ECUs include Counter-Timers on their outputs, so that they can synchronise their own loads.

In yet further embodiments one or more ECUs is configured and/or arranged to ballast primary loads controlled by other ECUs in a co-ordinated manner.

In the preceding description specific reference is made to vehicles and specific benefits can be gained when the methods of the disclosure are applied to vehicles. However, it will be appreciated that the principle and methods described herein may find advantageous application in electrical circuits outside of motor vehicles. Specifically it is envisaged that the methods described herein may be applied to any system of fast-varying current demand, with slow-varying current supply; or indeed any suitable system with an electrical power supply and electrical power demand that alters. Smooth changes of demand, mean the supply can more easily adapt to them.

The following set of numbered paragraphs comprise statements of invention: 1. A method of voltage regulation of an electric circuit having: (a) a generator providing an output voltage; (b) a primary load switchable between an on-state in which the primary load draws current from the electric circuit and an off-state in which the primary load does not draw current from the electric circuit; and (c) a ballast load switchable between an on-state in which the ballast load draws current from the electric circuit and an off-state in which the ballast load does not draw current from the electric circuit, the method comprising: (i) identifying that the primary load is required to be switched: a. from the on-state to the off-state or b. from the off-state to the on-state; and (ii) in response to said identifying: a. co-ordinating switching of the ballast load between the off-state and the on-state with switching said primary load to its off-state; or b. co-ordinating switching of the ballast load between the on-state and the off-state with switching said primary load to its on-state, such that the voltage of the electric circuit is regulated. 2. A method of voltage regulation according to paragraph 1 wherein the ballast load has a load-size that is less than the load size of the primary load. 3. A method of voltage regulation according to paragraph 1 wherein said co-ordinating switching of the ballast load is timed and/or arranged to reduce the size of any one instantaneous change in load on the electric circuit whilst at the same time facilitating a total change in load on the electric circuit that is equal to the load-size of the primary load. 4. A method of voltage regulation according to paragraph 1 wherein said co-ordinating switching of the ballast load is timed and/or arranged to enable the generator to adjust its voltage output in response to the change in load over a period of time in order to mitigate against the occurrence of a voltage spike that would otherwise occur due to switching the primary load to the on-state or to the off-state in the absence of co-ordinating switching of the ballast load. 5. A method of voltage regulation according to paragraph 1 wherein upon identifying that the primary load is required to be switched from the on-state to the off-state, said step of co-ordinating switching comprises: (i) switching the primary load to the off-state such that said primary load is no longer drawing current from the electric circuit; (ii) switching said at least one ballast load to the on-state substantially synchronously with switching said primary load to the off-state; and thereafter (iii) switching said ballast load to the off-state. 6. A method of voltage regulation according to paragraph 1 wherein upon identifying that the primary load is required to be switched from the off-state to the on-state, said step of co-ordinating switching comprises: (i) switching said ballast load to the on-state before switching said primary load to the on-state; (ii) maintaining said ballast load in the on-state for a period of time sufficient to allow the generator to adjust its voltage output in response to switching said ballast load to the on-state; (iii) switching the primary load to the on-state such that the primary load is drawing current from the electric circuit; and (iv) switching the ballast load to the off-state substantially synchronously with switching the primary load to the on-state. 7. A method of voltage regulation according to paragraph 1 wherein the ballast load comprises a set having a plurality of ballast loads and wherein upon identifying that the primary load is required to be switched from the on-state to the off-state, the method comprises co-ordinating switching all ballast loads of the set of ballast loads to the on-state with switching said primary load to its off-state; and comprises staggering switching the ballast loads of the set of ballast loads to the off-state. 8. A method of voltage regulation according to paragraph 7 wherein staggering switching the ballast loads of the set of ballast loads to the off-state comprises: (i) switching the set of ballast loads off in decreasing load-size order, starting with the largest ballast load of the set; or (ii) switching one or more ballast loads to the off-state and switching one or more other ballast loads of the set to the on-state in a timed and/or ordered sequence in order to stagger the reduction in load on the circuit in a step-wise manner. 9. A method of voltage regulation according to paragraph 1 wherein the ballast load comprises a set having a plurality of ballast loads and wherein upon identifying that the primary load is required to be switched from the off-state to the on-state, the method comprises staggering switching the ballast loads of the set of ballast loads to the on-state; and subsequently comprises co-ordinating switching all ballast loads of the set of ballast loads to the off-state with switching said primary load to its on-state. 