Modulation circuit for a light emitting device

• US 4,659,967 A
• Filed: 07/29/1985
• Issued: 04/21/1987
• Est. Priority Date: 07/29/1985
• Status: Expired due to Term

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Dahl, Randy L.
• Primary Examiner(s): Moore, David K.
• Assistant Examiner(s): Razavi, M.
• Application Number:
  US06/759,813
• Time in Patent Office: 631 Days
• Field of Search: 315/241, 315/209, 315/307, 315/171, 315/173, 315/205, 315/240, 340/782, 307/270, 307/254, 307/311
• US Class Current: 315/307
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light
• CPC Class Codes: H05B 45/30 Driver circuits

Abstract

The present invention consists of a modulation circuit used in a digital application. The modulation circuit is designed to provide an LED with a more analog type signal. This in turn causes the LED to emit a signal that is peaked rather than a constant square wave providing a better conversion frequency to the fundamental frequency.

Claims

1. A modulation circuit for a light emitting device having a power supply and a ground, said modulation circuit comprising:

voltage regulating means for regulating the voltage, said voltage regulating means having an input, an output and a reference line, said input being coupled to said power supply;

a resistor having a first end and a second end, said first end being coupled to said output of said voltage regulating means and said second end being coupled to said reference line of said voltage regulating means;

a capacitor having a first end and a second end, said first end being coupled to said second end of said resistor and said second end being coupled to said ground;

switch means for providing a signal, said switch means having an input, an output, and a control line, said input being coupled to said reference line of said voltage regulating means;

oscillating means for providing an oscillating signal, said oscillating means having an output being coupled to said control line of said switch means; and

light emitting device having an anode and a cathode, said anode being coupled to said output of said switch means and said cathode being coupled to said ground.

2. The modulation circuit of claim 1 wherein said switch means comprises a metal on silicon device having a source, a drain and a gate, said source being coupled to said reference of said voltage regulating means, said drain being coupled to said anode of said light emitting diode and said gate being coupled to said output of said oscillating means.

3. The modulation circuit of claim 1 wherein said oscillating means comprises a square wave generator having an output, said output being coupled to said gate line of said switch means.

4. A modulation circuit for a light emitting device having a power supply, a ground and an output being coupled to said light emitting device, said modulation circuit comprising:

voltage regulating means for regulating the voltage of said modulation circuit, said voltage regulating means having a first, second and third ports, said first port being coupled to said power supply of said modulation circuit;

modifying means comprising a resistor in series with a capacitor for modifying said voltage signal from said voltage regulating means, said modifying means having a first, second, third and fourth ports, said first port connecting said resistor to said second port of said voltage regulating means, said second port being coupled to said third port of said voltage regulating means, and said third port connecting said capacitor to said ground of said modulation circuit;

switch means for providing a signal, said switch means having an input, an output, and a control line, said input being coupled to said fourth port of said modifying means and said output being coupled to said output of said modulation circuit; and

oscillating means for providing an oscillating signal, said oscillating means having an output being coupled to said control line of said switch means.