Dynamic headroom control for LCD driver
First Claim
1. An LED driver controller, comprising:
- a voltage regulator for controlling an output voltage to a top of a plurality of LED strings responsive to at least a reference voltage;
a first circuitry associated with a first node at a bottom of a first LED string of the plurality of LED strings for comparing a voltage at the bottom of the first LED string with a high reference voltage and a low reference voltage;
a second circuitry associated with a second node at a bottom of a second LED string of the plurality of LED strings for comparing a voltage at the bottom of second LED string with a high reference voltage and a low reference voltage;
control logic for generating a first control signal when the voltage of at least one node at the bottom of one of the plurality of LED strings falls below the low reference voltage and for generating a second control signal when the voltage at the bottom of each node of the plurality of LED strings exceeds the high reference voltage;
second circuitry responsive to the first control signal and the second control signal for generating the reference voltage; and
wherein the second circuitry controls the reference voltage to cause the voltage at the bottom of a lowest voltage node of the plurality of LED strings to remain between the high reference voltage and the low reference voltage.
3 Assignments
0 Petitions
Accused Products
Abstract
An LED driver controller comprises a voltage regulator for controlling an output voltage to a top of a plurality of LED strings responsive to at least a reference voltage. A plurality of first circuitries each associated with a node at a bottom of each of the plurality of LED strings compares a voltage at the bottom of each of the plurality of LED strings with a high reference voltage and a low reference voltage. Control logic generates a first control signal when the voltage at the bottom of each node of the plurality of LED strings exceeds the high reference voltage and generates a second control signal when the voltage at least one of node of the plurality of LED strings falls below the low reference voltage. Second circuitry responsive to the first control signal and the second control signal generates the reference voltage. The reference voltage is controlled to cause the voltage at the bottom of the lowest voltage node of the plurality of LED strings to remain between the high reference voltage and the low reference voltage.
19 Citations
20 Claims
-
1. An LED driver controller, comprising:
-
a voltage regulator for controlling an output voltage to a top of a plurality of LED strings responsive to at least a reference voltage; a first circuitry associated with a first node at a bottom of a first LED string of the plurality of LED strings for comparing a voltage at the bottom of the first LED string with a high reference voltage and a low reference voltage; a second circuitry associated with a second node at a bottom of a second LED string of the plurality of LED strings for comparing a voltage at the bottom of second LED string with a high reference voltage and a low reference voltage; control logic for generating a first control signal when the voltage of at least one node at the bottom of one of the plurality of LED strings falls below the low reference voltage and for generating a second control signal when the voltage at the bottom of each node of the plurality of LED strings exceeds the high reference voltage; second circuitry responsive to the first control signal and the second control signal for generating the reference voltage; and wherein the second circuitry controls the reference voltage to cause the voltage at the bottom of a lowest voltage node of the plurality of LED strings to remain between the high reference voltage and the low reference voltage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
-
-
9. An LED driver controller, comprising:
-
a voltage regulator for controlling an output voltage to a top of a plurality of LED strings responsive to at least a reference voltage; a plurality of first circuitries each associated with a node at a bottom of each of the plurality of LED strings, the plurality of first circuitries each comprising; a first comparator for comparing the voltage at the node at the bottom of the LED string with the high reference voltage; a second comparator for comparing the voltage at the node at the bottom of the LED string with the low reference voltage; an AND function for generating a first control signal responsive to the voltage at the bottom of all nodes of the plurality of LED strings exceeding a high reference voltage; and an OR function for generating a second control signal responsive to the voltage at the bottom of at least one LED string falling below a low reference voltage; counter/stepping logic responsive to the first control signal and the second control signal for generating a digital control signal associated with a desired reference voltage; a digital to analog converter for generating the reference voltage in analog format responsive to the digital control signal; and wherein the second circuitry controls the reference voltage to cause the voltage at the bottom of a lowest voltage node of the plurality of LED strings to remain between the high reference voltage and the low reference voltage. - View Dependent Claims (10, 11, 12, 13)
-
-
14. A method for controlling an output voltage to a top of a plurality of LED strings, comprising the steps of:
-
generating an output voltage to the top of the plurality of LED strings responsive to at least a reference voltage; comparing a first voltage at the bottom of a first LED string of the plurality of LED strings with a high reference voltage and a low reference voltage; comparing a second voltage at the bottom of a second LED string of the plurality of LED strings with the high reference voltage and the low reference voltage; generating a first control signal when the voltage at the bottom of each node of the plurality of LED strings exceeds the high reference voltage; generating a second control signal when the voltage of at least one of node of the plurality of LED strings falls below the low reference voltage; generating the reference voltage responsive to the first control signal and the second control signal, wherein the reference voltage is controlled to cause the voltage at the bottom of a lowest voltage node of the plurality of LED strings to remain between the high reference voltage and the low reference voltage. - View Dependent Claims (15, 16, 17, 18, 19, 20)
-
Specification