MOS integrated circuit for driving light-emitting diodes

• US 5,061,861 A
• Filed: 05/04/1989
• Issued: 10/29/1991
• Est. Priority Date: 05/20/1988
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Sameshima, Kazuhiro, Ohnishi, Masaru
• Primary Examiner(s): Miller, Stanley D.
• Assistant Examiner(s): PHAN, TRONG Q
• Application Number:
  US07/347,492
• Time in Patent Office: 908 Days
• Field of Search: 307/311, 307/270, 307/571, 307/573, 307/577, 307/583, 307/584, 307/254, 307/241, 307/248, 307/244
• US Class Current: 327/109
• CPC Class Codes: G05F 3/262 using field-effect transistors only
• CPC Class Codes: G06K 15/1247 using an array of light sources, e.g. a linear array
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light
• CPC Class Codes: H05B 45/395 Linear regulators
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

An MOS integrated circuit for driving light-emitting diodes (LED'"'"'s) comprises first constant current circuits, each of which is for one of the LED'"'"'s and includes a first drive circuit for maintaining the drive current for the associated LED at a predetermined value established by a first reference voltage. The integrated circuit further includes a second constant current circuit which is connected to all of the first constant current circuits to form a mirror circuit with each of said first constant current circuits. A current detecting element detects a predetermined magnitude of current flowing therethrough and develops a current-representative detection voltage. A second drive circuit within the second constant current circuit responds to the detection voltage and a second reference voltage by maintaining said first reference voltage at a predetermined value so that the LED drive current is determined by the said detection voltage and second reference voltage.

Claims

1. An integrated circuit for driving at least first and second power using devices, comprising:

means for producing a first predetermined current;

a current matter, responsive to said first predetermined current, for producing a second predetermined current;

at least a first and a second driver devices;

said first driver device including means for driving said first power-using device with a third current;

said second driver device including means for driving said second power-using device with a fourth current;

said third current having a first predetermined relationship to said second current;

said fourth current having a second predetermined relationship to said second current;

said means for producing a first predetermined current including a resistor; and

means for permitting controlling a resistance of said resistor from a location external to said integrated circuit, whereby said first, second, third and fourth currents are controlled.

2. An integrated circuit according to claim 1 wherein said means for controlling includes means for permitting trimming of said resistor to a value effective to produce said first predetermined current.

3. An integrated circuit according to claim 1 wherein said means for controlling includes:

at least a second resistor;

switching means for selectively connecting said second resistor in parallel with said resistor; and

said at least a second resistor having a value effective, when selectively connected in parallel with said resistor or produce a parallel combination passing said first predetermined current.

4. An integrated circuit according to claim 3, wherein:

said switching means includes a switching transistor in series with said second resistor; and

means for permitting selective switching control of said switching transistor from said location external to said integrated circuit.

5. An integrated circuit according to claim 1 wherein said integrated circuit includes MOS devices.

6. An integrated circuit according to claim 1 wherein:

said current mirror includes a second resistor;

said first driver device includes a third resistor;

said second driver device includes a fourth resistor;

said second, third and fourth resistors being formed integrally on said integrated circuit; and

said second, third and fourth resistors having predetermined relationships effective for producing said third and fourth currents.

7. An integrated circuit according to claim 1, wherein:

said second, third and fourth resistances having substantially equal values of resistance; and

said first, second, third and fourth currents are substantially equal to each other.

8. An integrated circuit for driving at least first and second light-emitting diodes comprising:

means for producing a first predetermined current;

a current mirror, responsive to said first predetermined current for producing a second predetermined current;

said second predetermined current being substantially equal to said first predetermined current;

a first driver device for driving said first light-emitting diode;

said first driver device including means, responsive to said second predetermined current, for applying a third predetermined current to said first light-emitting diode;

said third predetermined current being substantially equal to said second predetermined current;

a second driver device for driving said second light-emitting diode;

said second driver device including means, responsive to said second predetermined current, for applying a fourth predetermined current to said second light-emitting diode;

said fourth predetermined current being substantially equal to said second predetermined current;

said means for producing a first predetermined current including a resistor;

said resistor determining an amplitude of said first predetermined current; and

means for permitting control of a resistance of said resistor from a location external to said integrated circuit, whereby said first, second, third and fourth predetermined currents are controlled to a preferred value.