GB2502374A - LED driver circuit - Google Patents

LED driver circuit Download PDF

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Publication number
GB2502374A
GB2502374A GB1210341.2A GB201210341A GB2502374A GB 2502374 A GB2502374 A GB 2502374A GB 201210341 A GB201210341 A GB 201210341A GB 2502374 A GB2502374 A GB 2502374A
Authority
GB
United Kingdom
Prior art keywords
rectifier
input
led
driver circuit
capacitors
Prior art date
Legal status (The legal status 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 status listed.)
Withdrawn
Application number
GB1210341.2A
Other versions
GB201210341D0 (en
Inventor
Bernard Frederick Fellerman
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
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 Individual filed Critical Individual
Publication of GB201210341D0 publication Critical patent/GB201210341D0/en
Priority to GBGB1218239.0A priority Critical patent/GB201218239D0/en
Publication of GB2502374A publication Critical patent/GB2502374A/en
Withdrawn legal-status Critical Current

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]
    • H05B45/30—Driver circuits
    • H05B45/37—Converter circuits
    • H05B45/3725—Switched mode power supply [SMPS]
    • H05B45/382—Switched mode power supply [SMPS] with galvanic isolation between input and output

Landscapes

  • Circuit Arrangement For Electric Light Sources In General (AREA)

Abstract

An LED driver circuit 1 comprises means 2 to connect to a sinusoidal AC mains input, a rectifier 3 to rectify the AC input to create a DC supply, said rectifier having an input 3A, 3B and an output 3C, 3D and an LED array X connected to the output of the rectifier. At least one pair of back to back capacitors 4A, 4B are provided in series with the input of the rectifier. A thermistor 5 may be provided in series with the input of the rectifier and the mains input.

Description

Title: LED Driver Circuit The present invention relates to a LED driver circuit.
It is known to provide arrays of LED lights driven by a low DC voltage often converting a mains voltage to a working DC voltage through a transformer and rectifier circuit. Such array of LEDs may be used in many applications such as lamps, street lights, shops, garages, gardens, car parks and the like, and are less costly to run than incandescent type light bulbs. In the case of lamps, the light output is restrained by the amount of power deliverable by the transformer which has to be quite small in order for it to fit in a casing which is equivalent in size to a conventional light bulb.
The invention seeks to provide an LED driver circuit which can deliver a greater light output to power input ratio than that knpwn hitherto and which can be made compact in size.
According to the present invention an LED driver circuit comprising: a) means to connect to a sinusoidal AC mains input, b) a rectifier to rectify the AC pulse to create a DC pulse, sai&rectifier having an input and output c) at least one pair of back to back capacitors in series with the input of the rectifier and the mains input, and d) one or more LEDs connected to be driven by the output of the rectifier.
Preferably back to back capacitors are electrolytic capacitors.
Preferably two pairs of back to back capacitors are provided.
Preferably a capacitor is provided across the LEDs.
Preferably a thermistor is provided in series with the input of the rectifier and the mains input.
The invention also relates to an LED lamp incorporating the above defined feeder circuit.
An embodiment of the invention will now be described with reference to the accompanying drawings showing a circuit diagram.
Referring to Figure 1 there is shown an LED driver circuit I for a string of LEDs X. Circuit I connects to a sinusoidal AC mains input 2.
A rectifier 3 is provided having an AC input 3A,3B and a DC output 3C,3D.
Two pairs of back to back electrolytic capacitors 4A,4B are provided wired is series with the input 3A,3B of the rectifier 3.
LEDs X are connected to the output 3C,3D of rectifier 3.
In use the capacitor values are selected so that the voltage across the LEDs X is at the correct operating voltage of the LEDs. The back to back capacitors also limit the current. Typical values of 6.8 or 5.6 uf may be used to deliver 350mA to a string of say fourteen LEDs. Back to back electrolyties allow their Operation on sine waves. It may be preferable to use 250v electrolytic capacitors because they have a tan delta of 0.15 whereas 400v versions are 0.2. This means that with 250v devices the self heating is reduced by 25% compared to 400v versions.
In order to prevent a current surge from damaging the LEDs X, an NTL thermistor 5 is provided in series with the input of the rectifier and the mains input, and a capacitor 6 is provided across the LEDs X. Preferably a thermistor is provided in series with the input of the rectifier and the mains input.
The circuit is very compact, and whilst it may be used to drive LEDs in a number of different applications, the circuit lends itself to being positioned inside of an LED lamp to replace conventional light bulbs.
Whilst a single pair of' back to back capacitors may be used, two pairs (or possibly more pairs) are preferred in order to keep the capacitors cool. Electrolytic capacitors work well and are economical, but other types of capacitors could also be used.
The circuit can be used with conventional mains dimmers whereby the LEDs can be dimmed.
Also the circuit provides a leading power factor which can help neutralise the effects of other appliances with lagging power factors.
The invention my take a form different to that specifically described above.
Further modifications will be apparent to those skilled in the art without departing from the scope of the present invention.

