WO2007000560A1

WO2007000560A1 - Power converter with dc-bus and multiple programmable dc outputs

Info

Publication number: WO2007000560A1
Application number: PCT/GB2005/002535
Authority: WO
Inventors: Alan Ross
Original assignee: Alan Ross
Priority date: 2005-06-29
Filing date: 2005-06-29
Publication date: 2007-01-04
Also published as: GB2441949A; GB2441949B; GB0801261D0

Abstract

A multi -charger and power converter system comprising a single mains input, a primary transformer for converting mains AC supply to a fixed DC supply, a plurality of DC -DC converters providing a plurality of outputs via a number of ports to meet the power requirements (voltage/current) of a very wide variety of electronic devices such as laptop computers that can be connected to the unit using cables with fixed or interchangeable connectors /tips as required to power or charge different laptops and other devices and with a power management system that enables numerous devices to be charged or powered directly through the multicharger unit from a single wall socket without tripping the ring mains or creating Health and Safety trip hazards from excessive numbers of trailing wires. The unit incorporates audio and visual safety alarms to indicate inappropriate or potentially dangerous use of ports and has a fail-safe mechanism to close down supply to prevent damage to devices and the unit if loads exceed the pre-specified upper 'safe' limits for any particular port.

Description

POWER CONVERTER WITH DC-BUS AND MULTIPLE PROGRAMMABLE DC OUTPUTS

This invention relates to a Power Converter Unit (PCU), which can be used during the normal operating mode of multiple mobile electronic devices, such as laptop computers, and for recharging their batteries.

Mobile electronic devices, such as laptop computers, are designed for normal operation using batteries usually fitted internally within the device. The manufacturers of these devices normally provide a power converter suitable for transforming the normal domestic mains power supply parameters into a form suitable for use not only to recharge the internal batteries but also to provide the power required for normal operation. These power converters contain an analogue transformer to reduce the normal domestic mains voltage as required.

With increasing computerisation, large numbers of laptops are now being deployed in educational establishments and other locations (eg major crime incident rooms) where there is a need for large numbers of laptops to be in use simultaneously but the physical constraints of limited power supply in such locations sometimes inhibit their optimal use. In a school environment, for example, where the number of electrical power sockets in the classroom is few, several power converters may need to be connected in parallel through a power strip or power extension to a single power socket when it is required to use a number of lap top computers simultaneously.

When the electrical supply is turned on to a power converter containing an analogue transformer an initial current surge occurs. When a number of such power converters are connected in parallel, the initial current surge is cumulative and can rise to a level which will cause the normal mains electrical supply protection systems to activate and switch off the power supply to the power converters. Also of course this arrangement is inefficient and the normal losses in each transformer are cumulative generating a

significant amount of heat; a single transformer with lower losses could be used as the basis of a power converter designed to supply multiple lap top computers. In addition the use of the laptops own power converters (via power extension sockets and power strips) often results in Health and Safety hazards resulting from numerous trailing wires and trip hazards when 15 -24 laptops are in use a classroom as is typically the case.

Other charger units are available from high street electrical retailers; these are designed for home electronics devices as a replacement for dry cell batteries. This means they generally only provide 3, 6, 9 or 12V, changed by a dial or other selector, altering the turns ratio in a transformer. These units typically, supply a single device and do not provide the voltage range to cope with the demand of the wide range of different voltages and currents required by the different laptops types They also still exhibit the same problem of excessive surges of current and Health and Safety risks of trailing wires in a classroom.

A smart battery charging system with reduced power consumption (GB 2 341 284 A) is known. This system is a set of batteries and a charger for use with a laptop. This has its own batteries, allowing for extended run time of a laptop, and the charger is designed to reduce power consumption. This charger requires a standard power supply with transformer to run it and therefore this system has the same disadvantages as those outlined above when multiple individual chargers are used in parallel to supply multiple laptop computers.

