Projection brightness adjustment method for controlling current output of power source and projector thereof

A projector comprising:

• a projection device;
• a power source electrically connected to the projection device for driving the projection device to project an image;
• a temperature sensor electrically connected to the projection device for detecting a working temperature of the projection device;
• and
• a processor electrically connected to the projection device, the temperature sensor and the power source, the processor calculating a pixel average amount corresponding to each pixel brightness level of the image according to a total pixel amount of the image and a total pixel brightness level amount of the image, the processor determining whether the working temperature is less than an upper operating-temperature limit of the power source, the processor determining a level amount of the pixel brightness levels having a pixel amount larger than the pixel average amount, the processor determining whether the level amount is less than or equal to half of the total brightness level amount, and the processor controlling the power source to output an overload current to the projection device for image projection when determining the working temperature is less than the upper operating-temperature limit and determining the level amount is less than or equal to half of the total brightness level amount, wherein the magnitude of the overload current is between a maximum current limit and the upper operating-current limit of the power source.