X-ray generator

An X-ray generator comprising:

• a booster configured to boost a first DC voltage supplied from a voltage source to a second DC voltage that is higher in magnitude than the first DC voltage;
• at least one capacitor configured to receive the second DC voltage and to generate a charging voltage;
• a converter configured to convert the charging voltage into a driving voltage;
• an X-ray source configured to receive the driving voltage and to emit X-rays;
• and
• a controller configured to control the booster, the converter, and the X-ray source,
• wherein the second DC voltage is variable, and
• the controller calculates a cooling time that is taken for the X-ray source to be cooled to below a predetermined temperature after the X-ray source emits X-rays, determines the magnitude of the second DC voltage according to the cooling time, and applies the second DC voltage to the capacitor for the cooling time.