LED Lighting System with Accurate Current Control

• US 20100156319A1
• Filed: 12/19/2008
• Published: 06/24/2010
• Est. Priority Date: 08/29/2008
• Status: Active Grant

• Current Assignee: Signify Holding B.V. (Signify N.V.)
• Original Assignee: Cirrus Logic Incorporated
• Inventors: Melanson, John Laurence
• Granted Patent: US 8,487,546 B2
• Time in Patent Office: Days
• US Class Current: 315/297
• CPC Class Codes: H05B 45/14 using electrical feedback from LEDs or from LED modules
• CPC Class Codes: H05B 45/20 Controlling the colour of the light
• CPC Class Codes: H05B 45/327 Burst dimming
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

A light emitting diode (LED) lighting system and method are disclosed. The LED lighting system and method include an LED controller to accurately control a current in an LED system. The LED controller includes components to calculate, based on the current and an active time period of an LED current time period, an actual charge amount delivered to the LED system wherein the LED current time period is duty cycle, modulated at a rate of greater than fifty (50) Hz and to utilize the actual charge amount to modify and provide a desired target charge amount to be delivered during a future active time period of the LED current time period. The LED system and method further involve components to compare the actual charge amount to a desired charge amount for the active time period and compensate for a difference between the actual charge amount and the desired charge amount during the future active time period.

Claims

1. A light emitting diode (LED) lighting system comprising:

an LED controller to control a current in an LED system, wherein the LED controller includes components to;

calculate, based on the current and an active time period of an LED current time period, an actual charge amount delivered to the LED system wherein the LED current time period is duty cycle modulated at a rate of greater than fifty (50) Hz; and

utilize the actual charge amount to modify and provide a desired target charge amount to be delivered during a future active time period of the LED current time period.

2. The LED lighting system of claim 1 wherein the LED controller controls dimming of the LED system.

3. The LED lighting system of claim 2 wherein the LED controller controls dimming of the LED system over a wide dimming frequency range.

4. The LED lighting system of claim 1 wherein the components to utilize the actual charge amount to modify and provide a desired target charge amount to be delivered during a future active time period further comprises:

components to compare the actual charge amount to a desired charge amount for the active time period and compensate for a difference between the actual charge amount and the desired charge amount during the future active time period.

5. The LED lighting system of claim 4 wherein the LED controller controls dimming of the LED system.

6. The LED lighting system of claim 5 wherein the LED controller comprises a dimming controller and a current controller wherein the dimming controller drives the current controller.

7. The LED lighting system of claim 6 wherein the dimming controller is driven by a dimming rate and the current controller is driven by a switching frequency rate and wherein the dimming rate is different than the switching frequency rate.

8. The LED lighting system of claim 7 wherein the dimming controller is a pulse width modulation (PWM) dimming controller.

9. The LED lighting system of claim 7 wherein the dimming controller is a delta-sigma modulator dimming controller.

10. The LED lighting system of claim 1 wherein the LED system comprises a number of LEDs.

11. A method for controlling a current in a light emitting diode (LED) system of an LED lighting system comprising:

duty cycle modulating the LED current time period at a rate of greater than fifty (50) Hz;

calculating, based on the current and an active time period of an LED current time period, an actual charge amount delivered to the LED system; and

utilizing the actual charge amount to modify and provide a desired target charge amount to be delivered during a future active time period of the LED current time period.

12. The method according to claim 11 further comprising:

comparing the actual charge amount to a desired charge amount for the active time period; and

compensating for a difference between the actual charge amount and the desired charge amount during the future active time period.

13. The method according to claim 12 wherein the method for controlling a current controls dimming of the LED system.

14. A current controller for controlling current to a light emitting diode (LED) system for an LED lighting system comprising:

components for receiving a dimming level signal from a dimming controller and for controlling and providing, based on the dimming level signal, an amount of drive current for driving the LED system; and

wherein the components are at least part of an LED controller to;

calculate, based on the current and an active time period of the LED current time period, an actual charge amount delivered to the LED system wherein the LED current time period is duty cycle modulated at a rate of greater than fifty (50); and

utilize the actual charge amount to modify and provide a desired target charge amount to be delivered during a future active time period of the LED current time period.

15. The current controller according to claim 14 wherein the current controller is operated at a switching frequency.

16. The current controller according to claim 14 wherein the current controller is a time-based controller for a controlled system.

17. The current controller according to claim 16 wherein the LED lighting system has an integration response and wherein the time-based controller further comprises:

a comparator that, while a control signal supplied to the LED system has a first state, detects, at a first time, a polarity change in a comparison of a sensed signal from the LED system and a reference signal;

time calculation logic that, based upon the first time, determines a second lime at which to change a state of a control signal supplied to the LED system; and

a modulator that, at the determined second time, changes the state of the control signal supplied to the LED system from the first slate to a second state.

18. A method for controlling current to a light emitting diode (LED) system for an LED lighting system comprising:

receiving a dimming level signal from a dimming controller; and

controlling and providing, based on the dimming level signal, an amount of drive current for driving the LED system; and

wherein the receiving and controlling and providing steps are at least part of an LED controller method to;

duty cycle modulate an LED current time period at a rate of greater than fifty (50) Hz;

calculate, based on the current and an active time period of the LED current time period, an actual charge amount delivered to the LED system; and

utilize the actual charge amount to modify and provide a desired target charge amount to be delivered during a future active time period of the LED current time period.

19. The method according to claim 18 wherein the LED lighting system has an integration response, said method comprising:

while a control signal supplied to the LED system is in a first state, detecting at a first time a polarity change in a comparison of a sensed signal from the LED system and a reference signal;

based upon the first time, determining a second time at which to change a state of a control signal supplied to the LED system; and

at the determined second time, changing the state of the control signal supplied to the LED system from the first state to a second state.

20. A delta-sigma modulated dimming controller for controlling a dimming level of a light emitting diode (LED) system for an LED lighting system comprising:

components for receiving a dimming control signal and driving a dimming level signal to a current controller for providing a current for driving the LED system; and

wherein the components are at least part of an LED controller to;

calculate, based on the current and an active time period of an LED current time period, an actual charge amount delivered to the LED system wherein the LED current time period is duty cycle modulated at a rate of greater than fifty (50) Hz; and

utilize the actual charge amount to modify and provide a desired target charge amount to be delivered during a future active time period of the LED current time period.

21. The delta-sigma modulated dimming controller according to claim 20, wherein the current controller controls and provides, based on the dimming level signal, an amount of drive current for driving the LED system.

22. A method for controlling a dimming level of a light emitting diode (LED) system for an LED lighting system utilizing a delta sigma modulator comprising:

receiving a dimming control signal; and

driving a dimming level signal to a current controller for providing a current for driving the LED system; and

wherein the receiving and driving steps are at least part of an LED controller method to;

duty cycle modulate the LED current time period at a rate of greater than fifty (50) Hz;

calculate, based on the current and an active time period of an LED current time period, an actual charge amount delivered to the LED system; and

utilize the actual charge amount to modify and provide a desired target charge amount to be delivered during a future active time period of the LED current time period.

23. The method according to claim 22, further comprises controlling and providing, by the current controller based on the dimming level signal received, an amount of drive current for driving the LED system.