A universal power supply (US 6,459,175 Bl) is also known. It is claimed that this

can be plugged into any device and automatically supply the correct power. However, it lacks any feedback as to the current status of the device being powered or charged. In this invention the connection to the mobile electronic device is made through the battery interface, rather than the external power supply, claiming to save the need for multiple adapters. However, there is no standard for battery connectors and it is necessary to remove the battery before the charger can be used. Batteries on laptops are not intended to be removed on a regular basis and the catch holding the battery in breaks quite easily after over-use. This also leads to a complicated installation process each time the power is to be connected. Conversely, the external power socket of the invention is always easily available as it is designed to be used regularly. Again this charger is designed to be able to power only one device at a time and therefore this system has the same current surge and Health and Safety disadvantages as those outlined above when multiple chargers are used in parallel to supply multiple laptop computers.

Also known is a connector assembly for electrical signal transfer among multiple devices (US 2003/0207603 Al). This device is a connector designed to work with multiple electronic devices by utilising the battery power interface rather than the external interface, in a similar way to US 6,459,175 Bl described above. This once again has the disadvantage associated with weak battery catches and complex installation. An electrical power strip with AC to DC power supply (WO 01/43266 Al) is also

known. This provides sockets for predefined fixed DC Voltages for computer peripherals as well as AC sockets for computers or other devices. This cannot provide the wide range of voltage/current configurations needed by the number and plurality of laptop types that can be served by the present invention. It also has no audio visual warnings or failsafe cut-out mechanisms indicating inappropriate or potentially damaging use leaving the connected laptops at risk of being damaged if the provided voltage or current exceeds safe limits for that laptop.

Also known is a power supply with integrated DC supplies for external devices and universal cable (WO 2004/068324 Al). This basically replaces conventional power strips or power socket extensions by providing some fixed voltage DC sockets for peripheral devices to be fitted. This device cannot supply the varied range of voltage /current configurations needed by the number and plurality of laptop types in use. It also does not overcome the problem of excessive current surge and health and safety trip hazards arising from use of conventional power strips or power extension sockets. It also cannot provide the audio/visual warnings and failsafe cut-outs to prevent potential damage to laptops if the safe limits are exceeded.

An electrical power distribution system (US patent 5,477,091) is known which comprises a central module supplying a distribution network. This system is essentially designed for use in office blocks or industrial sites to distribute AC and DC power between offices. It does not address the problem of limited power sockets in a classroom resulting in surges of current and cannot be used in the classroom or in cabinets for overnight charging of laptops or other similar purposes as the present invention does. In the context of this application "transformer" shall include any means for changing the parameters a power supply.

According to a first aspect of the invention there is provided a power converter as specified in Claim 1.

According to a second aspect of the invention there is provided a method of powering a plurality of electronic devices from a single mains connection without generating excessive surges of current which trips off the power supply.

According to the present invention there is provided a power converter system suitable for transforming the normal domestic mains power supply parameters from a single domestic socket, in a school classroom for example, into a form suitable for simultaneously recharging the batteries for multiple laptop computers or to provide the power required for their normal use. The Power Converter Unit is provided with a series of "ports", each of which can be separately configured or configured in user selectable groups to provide the specified power parameters for the connected device or devices. It is also provided with adapters and connectors to cater for wide variety of types and polarity of power connector provided by the manufacturers of the laptop computers.

Each port also has visual outputs to indicate the charging status (i.e. uncharged, partially charged and charged) of the rechargeable battery of the laptop computer or other device. Ports can also have an audio and visual output to give warning of incorrect usage or connection from that port to the laptop computer or other device and a failsafe cut-out mechanism to shut down the port if the specified safe load is exceeded. LED's are provided on the unit itself and in addition, external LEDS can be provided as remote indicators of charging status. Connectors at the rear of the power converter system permit the output voltages to be configured by a computer

using suitable software. Connectors at the rear enable connection of an external set of

LED' s and a remote configuring module, which module enables the power converter itself to be placed within a cabinet or attached to the inaccessible underside of furniture, for example.