10. A method of voltage regulation according to paragraph 9 wherein staggering switching the ballast loads of the set of ballast loads to the on-state comprises: (i) switching the set of ballast loads on in increasing load-size order, starting with the smallest ballast load of the set; or (ii) switching one or more ballast loads to the on-state and the switching one or more other ballast loads of the set to the on-state whilst switching one or more ballast loads to the off-state in a timed and/or ordered sequence in order to stagger the increase in load on the circuit in a step-wise manner. 11. A method of voltage regulation according to paragraph 1 wherein the ballast load comprises a set having a plurality of ballast loads and wherein said set of ballast loads are switched on or off in a staggered or sequential manner such that a total current draw on the electric circuit is changed: (i) in a step-wise ramped manner; (ii) in a substantially linear ramped manner; (iii) such that the rate of change of the current draw has an “S”-shaped profile; and/or (iv) in a more gradual or smooth manner than would otherwise occur if the primary load was switched either to the on-state or to the off-state in the absence of also switching the ballast load to the off-state or to the on-state. 12. A method of voltage regulation according to paragraph 1 wherein the ballast load comprises a set having a plurality of ballast loads and wherein each ballast load in the set of ballast loads has a different load-size to any of the other ballast loads in the set; or wherein two or more ballast loads in the set of ballast loads have substantially the same size. 13. A method of voltage regulation according to paragraph 1 comprising a variable current ballast load and wherein: (i) after co-ordinating switching the at least one ballast load between the off-state and the on-state with switching said primary load to its off-state the current drawn by said variable ballast load is steadily decreased; or (ii) before co-ordinating switching the at least one ballast load between the on-state and the off-state with switching said primary load to its on-state the current drawn by said variable ballast load is steadily increased. 14. A method of voltage regulation according to paragraph 1 wherein the ballast load is a dedicated ballast load provided only for the purpose of regulating the voltage of the electric circuit. 15. A method of voltage regulation according to paragraph 1 wherein the ballast load additionally functions as a second primary load when it is not functioning as a ballast load and wherein the method comprises: (i) co-ordinating switching a second ballast load between the off-state and the on-state with switching said second primary load to its off-state; or (ii) co-ordinating switching a second ballast load between the on-state and the off-state with switching said second primary load to its on-state. 16. A method of voltage regulation according to paragraph 1 when performed in a vehicle. 17. A system comprising: a control system and an electric circuit comprising: (a) a generator providing an output voltage; and (b) a primary load switchable between an on-state in which the primary load draws current from the electric circuit and an off-state in which the primary load does not draw current from the electric circuit; (c) a ballast load switchable between an on-state in which the ballast load draws current from the electric circuit and an off-state in which the ballast load does not draw current from the electric circuit; the control system being configured and/or arranged for: (i) identifying that the primary load is required to be switched from the on-state to the off-state or from the off-state to the on-state; and in response thereto (j) co-ordinating switching the ballast load between the off-state and the on-state with switching said primary load to its off-state; or co-ordinating switching the ballast load between the on-state and the off-state with switching said primary load to its on-state, such that the voltage of the electric circuit is regulated. 18. A vehicle comprising a system for providing electrical power to components of the vehicle, the system comprising an electric circuit and the system being configured and/or arranged to carry out the method of paragraph 1. 19. A vehicle according to paragraph 18 wherein said ballast load is provided by one or more of: (i) an electrical heater for a front windscreen of the vehicle; (ii) an electrical heater for a rear windscreen of the vehicle (iii) one or more heating elements for a driver or passenger seat; (iv) a heating element for a steering wheel; (v) an electrical heater for one or more side windows of the vehicle; (vi) a glow plug; and (vii) a heating element for the door mirrors. 20. A program for a control system configured and/or arranged, such that when the program is running on one or more processors of the control system, the control system is capable of performing the method according to paragraph 1. 21. A communications protocol for use in a data network comprising: a first control unit and a second control unit, the first and second control units being communicatively coupled via said data network, the first control unit for switching a first load on or off; and the second control unit for switching a second load on or off, wherein the communications protocol comprises: the first control unit: (i) determining a delay time; (ii) reading a real time off its clock; (iii) determining a designated time based upon said delay time and said real time; (iv) sending a message via said data network to the second control unit instructing the second control unit, at a designated time, either to switch the second load on or to switch the second load off; and (v) instructing a counter-timer within the first control unit, at the designated time, to switch the first load on or to switch the first load off, and thereby at the designated time the first and second control units switch the first and second loads respectively according to the instruction and in co-ordinated synchrony with one another.

