GB2419241A - DC lighting system with voltage capping - Google Patents

Abstract

A dc lighting controller 10 has an input for receiving a dc drive voltage 12 and a circuit 14 for processing the drive voltage to provide a modified output, and for capping the maximum effective voltage of the modified output. The modification and capping may be performed by a pulse-width modulation circuit. The pulse-width modulation circuit may also be used to provide a dimming function. By providing a lighting controller 10 which performs voltage capping, the need for a voltage regulation circuit serving a full lighting circuit is avoided. This enables a modular system to be designed. A system using only a few controllers (30, figure 4) can then be set up as a low-cost way of providing voltage regulation, prolonging the life of the lighting units (11). The controller 10 is equally effective for implementing a system with many lighting units 11 or circuits and still avoids the need for centralised voltage regulation. The circuit 20 may also ramp the effective voltage up and down at turn-on and turn-off respectively.

Description

241 924

DC LIGHTING SYSTEMS

This invention relates to do lighting systems, for example lighting systems operated by a do generator with battery backup.

Most road vehicles and small boats (less than 30 metros) use do lighting for the majority of the on-board lighting requirements. This uses an onboard battery bank as a back up to allow lighting at all times, for example when generators or engine mounted alternators cannot be used and an onshore power supply is not available.

The simplest form of battery operated lighting system operates at the voltage output of the battery. This voltage varies when the battery is being charged. For example, the battery for a 24 Volt system will be charged at 28.8 Volts. This excess voltage has the effect of shortening lamp life dramatically as well as causing the lights to dim visibly when the batteries are taken off charge.

In more expensive lighting systems, a voltage regulator circuit may be used to provide a more stable output voltage to the lighting circuit. This introduces additional expense to the lighting system.

The use of dimmer switches in these applications is known. Most commonly, a dimmer switch for do applications uses pulse width modulation (PWM) to vary an average output voltage. PWM operates to vary the duty cycle with a relatively high frequency.

A dimmer unit allows a user to select a desired brightness, but does not provide any protection against high voltages in systems which do not have a centralised voltage regulation circuit.

According to the invention, there is provided a do lighting controller, comprising: an input for receiving a dc drive voltage; and a circuit for processing the drive voltage, to provide a modified output, wherein the maximum effective voltage of the modified output is capped.

By providing a lighting controller which performs voltage capping, the need for a voltage regulation circuit serving a full lighting circuit is avoided. This enables a modular system to be designed. A system using only a few controllers can be set up as a low cost way of providing voltage regulation, thereby prolonging the life of the lighting units. The controller is equally effective for implementing a system with many lighting units or circuits and still avoids the need for centralized voltage regulation.

The circuit may comprise a pulse width modulation circuit, and the maximum effective voltage can then be capped using the pulse width modulation circuit.

The circuit preferably comprises a voltage measurement unit for determining the do drive voltage level (for example 12V, 24V or other voltage level). This enables the required processing to implement the voltage cap to be determined.

The circuit may further comprises means for ramping the effective voltage of the modified output up at turn-on and down at turn-off.

Preferably, the controller comprises a dimmer unit, and the effective output voltage is then modified in dependence on an input dimmer setting. The dimmer function can then be implemented using the PWM control which is also used for the voltage capping function. The invention can thus use dimmer switch circuitry for implementing both a voltage cap function and a dimmer function.

The dimmer unit may have a memory for storing one or more preset dimmer settings.

These can enable one or more mood settings to be defined and stored locally in the dimmer unit.

A do lighting system of the invention uses the dimmer units of the invention, and additionally has a control unit for remotely controlling the dimmer units. The control unit can then set multiple dimmer units to their memorised mood settings simultaneously. The design remains modular, however, with each additional dimmer unit 1lavilg its owls memory to enable the mood settings to be operated without the need to change the control unit. A plurality of dimmer units may each be controlled by the control unit.

The memory in each dimmer unit can store at least two dimmer switch settings, for example one off setting and one stored brightness level. This then enables a number of lights to be switched off centrally simultaneously.

There may also be a plurality of the control units, and they may then be area control units, for example for different decks of a boat. Each area control unit is then associated with a respective group of dimmer units, and the system can then further comprise a master control unit which is able to control each area control unit.

Preferably, the master control unit can effect switching off of the dimmer units associated with all control units and can effect switching of the dimmer units associated with all control units to their respective stored brightness level.

