LED display with control circuit

1. An active-matrix circuit for controlling an LED display pixel, the active-matrix circuit comprising:

a control circuit responsive to control signals for storing a luminance value in a storage circuit during a frame period;

a drive circuit responsive to the storage circuit for controlling current through an LED to emit light at a luminance level determined by the luminance value;

a luminance-value reduction circuit connected to the storage circuit that controls a reduction of the luminance value stored in the storage circuit during the frame period; and

a reduction-control circuit responsive to a reduction-control signal connected to the luminance-value reduction circuit to control rate at which the luminance value reduction circuit reduces the luminance value,

wherein the reduction-control circuit is a transistor, and

wherein:

the storage circuit comprises a capacitor for storing a charge representative of the luminance value,

the luminance-value reduction circuit comprises a resistor connected in parallel across the capacitor, and

the reduction-control transistor comprises connected in series with the resistor to control the flow of current through the resistor in response to the reduction-control signal.

2. The active-matrix circuit of claim 1 , wherein the control circuit or drive circuit comprises transistors formed on a substrate.

3. The active-matrix circuit of claim 1 , wherein the storage circuit comprises a capacitor for storing a charge representative of the luminance value.

4. The active-matrix circuit of claim 3 , wherein the luminance-value reduction circuit decreases the charge stored in the capacitor over time.

5. The active-matrix circuit of claim 4 , wherein the luminance-value reduction circuit comprises a resistor connected in parallel across the capacitor.

6. The active-matrix circuit of claim 4 , wherein the luminance-value reduction circuit comprises a transistor connected in parallel across the capacitor and responsive to a control signal to control rate at which the charge in the capacitor decreases over time.

7. The active-matrix circuit of claim 1 , wherein:

the control signals include a select signal for controlling the control circuit; and

the reduction-control signal comprises an inverse signal of the select signal.

8. The active-matrix circuit of claim 7 , wherein the reduction-control circuit comprises an inverter.

9. The active-matrix circuit of claim 8 , wherein the inverter comprises a transistor.

10. The active-matrix circuit of claim 1 , wherein the controlled reduction begins, without substantial delay, after the luminance value is stored in the storage circuit.

11. The active-matrix circuit of claim 1 , wherein the luminance value decreases continuously after the luminance value is stored in the storage circuit.

12. An active-matrix circuit for controlling an LED display pixel, the active-matrix circuit comprising:

a control circuit responsive to control signals for storing a luminance value in a storage circuit during a frame period;

a drive circuit responsive to the storage circuit for controlling current through an LED to emit light at a luminance level determined by the luminance value;

a luminance-value reduction circuit connected to the storage circuit that controls a reduction of the luminance value stored in the storage circuit during the frame period,

wherein the luminance value is held at a constant value for a first period less than the frame period after the luminance value is stored in the storage circuit and then is reduced at the conclusion of the first period.

13. A display device, comprising:

a plurality of light-emitting pixels formed over a substrate, each pixel including a light-emitting diode (LED) responsive to current to emit light and a pixel-driving circuit for providing current to the LED, each pixel-driving circuit further comprising:

a control circuit responsive to control signals for storing a luminance value in a storage circuit;

a drive circuit responsive to the storage circuit for controlling current through an LED to emit light at a luminance level determined by the luminance value;

a luminance-value reduction circuit connected to the storage circuit that reduces the luminance value stored in the storage circuit over time; and

a reduction-control circuit responsive to a reduction-control signal connected to the luminance-value reduction circuit to control rate at which the luminance value reduction circuit reduces the luminance value,

wherein the reduction-control circuit is a transistor, and

wherein:

the storage circuit comprises a capacitor for storing a charge representative of the luminance value,

the luminance-value reduction circuit comprises a resistor connected in parallel across the capacitor, and

the reduction-control transistor comprises connected in series with the resistor to control the flow of current through the resistor in response to the reduction-control signal.

14. The display device of claim 13 wherein the LEDs comprise organic light-emitting diodes.

15. The display device of claim 13 wherein the LEDs comprise inorganic light-emitting diodes.

16. The display device of claim 13 wherein the inorganic LEDs comprise quantum dots in a polycrystalline semiconductor matrix.

17. A method of reducing luminance of a display device within a frame period, the method comprising:

employing an LED pixel control signal to store a luminance value in a storage circuit to control current through an LED to emit light at a luminance level determined by the luminance value; and

controlling the reduction of the luminance value within a frame period by employing a luminance-value reduction circuit connected to the storage circuit to reduce the luminance value stored in the storage circuit,

wherein the luminance value is held at a constant value for a first period less than the frame period after the luminance value is stored and then is reduced at the conclusion of the first period.