Power supply, display device, and light source driving apparatus

A display device including a plurality of pixels, a lamp unit emitting light to the pixels, and a power supply applying a driving voltage to the lamp unit,

• wherein the power supply comprises:
• a DC-DC converter being supplied with an external DC input voltage and a first switching control signal and outputting a duty sensing signal of which a magnitude is varied in accordance with the first switching control signal, the duty sensing signal being indicative of a duty ratio of the first switching control signal, and the DC-DC converter converting the input voltage into a DC output voltage of a predetermined magnitude based on the first switching control signal;
• and
• a feedback controlling unit comparing the duty sensing signal with a first reference signal to adjust a duty ratio of the first switching control signal.

A current controlling apparatus controlling a DC-DC converter which is supplied with an external DC input voltage and a first switching control signal and outputs a duty sensing signal of which a magnitude is varied in accordance with the first switching control signal, the duty sensing signal being indicative of a duty ratio of the first switching control signal, and the DC-DC converter converts the input voltage into a DC output voltage of a predetermined magnitude based on the first switching control signal, the apparatus comprising:

• a current sensing unit changing the duty sensing signal into a sawtooth wave signal;
• a duty signal adjusting unit supplied with the input voltage and a second reference signal, the duty signal adjusting unit adjusting the second reference signal based on the variation of the input voltage to generate an adjusted second reference signal as the first reference signal;
• a comparator comparing the sawtooth wave signal with the first reference signal to output a pulse signal of an appropriate pulse width;
• and
• a duty ratio adjusting unit resetting a state of an output signal thereof when the pulse signal is applied, the output signal of the flip flop operative to adjust the duty ratio of the first switching control signal.

The apparatus of claim 17, wherein the current sensing unit comprises:

• a switching element having a control terminal supplied with a second switching control signal, an input terminal supplied with the duty sensing signal, and an output terminal connected to a constant voltage;
• a resistor connected to the duty sensing signal and commonly connected to the linear unit and the constant voltage;
• and
• a capacitor connected to the input terminal and the output terminal of the switching element.

A light source driving apparatus comprising

• a lamp unit having at least one light source,
• a power supply applying a driving voltage to the light source, and
• a signal controlling unit applying a lamp control signal to the light source,
• wherein the power supply comprises:
• a signal converting unit converting an externally applied AC voltage into a DC voltage;
• a DC-DC converter being supplied with the DC voltage and a first switching control signal and outputting a duty sensing signal of which a magnitude is varied in accordance with a first switching control signal, the duty sensing signal being indicative of a duty ratio of the first switching control signal, and the DC-DC converter converting the input voltage into a DC output voltage of a predetermined magnitude based on the first switching control signal;
• and
• a feedback controlling unit comparing the duty sensing signal with a first reference signal to adjust the duty ratio of the first switching control signal.