Claims

1. A communications protocol for use in a data network comprising: a first control unit and a second control unit, the first and second control units being communicatively coupled via said data network, the first control unit for switching a first load on or off, the first control unit having a first clock; and the second control unit for switching a second load on or off, the second control unit having a second clock, wherein the communications protocol comprises: the first control unit: (i) determining a delay time; (ii) reading a real time off the first clock; (iii) determining a designated time based upon said delay time and said real time; (iv) sending a message via said data network to the second control unit instructing the second control unit, at a designated time, either to switch the second load on or to switch the second load off; and (v) instructing a counter-timer within the first control unit, at the designated time, to switch the first load on or to switch the first load off, and thereby at the designated time the first and second control units switch the first and second loads respectively according to the instruction and in co-ordinated synchrony with one another.

2. A communications protocol as claimed in claim 1, wherein the communications protocol comprises: the second control unit: (i) receiving the message from the first control unit; and (ii) instructing a counter-timer within the second control unit, at the designated time, to switch the second load on or to switch the second load off.

3. A communications protocol as claimed in claim 1 or claim 2, wherein the communications protocol comprises: another control unit or one of the first and second control units sending out a time-stamp signal as an interrupt message; and the first and second control units upon receiving the time-stamp signal act immediately on the interrupt message and immediately reset the first and second clocks respectively.

4. A communications protocol as claimed in claim 3, wherein the first and second control units reset the first and second clocks respectively based upon receipt of the timestamp signal to the real time plus a known time taken by the first control unit or the second control unit to carry out the clock resetting activity.

5. A communications protocol as claimed in any one of the preceding claims, wherein the communications protocol provides co-ordinated or simultaneous switching of the first and second loads without simultaneous sending or receiving of command signals.

6. A communications protocol as claimed in any one of the preceding claims, wherein the first load is a primary load and the second load is a ballast load, the primary load and the ballast load being coupled to an electrical power sub-system.

7. A communications protocol as claimed in claim 6, wherein several commands, or the commands for a ballasting sequence are stored in the first and second control units such that switching of the primary load and the ballast load can be performed at the designated time with no further communication.

8. A communications protocol as claimed in claims 5 and 6, wherein the communications protocol switches the operation of the ballast load and the primary load to reduce or mitigate against voltage spikes or voltage dips.

9. A communications protocol as claimed in claim 6, wherein the first control unit and the second control unit that control the primary load and the ballast load respectively are on different serial data buses.

10. A communications protocol as claimed in any one of claims 1 to 5, wherein the communications protocol provides co-ordinated and simultaneous switching on of indicator lights and hazard lights of a vehicle.

11. A method of regulating voltage in an electric circuit having: (a) a generator providing an output voltage; (b) a primary load switchable between an on-state in which the primary load draws current from the electric circuit and an off-state in which the primary load does not draw current from the electric circuit; and (c) a ballast load switchable between an on-state in which the ballast load draws current from the electric circuit and an off-state in which the ballast load does not draw current from the electric circuit, the method comprising: (i) identifying that the primary load is required to be switched: a. from the on-state to the off-state; or b. from the off-state to the on-state; and (ii) in response to said identifying: a. co-ordinating switching of the ballast load between the off-state and the on-state with switching said primary load to its off-state; or b. co-ordinating switching of the ballast load between the on-state and the off-state with switching said primary load to its on-state, such that the voltage of the electric circuit is regulated.

