WO2008017877A1

WO2008017877A1 - Electrical connection circuit

Info

Publication number: WO2008017877A1
Application number: PCT/GB2007/003076
Authority: WO
Inventors: Karl Dorn
Original assignee: Karl Dorn
Priority date: 2006-08-11
Filing date: 2007-08-10
Publication date: 2008-02-14

Abstract

A circuit is described for connection between an appliance and a power supply. The circuit detects when the appliance is operating in a standby mode and automatically isolates the appliance from the power source either immediately or after a predetermined length of time of operation in the standby mode.

Description

ELECTRICAL CONNECTION CIRCUIT

Field of the invention

The present invention relates to an electrical circuit for connection between a source of electrical power and an appliance, the circuit being capable of being incorporated in a connector such as a plug or a wall socket or within an extension lead or a power supply lead.

Background of the invention

Several appliances are currently designed to operate in a standby mode in which the appliance is dormant but can be returned to a normal operating mode without the inconvenience of a warm — up period. In the case of computers, for example, having a standby mode avoids the need for cold rebooting, and therefore saves the user time and avoids inconvenience. Other appliances, such as televisions, can be returned to a normal operating mode by using an infrared remote control when they are in standby mode, which is not possible when their main ON-OFF switch is turned to the OFF position.

While having a standby mode offers advantages, such as those described above, it results in unnecessary consumption of electrical power. It is a popular misconception that appliances consume negligible electrical power when they are operating in standby mode. In reality, their power consumption is typically 85% of that during normal operation. Allowing appliances to operate in standby mode for prolonged periods is therefore hugely wasteful of energy and, having regard to current concerns about global warming, legislation is currently being considered in some countries to prohibit the provision of a standby mode in appliances manufactured in the future.

While the problem of energy wastage may be reduced in the future by modifying the design of appliances, there are currently numerous appliances in use which are left on in standby mode for prolonged periods of time, often inadvertently, resulting in unnecessarily high fuel bills to the consumer as well as harm to the environment.

Summary of the invention

With a view to mitigating the foregoing problem, the present invention provides circuit for connection between an appliance and a power supply, comprising means for detecting when the appliance is operating in a standby mode and means for automatically isolating the appliance from the power source either immediately or after a predetermined length of time of operation in the standby mode, wherein the means for detecting when the appliance is operating in a standby mode includes means for sensing the current drawn by the appliance and means for determining when the current drawn from the power supply drops below a threshold, characterised by means for determining the maximum steady current drawn by an appliance after initial activation and means for setting the threshold indicative of operation in a standby mode as a predetermined fraction of the maximum sensed steady current.

While it would be possible to inhibit standby operation totally, by setting the predetermined length of time to be negligible or no more than the time taken to ascertain that the appliance is operating in a standby mode, this is not preferred as there are benefits to the user in having an appliance on standby for a short time. It is only prolonged operation in standby mode that is unjustified and likely to be unintentional.

It is therefore preferred for the circuit to incorporate a timer and for it to disconnect the appliance from the power supply only after several minutes of operation in the standby mode have lapsed.

The means for isolating the appliance from the power supply may be self-resetting. This would be suitable for any appliance which, having been disconnected from the power supply, requires its own ON-OFF switch to be turned ON before it can again be operated. For appliances that would automatically return to a standby mode on reconnection to the power supply, it is possible for the means for isolating the appliance from the power supply to include a manual reset button or for it to be reset automatically if disconnected from the power supply. As a further alternative, the isolating means may be reset in response to toggling of the

ON-OFF switch of the appliance.

The connection circuit of the invention may either be incorporated into the plug or the power lead of an appliance or it may be incorporated into a wall socket or an extension lead. Alternatively, the circuit may be incorporated into the appliance body itself instead of the plug or power lead of the appliance. If built into a plug or power lead dedicated to one appliance, the invention will enable the appliance to be plugged into any power socket. If built into a socket, on the other hand, the connection circuit can prevent standby mode operation of any appliance plugged into it.

When appliances are first switched on, their current consumption may remain high for some time until a steady state is reached. For this reason, it is preferred for the connection circuit not to rely on instantaneous measurements of appliance current but on measurements averaged over a period of time sufficiently long to ensure a reliable reading, unaffected by brief transients.

Brief description of the drawings

The invention will now be described further, by way of example, with reference to the accompanying drawings, in which:

Fig. 1 is a block diagram of a connector in accordance with a first embodiment of the invention;

Fig. 2 is a modification of the connector shown in Fig. 1. Detailed description of the preferred embodiment(s)

The single figure shows a connection circuit having two inputs and two outputs. The two inputs are connected to the Live and Neutral of a mains supply and the two outputs lead to the Live and Neutral inputs of the appliance, which requires no internal modification. The illustrated circuit can be quite small physically and can therefore be built into the mains supply lead of the appliance or into the plug fitted to the mains supply lead. As a further alternative, the circuit can be built into a mains wall socket or into an extension lead. Furthermore, it is possible to have the circuit incorporated into the appliance body itself instead of the mains supply of the appliance.

