US 10,314,131 B1Granted

LED driver with brightness control and driving method thereof

AssigneeAnpec Electronics Corporation

InventorsWen-Yen Chen, Ming-Hung Chang

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Abstract

The present disclosure provides an LED driver with brightness control and a driving method thereof, which adjust a first rate of a first current mirror, a second rate of a second current mirror, and a reference current of a current source according to the brightness to be presented (related to image brightness information) to adaptively adjust an LED current flowing through an LED string, thereby reducing the loss of the LED current during operation over an operating current range. Besides, the LED driver with brightness control and the driving method thereof do not require that an operator adjusts the variation of the LED current in different operating current ranges in advance, thereby reducing the test time and cost and avoiding the operator from deciding a wrong adjustment amount.

Claims11

Dependent claims

A light-emitting diode (LED) driver with brightness control, used to reduce the loss of an LED current flowing through an LED string in an operating current range, and comprising:

a first current mirror, coupled to a current source, and generating a first current according to a reference current generated by the current source, wherein the first current is a reference current multiplied by a first rate;
a second current mirror, coupled to the first current mirror, coupled to the LED string via a drive transistor, and generating the LED current flowing through the LED string according to the first current, wherein the LED current is the first current multiplied by a second rate;
and
an LED controller, coupled to the current source, the first current mirror, and the second current mirror;
receiving image brightness information;
generating a first parameter, a second parameter, a digital signal, and a pulse-width modulation (PWM) signal according to the image brightness information;
and driving the LED string according to the PWM signal;
wherein the first current mirror adjusts the first rate according to the first parameter, the second current mirror adjusts the second rate according to the second parameter, and the LED controller adjusts the reference current according to the digital signal multiplied by a third rate, wherein a product obtained by multiplying the first rate, the second rate, and the third rate together is a fixed value.

5 more elements

A light-emitting diode (LED) driving method with brightness control, applicable to an LED driver, the LED driver comprising a first current mirror and a second current mirror, the first current mirror being coupled to a current source and the second current mirror, and the second current mirror being coupled to an LED string, to reduce the loss of an LED current flowing through the LED string in an operating current range, wherein the LED driving method comprises:

step (A):
receiving image brightness information, and generating a first parameter, a second parameter, a digital signal, and a pulse-width modulation (PWM) signal according to the image brightness information;
step (B):
adjusting a first rate of the first current mirror according to the first parameter, adjusting a second rate of the second current mirror according to the second parameter, and adjusting a reference current generated by the current source according to the digital signal multiplied by a third rate, wherein the second parameter is equal to the first parameter multiplied by the third rate;
step (C):
adjusting the reference current according to the first rate to generate a first current from the first current mirror to the second current mirror, and adjusting the first current according to the second rate to generate an LED current flowing through the LED string, wherein the first current is the reference current multiplied by the first rate, and the LED current is the first current multiplied by the second rate;
and
step (D):
driving the LED string according to the PWM signal.

6 more elements

Dependencies are inferred from the claim text.