AU2010100961A4

AU2010100961A4 - A control device

Info

Publication number: AU2010100961A4
Application number: AU2010100961A
Authority: AU
Inventors: Levent Ulgen
Original assignee: Wilson & Gilkes Pty Ltd
Current assignee: Wilson & Gilkes Pty Ltd
Priority date: 2010-09-01
Filing date: 2010-09-01
Publication date: 2010-10-07
Anticipated expiration: 2018-09-01
Also published as: AU2010100961B4

Description

AUSTRALIA F B RICE & CO Patent and Trade Mark Attorneys Patents Act 1990 WILSON & GILKES PTY LTD COMPLETE SPECIFICATION INNOVATION PATENT Invention Title: A control device The following statement is a full description of this invention including the best method of performing it known to us:- 2 Introduction The present invention relates to power supplies and in particular the invention provides a power switching control device for controlling the intermittent supply of power to a plurality of devices. 5 Background When a number of devices, such as battery charging devices are connected to a single power circuit, protected by a fuse or circuit breaker, the fuse or circuit breaker can open in the event of a large inrush current when the power is turned on or if the 10 number of connected devices approaches or exceeds the circuit's rating. When charging smaller batches of a group of devices, someone will be required to switch over the devices being charged after a current batch is fully charged, and remembering to do so at an appropriate time. In some circumstances the window for charging might not greatly exceed the time required to charge the device and so if there is a delay in the 15 switching over of devices, not all of the devices will charge in time. This may also be inconvenient if charging is occurring out of hours (e.g. over night) as it may require attendance of personnel at the location of the device outside normal hours of attendance. This is a particular issue with schools which provide laptop computers to 20 students. Racks with power outlets are often provided to allow all of the computers for a class to be charged essentially simultaneously. However school buildings built some time in the past will not have large numbers of power circuits installed in any particular room (the room might be provided with only a few power points running off a single circuit for example). If say 28 computers (for a typical class size of 28 students) are 25 connected to a single outlet then the protection device of the power circuit might trip at power on, particularly if other equipment is running on the same circuit. Summary The present invention consists in a control device comprising an input 30 connectable to a power source, a plurality of outputs intermittently supplying power to equipment connectable to each of the outputs, a plurality of switches, each switch connecting the input with one of the outputs and a controller controlling the switches, to open and close the switches at predetermined times, whereby closing of the switches is staggered such that at least one switch closes at a different time to at least one other 35 switch.

3 Preferably no two switches close simultaneously. Optionally the switches may be operated in sets whereby a set comprising one or more switches is open for an entire period of time when another set of one or more switches is closed. Alternatively sets of switches may be closed at staggered times but have overlapping closed periods. 5 In one embodiment closing times are staggered by 1 minute, however the delay between closings will be determined for the particular application and could range from 30 seconds to 10 minutes for example. Staggering turn on by larger periods can also be advantageous, for example staggering turn on by 30 minutes to 5 hours (nominally 1 hour) can result in the 10 charging current of a first batch of devices (and the resulting load on the mains circuit) reducing to a low value such that when a second batch is connected to the mains circuit, the circuit capacity is not exceeded. Alternatively by extending the staggering delay sufficiently the first batch can be fully charged (and disconnected) before the second batch is connected. 15 The total charging time for each switch (and therefore each batch) may be limited to a predetermined duration to avoid excess power usage. In that case charging may be limited to 2 to 5 hours per switch and would be typically set at 3 or 4 hours. The control device may comprise hard wired circuits including analog timers or digital counters to measure on and off timing of the switches, however preferably the 20 control function is provided by a microcontroller, such as a MicrochipTI PIC24TM series device, programmed to switch output signals at the appropriate times to drive the switches according to predetermined sequence. The input is preferably a mains supply input fitted with a mains connection plug device and outputs are preferably switched mains supply outputs fitted with mains 25 socket devices. The switches can be any suitable AC switching device such as solid state switches but are preferably relays. Brief description of the drawings An embodiment of a power supply will now be described by way of example 30 with reference to the accompanying drawings in which: Fig. I is a simplified block schematic of the control device; Fig. 2 is a timing diagram showing a first mode of operation;. Fig. 3 is a timing diagram showing a second mode of operation; and Figs. 4 & 5 provide a circuit schematic of a preferred embodiment of the control 35 device.

