WO2004095887A1 - Apparatus and method for operating current dependent electronic devices - Google Patents

Apparatus and method for operating current dependent electronic devices Download PDF

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Publication number
WO2004095887A1
WO2004095887A1 PCT/GB2004/001670 GB2004001670W WO2004095887A1 WO 2004095887 A1 WO2004095887 A1 WO 2004095887A1 GB 2004001670 W GB2004001670 W GB 2004001670W WO 2004095887 A1 WO2004095887 A1 WO 2004095887A1
Authority
WO
WIPO (PCT)
Prior art keywords
current
electronic devices
voltage output
voltage
regulator
Prior art date
Application number
PCT/GB2004/001670
Other languages
French (fr)
Inventor
Peter Langmead
Raymond Osborne
Original Assignee
Polastar Plc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Polastar Plc filed Critical Polastar Plc
Priority to EP04727942A priority Critical patent/EP1632111B1/en
Priority to DE602004002302T priority patent/DE602004002302T2/en
Publication of WO2004095887A1 publication Critical patent/WO2004095887A1/en

Links

Classifications

    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/10—Controlling the intensity of the light
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • H05B45/345—Current stabilisation; Maintaining constant current

Definitions

  • the present invention relates to an apparatus and method for operating one or more electronic devices which require a constant given current.
  • the invention concerns operating a number of current devices such as light emitting diodes (LEDs) mounted on conductive strip to provide an elongate lighting strip.
  • LEDs light emitting diodes
  • Such lighting strips are well-known for example to mark the way to emergency exits on aircraft . They comprise a plurality of LEDs mounted at intervals along a conductive strip encased in plastic. LEDs, in common with a number of other electrical devices, are current devices, that is they rely on a constant current to operate, rather than a constant voltage. The life and brightness of a LED can be maximised by accurately controlling the current.
  • Known lighting strips have a driver apparatus which is designed to operate a given number and a particular type of LED. If the driver is used on a strip having a different number of LEDs or a different type of LED, then the drive apparatus must be completely reset which is a time-consuming, awkward and inefficient process.
  • the present invention provides an apparatus for operating one or more electronic devices requiring a given current, comprising a regulator device providing a voltage output, and a feedback loop having a reference device connected to the voltage output and requiring the same current as the electronic devices, a measuring and conversion device operable to measure the current through the reference device and convert it to a voltage value and return it to the regulator device, wherein the regulator device is operable to adjust the output voltage in response to the voltage value until the measured current is equal to the given current required.
  • a reference device of the same type as the electronic device that is to be operated allows the regulator automatically to adjusted to produce an absolute voltage of the appropriate level to drive the remaining devices. In this way, the apparatus is able to produce the correct voltage, automatically compensating for both short and long term drift, for any type and number of electronic devices being used.
  • the measurement and conversion device consists of a resistor and a current monitor.
  • the electronic devices are typically light emitting diodes, mounted on a conductive strip having a plurality of conductive elements .
  • the electronic devices may be parallel connected devices which are polarity sensitive, and the regulator may be connected to a three phase bridge to operate the conductive elements in the strip, and a micro controller operable to control the sequence in which the LEDs on the strip are operated.
  • the regulator comprises a steady state DC device.
  • the invention also provides apparatus for emitting electromagnetic radiation (EMR) comprising a plurality of electronic devices operable to produce EMR when provided with a given current mounted on a conductive strip which is connected to an apparatus of the type described above.
  • EMR electromagnetic radiation