12. A method of voltage regulation according to claim 11 wherein the ballast load has a load-size that is less than the load size of the primary load.

13. A method of voltage regulation according to claim 11 or 12 wherein said coordinating switching of the ballast load is timed and/or arranged to reduce the size of any one instantaneous change in load on the electric circuit whilst at the same time facilitating a total change in load on the electric circuit that is equal to the load-size of the primary load.

14. A method of voltage regulation according to claim 11 or 12 wherein said coordinating switching of the ballast load is timed and/or arranged to enable the generator to adjust its voltage output in response to the change in load over a period of time in order to mitigate against the occurrence of a voltage spike that would otherwise occur due to switching the primary load to the on-state or to the off-state in the absence of co-ordinating switching of the ballast load.

15. A method of voltage regulation according to any one of claims 11 to 14 wherein upon identifying that the primary load is required to be switched from the on-state to the off-state, said step of co-ordinating switching comprises: (i) switching the primary load to the off-state such that said primary load is no longer drawing current from the electric circuit; (ii) switching said at least one ballast load to the on-state substantially synchronously with switching said primary load to the off-state; and thereafter (iii) switching said ballast load to the off-state.

16. A method of voltage regulation according to any one of claims 11 to 14 wherein upon identifying that the primary load is required to be switched from the off-state to the on-state, said step of co-ordinating switching comprises: (i) switching said ballast load to the on-state before switching said primary load to the on-state; (ii) maintaining said ballast load in the on-state for a period of time sufficient to allow the generator to adjust its voltage output in response to switching said ballast load to the on-state; (iii) switching the primary load to the on-state such that the primary load is drawing current from the electric circuit; and (iv) switching the ballast load to the off-state substantially synchronously with switching the primary load to the on-state.

17. A method of voltage regulation according to any one of claims 11 to 16 wherein the ballast load comprises a set having a plurality of ballast loads.

18. A method of voltage regulation according to claim 17 wherein upon identifying that the primary load is required to be switched from the on-state to the off-state, the method comprises co-ordinating switching all ballast loads of the set of ballast loads to the on-state with switching said primary load to its off-state; and comprises staggering switching the ballast loads of the set of ballast loads to the off-state.

19. A method of voltage regulation according to claim 18 wherein staggering switching the ballast loads of the set of ballast loads to the off-state comprises: (i) switching the set of ballast loads off in decreasing load-size order, starting with the largest ballast load of the set; or (ii) switching one or more ballast loads to the off-state and switching one or more other ballast loads of the set to the on-state in a timed and/or ordered sequence in order to stagger the reduction in load on the circuit in a step-wise manner.

20. A method of voltage regulation according to claim 17 wherein upon identifying that the primary load is required to be switched from the off-state to the on-state, the method comprises staggering switching the ballast loads of the set of ballast loads to the on-state; and subsequently comprises co-ordinating switching all ballast loads of the set of ballast loads to the off-state with switching said primary load to its on-state.

21. A method of voltage regulation according to claim 20 wherein staggering switching the ballast loads of the set of ballast loads to the on-state comprises: (i) switching the set of ballast loads on in increasing load-size order, starting with the smallest ballast load of the set; or (ii) switching one or more ballast loads to the on-state and the switching one or more other ballast loads of the set to the on-state whilst switching one or more ballast loads to the off-state in a timed and/or ordered sequence in order to stagger the increase in load on the circuit in a step-wise manner.

22. A method of voltage regulation according to any of claims 17 to 21 wherein said set of ballast loads are switched on or off in a staggered or sequential manner such that a total current draw on the electric circuit is changed: (i) in a step-wise ramped manner; (ii) in a substantially linear ramped manner; (iii) such that the rate of change of the current draw has an “S”-shaped profile; and/or (iv) in a more gradual or smooth manner than would otherwise occur if the primary load was switched either to the on-state or to the off-state in the absence of also switching the ballast load to the off-state or to the on-state.

23. A method of voltage regulation according to any of claims 17 to 22 wherein each ballast load in the set of ballast loads has a different load-size to any of the other ballast loads in the set.

