Key pin voltage switching power supply integrated circuit is a power supply terminal (VCC), excitation pulse output and input voltage detection, current detection input. The measuring pin on the voltage value and resistance value, and if the normal value of difference, in the peripheral components under normal conditions, can determine whether the integrated circuit has been damaged. Thick film integrated circuit with high power switch tube, but also through the measurement of B, E, C switches between positive and negative resistance value, to determine whether the normal switch.