  • the present invention also provides a method for operating one or more electronic devices requiring a given current, comprising the steps of providing a voltage output, supplying the voltage output to a reference device requiring the same current as the electronic devices, measuring the current in the reference device, converting the measured current to a voltage value and adjusting the voltage output in response to the voltage value until the measured current in the reference device is equal to the given current required by the electronic devices.
  • the method involves initially providing a voltage output sufficient to produce a current lower than the given current and gradually increasing the voltage output until the given current is obtained in the reference device.
  • FIG. 1 is a circuit diagram of one embodiment of apparatus in accordance with the present invention.
  • the principal feature of the present invention is that an electronic device of the same type as those to be operated is incorporated into a feedback loop of the apparatus.
  • a regulator device 10 is connected to the electronic devices to be driven.
  • the regulator 10 is preferably, but not exclusively, a steady state DC device for accuracy.
  • the electronic devices are LEDs (not shown) mounted on a conductive strip having three conductors 12.
  • a three- phase bridge 14 is connected between the regulator device 10 and the conductors 12.
  • the regulator 10 may also be connected to a micro controller 16, itself connected to the three-phase bridge 14, for example to control the sequence of operation of the LEDs in the conductive strip.
  • the regulator 10 is also provided with a feedback loop.
  • the voltage output from the regulator 10 also passes through a current measuring device such as a resistor 18 and a reference LED 20 of the same type as those in the strip which are to be driven.
  • the resistor 18 is also connected to a current monitor device 22. Together the resistor 18 and the current monitor 22 act to measure the current passing through the reference LED 20 and to convert it to a voltage. This is passed back to the regulator 10. Since the desired current for the LEDs in the conductive strip is known from the outset and the reference LED 20 is of the same type as the LEDs to be operated, this feedback loop allows the voltage output from the regulator 10 to be adjusted to the appropriate level so that the desired current is achieved.
  • the regulator 10 will initially be set to produce a voltage output which is lower than that required to provide the desired current .
  • the current through the reference LED 20 is then measured as the voltage output is gradually increased until the desired current through the reference LED 20 is achieved. At this point, the voltage output from the regulator 10 will be at the right level to operate the LEDs in the lighting strip in an optimum manner.
  • Another important feature of the lighting strip of the preferred embodiment of the present invention is that it is directly driven by a controlled voltage source thus removing the requirement for resistors within the lighting strip itself. Removal of the resistors from the lighting strip reduces the capacity for the lighting strip to heat up and consequently reduces the power consumption of the lighting strip.
  • Electro Magnetic Compatability can significantly reduce such interference by providing a standing DC voltage just below the threshold level required to operate the LEDs and superimposing small pulses which raise the voltage above the threshold in order to switch the LEDs on.
  • the switching voltage is thus a fraction of the full operating voltage then and the electro magnetic interference can be significantly reduced.
  • the voltage pulses can have soft edges .
  • the regulator 10 may be provided with separate feedback loops with a reference LED of each colour and the micro controller may be used to control which LEDs are to operate at a given time.
  • the present invention is not restricted to use with conductive strips having LEDs, or indeed to conductive strips having devices which emit visible light. The invention is equally applicable to use with devices producing other wavelengths in the electromagnetic spectrum, whether producing visible light or not.
  • the invention provides a simple and efficient manner in which to operate current devices, which is easily adaptable to operating different types and numbers of devices .

