Abstract: The present invention relates to an electric heater apparatus including a switch control part for controlling a switching part according to a control command of an air-conditioner controlling part; the switching part switched according to a switching control signal of the switch control part for supplying electric power of the power supply part from a heating part; and the heating part for receiving the electric power of the switching part and generating heat, wherein the switching part includes a plurality of switching modules set to control an output load of the heating part, and the switch control part operates one or more switching modules in serial order according to a target heating temperature.

Abstract: The present invention relates to an electric heater apparatus including a switch control part for controlling a switching part according to a control command of an air-conditioner controlling part; the switching part switched according to a switching control signal of the switch control part for supplying electric power of the power supply part from a heating part; and the heating part for receiving the electric power of the switching part and generating heat, wherein the switching part includes a plurality of switching modules set to control an output load of the heating part, and the switch control part operates one or more switching modules in serial order according to a target heating temperature.

Abstract: The present invention relates to an air-conditioning system for vehicles, in which expansion means and an internal heat exchanger are formed integrally with each other or expansion means, an internal heat exchanger and an accumulator are formed integrally with one another in an air-conditioning system using carbon dioxide (CO2) as refrigerant so as to minimize and simplify a refrigerant line, thereby reducing the cost and a loss of energy according to a reduction in the number of assembly processes thereof. The air-conditioning system includes a compressor, a gas cooler, expansion means and an evaporator as a refrigerant line for circulating refrigerant in this order.