The present invention provides a power supply apparatus for an LED lamp, which mainly uses an isolation transformer to convert a high voltage AC input signal into a low voltage AC signal and thus generate a driving voltage for driving an LED lamp, comprising: a waveform and frequency modulation module disposed on the primary side of the isolation transformer for modulating an input waveform and a frequency f; and a secondary rectifier filter module disposed on the secondary side of the isolation transformer for converting the low voltage AC signal after passing through the isolation transformer into the driving voltage. In this way, the power supply apparatus for an LED lamp utilizes the principle of persistence of vision of human eyes to modulate the waveforms and frequencies of voltages for driving LEDs and can still maintain the normal operation.