Circuits for eliminating ghosting phenomena in display panel having light emitters
The present disclosure provides a circuit for discharging parasitic capacitance in a display panel with common-anode topology having a plurality of light emitters, as well as a circuit for charging parasitic capacitance in a display panel with common-cathode topology. In the common-cathode topology, the circuit includes a three-terminal device having a gate, a source, and a drain, wherein one of the source and the drain is electrically coupled to a common cathode of the light emitters, and a mechanism for controlling the three-terminal device, the mechanism being electrically coupled to the gate. Shortly after a previously selected light emitter is unselected, the mechanism turns on the three-terminal device to form a conductive path between the source and the drain. The mechanism turns off the three-terminal device after a voltage at the common cathode is increased to a predetermined voltage level or after a maximum period of time lapses.
1. A circuit for eliminating ghost image in a display panel having a plurality of light emitters, the circuit comprising:
a first circuit branch;
a second circuit branch; and
a third circuit branch;
wherein the first circuit branch, the second circuit branch, and the third circuit branch are electrically coupled in parallel between a common cathode of the light emitters and a reference voltage;
wherein the first circuit branch forms a first conductive path to charge parasitic capacitance in the display panel shortly after a previously selected light emitter is unselected;
wherein the second branch forms a second conductive path to charge the parasitic capacitance immediately after a next light emitter is selected; and
wherein the third branch forms a third conductive path to charge the parasitic capacitance so long as the previously selected light emitter is unselected,
wherein the first circuit branch includes a first resistor having a first resistance, the second circuit branch includes a second resistor having a second resistance, and the third circuit branch includes a third resistor having a third resistance, and
wherein the first resistance is substantially less than the second resistance, and the second resistance is substantially less than the third resistance.
2. The circuit of claim 1 , wherein the first circuit branch comprises:
a first three-terminal device having a gate, a source, and a drain, wherein one of the source and the drain is electrically coupled to the common cathode; and
a mechanism for controlling the first three-terminal device, the mechanism being electrically coupled to the gate of the first three-terminal device;
wherein, shortly after the previously selected light emitter is unselected, the mechanism turns on the first three-terminal device to form the first conductive path, thereby charging the parasitic capacitance through the first conductive path; and
wherein the mechanism turns off the first three-terminal device after a voltage at the common cathode is increased to a predetermined voltage level or after a maximum period of time lapses.
3. The circuit of claim 1 , wherein the second circuit branch includes a second three-terminal device and a rising edge pulse generator.
4. The circuit of claim 3 , wherein, after a next light emitter is selected, the rising edge pulse generator generates a pulse signal to turn on the second three-terminal device, thereby forming the second current path.
5. The circuit of claim 4 , wherein the pulse signal has a pulse width of about 30 nanoseconds.
6. A display panel, comprising:
an array of light emitters having a plurality of rows of light emitters and a plurality of common cathode nodes, wherein cathodes of light emitters in each row are coupled to a corresponding common cathode node;
a power source electrically coupled to an anode of the light emitters;
a selection circuit including a plurality of switches for sequentially selecting one row of the light emitters at a given time, wherein each switch is electrically coupled to a common cathode node; and
a circuit for eliminating ghosting phenomena, the circuit comprising:
a first circuit branch;
a second circuit branch; and
a third circuit branch;
wherein the first circuit branch, the second circuit branch, and the third circuit branch are electrically coupled in parallel between a common cathode of the light emitters and a reference voltage;
wherein the first circuit branch forms a first conductive path to charge parasitic capacitance in the display panel shortly after a previously selected light emitter is unselected;
wherein the second branch forms a second conductive path to charge the parasitic capacitance immediately after a next light emitter is selected; and
wherein the third branch forms a third conductive path to charge the parasitic capacitance so long as the previously selected light emitter is unselected,
wherein the first circuit branch includes a first resistor having a first resistance, the second circuit branch includes a second resistor having a second resistance, and the third circuit branch includes a third resistor having a third resistance, and
wherein the first resistance is substantially less than the second resistance, and the second resistance is substantially less than the third resistance.