Claims (7)

  1. CLAIMS1. An LED driver circuit comprising: e) means to connect to a sinusoidal AC mains input, f) a rectifier to rectify the AC pulse to create a DC pulse, said rectifier having an input and out out g) at least one pair of back to back capacitors in series with the input of the rectifier and the mains input, and one or more LEDs connected to be driven by the output of the rectifier.
  2. 2. An LED driver circuit according to claim I. wherein the or each pair of back to back capacitors are electrolytic capacitors.
  3. 3. An LED driver circuit according to claim I or 2. two pairs of back to back capacitors are provided.
  4. 4. An LED feeder circuit according to any preceding claim, wherein a capacitor is orovided nrrn5 the tEDs.
  5. 5. An LED feeder circuit according to any preceding claim, wherein a thermistor is provided in series with the input of the rectifier and the mains input.
  6. 6. An LED feeder circuit substantially as hereinbefore described with reference to and as shown in the aceomnanving drawings.
  7. 7. An LED lamo having an LED feeder circuit according to any preceding claim.
GB1210341.2A 2012-05-25 2012-06-11 LED driver circuit Withdrawn GB2502374A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GBGB1218239.0A GB201218239D0 (en) 2012-05-25 2012-10-11 LED driver circuit

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GBGB1209329.0A GB201209329D0 (en) 2012-05-25 2012-05-25 LED driver circuit

Publications (2)

Publication Number Publication Date
GB201210341D0 GB201210341D0 (en) 2012-07-25
GB2502374A true GB2502374A (en) 2013-11-27

Family

ID=46545971

Family Applications (3)

Application Number Title Priority Date Filing Date
GBGB1209329.0A Ceased GB201209329D0 (en) 2012-05-25 2012-05-25 LED driver circuit
GB1210341.2A Withdrawn GB2502374A (en) 2012-05-25 2012-06-11 LED driver circuit
GBGB1218239.0A Ceased GB201218239D0 (en) 2012-05-25 2012-10-11 LED driver circuit

Family Applications Before (1)

Application Number Title Priority Date Filing Date
GBGB1209329.0A Ceased GB201209329D0 (en) 2012-05-25 2012-05-25 LED driver circuit

Family Applications After (1)

Application Number Title Priority Date Filing Date
GBGB1218239.0A Ceased GB201218239D0 (en) 2012-05-25 2012-10-11 LED driver circuit

Country Status (1)

Country Link
GB (3) GB201209329D0 (en)

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20100176735A1 (en) * 2009-01-15 2010-07-15 Chen-Sheng Yang LED light string assembly with constant current circuit
CN201875544U (en) * 2010-09-27 2011-06-22 四川竞祥半导体照明有限公司 Safety illumination work light for LED (light-emitting diode) machine tool

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20100176735A1 (en) * 2009-01-15 2010-07-15 Chen-Sheng Yang LED light string assembly with constant current circuit
CN201875544U (en) * 2010-09-27 2011-06-22 四川竞祥半导体照明有限公司 Safety illumination work light for LED (light-emitting diode) machine tool

Also Published As

Publication number Publication date
GB201209329D0 (en) 2012-07-11
GB201218239D0 (en) 2012-11-28
GB201210341D0 (en) 2012-07-25

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WAP Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1)