A series of electrical connectors and cables is provided to link the power converter system to any proprietary laptop computer or other device to be powered or charged from the system.

The Power Converter Unit can use a small number, which may be one, of electrical transformers to supply power to multiple laptop computers using a system of standard cables with inter changeable tips (to suit each laptop type/model). This unit is very efficient and the current surge on switching on the supply is much reduced compared with multiple chargers connected in parallel. This makes it possible for multiple laptop computers to be powered or charged from a single standard 13 -amp socket without tripping the ring mains as would occur if the laptops own chargers were used. The Power Converter Unit is very quiet in operation, making it ideal for use in classrooms or offices. The fact that individual power converters are not required for each laptop significantly reduces the numbers of trailing wires and trip hazards and hence reduces Health and Safety risks in schools.

The basic Multicharger / Power Converter Unit can be deployed /used in a number of ways as follows and some typical situations and illustrative embodiments of this invention are shown in figures 1-5 and outlined below. 1 As a Multicharger unit to charge up laptop batteries within a mobile IT suite or laptop storage cabinet. Figure 1 shows the unit placed in the rear compartment of a laptop cabinet 1. AC Power 2 is supplied to the unit 3 and it provides, via its 8 or 12

ports and suitable cables 4 the required voltage /current combinations as required by each individual laptop 5 stored in the cabinet. Depending upon the particular model of Multicharger unit used and the power needs of the laptop types connected to it, varying numbers of laptops (eg 8, 12 etc) can be charged from a single Multicharger Unit.

2 As a standalone power supply for laptops in use in a classroom. Figure 2 shows the Power Converter Unit 6 with cooling fans 25 connected to a single AC power socket 24 in a classroom. The unit then supplies the required power to allow a number of (in this case, eight) different laptops 7-14 to be operated without the need for their individual transformers. The power converter unit can either be placed in the middle of a large table with individual cables 15-22 radiating out from the unit ports to each laptop or it can be placed in the centre of a long bench table with cables of different lengths coming out from each side to serve a number of laptops to each side of the unit. LEDs 23 provide information on the status of each port and the device connected to it.

3 As an integral part of furniture to create an IT desk or table. Figure 3 shows the Power Converter Unit 26 attached with brackets to the underside of a desk or table 27. A single cable provides AC power to the unit and the unit then is used to deliver the required voltage/current configuration as required for the individual laptops to be used on that table. The unit can be configured with proprietary software via a remote panel 28 easily accessible from the top of the table. The cables (from the individual ports (typically eight or twelve) on the power converter unit are run along the underside of the table to flap covered holes 29-36 where they can be accessed for connection to laptops as and when necessary. By using a variable tip system at the end of each cable, the cables can be standardised with only the appropriate tips needing to be changed for whichever laptops are to be used. The power requirements (voltage/current) for the ports serving each laptop can be set via the proprietary software using the remote connection which is linked to the Power Converter Unit and enables it to be easily reconfigured for different laptop types or other low voltage electrical devices as needed.

4 As a standalone laptop battery charger. Figure 4 shows that another possible use of the device is to charge up laptop batteries remotely. This consists of the electronics from the Power Converter Unit being placed in a housing 37 powered by a connection to the AC mains 38 and attached to a universal stall or charging bay arrangement 39 where varying numbers of laptop batteries (not shown) could be charged up outside the laptop while the laptop itself is in use elsewhere powered by another multicharger unit. The appropriate connectors (not shown) would need to be used within each stall for each type of laptop battery. The Power converter unit would operate as it does in the laptop cabinets/mobile IT suites supplying the required voltage/current as appropriate to charge up each laptop battery.