24. A method of voltage regulation according to any of claims 17 to 22 wherein said two or more ballast loads in the set of ballast loads have substantially the same size.

25. A method of voltage regulation according to any of claims 11 to 24 comprising a variable current ballast load and wherein: (i) after co-ordinating switching the at least one ballast load between the off-state and the on-state with switching said primary load to its off-state the current drawn by said variable ballast load is steadily decreased; or (ii) before co-ordinating switching the at least one ballast load between the on-state and the off-state with switching said primary load to its on-state the current drawn by said variable ballast load is steadily increased.

26. A method of voltage regulation according to any one of claims 11 to 25 wherein the ballast load is a dedicated ballast load provided only for the purpose of regulating the voltage of the electric circuit.

27. A method of voltage regulation according to any one of claims 11 to 25 wherein the ballast load additionally functions as a second primary load when it is not functioning as a ballast load and wherein the method comprises: (i) co-ordinating switching a second ballast load between the off-state and the on-state with switching said second primary load to its off-state; or (ii) co-ordinating switching a second ballast load between the on-state and the off-state with switching said second primary load to its on-state.

28. A method of voltage regulation according to any one of claims 11 to 27 when performed in a vehicle.

29. A system comprising: a control system and an electric circuit comprising: (a) a generator providing an output voltage; and (b) a primary load switchable between an on-state in which the primary load draws current from the electric circuit and an off-state in which the primary load does not draw current from the electric circuit; (c) a ballast load switchable between an on-state in which the ballast load draws current from the electric circuit and an off-state in which the ballast load does not draw current from the electric circuit; the control system being configured for: (i) identifying that the primary load is required to be switched from the on-state to the off-state or from the off-state to the on-state; and in response thereto (j) co-ordinating switching the ballast load between the off-state and the on-state with switching said primary load to its off-state; or co-ordinating switching the ballast load between the on-state and the off-state with switching said primary load to its on-state, such that the voltage of the electric circuit is regulated.

30. A system according to claim 29 configured to perform the method according to any one of claims 12 to 27.

31. A vehicle comprising a system for providing electrical power to components of the vehicle, the system comprising an electric circuit and the system being configured to carry out the method of any of claims 11 to 27.

32. A vehicle according to claim 31 wherein said ballast load is provided by one or more of: (i) an electrical heater for a front windscreen of the vehicle; (ii) an electrical heater for a rear windscreen of the vehicle (iii) one or more heating elements for a driver or passenger seat; (iv) a heating element for a steering wheel; (v) an electrical heater for one or more side windows of the vehicle; (vi) aglow plug; and (vii) a heating element for the door mirrors.

33. A program for a control system configured such that when the program is running on one or more processors of the control system, the control system is capable of performing the method according to any of claims 11 to 27.

34. A communications protocol for use in a data network comprising: a first control unit and a second control unit, the first and second control units being communicatively coupled via said data network, the first control unit for switching a first load on or off; and the second control unit for switching a second load on or off, wherein the communications protocol comprises: the first control unit: (i) determining a delay time; (ii) reading a real time off its clock; (iii) determining a designated time based upon said delay time and said real time; (iv) sending a message via said data network to the second control unit instructing the second control unit, at a designated time, either to switch the second load on or to switch the second load off; and (v) instructing a counter-timer within the first control unit, at the designated time, to switch the first load on or to switch the first load off, and thereby at the designated time the first and second control units switch the first and second loads respectively according to the instruction and in co-ordinated synchrony with one another.

35. A vehicle comprising: a data network, a control system, and a system for providing electrical power to electrically-powered components of the vehicle including a primary load and a ballast load, wherein the system for providing electrical power to electrically-powered components of the vehicle comprises an electric circuit; wherein the control system comprises a first control unit for the primary load and a second control unit for the ballast load; wherein the control system is configured to carry out the communications protocol according to claim 1; and wherein the system for providing electrical power to electrically-powered components of the vehicle and the control system are configured to carry out the method according to any of claims 11 to 27.

36. A method, system, vehicle, program, or communications protocol substantially as herein described with reference to the accompanying figures.