Soft start solid state switch

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(11)

EP 0 285 417 A3

(12)	EUROPEAN PATENT APPLICATION

(88)	Date of publication A3:
	01.03.1989 Bulletin 1989/09

(43)	Date of publication A2:
	05.10.1988 Bulletin 1988/40

(21)	Application number: 88302885.4

(22)	Date of filing: 30.03.1988

(51)	International Patent Classification (IPC)⁴: H05B 39/02

(84)	Designated Contracting States:
	DE FR GB IT NL SE

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Priority:

31.03.1987 GB 8707636
17.03.1988 US 163534

(71)	Applicant: GENERAL ELECTRIC COMPANY
	Schenectady, NY 12345 (US)

(72)	Inventors:
	Carlson, Peter John Raleigh North Carolina 27612 (US) Hodgins, Robert George Raleigh North Carolina 27615 (US)

(74)	Representative: Kennington, Eric Alasdair et al
	London Patent Operation GENERAL ELECTRIC TECHNICAL SERVICES CO. Burdett House 15-16 Buckingham Street London WC2N 6DU London WC2N 6DU (GB)

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References cited: :

(54)	Soft start solid state switch

(57) The junction temperature rise of a power MOSFET (12;202;402) serially connected to a lamp (32;204;404) whose resistance nonlinearly increases during turn-on is moderated by the use of control circuitry which initially sets up a relatively low essentially constant current flow through the lamp and transistor and then automatically after the lamp resistance reaches a preselected level, the lamp is allowed to draw significantly more current. Alternatively, there is initially an essentially constant flow of current to the MOSFET gate, causing a gradual turn-on, until the lamp resistance reaches the preselected level. The size and therefore cost of the power MOSFET is reduced significantly because the magnitude of the current spike generated by turning on the lamp is significantly reduced by the use of the novel control circuitry.

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