It is also possible to employ .these principles in other related products to power other small low voltage electronic devices. It would be possible for example, to use a modified existing power supply to power additional devices. This would mean a situation normally requiring many power sockets and numerous individual chargers for different devices could get all the required power from a single socket by powering peripherals from a modified version of an existing transformer. Smaller Power Converter Units integrated into laptop transformers and compatible with

mobile devices such as mobile phones and Personal Desktop Assistants (PDAs), would allow a single socket to power all personal electronic devices. This would be especially useful when travelling internationally as it reduces the need to carry numerous individual transformers and plug adapters for each electronic device and would mean only one socket/plug adaptor would be required to power/charge all devices when travelling abroad. (Figure 5 illustrates its possible use in such a way and Example 2 below illustrates use of the invention for such a purpose).

5 As a convenient multicharger for international travellers. In Figure 5, AC supply is provided via a single adapter plug 40. The laptops own transformer 41 (redesigned to incorporate the multicharger technology of the present invention) now splits the available power permitting adequate power to be delivered to the laptop 43 via its power cable 42 and diverting part of the power to serve a number of ports (only four are shown here 44-47). These can either deliver fixed preset (manually or via software) voltages and DC current or can be adjustable values set via a toggle switch 48 with values displayed 49-50 beside each port. The ports can power/charge up all the various devices typically carried by business travellers when travelling overseas such as electric toothbrush 51, mobile printer 52, mobile phone 53, pda 54 etc.

This basic approach of diverting excess power to power other devices could also be applied to desktop computers by converting the multicharger device into a pc card (not shown) which could be inserted into the desktop pc card slots manage the incoming power supply and to make part of it available for peripheral devices so that all peripherals can be connected through the computer (via a number of external ports) rather than each device requiring its own transformers and mains power connections, thereby eliminating the tangle of wires, extension leads and fire risks which currently exist under/beside most desks where desktop computers are used.

Specific embodiments of the invention in terms of block diagrams and circuit diagrams will now be described through four examples. The first 2 examples (examples 1 and 2) show a design based on firmware /software control of the power supplied using a processor to control many of the functions and operations required. The second 2 examples ( examples 3 and 4 ) show a design based more on control via hardware and electronic components. In all 4 examples mains electricity is converted to direct current using one or more Power Supply Units (PSUs) such as a Power Research Technologies PRN300M-8 unit, (not shown) which can operate on ether 11Ov or 24Ov supply . This would allow mains electricity to vary from 110V to 240V without affecting the multi charger unit .

Examples 1 and 2, (based on software /firmware controls) comprise a standard multicharger & power converter unit for use in classrooms or offices and a smaller, more portable power converter unit for use by international travellers. Example 1, the standard multi charger, is represented by Figures 6-9, which show schematic diagrams of the key elements of the power converter system. Figure 6 shows the processor and interface. Figure 7 shows two sets of the core circuit. This core circuit can be repeated as many times as needed depending upon the number of ports to be served. Figure 8 shows the output processing and audio/visual outputs. Figure 9 shows the current limiter circuit as a fail safe device to prevent damage to the connected devices or the unit. The communications connections between the elements on different Figures are shown alphabetically (e.g. "a" in Figure 6 connects to "a" in Figure 7 and "c" in Figure 6 connects to "c" in Figure 8 etc).

In example 1 a fixed direct current supply 55 is provided to known DC-DC converters 56, which regulate the output voltage. The output from these can be adjusted by a processor 57. This processor 57 sends a signal to digital potentiometers 58, to adjust their resistance settings to change the resistance in the circuit in order to adjust the output from the digital DC-DC converters 56. This programmed potential set individually or as a group by the processor 57 for each output port 62 can be reset to new values through a standard external interface 59 by a personal computer (not shown) using proprietary software. These settings are stored and retained in memory even when the power converter system is disconnected from the mains electricity.

Once the potential is set in this way, current sensors 61 detect the current being drawn by any device attached to a port. These current sensors 61 send an output current signal f through a current limiter 66 and as a current signal h through a multiplexer 60 to the processor 57. The multiplexer switches the individual port outputs to the processor 57 one at a time and in sequence. The current limiter 66 limits the current up to a specified value for external device safety, causing port shutdown 67 if current is above the limit. The output voltage signal g is also sent to the processor 57 through a multiplexer 60.

