be separated from the lower housing unit 160 by a predetermined distance accordingly the power connection terminal 228 connected to the pad 410 of the inverter printed circuit board 400 may be disposed to be separated from the light shielding plate 222 by a predetermined distance determined by the spacing between the lower housing unit 160 and the inverter printed circuit board 400 furthermore in order to support the inverter printed circuit board 400 inserted into the power connection terminal 228 the board support 224 may be interposed between the power connection terminal 228 and the light shielding plate 222 in addition an auxiliary projection 165 for supporting the inverter printed circuit board 400 may be disposed on a lower surface of the lower housing unit 160 in another exemplary embodiment the auxiliary projection 165 may be disposed on an upper surface of the inverter printed circuit board 400 hereinafter the application of a lamp socket to different types of lower housing units with different thicknesses will be described with reference to fig5 and 8 fig8 is a front view illustrating an exemplary embodiment of a lower housing unit having a relatively thin thickness and an exemplary embodiment of the lamp socket of fig2 in an assembled state first referring to fig5 illustrating the lamp socket 200 securely inserted into the socket hole 162 of the lower housing unit 160 the position of a protruding portion of the fastening member 230 is determined by the thickness d 1 of the lower housing unit 160 in.