4 Detailed description of an embodiment of a power supply Referring to Fig. 1 the basic operation of a power control device will be explained. The purpose of the control device is to provide sequenced switching of a power source, which is preferably a mains supply but could be any power source 5 having limited capacity. In particular the device is useful for sequencing of battery chargers in a charging rack as might be used to charge students notebooks in a school classroom or charging other portable equipment such as restaurant table lamps, miner's lamps or portable instruments, for example. The device comprises a power input 11 which may be a plug lead fitted with a 10 mains power plug, a plurality of power outputs 12, 13, 14, 15, which may be standard mains power sockets, a series of power switching devices SWI, SW2,....SWn, each connected between the power input 1 and one or more of the power outputs 12, 13, 14, 15 to intermittently connect power to the outputs. The switches SWI, SW2,... SWn are controllable to be switched in a 15 predetermined sequence and for a predetermined time such that the output or outputs connected to each switch are independently energised and de-energised with regard to the remaining outputs allowing the equipment connected to the mains through each switch to be powered up at different times. By sequencing the turn on times of each switch to not coincide, the supply circuit can be protected from excessive current draw 20 due to the effects of inrush current at turn on or due to the total load exceeding the supply capacity, each of which will result in the primary supply protection device (e.g. fuse or circuit breaker) opening. Control of the switches SWI, SW2, ... SWn, is achieved by a control circuit ICI which in this case is a microcontroller but could also be a hardwired analog or digital 25 timer circuit. The microcontroller is powered from the input supply via a diode bridge DBI and a three terminal power regulator IC2. An unregulated 12 volt supply is also provided from the diode bridge DBI and is used to power intermediate switching devices described below which drive the switches SWI, SW2, ... SWn. A number of switching sequences are possible depending upon the total 30 potential connected load and the characteristics of the devices being powered. Referring to Fig. 2 one example of a timing sequence is illustrated graphically in which switch SWI is turned on at time tij for a period At,, followed after a delay duj by switch SW2 which is turned on at time t 1

,

2 for a period Ati, 2 , etc (and generally At 1 ,, Atl, 2 , ... Ati,, will be equal and d 1 ,i, di, 2 , ... di,r., will be equal). . In this sequence each 35 switch is turned on for a period Ati,n but the turn on times are staggered by a delay di,n such that if the total connected load (including any load not connected via this supply 5 control device) does not exceed the rating of the supply but the starting load due to inrush does exceed the supply rating then the staggered starting times will spread the inrush protecting the primary supply protection device from opening, except in the event of a genuine fault condition. 5 A second sequencing example is provided in fig. 3 in which switch SWI is turned on at time t 2

,

1 for a period At 2

,

1 followed after a delay d 2

,

1 by switch SW2 which is turned on at time t 2

,

2 for a period At 2

,

2 as before (and generally At 2

,

1 , At 2

,

2 , ... At2,n will be equal). However in this case the delay before turning on switch SW3 is significantly greater and may be after Switches SWI and SW2 are turned off. Switch 10 SW4 is turned on after a delay of d 2

,

3 after switch SW3 is turned on. In this sequence each switch is turned on for a period At 2 ,n and all of the turn on times are again staggered but they are grouped into a first set staggered by a delay d 2 ,j, a second set staggered by a delay d 2

,

3 and the second group are staggered from the first group by a delay d 2

,

1 which may or may not be greater than the turn on period At 2 ,n. In this case 15 the first group of switches may either turn on and off before the second group of switches turn on or alternatively the second group may turn on before the first group turn off, but after a sufficient delay that the current drawn by the devices connected to the first group has significantly reduced. This sequence prevents the supply circuit from opening if the potential total connected load (after the inrush period and assuming 20 all devices were charging simultaneously) exceeds the circuit rating. Referring to Fig. 4, ICI is a PIC 24 TM series Programmable Microcontroller from Microchip

