Reference voltage generation circuit, power source device, liquid crystal display device

A power source device comprising:

• a reference voltage generation circuit to generate a reference voltage;
• and
• a DC/DC converter to generate an output voltage from an input voltage according to the reference voltage;
• wherein the reference voltage generation circuit comprises:
• a first input stage including two npn transistors or two NMOS transistors having base terminals or gate terminals to which a variable voltage and a predetermined lower limit voltage are inputted, respectively;
• a first output stage including a pnp transistor or a PMOS transistor having an emitter terminal or a source terminal connected to an output terminal for the reference voltage;
• and
• a first amplifier stage to control the first output stage for equalizing the higher one of the variable voltage and the lower limit voltage with the reference voltage;
• wherein the second amplifier circuit comprises:
• a second input stage including two npn transistors or two NMOS transistors having base terminals or gate terminals to which the reference voltage and a predetermined higher limit voltage are inputted, respectively;
• a second output stage including a pnp transistor or a PMOS transistor having an emitter terminal or a source terminal connected to an output terminal of the reference voltage;
• and
• a second amplifier stage to control the second output stage for equalizing the reference voltage with the higher limit voltage.

A liquid crystal display device comprising:

• a temperature sensor which generates a temperature detection voltage, a voltage value of which fluctuates according to fluctuation of temperature;
• a power source device to generate an output voltage from an input voltage according to a reference voltage;
• a gate driver to generate a gate drive signal in response to a supplement of the output voltage;
• a source driver to generate a source drive signal;
• and
• a liquid crystal display panel which operates by receiving the gate drive signal and the source drive signal;
• wherein the power source device comprises:
• a reference voltage generation circuit to generate the reference voltage;
• a DC/DC converter to generate an output voltage from an input voltage according to the reference voltage;
• wherein the reference voltage generation circuit comprises:
• a first amplifier circuit;
• and
• a second amplifier circuit;
• wherein the first amplifier circuit comprises:
• a first input stage including two npn transistors or two NMOS transistors having base terminals or gate terminals to which the temperature detection voltage and a predetermined lower limit voltage are inputted, respectively;
• a first output stage including a pnp transistor or a PMOS transistor having an emitter terminal or a source terminal connected to an output terminal for the reference voltage;
• a first amplifier stage to control the first output stage for equalizing the higher one of the temperature detection voltage and the lower limit voltage with the reference voltage;
• wherein the second amplifier circuit comprises:
• a second input stage including two npn transistors or two NMOS transistors having base terminals or gate terminals to which the reference voltage and a predetermined higher limit voltage are inputted, respectively;
• a second output stage including a pnp transistor or a PMOS transistor having an emitter terminal or a source terminal connected to an output terminal for the reference voltage;
• a second amplifier to control the second output stage for equalizing the reference voltage and the higher limit voltage.