The output ports 62 supply the preset potential 63 to the connected device through cables (not shown) with appropriate connectors at each end to link the port to the device. An external device (not shown) may send and receive a signal d and from the processor 57 to indicate any special configuration which might be needed from any device. Information is received by the processor 57 and after comparison with predefined criteria and further processing 64, audio/visual warnings 65 are initiated as necessary.

A signal may be sent from an output port to a connected device to read the said device's power requirements and the power output from the port may be set to match the said requirements of the device.

Example 2 illustrates another application of the invention and Figures 10-13 show schematic diagrams of a more portable power converter system. Figure 10 shows the possible interfaces, both manual 77 and via proprietary software 70 (e.g. a microprocessor). Figure 11 shows two different versions of the core circuit, one with fixed output voltages and one permitting voltages to be adjusted. These core circuits can be repeated as many times as needed depending upon the number and type (fixed or variable voltage) of ports to be served. The output processing and visual outputs are represented in Figure 12. Figure 13 shows the current limiter circuit as a fail-safe device to prevent damage to the unit. The communications connections between the elements on different Figures of Example 2 are shown alphabetically (e.g. "a" in Figure 10 connects to "a" in Figure 11 while "b" in Figure 10 connects to "b" in Figure 12).

The mains electricity, which is typically 110 volts or 240 volts alternating current is converted to direct current 66 using an existing laptop charger (not shown). Part of the power is allowed to pass straight through 72 the unit to power the laptop and a small part of it is diverted to power other devices connected to the ports 73. This provides a fixed direct current (DC) supply 66 to known DC-DC converter 68, which regulates the output voltage. Depending upon the core circuit used, the voltage may be permanently fixed using a fixed voltage regulator 69 or left variable to be set as required. In the variable version of the core circuit, the resistance setting on the digital potentiometers 67 is adjusted manually or via software to change the resistance in the circuit to adjust the output from the DC-DC converter 68. This means the output ports 73 will continue to supply the programmed potential 74 once it has been set.

Once the potential is set in this way, current sensors 71 detect the current being drawn by any device attached to a port. These current sensors 71 send an output current signal c to the software 70 through a current limiter 78 and a multiplexer 80. The multiplexer switches the individual port outputs to the software 70 one at a time and in sequence. The current limiter 78 limits the current up to a value for external device safety, causing port shutdown 79 if current is above the limit. The output voltage signal d is also sent to the software 70 through a multiplexer 80.

The output ports 73 supply the preset potential 74 to the connected device through cables (not shown) with appropriate fixed or interchangeable connectors/tips at each end to link the port to the device.

Information is received by the software 70 and after comparison with predefined criteria and further processing 75 audio/visual warnings 76 are initiated as necessary.

Examples 3 and 4 show embodiments of the invention where most of the controls and functions are undertaken via hardware and components. For convenience and easier comparison, the same two units as used in earlier examples (ie a standard power converter unit and the second a smaller, more portable power converter unit) are described as Examples 3 and 4 respectively . Example 3 is represented by figures 14- 16, which show schematic diagrams of the key elements of the power converter system. Figure 14 shows the processor and interface. Figure 15 shows 2 sets of the core circuit. This core circuit can be repeated as many times as needed depending

upon the number of ports to be served. Figure 16 shows the output processing and audio/visual outputs. The communications connections between the elements on different figures are shown alphabetically (e.g. "a" in figure 14 connects to "a" in figure 15 and "c" in figure 15 connects to "c" in figure 16 etc).

The mains electricity ( typically 11Ov or 24Ov) is converted to direct current using one or more Power Supply Units (PSUs) such as Power Research Technologies PRN 300M-8 units (not shown). This provides a fixed direct current supply 81 to known digital switch mode transformers 82, which regulate the output voltage. The output from these can be adjusted by a proprietary processor 83. This processor 83 sends a signal to the known digital potentiometers 84, to adjust their resistance settings to change the resistance in the circuit in order to adjust the output from the digital switch mode transformers 82. This programmed potential set by the processor 83 for each output port 87 can be reset to new values through a standard external interface 85 by a personal computer (not shown) using proprietary software. These settings are stored in memory even when the power converter system is disconnected from the mains electricity.