An example of the invention will now be described in detail with reference to the accompanying drawings in which: Figure 1 shows a light controller of the invention; Figure 2 shows a first use of the light controller of Figure 1; Figure 3 shows a second use of the light controller of Figure 1; Figure 4 shows a first example of lighting system using the light controller of the invention; and Figure 5 shows a second example of lighting system using the light controller of the invention.

The invention provides a do light switch in which the do drive voltage is processed to provide a capped output. In its simplest form, the invention provides voltage regulation locally at each light switch, for protecting and prolonging the life of each lighting device. This enables a modular system to be developed, and makes voltage regulation practical even for low cost lighting installations. The invention provides further possibilities, including dimmer switch operation with shared use of circuitry and als provides a modular centralised control system.

An example of the invention will be described which combines all of these features.

However, it should be understood that simpler systems also fall within the scope of the invention.

Figure I shows an example of an implementation of the invention in the forth of a dimmer unit 10 (hereinafter referred to as a dimmer switch) for controlling a light 11.

The dimmer switch has a manual dimmer setting input 12 for operation by the user.

The setting is provided to an internal controller 14 which, in the example shown, has pulse width modulation (PWM) circuitry for modifying an input do voltage VDC, in particular to reduce the effective voltage by means of duty cycle control.

The controller receives an input not only from the manual input 12, but also from a memory 16 and from a system input CNTRL which is connected to a controlling circuit. The controlling circuit can also therefore operate the PWM circuit to provide a desired light output, in particular by instructing the controller to fetch a brightness setting from the local memory 16. The controller can also write to the memory, and the dimmer switch has an interface (not shown) allowing a user to set a dimmer brightness level in memory.

The dimmer switch may have a memory for storing one or more preset dimmer settings. These can enable one or more mood settings to be defined and stored locally in the dimmer switch.

The controller 14 implements not only a dimmer function but also implements a voltage capping function. In the example shown, the dimmer switch has a voltage measurement circuit 18 for measuring the do voltage level, and this is used to determine the PWM duty cycle required to cap the maximum voltage to the desired voltage, for example 24 Volts. The measured voltage is provided to the controller 14.

The controller 14 may also implement a ramp function, as shown schematically as 20.

Ramping of the effective output voltage at turn-on and at turn-off can also prolong the lifetime of the lighting units.

As shown in Figure 1, all circuits of the switch are powered by the dc voltage input.

The controller of the invention can be implemented in a number of different ways.

However, as shown in Figure 2, the controller 30 can be represented as a unit which receives a do voltage input "POWER" and provides a power output "LAMPS" for one or more lamps 11. The unit 30 has a dimmer control input "DIM CNTRL" which receives the input signal froth a dimmer switch 12, and also has an external control input "EXT CNTRL".

Figure 2 shows the use of the controller 30 to receive a do power voltage and provide a drive voltage to two lamps 11 which has been capped and which takes account of the input from a dimmer switch 12. In the example shown in Figure 2, the dimmer switch 12 has an on-off control 32 and a dimming control 34. As shown in Figure 2, a single dimmer switch 12 can be used to control multiple lamps.

The controller 30 of the invention can also be used simply to provide a voltage capping function. In this case, no dimming control input is provided to the unit 30, and each lamp 11 (or group of lamps) is controlled by an on-off switch 36. In the use of the controller 30 shown in Figure 3, the controller 30 defaults to an on state, namely power is supplied to the output "LAMPS". As will be shown in the examples below, the external control input "EXT CNTRL" can override this default operation of the controller 30 to provide a more flexible system.

Figure 4 shows a number of the controllers 30 of the invention used in a system with additional functionality.

Thee controllers 30 are shown, each of which implements local control of a lamp 11 (or group of lamps) by means of a local dinner switch 12. In addition, all three controllers 30 are also connected to a mood control unit 40, and this mood control unit connects to the external control input of each controller 30.

The mood control unit 40 instructs one or more of the controllers 30 to provide an output based on a memorised lighting level. This memorised lighting level is stored locally at each controller 30. For example, the desired output brightness may be set locally, and a control input is then provided at the mood control unit 40 to implement a memory storage function. This control input may be simply be a push button at the mood control unit. There may be many different mood settings, each of which provides desired settings for all the lamps controlled by the mood control unit 40.

The memory in each controller 30 can be implemented to reserve two memory positions for "off" and "resume" functions in addition to the multiple mood setting memory locations.

