LED matrix open/short detection apparatus and method
An apparatus to detect faulty connection of LED (open/short conditions) which may affect the function of LED display panel is presented. The apparatus basically controls the switches through control algorithm circuit to get the information of LED driver output pins voltage and compare them with two reference voltages to determine the open/short condition of individual LED.
1. An apparatus for detecting an open or short condition of a light emitting diode (LED) in a LED panel, the apparatus comprising:
a LED driver system to control the LED panel;
a control algorithm circuit to control the LED driver system;
a connection switches circuit to connect an output pin of the LED to a non-inverting input terminal of a comparator;
a comparator to compare a voltage of the LED output pin with first and second reference voltages;
a reference generation circuit to generate the first and second reference voltages,
wherein the LED driver system includes:
a first current source connected to a first terminal of the LED and controlled by a final from the control algorithm circuit, and
a second current source connected to a second terminal of the LED and controlled by a signal from the control algorithm circuit.
2. The apparatus according to claim 1 , further comprising:
a level shifter circuit to level shift input direct current (DC) voltage levels to a first reference DC voltage level.
3. The apparatus according to claim 2 , wherein the first reference DC voltage level is a first power supply voltage.
4. The apparatus according to claim 2 , wherein the first reference voltage is generated by voltage dividing a second power supply voltage.
5. The apparatus according to claim 2 , wherein the second reference voltage is generated via a small voltage drop across a resistor from a third power supply voltage.
6. The apparatus according to claim 5 , wherein the first reference voltage is lower in amplitude compared to the second reference voltage.
7. The apparatus according to claim 5 , wherein the third power supply voltage is the same as the first reference DC voltage level.
8. The apparatus according to claim 2 , wherein the connection switches circuit comprises a combination of a plurality of switches.
9. The apparatus according to claim 8 , wherein the switches are transmission gates.
10. The apparatus according to claim 1 , wherein the first current source is a metal oxide semiconductor transistor.
11. The apparatus according to claim 1 , further comprising:
a Signal Pass block to allow conditional outputting of LED output pin select signals outputted by said control algorithm circuit, based on an Enable signal; and
an Output Pass block to allow conditional outputting of a status of the open or short condition of the LED under test, based on the Enable signal.
12. The apparatus according to claim 11 , wherein the Signal Pass block is an AND logic circuit, comprising an array of AND gates.
13. The apparatus according to claim 12 , wherein the Output Pass block is a logic AND gate.
14. The apparatus according to claim 1 , wherein the LED driver system further includes:
a third current source connected to the second terminal of said LED and controlled by a signal from the control algorithm circuit, and
a fourth current source connected to the first terminal of said LED and controlled by a signal from the control algorithm circuit.