Universal hardware/software feedback control for high-frequency signals

• US 6,504,321 B2
• Filed: 02/06/2001
• Issued: 01/07/2003
• Est. Priority Date: 02/06/2001
• Status: Expired due to Term

• Current Assignee: Signify Holding B.V. (Signify N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Giannopoulos, Demetri, Wacyk, Ihor, Wang, Shenghong
• Primary Examiner(s): Wong, Don
• Assistant Examiner(s): A, Minh D
• Application Number:
  US09/777,275
• Publication Number:
  US 20020107584A1
• Time in Patent Office: 700 Days
• Field of Search: 315/291, 315/293, 315/294, 315/295, 315/316, 315/307, 315/DIG.4
• US Class Current: 315/291
• CPC Class Codes: G05B 11/28 using pulse-height modulation; using pulse-width modulation
• CPC Class Codes: G05B 15/02 electric
• CPC Class Codes: H05B 41/3921 with possibility of light intensity variations
• CPC Class Codes: H05B 41/3925 by frequency variation H05B41/3922 takes precedence

Abstract

A method and apparatus for providing closed loop feedback control is presented. The method consists of a hybrid software and hardware solution to take advantage of the useful attributes of both. Analog signals output by the device are sampled at a rate sufficient to preserve all necessary high frequency information, and preprocessed at high speed in hardware. The outputs of the preprocessing stage are then operated on in software at much lower speeds. The method and apparatus allow for the complex real time processing of feedback signals in the digital domain, yet allow the cost efficiencies and programming flexibility of a standard micro-controller to be utilized.

Claims

1. A method of providing feedback control to a circuit driving a lamp, comprising:

digitizing feedback signals from said lamp to produce corresponding digital signals of a first sample rate higher than a maximum data processing rate of a micro-processor;

multiplying said digital signals to generate a multiplied digital signal;

averaging said multiplied digital signal to a digital signal of a second sample rate within said maximum data processing rate of said microprocessor; and

processing said digital signal of said second rate by implementing a control algorithm at said microprocessor.

2. The method of claim 1 wherein said feedback signals comprises a voltage across and a current through said lamp.

3. The method of claim 1 wherein said feedback signals comprises high frequency components, and wherein said first sample rate is high enough to preserve all required high frequency information.

4. The method of claim 1 wherein said multiplying is done by a multiplier implemented as hardware.

5. The method of claim 1 wherein said processing is done in real time.

6. A method of providing feedback control comprising:

digitizing one or more feedback signals of a first sample rate higher than a maximum data processing rate of a microprocessor;

preprocessing said digitized signals to generate a preprocessed digital signal of a second sample rate within said maximum data processing rate of said micro-processor; and

processing said preprocessed digital signal of said second rate by implementing a software control algorithm at said microprocessor.

7. The method of claim 6 wherein said preprocessing is implemented by hardware.

8. The method of claim 6 wherein said preprocessing comprising averaging a signal of said first sample rate to a signal of said second rate.

9. The method of claim 6 wherein said preprocessing comprising multiplying said digitized signals of said first sample rate to a multiplied signal.

10. The method of claim 9 wherein said multiplying is done by a multiplier implemented in hardware.

11. The method of claim 6 wherein said first sample rate is high enough to protect all required high frequency information contained in said feedback signals.

12. The method of claim 11 wherein said first sample rate for digitizing said feedback signals is programmable.

13. The method of claim 8 wherein said second sample rate by said averaging is programmable.

14. The method of claim 6 wherein said feedback signals comprises a voltage across and a current though a lamp.

15. The method of claim 14 wherein said software control algorithm is one for controlling a ballast circuit driving said lamp.

16. Apparatus for providing feed back control comprising:

analog to digital converters for digitizing feedback signals at a first sample rate;

means for preprocessing said digitized signals of said first sample rate to generate a preprocessed signal of a second sample rate; and

a microprocessor for operating upon said preprocessed signal by implementing a software control algorithm;

wherein said first sample rate is higher than a maximum data processing rate of said microprocessor, and said second sample rate is within said maximum data processing rate of said microprocessor.

17. The apparatus of claim 16 wherein said preprocessing means is implemented in hardware.

18. The apparatus of claim 16 wherein said preprocessing means comprises an averaging module for averaging a signal of said first sample rate to a signal of said second sample rate.

19. The apparatus of claim 16 wherein said feedback signals comprise a voltage across and a current through a lamp.

20. The apparatus of claim 19 wherein said preprocessing means comprising a multiplier implemented in hardware for multiplying said digitized feedback signals.