Once the potential is set in this way, the known current sensors 86 detect the current being drawn by any device attached to a port. This information is processed 90 and used for the audio and visual outputs 89 The output ports 87 supply the preset potential 88 to the connected device through cables (not shown) with appropriate fixed or interchangeable connectors /tips at each end to link the port to the device.

Example 4 illustrates another hardware and component controlled application of the invention and Figures 17-19 show schematic diagrams of a more portable power converter system. Figure 17 shows the possible interfaces-Manual 102 and via proprietary software 95. Figure 18 shows 2 different versions of the core circuit, one with fixed output voltages and one permitting voltages to be adjusted These core circuits can be repeated as many times as needed depending upon the number and type (fixed or variable voltage) of ports to be served. Figure 19 shows the output processing and visual outputs. The communications connections between the elements on different figures are shown alphabetically (e.g. "a" in figure 17 connects to "a" in figure 18 while "b" and "c" in figure 18 connects to "b" and "c" in figure 19)

The mains electricity is converted to direct current 91 using the existing laptop charger (not shown). Part of the power is allowed to pass straight through the unit to power the laptop and a small part of it is diverted to power other devices connected to the ports 99. This provides a fixed direct current (DC) supply 91 to known digital switch mode transformers 93, which regulate the output voltage. Depending upon the core circuit used, the voltage may be permanently fixed using a fixed voltage regulator 94 or left variable to be set as required. In the variable version of the core circuit, the resistance setting on the potentiometers 92 is adjusted manually or via software to change the resistance in the circuit in order to adjust the output from the digital switch mode transformers 93. This means the output ports 99 will continue to supply the programmed potential as set. Once the potential is set in this way, the known current sensors 96 detect the current being drawn by any device attached to a port. This information is processed 101 and used for the visual outputs 100

The output ports 98 supply the preset potential 99 to the connected device through cables (not shown) with appropriate fixed or interchangeable connectors/tips at each end to link the port to the device.

Software is used to configure the multicharger unit so that it can supply the particular power (eg voltage /current combinations) needs of different laptops and other devices which might be charged or powered by the unit. The Software comprises a user friendly interface which leads users step by step through the process to configure the Multicharger unit to the desired settings. These steps and decisions/choices are presented in a sequence of computer screens that the user will find easy to follow. The flow chart for the configuration software is presented in figure 20. The proprietary software (which will be supplied with every unit) is first loaded onto the IT administrators laptop which is to be used for configuring the units. IT Administrators who will undertake the configuring will first need to register the software by internet and, if they wish, download the latest update of the data base of laptops which are supported by the unit .These steps have not been shown and are presumed to have been done before configuring commences. The IT administrator will have connected the multi charger unit to a power socket and will have connected his laptop to the multicharger with an appropriate connection as recommended ( eg usb cable) The process thereafter is illustrated in Figure 20 from the point that the IT Administrator is ready to configure the first unit. The starting point is the screen 103 where the software connection to the unit can be initiated by pressing the Setup button 106. There is also an option to update the laptop

database (via internet) from a remote server 105 by pressing the update button 104. Once the initial setting up 106 is successful 107 ( ie the screen confirms that the laptop is now connected and communicating correctly with the multicharger) , the start button 108 will permit access to the configuration procedure and will connect to the extensive laptop database 109 provided within the software supplied or the updated database as downloaded earlier from the manufacturers website . If database connection 109 carries no errors or problems whatsoever 110, a new screen 111 will be displayed where the user can record details for the unit (e.g. location, name, date, serial number etc for internal records/administrative/equipment control purposes). . Once details are recorded the user can press the " next " button 113 and if the details are recorded correctly 117 then details are stored and the port setting screen 116 will display