Abstract

An apparatus for operating one or more electronic devices requiring a given current is described, which comprises a regulator device (10) providing voltage output, and a feedback loop having a reference device connected to the voltage output and requiring the same current as the electronic devices, a measuring and conversion device operable to measure the current through the reference device and convert it to a voltage value and return it to the regulator device (10), wherein the regulator device (10) is operable to adjust the output voltage in response to the voltage value until the measured current is equal to the given current required.

Description

APPARATUS AND METHOD FOR OPERATING CURRENT DEPENDENT
ELECTRONIC DEVICES
The present invention relates to an apparatus and method for operating one or more electronic devices which require a constant given current. In particular, the invention concerns operating a number of current devices such as light emitting diodes (LEDs) mounted on conductive strip to provide an elongate lighting strip.
Such lighting strips are well-known for example to mark the way to emergency exits on aircraft . They comprise a plurality of LEDs mounted at intervals along a conductive strip encased in plastic. LEDs, in common with a number of other electrical devices, are current devices, that is they rely on a constant current to operate, rather than a constant voltage. The life and brightness of a LED can be maximised by accurately controlling the current.
Known lighting strips have a driver apparatus which is designed to operate a given number and a particular type of LED. If the driver is used on a strip having a different number of LEDs or a different type of LED, then the drive apparatus must be completely reset which is a time-consuming, awkward and inefficient process.
The present invention provides an apparatus for operating one or more electronic devices requiring a given current, comprising a regulator device providing a voltage output, and a feedback loop having a reference device connected to the voltage output and requiring the same current as the electronic devices, a measuring and conversion device operable to measure the current through the reference device and convert it to a voltage value and return it to the regulator device, wherein the regulator device is operable to adjust the output voltage in response to the voltage value until the measured current is equal to the given current required.
In the present invention, use of a reference device of the same type as the electronic device that is to be operated allows the regulator automatically to adjusted to produce an absolute voltage of the appropriate level to drive the remaining devices. In this way, the apparatus is able to produce the correct voltage, automatically compensating for both short and long term drift, for any type and number of electronic devices being used.
Preferably, the measurement and conversion device consists of a resistor and a current monitor.
The electronic devices are typically light emitting diodes, mounted on a conductive strip having a plurality of conductive elements .
The electronic devices may be parallel connected devices which are polarity sensitive, and the regulator may be connected to a three phase bridge to operate the conductive elements in the strip, and a micro controller operable to control the sequence in which the LEDs on the strip are operated. Preferably, the regulator comprises a steady state DC device.
In a further aspect, the invention also provides apparatus for emitting electromagnetic radiation (EMR) comprising a plurality of electronic devices operable to produce EMR when provided with a given current mounted on a conductive strip which is connected to an apparatus of the type described above.
The present invention also provides a method for operating one or more electronic devices requiring a given current, comprising the steps of providing a voltage output, supplying the voltage output to a reference device requiring the same current as the electronic devices, measuring the current in the reference device, converting the measured current to a voltage value and adjusting the voltage output in response to the voltage value until the measured current in the reference device is equal to the given current required by the electronic devices.
Preferably, the method involves initially providing a voltage output sufficient to produce a current lower than the given current and gradually increasing the voltage output until the given current is obtained in the reference device.
The present invention will now be described in more detail, by way of example only, with reference to Figure 1, which is a circuit diagram of one embodiment of apparatus in accordance with the present invention. The principal feature of the present invention is that an electronic device of the same type as those to be operated is incorporated into a feedback loop of the apparatus. As shown in Figure 1 a regulator device 10 is connected to the electronic devices to be driven. The regulator 10 is preferably, but not exclusively, a steady state DC device for accuracy. In this example, the electronic devices are LEDs (not shown) mounted on a conductive strip having three conductors 12. A three- phase bridge 14 is connected between the regulator device 10 and the conductors 12. The regulator 10 may also be connected to a micro controller 16, itself connected to the three-phase bridge 14, for example to control the sequence of operation of the LEDs in the conductive strip.
The regulator 10 is also provided with a feedback loop. The voltage output from the regulator 10 also passes through a current measuring device such as a resistor 18 and a reference LED 20 of the same type as those in the strip which are to be driven. The resistor 18 is also connected to a current monitor device 22. Together the resistor 18 and the current monitor 22 act to measure the current passing through the reference LED 20 and to convert it to a voltage. This is passed back to the regulator 10. Since the desired current for the LEDs in the conductive strip is known from the outset and the reference LED 20 is of the same type as the LEDs to be operated, this feedback loop allows the voltage output from the regulator 10 to be adjusted to the appropriate level so that the desired current is achieved. In operation, the regulator 10 will initially be set to produce a voltage output which is lower than that required to provide the desired current . The current through the reference LED 20 is then measured as the voltage output is gradually increased until the desired current through the reference LED 20 is achieved. At this point, the voltage output from the regulator 10 will be at the right level to operate the LEDs in the lighting strip in an optimum manner.
Another important feature of the lighting strip of the preferred embodiment of the present invention is that it is directly driven by a controlled voltage source thus removing the requirement for resistors within the lighting strip itself. Removal of the resistors from the lighting strip reduces the capacity for the lighting strip to heat up and consequently reduces the power consumption of the lighting strip.
Certain applications may also require minimisation of Electro Magnetic Compatability (EMC) interference for use in particularly sensitive environments. The present invention can significantly reduce such interference by providing a standing DC voltage just below the threshold level required to operate the LEDs and superimposing small pulses which raise the voltage above the threshold in order to switch the LEDs on. The switching voltage is thus a fraction of the full operating voltage then and the electro magnetic interference can be significantly reduced. For optimum performance the voltage pulses can have soft edges . It will be appreciated that a number of modifications and variations to the details described above can be made. For example, if the lighting strip includes LEDs of different colours, the regulator 10 may be provided with separate feedback loops with a reference LED of each colour and the micro controller may be used to control which LEDs are to operate at a given time. In addition, it will be appreciated that the present invention is not restricted to use with conductive strips having LEDs, or indeed to conductive strips having devices which emit visible light. The invention is equally applicable to use with devices producing other wavelengths in the electromagnetic spectrum, whether producing visible light or not.
The invention provides a simple and efficient manner in which to operate current devices, which is easily adaptable to operating different types and numbers of devices .