Within the circuit of the invention, there is an uninterrupted connection between the

Neutral input and output terminals whereas a resistor 10 and an electronic switch 12 are arranged in series with one another in the connection between the input and output Live terminals. The switch 12 is shown as being a triac but other forms of switch or relay may alternatively be used.

A DC power supply circuit 14 connected across the mains supply serves to provide reference Ov and 5v DC rails which are required for other components to be described below. To avoid the need for a transformer, the DC supply circuit may simply comprise a Zener diode and a smoothing circuit.

As the resistor 10 is connected in series with the appliance, the voltage developed across it is a measure of the current drawn by the appliance. This voltage is amplified by an amplifier 16 and supplied to a voltage sensing input of a PIC12F675 micro — controller 18 which sends a control signal to the triac 12 by way of a resistor 20. The micro-controller 18 is a small computer which can be pre — programmed to perform certain tasks, as described below, and includes, in addition to a processor, B-PROM memory to hold the instruction program and random access memory. One of the inputs of the micro — controller 18 is connected to the Neutral line of the mains supply and serves to detect zero crossings. This information is used for initial powering up of the circuit to send a signal to the triac 12 over the resistor 20, to render the triac 12 conductive, the signal being timed relative to a zero crossing of the mains voltage. This output of the microcontroller remains in a high state for as long as power is to be supplied to the appliance and its return to a low state will result in the triac 12 being switched off to isolate the appliance from the mains supply.

While current is drawn from the mains supply, a voltage proportional to the current drawn by the appliance is developed across the resistor 10. The resistor 10 needs to have a low value of resistance and the voltage drop across it is also small. For this reason, it is amplified by the amplifier 16 before being applied to the micro-controller 18. The micro-controller 18 after initial power up measures the applied voltage and averages it over a period of typically one minute. This period allows the current drawn by the appliance to reach a steady state and also enables short current spikes to be disregarded. This average is then stored in memory and used as the reference for the current consumed by the appliance during normal operation.

When at some time later the appliance is switched to operate in a standby mode, current will continue to flow through the resistor 10 but the value of the measured current will drop to a fraction of the stored steady state value for normal operation. Once again, it is not desirable to act on instantaneous measurements of the drawn current and it is averaged for a period of typically a minute to produce a steady state current reading. If this reading is below a certain threshold, typically 85% of the normal operation current, then the micro-controller generates a flag to indicate that standby operation has been detected.

It is possible to act on this flag to switch off the triac 12 without delay but it is preferred to permit standby mode to be used for a reasonable length of time, say thirty minutes. The flag therefore initiates a count of clock pulses which continues until a maximum count is reached or until the flag is cleared by the operator resuming normal operation of the appliance. If the maximum count is reached, corresponding to the lapsing of a maximum period of operation in standby mode, the output of the microcontroller 18 goes low to switch off the triac 12 and isolate the appliance from the mains supply.

The described connection circuit is intended to be incorporated into a plug or a main supply lead of an appliance. Once the appliance has been disconnected, the circuit can be reset by disconnecting the mains supply from the input side of the circuit. This can be done either by pulling the plug out of the wall socket or operating a switch on the wall socket. As a further possibility, it is possible to incorporate a radio or infra — red sensor to enable the circuit to be reset by the use of a remote control unit.

If the appliance is one that remains in an OFF state once the power supply to it has been discontinued, the circuit can be modified to reset itself after it has been triggered by a period of operation in standby mode.

If the circuit is built into a wall socket, it is not possible to disconnect the mains supply from its input side and in this case it is possible to provide a manual reset button or a sensor to enable the circuit to be reset using a remote control unit.

It is also possible for the circuit to be built into a power distribution device ("multi gang") which comprises more than one socket. The multi gang is plugged into a wall socket. In such an arrangement, one or more of the sockets in the multi gang are provided with the connection circuit. The circuit can be modified for use with a multi gang such that if one socket is provided with the connection circuit, the circuit can be adapted to isolate all the appliances connected to the other sockets of the multi gang when a standby mode is detected. This can occur immediately or after a predetermined period of time and also isolates the appliance connected to the socket comprising the connection circuit. In a further modification, a plug converter (not shown) for converting a plug of a first pin configuration to a second pin configuration can be provided with the connection circuit. In this arrangement, the connection circuit is contained within a housing of the plug converter and electrically connected to the pins having a second pin configuration which are considered the input of the connection circuit and the pins of the plug having the first configuration which is considered the output of the circuit. The circuit operates in the same manner as referred to with respect to Fig. 1.

The triac 12 could alternatively be controlled using a small burst fire following the mains zero crossing but such an approach may prove problematic in view of the non — uniform current drawn by some appliances. To overcome this issue the triac gate in the described preferred embodiment of the invention is driven continuously, which places a substantial current burden on the transformer — less power supply unit 14 and makes redundant the need to monitor the mains for zero — crossing. If desired, an opto — isolated triac driver may be used with built — in zero — crossing detection such as the M0N3043 -M.

