Granted Patent B2

US 8,581,828 · App. 12/772,067 · Granted Nov 12, 2013

Abstract

Claims (48)

1. A liquid crystal display, comprising:

backlight circuitry comprising a set of light emitting diodes (LEDs), wherein the set of LEDs are arranged in a plurality of strings of one or more LEDs;

a controller that receives a load metric that establishes load of the backlight circuitry, that receives an error value as an input, and that supplies a control signal value based on the load metric and also based on the error value, the controller comprising a plurality of compensation blocks, wherein a compensation block configures the control signal value;

power supply circuitry that receives the control signal value and regulates a voltage supplied to the backlight circuitry;

an efficiency regulator coupled to the backlight circuitry for monitoring one or more string voltages of one or more strings of the plurality of strings to determine a reference value based on the one or more string voltages; and

an error circuit that generates the error value as a difference between the reference value and a voltage value of the voltage supplied to the backlight circuitry.

2. The liquid crystal display of claim 1 , wherein the controller includes a selector component that switches from a first compensation block to a second compensation block based on the load metric so that the second compensation block receives the error value from the error circuit and supplies the control signal value based on the load metric and the error value to the power supply circuitry.

3. The liquid crystal display of claim 1 , wherein the load metric is determined in part by a pulse-width modulation (PWM) dimming profile of power applied to the backlight circuitry.

4. The liquid crystal display of claim 3 , further comprising:

a dimming component that applies the PWM dimming profile of power through application of phase-shifted PWM power to the plurality of strings of one or more LEDs.

5. The liquid crystal display of claim 4 , wherein the dimming component supplies the load metric.

6. The liquid crystal display of claim 3 , wherein the load metric is determined by the product of a duty cycle of the PWM dimming profile and a number of strings of one or more LEDs in the plurality of strings of one or more LEDs.

7. The liquid crystal display of claim 1 ,

wherein the compensation blocks are implemented as filters, each filter having a gain response different from other gain responses of other filters; and

wherein at least one compensation block in the plurality of compensation blocks is digital and implemented as a digital filter with at least one pole.

8. The liquid crystal display of claim 7 , wherein at least one memory register stores a control signal value for the at least one compensation block that is digital.

9. The liquid crystal display of claim 7 , wherein the digital filter is a one-zero, one-pole filter.

10. The liquid crystal display of claim 1 , wherein at least one compensation block in the plurality of compensation blocks is an analog element that includes a resistor, a capacitor, and an inductor.

11. The liquid crystal display of claim 2 , wherein the plurality of compensation blocks comprises two compensation blocks and the load metric adopts two values in equilibrium state, the selector component connects the first of the two compensation blocks to a compensation feedback circuit for the first of the two values of the load metric and the second of the two compensation blocks for the second of the two values of the load metric.

12. A method, comprising:

acquiring a load metric that conveys load of backlight circuitry in a liquid crystal display, wherein the backlight circuitry comprises a set of light emitting diodes (LEDs) arranged in a plurality of strings of one or more LEDs;

acquiring an error value generated as a difference between a reference value and a voltage value of a voltage applied to the backlight circuitry, wherein an efficiency regulator coupled to the backlight circuitry for monitoring one or more string voltages of one or more strings of the plurality of strings to determine the reference value based on the one or more string voltages;

supplying a control signal value based at least on the load metric and the error value; and

collecting the control signal value and regulating the voltage applied to the backlight circuitry.

13. The method of claim 12 , wherein the supplying includes:

disconnecting a first compensation block in a compensation feedback circuit in a backlighting system that includes the backlight circuitry; and

connecting a second compensation block to the compensation feedback circuit;

wherein the first compensation block has a first filter gain response, and

wherein the second compensation block has a second filter gain response different from the first filter gain response.

14. The method of claim 12 , wherein the supplying includes:

comparing a first load metric with a second load metric; and

if the first load metric is different from the second load metric:

selecting a first compensation block for connecting to a compensation feedback loop in a backlighting system that includes the backlight circuitry;

disconnecting a second compensation block that closes the compensation feedback circuit in the backlighting system; and

connecting the first compensation block to the compensation feedback circuit in the backlighting system.

15. The method of claim 12 , the acquiring includes:

configuring circuitry to deliver the load metric based at least on at least one of a load change, a change on a pulse-width modulation dimming profile, a schedule, or a predetermined period; and

receiving the load metric according at least in part to a configuration of the circuitry.

16. The method of claim 12 , further comprising:

generating the load metric, wherein the load metric is based at least on a pulse-width modulation (PMW) dimming profile; and

supplying the load metric.

17. An apparatus, comprising:

a plurality of compensation blocks, wherein a least one compensation block in the plurality of compensation blocks receives an input signal, the input signal generated as a difference between a reference value and a second value, and outputs a control signal; and

a selector component that acquires a value of load in light-emitting-diode (LED)-based backlight circuitry and, based on the value of the load, (i) selects a first compensation block in the plurality of compensation blocks, (ii) disconnects a second compensation block in the plurality of compensation blocks from a compensation feedback circuit, and (ii) connects the first compensation block to the compensation feedback circuit, the first compensation block outputs a control signal based on the value of the load,

wherein the LED-based backlight circuitry comprises a set of LEDs arranged in a plurality of strings of one or more LEDs, and wherein an efficiency regulator coupled to the LED-based backlight circuitry for monitoring one or more string voltages of one or more strings of the plurality of strings to determine the reference value based on the one or more string voltages.

18. The apparatus of claim 17 , wherein the value of the load is dictated at least in part by a phase-shifted pulse-width modulation (PWM) power waveform applied to the LED-based backlight circuitry.

19. The apparatus of claim 17 , wherein the plurality of compensation blocks are implemented as filters, each filter having a gain response different from other gain responses of other filters, and the plurality of compensation blocks includes a digital compensation block, an analog compensation block, or a combination thereof.

20. The liquid crystal display of claim 1 , wherein the voltage supplied to the backlight circuitry is regulated based on the reference value so that the voltage maintains the one or more string voltages of the one or more strings of the plurality of strings above a minimum voltage that ensures operation of respective constant current driver circuits coupled to the one or more strings, and wherein the efficiency regulator is coupled to the respective constant current driver circuits to monitor the one or more string voltages of the one or more strings.

Assignments (20)