Once on this screen 116 , the user is able to choose from three different setting methods 119 for setting ports to required power requirements .After the setting method is selected on screen, pressing the "next" button 119 initiates the setting process 120. Options for grouping ports for setting purposes include, all ports as a single group for setting 121, setting groups of ports 122 and setting the ports individually 123. Setting all ports either altogether 121, where only the first port is enabled and all other ports will be set to the same settings as selected for the first port 124 or individually 123 where all individual ports are enabled for setting on screen, will display the "Set Model" screen 126 where the user is invited to select the desired laptops from the database provided. When opting to set the ports into groups 122, the assign groups screen 127 will allow ports to be selected into desired groupings . After ports have been successfully allocated into groups 127 , pressing "next" button 131 makes the Set Model screen 126 available.

The Set Model screen 126 allows the user to select a laptop make and model from the extensive laptop database 134 provided within the software . This permits a very user friendly environment for selection of the make and model of the desired laptop for each port or groups of ports . The Set Voltage button 133 will send the configuration data to the unit and will set up the ports 136 on the multi charger to these desired settings if the data is correct and there are no errors 135. The Set Model screen 126 contains the facility to exit the software by pressing Exit button 137.

All screens during the setting process have the facility to call the help documentation 114 by pressing the Help button 115 in whichever screen the user is in at any point. The screens also have the facility to go back to the previous screens by pressing the back buttons 112, 118, 128. At set model screen 126, the back button 129 will work according to whether the previous screen was all one group 121, individual ports 123 or the groups of ports 122.

1 Efficiency in power management

The multicharger unit has a very efficient power management system which reduces the surge that can occur at a wall socket ( and which can trip a ring mains circuit ) when large numbers of laptops (connected to wall socket via extension cables) are switched on simultaneously, hi the case of eight laptops this would be done by replacing eight individual AC-DC converters that come with laptops with only four AC-DC converters within the Multicharger unit and by staged switching on of laptops so they are switched on in sequence a few milliseconds apart. The combined effect is to permit a larger number of laptops to be powered/ charged from single wall socket using the multicharger than can be done if using their individual AC-DC converters.

2 Software and Power drawn

The software and internal laptop data base is used to set each port to the characteristics of the laptop expected to use it (eg voltage and current requirements during operating or charging modes, and whether communications protocols are required before the laptop will charge or run). Each port can supply a max upper limit of 7 amps to a device connected to it. However, in the present standard eight port unit, each set of two ports 1 and 2 , 3 and 4 etc are supplied from a single 300w DC power supply unit and the maximum amps available to be drawn over the two ports is around 11.5 amps. Once the laptops have been selected for each port, the software tries to set the correct characteristics (voltage etc) for each port .However if it finds that the total amps required for any group of two ports exceeds the maximum available (11.5 amps) then it will permit only the first port to be set and will disable the second port until a less demanding laptop is assigned to that port which brings the total current drawn to below the threshold of 11.5 amps. The software also checks that the total power drawn (voltage x current) through the 2 ports does not exceed the maximum total power (300w , in this case ) available from the power supply serving those two ports. The software therefore checks that the settings specified for the ports do not exceed that capacity of the supply available

Claims

1 . A power converter comprising a single mains input, a primary transformer for converting a mains alternating current to a fixed direct current, a plurality of outputs, and a plurality of secondary transformers, each associated with one of the plurality of outputs, wherein the input to each of the secondary transformers is the fixed direct current output of the first transformer, and wherein the output of each of the secondary transformers is connected to a respective one of a plurality of output ports, power from any one output port being functional to power a device or charge a battery thereof, wherein the output power characteristics of each output port is configurable to match the power requirements of a connected device.

