Liquid crystal display device

A liquid crystal display device comprising:

• a liquid crystal display panel;
• a backlight having at least one light-emitting diode;
• and
• an LED drive circuit for driving said at least one light-emitting diode,
• wherein the LED drive circuit includes a constant voltage circuit for controlling a voltage outputted from an output terminal in such a manner that a voltage inputted to a feedback terminal becomes a constant voltage, a first current mirror circuit having a first transistor and a second transistor, a second current mirror circuit having a third transistor and a fourth transistor, and a resistive element connected to the feedback terminal of the constant voltage circuit,
• wherein said at least one light-emitting diode is connected between the output terminal of the constant voltage circuit and the fourth transistor,
• wherein a reference current flowing through the first transistor flows through the resistive element,
• wherein the second transistor allows a current corresponding to the current flowing through the first transistor to flow through the third transistor,
• wherein the fourth transistor allows a current corresponding to the current flowing through the third transistor to flow through said at least one light-emitting diode,
• wherein the LED drive circuit includes at least one diode connected between the first transistor and the resistive element,
• wherein the reference current does not flow through the at least one light-emitting diode,
• wherein the at least one diode is more particularly a first plural sequence of diodes, and the at least one light-emitting diode is more particularly a second plural sequence of light-emitting diodes,
• wherein each diode of the first plural sequence of diodes has a temperature dependence characteristic which is different from a temperature dependent characteristic of each light-emitting diode of the second plural sequence of light-emitting diodes, and
• wherein a number of diodes in the first plural sequence of diodes is set to have a forward voltage having a temperature dependence characteristic substantially coinciding with a temperature dependence characteristic of a forward voltage of the second plural sequence of light-emitting diodes.

A liquid crystal display device comprising:

• a liquid crystal display panel;
• a backlight having at least one light-emitting diode;
• and
• an LED drive circuit for driving said at least one light-emitting diode,
• wherein the LED drive circuit includes a constant voltage circuit for controlling a voltage outputted from an output terminal in such a manner that a voltage inputted to a feedback terminal becomes a constant voltage, a first current mirror circuit which has a first transistor and a second transistor, the first current mirror circuit allowing a current corresponding to a reference current flowing through the first transistor to flow through the second transistor, a second current mirror circuit which has a third transistor and a fourth transistor, the second current mirror circuit allowing a current corresponding to a current flowing through the third transistor to flow through the fourth transistor, and a resistive element connected between the feedback terminal of the constant voltage circuit and a reference voltage,
• wherein said at least one light-emitting diode is connected between the output terminal of the constant voltage circuit and a second electrode of the fourth transistor,
• wherein the first and second transistors have first electrodes each connected to the output terminal of the constant voltage circuit,
• wherein the third transistor has a second electrode connected to a second electrode of the second transistor and a first electrode connected to the reference voltage,
• wherein the fourth transistor has a first electrode connected to the reference voltage,
• wherein the LED drive circuit includes at least one diode connected between a second electrode of the first transistor and the resistive element,
• wherein the reference current does not flow through the light-emitting diode,
• wherein the at least one diode is more particularly a first plural sequence of diodes, and the at least one light-emitting diode is more particularly a second plural sequence of light-emitting diodes,
• wherein each diode of the first plural sequence of diodes has a temperature dependence characteristic which is different from a temperature dependent characteristic of each light-emitting diode of the second plural sequence of light-emitting diodes, and
• wherein a number of diodes in the first plural sequence of diodes is set to have a forward voltage having a temperature dependence characteristic substantially coinciding with a temperature dependence characteristic of a forward voltage of the second plural sequence of light-emitting diodes.