Control of illumination devices using DC-DC converters

Patent metadata

Field	Value
Publication number	US-9781784-B2
Application number	US-201414533763-A
Country	US
Kind code	B2
Filing date	Nov 5, 2014
Priority date	Nov 5, 2014
Publication date	Oct 3, 2017
Grant date	Oct 3, 2017

Abstract

In an embodiment, method of controlling an illumination device by an output signal of a DC-DC converter is disclosed. The output signal is controlled by a PWM signal. The method includes receiving a feedback signal corresponding to variation in the output signal with respect to a pre-determined output signal, and determining a target duty cycle of the PWM signal based on the feedback signal. The PWM signal of the target duty cycle is capable of enabling the DC-DC converter to generate the pre-determined output signal. The method includes providing the PWM signal of an effective duty cycle equal to the target duty cycle over N switching pulses of the PWM signal to the DC-DC converter. The method provides the PWM signal by providing M switching pulses of a first PWM signal of a first duty cycle, and N−M switching pulses of a second PWM signal of a second duty cycle.

First claim

What is claimed is:

1. A method of controlling an illumination device by an output signal of a DC-DC converter, the method comprising:
receiving a feedback signal based on the output signal of the DC-DC converter; and
controlling the output signal of the DC-DC converter by:
determining a target duty cycle of a target Pulse Width Modulation (PWM) signal based on comparing the feedback signal with a reference output signal of the DC-DC converter,
determining a combination of
M switching pulses of a first PWM signal of a first duty cycle and
N−M switching pulses of a second PWM signal of a second duty cycle such that the combination results in the target PWM signal over N switching pulses of the PWM signal, wherein M and N are positive integers, and
generating the target PWM signal based on the combination of the M switching pulses of the first PWM signal and the N−M switching pulses of the second PWM signal, wherein a duty cycle resolution of the target PWM signal is based on a relationship between a switching frequency of the DC-DC converter and a frequency of a pole formed due to components of the DC-DC converter.

2. The method of claim 1 , wherein determining the combination such that the combination results in the target PWM signal comprises determining the values of M, N, the first duty cycle, and the second duty cycle.

3. The method of claim 1 , wherein the feedback signal is a difference signal of the output signal and the reference output signal.

4. The method of claim 1 , wherein the DC-DC converter is a boost converter.

5. The method of claim 1 , wherein the DC-DC converter is a buck converter.

6. The method of claim 1 , wherein the DC-DC converter is a buck-boost converter.

7. The method of claim 1 , wherein the illumination device is a light emitting diode (LED) or a light amplification by stimulated emission of radiation (LASER) device used in a time-of-flight imaging application.

8. A pulse width modulation (PWM) illumination control circuit for controlling an illumination device, comprising:
a DC-DC converter for providing an output signal to the illumination device; and
a digital controller coupled to the DC-DC converter for controlling the output signal of the DC-DC converter, the digital controller receiving a feedback signal based on the output signal, the digital controller comprising:
a duty cycle adjuster to determine a target duty cycle of a target PWM signal based on comparing the feedback signal with a reference output signal of the DC-DC converter,
a dithering module coupled to the duty cycle adjuster, the dithering module to determine a combination of
M switching pulses of a first PWM signal of a first duty cycle and
N−M switching pulses of a second PWM signal of a second duty cycle such that the combination results in the target PWM signal over N switching pulses of the PWM signal, wherein M and N are positive integers, and

a PWM pulse generator coupled to the dithering module, the PWM pulse generator to generate the target PWM signal based on the combination of the M switching pulses of the first PWM signal and the N−M switching pulses of the second PWM signal,
wherein a duty cycle resolution of the target PWM signal is based on a relationship between a switching frequency of the DC-DC converter and a frequency of a pole formed due to components of the DC-DC converter.

9. The PWM illumination control circuit of claim 8 , wherein the PWM pulse generator generates the target PWM signal based on a PWM control signal generated by the dithering module, the dithering module configured to generate the PWM control signal based on a value of the first duty cycle and a value of the second duty cycle.

10. The PWM illumination control circuit of claim 8 , wherein the feedback signal is a difference signal of the output signal and the reference output signal.

11. The PWM illumination control circuit of claim 8 , wherein the DC-DC converter is a boost converter.

12. The PWM illumination control circuit of claim 8 , wherein the DC-DC converter is a buck converter.

13. The PWM illumination control circuit of claim 8 , wherein the DC-DC converter is a buck-boost converter.

14. The PWM illumination control circuit of claim 8 , wherein the illumination device is a light emitting diode (LED) used in a time-of-flight imaging application.

15. The PWM illumination control circuit of claim 8 , wherein the illumination device is a light amplification by stimulated emission of radiation (LASER) device used in a time-of-flight imaging application.

16. A method of controlling an illumination device by an output signal of a DC-DC converter, the method comprising:
receiving a feedback signal based on the output signal of the DC-DC converter; and
controlling the output signal of the DC-DC converter by:
determining a target duty cycle of a target Pulse Width Modulation (PWM) signal based on comparing the feedback signal with a reference output signal of the DC-DC converter, and
generating the target PWM signal having the target duty cycle based on a combination of two or more PWM signals, each PWM signal of the two or more PWM signals having distinct duty cycles, wherein a duty cycle resolution of the target PWM signal is based on a relationship between a switching frequency of the DC-DC converter and a frequency of a pole formed due to components of the DC-DC converter.

17. The method of claim 16 , wherein generating the target PWM signal comprises generating the target PWM signal having the target duty cycle over N switching pulses of the target PWM signal, wherein the N switching pulses comprises a combination of the one or more switching pulses of each of the two or more PWM signals.

18. The method of claim 16 , wherein the illumination device is one of a light emitting diode (LED) or a light amplification by stimulated emission of radiation (LASER) device used in a time-of-flight imaging application.

Assignees

• Texas Instruments Inc

Inventors

• Patil Bharath
• Venkataraman Jagannathan

Classifications

• G09G2320/064

  by time modulation of the brightness of the illumination source · CPC title

• Y10S362/80

  Light emitting diode · CPC title

• H02M3/156

  with automatic control of output voltage or current, e.g. switching regulators · CPC title

• H05B41/3927

  by pulse width modulation (H05B41/3922 takes precedence) · CPC title

• H05B33/0851

  Electricity · mapped topic