Method and apparatus for supplying power to light emitting diodes

(19)

(11)

EP 0 948 241 A3

(12)	EUROPEAN PATENT APPLICATION

(88)	Date of publication A3:
	27.12.2000 Bulletin 2000/52

(43)	Date of publication A2:
	06.10.1999 Bulletin 1999/40

(21)	Application number: 99660053.2

(22)	Date of filing: 25.03.1999

(51)	International Patent Classification (IPC)⁷: H05B 33/08

(84)	Designated Contracting States:
	AT BE CH CY DE DK ES FI FR GB GR IE IT LI LU MC NL PT SE
	Designated Extension States:
	AL LT LV MK RO SI

(30)

Priority:

30.03.1998 FI 980717

(71)	Applicant: TEKNOWARE OY
	15200 Lahti (FI)

(72)	Inventor:
	Pienisaari, Heikki 04600 Mäntsälä (FI)

(74)	Representative: Peltonen, Antti Sakari
	Kolster Oy Ab, Iso Roobertinkatu 23, P.O. Box 148 00121 Helsinki 00121 Helsinki (FI)

(54)	Method and apparatus for supplying power to light emitting diodes

(57) The invention relates to a method and an apparatus for supplying power to light emitting diodes connected to a light emitting diode matrix (MN) comprising one or more parallel connected light emitting diodes or a series connection thereof. The method comprises repeated phases where the amount of current in the main circuit formed of a series connection of the light emitting diode matrix (MN), a switching element (K1) and an inductance (N1) is monitored, the main circuit is opened by the switching element (K1) when the current of the main circuit reaches a predetermined value, whereby the current starts flowing through a zero diode circuit formed of a zero diode (D1) arranged on a circuit, the amount of current in the zero diode circuit is monitored, and the main circuit is closed by the switching element (K1) when the zero diode circuit current reaches a predetermined value.

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