When the mood control unit 40 sends an "off" instruction, all controllers 30 are controlled to ramp the associated lamps down to an off state. When the mood control unit 40 issues a "resume" instruction, each controller 30 resumes the associated lamp or lamps to the last brightness level in place before the previous "off" instruction.

This resumed brightness level may of course be off, full brightness, a memorised "mood" level or a manually set level.

As shown schematically in Figure 4, the mood control unit 40 can receive from a user a number of controls from the interface 42. The interface 42 is shown as providing levels O to 6 and an input "R". The O input is the "off" command referred to above, the "R" input is the resume function described above, and the levels 1-6 provide the possibility of setting six different mood levels for the full lighting system.

The controller 30 of the invention can be used in a system with multiple circuits, each with different capabilities.

Figure 5 shows a system in which one controller 30a is associated with a mood control unit 40, and two other controllers 30b, 30c simply provide local lighting control. The controller 30b is associated with a dimmer switch 12, whereas the controller 30c is associated with an on-off switch 36, and therefore simply implements a voltage capping function. Figure 5 shows a load shed module which enables the complete system to be controlled from a single location. This load shed module 50 is associated with an input interface 52 which simply allows off and resume inputs to be provided. In response to an off input from the interface 52, the module 50 sends an appropriate signal to the mood control unit 40, which is then responsible for all of the controllers 30 associated with that mood control unit 40, and the module 50 also sends control signals directly to the external control inputs of the stand alone controllers 30b, 30c.

Thus, the load shed module 50 can send instructions directly to a controller 30, either being used as a dimmer unit or as a voltage capping unit, or it can send instructions to a number of controllers 30 by means of an associated mood control unit 40.

The load shed module 50 enables groups of lighting circuits to be controlled from a single point. These groups relate to different quarters of a ship, for example. There may be a number of load shed modules 50 within a complete system, and these modules 50 can also receive instructions from one another. For example, there may be three load shed modules for three different areas of the system, and a fourth "global" module which acts as a master controller to the three other load shed modules.

It can be seen that the invention provides components enabling a modular lighting system of significant complexity to be developed. However, the invention still provides an efficient implementation of a small lighting system with less control functionality.

Only one example of the controller 30 has been described in detail. It will be clear to those skilled in the art that the functions implemented by the controllers 30 can be achieved in many different ways. A number of different uses of the modular controller have been shown, but it will be understood that there are many different lighting circuit configurations which can be created using the system of the invention.

Various other modifications will be apparent to those skilled in the art.

Claims (13)

1. A do lighting controller, comprising: an input for receiving a do drive voltage, and a circuit for processing the drive voltage, to provide a modified output, wherein the maximum effective voltage of the modified output is capped.

2. A controller as claimed in claim 1, wherein the circuit comprises a pulse width modulation circuit.

3. A controller as claimed in claim 2, wherein the maximum effective voltage is capped using the pulse width modulation circuit.

4. A controller as claimed in any preceding claim, wherein the circuit comprises a voltage measurement unit for detemmining the do drive voltage level.

5. A controller as claimed in any preceding claim, wherein the circuit further comprises means for ramping the effective voltage of the modified output up at sum-on.

6. A controller as claimed in any preceding claim, wherein the circuit further comprises means for ramping the effective voltage of the modified output down at tum off.

7. A controller as claimed in any preceding claim, comprising a lighting dimmer unit, wherein the effective output voltage is modified in dependence on an input dimmer setting.

8. A lighting diminer unit as claimed in claim 7, further comprising means for storing one or more preset dimmer settings.

9. A do lighting system comprising: at least one lighting dimmer unit as claimed in claim 8; and a control unit for remotely controlling the at least one lighting dimmer unit.

lO. A lighting system as claimed in claim 9, comprising a plurality of lighting dimmer units each controlled by the control unit.

11. A lighting system as claimed in claim 9 or 10, wherein the means for storing stores at least two dimmer settings, one for enabling the control unit to switch off the lighting dimmer unit and one for enabling the control unit to switch the lighting dimmer unit to a stored brightness level.

lO

12. A lighting system as claimed in any one of claims 9 to -11, comprising a plurality of the control units, each associated with a respective group of lighting dimmer units, and wherein the system further comprises a master control unit which is able to control each control unit.

13. A lighting system as claimed in claim 12, wherein the master control unit can effect switching off of the lighting dimmer units associated with all control units and can effect switching of the lighting dimmer units associated with all control units to their respective stored brightness level.