Stochastic signal density modulation for optical transducer control

• US 9,750,097 B1
• Filed: 11/18/2015
• Issued: 08/29/2017
• Est. Priority Date: 11/13/2006
• Status: Active Grant

• Current Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Original Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Inventors: Van Ess, David, Prendergast, Patrick N
• Primary Examiner(s): A, Minh D
• Application Number:
  US14/944,388
• Time in Patent Office: 650 Days
• Field of Search: 315224, 315299, 315291, 315307, 315317, 315318
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light
• CPC Class Codes: H05B 45/18 using temperature feedback
• CPC Class Codes: H05B 45/20 Controlling the colour of the light
• CPC Class Codes: H05B 45/30 Driver circuits
• CPC Class Codes: H05B 45/46 having LEDs disposed in parallel lines

Abstract

A controller for optical transducers uses stochastic signal density modulation to reduce electromagnetic interference.

Claims

1. A method comprising:

generating a first signal with a stochastic density;

comparing the first signal to an input signal with a density register value;

generating a modulation signal from the comparing the first signal and input signal; and

driving a controllable current supply with the modulation signal, the controllable current supply coupled to a light-emitting diode (LED).

2. The method of claim 1, wherein the first signal is based upon a pseudorandom number.

3. The method of claim 1, wherein the controllable current source is configured to modulate a brightness of the LED.

4. An apparatus comprising:

a controllable current supply coupled to a light-emitting diode (LED);

a stochastic signal density modulator (SSDM) coupled to the controllable current supply, wherein the SSDM is configured to provide a pseudorandom stochastic control signal to the controllable current supply, the pseudorandom stochastic control signal to control a light intensity output of the LED and to reduce electromagnetic interference, and derived from an output of the SSDM and a signal density register.

5. The apparatus of claim 4, wherein the SSDM comprises a stochastic state machine and is configured to generate a plurality of stochastic values.