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Title:
LIGHT EMITTING CIRCUIT
Document Type and Number:
Japanese Patent JPH11214183
Kind Code:
A
Abstract:

To provide a light emitting circuit which can provide controllable luminance over a wide range and can control luminance with high precision even in a case of low level luminance.

An analog voltage AV of 0 to 2 V is output from a D/A converter 20 and is given to a voltage current conversion part 30 in accordance with a digital value DV of 0 to 31 given from a light emitting control part 10. A drive current DI output from the voltage current conversion part 30 is controlled in 1 mA unit in a scope of 0 to 31 mA in accordance with the digital value DV. On the other hand, a drive current DI1 of a voltage current conversion part 40 is controlled in 4 mA unit in a scope of 0 to 124 mA, and a drive current DI1 of a voltage current conversion part 50 is controlled in 20 mA unit in a scope of 0 to 620 mA. Consequently, it is possible to control luminance of an LED 1 precisely over a wide scope even at a low level by turning on and off and controlling the voltage current conversion parts 40, 50 by scope specifying signals C1, C2.


Inventors:
ASANO ISAO
NAKAJIMA SATOSHI
Application Number:
JP1059698A
Publication Date:
August 06, 1999
Filing Date:
January 22, 1998
Export Citation:
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Assignee:
HOCHIKI CO
International Classes:
G08B17/103; G08B29/18; H05B37/02; H05B44/00; (IPC1-7): H05B37/02
Domestic Patent References:
JPH0696870A1994-04-08
JPH09101795A1997-04-15
JPH02195692A1990-08-02
JPH05344001A1993-12-24
JPH02207620A1990-08-17
JPH02280532A1990-11-16
JPH02277318A1990-11-13
JPH09270707A1997-10-14
JPH0793579B21995-10-09
JPH0528831Y21993-07-23
JPS4937237Y11974-10-11
Attorney, Agent or Firm:
Kakimoto Kyosei