Apparatus and method for driving displays
View Patent ↗Generally, displays, like liquid crystal displays (LCDs), use a DC-free addressing voltage in order to prevent decomposition of the display. Here, an integrated circuit (IC) is provided that compensates for temperature dependencies. This IC typically uses a thermistor or temperature varying element to measure the temperature of the display and adjusts the common reference voltage in response to the measured temperature.
1. An apparatus comprising:
an input pin;
a temperature measurement pin;
an amplifier that is coupled to the input pin and that generates a generates a reference voltage;
a switch that is coupled to the amplifier;
a current sensor that is coupled to the temperature measurement pin;
a first functional circuit that is coupled to the current sensor and that generates a first current;
a second functional circuit that receives the first current and a second current and that provides a difference between the first current and the second current to the switch; and
a controller that receives the first current and the second current, wherein the controller actuated the switch when the first current is greater than the second current.
2. The apparatus of claim 1 , wherein the apparatus further comprises a current source that is coupled to the first functional circuit so as to generate the first current.
3. The apparatus of claim 1 , wherein the apparatus further comprises:
a sensing pin;
a second current sensor that is coupled to the sensing pin;
a third functional circuit that is coupled to the second current sensor;
a current source that is coupled to the third functional circuit so as to generate the second current.
4. The apparatus of claim 1 , wherein the apparatus further comprises:
a sensing pin;
a second current sensor that is coupled to the sensing pin;
a third functional circuit that is coupled to the second current sensor; and
a current source that is coupled to the third functional circuit and the switch.
5. The apparatus of claim 1 , wherein the apparatus further comprises:
a plurality of control pins;
a digital-to-analog converter (DAC) that is coupled to each of the control pins;
memory that is coupled to the DAC;
a current setting stage that is coupled to the DAC; and
a current source that is coupled amplifier and the current setting stage.
6. An apparatus comprising:
an input circuit;
an input pin that is coupled to the input circuit;
a temperature measurement circuit
a temperature measurement pin that is coupled to the temperature measurement circuit;
an amplifier that is coupled to the input pin and that generates a generates a reference voltage;
a switch that is coupled to the amplifier;
a current sensor that is coupled to the temperature measurement pin;
a first functional circuit that is coupled to the current sensor and that generates a first current;
a second functional circuit that receives the first current and a second current and that provides a difference between the first current and the second current to the switch; and
a controller that receives the first current and the second current, wherein the controller actuated the switch when the first current is greater than the second current.
7. The apparatus of claim 6 , wherein the apparatus further comprises a current source that is coupled to the first functional circuit so as to generate the first current.
8. The apparatus of claim 6 , wherein the apparatus further comprises:
a sensing pin;
a second current sensor that is coupled to the sensing pin;
a third functional circuit that is coupled to the second current sensor;
a current source that is coupled to the third functional circuit so as to generate the second current.
9. The apparatus of claim 8 , wherein a resistor is coupled to the sensing pin.
10. The apparatus of claim 6 , wherein the apparatus further comprises:
a sensing pin;
a second current sensor that is coupled to the sensing pin;
a third functional circuit that is coupled to the second current sensor; and
a current source that is coupled to the third functional circuit and the switch.
11. The apparatus of claim 10 , wherein a resistor is coupled to the sensing pin.
12. The apparatus of claim 6 , wherein the apparatus further comprises:
a plurality of control pins;
a reset pin;
a DAC that is coupled to each of the control pins;
memory that is coupled to the DAC;
a current setting stage that is coupled to the DAC and the reset pin; and
a current source that is coupled amplifier and the current setting stage.
13. The apparatus of claim 12 , wherein a resistor is coupled to the reset pin.
14. The apparatus of claim 6 , wherein the temperature measurement circuit further comprises a thermistor.
15. The apparatus of claim 6 , wherein the input circuit further comprises a voltage divider.
16. An apparatus comprising:
an input circuit;
a temperature measurement circuit;
a first resistor;
a second resistor;
an integrated circuit having:
an input pin that is coupled to the input circuit;
a temperature measurement pin that is coupled to the temperature measurement circuit;
a first sensing pin that is coupled to the first resistor;
a second sensing pin that is coupled to the second resistor;
an amplifier that is coupled to the input pin and that generates a generates a reference voltage;
a switch that is coupled to the amplifier;
a current sensor that is coupled to the temperature measurement pin;
a first functional circuit that is coupled to the current sensor;
a first current source that is coupled to the first functional circuit so as to generate a first current;
a second current sensor that is coupled to the first sensing pin;
a second functional circuit that is coupled to the second sensing circuit;
a second current source that is coupled to the second functional circuit so as to generate a second current;
a third functional circuit that receives the first current and the second current and that provides a difference between the first current and the second current to the switch;
a third current sensor that is coupled to the second sensing pin;
a fourth functional circuit that is coupled to the third current sensor;
a third current source that is coupled to the fourth functional circuit and the switch, wherein the third current source generates a third current; and
a controller that receives the first current and the second current, wherein the controller actuated the switch when the first current is greater than the second current.
17. The apparatus of claim 16 , wherein the apparatus further comprises:
a plurality of control pins;
a reset pin;
a DAC that is coupled to each of the control pins;
memory that is coupled to the DAC;
a current setting stage that is coupled to the DAC and the reset pin; and
a current source that is coupled amplifier and the current setting stage.
18. The apparatus of claim 16 , wherein a resistor is coupled to the reset pin.
19. The apparatus of claim 16 , wherein the temperature measurement circuit further comprises a thermistor.
20. The apparatus of claim 16 , wherein the input circuit further comprises a voltage divider.