Backlight device and display device
View Patent ↗A resistive element is connected in series to a cathode terminal of an LED light source at a last stage (or an anode terminal of an LED light source at a first stage) of an LED chain, and a resistance value of the resistive element is configured to be variable in resistance value in accordance with a variation of voltage drops of the LEDs connected in series so that a resistance value of a resistive element connected to an LED chain having a large voltage drop has a smaller resistance value then a resistance value of a resistive element connected to an LED chain having a small voltage drop. With this configuration, the power, which has been wasted otherwise as heat in the backlight driver IC, may be dispersed to the resistive elements.
1. A backlight device, comprising:
a backlight module including a plurality of LED chains each being formed of a plurality of LED light sources connected in series; and
a backlight driver IC including a plurality of FET switches for driving the plurality of LED chains, respectively, wherein:
the backlight device further comprises a plurality of resistive elements each connected in series to a cathode terminal of an LED light source at a last stage of each of the plurality of LED chains, the plurality of LED chains and the plurality of resistive elements forming a plurality of series circuits;
the backlight device further comprises a power supply circuit connected to a first stage side of the plurality of series circuits formed of the plurality of LED chains and the plurality of resistive elements;
the plurality of series circuits formed of the plurality of LED chains and the plurality of resistive elements are each connected, on a last stage side thereof, to a drain terminal of each of the plurality of FET switches; and
a resistance value of a resistive element, of the plurality of resistive elements, connected to an LED chain having a first voltage drop which is a large voltage drop, is smaller than a resistance value of a resistive element, of the plurality of resistive elements, connected to an LED chain having a second voltage drop which is a small voltage drop with respect to the large voltage drop;
wherein a resistive element connected to an LED chain having a largest voltage drop value has a resistance value of substantially zero ohms;
wherein a resistive element connected to another LED chain than the LED chain having the largest voltage drop value has a resistance value obtained by dividing a difference between the voltage drop value of the LED chain having the largest voltage drop value and a voltage drop value of the another LED chain by a current value flowing through the another LED chain;
wherein one side of each of the plurality of resistive elements is connected to the drain terminal of each of the plurality of FET switches, the one side of each of the plurality of resistive elements being opposite to another side of each of the plurality of resistive elements to which each of the plurality of LED chains is connected; and
wherein each source terminal of the plurality of FET switches is connected to ground.
2. The backlight device according to claim 1 , wherein the power supply circuit supplies a power supply voltage to the plurality of series circuits formed of the plurality of LED chains and the plurality of resistive elements, the power supply voltage satisfying a voltage to be consumed by the LED chain that has the largest voltage drop value.
3. The backlight device according to claim 1 , wherein the plurality of resistive elements comprise variable resistors which are variable in resistance value.
4. A display device, comprising:
the backlight device according to claim 1 ; and
a display panel disposed on a front surface of the backlight module of the backlight device.