TM

, which provides the control function. DIP switches DPI provide 4 option switches which select particular functional options of the control program. Four switch control output signals RLY-1, RLY-2, RLY-3 & RLY-4, of the Microcontroller ICI are 25 used to operate switches that switch the AC Mains supply. The remaining circuit components in Fig. 4 are ancillary and will not be described in detail. Turning to Fig. 5, the switch control signals RLY-1, RLY-2, RLY-3 & RLY-4 are connected to MOSFETS TRI, TR2, TR3 & TR4 respectively which will switch on when the corresponding switch control signal is active. The MOSFETs TRI, TR2, 30 TR3 & TR4 in turn drive relay coils of relays RLY1, RLY2, RLY3 & RLY4 (which equate with switches SWI, SW2, SW3 & SW4 in Fig. 1). The contacts of Relays RLYI, RLY2, RLY3 & RLY4 are connected to the mains active line to switch the active output of AC outputs 12, 13, 14, & 15. LEDS LD1, LD2, LD3 & LD4 and associated series resistors RI, R2, R3 & R4 are connected across the relay coils and 35 indicate when the coils are activated.

6 A power supply comprising a transformer TX1, a bridge rectifier DB1 and capacitors C2 & C3 provide a 12 volt supply for the relay coils (and driver transistors TRI, TR2, TR3 & TR4), and a 3 terminal regulator and capacitors C4, C5 & C6 provide a regulated supply for the microcontroller ICI. 5 Use of the control device as well as making charging more convenient for students and teachers, also helps to protect the environment by limiting the charging time, and hence the power usage, to only approximately that required to charge the connected device (Laptop, lamp etc). The programmable microcontroller is combined with a 4 Position DIP Switch that permits the operation of the relays on the circuit 10 board in different modes (see below for mode details) The output relay contacts isolate the power cord (input) from any reverse EMF discharge when the respective output of the control device is inactive. The controller can deliver a constant I OA to the connected load(s) and is able to accommodate peak loads of up to 16A on the relay contacts (each relay contact is rated at 16A) 15 The DIP Switches DP1 provide the following functional options: 1. DIP Switch I - On = This switches the device into Test Mode (in which the timing of the control sequence is altered such that Minutes are changed to Seconds) 20 Off= Normal Mode (Minutes). This is provided to facilitate 100 % functional testing of the unit in a reasonable time frame. 2. DIP Switch 2 - Off & DIP Switch 3 - Off= A No Button Soft Start Function in which the device starts as soon as Power is applied at the input. The Normal Function is provided in which relays RLYl, RLY 2, RLY3 & RLY4 start 1 minute 25 apart and cycle continuously until power is removed from the input. (The setting on DIP Switch 4 is ignored). 3. DIP Switch 2 - Off & DIP Switch 3 - On = A Normal Button Start Function in which relays 1, 2, 3 & 4 start 1 minute apart after Start Switch J6 is pressed. (Charging Time is set by DIP Switch 4) 30 4. DIP Switch 2 - On & DIP Switch 3 - Off= An Alternate Button Start Function in which relays I & 2 start 1 minute apart and alternate every 60 Mins with Relays 3 & 4 which also start 1 minute apart. (Charging Time is set by DIP Switch 4) 5. DIP Switch 2-On & DIP Switch 3 - On = A Stepped Button Start Function in 35 which relays 1, 2, 3 & 4 start 1 hour apart. (Charge Time set by Dip Switch 4) 7 6. DIP Switch 4 Off (Function as per Dip Switch 2 & 3 settings) The device turns off after each Relay has charged for 3 Hours 7. DIP Switch 4 On (Function as per Dip Switch 2 & 3 settings) The device turns off after each Relay has charged for 4 Hours 5 It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims

1. A control device comprising an input connectable to a power source, a plurality of outputs intermittently supplying power to equipment connectable to each of the 5 outputs, a plurality of switches, each switch connecting the input with one of the outputs and a controller controlling the switches, to open and close the switches at predetermined times, whereby closing of the switches is staggered such that at least one switch closes at a different time to at least one other switch.

2. The device of claim I wherein the turn on time of each switch is staggered with 10 respect to the other switches.

3. The device of claim I wherein a total charging time for each switch is limited to a predetermined duration.

4. The device of claim I wherein the input is a mains supply input and is fitted with a mains connection plug device and outputs are switched mains supply outputs 15 fitted with mains socket devices.

5. A control device substantially as hereinbefore described with reference to any one or more of the accompanying drawings.