Claims

1. Apparatus for operating one or more electronic devices requiring a given current, comprising a regulator device providing voltage output, and a feedback loop having a reference device connected to the voltage output and requiring the same current as the electronic devices, a measuring and conversion device operable to measure the current through the reference device and convert it to a voltage value and return it to the regulator device, wherein the regulator device is operable to adjust the output voltage in response to the voltage value until the measured current is equal to the given current required.
2. Apparatus as claimed in claim 1, wherein the measurement and conversion device comprises a resistor and a current monitor.
3. Apparatus as claimed in claim 1 or claim 2, wherein the electronic devices comprises light emitting diodes mounted on a conductive strip having a plurality of conductive elements.
4. Apparatus as claimed in any preceding claim, wherein the electronic devices are parallel connected and polarity sensitive, and the regulator is connected to a three-phase bridge and a micro controller operable to control the sequence in which the LEDs on the conductive strip are operated.
5. Apparatus as claimed in any of the preceding claim, wherein the regulator device comprises a steady state DC device .
6. Apparatus for emitting electromagnetic radiation, comprising a plurality of electronic devices operable to emit electromagnetic radiation when provided with a given current mounted on a conductive strip and connected to apparatus as claimed in any claims 1 to 5.
7. A method for operating one or more electronic devices requiring a given current comprising the steps of providing a voltage output, supplying the voltage output to a reference device requiring the same current as the electronic devices measuring the current in the reference device, converting the measured current to a voltage value, and adjusting the voltage output in response to the voltage value until the measured current in the reference device is equal to the given current required by the electronic devices.
8. A method as claimed in claim 7, further comprising the step of initially providing a voltage output sufficient to provide a current lower than the given current and gradually increasing the voltage output until the measured current in the reference device is equal to the given current .
9. Apparatus for operating one of more electronic devices requiring a given current substantially as hereinbefore described and with reference to the accompanying drawing.
10. Apparatus for producing electromagnetic radiation substantially as hereinbefore described and with reference to the accompanying drawing .
11. A method for operating electronic devices requiring given current as substantially hereinbefore described and with reference to the accompanying drawing.
PCT/GB2004/001670 2003-04-16 2004-04-16 Apparatus and method for operating current dependent electronic devices WO2004095887A1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
EP04727942A EP1632111B1 (en) 2003-04-16 2004-04-16 Apparatus and method for operating current dependent electronic devices
DE602004002302T DE602004002302T2 (en) 2003-04-16 2004-04-16 DEVICE AND METHOD FOR OPERATING ELECTRONIC POWER DEVICES

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB0308815A GB2400691B (en) 2003-04-16 2003-04-16 Apparatus and method for operating current dependent electronic devices
GB0308815.0 2003-04-16

Publications (1)

Publication Number Publication Date
WO2004095887A1 true WO2004095887A1 (en) 2004-11-04

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Application Number Title Priority Date Filing Date
PCT/GB2004/001670 WO2004095887A1 (en) 2003-04-16 2004-04-16 Apparatus and method for operating current dependent electronic devices

Country Status (6)

Country Link
EP (1) EP1632111B1 (en)
AT (1) ATE339078T1 (en)
DE (1) DE602004002302T2 (en)
ES (1) ES2273249T3 (en)
GB (1) GB2400691B (en)
WO (1) WO2004095887A1 (en)

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4271408A (en) * 1978-10-17 1981-06-02 Stanley Electric Co., Ltd. Colored-light emitting display
GB2139340A (en) * 1983-04-30 1984-11-07 Bosch Gmbh Robert Light for motor vehicles
US4952949A (en) * 1989-11-28 1990-08-28 Hewlett-Packard Company LED printhead temperature compensation
EP0480650A1 (en) * 1990-10-12 1992-04-15 Hewlett-Packard Company Light emitting diode array current power supply
US20020014862A1 (en) * 2000-01-14 2002-02-07 Gilbert Fregoso Circuit for driving light-emitting diodes

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2106299B (en) * 1981-09-23 1985-06-19 Smiths Industries Plc Electroluminescent display devices
DE68921020T2 (en) * 1988-05-20 1995-06-29 Mitsubishi Electric Corp Integrated MOS circuit for controlling light-emitting diodes.
US4864216A (en) * 1989-01-19 1989-09-05 Hewlett-Packard Company Light emitting diode array current power supply
MY127343A (en) * 2001-01-29 2006-11-30 Semiconductor Energy Lab Light emitting device.
US6614191B2 (en) * 2001-02-02 2003-09-02 Hewlett-Packard Company System and method for illuminating light emitting diodes in a contact image sensor
DE10115388A1 (en) * 2001-03-28 2002-10-10 Patent Treuhand Ges Fuer Elektrische Gluehlampen Mbh Control circuit for an LED array

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4271408A (en) * 1978-10-17 1981-06-02 Stanley Electric Co., Ltd. Colored-light emitting display
GB2139340A (en) * 1983-04-30 1984-11-07 Bosch Gmbh Robert Light for motor vehicles
US4952949A (en) * 1989-11-28 1990-08-28 Hewlett-Packard Company LED printhead temperature compensation
EP0480650A1 (en) * 1990-10-12 1992-04-15 Hewlett-Packard Company Light emitting diode array current power supply
US20020014862A1 (en) * 2000-01-14 2002-02-07 Gilbert Fregoso Circuit for driving light-emitting diodes

Also Published As

Publication number Publication date
EP1632111A1 (en) 2006-03-08
DE602004002302D1 (en) 2006-10-19
DE602004002302T2 (en) 2007-04-05
EP1632111B1 (en) 2006-09-06
GB2400691B (en) 2005-10-26
GB0308815D0 (en) 2003-05-21
ATE339078T1 (en) 2006-09-15
ES2273249T3 (en) 2007-05-01
GB2400691A (en) 2004-10-20

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