Fig. 2 shows a modified embodiment of the invention shown in Fig. 1 including the remote sensor. Items with common reference numerals in Fig. 1 indicate the same features as in Fig. 1. The connection circuit is based on the same circuit as in Fig. 1 except that a sensing arrangement 22 is provided. The sensing arrangement 22, which is utilised when the circuit is incorporated into the plug or main supply lead of the appliance, or when the circuit is built into the wall socket, can include a radio or infra-red sensor.

The purpose of the sensing arrangement 22 is to enable remote resetting of the connection circuit. A remote control unit (not shown) would send a signal wirelessly to the sensing arrangement 22 and this would cause the connection circuit to be reset. The wireless transmission by the remote control unit could be through infrared or radio communication.

When the wireless transmission from the remote control unit takes the form of infra-red communication, the sensing arrangement 22 comprises an infrared receiver which is adapted to receive infrared signals from a remote control unit (not shown) containing an infrared transmitter. The receiver can be in the form of a separate unit to the circuit and is movable such that it can be positioned to be visible by the remote control unit. Furthermore, it is of a small size so that it can be moved to different locations. In order to communicate with the connection circuit, the infrared receiver comprises a radio transmitter adapted to send a radio signal at a particular frequency to the connection circuit which comprises a radio frequency receiver.

When the infrared receiver receives a signal from the remote control unit, this causes a radio signal to be transmitted from the infrared receiver at a frequency which matches the frequency of the radio frequency receiver in the connection circuit. The radio signal indicates that the connection circuit is to be reset and therefore causes the connection circuit to reset. One or more batteries can power the infrared transmitter and receiver.

It is also possible to dispense with the infrared communication from the sensing arrangement 22 such that only radio frequency communication is utilised. In such a case, the infrared transmitter and receiver are not required and the wireless transmission from a remote control unit (not shown) takes the form of radio communication. The remote control unit is provided with a radio frequency transmitter. This is set at a frequency to cause a reset signal to be sent to the radio frequency receiver of the connection circuit when a button or combination of buttons are pressed on the remote control unit. The remote control unit can be built into a remote control unit of the appliance if the connection circuit is built into the plug or power lead of the appliance or the appliance itself. Alternatively, a separate remote control unit can be provided which is configured only for use with the sensing arrangement 22. This is particularly appropriate when the connection circuit is built into a wall socket and not associated with any particular appliance.

One type of radio communication is Bluetooth® and the sensing arrangement 22 can be adapted for use with this type of communication. In particular, any device capable of communicating using this type of technology can be configured to operate as the remote control unit for use with the sensing arrangement 22, for example mobile telecommunication devices.

It will be appreciated that other forms of wireless communication can be utilised to send a reset signal form a remote location to the connection circuit.

If desired, a small LED may be used to indicate when the connection circuit has removed the power to the appliance. This could periodically flash to inform the user of the system status and would also make the device easier to locate to activate a soft reset if the circuit is fitted with a reset button.

It has been assumed that the circuit is used to connect an appliance to a mains supply, it is also applicable when the power supply is a vehicle battery. As a particular example, it is common to provide battery chargers for mobile telephones that plug into a cigar lighter socket of a motor vehicle. When a telephone battery has been fully charged, the current drawn by its charger drops but it continues to operate in a low power mode, which may be regarded as equivalent to a standby mode. Not only does this low current place an unnecessary drain on the vehicle battery but it is believed to affect the lifetime of the telephone battery adversely. By monitoring the current drawn by a battery charger, the circuit of the invention may be used to isolate it automatically from its power supply, be it a mains supply or a vehicle battery, once charging of the battery has been completed.

Claims

1. A circuit for connection between an appliance and a power supply, comprising means for detecting when the appliance is operating in a standby mode and means for automatically isolating the appliance from the power source either immediately or after a predetermined length of time of operation in the standby mode, wherein the means for detecting when the appliance is operating in a standby mode includes means for sensing the current drawn by the appliance and means for determining when the current drawn from the power supply drops below a threshold, characterised by means for determining the maximum steady current drawn by an appliance after initial activation and means for setting the threshold indicative of operation in a standby mode as a predetermined fraction of the maximum sensed steady current.

2. A circuit as claimed in claim 1, wherein the circuit includes a timer and is operative to disconnect the appliance from the power supply only after several minutes of operation in the standby mode have lapsed.

3. A circuit as claimed in claim 1 or 2, wherein the means for isolating the appliance from the power supply is self — resetting.

4. A circuit as claimed in claim 1 or 2, wherein the means for isolating the appliance from the power supply includes a manual reset button.

5. A circuit as claimed in claim 1 or 2, wherein the means for isolating the appliance from the power supply includes means for automatically resetting the isolating means when the circuit is disconnected from the power supply.

6. A circuit as claimed in claim 1 or 2, wherein the means for isolating the application from the power supply includes a radio or infra — red sensor to enable the circuit to be reset using a remote control unit.

7. An electrical device provided with the circuit as claimed in any one of the preceding claims, wherein the electrical device is one of the following: (a) a plug; (b) a power lead; (c) a power distribution device; (d) a wall socket; or (e) an appliance.