2. A power converter according to Claim 1, wherein a current limiter is associated with each of the ports.

3. A power converter according to Claim 2, wherein the secondary transformers are DC-DC converters.

4. A power converter according to Claim 2, wherein the secondary transformers comprise windings around a magnet.

5. A power converter according to Claim 2, wherein the secondary transformers comprise an electronic circuit.

6. A power converter according to Claim 5, wherein the electronic circuit is repeated for each output port.

7. A power converter according to Claim 6, wherein the electronic circuit includes a micro-processor.

8. A power converter according to any preceding claim, wherein one of the secondary transformers has priority over the other secondary transformers.

9. A power converter according to any preceding claims, wherein the output power characteristics of at least some of the output ports is selectable individually.

10. A power converter according to any preceding claim, wherein the output power characteristics of at least some of the output ports are selectable collectively.

1 1. A power converter according to any preceding claim, further including at least one potentiometer, the said output potential being selected by means of the at least one potentiometer.

12. A power converter according to Claim 11, wherein at least one potentiometer is a digital potentiometer.

13. A power converter according to any preceding claim, further comprising a current sensor arranged to sense the current drawn by a device attached to an output port.

14. A power converter according to any preceding claim, further comprising an audio device associated with each output port, in use the said audio device transmitting a signal representative of the status of a respective output port or a device connected to that port.

15. A power converter according to any preceding claim, further comprising a visual device associated with each output port, in use the said visual device transmitting a signal representative of the status of a respective output port or a device connected to that port.

16. A power converter according to Claim 15, wherein the visual device is a light emitting diode (LED).

1 7. A power converter according to Claim 15 or 16, wherein the visual and/or audio devices transmit signals derived from the current sensor.

1 8. A power converter according to Claim 15 or 16, wherein the or each visual device is located remotely from the power converter.

19. A power converter according to any preceding claim, further comprising configuration software for configuring the power delivered to an output port to match the power requirements of the powered device.

20. A power converter according to Claim 19, including at least one interface for connection of the converter to a computer device, wherein the said computer device is programmed with computer software for configuring the output potentials at the said output ports.

21. A power converter according to Claim 19 or 20, wherein the computer software interrogates a database of power settings, retrieves appropriate settings from the database, and configures the output port with the said settings.

22. A power converter according to any preceding claim, wherein the converter further comprises delay means, wherein power to the output ports is switched on sequentially.

23. A power converter according to Claim 22, wherein the delay period is in the order of milliseconds.

24. A power converter according to any preceding claim, wherein each of the output ports includes an electrical connector.

25. A power converter according to Claim 24, wherein at least one electrical connector is of different shape to at least one other electrical connector.

26. A power converter according to Claim 24 or 25, wherein at least one electrical connector is of different polarity to at least one other electrical connector.

27. A power converter according to any preceding claim, wherein the primary transformer is the transformer of a power device, and wherein a proportion of the power output of the transformer is diverted to power devices connected to the said output ports.

28. A power converter according to Claim 27, further comprising a potentiometer for varying the proportion of power diverted to the said output ports.

29. A power converter according to any preceding claim, wherein the said converter is mountable in a pc or a peripheral device attachable thereto and wherein power to the pc and peripherals attached thereto is distributed by the power converter.

30. A power converter according to Claim 29, wherein the converter is embodied in a PC card.

31. A power converter according to any preceding claim, comprising at least four output ports.

32. A power converter according to Claim 7, comprising between 4 and 15

output ports.

33. A lap top cabinet including a power converter according to any preceding claim.

34. A table including a power converter according to any of Claims 1 to 32.

35. A battery charger including a plurality of battery charging bays and a power converter according to any of Claims 1 to 32.

36. A power converter as described with reference to, and as shown in, the drawings.

37. A method of powering a plurality of electronic devices from a single mains connection comprising the steps of connecting a power converter as claimed in any of Claims 1 to 32 to the mains connection, and connecting at least one electronic device requiring a direct current supply to an output port of the power converter.

38. A method according to Claim 37, comprising the further step of adjusting the output potential of one or more of the output ports to match the supply requirements of the device connected thereto.